GB1246406A - Method of and apparatus for separating coarse and/or heavy particles from a mixture of granular solids with differing particle sizes and/or differing particle weights - Google Patents

Abstract

1,246,406. Pneumatic separation. METALLGESELLSCHAFT A.G. 9 Jan., 1969 [24 Jan., 1968], No. 1492/69. Heading B2H. [Also in Division C3] In an apparatus for separating granular solids according to size and/or density by an upward gas current, a mixture of the solids is held in a state of a relatively dense turbulent layer by the gas current in the upper region 2 of a vessel 1, Fig. 1, and in a state of a relatively loose turbulent suspension in a lower region 3 of the vessel of smaller cross-sectional area than the region 2, the regions 2, 3 being interconnected by a region 4 having an effective flow cross-sectional area smaller than that of the region 3 so that the velocity of the upwardly flowing gas is increased at the region 4, means 9, 10 being provided at the lower and upper ends of the vessel for removing the coarse and/or heavy and the fine and/or light solids respectively. The gas is introduced through a chamber 6 and through a perforated base member 5 above. An upwardly tapering member having a flat base, Fig. 10 (not shown), may be provided above and spaced from the member 5. The mixture of solids to be separated may be fed at 7 and 8. The restriction in the flow-cross sectional area in the region 4 may be provided by a perforated plate 12 below and above which perforations 13 in the shell of the vessel communicate with annular passages 14, 15 through which gas may be discharged or fed in. Alternatively, the flow restriction may be provided by inserting a fixed or axially movable conical headed insert in the region 4, or by tubes 26, Fig. 6, extending between upper and lower plates 27, 28 in the region 4, additional gas being fed at 30 and passing through roof-screened tubes 32 inserted in bores in the plate 27. The additional gas may alternatively be introduced through a bent tube 34, Fig. 7, extending through the perforated plate 12 and communicating at its upper end with radially extending perforated distributor tubes 38. Instead of being discharged through a Genual tube 9 the coarse and/or heavy solids may be removed via an annular chamber, Fig. 9 (not shown), surrounding the base member 5 and provided with a valve discharge line. In a reactor 50, Fig. 11, for the polymerisation of an olefin, e.g. ethylene or propylene, a dense turbulent layer of fine polymer and catalyst particles is provided in the upper section 51 and monomer gas to be polymerised is introduced through a line 62, a chamber 63, and a gas distribution grid 64 into a lower section 52 from which it flows upwardly via an accelerating contraction section 53 into the upper section 51 where growth of the polymer on the catalyst particles takes place. The large polymer particles which are formed are discharged downwardly against the upward gas current through the section 53 and into the section 52 where the particles are held in a loose suspension allowing polymerisation to be completed before they pass through a discharge tube 54 and a valve 55 to a storage vessel 56. To make up for the spent catalyst, a mixture of fine polymer and catalyst particles, which may be drawn from the surface of the turbulent layer through a valved discharge tube 59, is introduced continuously from a supply vessel 60 through a metering device 57 and a feed tube 58. The unreacted monomer gas passes through a line 66, a dust-separating cyclone 68 and gas coolers (not shown) and is recycled through the reactor by a compressor 70 connected to the line 62. Monomer gas used up during the reaction is replaced through a line 71, a pressure regulating valve 72 and a line 73 connected to the section 53. A partial gas current may be withdrawn from the lower reactor section 52 to be fed to the upper section via line 75 or to be discharged from the reactor via a line 76. The polymerisation may be effected at atmospheric pressure or at a pressure of up to 50 atmospheres.