GB507661A - Concentration of ores and other minerals by the sink and float process - Google Patents

Abstract

507,661. Wet-separating. PEARSON, A. Oct. 15, 1937, No. 28109. [Class 82 (ii)] In the " sink and float" process for concentrating minerals by the use of a substantially stable heavy suspension, the tendency of the viscosity of the suspension to increase during the process is controlled during the course of the process by adjusting the relative proportions of fine and coarse particles in the dispersed phase whilst keeping the specific gravity of the suspension'substantially constant, the adjustment being effected by removing a part of that portion of the dispersed phase the particle size of which is intermediate' that approaching brownian size and that which settles rapidly, and replacing it by a suitable amount of the dispersed phase of larger particle size. The initial suspension may be prepared by adding to a stable suspension in a liquid of finely levigated galena or other heavy substance which contains a relatively large proportion of particles approaching brownian size, the same substance of coarser grain size, until the desired specific gravity is attained. In the process indicated in the figure, galena concentrates at A are passed to a classifier B, preferably of the rake type, oversize particles from which are reduced in a ball mill C and returned to it. The overflow from the classifier is dewatered and made up into a suspension at E, from which the suspension passed to the vessel F where the sink-andfloat process is carried out. During the process the viscosity of the suspension increases due to attrition and the entrainment of fine particles of foreign matter of low specific gravity. A portion G1 of the medium is therefore withdrawn and subjected at H to a treatment which removes a portion I of the dispersed phase, the particle size of which is less than that at which rapid settlement takes place, but greater than that approaching brownian size, that is generally between 800 and 2000 B.S.I. mesh. The removal may be effected by gravity separation in a hydraulic or rake type classifier, or by froth flotation if fine particles of foreign matter have been entrained. The remaining solid galena concentrate HI thus obtained is returned to the classifier B, which is meanwhile operated to produce the necessary amount of larger size particles to restore the original size ratio in the suspension to be prepared at E so that this may have the same viscosity and specific gravity as the original suspension.