Control of pyrite addition in coal liquefaction process

A coal liquefaction process for producing a distillate liquid product which comprises passing hydrogen and a feed slurry comprising a calcium-containing feed coal containing at least 0.8 weight percent calcium based upon MF coal, recycle normally solid dissolved coal, recycle mineral residue and a distillate solvent to a coal liquefaction zone, measuring the calcium content of the ash of said feed coal and controlling the quantity of pyrite added to said feed slurry at a level determined by the concentration of calcium in said feed coal and in inverse proportion to said calcium content of said feed coal, reacting said slurry in a reaction zone at a temperature in the range of between about 399.degree. C. and about 482.degree. C. to dissolve said coal to form distillate liquid and normally solid dissolved coal, separating said reaction effluent into fractions, a first fraction comprising distillate boiling range liquid and a second fraction comprising normally solid dissolved coal and mineral residue, and recycling at least a portion of said distillate boiling range liquid, normally solid dissolved coal and mineral residue for mixing with said feed coal.