Studies on comminution mechanism of the dry tower mill KD-3

Abstract In order to obtain economically lot of fine particles, a dry tower mill KD-3, composed of a comminuting section, a classifying column and a collecting section, has been developed through this study. Grinding tests were carried out on limestone to clarify the comminution mechanism in the KD-3. A particular attention was paid to important factors such as the size of the grinding media (steel balls of10 mm,13 mm,16 mm,20 mm), the speed of the stirring screw (from 1.08 s −1 to 1.58 s −1 ) and the role of the net in the classifying column. The study has revealed an optimum efficiency for steel balls of20 mm size and a stirring screw rotating at 1.58 s −1 . Besides, a series of nets settled in the classifying column have improved the efficiency of the classifying operation by reducing the buoyancy of the materials and regulating the maximum size of products collected in the cyclone (d max is about 10 μm). The air flow rate in the duct and the pressure of drops in the column were approximately quadratic curves, but the d max of products collected in the cyclone was proportional to the pressure of drops in the classifying column.