Search

In order to investigate the breakage behavior of the feed in industrial secondary ball mills, the breakage characteristics of fine magnetite were analyzed. Magnetite particle breakage produces a bimodal particle size distribution that is consistent with the typical breakage characteristics of abrasion. The secondary ball mill can increase the surface area by reducing the diameter of steel balls to enhance the abrasion. Industrial application results show that after the abrasion of the secondary ball mill for grinding magnetite was enhanced, the circulating load of the grinding-classification system dropped by 29.90% and the specific energy of the secondary ball mill decreased by 39.14%. At the same time, the consumption of steel balls also dropped from 0.17 kg/t to 0.13 kg/t, a decrease of up to 20%. It should be noted that the reduction in the ball diameter should follow certain rules because if the energy of a single collision is lower than the critical breaking energy of the particles, the grinding process will be affected and thus have counterproductive effects.

A new approach to batch grinding kinetics was established based on the conventional population balance model, with magnetite as the experimental object. The distribution function commonly used in the population balance model is a sum of two power functions, i.e., Bi1=φ(xi−1x1+1−φ(xi−1x1)β. Based on the new finding that the cumulative mass fraction coarser than the size class of the discharge is consistent with the first-order grinding kinetic, the gi function of the new approach is only a single power function, i.e., =+k1xia, which will greatly reduce the parameter error and make the fit more accurate. The maximum error between simulation calculations and the actual experiment using the two methods did not exceed 1%, indicating that both models can accurately predict the fracture characteristics of magnetite. Because the new approach has fewer derived parameters, it addresses the conventional population balance model’s problems of large computational effort and poor fitting accuracy, making it more applicable to the study of the impact of parameters on the grinding status, with a simpler process and higher accuracy. In addition, this new method is applicable to minerals other than magnetite. Further research is required to verify its applicability to wide size ranges and continuous grinding.

Ceramic grinding, which in this paper is defined as a method of using ceramic materials as grinding media, is favored by many processing plants as an emerging high-efficiency and energy-saving grinding method. This paper investigates the effect of slurry mass concentration on the grinding characteristics of magnetite by taking the feed of the secondary ball mill for processing magnetite as the research object. The study results show that the slurry mass concentration significantly affects the ceramic ball grinding characteristics of magnetite, especially for coarse particles. When the grinding concentration is higher than 50%, the breakage rate of magnetite plummets to 1/3 of the value at low mass concentrations. The standard deviation of the breakage rate relative to the concentration gradually decreases as the feed size falls, indicating that the coarser the feed size, the more sensitive the ceramic ball grinding is to the concentration, and thus industrial secondary ceramic ball mills need to avoid grinding under high-quality concentrations. The change in the consistency parameter of distribution function and zero-order output characteristics signals a radical variation in the grinding characteristics of magnetite using the ceramic ball grinding method compared to conventional grinding. Because the ceramic ball grinding method can greatly reduce energy consumption while lowering the chance of overgrinding, this grinding method deserves more attention as the world works to reach carbon neutrality and emissions peak.