Patent GB-448852-A (GB)
Title: Method and apparatus for recovering values from ore pulp
IPC: B03D1/24
Filed: 1934-10-12
Abstract: 448,852. Concentrating ores. KRAUT, M., 2701, Van Ness Avenue, San Francisco, U.S.A. Oct. 12, 1934, No. 29250. [Class 82 (ii)] In the flotation concentration of ores the pulp is aerated by circulating part of the pulp through a confined or restricted passageway formed between a member rotating about a vertical axis and an enclosing wall and subjecting the pulp while so confined to an increase in velocity accompanied by aeration and to a squeezing or crowding pressure, the aerated pulp being then dispersed into the body of pulp. The rotary member may be provided with helical ribs which preferably form with the enclosing wall a confined spiral passage, the cross-section of which varies over at least part of its length. In the form shown, Fig. 1, the cell 10 is formed with an adjustable froth overflow 16<1> and the rear wall 13 slopes inwardly to direct the froth towards the weir. The lower parts of the walls slope inwardly to form a bottom 16 of relatively small area. Above the bottom 16 is mounted the aerating means comprising an outer shell 21 and an inner rotary conveying member 33 connected to a motor 35 by a sleeve 34. The member 33 is provided with helical ribs 37 which terminate at the top in substantially vertical ribs 40, and the upper portion of the shell 21 is provided with apertures 41 and is surrounded by a depending skirt 29 which may be provided with openings 32 and has a plurality of inwardly extending vertical flanges 31. The member 33 and sleeve 34 are hollow and communicate with the atmosphere through a valve 47, the member 33 being provided with slots 46 through which the air can pass to the spaces between the ribs 37. The shell 21 and the member 33 are formed so that the pulp is carried up with an increase in velocity so that air is drawn in through the slots 46 and the passage in which the pulp is confined is then restricted so that the aerated pulp is subjected to pressure and the air broken up into very small bubbles or forced into solution. In the form shown in Fig. 1, the shell 21 is cylindrical up to about its central point 25 and then flares outwardly whereas the member 33 is of conical form, the depth of the ribs 37 increasing from the central point to the bottom so that the crests of the ribs are always in close proximity to the shell 21. The capacity of the grooves formed between the ribs therefore decreases in the upward direction until the central point 25 of the shell is reached and the pulp is thus compressed. In another form the member 33 is cylindrical throughout and the shell 21 is made with a cylindrical upper half and an outwardly flaring lower half. In another form both the member 33 and the shell 21 are cylindrical throughout and the pitch of the helical rib 37 decreases from the bottom of the member to about its central point and then increases again so that the pulp is first compressed and then allowed to expand. In the form shown in Fig. 10, the shell 60 and the member 61 are cylindrical, the ribs 69 increase in pitch from the bottom to the top, and the upper part of the member 61 is formed with thick walls 67 so that the pulp is compressed. The walls 67 are of varying thickness as shown in Fig. 11. The air passes down a conduit inside the hollow member 61 and is discharged into the member through an opening at its lower end and, if desired, also through additional openings throughout its length, and passes into the pulp through slots 71. In all the forms the pulp which in its passage up the shell 21 has been aerated, compressed, and in some cases again allowed to expand, is discharged through the openings 41 in the shell into the space between the shell and the skirt 29, is directed downwardly by the flanges 31, and passes under the skirt and through the openings 32 therein into the main body of the pulp where the froth is formed. If desired the skirt and the flanges 31 may be omitted. In the form shown in Fig. 8, a cylindrical shell 21<a>, provided with openings 41<a> at about its central point, surrounds a hollow rotor 33<a> which has a conveying rib 37<a> at its lower end and an oppositely disposed conveying rib 37b at its upper end. Pulp is drawn in at both ends and aerated by air passing down the rotor 33<a> and through slots 46<a>. Owing to the small diameter of the openings 41<a> and the disposition of the conveying ribs the pulp is subjected to an increase of velocity and a squeezing or crowding pressure in the neighbourhood of the openings 41<a> through which it is discharged into the main body of the pulp. A plurality of aerating devices may be arranged in a single cell.