FGX Dry Processing Tests Conducted at Exxaro’s Northern Block Complex

Grazing trials on tall fescue pasture irrigated with gypsiferous mine water on rehabilitated mined land, run over several seasons. The work covers steer stocking rates, dry matter intake by cattle, and the factors that control pasture quality and intake, among them nitrogen fertilisation, stage of growth, sward structure and grazing intensity. Findings are reported study by study.

A modified alkaline barium calcium process was tested on coal mine acid drainage, using calcium hydroxide neutralisation, hydrogen sulphide metal removal and barium carbonate sulphate removal. Gypsum formation during water treatment fell by 80 per cent, cutting the sludge sent to costly downstream processing to a fifth. Temperature, reaction time, reagent ratios and feed particle size affected thermal treatment of the sludge.

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.