US3898156A - Hyperbolic magnet poles for sink-float separators - Google Patents

Hyperbolic magnet poles for sink-float separators Download PDF

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Publication number
US3898156A
US3898156A US454373A US45437374A US3898156A US 3898156 A US3898156 A US 3898156A US 454373 A US454373 A US 454373A US 45437374 A US45437374 A US 45437374A US 3898156 A US3898156 A US 3898156A
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United States
Prior art keywords
separator
magnetic
magnetic field
ferrofluid
axis
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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 - Lifetime
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US454373A
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English (en)
Inventor
Robert Kaiser
Leon Mir
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Avco Corp
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Avco Corp
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Publication date
Application filed by Avco Corp filed Critical Avco Corp
Priority to US454373A priority Critical patent/US3898156A/en
Priority to GB8574/75A priority patent/GB1504968A/en
Priority to DE19752509959 priority patent/DE2509959A1/de
Priority to CH298575A priority patent/CH595140A5/xx
Priority to NL7503359A priority patent/NL7503359A/xx
Priority to FR7508860A priority patent/FR2265458B3/fr
Priority to BE154686A priority patent/BE827098A/xx
Priority to IT21587/75A priority patent/IT1034590B/it
Priority to JP50034585A priority patent/JPS50130061A/ja
Application granted granted Critical
Publication of US3898156A publication Critical patent/US3898156A/en
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    • 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
    • B03C1/32—Magnetic separation acting on the medium containing the substance being separated, e.g. magneto-gravimetric-, magnetohydrostatic-, or magnetohydrodynamic separation

Definitions

  • ABSTRACT A hyperbolic magnet with pole which produces a constant magnetic gradient along an axis, usually a vertical axis, in a sink-float separator. Magnetic pieces are secured at the lateral edges of the poles to modify the magnetic field to prevent material being separated from being pinned to the outer walls of the separator and a mirror plate is adjustably separated from the end of the poles for tuning the magnetic field.
  • the present invention relates generally to sink-float separators and more particulary to a new magnetic pole design for sink-float separators.
  • a problem that arises in sink-float tank separators of the prior art is that the magnetic field is such that it results in the pinning of the materials which are to be separated against the outer walls of the separator, thereby jamming the free-flow in the vertical direction of the objects to be separated.
  • the present invention is a unique design of a magnet with hyperbolic poles and a mirror plate for sink-float separators to solve the problems of the prior art devices.
  • the rectangular hyperbolic magnetic pole pieces and the mirror plate are designed to produce a constant vertical magnetic gradient in the magnet gap.
  • the pole pieces are straight-line approximations of a portion of a hyperbola, said portions asymptotes being parallel to the direction of separation or gravity.
  • Magnetic pieces, or shims are secured to the lateral edges of the poles to locally modify the magnetic field to prevent the material being separated from being pinned to the outer walls of the separator by the force produced by the magnetic field of the poles.
  • the magnetic plate is adjustably separated from the ends of the poles to fine tune the magnetic field produced by the hyperbolic poles to provide a constant magnetic density throughout the ferrofluid.
  • An object of the present invention is to provide a magnetic pole design with the lower power requirements than the prior art devices.
  • Another object of the present invention is to provide a magnetic pole designed for use in the float-sink separator which provides a uniform vertical magnetic field gradient.
  • a further object of the present invention is to provide a magnetic pole design which is fine-tunable so as to achieve a uniform magnetic density across in a ferrofluid volume.
  • Still another object of the present invention is the modification of the magnetic field so as to prevent objects being separated from being pinned against the outer walls of the separator.
  • FIG. I is a hyperbolic curve from which the preferred embodiment of the magnetic poles were designed
  • FIG. 2 is a front view of a float-sink separator with the preferred hyperbolic poles
  • FIG. 3 is a front view of the gap defined by the hyperbolic poles and mirror plate of FIG. 2;
  • FIG. 4 is a view of the hyperbolic poles and mirror plate of FIG. 2 taken along Line 44 of FIG. 3;
  • FIG. 5 is a top view of the preferred embodiment shown in FIG. 3, showing a modification of the shims;
  • FIG. 6 is a graph of the magnetic field H along the Z axis.
  • FIG. 7 is a graph of magnetic parameters as a function of vertical height before and after fine tuning using the adjustments of the preferred embodiment.
  • the non-magnetic sink-float separator of the present invention is based on an unusual property of ferrofluids the ability to float a non-magnetic or weakly magnetic object of far greater density than the ferrofluid itself when the ferrofluid is placed in a suitable magnetic field.
  • Ferrofluids are very stable colloids of small (about A) magnetic particles. generally magnetite, suspended in a base liquid and stabilized by surface active agents. For sink-float separation, the base liquid could be, for example, a high flash point kerosene. The suspended particles do not settle out or agglomerate under the action of gravity or applied magnetic fields. A ferrofluid placed in a non-uniform magnetic field experiences a force directed along the magnetic field gradient. A consequence of this is that a non-magnetic object immersed in a ferrofluid experiences a force in the opposite sense and is expelled to the region of mini mum magnetic field.
  • a body of ferrofluid is held between the poles of an electromagnet which generates a magnetic field with a constant gradient; directed downward, in the direction of gravity. Consequently, a non-magnetic object immersed in the ferrofluid pool experiences a magnetic force in the upward direction.
  • this magnetic force can be made larger or smaller than the force of gravity on the non-magnetic object.
  • a ferrofluid in a suitable magnetic field with a gradient parallel to gravity, can be viewed as a liquid that has a controllable apparent density:
  • the apparent density of the ferrofluid In order to obtain accurate separations, it is necessary for the apparent density of the ferrofluid to be constant (within the accuracy desired) throughout the ferrofluid volume. Otherwise, the less dense objects might fall to the bottom in a region of an abnormally low apparent density and the more dense objects float in a region of abnormally high apparent density. This is accomplished by ensuring that the field throughout the separator is high enough to bring the ferrofluid magnetic dipole moment M close to its saturation value and that the vertical magnetic field gradientv" is essentially constant.
  • the value of the gradient along the y axis is controlled by the distance between the poles and the magnetizing current.
  • the value of 8 H/lS y is kept as constant as the separation to be made dictates.
  • the hyperbolic surface is also terminated at a finite value ofy, because for large values of y. the interpole distance becomes impractically small.
  • the preferred embodiment as shown in FIGS. 2, 3 and 4 includes the separator 10, having included therein two hyperbolic segments 12 and 14.
  • Each of the hyperbolic pole pieces 12 and 14 may be made up of a plurality of plane segments which approximate a portion of the hyperbolic surface as shown in FIG. 1.
  • the pole pieces may be cast as a unitary piece and the face machined to form the plane segments.
  • the hyperbolic pole pieces 12 and 14 are supported and secured to a yoke 16. Lying perpendicular to the y'axis on support blocks 18 is the mirror plate 20 and mirror plate support 22 discussed above. Though the mirror plate support block 18 is shown as blocks, they may be replaced by any device which will adjustably mount the mirror plate relative to the pole pieces 12 and 14 so as to fine tune the system. As will be discussed later, a system may be fine tuned so as to find the perfect distance from the mirror plate to the pole pieces 12 and 14.
  • Magnetic pieces 24 Secured to both ends of the magnetic pole pieces 12 and 14 are a plurality of magnetic pieces or shims 24.
  • Magnetic pieces 24 are used to provide a magnetic field distribution as shown in FIG. 6.
  • the shims increase the magnetic field at the marginal edges of the pole pieces to generate the hill-like perturbations 25 at the edge of the pole pieces.
  • the perturbation is provided to assist the material being separated to flow towards the center of the magnetic field. This action prevents the force produced by the magnetic field from pinning the mate rial against the container wall.
  • the magnetic field gradients found in the perturbations are generally in the direction shown by arrows 27 and 29. Materials to be separated which gravitates to a boundary 31 of the working volume, encounters the magnetic field gradient depicted by arrow 27. This material is forced back away from the boundary 31 by the outwardly directed lateral gradient 27 since, as discussed previously, the material tends to move toward regions of minimum magnetic field.
  • the pole pieces are designed to provide the dish-like configuration along the x axis as shown for the z axis of FIG. 6.
  • the modification of the shims to provide such a field modification is shown in FIG. 5 as 24' as being tapered in two planes.
  • the shims 24 are rectangular and have a generally tapered configuration in one plane which may vary between /z to 7, dependent upon the size and structure of the magnetic pole pieces.
  • the working volume" marked in FIG. 3 is the region where the vertical component of the gradient should be constant within This region is obtained by having the ideal hyperbolic shape of the poles approximated by the straight line cords that intersect on the hyperbola and the mirror plate.
  • the tapered shims along the edges of the poles are for the purpose of modifying the magnetic field and controlling the horizontal gradient.
  • an inwardly directed gradient is produced by the pole piece.
  • This gradient along the z axis, exerts a force that will push the materials in the ferrofluid towards the front and rear walls of the separator.
  • the shims modify the field to produce the field as shown in FIG. 6.
  • An outwardly pointed 2 component of the magnetic field gradient prevents the particles which are being separated from being pinned to the containers outer wall.
  • the objects to be separated move along the y axis which, as can be seen in FIG. 1, is one of the asymptotes of the hyperbola, of which the magnetic poles are sections.
  • FIG. 2 two coils 26 and 28 are wrapped around the yoke 16 behind pole pieces 12 and 14, respectively. It is to be understood that the magnetic field is of sufficient strength to support the ferrofluid therebetween.
  • a container 30, shown in FIG. 2 is included to restrict the ferrofluid to the working volume and provide the front and rear walls of the separation. When the top and bottom of box 30 are deleted, there is easy horizontal access to the pool of ferrofluid. Since magnetic forces also retain the ferrofluid in the gap of the magnet, conveyors or other means of introducing the feed or removing the separated products can be introduced directly into the ferrofluid pool without fluid leakage or sealing problems from front or back.
  • the mirror plate 20 is located in an optimum position to provide a constant gradient (Curve 33), and the magnetic moment M, the field intensity H, and the density p depicted as Curves 31, 32 and 37, respectively. As depicted in Curve 37, the density p is slightly less at the top of the magnetic pole than it is at the bottom.
  • the magnetic plate 20 may be varied to fine tune locally the system so as to achieve a constant p.
  • the height of the mirror plate 20 is determined by the height of the support blocks 18. When the mirror plate is lowered slightly, there is a large change in the field intensity H, a slight decrease in the magnetic moment M, and a relatively large increase in the vertical gradient in the vicinity of the mirror plate 20. If the mirror plate is lowered the proper amount, will increase in the vicinity of the mirror plate to provide a constant p throughout the working volume.
  • H. M. Wand p. as a function of height Y. after the adjustment. are represented as H. M. and p and are depicted by curves 35. 36. 34 and 38. respectively.
  • the hyperbolic magnetic design as depicted in FIGS. 2, 3 and 4 provide a constant p.
  • the mirror plate 20 is adjustable to increase in the vicinity of the mirror plate to a greater extent than M is decreased, so that a constant p can be realized.
  • the present design can separate any two non-ferrous materials whose density differs by 5 to 10% or more.
  • Apparent specific gravity of the ferrofluid can bc varied, from less than 1 g/cm to over 20 g/cm by a 5 mph: change in electric current flow through the coils of an energizing electromagnet. This range include from magnesium and aluminum (around 2-3 g/cm); through zinc, tin, brass, copper and lead (7-1 1 g/cm); up to gold and platinum 1922 g/cm).
  • Some magnetic materials may also be separated as long as they are less magnetic than the ferrofluid used.
  • the especially designed hyperbolic magnetic poles for use in a sink-float separator achieves the desired design requirements and utilizes low power requirements.
  • the design provides a constant vertical magnetic gradient and includes the adjustment of the mirror plate as defined in the system to provide a constant density along the vertical axis. Shim pieces are provided at the edges of the magnetic poles to modify the magnetic field so as to prevent the objects which are being separated from being pinned against the outer walls of the container.
  • the pole configuration of the present invention can be used in the process described in the previously mentioned patents.
  • the solid mixture to be separated is introduced into the pool of ferrofluids suspended between the poles by magnetization. Objects less dense than the apparent density of the ferrofluid float to the top, while those more dense sink to the bottom of the ferrofluid pool, resulting in a physical separation.
  • An upper and lower conveyor will remove the more dense and less dense materials. respectively, from the top and bottom of the pool. Since magnetic forces also retain the ferrofluid in the gap of the magnet, conveyors can be introduced directly into the pool without fluid leakage or sealing problems.
  • the separation can be carried out on a batch or continuous basis. Mixtures of three or more components can be separated by making two or more passes through the separator during which the apparent density of the ferrofluid is adjusted to produce one pure component per pass. Such mixtures could also be separated by a sequence of separators operating at appropriate apparent density levels, with partly separated mixtures being conveyed from one separator to the next until all separations are achieved.
  • a ferrofluid separator having a magnet including a pair of spaced pole pieces defining an air gap containing a magnetic field and a pool of ferrofluid disposed in said air gap and magnetic field, the improvement comprising:
  • pole pieces that are a' mirror image of each other with respect to an axis, and each of said pole pieces is a segment of a hypobolic surface
  • a mirror plate means disposed above and spaced from said pole pieces and air gap for creating a virtual image of said pole pieces.
  • each pole is formed by a plurality of pole pieces. each being a straight line approximation of a portion of said hyperbolic segment.
  • the separator as in claim 2 including means secured to said poles for preventing the materials to be separated from being pinned to the lateral walls of the ferrofluid pool.
  • the separator as in claim 1 to include means for maintaining a constant apparent density along said axis which includes means for adjusting the magnetic field intensity adjacent to said mirror plate.
  • said maintaining means includes said magentic plate, whose plane is perpendicular to said axis and said maintaining means being adjustable along said axis for varying the apparent density distribution of the magnetic field.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Magnetic Resonance Imaging Apparatus (AREA)
  • Water Treatment By Electricity Or Magnetism (AREA)
US454373A 1974-03-25 1974-03-25 Hyperbolic magnet poles for sink-float separators Expired - Lifetime US3898156A (en)

Priority Applications (9)

Application Number Priority Date Filing Date Title
US454373A US3898156A (en) 1974-03-25 1974-03-25 Hyperbolic magnet poles for sink-float separators
GB8574/75A GB1504968A (en) 1974-03-25 1975-02-28 Magnetic separation
DE19752509959 DE2509959A1 (de) 1974-03-25 1975-03-07 Hyperbolische magnetpole fuer absetzaufschlemm-abscheider
CH298575A CH595140A5 (hu) 1974-03-25 1975-03-10
NL7503359A NL7503359A (nl) 1974-03-25 1975-03-20 Magnetische bezinkingsafscheider.
FR7508860A FR2265458B3 (hu) 1974-03-25 1975-03-21
BE154686A BE827098A (nl) 1974-03-25 1975-03-24 Magnetische bezinkingsafscheider
IT21587/75A IT1034590B (it) 1974-03-25 1975-03-24 Poli iperbolici di elettromagnete per separatori di immersione e galleggiamento
JP50034585A JPS50130061A (hu) 1974-03-25 1975-03-24

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US454373A US3898156A (en) 1974-03-25 1974-03-25 Hyperbolic magnet poles for sink-float separators

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US3898156A true US3898156A (en) 1975-08-05

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US (1) US3898156A (hu)
JP (1) JPS50130061A (hu)
BE (1) BE827098A (hu)
CH (1) CH595140A5 (hu)
DE (1) DE2509959A1 (hu)
FR (1) FR2265458B3 (hu)
GB (1) GB1504968A (hu)
IT (1) IT1034590B (hu)
NL (1) NL7503359A (hu)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0362380A1 (de) * 1988-02-17 1990-04-11 Gosudarstvenny Proektno-Konstruktorsky Institut 'gipromashugleobogaschenie' Ferrohydrostatischer separator
EP0395761A1 (de) * 1988-07-26 1990-11-07 Gosudarstvenny Proektno-Konstruktorsky Institut 'gipromashugleobogaschenie' Ferrohydrostatische abtrennvorrichtung
US6041705A (en) * 1996-07-03 2000-03-28 Lintner; Alexander Rotary silk screen printing machine
US6851557B1 (en) * 1999-02-17 2005-02-08 Jan Svoboda Ferrohydrostatic separation method and apparatus
US20050178701A1 (en) * 2004-01-26 2005-08-18 General Electric Company Method for magnetic/ferrofluid separation of particle fractions
WO2005105314A1 (en) * 2004-05-05 2005-11-10 The University Of Nottingham Method and apparatus for controlling materials separation
US20090277733A1 (en) * 2007-05-19 2009-11-12 Stabilus Gmbh Kolben-Zylinderaggregat
US11383247B2 (en) * 2013-03-15 2022-07-12 Ancera, Llc Systems and methods for active particle separation
US11833526B2 (en) 2015-06-26 2023-12-05 Ancera Inc. Background defocusing and clearing in ferrofluid-based capture assays

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2550468B1 (fr) * 1983-08-10 1985-12-20 Pi Vtorichnykh Separateur magnetohydrostatique
JPS5946954U (ja) * 1983-08-18 1984-03-28 松下電器産業株式会社 帯状体の折畳み装置
DE4447362C2 (de) * 1994-12-21 1999-06-17 Enretec Polychemie Entsorgungs Vorrichtung zur Rückgewinnung von magnetischer Flüssigkeit

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1956760A (en) * 1931-05-08 1934-05-01 Mines Domaniales De Potasse Method and apparatus for the magnetic separation of mixed products
US2088364A (en) * 1934-09-22 1937-07-27 Edwin E Ellis Electromagnetic separator device
US2154010A (en) * 1937-01-16 1939-04-11 Queneau Augustin Leon Jean Electromagnetic separator device
US2768746A (en) * 1954-02-26 1956-10-30 Dings Magnetic Separator Co Magnetic filter
US3289836A (en) * 1964-10-14 1966-12-06 Weston David Method and apparatus for the magnetic separation of particulate materials
US3483969A (en) * 1967-07-05 1969-12-16 Avco Corp Material separation using ferromagnetic liquid techniques
US3788465A (en) * 1972-04-28 1974-01-29 Us Interior Device and process for magneto-gravimetric particle separation using non-vertical levitation forces

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1956760A (en) * 1931-05-08 1934-05-01 Mines Domaniales De Potasse Method and apparatus for the magnetic separation of mixed products
US2088364A (en) * 1934-09-22 1937-07-27 Edwin E Ellis Electromagnetic separator device
US2154010A (en) * 1937-01-16 1939-04-11 Queneau Augustin Leon Jean Electromagnetic separator device
US2768746A (en) * 1954-02-26 1956-10-30 Dings Magnetic Separator Co Magnetic filter
US3289836A (en) * 1964-10-14 1966-12-06 Weston David Method and apparatus for the magnetic separation of particulate materials
US3483969A (en) * 1967-07-05 1969-12-16 Avco Corp Material separation using ferromagnetic liquid techniques
US3788465A (en) * 1972-04-28 1974-01-29 Us Interior Device and process for magneto-gravimetric particle separation using non-vertical levitation forces

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0362380A1 (de) * 1988-02-17 1990-04-11 Gosudarstvenny Proektno-Konstruktorsky Institut 'gipromashugleobogaschenie' Ferrohydrostatischer separator
EP0362380A4 (en) * 1988-02-17 1990-12-27 Gipromashugleobogashe Ferrohydrostatic separator
EP0395761A1 (de) * 1988-07-26 1990-11-07 Gosudarstvenny Proektno-Konstruktorsky Institut 'gipromashugleobogaschenie' Ferrohydrostatische abtrennvorrichtung
EP0395761A4 (en) * 1988-07-26 1990-12-27 Gipromashugleobogashche Ferrohydrostatic separator
US6041705A (en) * 1996-07-03 2000-03-28 Lintner; Alexander Rotary silk screen printing machine
US6851557B1 (en) * 1999-02-17 2005-02-08 Jan Svoboda Ferrohydrostatic separation method and apparatus
US20050178701A1 (en) * 2004-01-26 2005-08-18 General Electric Company Method for magnetic/ferrofluid separation of particle fractions
US6994219B2 (en) * 2004-01-26 2006-02-07 General Electric Company Method for magnetic/ferrofluid separation of particle fractions
WO2005105314A1 (en) * 2004-05-05 2005-11-10 The University Of Nottingham Method and apparatus for controlling materials separation
US20090277733A1 (en) * 2007-05-19 2009-11-12 Stabilus Gmbh Kolben-Zylinderaggregat
US11383247B2 (en) * 2013-03-15 2022-07-12 Ancera, Llc Systems and methods for active particle separation
US11833526B2 (en) 2015-06-26 2023-12-05 Ancera Inc. Background defocusing and clearing in ferrofluid-based capture assays

Also Published As

Publication number Publication date
JPS50130061A (hu) 1975-10-14
BE827098A (nl) 1975-07-16
FR2265458A1 (hu) 1975-10-24
CH595140A5 (hu) 1978-01-31
DE2509959A1 (de) 1975-10-09
NL7503359A (nl) 1975-09-29
IT1034590B (it) 1979-10-10
FR2265458B3 (hu) 1978-07-28
GB1504968A (en) 1978-03-22

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