The effect of ball size, ball charge ratio, filling ratio of powder in ball charge in a tumbling ball mill and mill diameter on parameters of comminution kinetics equation and on a revice coefficient for a parameter were experimentally investigated. Tested powders were cement raw mix and cement clinker. In addition, a simulation of closed-circuit grinding was carried out as functions of the parameters. Using these results, ways to increase production capacity of closed-circuit grinding were investigated. The lower the filling ratio of powder in the ball charge under the condition of constant passing rate of powder through a mill, the more the production capacity increases both the raw mix and the clinker grinding. Balls of diameter of about 30 mm increase the capacity further in the grinding of the raw mix. On the other hand, a smaller size of balls still increases the capacity in grinding of the clinker under the condition that the fineness is controlled by 31 mu m sieving. Ball size, however, does not affect the capacity under the condition controlled by specific surface area.