Significant improvement of distillate yield can be obtained by the gas recycling in the coal liquefaction process. The gas recycling accelerates the stripping of light fraction with the concentrated slurry in the reactor. Heavy fraction can be hydrogenated effectively without increasing of hydrocarbon gases yield even though with a long residence time. This study summarized such effects by which compare the coal liquefaction performances in the case of stripping the light fraction and the case of not stripping using a 5L-gas flow type autoclave.
