Abstract: A process for liquefying coal involving heating only a portion of a the total process hydrogen stream to increase its temperature to a relatively high level and admixing said heated hydrogen with only a portion of the total coal slurry in the upstream region of a dissolver zone. The hydrogen stream has a relatively low specific heat and the addition thereto of a relatively small amount of heat increases its temperature to a level which is sufficiently high to initiate hydrocracking reactions when the hot hydrogen stream is intermixed with only a portion of the dissolver feed slurry, provided that the dissolver feed slurry contains recycle mineral residue in an amount adequate to catalyze hydrocracking reactions. Because the recycle mineral residue catalyzes the exothermic hydrocracking reactions, sufficient process heat is generated to permit addition to the dissolver zone in a downstream region thereof the remainder of dissolver feed slurry and process hydrogen in a relatively cool condition.

Abstract: A coal liquefaction process wherein a feed coal-solvent slurry is preheated in a thoroughly back-mixed preheater zone and then passed to a dissolver zone. Hot hydrogen is introduced to the process downstream from the preheater zone at or in advance of the dissolver zone and exothermic hydrocracking reactions occur in the dissolver zone. A dissolver zone effluent stream is passed through a vapor-liquid separator and separated hot dissolver vapor at process pressure is vented through the preheater zone wherein it is quenched to provide direct transfer to the preheater zone of the exothermic heat generated in the dissolver zone. The preheater zone is continuously vented to provide rapid removal of cooled vapor from the preheater zone and from the process, advantageously leaving an accumulation of liquid in the preheater zone boiling between the temperatures of the vapor-liquid separator and the preheater zone at process pressure.