CA2205339C - Magnetic cyclone and method of operating it - Google Patents
Magnetic cyclone and method of operating it Download PDFInfo
- Publication number
- CA2205339C CA2205339C CA002205339A CA2205339A CA2205339C CA 2205339 C CA2205339 C CA 2205339C CA 002205339 A CA002205339 A CA 002205339A CA 2205339 A CA2205339 A CA 2205339A CA 2205339 C CA2205339 C CA 2205339C
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- CA
- Canada
- Prior art keywords
- cyclone
- density
- dense medium
- particles
- magnet
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION 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
- B03C—MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03C1/00—Magnetic separation
- B03C1/02—Magnetic separation acting directly on the substance being separated
- B03C1/30—Combinations with other devices, not otherwise provided for
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- Cyclones (AREA)
Abstract
One aspect of the invention concerns a cyclone which has a cyclone vessel having an underflow and an overflow and an inlet for feed material. Means are provided to generate a vertically oriented magnetic field in the cyclone vessel for the purposes of controlling the operation thereof. Another aspect of the invention concerns a method of operating a cyclone vessel in which at least the density differential achieved by the cyclone is controlled by means of a vertically oriented magnetic field.
Description
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.
If 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.
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.
If 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 cyclone comprising a cyclone vessel for containing a magnetic dense medium and having an inlet fim feed material, an underflow and an overflow, and a vertically oriented magnetic field in the cyclone 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 preferred embodiments, 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 tree 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 bc; 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 comprising the steps of generating a vertically oriented magnetic field in 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.
The method is preferably implemented by means of a magnet arranged toroidally about the cyclone vessel. As indicated above, the 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.
In 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 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 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 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 ' ~ CA 02205339 1997-OS-14 FeSi forms the dense medium and which is employed in diamond recovery operations. It should however be understood that the principles of the invention are also applicable to the operation of cyclones used in mineral beneficiation processes where magnetic particles are to separated from non-magnetic particles and in the dewatering of dilute media.
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 0,5 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, in the form of a solenoid, and it may be of any suitable construction such as iron-yoke type or mufti-pole type. Means (not illustrated) are provided to vary the vertical position of the magnet 20 relative to the cyclone vessel, as 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.
According to the present invention there is provided a cyclone comprising a cyclone vessel for containing a magnetic dense medium and having an inlet fim feed material, an underflow and an overflow, and a vertically oriented magnetic field in the cyclone 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 preferred embodiments, 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 tree 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 bc; 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 comprising the steps of generating a vertically oriented magnetic field in 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.
The method is preferably implemented by means of a magnet arranged toroidally about the cyclone vessel. As indicated above, the 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.
In 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 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 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 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 ' ~ CA 02205339 1997-OS-14 FeSi forms the dense medium and which is employed in diamond recovery operations. It should however be understood that the principles of the invention are also applicable to the operation of cyclones used in mineral beneficiation processes where magnetic particles are to separated from non-magnetic particles and in the dewatering of dilute media.
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 0,5 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, in the form of a solenoid, and it may be of any suitable construction such as iron-yoke type or mufti-pole type. Means (not illustrated) are provided to vary the vertical position of the magnet 20 relative to the cyclone vessel, as 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.
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 l, 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 Fb the gravitational force on the particles, the symbol Fd the 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~to~a~>.
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 force will be outwards as shown in Figure 2.
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~~o~,~ can be varied. Because the resultant 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 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 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.
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 over the important operational parameters of the cyclone.
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 force will be outwards as shown in Figure 2.
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~~o~,~ can be varied. Because the resultant 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 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 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.
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 over the important operational parameters of the cyclone.
Claims (9)
1. A dense medium cyclone in which particles of a feed material are separated from one another according to their density in a magnetic dense medium, the cyclone comprising 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 therein 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 comprising means for supplying the coil of the electromagnet with a selectively variable current to vary the strength of the magnetic field.
5. A cyclone according to any one of claims 1 to 4 wherein the vertical position of the magnet relative to the cyclone vessel is variable.
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 comprising 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 than the density of the dense medium report to the overflow.
7. A method according to claim 6 including the step of selectively varying the vertical 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 includes a diamondiferous particulate material in a ferrosilicon suspension and the cyclone is operated in a manner to separate diamond particles from associated particles.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| ZA96/4132 | 1996-05-23 | ||
| ZA964132 | 1996-05-23 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2205339A1 CA2205339A1 (en) | 1997-11-23 |
| CA2205339C true CA2205339C (en) | 2006-07-04 |
Family
ID=25585698
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002205339A Expired - Fee Related CA2205339C (en) | 1996-05-23 | 1997-05-14 | Magnetic cyclone and method of operating it |
Country Status (2)
| Country | Link |
|---|---|
| AU (1) | AU731513B2 (en) |
| CA (1) | CA2205339C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103056049A (en) * | 2013-01-23 | 2013-04-24 | 武汉科技大学 | Overflow-discharge-type magnetic hydrocyclone |
| CN104624410A (en) * | 2015-01-20 | 2015-05-20 | 太原理工大学 | Method for adjusting separation density of dense medium cyclone |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB201403568D0 (en) * | 2014-02-28 | 2014-04-16 | Eco Nomic Innovations Ltd | Dense media deparation method |
| 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 |
Family Cites Families (1)
| 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 |
-
1997
- 1997-05-13 AU AU20828/97A patent/AU731513B2/en not_active Ceased
- 1997-05-14 CA CA002205339A patent/CA2205339C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103056049A (en) * | 2013-01-23 | 2013-04-24 | 武汉科技大学 | Overflow-discharge-type magnetic hydrocyclone |
| CN104624410A (en) * | 2015-01-20 | 2015-05-20 | 太原理工大学 | Method for adjusting separation density of dense medium cyclone |
Also Published As
| Publication number | Publication date |
|---|---|
| AU731513B2 (en) | 2001-03-29 |
| CA2205339A1 (en) | 1997-11-23 |
| AU2082897A (en) | 1997-11-27 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |