WO 2010/037162 PCT/AU2009/001254 Electro-ma2netic flux clarifier, thickener or separator FIELD OF THE INVENTION The present invention relates to a magnetically induced zonal clarifier, thickener or settler and 5 particularly, though not exclusively to an apparatus which includes a primary separation zone and a secondary separation zone, the operating conditions of the secondary separation zone being subject to a magnetic or electro induced force field and quiescent relative to the operating conditions of the primary separation zone to provide improved clarification of a feed slurry. 10 BACKGROUND TO THE INVENTION Australian Patent No. 667938 describes and illustrates various thickeners relying on gravity settling of solids in a slurry contained within a vessel. The slurry flows via a feed conduit to a feed cylinder or well which is located within an upper free settling region of the vessel. Any flocculant or coagulant agents added to the slurry are allowed to freely disperse through the slurry in the feed 15 cylinder or well. The flocculated slurry then passes into the upper free settling region, in one embodiment via several flocculating cylinders. A clarified liquid fraction moves upwardly through the vessel and is removed as a clarified liquid overflow, and a solids fraction settles under gravity and moves downwardly through the vessel into a lower compaction region. A thickened sludge can then be removed as an underflow from the base of the vessel. 20 Australian Patent No. 667938 relies on the inclusion of one or more inclined pathways defined by a series of angle-shaped members or inverted cones being arranged one upon the other. The inclined pathways are disposed within the lower compaction region to encourage clarified liquid within the thickened sludge to flow upwardly through the compaction region and into the upper free settling 25 region with a reported increase in the solids density of the underflow. In one embodiment of the thickener described in Australian Patent No. 667938, a conduit is connected between an uppermost cone of the series of inverted cones and the feed well so that some of the clarified liquid within the compaction region is recycled to tle feed well. The recycled clarified liquid contains 'seed flocs' which then combine with the feed slurry in the feed well. 30 Although the thickener of Australian Patent No. 667938 is an improvement on conventional gravity sedimentation devices it suffers from at least the following drawbacks: (i) the included pathways -1 - WO 2010/037162 PCT/AU2009/001254 are not particularly efficient in effectively increasing the solids density of the thickened sludge underflow: and (ii) the thickener is relatively ineffective in selectively separating various solid components from one another within the feed slurry. In some solids sorting applications it is desirable to split the solid flow streams to boost the purity concentration of one or more specific 5 elements within a desired discharge stream. Australian Patent No. 728638 filed by the Applicant describes and illustrates a clarifier or thickener which relies on a venturi effect, created as a flow of slurry is fed to a feed well through a feed line, to draw clarified liquor from the settling vessel into a mixer chamber located within the feed well. 10 The mixer chamber is designed to encourage turbulent mixing of the recycled clarified liquor with the feed slurry to automatically dilute the incoming feed slurry. The mixer chamber also promotes effective dispersion of various polymer coagulating or flocculating agents into the diluted feed slurry to condition the feed slurry. This design of thickener, clarifier or settler is essentially a shallow tank design which requires a fairly large cross-sectional area to realise effective settlement, 15 The apparatus and method of the present invention were developed with a view to improving on the performance of the prior art clarifiers described above for feed slurries containing magnetic and non-magnetic solids. 20 It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents forms part of the common general knowledge in the art, in Australia or in any other country. In the summary of the invention, the description and claims which follow, except where the contest requires otherwise due to express language or necessary implication, the work 'comprise' or variations such as 25 'comprises' or 'comprising' is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention. SUMMARY OF THE INVENTION 3o According to a first aspect of the present invention there is provided an electro-magnetic flux separator for removing materials affected by an electro-magnetic field from unaffected materials, the separator comprising: -2- WO 2010/037162 PCT/AU2009/001254 a primary separation zone arranged to receive a feed slurry and produce a semi-clarified liquor as solids in the feed slurry settle under gravity towards a lowermost portion of the primary separation zone; a secondary separation zone arranged to receive the semi-clarified liquor from the primary 5 separation zone and produce an overflow stream of clarified liquor plus unaffected solids, the secondary separation zone operating under quiescent conditions relative to the primary separation zone; a plurality of electro-magnetic field generating elements for controlling the flow of affected solids within the separator; 10 a feed line for delivering the feed slurry to the feedwell; an underflow outlet for discharging a solids underflow from a lowermost portion of the primary separation zone; and, an overflow outlet for removing clarified liquor from an uppermost portion of the secondary separation zone. 15 In one form, the plurality of electro-magnetic field generating elements is arranged in one or both of the primary separation zone and the secondary separation zone. The plurality of electro magnetic field generating elements may be used to generate a magnetic field or an electric field. In one form, the plurality of electro-magnetic field generating elements is selected from the group 20 consisting of: permanent magnets, induction magnets, electro-magnets, induction coils, electrical coils, electrical wire sections or any combination thereof. Advantageously, in one form, each of the plurality of electro-magnetic field generating elements is independently energizable. In one form, the plurality of independently energizable electro 25 magnetic elements is capable of being turned on and off simultaneously, sequentially, in waves, in pairs, or in groups. Alternatively or additionally, the plurality of independently energizable electro-magnetic elements is energized and de-energized in sequence to generate an electro magnetic force field of shifting intensity. Advantageously, the plurality of independently energizable electro-magnetic elements may be energized and de-energized in sequence to force 30 affected solids to be drawn downwardly towards the lowermost portion of the separator. -3- WO 2010/037162 PCT/AU2009/001254 In one form, the plurality of electro-magnetic field generating elements is mounted around or along the walls of the feedwell. The electro-magnetic flux separator may further comprise one or more downcomer(s) to direct the flow of slurry from the feedwell into the primary separation zone, and the plurality of electro-magnetic field generating elements is arranged continuously or at spaced 5 apart intervals along the length of the downcomer(s). In one form, the electro-magnetic flux separator may further comprise one or more flow baffle(s) arranged inside the separator within the secondary separation zone to encourage quiescent flow within the secondary separation zone. In one form, the plurality of electro-magnetic field 10 generating elements is arranged continuously or at spaced apart intervals along the length of the flow baffle(s). The one or more flow baffle(s) may include an outermost flow baffle concentric with an innermost flow baffle, each of the outermost flow baffle and the innermost flow baffle being segmented, and wherein the outermost flow baffle and the innermost flow baffle are arranged such that the gaps between the segments in the innermost flow baffle are offset from the gaps 15 between the segments in the outermost flow baffle. Alternatively or additionally each downcomer may be separately baffled using a corresponding number of downcomer baffles concentrically arranged around each downcomer to direct the flow of semi-clarified liquor from the primary separation zone towards the secondary separation zone. In this form, the plurality of electro magnetic field generating elements may be arranged continuously or at spaced apart intervals along 20 the length of the downcomer baffle(s) In one form, the plurality of elements may be arranged external or internal to the wall(s) of the downcomer(s), downcomer baffle(s) and flow baffle(s). When the separator has a frustoconical base, the plurality of electro-magnetic field generating elements may be arranged continuously or 25 at spaced apart intervals along the base. In one form, the electro-magnetic flux separator may further comprise one or more dilution liquor inlet(s) through which dilution liquor is injected in use, to encourage upward flow of semi-clarified liquor within the separator. In one form, the electro-magnetic flux separator may further comprise 30 an overflow baffle arranged inwardly and upwardly to form a flow barrier between the primary separation zone and the secondary separation zone. Advantageously, solids that settle in a lowermost area within the secondary separation zone adjacent to a first end of the overflow baffle -4.
WO 2010/037162 PCT/AU2009/001254 may be removed from the separator using a discharge outlet. The electro-magnetic flux separator may further comprise one or more lances for facilitating the movement of these settled solids towards the discharge outlet. s In one form, the electro-magnetic flux separator may further comprise a splitter which is used to physically separate the primary separation zone from the secondary separation zone and one or more hydraulic mixer(s) which are fed with dilution liquor piped through dilution liquor feed pipes to direct the flow of dilution liquor across the splitter so as to encourage the movement of settled solids towards a sump separation zone. In one form, the electro-magnetic flux separator may 10 further comprise one or more wipers to wipe affected material from the plurality of electro magnetic field generating elements. Alternatively or additionally, the electro-magnetic flux separator may further comprise a rake for directing the settled solids towards the lowermost portion of the primary separation zone, the rake 15 being provided with one or more rake arms and wherein a plurality of electro-magnetic field generating elements is provided on or adjacent to the rake. In this form, one or more wipers may be mounted on the arms of the rake such that each co-rotates with the other in use. In one form, the affected materials may be discharged from the separator via the overflow outlet 20 and the unaffected materials are discharged from the underflow outlet. The plurality of electromagnetic field generating elements may be arranged such that any given element has an alternating polarity relative to the polarity of a neighbouring element. In one form, adjacent magnets having alternating polarity may lie perpendicular or parallel to an overall downward direction of flow of affected materials. Alternatively, adjacent magnets having alternating polarity 25 may lie parallel to an overall upward direction of flow of affected materials. According to a second aspect of the present invention there is provided a method of removing materials affected by an electro-magnetic field from unaffected materials in an electro-magnetic flux separator, the method comprising the steps of: 30 delivering a feed slurry to a feedwell using a feed line; -5- WO 2010/037162 PCT/AU2009/001254 directing the flow of a feed slurry into a primary separation zone within the separator to produce a semi-clarified liquor as solids in the feed slurry settle under gravity towards a lowermost portion of the primary separation zone; receiving the semi-clarified liquor from the primary separation zone in a secondary 5 separation zone to produce an overflow stream of clarified liquor plus unaffected solids, the secondary separation zone operating under quiescent conditions relative to the primary separation zone; controlling the flow of affected solids within the separator using a plurality of electro magnetic field generating elements; 10 discharging a solids underflow from an underflow outlet at a lowermost portion of the primary separation zone; and, removing clarified liquor from an uppermost portion of the secondary separation zone at an overflow outlet. 15 In one form, the plurality of electro-magnetic field generating elements may be arranged in one or both of the primary separation zone and the secondary separation zone. In one form, each of the plurality of electro-magnetic field generating elements is independently energizable. The plurality of independently energizable electro-magnetic elements may be energized and de-energized in sequence to generate an electro-magnetic force field of shifting intensity. Advantageously, the 20 plurality of independently energizable electro-magnetic elements are energized and de-energized in sequence to force affected solids to be drawn downwardly towards the lowermost portion of the separator. According to a third aspect of the present invention there is provided an electro-magnetic flux 25 separator for removing materials affected by an electro-magnetic field from unaffected materials substantially as herein described with reference to and as illustrated in the accompanying representations. According to a fourth aspect of the present invention there is provided a method of removing 30 materials affected by an electro-magnetic field from unaffected materials in an electro-magnetic flux separator substantially as herein described with reference to and as illustrated in the accompanying representations. -6- WO 2010/037162 PCT/AU2009/001254 BRIEF DESCRIPTION OF THE DRAWINGS In order to achieve a better understanding of the nature of the present invention several preferred embodiments of a thickener or clarifier will now be described in some detail, by way of example only, with reference to the accompanying drawings in which: 5 Figure 1 is a side-sectional view of an embodiment of the separator of the present invention illustrating the primary separation zone secondary separation zone with a plurality of electro magnetic field generating elements provided on a downcomer to control the flow of affected solids by encouraging the affected materials to move in a desired direction; Figure 2 is a side-sectional view of another embodiment in which additional elements are 10 mounted around and along the walls of the feedwell; Figure 3 is a side-sectional view of another embodiment illustrating the use of one or more flow baffles within the secondary separation zone to encourage quiescent flow within that zone with a plurality of electro-magnetic field generating elements provided on the downcomer, the feedwell and the flow baffles; 15 Figure 4 is a side-section view of another embodiment having a plurality of downcomers separately baffled using a corresponding plurality of downcomer baffles used to direct the flow of semi-clarified liquor from the primary separation zone towards the secondary separation zone; Figure 5 is a side-section view of another embodiment in which each downcomer baffle is provided with a diverter in the form of a disk to limit the downward flow of slurry through the 20 downcomer baffle; Figure 6 is a side-section view of another embodiment in which the feedwell discharges the feed slurry within a flow baffle; Figure 7 is a side-section view of another embodiment in which each downcomer baffle is provided with a diverter in the form of a cone to limit the downward flow of slurry through the 25 downcomer baffle; Figure 8 is a side-section view of another embodiment in which dilution liquor is injected through one or more dilution liquor inlets to encourage upward flow of semi-clarified liquor within the separator; Figure 9 is a side-section view of another embodiment in which each the feed line 30 terminates in a tapered nozzle arranged within a mixer chamber in fluid communication with a suction port via a suction port conduit to auto-dilute the feed slurry prior to the introduction of the feed slurry to the primary separation zone; .- 7- WO 2010/037162 PCT/AU2009/001254 Figure 10 is a side-section view of another embodiment in which the plurality of electro magnetic field generating elements form a continuous flux core within each of the flow baffle(s) and each of the plurality of downcomer baffles; Figure 11 is a side-section view of another embodiment in which the separator is further 5 provided with an overflow baffle arranged to form a flow barrier between the primary separation zone and the secondary separation zone; Figure 12 is a variation on Figure 11 in which the flow baffle(s) are provided as segments which are arranged in circular alignment with respect to each other, as best seen in plan view; Figure 13 is a side-section view of another embodiment in which the lower end of the 10 downcomer includes a base having an undulating profile in cross-section such that portions of the base are raised relative to other portions of the base; Figure 14 is a side-section and plan view of another embodiment in which the segmented outermost flow baffle is concentric with the segmented innermost flow baffle such that the gaps between the segments in the innermost flow baffle are offset from the gaps between the segments 15 in the outermost flow baffle; Figure 15 is a side-section view of another embodiment in which the plurality of electro magnetic field generating elements is arranged at spaced apart intervals along the length of the downcomer baffles and along the length of the flow baffles as well as at or within the frustoconical 20 base of the separator; Figure 16 is a side-section view of another embodiment in which the separator is provided with a horizontally positioned splitter which is used to physically separate the primary separation zone from the secondary separation zone; Figure 17 is a variation on Figure 16 in which the splitter is arranged at an angle to the 25 horizontal plane; Figure 18 is a side-section and plan view of another embodiment in which the flow baffle(s) take the form of a plurality of rods or tubes instead of being provided as continuous sheets; Figure 19 is a variation on Figure 18 in which the rods are randomly arranged; Figure 20 is a side-section and plan view of another embodiment in which a rake is used in 30 combination with segmented flow baffles; Figure 21 is a side-section and plan view of another embodiment which illustrates the addition of wipers to wipe affected solids from the flow baffles; -8- WO 2010/037162 PCT/AU2009/001254 Figure 22 is a side-section and plan view of another embodiment in which a rake is used in combination with segmented arched flow baffles; Figure 23 is a side-section and plan view of another embodiment in which a rake is used in combination with continuous flow baffles having a sawtooth profile at the lower end; 5 Figure 24 is a side-section and plan view of another embodiment in which a rake is used in combination with a plurality of electro-magnetic field generating elements being arranged at the base of the separator; Figure 25 is a variation on Figure 24 in which the elements are provided in the underflow outlet for additional control; 10 Figure 26 is a side-section and plan view of another embodiment in which a rake is used in combination with continuous arched flow baffles with the injection of dilution liquor; Figure 27 is a partial side-section view of another embodiment in which the downcomer baffles are provided using a honeycomb-like array comprising a plurality of elongate box sections such that each downcomer is positioned within one of said elongate box sections; 15 Figure 28 is a side-section and plan view of another embodiment in which the flow baffles are provided with a plurality of electro-magnetic field generating elements of alternating polarity; Figure 29 is a partial side-section detailed view of the plurality of electro-magnetic field generating elements of alternating polarity of Figure 28; and, Figure 30 is a side-section and plan view of an alternative embodiment to that illustrated in 20 Figure 28. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Particular embodiments of the present invention are now described. Using the process and apparatus of the present invention, a flux field is used to encourage separation of affected material 25 from non-affected material. By way of example, magnetic or magentizable materials will be affected when they pass through a magnetic field, whereas non-magnetic or non-magentizable material will not. Similarly, electrically charged material or ionisable material will be affected when they come into contact with an electric field. The terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present 30 invention which is defined by the claims. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. -9 - WO 2010/037162 PCT/AU2009/001254 The term "electro-magnetic field generating elements" refers to elements which are capable to generating either an electrical field or a magnetic field. The tein "magnetic materials" as used throughout this specification refers to materials which are 5 capable of being attracted by a magnetic field. The material may be ferromagnetic by nature or become magnetized when it comes into contact with a magnetic field. The term 'ionic materials" as used throughout this specification refers to materials which are electrically charged and thus capable of being attracted by an electrical field. The material may be 10 charged by nature or become electrically charged when it comes into contact with an electrical field. The term "affected materials" as used throughout this specification refers to materials which are attracted by passing through the electrical or magnetic field generated by an electro-magnetic field 15 generating element. Analogously, the term "unaffected materials" refers to materials which are not attracted by passing through the electrical or magnetic field generated by an electro-magnetic field generating element. With reference to Figure 1 there is provided a thickener or clarifier flux separator 10 arranged to 20 receive a feed slurry comprising solids dispersed in a liquor. The solids present in the feed slurry include both affected and non-affected materials which can be jointly or independently recovered as described in greater detail below. The separator 10 has a primary separation zone 12 and a secondary separation zone 14. The primary separation zone 12 is arranged to receive the feed slurry from a feedwell 16 and produce a semi-clarified liquor as solids in the feed slurry are drawn 25 towards a lowermost portion 18 of the primary separation zone 12. The secondary separation zone 14 is arranged to receive the semi-clarified liquor from the primary separation zone 12 and produce an overflow stream of clarified liquor. The secondary separation zone 14 operates under quiescent conditions relative to the primary separation zone, with the primary separation zone being operated under conditions of relatively higher shear. The separator 10 is further provided with a plurality of 30 electro-magnetic field generating elements 20 arranged in the secondary separation zone 14 for controlling the flow of affected materials present in the liquor. A feed line 22 is provided for delivering the feed slurry to the feedwell 16. An underflow outlet 24 is provided for discharging a -10- WO 2010/037162 PCT/AU2009/001254 solids underflow from the lowermost portion 18 of the primary separation zone 12. The separator 10 also has an overflow outlet 28 for removing clarified liquor from an uppermost portion 30 of the secondary separation zone 14. Clarified liquor rises to the top of the secondary separation zone 14 and flows over a weir 32 into an overflow launder 34 arranged towards the uppermost portion 30 of 5 the secondary separation zone 14. The clarified liquor is released from the overflow launder 34 through the overflow outlet 28. The electro-magnetic field generated by the plurality of elements 20 is used to control the flow of affected solids by encouraging the affected materials to move in a desired direction. By way of 10 example, the plurality of elements 20 can be arranged in such a way so as to encourage the affected materials to move in a counter current direction to the direction of flow of high density solids settling under gravity. This electro-magnetically induced separation of affected solids enables more efficient separation of solids from the feed slurry than can be achieved using gravitation separation forces alone. Without wishing to be bound by theory, it is preferable for the plurality of 15 elements 20 to be arranged within the secondary separation zone 14 as the operating conditions in the secondary separation zone 14 are more quiescent relative to the higher shear flow regimes which operate within the primary separation zone 12. It is understood that the more quiescent conditions are more conducive to effective control of the movement of affected solids as fewer collisions occur with other materials. 20 The specific number, type and arrangement of the plurality of electro-magnetic field generating elements 20 can vary depending on such relevant factors as the type of feed slurry being treated in the separator 10 and the percentage, size and electrical or magnetic permeability of the types of materials present in the feed slurry. When used to generate a magnetic field, the plurality of 25 electro-magnetic field generating elements 20 may be permanent magnets, induction magnets, electro-magnets or any combination thereof. When used to generate an electrical field, the plurality of electro-magnetic field generating elements 20 may be induction magnets, electrical coils suitable for generating flux fields, electrical wire sections or any combination thereof. The greatest degree of control is achieved using a plurality of independently energizable electro 30 magnetic elements 20 which are capable of being turned on and off independently of each other. When a plurality of such independently energizable electro-magnetic elements is used, individual elements can be turned on and off simultaneously, sequentially, in waves, in pairs, or in groups to WO 2010/037162 PCT/AU2009/001254 allow greater control over the movement of the affected materials in the liquor. Such elements further allow the flux generated to be varied in both time and strength as desired to suit the type of affected material being separated. The plurality of electro-magnetic field generating elements 20 may be of any shape or size to suit the particular location in which they are being placed within the 5 separator and various non-limiting arrangements are described below. In the embodiment illustrated in Figure 1, one or more downwardly extending channels or "downcomer(s)" 44 is used to direct the flow of slurry from the feedwell 16 into the primary separation zone 12. The downcomer 44 has an upper end 46 and a lower end 48. In this 10 embodiment, the secondary separation zone 14 is arranged between the inner peripheral wall 42 of the separator 10 and the downcomer 44. The primary separation zone 12 is arranged within the area defined by the base 26 of the separator 10, below the lower end 48 of the downcomer 44. In Figure 1, the base 26 of the separator 10 is frustoconical, having an inwardly sloping wall to promote mass flow of the settling solids downwardly towards the underflow outlet 24. The feed slurry being 15 discharged from the downcomer 44 has a downward trajectory as it travels into the primary separation zone 12 causing semi-clarified liquor to be displaced upwardly through the secondary separation zone 14. It is to be understood that the term 'downward trajectory' does not imply that the feed slurry is forced to travel vertically downwardly but rather only that there is a downward vector to the direction of travel of the feed slurry as it is discharged into the primary separation 20 zone 12. In this embodiment, the plurality of electro-magnetic field generating elements 20 is arranged at spaced apart intervals along the length of the downcomer(s) 44 to generate an electric-magnetic field to control the flow of affected solids in the semi-clarified slurry within the secondary 25 separation zone 14. The plurality of elements 20 can be arranged external or internal to the wall(s) of the downcomer 44. In one form of the present invention, the plurality of elements 20 are permanent magnets and affected materials within both the feed slurry and the semi-clarified liquor in the secondary separation zone 14 will be attracted to move towards the plurality of elements 20. However, the high downward force and high degree of agitation occurring within the downcomer 30 44 encourages essentially all of the feed slurry inside of the downcomer 44 to flow out of the lower end 48 of the downcomer 44 and into the primary separation zone 12. The dense solids present in the feed slurry settle under gravity towards the lowermost portion 18 of the primary separation .12- WO 2010/037162 PCT/AU2009/001254 zone 12 while the lighter materials double back on themselves to rise upwardly into the secondary separation zone 14 in the form of a semi-clarified slurry. The affected solids present within the semi-clarified slurry are attracted by the electro-magnetic 5 field being generated by the plurality of elements 20 and move towards the plurality of elements 20 arranged alofig the downcomer 44. Without wishing to be bound by theory, it is understood that, over a period of time, the mass of affected material will build up and agglomerate as a larger aggregated mass, refermid to in the art as a "floc". As the mass of the floc increases, the outer layer of this mass of affected material will start to slough off the downcomer 44 under the influence of 10 gravity and slide or tumble down the downcomer 44. The floc will then fall off the lower end 48 of the downcomer 44 and settle under the influence of gravity towards the lowermost end 18 of the separator 10. In another form of the invention, the electro-magnetic force field generated along the length of the 15 downcomer 44 is varied by activating then de-activating a plurality of independently energizable electro-magnetic elements 20 in a sequence to generate an electro-magnetic force fields of shifting intensity along the length of the downcomer 44. To encourage the downward movement of magnetic material within the separator 10, the plurality of independently energizable elements 20 illustrated in Figure 1 are arranged at spaced-apart intervals along the length of the downcomer 44. 20 Whilst five such independently energizable electromagnets are illustrated in Figure 1, this number can vary. The first element 36 is arranged closest to the uppermost portion 30 of the secondary separation zone 14 and the fifth element 40 is arranged closest to the lowermost portion 18 of the primary separation zone 12. The second element 37, third element 38, and fourth element 39 are arranged in series between the first element 36 and the fifth element 40. In this form of the present 25 invention, the first element 36 is energized to generate an electro-magnetic field whilst the second, third, fourth and fifth elements (37, 38, and 39, respectively) are de-energized. In this way, affected materials are drawn towards the first element 36 at first instance. The second element 37 is then energized as the first element 36 is de-energized to encourage the affected materials to move downwardly towards the second element 37. The third element 38 is then energized as the 30 second element 37 is de-energized to encourage the affected materials to move downwardly towards the third element 38. By repeating this sequence, for the fourth and fifth elements (38 and 39, respectively), the affected materials can be drawn further down the downcomer 44. In this -13- WO 2010/037162 PCT/AU2009/001254 way, sequential switching on and off of the elements is used to control the movement of affected materials in a continual ripple to encourage the affected materials to travel downwardly towards the lowermost portion 18 of the separator 10. This promotes the preferential separation of affected material from the remainder of the feed slurry. 5 In the embodiment illustrated in Figure 2, for which like reference numerals refer to like parts, the plurality of electro-magnetic field generating elements 20 is arranged along the length of the downcomer 44 as described above in relation to Figure 1. In this embodiment, additional elements are mounted around and along the walls of the feedwell 16 to generate an electric-magnetic field 10 higher up within the secondary separation zone 14 to encourage further separation of any remaining affected solids in the increasingly clarified liquor that is flowing towards the uppermost portion 30 of the secondary separation zone 14. In this regard, the plurality of elements 20 can be arranged externally or internally within the walls of the feedwell 16. 15 In the embodiment illustrated in Figure 3 for which like reference numerals refer to like parts, the plurality of electro-magnetic field generating elements 20 is provided on the walls of the downcomer 44 and the feedwell 16 in the manner described above in relation to Figure 2. However, in this embodiment, additional electro-magnetic field generating elements 20 are provided on one or more flow baffles 50 arranged inside the separator 10 within the secondary 20 separation zone 14. Each flow baffle 50 has an upper end 52 and a lower end 54. The flow baffles 50 are provided within the secondary separation zone 14 to encourage quiescent flow within that zone to improve the degree of separation achieved using the separator. In the embodiment illustrated in Figure 3, two concentric circular flow baffles are shown, although this number can vary. It is equally permissible for the flow baffle(s) 50 to be provided in the form of a series of 25 segmented sections when viewed in plan view as described below in relation to Figure 14. In an analogous manner, the plurality of electro-magnetic field generating elements 20 may be provided in the form of continuous circular elements or in segments. Should the plurality of elements 20 require electric power or any other form of energy to energize them, this energy is directed to the elements 20 using a corresponding plurality of conduits or cables 56. 30 - 14 - WO 2010/037162 PCT/AU2009/001254 In the embodiment illustrated in Figure 4, for which like reference numerals refer to like parts, the feed slurry is released from the feedwell 16 into the primary separation zone 12 through a plurality of downcomers 44, each downcomer 44 having an upper end 46 and a lower end 48. In Figure 4, two such downcomers 44 are shown, but the separator 10 may equally be provided with any 5 number of downcomers 44 depending on the type of feed slurry and the size and capacity of the separator. To assist in directing the feed slurry through the downcomers 44, the upper end 46 of each downcomer 44 in the embodiment illustrated in Figure 4 terminates in a frustoconical portion 45 whereby the cross-sectional area of the upper end 46 of the downcomer 44 is greater than the cross-sectional area of the lower end 48 of the downcomer 44. Each of the plurality of 10 downcomers 44 is separately baffled using a corresponding plurality of downcomer baffles 58. Each downcomer baffle 58 has an upper end 60 and a lower end 62 and is concentrically arranged around one of the plurality of downcomers 44. For best results, the upper end 60 of each downcomer baffle 58 is higher than the lower end 48 of its corresponding downcomer 44. In this embodiment, the flow baffles 50 are concentrically spaced between the outer peripheral wall 42 of 15 the separator 10 and the feedwell 16. Each flow baffle 50 has an upper end 54 and a lower end 56. For best results, the lower end 54 of each flow baffle 50 in this embodiment is not higher than the upper end 60 of its corresponding downcomer baffle 58. The downcomer baffles 58 are used to direct the flow of semi-clarified liquor from the primary 20 separation zone 12 towards the secondary separation zone 14. Each of the downcomers 44 release the feed slurry from the feedwell 16 into the primary separation zone 12 at sufficient depth for the heavier solids to continue on a downward trajectory under the influence of gravity towards the lowermost portion 18 of the primary separation zone 12, causing semi-clarified liquor to be displaced upwards into the secondary separation zone 14. 25 In the embodiments illustrated in Figure 5 and Figure 7 for which like reference numerals refer to like parts, each of the plurality of downcomer baffles 58 is provided with a diverter 64 positioned adjacent to or just below the lower end 62 of each downcomer baffle 58. The diverter 64 is held in place by any suitable mechanical fastening means, for example, a plurality of wires or gussets 66. 30 The diverter 64 limits the downward flow of slurry through the downcomer baffle 58, forcing the lighter semi-clarified liquor to flow upwardly through the downcomer baffle 58 and to overflow at the upper end 60 of the downcomer baffle 58. In the embodiment illustrated in Figure 5, the -15- WO 2010/037162 PCT/AU2009/001254 diverter 64 takes the form of a disk. In the embodiment illustrated in Figure 7, the diverter 64 takes the form of a cone. In the embodiments illustrated in Figures 4, 5 and 7, the plurality of electro-magnetic field 5 generating elements 20 is arranged at spaced apart intervals along the length of the downcomer baffles 58 and along the length of the flow baffles 50 to generate an electric-magnetic field to control the flow of affected solids in the semi-clarified slurry within the secondary separation zone 14. The plurality of elements 20 can be arranged external or internal to the wall(s) of the downcomer baffles 56 and flow baffles 50. 10 In the embodiment illustrated in Figure 6 for which like reference numerals refer to like parts, the secondary separation zone 14 is arranged between the inner peripheral wall 42 of the separator 10 and the outer peripheral walls 55 of a plurality of concentric flow baffles 50. The primary separation zone 12 is defined by the frustoconical base 26 of the separator 10 below the lower end 15 54 of the flow baffle(s) 50 as well as the area within the innermost flow baffle 70 into which the feedwell 16 discharges the feed slurry. In this embodiment, the feed slurry discharged from the feedwell 16 travels downwardly through the innermost flow baffle 70 in an analogous manner to feed slurry flowing into a downcomer 44 in earlier embodiments. In this embodiment, the plurality of electro-magnetic field generating elements 20 is arranged at spaced apart intervals along the 20 length of the flow baffles 50 to generate an electric-magnetic field to control the flow of affected solids in the semi-clarified slurry within the secondary separation zone 14. The plurality of elements 20 can be arranged external or internal to the wall(s) of the flow baffles 50. The embodiment illustrated in Figure 8, for which the reference numerals refer to like parts, is an 25 alternative embodiment to that illustrated in Figure 4. In this embodiment, the feed slurry is released under the influence of gravity from the feedwell 16 into the primary separation zone 12 through the plurality of downcomers 44 as described above in relation to Figure 4. The frustoconical portion 45 is omitted as being entirely optional. Each of the plurality of downcomers 44 is separately baffled using a corresponding plurality of downcomer baffles 58 as described 30 above in relation to Figure 4. In this embodiment, the plurality of electro-magnetic field generating elements 20 is arranged at spaced apart intervals along the length of the downcomer baffles 58 and along the length of the flow baffles 50 as described above in relation to Figure 4 and -16- WO 2010/037162 PCT/AU2009/001254 the downcomer baffles 58 and the lower end 54 of each flow baffle 50 in this embodiment is not higher than the upper end 60 of its corresponding downcomer baffle 58. In the embodiment illustrated in Figure 8, dilution liquor is injected through one or more dilution 5 liquor inlets 80 to encourage upward flow of semi-clarified liquor within the separator 10. It will be appreciated by a person skilled in the art that any number of dilution liquor inlets 80 may be used instead of the three illustrated in Figure 8 to realise the desired higher upflow vectors which will carry the unaffected or lower density solids upward through the secondary separation zone 14. 10 In the embodiments illustrated in Figure 9 and 27, for which like reference numerals refer to like parts, the feed line 22 terminates in a tapered nozzle 82 arranged within a mixer chamber 84 which in turn is positioned inside the feedwell 16. The nozzle 82 is used to generate a venturi effect as the feed slurry is caused to flow through the feed line 22 into the feedwell 16. It will be appreciated by a person skilled in the art that alternative arrangements may be used instead of or in 15 combination with the tapered nozzle 82 to generate a venturi effect. Examples of suitable venturi arrangements are described in Australian Patent No. 728638, the contents of which are incorporated herein by reference. The mixer chamber 84 is in fluid communication with a suction port 86 via a suction port conduit 88. In use, the suction port 86 receives semi-clarified liquor that rises upwardly from the primary separation zone 12 as the solids settle. The venturi effect causes a 20 portion of the semi-clarified liquor received within the suction port 86 to be drawn up through the suction port conduit 88 into the mixer chamber 84. This portion of the semi-clarified liquor effectively auto-dilutes the feed slurry prior to the introduction of the feed slurry to the primary separation zone 12. 25 If desired, coagulant and/or flocculating polymers may be mixed into the feedwell 16 or mixer chamber 84 to produce a partially conditioned feed prior to the introduction of the feed slurry into the primary separation zone 12. In this regard, the mixer chamber 84 represents an ideal location for introducing the coagulant and/or flocculating polymers due to the rapid mixing that occurs here. It is particularly advantageous to be able to add these chemicals to a feed slurry that has been 30 partially diluted. The feedwell 16 represents a primary conditioning zone within which the solids in the feed slurry start to separate from one another as the slurry flow vector slows down. Some of the solids collide with each other under more gentle flow conditions than those experienced by the -17- WO 2010/037162 PCT/AU2009/001254 feed slurry so they may start to form flocs as the slurry flows through the feed line 22. As the flocs collide with each other and with other solids present in the feed slurry, the floc size increases in a process referred to as 'orthokinetic flocculation'. A secondary addition of coagulant or flocculant may be made into the pre-conditioning zone of the feedwell 16 if desired. 5 To facilitate entry of the semi-clarified liquor into the suction port 86, the suction port 86 is provided with one or more apertures 90 or launders (not shown) arranged to discourage the passage of solids into the suction port 86. In the embodiment illustrated in Figure 9, the feedwell 16 has a base 92 and the suction port 86 is fixed to an upper surface 94 of the base 92 of the 10 feedwell 16. The suction port 86 illustrated in Figure 9 is an embodiment which is able to be easily retrofitted to an existing feedwell 16. As illustrated in Figure 9, the suction port 86 may be one of a plurality of suction ports in fluid communication with the mixer chamber 84 via a corresponding plurality of suction port conduits 88. The suction ports 86 may be arranged in rings so that the suction of semi-clarified liquor is even over the entire cross sectional area of the base 92 of the 15 feedwell 16. In embodiment illustrated in Figure 9, the plurality of electro-magnetic field generating elements 20 is arranged at spaced apart intervals along the length of the downcomer baffles 58 and along the length of the flow baffles 50 as described above in relation to Figure 4 and the downcomer 44. 20 Additional elements 20 are provided on the fluted frustoconical lower end 48 of the downcomer 44. The fluted lower end 48 functions in the same way as a de-watering cone. In the embodiment illustrated in Figure 10, for which like reference numerals refer to like parts, the plurality of electro-magnetic field generating elements 20 are no longer arranged in spaced-apart 25 intervals. Instead, the elements 20 are arranged so as to form a continuous flux core within each of the flow baffle(s) 50 and each of the plurality of downcomer baffles 58. By switching the elements in sequence from top to bottom, a flux field is generated that attracts the affected materials drawing them down towards the lowermost portion 18 of the separator 10 in an analogous manner to that described above in relation to earlier embodiments. In the first instance 30 as the affected material drops downwardly from the lower end 54 of the flow baffles 50, it is attracted to plurality of elements 20 arranged on or within the downcomer baffles 58 and so is drawn further downwardly through the separator 10 to be discharged from the lower end 62 of the -18- WO 2010/037162 PCT/AU2009/001254 downcomer baffles 58. For best results, the lower end 54 of the flow baffles 50 are arranged to be below the upper end 60 of the downcomer baffles 58 to ensure that the affected material is readily attracted towards the plurality of elements 20 arranged on or within the downcomer baffles. 5 In the embodiment illustrated in Figure 11, for which like reference numerals refer to like parts, the separator 10 is further provided with an overflow baffle 96 arranged to form a flow barrier between the primary separation zone 12 and the secondary separation zone 14. The overflow baffle 96 has a first end 98 and a second end 100. The first end 98 of the overflow baffle 96 intersects the inner peripheral wall 42 of the separator 10. The overflow baffle 96 then extends inwardly towards the 10 centre of the separator 10 such that its second end 100 is arranged at a height at least equal to and preferably higher than the lower end 62 of the downcomer baffle 58. In the embodiment illustrated in Figure 11, the overflow baffle 96 slopes inwardly and upwardly such that its second end 100 terminates immediately adjacent to the outer peripheral wall 42 of the outermost downcomer baffle 58. In use, the solids within the partially clarified slurry which overflows from the upper end 60 of 15 the downcomer baffle 58 settle. under gravity and migrate down towards the lowermost area 102 within the secondary separation zone 14 adjacent to the first end 98 of the overflow baffle 96. The settled solids which collect within the area 102 are removed from the separator 10 using discharge outlet 104. In order to facilitate the movement of these settled solids towards the discharge outlet 104, the separator 10 is provided with one or more lances 106 which are orientated in any direction 20 best suited to the flushing of the settled solids towards discharge outlet 104. Dilution liquor is caused to flow through the one or more lances 106 to drive the settled solids within area 102 towards the discharge outlet 104. To minimise the potential for non-affected solids to weir over the upper end 60 of the downcomer baffles 58 then sink past the second end 100 of the overflow baffle 96, additional dilution liquor is injected through one or more dilution liquor lances 109 to 25 encourage upward flow of semi-clarified liquor within the separator 10 as described above in relation to Figure 8. In the embodiments illustrated in Figures 11 and 12, the plurality of electro-magnetic field generating elements 20 is arranged at spaced apart intervals along the length of the downcomer 30 baffles 58 and along the length of the flow baffles 50 to generate an electric-magnetic field to control the flow of affected solids in the semi-clarified slurry within the secondary separation zone 14. The plurality of elements 20 can be arranged external or internal to the wall(s) of the -19- WO 2010/037162 PCT/AU2009/001254 downcomer baffles 56 and flow baffles 50. In the embodiment illustrated in Figure 12, the flow baffle(s) 50 are provided as segments which are arranged in circular alignment with respect to each other, as best seen in plan view. Figure 12 also illustrates that the flow baffle(s) 50 may be hollow enabling the plurality of electro-magnetic force generating elements to be mounted inside the flow 5 baffles 50 so as to isolate the elements 20 from direct contact with potentially corrosive or abrasive process liquors. In the embodiment illustrated in Figure 13 for which like reference numerals refer to like parts, the lower end 48 of the downcomer 44 includes a base 107. The base 107 has an undulating profile in 10 cross-section such that portions of the base are raised relative to other portions of the base 107. In Figure 13, the undulating profile of the base 107 is a sawtooth shaped profile, but it could equally be arched in appearance in cross-section. In use, the feed slurry enters the separator 10 through the feedwell 16 and down through the downcomer 44. A plurality of flow apertures 108 is provided at the uppermost portions of the base 107 to allow material to flow out of the downcomer 44 and into 15 the upper section of primary separation zone 12 preferentially diffusing through the flow apertures 108 into the secondary separation zone 14. The plurality of flow apertures 108 is arranged at the highest portions of the undulating profile of the base. To further encourage the downward movement of magnetic material within the separator 10, the plurality of elements 20 illustrated in Figure 13 comprises five independently energizable electromagnets in a spaced-apart arrangement 20 along the length of the downcomer 44, which can be operated in an analogous manner as described above in relation to Figure 1. Whilst five such independently energizable electromagnets are illustrated in Figure 1, this number can vary. In this embodiment, the presence of the base 107 is used to encourage unaffected material to be dragged up over the overflow weir 32 and be discharged into the launder 34 prior to flowing off the separator at the outlet 28. The unaffected 25 material is therefore dragged upwardly through the separator 10 with the main flow vectors, whilst the affected material is initially attracted to the plurality of elements 20 arranged in the base 107. By switching the plurality of elements 20 on then off, the affected material is encouraged to sink to the bottom of the "saw tooth"- shaped base 107. When the plurality of elements 20 in the base 107 are de-energized, the affected material accumulated in the base 107 is released and sinks through 30 the primary separation zone 12 towards the lowermost portion 18 for removal from the separator 10. -20- WO 2010/037162 PCT/AU2009/001254 In the embodiment illustrated in Figure 14 for which like reference numerals refer to like parts, the flow baffle(s) 50 is arranged such that the outermost flow baffle 72 is concentric with the innermost flow baffle 70, the innermost flow baffle being arranged closer to the feedwell 16 and the outermost flow baffle 72 being arranged closer to the peripheral wall 42. Both the outermost 5 flow baffle 72 and the innermost flow baffle 70 are provided in segmented form. The outermost flow baffle 72 and the innermost flow baffle 70 are arranged such that the gaps 110 between the segments in the innermost flow baffle 70 are offset from the gaps 112 between the segments in the outermost flow baffle 72. This arrangement is used to enable the affected material to be dragged firstly down the outermost flow baffle 72 and then be encouraged to move preferentially across 10 onto the innermost flow baffle 70 prior to being discharged into the primary separation zone 12. Whilst two flow baffles are illustrated in Figure 14, any number of flow baffles may equally be used. In the embodiments illustrated in Figure 14, the plurality of electro-magnetic field generating 15 elements 20 is arranged at spaced apart intervals along the length of the downcomer baffles 58, along the length of the flow baffles 50, along the length of the downcomer 44 and around the feedwell 16 to generate an electric-magnetic field to control the flow of affected solids in the semi clarified slurry within the secondary separation zone 14. 20 In the embodiment illustrated in Figure 15, the plurality of electro-magnetic field generating elements 20 is arranged at spaced apart intervals along the length of the downcomer baffles 58 and along the length of the flow baffles 50 to generate an electric-magnetic field to control the flow of affected solids in the semi-clarified slurry within the secondary separation zone 14. In addition, the plurality of electro-magnetic field generating elements 20 is provided at or within the 25 frustoconical base 26 of the separator 10. This arrangement is used to further control the flow of affect materials downward towards the lowermost portion 18 of the primary separation zone 12 for removal through the underflow outlet 24. In the embodiment illustrated in Figure 16, for which like reference numerals refer to like parts, the 30 separator 10 is provided with a splitter 114 which is used to physically separate the primary separation zone 12 from the secondary separation zone 14. In this embodiment, the splitter 114 takes the form of a plate from which the downcomer baffles 58 are hung. In the embodiments -21- WO 2010/037162 PCT/AU2009/001254 illustrated in Figure 16 and 17, the plurality of electro-magnetic field generating elements 20 is arranged at spaced apart intervals along the length of the downcomer baffles 58 with neither embodiment using flow baffles 50. 5 In use, solids may accumulate on the splitter 114. To facilitate removal of these solids, the splitter 114 is provided with one or more hydraulic mixers 116 which are fed with dilution liquor piped through dilution liquor feed pipes 118. The hydraulic mixers 116 direct the flow of dilution liquor across the splitter 114 so as to encourage the movement of settled solids towards a sump separation zone 120. The sump separation zone 120 is sufficiently quiescent so as to allow solids to settle 10 under the influence of gravity towards the base 122 of the sump separation zone 120. The solids which have settled at the base 122 of the sump separation zone 120 are able to be discharged from the separator 10 through outlet 124. In this way, the non-affected materials are allowed to move up through the downcomer baffles 58 and rise above the splitter 114 before being swept towards the sump separation zone 120 by the hydraulic mixer(s) 116. The affected materials are drawn 15 downwardly past the diverter 64 arranged at the lower end 62 of the downcomer baffle 58. Thereafter, the affected materials are released to allow these solids to settle under gravity towards the lowermost portion 18 of the primary separation zone 12 before being discharged through underflow outlet 24. The splitter 114 can be arranged parallel to a horizontal plane as illustrated in Figure 16 or be sloping as illustrated in Figure 17. Arranging the splitter 114 at an angle to the 20 horizontal plane facilitates the movement of the settled solids towards the sump separation zone 120, reducing the workload on the hydraulic mixer(s) 116. The embodiment illustrated in Figure 18 for which like reference numerals refer to like parts, the arrangement is a variation of Figure 3 in which the flow baffle(s) 50 take the form of a plurality of 25 rods or tubes instead of being provided as continuous sheets. In the embodiment illustrated in Figure 18, the plurality of electro-magnetic field generating elements 20 is arranged at spaced apart intervals along the length of the rods or tubes to form circular arrays of elements as best seen in plan view. Any number of circular arrays may be set up in this way and the relative positions of each rod or tube may be either offset or aligned as best fits the process. The rods or tubes may 30 equally be arranged in a random pattern as illustrated in Figure 19 so as to present a more diffused electro-magnetic field if desired. - 22 - WO 2010/037162 PCT/AU2009/001254 In the embodiments illustrated in Figures 20, 23, 24, 25, 26 and 27, for which like reference numerals refer to like parts, the feed line 22 terminates in a tapered nozzle 82. The advantage of the tapered nozzle is that water and any air/gas bubbles present are stripped from particles present in the feed slurry. 5 In the embodiments illustrated in Figures 20, 21, 22, 23, 24, 25, and 26, for which like reference numerals refer to like parts, the separator 10 is provided with a rake 127 for directing the settled solids towards the lowermost portion 18 of the primary separation zone 12. The rake 127 is provided with one or more rake arms 130 upon which are mounted one or more wipers or scrapers 10 131 which are used to sweep the settled solids. The flow baffles 50 can be continuous as illustrated in plan view in Figure 23, 24, 25 and 26 or in segments as illustrated in Figure 20, 21 and 22. The flow baffles 50 can equally have a variety of different shapes, examples of which are illustrated in Figures 20, 22 and 23. In the embodiment 15 illustrated in Figure 22, the feed line 22 introduces the feed slurry into the top of the feedwell 16 from whence the slurry descends downwardly until it meets flow splitter 128, arranged at the base of the feedwell 16. The flow splitter 128 is used to discharge the feed slurry from the feedwell 16 with a horizontal thrust vector. In this embodiment, the flow baffles 50 have an arched shape in cross-section whereby the upper end 52 of the flow baffles 50 are wider than the lower end 54 of 20 the flow baffles 50. This shape is used so as not to impede the horizontal component of flow of the slurry as it is discharged from the feedwell 16 via the flow splitter 128. By enabling the slurry to move through or around the flow baffles it is feasible to obtain a more even distribution of materials within the liquor prior to the semi-clarified liquor moving upwards through the secondary separation zone 14. 25 In the embodiments illustrated in Figure 20, Figure 22 and Figure 23, the plurality of electro magnetic field generating elements 20 is arranged at spaced apart intervals along the length of the flow baffles 50 and along the length of the feedwell 16. The separator 10 may be provided with a plurality of electro-magnetic field generating elements on or adjacent to the rake 127. In the 30 embodiments illustrated in Figure 24 and Figure 25, the plurality of electro-magnetic field generating elements 20 is additionally provided at or within the frustoconical base 26 of the separator 10 below the rake 127. This arrangement is used to further control the flow of affect -23 - WO 2010/037162 PCT/AU2009/001254 materials downward towards the lowermost portion 18 of the primary separation zone 12 for removal through the underflow outlet 24. In Figure 24, the elements 20 arranged at the base 26 produce continuous flux, whereas in Figure 25, the elements 20 are provided in a spaced-apart relationship across the base 26. In Figure 25, the elements 20 are also provided in the underflow 5 outlet 24 for additional control. In the embodiments illustrated in Figure 20 and 26, the feedwell 16 is made relatively shallow in that the base 92 of the feedwell 16 is higher than the lower end 54 of the flow baffles 50. The embodiment illustrated in Figure 26 further shows the injection of dilution liquor as described 10 above in relation to Figure 8. The embodiment illustrated in Figure 21 is similar to that illustrated in Figure 20, except that the flow baffles 50 are in segments and the plurality of elements 20 are permanently energized. In this embodiment, one or more wipers 140 are provided to wipe the affected material from the plurality 15 of elements 20 towards a tail portion 142 of the flow baffle 50 which is free of electro-magnetic field generating elements 20. The affected material collected by the wipers 140 is able to form flocs as described above, with the flocs then sinking under the influence of gravity towards the lowermost portion 18 of the separator 10, which is essentially countercurrent to the main flow of liquor. The wipers 140 can be angled to encourage downward movement of affected material. 20 Advantageously, the wipers 140 are mounted on the arms 130 of the rake 127 such that each co rotates with the other in use. In the embodiment illustrated in Figure 27 for which like reference numerals refer to like parts, each downcomer 44 is provided with a corresponding downcomer baffle 58, the difference being 25 that the downcomer baffles 58 are provided using a honeycomb-like array 130 (seen in cross section in Figure 27) comprising a plurality of elongate box sections 132 such that each downcomer 44 is positioned within one of said elongate box sections 132. The array 130 further comprises a transverse member 134 arranged at a height below the lower end 48 of the downcomers 44. The transverse member 134 is provided with a plurality of target apertures 136 30 through which the solids may pass as they settle under gravity towards the lowermost portion 18 of the primary separation zone 12. In Figure 27, the honeycomb-like array 130 is arranged such that each downcomer baffle 58 is provided with a target 137 which in one example takes the form of a -24 - WO 2010/037162 PCT/AU2009/001254 disc or plate suspended by a series of gussets or wires 139 at a height that is below the lower end 48 of the downcomers 44. The advantage of this arrangement is that the downflow of feed slurry is deflected laterally making 5 it less likely that the compacting settled solids in the lowermost portion 18 of the primary separation zone 12 will be disturbed. In addition the strong upflow liquor flow vectors drag much of the unaffected material upwards to weir over the upper end 60 of the downcomer baffles 58 into the primary separation zone 12. Conversely, the affected material is attracted to the plurality of elements 20 when they are energized. The affected material is then drawn down below the intense 10 agitated sections of the array 130 to drop subsequently drop off the lower end 62 of the downcomer baffles 58 towards the lowermost portion 18 of the primary separation zone 12, thus separating much of the magnetically affected material from the unaffected material. The downcomer baffles 58 also serve to contain the flow of the feed slurry within the box sections 132 such that the majority of the displaced semi-clarified flow upwardly through the box sections 132 as the solids 15 settle under gravity towards the lowermost portion 18 of the primary separation zone 12. In this embodiment, the elements are arranged along the length of the downcomer baffles 58 and operate in an analogous manner to that described above in relation to earlier embodiments. In other embodiments of the invention illustrated in Figure 28, 29 and 30, the plurality of electro 20 magnetic field generating elements 20 is arranged at spaced apart intervals along the length of the flow baffles 50 and additionally provided at or within the frustoconical base 26 of the separator 10 below the rake 127. These arrangements are used to further control the flow of affect materials downward towards the lowermost portion 18 of the primary separation zone 12 for removal through the underflow outlet 24. The flow baffles 50 can have a variety of different shapes, 25 examples of which are illustrated in Figures 28 and 30. In the embodiments illustrated in Figures 28, 29 and 30, any given electromagnetic element 21 within the plurality of electromagnetic field generating elements 20 is arranged in such a way as to have an alternating polarity relative to the polarity of a neighbouring element 23. In Figures 28, 29 30 and 30, the plurality of electromagnetic field generating elements 20 are shown as if each element is frozen in time as a permanent magnets, using the well established convention whereby its first end is designated as being the north pole (labelled as "N") with its second end being designated as -25 - WO 2010/037162 PCT/AU2009/001254 the south pole (labelled as "S"). The plurality of electromagnetic elements 20 may be arranged such that adjacent magnets having alternating polarity lie perpendicular to the overall downward direction of flow of affected materials as illustrated in Figure 28) or parallel to the overall downward direction of flow of affected materials (as illustrated in Figure 29). It is understood that 5 the arrangement illustrated in Figure 29 encourages the generation of stronger magnetic fields bridging between any given electromagnetic element 21 and its neighbouring element 23. In use, the affected materials are attracted towards the electromagnetic elements 20 whilst the unaffected materials and liquor are pushed inwardly away from the elements 20 due to 10 displacement forces generated as the affected materials essentially push the unaffected material and excess liquor out of the way. In this way, the affected materials move downwardly under the combined influence of gravity, the alternating magnetic field, and displacement due to the upward movement of the semi-clarified liquor. 15 The electro-magnetic force field generated along the length of the feedwell 16 and/or the baffles 50 may be varied by activating then de-activating a plurality of independently energizable electro magnetic elements 20 in a sequence to generate an electro-magnetic force fields of shifting intensity along the length of the feedwell 16 to essentially "sweep" the affected solids towards the base 26 of the separator 10, in an analogous manner as that described above in relation to the 20 plurality of independently energizable electromagnetic elements arranged along the length of the downcomer in the embodiment illustrated in Figure 1. Using this approach, it is possible to run the separator 10 at higher flow rates as well as realising a higher efficiency of magnetic particle separation. 25 Now that the preferred embodiments of the present invention have been described in detail, the present invention has a number of advantages over the prior art. The plurality of electro-magnetic field generating elements 20 can thus be used for two purposes. The separator 10 can be operated so as to remove all solids from the feed slurry and produce a clarified liquor which has improved clarity compared to a conventional gravity separator (due to the elements being used to remove 30 affected solids from the semi-clarified liquor in the secondary separation zone 14). Alternatively, the separator 10 can be operated so as to selectively remove the affected solids from the feed slurry, allow a semi-clarified liquor containing unaffected solids to overflow the weir 32 and be -26
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WO 2010/037162 PCT/AU2009/001254 removed from the overflow launder 34 via the overflow outlet 28. Conversely the separator 10 may be designed such that the affected materials are discharged from the separator via the overflow outlet and the unaffected materials are discharged the underflow outlet. 5 It will be apparent to persons skilled in the relevant art that numerous variations and modifications can be made without departing from the basic inventive concepts. For example, the plurality of elements can be set up as grids of varying inter-element spacing. All such modifications and variations are considered to be within the scope of the present invention, the nature of which is to be determined from the foregoing description and the appended claims. 10 -27 -