Cement clinker grinding method using vertical roller mill and apparatus

Abstract

A method of grinding cement clinkers and a cement clinker grinding apparatus having a vertical roller mill are provided. In the method, feed material is ground by a table and rollers. Next, substantially all the resultant ground material is taken out from an underside of the table and then converted to a separator for classifying the ground material by a bucket elevator. The resultant coarse powder provided by the separator is returned to a center of the table. In grinding, an pressing force of each of the rollers onto the table is selected so that a roller pressure per full sectional area of the roller ranges from 10 to 15 kg/cm,. Further, a circulation quantity of the coarse powder to be returned to the vertical roller mill is selected from 100 to 300% of the feed material charged into the center of the table. And the liquid of 0.5 to 3% of the feed material to be ground such as water alone or a mixture of water and diethylene glycol is sprayed on the only frictional grinding zone which is positioned outside a position where a relative speed between said table and each of said rollers is equal to zero, in the radial direction of said table. By spraying the liquid on the only frictional grinding zone, the materials are involved firmly between the table and the roller to form the layer of the ground materials, so that the vibration of the roller and table are restrained