PURPOSE: To effectively and economically produce a deashed and highly concentrated coal-water slurry, by coarsely grinding coal, classifying the ground coal into fine grains, coarse grains and middle grains, and either deashing the fine grains to thereby remove the contained ash followed by blending with the middle grains and further finely grinding or deashing the fine grains followed by fine grinding and further blending with the middle grains.
CONSTITUTION: Coal is coarsely ground using a coarse grinder 1 so as to cause the max. grain diameter to range from o.3W5mm. The ground coal is classified using a classifying device 2 into fine grains A having a grain diameter ranging from 30W100μm or less, coarse grains B having a grain diameter of 300W600μm or more, and middle grains C having a grain diameter of middle size. The fine grains extracted from a fine grain outlet 3 are collected in a collector 5, mixed with water in a mixer 6, and deashed in a deashing device 7. Further, the mixture is dehydrated in a concentrator 8 to a solid content of, e.g., about 55%, and fed into a fine grinder 9. The fine grain slurry thus obtd. is blended with the middle grains C in a blender 10 at a ratio of coal to grains of 60:60, followed by addition of a dispersant, to obtain a deashed and highly concentrated coal-water slurry having a coal concn. of, e.g., 70W72%. Alternatively, a highly concentrated slurry can be obtd. by a process in which the fine grinder 9 and the blender 10 are replaced with each other so that fine grinding is performed after blending fine grains A with middle grains C.
MURANAKA TADASHI
KIKUCHI HIDEO
MIYADERA HIROSHI
BABCOCK HITACHI KK