PURPOSE: To make it possible to economically perform a coal hydrogenation process, in liquefying coal by reacting coal and hydrogen in the presence of a ferrous catalyst, by subjecting obtained formed crude oil to gravity concn. treatment while recirculating a lower oil layer to a coal hydrogenation process to reuse the same.
CONSTITUTION: In liquefying coal by reacting coal and hydrogen in hydrocarbon oil at high temp. under high pressure in the presence of a ferrous catalyst, the obtained formed crude oil is subjected to gravity concn. treatment while a high pressure atmosphere is held to form a lower oil layer in which a relatively large amount of a catalyst particle and ash in an amount not exceeding 70% of ash contained in the crude oil are suspended and this lower oil layer is recirculated to and used in a coal hydrogenation process while separated from the upper oil layer reduced in the amount of the catalyst particle. That is, the greater part of the catalyst can be recovered around a reactor and it is available from the standpoint of heat energy conservation. In addition, because separation is performed at a high temperature by a low viscosity slurry, there is no defect related to separation operation. Further, it is economical because the separated and recovered catalyst slurry is directly used.