Study on Movements of Steel Balls in Mill by Discrete Element Method

Based on Discrete Element Method(DEM), movements of steel balls were simulated by Particle Flow Code in 3 Dimensions (PFC 3D), the influences of ball diameter, ball filling rate, rotary speed rate of mill on steel balls´ movements were studied. The results showed that steel balls´ quantity increased, but surface area of steel balls enlarged, and void rate decreased at the same filling rate as steel ball´s diameter decreased, which indicated the grinding force of materials was stronger. Steel balls´ movements were relevant to rotary speed rate of mill and ball filling rate. As rotary speed rate and ball filling rate increased, the steel balls moved from cascading motion gradually to throwing motion, and became centrifugal motion after rotary speed rate exceeded certain value. When ball filling rate remained unchanged, the depart point of steel balls became higher, the dropping angle became smaller and throwing gap increased firstly then decreased with the rising of rotary speed rate. When rotary speed rate was 76%, the throwing gap distance reached to an maximum value and the impact crushing action was the strongest.