Hold-up weight in continuous wet ball milling: Relationship with the size distribution of the particulate contents of the mill

In the continuous mode of wet grinding operation, the amount of the particulate material present in the mill, commonly known as the hold-up weight, varies with the mill operating conditions and the breakage properties of the material being ground. How these variables affect various hold-up determining mixing and transport phe-nomena occurring in the mill is presently not well understood. Therefore, one finds only some material -dependent empirical and semi-empirical correlations in the literature. As the size distribution of the hold-up material also depends on the same mixing and transport phenomena, we used it as a basis to develop a new correlation. For our purposes, the experimental data on continuous grinding of limestone, feldspar, and quartz in a 40.6 cm long by 40. 6 cm diameter grate-discharge ball mill was found suitable. The feed rate of the solids, the weight percent of solids in the slurry, and the feed size distribution were the only operating variables covered. Using a particular dimensionless number to characterize the hold-up size distribution resulted in a material -independent correlation that also worked well for a higher-density sulfide ore ground in the same mill. More importantly, this correlation provides new insight and a better understanding of the experimental results than other correlations.