Patent GB-1325477-A (GB)
Title: Vacuum flotation apparatus
IPC: B03D1/04
Filed: 1970-11-11
Abstract: 1325477 Froth flotation A GOTTE 11 Nov 1970 [11 Nov 1969 11 Aug 1970] 53728/70 Heading B2H Solids are separated from an aqueous slurry by froth flotation by introducing the slurry containing the solids pretreated with frothflotation conditioning additives into one end of a flotation zone which is maintained under sub-atmospheric pressure and through which the slurry is caused to flow without formation of eddies, withdrawing slurry at least partially free of solids at the other end of the zone, and removing solids-containing froth from the. surface of the slurry, the froth being formed by air which under sub-atmospheric pressure separates out from the slurry as fine bubbles carrying the solids to the surface. As shown in Figs. 1 and 2, slurry containing flotation reagents is introduced from a vessel 19 through a conduit 20 and an inlet 3 into a trough 1 within a casing 2 which is maintained under vacuum. The trough increases in width and depth in the direction a of flow to create a laminar flow and has a slurry discharge outlet 4 which leads to a container 40 and is fitted with a valve 5 which serves to control the level of the slurry in the trough. The froth is removed by a skimmer having rotating paddles 15, 16, 17 into froth chambers 6, 7, 8 provided on one or both sides of the trough 1 and having froth discharge pipes 9, 10, 11 which lead into containers 90, 100, 110. The casing 2 and the containers 40, 90, 100, 110 are connected by means of pipes 18 to a vacuum pump. Compressed air may be introduced into the trough through a connection 31 and a porous body 30 to assist or prolong flotation. The flow of slurry may be made turbulent in a zone adjacent the downstream end of the trough by means of a baffle screen, Figs. 4 and 5 (not shown), consisting of one or more series of rods terminating below the surface of the slurry and/or by compressed air or airsaturated water or slurry (which may contain flotation reagents) introduced through porous sintered ceramic bodies or perforated pipes. Figs. 6 and 7 (not shown), at the bottom of the trough. In another arrangement, Figs. 8 and 9 (not shown), turbulence is provided by means of a stirrer below which fluid supply pipes open into the bottom of the trough and above which is provided a stabilizing grating. The turbulent zone produced by the stirrer is preferably separated from the laminar flow zone by a transverse wall which towards the base of the trough has one or more apertures for the passage of the slurry. In a further arrangement, Fig. 10, the trough has a steeply inclined base 11. The slurry treated in part 2 enters through an aperture. 3 into chamber 4 where it is set into movement by an agitator 5. The froth produced in this chamber is removed by a skimmer 8. The level of the slurry is adjusted by means of an adjustable overflow weir 10 over which tailings are discharged. A connection 7 serves to empty the apparatus. In Fig. 11a, the trough 1 is sub-divided by a vertical wall 40 having an opening 41 which can be opened or closed by a movable slide 42. When the slurry is to be subjected to intermediate aeration, the opening 41 is closed and the slurry is directed to an open tank 45 via a barometric leg 43 and removed from the tanks 45 via a pipe 49 to the part 1a, of the trough under vacuum existing in that part. Compressed air is introduced through a pipe 46 to produce a pumping action to overcome the vacuum in the trough 1. Other means of overcoming the vacuum are described. (For Figures see next page)