Patent GB-1117261-A (GB)
Title: Concentration process and apparatus
IPC: B07B1/54
Filed: 1966-05-24
Abstract: 1,117,261. Concentrating iron ores. ERIE DEVELOPMENT CO. 24 May, 1966 [26 May, 1965], No. 23019/66. Heading B2H. An iron ore concentrate having particles varying in size from 48 mesh to and including colloidal size is up-graded by subjecting an aqueous slurry of the concentrate to screening to separate as oversize material the relatively coarser iron-poor particles and as undersize material the relatively finer iron-rich particles; grinding the oversize material; separating the ground material into an iron-rich and an iron-poor fraction; and combining the ironrich fraction with the undersize material to give a final iron-enriched concentrate. The screening apparatus used may be in the form of a curved screening deck having spaced parallel rods or bars extending at right angles to the direction of the flow of slurry, Fig. 1, or of a flat screen inclined to the horizontal, Fig. 5 (not shown) and comprising spaced parallel rods or bars having a rectangular or trapezoidal cross-section. Screening may take place through a single screen, through which the material may be passed once or twice after re-slurrying the oversize fraction, or through two or more screens arranged in series, dilution water being added to the material as it passes from screen to screen. In Fig. I, an aqueous slurry of magnetite concentrates is fed from a tank 12 on to a primary curved screen 10 and the overflow fraction from screen 10 after dilution is fed on to a secondary curved screen 11. The oversize material from screen 11 is reduced in a ball mill 21 and separated in a hydrocyclone 22 into an oversize fraction 24 which is returned to the ball mill and an undersize fraction 26 which is passed to a magnetic separator to be separated into a tailing iron-poor fraction 31 and a concentrate iron-rich fraction 32. The latter fraction is combined with the ironrich underflow fractions from the screens 10, 11 and passed into a dewaterer 37 to obtain an iron-rich final concentrate 39. A knocker assembly for dislodging particles that become trapped between the bars of a curved screening deck, Figs. 2 and 3, comprises a striker member 111 at the end of an arm 110 fixedly secured to a sleeve 106 rotatably mounted on a shaft 105 between a fixed stop 115 and a spring 117 which bears against an adjustable stop 116. The shaft 105 carries a bent arm 120 which, on the shaft being rotated, engages the arm 110 and lifts it and the striker 111 upwardly. As it reaches its upward position, the striker arm 110 is engaged by an adjustably mounted wedge member 125 which serves to disengage the arm 110 from the lift arm 120 whereupon the assembly 106, 110, 111 swings downwardly and delivers a sharp blow to a striker plate 102 fixed to the underside of the screen. A second knocker and knocker plate may be provided downstream of the knocker assembly shown. Alternatively, two or more striker plates may be provided in parallel across the width of the screen frame and a corresponding number of striker assemblies are mounted on a single shaft, the assemblies being staggered by 90‹ or 180‹ if desired. Alternatively, the sharp blow can be imparted by a spring- loaded and cam-actuated mechanism or by a solenoid-operated or pneumatic impactor. In an arrangement for a flat inclined screen (201), Fig. 5 (not shown), an elongate striker plate (102<SP>1</SP>) is fixed to the rear of the screen frame and strikers (111), (111<SP>1</SP>) are arranged to impart blows simultaneously or successively to corresponding ends of the plate (102<SP>1</SP>).