11.1 Introduction to Gasification

In a drive for more efficient use of coal reducing net station heat rates and in a drive for reduced airborne emissions, gasification has emerged as an alternative to combustion. The idea of coupling a coal-based synthesis gas generator to a combustion turbine is not new; it was proposed by Wilhelm Gumz in 1950 ^[1], but only with the development of large, highly efficient turbines has it emerged as an economic possibility. The inherent possibility of pre-combustion CO ₂ removal at modest additional cost as practiced on a large scale in the ammonia industry has increased the interest in gasification for the generation of electric power ^[2].

Gasification can be described as the conversion of any carbonaceous feedstock into a gaseous product with a useful chemical heating value. Early processes for the production of gas from coal emphasized devolatilization and pyrolysis reactions creating a gas with significant hydrocarbon content for lighting purposes. These were the town gas processes of the 19th century. With the introduction of the incandescent mantle and the development of chemical syntheses at the beginning of the 20th century, the emphasis shifted to water gas and partial oxidation processes generating synthesis gas (or syngas), in which carbon monoxide and hydrogen are the principal components.

Syngas manufactured from coal, petroleum coke, and various other feedstocks such as refinery residues is processed into ammonia (for fertilizer production) and methanol. In both cases, gasification-based applicationsamount to about 10%...