Generation of Fine Coal In-Section

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.

A stand-alone device was built that detects micro-seismicity within 100 m of the roof and raises an alarm when preset thresholds are exceeded, giving early warning of goafing. Input parameters proved not to vary with geotechnical setting. Man-made noise triggering false alarms remained the main obstacle, addressed by signal conditioning and sensor placement.

Finite element simulation reproduced the rapid collapse of bord and pillar workings in the 2 Seam at a Witbank colliery, showing that progressive pillar deterioration triggers snap through of a strong sandstone plate in the overburden. Too little was known about the chosen collapse to back out a real pillar safety factor, so the calibration goal was not met.