At present, ball mill and rod mill are commonly grinding equipment used in concentrators. However, the ball mill and rod mill are both long cylindrical grinding equipment, which is not easy to distinguish from the machine's appearance. Actually, there are big differences between ball mill and rod mill. Generally, we can distinguish them and choose the right grinding equipment, based on its structure, grinding media, discharge method, grinding media filling rate, equipment performance, and application scope, etc.
Generally, the ratio of the diameter and length of the rod mill cylinder is between 1.5-2.0, and the inner surface on the end cover is in a vertical plane state. The ratio of the diameter and length of the ball mill cylinder is relatively small, usually equal to 1.0 or slightly greater than 1.0.
Rod mills usually use steel rods with a length greater than 500mm as grinding media, while ball mills use steel balls with a diameter of less than 100mm as grinding media. The difference in grinding media is most significant between the two grinding equipment.
For the ball mill, we can choose the overflow type and grid type discharge methods according to different production requirements. The grid-type ore discharge has a low slurry level, in which qualified products can be discharged in time, but sometimes the grid plate is easy to be blocked and inconvenient to maintenance; while the overflow-type discharge is easy to manage and repair, with a high discharge level, which will extend the retention time of slurry, and reduce the processing capacity.
For the rod mill without grid plate, there are mainly two types: overflow type and open type. The diameter of the hollow shaft at the discharge end is larger than the same specification ball mill.
The filling rate of grinding media refers to the percentage of grinding media occupied by the volume of grinding equipment, which would be affected by grinding methods, equipment structures, operating, and medium conditions. According to the practice, the filling rate of the ball mill is usually The filling rate of grinding media refers to the percentage of grinding media occupied by the volume of grinding equipment, which would be affected by grinding methods, equipment structures, operating, and medium conditions. According to the practice, the filling rate of the ball mill is usually 40%-50%, while that of the rod mill is, while that of the rod mill is 35%-45%.
The grinding media of the rod mill is in linear contact with the ore, resulting in a more uniform particle size. In addition, the processing capacity of the rod mill is greatly affected by the particle size of the ore. When the product size is The grinding media of the rod mill is in linear contact with the ore, resulting in a more uniform particle size. In addition, the processing capacity of the rod mill is greatly affected by the particle size of the ore. When the product size is 1-3mm, the processing capacity of the rod mill is greater than the ball mill of the same specification; when the product size is less than, the processing capacity of the rod mill is greater than the ball mill of the same specification; when the product size is less than 0.5mm, the grinding effect of the rod mill is far less than that of the ball mill of the specification.
The ball mill is in point contact with the ore, resulting in finer product particle size. In addition, the ball mill has a high production capacity and is easy to grind, but its over-grinding phenomenon is more serious.
In the gravity separation or magnetic separation process of rare metal ores, rod mills are often used to prevent over-grinding and dust pollution. In the second-stage grinding process, the rod mill is usually used as the first-stage open-circuit grinding, with larger production capacity and higher efficiency. When processing low-hardness and brittle materials, the rod mill can completely replace the cone crusher for fine crushing.
The ball mill is not suitable for the gravity separation process in metal ore beneficiation due to its fine grinding materials and prone to over-crushing, but it is widely used in other beneficiation processes.
The grinding mill continues to be one of the most important pieces of equipment in mineral processing plants. It is a well-known fact the efficient use of grinding machines can lead to major improvements in plant performance.
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