coal the material may have been mined by means of water in which case a slurry will be available after the wet grinding operation in any event preparation of a slurry is a well known technique in the art and as such there are a large number of technically proven processes which are readily adaptable for this method in the preferred process embodiment of the invention as outlined in fig1 wet brown coal feed 10 or another suitable solid carbonaceous substance prepared by passing through a crusher or other comminution unit and being crushed to a predetermined particle size preferably about minus 1 4 inch or smaller is pulverized and preheated not shown and enters mixing unit 12 wherein it is mixed with a recycled water stream 14 and during startup water from line 16 the resulting mixture is pumped through conduit 18 now forming a slurry in a pressurized system and enters heat exchange unit 20 the slurry is heated by contacting with a heated organic heat transfer fluid e g 34 mobiltherm 34 or the like and passes through line 22 into reactor unit 24 where is is further heated to about 150 u00b0 350 u00b0 c preferably about 250 u00b0 300 u00b0 c under a corresponding pressure sufficient to prevent vaporization of the water the heating of the slurry in the reactor unit is preferably accomplished by the condensation of the vapor of a second organic heat transfer fluid e g 34 dowtherm 34 or the like which enters the reactor unit 24 by line 28 the organic vapor being generated in boiler 30 the condensed organic vapor is recirculated to the boiler.