GB421890A - Improvements in or relating to the washing of coal - Google Patents

Abstract

421,890. Washing coal. MINERALS SEPARATION, Ltd., and WILLIAMS, P. T., 62, London Wall, London. June 27, 1933, No. 18321. [Class 82 (ii)] In a coal washery in which the coal is washed in jigs, trough washers, or other wet gravity separating apparatus, and the washed coal is passed over screens for separation of the water, the whole or part of the water passing through the screens is subjected to froth flotation to separate the fine coal, and the bulk or part of the tailings water from the flotation plant is passed to a settling tank from which the clarified water is returned to the washery. When part only of the water from the screens is to be treated, the remainder is returned direct from the coal screens to the jigs. The coarse particles may be separated from the water passing through the screens, e.g. by settling, before the latter is subjected to the flotation treatment, and the flotation concentrates may be subjected to one or more further flotation treatments. In the form shown, washed coal from jigs 11 passes on to screens 12 from which the water drains into a small settling tank 13 in which the coarse particles settle. The overflow from the tank 13 passes to a flotation apparatus 14 which preferably comprises one or more large boxes suitable for the treatment of dilute pulp. A small amount of frothing agent, e.g. cresol, is added to the pulp, and the small coal removed as a froth concentrate, which may be retreated one or more times in smaller cells 16. Fresh water is added to the last of the retreatment cells, and the tailings water from this cell is taken to the preceding cell, and so on, the tailings water from the first retreatment cell being returned to the jigs. The whole or part of the tailings water from the main flotation cell 14 is passed to a clarification vessel 17 where the clay slimes settle, the supernatant water being drawn off at 27 and returned to the jigs. If only part of the tailings water from the cell 14 is passed to the vessel 17 the remainder is returned direct to the jigs. The fine coal concentrates from the flotation treatment are passed to a dewatering apparatus 20 or to the coal screens 12. The coarse particles settling in the small tank 13 may be treated by a classifier 18 or tables or flotation apparatus, the coal recovered being passed to the dewatering apparatus 20 or the coal screens 12, and the tailings passed to a dewatering apparatus 19 and then to waste, the water from the apparatus 19 returning to the jigs. Specifications 122,454, 215,841, and 240,799, [all in Class 82 (ii)], are referred to.