Publications

A 30 tonne per hour pilot Allair dry jig upgraded run of mine coal to thermal coal specification, but could not effectively beneficiate finer duff. Cut point densities and EPM values matched other dry processing equipment, though the jig appeared to give better control of the parameters governing separation. Four tests ran on run of mine coal and two on duff.

Fine coal was screened at small apertures while surface moisture stayed below about 5 per cent. Above that, fines adhered to the coarser particles and screening became very difficult. The dual vibrating polyurethane mats stopped blinding and clogging, so screening area stayed available, but the screen action still could not dislodge fines from very damp coal.

A pilot brine concentrator treated Stage 3 reject effluent from a mine water reclamation plant, raising total dissolved solids from 24 g/L to 154 g/L at 88 per cent water recovery. The condensate met the national potable water specification. A separate run concentrated brine from 76 g/L to 145 g/L, solid salts were precipitated, and no scaling or fouling was seen.

A rating and ranking system was applied to South African coalfields and, separately, to the coal bearing countries elsewhere in the Southern African Development Community. The Waterberg ranked highest in South Africa and is the coalfield most worth detailed investigation as Witbank output declines. Botswana ranked highest among the other member states on contained resources and exploitation potential.

Tonnage estimates for the remaining low phosphorus resource could not be produced, because the phosphorus analyses supplied by mining companies did not state what had been measured. Distribution trends were still mapped. Coal at or below 0.010 per cent phosphorus is widespread in the Witbank Coalfield, restricted to the far northwestern Highveld, and follows a northwest to southeast band in eastern Ermelo.

Electrical and electromagnetic ground surveys were run over a Waterberg profile with borehole logs and three dimensional seismic data as control, to test whether cheaper methods can match seismic reflection for locating coal and faults. Resistivity tomography at two electrode spacings, frequency and time domain electromagnetics, controlled source audio magnetotellurics and magnetics were all acquired. Results are preliminary.

Cynodon dactylon outperformed Themeda triandra and Hyparrhenia hirta, reaching 100 per cent survival and cover at all three trial sites by 2007 with or without fertiliser. Acacia sieberana reached 97 per cent survival at Kleinkopje Colliery but grew poorly at Optimum and Syferfontein. Planting plugs suits slopes too steep for a planter machine and buffers against pasture grass intrusion.