Developing a Mechanised Cleaning System – for Cleaning Under and Around Moving Conveyors

A digital wetland map and linked database were compiled for the Upper Olifants River Catchment from existing literature, existing wetland layers and aerial photography. Wetlands cover about 2 147 km2, some 14 per cent of the 15 158 km2 catchment. The wetland layer is about 70 per cent accurate and its attributes about 60 per cent, so it suits baseline screening rather than site assessment.

Sub-seams within the No 2 Seam were characterised at a single test site using lithology, seam thickness, proximate analysis, petrography and geophysical logs, and a paleoenvironmental model was built from them. Wireline logs separated coal from interburden but could not resolve the individual zones, because the physical differences are too subtle. Better sedimentological models gave better reserve and resource estimates.

Ion exchange treatment of acid mine drainage from a closed KwaZulu-Natal colliery was piloted and shown to give effluent free processing, converting the salts into saleable products rather than sludge and brine. Reverse osmosis had previously produced water of discharge standard but left both. Combined flow from the two mine compartments averaged 4.6 megalitres a day.

Eutectic freeze crystallisation was compared with evaporative crystallisation as a route for treating hypersaline mine brine. Optimised commercial evaporative crystallisers use 40 to 50 kWh per cubic metre of feed. Laboratory work measured a eutectic temperature of -21.1 degrees Celsius for pure sodium chloride solution, and found that a large difference between coolant and solution caused scaling on the heat exchanger wall.