Patent GB-597871-A (GB)
Title: Improvements in gravity separation of materials
IPC: B03B5/62
Filed: 1943-08-06
Abstract: 597,871. Wet-separating. RAKOWSKY, V. Aug. 6, 1943, No. 12756. Convention date, Aug. 22, 1942. [Class 82 (ii)] In the gravity separation of materials having constituent particles of different specific gravities, the mixture is introduced into a substantially self-sustaining mass consisting of liquids such as water and not less than 50 per cent by weight of comminuted solids and supplied to a separating tank in such volume and such velocity as to maintain the solids in suspension, the specific gravity of which is lower than that of some at least of the light constituents of the mixture, imparting to the said mass an upward current of a velocity of the particles of the light constituents and not less than 7 feet per minute and removing the particles which float and sink, the upward current being produced under conditions which result in a substantially uniform composition of medium throughout the upward current. When the material contains at least three components having different specific gravities and the self-sustaining mass has a specific gravity greater than that of one component and lower than those of the other two, the particles of lower specific gravity than the fluid mass are floated off by normal gravity separation in one vessel and then the components which sink are further separated by treating them with the upward current in a separate vessel or vessels or in the same vessel. The material treated may be an ore containing light gangue and a plurality of minerals of differing specific gravity, the gangue being floated off in the upper zone of one vessel by the gravity separation and the minerals by the upward current in the lower zone. In applying the process to the treatment of a zine-lead ore in which the gangue has a specific gravity of 2.63, the zinc minerals 3.7-4 and the galena 7.5, the separating tank, Fig. 2, is a double cone 1 filled with a medium of suspended solids having a specific gravity of 2.7, the medium in the upper part of the cone being static and the cone in this portion being provided with rakes 16 attached to a hollow shaft and which serve to scrape any medium tending to cake on the walls of the cone. The ordinary discharge pipe 22 forms with an internal pipe 21 an annular space through which medium is forced down through the shaft 17 and pipe 19 to the centre of the pipe 21 and into the annular space through a plurality of openings 20. The amount of medium pumped back through the shaft 17 and pipes 19, 20 is at least equal to that flowing out through the pipes 21, 22 and above the portions 20 and as a result an upward current of 13 feet per minute in the space between the pipes 21, 22 and above the openings 20 is produced. Through the space flows practically all the medium discharged through the pipe 21 and a rising current is produced of such velocity that the zinc mineral particles float up and over the lip of the pipe 21, being discharged and elevated by an air lift 23 on to the zinc drain screen 24. The baffle 18 causes the zinc and like mineral particles which sink to be forced out to the side and on to the annular part with rising currents between the pipes 21, 22. The galena discharged through the pipe 22 is raised by an air-lift 5 on to the screen 6. The medium draining through screens 24, 6 flows through pipes 25, 31 and is pumped by pumps 32, 26 through pipes 37, 33 into a tank 9 from which the medium is returned to the separating tank through the hollow shaft 17 and pipe 19. The floating gangue is discharged over the lip 3 and drained on a screen 4, the drainage being returned to the tank 1 by an air-lift 28. Specification 525,804 is referred to.