Research on Incorporating a Pre-crushing Process

The addition of a pre-crushing process significantly impacts the entire semi-autogenous grinding-ball milling workflow. Incorporating pre-crushing first increases the processing capacity of the semi-autogenous mill while reducing its specific energy consumption. The product particle size from the semi-autogenous mill becomes coarser, resulting in a larger P80 value for the undersize fraction on the vibrating screen. Concurrently, the proportion of fine particles in the undersize material decreases, while the oversize material volume from the semi-autogenous mill increases. The pre-crushing process disrupts the original energy load balance between the SSM mill and ball mill. The ball mill's load increases rapidly. The increased throughput of the ball mill and the higher proportion of coarse particles in the feed material increase the ball mill's circulating load, resulting in coarser particle sizes of the material entering the separation process. If the SSM mill's throughput is further increased, the ball mill's processing capacity will become a bottleneck.

While the pre-crushing process enables higher throughput, it is achieved under extremely high steel ball filling rates and relatively low overall filling rates. This combination of filling rates is difficult to control and leads to excessive wear on lift bars and liners. Therefore, the following studies are required before implementing the pre-crushing process:

　　(1) When adding a pre-crushing process, the overall system throughput must be determined by considering the capacities of the ball mill, the hard rock crusher, and the flotation process, rather than arbitrarily increasing the semi-autogenous mill's throughput;

       (2) Accurate calculations must be performed for selecting the pre-crushing screen, including screen surface dimensions and upper/lower mesh sizes;

　　(3) Conduct precise calculations and selection for ball mills, tough rock crushers, and pre-crushing equipment.

Regarding the above aspects, initial ore testing should be conducted. After obtaining ore property parameters, software simulation can be used to calculate the new process scheme, thereby determining a reasonable modification plan.

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