Title of Invention

"AN APPARATUS FOR SEPERATING PARTICULATE MATERIAL"

Abstract

An apparatus for separating particulate material includes supporting means for supporting a bed of the particulate material, means for inducing particle-particle interaction of particulate material in the bed whereby lower density particulate material mi-grates towards the top of the bed, and separation means for separating at least a portion of said lower density material from an upper portion of the bed.

Full Text

The present invention relates to an apparatus for separating a particulate material. TECHNICAL FIELD Particulate material can be separated by a variety of techniques which can be broadly classified as wet techniques and dry techniques. Wet techniques can be used in cases where water is required for subsequent processing. However, where that is not the case, the introduction of water into a separation process is undesirable because it drastically increases costs associated with materials handling, thickening, filtration, drying etc. The present invention relates to an apparatus and method for the physical separation of particulate material. The present invention is primarily concerned with dry separation but it is to be understood that the present invention may be used as a wet technique. The present.invention is particularly suited but is not limited to the separation of particles'in the size range of 10~m-l00mm, more particularly 100~m-50mm, on the basis of differences in density (specific gravity). The present invention has particular, although not exclusive, application to the separation of particulate material in the mining and related industries. BACKGROUND ART Various prior art separation techniques have been proposed in which a "fluidised bed" of the- particulate material is formed by use of a flurdising or suspending agent such as air or water to achieve density separation. For example, US patent no. 3486620 discloses an apparatus for concentrating ore in which compressed air is upwardly directed through the particulate material and is arranged to lift lighter particles whilst having no or minimal affect on heavier particles. Australian patent application no. 10923/88 similarly teaches a method of dry separation of solids in which air is used as a fluidising agent. Australian patent application no. 28485/92 discloses a sizing and concentrating apparatus which utilises a vibrating launder in which the bottom of the lau.nc.er is formed of a plurality of spaced slats one plane of which is substantially horizontal to provide a stepped decline to produce a fluidised bed of particles of differing sizing and characteristics. The apparatus is said to be particularly useful in the case of particles in the range of minus 3mm and minus 75µm. The apparatus does not utilise a fluidising agent; however, it is said that the horizontal and vertical faces of each step of the stepped decline perform essential functions in particle transport and bed dilation. It is further said that the stepped decline which forms the particle bed base is vibrated such that the vibration promotes particle segregation and is essential for the proper functioning of the horizontal and vertical faces of each step. In contrast to prior art techniques, the present invention utilises an analogous mechanism to f luidi;=ation without the use of a fluidising agent by inducing particle-particle interaction of particulate material. As previously mentioned, the present invention rray be used as a wet technique but it is to be noted that, where water is used in a wet technique, the water is not required as a fluidising agent. DISCLOSURE OF THE INVENTION In a first aspect, the present invention provides an apparatus for separating particulate material, the apparatus including: supporting means for supporting a bed o;: the particulate material, means for inducing particle-particle interaction of particulate material in the bed whereby lower density particulate material migrates towards the top of ths bed, and separation means for separating at least a portion of said lower density material from an upper portion of the bed. In a second aspect, the present invention provides a method for separating particulate material, the method including the steps of: forming a bed of the particulate material, inducing particle-particle interaction of particulate material in the bed whereby lower density particulate material migrates towards the top of this bed, and separating at least a portion of said lower density material from an upper portion of the bed. Preferably, particle-particle interaction of particulate material in the bed is induced by subj=cting the supporting means to vibratory motion. The supporting means may take the . form of a trough mounted on a deck nf a vibrating frame. The frame may be vibrated by a Linear reciprocating motion which may be imparted to the frame at an angle to the piano of the dock. Alternatively, the frame may be vibrated by a non-linear motion, for example, a circular or elliptical motion. Non-linear motion may be imparted by a variable speed motor driving an out of balance flywheel- The vibratory motion may be a combination of a number of distinct vibratory motions. Preferably, the supporting means takes the form of a trough mounted on a deck which is in turn mounted on springs on a vibrating frame. The bed of particulate material is "fluidisesd" by the means for inducing particle-particle interaction in the absence of a fluidising agent. The extent of fluidisation of the bed can be controlled by controlling a number of variables including the nature oE the vibratory motion, the angle of the vibratory motion with respect to the supporting means, the amplitude of the motion, the frequency of the motion and the depth of the bed with the variables preferably optimised for a given sample of particulate material. The extent of fluidisation of the bed is largely determined by the amplitude of the motion which is preferably sufficisnt to induce particle-particle interaction of the particulate material allowing stratification of the bed but not so large as to induce too strong interaction between particles which obviates stratification and hence separation. The frequency of the motion largely affects the speed of interaction between particles within the bed and the rate at which lower density particles migrate upwardly through the bed. The bed depth is preferably at leasl abcmt S particle diameters which has been found to be sufficient to enable particle-particle interaction to be established with upward displacement of lower density particles. Particulate material may be separated by batch or continuous operation with continuous operation being preferred. The separation means can take a variety of forms. For example, material may be raked from the top of the bed; lower density material may be caused to flow over a weir or through an aperture; or, e.t an intermediate level in the bed lower density and higher density material may be caused to be separated by encountering a standard scrapper bar or cutter plate. The supporting means may be disposed substantially horizontally or may be inclined at an angle of up to about 45° and the nature of the motion from linear through elliptical to circular may be selected to optimise particle-particle interaction within the bed. Inclination of the supporting means may assist separation of lower density material by enabling the lower density particles to flow under gravity over .a weir or through an aperture in a lowered bed wall oncu they have migrated to an upper portion of the bed. The angle of inclination is preferably variable. A separation enhancing agent such as water or ferrosilicon particles may be added to the bed to enhance separation. Separation may be effected on a continuous basis with the apparatus preferably including feed means for introducing particulate material into the bed for continuous operation. The feed means preferably takes the form of a vibratory or belt feeder which may introduce particulate material at a point or as a curtain, preferably evenly across the width o:: the supporting means. A plurality of beds may be arranged to be used in series in accordance with the present invention. For example, particulate material separated from a firut bed may be introduced to another bed arranged to provide either improved separation at the same density or further separation at a different density. It will therefore be appreciated that an apparatus according to the present invention can be used to separate a feed of particulate material into various fractions with the densities of the particles in the various fractions being variable. Preferred embodiments of the present invention will now be described by way of example. Example 1 A batch test was conducted on a sample of iron ore in a rectangular trough 340mm wide by 2 60mm long by 60mm deep and mounted horizontally on a vibrating table in the form of a modified General Kinematics screen deck. The screen deck was modified by replacing the screens: with the trough. The size range of the feed material was 13-22mm. The test was conducted on an 8.3kg sample containing 4.6% gangue (SG Example 2 A batch test was conducted on a sample of ircn ore in the trough of Example 1 which was mounted on a modified Denver-Dillon screen deck at an inclination of about 8° to the horizontal. The screen deck was modified by replacing the screens with the trough. The 260mm sides of the trough were inclined at 8° with one of the 340mm rims being elevated with respect to the other of the 340mm rims. The size range of the feed material was 13-22mm. The test was conducted on an 8.0kg .'sample containing 6.4% gangue (SG A continuous test was conducted on a sample o:i iron ore (13-22JIUU) in a rectangular trough 3 00mm wide by 705mm long by 300mm deep and mounted horizontally on the screen deck of Example 2. The sample was continuously fed from a vibratory feeder to a point adjacent a corner of the trough at a feed rate of 700kg per hour. One of the longer walls was formed with a tail aperture for removal of lower density (tail) material. The aperture was rectangular, centrally located in the longer wall, 390mm wide, and extended from the upper edge of the longer wall to a maximum depth of 280mm. The size of the aperture was adjustable by raising and lowering a sliding gate; the upper edge of which formed the lower edge of the aperture. The width of the aperture was also adjustable. Throughout the example the gate was positioned such that the tail aperture was 390mm wide by 170mm deep. A product aperture for removal of higher density (product) material was formed in the other of the longer walls. The product aperture was located in the bottom corner of the longer wall remote from the corner at which the product was fed to the trough and was of adjustable size by provision of a sliding gate. The product aperture was in the form of a quadrant of radius 70mm. Throughout the example the gate was positioned such that the product aperture was wide open. The vibratory motion imparted to the trough was elliptical with the plane of the motion substantially normal to the long sides of the trough at a frequency of 50Hz and an amplitude of l-2mm. The elliptical vibratory motion was imparted by a variable speed motor driving a pair of standard out of balance flywheels connected by a drive shaft with the scree:.i deck weighted to modify the circular motion which would otherwise be induced. Particle-particle interactions were established in the bed resulting in fluidisation caused by the vibratory motion with lower SG material continuously collected from the tail aperture and higher SG material continuously collected from the product aperture. Good upgrading was achieved yielding a produ.ct of 64.9% FeT0TAL, 3.25% Si02 and 1.06% A1203 from a foed of 64.3% Fe, 3.67% Si02 and 1.31% A1203 (Table 1). This product assay is close to the theoretical maximum as established from heavy liquid analysis of 65.5% F^TOTAL' 2.69% Si02 and 0.98% Al2O3 for 82% recovery (Table 2). Table 1. Quantitative Result - Assay of Feed, Product and Tail (Table Removed) Table 2. Theoretical calculated assay basesd on removal of the gangue ($G (Table Removed) Example 4 A continuous test was conducted on a sample o:: iron ore (b-3 0mm) in a rectangular trough 3 00mm wide by 600mm long by 300mm deep and mounted horizontally on the screen deck of Example 2. The sample was continuously fed from a vibratory feeder to the middle of the trough as curtain between the long sides of the trough and substantially parallel to the short sides of the trough at a feed rate of 500kg per hour. One of the longer walls was formed with a tail aperture for removal of lower density (tail) material. The aperture was rectangular/ located adjacent a corner of the trough, 100mm wide, and extended from the upper edge of the longer wall to a maximum depth of 280mm. The size of the aperture was adjustable by raising and lowering a sliding gate; the upper edge of which formed the lower edge of the aperture. Throughout ■the example the gate was positioned such that the tail aperture was 100mm wide by 165mm deep. A triangular product aperture for removal of higher density (product) material was formed in the same longer wall as the tail aperture. The product aperture was located in the bottom of the longer wall adjacent the corner remote from the tail aperture and was of adjustable size by provision of a sliding gate. Throughout the example the gate was positioned such that the product aperture was a right angle triangle having a base of 100mm and a height of 12 0mm. The vibratory motion imparted to the trough was elliptical with the plane of the motion substantially normal to the long sides of the trough at a frequency of 70Hz and an amplitude of 0.5-lmm. The elliptical vibratory motion was imparted by a variable speed motor driving a pair of standard out of balance flywheels connected by a drive shaft with the screen deck weighted to modify the circular motion which would otherwise be induced. Particle-particle interactions were established in the bed resulting in fluidisation caused by the vibratory motion with lower SG material continuously collected from the tail aperture and higher SG material continuously collected from the product aperture. The quantitative results for the total lump sample of iron ore indicated good ore recovery of 88%, witi some upgrading of the feed (64.3% FeT0TAL, 3.46% Si02 and 1.3 6% A1203) to the product (64.5% FeT0TAL, 3.11% Si02 and 1-26% A1203) being achieved (Table 3). Table 3. Quantitative Result - Assay of Product and Tail (Table Removed) Example 5 A batch test was conducted on a 60g sample of a mixture of 75% by weight magnetite of SG 5.5 and :25% by weight silica of SG 2.65 in the rectangular trough of Example 1 mounted horizontally on the screen deck of Example 2 with a 3mm bed depth. The size range of the feed material was 100-300µm. The primary vibratory motion imparted to the trough was elliptical with the plane of the motion substantially normal to the long sides of the trough at a frequency of 50 Hz a:ad an amplitude of 1mm. The elliptical vibratory motion was imparted by a variable speed motor driving a pair of standard out of balance flywheels connected by a drive shaft with the screen deck weighted to modify the circular motion which would otherwise be induced. A secondary linear reciprocating vibratory motion was: also imparted to the trough. The secondary motion was a vertical motion at a frequency of 50 Hz and an amplitude of 1.5mm. Particle-particle interactions were established in the bed resulting in fluidisation caused by the vibratory motions. Two distinct bands were formed in the trough; the lower band (high SG) contained 95% by weight magnetite and 5% by weight silica and the upper band (low SG) contained 82% by weight magnetite and 38% by weight silica. WE CLAIM: 1. An apparatus for separating particulate material which comprises: (i) means comprising a trough mounted on a frame for supporting a bed of the particulate material to be separated, (ii) vibratory motion inducing means for inducing within said bed of material particle-particle interaction whereby lower density particulate material migrates towards the top of the bed, and (iii) means for separating at least a portion of said lower density material from an upper portion of the bed. 2. An apparatus as claimed in claim 1 wherein said vibratory motion inducing means for inducing particle-particle interaction is connected to said trough on which said bed of material is supported. 3. An apparatus as claimed in claim 1 or 2 wherein said vibratory motion inducing means comprises linear reciprocating motion inducing means. 4. An apparatus as claimed in claim 1 or 2 wherein said vibratory motion inducing means comprises circular or elliptical motion inducing means. 5 An apparatus as claimed in claim 1 or 2 wherein said vibratory motion inducing means comprises circular or elliptical motion inducing means and linear reciprocating motion means. 6. An apparatus as claimed in any one of claims 1 to 5 wherein feed means is provided for continuously introducing'particulate material into the bed while said separation means continuously separates said lower density particulate material from the bed of material supported on said trough. 7. An apparatus as claimed in claim 6 wherein said feed means comprises a vibratory or belt feeder. 8. An apparatus as claimed in any one of claims 1 to 7 wherein said separation means comprises a weir over which or an aperture through which said lower density material flows in use. 9. An apparatus as claimed in any one of claims 1 to 8 wherein a plurality of troughs each supporting a bed of particulate material is provided in series whereby particulate material separated from one of the beds is introduced into another of the beds for further separation. 10. An apparatus as claimed in any of the preceding claims wherein the bed is of a depth greater than 5 particle diameters.

Documents:

1691-del-1998-abstract.pdf

1691-del-1998-claims.pdf

1691-del-1998-complete specification (granted).pdf

1691-del-1998-correspondence-others.pdf

1691-del-1998-correspondence-po.pdf

1691-del-1998-description (complete).pdf

1691-DEL-1998-Form-1.pdf

1691-del-1998-form-19.pdf

1691-del-1998-form-2.pdf

1691-del-1998-form-4.pdf

1691-del-1998-form-6.pdf

1691-del-1998-gpa.pdf