INTEGRATED COAL LIQNEFACTION-GASIFICATION PLANT

摘要

Conversion of raw coal to distillate liquid and gaseous hydrocarbon products by solvent liquefaction in the presence of molecular hydrogen employing recycle of mineral residue is commonly performed at a higher thermal efficiency than conversion of coal to pipeline gas in a gasification process employing partial oxidation and methanation reactions. The prior art has disclosed a combination coal liquefaction-gasification plant employing recycle of mineral residue to the liquefaction zone wherein all the normally solid dissolved coal not converted to liquid or gaseous products in the liquefaction zone is passed to a gasification zone for conversion to hydrogen. In the prior art plant the amount of normally solid dissolved coal passed to the gasification zone is just sufficient to enable the gasification zone to produce the entire process hydrogen requirement. An unexpected improvement in thermal efficiency has now been achieved by increasing the amount of normally solid dissolved coal from the liquefaction zone (26) and passed to the gasification zone (76) to an amount sufficient to enable the gasification zone (76) to generate not only all of the hydrogen required by the liquefaction zone (26) but also to produce synthesis gas, and adapting the plant to utilize all or a significant amount of this synthesis gas as fuel in the plant. It would have been expected that shifting some of the processing load from the ordinarily more efficient liquefaction zone (26) to the ordinarily less efficient gasification zone (76) would decrease process efficiency, but the present invention unexpectedly achieves an overall efficiency increase by said shift by modifying the plant to permit in-plant combustion of the synthesis gas so produced.