GB799579A - Improvements in and relating to the separation of coal - Google Patents

Abstract

799,579. Washing granular materials. SIMON - CARVES, Ltd. Feb. 21, 1956 [March 1, 1955], No. 6007/55. Class 82(2) In a process for separating coal into constituents of different specific gravities, the coal is first subjected to a separation according to specific gravity in a trough or jig washer or other apparatus employing water for treating the coal; and is subsequently subjected to a separation according to specific gravity in a dense medium washer, a part of the clays removed in the first wet treatment being subsequently added to the dense medium separator in order to stabilize the medium. In Fig. 1, raw coal (e.g. up to 6 inches in size) is supplied at 1 to a jig washer box 2, to which water from a settling tank 4 is supplied via a pipe 3. After being washed in box 2 the coal passes to a draining screen 5, the liquid draining therefrom passing to a tank 6, the coal passing to a classifying screen 7 where small material (up to ¢ inch) is removed, the larger material being conveyed to a sink and float separator 8 supplied with dense medium of the correct density from a stock tank 11. Liquid collected in tank 6 is pumped to the settling tank 4, solid material accumulating at the bottom of tank 4 is removed from time to time, drained on a screen 10 and disposed of, the liquid draining to tank 6. Part of the clay-containing liquid in the settling tank 4 is led to the separator 8. Alternatively, this liquid may be conveyed, possibly through a thickener such as a cyclone 16, to the medium stock tank 11 to be mixed with the medium before it is pumped to the separator 8. Fig. 2 shows a medium recovery system. The sinks from separator 8 are sprayed with wash water on screen 27; the first part of the underflow is returned to the stock tank 11 and the second part to a dilute medium tank 24. The coal is washed by water on screen 30, the first part of the underflow being returned to the stock tank 11 and the second to the dilute medium tank 24. The medium is then pumped to a magnetic separator 35 where slimes, clay and water overflow and pass to tank 36, to be re-used as wash water. The medium from the bottom of tank 35 is pumped through a demagnetizer 37 to a splitter box 40 from which part of the medium is led to the stock tank 11 and the remainder to the magnetic separator 35. Some of the overflow from tank 36 may be taken to a cyclone 43 to be thickened and led to tank 11, the water from the cyclone returning to the wash water circuit. Alternatively, the slimes and clay may be taken for thickening to a cyclone 48 and then led to stock tank 11, the water being returned to tank 24. Specification 728,195 is referred to.