Patent GB-1194213-A (GB)
Title: Sorting of Granular Material at Separation Limits below 1 mm.
Inventor: RUMPF HANS
IPC: B07B4/02
Filed: 1967-08-31
Abstract: 1,194,213. Pneumatic separation. H. RUMPF. 31 Aug., 1967 [31 Aug., 1966; 17 Aug., 1967], No. 39943/67. Heading B2H. Granular material below 1 mm. in size is classified into coarse and fine fractions by pro jecting the material from a centrifugal scatter plate 4, Fig. 1, at a velocity of more than 5 meters per second into a transverse annular stream of sorting gas issuing from an annular nozzle 2 and flowing parallel to, or with a slight whirl relative to, the axis of the plate 4 whereby the coarse particles pass right through the stream and are collected into a receptacle 9 and the fine particles are entrained by the gas stream through a cylindrical annular duct 1 and are thereafter separated from the gas stream. The material is fed by way of a bucket wheel 16 and a tube 15 onto the scatter plate 4 which may have a concave or conical surface, Figs. 3-9 (not shown), and which may be provided with one or more rings of radial or curved vanes extending from, or from the vicinity of, the centre of the plate to a region at a distance from the outer edge of the plate so as too provide a relatively high radial velocity component to the material. The plate may also be provided with an annular groove or ridge at a distance from its edge to provide for uniform scattering of the material. The plate may be provided with a cover with a gap therebetween which may decrease towards the edge of the plate. The plate may be of the composite type comprising inner and outer ooaxially mounted plates which may be driven separately or through gearing at different speeds, Fig. 8 (not shown). A flow straightener 3 provided upstream of the nozzle 2 provides the parallel or whirling flow of sorting gas. An auxiliary nozzle 6 of smaller flow cross-section than nozzle 2 supplies supplementary sorting gas for loosening up agglomerations of fine particles or for detaching fine particles from coarse particles. A slidable shutter 8 provides an adjustable outlet 7 for coarse particles thereby regulating the separation limit. The receptacle 9 may be lined with rubber or may have rubber walls. Supplementary sorting gas is sucked through an inlet 11 by the action of gas passing with the coarse particles through the outlet 7. Further separation of fine particles is effected in the receptacle 9 by gravity and by supplementary sorting gas blown through slits 18 or porous plates 20 in the inclined wall 10 of the receptacle. The sorting gas and the fine particles are drawn off through a helical casing 21 and an outlet 22 and the coarse particles are discharged through a slot 23 or through orifices 25 closed by flaps into an open fluid bed channel 26. In Fig. 2, the nozzle for supplying the main stream of sorting gas is shown at 64 and supplementary gas may be admitted through an inlet 67. Further separation of fine particles is effected in the coarse particle-receptacle 66 by means of gas which is blown by means of a blower 76 into an annular duct 70 and which passes through a slotted annular nozzle 69 entraining the fine particles through a duct 74. Separation of the gas and fine particles take place in a cyclone 78 from which the gas is recirculated to the blower 76. A main fine cyclone separated is shown at 80. Alternatively, the duct 74, is connected to the fines-receiving duct 60 through an opening 87 so that the supplementary gas and all the fines pass into the cyclone 80, the cyclone 78 being dispensed with. In Fig. 10, the main sorting gas is supplied upwardly through a nozzle 2 and, charged with fine particles, leaves the sorting duct 1 tangentially into cyclones 50. Further separation 'of fine particles is effected by gravity in the receptacle 9, the fine particles being discharged in the gas via a tangential outlet connected to the cyclones 50 or to a supplementary separator.