Integrated coal liquefaction-gasification process

摘要

In a coal liquefaction process the yield of liquid coal is increased with a concomitant decrease in the yield of normally solid dissolved coal by recycle of a product slurry containing mineral residue. In an integrated coal liquefaction-gasification process employing product slurry recycle wherein the net yield of normally solid dissolved coal from the liquefaction zone comprises the entire hydrocarbonaceous feed to the gasification zone, a moderate net yield of normally solid dissolved coal is conducive to an optimized efficiency for the integrated process. However, it is frequently difficult to perform the process at slurry recycle rates which are sufficiently low to be economically practicable because of a pumpability constraint on the solids level in the feed coal mixing vessel. In the present process, mechanical operability is improved and enhanced conversion of normally solid dissolved coal is achieved by passing a portion of the liquefaction zone product slurry through a hydroclone with the hydroclone overflow stream constituting a second recycle slurry. Deployment of the second recycle slurry accomplishes selective recycle of relatively small particles of mineral residue and tends to reduce the yield of normally solid dissolved coal without resorting to excessive recycle rates, contributing to optimized efficiency for the integrated process.