Patent GB-1349603-A (GB)
Title: Methods of and apparatus for separating particulate material
IPC: B07B13/00
Filed: 1971-12-31
Abstract: 1349603 Separating solids COAL INDUSTRY (PATENTS) Ltd 17 Oct 1972 [31 Dec 1971] 60945/71 Heading B2H  In an apparatus, Fig. 1, for separating particulate material, e.g. damp, raw small coal, into oversize and undersize products, the material, e.g. from a bunker 8, is fed, e.g. by means of a conveyor 7, through an inlet 2 into an upper region of a container 1 and a surface layer of relatively coarse material moves down a path defined by the angle of repose of the particulate material in the container towards an overflow outlet 3 for the oversize product while relatively fine material is segregated from the surface layer and moves down the container towards an outlet 4 for the undersize product positioned adjacent to the base of the container. The outlet 3 is formed by a weir plate 10 extending across the width of the container and located below the level of a ledge 5 onto which the particulate material is dropped. A weir plate 6 is arranged across the container. An extraction conveyor 12 is located below the outlet 4. In operation, the particulate material builds up on the ledge 5 and forms its natural angle of repose. Consolidation of the material on the ledge prevents the relatively coarse heavy particles from penetrating into the material below the surface layer. As more material is fed through the inlet 2 it flows as a surface layer down a path defined by the angle of repose of the material and fills the container until it overflows through the outlet 3. The extraction conveyor 12 is then started and material is drawn through the outlet 4. Control means are provided for the conveyors 7 and 12 to ensure that an overflow condition exists and that the material moves slowly downwards towards the outlet 4. As the surface layer of material flows off the ledge 5 down the path defined by the angle of repose of the material the particles in the surface layer tend to be segregated into an upper band of coarse particles, a lower band of fine particles and an intermediate band of both particles. The lower band of particles tend to merge with the material beneath the surface layer and move down toward the outlet 4. The upper and intermediate bands continue to flow down the path until they reach the weir plate 6 where they tend to be intermixed as they flow over the plate 6 allowing the coarser particles in the intermediate band to pass into the upper band and to continue to flow along the path to be discharged over the plate 10 through the outlet 3. The fine particles which have passed over the weir plate 6 tend to merge with the material in the container and flow towards the outlet 4. In modification, the weir plates 6 and 10 may be adjustable; the plate 6 may be dispensed with; a plurality of plates similar to plate 6 may be provided; a scraper conveyor may be provided intermediate the ledge 5 and the outlet 3 to urge sticky material in the surface layer to flow towards the outlet 3; the container I may be vibrated. In another embodiment, Fig. 3 (not shown), the particulate material is fed through a central inlet and via an adjustable distributor towards each side of the container. The feed impacts on to a central cross plate and the surface layer flows towards an intermediate weir plate and an overflow outlet for the oversize product provided on each side of the container. In a further embodiment, Fig. 5, the material fed via inlet 22 passes through a rotary mixer 25 which breaks up agglomerates and falls on a circular plate 26 which may be rotatable. A rotary distributing disc is provided at 27, and a circular weir plate at 28. The container 21, which may be vibrated, is conical and has a circular overflow outlet 23 for the oversize product and a central outlet 24 for the undersize product.