Secondary Crushing Method & Circuit

A secondary crusher is frequently needed when the product from the primary crusher is too large for efficient grinding. In North America, the main type used is the cone crusher. It is a close cousin of the gyratory crusher, although the speed of the cone crusher is greater and it is designed to handle smaller pieces of rock.

Vibrating screens are used to control the size of the final product from the crusher building. Ore that falls through the openings in a screen is called undersize. It will find its way into the mill on a conveyor belt. Ore that is too large to fall through the openings is called oversize and it returns to the crusher along with a separate conveyor belt. This ore is called the circulating load.

Crusher buildings are typically equipped with dust control and ventilation systems designed to eliminate the buildup of harmful dust.

Must mills operate seven days a week, 24 hours a day, compared with the mine, which typically operates only five days a week. Because of this difference in work schedules, crushed ore must be stored on surface in sufficient quantities to keep the mill going around the clock. The customary place to store the ore is in a fine ore bin next the mill. These bins generally contain enough ore to keep the mill operating for at least 48 hours.