Why preconcentrate, and how?

Abstract

As high-grade deposits are depleted, mines are faced with lower feed grades. This requires the mining and processing of much larger volumes of material per tonne of product. 

The aim of preconcentration is to remove barren material as early in the process, and at as coarse a particle size as possible, to reduce the amount of material requiring downstream comminution and processing. 

Preconcentration can significantly improve the economics of a project by upgrading below cut-off grade material and/or increasing production rates.

Furthermore, gangue is usually high in silicates, harder and more competent than valuable minerals, so removal of this barren material prior to further comminution can significantly
reduce energy consumption and processing costs.

Ore transport requirements such as hoisting and truck or conveyor haulage may also be reduced, and there is less water consumption and a smaller volume of fine, wet tailings to dispose of per tonne of product.

There are several technologies that may be applicable for preconcentration including: gravity concentration, screening, sensor-based ore sorting (SBOS) and magnetic separation. The
suitability in each case depends on the ore properties as well as site and economic conditions.