The development of underground coal gasifi cation by Mike Rycroft, features editor

Underground coal gasification (UCG) coupled with carbon capture and storage (CCS) offers huge potential as a method of exploiting large coal resources on land and offshore. In addition to numerous projects worldwide, there are several projects both active and being planned in South Africa.

UCG is a method of converting unworked being used as the base reference. UCG does not reveal the true value. The UCGA coal, while still in the ground, into a somewhat “falls in the cracks” as far as is addressing this with the UN expert group combustible gas suitable for industrial regulatory treatment is concerned. In on resource classification and all agree heating, power generation, and the South Africa, UCG is specified as mining that it is better to work together towards a manufacture of hydrogen, diesel fuel in the proposed Mineral and Petroleum common solution. The economics of UCG or chemical feedstock. The economics resources development Act (MPRDA) can be very site specific, and depend are attractive, it offers carbon capture amendments. heavily on the coal seam characteristics. options, and the cost of operating and implementing UCG is lower than many There is a constant positioning of UCG What is needed for the industry to move other coal technologies. The technology in the context of coal mining. Pilot and forward? demonstration plants are an essential offers the possibility to exploit coal reserves  A level playing field, with other energy that are unmineable due to geological part of UCG resource prospecting, but sources (nuclear, oil and gas, wind, reasons and proximity to population prospecting timelines cater for conventional coal bed methane, coal mining) for centres, in a manner which will cause mining. Pilot and demonstration plants the licensing of UCG minimum impact on surface features under mining rights have other challenges.  Clear regulatory and environmental and minimise the pollution associated frameworks with mining. Details required  A recognised resource valuation Regulators may need to deal with standard such as a syngas index The development of UCG competing bids from other users of coal.  An industry recognised best practice According to Julie Lauder, CEO of the It is sometimes difficult for a new industry standard Underground Coal Gasification Association since others are already licensed. In (UCGA), UCG has the potential to countries such as Australia, there are issues  Industry recognised training significantly increase global coal stocks over overlapping tenements CBM/UCG, What is holding back UCG development? and turn these into a high value synthetic though both can be done at the same site! gas, cleanly, safely and cheaply. UCG Despite 50 years of trials no commercial There is no clear definition for UCG nor a could increase the world’s economically UCG project has been demonstrated, standard UCG reserve valuation formula. recoverable coal reserves substantially. according to John Kessels of the IEA [2]. Investors, bankers and analysts alike There is a steady decline in the quality Recent progress with pilot projects show of the coal produced with exhaustion would prefer an industry standard, giving considerable promise, and commercial of reserves of higher grade coals. Many one less uncertainty to worry about. The operations could be possible within countries are turning increasingly to the current coal valuation method relates to ten years, providing greatly increased use of indigenous reserves of lower quality mining and is not suitable for UCG as it confidence in the technology. coals, sometimes the only significant energy resource available. But there are many aspects and challenges in taking a new technology such as UCG to market [1].

Global UCG activity MoU’s have been signed in Canada, Hungary, India, Indonesia, Poland, South Africa, Turkey, USA, and Vietnam, and research projects are underway in Bulgaria, China, Germany and Japan. There is a huge upturn in interest and potential investment in Australia, which is leading the world. Many coal-rich nations have engaged in dialogue and investigation, with increased commercial activity and potential for the next few years.

Basic regulatory issues Modern UCG is a new industry and therefore new to everyone, the public, the media and also the regulators. Licensing policies for UCG are now being written in some countries, with mining usually Fig. 1: Block diagram of the UCG gas treatment process.

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Constraints There is a lack of understanding of the requirements of a successful UCG project by both investors and regulators, and the topic is poorly covered in the literature. In addition there is an acute shortage of people with appropriate inter- disciplinary academic and management skills and experience as well as a lack of understanding of the geological knowledge needed. UCG is being promoted by different industry groups who do not share knowledge and government support is lacking to underpin deployment of the technology. The major trials, over the last 50 years Fig. 2: Externally fired gas turbine. or more have been in the USSR, Europe, USA, Australia, South Africa and China, during which other technologies have of parameters which are controllable or providing greatly increased confidence progressed dramatically (e.g. computer measurable. Modelling can help, but few in the technology. Keeping more of the power and use, and directional drilling). models have been validated. Site selection knowledge in the public domain could Tests rarely ‘proved’ more than one or two criteria have not yet been well defined greatly enhance the chances of UCG aspects of the technology, and many as there is insufficient information and becoming an accepted and widely had unwanted side effects. The USSR experience. Environmental issues e.g. gas applicable technology. claimed commercial scale operations, escape through fractured rocks, or water but only some 15 – 20 Mt of coal was contamination have not been adequately Power for Africa gasified and syngas quality was variable. addressed. The process requires a unique The European model of large power The US DOE programme from 1973 – 1989 multi-disciplinary integration of knowledge plants is not the solution for providing addressed engineering concerns and from geology and hydrogeology with the under-developed rural areas with power, compared methods for enhancing coal thermodynamics of gasification. says Alan Golding of Analytika Holdings permeability. The development of the [3]. Current thinking is more inclined to controlled retracting injection point (CRIP) Site selection is key to success smaller more distributed power generation was a major advance. The single most important decision that will units which reduce distribution costs. Current pilot projects determine the technical and economic The advantage of UCG is that it can be performance of UCG is site selection. A economical at 60 MW. UCG commercial operations are being successful test in one location where the assessed in: There are many areas in Africa that are geology is favourable does not prove that without power that have coalfields that  Australia by Carbon Energy at UCG can be widely applied. It will need could be exploited using UCG, such as: Bloodwood Creek, and Linc Energy at a series of successful demonstrations in Chinchilla different geological settings to establish North East Basin  South Africa at Eskom’s Majuba power where UCG can be safely carried out on plant a commercial scale without environmental The only information is from drilling undertaken to the east in Zimbabwe.  China at the Gonggou mine, damage, as coals lie in such a wide There are indications that there could be Wulanchabu city, Inner Mongolia variety of geological settings, at different depths, seam thickness and with different thick occurrences at depth of coal but to  Canada (Alberta) Swan Hills at a depth permeabilities and properties. date no borehole has intersected coal in of 1400 m Botswana. Pilots have been successfully carried Linking UCG and CCS out with no reported environmental North West Basin The Bloodwood Creek development in problems. All are planning to expand Australia is being linked to a practical The most unexplored coal basin in to demonstration and then commercial demonstration of CCS. CCS may add Botswana is mapped as Upper Karoo (an scale. Relatively little has been published another site selection constraint in that area of sedimentary and volcanic rocks). about the outcomes (or the problems/ Any exploration that has been undertaken it will be easier to do if there are nearby challenges). is solely for water supply. Research into part-depleted oil wells or gas fields. Use of water borehole logs has indicated that this Advantages/opportunities the cavities formed in the coal seam by area is not necessarily Upper Karoo and this UCG has been suggested for CCS but this The process allows exploitation of coal area may have potential as an exploration will require an extensive effort to establish generally considered uneconomic for target as there are descriptions of black the conditions for long-term containment. conventional mining, with minimal surface shale and carbonaceous mudstone. disturbance as most of the ash remains Conclusions underground. UCG could provide low- Western Basin Despite 50 years of trials no commercial cost syngas in a number of countries with A largely unexplored coal basin in substantial coal resources. Significant trials UCG project has been demonstrated. The Botswana has known coal intersections. are now producing encouraging results but development of new technologies and Similar areas exist in Zambia, Tanzania and these are still on a very small scale (roughly the increase in the value of energy may Malawi. We should consider reversing our equivalent to 10 – 20 MW output). change this. There has been a great deal exploration philosophy – find the market of progress recently with some projects first! The deeper coalfields of Southern Restricting factors showing considerable promise. The and Eastern Africa might be able to The process takes place underground and current pilots could result in commercial- supply power to the more remote areas. out of sight and there are a limited number scale operations within four or five years Bringing power to these areas will facilitate

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development and therefore UCG can be seen in a positive light.

UCG projects in South Africa.

Eskom – Majuba Typical condensate production volume based on UCG Majuba piloting results to date are : Normal operation: 40 – 75 g/Nm3 of synthetic gas. Start up/ramp up: 110 – 200 g/Nm3 of synthetic gas. Gasifier shutdown: 500 – 2000 g/Nm3 of synthetic gas. Typical condensate consists of 90% water Fig. 3a: Location of the project. Fig. 3b: Coal seam thickness. and 10% hydrocarbons, ammonia and hydrogen sulphide. The problem lies with extraction of high value products from Challenges encountered include the the hydrocarbons, which can comprise UCG syngas [6]. These include: absence of off-the-shelf equipment for the UCG syngas application. Eskom’s recently benzene, toluene, ethyl benzene, and  Hydrogen extraction from UCG syngas. xylenes (BTEX), phenols, coal ash and tars, appointed engineering consultants will  Alternative power generation options aromatic hydrocarbons and sulphides, now be approached to co-develop a to gas turbines such as externally fired ammonia, boron, cyanide, carbon design with its research engineers. The gas turbines. monoxide and hydrogen sulphide. The design specification of the furnace and removal of hydrocarbons is a complex task. Treatment and reuse/disposal of UCG heat exchanger will be the gate keeper condensate has the objectives of for the project moving forward to the UCG power generation design challenges identifying the viable technologies to demonstration phase. The information centre around the integration of the gas remove hydrocarbons from the UCG gained from these research studies will treatment unit because the design is condensate and evaluating if the assist the UCG pilot operation in the based on a theoretical gas specification, proposed technologies are suitable at development of a basic design for a as the pilot plant cannot be operated or demonstration plant scale, while ensuring Majuba UCG open cycle gas turbine optimised to be completely representative that the overall integration of these stand- of commercial scale plant. Design (OCGT) power plant and the associated alone technologies provides a satisfactory risks include: undefined waxes, volatile Majuba UCG OCGT business case. condensate treatment system. metals, particulates, and wide range gas Sasol's involvement composition, condensate concentration, Two technologies were adjudicated as pressure and temperature requirements feasible and are currently being evaluated. The objective of Sasol in developing UCG for removal. is constructive engagement towards  Liquid-liquid extraction optimal UCG development, according Two processes are being looked at  Bioremediation to Wessel Bonnet of Sasol New Energy for integration, namely the particulate [7]. Sasol recognises concerns about scrubber and hydrogen sulphide removal. Bioremediation involves the biodegrading the unconventional nature of UCG, and In the scrubber there are a variety of of hydrocarbons and the removal of any potential development will follow design options including dry cold, dry ammonia. The current test involves a prescribed regulatory processes, as well hot, wet hot, and wet cold scrubbing. sample size of 1000:l of condensate and as extensive public participation to ensure There is a need to assess boundary feed has run over a period of six months. It an optimal project, following a responsible, conditions and effect on downstream was found possible to remove BTEX, PAH, step-wise approach to evaluate and processes when making the decision. aliphatic hydrocarbons and nitrogen demonstrate UCG . When considering the hydrogen sulphide compounds. A system for extracting removal stage, capital cost and removal hydrogen from UCG syngas was developed There are many similarities between fixed efficiencies are not the only criteria for by the South African Institute of Advanced bed gasification and UCG and Sasol technology selection. It is necessary to look Materials Chemistry (SAIAMC) at the has a rich history in developing and at emissions legislation and other factors University of Western Cape. The project operating surface gasification technology such as feed conditions (temperature, was co-funded by Eskom and had the value chains. More than 1-billion t of pressure, concentration), whether pre- objective of determining if 99,999% purity coal have been processed at Sasol or post combustion is to be used, utility H2 can be produced from UCG syngas. The Synfuels and more than 20-million gasifier requirements and ease of operation. Other project allowed the simultaneous testing operating hours, using 84 Mk IV Sasol necessary design considerations in the gas of a hydrogen sulphide adsorbent and a fixed-bed dry-bottom gasifiers producing handling process include auxiliary power selective hydrogen membrane system. > 3-million MN3/h. usage, turbine fuel specifications, fuel The externally fired gas turbine (EFGT) Sasol has the experience needed characterisation, acceptance by various project has the goal of determining the for assessment and characterisation technology providers, and available feasibility of the use of UCG syngas in an of coal reserves for optimum heating and cooling utilities. EFGT for power generation, by testing with beneficiation, including geo-hydrology; Research, testing and development of a modified truck turbo charger to operate coal characterisation; mine layout, as a gas turbine. This approach has the production scheduling; planning etc. It downstream UCG technology options benefits of limited fuel pre-treatment. also has experience in the fields of low According to Megashnee Munsamy of the Application of established post combustion temperature and low pressure gasification Sustainability Division of Eskom Holdings, flue gas cleaning technologies allows fundamentals and the handling and Eskom’s current focus areas downstream combustion of all fuel types; solid, liquid treatment of products. There are from production include treatment and and gaseous and provides an alternative unique challenges associated with low reuse/disposal of UCG condensate and path for use of the UCG syngas. temperature gasification, which Sasol

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has the experience to overcome. Sasol at a borehole spacing of one borehole workshop held in Johannesburg on has signed a general license agreement per 100 Ha was completed. Malatleng 24 April 2013. with Ergo Energy Technology for the use Mining conducted a drilling programme of their UCG technology. The bulk of any on behalf of BHP Billiton during 2008 and References UCG project investment will be in the 76 boreholes were drilled, logged and [1] J Lauder: “The Development of Underground value-chain, including gas treatment and sampled on the BHP tenements. Fig. 3 Coal Gasification: An overview of the growing UCG industry” FFF underground coal condensates treatment. shows details of the Africary project. gasification workshop, Johannesburg, 24 April 2013. Africary Theunissen Project Exxaro's involvement [2] J Kesells: “The IEA Clean Coal Centre UCG Network & Highlights from the 2012 UCG Africary has signed an MoU with an According to a report in the media [7], workshop in Banff” FFF underground coal international power company that will Exxaro has obtained a licence to deploy gasification workshop, Johannesburg, 24 April build, own and operate a 60 MW CCGT underground coal gasification technology 2013. and buy the UCG produced syngas as a from Linc Energy. The technology to be used [3] A Golding: “UCG a solution to Africa's Rural fuel gas from the company, according Power Supply Challenges?” FFF underground could reportedly combine power generation coal gasification workshop, Johannesburg, to Johan Brand, consultant to Africary and gas-to-liquids (GTL) production. Should 24 April 2013. [9]. This project is expected to transform it be pursued, the electricity-generating [4] Dr. M van der Riet. “Underground coal the face of coal mining and electricity potential of the first plant is reported as not gasification” Energize, March 2008. production in South Africa, by independent less than 200 MW. Any GTL facility will have [5] T Abboo: “UCG Research & Development: electricity production utilising domestic Emerging Issues on the Road to a capacity of greater than 10 000 bbl/d. coal. The Africary rights include all coal Commercialisation” FFF underground coal gasification workshop, Johannesburg, 24 April exploration licences previously owned IEA CCC report on UCG 2013. by BHP Billiton. The occurrence of the [6] M Munsamy: “Research, Testing and Theunissen coal deposit is well known, as This report, by Gordon Couch of the IEA Development of Downstream UCG during the exploration for gold numerous Clean Coal Centre, was published in July Technology Options” FFF underground coal boreholes intersected coal. Trans-Natal 2009 and covers what UCG involves, the gasification workshop, Johannesburg, 24 April 2013. Coal Corporation did a large amount technologies applicable, UCG potential, trials and prospective developments, [7] W Bonnet: “UCG business update” FFF of the historic exploration and these underground coal gasification workshop, boreholes (534 boreholes) have been geological and environmental issues as Johannesburg, 24 April 2013. partially electronically captured to enable well as syngas use. [8] J Brand: “Structuring and Finance of the the preliminary modelling of the coalfield. Theunissen UCG Project” FFF underground Prospecting for coal started in 1980 in Acknowledgement coal gasification workshop, Johannesburg, 24 April 2013. the Theunissen coal field and Trans-Natal This article contains extracts and [9] T Creamer: “Exxaro, Linc Energy plan to had completed 240 boreholes by 1981. summaries of presentations made at finalise bankable UCG study by mid-2016” By February 1982 a drilling programme the FFF underground coal gasification Engineering News, 30 May 2013. 

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