Influence of Mill Ventilation on Grinding Efficiency.

The reason why closed-circuit grinding is far more economical than open-circuit grinding is the coarser material in the closed-circuit grinding mill. By ventilation of mills, ground material is drawn out from the mill with the ventilation air, the material remaining in the mill thus becoming coarser, which improves grinding economy. In fully air-swept mills, the strong ventilation may cause internal separation, which is of great importance to the grinding. This is probably the reason why fully air-swept mills often operate as economically as semi air-swept mills.