Magnetic separation system and method for separating

Information

  • Patent Grant
  • 6832691
  • Patent Number
    6,832,691
  • Date Filed
    Friday, April 19, 2002
    22 years ago
  • Date Issued
    Tuesday, December 21, 2004
    20 years ago
Abstract
A magnetic separator system comprises a feed chute having an adjustable feed chute floor portion for controlling the release of discharge slurry from the feed chute onto a rotating magnetic drum separator. Adjusting the adjustable chute floor portion controls where discharge slurry released from the feed chute contacts the outer surface of the drum, allowing the contact point to be maintained for optimal separation simply through such adjustments. Precise control over flow of discharge slurry onto the drum notwithstanding variations in flow of discharge slurry permits the system to use an open construction, which is more compact and which reduces wear and abrasion and makes the system more accessible for repair. The field of attraction from magnets within the drum extends not only around the circumference of the drum, but also into the feed chute over the adjustable feed chute floor portion. This enables magnetic separation to take place in two phases: both while the discharge slurry is still flowing in the feed chute, and after the discharge slurry falls into contact with the drum. The drum is preferably covered by a replaceable protective lining constructed in segments that are easily installed and removed, but which overlap and interlock with one another to form a sealed protective lining.
Description




TECHNICAL FIELD




This application relates to a system for separating metallic contaminants from an ore slurry.




BACKGROUND




The mining industry utilizes various devices to separate valuable minerals from host contaminants after extraction from the earth. Initially, the ore preparation procedure involves crushing the run-of-mine rock from several feet in size down to approximately 1 to 3 inches. This preliminary crushing step is followed by one or more stages of grinding to reduce the ore to an average size of less than 1 millimeter. These latter grinding steps typically use large rotating cylindrical mills containing a charge of spherical steel balls that are used as a grinding media. The balls are in a constant tumbling motion due to the rotation of the mill. The ore is fed into one end of the mill, progresses through the grinding chamber, and is discharged from the opposite end. As the ore progresses through the mill, the grinding media impacts the material, resulting in fracture and breakage of the individual pieces into smaller and smaller particles.




The tumbling motion of the balls can also result in fracture of the balls themselves. Additionally, mechanical abrasion will wear the ball surface causing a reduction in size of the grinding media. The net results of this process are the generation of various shapes of steel which are significantly smaller than the original spherical balls, and the further contamination of the ore with metal fragments from the balls. Depending on the mill design, these fragments will discharge with the ground-up ore particles and flow to downstream equipment.




The ball fragments cause two distinct problems in ore processing facilities. The first is wear on subsequent equipment. Grinding is typically a wet process and the ore/water slurry is pumped between various unit operations. The metallic fragments cause significant wear on pumps, piping, and other downstream equipment. The costs associated with maintenance downtime and equipment repair/replacement can be substantial. Second, the ball fragments reduce the efficiency of the grinding mill itself. In most grinding operations, the balls and ball fragments that discharge from the grinding mill are returned to the grinding circuit with new ore feed. As a result, a substantial build-up of fragments can occur in the grinding mill occupying volume that would otherwise be filled by mineral slurry. This loss in active mill volume can decrease the mill capacity by a substantial amount. Furthermore, the small mass of the fragments does not provide a sufficient impact force to effectively fracture the mineral particles in the grinding mill.




U.S. Pat. No. 2,332,701 recognizes the problem represented by worn and fragmented grinding media in ball mills, and discloses a ball mill that continuously discharges grinding media with the ground material and returns to the feed end of the mill only that portion of the grinding media which is in good condition and of the correct size. A trommel screen sorts the output and an elevator conducts the useful grinding media back to the feed end of the mill. However, the trommel screen would not be able to separate out ball fragments smaller than the holes in the trommel screen, and the trommel screen cannot be made too fine or else it would become clogged by the ore slurry.




Recognizing the limitations of physical screening/separation, methods have been developed in the art for separating ferrous material from non-ferrous wet or dry materials using magnetic drum separators, which are well-known in the art. One of such methods is exemplified by U.S. Pat. No. 6,149,014, which discloses a top-fed, wet magnetic drum separator to remove metallic contaminants from the discharge slurry of an operating grinding mill. In the invention disclosed in U.S. Pat. No. 6,149,014, slurry discharging from the grinding mill enters an enclosed feed box located on top of the separator. The enclosed feed box provides a physical velocity break, minimizes turbulence, and then spreads the mineral slurry on the drum surface in a contained manner by means of a flexible “feed introducer” that extends from the feed box to actually engage the drum surface; the velocity break section is expressly required to be large enough to provide overflow of feed material. The feed box and drum surface are rubber-lined to minimize wear. Barrier walls attached to and rotatable with the drum surface contain the flow of slurry in conjunction with a sealed, curved, stationary cover located over the barrier walls to force slurry around the curvature of the drum, thereby maintaining the slurry in sufficient contact with the drum to enable magnetic separation to take place. Without the cover to contain it, the slurry would tend to be ejected from the enclosed feed box at a relatively high velocity with little contact with the drum surface and little opportunity for magnetic separation to take place. Once the cover forces the slurry into contact with the drum, a fixed magnet assembly arranged in an arc within the drum from approximately 26 to 218.5 degrees (pole center-to-center) starts attracting ferrous material within that slurry so as to begin the process of magnetic separation.




Further, U.S. Pat. No. 6,149,014 teaches the use of cleats on the drum surface to ensure transfer of metal fragments around the drum surface and discharge beyond the last pole. A partitioned product hopper is located around the lower portion of the separator, configured with a physical splitter positioned before the last pole to physically partition metallic fragments from the slurry. A drum spray bar is located beyond the last pole to remove solids that continue to adhere to the drum surface after the slurry and any metal fragments have fallen off, to prepare and clean the drum surface to receive further slurry from the feed box for separation.




The method and apparatus used in the U.S. Pat. No. 6,149,014 invention have a number of disadvantages:




(1) Expressly required by U.S. Pat. No. 6,149,014 is an enclosed discharge slurry feed box large enough to provide for overflow capacity and a velocity break section, resulting in unnecessary size and capacity to hold the tremendously large volumes of discharge slurry that are periodically generated during the grinding mill production cycle. The overflow capacity necessarily requires the feed box capacity be sufficiently large to accommodate maximum volume, which is wasteful, and thereby underutilizes that capacity at other times, necessarily making the U.S. Pat. No. 6,149,014 invention excessively large when space constraints are often a prevalent concern in or around grinding mills. This excess volume capacity and size, renders the invention less useful in many field applications without expensive retrofits.




(2) In the U.S. Pat. No. 6,149,014 invention, all of the discharge slurry is forced through an enclosed feed box and directly into a very confined conduit made up of the outer surface of the drum shell, the barrier walls, and the stationary cover. Therefore, the velocity break section in the feed box is essential to prevent the slurry from overwhelming the magnetic drum, there being no other means provided for this purpose. This necessarily increases the amount of wear and abrasion in the feed box, on the outer surface of the drum shell, on the barrier walls, and on the stationary cover used to guide the slurry around the curvature of the outer surface of the drum shell.




(3) In addition to the wear and abrasion created by the full volume and rate of flow emanating from the discharge slurry, the invention is a fully enclosed system that can generate head pressure within the confines of the internal vessels and greatly increases the risk of wear, abrasion, and internal damage.




(4) The U.S. Pat. No. 6,149,014 invention is fully enclosed, making it difficult to maintain and repair. Although it is internally lined with rubber to resist wear and abrasion, standard rubber lining is not designed for quick replacement and is not easily accessible without substantially dismantling the device. This is a costly and time-consuming problem, especially in the milling industry where long shutdowns for repair or replacement are extraordinarily expensive for milling operations.




(5) The system disclosed in U.S. Pat. No. 6,149,014 would not work if it were not fully enclosed. The stationary cover is required to contain the slurry against the outer surface of the drum; otherwise, any slurry being ejected from the enclosed feed box at high velocity or volume would not be kept within sufficient contact with the drum to enable magnetic separation to take place.




SUMMARY OF INVENTION




This invention provides a magnetic separator system comprising an open trunnion discharge feed chute and an open magnetic drum separator for separating ferrous material from a discharge slurry. In particular, a magnetic separation system according to the present invention comprises:




(1) a feed chute for receiving discharge slurry, the feed chute comprising walls and a feed chute floor, the feed chute floor having an adjustable feed chute floor portion for controlling the release of discharge slurry from the feed chute; and




(2) a magnetic drum separator comprising a drum rotatable about an axis below the feed chute, the drum having a generally cylindrical outer surface and having a fixed magnet assembly within that rotating outer surface.




By adjusting the adjustable chute floor portion, the user can control where discharge slurry released from the feed chute contacts the outer surface of the drum. Therefore, simply by adjusting the adjustable chute floor portion of the feed chute, the flow of discharge slurry can be made to contact the outer surface of the drum only at the optimal point of contact, and that optimal point of contact can be maintained in this same way, thereby compensating for variations in the flow of discharge slurry. This ability to control with precision the flow of discharge slurry onto the outer surface of the drum permits the system to use an open construction, rather than an enclosed construction as required in prior art system to force discharge slurry into contact with the drum. This open construction not only reduces wear and tear given that discharge slurry is no longer being forced through physical enclosures, but the open construction also provides greater ease of accessibility for repair and replacement where needed. Further, the open feed chute eliminates the need for an unnecessarily large feed box with a separate overflow section, so the magnetic separation system of this invention can be of a more compact construction. Also, a physical velocity break is no longer necessary since this invention already compensates for variations in flow of discharge slurry.




In operation, a method of removing ferrous material from a discharge slurry flow according to this invention comprises:




(1) discharging discharge slurry into the feed chute described above;




(2) releasing the discharge slurry from the feed chute onto the outer surface of the rotating drum described above;




(3) rotating said outer surface of the drum in the direction of the flow of said discharge slurry;




(4) adjusting the adjustable feed chute floor portion so as to maintain, at a predetermined point, the area at which discharge slurry released from the feed chute contacts the outer surface of the drum;




(5) separating ferrous material from the discharge slurry by magnetically attracting ferrous material to the drum while allowing non-ferrous discharge slurry to flow past and off the drum; and




(6) conveying ferrous material away from the non-ferrous discharge slurry and then discharging the ferrous material from the drum at a different location.




The radial field of magnetic attraction provided by the fixed magnet assembly preferably extends not just around the circumference of the drum, but also into the feed chute over the adjustable feed chute floor portion. This enables magnetic separation to take place in two phases: the first phase taking place while the discharge slurry is still flowing in the feed chute, and the second phase taking place after the discharge slurry falls into contact with the outer surface of the drum.




Preferably, the drum is covered by a replaceable protective lining constructed in segments that are easily installed and removed, but which overlap and interlock with one another to form a sealed protective lining. The segments are all preferably constructed of a non-ferrous elastomeric material. The outer surface of the drum also preferably has a plurality of cleats to assist the transfer of ferrous material around that outer surface. The cleats are preferably strengthened by a metallic bar through the length of each cleat.




An electronically-controlled adjuster can be programmed to automatically adjust the adjustable feed chute floor portion in response to variations in flow of discharge slurry. Further, a variable speed motor can be used to rotate the drum, varying the speed of rotation in response to variations in the flow of discharge slurry. This would not have been effective in respect of prior art enclosed systems, since increasing the speed of rotation would simply create more pressure within the physical enclosures and cause more wear and abrasion.











BRIEF DESCRIPTION OF DRAWINGS





FIG. 1

is a cross-sectional side view showing a magnetic separation system according to the invention, comprising an open trunnion discharge feed chute and a magnetic drum separator.





FIG. 2

is a top perspective, partially cut-away view of the magnetic separation system of FIG.


1


.





FIG. 3

is an exploded top perspective, partially cut-away view of the magnetic separation system of FIG.


2


.





FIG. 4

is a top plan view of the feed chute portion of the magnetic separation system.





FIG. 5

is a cross-sectional side view of an adjustable flow plate forming a portion of the floor of the feed chute, showing said adjustable flow plate in a position fully extended from its flow plate housing so as to permit replacement of that adjustable flow plate.





FIG. 6

is a cross-sectional side view of the adjustable flow plate in an operating position.





FIG. 7

is a top plan view of the fully extended adjustable flow plate of FIG.


5


.





FIG. 8

is a schematic cross-sectional side view of the magnetic drum separator portion of the magnetic separation system.





FIG. 9

is an exploded perspective view of the magnetic drum separator.





FIG. 10

is a schematic perspective side view of the outer shell and protective drum liner of the magnetic drum separator.





FIG. 11

is a close-up, schematic perspective side view of a portion of the outer shell of the magnetic drum separator showing how two adjacent liner segments overlap, interlock, and seal.





FIG. 12

is a front elevation view and partially cross-sectional side view of a protective sidewall liner for an end plate of the magnetic drum separator.











DESCRIPTION




Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.




As illustrated in

FIGS. 1

,


2


, and


3


, a magnetic separator system according to the invention comprises an open trunnion discharge feed chute


1


and a magnetic drum separator


11


for separating ferrous material


17


from a discharge slurry


12


. Discharge slurry


12


comprises ferrous material


17


, crushed ore, and water. Ferrous material


17


comprises worn grinding media chips and other ferrous particles.




Trunnion Discharge Feed Chute




Referring to

FIGS. 1

,


2


,


3


,


4


, and


6


, feed chute


1


comprises two chute walls


2


, a rear backwash retainer


3


, and a chute floor


4


. Structural cross supports


30


connect chute walls


2


above chute floor


4


, and an optional rubber damper curtain


31


is suspended from each structural cross support


30


. Chute floor


4


in turn comprises:




(1) a fixed floor segment


4




a;






(2) a replaceable, ferrous, abrasion-resistant floor wear plate


4




b;


and




(3) an adjustable flow plate


4




c


retractable into a flow plate housing


6


below floor wear plate


4




b.






As shown in

FIGS. 3

,


5


, and


6


, adjustable flow plate


4




c


retracts into a flow plate housing


6


. In particular, adjustable flow plate


4




c


retracts into a recessed area


6




a


of flow plate housing


6


. Flow plate housing


6


is attached to fixed floor segment


4




a


such that the upper surface


6




b


of flow plate housing


6


is flush with and contiguous to the upper surface of fixed floor segment


4




a


. Floor wear plate


4




b


is then attached above fixed floor segment


4




a


and upper surface


6




b


. The result is a relatively smooth chute floor


4


with a very mild downward slope (approximately 2% to 3%) from backwash retainer


3


to the leading edge


10


of adjustable flow plate


4




c


. Floor wear plate


4




b


may be attached to fixed floor segment


4




a


and upper surface


6




b


by various means, but preferably by the use of a magnetic wear plate retainer


7


such as that taught in U.S. Pat. No. 6,303,241. Where floor wear plate


4




b


is attached to fixed floor segment


4




a


and upper surface


6




b


by magnetic means such as wear plate retainer


7


, then preferably, as shown in

FIGS. 3

,


5


, and


6


, a wear plate stop


6




c


extends upwardly from the outer edge of upper surface


6




b


to further prevent any horizontal movement or slippage in floor wear plate


4




b


. A rubber wiper


14


extends outwardly from wear plate stop


6




c


and downward toward adjustable flow plate


4




c


in order to provide a smooth transition from floor wear plate


4




b


to adjustable flow plate


4




c


for discharge slurry


12


. In the top plan view of feed chute


1


illustrated in

FIG. 4

, the area in fine crosshatching represents floor wear plate


4




b


, and the large superimposed single cross represents that portion of floor wear plate


4




b


covering upper surface


6




b


of flow plate housing


6


.




Adjustable flow plate


4




c


should be comprised of a non-ferrous abrasion-resistant wear plate or a non-ferrous elastomer, the preferred embodiment being an 80A durometer polyurethane (such as Uniroyal Vibrathane™ 8083). Adjustable flow plate


4




c


extends outward from or retracts inward into flow plate housing


6


to permit the length of chute floor


4


along the bottom of feed chute


1


to be adjusted. Adjustable flow plate


4




c


may be actuated inward or outward by means of actuators


5


located beneath chute floor


4


. In

FIGS. 1

,


5


, and


6


, actuators


5


are depicted as synchronized ball-screw actuators, but actuators


5


can take the form of any suitable actuators, including mechanical, electric, pneumatic, or hydraulic actuators.




Referring to

FIGS. 5 and 6

, adjustable flow plate


4




c


preferably comprises three components:




(1) the lower surface being a non-ferrous steel structural supporting plate


8




a;






(2) the upper surface being a replaceable non-ferrous wear surface


8




b;


and




(3) the leading edge


10


of adjustable flow plate


4




c


comprising a highly wear-resistant, non-ferrous ceramic material forming a ceramic leading edge


8




c.






Wear surface


8




b


may be attached to support plate


8




a


by any suitable means, including by means of stainless steel countersunk fastening screws


8




d


as illustrated in

FIGS. 5 and 6

. Wear surface


8




b


may be comprised of a non-ferrous abrasion-resistant wear plate or a non-ferrous abrasion-resistant elastomer such as a polyurethane. Wear surface


8




b


in its preferred embodiment is comprised of a highly abrasion-resistant 80A durometer polyurethane material (Uniroyal Vibrathane™ 8083), but could be comprised of any number of other non-ferrous elastomeric, metallic or composite materials, including ceramic or non-ferrous steel, to enhance the non-abrasive properties of wear surface


8




b.


Although wear surface


8




b


is highly abrasive-resistant on its own, the embedding of ceramic leading edge


8




c


is a preferred embodiment, by reason of the increased longevity offered by the even more abrasion-resistant protection provided by ceramic leading edge


8




c.






Wear surface


8




b


should be a non-ferrous material to ensure that there is no interference with the magnetic field configuration generated by magnetic drum separator


11


, which, as explained in detail below, extends upwardly from magnetic drum separator


11


to affect discharge slurry


12


even as it flows over adjustable flow plate


4




c


. Ceramic leading edge


8




c


and fastening screws


8




d


should be non-ferrous for the same reason.




For ease of replacement of wear surface


8




b


, adjustable flow plate


4




c


is preferably fully extendable outward from flow plate housing


6


such that the entirety of wear surface


8




b


is extendable beyond rubber wiper


14


for ease of access to fastening screws


8




d


. This is illustrated in

FIG. 5

, where actuators


5


are fully extended in order to extend wear surface


8




b


beyond rubber wiper


14


. While adjustable flow plate


4




c


is fully extended as shown in

FIG. 5

, wear surface


8




b


is easily removed from supporting plate


8




a


by unscrewing fastening screws


8




d


. A new replaceable wear surface


8




b


can then be fitted into place and re-fastened using fastening screws


8




d


. Adjustable flow plate


4




c


can then be retracted inwardly into flow plate housing


6


to an operating position as shown in FIG.


6


. In its operating position, wear surface


8




b


is partially retracted under upper surface


6




b


of flow plate housing


6


, and fastening screws


8




d


are protected from exposure to the abrasive effects of discharge slurry


12


. As illustrated in

FIG. 6

, the surface seal offered by rubber wiper


14


prevents discharge slurry


12


, which is flowing in direction


13


, from flowing backwards into recessed area


6




a


of flow plate housing


6


.




Magnetic Drum Separator




Referring to

FIGS. 1

,


2


,


3


, and


9


, magnetic drum separator


11


comprises a magnetic drum


16


rotatable in direction


27


about a drum shaft


29


supported for axial rotation below feed chute


1


. As shown in

FIG. 9

, an end plate


25


is inserted onto drum shaft


29


at each of the two ends of magnetic drum


16


and attached in place by any suitable means. End plates


25


serve as barrier walls to prevent discharge slurry


12


or ferrous material


17


from spilling over the sides of magnetic drum


16


. Otherwise, magnetic drum


16


is completely unenclosed. In particular, there is no cover element that physically forces discharge slurry


12


into contact with magnetic drum


16


. There is also no “feed introducer” or any other flexible element that extends from feed chute


1


into physical engagement with magnetic drum


16


to physically force discharge slurry onto magnetic drum


16


.




Within magnetic drum


16


are one or more magnetic elements


16




a


comprising either ferrite or rare-earth magnetic material or a combination thereof. Referring to

FIGS. 1

,


3


, and


8


, magnetic elements


16




a


are arranged within magnetic drum


16


in an arc from approximately negative 25 degrees (measured relative to the “12:00 o'clock” dead center position at the top of magnetic drum


16


, and measured in rotation direction


27


) to positive 215 degrees, providing a 240-degree radial field of magnetic attraction


18


about the circumference of magnetic drum


16


. Referring to

FIG. 8

, the initial negative 25 degrees from the 12:00 o'clock dead center portion of the 240 degree radial field of magnetic attraction


18


is an important advance over the prior art, by reason that it permits field of magnetic attraction


18


to extend over a portion of chute floor


4


, namely adjustable flow plate


4




c


. In the known prior art, the magnetic field of attraction was designed to commence only at or near the point where the discharge slurry first contacts the magnetic drum. In the present invention, however, the field of magnetic attraction


18


emanating from magnetic drum separator


11


operates not only on ferrous material


17


after discharge slurry


12


falls from feed chute


1


into contact with the outer drum surface


11




a


of magnetic drum separator


11


, but it also operates on ferrous material


17


even while discharge slurry


12


is still flowing within feed chute


1


over adjustable flow plate


4




c


. This feature is explained in more detail below.




Referring to

FIGS. 1

,


3


, and


9


, magnetic drum


16


has an outer shell


15


from which outwardly extends a plurality of cleats


20


. Cleats


20


constitute a reliable means of ensuring ferrous material


17


is forced along the outer surface


11




a


of magnetic drum separator


11


as magnetic drum


16


rotates in direction


27


. Each of cleats


20


is preferably at least one inch high, and made of wear-resistant material. Also, in order for magnetic drum separator


11


to function properly and effectively, each of cleats


20


should be composed of a non-ferrous material to avoid interference with the field of magnetic attraction


18


generated by magnetic drum separator


11


.




In a preferred embodiment of this invention, cleats


20


are integrated into a replaceable abrasion-resistant outer drum liner


15




a


covering outer drum shell


15


. In a particularly preferred embodiment illustrated in

FIG. 10

, outer drum liner


15




a


comprises a plurality of replaceable non-ferrous curved liner segments


21


each having a cleat


20


as an integral part thereof along one straight edge thereof, which plurality of liner segments


21


together overlap and interlock to form outer drum liner


15




a


, each cleat


20


acting as a seal between adjacent liner segments


21


by overlapping a cleat joint edge


20




a


of the adjoining liner segment


21


. Liner segments


21


are preferably equal in size, for interchangeability and ease of replacement as well as for more effective movement of ferrous material


17


along outer drum surface


11




a


. Accordingly, the present invention utilizes cleats


20


not only to achieve the well-known function of forcing ferrous material


17


along outer drum surface


11




a


, but also to produce a novel overlapping seal between the plurality of liner segments


21


that together form outer drum liner


15




a


, as best illustrated in

FIGS. 10 and 11

.




Referring to

FIGS. 9 and 12

, each end plate


25


preferably also has a protective liner in the form of a non-ferrous replaceable abrasion-resistant sidewall liner


22


. Each sidewall liner


22


is preferably of a two-piece construction for ease of replacement and designed for overlapping, interlocking, sealing fit with outer drum liner


15




a


. As shown in

FIGS. 10 and 11

, each liner segment


21


has a recess


21




a


at each of its ends for receiving a corresponding edge of sidewall liner


22


. In this regard, as shown in

FIG. 12

, each sidewall liner


22


has a corresponding keyed edge


22




a


for an overlapping, interlocking, sealing fit with a corresponding recess


21




a


of a liner segment


21


. Each sidewall liner


22


also has a recess


22




b


for interlocking fit and seal with each of the plurality of cleats


20


. Sidewall liners


22


are attached to end plates


25


by means of fasteners


24


or other suitable means. By way of example, in

FIG. 9

, fasteners


24


are depicted as stainless steel fastening screws, although other known fastening means will work as well.




The combination of all surface liner segments


21


and sidewall liners


22


joined together at the respective sealed joints form a non-ferrous abrasion-resistant replaceable lining


23


for the entire magnetic drum separator


11


. Although the components of separator lining


23


, namely liner segments


21


and sidewall liners


22


, may be comprised of either a non-ferrous metallic alloy material or an elastomeric material, the preferred embodiment is a non-ferrous highly abrasion-resistant elastomeric material such as an 80A durometer polyurethane material (Uniroyal Vibrathane™ 8083), which can also be impregnated with ceramic or other highly abrasion-resistant materials into the elastomeric host material for even greater abrasion-resistant capability. Prior art magnetic drum separators are usually lined with a non-ferrous metal such as stainless steel, although U.S. Pat. No. 6,149,014 discloses a rubber lining.




This invention provides a novel overlapping and interlocking arrangement between the various components forming the separator lining


23


, which allows the advantages of ease of installation and removal of the component parts for repair and replacement, while maintaining a secure fit and strong protective seal against the highly abrasive discharge slurry


12


during operation. In addition to the novel overlapping and interlocking arrangement between the plurality of surface liner segments


21


and sidewall liners


22


forming a secure fit and protective seal between the components of separator lining


23


, recesses


22




b


at the base of sidewall liners


22


, corresponding to and receiving the protruding ends of cleats


20


, further anchor and strengthen both cleats


20


and the entire separator lining


23


simultaneously. Although there are many means or methods of overlapping and interlocking independent surface segments, the design depicted in

FIGS. 9

,


10


,


11


, and


12


for separator lining


23


is the preferred embodiment, as it combines ease of assembly for onsite field installations with structural strength of overlapping and interlocking joints. This serves to seal the joints between liner segments


21


and sidewall liners


22


to protect the underlying surface of outer drum shell


15


from exposure to the highly abrasive discharge slurry


12


. The overlapping and interlocking surface segments comprising separator lining


23


act to seal the joints between liner segments


21


and sidewall liners


22


, but for added sealing capabilities, a urethane sealing agent can easily be introduced at these points during assembly and change-out, where the field application necessitates it.




In addition to the strength offered by the overlapping and interlocking joints of liner segments


21


, particularly at cleats


20


, the preferred embodiment of the invention includes a further strengthening device in the form of a non-ferrous metallic bar


28


within each cleat


20


, as shown in

FIGS. 9

,


10


, and


11


. Metallic bar


28


can be made of stainless steel or a non-ferrous alloy shaped as a round or rectangular bar. Metallic bar


28


is embedded into and runs the entire length of each cleat


20


. At each end of each metallic bar


28


is preferably a threaded insert


26




a


into which a fastener


26


can be threaded to securely attach each liner segment


21


to end plates


25


. Fasteners


26


can, for example, be stainless steel fastening screws that screw through holes in end plates


25


into threaded inserts


26




a


, and securely fasten the ends of cleats


20


into corresponding recesses


22




b


. The extremely high volume and rate of flow of discharge slurry


12


from most medium and large-sized grinding mills place tremendous flow force on the outer drum surface


11




a


, and particularly at cleats


20


, which constitutes the area of greatest loading of the massive volume and weight of discharge slurry


12


. Metallic bars


28


assist in maintaining the strength, shape and structured integrity of outer drum liner


15




a


, especially at cleats


20


.




The components of a magnetic separation system according to the present invention are designed for ease of field maintenance, and to allow quick and easy replacement of all worn, abraded, or damaged surfaces during change-out procedures. The assembly of components constituting separator lining


23


is specifically designed with this purpose in mind. The assembly or change-out procedures contemplated in the design of this invention allows quick and easy removal and replacement of liner segments


21


and sidewall liners


22


, using rudimentary hand tools (such as a crescent wrench, ratchet wrench, and/or pry-bar), in limited working space, as is often the case in field change-out situations.




Referring to

FIGS. 9

,


10


,


11


, and


12


, the ease of installation and change-out procedures embodied in the design of the invention is achieved by the following simple disassembly steps:




(1) To remove the sidewall liners


22


, unfasten fasteners


24


, and then simply lift out each piece of the two-piece sidewall liners


22


.




(2) To remove the plurality of liner segments


21


, unfasten the corresponding fasteners


26


and then simply lift out each liner segment


21


, each liner segment


21


having a cleat


20


attached along one edge.




(3) The components can be inspected on site, and those not requiring replacement can be reinstalled along with the replacement components.




This invention is designed to allow the various component parts of magnetic drum separator


11


, and especially the various surface components of separator lining


23


to be simply, easily, and quickly removed and replaced whether due to abrasion, wear, or damage in the field, on site, and even in difficult, constrained and especially inaccessible settings with only a few rudimentary hand tools. These advantages in the design of the magnetic separation system according to the invention are not demonstrated in the prior art, and provide the grinding mill operator with a convenient and cost-effective labour-saving and time-saving method to remove and replace worn or damaged parts in both unanticipated breakdown or shutdown situations, as well as routine planned change-out situations.




The replacement of the various components of separator liner


23


is essentially the reversal of the disassembly procedures:




(1) Each liner segment


21


is fitted onto magnetic drum


16


as illustrated in

FIGS. 10 and 11

. Care must be taken to ensure the liner segments


21


are installed in the correct orientation, which is with the cleat joint edge


20




a


being on the leading edge of each cleat


20


in the same direction


27


as magnetic drum


16


rotates, thereby better protecting cleat joint edge


20




a


from discharge slurry


12


. Referring to

FIGS. 1

,


2


, and


10


, discharge slurry


12


flows in direction


13


, which results in it discharging from feed chute


1


onto outer drum surface


11




a


as magnetic drum


16


rotates in a direction


27


that is the same as direction


13


. Having joint edge


20




a


on the leading edge of cleats


20


as magnetic drum rotates in direction


27


minimizes the abrasion or wear exposure to each cleat joint edge


20




a.






(2) Once the plurality of liner segments


21


is installed in place, sidewall liners


22


are fitted into place over end plates


25


. The relative softness and pliable nature of the polyurethane sidewall liners


22


and the polyurethane liner segments


21


allow all surface segments to be easily fitted together to form the tightly sealed joints of separator lining


23


.




(3) Referring to

FIG. 9

, in order to firmly secure the fitted surface segments, fasteners


24


secure sidewall liners


22


in place. Then the ends of cleats


20


are fitted into corresponding recesses


22




b


, and fasteners


26


are tightened. This step seals the overlapping and interlocking joints in separator lining


23


. Where desirable, a polyurethane bonding agent can be easily applied on site installations, to increase the bonding and sealing capacity of the joints.




(4) The process of fastening sidewall liners


22


and the ends of cleats


20


into corresponding recesses


22




b


with fasteners


26


eliminates any gap and improves the seal between outer drum liner


15




a


and sidewall liners


22


.




Operation of Magnetic Separation System




Feed chute


1


and magnetic drum separator


11


interact so as to provide an improved system for magnetically separating ferrous material


17


from discharge slurry


12


. Referring to

FIGS. 1 and 2

, as discharge slurry


12


exits the grinding mill (not shown) through discharge outlet


9


, the rate of flow of discharge slurry


12


can vary greatly with production variables such as: (a) the speed of rotation of the grinding mill; (b) the rate of throughput of ore; (c) the volume capacity of the grinding mill's interior, which varies as a function of the amount of grinding media introduced and removed as well as the degree of wear of the grinding mill liner; (d) the volume of water introduced to create the slurry; and (e) the coarse grade mesh of the mill trunnion discharge cover screen (not shown) located at discharge outlet


9


. The variability of the flow of discharge slurry


12


over the production cycle of the grinding mill is an important factor for determining the optimal design of an efficient magnetic drum separator system. Referring to

FIGS. 1 and 2

, at least the following three objectives are addressed by the present invention in achieving optimal efficiency in transferring discharge slurry


12


to the exposed outer drum surface


11




a


of magnetic drum separator


11


:




(1) the system will cause ferrous material


17


to tend to settle to chute floor


4


, resulting in closer proximity to magnetic drum separator


11


and thereby enhancing the ability of magnetic drum separator


11


to attract ferrous material


17


to wear surface


8




b


of adjustable flow plate


4




c


, and in turn to outer drum surface


11




a


of magnetic drum separator


11


;




(2) the system ensures an even distribution of discharge slurry


12


over outer drum surface


11




a


of magnetic drum separator


11


; and




(3) the system allows discharge slurry


12


to contact outer drum surface


11




a


of magnetic drum separator


11


at the optimal point of contact, and remains there, so as to achieve maximum magnetic attraction and adhesion of ferrous material


17


to outer drum surface


11




a


of magnetic drum separator


11


.




In

FIG. 1

, discharge slurry


12


is discharged from the grinding mill (not shown) through discharge outlet


9


into feed chute


1


, and flows in direction


13


by reason of the combination of the discharge flow pressure generated by the milling process, and the mild (2% to 3%) downward slope of chute floor


4


. The effect of gravity and the flow of discharge slurry


12


down feed chute


1


has the natural effect of helping ferrous material


17


settle to feed chute floor


4


and distributing discharge slurry


12


relatively evenly over the entire surface of chute floor


4


as discharge slurry


12


is contained between chute walls


2


. Damper curtains


31


also assist in guiding discharge slurry


12


downward toward chute floor


4


. This in turn contributes to a relatively even distribution of discharge slurry


12


flowing from leading edge


10


of feed chute


1


to outer drum surface


11




a


of magnetic drum separator


11


, although, in the absence of any movement of adjustable flow plate


4




c


, the precise point on outer drum surface


11




a


at which falling discharge slurry


12


initially contacts magnetic drum separator


11


may still vary depending on the velocity and volume of the flow of discharge slurry


12


as it leaves leading edge


10


.




In particular, referring to

FIGS. 1 and 8

, significant variability in flow rate and volume of discharge slurry


12


causes discharge slurry


12


to leave leading edge


10


of feed chute


1


at varying rates and volumes, and in turn, causes corresponding variations as to where discharge slurry


12


first contacts outer drum surface


11




a


of magnetic drum separator


11


since this is an open system having no cover or other enclosure, and no “feed introducer” extending from feed chute


1


into engagement with outer drum surface


11




a


, to force discharge slurry


12


against outer drum surface


11




a


by deflection or other physical means. Therefore, if discharge slurry


12


leaves leading edge


10


at a low velocity or volume, the initial magnetic contact area


11




b


will likely tend to be in a higher portion of outer drum surface


11




a


. However, if discharge slurry


12


leaves leading edge


10


at a high velocity or volume, initial magnetic contact area


11




b


will likely tend to be in the middle portion of outer drum surface


11




a


or will not contact outer drum surface


11




a


at all. The fact that variations in rate and volume of flow of discharge slurry


12


results in corresponding variations in initial magnetic contact area


11




b


creates a challenge in that the optimum level of magnetic separation efficiency achieved from magnetic drum separator


11


cannot be maintained as long as these flow variations occur, without concurrently adjusting initial magnetic contact area


11




b.






This invention overcomes that problem by allowing initial magnetic contact area


11




b


to be varied in response to variations in the volume and flow of discharge slurry


12


so as to continually ensure initial magnetic contact area


11




b


of discharge slurry


12


achieves the maximum magnetic attraction and adhesion of ferrous material


17


. Referring to

FIG. 8

, a magnetic separation system according to this invention allows initial magnetic contact area


11




b


to be adjusted to always coincide with an optimal initial contact area


11




c


simply by adjusting the extension of adjustable flow plate


4




c


to compensate for variations in the volume and flow of discharge slurry


12


. As can be seen from

FIGS. 1 and 8

, changing the length of extension of adjustable flow plate


4




c


in turn will tend to change the position of initial magnetic contact area


11




b


. If discharge slurry


12


is flowing at a relatively high volume or velocity, causing discharge slurry


12


to contact outer drum surface


11




a


at an initial magnetic contact area


11




b


that is beyond optimal initial contact area


11




c


, then adjustable flow plate


4




c


can simply be retracted inward into recessed area


6




a


until initial magnetic contact area


11




b


once again coincides with optimal initial contact area


11




c.


On the other hand, if discharge slurry


12


is flowing at a relatively low volume or velocity, causing discharge slurry


12


to contact outer drum surface


11




a


at an initial magnetic contact area


11




b


that is short of optimal initial contact area


11




c


, then adjustable flow plate


4




c


can simply be extended outward from recessed area


6




a


until initial magnetic contact area


11




b


once again coincides with optimal initial contact area


11




c.






Referring to

FIGS. 1 and 8

, a magnetic separation system according to the present invention preferably utilizes the following two-phase magnetic separation process, both phases affected by adjustments in adjustable flow plate


4




c:






(1) in the first phase, a field of magnetic attraction


18


emanates from magnetic drum


16


over adjustable flow plate


4




c


to create an adjustable area of “primary” magnetic attraction within feed chute


1


, so that the magnetic separation process commences even before discharge slurry


12


leaves feed chute


1


and comes into contact outer drum surface


11




a


; and




(2) in the second phase, the same radial field of magnetic attraction


18


creates an adjustable area of “secondary” magnetic attraction on outer drum surface


11




a


between adjustable initial magnetic contact area


11




b


and a discharge point


32


where ferrous material


17


leaves magnetic drum


16


and falls into a discharge chute


33


.




Both the “primary” and “secondary” areas of magnetic attraction are adjustable because both are affected by adjustments in adjustable flow plate


4




c


. The field of magnetic attraction


18


operating over the upper surface area of adjustable flow plate


4




c


between points


18




a


and


18




b


in

FIG. 8

, causes ferrous material


17


to be magnetically attracted to the upper surface of adjustable flow plate


4




c


, while the non-ferrous ore slurry


34


continues to flow at the same rate as discharge slurry


12


did immediately prior to reaching the adjustable area of primary magnetic attraction between points


18




a


and


18




b


. The difference in the inertia of non-ferrous ore slurry


34


and the magnetically-attracted ferrous material


17


further promotes the separation process between the materials.




The adjustable area of primary magnetic attraction between points


18




b


and


18




a


therefore simultaneously attracts and slows down the rate of flow of ferrous material


17


, thereby assisting with the separation process as discharge slurry


12


and ferrous material


17


reach the adjustable area of secondary magnetic attraction between points


19




b


and


19




a


on outer drum surface


11




a


. Adjustable flow plate


4




c


is positioned to achieve the maximum magnetic attraction and adhesion between ferrous material


17


and outer drum surface


11




a


, and to maintain the optimal area of initial magnetic contact


11




c


shown in FIG.


8


. The primary magnetic attraction stage is functionally dependent on the secondary magnetic separation stage since adjustable flow plate


4




c


simultaneously controls both the adjustable area of primary magnetic attraction between points


18




a


and


18




b


, as well as the initial magnetic contact area


11




b


for discharge slurry


12


on outer drum surface


11




a


in the adjustable area of secondary magnetic attraction between points


19




a


to


19




b.






The method employed by the invention whereby the primary magnetic attraction phase and the secondary separation phase are adjusted to maintain the optimal initial contact area


11




c


, as the rate or volume of the flow of discharge slurry


12


varies over the grinding mill production cycle, is as follows:




(1) As the flow of discharge slurry


12


decreases, so does the velocity of discharge slurry


12


leaving feed chute


1


. Adjustable flow plate


4




c


is extended outward to reduce the volume of discharge slurry


12


on outer drum surface


11




a


, therefore reducing unnecessary wear on outer drum liner


15




a


. At the same time, extending adjustable flow plate


4




c


increases the adjustable area of primary magnetic attraction between points


18




b


and


18




a


in

FIG. 8

up to a range approaching the full 25 degrees, and therefore more magnetic separation can take place over adjustable flow plate


4




c


during this first phase before discharge slurry


12


even leaves feed chute


1


. Further, by adjusting adjustable flow plate


4




c


, ferrous material


17


can be optimally positioned to be fed onto outer drum surface


11




a


at the optimal initial contact area


11




c


and maintained there to improve the second phase of magnetic separation.




(2) Where there is an increasingly large volume or high rate of flow of discharge slurry


12


, adjustable flow plate


4




c


is retracted inward, thus allowing the larger volume or higher velocity of discharge slurry


12


to be more extensively exposed to outer drum surface


11




a


, therefore greatly increasing the extent of magnetic attraction and adhesion operating on discharge slurry


12


as the adjustable area of secondary magnetic attraction between points


19




b


and


19




a


in

FIG. 8

is increased from 215 degrees to approach the full 240 degrees along outer drum surface


11




a.






(3) Effective and efficient extraction and separation of ferrous material


17


from discharge slurry


12


is accomplished by utilizing feed chute


1


as explained above. Adjustable flow plate


4




c


, the primary magnetic separation process, and the secondary magnetic separation process according to this invention achieve the objectives mentioned above as being desirable for magnetic separation by:




(a) evenly distributing discharge slurry


12


over chute floor


4


, and over outer drum surface


11




a;






(b) slowing down the velocity of ferrous material


17


by attracting it to wear surface


8




b


of adjustable flow plate


4




c


, while allowing non-ferrous ore slurry


34


to continue to flow at the same velocity as discharge slurry


12


did prior to reaching the adjustable area of primary magnetic attraction between points


18




b


and


18




a


in

FIG. 8

, thus effecting a primary magnetic separation process even before discharge slurry


12


ever contacts magnetic drum


16


, and all without a physical velocity break for discharge slurry


12


since it is preferable for non-ferrous ore slurry


34


to continue at the same velocity while only ferrous material


17


slows down;




(c) completing the separation of ferrous material


17


from non-ferrous ore slurry


34


through the secondary separation process where ferrous material


17


is attracted and adhered to the more powerful magnetic force exerted by direct contact between ferrous material


17


and outer drum surface


11




a


in the adjustable area of secondary magnetic attraction between points


19




b


and


19




a;






(d) causing all ferrous material


17


to be exposed to a large area of magnetic force, which ensures that ferrous material


17


will be separated from non-ferrous ore slurry


34


;




(e) referring to

FIG. 1

, allowing non-ferrous ore slurry


34


to continue forward through gravity and momentum in the direction


13


of discharge slurry


12


as it is discharged from leading edge


10


of adjustable flow plate


4




c


, the forward inertia of non-ferrous ore slurry


34


not being affected by the magnetic force operating on ferrous material


17


, such that non-ferrous ore slurry


34


will fall into a catchment area (not shown) free of ferrous material


17


and ready for further processing in the mill cycle;




(f) referring to

FIG. 1

, using a spray applicator


35


to spray ferrous material


17


with water, preferably while ferrous material


17


is still rotating through the adjustable area of secondary magnetic attraction between points


19




b


and


19




a;


and




(g) continuing to rotate magnetic drum


16


so that ferrous material


17


retained on outer drum surface


11




a


by the radial field of magnetic attraction


18


and by cleats


20


rotates through the adjustable area of secondary magnetic attraction between points


19




b


and


19




a


until the radial field of magnetic attraction


18


ends at discharge point


32


, whereupon gravity operates to cause ferrous material


17


to fall into discharge chute


33


.




(iv) The invention achieves the combined objectives of maximizing the efficient separation of ferrous material


17


from discharge slurry


12


, while minimizing the costs of wear and tear on the invention apparatus through the separation process. This is achieved by adjusting the exposure of outer drum surface


11




a


to the highly abrasive discharge slurry


12


in order to minimize the wear and abrasion caused by the significant variations in the volume and rate of flow of discharge slurry


12


during the production cycle of the grinding mill. The invention exposes only outer drum liner


15




a


to the full flow of the abrasive discharge slurry


12


when the rate and volume of flow is at the highest levels, and thereby necessitates the maximum level of magnetic force to be exerted by magnetic drum separator


11


, which is achieved by exposing ferrous material


17


to the maximum surface area of outer drum liner


15




a


. At other periods in the grinding mill production cycle when the rate and volume of flow is less, then less magnetic force is required for the separation process, and less exposure of outer drum surface


11




a


to the abrasive discharge slurry


12


is necessary.




(v) The invention design achieves efficient separation over the life of the grinding mill production cycle by adjusting to significant variations in the volume and rate of flow of discharge slurry


12


, while also promoting conservation of its wear surfaces and extension of its production life cycle by minimizing exposure of outer drum surface


11




a


to the highly abrasive effects of discharge slurry


12


.




Further, the present invention overcomes many of the costly and inconvenient design characteristics of the prior art, including the following:




(1) The invention eliminates the enclosed feed box, and instead uses an open trunnion discharge feed chute


1


from discharge outlet


9


to leading edge


10


of an adjustable flow plate


4




c.






(2) As the entire separation process of the invention is designed in an open feed chute layout, it is very accessible for repair, replacement, and change-out.




(3) To further facilitate repair, replacement, and change-out, the wear surfaces have all been designed for quick change-out. This is achieved by using magnetic wear plate retainer


7


to fasten floor wear plate


4




b


, as well as the quick change-out design of adjustable flow plate


4




c


and the various surface components of lining


23


.




(4) Adjustable flow plate


4




c


eliminates the need for:




(a) an overflow capacity area in the feed box;




(b) an abrasion-susceptible velocity break; or




(c) a stationary cover for forcing all of discharge slurry


12


against the outer drum surface of outer drum surface


11




a


, as per U.S. Pat. No. 6,149,014 (which is susceptible to heavy abrasion and possibly head pressure build-up).




(5) The invention is more compact than the prior art in size and potentially more adaptable to constrained space applications often prevalent in existing grinding mill industry plant sites.




(6) There is much less risk of damage, wear, and abrasion in the present invention compared to prior art by the nature of the open trunnion discharge design of feed chute


1


, since there is less of outer drum surface


11




a


necessarily in contact with the abrasive discharge slurry


12


, and no risk of head pressure build-up.




(7) The present invention is very accessible for quick on-the-job repairs or removal and replacement of parts with minimal or no down time to the grinding mill production process.




(8) The invention is designed for the operator to adjust the magnetic drum separation process in response to variable flow of discharge slurry


12


volumes and/or velocity with a simple control command that extends or retracts adjustable flow plate


4




c


to attain the optimal initial contact area


11




c


of flow of discharge slurry


12


and the external surface of outer drum liner


15




a


. This in turn, maximizes the magnetic attraction and adhesion capability of magnetic drum separator


11


in separating ferrous material


17


from non-ferrous ore slurry


34


.




Of course, an electronically-controlled adjuster (not shown) can be programmed to automatically adjust adjustable flow plate


4




c


based on input from a flow volume sensor (not shown) to avoid manual operator adjustment to maintain maximum separation efficiency.




Further, in light of the fact that the direction


27


in which magnetic drum


16


rotates is the same direction as the direction


13


in which discharge slurry


12


flows, a variable speed motor (not shown) can also be employed to vary the revolutions per minute (RPM) of magnetic drum


16


in response to variations in rate and volume of flow of discharge slurry


12


during the grinding mill production cycle. The effect of increasing the rate of RPM of magnetic drum


16


in direct relation to the increase in the rate and volume of flow of discharge slurry


12


is to reduce the wear and abrasion on outer drum liner


15




a


. This is due to the increased RPM in direct relation to the increased rate and volume of flow of discharge slurry


12


, thereby reducing the resistance of magnetic drum separator


11


to the increased rate and volume of flow of discharge slurry


12


over outer drum surface


11




a


. The use of a variable speed motor, although very useful in reducing wear and abrasion in respect of the present invention, would not have been effective in a prior art enclosed magnetic drum separator; not only might a variable speed motor have had no ameliorating effect on abrasion-related wear or damage in an enclosed system, but it might even have increased the amount of abrasion-related wear, damage, and possible head pressure build-up, as increasing the RPM of the drum would increase the rate and volume of discharge slurry


12


forced through the enclosed system.




Although the general concept of using a magnetic drum separator


11


rotating about a fixed drum shaft


29


in the same direction


13


as the flow of discharge slurry


12


, as a means of separating ferrous material


17


from discharge slurry


12


, is well-known to those skilled in the art, the present invention goes far beyond the prior art. In addition to the very significant advances derived just from adjustable flow plate


4




c


, the invention has many other beneficial features, including the following:




(1) This invention preferably uses a unique design for overlapping and interlocking a plurality of replaceable, non-ferrous drum liner segments


21


, each having a cleat


20


integrated therein along one edge and comprised of


80


A durometer polyurethane (or some other similarly highly abrasion-resistant elastomeric material), that in combination forms a replaceable, abrasion-resistant outer drum liner


15




a.






(2) This invention preferably uses non-ferrous abrasion-resistant elastomeric material for the plurality of surface segments forming the non-ferrous, abrasion-resistant, replaceable separator lining


23


, simultaneously forming both a strong joint between the liner segments


21


and the sidewall liners


22


, while at the same time being easily and quickly removable and replaceable.




(3) This invention preferably uses a non-ferrous, metal bar


28


within each cleat


20


to provide greater structural strength and support to both the liner segments


21


and the cleats


20


, while at the same time, being utilized to create greater structured integrity and stability to the magnetic drum separator


11


as a whole.




(4) This invention preferably allows the design and integration of the liner segments


21


and sidewall liners


22


to be fastened to both of the end plates


25


, while fastening them together as a complete unit using fasteners


26


, which serves to allow the assembled magnetic drum separator


11


to have strength, stability, and structural integrity, while permitting it to be quickly and easily disassembled, thereby making on-site field repairs or change-outs quick, easy, and simple with only rudimentary hand tools.




(5) This invention preferably uses polyurethane wear surface components, which are quickly and easily removed and replaced, and which allow a minimum of down time with on-site replacement of some or all wear surface components, whether due to emergency on-site field repairs or during regular change-out.




(6) The use of replaceable polyurethane wear surface components further allows operators to replace only those components actually abraded, worn, or damaged and saves the expense of unnecessary replacement of wear surface components.




(7) Although U.S. Pat. No. 6,149,014 discloses its own method for separating non-ferrous ore slurry


34


from ferrous material


17


, U.S. Pat. No. 6,149,014 teaches an enclosed system incorporating a partitioned product hopper having an externally adjustable splitter to partition metallic fragments from the bulk slurry flow. The present invention does not require a physical splitter, and simply uses a combination of magnetic force, inertia, and gravity to separate and direct the discharge of both non-ferrous ore slurry


34


and ferrous material


17


into the respective receptacles designed for each. This reduces wear and tear, and the likelihood of mechanical failure or malfunction.




(8) U.S. Pat. No. 6,149,014 teaches the use of a drum spray bar to clean the magnetic drum after both the bulk slurry and the ferrous material have already fallen off, in order to clean the drum surface for further use. In the present invention, spray applicator


35


is located to spray ferrous material


17


with water while ferrous material


17


is still in contact with outer drum surface


11




a


. This accomplishes the dual purpose of cleaning not only debris and residual discharge slurry


12


off of outer drum surface


11




a


, which enhances the magnetic attraction and retention capability of magnetic drum


16


, but also cleaning ferrous material


17


as well. This advancement is valuable as ferrous material


17


is recyclable, and is worth more per ton if it can be delivered clean to the recycler. In the present invention, no separate cleaning step is required for ferrous material


17


after it leaves outer drum surface


11




a.






(9) The novelty and inventiveness of the magnetic drum separator as disclosed in this invention is equally applicable to any other application calling for a magnetic separation system, and is not limited to its application in the present embodiment as a mill trunnion magnetic drum separator


11


used in concert with a mill trunnion discharge feed chute


1


to separate ferrous material from mill trunnion discharge slurry


12


.




As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.



Claims
  • 1. A magnetic separation system to remove ferrous material from a discharge slurry of an operating grinding mill comprising:(a) a feed chute for receiving discharge slurry, said feed chute comprising walls and a feed chute floor having an adjustable feed chute floor portion for controlling the release of discharge slurry from said feed chute, and said feed chute further comprising an electronically-controlled adjuster programmed to automatically adjust said adjustable feed chute floor portion in response to changes in flow of discharge slurry; and (b) a magnetic drum separator comprising a drum rotatable about an axis below said feed chute, said drum having a generally cylindrical outer surface and having a fixed magnet assembly within said cylindrical outer surface, wherein adjustment of said adjustable chute floor portion controls where discharge slurry released from said feed chute will contact said outer surface of said drum.
  • 2. A magnetic separation system as claimed in claim 1, wherein said fixed magnet assembly provides a radial field of magnetic attraction extending over at least half of the circumference of said drum.
  • 3. A magnetic separation system as claimed in claim 2, wherein said fixed magnet assembly provides at least a 240-degree radial field of magnetic attraction about the circumference of said drum.
  • 4. A magnetic separation system as claimed in claim 1, wherein said fixed magnet assembly provides a radial field of magnetic attraction extending over said adjustable feed chute floor portion when said adjustable feed chute floor portion is in its most extended position.
  • 5. A magnetic separation system as claimed in claim 1, wherein said magnetic drum separator is covered by a replaceable protective lining.
  • 6. A magnetic separation system as claimed in claim 5, wherein said lining is comprised of a non-ferrous elastomeric material.
  • 7. A magnetic separation system as claimed in claim 1, wherein said magnetic drum separator further comprises an end plate at each end of said drum, and wherein said outer surface of said drum and said end plates together define an unenclosed passage for the flow of discharge slurry released from said feed chute.
  • 8. A magnetic separation system as claimed in claim 1, further comprising a plurality of cleats affixed to said outer surface of said drum and extending longitudinally across said outer surface to assist the transfer of ferrous material.
  • 9. A magnetic separation system as claimed in claim 8, wherein each cleat has therethrough a metallic bar.
  • 10. A magnetic separation system as claimed in claim 1, wherein said drum is covered by a replaceable protective lining having a plurality of cleats extending therefrom longitudinally across said outer surface of said drum.
  • 11. A magnetic separation system as claimed in claim 10, wherein each cleat has therethrough a metallic bar.
  • 12. A magnetic separation system as claimed in claim 1, wherein said adjustable feed chute floor portion is non-ferrous.
  • 13. A magnetic separation system as claimed in claim 1, wherein the top surface of said adjustable feed chute floor portion is a replaceable, abrasion-resistant wear plate.
  • 14. A magnetic separation system as claimed in claim 1, wherein said feed chute further comprises a rubber damper curtain suspended above said feed chute floor.
  • 15. A magnetic separation system as claimed in claim 1, further comprising a variable speed motor for adjusting the speed of rotation of said drum in response to variations in flow of discharge slurry.
  • 16. A magnetic separation system to remove ferrous material from a discharge slurry of an operating grinding mill comprising:(a) a feed chute for receiving discharge slurry, said feed chute comprising walls and a feed chute floor having an adjustable feed chute floor portion for continuing the release of discharge slurry from said feed chute; and (b) a magnetic drum separator comprising a drum rotatable about an axis below said feed chute, said drum having a generally cylindrical outer surface and having a fixed magnet assembly within said cylindrical outer surface, wherein adjustment of said adjustable chute floor portion controls where discharge slurry released from said feed chute will contact said outer surface of said drum, and wherein said drum is covered by a replaceable protective lining having a plurality of cleats extending therefrom longitudinally across said outer surface of said drum, and wherein said lining consists of a plurality of liner segments each having a cleat Integrated therein along one longitudinal edge thereof, which liner segments together overlap and interlock on said drum to form said lining, with each of said cleats forming a seal over the joint between adjacent liner segments.
  • 17. A magnetic separation system as claimed in claim 16, wherein each cleat has therethrough a metallic bar.
  • 18. A magnetic separation system as claimed in claim 16, wherein said liner segments are comprised of a non-ferrous elastomeric material.
  • 19. A magnetic separation system as claimed in claim 16, wherein said magnetic drum separator further comprises an end plate at each end of said drum, and wherein each end plate is covered with a replaceable protective sidewall liner, said sidewall liner comprising segments each having a keyed edge for an interlocking fit with a corresponding recess at the end of one of said liner segments, and wherein said liner segments and said sidewall liners together form a replaceable protective lining for the entire magnetic drum separator.
  • 20. A magnetic separation system as claimed in claim 19, wherein said liner segments and said sidewall liners are comprised of a non-ferrous elastomeric material.
  • 21. A magnetic separation system as claimed in claim 1, wherein said feed chute is an open, trunnion discharge feed chute.
  • 22. A magnetic separation system as claimed in claim 1, wherein said feed chute floor has a downward slope of 2% to 3% for discharge slurry to flow down before being released from said feed chute.
  • 23. A magnetic separation system as claimed in claim 22, wherein the top surface of a portion of said feed chute floor comprises a replaceable, abrasion-resistant wear plate.
  • 24. A magnetic separation system as claimed in claim 23, wherein said wear plate is ferrous.
  • 25. A magnetic separation system as claimed in claim 24, wherein said wear plate is secured in place within said feed chute using a magnetic retainer.
  • 26. A feed chute for receiving discharge slurry for controlled release onto a magnetic drum separator, said feed chute comprising walls and a feed chute floor having an adjustable feed chute floor portion, and said feed chute further comprising an electronically-controlled adjuster, programmed to automatically adjust said adjustable feed chute floor portion in response to variations in flow of discharge slurry, wherein adjustment of said adjustable chute floor portion controls where discharge slurry released from said feed chute will contact said magnetic drum separator.
  • 27. A feed chute as claimed in claim 26, wherein said feed chute floor has a downward slope of 2% to 3% for discharge slurry to flow down before being released from said feed chute.
  • 28. A feed chute as claimed in claim 26, wherein the top surface of said feed chute floor comprises a replaceable, abrasion-resistant wear plate.
  • 29. A feed chute as claimed in claim 28, wherein said wear plate is ferrous.
  • 30. A feed chute as claimed in claim 29, wherein said wear plate is secured in place within said feed chute using a magnetic retainer.
  • 31. A feed chute as claimed in claim 26, wherein said adjustable feed chute floor portion is non-ferrous.
  • 32. A feed chute as claimed in claim 26, wherein the top of said adjustable feed chute floor portion is a replaceable, abrasion-resistant wear plate.
  • 33. A feed chute as claimed in claim 26, wherein said feed chute further comprises a rubber damper curtain for further controlling the flow of discharge slurry.
  • 34. A method of removing ferrous material from a discharge slurry flow comprising:(a) discharging discharge slurry into a feed chute, said feed chute comprising a feed chute floor having an adjustable feed chute floor portion; (b) releasing said discharge slurry from said feed chute onto the outer surface of a rotating drum, said drum having a fixed magnet assembly within said outer surface for providing a radial field of magnetic attraction extending over a portion of the circumference of said drum; (c) rotating said outer surface of said drum in the direction of the flow of said discharge slurry; (d) adjusting said adjustable feed chute floor portion so as to maintain, at a predetermined point, the area at which discharge slurry released from said feed chute contacts said outer surface of said drum, wherein said adjustment step comprises using an electronically-controlled adjuster programmed to automatically adjust said adjustable feed chute floor portion in response to variations in flow of diacharge slurry; (e) separating ferrous material from said discharge slurry by magnetically attracting ferrous material to said drum while allowing non-ferrous discharge slurry to flow past and off said drum; and (f) conveying ferrous material away from said non-ferrous discharge slurry and then discharging said ferrous material from said drum.
  • 35. A method as claimed in claim 34, wherein said fixed magnet assembly provides at least a 240-degree radial field of magnetic attraction about the circumference of said drum.
  • 36. A method as claimed in claim 34, wherein said fixed magnet assembly provides a radial field of magnetic attraction extending over said adjustable feed chute floor portion when adjustable feed chute floor portion is in its most extended position.
  • 37. A method as claimed in claim 36, further comprising, in respect of discharge slurry as it flows through said feed chute, magnetically attracting ferrous material from said discharge slurry downward toward said adjustable feed chute floor portion.
  • 38. A method as claimed in claim 34, further comprising spraying said ferrous material with water at an area on said outer surface of said drum where said ferrous material is still magnetically attracted to said drum.
  • 39. A method as claimed in claim 34, further comprising covering said magnetic drum with a replaceable protective lining.
  • 40. A method as claimed in claim 39, wherein said protective lining comprises a plurality of liner segments that overlap and interlock with one another for a sealing fit.
  • 41. A method as claimed in claim 34, wherein said feed chute is an open, trunnion discharge feed chute.
  • 42. A method as claimed in claim 34, wherein discharge slurry flows down a slope of 2% to 3% over said feed chute floor before being released from said feed chute.
  • 43. A method of removing ferrous material from a discharge slurry flow comprising:(a) discharging discharge slurry into a feed chute, said feed chute comprising a feed chute floor having an adjustable feed chute floor portion; (b) releasing said discharge slurry from said feed chute onto the outer surface of a rotating drum, said drum having a fixed magnet assembly within said outer surface for providing a radial field of magnetic attraction extending over a portion of the circumference of said drum; (c) rotating said outer surface of said drum in the direction of the flow of said discharge slurry, wherein said rotation step comprises using a variable speed motor for adjusting the speed of rotation of said outer surface of said drum in response to variations in flow of discharge slurry; (d) adjusting said adjustable feed chute floor portion so as to maintain, at a predetermined point, the area at which discharge slurry released from said feed chute contacts said outer surface of said drum; (e) separating ferrous material from said discharge slurry by magnetically attracting ferrous material to said drum while allowing non-ferrous discharge slurry to flow past and off said drum: and (f) conveying ferrous material away from said non-ferrous discharge slurry and then discharging said ferrous material from said drum.
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