Coal Upgrading to Reduce CO2 Emissions
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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).