Abstract: A shelf for protecting the inner surface of a vertical shell of a pulverizer against wear. It is partially replaceable. The shell accommodates a screw shaft and is filled with a pulverizing medium and a material to be pulverized. At least one of them is magnetizable. The shelf is made up of vertical and circumferential ribs and mounted in the shell. It is divided both vertically and circumferentially into a plurality of blocks that are coupled together by bolts and nuts. Magnets are provided in the spaces defined by the ribs. By turning the screw shaft, the pulverizing medium is pushed radially outward and partially trapped in the above spaces, thus forming a wear protective lining. When any of the ribs is worn, only the block that includes this rib is replaced with a new one.

Abstract: A vertical medium-stirring type pulverizer has a wear-preventive structure for preventing wear of its screw blade. The structure includes a plurality of magnets provided on the top surface of the screw blade. At least one of the pulverizing medium and the material to he pulverized which are contained in the pulverizing shell of the pulverizer is a magnetic material. The magnets serve to attract the magnetic medium or material thereto to form a lining on the top surface of the screw blade. A similar wear-preventive structure may be provided on the inner surface of the shell to prevent wear of the inner surface of the shell.