Method of improving yield in a coal liquefaction product deashing process

Abstract

A coal deashing process wherein a feed mixture comprising soluble coal products, insoluble coal products and solvent is separated in a first separation zone into a first heavy phase and a first light phase comprising soluble coal products, solvent and some insoluble coal products. The first light phase is withdrawn and introduced into a second separation zone wherein it separates into a second heavy phase comprising insoluble coal products, soluble coal products and some solvent and a second light phase comprising soluble coal products and solvent. The second heavy phase is withdrawn and at least a portion is recycled to the first separation zone to increase the yield of separable soluble coal products ultimately recovered by the process. In alternate embodiments, additional solvent can be added to the first light phase before introduction into the second separation zone or the recycled portion of the second heavy phase may be introduced into a treatment zone before reintroduction into the first separation zone. The treatment zone effects an increase in the molecular weight of at least a portion of the recycled second heavy phase which facilitates subsequent separation in the first separation zone.