Patent GB-531822-A (GB)
Title: Improvements in a process and apparatus for separating granular material
IPC: B03B11/00
Filed: 1939-06-05
Abstract: 531,822. Wet-separating. HIRST, A. A., and SIMON-CARVES, Ltd. June 5, 1939, No. 16404. [Class 82 (ii)] In a process for separating granular material in which the material is subjected to a primary treatment in a relatively shallow main body of separating fluid forming part of a suspension the material of less density rising to the top of the fluid and that of greater density falling and being given a secondary treatment in one or more pockets projecting from the underside of the main body the density of the suspension is maintained substantially constant and greater than that of the fluid by removing from each pocket in a controlled manner settled sand with or without suspension. The material to be treated is fed by a shoot 39 on to a horizontal channel 40 and then by a shoot 41 into a suspension of sand in water contained in a trough 10 provided with inclined ends 11, 12 and a flat or slightly curved bottom 13. Extending through the trough 10 is a scraper 16 provided with blades of substantially U-shape and mounted on members 20 rotatably mounted on the trough, one member 20 being driven by a chain 21 from driving means. Pockets 14, 15 are provided in the part 13 of the container, each pocket having shield plates 22 mounted thereon and a cover plate 23 adjustably mounted on the base 13. Each pocket is provided with a vertical extension 24, Fig. 2, and an inclined extension 25, an endless scraping band 26 mounted on members 27 passing through the extensions. Slidable adjustable baffles 28 mounted on control rods 29 control the depth of flow across the pocket from the extensions 24, 25. Material removed from the bottom of the scraper falls through an adjustable opening provided by a plate 33 and falls into a perforated screen or jigger 34. upon the first portion of which the material is drained of suspension which is collected in a cone 35. whilst on a further portion the material is washed by liquids from sprays 36, spray liquid being collected in the cone 37 and washed material discharged down a shoot 38. An adjustable partition 30. is mounted in the trough 10 for the regulating of the velocity and/or the depth of the under flow below it. The material floating in the suspension is removed bY a comb convever 42 and deposited on a screen 44 in a channel 31 being drained of suspension and washed as described in connection with the screen 34. The density of the susnension in the trough 10 is maintained substantially constant by passing the suspension from the cones 35 by pipes 51, 54 and the channel 31 to a reserve tank 48. Fig. 1, being pumped therefrom bv a pump through a pipe 49 to the inlet end of the container 10. Intimate mixture of the suspension in the tank 48 is produced by a circulating pipe 52 provided with a pump 53. The underflow from the cone 37 and that under the screen 44 is conveyed bv pipes 54 to a dilute suspension tank 55. provided at the top with a screen or jigger 56, on which it is washed by sprayers 57, the underflow being forced by, a pump 59 through a pipe 60 into a settling tank 61 having an overflow 62 from. which clear suspension passes through a pipe 63 to a density control device 70 for mixing the over flow with thickened underflow from the tank 61 this mixture passing by a pipe 68 to the tank 48. A pipe 64 leads from the overflow 62 to a tank 65 connected to the sprays ,36, 45 and 57. To control the density of the suspension in each pocket, a pipe 71 connects the extensions 24, 25 and communicates through a two-way valve 73 with a pipe 74 leading to the tank 48. The part of the pipe 71 leading to the extension 24 is provided with a pump 72 by which the suspension can be circulated between the extensions 24, 25 and suspension can be withdrawn at a controlled rate by the byepass 74. In an alternative method of withdrawing the suspension at a controlled rate when using an endless scraper, the form and speed of operation of the scraper control the rate of removal of suspensions and settled sand and thus control the density of the material remaining in the pocket. The speed of the scraper must be such that all particles of granular material sinking in the pocket are removed by the scraper, and the form of the scrapers used in the pockets may be different in each case so that the amount of material removed therefrom will be different and so the -density of the suspension in the pockets will be different. Specification 530,787 is referred to.