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According to the different discharge ends, the ball mill can be divided into three types: grid type ball mill, overflow type ball mill and peripheral discharge type ball mill. In practice, peripheral discharge ball mills are rarely used; grid ball mills and overflow ball mills are commonly used. What are the commonalities and differences between them? Under what circumstances is a grid ball mill a better choice? What is the overflow ball mill? Here, we will give you a brief introduction.
The overflow ball mill and the grid ball mill have basically the same structure, and both are composed of a shell, a feed end, a discharge end, a main bearing, and a transmission and lubrication system.
1 Feeding end. The main part of the feed end of the overflow ball mill is a spiral blade that is opposite to the direction of rotation of the mill; while the grid ball mill is a grid plate.
2 Principle of discharge. The ground ore powder in the overflow ball mill overflows outward by virtue of the height difference between the hollow journals at the discharge end and the feed end. At the same time, the steel balls and remaining ore particles first settle to the bottom of the reverse spiral blade, and then are transported back to the mill. The overflow ball mill is a high-level discharge ore. In contrast, the fine particles of the grid ball mill are discharged through the grid plate, which belongs to the low-level discharge.
3 Different motion states of steel balls. The speed of the overflow ball mill is low, and the steel ball will continue to fall after rising to a certain level, so its force is mainly grinding, and the impact force is supplemented. However, the grid ball mill has a higher speed, and the steel balls are thrown off. The force is mainly impact and grinding is a supplementary force.
4 Grinding fineness. Compared with the grid ball mill of the same specification, the overflow ball mill has a lower productivity, about 10% to 15%, but its grinding products are finer.
Ball mill is one of the most common equipment items in mineral processing plants. Its job is to grind rock by rolling in a large metal cylinder with steel balls, which is very energy
intensive. In fact, grinding costs in mining operations account for a large part of total energy costs. One way to make full use of the capacity of the ball mill is to convert it from an overflow port to a slag discharge port. This can allow operations to increase factory throughput or reduce product size, both of which can help increase revenue, but there are several factors to consider before making a switch decision.To convert the ball mill from overflow to grate discharge, a grate must be installed at the discharge end of the mill. The grate fixes the ball in the mill, but allows the slurry to pass through, and then the pulp lifter pumps it out of the mill. This is different from an overflow mill, which keeps the mud and balls inside until the mud accumulates to a level that can overflow from the discharge trunnion.