Crushing apparatus and crushing method

Abstract

Materials such as cement clinker are crushed by utilizing a crushing apparatus including a vertical roller mill provided with a rotatable table and a plurality of rollers and a distributing device for distributing materials preliminarily crushed by the vertical roller mill. The materials to be crushed is fed into the vertical roller mill, the materials are crushed between the table and the rollers by a pressing force applied to the rollers and substantially the whole amount of the crushed materials is then taken out from the vertical roller mill and conveyed to the distributing device. The crushed materials once conveyed to the distributing device is returned partially as they are to the vertical roller mill and again crushed together with the materials newly fed into the vertical roller mill. The materials are returned to the vertical roller mill by about 20% or more in weight ratio with respect to the newly fed materials when cement clinker is utilized as the materials to be crushed. The returning amount of the crushed materials are controlled in accordance with a power consumption of the rotatable table of the vertical roller mill, and the pressing force of the rollers is controlled in accordance with a power consumption of the rotatable table of the vertical roller mill. The crushed materials are fed to a tube mill installed downstream the vertical roller mill for carrying out a secondary crushing operation.