Patent GB-1482113-A (GB)
Title: Method and apparatus for separating particles of different specific gravities carried in a liquid suspension
IPC: B04C5/081
Filed: 1974-07-24
Abstract: 1482113 Hydrocyclones BOISE CASCADE CORP 24 July 1974 [24 July 1973] 32726/74 Heading B2P A hydrocyclone for separating particles of different specific gravities carried in a liquid suspension, comprises a vertically-arranged housing 2 enclosing a separation chamber 4, an inlet 6 for introducing the suspension tangentially into the upper end of the chamber, a first outlet 12c communicating with the lower end of the chamber for discharging heavier particles which, in operation, pass down the chamber in an outer helical path adjacent the side wall of the chamber, upwardly convergent conical diverter means 12 centrally mounted in the bottom of the chamber for establishing in the central portion thereof, inside the outer helical path, an upwardly directed helical vortex flow of lighter particles, and a second outlet 18 communicating with the central portion of the upper end of the chamber for removing lighter particles therefrom. The outlet 12c is formed as a tangential slot which opens into a chamber 12d defined by a tubular bottom portion 12a of the diverter means 12. The chamber 12d communicates with a discharge conduit 14 provided with a throttle valve 16 for regulating the back pressure in the chambers 12d and 4. In a modification, the housing has a lower frusto-conical portion, the outlet for the lighter particles is cylindrical and the diverter has a curved peripheral wall. In a waste paper cleaning plant shown in Fig. 5, reclaimed waste paper suspension, which includes cellulose pulp fibres and heavy and light impurities having specific gravities respectively higher and lower than that of the fibres, is pumped from a supply tank 150 at a pressure of 30-50 p.s.i.g. through a tangential inlet 226 at the upper end of a first hydrocyclone 224. A suspension containing the heavy impurities and some reclaimable pulp fibres are discharged via a lower outlet 228 into a tank 154. A suspension containing the bulk of the fibres and the light impurities are discharged at a pressure of 5 p.s.i.g. via an upper outlet into a chamber 234 from which it is fed via a conduit 238 tangentially into the upper end of a second hydrocyclone 222 having diverter means 312. The acceptable cellulose fibres are discharged through a lower outlet 308 and a suspension containing the light impurities and some cellulose fibres are discharged via an upper outlet 320 into a tank 170 from which it is pumped into a third hydrocyclone 402. The light impurities are discharged as final light rejects via an outlet 410 and a suspension of cellulose fibres is discharged through an outlet 408 and returned to the tank 150. From the tank 154 the suspension is pumped into a fourth hydrocyclone 160 of the two-chamber type for separation into final heavy rejects discharged through outlet 162 and a suspension containing the cellulose pulp fibres and some heavy impurities which is returned to the tank 150 via an outlet 164 and/or to the tank 154 via an outlet 166. In a modification, the member 318 at the top of hydrocyclone 222 may be provided with an upper axial outlet for air and with a side outlet for the suspension of light impurities and cellulose fibres.