The speed of the drum is 15-25 rpm. The steel ball in the working cylinder continuously impacts and extrudes the coal block, and grinds the coal block into ultrafine mill. Then the coal is dried by hot air into the drum and the ultrafine mill is sent out. 

After separation by the separator, the ultrafine mill with a certain size is sent into the ultrafine mill bin or directly into the ultrafine mill burner. Steel vertical mill is bulky, high power consumption and noisy, but it is suitable for grinding hard anthracite because of its wide range of adaptability and reliable operation. 

Medium-speed coal vertical roller mill The speed ranges from 50 to 300 rpm, and there are many kinds. Common mills are flat disk mill, bowl mill, E-type mill and roller mill. Their common feature is that the grinding parts are composed of two groups of relatively moving grinding bodies. Coal blocks are crushed between the surfaces of the two groups of grinding bodies.