GB1572722A - Magnetic separator - Google Patents

Description

(54) MAGNETIC SEPARATOR (71) We, INTERNATIONAL RESEARCH & DEVELOPMENT COM PANY LIMITED, a British Company, of Fossway, Newcastle-upon-Tyne, NE6 2YD, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a magnetic separator and is particularly, although not exclusively, applicable to magnetic separators of the type required to separate magnetic or paramagnetic particles from a fluid.

The prior art is replete with constructions of high-gradient magnetic separators which are, however, all basically derived from an early design which consists of a matrix of steel wool surrounded by an electromagnetic structure which creates a high intensity magnetic field within the matrix. The passage of a fluid containing magnetic and/or paramagnetic particles through the matrix causes the particles to adhere to the individual steel fibres which have a diameter typically of the order of 50-150,am. One problem with this type of separator is that involved in cleaning the matrix after use and numerous proposals have been made for flushing and backflushing to remove the trapped particles in such a way as to enable the separation process and cleaning process to be carried out almost continuously with the minimum of supervision.

The operation of a high-gradient magnetic separator utilizes the fact that a magnetic particle in a spatially varying magnetic field will experience a net tractive force. The magnitude of this force increases, for both paramagnetic and ferromagnetic particles, as the local field gradient increases. Thus with suitably large field gradients it follows that it should be possible to separate a mixture of magnetic and non-magnetic particles.

In accordance with the present invention there is provided a magnetic separator comprising a plurality of magnetic coils spaced along a common axis and defining a passage for the flow of fluid through the centres of the coils along the said axis, alternate coils being energized to produce opposed axial fields such that there is a radially outwardly directed field in the annular space between each pair of adjacent coils with a region of high magnetic field gradient at the inner periphery of the said space to catch ferromagnetic or paramagnetic particles contained in the fluid flowing through the passage.

The magnetic coils are preferably flat pancake coils, spirally wound, and having a spacing between them which is the same across the radial dimension of the coil.

The value of the magnetic excitation and the spacing of the coils is selected for optimum performance. The spacing may be different between different pairs of coils. For example the spacing may change progressively in the direction of flow of the fluid in order to remove strongly magnetic particles at an early stage and the less magnetic particles at a later stage. Magnetic pole pieces may be employed to enhance the field gradient in the said regions.

Means may be provided for imparting a degree of turbulence to the fluid flow so that the particles trapped in the regions of high magnetic field gradient can flow outwards through the spaces between the magnetic coils.

If laminar flow of the fluid is employed the separated particles will be deposited on the side of the flow passage and will then have to be removed by periodic flushing with the coils de-energized.

The invention will be described in more detail with the aid of an example illustrated in the drawing accompanying the provisional specification, which is a diagrammatic rep resentation of the coil disposition in a magnetic separator in accordance with the invention.

As shown in the drawings five annular disc or pancake coils 10 to 14 are spaced along a vertical axis or centreline with a uniform spacing of 8 between each pair of coils. The coils are mounted in a vessel (not shown) and define a passage 15 for the flow of liquid between an inlet and an outlet opening of the vessel.

The magnetic coils 10-14 are energised so that coils 10, 12, 14 have a positive magnetic polarity and coils 11 and 13 have a negative magnetic polarity so that the cross-hatched regions 16, 17, 18, 19 delineate regions of high magnetic gradient; the force in these regions will be dependent upon the excitation of the coils and the spacing 8 between adjacent coils, the resultant direction of the magnetic force will be normal to the axis of the separator, as shown by the arrows.

In operation, fluid containing magnetic and/or paramagnetic particles is directed through the annulus 15 and the coils are energised as described above. The action of the separator is to capture the magnetic and/or paramagnetic particles in regions 16-19 and to drive these towards the spaces between the coils. By also imparting a degree of turbulence to the fluid it will be possible to extract the particles from these regions for collection outside the separator.

It will be appreciated that the embodiment described above comprises only the basic diagrammatic outline of a magnetic separator and that constructional details have been omitted such as those of the containing vessel, inlet connections and electrical connections; these details are well known in the art and do not form a part of the present invention.

Alternative means of collection of the extracted particles may be adopted when laminar flow of the liquid is applied and this will involve allowing the particles to become deposited on the rim of the container and removing these by periodic flushing with the coils de-energised.

WHAT WE CLAIM IS: 1. A magnetic separator comprising a plurality of magnetic coils spaced along a common axis and defining a passage for the flow of fluid through the centres of the coils along the said axis, alternate coils being energized to produce opposed axial fields such that there is a radially outwardly directed field in the annular space between each pair of adjacent coils with a region of high magnetic field gradient at the inner periphery of the said space to catch ferromagnetic or paramagnetic particles contained in the fluid flowing through the passage.

2. A magnetic separator as claimed in Claim 1 in which the magnetic coils are flat pancake coils.

3. A magnetic separator as claimed in Claim 1 or 2 including means for imparting turbulence to the fluid flowing through the passage to enable the separated particles to pass radially outwards between the coils.

4. A magnetic separator substantially as described with reference to the drawing accompanying the provisional specification.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. resentation of the coil disposition in a magnetic separator in accordance with the invention. As shown in the drawings five annular disc or pancake coils 10 to 14 are spaced along a vertical axis or centreline with a uniform spacing of 8 between each pair of coils. The coils are mounted in a vessel (not shown) and define a passage 15 for the flow of liquid between an inlet and an outlet opening of the vessel. The magnetic coils 10-14 are energised so that coils 10, 12, 14 have a positive magnetic polarity and coils 11 and 13 have a negative magnetic polarity so that the cross-hatched regions 16, 17, 18, 19 delineate regions of high magnetic gradient; the force in these regions will be dependent upon the excitation of the coils and the spacing 8 between adjacent coils, the resultant direction of the magnetic force will be normal to the axis of the separator, as shown by the arrows. In operation, fluid containing magnetic and/or paramagnetic particles is directed through the annulus 15 and the coils are energised as described above. The action of the separator is to capture the magnetic and/or paramagnetic particles in regions 16-19 and to drive these towards the spaces between the coils. By also imparting a degree of turbulence to the fluid it will be possible to extract the particles from these regions for collection outside the separator. It will be appreciated that the embodiment described above comprises only the basic diagrammatic outline of a magnetic separator and that constructional details have been omitted such as those of the containing vessel, inlet connections and electrical connections; these details are well known in the art and do not form a part of the present invention. Alternative means of collection of the extracted particles may be adopted when laminar flow of the liquid is applied and this will involve allowing the particles to become deposited on the rim of the container and removing these by periodic flushing with the coils de-energised. WHAT WE CLAIM IS:

1. A magnetic separator comprising a plurality of magnetic coils spaced along a common axis and defining a passage for the flow of fluid through the centres of the coils along the said axis, alternate coils being energized to produce opposed axial fields such that there is a radially outwardly directed field in the annular space between each pair of adjacent coils with a region of high magnetic field gradient at the inner periphery of the said space to catch ferromagnetic or paramagnetic particles contained in the fluid flowing through the passage.

2. A magnetic separator as claimed in Claim 1 in which the magnetic coils are flat pancake coils.

3. A magnetic separator as claimed in Claim 1 or 2 including means for imparting turbulence to the fluid flowing through the passage to enable the separated particles to pass radially outwards between the coils.

4. A magnetic separator substantially as described with reference to the drawing accompanying the provisional specification.