BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to improvements to an electrostatic separator and more specifically to an adjustable gap in a belt-type electrostatic separator.

2. Description of the Related Art The need for the separation of materials is widespread. Many mineral ores are found in an impure state and economic recovery necessitates the separation of impurities from the valuable mineral. Often the ore and the ganges are intimately associated together, so that pulverization of the solid is necessary prior to separation. In a belt-type electrostatic separator such as is described in U.S. Patents 4,839,032 and 4.874,507 and as illustrated in the schematic diagram FIG. 1, an electric field is generated between two electrodes 10, 12, and an open mesh belt 18, having belt sections 18A and 18B, is moved within a gap 15, having a dimension d, between the two electrodes so as to form two streams of particulate material moving in relatively opposite directions, as indicated by arrows 19A and 19B. The electric field moves charged particles according to their sign of charge from one stream to the other. This type of separator has shown tremendous advantages over other types of electrostatic separators. For example while conventional electrostatic separators do not process well particles below 100 microns, the belt type of electrostatic separator has demonstrated very good separation of mixtures of particles with mean sizes below 5 microns. In addition, commercial sized units manufactured and sold by Separation Technologies, Inc., 10 Kearney Road, Needham. Massachusetts have processed in excess of 25 tons per hour of fly ash to remove unburned carbon for fuel recovery and to render an inorganic fraction suitable for use as a pozzolanic additive to concrete.

SUMMARY OF THE INVENTION However, it is often desirable to optimize the belt-type electrostatic separator by adjusting parameters within the separator. In addition, it is often desirable to adjust these parameters while

the separator is in operation. For example, there is a need to optimize the belt-type electrostatic separator in response to variations in feed material, ambient humidity under which the separator is operated, wear of the belt in the separator, to provide for changes in the performance specification of the separator, and the like. Accordingly, it is an object of the present invention to provide an improved electrostatic belt-type separator and method for separating different species of a mixture of particles.

According to one aspect of the invention, an apparatus for separating different components of a mixture of material includes a separation chamber having electrode means defining confronting electrode surfaces having a gap between the confronting electrode surfaces and for adjusting the gap between the confronting electrode surfaces. In addition, the apparatus includes a source of a separation influence that applies the separation influence across the gap toward at least one of the confronting electrode surfaces. The apparatus also includes a belt assembly that mechanically transports the mixture of material in two streams running transversely to the separation influence so that components of the mixture of material are deflected according to their influenceability to the separation influence into two transverse streams. Further, the apparatus includes at least one exit port at an end of the separation chamber to remove the components from the separation chamber.

With this arrangement, a separator having an improved separation performance is provided. More particularly, the separator allows for compensation of performance while the separator is operating. In addition, the separator allows for adjustment of the gap between the confronting electrode surfaces to compensate the separator in response to different conditions such as variations in the mixture of material, the ambient humidity at which the separator is operated, any wear in the belt, as well as to enhance separation of the mixture of material. According to another aspect of the invention, a method of separating different components of a mixture of material in a separation chamber having electrode means defining confronting electrode surfaces having a gap between the confronting electrode surfaces and for adjusting the gap between the confronting electrode surfaces includes impressing a separation influence toward at least one of the confronting electrode surfaces and separating the different components of the mixture of the material in a direction of the separation influence according to their relative influenceability to the separation influence. In addition, the method includes moving the components of like net influenceability in streams of unlike net influenceability

substantially parallel to each other and transversely to the separation influence and removing the separated components of the mixture from the streams. Further, the method includes adjusting the gap between the confronting electrode surfaces to enhance the separation of the different components. With this arrangement, an improved method of separating the different components from the mixture of material is provided. In addition, this method allows compensating the separator while the separator is operating in response to varying conditions.

Brief Description of the Drawings It is to be understood that the drawings are for the purpose of illustration only and are not intended as a definition of the limits of the invention. The foregoing and other objects and advantages of the present invention will become apparent with reference to the following detailed description when taken in conjunction with the following drawings in which:

FIG. 1 is a schematic illustration of a belt-type electrostatic separation employing a continuous belt to transport particles into streams running in opposite directions;

FIG. 2 is a schematic illustration of a complete electrostatic separator according to an embodiment of the present invention;

FIG. 3 is a side elevational view of the electrostatic separator of FIG. 2; FIG. 4 is a top plan view of the electrostatic separator of FIG. 2; FIG. 5 is a partially broken away cross-sectional side view taken along line 5-5 of FIG. 4 of the electrostatic separator of FIG. 2;

FIG. 6 is a cross-sectional plan view taken along line 6-6 of FIG. 5 of the electrostatic separator of FIG.5;

FIG. 7 is a cross-sectional end view taken along line 7-7 of the electrostatic separator of FIG. 5;

FIG. 7A is an exploded view of the electrostatic separator of FIG. 7 detailing a urethane foam core including a rubber seal.

FIG. 8 is a partial cross-sectionai view of frame restraints of the electrostatic separator of FIG. 5 taken along line 8-8; FIG. 9 is a schematic view of a preferred embodiment of a lifter assembly of the electrostatic separator of FIG. 2;

FIG. 10 is a schematic view of one embodiment of a lifter mechanism using a wedge and roller arrangement of the lifter assembly;

FIG. 1 1 is a schematic view of an alternative embodiment of the lifter mechanism using a cam plate and roller arrangement; FIG. 12 is another alternative embodiment of the lifter mechanism also using a cam plate and roller arrangement;

FIG. 13 is still another alternative embodiment of the lifter mechanism using a single link mechanism;

FIG. 14 is a further alternative embodiment of the lifter mechanism utilizing a double- 1 ink arrangement ;

FIG. 15 is an additional alternative embodiment of the lifter mechanism using a worm gear arrangement;

FIG. 16 is still another alternative embodiment of the lifter mechanism using an eccentric cam and crank arm arrangement; FIG. 17 is still another alternative embodiment of the lifter mechanism utilizing a jack screw arrangement;

FIG. 18 is a schematic view of a preferred embodiment of an electrode panel frame restraint of the lifting assembly;

FIG. 19 is an alternative embodiment of the electrode panel frame restraint utilizing a simple link assembly;

FIG. 20 is still another alternative embodiment of the electrode panel frame restraint utilizing a Watts linkage assembly;

FIG. 21 is a schematic diagram of a preferred embodiment of a lifter drive mechanism of the lifting assembly using a reduction gear box and a link mechanism; FIG. 22 is a schematic diagram of an alternative lifter drive mechanism using a leadscrew arrangement;

FIG. 23 is another alternative embodiment of the lifter drive mechanism using a hydraulic cylinder arrangement; and

FIG. 24 is still another alternative embodiment of the lifter drive mechanism using a rack and pinion arrangement.

DETAILED DESCRIPTION OF THE DRAWINGS

The belt type electrostatic separator described in U.S. Patents 4,839,032 and 4.874,507, herein incoφorated by reference, is illustrated in FIG. 1. As discussed above, an electric field is established in a thin gap 15, preferably about 10mm, between two extended substantially imperforate electrodes 10 and 12. An endless belt 18, preferably an open mesh of dielectric or dielectric-coated screen-like material is supported on rollers 20, 22. The rollers 20, 22 are disposed at each end of the apparatus, with respective belt sections 18A and 18B located in the spaces between the electrodes 10 and 12. Tension rollers 20A and 22A, respectively, maintain the belt sections 18A and 18B taut. When the support rollers 20, 22 are rotated, for example, clockwise around their respective axes 21 and 23, as is indicated in FIG. 1, the belt sections 18A and 18B move in relatively opposite directions, as is indicated by arrows 19A and 19B, respectively.

In the apparatus of FIG. 1, the particular material to be treated (e.g. fly ash) is introduced into the apparatus via a slot-like opening 11 in one of the electrodes 10. Separated products (e.g. carbon and low carbon ash) are taken out of the apparatus at the ends 26 and 28. The electric field in the gap 15 will appear between the electrodes 10, 12. Assuming the electrodes 10, 12 are at relative electric potentials (-) and (+), respectively, the belt section 18A adjacent the first electrode 10 will carry positively-charged particles (e.g. high carbon) and the belt section 18B adjacent the second electrode 12 will carry negatively-charged particles (e.g. low carbon ash). In other words, separation is accomplished by migration of charged particles in response to the force exerted by the electric field on the charged particles. It is to be appreciated that the electrodes 10, 12 can be biased in different ways and that such modifications are intended. FIG. 2 is an overall schematic view of an embodiment of the electrostatic separator according to the present invention. The parts of the apparatus that are common to FIG. 1 bear the same reference characters. The electrostatic field is established between the electrodes 10 and 12 and feed is introduced at any one of the plurality of input ports 1 1. The input ports 11 that are not used are sealed. A motor assembly 30 located at either one of or both ends of the separator, mechanically moves the belt sections 18A and 18B between the electrodes 10 and 12 on rollers 20 and 22. The mixture of material to be treated is separated into streams of components of like net influenceability to the electric potentials disposed on electrodes 10 and 12. The streams of like net influenceability travel the length of the separator transversely to the separation influence

and the separated products are removed from the apparatus at the ends 26 and 28.

In the present invention, an improved electrostatic separator and method of providing increased quality and yield of separated materials is provided. In addition, the present invention allows adjustment of the gap distance d to be made while the apparatus is in operation. During operation of the separator of FIGS. 1-2, a number of parameters can be adjusted so as to change an amount and a degree of separation. These parameters include a speed at which the belt segments 18A, 18B are moved in opposite directions, a composition of the belt 18, and the positions 11 along the length of electrode 10 at which the feed material is introduced. However, a problem encountered when making such adjustments is that these parameters typically cannot be adjusted while the machine is in operation.

It is known that the degree of separation of the charged particles in an electric field is a function of the force exerted on the particles by the applied electric field. Referring to Equation (1), the force (F) on a charged particle is equal to the product of the electric field (E) and the magnitude (M) of charge on the particle. F=E.M (1)

Referring to Equation 2, for a voltage induced across a parallel plate geometry such as the separator of Fig. 1, it is known that the electric field is equal to the gradient in potential, or the applied voltage (V) divided by the distance (d) between the two electrodes.

E = V/d (2) Thus, the applied voltage (V) affects the degree of separation. However, it has been experimentally determined that for certain materials treated using the separators of FIGS. 1-2, the applied voltage is not a strong parameter for controlling the degree of separation in the electrostatic separator. In particular it has been found that above a certain voltage threshold, the applied voltage can be varied over a broad range with little if any change in the degree of separation.

The counter current belt type separator of FIG. 1 has been operated with a high electric field, on the order of many times larger than fields used in conventional free fall, and other types of electrostatic separators. Suφrisingly, it has been determined that once the threshold voltage is achieved, variations of up to 20% in the applied voltage (v) made little difference in the degree of separation. Since a variation in the applied voltage also results in a variation in the appiied electric field, as shown in Equation (2), it would be a natural conclusion with respect to these

materials that, once the predetermined threshold voltage is achieved, variations in the electric field (E) would also have little impact on the degree of separation. It is suφrising, therefore that it has been experimentally determined that changing the gap spacing (d) between electrodes 10, 12 does have a large impact on the degree of separation for these materials. For some materials, this impact is so significant that the real time adjustment of the gap (15) becomes a valuable parameter to adjust during operation.

Table 1 is a summary of experimental results of varying the electrode voltage, the gap spacing (d), and the electric field in the separator of FIGS. 1-2. In particular. Table 1 summarizes data generated with a laboratory size belt type electrostatic separator when separating unburned carbon from coal derived fly ash. Rows 1-4 summarize separation of fly ash using a fixed gap spacing d of 380 mils at different applied electrode voltages ranging from 5kV to 9kV resulting in different applied electric fields. As shown in rows 1 through 4, when the electric field is increased from 5.18 x IO ⁵ V/m to 9.32 x 10 ⁵ V/m, the degree of separation clearly increases. In particular, the concentration of ash and carbon increases in stream 1 and stream 2. respectively.

Rows 5-8 of Table 1 summarize results of the separation of fly ash using a fixed gap spacing d of 380 mils at higher electric fields, in particular > 9.32 x 10 ⁵ V/m. As is seen in rows 5-8, when the electric field is increased from 9.32 x IO ⁵ to 1.24 x IO ⁶ V/m, the degree of separation is virtually unchanged. In particular, the differences in the concentration in both streams 1 and 2 are insignificant as a function of the increased electric field. Thus, as discussed above, it has been determined that the separation effectiveness of belt-type electrostatic separator as illustrated in FIGS. 1-2 is a function of the electric field below a certain threshold voltage, and is not a function of an increased electric field above the threshold voltage.

Columns 9-19 of Table 1 illustrate the separation of fly ash as a function of the gap distance (d). In particular, rows 9-11 illustrate the separation of fly ash using a belt speed of 30 feed per second with a gap distance d varying from 380 mils to 350 mils. As can be seen, the separation improves with a smaller gap width of 350 mils. In particular, the stream 2 has a higher concentration of carbon using a gap spacing of 350 mils. Rows 12-19 also illustrate the effect on separation when the gap spacing is reduced from 380 mils to 350 mils at a belt speed of 45 feet per second. In particular, a reduction in the gap spacing from 380 mils to 350 mils results in a 22 percent increase in carbon concentration in stream 2.

In the embodiment of the electrostatic separator shown in FIG. 1, the gap distance d was set by using shims of known thickness. Although the gap could be adjusted accurately using the shims, the difficulty and time consuming nature of changing the shims was such that the gap 15 could only be changed rarely. Accordingly, it was not feasible to use gap adjustment as a process variable to adjust the performance of the separator while it was operating. Thus, according to an embodiment of the present invention there is provided an online gap adjustment mechanism which uses the gap spacing (d) as a process variable.

The electrostatic separator including the gap adjusting mechanism of the present invention has several requirements that should be met. In particular, the electrodes 10, 12 should be maintained flat and in their proper gap spacing d. In addition, the movable parts of the separator should be sealed such that the material being separated does not leak out. Further, the applied voltage (V) on the electrodes, which can be on the order of several kVs should be safely and properly isolated from the rest of the machine. In addition, the mechanism should provide supporting structure for the electrodes to enable relative motion of the belt 18 between the two electrodes 10, 12 while maintaining a stable and controlled gap spacing d.

FIG. 3 is a side elevational view of an embodiment of the electrostatic separator including the gap adjusting mechanism according to the present invention. Parts of the apparatus that are common to FIGS. 1-2 bear the same reference characters. In general, the separator apparatus includes a hinged lid assembly 32 which is hinged at one side and which is held in a closed position, sealing the separator, by a plurality of toggle links 34 disposed along a length of the separator. Within the hinged lid assembly 32, an upper electrode assembly 10 is held spaced apart from the lid assembly by a plurality of standoffs 36 disposed along the length of the lid assembly between the electrode 10 and the lid. A bottom electrode assembly 12 is coupled to the gap adjusting mechanism to move the bottom electrode 12 up and down relative to the top electrode 10 so as to change the gap spacing d. Thus in the embodiment of FIG. 3, the gap spacing d is adjusted by moving the bottom electrode assembly 12 with respect to the top electrode assembly 10. However, it is to be appreciated that modifications to this including moving the top electrode with respect to the bottom electrode or moving both electrodes with respect to each other are also possible and such modifications are intended. The gap adjusting mechanism includes a lifter mechanism 38, an electrode panel frame restraint 40 and a lifter drive mechanism 42. The lifter mechanism utilizes a drive force

provided by the lifter drive mechanism 42 and transforms this drive force into a lifting force to provide movement of the electrode panel assembly 12 in a selected direction either toward or away from the upper electrode panel assembly 10. In particular, the lifter mechanism provides movement of the electrode in an up and down vertical direction as illustrated by the arrows of FIG. 2. The electrode panel restraint 40 ensures that the electrode panel is adjusted only in the vertical direction. The lifter drive mechanism 42 provides the drive force to the lifter mechanism for raising and lowering the electrode panel assembly 12.

It is to be appreciated that the electrode panel assembly 12 should be rigid enough to transmit the lifting force from the lifter mechanism 38 while maintaining the bottom electrode assembly 12 parallel to the top electrode assembly 10 with the gap spacing d. In addition, it is to be appreciated that the electrode panel restraint 40 should allow movement of the bottom electrode assembly 12 in the vertical direction toward or away from the top electrode assembly while minimizing movement of the bottom electrode assembly 12 in a longitudinal direction parallel to the length of the separator. FIG. 4 is a top plan view of the embodiment of the electrostatic separator as shown in

FIG. 3. Parts of the apparatus that are common to FIGS. 1-3 bear the same reference characters. As can be seen from FIG. 4 the lid assembly 32 is hinged with hinges 43 at one side of the separator along the longitudinal length of the separator and is held in place at the other side of the separator by the plurality of toggle links 34. In addition, there is disclosed in FIG. 4 an embodiment of the lifter drive mechanism 42 including a reduction gear box and link mechanism connected to a hand-crank 45. Although this embodiment of the lifter drive mechanism is shown in FIGS. 3-4, it is to be appreciated that alternative embodiments of the lifter drive mechanism as shown in detail in FIGS. 21-24 and as discussed below are intended to be covered by the scope of the present invention. In addition, it is to be appreciated that the lifter drive mechanism could, for example, also be connected to a motor as an alternative to the hand crank 45 in order to provide the desired drive force.

FIG. 5 is a partially broken away cross-sectional side elevational view taken along 5-5 of the separator of FIG. 4. In addition, FIG. 6 is a cross-sectional plan view taken along line 6-6 of the separator of FIG. 5. Further FIG. 9 is a schematic diagram of a preferred embodiment of the lifter mechanism. The lifter mechanism as shown in FIGS. 5-6, and 9 includes a cam plate and roller arrangement which is disposed between a shuttle frame 44 and the lower electrode panel

frame 82. The panel frame 82 supports the lower electrode assembly 72, as shown in more detail of FIG. 8, with a plurality of standoffs 84. Referring to FIG. 9, the cam plates 46 are formed with an elongated, inclined cam slot 48. Within each cam slot 48 there is supported a lift roller 50. The lower electrode panel frame 82 is raised and lowered in the vertical direction by driving the shuttle frame 44 forward and backward in a horizontal direction. In particular, adjusting the position of the shuttle frame in the horizontal direction causes the lift roller 50 to ride up or down the cam slots 48, thereby raising or lowering the lower electrode panel frame 82. In addition, support rollers 52 are positioned above and below the shuttle frame 44 to rotatably engage an upper surface and a lower surface of the shuttle frame 44 to maintain the shuttle frame parallel to the lower electrode panel 12 as the shuttle frame is driven in the horizontal direction.

The preferred embodiment of the gap adjusting mechanism (FIG. 9) includes the electrode panel restraint 40 which has a restraining plate 54 and a roller 56 rotatably mounted to a fixed support (not shown). The restraining plate 54 is rigidly attached to the lower electrode panel frame 82 and has a vertically elongated slot 58. The roller 56 acts as a sliding pin joint with the slot 56 to minimize movement of the lower electrode panel assembly in the horizontal direction while allowing movement of the electrode panel assembly in the vertical direction. It is to be appreciated that other embodiments of the electrode panel frame restraint as shown, in particular, in FIGS. 18-20 can also be used and are intended to be covered by the scope of the present invention. The gap adjusting mechanism 42 as shown in the preferred embodiment of FIG. 9 also includes the lifter drive mechanism 42 having a reduction gear box 60, and an output arm 64 rotatably connected to the reduction gear box. A plurality of link arms 62 link output arms 64, which are coupled to a drive shaft 72, to a cross member 68 of the shuttle frame 44 via a drive plate 70. In particular, the link arm 62 is pivotally interconnected between the output arms 64 and the drive plates 70. Rotation of the drive shaft 72, which is coupled to the gear box 60 through bearing assembly 74, produces a force which is converted by the plurality of output arms 64 and the links 70 into a drive force that is transmitted to the drive plate 70 and to the shuttle frame 44 to move the shuttle frame in the horizontal direction.

Referring now to FIG. 7, there is shown a cross-sectional end view taken along line 7-7 of the separator of FIG. 5. In addition, FIG. 8 is a cross-sectional view of the frame restraint of the lower panel frame assembly 82 taken along line 8-8 of FIG. 5. Again, parts of the apparatus that

are common bear the same reference characters. Referring to FIG. 7, each of the upper electrode panel assembly 10 and the lower panel electrode assembly 12 are made up of electrode tiles 76 and 78, respectively. In a preferred embodiment of the invention, the electrode tiles are formed from silicon carbide. In addition, each of the electrode tiles 76 and 78 is mounted on a insulating core 80 and 82, respectively. In a preferred embodiment of the invention, the insulating core is a urethane foam core. FIG. 7A is an exploded view of the urethan foam core 82. There is a channel 81 cut into the urethane foam core 82, which contains a rubber seal 83. The rubber seal 83 and gap 81 form a sliding seal which confines the product to the gap region 15. Further, each of the electrode assemblies has a backing sheet to provide rigidity and to transform the drive force into a lifting force to provide the positive movement of the electrode panel assembly in a selected direction. In a preferred embodiment of the invention, the backing sheet is made of Kevlar.

As illustrated in FIGS. 7-8, the lower electrode assembly 12 is connected to the shuttle frame 44 by the lift frame 82 which is spaced apart from the lower electrode assembly 12 by a plurality of standoffs 84. In addition, the shuttle frame 44 is adapted to travel along a guide rail 86 in the horizontal direction. The separator apparatus of the present invention is also provided with side plates 88 to seal the separator. The shuttle frame 44 is offset from the side plates by standoffs 90.

As briefly described above, numerous embodiments of the gap adjusting mechanism including the lifter mechanism 38, the electrode panel frame restraint 40 and the lifter drive mechanism 42 can be utilized to adjust the spacing d between the electrodes 10, 12. A number of illustrative embodiments for the lifter mechanism 38 are shown in FIGS. 10-17. Each lifter mechanism embodiment provides positive movement of the lower electrode 12 in an up and down vertical direction V. Similarly, illustrative embodiments for the electrode panel frame restraint 40 and the lifter drive mechanism 42 are respectively shown in FIGS. 18-20 and FIGS. 21-24.

One illustrative embodiment for the lifter mechanism 42 using a wedge and roller arrangement is shown in FIG. 10. The lifter mechanism includes a shuttle frame 44, a plurality of wedges 1004, and a plurality of lift rollers 1006 . It is to be appreciated that the number of wedges and rollers depends upon the size and support required for a particular electrode. The wedges 1004 are attached to the shuttle frame 44 and the lift rollers 1006 are rotatably mounted

to the electrode panel frame 82. Each wedge 1004 has an inclined wedge surface 1008 to engage a lift roller 1006 for adjustably supporting the electrode panel frame 82.

Movement of the wedges 1004 in a front and back horizontal direction H relative to the electrode panel frame 82 raises and lowers the electrode panel frame 82 in the vertical direction V in response to the interaction between the lift rollers 1006 and the wedge surfaces 1008. Movement of the wedges is accomplished using the lifter drive mechanism (not shown) which drives the shuttle frame 44 in the horizontal direction H. As illustrated, when the shuttle frame 44 is driven in a forward direction F, the wedges provide a positive force that urges the lift rollers 1006 to ride up the incline of the wedge surface 1008, thereby raising the electrode panel frame in an upward vertical direction U. Conversely, the electrode panel frame can be lowered by driving the shuttle frame 44 in a backward direction (not shown) so that the weight of the structure supported by the shuttle frame urges the lift rollers 1006 to ride down the incline of the wedge surface 1008. The shuttle frame 44 itself is supported on support rollers 50 for maintaining the shuttle frame 44 in a horizontal position parallel to the electrode panel assembly 12 as the shuttle frame is driven forward and backward in the horizontal direction H. The weight of the structure supported by the shuttle frame maintains the shuttle frame in contact with the support rollers.

Other illustrative embodiments utilizing inclined surfaces to raise and lower the electrode panel frame 82 are shown in FIGS. 1 1 and 12. In particular, these embodiments for a lifter mechanism use a cam plate and roller arrangement. Similar to the wedge mechanism described above, the lifter mechanisms shown in FIGS. 1 1 and 12 include a shuttle frame 44, a plurality of cam plates 1 104, 1204, and a plurality of lift rollers 1 106, 1206. Each cam plate 1 104, 1204 has an elongated, inclined cam slot 1108, 1208 within which is supported a lift roller 1 106, 1206. Each cam slot 1108, 1208 has parallel cam surfaces 1110, 1210 for engaging and maintaining the lift roller within the slot. Furthermore, the cam surfaces provide a positive force to the lift roller when both raising and lowering the electrode panel frame 82.

Similar to the wedge mechanism described above, the electrode panel frame can be raised and lowered in the vertical direction V by driving the shuttle frame 44, forward and backward in the horizontal direction H. Adjusting the position of the shuttle frame in the horizontal direction H relative to the electrode panel frame urges the lift rollers 1106, 1206 to ride up or down the cam slots 1108, 1208 along the cam surfaces, thereby raising or lowering the electrode panel

frame. Support rollers 50 are positioned above and below the shuttle frame 44 to rotatably engage the upper and lower surface, respectively, of the shuttle frame to maintain the shuttle frame parallel to the lower electrode panel assembly 12 as the shuttle frame is driven in the horizontal direction. It is to be appreciated however, that in each of the embodiments described, support rollers are not necessarily required above the shuttle frame when the weight of the structure supported by the shuttle frame is sufficient to maintain the frame in contact with the lower support rollers.

The embodiments of the lifter mechanism illustrated in FIGS. 1 1 and 12 differ from each other in the specific arrangement of cam plates and lift rollers. In the FIG. 11 embodiment, the cam plates 1 104 are attached to the shuttle frame 44, and the lift rollers 1106 are rotatably mounted to the electrode panel frame 82. Conversely, in FIG. 12, the cam plates 1204 are attached to the electrode panel frame 82, and the lift rollers 1206 are rotatably mounted to the shuttle frame 44.

An alternative embodiment for a lifter mechanism using a single link mechanism is shown in FIG. 13. This lifter mechanism includes the shuttle frame 44, and a plurality of link arms 1304 pivotally connected between the shuttle frame 44 and the electrode panel frame 82. One end of each link arm 1304 is pivotally connected to the electrode panel frame 82 at the electrode panel frame pivot point 1306. The opposite end of each link arm is pivotally connected to the shuttle frame 44 at the shuttle frame pivot point 1308. Again, support rollers 1306 are positioned below and above the shuttle frame 44 to engage respectively the lower and upper surface of the shuttle frame and maintain the shuttle frame parallel to the electrode panel frame 82.

Because the electrode panel frame restraint (not shown) allows only vertical movement of the electrode panel frame, movement of the shuttle frame 44 forward or backward in the horizontal direction H rotates each link arm 1304 about the panel frame pivot point 1306. This rotation of the link arms relative to the electrode panel frame raises and lowers the electrode panel frame. When the link arms are positioned so that the shuttle frame pivot points 1308 vertically align with the electrode panel frame pivot points 1306, the link arms 1304 raise the electrode panel to its maximum height relative to the shuttle frame. The electrode panel frame is lowered as the shuttle frame rotates the link arms to separate the distance between the pivot points 1306, 1308 in the horizontal direction. As the horizontal distance between the pivot

points increases, the vertical height of the link arms decreases.

Another illustrative embodiment of the lifter mechanism using link arms is shown in FIG. 14. In particular, the lifter mechanism use a double link arrangement that includes a lifter frame 1402, a pair of upper link arms 1404, and a plurality of lower link arms 1406. Each upper link 5 arm 1404 pivotally interconnects the lifter frame 1402 and the electrode panel frame 82 at an upper pivot point 1408 of the lifter frame and an electrode panel frame pivot point 1410, respectively. Each lower link arm 1406 pivotally interconnects the lifter frame 1402 to a fixed pivot support 1412 at a lower pivot point 1414 of the lifter frame and a support pivot point 1416, respectively. The panel frame pivot point 1410 is positioned in vertical alignment with the l o support pivot point 1416.

The electrode panel height can be adjusted by driving the lifter frame forward or backward in the horizontal direction H to rotate the upper link arms 1404 and the lower link arms 1406 relative to the panel frame and support pivot points 1410, 1412. Similar to the single link arm mechanism described above, the effective vertical height of the link arms 1404, 1406 is

15 proportional to the horizontal distance between the pivot points for each link arm. Accordingly, the electrode panel frame 82 attains its maximum height when the lifter frame pivot points 1408, 1414 vertically align with the frame and support pivot points 1410, 1416 so that there is no horizontal distance between pivot points. As the upper and lower pivot points 1408, 1414 are rotated out of vertical alignment with the frame and support pivot points 1410, 1412. the vertical

20 height of the link arms decreases, thereby lowering the height of the electrode panel frame.

Furthermore, it is to be appreciated that the change in height relative to the change in horizontal movement is greater using the double link mechanism as compared to the single link mechanism.

A further illustrative embodiment for the lifter mechanism uses a worm gear mechanism as shown in FIG. 15. This lifter mechanism includes a worm shaft 1502 rotatably supported

25 along its length with support journals 1504, a plurality of worm gears 1506 which engage worm threads 1508 formed on portions of the worm shaft, and a plurality of cams 1512 which adjustably support the electrode panel frame 82. Each worm gear 1506 and cam 1512 is rotatably mounted to a gear shaft 1510 along an axis transverse to the worm shaft. Each cam is mounted on the gear shaft in a non-concentric arrangement with its geometric center offset from

30 the gear shaft axis so that the cam rotates relative to the gear shaft in an eccentric manner. This arrangement establishes a cam support radius r between the gear shaft 1510 and the bottom of the

electrode panel frame 82 that can be varied according to the particular rotational position of the cam 1512 relative to the electrode panel frame.

Changing the cam support radius r by rotating the cam with the worm gear 1506 adjusts the height of the electrode panel frame 82. Rotation of the worm shaft with the lifter drive mechanism rotates the worm gear 1506 by transmitting the worm shaft rotational force through the worm threads 1508 to the worm gear. The worm gear 1506 rotates the gear shaft 1510 which in turn rotates the cam 1512 so that the cam support surface 1514, which supports the electrode panel frame 82, adjusts the height of the electrode panel frame 82 by varying the cam support radius r between the gear shaft 1510 and the cam support surface 1514. Although illustrated with a circular cam positioned nonconcentrically with respect to the gear shaft, the cam 1512 could be shaped with a non-circular cam surface 1514 to provide similar results.

FIG. 16 is an illustrative embodiment of another lifter mechanism using an eccentric cam and crank arms to adjust the height of the electrode panel frame 82. The lifter mechanism of this embodiment includes the shuttle frame 44, a plurality of eccentric cams 1604 which are mounted to a rotatable shaft 1606, and a plurality of crank arms 1608 interconnecting the shuttle frame to each shaft. As described above for the worm gear mechanism, each eccentric cam 1604 has a cam support surface 1610 for adjustably supporting the electrode panel frame 82.

As each eccentric cam 1604 is rotated by its shaft 1606, the cam support radius r between the shaft and the cam support surface varies in the vertical direction, thereby adjusting the height of the electrode panel frame relative to the shaft. Movement of the shuttle frame 44 in a forward and backward horizontal direction H rotates each crank arm 1608, which are pivotally connected to the shuttle frame, so that the crank arms rotate each shaft and eccentric cam. Alternatively, the crank arms could be attached directly to the eccentric cams so that movement of the crank arms is transmitted directly to the cams. Another illustrative embodiment for the lifter mechanism using a jack screw mechanism is shown in FIG. 17. The jack screw lifter mechanism includes a support frame 1702, a plurality of jack screws 1704 extending through the support frame in the vertical direction V to support the electrode panel frame, a plurality of pulleys 1706 rotatably attached to the jack screws below the support frame, and a drive belt 1708 which engages and rotates the pulleys. The support frame 1702 is rigidly supported below the electrode panel frame 82 in a fixed position parallel to the frame 82. The support frame 1702 has threaded holes 1710 through which the jack screws

1704 adjustably extend to support the electrode panel frame 82. Each pulley 1706 is rotatably attached to the end of each jack screw 1704 opposite the end of the jack screw supporting the electrode panel frame 82.

The lifter drive mechanism (not shown) drives the drive belt to rotate the pulleys 1706. Each pulley in turn rotates a jack screw causing the jack screw to be either raised or lowered in an axial direction relative to the support frame 1702 due to the interaction between the jack screw threads and the corresponding hole threads in the support frame, thereby raising or lowering the electrode panel frame. In this embodiment, raising and lowering the jack screws is achieved by rotating the pulleys respectively in a clockwise and counter-clockwise direction. The pulleys 1706 and the drive belt 1708 should be configured so that the drive belt drives the pulleys in a positive manner. One embodiment for delivering positive drive to the pulleys includes pulleys 1706 in the form of a sprocket having teeth to engage the drive belt 1708 in the form of a link-type chain. Alternatively, the drive belt could be provided with teeth, such as a timing belt, to engage the pulleys. It should be appreciated, however, that other variations for the pulleys and the drive belt, which could rotate the jack screws, are within the intended scope of the jack screw mechanism.

As discussed above, the gap adjusting mechanism uses an electrode panel frame restraint 40 to minimize movement of the electrode panel in the horizontal direction parallel to the opposing electrode panel 12, and at the same time to adjust the electrode panel in the vertical direction. Several embodiments for an electrode panel frame restraint 40 are illustrated in FIGS. 18-20.

A preferred embodiment for the electrode panel frame restraint uses a roller mechanism as shown in FIG. 18. The electrode panel frame restraint includes a restraining plate 1802, and a roller 1804 rotatably mounted to a fixed support 1806. The restraining plate 1802, which is rigidly attached to the electrode panel frame 82, has an elongated, vertical slot 1808. The roller 1804, which acts as a sliding pin joint, interacts with the slot 1808 to minimize movement of the electrode panel frame in the horizontal direction H, while allowing adjustment of the electrode panel frame in a vertical direction V. In particular, the roller 1804 engages the vertical surfaces 1810 of the slot to inhibit movement of the restraining plate 1802 in the horizontal direction H. Another embodiment for an electrode panel frame restraint uses a simple link mechanism as shown in FIG. 19. This embodiment of the frame restraint includes a link arm 1902 having

one end pivotally mounted to a fixed support 1904 and its opposite end pivotally connected to the electrode panel frame 82 at a panel frame pivot point 1906. In this embodiment, raising the electrode panel frame in an upward direction U pivots the link arm 1902 about its support 1904 in a clockwise direction CW. Because the link arm 1092 has a fixed length, and the panel frame pivot point 1906 is fixed relative to the panel frame, raising the electrode panel frame rotates the panel frame pivot point 1906 along an arc relative to the support 1904, thereby causing the electrode panel to move in a horizontal and vertical direction. However, horizontal movement of the electrode panel can be reduced to an amount which will not detrimentally impact the operation of the electrostatic separator by using a link arm 1902 that has a length that results in insignificant horizontal movement of the electrode panel for the desired vertical movement of the electrode panel.

Still another embodiment for an electrode panel frame restraint using a Watts linkage is shown in FIG. 20. The frame restraint includes a restraining plate 2002, a connecting plate 2004, and a pair of link arms 2006, 2008. The restraining plate 2002 is rigidly attached to the electrode panel frame 82, and the connecting plate 2004 is rotatably mounted to the restraining plate on a connecting plate shaft 2014. One end of each link arm 2006, 2008 is pivotally connected to a fixed support 2010, 2012, and the opposite end of each link arm is pivotally connected to the connecting plate 2004 on diametrically opposite sides of the connecting plate shaft 2014.

In this embodiment, movement of the electrode panel frame 82 in the horizontal direction H is minimized by opposing forces generated by the link arms, which coact with the connecting plate shaft 2014. When the lifter mechanism (not shown) raises the electrode panel frame in an upward direction U, the connecting plate shaft 2014 is likewise raised along with the restraining plate 2002. As the restraining plate 2002 is raised, the connecting plate 2004 is similarly raised causing the link arms 2006, 2008 to pivot about their supports 2010. 2012 in a counter-clockwise direction CCW and a clockwise direction CW, respectively. Because each link arm pivots about a fixed support, the ends of the link arms opposite the fixed supports pivot about the supports in an arc resulting in both vertical and horizontal movement of each pivoting end 2016, 2018. However, the arcuate movement of the pivoting ends 2016, 2018 rotates the connecting plate 2004 relative to the restraining plate 2002 in a clockwise direction on the connecting plate shaft 2014. Thus, the connecting plate 2004 compensates for the opposing arcuate movement of the pivoting ends 2016, 2018 of the link arms 2006, 2008, respectively, thereby minimizing

movement of the electrode panel frame 82 in the horizontal direction H.

As discussed above, the gap adjusting mechanism also includes a lifter drive mechanism to provide a drive force to the lifter mechanism for raising and lowering the electrode panel frame. Various embodiments for a lifter drive mechanism can be used in the gap adjusting mechanism. Several illustrative embodiments for the lifter drive mechanism are illustrated in FIGS. 21-24.

A preferred embodiment for the lifter drive mechanism using a reduction gear box and link mechanism is shown in FIG. 21. The lifter drive mechanism includes the reduction gear box 60, the output arm 64 rotatably connected to the reduction gear box through the crank shaft 72, the link arm 62, and the drive plate 70. As illustrated, the drive plate 70 is attached to the shuttle frame 82, and the link arm 62 is pivotally interconnected between the output arm 64 and the drive plate 70. Rotation of the crank shaft 72 of the reduction gear box 60 produces an output power which is converted by the output arm 64 and link arm 62 into a drive force that is transmitted to the drive plate 70. In particular, the crank shaft 72 can rotate the output arm 64 in a clockwise direction CW to drive the link arm 62 toward the drive plate 70, which in turn drives the shuttle frame 44 in a forward direction F. Conversely, rotating the output arm 64 in a counter-clockwise directions pulls the link arm away from the drive plate, thereby driving the shuttle frame in a backward direction (not shown). The output force from the gear box can be generated by manually rotating the crank shaft 72 with a hand wheel 44. Alternatively, an input device (e.g., a motor) could be connected to the crank shaft reduction gear box, or directly to the output arm, to provide the drive force for moving the shuttle frame.

An illustrative embodiment for the lifter drive mechanism uses a leadscrew arrangement as shown in FIG. 22. This drive mechanism includes a leadscrew 2202, and a drive plate 2204 which is attached to the shuttle frame 82. The leadscrew 2202 can be a threaded rod which mates with corresponding threads provided on the drive plate 2204. The threads of the leadscrew interact with the threads of the drive plate so that rotating the leadscrew 2202 moves the drive plate along the length of the rod, thereby driving the shuttle frame in the desired horizontal direction. The leadscrew 2202 could be rotated manually or with other conventional power input devices (not shown). Another illustrative embodiment for a lifter drive mechanism uses a hydraulic cylinder as shown in FIG. 23. This drive mechanism includes a hydraulic cylinder 2302 which has a piston

2304 that can be extended or retracted from the cylinder, and a drive plate 2306 attached to the shuttle frame 82. The cylinder piston 2304 is connected to the drive plate 2306 so that when the cylinder 2302 drives the piston 2304 in a forward direction F, the drive plate 2306 moves the shuttle frame 44 in the forward direction F. Conversely, retracting the piston 2304 into the cylinder 2302 pulls the drive plate 2306 in a rearward direction causing the shuttle frame to likewise move in the rearward direction.

A further illustrative embodiment for a lifter drive mechanism using a rack and pinion mechanism is shown in FIG. 24. The drive mechanism includes a pinion gear 2402 rotatably mounted to a pinion shaft 2404 along an axis that is transverse to the horizontal direction H of movement of the shuttle frame 44, and a rack 2406 mounted to the shuttle frame 44 to engage the pinion gear 2402. Rotation of the pinion gear 2402 on the pinion shaft 2404 drives the rack 2406 in the horizontal direction H, thereby moving the shuttle frame in the horizontal direction. As shown in FIG. 24, rotating the pinion gear 2402 in a clockwise direction CW, drives the shuttle frame in the forward direction F. Conversely, rotating the pinion gear in a counter-clockwise direction would drive the shuttle frame in a rearward direction (not shown). The pinion gear 2402 can be rotated manually or with other conventional power input devices (not shown).

According to the invention, materials are separated in a separation chamber, wherein the separation chamber has a gap dimension d between confronting electrodes surfaces. A mixture to be separated is admitted into the separation chamber of an opening along the length of the chamber, and a separation influence is imposed across the gap spacing d of the separation chamber. Differentially separated components of the mixture are mechanically moved transversely to the separation influence whereby continued application of the separation influence and continuous motion of the differentially separated components results in an integration of the separation so as to produce substantial separation across the length of the separation chamber in the direction of movement of the layers. The method also includes adjusting the gap between the confronting electrode surfaces to enhance the separation of the components.

The invention is applicable to a wide variety of physical mixtures, such as the benification of ores. It has been found to be particularly useful in the separation of unburned carbon from coal derived fly ash. During the combustion of coal for the generation of electric power, coal is pulverized and burned in the boiler as a dispersed powder. The particles are

heated by radiation from the existing flame, and the combustible particles burn while the noncombustible particles melt. Upon exiting the boiler, the combustion products are cooled so as to use the heat for steam generation, this cooling quenches the mineral particles in a glassy state. These alumina and silica containing glasses are good polozolans, which upon reaction with lime, generate cementacious products. However, carbon is detrimental to the use of fly ash as a pozolan, particularly in concrete where air entraining agents are required. Therefore, there is a need to separate the carbon from the fly ash. The present invention has been used to separate carbon and low carbon ash from fly ash with increased quality and yield.

One feature of electrostatic separator of the present invention is the ability of the belt 18 to sweep the electrodes 10, 12 clean and to prevent the adherence of layers of material to the electrodes and the belt. This is, however, sometimes difficult to achieve. The rapidly moving belt can keep a path clear, but when the electrode gap spacing d is set wide enough such that there is excess clearance, the action of the belt is insufficient to keep the electrodes clear. The adherence of a layer of material is also dependent upon a number of other factors having to do with the feed and the separator. For example, some layers can be held on only by electrostatic forces and brush off easily when the machine is opened up. Other layers can be hard and adherent and must be scraped off with a hard tool, or scrubbed off with a cleaning liquid. The influence of a layer of material on the separation efficiency is also dependent upon the materials being separated. For some materials a thin layer is of no consequence, while for others, a thin layer can be quite detrimental.

Accordingly, this invention provides improvements to the construction of belt type electrostatic separators, and provides for improved separation, including both higher levels of separation and improved recovery of the desired products. In addition, the separator is more amenable to adjustment of its performance and thus can respond to process upsets and changes in the feed material. Further, deterioration of performance of the separator between periodic maintenance is under better control, and the wear life of belts can be extended.

Thus, the belt-type separator of the present invention provides improved control of separator performance. In addition, it allows adjustment of separator while operating in response to variations in feed material, ambient humidity, belt wear, and changes in product specification. Further, it provides a reduced torque at start-up, and control of build up of layers of contamination on the electrodes and belts over time. Still further, the separator is easier to

maintain.

Having thus described several particular embodiments of the invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only and is limited only as defined in the following claims and the equivalents thereto.

What is claimed is: