Patent GB-1114395-A (GB)
Title: Hydraulic sizing apparatus with primary and secondary hindered settling columns
Inventor: EVANS ROBERT DONALD
IPC: B03B5/62
Filed: 1967-02-24
Abstract: 1,114,395. Wet separating. CONTINENTAL OIL CO. 24 Feb., 1967, No. 8867/67. Heading B2H. In an apparatus for classifying solid particles according to size, Figure 1, primary and secondary hindered settling columns 10, 22 are disposed beneath a free settling tank 14, the column 22 having a smaller cross-sectional area.than the column 10. The columns 10, 22 have lower portions 18, 28 defining collection chambers 20, 30 of larger cross-sectional area than the corresponding upper portions 12, 24 of the columns respectively. Additional liquid is supplied through a common header 48 and valved pipes 44, 46 to subsidiary chambers 40. 42 formed below perforated plates 36, 38 spaced from the bottom of the chambers 20, 30 so that the additional liquid rises in a plurality of streams through the perforated plates. Pipes 52, 54. which may be of the siphon type supplied with liquid via a common header 68 and valved pipes 64, 66, are provided for the discharge of particles of different sizes. In operation, the valves 44a and 46a are adjusted so that the upward flow rate of liquid in the portion 24 of the secondary column 22 is greater than that in the portion 12 of the primary column 10. The particles to be classified are fed as a slurry to the tank 14. Lighter particles 86 are drawn upwardly by the upward flow of liquid for discharge as a fine product. Heavier coarser particles 88, 90 pass downwardly within the column portion 12 where they are in a state of teeter and progress downwards into the chamber 20 where due to the larger cross-section the upward flow rate of liquid decreases. The intermediate size particles 88 are removed by the siphon discharge pipe 52 as a coarse product. Finally. the largest particles 90 after passing through the column portion 24 are removed from the chamber 30 as an extra-coarse product by means of the siphon discharge pipe 54. Very heavy particles are discharged intermittently from the chamber 30 through a valved pipe 80. The subsidiary chambers 40, 42, may be cleaned by opening valves 76, 78 on pipes 72, 74. In the embodiment shown in Figure 2, settling columns 100, 102 are disposed within the settling tank 14 and are connected via pipes 112, 114 to a box 116 for discharge of the fine product. Air vents controlled by float valves (not shown) are provided at 124, 126. The tank 14 is provided at its upper end with a launder 96 for the overflow of very fine particles. Discharge through the siphon pipes 52, 54 is controlled by a float chambers 140. 142 which are adjustably mounted on, and are in communication with, a hydrostatic pipe 148 which is responsive to the pressure existing in the collection chamber 20 and governs the supply of air from air tubes 144, 146 through the float chambers to the top of the siphon pipes 52, 54. By positioning the float chamber 142 below the chamber 140 the supply of air to the siphon pipe 54 may be made effectively responsive to the pressure in the chamber 30 assuming the latter to be greater than that in the chamber 20. This may not always be the case and, alternatively, a separate hydrostatic pipe leading from the chamber 30 may be employed to control the supply of air through float chamber 142 to siphon pipe 54.