Patent GB-704890-A (GB)
Title: Process and apparatus for separating mixtures of particles differing in specific gravity and particle size, into fractions according to specific gravity
IPC: B04C5/16
Filed: 1951-05-29
Abstract: 704,890. Centrifugal separators; washing granular material. MAATSCHAPPIJ VOOR KOLENWERKING STAMIGARBON N. V. May 29, 1951 [May 30, 1950; June 24, 1950; June 24, 1950; May 25, 1951], No. 12625/51. Classes 23 and 82 (2) A mixture of solid particles is separated into a fraction consisting of particles having a density above a separating density and a fraction consisting of particles below the separating density by mixing the particles with a carrier fluid, and passing the resultant mixture through a hydrocyclone having the diameter of the outlet for the heavier fraction not greater than 0.7 times the diameter of the outlet for the lighter fraction, and the included angle of its " conical part " lying between 50 degrees and 90 degrees. The term " conical part " includes solids of revolution having walls concave or convex towards the axis. If the carrier fluid is a liquid or liquid solution the separating density is greater than the density of the liquid or solution, and if the carrier fluid is a suspension of solids in a liquid the separating density is greater than the density of the suspension discharged with the heavier fraction. The carrier suspension may be formed from finely divided particles of either of the fractions. As shown in Fig. 1 the outlet 4 for the heavier fraction has exchangeable rings 5 for adjusting its diameter, and the outlet for the lighter fraction is defined by an axially adjustable tube 6 which discharges into a chamber 9. In a modification, Fig. 3 (not shown), the chamber is displaced from the cyclone, and the diameter of the outlet for the heavier fraction is varied by means of an inflatable annulus. In a further modification, Figs. 5, 6 (not shown), four hydro-cyclones are arranged in parallel about a common feed pipe to form a multi-hydro-cyclone and the lighter fractions from the cyclones are collected in a common chamber. By suitable choice of back pressure exerted at the outlet for the lighter fraction from the hydro-cyclone together with adjustments in the diameter of the outlet for the heavier fraction and in the axial position of the tube defining the outlet for the lighter fraction, separating densities of as great as 1.6 times the density of the carrier liquid or solution, or 1.6 times the density of the density of the carrier suspension discharged with the heavier fraction may be obtained. In the plant shown in Fig. 7 a mixture of particles from a tank 38 is fed to a multi-hydro-cyclone 60 having a low separating density, and the heavier fraction from the cyclone 60 is fed to a multi-hydrocyclone 50 having a high separating density. The final fractions, the lighter fraction from the cyclone 60 and the heavier fraction from the cyclone 50, are led away by pipes 66, 55 respectively. Tanks 61, 51 are provided for thinning the mixture before it passes through pumps 63, 53. In a modification of the plant, Fig. 8 (not shown), the mixture is first fed to the cyclone having a high separating density and the lighter fraction from this cyclone is fed to the cyclone having a low separating density. In the plant shown in Fig. 9 a mixture of particles is first separated in a multi-hydro-cyclone 40 having a medium separating density, the heavier fraction from the cyclone 40 is fed to a multi-hydrocyclone 50 having a high separating density, the lighter fractions from the cyclones 40, 50 are fed to a multi-hydro-cyclone 60 having a low separating density, and the final fractions, the lighter fraction from the cyclone 60 and the heavier fraction from the cyclone 50, are led away by pipes 66, 55 respectively. In modifications of the plant shown in Fig. 9, Figs. 10, 11 (not shown), the cyclones are arranged in different orders. The Specification gives examples of mixtures treated and of carrier fluids together with dimensions of hydro-cyclones according to the invention. Specifications 528,590, 601,063, 601,166 and 693,649 are referred to.