Abstract: The invention relates to an apparatus and method for producing a free flowing coal suspension high in solids content. The coal is ground in at least two stages utilizing a mill having a calibrating effect in one stage and a mill without calibrating effect in another stage and adding a sub-quantity of viscosity reducing additive to the coal before each grinding. A drying of the coal or reconcentration of the suspension is not required. A roller mill operating on the principle of materials bed comminution is preferred as the non-calibrating mill in the first grinding stage and a rotating drum mill or a vibration grinding mill with rods as grinding bodies is preferred as the calibrating mill.