Coal is making a comeback, in gaseous and liquid forms, as the fossil fuel of choice
access to conventional energy resources will soon become a problem in future since estimates suggest that global reserves will last 40 years. In contrast, coal may last another 240 years. Compared to petroleum and natural gas, coal is inferior, generates less energy when burnt and emits a greater volume of sulphur oxides and other pollutants. As a solid, coal is more difficult to transport. But these obstacles can now be surmounted by converting coal into liquid or gaseous forms. These forms are easier to handle and friendlier to the environment.
The technologies for converting coal into liquid and gas fuels are being developed in Japan, Europe and the us. New Energy and Industrial Technology Development Organisation (nedo), an affiliate of the Japanese ministry of international trade and industry (miti) has developed the technology to convert coal into a liquid fuel. In this liquefaction process, coal is pulverised and mixed with a catalyst in a liquid solvent. Under hot pressurised conditions, mole cular bonds break and the powdered coal turns into liquid. nedo's pilot plant utilises a high performance iron-sulphide catalyst to yield 50 per cent light oil -- a world record for conversion efficiency. The efficiency of the process is now being put to test in a large pilot plant in Kashima, Japan. The plant is scheduled to convert 150 metric tonnes of coal per day into liquid fuel. nedo has also started a project to convert coal into fuel gas similar to natural gas.
Power generation with gasified coal has a heat efficiency of 45 to 47 per cent, which is a significant improvement on the 40 per cent heat efficiency of a typical coal-burning power plant. As an added benefit, the volume of carbon dioxide released per unit of electric power can be reduced by about 15 per cent.
With basic technologies for coal liquefaction and gasification established, scientists are turning to a major problem in economics. The liquid fuel that nedo makes from coal has a price tag of around us $20-25 per barrel, too expensive currently to compete against crude oil. One major way to cut the cost is to raise the efficiency at which coal is converted into liquid fuel. The private sector is leading in the manufacture of gasified coal in Japan. Companies such as Mitsubishi Heavy Industries Ltd and Hitachi Ltd have completed work on fundamental technologies for this and are moving on to the practical stage of development.
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