Can old bord-and-pillar workings be mapped from surface?
Desktop review updating two earlier assessments, weighing borehole scanning, robots and unmanned aerial platforms as routes to locating old workings ahead of opencast drilling and blasting.
No surface geophysical method can map individual bords and pillars at the depths typical of the Witbank coalfield, a limit the review attributed to physics rather than to technology, since the targets are small relative to their depth and conductive layers often lie above the seam. Borehole laser scanning remains the workable option, with sonar suited to flooded workings.
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Recovery of Rare Earth Elements by J Nkuna.pdf
Flotation, calcination and leaching tests on run of mine and discard coal, with mineralogy of the rare earth bearing grains. For processing researchers and waste stream owners.
What this report foundRun of mine and discard coal carried total rare earth contents of 260 and 265 ppm, above the 130 ppm cut off grade used for coal.
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Run of mine and discard coal carried total rare earth contents of 260 and 265 ppm, above the 130 ppm cut off grade used for coal. Flotation with an emulsion binder did not raise those concentrations in either the product or the tailings streams. Calcination did, lifting totals to between 285 and 289 ppm, with most rare earths leaching within the first fifteen minutes.
Geotechnical Factors Associated With Previously Mined Areas of Coal and Their Impact on Subsequent Extraction
2002
Masters research on pillar extraction in the Witbank Coalfield, ranking the ground conditions that decide method choice and safety, for rock engineers and mine planners.
What this report foundGeotechnical factors affecting secondary extraction were identified from interviews with collieries already re-mining pillars and with people experienced in...
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Geotechnical factors affecting secondary extraction were identified from interviews with collieries already re-mining pillars and with people experienced in stooping, then quantified and ranked against the different aspects of the work. No single factor governs the outcome. Factors interact, so choosing a method and working safely in old workings depends on managing them together across disciplines.
Upgrading of coal fines with a Centrifugal Concentrator
Bench and pilot testing of four centrifugal concentrator models on fine coal from two collieries, with operating variables that resisted correlation flagged for further work. For plant metallurgists.
What this report foundFour centrifugal concentrators all cut ash in fine coal, with desliming the decisive step.
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Four centrifugal concentrators all cut ash in fine coal, with desliming the decisive step. The best unit took ash from 35.2% to 18.47% and sulphur from 0.68% to 0.36% in a single stage, raising calorific value from 23.78 to 26.16 MJ/kg. Pilot work reached 19% ash on thickener underflow and reconstituted spiral feed.