GB1369020A - Method and apparatus for discharging compacted waste material from solid jacket centrifuges - Google Patents

Abstract

1369020 Centrifugal separators AMBERGER KAOLINWERKE GmbH 21 Dec 1971 [22 Dec 1970] 59363/71 Heading B2P In a method of discharging compacted waste material from a shaft-driven, solid-drum centrifuge byway of selectively operable waste discharge passages in the centrifuge drum after first enhancing flocculation of solid particles in a suspension to be compacted and then facilitating movement of the compacted waste material along the inner surface of the drum towards the waste discharge passages, successive abrupt changes in the angular velocity (i.e. jolts) to either the drive shaft or the drum so that inertial forces produced by each such abrupt change cause flocculation of the solid particles to be enhanced, compacted waste material next adjacent the inner surface of the drum to be displaced towards the discharge passages, and these passages to be opened. The centrifuge drum comprises a central waste collecting part 2 having waste discharge openings 5 and sedimentation parts 3 with overflow weirs 21 for clear. liquid. The drum is rotated by a hollow shaft 1 which is keyed to a star-like drive member 9 the arms of which are in engagement with the drum at their ends. The suspension to be treated is fed in the direction of arrow 6 through the shaft 1 and and passes through openings 7 therein into a rotating sleeve 8a having discharge apertures 8b communicating with the interior of the drum. Braking and acceleration jolts are applied to the shaft 1 via a brake 10 or by means of a coupling 22 which rotates with, and is connected to, the shaft 1 and which can be brought into engagement for a short period of time with a rotating braking element 23 which is journalled on a sleeve, which is keyed to the shaft by ball bearings 24. The element 23 may be driven at a lower speed than the shaft 1 before engagement by the coupling 22, e.g. by a friction drive which is automatically disconnected from the element 23 when the latter is engaged by the coupling 22. The drum wall may be provided with inwardly extending projections 4, Fig. 3, having drive and stop abutment surfaces 4' and 4" for engagement respectively with surfaces 9' and 9" on the arms of the star drive member 9 which can be angularly displaced relative to the drum. Each projection 4 has a passage opening in its drive abutment surface and communicating with a respective discharge aperture 5 in the drum. During normal rotation of the drum the surfaces 9' of the arms engage the drive abutment surfaces 4' of the projections thereby transmitting driving torque from the shaft 1. When the shaft 1 is braked, the drum due to its greater inertia rotates at a greater speed than the shaft 1 and its associated drive member 9 so that the stop abutment surfaces 4" come into contact with the surfaces 9", of the arms and the apertures 5 are opened to discharge. When braking is discontinued the arms are accelerated again to the speed of the drum and close the discharge apertures. Braking may be controlled automatically by means of a photocell which is mounted below the drum adjacent one of the weirs 21 or adjacent an opening in the drum situated near one of the weirs and which acts when the clear liquid becomes turbid. Other means associated with the arms of the drive member 9 to control the opening or closing of the discharge apertures are described. The braking and acceleration jolts are also transmitted to the suspension and enhance flocculation of the waste mat erial with or without the addition of a flocculating agent to the suspension. The jolts also facilitate movement of the accumulated waste material from the inner surfaces of the sedimentation parts 3 of the drum towards the waste colling part 2. This movement can be enhanced by helically disposed guide worms or shutter-like claws welded on the inner surfaces of the parts 3. The sleeve 8a through which the suspension is supplied to the drum may be driven above or below the rotational velocity of the drum through a toothed belt or chain drive or through gearing 11, Fig. 1. Alternatively, a hydraulic drive may be provided by the clear liquid discharging by way of the over-flow weir 21 of one of the drum sedimentation parts 3 to the interior of a paddle wheel 41, Fig. 8, firmly connected in the part 3. The liquid is conducted to the outer diameter of the wheel where it is accelerated to a speed greater than the rotational speed in the region of the overflow weir. The liquid then flows radially inwardly through an anular space 4b and enters a turbine wheel 44 rigidly connected to the sleeve 8a which is thus driven at a higher speed than the drum. In another arrangement, Fig. 9 (not shown), the clear liquid discharges over the weir directly through a turbine wheel which drives the sleeve 8a, at a lower speed than the drum.