Gasification is a process to upgrade a solid feedstock, which is difficult to handle, by removing undesirable impurities and converting it into a gaseous form that can be purified and used directly as a fuel or further reacted to produce other gaseous or liquid fuels, or chemicals. There are many reasons for the interest in gasification as a process for utilizing coal. Liquid and gaseous fuels are easier to handle and use than coal, whether the fuel is used for heating, cooking, transportation, or power production. Shipping coal can be difficult and labor intensive and can have negative environmental impacts. Impurities in coal can be more readily removed through gasification than when utilized directly. Synthetic fuels burn more cleanly than coal, and fewer sulfur and nitrogen oxides are formed during combustion. Carbon capture and sequestration is easier in a gasification system than in a combustion system, which is important with carbon dioxide being considered for regulation as a pollutant. Gasification of coal is especially attractive to nations that have coal reserves and lack reserves of oil and gas or are depleting them. And, finally, gasification of coal reduces the concerns of volatile swings in availability and cost of gaseous or liquid fuels that are experienced with petroleum or natural gas. Although the use of coal gasification is currently rather limited, this technology is poised to be the technology of the future for the production of electricity, steam, chemicals, and fuels such as hydrogen. This is further expanded upon in Chapter 7 (Future Power Generation).

This section summarizes gasification as a technology for utilizing coal, beginning with a brief introduction of the history of gasification. This is followed by a discussion of gasification principles and a review of gasifier types, specifically those that are commercially available. The influence of coal properties on gasification is presented and the regional distribution of gasifiers in the world is briefly discussed, followed by brief descriptions of the main gasification technologies currently being used.

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