With energy costs increasing and ore grades diminishing, the role of pre-concentration in hard rock mining operations has been gaining greater interest. To maximise energy conservation, the pre-concentration process should be conducted at as coarse a grind size as possible, while minimising loss of pay metals. Dense medium separation (DMS) is a robust process that can be conducted at particle sizes as coarse as 300 mm and as fine as 500 µm with high separation efficiency, depending on liberation characteristic of the value minerals. The DMS involves three steps: feed preparation, dense medium separation, and ferrous-based media recovery. This paper discusses each of these processing steps, but focus will be given to the dense medium separation stage. Various types of dense medium separation equipment are reviewed. Pilot plant campaign case studies conducted at the SGS Lakefield site are presented, which have included a variety of mineral systems such as spodumene, sulphide-bearing gold ores, and complex sulphide ores. These case studies demonstrate for amenable ores, mass rejection of 2--60% is possible while maintaining recoveries of greater than 90% in most cases.
This paper was presented at SAG 2015, and may be downloaded here.