METHOD FOR COMBINING COAL LIQUEFACTION AND GASIFICATION PROCESSES

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 process employing recycle of mineral residue in the liquefaction zone wherein all the normally solid dissolved coal produced in the liquefaction zone is passed to a gasification zone for conversion to hydrogen, where the amount of normally solid dissolved coal prepared and passed to the gasification zone is just sufficient to enable the gasification zone to produce the exact hydrogen requirement of the process. The present invention provides an unexpected improvement in the thermal efficiency of the combination process by utilizing formulas based on feed coal characteristics to calculate an amount of normally solid dissolved coal to be 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 for use as fuel in the liquefaction zone. 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.