Desktop Guideline on the Selection of Bulking and Settling Factors for Opencast Mines in Mpumalanga, South Africa

A compound dry cleaning machine de-stoned low grade raw coal without using water, but separation efficiency was low, with high relative density cut points and EPM values in the order of 0.3. Misplaced material was heavy and coal below 6 mm reported to product almost indiscriminately. The unit is cheap to buy and run, needs only crushing to 50 mm, and gives high throughput.

Mapping abandoned, inaccessible bord and pillar workings comes down to two options: borehole deployed laser or sonar scanning, or sensors carried in by unmanned vehicles. Drone mounted laser scanning for air filled voids and sonar carried by small submersibles for flooded workings were judged the most promising, but intrinsic safety, deployment and the risk of losing equipment still favour borehole methods for occasional use.

Prices for calcium and magnesium sulphate are recorded for South Africa and for world markets as at mid 2012, together with price trends and the groundwater chemistry that governs which salts a mine water stream will yield. The figures were assembled to support feasibility studies on a eutectic freeze crystallisation plant and an ion exchange plant.