High Pressure Grinding Rolls (HPGR) technology is the continuous version of the confined particle-bed breakage. Feed size distribution has a key role in total specific energy consumption and product size reduction. Fines in the HPGR feed are defined as relatively small particles that should not undergo much breakage while assisting the breakage of larger particles. Extensive testwork has been performed on a 200 mm by 100 mm lab-scale HPGR at the University of Utah on different ore types. Various artificial feed size distributions have been prepared by mixing large narrow-sized particles as the main portion of the feed and different sizes and percentages of fines to complete single-pass and closed-circuit tests. The effect of the fines content is evidently dependent upon the size ratio between the feed main portion and the fines. In addition, fine particles help with better energy transformation in the grinding zone to a specific level depending on the size for the feed main particles. The presence of the fines in the closed-circuit configuration helps with improving the breakage rate and the total energy consumption when compared with closed-circuit grinding on a narrow-sized feed.
S. Rashidi and R. Rajamani; University of Utah, Salt Lake City, UT