Comparison of grinding characteristics in high-pressure grinding roller (HPGR) and cone crusher (CC)

We comparatively studied the ball mill grinding characteristics of comminuted hematite products using a high-pressure grinding roll (HPGR) and a conventional cone crusher (CC). The major properties, including grinding kinetics and technical efficiency (Et), were investigated. The parameters in m-th order grinding kinetics were analyzed, and grinding specific rates were visualized. Ore particles experienced three inherent stages in ball grinding mills, that is i) rapid grinding of coarse fraction, ii) dynamic grinding of medium size fraction, and iii) single grinding of medium size fraction. Particles with size -0.043+0.031 mm were used into dynamic grinding stage earlier than particles -0.105+0.043 mm, and then over-grinding of fines occurred easily. Compared with CC products, HPGR products had significantly shorter turning time points in three breakage stages, implying that HPGR products were ground faster with earlier occurrence of fines over-grinding. HPGR products gave lower Et at a decreasing rate than the CC products for -2.0 mm and -0.5 mm feeds. Then, it showed a slightly higher value of Et for -2.0+0.5 mm feed. This indicated that fines over-grinding in HPGR full-size products were more serious under the condition of coarse grinding, whereas the efficiency was higher, and over-grinding weakened significantly in HPGR coarse products because of screening-out fines.