PURPOSE: To attain a scale expansion of an apparatus without affecting the liquefied oil yield, by reacting a slurry containing. coal, a solvent and a catalyst with a hydrogen-contg. gas under specific conditions so as to effect liquefaction.
CONSTITUTION: A slurry obtained by mixing together coal, a solvent and a catalyst and a hydrogen-containing gas are introduced into a high-temperature, high-pressure reactor column, and liquefaction is performed under conditions such that the temp. is 430-470oC, the hydrogen gas pressure is 100-200 atm and the reaction time is 0.5-2.0 hr., while regulating the gas superficial velocity in the reactor column so as to satisfy the formula relative to the liq. superficial velocity (wherein Ug is a gas superficial velocity, cm/s, in a reactor column; Ut is a liq. superficial velocity, cm/s, in a reactor column, and a and c are constants). Gas-liquid separation of the slurry is conducted, and the slurry is separated into a product oil, a cycle stock, and a residue. The cycle stock is hydrogenated under conditions such that the temp. is 300-400oC, the reaction time is 0.5-2.0 hr. and the hydrogen gas pressure is 100-200 atm. Gas-liquid separation of the stock is conducted, and the stock is then separated by distillation into a light oil and a heavy oil. The heavy oil is recycled as a solvent for slurry preparation.