Patent GB-1360122-A (GB)
Title: Vortex cleaner
IPC: D21D5/18
Filed: 1972-05-08
Abstract: 1360122 Centrifugal separators K A SKARDAL 8 May 1972 [21 May 1971] 21342/72 Heading B2P A vortex cleaner for removing impurities from a fibre suspension comprises a toroidal vortex chamber 1, Figs. 4 and and 5, the wall of which is provided with an annular inlet opening 2 for the fibre suspension to be cleaned extending coaxially relative to the axis of symmetry of the vortex chamber and means 3, 7 for feeding the fibre suspension into the chamber through the opening 2 substantially along the entire length thereof and in a direction of flow having a component which is tangential with respect to the cross-section of the chamber 1, the chamber being provided with an internal partition wall 10 having a central opening 11 communicating with a discharge conduit 17 for the accept fraction of the fibre suspension on one side of the wall 10, and the wall of the vortex chamber 1 having a discharge opening 12 for the reject fraction disposed adjacent to, and on the opposite side of, the wall 10. The suspension is introduced through an outlet pipe 3 and is fed by a rotating impeller 7 through the opening 2 so that it forms a helical vortex flow about the circular centre line 9 in the toroidal chamber 1. The accept fraction passing through a vortex finder pipe 18 and the opening 11 in the partition wall 10 enters a space 14, defined between the wall 10 and another inclined partition wall 15 before being discharged through the conduit 17. Alternatively, the conduit 17 may be connected directly to the opening 11. A reject discharge conduit 13 is connected at one end to the opening 12 and at the other end, through a sight glass tube 19 and a T-joint 20, Fig. 7, to a horizontal pipe 21 at one end of which a piston 22 is moved at repeated intervals by a pneumatic cylinder 23 so as to discharge the reject fraction at the other end of the pipe past a weighted or spring loaded flap 25. Back-washing is effected at 26 to prevent any portion of the accept fraction from being entrained with the reject fraction. In a two-stage clearing operation, the reject fraction issuing from a first vortex cleaner of the type described and containing a proportion to maintain the helical flow in the vortex cleaner of the conventional conical type from which an accept fraction is re-circulated to the first vortex cleaner. This can be done by mixing this second accept fraction with the initial fibre suspension supplied to the first vortex cleaner. Alternatively, the second accept fraction is fed through a separate inlet conduit 30, Fig. 6, connected to the first vortex cleaner and communicating with a space 28 formed between the partition wall 15 and an additional wall 27 which is provided with an opening 31 and a pipe 32 projecting axially into the vortex chamber 1.  In another embodiment, Fig. 8 (not shown), the vortex is mounted directly in the bottom of a pulper from which fibre suspension is fed to the toroidal vortex chamber by means a rotating impeller. The latter has radial blades on its upper side which serve as agitators in the pulper and also feed the suspension into the vortex chamber. The impeller is also provided with blades on its lower side which serve to maintain the helical flow in the vortex chamber. In a further embodiment, Fig. 9 (not shown), the top (1C) of the vortex chamber is flat instead of conical and the impeller disc (7b) is correspondingly planer. In a still further embodiment, Fig. 10 (not shown), the fibre suspension is supplied through a descending conduit (35) and is fed into the vortex chamber (1) through its annular opening (2) by a propeller (36) which has its shaft (37) journalled in the centre of the chamber and its blades (36a) projecting somewhat into the chamber to assist in maintaining the helical flow therein.