Abstract:
An anode box sized and configured for retaining an anode plate therein is disclosed for use in an electrolytic tank of the type used for electrowinning or electrorefining. The anode box is unitarily formed, thereby rendering the device more resistant to degradation typically caused by the harsh environment of the electrolytic tank. The anode box is also formed with spacer structures which protect and isolate the anode plate from contact with the diaphragm, when used, and from contact with adjacent cathode frames. The anode box may include other elements, such as a port through which liberated gases may be withdrawn.

Description:
BACKGROUND  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to electrometallurgical processes, namely electrowinning and electrorefining, in which metals are recovered or refined using industrial-scale electrolysis apparatus. Specifically, this invention relates to an improved anode box design for use in such processes.  
           [0003]    2. Description of Related Art  
           [0004]    Use of large industrial electrolytic cells for the recovery or refining of metals is well-known and widely practiced, particularly in the mining and metallurgy industry. The design or configuration of large industrial electrolytic cells varies, but they usually comprise a tank containing one or more cathodes positioned in proximity to one or more anodes in a bath of electrolyte. A very common configuration of such apparatus is an elongated tank containing a plurality of vertically-oriented cathode plates alternating with a plurality of anodes.  
           [0005]    In the process of recovering metals from the electrolyte, i.e., electrowinning, the electrolyte is a purified solution which contains the recoverable metal and the anodes are insoluble. Each anode in the tank is encased in a sheath or diaphragm of porous media through which the electrolyte moves. When an electrical current in applied, electrolyte moves through the diaphragm causing deposition of the metal species on the cathode with a corresponding decrease in acidity in the fluid within the diaphragm, i.e., in the anolyte, and liberation of a gas. The anode, including the diaphragm, is usually designed to carry the gas away from the anode and to remove anolyte from within the diaphragm to maintain and/or optimize the electrowinning process. Examples of electrowinning cells are disclosed in U.S. Pat. No. 4,210,653 and U.S. Pat. No. 4,288,305.  
           [0006]    In electrorefining, a target metal is purified or refined from an anode made of the target metal. Application of electricity to the anode causes the target metal to migrate through the electrolyte to the cathode where it is deposited. In most electrorefining processes, the anode is not encased in a diaphragm. However, the refining of some metals causes a sludge of impurities to form in the bottom of the tank, which can be avoided by placing a diaphragm about the anode.  
           [0007]    Anodes used in electrometallurgical processes as previously described typically exist in the form of a flat plate of metal having a bar positioned at one end for hanging the anode in the tank and for providing an electrical bus between the anodes of the tank. U.S. Pat. No. 3,981,353 discloses, for example, a method of producing anode plates for electrowinning processes. U.S. Pat. No. 4,201,653 further discloses a means for separating the diaphragm from the anode plate by providing a spacing device, in recognition of the fact that contact between the diaphragm and anode plate in electrowinning reduces the efficient operation of the process. Other anode designs are disclosed in the prior art in which the anode is not in the form of a plate. Thus, for example, U.S. Pat. No. 5,277,777 describes an anode formed of fork-shaped elements which are maintained in a framework.  
           [0008]    The environment of electrometallurgical processing tanks is very harsh on both the cathodes and the anodes. Both the cathodes and anodes can undergo warping as a result of the processing. Further, the cathodes are removed after a processing cycle to remove the metals deposited on the cathode. While the anode, particularly in electrowinning processes, does not need to be withdrawn from the tank as frequently as the cathodes, they nonetheless are subject to contact by the cathodes as the cathodes are being removed, and the anodes can be damaged as a result. Others have recognized the need to protect and isolate the anode plate; however, prior efforts to provide an a protective cover have resulted in the production of devices which are, themselves, subject to degradation from the harsh environment of an electrolytic tank. In particular, anode boxes of the known art are structured from many separate pieces which are bonded together, rendering the device structurally weak and vulnerable to chemical degradation.  
           [0009]    It would be advantageous to the art, therefore, to provide a protective member for an anode which is structured to protect and stabilize the anode in both electrowinning and electrorefining processes and to provide isolation from the diaphragm (when used) and adjacent cathodes. It would further be advantageous to provide a protective member for an anode which is structured to resist the damage or degradation which inherently results from exposure to the environment of an electrolyte tank.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    In accordance with the present invention, an anode box is provided in which an anode plate is positionable for placement in an electrolytic tank. The anode box is structured to protect and stabilize the anode plate and to isolate the anode from adjacent cathode plates and from the diaphragm, when used. The structure of the present invention is particularly advantageous in that it is unitarily formed, comprising two or three pieces, from materials which render the anode box relatively resistant to chemical and mechanical degradation, thereby providing better protection to the anode plate. The anode box of the present invention may be employed in both electrowinning and electrorefining processes.  
           [0011]    The present invention comprises a frame sized to receive an anode plate therein. Specifically, the anode box comprises a frame body having two opposing long sides and a third side joining the two opposing long sides together. The outer-facing or peripheral edges of frame may be preferably shaped to facilitate placement of diaphragm or media bag about the frame body. A continuous, U-shaped slot is formed along the three sides of the body and the open fourth side of the frame thereby provides for insertion of an anode plate into the frame with the peripheral sides of the anode plate being supported by the U-shaped slot. A plurality of spacers extend between the sides of the frame body to isolate the anode plate from contact with an adjacent cathode or a diaphragm. The spacers have inwardly projecting members which contact the anode plate to help center the anode plate within the frame body and to provide a space about the anode plate through which gas liberated in the electrolytic process can escape.  
           [0012]    A removable hood structured to span the two opposing long sides is positionable on the frame body to provide a fourth side of the frame body, thereby fully enclosing the anode plate therewithin. The removable hood is structured to support an electrical bus and has a gas release mechanism for releasing chemically-liberated gas from around the anode plate. The removable hood may also be configured with an attachment structure to which a diaphragm, or bag of porous media, may be attached.  
           [0013]    The anode box of the present invention is unitarily and integrally formed from materials which are comparatively resistant to chemical and mechanical degradation. For example, the frame body, including the sides and spacers, is formed from polymer materials, such as polypropylene, PVC (polyvinyl chloride) or other materials. A particularly suitable material may, for example, be polypropylene in which is incorporated glass beads. The anode box may preferentially be made by a molding process. The frame body may also be formed by extrusion and then processed by known milling techniques to provide the desired configuration. The anode box of the present invention is, therefore, structurally strong to protect the anode plate and reduce warping of the anode plate, and, because it is unitarily formed, it is not subject to degradation. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0014]    In the drawings, which illustrate what is currently considered to be the best mode for carrying out the invention:  
         [0015]    [0015]FIG. 1 is a perspective view of the anode box of the invention, shown in an exploded view;  
         [0016]    [0016]FIG. 2 is a view in lateral cross section of a portion of the anode box shown in FIG. 1, taken at line  2 - 2 ;  
         [0017]    [0017]FIG. 3 is a perspective view of the anode box shown in FIG. 1, having a diaphragm (shown in phantom) positioned over the anode box; and  
         [0018]    [0018]FIG. 4 is a view in longitudinal cross section of the anode box shown in FIG. 1, taken at line  4 - 4 .  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]    [0019]FIG. 1 illustrates the anode box  10  of the present invention which generally comprises a frame body  12  and a removable hood  14 . The frame body  12  is further comprised of a first side  16  and a second side  18  oriented in opposition, and parallel, to the first side  16 . The frame body  12  also has a third side  20  positioned between the first side  16  and second side  18  of the frame body  12  to provide a three-sided frame structure. An open channel  24  is formed along the inner-facing edge  26  of the first side  16 , third side  20  and second side  18  of the frame body  12 , thereby forming a continuous channel  24  or slot which is sized to receive the peripheral edge of a planar anode plate  30 , a bottom portion of which is suggested by phantom line in FIG. 1.  
         [0020]    The anode box  10  of the present invention further includes a plurality of spacers  34  which extend between the sides of the frame body  12 . The number of spacers  34  may vary and may be positioned in any direction relative to the sides of the frame body  12 . FIG. 1 illustrates but one exemplar configuration where there are a plurality of spacers  34  extending at right angles to each other to form a lattice-like structure on either side of the channel  24  of the frame body  12 . That is, a number of parallel and spaced-apart members, nominally designated as horizontal spacers  36 , extend between the first side  16  and second side  18  of the frame body  12 . A plurality of parallel and spaced-apart members, nominally designated as vertical spacers  38 , extend from the third side  20  and intersect the horizontal spacers  36  to form a lattice configuration. A first assemblage  40  of horizontal spacers  36  and vertical spacers  38  is positioned on one side of the continuous channel  24  and a second assemblage  42  of horizontal spacers  36  and vertical spacers  38  is positioned on the other side of the continuous channel  24  such that a lattice configuration of spacers lies adjacent each side of the anode plate  30 .  
         [0021]    The configuration of the spacers  34  is further shown in FIG. 2 where it can be seen that the first assemblage  40  of horizontal spacers  36  and vertical spacers  38  is positioned on one side of the anode plate  30  (shown in phantom) and the second assemblage  42  of horizontal spacers  36  and vertical spacers  38  is positioned on the other side of the anode plate  30 . It can further be seen that bosses  44  are formed along the spacers  34  (either the horizontal spacers  36  and/or the vertical spacers  38 ) to extend in the direction of the continuous channel  24  (not shown in FIG. 2). The bosses  44  extend in the proximity of the anode plate  30  may or extend a sufficient distance to contact the anode plate  30 . The bosses  44  keep the anode  30  positioned within the frame body  12  and spaced apart from the spacers  34 . Additionally, a space  46  is provided between the anode plate  30  and the spacers  34  through which chemically-liberated gas may move during the electrolytic process, as explained more fully below.  
         [0022]    Referring again to FIG. 1, it should be noted that the frame body  12  is unitarily formed such that the sides and spacers are integrally formed, from the same material, in a single unit. In one embodiment of the invention, the frame body  12  is singularly formed with three continuous sides and opposing spacer assemblies on either side of the continuous channel. In an alternative embodiment, which is suggested in FIG. 1, the frame body  12  may comprise two unitarily formed, mirror-image lateral sides  48 ,  50  which are joined along a peripheral edge to form a seam or joint  52 . In the latter embodiment, the two lateral sides  48 ,  50  may be joined by such means as adhesive bonding and/or securement apparatus, such as screws  54 .  
         [0023]    The anode box  10  of the present invention further includes a removable hood  14  which is sized to fit over the frame body  12 , as shown more clearly in FIG. 3. The removable hood  14  provides a forth side to the anode box  10  which effectively encloses the anode plate therewithin. The removable hood  14  generally has a top  56  and a substantially continuous wall member  58  extending from the top  56 . The removable hood  14  may be configured with a securement structure  60  for attaching a diaphragm, or porous media bag, to the anode box  10  when desired. In the illustrated embodiment of FIG. 1, the securement structure  60  is a continuous groove  62  formed along the continuous side wall member  58  to which the diaphragm  66  (FIG. 3, shown in phantom) may be caulked or held by a flexible spline  68 , as shown in FIG. 4.  
         [0024]    The removable hood  14  is also configured with at least one electrical connector port  70 , two such electrical connector ports  70  being illustrated in FIGS. 1 and 3. The electrical connector port  70  provides a means for contacting a source of electricity to the anode plate  30  to power the electrolytic process, and preferably is structured to further provide an electrical bus between or with other anode plates in a tank. In the anode box  10  illustrated in FIGS. 1, 3 and  4 , the electrical connector port  70  is configured as a hollow standpipe through which a conductive pin  72  is positionable. The conductive pin  72 , as shown in FIG. 4, is sized in length to extend from a position above the electrical connector port  70 , through a conductive connecting bar  76  and through the electrical connector port  70  to contact the anode plate  30 . The conductive connecting bar  76  spans between the anode plates in an electrolytic tank containing a plurality of cathodes and anodes. The conductive pin  72  may be secured in place by, for example, a nut  78 . An electrode seal  80  is provided about the connecting pin  72 .  
         [0025]    The removable hood  14  may also be configured with a gas vent  82  through which chemically-liberated gas moving through the space  46  between the anode plate  30  and frame body  12  is released. The liberated gas may be vented to the atmosphere through the gas vent  82  or may be vented via a hose (not shown) connected to the gas vent  82 . The removable hood  14  may also be configured with attachment members  84  for securing the removable hood  14  to the frame body  12  during use.  
         [0026]    The anode box of the present invention provides a device for enclosing an anode plate in an electrolytic tank used for electrowinning or electrorefining. The anode box is particularly configured to protect and isolate the anode plate from contact with the diaphragm, when one is use, and from contact with adjacent cathodes. Moreover, the unitary formation of the anode box of the present invention renders it significantly more resistant to degradation or damage from the environment of the electrolytic tank and, therefore, provides better protection for the anode plate. Many variations may be made in the configuration of the anode box to achieve the objectives enumerated above. Thus, reference herein to specific details of the structure and function of the invention is by reference only and not by way of limitation. Those skilled in the art will recognize that changes may be made to the invention to adapt it accordingly.