Behaviour of Low Rank High Moisture Coal in Large Stockpile under Ambient Conditions

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Authors : Naveen Chandralal, Mahapatra D., Shome D., Dasgupta P.


The low rank high moisture of coal from East Kalimantan, Indonesia has been tested in large stockpiles to understand the possibilities of lowering their total moisture content under ambient conditions. The results from the small scale drying tests indicate a strong potential to significantly reduce the “as mined” moisture content of high moisture low rank coal. All tests showed consistent losses over time with an average weight loss of 27% for the 22 day test period. These test show the maximum possible natural drying potential with no impediments to drainage and no additional moisture load from rainfall. It can be expected that drainage will allow reduction in moisture.

The size distribution shows a mean size of 10mm and low proportions of ultra-fine material, which makes the crushed coal suitable for stockpile drainage as there should be ample clearance between particles. Dry conditions allowed the piles to drain free moisture at a loss rate of between 0.7 and 1.7% per day. Additional rain periods ensured that the overall effect was a gain in moisture for the trial period. It would be apparent that the greatest drying benefit would be gained by sheltering the coal from rain. Any drying benefits gained by stockpiling could be reversed by rainfall exposure. This evaluation would suggest that, without consideration for the weather condition effecting the stockpile temperature and moisture, a natural drainage period of between 18 and 25 days would assist in the reduction of moisture associated with the high moisture low rank coal.


Low rank, Coal, Stockpile, Total Moisture, Rainfall, Rain


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