Production of gaseous or liquid hydrocarbon fuels from coal (1) by direct addition of hydrogen to form methane (hydrogasification); (2) by reacting steam with hot coal (800C) in the presence of air or oxygen to form carbon monoxide and hydrogen (synthesis gas), followed by a methanation reaction (Fischer-Tropsch method); (3) by underground aeration. In methods (1) and (2), the coal enters the reaction sequence in finely divided form; hydrocarbon gases, naphtha, and fuel oils of various grades can be produced by several modifications. In method (3), air is pumped down to previously ignited coal seams and the combustible products evolved are collected. Many variations of methods (1) and (2) have been researched in the U.S., but none is economically competitive with crude oil. Several have advanced to the pilot stage, and projections of cost, investment, and installation for large-scale operation have been made. Environmental and geographic considerations have also been investigated. The controlling factor for future development is the price of crude. All three methods mentioned are technically feasible. During World War II hydrocarbon fuels were produced from coal on a large scale in Germany by both hydrogasification and Fischer-Tropsch methods. Large-scale coal conversion has been successfully achieved by the Lurgi and Sasol methods; the latter, in South Africa, is a large-scale installation utilizing the Fischer-Tropsch technology. The Lurgi technique is in production at a number of locations. Catalytic gasification of peat for production of methanol is now utilized on a commercial scale; use of lignite and wood for this purpose is under development.See Fischer-Tropsch Process; Synthesis Gas.
