Coal upgrading to reduce CO2 emissions

Gordon R Couch

CCC/67

October 2002

Copyright © IEA Clean Coal Centre

ISBN 92-9029-382-9

Abstract

Coal can be upgraded before use by washing, drying (mainly in the case of low rank coals) or briquetting/pelletising. Of 3000 Mt/y of bituminous coal that is produced, only some 1500 Mt is washed, and some of this washing is not optimised. Most lower rank coals are not currently upgraded before use. The report includes a review of the methods available, and a country by country review of the potential for additional upgrading. This is in the context that coal consumption is seen by the IEA as increasing by some 40% between 1997 and 2020. The impact of coal upgrading on the thermal efficiency of coal use is discussed, and the countries where there could be the greatest impact are identified. Acronyms and abbreviations ad air dried g/cm3 grams per cubic centimetre adb air dried basis Gt Gigatonnes ADMFB air based dense-medium fluidised bed kWh killowatt hours af ash free MJ/kg Megajoules/kilogramme ar as received mm millimetres BFBC bubbling fluidised bed combustion Mt Million tonnes CCT clean coal technology mtce million tonnes of coal equivalent CDL coal derived liquids mtoe million tonnes of oil equivalent CFBC circulating fluidised bed combustion t tonnes CIAB Coal Industry Advisory Board tph tonnes per hour CPP Coal Preparation Plant CQE Coal Quality Expert $ = US$ unless otherwise specified CQIM Coal Quality Impact Model CWM coal water mixture db dry basis DM dense medium (used in coal preparation) DOE Department of Energy FBC fluidised bed combustion FSU former Soviet Union FYROM Former Yugoslavian Republic of Macedonia GDP gross domestic product HGI Hardgrove Grindability Index HTD hydrothermal dewatering IDGCC integrated drying gasification combined cycle IEA International Energy Agency IGCC integrated gasification combined cycle LFC liquids from coal LHV lower heating value MTE mechanisch-thermische entwässerung OECD Organisation for Economic Cooperation and Development PC pulverised coal PCC pulverised coal combustion PDF process derived fuel PLF plant load factor RD relative density rom run of mine SEB State Electricity Board SNG substitute natural gas SPC State Power Corporation UCC ultraclean coal UGC underground gasification of coal UHV useful heat value UNFCCC United Nations Framework Convention on Climate Change VM volatile matter WEC World Energy Council WTA wirbelschicht-trocknung mit interner abwärmenutzung WTO World Trade Organisation

2 IEA CLEAN COAL CENTRE Contents

1 Introduction 5

2 Coal preparation possibilities 6 2.1 Coal washing 6 2.2 Dry separation methods 8 2.3 Washery costs 10 2.4 The preparation of ultraclean coal 12

3 Drying low rank coals 14 3.1 Flue gas recirculation 15 3.2 External drying methods 15 3.2.1 Tubular dryer 15 3.2.2 Fluidised bed dryer 15 3.2.3 Mechanical-thermal dewatering 16 3.3 Work in different countries 16

4 Briquetting and pelletising 19 4.1 Briquetting with a binder 20 4.2 Binderless briquettes 22 4.3 Pelletising 23 4.4 Extrusion 23 4.5 The costs of agglomeration 23

5 Advanced coal upgrading processes 24 5.1 Demonstration projects in the USA 24 5.2 Australian work 26 5.3 Indonesian work 26 5.4 Underground coal gasification 27

6 Coals with upgrading potential 28 6.1 Australia 29 6.2 Brazil 29 6.3 Bulgaria 32 6.4 Canada 32 6.5 China 32 6.6 Czech Republic 34 6.7 Germany 35 6.8 Greece 35 6.9 Hungary 35 6.10 India 36 6.11 Indonesia 36 6.12 Kazahkstan 37 6.13 Laos 37 6.14 Mexico 37 6.15 New Zealand 38 6.16 North Korea (Democratic People's Republic) 38 6.17 Pakistan 38 6.18 Poland 38 6.19 Republic of Korea (South Korea) 39 6.20 Romania 39 6.21 Russian Federation 39 6.22 South Africa 40 6.23 Spain 40 6.24 Thailand 41 6.25 Turkey 41 6.26 Ukraine 42 6.27 UK 42 6.28 USA 43

Coal upgrading to reduce CO2 emissions 3 7 Energy transportation and market organisation 45 7.1 Coal pricing policies 45 7.2 Coal transportation 46 7.2.1 Coal characterisation for transportation 46 7.3 Coal transport versus coal-by-wire 48 7.4 The effects of liberalised markets 49 7.5 The impacts of national emissions limits and of emissions trading 51 7.6 The regulatory framework 51

8 The effects of coal upgrading 52 8.1 On existing PCC boiler efficiency 52 8.2 On the application of advanced CCTs 55 8.3 On industrial and domestic use 55

9 Potential for CO2 reductions 57 9.1 Coal tonnages that can be upgraded 57 9.2 Prospective increases in thermal efficiency 60 9.2.1 In coal-fired boilers 60 9.2.2 By using briquettes 62 9.3 Overall benefits from upgrading 63 9.4 Global CO2 emissions 63 9.4.1 Reductions associated with coal upgrading 64

10 Conclusions 66

11 References 67

4 IEA CLEAN COAL CENTRE 1 Introduction

There has been extensive public debate about the possibility thermal efficiency, and hence on the amount of CO2 of an increase in the natural greenhouse effect resulting from produced per MWe of power produced. In this report, the changes in the composition of the earth’s atmosphere. The effects of coal upgrading on both boiler and gasifier principal contributors to this are CO2, CH4 and the CFC operation are discussed and assessed. There would also be gases. There is widespread concern about the possible long- benefits when the coal is used on an industrial or domestic term effects of climate change which may result from the scale, although these are less easy to quantify. increase in concentration of the greenhouse gases. As a result, the precautionary principle is being strongly In many countries, coal is already prepared and washed promoted, and there is pressure to reduce the amount of before use, although it might well be possible to remove greenhouse gases emitted. In most developed countries, more of the impurities present, albeit with a reduced product specific targets have been set for reducing the emissions of yield. Some large coal consumers, however, only wash a CO2 during the next ten or twenty years, in line with the small proportion of the coal used both for power generation targets set in the Kyoto agreement of 1997. As coal and for smaller-scale applications. In addition, substantial combustion, and the use of other fossil fuels, results in the quantities of lignites and brown coals are used without formation of CO2, there is a need to consider ways of pretreatment or upgrading. This means that there is scope for reducing the amount produced. There is particular concern efficiency improvements in coal-fired plant by upgrading the about environmental issues, including the question of CO2 coal prior to use by washing and/or by drying, thus reducing emissions, in countries like China and India where the use of its ash and/or moisture content, and by improving its fossil fuel-based energy is likely to grow significantly. consistency. These efficiency improvements would be accompanied by a reduction in CO2 emissions, and possibly In relation to coal use, a reduction is being sought in the by other parallel benefits, such as a reduction in the amount amount of CO2 emissions from industrial boilers and from of SO2 formed. While this would only make a relatively plants generating electrical power. Since coal accounts for small contribution towards meeting the reduction targets for 26% of the primary energy used worldwide, and total coal CO2 emissions, it is potentially achievable with proven consumption is forecast to grow by 1.7%/y up to 2020, these technology and with equipment that could be installed quite emissions are of considerable importance. The growth in quickly. coal use is slightly slower than the overall increase in primary energy consumption worldwide, which is projected In most of the literature, when various methods of reducing to increase by 2%/y (IEA, 2001a). global CO2 emissions are discussed, the possible contribution of coal upgrading is ignored. What is considered Most coal is used for large-scale power generation, and it is is the use of new technologies, such as IGCC, supercritical in this area that attention is focused although there are steam PCC and others; the wider application of potential benefits from tackling smaller-scale use as well. co-generation; fuel substitution, and the wider use of Reductions may be achieved by the use of more efficient renewable energy sources. The sequestration (storage) of the clean coal technologies, including the application of CO2 produced is also the subject of widespread discussion in integrated gasification combined cycle (IGCC) and the use of published material. supercritical steam cycles in pulverised coal combustion (PCC) boilers. It can also be achieved by the more efficient In this study, the applicability of coal preparation techniques operation of existing boilers, and this benefit can be realised are discussed, together with coal drying for the low rank relatively quickly and at lower cost. coals and briquetting for coal fines. The potential for upgrading is assessed, with associated increases in the Because of the large number of existing coal-fired boilers, thermal efficiency of use and resultant reductions in CO2 supercritical PCC boilers and IGCC plants will only come emissions per MWe of power generated. Related issues, such into use gradually, as new coal-fired units are built, or as as coal transportation and market organisation in the units are retrofitted. There are still substantial numbers of countries with the greatest potential for benefits from subcritical PCC boilers being built (Couch, 1997, 1999). The upgrading are discussed, together with a summary of the largest potential reductions in CO2 emissions from coal-fired parallel benefits in the reduction of the amount of ash to be boilers in the near term would therefore come from increases disposed of from a power station, and possible reductions in in efficiency in the 4000 or so existing units. In the longer the formation of SO2. term, coal-fired power generation units operating at thermal efficiencies in the 45–50% range will contribute to a considerable reduction in CO2 emissions per unit of power generated, compared with the use of existing plant using technologies which operate at efficiencies broadly in the 30–35% range.

In all situations, the quality of the coal used in a boiler or gasifier makes an impact on its overall behaviour, on its

Coal upgrading to reduce CO2 emissions 5 2 Coal preparation possibilities

The necessary starting point for making power generation the density difference between particles. The substantial more efficient is the quality and consistency of the coal feed differences between the northern and southern hemisphere to any combustion or gasification process. This study coals are discussed in detail by Stach and others (1982). considers the potential effects on the emissions of CO2 of coal preparation, discussed in this chapter, and of coal drying Roughly half the bituminous coals mined worldwide are not or briquetting, discussed in Chapters 3 and 4. Many washed, and most low rank coal is used run of mine (rom) commentators ignore the effects of using cleaner, dryer coals material. For thermal coals, the level of preparation is limited on overall CO2 emissions both using the newer advanced by the demands of a competitive market which means that clean coal technologies and in conventional PCC units. In washing costs are minimised. The details of coal production this study the effects are quantified, and shown to have in 1999 are presented in Table 1. This shows that over potential significance. 3800 Mt/y of coal is used in the country where it is mined, and nearly one quarter of it is low rank coal. 2.1 Coal washing Of the 3000 Mt/y of bituminous coal produced, some Coal washing is often described as preparation (for particular 1500 Mt/y is washed. Some of this washing is not optimised, markets) or cleaning (by reducing the amount of mineral and only the coarse fraction is treated. Most of the lower matter and/or sulphur in the product coal). Since virtually all rank coals are not upgraded before use. Selective mining is the processes are water-based, washing is a convenient term carried out in some places to improve the quality of low rank to use. Because preparation is the principal way of upgrading coals, but less than 100 Mt/y is dried or washed before use. bituminous coals, the basic principles are outlined here. The These numbers indicate the scope that exists for further coal objective of the operations is to recover the maximum upgrading which will affect the efficiency of its use, with practical amount of organic coal. In line with the principles resultant effects on CO2 emissions when it is combusted. The discussed in the Clean Coal Centre report on Power from potential for reductions is discussed on a country by country coal – where to remove impurities? (Couch, 1995) the basis in Chapter 5. overall objective is to optimise the profitability of the whole coal-to-electricity chain, or for industrial use, the coal-to- Coal preparation and coal cleaning have been discussed in steam route. earlier Clean Coal Centre reports, including Advanced coal cleaning technology (Couch, 1991) and Adding value to coal Washing operations are carried out mainly on bituminous cleaning wastes (Couch, 1998). and anthracitic coals, as the characteristics of subbituminous coals and lignite (brown coals) do not lend themselves to The mineral matter content of coals as mined, can range separation of mineral matter by this means, except in a few from 5 to 50% and affects the heating value of the coal and cases. The low rank coals have high moisture contents, and its deposition characteristics in a boiler. It can thus affect the most important aspect of upgrading is usually drying, heat losses from the system and boiler efficiency. The size, which is discussed in Chapter 3. There is, however, thought distribution and nature of the mineral matter through the run being given to the cleaning of the western US subbituminous of mine (rom) coal can vary widely and depend both on its coals, possibly using dry methods. The focus is on increasing occurrence in the coal seam and on the mining method. the heat content and possibly reducing the mercury content (Alderman, 2002). This would also result in some reduction Washing operations are generally carried out within three in CO2 emissions from the use of these coals. distinct size ranges. These are coarse coal, which is broadly from 150 to 10 mm size, intermediate, from 10 to 0.5 mm The broad differences between the Carboniferous coals (500 µm) and fines, below 500 µm size. Not all operations fit largely from the northern hemisphere and the Permian coals perfectly into these ranges, but the various methods of from the southern hemisphere are important. This is because, separation lend themselves to achieving sharper separations historically, most users in Europe and the USA have used with coal particles of a broadly uniform size. local Carboniferous coals. During the last 20–30 years, commercially competitive coals from the southern The first operation in most coal preparation plants (CPPs) is hemisphere (Gondwana region) have been taking an crushing to eliminate large lumps of coal (over 100 or increasing share of the market in internationally traded coals. 150 mm size). This is followed by screening to produce different size cuts for treatment. Three levels of cleaning are While there are coals from most geological ages spread commonly used (Osborne, 1988a): around in different continents, in the bituminous coals from ● level 1, coarse coal treatment only; the northern hemisphere, the mineral matter tends to be ● level 2, coarse coal and intermediates are washed; present in a coarse crystalline form. In the Gondwana coals ● level 3, coarse, intermediates and fines are all from the south, such as those from Australia, India and South cleaned/separated. Africa, much of the mineral matter tends to be much more finely dispersed through the coal structure, and as a result it Coarse and intermediate sizes of coal are normally washed in is more difficult to ‘clean’ these coals by processes based on a jig or using a dense medium bath or cyclone, in order to

6 IEA CLEAN COAL CENTRE Coal preparation possibilities

Table 1 Worldwide coal production, 1999 (World Energy Council, 2001; IEA, 2001b)

Country Bituminous, Mt* Subbituminous, Mt* Lignite, Mt* Total, Mt* Amount exported, Mt†

China 985 – 45 1030 37 USA 568 352 76.5 996.5 53 India 292 – 22 314 – Australia 222 16 66 304 172 Russian Fed 166 – 83.5 249.5 28 South Africa 224 – – 224 66 Germany 40.5 – 161 201.5 – Poland 110 – 61 171 25 Ukraine 35 46 1 82 2 North Korea 60 21.5 – 81.5 – Canada 36.5 24 12 72.5 34 Indonesia 71 – – 71 54 Tur key 2 – 65 67 – Greece – – 62 62 – Czech Rep 14.5 44 0.5 59 6 Kazakhstan 56 – 2 58 na UK 37 – – 37 1 Colombia 33 – – 33 30 Serbia – – 30.5 30.5 – Bulgaria – – 26 26 – Spain 13 4 8.5 25.5 0.4 Romania – 3 20 23 – Thailand – – 18 18 – Hungary 1 6.5 7.5 15 – Mexico 2 8 – 10 – Vietnam 9 – – 9 3 FYR Macedonia – 8.5 8.5 – – Venezuela 6.5 – – 6.5 6 Brazil 6 – – 6 – France 4.5 – 0.5 5 0.5 Zimbabwe 5 – – 5 – Mongolia 1.5 – 3.5 5 – Slovenia – 0.8 3.8 4.6 – South Korea – 4 – 4 – Slovakia – – 3.7 3.7 – New Zealand 1.6 1.7 0.2 3.5 1.3 Pakistan – 3 – 3 – Uzbekistan – – 3 3 – Other 7.4 3.3 3.8 14.5 World total Mt 3010 538 795 4343 519

– indicates that the amount involved is generally less than 1 Mt/y, and may be zero na not available * WEC statistics † IEA statistics

Coal upgrading to reduce CO2 emissions 7 Coal preparation possibilities achieve a separation of cleaner coal particles by density themselves are generally well established, but their difference. The first and most basic priority is the removal of application in CPPs in some countries is not yet widespread. loose shale from the coal, followed by the removal of particles with a high rock/mineral matter content. Different The amount of fines present in the coal to be washed is levels of relative density are used to separate particles with determined by a number of factors. One is the friability of various proportions of mineral matter. If a very low relative the coal (how easily it breaks during handling), and another density is used then only the cleanest coal particles will is the mining method used. Considerable amounts of fines report to the ‘clean coal’ stream. Economics will determine can be generated by mechanical extraction and/or blasting. the optimum relative density of separation for a particular The amount of fines also depends on how much deliberate coal, to meet specific aims. Fines are separated by methods breakage is undertaken in order to make the coal more which exploit the differences in wetting characteristics handleable. Because fines are more difficult to dewater and between organic coal and the interspersed mineral matter. to handle after cleaning, deliberate breakage is normally minimised, although this also reduces the liberation of A simple washing plant may use only one separator (a jig or mineral components see Couch (1991). Upgrading coals to a dense medium drum) to separate as wide a range of minimise CO2 emissions, and/or to reduce the amounts of particle sizes as possible. Fines would normally be screened some trace elements present, may involve some deliberate out and probably back-added to the cleaned coal. Such a breakage to increase liberation. The cleaned coal product plant will tend to reject more usable carbon than a may then require drying before combustion, and the process multi-stage plant where each size range is separated route will be relatively costly. optimally. In more complex plants, units such as dense medium cyclones, washing tables, spirals, and 2.2 Dry separation methods hydrocyclones, are used for recovering more coal from particular size ranges, based on density difference between There is a considerable incentive to develop dry separation particles. Selective agglomeration and flotation based on the methods for application: differences in surface properties are also used. For discussion ● in areas where water is in short supply, as in parts of of the various separation units and their potential application, China, and in the western coalfields in the USA; see Advanced Coal Cleaning Technology (Couch, 1991), ● where severe winter conditions mean that wet coal is together with the larger texts by Osborne (1988a,b) and difficult to transport as the surface water freezes; Leonard (1991). ● for some lower rank coals (brown coals, long flame coal and gas coals of low coalification) which tend to form The separation processes chosen will be the result of: slimes during wet processing (Luo and Chen, 2001). ● coal washability assessment; ● forecast variations in the quality of rom coal over Dry methods are based on the differences in physical 10–15 years of production; properties between particles such as density, lustrousness, ● market and regulatory requirements, which will include magnetic conductivity, electric conductivity and frictional the effects of carbon taxes and of national regulations coefficients. Based on the use of air, pneumatic oscillating relating to total CO2 emissions; tables and air jigs were in common use up until the 1960s ● assessments of the capital and operating costs of the and 1970s. They are best suited to the size range 25 to 6 mm, washing plant; of the value of production of the different but have been used over the range 75 to 0.3 mm. Their main streams and of the costs of waste disposal. application has been for rough separations at high relative densities (removing particles which consist almost entirely of In a paper entitled Performance evaluation and optimisation mineral matter, which are therefore heavy, and not easily of CPPs, Mikhail and Salama, (1997), defined the objective lifted). as being to determine the optimum combination cutpoint values of different processes/units which maximise the The processes either involve some kind of fluidisation, or use overall plant yield while the coal product meets a target ash electrostatic methods. The fluidisation methods use air as the value. As part of the optimisation routine, some constraints medium and are generally suitable for intermediate particle are imposed on the cutpoints to satisfy certain physical sizes. The electrostatic methods are more applicable to fines. limitations. The maximum permissible feedrates, and coal Air based processes tend only to work well for fairly narrow washabilities (ash and sulphur distributions for example) in size ranges, and also involve dust removal before the air is the various unit operations are required. The optimisation exhausted. focused on the value of the recovered coal and in meeting product specifications in terms of ash, moisture and sulphur A method which has been developed recently in China uses contents. an air based dense-medium fluidised bed ADMFB (Chen and Yang, 1997). This uses an air-solids suspension as the With the increasing attention paid to the emissions from both beneficiating medium which has a consistent density and is power plants and industrial boilers, new constraints are being analagous to the water based dense-medium systems using set on the operation of CPPs. These may include fine magnetite. A 50 t/h demonstration plant has been specifications on permissible limits for various trace operated at the China University of Mining and Technology, elements in the coals used, and this means, in effect, that and others have been installed on CPPs. The unit is shown in washing may have to be carried out on some thermal coals as Figure 1, and is designed to treat a feed in the range 50 to thoroughly as it is for coking coals. The technologies 6 mm. The bed height used is about 400 mm. The dense

8 IEA CLEAN COAL CENTRE Coal preparation possibilities

dust coal dust feedstock dense (6-50 mm) medium

conveyor

clean coal tailings

compressed air

Figure 1 Chinese 50 t/h dry separator using air-dense medium fluidised bed (Chen and Yang, 1997) medium is a mixture of magnetite and fine coal, and it is Machine schematic claimed that the density of the medium can be controlled within the range 1.3 to 2.2 g/cm3 (Chen, 1997). support

Work is ongoing to try to extend the size ranges that can be suspension treated. A vibrating ADMFB has been tested on the size mechanism range 6 to 0.5 mm while a deeper bed up to 1200 mm has vibrator been used to separate coal sized 50 to 300 mm. For fines separation finer particles are needed to produce the dense coal feed medium, and it is necessary to suppress the tendency to form separating deck bubbles in the bed. Laboratory scale tests with a vibrating bed showed that it is possible to reduce the ash content from baffle plate 16% to 8% while obtaining an 80% yield with a fine feed in the range 6 to 0.5 mm. air chamber air In a parallel development carried out by the China Coal Research Institute, a dry separator has been developed using an autogenous medium simply based on the use of fine coal clean coal middlings refuse and air. The operation of the FGX-3 machine is shown in Figure 2. The raw coal is fed into the machine to form a bed on the deck. The lowest particles are in contact with the Mechanism of material separation vibrating deck, and move from the discharge baffle plate towards the back plate. When they reach this the particles are back plate forced upwards by the vibration induced forces. The particles direction of in the upper layer will slide downward along the surface vibration layer to the discharge baffle. The lightest, cleanest particles will pass over the top of the baffle as clean coal product. Heavier particles will tend to undergo a helical motion travelling towards the refuse end of the machine. As the deck clean coal gradually reduces in width, the lower density particles discharge as middlings over the baffle plate while at the air chamber refuse end the particles with the maximum amount of pyrite discharge baffle plate deck air duct and mineral matter finally come over the baffle plate. The air passing through enhances particle mobility and separation precision is promoted by the relatively stable gaseous-solid compressed air suspension of air and fine coal particles that develops. With the combined effect of both airflow and vibration, the stratification by density is enhanced and realised. If required, Figure 2 The FGX-3 dry coal cleaning machine the middlings can be recirculated for further separation. Air (Lu and others, 1999) consumption is about a third of that needed for a

Coal upgrading to reduce CO2 emissions 9 Coal preparation possibilities conventional pneumatic system as it is only needed for 2.3 Washery costs loosening the bed material, and this reduces the size of the dust collection equipment needed. The moisture content of Power plant operators are becoming increasingly aware of the coal tends to be reduced. the costs of using coals containing large amounts of mineral matter. As a result, where there is competition, they are More than twenty of these 30 t/h machines have been tending to place more restrictions on the coal specification installed at mines, treating a wide range of coal types. The for power plant consumption or will only offer a lower price process is particularly suited to: for poorer quality, lower-grade, coals. ● deshaling power station coal, giving it an increased lower heating value (LHV) and lower ash content; Washing costs commonly fall in the 2–5 US$/t range, ● cleaning low rank coals and those liable to undergo size although more thorough coal cleaning (such as that carried degradation in water; out on coking coals) can cost up to 10 $/t since not only are ● easy-to-clean coals; the processing costs higher, but the product yield is reduced. ● reducing the sulphur content where the sulphur is largely present as granular pyrite; Washing costs in the USA are quoted as being 1.50–2.50 $/t ● cleaning coal at a power plant site; for coarse coal (Yoon and Luttrell, 1997). In a plant with a ● applications in areas where water is in short supply. coal feed which has a high proportion of fines, and having a complex flowsheet, recovering the maximum amount of coal Experience with these machines at particular mines includes from each size range can cost up to 4–5 $/t overall. Fines that at Lumaojiang where the LHV was increased from 17.5 may cost some 4.50–7.50 $/t to wash and normally comprise to 21.5 MJ/kg, and the ash content reduced from 50% to 10–40% of the total. 30% with a yield of over 90%. At Lingxin, the LHV was increased from 18 to 21.5 MJ/kg and the ash content reduced Detailed washing costs for coals in Kazakhstan were from 24% to 13%. assessed by Popovic and others, (1996). Five flowsheets were considered for a plant handling 900 t/h. The In the USA, a 50 t/h air jig has been tested at a western specification was for a unit to operate 5000 h/y, and produce Colorado mine. It was shown to be able to process a wide range a 70% yield of clean coal with an ash content of below 36%. of feed quality, with rom coal from low to high ash content, Details of the flowsheets and the estimated costs are given in both sized and unsized coal, and some wet feed (Alderman, Table 2. The cost of the raw coal was only about 9 US$/t, 2002). In view of the fact that many western US coalfields are while operating costs ranged from 3–5 $/t based on cleaned in areas where water is scarce, and that adding water (through a product, and the distributed capital costs ranged from $0.7 to washing process) to a high moisture content coal is unattractive, $1.5. None of the flowsheets included cleaning of the fines. dry beneficiation may be a viable technology which will be It is implied, but only explicitly stated for one of the circuits increasingly used to improve coal quality. assessed. that the uncleaned finer fractions are back added to

Table 2 Coal washing costs (Popovic and others, 1996)

Clean coal Clean coal Capital cost, Operating cost, Total cost, Flowsheet summary yield, % production, Mt/y US$million US$/t US$/t

Screen at 13 mm, DM vessel treating 67 3.35 11.6 3.1 13.1 130x13 mm coal

Screen at 13 mm, Baum jig treating 64 3.19 11.6 3.1 13.6 130x13 mm coal

Screen at 4 mm, Two circuit DM wash 72 3.58 15.3 3.7 13.4 treating 150x4 mm coal

Baum jig treating 150x0 mm coal, with recovery to 64 3.74 18.5 5.0 15.4 0.15 mm

Three circuit wash treating 150x0 mm coal, with recovery 69 3.97 18.9 5.1 14.8 to 0.15 mm

the costs are expressed in terms of tonnes of cleaned coal.

10 IEA CLEAN COAL CENTRE Coal preparation possibilities the cleaned coal in order to maintain the yield at around insignificant. If coals are more thoroughly cleaned in order 70%. This is common practice in many countries for coals to improve boiler efficiency to reduce CO2 emissions, then for power station use. the amount of waste would almost certainly increase, with a proportional increase in costs. In an IEA analysis (IEA, 2001a), washing costs were estimated to range from 1.5 to 5.5 US$/t. The capital cost of In addition, the costs of residues disposal will tend to rise as setting up modern and effective cleaning plants can approach environmental regulations become increasingly stringent. To 70,000 US$/tph of capacity, so a CPP to process 2–3 Mt/y of avoid later CO2 emissions, for example, the wastes must be coking coal (upgraded to a demanding specification) may packed down and covered in such a way that they do not have a capital cost as high as US$40 million. These costs subsequently spontaneously combust (thus negating the will vary considerably, depending on where the plant is built, reason for upgrading in the context of this study). In addition as land values, service provision, labour and equipment costs the possible leaching of undesirable components into ground will differ in different parts of the world. waters must be guarded against.

Washing costs can be spread across a spectrum of products, All delivered coal costs and the different contributions to with the highest grade often carrying the largest proportion. those costs, are site and deposit specific. They depend on the Wastes, in this context, might be allocated a negative value nature of the deposit, the coal specifications to be met, and as most are eventually dumped. When the objective of the distance from mine to user. upgrading is to minimise CO2 emissions by increasing boiler efficiency, then some value needs to be attached to the As discussed earlier, the objective of coal washing is to ‘avoided’ CO2 to be offset against any increase in the cost of optimise the economics of coal use. Most coals that are the washed coal. This is affected both by the processing traded on the international market, and inside large countries costs, and by the reduced yield of cleaned coal if the like the USA, are already cleaned to a level that represents a specification is more stringent. perceived economic optimum. While there may be some scope for further upgrading, this is likely to be relatively These upgrading costs need to be put in the context of rom costly. The costs of coal preparation, however, represent only coal production costs which depend on: a tiny proportion of the total costs of the coal-to-electricity ● the amount of overburden to be moved in open pit chain. Lockhart and Wright quote the different costs involved mining; in the use of an exported Australian coal as shown in ● seam depth and distance from the shaft or drift, in Table 3. underground mining; ● seam thickness; Costs are always site and situation specific, and in the ● seam continuity and the extent of faulting; example quoted, the costs of emissions control is estimated ● hydrogeological conditions; to be around 30% of the total. In an earlier Clean Coal ● the seam methane content. Centre report Air pollution control costs for coal-fired power stations Wu (2001) established a general guideline figure The costs will rise if the coal is more selectively mined. This more like 20% for the overall costs of emissions controls. is another way of upgrading the coal, and will tend to increase the amount of material to be disposed of during the A CPP can produce several products from the different size mining operation. This is, of course, put back in the mine ranges of the coal being treated. As a minimum, there will be where there is an open pit operation. two products, one is the cleaned coal product, and the other is a waste stream for disposal. Most plants have several Production costs are typically in the range 15–35 US$/t for products, including the cleanest coal stream consisting of the bituminous coals used for power production. Delivered coarse coal, a product with a higher ash content, possibly of costs may be higher, depending on the distance involved and intermediate size, and a cleaned ‘fines’ product, together the method of transport. Some coals are mined from open with waste streams associated with all three size ranges. pits at costs which can be as low as 5 $/t, but many of these Sometimes the product streams are recombined to make a are of low rank. Some high grade bituminous coals are composite product including a wide range of particle sizes, mined from open pits, but many are mined underground but with a minimum ash and sulphur content. where the seams are deeper. About half the (bituminous) coals mined are already washed The cost of waste disposal from CPPs generally represents to a level which is close to the economic optimum under less than 10% of the total, but it can easily be 5–8 US$/t of current conditions. This means that about half the world’s waste solids (Chugh and others, 1997), which is not bituminous coal is used without any upgrading. It also means

Table 3 The costs of power generation based on exported Australian coal expressed as US¢/kWh (Lockhart and Wright, 1997)

Milling combustion Emissions controls: Solid residues Mining Coal preparation Transport generation particulates, NOx, SO2 disposal

1.0–1.5 0.1–0.2 0.6–0.8 3.0–3.5 1.3–1.6 variable

Coal upgrading to reduce CO2 emissions 11 Coal preparation possibilities that if the ground rules change with (for example) financial involves an alkaline leaching process. The coal is reacted incentives being introduced for reducing CO2 emissions with caustic soda in a digester at 230ºC. The mineral matter, when the coal is used, there could be further opportunities mainly clay and silica is either dissolved or converted into for upgrading as discussed in this study. However, coal sodalite (Na4Si3Al3O12(OH)). After discharge the coal is preparation involves costs, which must be justified. The more separated from the digester liquor and fed to an acid-soak intensive the cleaning, the more expensive the process tank where the sodalite is converted into soluble salts. becomes. Not only is the processing itself more complex and Finally the coal is water washed and the soluble salts leach costly, but as a cleaner product is required, the yield out, see Figure 3. In 2002 the pilot plant at Cessnock, NSW, generally goes down. This means a smaller amount over was being commissioned. It is intended to establish the which to spread the production costs, and the disposal costs engineering data required for a commercial scale unit, and to for the waste stream will increase proportionately. provide tonnage quantities of UCC for gas turbine trials to be undertaken in Japan (Australian Coal Association, 2002). The other general problem is that in order to produce a much cleaner coal product (for combustion) it may be necessary to The intention is to produce a coal with <0.2% ash and crush some of the intermediate size particles to increase the <60 ppm of residual Na, silicon and aluminium removal liberation of some of the mineral matter. This, in turn means efficiency typically exceeds 99%. Iron removal is in the that there are more fines present which can be difficult to 90–96% range but only about 50% of the titanium is dewater. With the additional fines, processing costs increase. removed. The ultra low ash levels and very small particle size of any residual ash arising from the UCC product gives There are thus practical limitations to the amount of coal it the potential for use in gas-turbine units which would have cleaning which is economically possible, and every coal high thermal efficiencies and hence reduced CO2 emissions. must be assessed before deciding what is the optimum The study is being carried on jointly by Australia and Japan, amount of washing. This view must take into account and the results from a demonstration plant would be used to variations and changes that may be expected over a number establish the process economics with greater certainty. In of years in the coal to be mined from a particular seam, or earlier work in the USA the Gravimelt process was estimated possibly from a mixture of seams. Ultimately the economics to cost as much as 75 $/t of product, so clearly this new of washing and those associated with downstream processes process would need to be considerably more economic if it is will determine what is practical and what is done. to become a viable commercial option. The process is no longer being developed.

2.4 The preparation of ultraclean Another chemical cleaning process, CENfuel, is being coal actively developed in West Virginia, USA. This is based on the use of strong acid, rather than strong alkali. It has been Work is ongoing in Australia, Japan and the USA to prepare under test for as long as 25 years. A 50 kt/y an ultraclean coal (UCC) with an ash content of <0.2% pilot/demonstration unit was built in Japan, and over which could be used as a fuel for direct firing into 120 different coals tested and assessed. Product samples have gas-turbine combined-cycle power generation units. Earlier been used in turbine tests at Hitachi Zosen and Germany’s work on this is reported in Couch (1991), where both the Brown Boveri. Currently, a further demonstration plant to Gravimelt process based on the use of strong caustic and the produce quantities of UCC for assessment in the USA has Otisca T process based on selective agglomeration are been built in West Virginia (Blankinship, 2002a). described. The process involves size reduction of the coal to –2 mm Current Australian work is reported by Clark and others size. The coal is reacted with what is described in the (1999) relating to the possible preparation of an ultraclean technical literature about the process as fluorine acid. The coal. Work was reported to be at a preliminary stage, and a make-up additive is fluosilicic acid (H2SiF6) which is highly pilot/demonstration plant has been designed. The technology corrosive and toxic, and attacks both glass and stoneware. Its

caustic make-up acid water

coal SLURRY DIGESTER SEPARATOR ACID SEPARATOR HYDROTHERMAL UCC feed MAKE-UP (230°C) (solids/liquids) BATH (solids/liquids) WASH BRIQUETTING product

lime caustic soluble salts regeneration lime by-product

heat by-product exchanger

Figure 3 UCC pilot plant schematic (Australian Coal Association, 2002)

12 IEA CLEAN COAL CENTRE Coal preparation possibilities

make-up coal feed -2 mm fluosilicic acid HYDROLYSER DRYER silica (SiO2) (H SiF ) silicon 2 6 tetrafluoride (SiF4) fluorine acid ACID PLANT REACTORS

SEPARATOR iron sulphide (FeS)

DISTILLATION ABSORBER FILTER 1

WASHING fluosilicic acid

stack FILTER 2

exhaust gas DRYER

power generation gas turbine

combustion UCC product

air

Figure 4 CENfuel plant schematic (Cenfuel, 2002) properties are essential in terms of attacking the impurities Commentary present in the coal, but it will be quite a challenge to handle such a material on an industrial production unit. The fluorine Coal preparation is carried out according to well established removes a number of key ash components such as aluminium, procedures on about half the bituminous coal which is mined silica and mercury, together with inorganic sulphur see worldwide. A considerable amount of development work is Figure 4. Reaction by-products include silicon tetrafluoride being undertaken to optimise the separations achievable by (SiF4) gas. The SiF4 is processed through a hydrolyser to washing, and to make dry beneficiation methods practical produce SiO2, while the H2SiF6 recycles to a washing stage. and commercial. Preparation costs are an important factor The (reacted) coal passes through a separator, where the iron affecting the use of different technologies. The discussion in sulphide (FeS) is removed, together with other heavy metals. this chapter, together with that in Chapters 3 and 4, provides The remaining mix passes to a solids-liquid separator (filter the basis and background for the later consideration of which 1). The filtered coal product is washed with aqueous coals have upgrading potential and on the potential for fluosilicic acid. Filtered solids and silicon tetrafluoride gas achieving reductions in CO2 emissions. are recycled via an acid treatment stage.

The cleaned coal product is again filtered, and then passes through a flash dryer operating at 250–400ºC, removing any residual hydroflurosilicic acid and forming a light free-flowing granular product. Liberated hydrogen fluoride and silicon tetrafluoride gases are recycled via the acid treatment stage. It is claimed that the process has potential for commercial development because of: ● the very low ash content coal product which can be used to fire a gas turbine; ● the unique way in which the hydrosilicic acid is regenerated; ● saleable by-products which can be produced (Bellemare, 2002); and, ● the renewed interest in the use of coal with minimal emissions.

Coal upgrading to reduce CO2 emissions 13 3 Drying low rank coals

Low rank coals include the brown coals and lignites, Germany (associated with the brown coal deposits in both together with some of the lower-rank subbituminous coals. the east and west of the country), in Russia (associated with Different terminologies are used in different parts of the the Kansk-Ashinsk deposits) and in the USA (associated world. The occurrence and use of both lignites and brown with the lignites in North Dakota and the subbituminous coals is discussed in earlier Clean Coal Centre reports on coals in the western states of Wyoming and Montana). Some Lignite resources and characteristics and Power generation work has been done on drying the western US coals prior to from lignite (Couch, 1988, 1989). use, but the removal of moisture increases the risk of spontaneous combustion – as it does in most low rank coals. The low rank coals have moisture contents in the range 30–70%, and are rich in oxygen, 10–30% wt (db). The ash As a result of this, the most promising process route content of low rank coals varies very widely, with most involving the drying of low rank coals is to dry the coal falling within the range 3–40%. The result of the moisture immediately before combustion using some of the low grade and ash content is that the lower heating value (LHV) of the heat available from the turbine exhaust on a power plant. coal is generally in the range 4–16 MJ/kg, considerably Currently, on most power plants using lignites, drying is below that for most bituminous coals. carried out in and around the mill by recirculating some of the flue gases from the upper part of the boiler. This means Pleasance (1996) says that low rank coals account for that the boiler has to be considerably increased in size, to roughly 30% of the world’s total economically recoverable cope with the 30–40% of recirculated gas, together with all coal energy reserves, although they currently satisfy only the water vapour formed. If the lignite could be dried about 3% of the demand. He is probably referring to the very externally, a much smaller boiler could be used, and this is high moisture content coals such as those in the Latrobe currently to be tested further at the new plant at Valley in Victoria, Australia. Taking the WEC figures, in Neiderhausen in Germany. When a high moisture content tonnage terms, the low rank coals (subbituminous and brown coal is used in a PCC unit, the maximum thermal lignite) account for as much as 45% of the total reserves, efficiency achievable is some 1.5–2% lower than that for an while usage represents about 30% (World Energy Council, equivalent hard coal, because of the water content. 2001). Taking into account the different heat contents of the coals, the low rank coal amounts to 10–15% of the total A recent evaluation of the effects of drying Greek lignites heating value of the coal used worldwide. In the IEA figures, was carried out by the National Technical University of the subbituminous coals in the USA are classified as hard Athens (Kakaras, 1999). The study looked at the effects of coal, and this makes a significant difference to any pre-drying on units using subcritical PCC. breakdown as nearly 0.4 Gt/y are produced, and the reserves there are assessed to be some 100 Gt. The moisture in brown coals is held in three distinct ways. In the Greek study, it is described as follows: One of the reasons for the relatively high assessment of the ● about half the water (44–65%) is held on the surface of amount of recoverable coal is that the reserves nearly all lie the particles; near the surface, and the seams are usually thicker than those ● a large proportion (20–44%) is held in what are of the deeper bituminous coals. In the long term, because of described as macropores with a diameter in the safety considerations, underground mining may become less 20–120 nm range where the heat of desorption is equal acceptable or and/or proportionately more costly. This means to latent heat of evaporation; that as other energy sources become depleted and are ● only about 20% is held in micropores, generally sized therefore more expensive, low rank coals may be able to 3–5 nm. Here the moisture is bound to the coal by compete as a source of primary energy. This is provided that stronger forces than those simply due to the water suitable technology has been developed to facilitate their molecules. There are extremely thin molecular layers, extraction and use in an environmentally acceptable way. and there are various hydrogen bridges formed so that the heat of desorption is more than the latent heat of Currently, some 900 Mt/y of brown coals are mined (IEA, evaporation. 2001b), and most are used for power generation. In the western US there are large reserves of relatively high grade In the Kakaras (1999) paper, an assessment was made of the low rank coals which are on the borderline between being implications of the application of pre-drying to the Agios classified as a brown coal or a bituminous coal. Substantial Dimitrios unit number 5 in Greece. This has a capacity of quantities are used and are transported over long distances 350 MWe, was commissioned in 1997, and uses PCC and for power generation, because of their low sulphur content, subcritical steam at 20 MPa. It is fuelled by Ptolemais lignite and in the IEA statistics, these are recorded with the with typical rom characteristics including an LHV of bituminous coals. 5.6 MJ/kg, moisture content 55% and ash content 15%. For the purpose of the computer modelling exercise carried out, A considerable amount of work has been undertaken on the dried coal fed to the boiler was assumed to be 15% from upgrading the low rank coals, particularly in Australia a tubular dryer or a fluidised bed system, or 22% from (associated with the Latrobe Valley deposits in Victoria), in mechanical-thermal dewatering.

14 IEA CLEAN COAL CENTRE Drying low rank coals

In the comparisons, the base case plant thermal efficiency raw brown coal was 37%. Using a tubular dryer and extracting steam at 0.23 MPa and 200ºC, it could be increased to 41.8%. Using a fluidised bed dryer and with the dryer steam compressed to 0.32 MPa it could be as high as 44% while using the mechanical-thermal method, the overall efficiency could be air + evaporated moisture at 110°C increased to 44.5%, because the energy demand for drying is minimal. The other two methods (using the well proven tubular dryer method or the fluidised bed dryer) are less mechanically complex. Overall increases in operating efficiency of 5–7% are thus feasible using pre-drying. hot steam

3.1 Flue gas recirculation motor In conventional PCC systems, the incoming brown coal is normally dried by recirculating hot flue gases at 800–1000ºC condensed from the upper part of the boiler. This results in the need for steam a substantial increase in the crossectional area of the boiler, to accommodate the gas recycle. In the brown coal, the moisture content is reduced from 50–60% in the feed material to 17–20% at the inlet to the mills. The process dried coal however is not particularly efficient, as the temperature Figure 5 Tubular dryer schematic (Kakaras, 1999) driving force is much greater than that which is needed. The temperature needed for evaporation of the fuel moisture is only 110–120ºC, and thus there are opportunities for raw brown coal reducing the energy consumption involved in pre-drying.

DUST 3.2 External drying methods FILTER DRYER compressors The main external drying methods available are detailed below. These have the advantage of considerably increased fluidised bed flexibility in operation although separate process units are 150°C fluidising coal steam required. preheater

dried coal cooler 3.2.1 Tubular dryer 65°C

The one with which there is the most industrial scale condensed experience is the tubular dryer. It has been widely used in cooler water Australia, Germany and India in connection with lignite/brown coal briquetting. The plant consists, typically, Figure 6 Fluidised bed dryer schematic (Kakaras, of an inclined shell and tube heat exchanger see Figure 5. 1999) The shell is heated by low pressure (waste) steam at 0.4–0.5 MPa and 180ºC. Brown coal (<10 mm size) passes brown coal feed through the tubes, and is dried to 12–15% moisture content.

3.2.2 Fluidised bed dryer pressure An alternative method which has been demonstrated at pilot scale in Germany is the fluidised bed dryer developed by steam Rheinbraun. It is also called WTA, the abbreviation for pressure Wirbelschicht-Trocknung mit interner Abwärmenutzung in plate German. In this, the raw brown coal (<6 mm size) is coal fll preheated to 65ºC by condensed water – in a heat exchanger. MTE MTE It is then fed into a fluidised bed where the medium is lightly waste waste water water superheated steam see Figure 6. After the particulates are ‘hot’ ‘cold’ removed, the steam and evaporated water are passed through a steam compressor where its temperature and pressure are raised to around 150ºC and 0.4–0.5 MPa. The main part of dried coal the steam heats the fluidised brown coal indirectly through heat exchange tubes in the dryer. Some is used to fluidise the Figure 7 Mechanical-thermal dewatering bed, and its volume is increased as moisture is released from schematic (Kakaras, 1999) the brown coal particles. Steam condensate is used both to

Coal upgrading to reduce CO2 emissions 15 Drying low rank coals preheat the incoming coal and to cool the steam compressor. stockpile was designed to hold up to 13,000 t. The drying The pilot plant has a capacity of more than 50 t/h and has process removes only the water that is easily removed, and processed more than 50,000 t of brown coal, so the system reduces the moisture from about 38% to around 30%. Drying has been thoroughly tried and tested. time was up to three days, and this contrasts sharply with the more traditional approach of rapid drying using high 3.2.3 Mechanical-thermal dewatering temperatures. In tests using more than 14,000 t of dried lignite, it was shown to increase the boiler efficiency by Another method has been tried out only on a smaller scale. It approximately 2%, with reductions in both fan and pulveriser involves mechanical-thermal dewatering and is based on horsepower. Preliminary cost estimates indicated that the air the fact that much of the water present is not strongly bound volumes being used could be scaled-up to cost less than to the coal. It is also called MTE which is the abbreviation 0.5 US$/t. The next stages in the development programme for Mechanisch-Thermische Entwässerung in German. The will be to establish whether a static or fluidised bed system raw coal is slightly pre-pressurised by a press stamp, and would be the most cost efficient. The intention is to develop then hot water is distributed evenly on its surface by a system that could pre-dry the whole of the coal feed – sprinklers see Figure 7. Saturated steam is introduced into some 7 Mt/y – and which would be applicable to other the chamber and the hot water flows through the coal lignite-fired stations (Blankinship, 2002b; Alderman, 2002). releasing nearly all its heat content. The coal temperature An outline scheme to combine the use of an air jig with a rises to 150–180ºC. Water leaves the chamber at around magnetic separator for the dry fines generated is shown in ambient temperature. The process is repeated, using Figure 8. It would potentially upgrade a western US coal pressures up to 6 MPa. This remains a somewhat with a heating value of around 15 MJ/kg to as much as cumbersome and complex method. 20 MJ/kg, with a range of benefits in terms of reduced emissions, including those of CO2. 3.3 Work in different countries In Australia, a considerable amount of work has been put At Neiderhausen in Germany, Unit K is due to be commissioned in 2002. It is a lignite burning unit with 14.4 MJ/kg coal feed 1000 MWe capacity which is using optimised state-of-the art magnetic plant technology. This includes: separation ● ten stages of feed water preheat; baghouse ● a flue gas waste heat recovery system integrated in the flue gas path; fines 19.8 MJ/kg ● the use of very low pressures (29/35 mbar) in the two cleaned coal 18.4 MJ/kg stage condenser; COAL DRYER ● changes in the regulations relating to the operating air jig reserve needed for frequency control on the grid, POWER PLANT reducing the reserve from 5% to 2% ● reductions in internal power consumption. waste heat from power plant As a result, the design thermal efficiency of the new unit is 45%, which is nearly 10% higher than the efficiency of the Figure 8 The integration of dry cleaning earlier generation of 600 MWe units built in the 1980s. The processes to upgrade western US coals next development step in the technology is seen as being the (Alderman, 2002) integration of lignite drying into the concept, which is anticipated to raise the plant efficiency by as much as 4–5% raw coal feed waste gases above the 45% level. To test the new drying processes, a (62% moisture) 90 t/h pilot/demonstration drying unit using fluidised-bed technology is being built at the Neiderhausen site. Also, a 12 t/h thermo-mechanical dryer is being built there COOLER (Kallmeyer, 2000). By 2004 or 2005 there should be pressure sufficient accumulated experience with operating these reducer SEPARATOR water C systems so that a secure economic assessment can be made mill ° of their application. high pressure 300 pump REACTOR In the USA, a lignite drying system is being developed at the water HEATER Coal Creek generating plant where there are two 500 MWe dried centrifuge coal units. The lignite comes from the Falkirk mine, and a large open stockpile was used to test the concept. Heated air at slurry product 40–50ºC was distributed through a manifold under the pile. slurry 75% Plant waste heat was used to heat the air. In the test work at moisture 50% Coal Creek, a grid of 75 cm diameter air distribution pipes moisture was sited under the stack. The pipe sides were covered with Figure 9 HTD process (Allardice, 2000) a heavy expanded mesh to prevent plugging, and the

16 IEA CLEAN COAL CENTRE Drying low rank coals into the development of the Hydrothermal Dewatering others, 2001). The products have also been compared (HTD) process. This has been demonstrated at pilot scale, (Chaffee and others, 2000). and involves heat treating a coal slurry at about 300ºC under sufficient pressure to prevent evaporation taking place. Water The steam drying was carried out in a small batch autoclave, is released from the brown coal in liquid form and after covering the temperature range from 130ºC to 350ºC. For the cooling and depressurising, excess water can be separated HTD tests a coal-water slurry was loaded into a small reactor from the slurry. The process is equivalent to the accelerated and tested under pressure at various temperatures. The MTE coalification of the young brown coal and the product is an experiments were conducted by placing raw coal inside a upgraded and pumpable coal slurry with an energy content compression-permeability cell. This was filled with distilled greater than that of the rom coal, see Figure 9. water to expel any air, then sealed and heated to the desired temperature (from ambient up to 250ºC). The sample was Tests have been carried out to compare the effects of then compressed while the water expelled passed through a evaporative drying (using superheated steam), compared with glass-fibre filter paper. HTD and MTE where the water is removed as a liquid. Loy Yang brown coal from the Latrobe Valley in Australia was Different processes have quite different effects, which will used, with a moisture content of around 60% (Favas and influence the behaviour of the coal product when used. All

2.0 effect of effect of effect of effect of temperature temperature mechanical temperature on steam drying on MTE pressure on HTD processing on MTE processing (6MPa) processing 1.8 (200°C)

1.6

1.4 0.67

1.2 0.65 0.62 0.56 0.55 0.55 0.22 0.52 0.51 0.50 0.48 0.48 0.48 1.0 Pore volume, ml/g Pore 0.30 0.90 0.31 0.23 0.29 0.22 0.25 0.69 0.230.23 0.84 0.74 0.20 0.55 0.18 0.46 0.22 0.20

0.8 0.20 0.17 0.14 0.14 0.15 0.16 0.13 0.13 0.10 0.12 0.12 0.54 0.09 0.09 0.11 0.10

0.6

0.4 0.73 0.73 0.73 0.73 0.73 0.72 0.28 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.710.71 0.71 0.15 0.46 0.29 0.22 0.710.71 0.71 0.71 0.30 0.20

0.2

0 C C C C C C C C C C C C C C C C C C C C C C ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° 6MPa 9MPa 180 200 230 250 180 200 230 250 300 320 180 200 230 250 300 320 130 150 280 310 350 330 12MPa coal for MTE/HTD tests coal for steam drying tests

volume occupied by carbon micropore volume large pore volume Figure 10 Changes in the pore volume of Loy Yang coal with MTE, HTD and steam drying (Favas and others, 2001)

Coal upgrading to reduce CO2 emissions 17 Drying low rank coals reduce the moisture content of the coal, although there are limits on the reduction that can be obtained by MTE. The effects of different conditions on the pore structure of the coal are illustrated in Figure 10, and this is of potential significance as it can affect the subsequent pick-up of water after the drying process. MTE products have smaller intra-particle pore volumes than HTD products, and processing temperature has a considerable effect. Some variations are attributable to changes in the rigidity of the coal structure at temperatures above 230ºC which results in less shrinkage when the material is dried to zero moisture for pore volume determination. Since all these methods are being considered for large-scale use in conjunction with coal-fired power generation, an understanding of the effects of the different processes is important.

18 IEA CLEAN COAL CENTRE 4 Briquetting and pelletising

For both industrial and domestic use, briquetting is a useful Reconstituted coal products have been used in the past as form of coal upgrading. Small boilers have traditionally used smokeless fuels in countries such as Germany, the UK and sized coal as the feedstock. Household coal is commonly the USA on a considerable scale. Generally the products marketed as nuts, cobbles and beans – representing different were of relatively high value for domestic use. Briquettes can size ranges of coal. Briquettes have also been used on a replace sized coal in residential stoves, in industrial boilers substantial scale in moving bed gasifiers, where the need is and in the coal gas furnaces used in chemical production, for a lump feed, and briquetting facilitates the use of fines. machinery and glass industries. They can be made from coal fines which provide a very low cost raw material or from With the increase in mechanised mining, there is often an some low rank coals. In addition, the briquettes can be made over-supply of fines in the coal, and a lower proportion of with limestone as an additive, thus providing some sulphur the necessary size fractions for industrial and domestic use. capture during combustion. Briquetted and pelletised coal is This is particularly true in China, but is also the case to a produced on a limited scale in various places, but large-scale lesser extent in India, and also in several countries in the applications have been limited because the processes are FSU. Briquettes or pellets can provide a satisfactory relatively expensive. Binder costs in particular, have been substitute fuel, using the excess fines. Briquettes burn even high, and much of the development work in this area has more efficiently than sized coal, and the benefits in terms of been in trying to find cheap but effective binders (Mehta and efficiency gains are discussed in Section 9.2.2. Parekh, 1995).

Briquettes produced by hot pressing consist of partially Table 4 The advantages and disadvantages of carbonised coal, and in some markets, it is a great advantage agglomeration technologies (modified if they can be sold as a smokeless fuel with low ash and from Whitehead, 1997) sulphur content. The production of a briquette can involve the removal of some (or most) of the volatile matter present – Simplest technique so that the product burns smokelessly. – Cheapest – Simple binders can be In reviewing the various methods of agglomeration used, such as water technology, Whitehead (1997) summarised the advantages Mixer agglomeration – Weakest product and disadvantages as outlined in Table 4. The choice of – Converts dust to crumb- technology for a particular application depends on: size product ● the nature of the coal used; – Possible use to condition coals for nearby use ● required product characteristics, including its handleability and strength; ● coal cost and product value (and the differential between – Simple concept them); – Next cheapest ● binder availability and cost. – Relatively weak product Disk pelletisers (or drums) – Can make pellets 5-80 mm Not all briquettes need to be strong enough to be handled diameter and transferred to remote sites. Some will be used on the site – Used for iron ore as a first where they are produced, and used directly as a fuel or as a stage in processing feed to a gasifier. – Relatively expensive Briquetting requires a product containing very little moisture, – Needs good binders whereas it is possible to pelletise a fine coal containing up to – Uniform product size, with 30% of water (Conkle and Raghavan, 1992). As current ovoid or pillow shape dewatering techniques can produce a product at around 25% Roll press briquetter moisture, pelletising is the more likely process route. – Is the only method used in western Europe to make All the processes are coal-specific in application. Successful smokeless briquettes for development depends both on extensive test and assessment domestic use work, and on a secure supply of a coal whose key properties – Relatively expensive are consistent in relation to the process and possibly the – May not need a binder binder being applied. It is a common shortcoming of – A brick shape product is assessment work that little effort is made to ensure that the typical material under test is representative of that which would be Extrusion – Product strength can be used under production conditions over the following ten or problematic fifteen years, during which the plant investment costs will be – Is the traditional method for recovered. briquetting both peat and brown coal

Coal upgrading to reduce CO2 emissions 19 Briquetting and pelletising

In Australia, binderless briquettes are used in power stations Lime carbonated briquettes for producing syngas or for to maintain combustion stability when the as-mined brown formed coke are produced on a small-scale industrial basis. coal is of poor quality. In China, large quantities of Briquettes for use in industrial boilers or in locomotives are briquettes are used both domestically and industrially, and at the commercial demonstration stage (Qin, 1997). production totals more than 50 Mt/y. So-called honeycomb briquettes are widely used. The principal focus for development relating to briquette use is the possibility of incorporating materials capable of In 1990, coal briquette production in China was reported to capturing sulphur (Wang and others, 1997). However, there be 33 Mt for domestic use and 22 Mt for industry (Zhongjian are other advantages related to briquette combustion and and others, 1997), including use in roadside stoves outside gasification associated with the fact that it is easier to control small restaurants, see Figure 11. For slightly larger-scale use, (and hence optimise) the reaction conditions compared with briquettes burn more efficiently, and the use of briquettes is the use of ungraded, variable and poor quality coal. likely to grow. Anthracite honeycomb briquettes are widely used domestically, and the technology is well established. Most briquetting machines used in China are double roll presses, operating at about 300 kg/cm2 pressure. This is a low pressure compared with the presses that were commonly used in western Europe during the 1960s to 1980s and probably results in the production of more friable briquettes. There is a considerable amount of research and development going on in China into binders and processing conditions both to improve briquette quality, and reduce costs (Qin, 1997; Liu and Gao, 1997).

The briquetting of coal is being seriously considered in a number of countries in eastern Europe, and in Indonesia, among other places (Whitehead, 1997). It is of particular value where coal is used domestically or for small-scale industrial use. There are some relatively small-scale activities of long standing producing products for use as industrial heating fuels and barbeque briquettes.

4.1 Briquetting with a binder Briquetting usually involves the formation of egg-shaped agglomerates by the use of compressive force. The use of binders facilitates the production of briquettes using bituminous coal fines which are non-caking. This can be a convenient way of upgrading a lowest value part of a rom coal, or of the fines from a CPP. As coal matures it becomes harder, and it is more difficult to briquette without the use of a binder. Briquetting requires the initiation of shear stresses which facilitate the rearrangement of the coal particles into a stable briquette structure. In roller presses, see Figure 12, this can be achieved by using two different circumferential speeds on the two opposing rollers. If the pressure is not enough, then the coal must be ground to a finer size. Hot briquetting, involves pre-heating the coal to a temperature of around 400ºC where it softens, making briquetting easier.

The range of pressures used is reviewed by Kural (1994): ● low pressure presses operate at pressures up to 500 kg/cm2; ● medium pressure presses in the range 500–1200 kg/cm2; ● high pressure presses in the range 1200–2500 kg/cm2.

A typical hot-briquetting plant using a pitch binder and high pressure presses is shown in Figure 13. It incorporates a screen to ensure the fineness of the coal, a drum dryer together with dust removal equipment on the exit air, a Figure 11 Small scale coal use, and honeycomb pitch/coal mixer and a feed of the mix to the roller press briquettes used in Xian, China followed by cooling before storage. A low volatile coal or coal blend may be briquetted with a binder at a temperature

20 IEA CLEAN COAL CENTRE Briquetting and pelletising

Briquetting transportation distance. It is mixed with pitch in a screw conveyor and transferred to the steam heated pug mill. Generally, the water content of the coal should be below 4% before it is mixed with the pitch. Condensate from the steam and other water can affect the interfacial interactions between the coal and the binder which in turn influences the briquette strength. Some water is subsequently lost from the screw conveyor before the mixture is pressed/briquetted. The so-called green briquettes then need time to cool and to develop their internal strength for subsequent handling.

In practice, a wide variety of different binders and of processes have been used to produce briquettes. Virtually all involve coal drying, mixing with the binder at elevated temperature, pressing and subsequent controlled cooling (Speight, 1994). Such processes can produce high grade Disk pelleting smokeless fuels, but may require relatively expensive coals n spray as the feedstock. In recent years there has been a move away tio ta from the use of traditional pitch and tar based binders ro because of their association with carcinogenic components. final pellets In many situations, the emphasis is on the development of a practical process which will use coal fines of variable quality to make a useable product at minimum cost. Such processes feed will be simplified versions of the one described, and process product details (and in particular the temperatures needed) will depend on the binder used.

disk Briquetting depends on a number of factors, and these include: Roller and die pelletisation ● coal type and moisture content; ● binder; ● coal size, size distribution and pretreatment; ● temperature; ● briquetting pressure and pressing time; ● whether or not additional materials are incorporated, such as sorbents for SO2 or low cost biomass. These tend to reduce the briquette strength.

A wide range of binders can be used, including matrix binders like asphalt; film-type binders which are usually Extrusion solutions or dispersions; chemical type which rely on feed extrudates reaction with the coal, and lubricant-type which function by reducing interparticulate friction. Oil or water may fulfil this function or solids such as dry starch, talc, stearic acid or graphite (Kural, 1994). The most commonly used binders are coal-tar pitch, bitumen, sulphite liquor and starch materials. Mechanical stability, water resistance and combustion properties are the key product parameters.

Briquettes can be classified and described, as here, by production method (roller press or impact, cold or hot, high auger die pressure or low pressure, and with or without a binder). Alternatively, they can be classified by use/function, as in Figure 12 Briquetting and pelletising (Conkle and Figure 14 which describes uses in China, the world’s largest Raghavan, 1992) users of briquettes. as high as 750–800ºC. Poorer quality coals might undergo While there are countless different binder systems available partial carbonisation at temperatures in the range 400–700ºC, for briquette production, there has been a switch away from and then be hot briquetted using a caking coal as the binder. traditional pitch and bitumen-based systems in western Europe. They have largely been replaced by binders based on In the plant, the dried coal leaves the bunker at a temperature starch or molasses mixed with acid, or by clays or even of 30–80ºC, depending on the bunker size and the cement. Some processes require a post briquetting curing

Coal upgrading to reduce CO2 emissions 21 Briquetting and pelletising

separator ESP raw coal bunker

pitch bunker crusher crusher dust recycle bunker bunker dry coal pitch dust screen bunker grinder removal unit

weight-belt weight-belt feeder feeder feeding hopper mixing screw conveyor dryer pug mill

furnace evaporation screw

roller press

briquette Figure 13 Simplified flowsheet for a hard coal briquetting plant (Speight, 1994)

for industrial boilers fuel briquette for industrial kilns for locomotives

gasification briquette for gas production in fertilizer industry industrial briquette for industrial fuel gas

briquetting coke & briquette for coking briquette upper-ignition honeycomb briquette honeycomb briquette common honeycomb briquette briquette for air hanger heaters square briquette for roasting

household briquette

for household cooking and heating briquette (egg-shaped) for chafing dish for heating for roasting

Figure 14 The classification of briquettes by function (ESMAP, 2001) and/or drying stage to produce a product with adequate selectively. In Australia, the Morwell plant is supplied with strength. The simplest systems generally cost considerably less. material from the Yallourn mine some five miles away, because the local brown coal was found to cause 4.2 Binderless briquettes disproportionate problems. In particular the nature and quantity of the ash are of prime importance. Ash can reduce Binderless briquettes can be made from many different coals, the tendency to agglomerate and/or cause excessive wear in but the necessary properties to make a good product the presses due to abrasion. An ash content of below 2% is economically are quite specific. Low rank coals generally normally required. make stronger briquettes. In Germany and in India, briquetting plants are fed with material that is mined The commonly used briquetting process involves size

22 IEA CLEAN COAL CENTRE Briquetting and pelletising reduction of the raw feed to a range that depends on the 4.4 Extrusion material properties. It is common to use feed coal of less than 6 mm in size, but may be considerably finer. The Extrusion involves the formation of a toothpaste-like crushed material is passed to a tubular dryer which is material by pressing a plastic mix of fine coal, water and effectively an inclined shell and tube heat exchanger. The binder through a cylindrical die (see Figure 12). The mix is wet feed passes through the tubes which are heated to around moved along by an auger inside the extruder barrel. The mix 170/180ºC by low pressure steam, possibly using the turbine which extrudes through the die on the end is cut into short exhaust from a nearby power plant. The drum rotates at 4 to lengths by a knife blade. The equipment has relatively high 5 rpm and is inclined at around 10 degrees. The moisture operating costs, as there will be considerable wear. Again the content of the coal is reduced to 15% or below. The figure product must be dried before handling and transportation. will vary depending on the requirements of the particular material but bears a critical relationship to the maximum 4.5 The costs of agglomeration strength of the resulting briquettes. The costs of agglomeration are considerable. Although the Briquetting behaviour will depend on a number of factors feedstock is often of low value (the fines from a CPP for including hardness, particle size, moisture, ash content and example), processing can be costly. For a western European nature, capillary volume and humic acid ratio (Schinzel, location, the costs per tonne of product, including capital 1981). All these factors can affect the density and strength of charges and operating costs, for producing a high quality the briquette product. Its surface properties are also briquette are likely to be in the range 50–100 US$/t of important. Briquetting behaviour is not wholly predictable, product. By contrast, smaller-scale operations involving as Australian experience at Morwell has demonstrated. mixer agglomeration may cost as little as 2–4 $/t while Thorough test work on representative samples of the raw pelletisation is likely to be in the range 8–30 $/t of product feed, together with samples which represent the kind of (Whitehead, 1997). The less costly processes produce a changes to be expected during mining operations are needed. much weaker product which it may not be possible to handle and transport over any distance. The costs in countries like A reciprocating ram extrusion press is commonly used to China and India would probably be considerably lower, form the briquettes. This is usually carried out in the based on lower engineering and labour costs, and less temperature range 28–65ºC where the enhanced plasticity of stringent environmental regulation. In one assessment, the various particles promotes bonding. The pressure used is in capital cost of setting up a honeycomb briquetting plant was the 50–150 MPa range. said to be 8 US$/t while processing costs were 3–15 $/t dependent on the process and the product (Qin, 1997). Ring roll presses are also used, depending on the properties of the lignite/brown coal involved. For coals that are difficult In western Europe, the briquetting processes commonly used to briquette, the ring roller press is preferred. have been for hot-briquetting to produce high quality products. In China, the emphasis has been on finding 4.3 Pelletising suitable binders that can be effective for cold-briquetting. Disk pelletising is the formation of sphere-shaped balls by ‘rolling’ the fine coal on a rotating, inclined pan. Moist coal can be fed to the pan and a nucleating water spray initiates ball formation. Additional water from the sprays causes coal to adhere to the rolling balls, which grow steadily. They eventually gain sufficient weight to be thrown off the pan edge. The pan angle and speed of rotation can be used to control the size of the balls, see Figure 12.

A relatively high moisture content feed is needed (20% over air dried levels), and the process is relatively inexpensive to operate. The moisture content needs to be over 40% for ultra-clean ultra-fine coal, but it can be less where the ash content is high. The product must be dried before it becomes strong and durable enough for transportation and handling.

In roller and die pelletisation in a roll press, coal, water and binder are forced through a short annular die to produce hot, strong and potentially durable pellets. The mixture is pushed through by a roller which rotates inside the die, and the extrudates are cut to size by an external knife blade. The method is only suitable for mixtures with a low moisture content (below 12%).

Coal upgrading to reduce CO2 emissions 23 5 Advanced coal upgrading processes

Coal can be upgraded in a number of ways. Most of the during the following five years the plant processed well over process routes are well known theoretically, but limited use 200,000 t of coal. has been made of them as the economics have not been favourable. This study is looking primarily at the effects of The process uses a coal feed from 30–500 mm size. The coal preparation, drying and briquetting, but there are some plant can process nearly 1000 t/d, and the first step is to other processes being considered which require a brief supply a rotary grate dryer which uses a hot, low oxygen, discussion. recycle gas stream to drive off most of the moisture. Figure 15 shows the plant process route. From the dryer, the With the increasing emphasis on the need to use coal in an solids are fed to the pyroliser, where the coal is heated to environmentally friendly way the economics will change. about 540ºC on another rotary grate. The heating rate and Process costs and the overall economics of coal use will be residence time must be carefully controlled. Decomposition affected by: reactions include the rupture of chemical linkages between ● technical progress; larger molecular groups, releasing fragments in the vapour ● changes in environmental regulation; and, phase which are no longer bound into the coal matrix. The ● the opportunities created by the increasing use of higher molecular weight products thus formed are later emissions trading. condensed and collected in the liquids recovery section of the plant. The solids pass into a vibrating fluidised bed unit In the past, coal has been gasified in substantial quantities to where oxidative deactivation takes place with cooling, produce liquid fuels, as at SASOL in South Africa, during rehydration and stabilisation. After this, the solid process the period of international sanctions. In the 1980s, the derived fuel (PDF) is cooled to near ambient temperature in coal-to-SNG plant at Great Plains, North Dakota, USA was an indirect rotary cooler. A controlled amount of water is built, and is still operational. Both activities were based on added in the cooler to rehydrate the solid to near its the use of Lurgi moving-bed gasifiers which can only use a equilibrium moisture content. On leaving the plant, the solids coarse coal feed. It thus needs either large size coal, or a are not completely stabilised with regard to oxygen and feed of briquettes. In addition, low rank coals with moisture water contents, and must be left on a stockpile for a while. contents of >45% have routinely been dried and milled together using recycled flue gas from the upper part of the The coal derived liquids (CDL) produced are quenched and coal-fired boiler, see Couch (1989) and Smith (2001). collected. Typical properties of the rom coal and of the products are shown in Table 5. The CDL has properties A considerable amount of work has been undertaken with which are close to those of No 6 fuel oil, but it contains the support of the USA Department of Energy Clean Coal more solids and water than had been hoped. On a Programme during the 1990s. There is now a commercial plant, CDL would probably be upgraded to government/industry/academia partnership supported by the cresylic acid, pitch, refinery feedstock and an oxygenated Department of Energy (DOE) called Vision 21 which seeks middle distillate. to establish the technology base for the use of ultra clean energy plants in the future. This includes the use of coal, and Stabilisation of the PDF product proved to be somewhat its upgrading, with the aim of having systems available that more difficult than had been expected. It had all the could operate at up to 60% thermal efficiency with near zero advantages of a Powder River Basin coal but with a emissions. Within the R & D programme being undertaken, significantly increased heating value. In a commercial each technology is being regarded as a module which can operation, PDF might be marketed for metallurgical use to later be combined with others to achieve the efficiency, replace pulverised coal which is injected into the blast environmental and cost goals set. While it is too early to furnace. comment on the likely outcome of the developments, this is perhaps the ultimate concept in terms of coal upgrading for During the operation of the demonstration plant from 1992 energy use, and both could and should bring major benefits to 1997, a great deal of practical experience was gained, and during the next two or three decades in terms of reducing the products were thoroughly tested by possible commercial both CO2 emissions and other environmental impacts. users. On this basis, the economics of a commercial plant using either US, Russian or Indonesian coals were assessed 5.1 Demonstration projects in the (US DOE, 2001). USA Another process which has been demonstrated on a substantial scale is SynCoal, developed by the Rosebud A process has been demonstrated on a substantial scale in SynCoal Partnership. This upgrades low rank coals by a the USA during the 1990s, using a mild gasification process, combination of thermal processing and physical cleaning which is particularly suited to low rank coals (Wang and (Sheldon and Frank, 1997). The process consists of three others, 1997). The Liquids From Coal (LFC) process was steps: operated at the ENCOAL plant in the Powder River Basin, ● thermal treatment in an inert atmosphere. The coal from at the Buckskin Mine, Wyoming. Start up was in 1992, and the Rosebud mine is fed to a vibratory fluidised bed

24 IEA CLEAN COAL CENTRE Advanced coal upgrading processes

raw coal

CYCLONE FGD SCREEN DRYER blower stack

dryer combustor

PYROLYSER

CYCLONE

COOLER PDF DEACTIVATION STORAGE SILO AIR FINISHER

PYROLYSER COMBUSTOR

CDL blower

QUENCH ESP

solid path process gas path CDL dryer gas path STORAGE liquid path

Figure 15 Process flow diagram of the ENCOAL plant (Wang and others, 1997) sealing the dried product. Particle shrinkage causes Table 5 The ENCOAL plant, typical rom coal fracturing and liberates some of the mineral matter; and product analyses (Wang and others, ● cooling using an inert gas. The intermediate product is 1997) cooled to less than 65ºC by contact with CO2 or N2 in a Buckskin vibrating fluidised bed cooler; Property PDF CDL coal ● pneumatic cleaning. The cooled coal is fed to deep bed Moisture, % 29 10 stratifiers where gentle air fluidisation and vibration separate mineral matter from the coal. The lighter Ash, % 5.3 7.6 fractions are sent to a product conveyor while heavier VM, % 31 26 fractions go to fluidised bed separators for additional product recovery. Fixed carbon, % 35 57

Heat content, MJ/kg 19.7 25.9 The plant was operated from 1992 to 1998 and about 1 Mt of SynCoal products were produced. Three different coals were API gravity 1.3–3.2 used, including Montana subbituminous coal and North Sulphur, % 0.3–0.5 Dakota lignites, and there were test burns of the products in both utility and industrial boilers. As with any pioneering Viscosity at 50°C 280 plant, issues emerged which needed addressing. A CO2 Pour point, °C 19–32 inerting system was added to prevent self heating in the product storage areas and enhance product stability during Flash point, °C 74 transit to customers. It might be noted that this will, of Solids, % 2–4 course, slightly increase overall CO2 emissions from the processing and use of the coal. There were some unresolved Ash, % 0.2–0.4 problems with dust formation when handling the product which would require further development work to address. dryer where surface moisture is removed using hot combustion gas. It is further heated to just over 300ºC in The K-Fuel process was patented and developed at pilot a second vibratory reactor to remove chemically bound scale in the 1980s and 90s, and the knowledge gained has water, carboxyl groups and volatile sulphur compounds. resulted in a process called K-Fuel Plus. This consists of a In addition, a small amount of tar is released, partially pressurised and heated reactor which is essentially a tube and

Coal upgrading to reduce CO2 emissions 25 Advanced coal upgrading processes

to stack steam

coal feed N2 filter combustor steam turbine lockhopper cyclone boiler

gasifier dryer compressor gas turbine condenser weigh ash/char hopper

air

CO2 heat recovery

ash/char

Figure 16 The IDGCC process (Allardice, 2000) 1400 shell heat exchanger. The coal fills the top and bottom cones for the reactor, and the inside of the tubes. It is treated at 250ºC, at 4–4.5 MPa with a cycle time of about 30 minutes. Charging and discharge is via lock hoppers, which makes the 1200 process semi-continuous, and allows the product to be flash cooled. The coal feed is sized to improve heat transfer and plant reliability, although this would affect the economics of 1000 large-scale use. The product is upgraded from an HHV of 20 MJ/kg to 26 MJ/kg, and the moisture content reduced from 28% to 8%. The ash content is slightly increased at 6.4% compared with 5.3% while the volatiles increase from 800 32% to 40%. The mercury content is reduced from 0.15 ppm to 0.03 ppm using a typical Powder River Basin coal. The product has been tested at the Clifty Creek power plant in Indiana, USA. There are plans to build a 3 Mt/y plant as a 600 commercial demonstration of the technology (Sanyal, 2002). Carbon dioxide emission, kg/MWh 5.2 Australian work 400 In Australia there is considerable interest in the integrated drying and gasification (IDGCC) of brown coal, and a 10 MWth development facility at Morwell, Victoria, has been 200 extensively tested. Hot fuel gas from the gasifier is used to dry the feed coal in a direct contact entrained flow dryer operating under pressure. A process diagram is shown in 0 Figure 16. It involves combined cycle power generation GT CC - IGCC - IDGCC - Boiler - Boiler - using both gas and steam turbines. The gasifier is an natural black low rank black low rank gas coal coal coal coal air-blown circulating fluidised bed unit operating at about 900ºC, below the ash melting point. It operates at a pressure Figure 17 Typical ranges of CO2 emissions for of 2.5 MPa. The product gas is cooled in the coal dryer to different fuels and technologies about 300ºC for filtering before passing on through the gas (Anderson and others, 1998) turbine and then through a heat recovery unit which heats the steam. Such a process could reduce the CO2 emissions from 5.3 Indonesian work the use of Victorian brown coals by as much as 25% (Anderson and others, 1998). In Figure 17 the estimated CO2 Some processes for upgrading low rank coals have been emissions using different coals and different technologies are developed to commercial scale, and these are discussed in compared with those from a gas turbine unit in combined Lignite upgrading (Couch, 1990). Recent work is reported in cycle using natural gas as a fuel, and shows that IDGCC can which Banko coal (from southern Summatra) was first dried compete with both combustors and gasifiers using hard using superheated steam, and then 2–4 wt% of tar at coals. 150–200ºC was added and thoroughly mixed before the

26 IEA CLEAN COAL CENTRE Advanced coal upgrading processes product was allowed to cool. Various CWMs were prepared using upgraded pulverised coal using 0.4% of polystyrene sulphonate (Suwono and Hamdani, 1999). While the process has only been developed on a laboratory scale, it illustrates the potential for upgrading coals for applications other than for power generation.

5.4 Underground coal gasification Another possible long term route for upgrading coal for energy use is by underground coal gasification (UGC). This has been used in various countries of the former Soviet Union (FSU) since the 1930s to produce a supplementary fuel for power station boilers. The techniques used were labour intensive, and economic considerations have resulted in the closure of many of the sites. Interest in UGC has been sporadic, with the major efforts and trials being those in the USA in the 1970s and in Europe in the 1990s.

The use of modern drilling techniques has opened up new possibilities. There is interest in the use of oxygen based UGC at depths which are sufficient to allow operation at a pressure of around 10 MPa. This would open up the possibility of producing a product gas stream which could be precleaned (removing sulphur compounds) and then enriched in hydrogen using a water-gas shift reactor. This uses a catalyst to shift the water present towards H2, in exchange for the production of CO shifting to CO2. The hydrogen and carbon containing gases could be separated, and processes to achieve this are being studied. Finally the fuel gases can be used to generate power while the CO2 can be sequestered, and put back into underground areas from which the coal has been used (leaving behind underground caverns). It is claimed that such a process could achieve an overall efficiency of some 38% with considerably less environmental impact than conventional coal fired power generation technology (Beath and others, 2001).

A project at Chinchilla, QLD, Australia could become the world’s first commercial UGC scheme. and is scheduled to start up in 2003. It is planned to gasify with an air steam mixture, and for the low to medium heat value syngas to power a 45 MWe gas turbine, with further recovered heat powering a 22 MWe steam turbine. There are a number of other UGC projects at various stages of development, and there have been several pilot projects in China. Feasibility studies have been conducted in India, New Zealand, Pakistan and Thailand. Proponents for UGC say that the heat can be used in combined cycle mode at relatively high efficiency, and that otherwise unuseable reserves can be gasified. Sceptics say that the application of the technology is highly site specific, and that every gasification site is different. It will be difficult both to learn from experience, and also to achieve the economies of scale associated with other methods of coal use (International Coal Report, 2002b).

Coal upgrading to reduce CO2 emissions 27 6 Coals with upgrading potential

The first stage of coal utilisation and of the example, upgrading a coal by washing more thoroughly or coal-to-electricity chain is that of feedstock preparation, by drying, should produce a fuel with a higher heat content. which involves cleaning, drying and size reduction. A This should burn more efficiently, reducing CO2 production number of technologies being developed to ensure that coal per unit of power produced, but the flame temperature is can be used in an environmentally acceptable way are shown likely to increase, thus increasing the amount of NOx formed in Figure 18. These involve emissions reduction, the use of at the same time. The combustion conditions also affect the solid residues and possible CO2 sequestration. The range of properties of the fly ash formed and collected. These emissions reduction methods being investigated under the interactions are discussed in a Clean Coal Centre Report US Department of Energy environmental programme include Interactions for emissions control for coal-fired plants nearly all of those considered worldwide. (Hjalmarsson, 1992), and integrated air pollution control is discussed by Nalbandian (2002). In addition to the technologies that can be used to reduce the emissions from power generation plants, there are others that Some coals are not upgraded in any way before use, apart are relevant to the use of coal in industrial boilers, and in from size reduction to facilitate handling, and rom material is domestic grates and cookers. These include briquetting, and simply stocked and subsequently burned. Other coals possibly incorporating lime into the briquettes. undergo some upgrading, but only a relatively small proportion are cleaned in all size ranges to level 3 (as There are two quite separate aspects to the impact of coal described in Chapter 2), and most of this coal is for upgrading. One is the possible short-term benefits including metallurgical use. In this chapter, there is a reductions in CO2 emissions which result from using country-by-country review of coal preparation practice, and a upgraded coals in existing power plant boilers. The other is broad assessment of the amounts of coal that might be the longer-term benefits arising from the use of advanced upgraded to reduce CO2 emissions and provide other CCTs which may demand the use of upgraded coal anyway benefits. in order to realise their potential for increased thermal efficiency. Internationally traded coals which represent about 17% of total bituminous coal production are generally thoroughly Power plant operators are working within increasingly washed before sale in a competitive market. A third of the stringent regulations on all kinds of emissions, including CO, traded coals (about 200 Mt/y) are sold for coking, and are particulates, NOx and SO2. These impose limitations on the washed to extremely tight specifications in terms of the range of operating conditions permissible. There can be impurities present. The thermal coals (nearly 400 Mt/y) are interactions between different requirements, and, for washed a little less thoroughly, as the specifications set are

Air emissions that cause no adverse effects on human health, the environment, or the global climate

CO2 sequestration

solid coal combustion by-products (CCBs)

Feedstock Advanced Integrated emissions Utilisation of preparation combustion capture and control CCB materials pulverising low-NOx burners ESP field testing and environmental cleaning advanced controls fabric filters verification of new applications NOx re-burning catalytic/non-catalytic • mine reclaimation Over fire air NOx reduction • road construction limestone scrubbing • high-value products catalytic conversion • agriculture physical adsorbents mitigating effects of system chemical adsorbents changes on established membranes applications novel concepts

Figure 18 Portfolio of emissions reduction technologies in the full life cycle of PCC electricity generation in the US DOE programme (Smouse and others, 2000)

28 IEA CLEAN COAL CENTRE Coals with upgrading potential not as exacting. Nonetheless the washing is carried out to average plant capacity in the world at 836 t/h (Kempnich, what is perceived as the current economic optimum for coal 2000a,b). The estimate of plant utilisation suggests that there use in boilers. is spare capacity, see Table 6.1. Virtually all the coal which is exported is washed to an economic optimum. Coking coals There may be scope for the deeper cleaning of coals that are are nearly all washed to the highest specification, but whether already washed, which represent something over 50% of the washing steam coals as intensively would be economically total of bituminous coals mined. This is associated with the justified is doubtful. Many power stations in Australia use an fact that some CPPs are quite old, and do not use the latest intermediate product from a CPP, some of it coming from the technology. In addition, many only treat the coarse size coking coal washeries. While this can have a relatively high fraction, bypassing the intermediate and fines sizes without ash content (of 30–35%) much of it is used in relatively treatment. There is also scope for the washing of coals which modern and efficient power stations, although most use are not currently prepared (over 1500 Mt/y) and for the drying subcritical steam. There is relatively little scope in the short or possibly the dry beneficiation of low rank coals (up to term for additional upgrading to reduce CO2 emissions, 900 Mt/y). However, the potential costs are quite high, and it although more care may need to be taken to ensure that the would be necessary to establish and quantify the benefits to CPP wastes cannot oxidise after they have been dumped. As justify the additional expenditure involved. CPPs involve most CPPs are at the minemouth, the wastes are dumped at significant capital expenditure, as do the addition of fines the minesite, and it is necessary to ensure that air/oxygen treatment units to existing plant; there are operating cost cannot reach the material. As clean coal technology (CCT) implications as well. Overall costs were discussed in units replace subcritical steam PCC boilers there may be Chapter 2. some scope for coal preparation to more stringent specifications than that which is commonly carried out now. In a recent review of the top ten producers covering 95% of world production, Kempnich (2000a,b) assessed the amount Upgrading by drying of prepared coal in 1998, see Table 6. The figures are discussed in the sections covering the relevant countries, and The Latrobe Valley brown coals typically have a moisture then in the overview at the end of the chapter. In the table the content in the range between 50 and 65%. Their ash content countries are listed in descending order of coal production. is low, and is typically between 1 and 3%, and the coal sulphur content is also low. The LHV of the coal as received This chapter includes a country by country review, presented generally lies between 9 and 14 MJ/kg. The South Australian in alphabetical order. In each case the coal reserves are brown coals have somewhat different characteristics, and discussed, together with current production. There is then a some have a moisture content in the 30–35% region while discussion about the potential for upgrading the coals by these coals tend to have a higher ash content which lies either washing or drying. between 10% and 25%. They tend to have a high sodium chloride (salt) content, making them difficult to use. There 6.1 Australia are wide differences between the characteristics of different deposits. The LHV of these coals ranges from 9 to18 MJ/kg The main Australian reserves of bituminous coal are in New as received, with most of them being below 16 MJ/kg. South Wales and Queensland. The proved recoverable reserves amount to 42.5 Gt. (World Energy Council, 2001). Because of the large tonnages of brown coals used and their Production in 1999 was 222 Mt. high moisture content, there is clearly considerable potential to reduce CO2 emissions from their combustion by Proved recoverable reserves of brown coal are estimated to pre-drying the coal before use. Currently they are burned in be 39.5 Gt (World Energy Council, 2001). The figure very large boilers which are designed not only to handle the combines the reserves which are classified as lignite and volume of water vapour, but also up to 40% of the flue gases subbituminous coal, Production in 1999 is quoted as 66 Mt which are recycled to dry the incoming rom coal. With of lignite and 16 Mt of subbituminous. Australia has one of appropriate economic incentives to utilise the resource more the world’s largest brown coal deposits in the Latrobe Valley efficiently, the technology used at Neiderhausen in Germany in Victoria. The coal lies near the surface in seams up to might be usefully applied. As with the bituminous coal-fired 150 m thick. There are smaller brown coal deposits boilers, when the existing subcritical PCC units are replaced, elsewhere, particularly in South Australia. there may be scope for additional coal upgrading before it is fed to the boiler or gasifier. Australia is the fourth largest coal producer in the world and by far the world’s largest coal exporter. Production in 2000 6.2 Brazil increased to 238 Mt of bituminous coal and 68 Mt of brown coal (IEA, 2001b). In 1999, exports totalled over 170 Mt, of Brazil has coal reserves in the southern part of the country, which over 90 Mt was coking coal. south of Paraná, and just north of the Uruguayan border. The accessible coal is mainly of high ash and variable sulphur Upgrading by coal cleaning content. Recoverable reserves were estimated to be some 3 Gt, in the early 1990s, but the estimates were increased Australia washes a high proportion of its hard coal sharply in the 1998 and 2001 WEC assessments are quoted production. In 1998, 224 Mt out of 275 Mt was cleaned. It as being 12 Gt of subbituminous coal out of a proved had 64 CPPs, many of them large ones, with the highest amount in place of 17 Gt. The 12 Gt looks to be a rather

Coal upgrading to reduce CO2 emissions 29 Coals with upgrading potential

Table 6 The status of coal preparation in the major producing countries based on 1998 figures (modified from Kempnich, 2000; Stratum Resources, 2001)

Prep rom Washed Average Number Average Saleabl plant Exports, Country prod’n, product, recovery, of capacity, Comments e prod’n feed, Mt Mt Mt % CPPs t/h Mt

Most plants use jigs, and are attached to small local mines with a capacity of China 1316 1236 338 258 32 76 1574 51 <100,000 t/y. The products are mainly metallurgical coals and those for export. Only around 25% of production is washed.

Most plants use dense-medium systems and jigs account for only 8% of capacity. A high proportion of US bituminous coal is USA* 1087 936 619 468 71 76 255 783 washed. Washing is inappropriate for the increasing amounts of Powder River Basin subbituminous coal used.

The plants are mainly for preparing metallurgical coals. Dense- medium systems India 327 303 54 30 0 56 26 493 account for nearly half the capacity. Only some 20–25% of production is washed.

As some 75% of the coal is exported, the amount washed exceeds 80%. Domestic power plants often use a middlings (lower grade) product from a CPP. Dense-medium Australia 270 219 224 170 167 76 64 837 systems account for nearly 70% of capacity, and jigs about 15%. Efficient fines cleaning methods (froth flotation, Jameson and Microcel columns) are widely used. Russian units include many large factory- like central washeries which are stand-alone complexes producing a wide range of coals for the domestic and industrial market as well as for power generation. The coal industry is being restructured, and there is limited data on exactly what is happening. FSU† 320 290 110 80 23 72 65 545 The Ukraine coal industry has been in severe crisis since 1990, and no significant capital has been deployed. Although there were 64 plants in 1998, some of them factory style with high manning levels together with extensive infrastructure and community support functions, only 25% of the capacity was being used. The use of dense-medium units dominates. Both export coal and much of that used domestically, is cleaned. Grootegeluk is the largest CPP in the world with a total South capacity of 8200 t/h using five 287 223 244 181 67 74 60 645 Africa streams,including two of 3300 t/h. Some 50% of production is used for power generation and other heating use. 18% is converted to synthetic fuels and petrochemicals while 32% is exported. As with Russia, the Polish coal industry is undergoing substantial restructuring, with mine and CPP closures. Eight CPPs produce metallurgical coals while most of Poland 155 117 98 59 28 60 60 650 the rest use dense-medium units for +150 mm coal while jigs treat the 150+20 mm fraction. 25% of hard coal production is exported.

30 IEA CLEAN COAL CENTRE Coals with upgrading potential

The studies cited here included no information on Germany. Generally, bituminous coal is cleaned to quite a high specification, but production is falling steadily with the removal of production subsidies. In 1999 bituminous coal Germany 202‡ – – – – – – – production was 41 Mt. By 2001 it is expected to drop to 32 Mt (IEA, 2001b). More than 95% of bituminous coal is washed (Couch, 1991) and the predominant technology used for separations in Germany is jigs.

Little is known about the situation in North Korea. Coal resources are considerable, but North are mainly brown coals (mined underground 82‡ – – – – – – – Korea in the Anju coalfield some 80 km from Pyongyang) and some anthracites, see also Section 6.16.

Canada is a major coal exporter, and dense- Canada 92 75 52 35 34 67 13 749 medium CPPs dominate.

Production in Indonesia has increased rapidly, mainly for export. It doubled between 1993 and 1998. Much of the coal produced Indonesia 64 61 15 12 47 78 13 247 has a high moisture content but is low in ash, and therefore does not require washing. Only 15 Mt/y is fed to CPPs. Use of jigs is widespread.

Production in the UK has been falling as the economically mineable reserves are extracted. There should be some spare UK 55 41 42 27 1 65 30 440 washing capacity. Coal is also washed in small units at opencast sites or where coal from old tips is being recovered.

* USA data clearly includes the Powder River Basin subbituminous coals which are not generally washed, and similarly the Canadian data includes the subbituminous coal mined † FSU data includes Russia, Ukraine and Kazakhstan ‡ in 1999 (WEC figures) high proportion of the reserves, and in view of the low grade Brazil imports substantial quantities of coking coal (11 Mt in of the coal, the 3 Gt is possibly more realistic. 2000), together with an increasing amount of thermal coal, estimated to be 2.6 Mt in 2000 (IEA, 2001b). As there is By far the largest amount of this coal is in the Rio Grande do substantial overdependence on hydropower for generating Sul province (Baruya and Clarke, 1996; World Energy electricity, Brazil is looking at ways of diversifying the Council, 2001). Production in 1999 was 5.6 Mt, all of which sources for power, imports of coal may increase. was classified in the WEC statistics as bituminous, in spite of the fact that the reserves are subbituminous. About Upgrading by coal cleaning three-quarters of the coal is used for power generation. The coal is described as having an average heating value (af basis) The thermal efficiency of the coal-fired power plants in of 16.5 MJ/kg, with a range of 12 to 26. Ash content (db) is Brazil is probably quite low, and there may well be scope for 45% average, ranging from 20% to 57%. Sulphur content reducing CO2 emissions by coal upgrading and improving averages 2.3% (db) ranging from 0.5% to 6.5%. plant efficiencies both in existing plants, and in new units which may be built. If indigenous coal is to be used there Mining has been associated with environmental degradation. may well be opportunities for some upgrading before use, There are large dumps up to 20 m high, in which waste coal but there will need to be an obvious economic benefit to the can be oxidised, releasing uncontrolled CO2 and SO2 into the power generators to encourage this. atmosphere. It is estimated that two-thirds of the watershed in the Santa Catarina region has been adversely affected by Upgrading by coal drying pollution arising from the mining. The potential costs associated with coal use in an environmentally acceptable As the main problems with Brazilian coals are the high ash way will affect its use in the longer term, notwithstanding and sulphur contents, drying would probably not be the substantial reserves (Santana and others, 1996). required.

Coal upgrading to reduce CO2 emissions 31 Coals with upgrading potential 6.3 Bulgaria 6.4 Canada

Bulgarian coal reserves are mainly of low grade (with high Canada has proved recoverable reserves of 3.5 Gt of moisture, high ash and high sulphur content) lignite. These bituminous coal, 0.9 Gt of subbituminous and 2.2 Gt of are located in the Maritsa basin. The proved recoverable lignite. Coal production in 1999 was of 36.5 Mt of reserves are 2.7 Gt, and in 1999 coal production totalled bituminous, 24 Mt of subbituminous and 11.5 Mt of lignite 26 Mt (World Energy Council, 2001). The largest deposit at (World Energy Council, 2001). Some three-quarters of the Maritza-Iztok has an average moisture content of 55%, ash bituminous coal (27.8 Mt) was exported, mainly for content of 34% and sulphur content of 2% (East European metallurgical use. Much of the lower rank coal was used for Energy Report, 1995). The LHV is around 6–7 MJ/kg as- minemouth power generation. The lignites are located received which is one of the lowest calorific value coals mainly in Saskatchewan. In addition to its indigenous burned anywhere in the world. production, Canada imports significant amounts of coal mainly from the USA, mainly in the east. Imports comprised Because of the lack of other indigenous energy resources, the 4 Mt of coking coal and 13 Mt of steam coal in 2000 (IEA, lignite resources are of considerable importance. The 2001b). coal-fired power plants which produce some 30% of the electricity generated were mainly built in the 1960s and Upgrading by coal cleaning 1970s, and are in urgent need of upgrading. To reduce pollution levels, desulphurisation is essential. Canada has 13 CPPs, with a high average plant capacity, and a relatively high level of utilisation (see Table 6). A high There is considerable potential for the application of proportion of Canadian bituminous coals are already washed appropriate CCTs to facilitate the longer-term use of the to an economic optimum, with much of it being exported as indigenous lignites, and to ensure cleaner and more efficient coking coals, and some of the middlings product being used use of the resource. Investment decisions may be affected by for power generation. A problem with Canadian coals is that the eventual decision made about the timing of the they tend to be friable, thus involving a relatively high decommissioning of the Kozloudy nuclear power plant, proportion of fines which increases the difficulty and cost of which supplies nearly half of Bulgaria’s electricity output. cleaning. There is likely to be only limited opportunity for The various options are discussed by Vassilev and Christov reducing CO2 emissions by more thorough cleaning. (1998) and in East European Energy Report (1998). Upgrading by coal drying Upgrading by coal cleaning For the longer-term use of the Saskatchewan lignites, Because the coals are subbituminous, conventional coal consideration should be given when replacing coal-fired washing processes are probably inapplicable, but it may be capacity to incorporating drying into the process. that a combination of drying and washing might be applied, though such a route would be relatively costly. Dry 6.5 China beneficiation may be an option. It may be that, with judicious selective mining and the increased use of on line Coal reserves are classified as 62 Gt of anthracite and coal analysers together with some stock blending, a coal feed bituminous coal, together with 52 Gt of subbituminous and with more consistent properties could be fed to the boilers lignite (World Energy Council, 2001). The major deposits resulting in small gains in efficiency. are described by Walker (2000). The average ash content of rom coal is estimated to be as high as 30% (Shiyu, 1997), Upgrading by coal drying and the distribution of ash in the reserves is shown in Table 7, on a dry basis. It should be noted that the ash Because of the high moisture content, coal drying should be content of rom coal may be somewhat higher, since some considered seriously for PCC boilers, or for IGCC if that is additional rock and dirt may be extracted at the same time, adopted because of the high coal sulphur content. The most especially with mechanised methods. obvious technology to be used for the Bulgarian coals is CFBC where the high moisture high ash content feed has less impact The reserves are situated unevenly around the country, and than with PCC or IGCC. Although CFBC boilers are fairly many are located in remote areas in northern China. tolerant of coal quality variations, they will operate more Reserves in the southeast, nearest some of the most rapidly efficiently with a consistent feed, thus reducing CO2 emissions. developing industrial areas, are relatively high in sulphur

Table 7 Ash distribution in Chinese coal reserves (McCulloch and Baillie, 2002)

<10 % ash (db) 10-30% ash (db) >30% ash (db) low ash medium ash high ash Steam coal, % 17.2 77.1 5.7

Coking coal, % 7.6 84.6 7.8

Total, % 11.8 81.3 6.9

32 IEA CLEAN COAL CENTRE Coals with upgrading potential content. Much of the coal has an LHV, as received, in the important. It is estimated that the coal used in Hunan region 8–12 MJ/kg because of the impurities present. Since province, for example, typically contains >20% of refuse, the industry has been centrally controlled for many years, and >25% of ash. The refuse is stone mixed with the coal realistic economics do not yet apply within the Chinese coal while the ash is mineral matter contained in the coal industry, and the necessary adjustments will most probably (ESMAP, 2001). This has significant implications for the take many years to be realised. efficiency of use and for the amounts of residue formed. The use of an air-based moving bed jig on such coals could be There are large amounts of lignite, which is said to be older highly beneficial. than the brown coals found in Australia and Germany, described by Zhenzhong and others (1997). Reserves of One factor in China is that with increased mechanisation in subbituminous and lignite are said to be 52 Gt. Many of the mines, coal quality is declining, and thus more coal these deposits are not currently exploited, and lignite preparation is needed, just to maintain quality at current production is quoted as being only 30 Mt/y out of a total of levels. Although nearly 20% of the steam coal reserves have some 1000 Mt/y. As deeper reserves of bituminous coals are an ash content below 10% (db), this does not necessarily exploited, lignite use may become more competitive, in represent the proportion in rom coal. Some of the low ash which case, drying will become an increasingly important coal may be in unexploited low rank coal reserves, and topic. additionally, dirt and stone are commonly added to the coal during mining operations. In China, only about half the coal produced is used to generate power. The other half is used in industrial boilers Another factor is the geographical mis-match between coal and coal-fired kilns; in household stoves and for producing and coal consuming regions. The main producing coke-making. There are about 500,000 industrial boilers, of areas are in the centre-north and the north-east of the which 90% are old fashioned layer-combustion types with country. The principal consumers are in the east and low efficiency (Du and Liu, 1999). The average unit capacity south-east. Over 600 Mt/y of coal is transported over long of these boilers is 2.4 t/h of steam, and less than 5% of them distances, and of this, 450 Mt/y is raw unwashed coal. are oil or gas fired. Medium and small coal-fired boilers Potentially some 15% of this is waste material that could be mainly use unwashed raw coal with a high ash content and a removed by washing, and this means that nearly 70 Mt/y is high proportion of fines. Poor quality fuel results in low transported unnecessarily. As the rail system is already boiler efficiency and poor combustion stability. As a result, overloaded, this has major implications relating to the supply spare boilers are often installed in order to maintain steam of coal to the customer (IEA, 1999). It is thought that output. It is estimated that coal use could be reduced by as China’s (low) coal prices could be affected by its entry into much as 60 Mt by the use of more efficient equipment and the World Trade Organisation (WTO). This is because WTO prepared coals (Wu and Xu, 1999). This would result in very rules do not allow the subsidy of exports, and thus rail substantial reductions in CO2 emissions. As a result of the freight may have to be charged at realistic levels extensive industrial and household use, there is considerable (International Coal Report, 2002a). The impact of the rules interest in coal briquetting as a method of upgrading, using on coal used internally is less clear. The question of transport fines, and in the development of coal-water mixtures. costs is discussed further in Chapter 6 in conjunction with the alternative strategy of using the coal-by-wire route. Upgrading by coal cleaning Chen and Wu (1999) say that under current economic and As it is the world’s largest coal producer, what happens in technical conditions in China, the most economic way to China is of particular importance. Only some 25% of the reduce SO2 and dust emissions would be to improve the coal coal produced is washed, and even that amount is not quality by washing. While the focus of the paper was on intensively cleaned, except for some of the coals used for reducing SO2 emissions, there would be significant coking. The amount of washed coal produced was 258 Mt in reductions in CO2 emissions as well. Among the measures 1998, and so with the reduced production of coal in 1999 that would substantially improve the situation in China with and 2000, the percentage figure may be somewhat higher, respect to coal washing are: and nearly half the coal produced by the large state-owned ● the use of high-efficiency coal preparation equipment; mines is washed. Of the total amount of washed coal, ● enhanced reliability through thorough maintenance 110 Mt is for coking. Something around 50 Mt of it is programmes; exported. The plants which are washing thermal coals are ● the application of state-of-the-art automation and control mainly simple jig units of Chinese manufacture. Much of the systems on CPPs (see Couch, 1996); equipment is old and ineffective. ● the use of central washeries in areas with many small township or village mines; Chinese coals are described as being moderately difficult to ● setting up a price structure that encourages the use of wash, and for an average steam coal being separated at better quality coal, and a regulatory system that is 1.6 RD, there could be 10–20% of near gravity material (ie enforced and which encourages the use of high grade at 1.6±0.1 RD). It is possible to envisage ash reductions from coals a rom coal at 25–30% ash to 10–15% ash, which would bring considerable benefits. In some areas, and particularly in the northern coal mining areas, water shortages are a major constraint on the possible Coal preparation for industrial and domestic use is also application of coal preparation (IEA, 1999). As a result of

Coal upgrading to reduce CO2 emissions 33 Coals with upgrading potential this, there has been considerable interest in the development of the amount of coal used worldwide, there is scope both of air-based processes, although these are generally less for fuel substitution, and for ensuring that the coal is used effective than water-based separations. Alternatively, the more efficiently. Some 140 Mt is used domestically. Much of increased recycle of water and/or the use of mine waters, it is used with a thermal efficiency of only 15%, whereas it may make CPPs operable. This is likely to increase operating has been demonstrated that with upgraded coal and well costs considerably, but may still be justified in terms of designed equipment, the efficiency can be over 60% – an reduced transport costs for the coal, and improved thermal enormous increase. At the same time as decreasing CO2 efficiencies during combustion as well as reduced volumes emissions, particulate, SO2 and CO emissions would also be of ash for disposal. reduced substantially (Wu and Xu, 1999).

There is enormous scope for the increased use of coal Coal provides approximately one third of the fuel gas used in cleaning/upgrading in China for power production. Although city households in China. The balance is supplied by natural there are more than 1500 CPPs, half of them are village or gas and liquified petroleum gas. Coal-based fuel gas is also township based, and most are for the production of coking used in industry. The coal-based gas comes either from coal. With the growth in China’s coal export business for coking or from gasification. The possible development of both thermal and coking coal, any increase in the amount of coal gasification in China, including the use of fluidised bed coal washed is likely to go into this market. In 2000, China and of entrained flow gasifiers is discussed by Xu (1999). A exported more than 50 Mt of coal, mainly for the thermal plan to build a 300–400 MWe demonstration IGCC plant at market. In a review of development strategy in China, Zhang the Yantai power plant in Shandong province was approved (1999) does not forecast any rapid expansion of coal washing in 1999. It will be designed to burn a high sulphur content capacity in the near term. The amount produced in 1995 was coal (2.5–3%) from Yanzhou (Xu, 2000). While a quoted as 280 Mt, in 2000 as 290 Mt and the forecast for considerable amount of work will need to be done, if there is 2010 is estimated to be only 300 Mt, a very modest increase. more widespread use of more advanced technologies then in By 2020, it is forecast to increase sharply to 530 Mt. most cases, coal upgrading is likely to be a major contributor to such processes. This is because the amount and behaviour Most boilers in China are designed to accommodate low of the mineral matter present in coal tend to be even more grade, high ash coal with an LHV of about 21 MJ/kg and an important in gasification processes than they do in ash content of 25–30%. To gain the maximum advantage combustion. from using a washed coal it would be necessary to modify the heat transfer surfaces to match the heat release Government policies in relation to the use of clean coal characteristics of the cleaned coal (ESMAP, 2001). While technologies in China, including coal upgrading, are this involves a cost, there should be a substantial overall reviewed by Dou and Hu (1999). Premier Li Peng is quoted benefit from the use of higher quality steam coal, including a as saying in 1997 that coal use and energy development reduction in CO2 emissions of more than 10%. Where large should go hand in hand with the implementation of new high-efficiency boilers are built, for their satisfactory environmental controls. In the same year, the ninth five-year operation, it will be necessary to ensure that a stable and plan outlined objectives to be achieved by 2010. These secure supply of upgraded coal is available. included a rapid increase in plant capacity for coal preparation to a total of just over 800 Mt by 2010. In Upgrading by coal drying addition, an expansion in the use of coal briquettes and of coal-water slurries was planned. Increased use of CFBC The production of lignite was 45 Mt which, although only a boilers is planned, and while these can facilitate substantial small proportion of the total is still a significant quantity. As reductions in the emissions of SO2, there are disadvantages it will probably all have been mined in open pits, costs are in terms of the increase in the emissions of N2O which is a probably considerably lower than those for other coals mined significant greenhouse gas. A great deal of research has been underground. Thus there is likely to be potential for the carried out into coal liquefaction. Based on some of this increased use of coal drying with some reduction in CO2 work, and on the availability of cheap brown coal deposits in emissions as the use of these low rank coals may increase. Yunan and Heilongjijang said to be particularly suitable for liquefaction, there is continuing interest. Other aspects of upgrading With the various rapid changes taking place in China, it is Because of the widespread industrial and domestic use of difficult to tell how far these policies have been successful. coal, there are a number of interdependent issues. The There is certainly more consciousness and concern about provision of upgraded forms of coal, both in terms of washed environmental conditions, but there is also an increasing and graded products, and of high-grade briquettes could have understanding of the real cost of various courses of action. a considerable effect on the efficiency of coal use. The China will have some difficult decisions to make in relation increase in efficiency would only be fully realised with to the use of coal upgrading in order to reduce CO2 investment in the boilers and stoves used so that modern emissions, and as yet, there are few financial mechanisms in technologies could be applied. Currently, even in the big place to encourage efficient use. cities, coal is widely used in small roadside restaurants, in semi-open stoves. This use is very inefficient, and results in a 6.6 Czech Republic considerable amount of pollution. As some 400 Mt/y of coal is used industrially and domestically, representing some 10% The Czech Republic has proved recoverable reserves of

34 IEA CLEAN COAL CENTRE Coals with upgrading potential

2.1 Gt of bituminous coal, 3.4 Gt of subbituminous and world of brown coal. This came from open pit mines, and 0.1 Gt of lignite. In 1999, production was of 14.5 Mt of production was over 300 Mt/y. Following reunification, the bituminous coal, 44 Mt of subbituminous and 0.5 Mt of industry (in the former eastern region) was scaled down, so lignite (World Energy Council, 2001). Looking at the that production is now nearer 70 Mt/y, principally to supply reserves from a different perspective, those in active mines several newly-built supercritical PCC power plants. In the were assessed as 0.4 Gt of bituminous coal, 1.6 Gt of Rhenish area of west Germany, the production of brown coal subbituminous and 0.05 Gt of lignite. At least 1 Gt of has continued at a rate of around 100 Mt/y. As the reserves additional subbituminous reserves are blocked by limits on in particular open pits come near to exhaustion, there has mining imposed by the government on environmental been discussion about the environmental impact of opening grounds (IEA, 2001c). up new areas for mining, and some opposition to this development. Total brown coal production in 1999 was Nearly 80% of the bituminous coal comes from Ostrava 161 Mt. where the coalfield is an extension of the Upper Silesian deposit in Poland. Much of the rest comes from Kladno. Upgrading by coal cleaning Coal is mined at depths of 700–1000 m. Just over half is coking coal, and of this, 3.5 Mt was exported in 1999. In A very high proportion of German hard coal production is addition, 2.6 Mt of steam coal was exported. Some 1.6 Mt of washed, and there is little potential for further upgrading. coal is imported. Upgrading by coal drying The subbituminous coal is mined principally from the border area with Germany around Most and Sokolov. Ash contents Because large tonnages of brown coal will continue to be vary from 24–44%, the moisture content averages 30%, but used, there is considerable interest in pre-drying the coal can be as high as 55%, while sulphur content ranges from before use. At the new 1000 MWe unit at Neiderhausen 0.5–6.0% (Couch and others, 1990). A small amount which is due to be commissioned during 2002 there are plans (3 Mt/y) of brown coal is exported to nearby German power to operate a demonstration-scale drying unit. stations. While production is declining, it is estimated that demand will still be over 30 Mt in 2010 (IEA, 2001c). 6.8 Greece Upgrading by coal cleaning Greece has 2.9 Gt of recoverable reserves, mainly of low grade lignite (World Energy Council, 2001). Most of the As much of the bituminous coal production is coking coal, reserves are located around Ptolemais in the north of the and/or is exported, there will be limited opportunity for country, and Megalopolis in the Peleponese in the south further upgrading. (IEA, 1998a; Couch, 1988). Production is considerable, at 62 Mt/y in 1999, and most of it is used for power generation. Upgrading by coal drying The Greek lignites are amongst the lowest grade coals used anywhere in the world. Virtually all is used for power Given the nature of the subbituminous coal there will be generation, and there is installed capacity of approximately some scope for upgrading by selective mining. CO2 5400 MWe, and two new 330 MWe supercritical PCC units reductions from coal washing or drying would be limited, are being built at Florina, Meliti-Achlada, where the coal has although if the coal is to continue to be used, tests should be only 40% moisture, but up to 20% ash (Kakaras, 1999). The carried out to assess what can be done economically. Until existing units operate at overall thermal efficiencies ranging recently, the main focus in connection with coal use has been from 25 to 34% and most of the more modern 300 MWe reducing emissions of particulates, SO2 and NOx. In this units have efficiencies of 30–32%. connection, the most economic approach has been to clean the flue gases generated from combustion. If reductions in Upgrading CO2 emissions are given an economic value, then the position may change, and the upgrading of coal by washing Most of the lignites used have a moisture content of around or drying before use might be viable. 60%. The ash content is commonly in the range 12–18%, although the average would be about 13%. Because of the 6.7 Germany high moisture content there will be some possibilities of upgrading by pre-drying the coals. As the Florina units have Germany has recoverable reserves of some 23 Gt of not yet been commissioned, it is not yet known how bituminous coal and 43 Gt of brown coal/lignite (World variations in the coal quality will affect their operation, but Energy Council, 2001). Coal has been mined in Germany in the design specification is for a lignite feed with an LHV of substantial quantities for well over a century. Consequently, 6.7–9.6 MJ/kg, ash of 13–40 wt%, moisture of 30–44 wt% much of the easily extracted coal has already been taken, and and sulphur of 0.4–2.7 wt%. These are very wide ranges, and the cost of deep-mined bituminous coal has increased. it will be interesting to see how well the supercritical boilers Production in 1999 was of 40.5 Mt, and fell by about 4 Mt/y cope with the variations. during each of the three preceding years. Imported coal is now competitive in many parts of the country. 6.9 Hungary Prior to 1989, East Germany was the largest producer in the Hungary is quoted as having no recoverable reserves of

Coal upgrading to reduce CO2 emissions 35 Coals with upgrading potential bituminous coal, 0.08 Gt of brown coal and just over 1 Gt of power generation units, and loss of availability. Most power lignite (World Energy Council, 2001). This is a substantial station coal is not washed, and in many places there is a reduction from the estimates in 1998 when the equivalent supply shortage. figures were 0.6 Mt of bituminous coal, 1 Gt of brown coal and nearly 3 Gt of lignite. Production in 1999 was of 0.7 Mt Government policy is to increase the amount of washed coal of bituminous coal and 14 Mt of the low rank coals. used in power plants substantially, and there is a regulation that all coal transported more than 1000 km must have an Upgrading ash content of less than 34%, which would generally be equivalent to a coal whose coarse fraction has been washed The combined ash and moisture contents of the low rank in a jig. One of the difficulties in India is that coal prices do coals are generally in the 50–60% range, so there may be not reflect quality in any meaningful sense. For example, some opportunities for upgrading, since they are used as rom once the 34% ash content has been reached, there is little material. additional incentive to clean the coal further. The average recovery of coal in India is particularly low (at 56%) but this 6.10 India reflects not only the inherent washability characteristics of the coal but the fact that such a high proportion of it is for India has recoverable reserves of over 82 Gt of bituminous metallurgical use. In India, some of the washery so-called coal, and 2 Gt of lignite (World Energy Council, 2001). The ‘wastes’ are subsequently burned in small bubbling FBC principal reserves are variously described as being either boilers (Couch, 1998). bituminous or subbituminous, and much of the coal has properties that are probably near the borderline for There is enormous scope for the application of coal cleaning distinguishing the different characteristics. The country is the to deshale rom coal, and to do some further separation. This third largest coal producer in the world, and some two-thirds is in spite of the fact that the coal washability characteristics of the electricity generated comes from coal-fired plants. are fairly poor. In terms of the coal heating value, account must be taken of the fact that washing will remove some The coal is predominantly of high ash, but low sulphur mineral matter, but the coal will probably have a higher content. As India was part of the Gondwana continent, the moisture content. Washing to remove loose stone and mineral matter tends to be finely disseminated, and therefore mineral matter should provide a more consistent feed to the difficult to remove by washing. The coals in Bihar and West power plants, and reduce mill wear. Bengal have good coking properties; in Assam the coals have a high sulphur content while in Gujarat and Tamil Nadu the Upgrading by coal drying main deposits are of high ash lignites. In other states, including Madhya Pradesh, Uttar Pradesh, Orissa and The opportunities for this in India are quite limited. Most of Addhra Pradesh the deposits are mainly of a low grade, high the lignites, and particularly those in the largest deposit at ash content, bituminous coal. Most of the coal is on the Neyveli in Tamil Nadu, have a high ash content as well as eastern side of the country, so that long distances are elevated moisture content. While it might be possible to involved for transporting fuel to power plants in places to the remove some of the water from the coal before combustion, west, such as Delhi, Hyderabad and Mumbai (Bombay). it is unlikely to be an economic process.

Coal production and use has grown steadily through the 6.11 Indonesia 1990s from 155 Mt/y in 1985 to 300 Mt/y in 1995. By 1999 it was 314 Mt. Virtually all the increase comes from surface The recoverable reserves of coal in Indonesia are estimated mining, as the production from underground mines has to be more than 5 Gt. They consist of 790 Mt of bituminous, remained at around 50 Mt/y. Coal quality is generally poor, 1400 Mt of subbituminous and 3000 Mt of lignite (World with ash contents in the range 25–45% and LHVs commonly Energy Council, 2001). The quality of Indonesian coals is below 20 MJ/kg. Moisture content is typically in the 8–15% discussed in Indonesian coal prospects to 2010 (Jolly and range, and with only a few exceptions, the sulphur content is others, 1994). More than 65% of the reserves are on below 1%. Sumatra, with the remainder being on Kalimantan. While the largest reserves are of relatively low grade lignite in southern Upgrading by coal cleaning Sumatra, these are not generally being exploited. Most of the bituminous and subbituminous coal is on Kalimantan. In 1998 there were 26 CPPs in India with an average capacity of 493 t/h. Of these, 23 were for the production of Practically all the new mine development has been on metallurgical coals (Kempnich, 2000a,b). In the small Kalimantan. A wide range of coals are produced, including number of plants producing steam coals, only the coarse coal some with exceptionally low ash and/or sulphur contents. PT is washed. Even in the relatively new Piparwar plant which Andaro Indonesia, for example, produces Envirocoal with an has a capacity of over 1500 t/h, only 50% of the rom coal is ash content of 1% and sulphur content of 0.1%, and Wara treated in the Baum jigs, and this is the fraction >13 mm coal with an ash content of 2% and sulphur 0.15%. The size. moisture content of these coals is relatively high at 25 and 35% respectively, with a LHV of 20–25 MJ/kg, indicating The relatively low quality together with the variability in the that their rank is subbituminous. Most other Kalimantan coal supplied, results in low thermal efficiencies in many coals have ash contents in the 4–7% range (which is very

36 IEA CLEAN COAL CENTRE Coals with upgrading potential low by international standards), together with sulphur coals, there is likely to be considerable scope for the contents below 1%, and most have LHVs in the range application of coal washing to upgrade the coals used 26–30 MJ/kg with moisture contents in the range 10–20%. A internally for power generation, provided production costs can small proportion of the production lies outside these ranges, be contained. The whole industry is going through a stage of details of which are given by Jolly and others (1994). modernisation and restructuring. Many of the assumptions made in past decades are being questioned, and there may be Upgrading further reductions in the amount produced. In 1998 there were just 13 CPPs, with only 10 Mt/y of rom Upgrading by coal drying coal being fed to them. Because of the quality of the coal being mined, there is currently little potential for the The amount of lignite mined is small. It was only 1.8 Mt in increased use of coal washing. Similarly there is little 1999, so the scope for reducing CO2 emissions by pre-drying prospect of coal drying being used practically and is quite limited. economically for these coals. If the low grade coals in Summatra are exploited in the future, or higher ash content 6.13 Laos Kalimantan coals, then the situation may change. Limited quantities of coal have been identified, although the 6.12 Kazakhstan reserves are not well defined. Some have been explored in sufficient detail to support a plan for mining lignite at The recoverable reserves in Kazakhstan are estimated to be Hongsa. The reserves at this site are quoted as being some 31 Gt of bituminous coal and 3 Gt of lignite (World Energy 800 Mt (Power in Asia, 1997). Earlier estimates of the Council, 2001). There is a large coal industry, although reserves quoted figures of only 170 Mt of lignite, together output has dropped since the break-up of the FSU. The with 56 Mt of bituminous (Breeze, 1996). The reserves are reduction is partly due to a sharp drop in the demand for not listed in the 2001 WEC survey. electricity. Coal output in 1993 was 112 Mt. It declined to 76 Mt in 1996 and to 58 Mt in 1999. Joint venture companies have bought concessions to enable them to use some of the lignite in Laos for minemouth The two main coal basins are around Karaganda, producing a power plants to generate power for export to Thailand range of coals, some of which are suitable for coking, and (Power in Asia, 1997). These developments were hit by the Ekibastuz where the product is primarily a coal suitable for Asian economic crisis of 1998, which had a substantial effect power generation. In Karaganda, most of the mines are on Thailand, and has caused a delay in investment. underground whereas Ekibastuz has three huge open pit Electricity exports, however, could make a valuable mines (Walker, 1994, 2000). contribution to the Laotian economy (Power in Asia, 1998).

The Karaganda basin covers an area of some 3600 km2, with Upgrading reserves estimated as 45 Gt. Mining depths vary from an average of 400 m in the Tentec region to over 700 m around It is too early to assess the potential for upgrading these Shaklan. A small proportion of the output is from open pits. coals, but if new coal-fired power generating capacity is The Karaganda coals are mainly of high ash content, ranging built, it would seem sensible to design it to burn/use an from 15–45% and high sulphur content in the range 1–5%. upgraded coal feedstock, thus minimising CO2 emissions and bringing other benefits. The Ekibastuz basin is smaller, with an area of only 160 km2 and reserves of 8 Gt. These are mainly in three 6.14 Mexico Carboniferous seams of subbituminous coal with a combined thickness of 140 m in places. Pit depths in 1993 lay between A number of coal deposits are scattered throughout the 80 and 190 m. Ekibastuz coals have 33–41% ash and country. They are mainly of high ash low grade coal, but considerably lower sulphur, from 0.6–0.8%. For many years, some is mined for coking, as well as some for power Ekibuastuz coal was mined and transported to western generation. The largest area is around Coahuila near the Siberia for power generation, but this trade has decreased. border with the USA where the reserves are near the surface, but are gassy. The proved recoverable reserves are estimated There are large unexploited reserves of brown coal in the to be 0.9 Gt of bituminous, 0.3 of subbituminous, and a Turgai basin at Kushmurnskoe and Orlovskoe. It is thought small amount of lignite. Coal production in 1999 was 2.4 Mt that coal demand both for domestic use and export will grow of bituminous and 7.7 Mt of subbituminous, nearly 20% during the coming decade as economic activity picks up. more than in 1996 (World Energy Council, 2001). Coal use for power generation averaged 3–4 Mt/y in the early 1990s, Upgrading by coal cleaning mainly from indigenous production. In line with other countries in the FSU, it is unlikely that coal Upgrading washing had a high priority, other than for the production of coking coals. More than 50 Mt/y of bituminous coal is The potential for upgrading these coals, which are used in produced. The coals have relatively high ash contents, mostly fairly modest quantity, is limited, and not explored further in the range 30–45%, and as they are northern hemisphere here.

Coal upgrading to reduce CO2 emissions 37 Coals with upgrading potential 6.15 New Zealand Recoverable reserves are estimated to be 2.3 Gt, all of subbituminous coal (World Energy Council, 2001). There are New Zealand has recoverable reserves of only 30 Mt of measured resources of about 50 Mt in both Balochistan and bituminous coal, 200 Mt of subbituminous and over 300 Mt Punjab. In Sindh province there are larger deposits, including of lignite. Production in 1999 was 1.6 Mt of bituminous, the Lakhra field with 250 Mt of measured resource, and the 1.7 Mt of subbituminous and 0.2 Mt of lignite (World Thar field with over 2.5 Gt, and a further 170 Gt of inferred Energy Council, 2001). The main lignite reserves are at the and hypothetical deposit. Exploration of the Thar field is at southern end of South Island, a long way from the principal an early stage, and the various stages of assessment, mine areas of energy use. Assessments were made during the planning, financial approval and development will take 1980s of the economics of minemouth power generation several years to complete (SanFilipo and Khan, 1994). using these reserves and of taking the power across South Island and via an undersea cable to North Island (Couch, Coal production during the1990s was 3 to 3.5 Mt/y, mainly 1990). This scheme was not seen as being competitive at the of lower rank coals. These were used principally for brick time, and the reserves have not been exploited other than on production. a very small scale. Upgrading Upgrading The potential reductions in CO2 emissions attainable through The potential for upgrading these coals, which are used in upgrading are limited because of the small tonnages fairly modest quantity, is limited, and not explored further currently involved. If the Thar or Lakhra fields are here. developed, this situation would change.

6.16 North Korea (Democratic 6.18 Poland People’s Republic) Poland has recoverable reserves of some 20 Gt of bituminous coal, and just under 2 Gt of lignite. Production in 1999 was While relatively little is known about what is happening in 110 Mt of bituminous coal and 61 Mt of brown coal (World North Korea, the WEC survey quotes the proved reserves as Energy Council, 2001). As the country has been adjusting to being 0.3 Gt of bituminous coal and 0.3 Gt of the economic conventions of the OECD, uneconomic mining subbituminous. Production in 1999 is said to be 82 Mt, operations have been closed down, and the production of comprising 60 Mt of bituminous and 22 Mt of bituminous coal has been declining. It had fallen from subbituminous (World Energy Council, 2001). This makes 138 Mt in 1996. North Korea the tenth largest coal producer in the world. With over 100 Mt/y of output of hard coal, Poland is In a review of power production, Breeze (1997), says that the Europe’s largest producer. While production has dropped main sources are hydropower and coal-fired generation. The sharply, the necessary restructuring of the industry is now country has developed an inward-looking self-reliant substantially complete. The various forecasts suggest an economy. The collapse of the Soviet Union and subsequent increasing role for hard coal in power generation, some insistence by China that North Korea pay for oil at world reduction in demand for industrial heating and a reduction in prices exacerbated the country’s economic problems. Both overall demand from 100 Mt/y now to around 84–88 Mt/y by the power production industry, and coal mining are likely to 2010 and 82–84 Mt/y by 2020 (Karbownik, 2001). Over the carry all the hallmarks of a centralised communist same period, demand for brown coal for power generation is bureaucracy. The nominal capacity was quoted as 9500 MWe expected to remain at a stable level of about 65 Mt/y. in the mid 1990s, of which 4,500 was thermal. It may well be that not all of this is serviceable. In common with a number of other countries where coal is used internally, there has been little interest in the use of good Work carried out under the United Nations Development quality coal. The power plants were designed to accept coal Programme is described by Strauss (1998). This looked at with an ash content from 20–35%, and newer ones were built mining in the Anju coalfield some 80 km north of to accept an even higher ash content. As a result, intensive coal Pyongyang. This described the industrial infrastructure of the cleaning was not required. Even with the recent modernisation country as being severely weakened. of the coal-fired plants, a coal ash content of 18–25% was assumed, and the broad coal specification used was for an Upgrading LHV of 21 MJ/kg, ash content 22% and sulphur content 0.9%. There is insufficient information from which to make any Brown coal production is from open pits, and has not assessment of the role that might be played by coal declined nearly so sharply. The largest single brown coal upgrading, but it seems fairly likely that relatively low producer is Belchatów with a capacity of almost 40 Mt/y, quality coals are probably being used. feeding a minemouth power plant of 4320 MWe capacity. Turów is another large capacity brown coal mine feeding a 6.17 Pakistan 2000 MWe capacity power plant. There is considerable pressure to reduce the emissions from coal-fired power Pakistan has potentially significant coal resources. plants, and in particular the emissions of SO2.

38 IEA CLEAN COAL CENTRE Coals with upgrading potential Upgrading by coal cleaning of high ash low value anthracite. Production in 1999 was 4 Mt (World Energy Council, 2001). Large amounts of coal Poland’s export coal (18 Mt) and that used for coking (17 Mt) are imported, but there is some use of indigenous coal for is all washed. Much of the steam coal used internally is either power production. not washed at all, or only coarse coal is washed. In 1998, Poland had 60 CPPs although several were being closed Upgrading down. Only eight were producing metallurgical coals with cleaning of the full size range (Kempnich, 2000a,b). A There may be some scope for more intensive washing of the shortage of capital has meant that there has been little coal, but the tonnages involved are small. investment in the industry, but as a result there is probably considerable potential for further coal cleaning resulting in a 6.20 Romania number of operational benefits, including reductions in CO2 emissions because the boilers operate more efficiently. Romania has extensive coal reserves, widely dispersed through the country, but these are mainly of low grade, low Poland has 49 CPPs of which twelve were built during the rank coals. Proved recoverable reserves are estimated as 1990s. Only 16 plants have flotation sections for fines being just under 1.5 Gt. Most of these are low grade lignites treatment. Production capacity is for 91 Mt/y of raw coal, but with a moisture content varying from 35–50%, an ash the plants are not fully utilised. In 1999, utilisation was 68% content of some 50% (db) and consequently a LHV of of the coarse coal washing capacity, 79% of the intermediate 6–7 MJ/kg (Couch and others, 1990; World Energy Council, coal capacity and 66% of the flotation capacity. Some mines 2001). Production was 2.7 Mt of subbituminous and 20 Mt do not have a CPP. of lignite in 1999. The quality of the indigenous coal is so poor that it is unlikely to warrant the construction of new Coking coals are produced with intensive cleaning, including coal-fired power plants as higher grade fuels could be some crushing of both raw coal and middlings to increase imported for power generation. the liberation of mineral matter. The LHV averages 29.5 MJ/kg, ash content 7% and sulphur content 0.7%. Upgrading Research shows that the thermal coals could relatively easily Because the low rank coals are a valuable indigenous be cleaned to achieve an ash content of 8–12%, and at a resource, there may be some scope for upgrading in order to number of mines it would be possible to clean the coal down increase the overall thermal efficiency of use. to an ash content of 4–6%. There is currently only a very small demand for such coal, and for power production, only 6.21 Russian Federation coarse coal cleaning is generally used (Blaschke and Nycz, 2001). The Russian Federation has massive recoverable reserves of coal. These consist of 49 Gt of bituminous coal, 97 Gt of If greater attention were paid to boiler thermal efficiency to subbituminous and 10 Gt of lignite. It should be noted that reduce CO2 emissions, there is considerable scope in Poland as in other FSU countries, mineral resources were evaluated for producing an upgraded hard coal product in which the in the past using different criteria to those used in the average ash content is halved. To get the maximum benefit western world. The re-estimation of reserves under market from such a change, new boilers should be built designed to conditions is still continuing, and will generally remove burn the upgraded product. some of the former ‘reserves’ from the national inventory when completed (Walker, 2000). According to Shchannikov Upgrading by coal drying and others (2001), some 90% of Russian coal reserves are situated east of the Urals (outside European Russia). About With the brown coals, the possibilities of upgrading are half are low rank brown coals, mainly situated in the east. somewhat more limited. At Turów, which is one of the large The biggest brown coal deposit is in the Kansk-Achinsk power plants with 2000 MWe capacity, the boilers have all basin. been retrofitted with FBC units. The potential efficiency gains from predrying would probably not justify the cost. At Production in 1999 was of 166 Mt of bituminous, and 83 Mt Belchatow, where there is a further 4340 MWe of capacity of lignite (World Energy Council, 2001). Coal production built in the 1980s, predrying might be considered when the fell sharply during the 1990s from a peak of 425 Mt/y in units are replaced or refurbished. An additional 800 MWe 1988, but it has now stabilised, and in fact increased slightly unit has been the subject of extensive discussion, although during the last two or three years. no decision about it has yet been taken. This might well benefit from the experience gained at Neiderhaussen in With economic restructuring, many uneconomic mines have Germany. been closed. By 2000, 140 of the most loss-making mines had been shut and 25 more are due for closure by 2003 (IEA, 2001b). Much of the bituminous coal is of high grade, but 6.19 Republic of Korea (South there are large amounts of low value brown coal. Investment Korea) is going into the construction of new mines, both on the surface and underground and focused in the South Korea has some 78 Mt of recoverable reserves, mainly Kuznetsk/Kuzbass and Far Eastern regions. The government

Coal upgrading to reduce CO2 emissions 39 Coals with upgrading potential is trying to increase the amount of coal-generated electricity severe weather, and the ease with which coal freezes and from 34 to 44% of the total, and also to increase its export becomes a solid block. capacity for coal. Just over 20% of the hard coal production was exported in 2000. Because of the sheer size of the With the restructuring and mine closures, it is probable that country, transport costs can be considerable. the coal washing capacity was not all in the right place, although the tendency to provide central washeries which In a review of Russia’s energy strategy up to 2020, Klimov serve several mines means that the Russian system can adjust (2001), envisaged that coal output would increase to to new situations. Only one new CPP was being built 340–400 Mt/y, while Krapchin and Petrovskaya (2001) towards the end of the 1990s and that is the 2 Mt/y plant at forecast a total requirement of as much as 600 Mt/y of coal Obukhovskaya (Sazykin, 1997). The construction of new by 2020. It is intended to reduce dependence on gas. The CPPs should have a high priority for a number of reasons, current position is that coal use has been restrained by only one of which is the reduction of CO2 emissions. The unreasonably low gas prices. In a good number of plants others include reducing transport costs, producing a higher designed to be coal-fired, gas is now used, particularly in the grade and more consistent fuel to reduce operating costs and Urals. These should be amongst the first plants to return to reducing SO2 emissions. coal burning. In the longer term, it is expected that the biggest increases in coal production will be in the Kansk- Upgrading by coal drying Achinsk brown coal basin and the nearby Kutznetsk basin. Similarly, with the large quantities of brown coal used in The upgading of coal to ensure a consistent supply of central Russia, it is probable that there is scope for reducing homogeneous composition and high quality is said to be an CO2 emissions by pre-drying. There are also opportunities essential part of the strategy (Klimov, 2001). It is envisaged for the application of some of the more advanced coal that much of the increased production will come from open upgrading methods developed in Australia and the USA and pit mines. Currently, the price levels for mined coal are discussed in Chapter 5. Given the relative remoteness of the largely determined by state subsidies, and there needs to be a central/eastern brown coal deposits, there is a considerable transition to a more realistic heat-value based system. As incentive to develop technologies appropriate to these coals. both the Kuznetsk and Kansk-Achinsk basins are situated This is discussed by Malyshev (1999) and Golovina (2001). some 3000–4000 km from European Russia, the infrastructure for coal transport and its cost will be major 6.22 South Africa factors affecting this development. The coal can also fuel local power stations which would facilitate industrial There are 50 Gt of recoverable reserves of bituminous coal development in the area. Expansion of production in the (World Energy Council, 2001). These are located in eighteen Kuznetsk basin up to 140 Mt/y by 2010 can be achieved by principal coalfields. Production in 1999 was 224 Mt/y, and developing new open pit mines. The coal can be used for South Africa is a major coal exporter. About half the both coking and thermal applications, and could permit production is currently from underground pits, and the substantial development in the Yerunakovsky region. proportion mined from the surface is increasing slowly. Some 60 Mt/y of coal is exported, all of which is washed, to Since Russia is a cold country with a severe climate, it is not improve its quality. Coal used domestically for power likely that the CO2 issue, and the effects of global warming generation is mainly unwashed rom production, resulting in are going to have a high priority in the near future. Other the generation of large quantities of waste (IEA, 1996b). emissions such as SO2 and NOx are likely to be tackled first (Martynova, 2001). Upgrading Upgrading by coal washing Because of the relatively poor washability characteristics of South African coals, the possibilities for cleaning are limited, Most CPPs were built in the 1960s with parts manufactured although since the tonnages involved are considerable it may in Ukraine or Kazakhstan. This has made it difficult to obtain be worth some further effort. both new equipment and spares. In 1999, only 41 of the 71 CPPs working in 1992 were still operational (IEA, 2002). 6.23 Spain The typical flowsheet of a Russian CPP in the 1970s and 80s, consisted of: Spain has recoverable reserves of 200 Mt of bituminous coal, ● a heavy-medium vessel for the +13 mm coal; 400 Mt of subbituminous and 60 Mt of lignite. Most of the ● a jig for 13+0.5 mm size; lower rank coals are of low value, with the black lignite ● flotation for 0.5 mm; (subbituminous coal) around Teruel having high ash and ● thermal drying for all the 13 mm cleaned material (from sulphur contents. Production in 1999 was 13 Mt of both the jig and the flotation cells). bituminous, 4 Mt of subbituminous and 8.5 Mt of lignite (World Energy Council, 2001). A considerable amount of During the 1990s, a fourth circuit was added to wash coal is imported, and the domestic industry has been 1+0.2 mm size using spirals, and reduce the amount of fines adjusting to compete with world coal prices. Coal mining is floated. Decanter screens and screen bowl centrifuges were still subsidised. As this is phased out, domestic production introduced to reduce/eliminate the need for thermal drying. may fall, although there are important local employment Moisture is a major issue in Russian coals because of the issues. Factor that will mitigate against domestic coals are

40 IEA CLEAN COAL CENTRE Coals with upgrading potential that some have high sulphur content, some are of low grade, Table 8 Ash composition (%) of two Turkish and environmental requirements will increase the cost to the ‘lignites’ (Kok and others, 2001) power generators of its use (IEA, 2001e). Compound Tunçbilek Afsin-Elbistan Upgrading SiO2 53.3 8.3 The opportunities for upgrading are limited in view of the high cost of the coal. Al2O3 21.0 6.9

Fe2O3 11.4 2.6 6.24 Thailand CaO 2.3 54.3

Thailand has extensive reserves of coal, all of which are of MgO 6.8 1.5 low rank (lignite). Some also have a high sulphur content. The proved recoverable reserves are estimated to be 1.3 Gt Na2O 0.01 0.05 (World Energy Council, 2001). The biggest reserves are in K2O 1.0 0.1 the north-west, including the large producing coalfield at Mae Moh. There are also a few scattered deposits on the SO3 2.2 16.1 peninsular to the south. Production in 1999 was 18 Mt. between gas and coal use, but current projections show a Upgrading significant rise in CO2 emissions. There may be some opportunity for upgrading the lignites, An aspect which is not widely discussed in the literature is but as they tend to have a high sulphur content, drying has a that the coals described as ‘lignites’ have widely differing lower priority when considering upgrading. properties. This is illustrated in Table 8 where the ash composition of two of the Turkish lignites are compared, and 6.25 Turkey Table 9 which gives the analyses of different coals which supply existing power plants. All are described as being Turkey has recoverable reserves of 280 Mt of bituminous coal, lignites in much of the literature. 760 Mt of subbituminous and 2600 Mt of lignite. The lignites are mainly of high ash and high sulphur content and some Upgrading 60% of the resource has an LHV of <6.3 MJ/kg. Production in 1999 was of 2 Mt of bituminous coal and 65 Mt of lignite, In view of the huge increase foreseen in the use of the low much of which was used for power production (World Energy grade lignite, the question of upgrading is of great Council, 2001). Lignite production has increased significantly importance. Some 50–70% of the lignite is water or ash, and in recent years but the overall economics of power generation its quality is highly variable. In a report from the Energy from the high sulphur lignite is questioned in IEA (2001d). Technology Support Unit in the UK, Knight and others This is partly because of the potential cost of emissions (2002) reported that there was little concern at the lignite control to reduce pollution, and partly because the relationship mines about coal quality. between the mining company and the state electricity company is not entirely clear. The mining company is The first steps towards upgrading could include: profitable, but the electricity company is not. ● an adjustment of pricing policies to encourage the Hard coal is found and mined only in the Zonguldak basin, production of higher grade material; which has a complex geological structure making ● selective mining; mechanised mining difficult. About 10 Mt/y of coal is ● on-line analysis to check lignite quality, and to transfer imported for coking and for domestic use. However, it out of specification material to a dump; represents about a third of Turkey’s coal consumption on a ● the use of upgrading processes in conjunction with heat content basis. Some 40% of the lignite resources are in minemouth power generation, particularly the Afsin-Elbistan basin, southeast of Ankara while much of pre-combustion drying, and possibly dry beneficiation. the rest (where most of the mining takes place) is in western Turkey. The largest production area is in the northwest. A very considerable amount of research work has been carried out on possible methods of upgrading Turkish Government plans are for a dramatic increase in the amount lignites, including: of coal used up to 2020. Lignite production is seen as ● washability characteristics (Ermisoglu N, 1995; Cebeci increasing to about 180 Mt/y and coal imports to 150 Mt/y. and others, 1996; Aydin and others, 1996); The plans are based on the needs of a growing population ● thermal treatment and magnetic separation (Onal and and to provide for higher living standards. It is also based on others, 1999); the desire to minimise energy imports and retain some ● bioleaching of sulphur (Bozdemir and others, 1996; capacity which is based on an indigenous resource. The Durosoy and others, 1997); energy imports will be principally natural gas and traded ● briquetting (Akgun and others, 1989; Beker and bituminous coal. The long term effects of the future Kucukbayrak, 1996; Beker, 1997) privatisation of the energy markets may alter the balance ● caustic leaching (Renda and others, 1994).

Coal upgrading to reduce CO2 emissions 41 Coals with upgrading potential

Table 9 The different lignites feeding coal-fired plants in Turkey (Karayigit and others, 2000)

Location

Cayirhan Seyitomer Tunçbilek Tunçbilek Orthaneli Soma

A3 B4-5 A

Lignite analysis

moisture, % (ar) 27 32 23 21 33 14

ash, % (ad) 50 50 23 53 41 26

VM, % (ad) 28 24 32 20 31 33

FC, % (ad) 16 16 39 18 17 35

sulphur, % (ad) 3.3 1.4 2.4 1.3 1.2 1.1

LHV MJ/kg 12.2 10 20.9 10 10.8 19.2

Power plant

generating capacity (MWe) 300 600 129 300 210 44

number of units 2 4 1 2 1 2

Coal age Miocene Miocene Miocene Miocene Miocene Miocene

* using beneficiated Zonguldak bituminous coal near the Black Sea coast

The wide variations in the properties of the Turkish lignites, coal and 10% anthracite. Production in 1999 was 82 Mt, well see Tables 8 and 9, suggests that the different deposits need below the levels of ten years earlier when it was double that careful assessment before determining the most appropriate amount. In 2001 the Ukranian cabinet approved an process route for upgrading and hence optimising their use. investment and restructuring programme for the coal industry The Zonguldak coal is Carboniferous, being deposited involving potential expenditure of up to US$9000 million between 345 and 325 My ago. By comparison, the lignites over the next ten years (Coal Week International, 2001). This date mainly from the Miocene and Pliocene. While different is an ambitious plan to stabilise the industry in the context of authors define the precise geological periods differently, they a poor safety record, low productivity, unpaid wages, huge are midway through the Tertiary period which started some debts and low morale amongst the workforce (Walker, 2000). 65 My ago. In the earlier parts of the Tertiary, temperatures Other similar proposals and plans in recent years since the on the earths surface rose. In the following Ogliocene break-up of the Soviet Union have not been realised. (preceding the Miocene), temperatures fell, and some of the seas receded. In the Miocene (probably around 20–30 Upgrading million years ago) temperatures dropped further and the withdrawal of the seas continued. A further drop in Along with the rest of the industry, coal preparation facilities temperature led to the Ice Ages of the Pleistocene. It was the are being restructured. Although there were 64 CPPs in geological background to the formation of most of the 1998, some of them factory style with high manning levels Turkish lignites, and the relatively rapid changes taking place and extensive infrastructure and community support account for the variability in properties. functions, only 25% of the capacity was being used. There will be considerable scope for optimisation, and for 6.26 Ukraine increasing the amount of upgrading. Ukraine has considerable reserves of bituminous and 6.27 UK anthracitic coals. The main deposits are in the Donetsk basin which extends into the Russian Federation in the east, see The UK has recoverable reserves of 1 Gt of bituminous coal Walker (2000). There are also significant deposits of lignite and 0.5 Gt of lignite (which is in Northern Ireland). in the Dnieper basin (IEA, 1996a), but these were not seen Production of bituminous coal was 37 Mt in 1999. No lignite as being of economic significance under the previous Soviet is currently mined (World Energy Council, 2001). In a note regime, and are unlikely to be economically exploitable now. attached to the WEC statistics, it says that in view of the They would require a considerable amount of exploration decline of the British coal industry, it is difficult to quantify and assessment before use. Proved recoverable reserves of coal resources in line with the definitions of the survey. As coal in the Ukraine are estimated to be around 34 Gt, of recently as 1991/92, British Coal was estimating 190 Gt of which 16 Gt are of bituminous coal, a further 16 Gt are coal-in-place, defined as coal in seams of more than 0.6 m subbituminous and 2 Gt are lignite (World Energy Council, thick and less than 1200 m deep. The figure was qualified by 2001). Within the resource, some 30% is said to be coking the statement that ‘the working of these resources will

42 IEA CLEAN COAL CENTRE Coals with upgrading potential

Soma Soma Yatagan Yenikoy Elbistan Kangal Catalagesi*

B1-4 B5-6

17 21 32 25 47 33 14

44 64 39 56 35 37 56

29 21 33 31 40 38 17

21 8 18 6 16 15 25

0.7 0.8 2.6 3.5 3.2 4.8 0.4

10.4 5.7 12.8 7.7 11.2 14.7 17.4

660 330 630 420 1360 300 300

4 2 3 2 4 2 2 Pliocene/ Miocene Miocene Miocene Miocene Pleiocene Westphalian Pleistocene

depend on both economic circumstances and strategic may accept lower thermal efficiency as a result and yet considerations’. Since 1999, coal production has continued operate the plant more profitably. to decline, and is currently at a level of just over 30 Mt/y. Many CPPs in the USA were designed and built at a time Upgrading when the regulatory background to power plant operation was less stringent. This means that there is considerable The opportunity for further upgrading of the coal mined in scope using established technology to produce cleaner the UK is quite limited, other than by increasing the amount products. of fine coal cleaned. Armor (1996) highlights the fact that in the mid-1990s the 6.28 USA US electric utilities burned about $30 billion of fossil fuels. This accounted for 70–80% of the operating costs of the The USA has massive recoverable reserves, and is the plants. There is thus considerable pressure to use lower cost second largest coal producer in the world, after China. The fuels while accepting lower efficiencies and higher heat reserves comprise 116 Gt of bituminous coal, 101 Gt of rates. subbituminous and 33 Mt of lignite. Production in 1996 was of 568 Mt of bituminous coal, 352 Mt of subbituminous The US Climate Challenge programme introduced in 1993 (classified in IEA statistics as hard coal) and 77 Mt of by the DOE sought to return greenhouse gas emissions to lignite. By 2000 total production was just under 1000 Mt 1990 levels by the year 2000. Part of this was to be achieved (IEA, 2001b), with the production of low sulphur by planting trees, and part by an increase in the use of subbituminous coal from the Powder River basin increasing, renewables. Projecting into the future, beyond 2000, there at the expense of higher sulphur content eastern coals. Coal was a national energy strategy to reduce total consumption exports dropped from more than 80 Mt/y in 1995 to 53 Mt/y and to start replacing some PCC plant with more efficient in 2000. combined cycle units. Some units would be gas-fired and some coal-fired. Plants might use advanced steam conditions. Upgrading by coal cleaning The effects of various scenarios are shown in Figure 19 where the problems in getting back to 1990 levels are In the USA, where coal-fired power generation provides illustrated. Armor (1996) also makes the point that increased about half of the electricity, there is likely to be some scope gas use could be accompanied by significant methane for the use of more coal upgrading. This is because the leakage at both the well head and from pipelines, and this economic basis for current decision making does not include would offset some of the gains in greenhouse gas terms. The considerations related to CO2 emissions. The decisions made ‘evolving technology scenario’ is based on the likely timing relating to power station economics will be strongly for introducing commercialised advanced coal and gas fired influenced by the fuel cost per heat unit. If a lower grade of power plants. The ‘accelerated technology scenario’ is based coal can be bought more cheaply, the power station operator on the replacement of old plants at a greatly accelerated rate.

Coal upgrading to reduce CO2 emissions 43 Coals with upgrading potential

5000 3

4000 2.5 frozen technology

CO2 reduction through improved technology emissions, bilion tonnes 2 Total generation, billion kWh Total total CO generation 3000 growth 2

CO2 reduction through accelerated application of new technology

shortfall in getting back to 1990 levels

1990 CO2 level 2000 1.5 1990 1995 2000 2005 2010 Year

Figure 19 Various scenarios for reducing CO2 emissions (Armor, 1996) There would be a substantial need for cleaner higher quality user, compared with taking the coal to near the point of use coal in both scenarios. Coal fired gasifiers and PCC units and distributing the electricity locally. The North Dakota with supercritical steam conditions both work more lignites are mainly used in power plants close to the mine, as efficiently with an upgraded coal feed, and they are less they are not thought to be worth transporting. Coal drying forgiving than older subcritical steam PCC units which will before use might be usefully applied to increase power plant burn a much wider range of coals and can cope with more thermal efficiency. With the subbituminous coals, until the variability. Neither approach manages to reduce CO2 question of spontaneous combustion is addressed, drying will emissions to their 1990 levels. not, probably, be carried out, other than for minemouth plants. Upgrading by coal drying In view of the very substantial amounts of low rank coals being used, both of lignites in the Dakotas, and subbituminous coal from the Powder River Basin, there is potential for upgrading. Some of the more advanced work was discussed in Chapter 5. One of the problems with coal drying before transportation is that the dried product tends to be much more vulnerable to spontaneous combustion. While some work has been done to mitigate the problems, most of the possible methods are expensive, and as a result are not practical.

The choice, as in other places, is that between minemouth power generation, and transporting the energy by wire to the

44 IEA CLEAN COAL CENTRE 7 Energy transportation and market organisation

The degree to which coal is upgraded before use is low coal prices) to justify the cost of cleaning. Reductions in dependent on a number of factors. These include not only the sulphur content only attract a premium when the sulphur nature of the coal, but the ability of existing boilers to use a amount changes by more than 0.5%, and if smaller low grade product. The factors also include: reductions resulted in increased value, this would promote ● pricing policies, for coal and for other fuels; coal preparation (ESMAP, 2001). ● the coal transportation infrastructure; ● the infrastructure for electricity distribution; India has the opposite problem in terms of production, and ● the effects of liberalised markets; has started to import some coals, particularly for ● the impacts of national emissions limits and of metallurgical use. However, although much of the coal emissions trading; produced in India is of poor quality, many power plant ● the regulatory framework. managers are willing to take almost anything that they can get hold of, because supplies are so short. This does not 7.1 Coal pricing policies encourage the use of upgraded coals. As restructuring of both the coal mining sector, and of the State Electricity There are a number of price mechanisms which can be used Boards takes place, and as more generating capacity comes to encourage the use of cleaner, higher-quality coal. With on line possibly using some imported coals, the situation internationally traded coals, there is already a mechanism will change. A more flexible pricing policy not tied to the which works well, based on a competitive market, although Grade structure, which is currently the basis for coal this is skewed by the differing distances that coal has to be marketing (see Table 10), would contribute to a more transported to reach its market. Where traded coals can be realistic assessment of the benefits of upgrading. delivered at prices that are competitive with those mined locally, this will tend to reduce the price charged and to raise Currently, coal grades are based on their Useful Heat Value the efficiency of the mining operations. This is effectively (UHV) as set out in Table 10. The grading system is what has happened in a number of countries in Europe, unique to India (Sachdev, 1997), and was introduced to including Germany and the UK. promote the use of poor quality coals. The UHV is derived from the equation (Gollakota and others, 1998): The market is also affected by differing national policies covering emissions. In the USA, lower cost western coals are UHV = 8900 138 (ash% + moisture%) kcal/kg being increasingly used, primarily because of their lower (1 kcal/kg = 0.00419 MJ/kg) sulphur content. In countries like China and India, where huge quantities of coal are used internally, current pricing The band widths used for grading are quite wide, and in policies do not necessarily encourage the use of upgraded practice, instead of receiving the average UHV for the coals (Du and Liu, 1999). This is because the higher price grade ordered, power stations commonly receive coal which may be paid for a higher grade product does not which is either at the lowest value for the contracted grade, necessarily cover the cost of upgrading, and there is no or is in the lowest grade band. It should be noted that coal financial benefit from any reduction in emissions. prices are averaged, as is common in state owned and other very large enterprises. In fact, mining costs of coals In China, there has been overproduction of coal during the of the various grades will vary depending on the mine past three or four years, and this has driven the price of coal location and the local geology, and will differ from mine down. Steps are being taken to close many smaller unsafe to mine. local mines, thus reducing overcapacity, but this is not easy. In the recent World Bank report assessing the possible use of Most power station coals, representing more than 80% of clean coal technologies in China, relatively little was said the output in India, are in grades F and G. To a power about pricing. However, in the discussion about coal plant manager, there is a very significant difference in the preparation, it said that the current ratio of washed steam value of a coal which has (say) 11 MJ/kg UHV compared coal to raw steam coal is too low to encourage cleaning. with one that has 13.5 MJ/kg. If there is little or no benefit Currently the price ratio is about 1.2 to 1 for washed coal to to the mine from upgrading, the coal is likely to be raw coal while it needs to be nearer 1.5 to 1 (at today’s very delivered with a UHV near the minimum permissible.

Table 10 The grading and pricing of Indian thermal coals (Kant, 1995)

Grade D E F G

UHV, MJ/kg 20.7–17.6 17.6–14.1 14.1–10.0 10.0–5.5

Band width, MJ/kg 3.1 3.5 4.1 4.5 Total mine cost, 524 436 369 292 approximate Rs/t

Coal upgrading to reduce CO2 emissions 45 Energy transportation and market organisation

About three-quarters of India’s electric power comes from markets have become deregulated and more openly coal-fired plant. The country has extensive coal reserves, but competitive, fuel supply and power generation have been little gas or oil. The price structure and various tariffs levied increasingly regarded as completely separate activities. on imported fuels have contributed to the dominance of coal. Particularly in Europe, more electricity is being supplied While there may be some expansion of nuclear capacity, and across national boundaries. some growth in the use of gas, coal consumption for power generation will grow quickly, as there are power shortages in Associated with these changes, there are questions that relate many parts of the country (IEA, 2000). India also lacks an both to the security of supply under adverse conditions, and interconnected electricity grid to transfer power from states long term trends in costs. As most major investments, for with a surplus to those with a shortage. Many decisions in example in building power plants or major transmission lines, the energy sector have, until recently, been taken by state or imply a time horizon that stretches well beyond twenty years, central government, and the country is moving only slowly what happens in ten or fifteen years time is of importance. towards a more open and competitive system in the energy sector. Both China and India have significant coal transportation bottlenecks, and in parts of both countries the railways In a recent assessment by the IEA Coal Industry Advisory cannot always cope with the tonnages involved. As power Board (CIAB, 2002), the potential advantages of coal demand and coal use grows, these problems are likely to get washing were clearly recognised, and summarised as: worse. Part of the answer will be to reduce the amount of ● reducing transport costs because of the lower ash content; inert material carried, and to improve the organisation and ● increased grinding capacity; and reduced burner wear; capacity of the rail transport system. There is also a need to ● improved thermal efficiency with less slagging and look at the possibilities of generating power at the fouling; minemouth, and taking the electricity by wire. ● reduced maintenance costs and increased plant load factor. It is difficult to establish real long term costs and their However, factors associated with both coal and electricity probable trends, in places like China and India. This is pricing mean that the necessary plants may not be built. This because mining, coal transportation and power generation is because: have been under state control for many years, so the ● the impact of coal quality has not been seriously perceived economics of many activities may be unrealistic. It considered and costed; inevitably takes many years to adjust to the basic approaches ● washing results in coal losses between 8 and 15% and of a free and/or partly regulated market, thus establishing the high proportion of carbon in the rejects means that more realistic economics. special measures must be taken to avoid fires where the material is dumped, or the rejects must be used in minemouth FBCs; 7.2.1 Coal characterisation for ● mining companies are not sufficiently profitable to fund transportation the necessary investment and producers and consumers hold each other responsible for undertaking the Coal upgrading and its benefits are dependent on its accurate necessary investment. characterisation and analysis at different stages in the production and distribution chain. Without a knowledge base Thus price factors are likely to hold back investment in provided by test and analytical work on the specific coal washeries which could have a significant effect on the supply to a power generating unit, it is not possible to reduction of CO2 emissions from coal fired power generation provide quality assurance, and the whole purpose of in India. upgrading is thus negated.

In Russia, price reform in the energy sector was singled out The main stages in the coal-to-user chain are illustrated in as the most important change necessary to enable the energy Figure 20 which includes the alternatives of transportation by supplies to match the forecast growth in GDP of 6%/y up to sea (as used by many coal exporters) or overland (as used 2020 (IEA, 2002). Domestic energy prices are still internally by many of the worlds largest coal producers). subsidised as a result of the policies applied by the government of the Soviet Union. Current energy exports Product consistency and quality are achieved by a provide Russia with about one third of its foreign exchange combination of careful mine planning which involves earnings, but output of oil is in decline, and the whole sector, selective mining, beneficiation/cleaning and appropriate including coal production, as discussed in Section 6.21 blending, and then stockpile procedures and monitoring both requires substantial investment. Much of the money will before and after transportation. need to come from abroad. The realistic pricing of coal transportation will also have a significant impact on Coal characterisation is the foundation stone of quality investment and hence on coal use. control, and it is important that the people involved in each stage of the coal-to-user chain understand the significance of 7.2 Coal transportation the various parameters. In order to achieve strong partnerships between miners, transporters and users, all The pattern of energy transportation and market organisation aspects of the coal’s behaviour need to be understood in different countries varies widely. In many countries, as (Osborne and Hall, 1996). In the users context, this includes:

46 IEA CLEAN COAL CENTRE Energy transportation and market organisation

EXTRACTION - detailed exploration - surface - selective mining - underground - managing the mining operation for quality - preliminary size reduction for - separation of dirt on transport systems handling - separate stoarge

- exclusion of ‘foreign’ material by good design and maintenance STORAGE HOMOGENISATION of stockyard and transport systems AND/OR TRANSPORT (eg covered storage, concrete hardstands, good housekeeping) - stacking/reclaiming - blending - loading ship or wagons

PREPARATION - sizing separation and removal of impurities prior to use - cleaning - blending - dewatering

PCC FBC GASIFICATION

power production

Figure 20 Stages in the coal-to-user chain (modified from Couch, 1991; Osborne, 1997)

● handling and storage characteristics; ● ash fusion temperature; ● ease of grinding and pulverising; ● the Hardgrove Grindability Index. ● combustion characteristics; ● the mineral matter present and its behaviour at high The practices which have grown up to facilitate coal trading temperature, with the interactions of different have generally ensured the supply of coal to well understood components; levels of quality. These could usefully be applied to coals ● the environmental implications of its handling and use. used within a country to improve the relationships between suppliers and customers, and enable people to use upgraded During the ‘coal chain’, from mining through to use, rom coal with confidence. The principles can even be applied coal is significantly transformed into a specific product with where there is minemouth use with the supplier as the mine tight limits set on many of its properties to ensure efficient and the customer as the power plant. use. While most of the test methods available are essentially empirical in nature, there are standard well-established The context in which the costs arise is illustrated in methods that can be used by both coal producers and users. Figure 20, and Table 3 shows a cost breakdown in the coal- The parameters associated with coal handling are not to-electricity chain for Australian export coals into a market susceptible to standard tests as they depend on particle size such as that in Europe, where there are relatively stringent distribution and on how much surface moisture is present, emissions regulations. While each coal supply and use chain among other things. is unique, and presents its own opportunities, the diagram illustrates the relatively high costs at the user end. These are Among the parameters that may have specified limits within some 75% in the example quoted. Under other conditions, a supply contract are: the proportion might be somewhat lower, and it depends on ● heating value; the nature of the coal, the age and condition of the boiler, ● moisture content; and the regulations governing plant emissions. ● sulphur content; ● ash content, together with possible limits on certain ash It is clear that optimising both the mining and washing forming (inorganic) components; operations to improve the quality of the coal used, could

Coal upgrading to reduce CO2 emissions 47 Energy transportation and market organisation have a substantial effect on the users costs. Any changes Remote would have an effect both on the nature and amount of PCC washery wastes. The importance of the various components unit lowest ash product in the coal-to-electricity chain are discussed by Couch 500 MWe (1995) and by Osborne (1997).

Although only a relatively small contributor to the chain CFBC high ash coal described above, washing and upgrading the coal to reduce unit MINE WASHERY the operating cost of the boiler involves a significant increase 150 MWe reject in the fuel cost. This can be anything from 2 US$/t using the BFBC simplest one-step process to as much as 10 US$/t for a really unit complex washing operation where there is a high proportion of very fine material. The fines may have been deliberately residues generated in order to promote liberation of the mineral ash matter (Couch, 1991). The overall amount includes the cost of waste disposal, and is commonly expressed, as above, in Figure 21 The integration of coal washing with terms of the cost per tonne of cleaned coal product. both PCC and FBC boilers generally need to be approved or made at governmental 7.3 Coal transport versus level. At the very least, government support may be needed coal-by-wire to facilitate particular developments. The need for integrated energy planning is highlighted by Bose (1997). The decision Since more than 80% of the coal produced worldwide is about siting new power generation capacity may depend on: used in the country where it is mined, internal (overland) ● whether there is spare capacity on an existing railway transport costs are of great significance. The main bulk line linking the site with the mines; carrier of coal in China, the USA, India and Russia (where ● the costs of solid residues disposal near the consumers one half of the world’s coal is used) is the railways. In the site. This will almost certainly be much cheaper in or big coal exporting countries like Australia and South Africa, near the mine where the coal is produced; coal is taken to the coastal ports by rail. Road transport in ● emissions regulations, which may be slightly more lorries is more flexible, but is relatively expensive and more relaxed near a mine site than they are near a big city; environmentally intrusive. It is used mainly over short ● the terrain between the mine site and the electricity distances. There will also be some coastal shipping, and consumer/s, and whether or not high voltage cables barges that use internal waterways. could be guaranteed to provide a reliable supply. In areas of extreme climate (for example in Siberia or parts The cost of taking coal long distances; of loading and of northern China), coal can be supplied by rail when unloading it, and stacking it are very considerable. It can the weather is good, and stored locally to last through easily cost half as much again to transport the coal as it does the winter. If an area depends entirely on overhead to mine and prepare it. In parts of the world where the power lines it may be more vulnerable in the event of climate is extreme, there can be problems in loading and severe weather; unloading coal when it is freezing and coal stacks become ● whether or not there is an existing underutilised power solid lumps. In North America, coal is commonly stocked in grid for distribution; large silos, where it is protected from the most extreme ● the cost of power losses compared with those for weather. During the monsoon in India, coal stacks can loading and unloading coal, which will be accompanied become saturated with surface water, making the coal by some degradation in the form of both breakage and temporarily unusable. The provision of some covered storage contamination. is needed. In both China and India the demand for electric power is In every situation, when planning new power plants, it is forecast to rise substantially during the next twenty years and necessary to compare the long term costs of carrying out a investment will be required in new facilities both for power mining operation, of coal preparation and of transporting the generation and for distribution. In both countries it is likely coal to a distant power station which is local to the consumer that coal will play a large part in meeting increased demand, with those of constructing a minemouth power plant, and so decisions about where to invest – in improving the high voltage cables to take the power (possibly over several infrastructure for transporting coal or in increasing the hundred miles) to the customer. Each method has its capacity for the long distance transmission of substantial advantages and disadvantages. One method for making the amounts of power. best use of a coal resource in the Indian context is to wash the coal at the minemouth, and transport the higher grade Transport costs for traded coals can range typically from product to distant PCC units for power generation while about 5 US$/t from South Africa to Europe, or Australia to burning the lower grade product locally using FBC boilers, Japan, to nearer 10 $/t from Australia to Europe. These are see Figure 21. based on long distance transport in large ocean tankers. Inside producer countries transport costs between the mine Overall assessments and planning decisions on this scale and power station will be dependent on the distance

48 IEA CLEAN COAL CENTRE Energy transportation and market organisation involved, the method used, and on whether or not there is an plants which are less than 1000 km from the mine are likely existing infrastructure. Loading or stacking coal at any stage to receive a higher ash content fuel as a result. The purpose during its transportation costs at least another 1 or 1.50 $/t behind the directive is to encourage the use of coal each time it is done, so it is important to minimise the washing/upgrading for thermal coals, but it will be some number of intermediate stages en route. time before the new plants needed will be built.

China has particular problems. Coal is transported over long Bose (1997) discusses the relative merits of coal distances, as described in Section 6.5. An average of 620 Mt transportation versus transmission by high voltage cable. It is are taken an average distance of 580 km. Because of suggested that for much of the country, pithead generation transportation bottlenecks, Chinese officials have proposed a with the transmission of power could be cheaper than the strategy of transporting ‘coal-by-wire’. This would involve development of more distant generation facilities and local the construction of mine-mouth power stations in the coal load centres. A switch of policy in this direction would, mining regions, and providing a distribution grid to take the however, require the construction of long transmission lines power to the high demand centres. However, given the involving large amounts of capital investment and difficulties serious water shortage in the northern regions which affects in obtaining permitting and planning permissions. With the every aspect of economic and social development, this growth in coal demand, it is likely that parts of the railway strategy is not easily implemented or costed. Whether or not system may become overloaded. With the increased use of the establishment of very large thermal capacity in the dry coal washing, railway capacity can be increased which regions can be justified on a broader economic and social would provide more time for making the necessary long term basis is a complex issue which has not yet been resolved decisions. (IEA, 1999).

India has similar problems to those in China in terms of long 7.4 The effects of liberalised transport distances. The main coalfields are on the eastern markets side of the country, while many large consumers are long distances away. While India has a good railway The international market in coal, and in other fuels, has been infrastructure, much of the equipment used is old, and it effectively liberalised for many decades, and hence is would not easily cope with the forecast growth in coal use thoroughly competitive. Inside many of the major coal from around 300 Mt in 2000 to 610 Mt in 2020. As much as producing countries, free market conditions do not really 50 Mt of this may be in the form of imports (IEA, 2001a), apply, particularly to the purchase and use of coal. It has which will ease the internal transport/distribution problems. been traditional in many countries to encourage the In 1996-97, roughly 200 Mt of coal was used for power production of indigenous fuels, particularly coal, and this has generation, and half of it was transported more than 200 km. included the use of government subsidies. Some elements of Just over 50 Mt (ie a quarter) was transported more than subsidy remain, particularly in Germany. Countries which 1000 km (Selvakumaran and others, 1997; Selvakumaran still have partially regulated markets for coal include China, and Vasudevan, 1998). India and Russia. The costs of coal transportation have been effectively subsidised by central control, and there is control The recent Indian government regulation that any coal over who buys what from where. transported more than 1000 km must have an ash content of 32±2% should encourage the development of coal washeries, Where electricity markets have been liberalised and although what is probably needed is a fully flexible coal deregulated as in the USA and in many parts of Europe, there pricing policy such that higher grade, lower ash content coal, is a great deal more competition between fuels, and to an attracts a considerably higher price. There are conflicting extent between the supplies of different coals. European reports about how successful this regulation has been. It was generators are using increasing quantities of internationally reported in May 2002 that the requirement has been met at traded coals. The competition has tended to mean that plant the 35 power plants receiving coal from mines more than operators will assess the overall costs/economics of using 1000 km away. They consume some 95–100 Mt/y of coal, different grades or qualities of coal. The highest coal quality only a small part of which is washed. A total of some which would probably give the highest thermal efficiency 220–230 Mt/y is used for power generation, and the supply (and lowest CO2 emissions) is not necessarily the one chosen. of 32% ash coal was achieved largely by a remix of the It is not always easy to assess precisely the overall economics supplies going to those units. Only two plants have been of using coals of different quality, as the issues are complex, identified that may need to use some imported coal to meet with some effects being short term (and more easily the regulation (International Coal Report, 2002c). The measured) while others (like corrosion) are long term and not problems identified a month later (International Coal Report, always easily attributable to a particular coal characteristic. 2002d) revolved around the difficulties involved in blending When thoroughly validated with particular coals, models like a lower ash coal at the power plant when a delivery of (say) the CQIM and CQE can help in quantifying the economic 45% ash coal is received. Most Indian power stations operate effects of the use of different coals. on a ‘train-to-furnace’ basis, and coal is used almost as soon as it arrives. In addition, the supply of indigenous low ash Any move to reduce the amount of CO2 emitted would need coal (at about 18% ash) is mainly used for cokemaking. to be backed up with appropriate fiscal or regulatory Clearly the net result of the change will be beneficial in the policies, and a cost element associated with the emission long term as it will reduce rail transport costs, but some might have to be included. This could cover only marginal

Coal upgrading to reduce CO2 emissions 49 Energy transportation and market organisation emissions above some agreed base or minimum amount, most states, and it could be as much as 25% in certain providing incentives for small (but still possibly valuable) places; reductions, such as those achievable using methods such as ● the supply of free or subsidised electricity, particularly coal upgrading before use. to the agricultural sector has been a political issue and has not encouraged the efficient use of energy (Neogi, In Europe, the electricity market is liberalising, although 1997). there is still some way to go before there is an open market. The liberalisation is leading to more exchanges of electric There is thus an urgent need for restructuring, and for putting power, more trading and hence more intense competition the industry on a sound footing, possibly starting with the with accompanying pressures to achieve cost savings. At the upgrading of the metering system to ensure that power same time, generators have to comply with more and more generated is accounted for and eventually paid for. Without stringent environmental requirements. This raises serious reforms which would make the SEBs solvent, it is difficult to questions about how cost effectiveness and environmental make investment decisions, and difficult to persuade IPPs to concerns can be reconciled in an open electricity market build new plant. (Bourdier and others, 2002). It is in this context that questions about the value of coal upgrading which can bring In India there is a shortage of coal, and many plant managers operational benefits and reduce CO2 emissions, must be are glad to get their hands on anything that is available. As a considered. result, coal quality and thermal efficiency are not currently the most important issues for a manager. However, as the In China, some liberalisation and an oversupply of coal, has various structural issues are tackled, and as the immediate had the result that power plant operators have been able to requirement for all coal transported over 1000 km to be obtain the cheapest coals available. This has added below 34% ash, coal quality should move rapidly up the considerably to coal variability and plant operators may have agenda for the power generators, as poor quality coal causes accepted reductions in plant thermal efficiency in order to low thermal efficiencies and poor plant availabilities both of make use of a lower grade but cheaper coal. This is what is which have cost implications. implied by comments in Zhou and Mi (2000). The restructuring programme for the power industry has moved Flexible operating conditions forward recently (Global Private Power, 2002). Agreement has been reached in the politburo, the country’s highest One of the results of deregulation and of the application of decision-making body. It is intended to separate the competitive markets is that many more coal-fired units are transmission and generation assets of the State Power required to load follow than was previously the case. It is Corporation (SPC). There will be up to six regional grid essential that operational controls can achieve stable, reliable companies, and four competing generation companies. and repeatable start-ups and shut-downs, and good turn-down According to some reports each company will have more ratios (Mayfield and others, 1999). There are an increasing than 30 GWe of capacity after the reforms are implemented, number of interlocking and interrelated variables that must all making them very substantial players. Unbundling the SPC be taken into account. When operating on lower loads (or will represent an enormous and time-consuming task. The variable loads), there is, for example, a minimum feedwater generation companies will be central to the development of flow necessary to ensure proper cooling of the furnace walls. the electricity market in China which should become more To achieve low NOx emissions, the amount and distribution liberalised as competition is introduced progressively. These of the combustion air is critical – as is the pulverised coal developments are relevant to questions relating both to the distribution. Poor combustion can result in unacceptably high planning of new coal-fired capacity and of the choice of carbon in ash amounts. To avoid ash deposition, ash coals used and the coal qualities demanded. properties must avoid ‘stickyness’, and flue gas velocities must be high enough to encourage the free passage of fly ash. The Indian electricity industry is largely controlled by State At loads well below the boiler maximum rating, the Electricity Boards (SEBs) and by some central government consistency of the coal feed may become more of an issue in Corporations. The SEBs are vertically integrated order to maintain satisfactory combustion conditions. organisations controlling generation, transmission and distribution (Shahi, 1997). There are a number of serious Implications for plant management problems: ● in many parts of the country power cuts are common; One of the results of the change in market conditions is that ● there is inadequate available capacity, and a lack of load the person overseeing the new ‘kilowatt factory’ must change management; from being a plant manager into a business manager. The ● many of the distribution networks are weak and fragile; traditional target of high plant availability remains as ● transmission and distribution losses are reported to be important as ever, but today’s power plant must hit that target 18%, which is about double those in countries like under tight new constraints. These include: South Korea, Taiwan and Thailand. According to ● minimising long-term operating and maintenance costs; knowledgeable studies, peak time losses could be as ● minimising fuel costs; high as 48%; ● being flexible enough to take advantage of varying ● electricity metering is inadequate and unreliable, making power prices, possibly at different times of the day; commercial operation very difficult for many SEBs; ● meeting emissions regulations and other statutory ● the pilfering/theft of electricity is a major feature in requirements.

50 IEA CLEAN COAL CENTRE Energy transportation and market organisation

In deregulated and liberalised markets, plant managers must other participants. The incentive funds from the government wield a balanced blend of skills in engineering, accounting, will be paid to companies who achieve their emissions contract administration, safety, environmental requirements savings targets. and human resources (Makansi and Swanekamp, 1999). Many will need additional training to achieve this balance, While the scheme does not cover power generators, it does, and all can learn from meeting others involved at industry in principle, cover industrial users of coal. The scheme is conferences and workshops. Because of the speed of change likely to provide the necessary experience for a wider in some countries, it is important for companies and application of such trading schemes, and the coal industry operators to take account of the new management needs as and power generators should at least prepare for the possible well as looking at the technical issues relating to coal/fuel application of such trading schemes by, say, 2010. Before quality and the operational results achieved. such changes, there must be a careful evaluation of the likely effects, both on climate change and on energy prices, and in 7.5 The impacts of national particular the cost of electricity. emissions limits and of As the provisions of the Kyoto agreement are implemented emissions trading in various countries the use of various mechanisms for achieving CO2 emission reductions will extend. Emissions Investment and taxation policies can be used to encourage trading schemes are likely to be one such mechanism. Coal the use of new units using the latest clean coal technologies, upgrading can make a direct contribution to these reductions and possibly to encourage the retrofit of older plants. and emissions trading is one way in which the costs involved can be offset. Air pollution control requirements can provide incentive for the use of upgraded coals and/or for the use of CCTs, but 7.6 The regulatory framework these incentives are only of use if the requirements are enforced. In a report on China, one plant manager is reported The regulatory framework within which coal is traded can as saying that FGD might be more appealing if local have a considerable effect on its use and on the quality of the environmental bureaus actually carried out central coal used. In some countries, the regulations require that government policies on the fees due to be paid for SO2 only low sulphur content coal can be used – to reduce SO2 emissions. Fees covering the emission of various pollutants emissions – where boilers are not fitted with FGD. which violate air quality standards have not been adjusted regularly for inflation (Ohshita and Ortolano, 1999). It would be possible, and probably desirable in many countries, to introduce a regulation such that only washed Trading in emissions permits was pioneered in the USA thermal coals can be used in new power plants. An during the late 1990s with a scheme covering SO2 emissions. appropriate maximum ash content might be specified. There There are discussions taking place about extending the has been a move in this direction in India where all coal principle to cover NOx emissions. transported more than 1000 km has to have an ash content of below 32±2%, but this is only a relatively small step. The main effects of emissions trading in the USA have been the increased use of low sulphur content western Since the reductions in CO2 emissions from using upgraded subbituminous coals together with the construction of more coals are relatively modest, a regulatory framework and FGD facilities attached to coal-fired power plants. In many possibly appropriate fiscal or tax incentives may be needed other countries, reductions in SO2 emissions have been to encourage the use of upgraded coal. These must be geared achieved by regulation in that individual units are not to give benefits and incentives to plants where reductions of allowed to emit more than a certain amount of the pollutant. (say) five or ten per cent may be achievable. All such regulations and/or fiscal measures must be based on an The world’s first economy-wide greenhouse gas trading understanding of the processes and mechanisms involved, so system was launched in the UK in 2001. It is a voluntary that they can result in maximum benefit at minimum overall scheme backed by a government incentive of £215 million cost. In Market mechanisms for greenhouse gas emissions over the period 2003-08. During this initial period, the reduction (Rousaki, 2001), various methods including electricity generators will not be participants as there was carbon/energy taxes, subsidies, voluntary agreements and concern that it might cause the generators to switch too emissions trading mechanisms are discussed, and this subject rapidly from coal to gas. The EU wants to see a European- is not pursued further here. wide scheme by 2005 (Power in Europe, 2001).

The UK scheme was devised by the Emissions Trading Group which was set up in June 1999. It is supported by government and by more than a hundred companies and trade bodies. It is estimated that a successful trading scheme could deliver carbon savings of 2 Mt/y (7.7 Mt/y of CO2). Under the scheme, a company accepts a cap on its emissions. If it emits less than its cap, it can sell its excess saving, or can bank it. If it exceeds its cap, it must buy permits from

Coal upgrading to reduce CO2 emissions 51 8 The effects of coal upgrading

Coal upgrading has a number of effects. Washing will result maintenance costs. In this connection, it is not only the in reductions in the amounts of mineral matter present, amount of ash present that is of significance, but its although there may be a small increase in moisture content. composition; There are likely to be reductions in the amounts of trace ● the coal moisture content. Energy is needed to evaporate elements present, and reductions in sulphur content. Drying the water in the coal, and some of this is lost in the flue will reduce the moisture content, and hence increase the gases. In addition, with high moisture contents, the heating value. Briquetting will improve the combustion furnace temperature is generally lower, reducing heat characteristics and facilitate the inclusion of additives which transfer rates. Thus a lower moisture content in the coal will capture the sulphur present. generally increases boiler efficiency; ● coal reactivity which is governed by volatile content and The increases in heating value of the coal which are the result petrographic composition, affects the combustion rate of upgrading, and improvements in the fuel consistency result and hence flame stability and the residence time in more efficient and controllable combustion. As a result, the necessary for complete burnout. thermal efficiency of both boilers and stoves is increased and CO2 emissions per unit of energy used are reduced. Coal upgrading affects the ash content, and sometimes the ash composition, and also the coal moisture content. It does There are other process implications of coal upgrading, but not impact the coal reactivity which is an inherent property they are mainly second order effects in terms of boiler of a particular coal being used. Generally, reductions in both efficiency. Reducing the ash content (mineral matter content) the ash and moisture content of the coal results in higher of a coal may make it easier to grind, so that the energy used overall thermal efficiency, and this increase can be as much in the mills is reduced and the coal may be milled to a slightly as 5 percentage points. finer size, thus burning out more quickly. The amount of pyrite present is likely to be reduced in a washed coal thus The beneficiation or upgrading of a thermal coal is intended reducing the load on any flue gas desulphurisation (FGD) unit, not only to improve its combustion properties, but to minimise or on the amount of SO2 emitted if there is no FGD stage. the presence of abrasive and corrosive materials. These can adversely affect the pulverisers, classifiers, PC distribution Possible negative aspects of coal upgrading include: pipes, heat exchanger tubes in the boiler and induced draft fans. ● increased amounts of washery wastes for disposal and The presence of the mineral matter leads to both fouling and reduced amounts of product (ie there will be more slagging causing reductions in the boiler thermal efficiency, carbon ‘loss’); and possible longer term damage to the heat exchangers (steam ● effluents and emissions from a coal drying unit; superheaters and reheaters – and the economiser). ● an increased spontaneous combustion tendency in dried low rank coals. The relation between coal quality and boiler performance is a complex one. The boiler, once built, has built-in inflexibilities, in that the heat transfer areas in different parts 8.1 On existing PCC boiler of the boiler are determined, mill capacity and pulverised efficiency coal distribution are determined, as is the flexibility in supplying combustion air. Coal-fired boilers are designed for Coal quality has a number of important impacts on boiler a ‘design’ coal, while in practice the fuel may differ from the efficiency and power plant operation. In the boiler, design specification in important respects. An upgraded coal combustion converts the chemical energy in the coal to may provide a fuel with a lower ash content, increased thermal energy, and transfers the heat produced to convert heating value and which ensures that the boiler can operate water into superheated steam at high temperature. The at a higher thermal efficiency than its design value. There energy stored in the high pressure steam is then released in may be limitations to the effects of the improvement, in that the turbine and converted into electricity. the boiler is working in tandem with a steam turbine, and the overall efficiency is that of the combined system. A number of coal properties affect boiler performance and efficiency (Juniper and Pohl, 1997), and hence the amount of There are surprisingly few detailed studies on the effects of CO2 produced per MWe of electricity generated. These are using a cleaned coal in a coal-fired boiler compared with principally: rom material. This is because if a boiler has been operating ● the amount of ash in the coal. This results principally unsatisfactorily, a decision is likely to be made to switch to from the mineral matter present, although with lower an alternative coal supply rather than to upgrade/wash the rank coals the amount of organically bound material can existing supply. This is because of the substantial lead time become significant. The solids leaving the system take and investment involved in building a CPP. While the effects some heat with them, but the principal effects of the ash of coal quality on plant performance will certainly be are to interfere with heat transfer in the boiler (Couch, assessed by the larger power generators, much of the 1994). Ash deposition on heat transfer surfaces can have knowledge will be regarded as proprietary information and a marked impact on boiler efficiency, availability and on consequently is not published.

52 IEA CLEAN COAL CENTRE The effects of coal upgrading Studies in China Studies in India

While most of the steam coal used in China is not washed, In India a comprehensive study on the practical and an example of the benefits obtained from using a higher economic results of the use of upgraded coal in power plants quality coal, is quoted (ESMAP, 2001). The Taiyuan CPP has been carried out (Kant, 1995). Pricing policies were provides a washed coal whose ash content has been reduced discussed in Section 7.1. from 30% to 15%, and sulphur content from 2.1% to 1.2%. On a 300 MWe unit at Huangtai in Shandong province Coal upgrading can be achieved by the reduction of dirt and burning an unwashed coal from Hebei province with an LHV rock during mining, the separation of stone and slate in of 21 MJ/kg coal consumption was 980,000 t/y. On changing primary crushers and coal washing at the minemouth. In the to a washed Taiyuan coal from Shanxi, with an LHV of study, an economic analysis shows that the case for 27 MJ/kg, coal consumption dropped to 790,000 t/y. There upgrading is strong, for coal-fired power stations more than were reductions in auxiliary power consumption and in 200 km from the mine. The beneficiation of two grades of maintenance costs, particularly those associated with milling. coal is considered, in both cases using a simple jig treating The improvement in coal quality helped to stabilise boiler +13 mm coal. The probable increase in moisture content of combustion conditions such that oil support was no longer the washed coal does not seem to have been taken into required. There were resultant decreases in the number of account, although this will only affect the outcome trains required for transporting coal to the plant, and in the marginally by a few percentage points. It might push the amount of fly ash for disposal. ‘break even’ distance where there is an advantage in upgrading from just over 200 km to perhaps 300 km. Even after allowing for the costs of boiler modifications involving changes to the heat transfer sections, and Upgrading a G grade coal with a UHV of 10 MJ/kg to an especially the waterwall refractory, to maintain the design E grade with a UHV of 16.1 MJ/kg results in a 71% yield, steam conditions, there were overall cost savings. The while upgrading an F grade coal with 11.2 MJ/kg to reduction in CO2 emissions was not quantified as the 16.1 MJ/kg can be done with a yield of 78%, see Table 11 . principal incentive for the change was the reduction in These figures will be based on average washability data for sulphur content which meant that it was not necessary to Indian coals, and there would in practice be mine-to-mine retrofit a FGD unit. variation. In the study, the rejects contain around 65% ash,

Table 11 Typical results for the beneficiation of Indian thermal coals (Kant, 1995)

G grade coal F grade coal

raw coal clean coal rejects raw coal clean coal rejects

Ash, % ar 40 30 64.5 37.9 30 65.9

Moisture, % total 10 10 10 10 10 10

Grade, UHV, MJ/kg G E ungraded F E ungraded

Yield % 100 71 29 100 78 22

Cost/sale value Rs/t 292 525 80 396 600 80

Coal cost at power station

at 200 km distance, 432 665 – 509 740 –

at 600 km, 672 905 – 749 980 –

at 1000 km 912 1145 – 989 1220 –

Energy cost at power station Rs/106 kcal or 4200 MJ

at 200 km distance, 181 173 – 189 193 –

at 600 km, 282 236 – 278 255 –

at 1000 km 382 298 – 368 318 –

Coal upgrading to reduce CO2 emissions 53 The effects of coal upgrading and can be burned in small minemouth FBC boilers see The principal and most widely used models are the CQIM Couch, (1998). They are valued at 80 Rs/t. However, if the and CQE developed in the USA, but others have been overall reduction of CO2 emissions is included as a principal established for use within particular utilities, and for use by objective of the coal beneficiation, then this use may have to coal producers to help assess coal value. be questioned. The FBC boilers would not be as thermally efficient as the PCC boilers burning the upgraded coal. If the With the increased power of computers, and the availability rejects are dumped rather than burned, then the economics of more data, models can be used to represent extremely presented in the Kant (1995) paper would have to be complex situations. Potentially, computer simulations can adjusted, but it would only increase the cost of the give insight into the phenomena occurring inside the beneficiated coal by about 3–4%. The projected reduction in combustion fireball, and during the subsequent flow of the CO2 emissions from the use of the upgraded coals is around hot gases through the banks of heat transfer tubes. In 4.5% and there are a number of other environmental gains. addition, overall models can be validated and developed with These include a substantial reduction in the amount of ash the input of empirical data, based on experience. The results for disposal from the power plant, and reductions in SO2 can then be used to make predictions about the effects of a emissions. There are also significant gains in equipment change on coal quality on the operation of a boiler. reliability, boiler operational stability (and hence a decrease in oil consumption), an increase in availability and decreased The CQE utilises several models, including the: maintenance costs. With existing plants it is possible to ● Coal Quality Impact Model (CQIM); achieve additional power output without capital cost, other ● NOx Prediction Model (NOxPERT); than that involved in the construction of the necessary CPPs. ● Acid Rain Advisor (ARA); It might be advantageous to spend some capital to optimise ● Boiler Expert, comprising the Slagging Expert the gains from having a consistent upgraded fuel supply, but (SLAGGO) and Fouling Expert (FOULER). that could be assessed in a separate exercise. This should further reduce overall CO2 emissions per MWe generated. It provides coal burning utilities with a predictive tool to help the selection of coal (and hence of the optimum coal In addition to coal upgrading, other changes in boiler quality/degree of upgrading) for a specific boiler. The operating conditions can also affect (and improve) boiler assessment looks at operational efficiency, cost and efficiency. These include rehabilitating or replacing some of emissions. The software has been distributed to 35 utilities in the auxiliary equipment such as mills and fans. Also the USA, and to one in the UK, through membership of controlling the amount of excess oxygen present, and EPRI, and it is available for use worldwide (US DOE, 2001). ensuring good distribution of the pulverised coal in the A considerable amount of test work is necessary to validate boiler. the constituent models for a particular unit, and most of the work to date has been based on US coals. It was reported by Studies in the USA Thompson and Giovanni (1993), that to evaluate a CQIM covering two different coals including pulveriser and There have been some studies into the impact of coal quality precipitator testing, could cost more than US$0.5 million. on boiler performance, mainly dating from the 1980s and early 1990s. At the Cumberland and Paradise plants in Utilities will always select test methods so as to maximise Tennessee, USA, coal preparation was initiated in the 1980s the information gained at minimum cost, so some to reduce the sulphur content of the coal, but there were smaller-scale results may be incorporated. The existence of additional benefits in having an upgraded coal. With the use the models offers the possibility of building up a substantial of upgraded coal, for example, boiler efficiency rose 1.5% body of experience relating to the effects of coal upgrading from around 88% because of a decrease in the use of excess on the thermal efficiency of operation and hence of assessing air from 138% to 128%. This was a direct result of the the potential for reducing CO2 emissions. elimination of slagging and fouling problems which had occurred when rom coal was used (Smith, 1988). At the Where the economics of coal supplies to an existing power Keystone plant in Indiana, built in the late 1960s, firstly station are being evaluated, capital charges are fixed. and the selective mining was introduced, and then a CPP was built in principal variable cost factors are: the mid-1980s. The plant has two 936 MWe supercritical ● fuel costs, which are the net costs of the delivered coal boilers. As a result of the improvement in coal quality, unit less the value of any by-products or with the added availability increased from 64% to 70% while the average disposal costs; hourly net generation achieved increased from 730 to ● operating and maintenance costs, to which the pulverising 780 MWe (Harrison and others, 1997). The improvements in plant contribute some 30%, and which are affected by the plant performance would have been accompanied by a slagging and fouling behaviour of the ash; ● reduction in CO2 emissions per unit generated although at the amount of auxiliary power used which affects the the time, this was not thought to be an important issue, and power available for sale, and is influenced by coal the emphasis was on overall cost reduction. properties and the behaviour of the mineral matter.

The use of models In a study on the impact of coal properties on PCC generation, the cost implications were assessed (Juniper and During the 1990s, a number of models were developed to Pohl, 1996). The results are presented in Table 12. In the list quantify the effects of coal quality on boiler performance. the base case condition is mentioned first:

54 IEA CLEAN COAL CENTRE The effects of coal upgrading

Table 12 Estimated bulk energy costs for different coals (Juniper and Pohl, 1996)

base high low high high Coal information high ash low LHV high iron case moisture volatile quartz sulphur LHV, MJ/kg ar 27.4 26.8 26.1 27.4 25.2 27.4 27.4 27.4

ash content, % ar 11.3 11.0 15.0 11.3 11.3 11.3 11.3 11.3

carbon in ash, % 4.8 4.8 3.5 8.9 4.8 4.8 4.8 4.8

coal price, A$/t 70 68.48 66.69 70.00 64.44 70.00 70.00 70.00

ash sale, A$/t of coal 1.92 1.87 2.55 0.00 1.92 1.92 1.92 1.92

residue, A$/t of coal 1.35 1.32 1.80 9.01 1.35 1.35 1.35 1.35

net coal price, A$/t 69.44 67.93 65.94 79.01 63.88 69.44 69.44 69.44

Costs

fuel costs, million A$/y 187.7 188.1 187.2 215.3 187.3 187.7 187.7 187.7

O&M, million A$/y 25.4 25.42 25.97 25.43 25.60 25.59 26.03 25.88

power generated, GWh/y 7.337 7.335 7.328 7.336 7.327 7.337 7.337 7.320

power supply cost, ¢/kWh 2.904 2.911 2.909 3.282 2.906 2.907 2.913 2.918

change, ±% – +0.24 + 0.17 +13.02 +0.07 +0.10 +0.31 +0.48

the data are assumed to refer to the costs in Australian dollars

● increase in the moisture content from 8 to 10% (high generation costs of a number of other coal properties over moisture); and above the coal cost in terms of its energy content. ● increase in the ash content from 12% to 16% adb (high ash); Although the exercise is only based on the use of a simple ● reduction in the volatile matter content from 34% to power generation cost model, it illustrates the potential gains 25% daf (low volatile); from upgrading, where ash content (for example) might be ● reduction in the specific energy (LHV ar) from 27.4 to reduced by 10% or 15% (compared with the 4% in the 25.2 MJ/kg daf (low specific energy); study), and the ash deposition characteristics may also be ● reduction in the Hardgrove Index HGI from 55 to 45 improved. (low HGI); ● increase in the amount of free quartz present by 70% (high quartz); 8.2 On the application of advanced ● increase in the Fe2O3 in the ash from 7.7 to 12.0% to CCTs assess the impact of slagging (high iron); ● increase in the sulphur content from 0.5 to1.3% adb to Because of lack of operational experience, it is not possible assess the impact on FGD costs (high sulphur). to assess accurately the impacts of coal quality variations on the use of IGCC or of PFBC, and there is limited experience While the particular example probably illustrates the effects with PCC using supercritical steam in plants commissioned relating to different coals exported to Japan and used in a during the past ten years. With IGCC, lower grade coals plant fitted with FGD, the order of magnitude of the different would probably be used in a fluidised bed gasifier, while effects is relevant. Even quite small changes in coal quality most commercial-scale experience is based on entrained flow can affect the cost of the power generated. The relative gasifiers for which a high ash content or high moisture ranking of the properties in order of the least impact to the content coal would be unsuitable. The only entrained flow most impact was: IGCC unit operating with a low grade coal is that at Puertallano in Spain where the coal is blended with petcoke ● Base < low LHV < high quartz < high ash < high in a 50:50 mix. With the exception of the big units in eastern moisture < high iron < high sulphur < low volatiles Germany using brown coal, nearly all the supercritical PCC units use high quality coals. The assessment was somewhat overshadowed by the effect of the use of a coal with a low volatiles content which meant 8.3 On industrial and domestic use that the carbon in ash was so high that it could not be sold to cement manufacturers, so it acquired a negative ‘value’. It For smaller-scale use, coal briquettes offer significant does however show the cost benefit of using a lower sulphur advantages over the use of sized coal which is what has content coal, and of the importance of the deposition traditionally been used. The following information is quoted characteristics of the ash. It also illustrates the impact on as applying to China, but much the same will be true in other

Coal upgrading to reduce CO2 emissions 55 The effects of coal upgrading countries where raw coal is used industrially and domestically (ESMAP, 2001).

For residential stoves, and for small-scale cooking, the thermal efficiency averages around 15% when burning coal. Switching to egg-shaped coal briquettes in an appropriate low-cost stove, the thermal efficiency can be increased to 20–25%, and using honeycomb briquettes the thermal efficiency can be increased to as much as 30–50%. Using a specially designed high efficiency stove, thermal efficiencies of as much as 60% can be achieved.

For industrial-scale use, in boilers, kilns and steam locomotives, improvements in thermal efficiency of around 5 percentage points from perhaps 25% to 30% can be expected from the use of briquettes.

In addition to these gains in thermal efficiency, and resultant reduction in CO2 emissions which could be of the order of 20–25%, other pollutants would be reduced. Compared with the use of lump coal, honeycomb briquettes used domestically can reduce particulates by 40–60%, CO by 80%, NOx by 55%, benzo(a)pyrene by 90% and SO2 emissions by 40–60% provided desulphurisation additives are incorporated. In industrial use, the reductions can be 60% for particulates, 25% for NOx, 50% for benzo(a)pyrene and 40–60% for SO2 .

56 IEA CLEAN COAL CENTRE 9 Potential for CO2 reductions

The starting point for assessing the potential for coal this is associated with the availability of substantial upgrading to play a significant part in reducing CO2 quantities of natural gas, including that in Russia, and with emissions is the IEA projection for worldwide coal use the impact of tightening environmental regulation. 2000-20 (IEA, 2001a). The projection is that from 2002-20, more than 100 Gt of coal will be used, most of it for power Forecast changes up to 2020 include: generation. In 1997, 61% of the coal produced was used for ● a steady increase in use in the USA, principally for power generation. By 2020, this proportion will have power generation. The Energy Information increased to 69%. This translates into a 68% increase in the Administration forecasts growth in coal production from amount of coal used for power generation in 2020 compared 980 Mt in 2000 to 1260 Mt in 2020 (Generation Week, with 1997, while coal production itself has only increased by 2001). There will be a significant increase in the 50%. proportion of the coal coming from western mines, and by 2020, nearly two-thirds of the coal will be from these Much of the coal will be used in existing power plants, mines. This means longer rail transportation distances although some will be used in the more efficient supercritical (and costs) for bulk users in the eastern US, and will steam PCC or IGCC units that are likely to be built to increase interest in coal drying before transportation to replace older, smaller and more polluting units, and to reduce costs as most of the coal is subbituminous. In provide any additional capacity needed. It is in the existing addition, the coal-fired units in the USA are commonly units that the greatest opportunities exist for reducing around 500–600 MWe in size, and their average age is emissions while units using the newer technologies may over 30 years (Armor, 2001). In order to maintain require the use of upgraded coals in order to operate output, a considerable number of new (or retrofitted) efficiently on a long term basis. While any such prediction is units will be needed, in addition to others that will subject to some error, and the key uncertainly is the impact increase the total coal-fired capacity; of future environmental policies, it is quite clear that a very ● in China the situation is less easy to forecast. There is substantial amount of coal will be used. likely to be a steady growth in the use of coal for power generation, but only about half the coal is currently used Alongside this, both lignite and hard coal fired units emit in this way. Substantial quantities are used for both more CO2 per kWh of power produced, so reductions are of domestic and industrial heating, and as a base for more significance than they are for other fuels and power chemicals production. Some 180 Mt/y is currently used generation sources. for coking, and this is likely to reduce to around 120–130 Mt/y as the use of primitive coking ovens is phased out. China is seeking to close (or at least licence) 9.1 Coal tonnages that can be a great number of the village and township mines, not upgraded least because of their poor safety record (more than 5000 miners were killed last year). In addition these Until recently, CO2 emissions have not been considered as a mines have low production costs and thus undercut the major factor when designing new plant. Other emissions, price of coal coming from larger, safer and well such as those of particulates, SO2 and NOx have been regulated units. The use of coal on a small scale for regulated, and have therefore been the subject of strict domestic and industrial use is likely to decline, as it did control in many countries. The choice of both fuel and in developed countries from the 1960s onwards, because technology has been based on economic assessments and on of the difficulties in controlling pollution; factors such as the security of supply. The assessments will ● in India, the use of coal is likely to grow, as it is the have included some measure of expected changes during the country’s main indigenous energy source. There are, potential 30–40 year life of a major unit built, but these are however, problems with the use of local coals because of very difficult to assess. Thermal efficiency has been mainly a their high ash content and poor washability contributor to a reduction in fuel costs, and some plants have characteristics. Some of the demand in India may be met been deliberately designed to burn low grade, low cost coal by imported coal; at a lower thermal efficiency simply because the overall ● other big coal producers include Australia, Russia, South economic outcome was seen as favourable. Africa, Germany, Poland, Ukraine, Turkey, Greece and North Korea. Some countries, like Japan, South Korea Forecast changes in the demand for coal are shown in and several in Europe, are significant coal importers. In Table 13, based on IEA predictions. Note that they are each country it will be the availability of alternative expressed in mtce, and not Mt of production, and therefore fuels at a competitive cost that will determine changes in do not distinguish between the bituminous coals and those of the levels of coal use. In countries who import, the coal lower rank. While such assessments are difficult, and will used has already been upgraded, whereas much of the inevitably not be precisely followed, the trends are likely to coal used inside the country where it has been produced be broadly correct, with increasing amounts of coal being has not been upgraded. used worldwide, particularly in China, India and the USA. Only in OECD Europe is a drop in coal use foreseen, and Based on the figures quoted earlier in this chapter, and the

Coal upgrading to reduce CO2 emissions 57 Potential for CO2 reductions

Table 13 Forecast growth in world coal use (based on IEA, 2001a,b)

1997 2020

demand, Mtce %share for power demand, Mtce %share for power annual % increase

Europe 490 66 430 78 –0.6

North America 775 92 925 94 0.8

Pacific 185 57 205 68 0.4

OECD total 1450 79 1560 86 0.3

Africa 125 57 200 57 2.2

China 940 40 1680 55 2.6

India 220 67 520 76 3.5

Other Asia 145 46 325 71 3.6

Latin America 40 35 80 53 3.1

Middle East 10 83 25 89 4.4

Transition economies 290 48 400 55 1.5

Non-OECD total 1770 47 3230 60 2.6

World total 3220 61 4790 69 1.7

note that the demand figures relate to countries consuming coal, including the 12% of the world's total coal production which is internationally traded. In converting the original table from Mtoe to Mtce, the factor of 0.7 Mtoe = 1 Mtce has been used country by country discussion, a broad estimate of the and there is little potential for further upgrading, as most amount of coal in various parts of the world that could be is already washed. usefully upgraded (with resultant reductions in CO2 emissions) is given in Table 14. The IEA assessment is that the reserve base in OECD Europe is becoming increasingly depleted, and that In OECD Europe, the main producers are: production will continue to decline, underlying the need for ● the Czech Republic, where coal use is seen to be a reliable and competitive international coal market so that declining and the potential for upgrading is marginal; demand can be met by imports where necessary (IEA, ● Germany, where, again, production will decline, but 2001a). where there are substantial amounts of low rank coal used which could be upgraded by drying. In the table it In OECD North America the two producers are: is estimated that 90 Mt/y could be upgraded usefully in ● Canada, where production is seen as growing only 2002 and 70 Mt/y in 2020; slightly, and some 10 Mt/y of bituminous coal and ● Greece, where the use of low rank coals is seen as 20 Mt/y of low rank coal might usefully be upgraded; growing, and it is estimated that 40 Mt/y could currently and, be usefully upgraded, and 50 Mt/y in 2020; ● the USA, where coal production and use are seen as ● Poland, where coal production is declining, and growing significantly, particularly of lower rank currently 20 Mt/y of bituminous coal and 30 Mt/y of subbituminous coal. The amounts that might be usefully brown coal could be usefully upgraded, while in 2020 it upgraded are estimated to be 40 Mt/y of bituminous coal would reduce to 15 Mt/y and 25 Mt/y; and 200 Mt/y of low rank coal currently, and 30 Mt/y of ● Spain, where production is seen to be declining, and bituminous and 350 Mt/y of low rank coal in 2020. there is little potential for further upgrading; There may be some additional tonnages of bituminous ● Turkey, where production of its low grade lignites is coal that could usefully be more thoroughly washed, but seen as increasing, and some 40 Mt/y could currently be it is difficult to estimate what this amount is. The upgraded, rising to 80 Mt/y by 2020; various regulatory pressures on power generators will ● the UK where coal production is seen to be declining, tend to encourage the use of cleaner coals.

58 IEA CLEAN COAL CENTRE Potential for CO2 reductions

Table 14 Potential for upgrading (Approximate figures based on IEA, 2001a,b, together with data from this report)

2002 – potential for upgrading, Mt 2020 – potential for upgrading, Mt

bituminous low rank bituminous low rank

OECD

Europe 20 200 15 230

North America 50 220 40 370

Pacific 10 50 10 50

Non-OECD

Africa 20 0 25 0

China 500 20 1000 50

India 200 20 400 30

other Asia 10 20 20 30

Latin America 20 0 30 0

Middle East 0 0 0 0

Transition economies 50 30 70 40

World total 880 560 1610 800

these numbers represent the amounts of coal produced, but not necessarily consumed in the country of origin the numbers relate to the total amount of coal consumed in 2002 of just under 4500 Mt/y and an estimate of something over 6000 Mt/y in 2020. the amount of coal which is internationally traded is forecast to grow from more than 500 Mt/y currently to 700–800 Mt/y by 2020

In the OECD Pacific region, the only significant player is be upgraded, and by 2020, the amounts could well be Australia where a high proportion of the bituminous coal is 1000 Mt/y of bituminous, and 50 Mt/y of low rank coal. already washed, and much of it is exported. Approximately 10 Mt/y of bituminous coal and 50 Mt/y of low rank brown In India, the increase in coal use (1997-2020) is forecast to coal might usefully be upgraded, and this is not likely to be nearly 140%, and while some of this may be imported change much, even as coal production rises. coal, most will be indigenous production. From the forecasts reported here, it is some 200 Mt/y of production of In the non-OECD regions, there are fewer projections of bituminous coal that could be usefully upgraded plus growth rates for coal production. There are several major 20 Mt/y of low rank coal, currently, and this amount will coal producers, including China and India, where much of increase to 400 Mt/y of bituminous and 30 Mt/y of lignite. the thermal coal used has not been washed. In both countries, much of the washed coal is used in coke ovens or The countries which are included as ‘non-OECD, other Asia’ in China it is exported. include Bangladesh, Indonesia, Korea, Malaysia, Pakistan, Philippines, Thailand and Vietnam. Of these, only Indonesia, In non-OECD Africa, the dominant producer is South Africa, Thailand and Vietnam have significant coal production. which is a major exporting country. Because much of the Demand, overall, is forecast to increase by 125% from 1997 coal is exported, most is washed, but there is still scope for to 2020. The main country where additional upgrading might some additional upgrading, and the estimate here is that the contribute to reducing CO2 emissions is Indonesia from amount which could be upgraded will increase from 20 Mt/y which large amounts of coal are exported. Because most currently to 25 Mt/y in 2020. coals are already upgraded, the scope for additional effort is limited, and the overall estimates of the tonnages that might In China, a huge increase in coal production and use is usefully be upgraded from the other-Asia area are currently forecast. From 1997 to 2020, the increase is 80%. Because 10 Mt/y of bituminous coal and 20 Mt/y of low rank coal, most coal is not currently upgraded before use, there is and by 2020, 20 Mt/y of bituminous coal and 30 Mt/y of low enormous scope for coal washing/preparation. Relatively rank coal. small amounts of low rank coal are used, although this may well increase because underground mining currently The coal producing countries of Latin America are Brazil, predominates. The overall estimates relate to orders of Chile, Colombia, Mexico and Venezuela. Brazil, Chile and magnitude rather than precise tonnages of coal. The broad Mexico have generally low grade coals while Colombia and estimates from this exercise are that some 500 Mt/y of Venezuela are significant coal exporters, with coals upgraded bituminous coal and 20 Mt/y of low rank coal could usefully for the international market. It is estimated that the amount

Coal upgrading to reduce CO2 emissions 59 Potential for CO2 reductions of coal which could currently be usefully upgraded is 18 Sulphur, wt% 20 Mt/y, and that this will increase to 30 Mt/y by 2020. 17 Moisture, wt% 16 Ash, wt% 15 The coal producing countries in transition include Bulgaria, 14 Kazakhstan, Romania and Russia. Some have very low grade 13 reserves. Russia has a wide range of reserves, including low 12 11 rank, bituminous and anthracite. Consumption is forecast to 10 increase by some 40% from 1997 to 2020, a modest 9 increase. For upgrading, the tonnages which might usefully % As-fired, 8 be treated are currently 50 Mt/y of bituminous and 30 Mt/y 7 6 of low rank, and by 2020 it could be 70 Mt/y of bituminous 5 and 40 Mt/y of low rank. 4 3 While all these figures are very approximate, they provide an 2 ‘order of magnitude’ assessment of the potential for further 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 coal upgrading. Interest in the low rank coals is (perhaps Annual average surprisingly) concentrated within the OECD countries, with Figure 22 Coal quality changes at the Cumberland the brown coals of Australia and Germany, and the power plant (Smith 1988) subbituminous coals in the western USA being dominant. There are also large potential tonnages in Kansk-Ashinsk, in Russia, and in Turkey. For bituminous coals, the greatest 90.0 opportunities are clearly in China and India. 89.8 89.6 89.4 9.2 Prospective increases in 89.2 89.0 thermal efficiency 88.8 88.6 Along with fuel quality, there are many factors that affect the 88.4 efficiency of coal-fired power generation and distribution, all 88.2 of which will impact on the amount of fuel used, and the % Boiler efficiency, 88.0 CO emitted. These include: 87.8 Unit 1 2 87.6 Unit 2 ● the equipment (boiler and ancillaries) design and its 87.4 maintenance; 87.2 ● the use of outdated instrumentation and inadequate 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 controls; Annual average ● operation in an environment of fluctuating grid conditions; Figure 23 Boiler efficiency changes at the ● high transmission and distribution losses. Cumberland power plant (Smith, 1988) This section concentrates on the efficiencies achieved, and The resultant boiler efficiency improvements were on reductions in CO2 emissions associated with improved significant, see Figure 23. The average efficiency increased fuel quality. from about 87.8% to 89.6% in one boiler and 89.2% in the other when the cleaned coal was used (Smith, 1988).

9.2.1 In coal-fired boilers In India There have been few published studies which quantify the In an extensive study in India, Bhatt and Jothibasu (1999), effects of using different quality coal on boiler performance. Bhatt and Rajkumar (1999), Bhatt and Mandi (1999) and Part of the reason for this is that although a great many Bhatt and others (1999), discuss the possibilities of plants have used coals of different qualities, the data performance enhancement in coal fired power plants. Coal obtained are regarded as being proprietary. Some of the fired units produce three-quarters of the electricity used. The studies were touched on in the context of the effects of coal units have conventional natural circulation, single drum, upgrading in Chapter 8, while here the focus is on CO2 subcritical, radiant boilers, and most are tangentially fired reductions through increased overall thermal efficiency. from the corners. The basic problem faced by the power stations is the supply of variable high ash content coals with One important study is that carried out at the Cumberland a heating value of 12.5 to 14 MJ/kg; ash content 40–50%, plant in the USA during the 1980s. The plant has two quartz in ash 8–18% and silica in ash 60–80%. The high ash identical 1300 MWe boilers which were built at the end of and quartz burdens create high rates of erosion, poor the 1970s. They were operated on rom coal for a number of emissivity and flame temperature in the furnace, poor years, but in 1981 a CPP was commissioned, and the coal radiative transfer and hence the need for enhanced quality improved, see Figure 22. The main objective was to convective transfer and blockages in the furnace parts where reduce the sulphur content of the coal, but at the same time there is a dense matrix of tubes, such as in the economiser. the ash was reduced from around 14–15% to less than 10%. Because of the ash, it is difficult for the pulverisers to mill to

60 IEA CLEAN COAL CENTRE Potential for CO2 reductions

Table 15 Design and operating efficiencies of coal-fired units of different sizes in India (Bhatt, 2000)

Design efficiencies (%) at rated capacity Design greenhouse emissions at rated capacity, Unit size, MWe gross auxiliary T & D kg/kWh

500 37.0 95.5 90.0 1.312

210 36.1 93.4 90.0 1.377

120 33.4 92.5 90.0 1.503

62.5 30.0 91.3 90.0 1.696

30 27.7 90.9 90.0 1.841

average 36.00 94.0 90.0 1.371

Operating efficiencies (%) at rated capacity Operating greenhouse emissions at rated capacity,

gross auxiliary T & D kg/kWh

500 32.5 92.7 78.0 1.335

210 31.3 90.5 78.0 1.420

120 26.1 89.0 78.0 1.731

62.5 24.5 88.7 78.0 1.850

30 22.0 88.0 78.0 2.077

average 30.0 90.0 78.0 1.489

T & D = transmission and distribution the required fineness and the coarse coal passing into the small units, some of which were installed in the 1950s and furnace creates a range of problems. 1960s. The design and operating efficiencies of the different size units is shown in Table 15. The data shows the The coal quality related difficulties are because of the substantial increase in thermal efficiency achieved with the presence of oversized coal (over 400 mm size lumps), use of larger units. It also illustrates the difference between excessive fines, sometimes over 60%, excessive moisture, design values and those achieved under operating conditions. sometimes over 20%, and the presence of extraneous Coal upgrading would make a contribution to increasing the materials such as stones and mud. There can also be an operating efficiencies. excessive low volatile fraction in the coal. Coal cleaning/upgrading has been shown to reduce erosion rates In Table 16 a range of values of efficiencies and of on boiler components by as much as 50–60%, with a greenhouse gas emissions for Indian power stations is reduction in annual maintenance costs of some 35%. It presented. This shows the reductions which can be obtained should also result in better performance in the pulverisers from the use of larger boilers; of coal upgrading; of the and a reduction in carbon in ash because of the finer grind application of the best current technology throughout the achieved. It should also result in easier control of excess air generation and distribution system; and the use of state-of- levels and a reduction in the need for sootblowing. the art technology (which would require coals of consistent quality and with as little ash as possible). The assumption In a discussion of the situation in India, Bhatt (2000) estimated made in this table about state-of-the-art technology is that that the use of state-of-the-art technology relating to coal the current progress towards overall thermal efficiencies of quality, boiler/generator design, instrumentation and control, 50% will be maintained. At the moment, the highest thermal and high voltage distribution systems, could reduce CO2 efficiencies obtained in coal-fired units are in the 45% emissions to nearly 45% of their present level. For a given region, but efforts are being maintained to develop new consumption level, CO2 emissions could be halved, and the alloys to enable supercritical steam PCC units to operate at first stage in achieving that reduction would be the introduction temperatures up to 700ºC and to enable gas turbines in IGCC of coal washing and upgrading to provide a consistent, lower units to operate with higher inlet temperatures. ash content feedstock for power generation plants. Of the major parameters which can bring immediate It will also be necessary to replace old small units whose improvements to the efficiency of energy utilisation, Bhatt thermal efficiency is considerably lower than that which is (2000) lists: now readily achievable. In India, some 50% of the installed ● control of the ash in coal (ie coal upgrading); coal-fired capacity is accounted for by units of 210 MWe, ● improving the plant load factor (PLF) which is affected while 20% comes from 500 MWe units. There are still many by the quality of the coal among other factors;

Coal upgrading to reduce CO2 emissions 61 Potential for CO2 reductions

Table 16 The range of efficiencies and of greenhouse gas emissions for coal-fired Indian power stations (Bhatt, 2000)

Operating efficiencies (%) at rated capacity Operating greenhouse emissions at rated capacity

gross auxiliary T&D kg/kWh

Current range of operating 22.0–33.0 88.0–92.7 58–84 1.224–2.798 values

Current all-Indiaaverage value 30.0 90.0 78.0 1.489

Best practice with existing 37.0 95.0 83.8 1.065 technology (subcritical steam)

State-of-the-art technology 50.0 96.0 94.0 0.695

T&D = transmission and distribution

93 15% clearly a potential source of reductions in greenhouse gas emissions. This will involve network optimisation, reconfiguration and renovation, and possibly the introduction of higher voltage distribution systems. The introduction of 91 instrumentation and control systems for Supervisory Control 12% and Data Acquisition (SCADA) are likely to result in a significant reduction in transmission losses. 10% In other countries 89 It is probable that there is much the same situation in China 4% in relation to the overall efficiency of coal-fired power generation, with some small old units in need of moisture replacement, and an inefficient transmission system. China

index, kg/GJ 87 2 has invested in just a few large supercritical steam coal-fired

CO units, and has some modernised systems. However, as in India, as much as 15% of the rural population have no power supplies at all, and much of the modernisation has taken 85 place around the coastal cities in the south-west, like 30 40 50 60 70 Shanghai which have rapidly industrialised. There are still Ash, % huge quantities of unwashed coal used in China. Because the amounts are even greater than in India, there are substantial potential CO2 reductions to be had. Figure 24 Variation of specific CO2 generation per GJ with varying ash and moisture contents in the coal (Bhatt, 2000) In the USA, much of the coal used for power generation will have undergone some upgrading. The main focus on the ● performance enhancement through plant overhaul and environmental front in recent times has been the reduction of regular maintenance; SO2 emissions. Limits have been set, and there is a trading ● the effects of plant renovation and modernisation. system in emissions permits. One outcome of this has been the greatly increased use of Powder River Basin As the coal quality deteriorates, greenhouse gas emissions subbituminous coal which is low in sulphur, which may well increase. The low-grade coals used in India have specific have contributed to a small increase in CO2 emissions CO2 generation indices in the range of 85–93 kg/GJ. The because of its reduced heating value compared with an variation in CO2 generation for coals with varying ash and eastern bituminous coal. moisture content is shown in Figure 24. 9.2.2 By using briquettes It is estimated that the potential for greenhouse gas reduction is 2–5% for operational optimisation and improved PLF; 5–9% Briquettes tend to burn more efficiently than sized coal. This for thorough plant overhauls, and 17–22% for major plant can bring substantial benefits in terms of the thermal renovation and modernisation. While these figures indicate that efficiency of combustion devices, and hence in terms of the major contribution to the reduction of CO2 emissions will reductions in CO2 emissions. come from plant overhaul and replacement, coal upgrading will make a significant contribution to each of these options. In existing residential ovens and stoves used for heating or cooking, the thermal efficiency averages just 15% in China. In addition, the transmission and distribution efficiency is With the use of a new stove and a switch to using

62 IEA CLEAN COAL CENTRE Potential for CO2 reductions egg-shaped briquettes, thermal efficiencies of 20–25% can ● lower ash and/or moisture content in the coal; be achieved. Honeycomb briquettes, which are the most ● higher LHVs; common briquette in China, offer an even higher thermal ● reduced transport volumes (and hence cost); efficiency, in the range 30–50% in low cost (100 yuan or ● reduced sulphur content (in many cases); US$15) new stoves. In a more sophisticated stove costing ● reduction in the amounts of various trace elements 500 yuan or US$75, the thermal efficiency can reach 60%. present in most cases; ● much more consistent coal quality. In industrial boilers, kilns and steam locomotives, the use of briquettes can improve thermal efficiencies and reduce coal Coal upgrading should be considered as an essential use by 10–20% (ESMAP, 2001). contributor to increasing the efficiency of coal fired power generation. In many places in the world it would go hand-in- In a study reported by Minchener (1999), the effects of hand with other actions, including changes to the heat improving the quality of briquettes used in various transfer surfaces in the boiler to take advantage of the applications are shown to increase combustion efficiency and improved combustion conditions. It is thus not easy to isolate hence reduce CO2 emissions. In Guihzou province a the precise effect solely of the upgrading on thermal demonstration was carried out at the Shuitian Briquetting efficiency and consequently on CO2 emissions. Plant. This has a single process line with a capacity of 25 t/h. Process control at the plant was considerably improved with Coal upgrading will facilitate the use of the CCTs being the use of a vibratory feeder and belt weigher to control the developed, and of modern boiler design. In China and India, feed rate and variable screw feeders for accurate additions of and in some other developing countries, the average thermal binder and lime. New binders were tried, but costs in China efficiency of the coal-fired units in use is between 27 and made it difficult to use the materials which would have been 29%. The reasons for the low efficiency (which results in used in a western country. Further work is needed by Chinese relatively high CO2 emissions) include small unit size, the experts to find a locally effective binder system at an inconsistent and poor quality coal being used, and low load acceptable cost. Even with the process modifications made, factors associated with poor availability. The effects of coal the briquette quality and consistency were improved, and users upgrading with the resultant supply of a more consistent fuel reported an increase in combustion efficiency of 4–5 would be to increase the average thermal efficiency by at percentage points. The increase was from 85–89% in one case least 2–3 percentage points on existing PCC boilers. It would and 73–78% in another. In a test on a bath house boiler, the make an even greater contribution where new and use of briquettes increased the combustion efficiency by appropriately designed plant is built. 16 percentage points compared to the use of raw coal, raising the boiler efficiency to 67%, with a corresponding increase in The overall reductions in CO2 emissions which are possible steam output from 270 to 330 kg/h. cannot be quantified, but along with other plant and operational measures there are substantial potential benefits to be gained The main focus of this work has been the reduction in SO2 from upgrading coal before use. Based on IEA projections, and emissions associated with the incorporation of lime in the the assessments in this report, an additional 100 Gt of coal briquettes, and reduced emissions of particulates. The could usefully be upgraded between now and 2020 compared interest in combustion efficiency has been associated with with current practice. Based on the operating efficiencies for the balance between the increased cost of using briquettes Indian power plants quoted in Tables 15 and 16, it would compared to raw coal against the reduced quantity of appear that there is potential for increasing the average briquettes required. In order to encourage the use of efficiency of generation from 30 to 35% using current well briquettes there may need to be regulatory pressure or established technology. The largest contribution to this would incentives of some kind. Minchener (1999) estimated that if be coal upgrading. As noted above, some changes in the heat 20% of Chinese boilers burned briquettes, there could be transfer areas in boilers would be necessary to take advantage reductions in CO2 emissions of 100,000 t/y. Growth in the of the improved coal quality. Such a change could be achieved use of briquettes is forecast by Zhang (1999). These are for in both China and India – and in some other places using low both domestic and industrial use. In 1995 use was 50 Mt, grade coals such as Greece, Russia and Turkey. From the units and in 2000 it was forecast to be 60 Mt. By 2020, use is concerned, the reduction in CO2 emissions would be about expected to grow to 80 Mt. 12%, see Figure 25. Even in the USA, there should be some additional scope for upgrading, and this is significant because of the large tonnages used. In Australia, Germany and the USA 9.3 Overall benefits from there are opportunities for the use of drying. upgrading The application of new technologies, including PCC boilers The potential benefits to be obtained from coal preparation using supercritical steam cycles, and of IGCC which can were discussed in an earlier Clean Coal Centre report increase the average thermal efficiency of a generation unit (Couch, 2000). This study has focused on the impacts on to 40–45% would be dependent, largely, on the availability greenhouse gas (CO2) emissions, and has widened the of upgraded coals. perspective to include other forms of coal upgrading, including drying and briquetting. 9.4 Global CO2 emissions The overall benefits include: Although climate change is thought to be one of the most

Coal upgrading to reduce CO2 emissions 63 Potential for CO2 reductions

2.00 25000

1.80 20000

1.60 , Mt

2 15000 CO 1.40 5000 CO2 emissions 1.20

emissions 0 2 1.00 1971 1975 1979 1983 1987 1991 1995 1999 Year 0.80 coal oil gas

t coal used/CO Figure 26 CO emissions by fuel, worldwide totals 0.60 t coal used 2 (IEA, 2001f) 0.40

10000 0.20 9000 8000 0.00 7000 20 25 30 35 40 45 50 55 60 6000 Thermal efficiency, % 5000 4000

efficiency % CO2 emissions tonnes of coal used 3000 20 1.734 0.676 2000

25 1.387 0.541 Electricity generation, TWh 1000 30 1.156 0.450 35 0.991 0.388 0 40 0.867 0.338 1971 1975 1979 1983 1987 1991 1995 1999 45 0.771 0.300 Year 50 0.694 0.270 55 0.631 0.246 coal oil gas nuclear hydro other 60 0.578 0.225 Figure 27 Electricity generation by fuel, worldwide Figure 25 Change in CO2 emissions at different (IEA, 2001f) thermal efficiencies (World Coal Institute, 1998) The estimates of CO2 emissions worldwide by fuel type are shown in Figure 26, and the fuel used for power generation significant challenges facing the international community, is shown in Figure 27. The figures cover the period 1971-98, there is difficulty in determining how to count the emissions and current IEA projections are that the amount of coal used reductions which accrue from projects, and from changes in 2020 will be nearly 50% more than that used in 1997 such as those discussed in this report. One solution to the (IEA, 2001a). Thus, given the aims of the UNFCCC any and problem is to develop emission baselines, against which every contribution to reducing the CO2 emissions from coal particular projects can be measured, and this is discussed in use is of importance. Emission Baselines. Estimating the Unknown (IEA, 2000). The projected growth in coal demand is shown in Table 13. The ultimate objective of the 1992 United Nations Growth is forecast in every area, except in Europe. The most Framework Convention on Climate Change (UNFCCC) as significant increases are those in Asia and North America set out in Article 2 is the ‘stabilisation of greenhouse gas which account for some 90% of the growth worldwide. In concentrations in the atmosphere at a level that would India the use of coal is seen as more than doubling, with an prevent dangerous anthropogenic interference with the average annual growth rate of 3.5%. In China it is 2.6%, and climate system’. Given the world’s need for energy, ways of in North America, 0.8%. mitigating the formation of greenhouse gases become increasingly important. 9.4.1 Reductions associated with coal upgrading In this section, the overall figures for CO2 emissions are discussed, together with the situation in four countries who In terms of the CO2 emissions involved, the graphs in make a significant contribution to the world total, and Figures 28, 29 and 30 show the CO2 emissions, and fuel use illustrate the order of magnitude of the opportunities patterns in the three largest coal-using countries. The available. The approach concentrates on the use of coal for improvements in the overall thermal efficiency of coal use power generation, and in China on other uses as well. associated with the use of upgraded coals, particularly in

64 IEA CLEAN COAL CENTRE Potential for CO2 reductions

3500 small unit size, in many cases, inconsistent and poor quality coal being used, together with low load factors associated 3000 with poor availability or even lack of fuel supply (IEA, 2500 1998b; Power in Asia, 1999). The effects of coal upgrading, 2000 with the resultant supply of a more consistent, lower ash , Mt 2 content fuel, could be to increase the average thermal 1500 CO efficiency by at least 2–3 percentage points on existing PCC 1000 boilers, possibly as much as 4–5 percentage points. There 500 can be even bigger increases with boiler upgrades and with the use of larger newer units, but the supply of higher grade 0 coal is an essential contribution. The effect of a change in 1971 1975 1979 1983 1987 1991 1995 1999 efficiency from, say, 28% to, say, 33% is shown in Figure Year 25, and a reduction in CO2 emissions of up to 15%, or some coal oil gas 190 g/kWh generated is achievable. If the average efficiency is raised from 33 to 38% a further reduction of some 175 g/kWh is achievable. With the widespread application of Figure 28 CO2 emissions by fuel in China (IEA, 2001f) the state-of-the-art technologies such as supercritical steam PCC or of IGCC, which also benefit from the use of 6000 upgraded coals, average efficiencies might be brought up to nearer 43%. 5000

4000 While these figures should only be used to indicate the order of magnitude of any possible savings, what is indicated is the , Mt 2 3000 potential for reducing CO2 emissions from one third of the

CO world’s coal production (which is not currently upgraded) by 2000 at least 15%, and possibly more. This is shown in Table 14 1000 and discussed in Section 9.1.

0 There is a similar story in India, where the power station 1971 1975 1979 1983 1987 1991 1995 1999 coals are not generally washed, and where there are Year shortages of supply, such that power station managers will coal oil gas take almost any grade of coal which they can get their hands on, without worrying too much about consistency or quality. Average thermal efficiencies for power generating plant, Figure 29 CO2 emissions by fuel in the USA (IEA, 2001f) predominantly coal-fired, are quoted as being 27% in 1995 (IEA, 1998b), and as 30% by Bhatt (2000). Since part of the 1000 reason for these low efficiencies is the use of unwashed, low 900 grade and inconsistent quality coals, there is room for 800 improvement, and for reducing CO2 emissions per MWe 700 generated, as a result. 600 , Mt 2 500 The kind of overall reductions achieved from the upgrading

CO 400 of the additional one third of the coal produced worldwide 300 would be of the order of 15% from that coal, representing 200 about 5% of the world total from coal use in the period up to 100 2020. 0 1971 1975 1979 1983 1987 1991 1995 1999 Year coal oil gas

Figure 30 CO2 emissions by fuel in India (IEA, 2001f) Asia, would have a small but significant effect on the total emissions for a given level of coal use. Taking the example of China, where coal upgrading could have a significant effect on CO2 emissions. The average thermal efficiency of the coal-fired units is quoted as being between 27 and 29%. This compares with an average efficiency of around 38% in OECD countries. The reasons for the relatively low efficiency (which results in increased CO2 emissions) include

Coal upgrading to reduce CO2 emissions 65 10 Conclusions

Coal upgrading before use is not commonly discussed when for assessing the impact of coal quality on boiler operation considering which CCTs can make a significant contribution are complex and there are many interacting variables. More to programmes to reduce CO2 emissions. While its work is needed in this area. contribution is limited, upgrading is a key stage in coal utilisation and in the coal-to-electricity chain. It also has an Since the reductions in CO2 emissions from using upgraded important role to play in industrial and domestic use. coals are relatively modest, a regulatory framework and possibly appropriate fiscal or tax incentives may be needed The greatest potential for upgrading is in the coals from: to encourage the use of upgraded coal. These must be geared ● China, where relatively little thermal coal is washed and to give benefits and incentives to plants where reductions of where coal use is seen as increasing at the rate of (say) five or ten per cent may be achievable. All such 2.6%/y up to 2020; regulations and/or fiscal measures must be based on an ● the USA, where although much of the thermal coal is understanding of the processes and mechanisms involved, so washed, there are opportunities for deeper cleaning, and that they can result in maximum benefit at minimum overall possibly for drying the increasing amounts of cost. subbituminous coal used. Coal use is seen as increasing at the rate of 0.8%/y to 2020; It is not easy to isolate the precise effect solely of the ● India, where little of the thermal coal is washed, and upgrading on thermal efficiency and consequently on CO2 coal use is seen as increasing at the rate of 3.6%/y to emissions, but it is the use of this well established 2020. technology alongside others which will bring maximum benefit. In China and India, the effects of coal upgrading There are also significant opportunities in countries like with the resultant supply of a more consistent fuel would be Greece, Russia and Turkey, and possibly with the brown to increase the average thermal efficiency by at least coals in Germany and Australia. In all cases, large quantities 2–3 percentage points on existing PCC boilers. It would of coal are due to be used for power generation up to (and make an even greater contribution where new and beyond) 2020. appropriately designed plant is built. Coal upgrading should be considered as an essential contributor to increasing the A high proportion of traded steam coals are washed, but efficiency of coal fired power generation. In many places in these account for only around 17% of the bituminous coal the world it would go hand-in-hand with other actions, produced, and only 12% of total worldwide coal production. including changes to the heat transfer surfaces in the boiler Traded coals have to meet stringent specifications set by to take advantage of the improved combustion conditions. In power plant purchasers in a competitive market, but there is addition, the application of some of the developing CCTs the trade-off between using a higher grade coal at increased such as IGCC and supercritical PCC require the use of a cost compared with using a lower grade, cheaper one and high grade coal to achieve the maximum overall thermal accepting increased operating costs. Using a lower grade efficiency. Even FBC which is suitable for lower grade coals coal usually results in reduced thermal efficiency and will operate more efficiently with a higher grade feed. With increased CO2 emissions. global CO2 emissions from coal use estimated to be around 8 Gt/y, intensive coal upgrading could contribute to as much With the exception of the Kansk-Achinsk brown coals in as 0.3 to 0.5 Gt/y of avoided CO2, which would be a useful Russia, the largest tonnage use of low rank coals is in OECD amount in the context of the need to reduce overall countries. Hence the main places where coal drying may be greenhouse gas emissions. appropriate are Australia, Germany and the USA, together with Greece and Turkey (which use low grade lignites) – as well as in Russia.

The potential additional amount of coal that could be upgraded in 2002 resulting in reduced CO2 emissions is estimated to be 880 Mt/y of bituminous coal and 560 Mt/y of low rank coal. These amounts increase to 1600 Mt/y of bituminous coal and 800 Mt/y of low rank coal by 2020. These amounts are in the context of total coal usage in 2002 of approximately 4500 Mt/y rising to over 6000 Mt/y (4500 mtce is the IEA estimate for coal demand) by 2020.

The overall effects of coal quality on plant operation and hence profitability are still not always fully understood. The development of tools like the Coal Quality Impact Model have been important, but this needs validation in different places based on the boilers and coals used. The procedures

66 IEA CLEAN COAL CENTRE 11 References

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