GB664290A - An improved process for the separation according to specific gravity of mixtures of particles differing in grain size and specific gravity - Google Patents

Abstract

The invention relates to a continuous process for the separation, according to specific gravity, of mixtures of particles differing in grain size and specific gravity, in which the mixture is passed continuously under pressure through one or more cyclones in a liquid suspension of fine specifically heavy particles obtained from the mixture to be separated, the concentration of such suspension-forming particles being such that substantially no specifically light particles will leave the cyclone together with the specifically heavy fraction, and in which the light fraction resulting from the cyclonic separation is subjected to a preliminary separation according to particle size, e.g. screening, to remove the coarsest particles of such fraction and the remainder of such fraction is subsequently separated to remove therefrom some at least of the finest particles therein. The invention resides in that the heavy fraction from the cyclone is sized, e.g. by screening, to remove the coarsest particles therein and thus, by means of classification or fractionation, the particles in the remaining part of the heavy fraction which are coarser than the fine specifically heavy suspension-forming particles therein, are separated from such suspension-forming particles and then wholly or in part crushed to a size corresponding with the grain size of the said suspension-forming particles, the uncrushed part of the said coarser particles being carried off, and the crushed particles, together with the suspension-forming particles separated therefrom prior to the crushing, and the suspension recovered from the light fraction, being recirculated for suspending the mixture to be separated. The heavy particles left after the first sizing may be separated into three fractions, the largest being discharged and the middle fraction crushed as stated above. Flow sheets for coal/shale separation and iron ore/gangue separation are included in the Specification, the shale and iron ore being the heavy fractions respectively. The first light particles are removed by froth flotation and in the case of the iron ore/gangue separation the suspension medium is magnetite, the additional step of magnetic separation being used in the process to discriminate between magnetite and haematite particles of the finer sizes, i.e. those particles not being removed by the initial screening steps, of both ore and gangue (heavy and light fractions). Specifications 601,063 and 665,957 are referred to.