Critical Geotechnical Factors Impacting on Reserves in Previously Mined Areas in the Northern Witbank-highveld Coalfield

Market prices are set out for sodium sulphate, sodium chloride, sodium nitrate, potassium nitrate and potassium chloride, in South Africa and abroad, as at early 2011, with Chinese supplier quotes alongside United States averages. The work was done to test whether salts recovered from mine water brine could be sold at a worthwhile price.

Conveyance legislation promulgated in 2008 and enforced soon after left the coal industry without a lawful way to clean near and under running conveyors. The first phase defined the problem, recorded the cleaning practices mines already use successfully, and built a structured database of mechanised platform options worth pursuing. High risk areas remain drives, take ups, snub and tail pulleys and transfer points.

Dense medium cyclones on the fine coal fraction lifted product yield well above the spiral circuit they were compared against and gave closer control of product quality. Cut point density control proved the hardest part of running the plant, medium properties being critical. Magnetic separator capacity had to match the duty, and a basement was needed to contain and recover medium spillage.