COAL LIQUEFACTION PROCESS WITH IMPROVED SLURRY RECYCLE SYSTEM.

摘要

In a coal liquefaction process including recycle of a product slurry comprising normally solid dissolved coal and mineral residue, the minimum slurry recycle rate is determined by a pumpability constraint on the solids level of the slurry contained in the feed coal mixing vessel. If the solids level in the feed coal mixing vessel rises above the constraint level, the slurry recycle rate must increase. For coals which generate a high mineral residue content, adequate dilution of the slurry in the feed coal mixing vessel requires the slurry recycle rate to rise to an economically impracticable level. In the present process, mechanical operability is improved and enhanced conversion of normally solid dissolved coal is achieved at a given constraint solids level 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 increases the proportion of relatively small more catalytically active particles of mineral residue within the process.