Field of the invention

The invention relates to a method for controlling the electrical circuit in an electrolytic process of electrorefining or electrowinning of metal as defined in the preamble of independent claim 1.

The invention relates also to an arrangement for controlling the electrical circuit in an electrolytic process of electrorefining or electrowinning of metal as defined in the preamble of independent claim 14.

Background of the invention

In metal electrowinning a current is passed from an inert anode to a cathode through a liquid electrolyte solution containing said metal so that the metal is extracted and it is deposited onto the cathode. Periodically, the cathodes in each electrolysis cell must be harvested to remove the metal that has been deposited onto the cathodes. The electrolysis cells are typically arranged with electrically conductive anodes and cathodes interleaved alternately inside the cell and the cell is filled with electrolyte that contains the metal of interest. The anodes and cathodes are arranged inside the cell so that electric current passes through the anode, the electrolyte and the cathode. These anodes and cathodes are connected electrically in parallel inside the cell. When a number of electrolysis cells are employed, then the cells are positioned adjacent to each other and each adjacent cell is connected electrically in series. When the cathodes are removed from a cell to harvest the metal that has been deposited onto them, the electrical circuit will be broken if all of the cathodes from a particular cell are removed at the same time. This would cause the remaining cells in the same electrical circuit to stop operating in electrolysis mode whenever a cell is harvested. To prevent this stoppage occurring, the normal practice is to remove only a portion of the cathodes from one cell at one time, (say one third or one half of the cathodes).

The present harvesting method described above requires that the crane makes two or three trips to and from each electrolysis cell to harvest all of the cathodes. If only one third or one half of the cathodes are harvested from each cell at the same time, then the crane must return to the same cell four or six times to ensure that the cell is fully harvested. (To remove and again to replace the cathodes into the cell). If acid mist capture hoods are employed to help capture acid mist that may occur during the electrolysis process, the crane must also remove and replace the hood each time it moves to a cell.

During the period when a cell is being harvested, and a portion of the cathodes are removed, the remaining anode and cathode "pairs" in that particular cell will operate with higher current, than under normal operation. This higher current may increase the potential for short circuits to develop and reduce cathode quality. Objective of the invention

The objective of the invention is to provide a method and an arrangement for shorting an electrolytic cell during the period when all of the cathodes in that cell are removed and to also allow the remaining electrolytic cells in the same electrical circuit to maintain electrolytic operation. Note that this invention will also provide a method and an arrangement for shorting an electrolytic cell during the period when all of the anodes in that cell are removed and to also allow the remaining electrolytic cells in the same electrical circuit to maintain electrolytic operation.

Short description of the invention

The method for controlling the electrical circuit in an electrolytic process of electrorefining or electrowinning of metal is characterized by the definitions of independent claim 1.

Preferred embodiments of the method are defined in the dependent claims 2 to 13.

The arrangement for controlling the electrical circuit in an electrolytic process of electrorefining or electrowinning of metal is characterized by the definitions of independent claim 14.

Preferred embodiments of the arrangement are defined in the dependent claims 15 to 26.

The invention relates also to the use of the method according to any of the claims 1 to 13 when transferring second electrodes in the form of cathodes from and/or to an electrolytic cell as defined in claim 27.

The invention relates also to the use of the method according to any of the claims 1 to 13 when transferring second electrodes in the form of anodes from and/or to an electrolytic cell as defined in claim 28.

The invention relates also to the use of the arrangement according to any of the claims 14 to 26 when transferring second electrodes in the form of cathodes from and/or to an electrolytic cell as defined in claim 29.

The invention relates also to the use of the arrangement according to any of the claims 14 to 26 when transferring second electrodes in the form of anodes from and/or to an electrolytic cell as defined in claim 30.

The problem is solved by the use of at least one shorting device block to deliberately short circuit the electrolytic cell. This allows all of the second electrodes, which can be either all cathodes in the electrolytic cell to be removed for harvesting at one time, or all the anodes in the electrolytic cell to be removed for replacing at one time. During that time the remaining tankhouse electrolytic cells continue normal electrolytic operation until they in turn are short-circuited and harvested.

Because all second electrodes in the form of cathodes from a cell can be removed at one time, the number of crane journeys between the electrolytic cell and the cathode stripping machine is significantly reduced and the crane is used in a time efficient manner. This will improve the overall tankhouse harvesting efficiency and logistics. The shorting device block is preferably, but not necessarily, designed so that it will align to the correct position and can be positioned under the normal positioning tolerances of the transfer apparatus, this will ensure that the operation is straightforward and manageable by regular crane operators.

The transfer apparatus can be upgraded to allow for lifting the additional weight and harvesting of all second electrodes in the form of cathodes at one time. In addition, the guide frame of the transfer apparatus can be modified with hooks for the shorting device blocks to be lifted and placed into position before the second electrodes in the form of cathodes are lifted (harvested) from an electrolytic cell or before the second electrode in the form of anodes are lifted (for replacement) from an electrolytic cell.

The shorting device blocks are either individual blocks or multi-contact blocks that are placed by the transfer apparatus onto the cell that is to be harvested. The shorting device blocks are placed to connect each first electrode with the electrical connector (busbar) on the side of the cell from which the first electrodes are normally insulated. The placing of the shorting device block makes the first electrode electrically connected to the electrical connectors (busbars) on both sides of the cell and effectively provides a short circuit for that electrolytic cell. Once the electrolytic cell is short-circuited, either all the second electrodes in the form of cathodes in that electrolytic cell can be removed for harvesting, or all the second electrodes in the form of anodes in that electrolytic cell can be removed for replacing. With this procedure, there is no break in the tankhouse electrical circuit.

The shorting device block may be designed to connect the first electrodes of adjacent cells either by location from the first electrode hanger bar, which is either an anode hanger bar or a cathode hanger bar), to the busbar, or alternatively from the first electrode hanger bar to the first electrode hanger bar of the adjacent cell. When an auxiliary current equalizer bar (double contact busbar system) is used, the shorting device block may be alternatively designed to connect from the auxiliary current equalizer bar to the electrical connector (busbar) or from the auxiliary current equalizer bar to the first electrode hanger bar of the adjacent cell.

This invention provides a method to harvest all of the cathodes in a cell at one time, and maintain the electrical circuit to the remaining electrolysis cells by means of a cell shorting device. The ability to harvest all of the cathodes of a cell at the same time (instead of conventionally required two or three times) reduces the number of crane journeys, simplifies the crane and harvesting logistics and increases the cell electrolytic operating time. This increases operation efficiency, availability and production. This invention also ensures that electrodes are not be subjected to periods of high current, which helps to promote consistent high quality cathode product.

The shorting device block may be designed so that the weight of the shorting device block ensures that it remains in position with effective electrical contact until the transfer apparatus or crane removes it either after the new cathodes without electrolytically deposited metal have been replaced into the cell or after new anodes such as cast anodes have been replaced into the cell. Removing the shorting device blocks makes the current resume its original path through the first electrodes and the second electrodes i.e. the anodes, the electrolyte and the cathodes, starting the electrolysis process in that cell once again.

If a shorting device block should accidentally touch the second electrode hanger bar during the positioning process, this will not cause any problem, since the second electrode is carrying the current until such time that the shorting device block makes the short circuit and takes the current.

The invention can be used to replace second electrodes in the form of cathodes of various type, including permanent type cathodes onto which a metal is deposited, and starter sheet type cathodes where the cathode starter sheet is the same metal as is deposited.

The invention can be used to remove and replace second electrodes in the form of anodes of various types, both lead (Pb) type or other metal or alternative material anodes in an electrolytic cell while maintaining the electrical circuit and electrolytic operation of the remaining electrolytic cells.

This method of harvesting allows the electrical circuit to be maintained throughout the remaining cells in the same electrical circuit when a cell is being harvested, and allows the remaining cells to maintain electrolytic operation on a continuous basis. It is usual to use an overhead crane to remove and replace the cathodes from each cell and transfer them to and from the harvesting location, although other transfer apparatus designs may be used.

List of figures

In the following the invention will described in more detail by referring to the figure, which Figure 1 shows an embodiment of a transfer apparatus,

Figure 2 shows in cut- view three adjacent parallel electrolytic cells each containing second electrodes in the form of cathodes and first electrodes in the form of anodes in alternating order,

Figure 3 shows the two adjacent parallel electrolytic cells shown in figure 2 in a state where a shorting device block has been arranged into position on top of a cell walls 8 between the two electrolytic cells.

Figure 4 shows the two adjacent parallel electrolytic cells shown in figure 3 in a state where second electrodes in the form of cathodes are lifted from the electrolytic cell that has been short- circuited from the electrical circuit,

Figures 5 to 8 shows a first embodiment of a busbar between two adjacent electrolytic cells and parts of second electrodes in the form of cathodes and first electrodes in the form of anodes connected to or insulated from the busbar,

Figure 9 shows the first embodiment shown in figures 5 to 8 in a situation, where one electrolytic cell is short-circuited by means of a shorting device block,

Figures 10 to 13 shows a second embodiment of a busbar together with two auxiliary current equalizer busbars between two adjacent electrolytic cells and parts of second electrodes in the form of cathodes and first electrodes in the form of anodes connected to the busbars,

Figure 14 shows the second embodiment shown in figures 10 to 13 in a situation, where one electrolytic cell is short-circuited by means of a shorting device block,

Figures 15 to 18 shows a third embodiment of a busbar between two adjacent electrolytic cells and parts of second electrodes in the form of cathodes and first electrodes in the form of anodes connected to or insulated from the busbar,

Figure 19 shows the third embodiment shown in figures 15 to 18 in a situation, where one electrolytic cell is short-circuited by means of a shorting device block,

Figures 20 to 23 shows a fourth embodiment of a busbar together with two auxiliary current equalizer busbars between two adjacent electrolytic cell and parts of second electrodes in the form of cathodes and a first electrodes in the form of anodes connected to the busbars,

Figure 24 shows the fourth embodiment shown in figures 20 to 23 in a situation, where one electrolytic cell is short-circuited by means of a shorting device block,

Figure 25 shows an electrical connection that is possible by using a shorting device block to short circuit one electrolytic cell,

Figure 26 shows another electrical connection that is possible by using a shorting device block to short circuit one electrolytic cell,

Figure 27 shows yet another electrical connection that is possible by using a shorting device block to short circuit one electrolytic cell, and

Figure 28 shows still another electrical connection that is possible by using a shorting device block to short circuit one electrolytic cell.

Detailed description

First the method for controlling the electrical circuit in an electrolytic process of electrorefining or electrowinning of metal and some embodiments and variants of the method will be described in greater detail.

In the method a number of electrolytic cells 3 is arranged as a cell group.

The electrolytic cells 3 are mutually separated by the cell walls 8.

In each electrolytic cell 3, there is arranged in alternating order, a number of first electrodes 1, such as anodes, and second electrodes 2, such as cathodes.

The first electrodes 1 and the second electrodes 2 are suspended in electrolyte (not shown in the figures) in the electrolytic cell 3, so that that in each electrolytic cell 3 there is arranged a first electrode 1 next to each second electrode 2, and so that the first electrodes 1, the second electrodes 2 and the electrolyte in the electrolytic cell 3 form a part of the electrical circuit.

Each first electrode 1 is suspended in said electrolyte in the electrolytic cell 3 by a first electrode hanger bar 16 of the first electrode 1 by supporting each first electrode hanger bar 16 of the first electrodes 1 on busbars 4 located on the cell walls 8.

Each second electrode 2 is suspended in said electrolyte in the electrolytic cell 3 by a second electrode hanger bar 17 of the second electrode 2 by supporting each second electrode hanger bar 17 of the second electrodes 2 on busbars 4 located on the cell walls 8.

All of the second electrodes 2 of an electrolytic cell 3 are electrically connected to all the first electrodes 1 of an adjacent electrolytic cell 3 via a busbar 4 that is located above the cell walls 8 between the two adjacent electrolytic cells 3.

The method comprises electrically connecting at least one first electrode 1 of an electrolytic cell 3 to at least one first electrode 1 of an adjacent electrolytic cell 3 by placing at least one shorting device block 7 into a position to short circuit said electrolytic cell 3 to provide with the shorting device block 7 and with the first electrodes 1 a path for the electrical circuit in the electrolytic process past the second electrodes 2 and the electrolyte in said electrolytic cell to the first electrodes 1 of said adjacent electrolytic cell 3.

The method may comprise electrically connecting at least one first electrode 1 of the electrolytic cell 3 to at least one first electrode 1 of the adjacent electrolytic cell 3 by placing at least one of the shorting device blocks 7 into a position in direct contact with the first electrode hanger bar 16 of a first electrode 1 of the electrolytic cell 3 and in contact with the busbar 4, which is located above the cell walls 8 between the two adjacent electrolytic cells 3 and which is in contact with the first electrode hanger bar 16 of the first electrodes 1 of the adjacent electrolytic cell 3.

The method may comprise electrically connecting at least one first electrode 1 of the electrolytic cell 3 to at least one first electrode 1 of an adjacent electrolytic cell 3 by placing at least one shorting device block 7 into a position in direct contact with the first electrode hanger bar 16 of said at least onea first electrode 1 of the electrolytic cell 3 and in direct contact with the first electrode hanger bar 16 of said at least one first electrode 1 of the adjacent electrolytic cell 3.

The method may comprise arranging at least one shorting device block 7 at a transfer apparatus 9 configured to transfer first electrodes 1 and second electrodes 2 to and/or from electrolytic cells 3, and electrically connecting at least one first electrode 1 of the electrolytic cell 3 to at least one first electrode 1 of the adjacent electrolytic cell 3 by placing at least one shorting device block 7 into position by means of the transfer apparatus 9. In such case, the method may comprise arranging at least one shorting device block 7 immovably or movably at the transfer apparatus 9. In such case the method can comprise arranging at least one shorting device block 7 with a guiding frame 10 of an overhead crane 11 of the transfer apparatus 9, which guiding frame 10 is configured to guide a grab device of the overhead crane 11 with respect to electrolytic cells 3 of the transfer apparatus 9. The overhead crane 11 can comprise a trolley 12 and hooks 13 connected to a grab device 14 that is suspended from the trolley 12.

The method can comprise providing the shorting device blocks 7 of electrically conducting material such as copper or copper alloy.

The method can comprise providing spaces 15 such as passages or openings in and/or between shorting device blocks 7 that will allow the second electrodes 2 in the form of cathodes to be removed from the electrolytic cell 3.

The method can comprise providing spaces 15 such as passages or openings in and/or between shorting device blocks 7 that will allow the second electrodes 2 in the form of anodes to be removed from the electrolytic cell 3. In such case the shorting blocks 7 are preferably, but not necessarily, arranged above the cell wall 8 so that the spaces 15 are located above the second electrode hanger bar 17 of the second electrodes 2.

The method comprises preferably, but not necessarily, arranging the shorting blocks 7 above the cell wall 8 so that the headroom above the electrolytic cell 3 i.e. the headroom above the electrolyte in the electrolytic cell 3 in the is free of at least one of any shorting device blocks 7 and any part of any shorting device block 7. This allows lifting and lowering of the second electrodes 2 from the electrolytic cell 3 when the electrolytic cell 3 is short-circuited.

The method comprises preferably, but not necessarily, arranging the shorting blocks 7 above the cell wall 8 so that the headroom above each second electrode 2 in the electrolytic cell 3 is free of at least one of any shorting device blocks 7 and any part of any shorting device block 7. This allows lifting and lowering of the second electrodes 2 from the electrolytic cell 3 when the electrolytic cell 3 is short-circuited.

The method comprises preferably, but not necessarily, arranging the shorting blocks 7 above the cell wall 8 so that the headroom above the second electrode hanger bar 17 of each second electrode 2 in the electrolytic cell 3 is free of at least one of any shorting device blocks 7 and any part of any shorting device block 7. This allows lifting and lowering of the second electrodes 2 from the electrolytic cell 3 when the electrolytic cell 3 is short-circuited.

The shorting device block may be designed to connect the first electrodes 1 of adjacent cells either by location from the first electrode hanger bar 16 to the busbar, or alternatively from the first electrode hanger bar 16 to the first electrode hanger bar 16 of the adjacent cell. When an auxiliary current equalizer bar 5, i.e. a double contact busbar system, is used, the shorting device block may be alternatively designed to connect from the auxiliary current equalizer bar 5 to the electrical connector (busbar) or from the auxiliary current equalizer bar 5 to the first electrode hanger bar 16 of the adjacent cell.

Next the arrangement for controlling the electrical circuit in an electrolytic process of electrorefining or electrowinning of metal and some embodiments and variants of the arrangement will be described in greater detail.

In the arrangement a number of electrolytic cells 3 is arranged as a cell group.

The electrolytic cells 3 are mutually separated by the cell walls 8.

In each electrolytic cell 3, there is arranged in alternating order, a number of first electrodes 1, such as anodes, and second electrodes 2, such as cathodes.

The first electrodes 1 and the second electrodes 2 are suspended in electrolyte (not shown in the figures) in the electrolytic cell 3, so that that in each electrolytic cell 3 there is arranged a first electrode 1 next to each second electrode 2 and so that the first electrodes 1, the second electrodes 2 and the electrolyte in the electrolytic cell 3 form a part of the electrical circuit.

Each first electrode 1 is suspended in said electrolyte in the electrolytic cell 3 by a first electrode hanger bar 16 of the first electrode 1 by each first electrode hanger bar 16 of the first electrodes 1 being supported on busbars 4 located on the cell walls 8.

Each second electrode 2 is suspended in said electrolyte in the electrolytic cell 3 by a second electrode hanger bar 17 of the second electrode 2 by each second electrode hanger bar 17 of the second electrodes 2 being supported on busbars 4 located on the cell walls 8.

All of the second electrodes 2 of an electrolytic cell 3 are electrically connected to all the first electrodes 1 of an adjacent electrolytic cell 3 via a busbar 4 that is located above the cell walls 8 between the two adjacent electrolytic cells 3.

The arrangement is configured to electrically connect at least one first electrode 1 of an electrolytic cell 3 to at least one first electrode 1 of an adjacent electrolytic cell 3 by placing at least one shorting device block 7 into a position to short circuit said electrolytic cell 3 to provide with the shorting device block 7 and with the first electrodes 1 a path for the electrical circuit in the electrolytic process past the second electrodes 2 and the electrolyte in said electrolytic cell to the first electrodes 1 of said adjacent electrolytic cell 3.

The arrangement may be configured to electrically connect at least one first electrode 1 of the electrolytic cell 3 to at least one first electrode 1 of the adjacent electrolytic cell 3 by placing at least one shorting device block 7 into a position in direct contact with the first electrode hanger bar 16 of a first electrode 1 of the electrolytic cell 3 and in contact with the busbar 4, which is located above the cell walls 8 between the two adjacent electrolytic cells 3 and which is in contact with the first electrode hanger bar 16 of the first electrodes 1 of the adjacent electrolytic cell 3.

The arrangement may be configured to electrically connect at least one first electrode 1 of the electrolytic cell 3 to at least one first electrode 1 of an adjacent electrolytic cell 3 by placing at least one shorting device block 7 into a position in direct contact with the first electrode hanger bar 16 of said at least one first electrode 1 of the electrolytic cell 3 and in direct contact with the first electrode hanger bar 16 of said at least one first electrode 1 of the adjacent electrolytic cell 3.

In the arrangement, the shorting device blocks 7 can, as shown in the embodiment illustrated in figure 1, at a transfer apparatus 9 configured to transfer first electrodes 1 and second electrodes 2 to electrolytic cells 3, and the arrangement can be configured to electrically connect at least one first electrode 1 of the electrolytic cell 3 to at least one first electrode 1 of the adjacent electrolytic cell 3 by placing at least one shorting device block 7 into position by means of the transfer apparatus 9. In such case, the arrangement can be configured by arranging at least one shorting device block 7 immovably or movable at the transfer apparatus 9. In the arrangement at least one shorting device block 7 can be arranged at a guiding frame 10 of an overhead crane 11 of the transfer apparatus 9, which guiding frame 10 is configured to guide a grab device of the overhead crane 11 with respect to electrolytic cells 3 of the transfer apparatus 9, as in the embodiment illustrated in figure 1. The overhead crane 11 can comprise a trolley 12 and hooks 13 connected to a grab device 14 that is suspended from the trolley 12.

The arrangement can be configured to provide the shorting device blocks 7 of electrically conducting material such as copper or copper alloy.

The arrangement can be configured to provide spaces 15 such as passages or openings in and/or between shorting device blocks 7 that will allow the second electrodes 2 in the form of cathodes to be removed from the electrolytic cell 3.

The arrangement can be configured to provide spaces 15 such as passages or openings in and/or between shorting device blocks 7 that will allow the second electrodes 2 in the form of anodes to be removed from the electrolytic cell 3. In such case, the shorting blocks 7 can be arranged above the cell wall 8 so that the spaces 15 are located above the second electrode hanger bar 17 of the second electrodes 2.

In the arrangement, the shorting blocks 7 can be arranged above the cell wall 8 so that the shorting blocks 7 so that the headroom above the electrolytic cell 3 is free of any shorting device blocks 7. This allows lifting and lowering of the second electrodes 2 from the electrolytic cell 3 when the electrolytic cell 3 is short-circuited.

In the arrangement, the shorting blocks 7 can be arranged above the cell wall 8 so that the shorting blocks 7 so that the headroom above the second electrodes 2 in the electrolytic cell 3 is free of at least one any shorting device blocks 7 and any part of any shorting device block 7. This allows lifting and lowering of the second electrodes 2 from the electrolytic cell 3 when the electrolytic cell 3 is short-circuited.

In the arrangement, the shorting blocks 7 can be arranged above the cell wall 8 so that the shorting blocks 7 so that the headroom above the second electrode hanged bar of each second electrode 2 in the electrolytic cell 3 is free of at least one any shorting device blocks 7 and any part of any shorting device block 7. This allows lifting and lowering of the second electrodes 2 from the electrolytic cell 3 when the electrolytic cell 3 is short-circuited.

The shorting device block may be designed to connect the first electrodes of adjacent cells either by location from the first electrode hanger bar 16 to the busbar, or alternatively from the first electrode hanger bar 16 to the first electrode hanger bar 16 of the adjacent cell. When an auxiliary current equalizer bar 5, i.e. a double contact busbar system, is used, the shorting device block may be alternatively designed to connect from the auxiliary current equalizer bar 5 to the electrical connector (busbar) or from the auxiliary current equalizer bar 5 to the first electrode hanger bar 16 of the adjacent cell.

The invention relates also to the use of the method according to any embodiment described herein when transferring second electrodes 2 in the form of cathodes from and/or to an electrolytic cell 3.

The invention relates also to the use of the method according to any embodiment described herein when transferring second electrodes 2 in the form of anodes from and/or to an electrolytic cell 3. The invention relates also to the use of the arrangement according to any embodiment described herein when transferring second electrodes 2 in the form of cathodes from and/or to an electrolytic cell 3.

The invention relates also to the use of the arrangement according to any embodiment described herein when transferring second electrodes 2 in the form of anodes from and/or to an electrolytic cell 3.

It is apparent to a person skilled in the art that as technology advances, the basic idea of the invention can be implemented in various ways. The invention and its embodiments are therefore not restricted to the above examples, but they may vary within the scope of the claims.