Hydrogen production coal/coke gasification

Processes for hydrogen gasification, hydrogen pyrolysis, or coking of coal usually produce Hquid co-products. The Hygas process produces about 6% Hquids as benzene, toluene, and xylene. Substitution of petroleum residuum for the coal-derived process oil has been used in studies of coal Hquefaction and offers promise as a lower cost technology (104). 

Processes and equipment for the gasification of inferior coke and chars from low-temperature carbonization of subbituminous and lignitic coals were developed in Germany (13), where the relatively large yield of low-temperature tar was welcomed as raw material for hydrogenation processes. The market for low-temperature tar in the United States has been too small and the selling price too low to encourage the use of low-temperature chars for gas production. 

From a more practical viewpoint, the solvent extraction of bituminous coals has been used as a means of coproducing clean liquid transportation fuels as well as solid fuels for gasification. Coal solvents are created by hydrogenating coal tar distillate fractions to the level of a fraction of a percent, thus enabling bituminous coal to enter the liquid phase under conditions of high temperature (above 400°C [750°F]). The pressure is controlled by the vapor pressure of the solvent and the cracked coal. Once liqnefied, mineral matter can be removed via centrifnga-tion, and the resultant heavy oil prodnct can be processed to make pitches, cokes, as well as lighter products. 

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