Energy considerations in compressive and impact crushing of rock

A cone crusher and a vertical shaft impact (VSI) crusher were operated in closed circuit to compare the performance of the two different crushing machines. The crushers were operated in closed circuit with a 9 mm final screen aperture size. A comparison of capacity, size reduction and power draw shows that the VSI crusher is significantly more energy efficient than the cone crusher, and it produces significantly more fine material. The study also shows that the recirculating load is higher with the VSI than with the cone crusher. Compared to the cone crusher, the VSI product contained 65% more material smaller than 1 mm while at the same time consuming less power. An alternative energy measure was introduced to assess the value of feeding a finer product to a grinding mill. This measure suggests that a VSI can save 2–14% of the energy consumed in grinding, depending on the energy model used and the final product size. This estimate is in agreement with an energy saving of 11.8% observed in an iron ore application where VSI’s were introduced as a crushing step preceding the grinding circuit.