Abstract: A high-concentration coal-water slurry of a coal concentration as high as 71 percent by weight at a viscosity of 2,000 cp (at 25.degree. C.) can be produced by first coarsely crushing a starting coal, further pulverizing 95 to 30 percent by weight of the coarsely crushed thus obtained, subjecting the finely pulverized coal thus obtained, together with the remainder of the coarsely crushed coal, to crushing in a wet-type crusher, and pulverizing and adjusting the coal particles to a particle size constitution of 20 to 30 percent by weight of 200-mesh size and larger and 80 percent by weight or less of 350-mesh size and smaller.

Abstract: This process, which comprises subjecting coal to gravity classification to classify into a low ash coal, a middle ash coal and a high ash coal; deashing the middle ash coal by flotation; and using the deashed middle ash coal together with the low ash coal as the materials for producing a coal-water slurry, provides a low ash content and high solid content coal-water slurry in a high coal recovery as well as economically. This coal-water slurry is able to handle, store and burn as are fuel oils.

Abstract: High concentrated coal-water slurry is produced by coarsely crushing coal, thereafter pulverizing the coarsely crushed coal, together with water and a slurry dispersant, according to necessity, in a wet-type ball mill, and feeding back one portion of the finely pulverized coal slurry thus obtained into the inlet of the wet-type ball mill.