AU731513B2 - Magnetic cyclone and method of operating it - Google Patents

Magnetic cyclone and method of operating it Download PDF

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Publication number
AU731513B2
AU731513B2 AU20828/97A AU2082897A AU731513B2 AU 731513 B2 AU731513 B2 AU 731513B2 AU 20828/97 A AU20828/97 A AU 20828/97A AU 2082897 A AU2082897 A AU 2082897A AU 731513 B2 AU731513 B2 AU 731513B2
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Australia
Prior art keywords
cyclone
density
dense medium
particles
magnet
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AU20828/97A
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AU2082897A (en
Inventor
Quentin Peter Campbell
Jan Svoboda
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De Beers Consolidated Mines Ltd
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De Beers Consolidated Mines Ltd
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Publication of AU2082897A publication Critical patent/AU2082897A/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B03SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03CMAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
    • B03C1/00Magnetic separation
    • B03C1/02Magnetic separation acting directly on the substance being separated
    • B03C1/30Combinations with other devices, not otherwise provided for

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  • Cyclones (AREA)

Description

I,
AUSTRALIA
Patents Act COMPLETE SPECIFICATION
(ORIGINAL)
Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority Related Art: Name of Applicant: De Beers Consolidated Mines Limited Actual Inventor(s): Jan Svoboda Quentin Peter Campbell Address for Service: PHILLIPS ORMONDE FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne 3000 AUSTRALIA Invention Title: MAGNETIC CYCLONE AND METHOD OF OPERATING IT Our Ref 490491 POF Code: 1503/304551 The following statement is a full description of this invention, including the best method of performing it known to applicant(s): 'S"~o aBe" 2 BACKGROUND TO THE INVENTION THIS invention relates to a magnetic cyclone and to a method of operating a magnetic cyclone.
One of the critical parameters in the operation of dense medium cyclones, which are used inter alia in dense medium diamond separation processes, is the density differential between the overflow and underflow streams produced by the cyclone. It is generally accepted that the density differential should have a constant value of between 0,2 and 0,5 specific gravity units.
oIf the density differential is too high, there is a wide range of densities present in the cyclone and excessive middlings particles with a high retention time, thereby reducing the speed at which the cyclone can operate. If the .****density differential is too low, inadequate recovery of the valuable component, typically diamond, is achieved.
•Magnetic cyclones, in which a magnetic field is applied to the cyclone vessel, are known. A feature common to all known magnetic cyclones is the use of a horizontally oriented magnetic field which draws magnetic, i.e.
magnetisable, particles to the side of the cyclone vessel from where they are moved to the underflow spigot in the material flow. Attempts have been made to use magnetic cyclones of this type in mineral beneficiation processes, such as in the recovery of magnetite, but the known technology has not received wide acceptance for various reasons including insufficient mineral recovery, undesirable flocculation of the magnetic particles resulting in poor concentrate grades and product accumulation in the cyclone.
SUMMARY OF THE INVENTION According to the present invention there is provided a dense medium cyclone in which particles of a feed material are to be separated from one another according to their density in a magnetic dense medium, the cyclone including a cyclone vessel for containing the magnetic dense medium and having an inlet for feed material, an underflow and an overflow, and a magnet arranged toroidal!y about the cyclone vessel to generate a vertically oriented magnetic field in the vessel for controlling the density of the dense medium such that particles having a density exceeding that of the dense medium report to the underflow while particles having a density less than the density of the dense medium report to the overflow.
In the cyclone of the invention, the field generating means comprises a magnet arranged toroidally about the cyclone vessel. The magnet may be a permanent magnet or an electromagnet. In the latter case, it is preferred that the coil of the electromagnet be supplied with a selectively variable current whereby the strength of the magnetic field be varied. Irrespective of whether the magnet is a permanent magnet or an electromagnet, it is preferred that the vertical position of the magnet be variable.
According to another aspect of the invention there is provided a method of operating a dense medium cyclone in which particles of a feed material are to be separated from one another according to their density in a magnetic dense medium in a cyclone vessel having an inlet for the feed material, an underflow and an overflow, the method S- 25 including the steps of generating a vertically oriented magnetic field in the cyclone vessel, by means of a toroidal magnet arranged about the cyclone vessel, thereby to •control the density of the dense medium such that particles having a density exceeding that of the dense medium report to the underflow while particles having a density less S•than the density of the dense medium report to the overflow. As indicated above, the 30 magnetic field strength and or the vertical position of the magnet may be variable to •enhance the operational control which is achieved by the method.
one application, the invention proposes that the method be used to control at least the density differential between the underflow stream and the overflow stream in a dense medium cyclone, typically one using a magnetic W:mnary\MMHNODEL20828.doc 4 medium such as ferrosilicon (FeSi). In addition, the method may be used to control the cut point density and the sharpness of the separation.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 diagrammatically illustrates a magnetic cyclone oooo according to the invention; Figure 2 diagrammatically illustrates the forces acting on particles in the cyclone; Figure 3 graphically illustrates an experimental relationship between density differential and magnetic field 0 strength for different positions of the magnet; and Figure 4 shows a series of Tromp curves demonstrating relationships between density cut point, sharpness of separation and magnetic field strength.
SPECIFIC DESCRIPTION The invention is described hereunder in its application to the control of the operating parameters of a dense medium cyclone, typically one in which FeSi forms the dense medium and which is employed in diamond recovery operations.
The magnetic cyclone 10 seen in Figure 1 includes a cyclone vessel 12 of generally conventional construction. The cyclone vessel has an underflow spigot 14 at its lower end, a vortex finder 16 serving as an overflow at its upper end, and a material feed inlet 18 through which feed material is introduced. In a diamond recovery operation, the feed material may, for instance comprise diamondiferous particles in a dense ferrosilicon suspension. In this specific application, it is desirable to control the density differential within close limits, typically at a value between 0,2 and specific gravity units, to ensure comprehensive recovery of the diamond particles in the underflow.
A toroidal magnet 20 is arranged concentrically about the cyclone vessel, as illustrated, and generates a vertically oriented magnetic field indicated by the numeral 22. The magnet may be a permanent magnet or an electromagnet, Sin the form of a solenoid, and it may be of any suitable construction such as iron-yoke type or multi-pole type. Means (not illustrated) are provided to vary the vertical position of the magnet 20 relative to the cyclone vessel, as "i S• indicated by the arrows 24. In addition, in the case of an electromagnet, current control means (not illustrated) are provided to vary the current supplied to the coil of the electromagnet and thereby vary the strength of the magnetic field 22 which is generated.
0: i 0 Y., 6 It is possible to vary the orientation of the magnetic field 22, i.e. upwards or downwards, by varying the vertical position of the magnet 20 in relation to the cyclone vessel. In Figure 1, the magnetic field gradient and hence the magnetic force is illustrated by the arrow 26 as upwardly directed. Figure 2 illustrates a situation where the magnetic field at the axis of the cyclone is oriented vertically downwardly. The symbol Fm represents the magnetic force on magnetic particles in the cyclone attributable to the magnetic field, the symbol Fg the gravitational force on the particles, the symbol F d the o.
hydrodynamic drag force on the particles and the symbol F, the centrifugal force on the particles. The resultant of these forces is indicated by the symbol F(total).
In a simple solenoid, the magnetic force is always directed towards the centre of the solenoid irrespective of whether the solenoid is in the upper or lower part of the cyclone. The direction of the resultant force is determined by the magnitude of the other relevant forces, such as gravitational force and hydrodynamic drag force. In any case, however, the direction of the total *S force will be outwards as shown in Figure 2.
5*5555 It is possible to wind the solenoid in such a way that the magnetic force is directed not towards the centre of the solenoid, but outwards away from the centre. This can, for instance, be achieved by placing more turns of the solenoid wire on the upper and/or lower ends of the solenoid rather than at the centre. Such techniques provide additional flexibility in determining the direction of the magnetic force.
Clearly by varying the vertical position of the magnet the orientation and magnitude of the resultant force F(to,,tal) can be varied. Because the resultant L 7 force acting on the particle determines whether it reports to the underflow or the overflow of the cyclone vessel, this feature can advantageously be used to control of the density differential between the underflow and overflow and the density cut point, i.e. the density value at which the distinction is made between material which will report to the underflow and that which will report to the overflow.
In situations where the magnet 20 is an electromagnet, varying the current ~supplied to the coil of the electromagnet will also vary the strength of the magnetic field and hence the value of Fm. This feature may also be used advantageously to apply a further control to the relevant parameters such as density differential and cut point. In situations where the magnet 20 is a oooo permanent magnet with a fixed field strength, the necessary control of the operational parameters of the cyclone would be achieved solely by variation of the vertical position of the magnet.
Figure 3 graphically illustrates experimental results confirming the variation *of density differential which can be achieved using an electromagnet with oooo• S* variable supply current to vary the strength of the magnetic field, as represented on the horizontal axis. Figure 3 also illustrates that a further control on density differential can be achieved by varying the vertical position of the magnet, as indicated by the three curves indicating experimental results obtained with the magnet positioned respectively at a top position, a middle position and a bottom position. In the experimental model the top position of the magnet was flush with the lower end of the vortex finder, the bottom position of the magnet was flush with the underflow spigot and the middle position was mid-way between the top and bottom positions.
-8- Figure 4 shows several Tromp curves for different magnetic field strengths and serves to illustrate relationships between density cut point and sharpness of the separation which is achieved, and the magnetic field strength The experimental results were obtained using a 100mm diameter cyclone vessel and a ferrosilicon suspension incorporating density tracers.
•It is anticipated that the invention will enable close controls to be maintained t over the important operational parameters of the cyclone.
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Claims (8)

1. A dense medium cyclone in which particles of a feed material are to be separated from one another according to their density in a magnetic dense medium, the cyclone including a cyclone vessel for containing the magnetic dense medium and having an inlet for feed material, an underflow and an overflow, and a magnet arranged toroidally about the cyclone vessel to generate a vertically oriented magnetic field in the vessel for controlling the density of the dense medium such that particles having a density exceeding that of the dense medium report to the underflow while particles having a density less than the density of the dense medium report to the overflow.
2. A cyclone according to claim 1 wherein the magnet is a permanent magnet.
3. A cyclone according to claim 1 wherein the magnet is an electromagnet.
4. A cyclone according to claim 3 including means for supplying the coil of the electromagnet with a selectively variable current to vary the strength of the 20 magnetic field. e A cyclone according to any one of the preceding claims wherein the vertical position of the magnet relative to the cyclone vessel is variable. 25 6. A method of operating a dense medium cyclone in which particles of a feed material are to be separated from one another according to their density in a magnetic dense medium in a cyclone vessel having an inlet for the feed material, an underflow and an overflow, the method including the steps of generating a vertically oriented magnetic field in the cyclone vessel, by means 0 30 of a toroidal magnet arranged about the cyclone vessel, thereby to control the density of the dense medium such that particles having a density exceeding that of the dense medium report to the underflow while particles having a density less than the density of the dense medium report to the overflow. W:mary\MMHNODEL20828.doc
7. A method according to claim 6 including the step of selectively varying the magnetic position of the magnet relative to the cyclone vessel.
8. A method according to either one of claims 6 or 7 wherein the magnet is an electromagnet, the method. including the step of selectively varying the current supplied to the coil of the electromagnet.
9. A method according to any one of claims 6 to 8 wherein the feed material contains diamondiferous materials in a ferrosilicon suspension and the cyclone is operated in a manner to separate diamond particles from associated particles. A cyclone substantially as herein described with reference to the accompanying drawings.
11. A method of operating a cyclone substantially as herein described with reference to the accompanying drawings. DATED: 12 January, 2001 PHILLIPS ORMONDE FITZPATRICK Patent Attorneys for: DE BEERS CONSOLIDATED MINES LIMITED 0 W:Vmary"MMHNODEL\20828.doc
AU20828/97A 1996-05-23 1997-05-13 Magnetic cyclone and method of operating it Ceased AU731513B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ZA964132 1996-05-23
ZA96/4132 1996-05-23

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Publication Number Publication Date
AU2082897A AU2082897A (en) 1997-11-27
AU731513B2 true AU731513B2 (en) 2001-03-29

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CA (1) CA2205339C (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103056049B (en) * 2013-01-23 2014-02-26 武汉科技大学 Overflow-discharge-type magnetic hydrocyclone
GB201403568D0 (en) * 2014-02-28 2014-04-16 Eco Nomic Innovations Ltd Dense media deparation method
CN104624410B (en) * 2015-01-20 2017-10-10 太原理工大学 A kind of method for adjusting dual medium cyclone dressing density
CN109092577B (en) * 2018-07-20 2020-06-16 太原理工大学 Method for indirectly reducing medium consumption of heavy medium cyclone separation process by using external magnetic field

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU1049113A1 (en) * 1982-06-14 1983-10-23 Московский Ордена Трудового Красного Знамени Институт Химического Машиностроения Hydraulic cyclone

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU1049113A1 (en) * 1982-06-14 1983-10-23 Московский Ордена Трудового Красного Знамени Институт Химического Машиностроения Hydraulic cyclone

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CA2205339C (en) 2006-07-04
CA2205339A1 (en) 1997-11-23

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