PURPOSE: To effect the deashing of coal in high ash removal and high recovery, by crushing a concentrated aqueous slurry of coal with a wet-pulverizer, recovering the coal having low ash content by flotation, collecting the coal having high ash content from the tail of the flotation apparatus, and recovering the coal from the collected coal by a classifier in the form of flock.

CONSTITUTION: A concentrated aqueous slurry of coal composed of 60W85wt% coal, 0.01W5.0wt% surfactant (based on the coal) and remaining part of water, is deashed by the following procedures. The powdery coal 4 prepared by the wetpulverization with a wet-pulverizer is diluted with water 5 in the concentration adjusting tank 41, added with the collecting agent 11 and frothing agent 12 in the conditioning tank 42, sent to the flotation apparatus 43 after agitation, and separated into the coal 13 having low ash content (refined coal) and the coal 14 having high ash content (tail). The tail 14 in the flotation appratus 43 is mixed with a binder 15 such as heavy oil, etc. in the mixer 44. Only the carbon component in the tail 14 having high ash content is coagulated in the form of flock in the coagulation tank 45, and is recovered in the form of flock by a classifier 46 capable of classifying at a particle diameter of 200 mesh.