AN APPARATUS AND A METHOD FOR SEPARATING ONE SOLID COMPONENT FROM ANOTHER SOLID COMPONENT IN SUSPENSION IN A LIQUID

Abstract: A separator is disclosed for separating out a first solid component from a mixture thereof with a liquid and a second solid component which is of smaller average particle size than the first solid component, the first and second solid com­ ponents being in suspension in the liquid and with the per­ centage by mass of the second solid component being sub­ stantially greater than that of the first solid component. The separator includes an endless cloth which is foraminous and has foramen which are of a suitable size to permit the second solid component to pass therethrough and to impede the passage therethrough of the first solid component; a feed means for feeding the liquid and the solid components onto the cloth; a liquid collecting means for collecting liquid and material that has passed through the cloth; a first component removal and collecting means for removing material from the cloth and collecting it; and a drive means for displacing the cloth past the feed means, the liquid collecting means and the first component removal and collecting means.

Description: This invention relates to an apparatus for, and to a method of, separating a first solid component from a mixture thereof with a liquid and a second solid component, the first and second solid components being in suspension in the liquid. The Applicant is aware of a large number of apparatus and methods for separating one solid component from another. Screens and cyclones are examples of such apparatus. It is proposed in this specification that an endless travelling cloth be used as the separating medium. FR-A-1334725 describes a gravity operable separator for separating sand particles according to particle size from a sand/water mixture, the separating medium comprising an endless inclined foraminous cloth screen which has foramen which are of a suitable size to permit small sand particles to pass therethrough and to impede the passage therethrough of relatively large sand particles. The cloth moves as the mixture is fed onto it, the cloth being driven by suitable drive means. The means for feeding the mixture onto the cloth includes a feed box that has a floor plate which has a number of distributed feed openings and which is spaced from the cloth for feeding the mixture directly onto a small portion of the cloth in a distributed and continuous manner. Liquid collecting means (located beneath that part of the cloth defining the operative separating region) and relatively large particle removal and collecting means permit the sand retained on the cloth to be removed from the apparatus separately from the sand that has passed with the water through the cloth. FR-A-2285935 describes a gravity operable separator in which the screen is horizontal and defines an extended operative separating region and the mixture is fed onto a portion of the operative separating region. However, the screen is neither foraminous nor of cloth. The Applicant has now found surprisingly that foraminous cloth screens can be employed horizontally to define an extended operative separating region and in such a way that the mixture is fed onto substantially all of the operative separating region, to provide a novel and advantageous gravity operable separator and separating method. With the present invention, the object is to avoid the disadvantages of the prior art apparatus and methods in separating a first solid component from a second solid component, with there being substantially more of the second solid component than there is of the first solid component, so that much more solid material passes through the apparatus than is removed by it. According to the present invention there is provided a gravity operable separator for separating out a first solid component from a mixture thereof with a liquid and a second solid component which is of smaller average particle size than the first solid component, the first and second solid components being in suspension in the liquid and with the percentage by mass of the second solid component being substantially greater than that of the first solid component, which includes an endless cloth which is foraminous and has foramen which are of a suitable size to permit the second solid component to pass therethrough and to impede the passage therethrough of the first solid component; a feed means for feeding the liquid and the solid components onto the cloth, the feed means including a feed box that has a floor plate which has a number of distributed feed openings and which is spaced from the cloth for feeding the liquid and the solid components directly onto the cloth in a distributed and continuous manner; a liquid collecting means located beneath that part of the cloth defining an operative separating region, for collecting liquid and material that has passed through the cloth; a first component removal and collecting means for removing material from the cloth and collecting it; and a drive means for continuously displacing the cloth past the feed means, the liquid collecting means and first component removal and collecting means whilst the liquid and the solid components are being fed onto the cloth, characterised in that a part of the cloth is substantially horizontal and defines an extended operative separating region; and the floor plate of the feed box extends over substantially all of the operative separating region of the cloth, so as to feed the mixture onto the cloth in a distributed manner over said region. The material may pass through the cloth under the action only of gravity without utilising an artificially created vacuum. Further according to the invention there is provided a method of separating out a first solid component from a mixture thereof with a liquid and a second solid component which is of smaller average particle size than the first solid component, the first and second solid components being in suspension in the liquid and with the percentage by mass of the second component being substantially greater than that of the first component, which includes feeding the liquid and the solid components onto an endless cloth which has foramen of a suitable size to permit the passage therethrough of the second solid component and to impede the passage therethrough of the first solid component, said feeding comprising charging the liquid and the solid components into a feed box which has a floor plate which has a number of distributed feed openings and which is spaced from the cloth, the feeding taking place through the openings directly onto the cloth in a distributed and continuous manner; displacing the cloth whilst the liquid and the solid components are being fed thereon; collecting liquid and other material that has passed through the cloth; and removing from the cloth first component particles and collecting them, characterised in that a part of the cloth is substantially horizontal and defines an extended operative separating region; and the liquid and solid components are fed onto substantially all of the operative separating region of the cloth by means of said feed box, the said floor plate of which extends over substantially all of the operative separating region of the cloth, so as to feed the mixture onto the cloth in a distributed manner over said region, to allow the liquid and second component particles to pass through the cloth under the action of gravity only. It will be appreciated that the first solid component and the second solid component may be particles of different size, shape or configuration although they are of the same material. Thus, coarse particles may be removed from a slurry after a milling operation. Instead, they may be different materials. In particular, the first solid component may be wood chips and the second solid component may be a gold-bearing chemical composition. Thus, the cloth may be such that particles having a size of less than 200 microns may pass through and particles of a greater size are retained thereon. Thus, for this application, the cloth may have foramen of about 250 microns. It will also be appreciated that the first solid component that is retained on the cloth is substantially removed by any suitable process which may be a mechanical process. Referring to the cloth, it may be of a synthetic monofilament fabric. It may also be woven and may be of polypropylene, polyester or a polyamide material. Further, it may be of a single, double or triple layer monofilament fabric. The cloth preferably extends over a region in a substantially horizontal manner, this being the operative separating region of the cloth. The liquid collecting means, in the form of a trough, is then located below the cloth in this region. The mixture may then be fed onto the operative separating region by means of a feed box located above the said region. The feed box may have a floor that extends over substantially the entire separating region and is spaced from the cloth. The floor then has feed apertures which are distributed over substantially its entire area such that the liquid with the components in suspension therein is fed onto substantially the entire operative separating region. Jets may be provided, below the cloth in the operative separating region, in order to spray water onto and through the cloth in an attempt to repulp the solids and prevent the formation of a layer of solid material on the cloth, which would stop the second solid component passing through the cloth, which is the stated objective. The invention is now described, by way of an example, with reference to the accompanying drawings, in which:- Figure 1 shows a side view of a separator in accordance with the invention; Figure 2 shows a plan view of the separator; Figure 3 shows an end view of the separator: and Figure 4 shows a sectioned view of the separator along line IV-IV in Figure 1. Referring to the drawings, a separator is shown therein, designated generally by reference numeral 10. The separator 10 has an endless cloth 12 which is supported on a number of support rollers 14 to define a horizontal separating region and also passes over a number of other rollers, including a drive roller 16. Beneath the support rollers 14 there is a collecting trough 18 which has an outlet 20. Material that is to be separated is fed onto the cloth 12 by means of a feed box 22. The feed box 22 has side walls 24, end walls 26 and a floor 28. An inlet 32 is provided in the rear end wall 26. The floor 28 has a number of circular apertures 34 that have a diameter of 1 to 2 cms and which are distributed over substantially the entire floor 28. The floor 28 is spaced a few centimetres from the cloth 12, and extends over a substantial part of the operative separating region. Thus, the feed box 22 feeds material to be separated, in a distributed manner, onto substantially all of the operative separating region. The cloth 12 is a fabric that is woven from a suitable synthetic mono-filament material. The material may be polypropylene, polyester or polyamide. The cloth is woven to have apertures of a suitable size depending on the application for which it is intended. Thus, in one application where it is desired to separate wood particles which are carried in a slurry of gold-bearing particles in suspension in water, in which the gold-bearing particles have a maximum particle size of about 200 microns, the cloth is provided with apertures of about 250 microns in size. Thus, when the material to be separated is fed onto the cloth 12 by means of the feed box 22 the slurry passes through the cloth 12 under the action of gravity to be collected in the trough 18 whereas the wood particles remain behind on the cloth 12. These are then washed off the cloth 12 to be collected in a trough 30. Sprays 36 are located below the cloth 12 in the operative region, ie between support rollers 14, to spray water onto and through the cloth 12, to repulp any solid material tending to form a layer on the cloth 12. The cloth 12 is driven at a speed of between 2 and 9 metres/minute if wood particles are to be removed from gold bearing slurry and between 5 and 30 metres/minute when particles that are too large are to be removed from a slurry after a milling operation. By means of the invention, an apparatus and method are provided whereby, in general, larger particles that form a small part of the solid material in suspension in a liquid may be removed therefrom in a continuous manner, and in particular, wood particles may be easily removed from a gold bearing slurry.

Claims: A gravity operable separator for separating out a first solid component from a mixture thereof with a liquid and a second solid component which is of smaller average particle size than the first solid component, the first and second solid components being in suspension in the liquid and with the percentage by mass of the second solid component being substantially greater than that of the first solid component, which includes an endless cloth (12) which is foraminous and has foramen which are of a suitable size to permit the second solid component to pass therethrough and to impede the passage therethrough of the first solid component; a feed means for feeding the liquid and the solid components onto the cloth, the feed means including a feed box (22) that has a floor plate (28) which has a number of distributed feed openings (34) and which is spaced from the cloth for feeding the liquid and the solid component directly onto the cloth in a distributed and continuous manner; a liquid collecting means (18) located beneath that part of the cloth defining an operative separating region, for collecting liquid and material that has passed through the cloth; a first component removal and collecting means (30) for removing material from the cloth and collecting it; and a drive means (16) for continuously displacing the cloth past the feed means, the liquid collecting means and first component removal and collecting means whilst the liquid and the solid components are being fed onto the cloth, characterised in that a part of the cloth (12) is substantially horizontal and defines an extended operative separating region; and the floor plate (28) of the feed box (22) extends over substantially all of the operative separating region of the cloth, so as to feed the mixture onto the cloth in a distributed manner over said region. A separator as claimed in Claim 1, wherein separation is effected by means of gravity only. A separator as claimed in Claim 1 or Claim 2, wherein the cloth is of a synthetic mono-filament fabric. A separator as claimed in Claim 3, wherein the cloth is of a woven fabric. A separator as claimed in Claim 3, wherein the cloth is of a single, double or triple layer monofilament fabric. A separator as claimed in any one of the preceding claims, further including a spray means (36) for spraying liquid onto the underneath surface of the cloth that is located immediately beneath the feed means. A separator as claimed in any one of the preceding claims for removing wood chips from a mixture thereof with gold-bearing particles. A separator as claimed in any one of the preceding claims 1 to 6 for removing coarse particles from a slurry after a milling operation. A method of separating out a first solid component from a mixture thereof with a liquid and a second solid component which is of smaller average particle size than the first solid component, the first and second solid components being in suspension in the liquid and with the percentage by mass of the second component being substantially greater than that of the first component, which includes feeding the liquid and the solid components onto an endless cloth (12) which has foramen of a suitable size to permit the passage therethrough of the second solid component and to impede the passage therethrough of the first solid component, said feeding comprising charging the liquid and the solid components into a feed box (22) which has a floor plate (28) which has a number of distributed feed openings (34) and which is spaced from the cloth, the feeding taking place through the openings directly onto the cloth in a distributed and continuous manner; displacing the cloth whilst the liquid and the solid components are being fed thereon; collecting liquid and other material that has passed through the cloth; and removing from the cloth first component particles and collecting them, characterised in that a part of the cloth (12) is substantially horizontal and defines an extended operative separating region; and the liquid and solid components are fed onto substantially all of the operative separating region of the cloth by means of said feed box (22), the said floor plate (28) of which extends over substantially all of the operative separating region of the cloth, so as to feed the mixture onto the cloth in a distributed manner over said region, to allow the liquid and second component particles to pass through the cloth under the action of gravity only. A method as claimed in Claim 9, wherein the cloth is displaced at a speed of between 2 and 30 metres/minute. A method as claimed in Claim 9 or Claim 10, further including spraying liquid onto the underneath of that part of the cloth onto which material is being fed. A method as claimed in any one of Claims 9 to 11, wherein the first solid component is wood chips and the second solid component is a particulate ore containing a precious metal. A method as claimed in any one of Claims 9 to 11, wherein the first solid component comprises carbon particles and the second solid component comprises particulate ore. A method as claimed in any one of Claims 9 to 11, wherein the first solid component comprises coarse particles and the second solid component comprises fine particles resulting from a milling operation.

Inventors: AMM, ERROL THOMAS, ARBUTHNOT, IAN MACDONALD, DAVIDSON, RAYMOND JOHN
Applicants: ANGLO AMERICAN CORPORATION OF SOUTH AFRICA LIMITED
Application year: 1985
Main classification: B07B1
IPC codes: B07B1, B03B7