COAL GASIFICATION: OPENING COAL TO NEW MARKETS

摘要

Transforming coal into a clean synthesis gas using advanced gasification technology is a metamorphosis that opens coal to new markets. Once the coal is in gaseous form, the high efficiencies associated with gas turbine combined cycle performance now become accessible to coal. This is the rationale behind the Integrated Coal Gasification Combined Cycle (IGCC) concept. However, once the clean synthesis gas has been produced from the coal, it is even more efficient to use this gas to synthesize other products like ultra clean transportation fuels, chemicals, or hydrogen in addition to electric power. For example using the clean synthesis gas in a once through Fischer-Tropsch (F-T) process produces ultra clean liquid transportation fuels in addition to electric power. This approach avoids the inefficiencies of carbon dioxide removal, synthesis gas recycle, and light hydrocarbon reforming that would be necessary in configurations producing just F-T fuels. The clean synthesis gas can also be used to produce chemicals like methanol and dimethyl ether, or can be shifted to produce pure hydrogen. Gasification essentially allows coal to be used as cleanly as natural gas. It allows production of electric power using advanced combined cycle technology at high efficiency. Sulfur is recovered as elemental sulfur rather than being emitted as SOx, NOx is low, and the residual coal ash is transformed into a non-leachable slag. It allows production of hydrogen, chemicals, and non-polluting ultra clean transportation fuels. Also coal gasification configurations can produce a concentrated stream of almost pure carbon dioxide that could readily be sequestered once sequestration technology is developed. This paper describes in detail how coal gasification can be used to produce electric power, ultra clean fuels, and hydrogen. Configurations that produce multiple products are analyzed together with zero emissions facilities that include carbon dioxide sequestration. The performance and economics of these facilities are detailed. The paper concludes that advanced gasification technology is the most efficient and environmentally responsible way to utilize the world's vast and valuable resources of coal.