Patent GB-361906-A (GB)
Title: Improvements in and relating to the washing and draining of coal or other minerals
IPC: B03B5/44
Filed: 1930-06-23
Abstract: 361,906. Filtering and straining liquids. CLEAN COAL CO., Ltd., LESSING, R., and ALLEN, R. H., Medway House, Horseferry Road, London. June 23, 1930, No. 19045. [Class 46.] In treating coal or other unground lumpy mineral to remove aqueous solutions mixed therewith the mineral is immersed in a body of weaker aqueous solution and then withdrawn out of the body of liquid up an inclined imperforate surface, being finally passed over a perforated surface to drain off remaining liquid. The process is particularly applicable to the treatment of the concentrate or refuse after a separation in an aqueous solution, e.g. a solution of calcium chloride. In the apparatus shown in Fig. 1 coal and shale are separated in an aqueous solution of calcium chloride in the tank 3, the float being removed by a conveyer 5 and passed over a screen 4, the liquid draining into the vessel 6 being returned by pumps 7, 8 to the tank 3. Alternatively, the coal may be drained by passing it over vibrating screens and the liquor may then be replaced by more dilute liquor. The drained coal falls into the lower end of a trough 9 containing a weaker solution of calcium chloride than that adhering to the coal and is conveyed up the sloping side 12 and over a sieve 13 by a scraper conveyer 10 with perforated scraper plates 11. The solution passing through the sieve 13 into a vessel 14 is collected in a tank 15 for reconcentration. The coal falls from the end of the sieve 13 into the lower end of a second trough 16 in which it is subjected to a treatment similar to that in the trough 9, the liquid draining through the sieve 19 of the second trough into a vessel 20 being pumped back to the lower end of the first trough 9 where it forms the body of weaker solution into which the coal falls. The coal from the sieve 19 falls down a shoot 22 into the lower end of a third trough 23 where it is again treated in a similar manner, the liquid draining off being pumped back to the trough 16. Any number of troughs may be used with solutions of successively decreasing concentration, the coal falling finally into a hopper 29 in a trough 30 from which it is drawn up a covered incline 32 by a conveyer 31 against a counter current of water sprayed on the coal at 34 and then over a sloping sieve 37 to a drier if desired. The liquid in the hopper 29 is maintained at a constant level by an overflow pipe 35 which feeds the excess through a pump 36 to the lower end of the trough 23. The liquid draining through the sieve .37 may pass to waste through a pipe 40. The troughs 9, 16, 23, 30 may be arranged so that the liquid draining through the sieves passes to the lower end of the preceding trough by gravity. In a modification, Fig. 2, the coal preferably after draining is fed to a basin 41 at the lower end of an inclined trough provided with a cover or baffle-plate 44. Water supplied at 45 flows down the trough through the coal, which is carried up the inclined wall by a conveyer 43, and forms a pool of weak solution in the basin 41. An overflow pipe 46 is provided to maintain constant the level of liquid in the basin. The coal is finally drawn over a sieve 48. In the form shown in Fig. 3 the baffle-plate 44 is united to the walls of the trough forming an inclined tunnel, the lower end being shaped to form a hopper 41 with overflow 46. Weak solution may be fed in at 49. The apparatus shown in Figs. 2 and 3 may constitute the final stage in the process described with reference to Fig. 1. The coal may be finally freed from any weak solution by allowing it to fall through a body of water to an elevator which raises it to a draining device. According to the Provisional Specification, the sieves may be vibrating or reciprocating screens which act as conveyers for the material or may be divided into sections and caused to vibrate or reciprocate in a direction perpendicular to their surfaces, the material being moved over them by scraper conveyers. Specifications 276,723, 282,874, 325,031, [all in Class 82 (ii), Washing granular &c.], and 341,863, are referred to.