A wise choice for limestone and coal grinding in the cement industry

Vertical roller mills (VRMs) have been used for limestone and coal grinding in the cement industry for many years due to their high drying capacity, low energy consumption, compactness, and reliability in operation. The largest mill in operation has an installed power of 1000 KW and grinds 400 t/h of lump feed down to 85% passing 90 Pm. Cement grinding by a VRM has found applications in pregrinding systems, advanced pregrinding systems, and finish grinding systems.

In a Vertical roller mill, the interparticle comminution takes place in a material filled gap between the rotating table and the grinding rollers. The mill feed is charged to the center of the table and moves, affected by centrifugal forces and friction, toward the table’s edge. On its way, it is nipped by two, three, four, or six conical rollers installed at the outside rim of the table. The rollers are attached to hydraulic cylinders that provide the grinding force for comminution of the material. The ground particles leave with the airstream and are taken up by the separator incorporated into the casing of the mill. The fine product reports to the mill discharge, and the coarse reject of the separator falls back onto the table as a recirculating load.