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For more information or questions, please contact us on UCG@eskom.co.za
Q. What does the word UCG stand for?
A. UCG is an acronym for Underground Coal Gasification, an advanced clean coal technology for directly converting coal in the ground into energy. A matrix of boreholes is drilled into the coal seam, sealed wells are created, the coal is ignited and air is pumped into the injection wells. Fire is essentially used to “mine” the coal, and produce syngas which can be used directly as a fuel for power generation. This process avoids the need for coal mining, transportation, preparation, the gasifier equipment, and the transportation and disposal of ash. This optimisation has cost, labour and environmental benefits.
Q What are the impact on animals in the area?
A. Firstly, the UCG process requires a high temperature to gasify the coal underground. However, the coal seam is on average 300 metres below ground in the case of the Majuba coalfield. Secondly, the surface is expected to subside, as per any underground mining operation. The subsidence is being monitored and modelled, and is expected to be gradual [centimetres per year]. It is expected that animals on the surface will feel neither effect.
Q. Could the ground cave in once the coal has burned?
A. The coal seam is on average 300 metres underground in the case of the Majuba coalfield, and the coal seam is some 3 to 5 metres thick. The coal itself contains some 35% ash (incombustible material), which remains behind after the UCG process is complete. The net result on the surface is moderate and gradual [centimetres per year] subsidence.
Q. How long would it take to burn the coal in a radius of 5Km?
A. This depends entirely on how much coal is under the 5km radius, and the geology and quality thereof. In the case of the Majuba coalfield, a 5km radius would contain 400-500 million tonnes of coal, which should be sufficient for a 2000 MW UCG-IGCC power station for its lifetime, assuming some contingency.
Q. Would there be an environmental Impact due to the coal burning beneath ?
A. The UCG process requires a high temperature coal gasification process to be in close proximity with the surrounding environment. Eskom perceives the biggest risk to be contamination of underground aquifers and surface water courses. Eskom has recognised this risk right from the initial conceptual studies, and has gone to great lengths to ensure preservation of the environment with the introduction of several mitigation measures.
The best strategy is to not pollute aquifers and surface water courses at all, and to achieve this Eskom has engaged the world’s leading UCG experts Ergo Exergy Technologies Inc. (Canada) whose specific technology strategy is to run their UCG process at a negative hydraulic gradient. This in effect forces water influx into the process, meaning that there is less risk of reverse flow from the UCG process into the environment.
Along with this strategy, one needs to monitor aquifers and surface water courses regularly and diligently, to ensure early detection if there is any contamination. Again, with the expert guidance of Ergo Exergy Technologies Inc. (Canada) and local hydrogeology experts, a comprehensive monitoring system and program has been installed.
Q. Can this affect climate change?
A. Power generation with the combined UCG-IGCC is classified as an advanced clean coal technology, with far lower greenhouse gas emissions, NOx (nitrous oxides), SOx (sulphur oxides) and particulate matter emissions than present commercial available coal technologies.
A. Dry cooled UCG-IGCC will achieve far lower water consumption than for equivalently sized conventional dry cooled sub-critical pulverised coal plant with flue gas desulphurisation.
A. UCG-IGCC enables consideration of carbon dioxide capture, and subsequent storage. Eskom, is part of the national carbon sequestration (ie. Storage) activities, conducted under the auspices of SANERI.
Q. What is the project all about ?
A. This is an Eskom project, intending to develop and prove underground coal gasification technology in South Africa. The technology involves converting coal underground into a gas fuel, for subsequent use to generate electricity. The intent is to prove commercial viability of a UCG mine and (Integrated Gasification Combined Cycle) power station in the present location, for a minimum 35 year life.
Q. Who came up with this idea ?
A. The concept of the technology is more than 150 years old, but up to now has only been implemented commercially in the former Soviet Union. Eskom saw the potential, and decided to implement a research project. This has now expanded into a demonstration project, as the process has proved itself successful thus far. The UCG technology is provided by a company called Ergo Exergy Technologies Inc. of Canada, who comprise expertise drawn from the former Soviet Union UCG operations.
Q. Where else is this technology used, apart from South Africa ?
A. It started in the former Soviet Union, but has also been piloted in Australia, New Zealand, EU and the USA. It is being developed now in several other countries, including Alaska, Canada, China, Hungary, India, Italy, New Zealand, Pakistan, USA, UK, etc.
Q. Who else is developing this technology in South Africa, apart from Eskom ?
A. There have been several expressions of interest, but only Sasol is actively developing.
Q. How sure is Eskom that this technology is going to work in South Africa ?
A. The pilot plant has run successfully since 20th January 2007. Eskom is undertaking a staged development, with each phase dependent on the success of the former stage. This mitigates risk, and allows the technology transfer to take place.
Q. How is the process lit ?
A. This is a proprietary part of the technology, but essentially ignition requires air, heat and a fuel.
Q. Once the coal is lit, does it continue burning forever ? How do you control the process ?
A. No – the process requires fuel, heat and air. The coal seam is naturally under water, so the only air available is introduced into the coal seam from the surface. Without this air, the process will drown.
Q. What environmental risks are there ? How clean is the process ?
A. Wells are cased with steel and cemented continuously down to the coal seam. Geophysical logging is performed to ensure well casing integrity. Subsidence and groundwater quality in the area is continuously monitored.
A. Power generation with the combined UCG-IGCC is classified as an advanced clean coal technology, with far lower greenhouse gas emissions, NOx (nitrous oxides), SOx (sulphur oxides) and particulate matter emissions than present commercial available coal technologies.
A. Dry cooled UCG-IGCC will achieve far lower water consumption than for equivalently sized conventional dry cooled sub-critical pulverised coal plant with flue gas desulphurisation.
Q. Can the CO2 from UCG be disposed of (sequestered) ?
A. There are two opportunities to separate CO2 from UCG – the first being prior to combustion, and the second being post-combustion. The first opportunity is substantially more cost effective, and can remove the approximately 15% CO2 content in the UCG gas. Sequestration “sinks” still need to be identified, which could include geological storage.
Q. How much coal is consumed ?
A. The Eskom Majuba pilot plant presently consumes 100 tons of coal per day, at a production rate of 15,000 normal cubic metres per hour. This pilot plant can operate at 5000 Normal cubic metres per hour, but production is being kept to the minimum to conserve coal and energy.
Q. What is produced ?
A. A synthetic gas comprising carbon monoxide, hydrogen, methane and carbon dioxide.
Q. How does gas produce electricity ?
A. The gas can either be burnt to raise steam, for usage in turning a steam turbine to convert to mechanical and thereafter electrical energy. Alternatively the gas can be first used to directly generate mechanical then electrical energy, with a combined cycle that generates steam from the waste heat. The latter is ultimately the most efficient process.
Q. Why is Eskom conducting mining development ?
A. This allows high efficiency power generation to be integrated with high efficiency mining.
Q. How many new jobs ? How does the local community benefit ?
A. A nominal 2000 Megawatt UCG mine and (Integrated Gasification Combined Cycle) power station would typically create more than 1000 permanent jobs, excluding contractors.
Q. How does the country benefit ? What business opportunities are there ?
A. Apart from the new jobs, there will be opportunities for new suppliers, and partnerships.
Q.Social and labour commitments?
A. As required by the Minerals and Petroleum Resources Development Act (2004), there will be comprehensive social commitment focusing on particularly the local community.
Q. Is the community going to be safe ? Will they need to move ?
A. The plant will be designed to the highest standards, to ensure safety. The mine plan will take cognisance of existing communities, structures, and archaeological and historical sites. Where appropriate, existing residents will be relocated or compensated.
Q. Is the mining process efficient ?
A. As a mining process, it is the most efficient underground mining technology known in terms of coal extraction. In the Majuba coalfield, the pilot plant has achieved up to 83% extraction, whereas conventional mining could not achieve more than 25% extraction due to the geological disruptions.
Q. Is the process expensive ?
A. The process cost will be unique for every site, depending on local geology, depth and quality of coal etc. Eskom is currently establishing actual costs with the pilot and demonstration plants, and evidence to date indicates very reasonable mining costs.
Q. Will this technology change the price of electricity ?
A. Cost effective mining of a gas fuel will open the door for implementation of gas turbine combined cycle plant, which has a lower capital cost than conventional coal plant. This implies potential for generating electricity more cost effectively than with the equivalent new conventional power station.
Q. Who is paying for Eskom’s technology development ?
A. Eskom is currently paying for the technology research and demonstration through its RD&D budget. Any technology emerging from this process will need to be funded as would any other large asset, through funds raised externally.
Q. Does the surface subside ?
A. The surface is expected to subside, as per any underground mining operation. The subsidence is being monitored and modelled, and is expected to be gradual [centimetres per year].
Q. What is the temperature underground ? Does the ground get hot ?
A. The process runs at up to 1200 degrees Celsius, but this will only heat the rocks some 40 metres above the coal seam. The coal seam is on average 300 metres underground in the case of the Majuba coalfield. The only heat transferred to the surface is via radiation from the production wells.
Q. In what condition is the cavity underground left ? Can the ground on the surface be rehabilitated ?
A. The UCG cavity will be flushed prior to moving on. Surface pipes and wells are all temporary, and will be dismantled. The wells will then be cemented closed and cut off below surface.
Q. Is this project going to only be at Majuba, or elsewhere in South Africa ?
A. The technology is suitable for coals that are typically considered to be unminable. This implies that almost all provinces hold potential.
Q. Will this technology be integrated into existing power stations ?
A. It can be, to displace coal combustion. However it is optimally used for new power stations, based on the advanced clean coal technology of Integrated Gasification Combined Cycle, which offers higher efficiency.
Q. How will we know that the coal is all burnt underground ? or how much is burnt ?
A. The quantities of air injected underground, and the quantities and composition of products can be balanced. The balance determines the coal utilisation. | 
