Wet Pre-Concentration of Low-Grade Hematite in High-Pressure Grinding Roller

The wet pre-concentration of comminuted hematite in high-pressure grinding roller was studied, using the cylindrical ferromagnetic medium in a high gradient magnetic separator. The effects of various factors including rod diameter, rod gap and background magnetic field intensity (BMFI) on the performances of pre-concentration in different size feeds are emphatically investigated. The results showed that as the rod diameter increased, the rod gap decreased and the BMFI increased, the tailings grade and the tailings yield reduced, but the concentrates recovery raised. This variation was regardless of the feed size distribution. After the classifying pre-concentration, the overall concentrate grade increases by 9.56 percentage points and the concentrate recovery is up to the 82.67% with a tailing grade of 10.68% and a tailing yield of 40.31%. Compared with the classifying pre-concentration, the full size pre-concentration produced a concentrate with a lower grade only increased by 6.61 percentage points and the higher recovery of 92.32%. The tailings, with a lower yield of only 26.62% and a lower grade of 7.39%, was mainly produced from the fine feed. The coarse feed in the full size pre-concentration was not separated effectively.