“Coarsening” of ball mill is an abnormal phenomenon that the fineness of grinding products is significantly coarser and difficult to control. It generally occurs in double bin open circuit tube mill with small length diameter ratio. Coarsening of the ball mill will increase the energy consumption of the ball mill, cause waste, and large particle size will also affect the subsequent sorting. Therefore, coarsening of the ball mill should be avoided in the actual production. Fodamon engineer summarized several reasons and solutions as follows.
The main reason for the “coarsening” of the ball mill is that the capacity of the coarse grinding bin is too strong and the capacity of the fine grinding bin is insufficient. The reasons why the grinding capacity of the coarse grinding bin is significantly higher than that of the fine grinding bin are as follows:
a. If the load of abrasive body in the coarse grinding bin is too small, the diameter of steel ball is too small, or the filling rate of abrasive body in the fine grinding bin is much lower than that in the coarse grinding bin, increase the load of abrasive body, adjust the grading of abrasive body, increase the proportion of large ball, or appropriately increase the filling rate of abrasive body in the fine grinding bin.
b. If the feeding amount is too much or increases sharply in a short time, try to ensure that the feeding amount is compatible with the crushing capacity of the bin and prevent the sudden increase of feeding amount.
c. If the gap of the grate joint of the compartment board is too large, the reinforcement can be welded at the place where the gap is too large by electric welding.
d. If the abrasive body moves out of the warehouse due to the damage or falling of the compartment plate, the compartment plate shall be replaced or installed, and the confused abrasive body shall be sorted.
e. If the ore particle size is too large, the ore particle size shall be reduced. Before the ore particle size problem is solved, appropriately increase the ball diameter of one bin of steel ball, or temporarily reduce the feeding amount.
f. If the crushing capacity of one bin is greatly reduced due to the phenomenon of “full grinding” in one bin, the problem of “full grinding” shall be eliminated and prevented.
In case of “rough running”, the cause shall be found out and targeted measures shall be taken to solve it. In addition, the operator shall timely adjust the ore feeding amount, grinding concentration and sand return amount of the grinder according to the ore properties and feeding particle size, so as to ensure that the grading overflow fineness meets the process requirements and create good conditions for separation operation.