GB2209689A - Magnetic separation of particles - Google Patents

Magnetic separation of particles Download PDF

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Publication number
GB2209689A
GB2209689A GB8821003A GB8821003A GB2209689A GB 2209689 A GB2209689 A GB 2209689A GB 8821003 A GB8821003 A GB 8821003A GB 8821003 A GB8821003 A GB 8821003A GB 2209689 A GB2209689 A GB 2209689A
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GB
United Kingdom
Prior art keywords
particles
cable
cables
portions
cable portions
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.)
Withdrawn
Application number
GB8821003A
Other versions
GB8821003D0 (en
Inventor
Richard Gerber
Mark Harold Watmough
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sellafield Ltd
Original Assignee
British Nuclear Fuels PLC
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by British Nuclear Fuels PLC filed Critical British Nuclear Fuels PLC
Publication of GB8821003D0 publication Critical patent/GB8821003D0/en
Publication of GB2209689A publication Critical patent/GB2209689A/en
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • B03C1/035Open gradient magnetic separators, i.e. separators in which the gap is unobstructed, characterised by the configuration of the gap

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  • Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)

Abstract

Particles are released at end 38 of a vibrating table 36 supplied from a hopper 40 and fall past a device 10 in which parallel superimposed super conducting cables 16, 18 produce a magnetic field in the region of the descending particles. The table 36 is level with the uppermost cable or raised above the table by the radius of the cable. The cables are held in clamp 24 and cooled in cryostat vessel 26. The side 28 of the device is provided with a wiper 32. Strongly magnetic particles are attracted to side 28 and can be removed by wiper 32, weakly magnetic particles fall into box 48, and non-magnetic particles into box 46. A movable wall 50 enables adjustment of the relative widths of boxes 46, 48. Under certain conditions the deflection of the particles is independent of their shape and size. <IMAGE>

Description

Magnetic Separation of particles This invention relates to magnetic separation of particles.
According to one aspect of the present invention there is provided apparatus for separating particles magnetically, said apparatus comprising two substantially parallel superconducting cables (or cable portions) energised in opposite directions and disposed one above the other at a predetermined distance, means for releasing particles to be separated at a position substantially level with, or up to (A/K), where A is the cross-sectional area of a cable or cable portion, above the level of the upper edge of the upper cable or cable portion, and means for collecting separated said particles after they have passed the magnetic field produced by the cables or cable portions.
The collecting means may be disposed below the lower of the two cables or cable portions.
According to another aspect of the present invention there is provided a method of separating particles magnetically, said method comprising releasing the particles with substantially zero velocity in the vertical direction from a position substantially level with, or up to (A/ where A is the cross-sectional area of a cable or cable portion, above the level of the upper edge of the upper of two substantially parallel superconducting cables or cable portions disposed one above the other at a predetermined distance, allowing the particle to fall through the magnetic field induced by the cables or cable portions to cause the particles to be deflected according to their magnetic properties, and collecting those particles that do not adhere to the cables or cable portions.
Preferably, the cables or cable portions are linked at their respective ends to form a flattened coil.
The cables or cable portions may be of substantially square or substantially circular cross-section.
Desirably, the cables or cable portions are spaced apart so that the centre-to-centre distance between the cables or cable portions is in the range 3.5 (A/f to 4.5 (A/X)+, where A is the cross-sectional area of a cable or cable portion.
Conveniently, the cables or cable portions are located by clamping means to reduce any movement of the cables or cable portions due to magnetic fields induced.
The apparatus may be provided with a wiper for removing any particles which adhere to the cables or cable portions or to a housing for the cables or cable portions.
The means for releasing the particles may comprise a table arranged to be vibrated so that the particles fall off an edge of the table.
Preferably, the position of release of the particles in relation to the size of the particles is selected such that
b 19n2(L-a)\3 2/'X CFmx? where b is the radius of particles n is the viscocity of air a is the equivalent radius of a cable or cable portion and is defined as (A/#) where A is the cross-sectional area of the cable or cable portion # is the density of the particles X is the volume susceptibility of the particles (Fmx) is the average force density over the extent of the separators L is horizontal distance from the centre of a cable or cable portion to the position of release.
The invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic front view of a magnetic separator; and Figure 2 is a diagrammatic view on the line II-II of Figure 1 and showing, in addition the particle feed system.
Referring to the drawings, a linear open gradient magnetic separator 10 comprises a linear superconducting coil 12 formed from a superconducting cable, and a particle feed system 14.
The coil 12 comprises an upper straight portion 16, a lower straight portion 18 disposed substantially vertically below, and substantially parallel to, the upper straight portion 16, and a pair of arcuate end portions 20 and 22 which link respective ends of the upper straight portion 16 to the lower straight portion 18 to form the coil 12.
As shown in Figure 2, the upper straight portion 16 and lower straight portion 18 are of square crosssection, and the coil 12 is located in a generally E-shaped clamp or support 24. The clamp 24 is supported inside a cryostat vessel 26, formed from non-magnetic steel, with the upper and lower straight portions 16, 18 adjacent to a wall 28 of the vessel 26. A wiper 30 ismounted on guides 32 and 34 (see Figure 1) for reciprocating motion in the direction of the upper and lower straight portions 16, 18 and so that the wiper 30 is adjacent to the wall 28 of the vessel 26.
The feed system 14 comprises a table 36 having an inclined end 38 and a hopper 40 provided on the upper surface 42 of the table 36 and which supplies particles to the upper surface 42 via a variable throat 44. The table 36 is arranged with its upper surface substantially horizontal and such that the inclined end 38 is a predetermined distance from the coil 12 and the lower edge of the inclined end 38 is level with the top of the upper straight portion 16. A vibrator (not shown) is provided to vibrate the table 36 and hence to effect movement of particles on the upper surface 42 of the table 36.
A collecting box 45 is disposed below the coil 12 and extends lengthwise between the extremities of the arcuate portions 20 and 22 and widthwise from a point below the table 36 to a point below the coil 12. The collecting box 45 is divided lengthwise into a trough 46 for non-magnetic particles and a trough 48 for weakly magnetic particles by a splitter plate 50 which is moveable towards and from the coil 12 to vary the width of the troughs 46 and 48. Two strong magnetic particle collecting boxes 52 and 54 are provided at either end of the wall 28 of the vessel 26.
In use, particles are supplied to the upper surface 42 of the table 36 which is vibrated. The particles move over the surface 42 of the table, travel down the inclined end 38 and then fall downwards past the coil 12.
The coil 12 is cooled in the cryostat vessel 26 and energised such that the upper straight portion 16 and lower straight portion 18 are energised in opposite directions and hence induce a magnetic field in their vicinity. As the particles fall past the coil 12 they are deflected as a result of the presence of the magnetic field, the extent of deflection depending on the magnetic properties of the particles. The distance of the lower edge of the inclined end 38 from the coil 12 and the position of the splitter plate 50 are selected so that strongly magnetic particles impinge on, and adhere to, the wall 28 of the vessel 26, weakly magnetic particles are deposited in the weakly magnetic particle trough 46 and the non-magnetic particles are deposited in the trough 48. The wiper 30 removes the strongly magnetic particles from the wall 28 and deposits them in the boxes 52 and 54.
It has been found that the maximum deflection of particles is achieved when the centre-to-centre distance between the upper straight portion 16 and lower straight portion 18 is in the range 3.5 (A/R) 2 to 4.5 (A/)21 and preferably substantially equal to 4 (A/R), where A is the cross-sectional area of either one of the porti.ons 16 or 18. Thus when the straight portions 16, 18 are of circular cross-section this centre-to-centre distance is in the range 3.5a to 4.5a and preferably substantially 4a, where a is the radius of a straight portion.
It has also been found that the optimum position of release of the particles, that is the position of the lower edge of the inclined end 38 of the table 36, is at a position between the top of the upper straight portion 16 and a point equal to (A/T)} above the top of the upper straight portion 16, and is preferably substantially level with the top of the upper straight portion 16. The particles are released from the optimum position referred to with a velocity in the vertical direction substantially equal to zero.
The position of release of the particles in relation to the size of the particles is selected such that
b > ~~~~~ 2tX < Fmx > where b is the radius of particles n is the viscocity of air a is the equivalent radius of,sa cable and is defined as (h where A is the cross-sectional area of the cable is is the density of the particles X is the volume susceptibility of the particles AFmx is the average force density over the extent of the separator L is horizontal distance from the centre of a cable to the position of release It has been found that when this condition is satisfied the deflection of the particles is independent of their shape and size and hence depends only on their magnetic properties, therefore enabling separation of particles of different chemical composition irrespective of the shape or size of the particles. Consequently, it is preferred that the above condition is satisfied for substantially all of the particles to be separated.
The separator can be used to remove radioactive particles from streams, such as in ventilation systems.
The separator can also be used to concentrate particles before their analysis in, for example, the nuclear industry or steel industry. Upgrading of alloys, de-sulphurisation of coal and benefication of mineral ores can also be achieved by use of the separator.

Claims (12)

Claims
1. Apparatus for separating particles magnetically comprising two substantially parallel superconducting cables (or cable portions) energised in opposite directions and disposed one above the other at a predetermined distance, means for releasing particles to be separated at a position substantially level with, or up to (A/x), where A is the cross-sectional area of a cable or cable portion, above the level of the upper edge of the upper cable or cable portion, and means for collecting separated said particles after they have passed the magnetic field produced by the cables or cable portion.
2. Apparatus as claimed in claim 1, in which the collecting means is disposed below the lower of the two cables or cable portionS.
3. Apparatus as claimed in claim 1 or claim 2, in which the cables or cable portions are linked at their ends to form a coil.
4. Apparatus as claimed in any preceding claim, in which the cables or cable portions are of square cross-section.
5. Apparatus as claimed in any of claims 1 to 3, in which the cables or cable portions are of circular cross-section.
6. Apparatus as calimed in any preceding claim, in which the cables or cable portions are spaced apart so that the centre-to-centre distance between the cables or cable portions is in the range 3.5 (A/v)} to 4.5 (A/g), where A is the cross-sectional area of a cable or cable portion.
7. Apparatus as claimed in any preceding claim, comprising a wiper for removing particles which adhere to the cables or cable portions or to a housing for the cables or cable portions.
8. Apparatus as calimed in any preceding claim, in which the means for releasing the particles comprises a table arranged to be vibrated so that the particles fall off on an edge of the table.
9. A method of separating particles magnetically comprising releasing the particles with substantially zero velocity in the vertical direction from a position substantially level with, or up to (AZ where A is the cross-sectional area of a cable or cable portion, above the level of the upper edge of the upper of two substantially parallel superconducting cables or cable portions disposed one above the other at a predetermined distance, allowing the particles to fall through the magnetic field induced by the cables or cable portions to cause the particles to be deflected according to their magnetic properties, and collecting those particles that do not adhere to the cables or cable portions.
10. A method or apparatus as claimed in any preceding claim, in which the position of release of the particles in relation to the size of the particles is selected such that
b ~~~~~~ 2 #X < Fmx > where b is the radius of particles n is the viscocity of air a is the equivalent radius of a cable or cable portion and is defined as (A/)12 where A is the cross-sectional area of the cable or cable portion # is the density of the particles X is the volume susceptibility of the particles cFmx > is the average force density over the extent of the separators L is horizontal distance from the centre of a cable or cable portion to the position of release.
11. A method of separating particles magnetically substantially as hereinbefore described.
12. Apparatus for separating particles magnetically substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
GB8821003A 1987-09-14 1988-09-07 Magnetic separation of particles Withdrawn GB2209689A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB878721521A GB8721521D0 (en) 1987-09-14 1987-09-14 Magnetic separation

Publications (2)

Publication Number Publication Date
GB8821003D0 GB8821003D0 (en) 1988-10-05
GB2209689A true GB2209689A (en) 1989-05-24

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GB878721521A Pending GB8721521D0 (en) 1987-09-14 1987-09-14 Magnetic separation
GB8821003A Withdrawn GB2209689A (en) 1987-09-14 1988-09-07 Magnetic separation of particles

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GB878721521A Pending GB8721521D0 (en) 1987-09-14 1987-09-14 Magnetic separation

Country Status (1)

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GB (2) GB8721521D0 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101850300A (en) * 2010-06-02 2010-10-06 江苏旌凯中科超导高技术有限公司 Superconducting magnetic separation device
CN101920223A (en) * 2010-06-02 2010-12-22 江苏旌凯中科超导高技术有限公司 Superconductive magnetic separating device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101850300A (en) * 2010-06-02 2010-10-06 江苏旌凯中科超导高技术有限公司 Superconducting magnetic separation device
CN101920223A (en) * 2010-06-02 2010-12-22 江苏旌凯中科超导高技术有限公司 Superconductive magnetic separating device

Also Published As

Publication number Publication date
GB8721521D0 (en) 1987-10-21
GB8821003D0 (en) 1988-10-05

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