Integrated coal liquefaction-gasification process

Abstract

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 process 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, where the amount of normally solid dissolved coal passed to the gasification zone is just sufficient to enable the gasification zone to produce the process hydrogen requirement. The process of the present invention provides an unexpected improvement in the thermal efficiency of the combination process by increasing the amount of normally solid dissolved coal prepared in the liquefaction zone and passed to the gasification zone to enable the gasification zone to generate not only all of the hydrogen required by the liquefaction zone but also to produce synthesis gas in an amount adequate to supply all or a significant amount of the fuel requirements of the process. It would have been expected that shifting some of the processing load from the ordinarily more efficient liquefaction zone to the ordinarily less efficient gasification zone would decrease process efficiency, but the present combination process unexpectedly achieves an overall efficiency increase by said shift.