GB697268A - Improvements in process and apparatus for separating material according to its specific gravity - Google Patents

Abstract

697.268. Washing granular materials. FAIRWEATHER, H G. C. (RAKOWSKY, V.). Aug. 31, 1951, No 20555/51. Class 82(ii) A sink and float process of separating material into light' and heavy fractions comprises feeding the material into a bath of self-sustaining separating medium whereby a supernatant zone of low medium content is formed, overflowing the supernatant zone, overflowing medium and floats immediately below t h e supernatant zone, draining the products from both these overflows and recirculating at least a portion of the drainage from the product containing the float material, washing adherent medium from the float material, cleaning at least some of the washings and returning the cleaned medium at a predetermined density to the separating medium, thickening the drainage from the supernatant zone and returning this thickened product to the separating zone. In the process shown in the flow sheet, Fig. 1, the separatory vessel receives the feed and make-up medium and the sink and float products are removed and screened, the drainage then being returned to the vessel. The sink and float products are then washed and the washing, with the optional addition of some of the sink and float drainings, are passed, via a magnetizing element if the medium'is magnetic, to a thickener. The thickened medium is then cleaned, dewatered, demagnetized and returned as make-up medium. The supernatant zone, removed from the separatory vessel, is screened and the drainings are either (a) combined with the sink and float washings for thickening therewith, or (b) passed to a separate thickener and returned as part of the make-up medium. The density of the make-up medium may be controlled by automatically varying the amount of return water supplied. In theform of separatory vessel shown in Fig. 3, the float material flows over a lower weir 4 while the supernatant water layer which is built up by a curved baffle 11 is skimmed off together with some light waste 14 by an adjustable weir 8. Specification 546,847 is referred to.