Preparation of solid fuel-water slurries

A process for the preparation of a pumpable solid fuel-water slurry having a solids content measured on a dry basis of between about 50 and 60% by weight said solid fuel having a particle size such that at least 70% passes through a 200 mesh sieve which comprises subjecting finely-divided solid fuel selected from the group consisting of sub-bituminous coal and lignite to a hydrothermal treatment by forming a mixture of finely-divided solid fuel and water, heating the mixture to a temperature between about 300 and 700.degree. F. under a pressure sufficient to maintain water in the liquid phase for a period of time between 1 minute and 2 hours under non-oxidizing conditions, separating the solid fuel from the water used to form said mixture and adding to said hydrothermally treated fuel having a particle size such that at least 70% passes through a 200 mesh sieve water in an amount to form a slurry containing about 50 to 60 wt. % solid fuel and also adding as a surface active agent a salt of an organic sulfonic acid in an amount to confer pumpability to said slurry.