With the continuous improvement of mechanization level in the world, ball mill also develops to the trend of large-scale. But after the large-scale, coupled with ball mill equipment structure, process configuration, and other factors, resulting in production cost increased, grinding efficiency decreased. Next Fote machinery(ftmmachine.com) will analysis the reasons for the reduction of grinding efficiency and puts forward some measures.
1. The reasons for ball mill low grinding efficiency
(1) The influence of equipment structure on grinding efficiency
①The influence of central ore-giving defects
The ore-giving method of ball mill is central ore-giving, which means the ore-giving device is fixed, while the ore-giving side is rotating. The two contact through seal pad, which prevents the pulp in the ball mill backflow. When the pulp in the ball mill is too much, it must scour to the seal pad in the bottom of the ball mill ore-giving side, exacerbates wear of seal pad, which will lead to the tightness reduced, then the pulp will fall to the ore-giving side from the gap. In the production, to avoid the pulp backflow, we have to decrease the ball mill capacity, thereby decreases the level of pulp in the ball mill, reduces backflow phenomenon. In addition, the ball mill filling rate is difficult to improve, which means the number of grinding media involved in grinding is lacking. The ore gets into ball mill can’t be fully grinding, increases the amount of return sand, limits the improvement of ball mill utilization rate, ton power consumption and ball consumption must rise correspondingly.
②The influence of ball mill discharge defects
The effective diameter of the ball mill discharge central h*** is 1180 mm, the effective diameter ratio is 1: 3.18. If the relative size isn’t enough, will affect pulp in ball mill rapid discharge. When the ratio of length and diameter increased from 1.2: 1 to 1.37:1, the working efficiency will be reduced, the pulp volume in the ball mill is large will affect the improvement of utilization rate. To speed up the discharge, we must reduce the grinding density and improve the fluidity. If the pulp flows too fast, it will also interfere steel ball grinding effect, affects the contact time between pulp and grinding media. At the same time increases the difficulty of grinding media captures the ore particles and “ball grind ball, ball hit ball” rate, which is not only bad for grinding efficiency but also increases the ball consumption.
(2) The influence of process configuration on large ball mill
Ball mill is used as first stage grinding mill, it always composed of a closed-circuit with other classification equipment, the configured classification equipment mainly are spiral classifier and hydro-cyclone. Configured hydro-cyclone, in the absence of natural height difference, all need a slurry pump to send the ore from ball mill to the hydro-cyclone. Especially when hydro-cyclone and first stage mill forms closed-circuit grinding process, hydro-cyclone sink sand needs to return to the first stage mill, there is more need to configure slurry pump. Slurry pump motor power is several times higher than spiral classifier motor power. Ball mill diameter and length size are large, but there is no large-scale spiral classifier can be matched with it for now, so it almost forms a grinding classification process with configured hydro-cyclone. Ball mill discharge usually uses hydro-cyclone to do classification, the motor power of slurry pump can up to 400kwh, the ton ore processing power ration is greater than 1.21kwh, this is one of the reasons of high energy consumption of ball mill classification.