Underground coal gasification: An option indeed

With the increase in population, demand for energy will also grow sharply besides the present gap between demand and supply. The most eminent challenge is that expected demand for electricity during the coming decades would require doubling the power generation capacity in the country. Most of the countries are heavily dependent on coal while Bangladesh, totally dependent on natural gas, is an exception to the case. Unutilised coal and underground coal gasification could be an open option to resolve the country's not only the present short fall but also to fulfill future demand. Underground coal gasification is a new technology to make clean energy by controlled combustion of underground coal to produce water gas. Divided by gasification channel, the technology covers two types: i. e. the type without wells (drilling holes as the gasification channel) and the type with wells (artificial channels as the gasification channel). The former Soviet Union pioneered the field tests of underground coal gasification. Besides the former Soviet Union, US, UK, France, Germany, Belgium and many countries, including India, conducted the tests of underground coal gasification early or late in the 20th century because of energy crisis. Study on underground coal gasification began in the '80s of the last century in China. China University of Mining Technology developed the technique of "Long channel, large section two stages" for underground coal gasification, which had been applied successfully in Shandong, Hebei and Shanxi provinces. The key technology of underground coal gasification is the stove building and the control of gasification. The water gas from underground coal gasification can be used for combined cycle power generation, pure hydrogen extraction, chemical feeding materials, industrial fuel gas, residential gas etc. Underground coal gasification (UCG) has re-emerged as an energy technology for coal conversion and utilisation given its attractive economics, ability to access inaccessible coals, and versatility of use. Based on published and new cost estimates, engineering analyses, and new commercial pilots it appears that UCG can produce syngas for 12 to 14 of the cost compared to surface gasifiers. New pilots announced in India, Canada, New Zealand, Wyoming, Alberta, China, and Australia to commence in 2009-2010 are preludes to commercial projects to produce hydrogen, power, liquid fuels, and chemicals. Importantly, UCG may have special promise in combination with carbon capture and sequestration (CCS). It is evident that international interest in the commercialisation of UCG technology has grown significantly over the last five years. The current projects in South Africa and potential developments in India have been well publicised, while Cougar Energy has recently announced its commitment to investigating the potential for a large power station in the Thar coal field in Pakistan. Walker estimated that the cost of power generated in Australia in an IGCC plant using UCG gas as a fuel could be in the range US1.0-1.5 ckWh depending on plant size. Even allowing for increased costs with time, and more difficult construction conditions in some Asian countries, the cost of power might be expected to be well below their prevailing costs which generally exceed US4ckWh. Two specific project situations might illustrate the range of opportunities which may develop in the future. The first example relates to countries such as India and Pakistan, where significant and growing power shortages exist, and blackouts are common even in the capital cities. Both countries have very large coal deposits which are deep (>150m) and uneconomic for open cut mining. The prospect for development of large long-term power projects (>1000MW) using gas from UCG plants as a fuel is high, once local approval systems have adjusted to the new technology, and project financing can be achieved. At the other end of the project size spectrum lies Indonesia, made up of a number of islands, with the main population centres being on the island of Java, which has no significant coal deposit, and whose power needs are serviced by large power plants using imported coal or natural gas as a fuel. The coal is mined from significant coal deposits on the islands of Kalimantan and Sumatra. On these islands, the population is smaller and widespread, and it would be hard to justify construction of the large coal-fired power stations which are required to achieve low power costs. In such situations, the prospect of using UCG on deeper deposits, with smaller power plants (eg 70MW combined cycle) creates the opportunity to provide low-cost distributed power at the appropriate scale, with modular size increases available to match population growth. It is now evident that this activity is spread amongst a wide range of countries on every continent, and that a number of financially viable operations will be created over the next few years. The economic attraction of the low cost of UCG gas gives encouragement that a number of Asian countries which have increasing power needs, and a supply of coal at depth, may benefit significantly from the introduction of the technology. Energy is essential for mankind and always will be. Research suggests that liquid products can be obtained from coal, but that is not suitable for use as cooking coal. Its heating value is 11,040 BTUIb with low sulfur content. It will be suitable for combustion to produce power. This can solve our power crisis to a great extent. Underground coal gasification may be a suitable environmentally friendly technology for obtaining valuable products from coal. The writer, an engineer, is studying MBA (Finance) at Dhaka University, and can be reached at E-mail : shafiq@iidfc.com