MXPA96006033A - Method and apparatus to treat ashes volan - Google Patents

Abstract

The present invention relates to an electrostatic separator for the separation of a mixture of particles having as components thereof substantially electrically conductive particles and substantially electrically non-conductive particles, said apparatus comprising: a plurality of separation zones spaced vertically one from the other to define upper and lower separation zones, each separation zone comprising a pair of spaced parallel flat electrodes defining a sloping downward path having a lower conveying surface and a separate upper collecting surface thereof, said separate separation zones in a vertical manner in an alternate inclination with a lower end of a transport surface of a separation zone which is placed above an upper end of a transport surface of a successive subsequent separation zone, to define a tray serpentine ectoria through which a component of said mixture can pass under the influence of gravity, an energy source coupled with said electrodes to provide a high voltage potential difference between each pair of electrodes mentioned to generate an electric field between them, the respective electrodes comprising the transpore surface of each path that is placed electro-etically to earth, a feeder which feeds the mixture of particles as a thin layer on the transport surface of a more superior separation zone; collector associated with the collecting surface of each separation zone to collect substantially electrically conductive attracted to said collecting surface from the corresponding transport surface under the influence of said electric field; a second collector associated with a separation zone for collecting substantially electric particles; substantially non-conductive from which the conductive particles have been removed, and the separation zones, energy source and collectors positioned and provided in such a way that substantially non-conductive particles pass through said transport surfaces and are discharged from a respective lower end of them and are collected by said second collection

Description

METHOD AND APPARATUS FOR TREATING FLYING ASHES FIELD OF THE INVENTION This invention relates to an apparatus and method for the electrostatic separation of mixtures of particulate materials having different electrical properties, and in particular, to the separation of mixtures of substantially electrically conductive and substantially non-conductive materials.

BACKGROUND OF THE INVENTION The apparatus and method of the invention relate particularly, but not exclusively, to the separation of carbonaceous materials from fly ash obtained from the combustion or incineration processes typically employed in coal-fired power generators, wall-mounted kilns, and furnaces for roasting / calcining minerals, as well as municipal waste incinerators. Fly ash is obtained in large quantities from electric power generators that burn coal, and in general these recovered fly ash is used as a replacement or complement for cement powder in concrete manufacturing. Depending on the quality of the coal used as fuel, and the efficiency of the combustion process, the recovered fly ash may contain different amounts of partially burned carbon particles up to about 10 to 12 weight percent. Internationally accepted standards for pozzolans, in particular fly ash, in the manufacture of concrete, generally limit the amount of unburned coal in fly ash to less than 4 percent, and consequently, fly ash from many potential sources does not They can be used in the manufacture of concrete. As environmental concerns and regulations regarding NOx and Sxo emissions from coal-fired furnaces increase, baking practices or operating conditions have been changed to reduce these emissions, with the result that the carbon content of the fly ash has been increased, thus precluding the previously acceptable sources. There are many economic benefits that can be obtained from the continuous use of fly ash in the production of cement dust, and in accordance with the above, there is a need to remove excessive amounts of coal from the fly ash with an economically viable process. The electrostatic separation of particulate materials that have different electrical properties is well known, and generally falls into four categories: Electrophoresis, Conductive Induction, Contact Load, and Dielectrophoresis. In the electrophoretic separation, the mixtures of conductive and non-conductive particles are ionized in a corona discharge field, in such a way that all the particles acquire a similar surface charge. The initially charged particles are attracted to the surface of a rotating metal roll to ground, or of a stationary sloped metal plate, also to ground, having a convexly curved surface. The roller or ground plate allows the charge on the conductive particles to dissipate rapidly, and as the particles rotate with the metal roller or slide on the convex surface of the stationary plate, a combination of gravity forces is applied and centrifuges to the particles. The conductive particles, which are substantially discharged, leave the surface of the roller or the plate first under the influence of the applied forces while the charged non-conducting particles hang towards the surface for a longer period until the gravity forces exceed to the forces of attraction between the charged particles and the surface to earth on which they move. A separator directs the conductive and non-conductive particles that travel through different trajectories, to respective collection regions. Conductive induction involves the transport of a mixture of conductive and non-conductive particles on an earthed metal roll or a curved slanted metal plate through an electrostatic field generated by a separate electrode having a charge opposite to that of the roll or the plate. Conductive particles on the transport surface, they acquire a load of equal sign to that of the transport surface, both by the conduction from the transport surface, and by the induction by the separated electrode of opposite load. When the conductive particles become charged, they are attracted to the electrode, and in a manner similar to that described above, the charged and discharged particles follow different paths as they leave the surface of the transport element, to facilitate the separation of a conventional way. Contact loading is one of the oldest forms of particle separation, and relies on the natural or triboelectric charge induced by direct contact with a charged surface or by friction. The charged particles are allowed to fall freely in an electrostatic field between electrodes of an opposite potential that attract the respectively opposite charge particles to form separate paths divided by a separator. Dielectrophoresis is similar to electrophoresis, except that the separation of the particles depends on the polarizability of a material in a non-uniform electric field. There are many factors that affect the choice of the electrostatic separator for mixtures of particulate materials, and these depend a lot on the different electrical and physical properties between the materials that are to be separated. For example, electrophoresis is commonly used to separate beach sands and alluvial tin minerals, iron silica and chromite minerals, and the separation of metallic and non-metallic constituents. Conductive induction separation is often used in the final cleaning of rutile and zirconium, and in the removal of foreign contaminants from food materials. Dielectrophoresis is used to separate tea fibers, plastic paper, and fibrous non-fibrous materials. Contact loading is rarely used in commercial applications as a single process, but is used in other hybrid or combination electrostatic processes. One of these hybrid processes, described in U.S. Patent No. 3,625,360 employs a corona discharge to charge a mixture of particles before allowing the particles to fall freely through an electrostatic field between separate electrodes. The particles fall freely through a corona discharge ionization chamber, and impact a series of ground screens before being dropped again freely through an electrostatic field with a separator below it. The German Patent specification Number DE 3152018-C, also discloses a free-falling electrostatic separation process, in which the particles are charged by "spraying" electrodes, before traversing through an electrostatic field in an air stream. British Patent Number 1349995 discloses a particle separator that imparts a curved path to the particles, by exposing them to magnetic and electric fields orthogonally configured to one another. The Russian Patent Specifications Numbers SU-822899 and SU-288907 describe electrostatic separators wherein the lower electrode is formed as a perforated mesh. SU-822899 discloses a plurality of perforated meshes below the lower electrode mesh, to classify the particles passing through the meshes. The Russian document SU-288907 describes a lower perforated electrode as a vibrating screen, and an air jet is used to remove the fine particles adhering to the electrodes. Another hybrid electrostatic separator is described in Russian Patent Specification Number SU1375346, where the particles are triboelectrically charged onto a vibrating feeder, and then passed to the electric fields created by diverging electrodes. The combined actions of the electrodes and a sawtooth flange through the feeding path, help to separate the particles. U.S. Patent No. 3,720,312 describes the electrostatic separation of particulate minerals by an apparatus having a pair of separate plates of a dielectric material, between which the particulate material is fed. The material in r "particles is propelled longitudinally by a vibratory feeder attached to the lower plate. Divergent parallel sets of electrodes are placed on the external surfaces of the dielectric plates, and energized with an alternating current voltage. The portion of the particulate material is repelled by the electric fields, and moves laterally in relation to another particulate material that runs longitudinally of the plates. The prior art references represent a very small exemplification of a large plethora of electrostatic separators of the prior art. The existence of this large number of prior art references illustrate not only a continuing need to improve the efficiency of these spacers, but also that, in most cases, electrostatic separators are designed in general for the separation of a specific mixture of similar components or mixtures; which have a particle size on the scale of 75 microns to 1 millimeter in the case of inorganic sands and minerals, or up to 3 millimeters in the case of organic particles. Apart from a small number of prior art documents described below, dealing with the separation of carbon particles from fly ash, nothing of the prior art refers to the separation or classification of matter into very fine particles having a ,, .- particle size in the scale of 10 to 200 microns, and a volume density of less than 1.0. Actually, there are no electrostatic separators commercially available that can separate carbon particles from fly ash on an economical basis. In the electrostatic separation of carbonaceous materials from fly ash, the prior art suggests a relatively limited range of separators designed specifically for this purpose.

The Russian Patent Specification Number SU994013 suggests the pretreatment of the fly ash of the power station at 1, 200 ° C-1, 500 ° C, to form a mixture of small glass granules (70 to 80 percent) and Coke coal grains (20 to 30 percent). This material previously treated, is then subjected to the electric field of a conventional drum-type corona discharge separator. Australian Patent Applications Numbers AU 21349/83 and AU 21350/83, describe an apparatus wherein an electrode is mounted on a conventional vibratory feeder, and second electrodes are mounted above the first electrode, each at an acute angle (typically of 12 ° C) in a lateral direction upwards and outwards. The electrodes are energized by a high-voltage alternating current source, and result in curved field lines on each side of the electrode assemblies. The apparatus operates in a manner similar to that of U.S. Patent Number 3,720,312 described above, but in addition, it uses air jets from a perforated bottom electrode, and an external jet, to fluidize the particulate material, aiding in this way both to the separation and to the passage through the apparatus. Australian Patent Specification AU Number 21350/83 describes a variation of the apparatus of Australian Patent Specification No. 21349/83, in which the upper electrode assembly comprises regions of different potential. Both Australian Applications Nos. 21349/843 and 21350/83 suggest that the initial charge of the carbon particles may be the result of ionization, triboelectrification, conductive induction, or a combination thereof. US Patents Nos. 4839032 and 4874507 disclose closely spaced electrode plates (10 millimeters or less) with a perforated thin sheet of dielectric material located in the center of the space between the electrodes. A perforated continuous band (Kevlar coated with PTFE (Registered Trade Mark)) is located on each side of the dielectric plate, and in operation, the adjacent portions of the band are separated when the plate moves in opposite directions. The particulate material is fed through an opening in an electrode, and the friction between the particles results in the triboelectrification of the particles. The applied electric field causes the charged particles to migrate to an opposing charge electrode, upon which they are collected by the perforated band, and move respectively towards the opposite ends of the collection apparatus. Although many of the electrostatic separators of the prior art are generally effective for their intended purpose, all suffer from one or more disadvantages in terms of production speed, degree of separation, energy consumption, maintenance costs, and high capital cost. Where the separation of high value and similar minerals is concerned, the speed of production, the energy consumption, and the capital cost of the separation apparatus are not major considerations. In the case of low value materials, such as fly ash, however, these matters can contribute significantly to the financial viability of the separation process.

SUMMARY OF THE INVEN It is an object of the present inven to provide an electrostatic separator that overcomes or alleviates at least some of the drawbacks of the prior art separators, and to provide a method and apparatus particularly suitable for the separation of carbonaceous materials from fly ash. . According to one aspect of the inven, there is provided an electrostatic separator for the separation of a mixture of substally electrically conductive particles and substally electrically non-conductive particles, the apparatus comprising: a plurality of separation zones, each separation zone comprising a pair of spaced apart parallel flat electrodes defining a downward inclined path, having a lower conveying surface and an upper collecting surface separated therefrom, the separation zones being vertically spaced at an alternate slope with a lower end of a transport surface of a separation zone which is placed above an upper end of a transport surface of a subsequent successive separation zone, to define a serpee path through which at least one component of this mixture may pass under the influence of gravity; an energy source coupled with the electrodes to provide, in use, a high voltage potel difference between each of the pair of electrodes, to generate an electric field therebetween, the respective electrodes comprising the transport surface of each path that is electrically grounded; a feed element adapted to feed a particulate material as a thin layer onto the surface of a higher conveying surface; a first collecting element associated with the collecting surface of each separation zone, to collect the particulate material attracted to the collecting surface under the influence of the electric field; and a second harvesting element associated with a lower conveyor surface, for collecting a component of a particulate mixture from which another component has been separated. The flat electrodes are suitably comprised of metal plates. Suitably, the electrode of the collecting surface is comprised of aluminum or an aluminum alloy. Preferably, the electrode of the transport surface comprises an abrasion resistant material. The electrode of the transport surface may comprise stainless steel or a wear-resistant metal alloy. If required, the electrode of the transport surface may comprise a wear resistant surface, such as an electrically conductive ceramic material, or a cermet. Suitably, the peripheral edges of the electrodes are configured to minimize arcing. If required, the electrodes can be adjusted to selectively vary the angle of inclination. The electrodes can have an angle of inclination on the scale of 45 ° to 85 ° in relation to the horizontal. If required, some or all of the transport electrodes may include a heat source. Also, if required, some or all of the transport electrodes may comprise a vibration element to assist in the transport of the particulate material thereon in a thin layer. The power source can comprise any element suitable for supplying an electric potel in the range of 15 to 50 KV. The feeding element may comprise a vibrating feeder. Preferably, the feeding element comprises an introduction element in association with the vibratory feeder, for selectively feeding the particulate material to the vibratory feeder at a predetermined speed. Suitably, the introduction element comprises a rotary valve located at the base of a feed hopper.

If required, the feed hopper may include a heat source to keep the particulate material therein at a predetermined temperature. The feed hopper may include an element to prevent bridging of the particulate material in the hopper. The first and second collection elements suitably comprise storage hoppers adapted for the selective removal of the respective components of the particle mixtures. According to a second aspect of the invention, there is provided a method for separating particles of coal from particulate fly ash, this method comprising the steps of: feeding, under the influence of gravity, a thin layer of fly ash on the surface of a series of alternately inclined flat transport electrodes defining a vertical serpentine path, wherein a collecting electrode is spaced apart from, and parallel to, each of the transport electrodes; applying a high voltage electrical potential between the transport and collecting electrodes, to create a substantially uniform electric field between the electrodes, the transport electrodes being electrically grounded, whereby, in use, the carbon particles contained in the particulate fly ash, acquire, through conductive induction, a load of opposite sign to that of the collecting electrodes, and are attracted to the collecting electrodes, moving away from the trajectory of the particles substantially not loaded with fly ash on the electrodes of transport, the carbon particles being collected in a first collecting element associated with each of the collecting electrodes, and the fly ash particles being collected in a second collecting element associated with a lower transport electrode in the serpentine path. Suitably, the fly ash is introduced into the serpentine path at a temperature in the range of 50 ° C to 130 ° C. Preferably, the fly ash is introduced at a temperature in the range of 95 ° C to 110 ° C. The potential difference between the electrodes can be in the range of 15 to 50 KV. Suitably, the potential difference between the electrodes is in the range of 25 to 40 KV. Preferably, the potential difference between the electrodes is in the range of 30 to 35 KV. More preferably, the potential difference between the electrodes is a direct current potential.

If required, the potential difference can be continuous or intermittent.

BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more easily understood and put into practical effect, reference will now be made to the preferred embodiments of the invention illustrated in the accompanying drawings, in which: Figure 1 schematically illustrates a frontal elevation in cross section of an electrostatic fly ash separator. Figure 2 illustrates a partial cross-sectional view of a separation chamber. Figure 3 illustrates a lateral elevation of the apparatus of Figure 2. Figure 4 illustrates a front elevational and cross-sectional view of a feeding mechanism. Figure 5 illustrates a partially sectioned side view of the apparatus of Figure 4.

DETAILED DESCRIPTION In Figure 1, the separation apparatus comprises a housing 1 having a fly ash feed hopper 2 located in its upper part. The hopper can be fed by any suitable lifting element (not shown), such as a pneumatic hoist, a screw auger, a belt or bucket conveyor. The side walls 3 of the hopper 2 can have electric heating elements (not shown) connected thereto to keep the fly ash at a predetermined temperature. Located below the feed hopper 2, there is a vibratory feeder 4 having opposed inclined feed surfaces 5. The feeder 4 is elastically mounted on springs 6, and a vibratory movement is imparted thereto by means of a rotating shaft 7 having eccentric masses (not shown). If required, these eccentric masses may be in the form of cam surfaces which engage an impactor plate (not shown) mounted on the underside of the feed surfaces 5. Located immediately below the ends of the feed surfaces 5, are the flat transport electrodes inclined downwards 8, and separated from them, are the parallel collectors 9 supported on isolated assemblies 10. The separated transport and collection electrodes 8, 9 each define a separation zone 11. Immediately below the upper separation zones 11, are the opposingly inclined separation zones 11, the lower end of the transport electrode 8 being placed above the upper end of a transport electrode 8a, to collect any particulate matter falling from the electrode of transport 8 from above. The vertically separate set of alternately inclined transport electrodes 8, 8a defines a serpentine path for the particulate material which runs under the influence of gravity through the successive transport electrodes 8, 8a, ending at a transport electrode lower 8b. The lowermost electrodes 8b direct the flow of fly ash towards the outlet ducts 12. Located under the lower end of each collecting electrode 9, 9a, there is a collection launcher 13 which directs the coal particles, collected from the ash stream flyers, by means of ducts 14 to hoppers 15. In use, coal-contaminated fly ash, which typically has a particle size in the range of 10 to 250 microns, is introduced at a temperature of about 100 ° C. at 110 ° C, on the vibratory feeder 6. A flow separator (not shown) divides the stream uniformly into opposingly inclined feed surfaces 5, which distribute the particulate matter in a thin layer through the upper surface of the electrodes of overhead transport 8. A direct current potential difference of approximately 35 KV is maintained between the respective pairs of electrical 8, 9, with the transport electrodes 8, 8a all electrically grounded, with a positive potential. As the thin layer moves across the surface of the transport electrodes 8, the particles are in direct contact with the positively charged plate. Under the operating conditions of the apparatus, the particles of the fly ash are substantially non-conductive in relation to the carbon particles, and as such, pass through each separation zone largely unaffected. However, carbon particles, by virtue of direct contact with the positively charged transport electrode, and also due to the inductive effects of the applied electric field, acquire a positive charge. When loaded by this conduction induction process, the positively charged particles are then attracted to the negatively charged collector electrodes. 9. Depending on the degree of charge acquired by the carbon particles and the mass of the particles, some will be attracted to the electrode relatively loaded collector 9, upon which, they are discharged on contact, and fall into a respective collection launcher 13. Other coal particles having, say, a lower degree of charge, and / or a greater mass, will depart from the transport electrodes 8, and under the combined effects of gravity and the electrostatic force applied in the separation zones 11, will follow an arched path towards the collection launchers 13. During the separation process, the upper edges of the transport electrodes 8 act as separators for dividing the coal particle and fly ash streams. The accumulation of carbon particles on the collector electrodes 9 is minimized by the steep angle of inclination, as well as by the effects of the carbon particles impacting the collector electrodes 9 with a considerable speed. Figure 2 shows a partial sectional view of the region of the separation chamber of the apparatus of Figure 1, and the collection element. The end walls of the separation chamber 16 include access gates 17 for maintenance, and it will be noted that the electrodes 8, 9 are pivotally mounted to enable a selective adjustment of the angles of inclination of the electrodes, to compensate for the variations in the properties of fly ash obtained from different sources.

Figure 3 shows a side elevation of the apparatus of Figure 2, with side panels 18 that can be removed for maintenance purposes. Figures 4 and 5 show an enlarged view of the feeding mechanism of the apparatus shown in Figure 1. Supported on the frame 20, there is a rotary valve 21 having a rotor 22 supported on the bearings 23 to rotate about the arrow 24. For convenience, as shown in Figure 5, the feeding mechanism comprises a pair of rotary valves 21, 21a, each with a respective feed hopper 25, 25a, engaging the adjacent ends of the arrows 24, 24a to allow operation by a single pulse mechanism (not shown). The rotor 22 comprises a plurality of elongated slots 26 spaced around a cylindrical wall surface 27 which fits into a housing 28 having opposite walls with a partial cylindrical concave recess complementary to the wall surface 27 of the rotor 22, to form a seal between the hopper 25 and the feed throat 29. As the rotor 22 of the valve rotates at a predetermined speed, fly ash is introduced into the feed throat 29, where, by means of the guides 30, the The feed is directed on an adjustable separator 31 which is adapted to allow the feed stream to be evenly divided over the feed surfaces 32, 32a of the vibratory feeder. Typically, an apparatus of the type shown in Figures 1 to 3, may comprise separate electrodes of 100 millimeters to 300 millimeters (preferably 190 millimeters), measuring the electrodes from 100 millimeters to 800 millimeters (preferably 500 millimeters) in width ( length of the flow path). The electrodes can be of any suitable length (feed width), suitably of the order of 2 meters. An apparatus of these preferred dimensions is capable of processing between 1.5 and 4 tons of fly ash per hour. It can be easily seen by an expert, that many modifications and variations can be made to the different aspects of the invention, without departing from its spirit and scope. For example, depending on the quality of the fly ash feed material and the required degree of carbon separation, the number of vertically separated separation zones can be increased or decreased at will. The modular nature of the apparatus allows a plurality of separators to be interconnected end to end, to allow filling of the feed hoppers by one or more lifting elements, and rotating valves to be operated by a single drive element. Although the method and apparatus have been described with particular reference to the separation of coal particles from fly ash, it is considered that, an appropriate modification, the apparatus may be applicable to the separation of other mixtures into fine particles of relatively conductive materials and no drivers

Claims (25)

1. An electrostatic separator for the separation of a mixture of substantially electrically conductive particles and substantially electrically non-conductive particles, this apparatus comprising: a plurality of separation zones, each separation zone comprising a pair of separate parallel flat electrodes defining an inclined path towards below, having a lower conveying surface and an upper collecting surface separated therefrom, the separation zones being separated in a vertical manner in an alternate slope with a lower end of a conveying surface of a separation zone that is placed on top of an upper end of a conveying surface of a succeeding successive separation zone, to define a serpentine path through which at least one component of this mixture can pass under the influence of gravity; an energy source coupled with the electrodes to provide, in use, a high voltage potential difference between each of the pair of electrodes, to generate an electric field therebetween, the respective electrodes comprising the transport surface of each path that is electrically grounded; a feed element adapted to feed a particulate material as a thin layer onto the surface of a higher conveying surface; a first collecting element associated with the collecting surface of each separation zone, to collect the particulate material attracted to the collecting surface under the influence of the electric field; and a second harvesting element associated with a lower conveyor surface, for collecting a component of a particulate mixture from which another component has been separated.

2. A spacer as claimed in claim 1, wherein the flat electrodes are suitably comprised of metal plates.

3. A spacer as claimed in claim 2, wherein the electrode of the collecting surface is comprised of aluminum or an aluminum alloy.

4. A spacer as claimed in claim 2, wherein the electrode of the transport surface comprises an abrasion resistant material.

5. A spacer as claimed in claim 4, wherein the electrode of the transport surface may comprise stainless steel or a wear-resistant metal alloy.

A spacer as claimed in claim 1, wherein the electrode of the transport surface comprises a wear resistant surface in the form of an electrically conductive ceramic material or a cermet.

A spacer as claimed in any of the preceding claims, wherein the peripheral edges of the electrodes are configured to minimize arcing.

A spacer as claimed in any of the preceding claims, wherein the electrodes are adjustably mounted to selectively vary the angle of inclination.

9. A spacer as claimed in claim 8, wherein the electrodes are inclined on the scale of 45 ° to 85 ° relative to the horizontal.

A separator as claimed in any of the preceding claims, wherein some or all of the transport electrodes include a heat source.

A separator as claimed in any of the preceding claims, wherein some or all of the transport electrodes comprise a vibration element to assist in transporting the particulate material thereon in a thin layer.

12. A separator as claimed in any of the preceding claims, wherein the energy source comprises an element for supplying an electric potential in the range of 15 to 50 KV.

13. A spacer as claimed in any of the preceding claims, wherein the feeding element comprises a vibrating feeder.

A spacer as claimed in claim 13, wherein the feeding element comprises an introduction element in association with the vibratory feeder, for selectively feeding a particulate material to the vibratory feeder at a predetermined speed.

15. A spacer as claimed in claim 14, wherein the insert includes a rotary valve located at the base of a feed hopper.

16. A spacer as claimed in any of the preceding claims, wherein the feed hopper includes a heat source for maintaining the particulate material therein at a predetermined temperature.

17. A separator as claimed in any of the preceding claims, wherein the first and second collection elements each comprise a storage hopper adapted to selectively remove the respective components of the particle mixtures.

18. A method for separating particles of coal from particulate fly ash, this method comprising the steps of: feeding, under the influence of gravity, a thin layer of fly ash on the surface of a series of alternately inclined flat transport electrodes defining a vertical serpentine path, wherein a collecting electrode is spaced from, and parallel to, each of the transport electrodes; applying a high voltage electrical potential between the transport and collecting electrodes, to create a substantially uniform electric field between the electrodes, the transport electrodes being electrically grounded, whereby, in use, the carbon particles contained in the particulate fly ash, acquire, through conductive induction, a load of opposite sign to that of the collecting electrodes, and are attracted to the collecting electrodes, moving away from the trajectory of the particles substantially not loaded with fly ash on the electrodes of transport, the carbon particles being collected in a first collecting element associated with each of the collecting electrodes, and the fly ash particles being collected in a second collecting element associated with a lower transport electrode in the serpentine path.

19. A method as claimed in claim 18, wherein fly ash is introduced into the serpentine path, at a temperature in the range of 50 ° C to 130 ° C.

20. A method as claimed in claim 19, wherein fly ash is introduced at a temperature in the range of 95 ° C to 110 ° C.

21. A method as claimed in any of claims 18 to 20, wherein the potential difference between the electrodes may be in the range of 15 to 50 KV.

22. A method as claimed in the claim 21, where the potential difference between the electrodes is in the range of 25 to 40 KV.

23. A method as claimed in the claim 22, where the potential difference between the electrodes is in the range of 30 to 35 KV.

24. A method as claimed in any of claims 18 to 23, wherein the potential difference between the electrodes is a direct current potential.

25. A method as claimed in claim 24, wherein the potential difference is continuous or intermittent.