Patent GB-740588-A (GB)
Title: Improvements relating to the separation of gases and other foreign matter from liquids, particularly pulp suspensions
IPC: B04C5/14
Filed: 1953-08-27
Abstract: 740,588. Centrifugal separators. FREEMAN, H., and BOADWAY, J. D. Aug. 27, 1953 [Sept. 24, 1952; Dec. 6, 1952; Dec. 6, 1952; Jan. 13, 1953; Jan. 13, 1953], No. 23717/53. Class 23. Solids and gases are removed from liquids in a process in which a non-rotary separator is operated so that a liquid-free core is formed, gas being evacuated from the core to maintain subatmospheric pressure in the core. Fig. 1 shows a separator suitable for purifying paper pulp and comprising a convergent inlet 11 directing the pulp tangentially into a separating chamber 10, an outlet 21 for purified pulp and some gas connected to suction means, an outlet 18 for gas connected to suction means and an outlet 20 for solids separated from the pulp. In the modification shown in Fig. 12 the purified pulp and separated solids are discharged under pressure so that gas is only evacuated by suction means. As the separated solids pass a gas outlet 107 into a chamber 123 some of their kinetic energy is converted into pressure energy so that they are discharged at pressure through the outlet 111. The purified pulp and some of the separated gas pass upwardly through the outlet 115 to a chamber 120, some of the kinetic energy of the pulp being converted into potential energy before discharge through a divergent outlet 121 and the gas being discharged through an outlet 108. In a further modification, Fig. 14 (not shown), the gas is discharged from both ends of the separator, the pulp to be separated first passing through a disclike chamber before entering a cylindrical separating chamber and the pulp and separated solids being discharged from the end of the separator remote from the inlet by means of two disc-like chambers having tangential outlets. In the modification shown in Fig. 16 all the separated gas is evacuated through an outlet 158 adjacent the inlet 151, and the pulp and solids are removed from the separator from the end remote from the inlet, the outlet for pulp being connected to a suction pipe 166 and the separated solids being discharged through a pipe 164. In a modification of the construction shown in Fig. 16 a body is centrally placed in the separator adjacent the outlet 164, to prevent gas entraining with the separated pulp. In a modification, Fig. 19 (not shown), the separator comprises a hydro-cyclone having the tapering part discharging into a vacuum chamber, the purified pulp discharging through a concentric outlet adjacent the inlet, and the separated solids and gas discharging into the vacuum chamber from which they are separately removed. In the plant shown in Fig. 2 pulp, at about 100 F., from a pipe 31 first passes through a separator 10a similar to that shown in Fig. 1, the purified pulp and separated gas from the separator 10a being directed to a separator 33 which separates the gas from the purified pulp and is as shown in Fig. 8. The gas outlet of the separator 33 is connected by pipes 34, 35, 36 to a vacuum pump 37. Cold water is supplied at 41 to condense any vapour present in the gas, the condensed vapour falling through a pipe 42 and a further pipe 43 which is over 32 feet long and into the top of which gas from the separator 10a is discharged. The purified pulp from the separator 33 is discharged into the head box 40 of a paper making machine by means of a pipe 38 over 32 feet long. The pulp discharged from the separator 10a with the separated solids is separated in a hydrocyclone 80 and discharged into the headbox. Up to 90 per cent of the gas is usually separated from the pulp. In modifications of the plant shown in Fig. 2, any of the modification of the hydro-cyclone shown in Fig. 1 may be used for the separator 10a. In the separator 33, Fig. 8, the tapering lower part of the separator and the inclination of the tangential pulp inlet 32 are so shaped and arranged that the inner parts of the layer of pulp in the lower part of the separator tend to move upwardly and the outer parts of the layer tend to move downwardly. The separated gas is withdrawn through the outlet pipe 34 connected to the suction means, and the pulp free of gas is withdrawn by the suction pipe 38. Dimensions and performance figures for the apparatus are given in the Specification.