Abstract: A process for thermochemical beneficiation of carbonaceous solids including a fraction of particles of a size less than 1/4 inch across is provided. The process includes steps of providing a reactor vessel including therein a retaining structure operably positioned to separate a portion of carbonaceous solids from a wall of the reactor vessel, with a free standing liquids region therebetween. The process includes providing a portion of carbonaceous solids piled above an uppermost liquid level of process liquid within the reactor vessel. The disclosure also provides a preferred reactor arrangement for conduct of the process.