What is Overgrinding and how to avoid Over-grinding in comminution circuits?

Question: What is Overgrinding and how to avoid Over-grinding in comminution circuits?

Reply: Overgrinding is a major concern in grinding circuits because it (1) wastes energy, and (2) can result in valuable minerals being ground to such fine sizes that they are difficult to process. Overgrinding can be particularly severe in grinding circuits that are processing mixtures of minerals of different densities while using classifiers for size control. This results in the highdensity minerals that have already reached the target size being retained in the circuit and ground to a finer size than the low-density minerals. While this problem could, in principle, be solved by the use of screens for size control, in practice, screening costs become excessive for fine grinding due to high maintenance and low screening efficiency. A novel approach is to redesign the circuit so that the particles that are very close to the target size can be separated out and handled differently than particles that are definitely coarser than the target size. Simulations of this type of approach are presented.