Progress 1n. Coal T echn1ology: Coal Preparation
G ENERALLY, the necessity for mining coals of higher impurity content, the drive for lower costs by intensive mine mechanization, changing market requirements, and the increasing competition of oil and natural gas, have continued to result in an upward rise in coal preparation, and have necessitated a more intensive study of coal preparation problems. Increasing adoption of continuous mining equipment, for example, is introducing new problems in coal preparation. Limited experimental work in the United States ( 1) shows that the effect of the continuous miner on size distribution varies with the characteristics of the seam. In some seams, the fines problem is lessened, in others it is greatly aggravated. Generally there is a decrease in the relative amount of the top sizes (plus 2 in.) and a substantial increase in the intermediate sizes (down to about 1/ 8 in.). Contrary to expected results, where continuous miners with vertical-moving cutting heads are used, an increase in impurities in the slack sizes does not necessarily occur where draw slate is taken. This is because the draw-slate tends to be kicked out in lump form. However, if a seam contains bands and lenses of impurities they are bound to be in the mined product. In addition, because of the use of from 3 to 12 gallons of water to allay dust in .continuous mining, the slack sizes are wet, sometimes containing 12 to 15 per cent water, a factor which enhances problems of screening and drying to meet market requirements . These changes in the coal as mined will, it is anticipated, require certain plant changes. Coarse-coal picking operations may be eliminated or reduced. Screening of the fines may have to be done wet and, for those mines where the fines are greatly increased, additional facilities will be needed for water clarification, where wet cleaning methods are employed. In addition, the capacity requirements of certain equipment will be greatly different for continuous-mined coal as compared to conventionally-mined coal.
Capacity, Coal, Coal preparation, Fine Coals in Great Britain, jig, magnetite, specific gravity, United States, Fines, Magnetite, Mine, Plants, separator, Water, Waters