Gasification and Indirect Liquefaction

Abstract

To produce liquid fuels from coal, either direct or indirect liquefaction routes can be used. The discussion of the former route is the subject of Chapter 6; the latter route will be discussed here. The indirect liquefaction route consists of the conversion of coal to synthesis gas (hydrogen plus carbon monoxide), and then the conversion of the synthesis gas to liquid fuels, such as alcohols or hydrocarbons. The major processing steps include the following: Coal gasification using steam and oxygen to form hydrogen and carbon monoxide. Synthesis gas purification to remove particulate matter, carbon dioxide, ammonia, hydrogen sulfide, carbonyl sulfide, and other undesirable impurities. A water-gas shift process to react some carbon monoxide with steam to give hydrogen. The removal of carbon dioxide formed in the water-gas shift process. Synthesis gas conversion to form alcohols or hydrocarbons. Final product upgrading to convert the alcohols or hydrocarbons obtained from the synthesis gas conversion step into some specific marketable products.