PURPOSE: To facilitate conversion of fuel for medium and small types of boilers into coal by a method wherein after having been pulverized, the pulverized coal are classified in a multi-stage by a narrow range of particle size, the respective sort of coals classified are treated as products thereof.
CONSTITUTION: Drying out and crushing of raw coal (b) are performed simultaneously in the impact type coarse crusher 1, and the coarse pulverized coal (c) having overcome the upstream current in a coarse crusher, are recovered by a classifier 3. The dried coarse pulverized coal riding on a hot air stream current in the coarse crusher, are stored successively in the hopper 6. The pulverized coal group in the pulverizer 10 at a low flux rate are dropped into a multi-stage classifier 12, which are separated by a particulate diameter as the secondary and the tertiry products (d), (e) respectively, and the remaining ultra- pulverized coal riding on a air stream current are totally recovered by the bag filter 13, which are classified as the ultra size of below 15μm, the quartic product (f), and are recovered. By this production mechanism, it is possible to facilitate the fuel conversion for the medium and small type boilers into the coal.