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
  • B03C1/005—Pretreatment specially adapted for magnetic separation
  • B03C1/01—Pretreatment specially adapted for magnetic separation by addition of magnetic adjuvants
• • 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
• • 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

Definitions

• This invention relates to an improved apparatus and method for magnetic separation.
• the invention is especially concerned with the use of adsorption and diffusion effects to assist in the selective recovery of non-magnetic materials by the use of magnetic materials.
• magnetic separators have generally been designed around one of two principles.
• the first and most generally used design is the single-surface- type magnetic separator, i.e., in which the magnetic field-producing elements also directly produce the field gradients.
• Examples of these single-surface separators includes grade suspended magnets, pulleys and drums.
• a drum separator may have permanent magnets or electromagnets to produce both the magnetic fields and the gradients on the trapping surface of the drum.
• the second most common design is the matrix-type magnetic separator wherein an electromagnetic coil or
• the working volume contains a ferro-magnetic structure which' is magnetised to produce strong, magnetic-field gradients on the sharp edges or small radius-of-curvature elements of the structure. Further details•of separators ' of both of these types may be found in the literature, for example, in irk-Othmer "Encyclopaedia of Chemical Technology", Third Edition, Volume 14, John Wiley & Sons.
• the method as described in the literature are usually employed to separate magnetic particles from non-magnetic particles. It is also known, however, to use magnetic particles as adsorbents for non-magnetic material, e.g. , where the surface of the particles is able to exert some attractive effect on the other material. Examples include the adsorption of oil onto the hydrophobic surface of magnetite.
• magnetic- particles or fibres have been used to bring about iltration by entrainment of non-magnetic particles in a mess of the ' magnetic particles or fibres " which can be caused to " contract and expel solvent or supporting liquid.
• the present invention is not concerned with the normal processes of magnetic separation and filtration. Rather, the invention is concerned with facilitating the handling and treatment of hydrophobic * non-magnetic substances by the use of magnetic materials, particularly those having hydrophobic surface properties.
• poles may be constituted by the poles of- a permanent magnet but generally it will be more convenient to use electromagnets.
• the magnetic field may be removed, e.g., by temporarily switching off or reducing the exciting 0 . current in the windings of the electromagnets generating the field.
• This process allows the plug to move downwards a small distance whereupon the magnetic field is again applied and a new plug created on top of the initial plug while, magnetic particles with the entrained or adsorbed non-magnetic substance, are lost from the plug into the effluent liquid stream.
• the magnetic particles can then be removed from the effluent stream by any suitable means, usually and most desirably, a magnetic separator of conventional or any other type.
• the invention also provides apparatus for carrying out " .the above method, the said apparatus comprising a conduit for passage of liquid and . magnetic field generating means on opposing sides of the conduit, said field generating means comprising at ⁇ -least two- airs of opposed magnetic poles, said pairs being of opposite polarity and being arranged in spaced relationship so as to produce a magnetic field which is extended in the longitudinal direction of the conduit and in which, over at least a substantial proportion of its length, the product of-the magnetic field intensity and gradient is constant.
• More than two pairs of magnetic poles can be used if desired thereby providing a still further extended field.
• the poles are preferably the poles of electromagnets.
• the poles Preferably also the poles have a general form of a cusp generated by the intersection of two circles or similarly curved figures with the apex of the cusp adjacent to conduit.
• Other pole shapes are, however, possible, the only limitations being that the field must have the specified characteristics.
• the method and apparatus of the invention are of ' particular value fox the recovery by adsorption of bacterial or algal cells which are adsorbable onto magnetite or other magnetic materials by hydrophobic effects and which are present at low concentrations in aqueous suspensions.
• One application of particular importance is the harvesting from saline waters of algae of the genus Dunalielia for. subsequent recovery from the algae of valuable -substances including beta-carotene and glycerol, for example as described in Australian Patent Application No. PF 1093/81.
• Magnetite is a particularly suitable material for this purpose but . other magnetic minerals such as haematite may also be used.
• the method of the invention is also applicable to a wide range of other uses.
• hydrophobic substances adsorbed on magnetic substrates according to the " teaching of the invention may be subjected _in situ to various physical and chemical treatments before being desorbed from the substrate.
• the drawing shows a cross section of the apparatus.
• the conduit 1 is of elongated rectangular cross section (as shown in the drawing, its widest dimension extends vertically through the plane of the paper) .
• On either side of the conduit is a shaped low carbon iron block 3.
• the blocks 3 constitute the armatures of an electromagnet and define longitudinally- extending channels housing the windings 5 of the electromagnets. These channels partly define the pole pieces of the electromagnets which, as shown in the drawing, are generally cusp shaped at their ends with the apexes of the cusps adjacent to conduit.
• the windings are connected in such a fashion that, when the magnet is energised the two " se ' ts of pole pieces are of opposite polarity, as shown in the drawing.
• Bands 4 extend the. length of the blocks and are joined across the faces of the blocks to complete the magnetic circuit.
• the magnetic field thus generated is such that the product of the magnetic field-intensity and * the * field gradient (i.e., the differential of the magnetic field intensity) is constant along that part of the conduit defined by the two " sets of poles except for a * singularity on the axis of symmetry 2 of the poles.
• the magnetic particles When the field is energised and a liquid stream containing magnetic particles is passed downwards through the conduit, the magnetic particles form threads extending between the singularities 2 and thereby form a column or plug of the magnetic particles within the conduit.
• the thus formed plug is
• Width (each block) approx. 1.5" - (38mm)
• the energizing coils each contained 100 turns.
• the apparatus used included the experimental electromagnet assembly described above.
• the conduit used as the- column was a rectangular tube with an outside cross section of approximately 7/8" x 1/4" ' (22.2 x 6.4mm) and inside measurements of approximately 3/8" x 1/16" (9.5 x 1.6mm).
• the length of the column was approximately 9" (230mm) .
• the column was arranged between the poles of the magnet assembly and the top connected to a. container with a stirrer in which the test suspension was placed.
• the magnetic material used was silanised magnetite prepared as described in our copending Australian patent application No. F 1093/81.
• Dried 120 mesh (BSS) magnetite was treated with a 1% 5 solution of dichlorodi ethyl silane in petroleum ether at ambient temperature for three hours.
• the treated magnetite was separated from the solvent by decantation and draining with the aid of a magnet, dried for half an hour and then demagnetised.

Landscapes

• Water Treatment By Electricity Or Magnetism (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)
• Treatment Of Liquids With Adsorbents In General (AREA)

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Citations (2)

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• 1982
  • 1982-10-13 WO PCT/AU1982/000168 patent/WO1983001398A1/en not_active Application Discontinuation
  • 1982-10-13 JP JP50307682A patent/JPS58501662A/ja active Pending
  • 1982-10-13 EP EP19820903031 patent/EP0090827A4/de not_active Withdrawn

Patent Citations (2)

Non-Patent Citations (2)

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