ANODE SERVICING ASSEMBLY FOR AN ALUMINIUM ELECTROLYSIS PLANT, AND METHODS FOR OPERATING THE SAME

Abstract

An anode servicing assembly (30, 35) for an aluminium electrolysis plant, said aluminium electrolysis plant comprising at least one line (L1, L2) of electrolysis cells (C1-Cn, C1-Cn) connected in series, each cell having a plurality of anode assemblies (5) connected to an anode beam,

said anode servicing assembly comprising: an elongated body (31), running means adapted to allow movement of said elongated body along a running direction, substantially parallel to main axis of said line (L1, L2), an anode servicing machine (32) mounted on said elongated body, said anode servicing machine comprising at least two operating devices (45, 55, 65, 75, 85, 95), each adapted to fulfil at least one specific function different from cell lifting and anode beam raising, at least two support assemblies (40, 50, 60, 62, 70, 72, 80, 81, 82, 83, 90, 91, 92, 93), each adapted to support a respective operating device with respect to said elongated body,
said operating devices (45, 55, 65, 75, 85, 95) being movable independently the one with respect to the other, along at least one of a longitudinal axis (L31) of said elongated body (31) and a vertical axis (ZZ).

Claims

1-14. (canceled)

15. An anode servicing assembly for an aluminium electrolysis plant having at least one line of electrolysis cells connected in series, each electrolysis cell being connected to a cathodic busbar and each electrolysis cell having a plurality of anode assemblies connected to an anode beam, the anode servicing assembly comprising: an elongated body formed as a beam; a running mechanism adapted to allow movement of the elongated body along a running direction substantially parallel to a main axis of the at least one line; and an anode servicing machine mounted on the elongated body, the anode servicing machine including: at least two operating devices, each operating device adapted to fulfil at least one specific anode servicing function, the anode servicing function being different from cell lifting and anode beam raising, at least two support assemblies, each support assembly adapted to support a respective operating device with respect to the elongated body, the at least two operating devices being movable independently the one with respect to the other, along at least one of a longitudinal axis of the elongated body and a vertical axis.

16. The anode servicing assembly of claim 15, wherein at least one support assembly of the at least two support assemblies comprises at least one carrier movable with respect to the elongated body along the longitudinal axis of the elongated body, the respective operating device being fixed with respect to the at least one carrier, at least in translation.

17. The anode servicing assembly of claim 14, wherein at least one support assembly of the at least two support assemblies comprises: at least one carrier movable with respect to the elongated body along the longitudinal axis of the elongated body, and at least one drive member provided with a driving mechanism adapted to move a corresponding operating device with respect to the at least one carrier along the vertical axis.

18. The anode servicing assembly of claim 17, wherein at least one support assembly of the at least two support assemblies comprises two carriers, and two drive members, the driving mechanism being adapted to move one single operating device with respect to the two carriers along the vertical axis.

19. The anode servicing assembly of claim 18, wherein the elongated body comprises at least two parallel rails, at least one rail being provided with at least one track for translation motion of at least one carrier of the two carriers.

20. The anode servicing assembly of claim 14, wherein at least one specific anode servicing function is chosen between: lifting a new anode, vacuum cleaning anode cover material surrounding and/or covering an anode, sawing solid crust material surrounding an anode, lifting of the spent anode, placing the new anode at specific height, adding anode cover material on and around an anode, recording images representative of the position and the shape of an anode, moving a hood panel giving access to an anode, and moving back the hood panels after completing the anode change.

21. The anode servicing assembly of claim 14, wherein each operating device of the at least two operating devices has a lifting power that is less than 10 metric tons.

22. The anode servicing assembly of claim 14, further comprising at least two lifting operating devices adapted for lifting a respective anode assembly.

23. The anode servicing assembly of claim 22, further comprising a multi-use operating device having a head adapted to cooperate with: first tools detachably fixed on a distinct operating device, and/or second tools detachably fixed on the multi-use operating device.

24. An aluminium electrolysis plant, comprising: at least one line of electrolysis cells of substantially rectangular shape, the at least one line having at least one anode servicing assembly that includes; a body, a running mechanism adapted to allow movement of the body along the running direction, and an anode servicing machine mounted on the body and adapted to fulfil at least one specific anode servicing function that includes at least one of a heavy lifting function, and/or a main function that is distinct from the at least one specific anode servicing functions, a first connector for electrically connecting the electrolysis cells in series; a second connector for connecting a cathodic busbar of a cell to an anode beam of a downstream electrolysis cell; at least one heavy lifting assembly including: a first elongated body formed as a beam, a first running mechanism adapted to allow movement of the first elongated body along a running direction, substantially parallel to main axis of the at least one line, a heavy lifting machine mounted on the first elongated body and adapted to fulfil at least one heavy lifting function which includes lifting of pre-lined pot shells, pot shells with failed linings, and superstructures; at least one pot tending assembly including: a second elongated body formed as a beam, a second running mechanism adapted to allow movement of the second elongated body along a running direction, substantially parallel to main axis of the at least one line, a pot tending machine mounted on the second elongated body and adapted to fulfil at least one main function which includes raising of anode beams and tapping, wherein at least one of the specific anode servicing functions is distinct from heavy lifting functions and main functions of the main type.

25. The aluminium electrolysis plant of claim 24, further comprising at least one common running path adapted to cooperate with the first running mechanism and the second running mechanism and/or the pot tending assembly.

26. The aluminium electrolysis plant of claim 24, further comprising two common running paths provided on either side of the electrolysis cells, with reference to a transversal axis of the at least one line.

27. A method of operating an anode servicing assembly of an aluminium electrolysis plant, the method comprising: lifting a replacement anode assembly with a first lifting operating device of the anode servicing assembly, the replacement anode assembly to replace a spent anode assembly; moving the anode servicing assembly that is carrying the replacement anode assembly, adjacent to the spent anode assembly; lifting the spent anode assembly with a second lifting operating device of the anode servicing assembly; placing the replacement anode assembly at an original location of the spent anode assembly; analysing a shape of the spent anode assembly to determine a height position of the replacement anode; vacuum cleaning material surrounding the spent anode assembly, stocking at least part of the material and pouring at least part of a stocked material around the replacement anode assembly.

28. The method of claim 27, further comprising: positioning a heavy lifting assembly or a pot tending assembly of the anode servicing assembly above one given electrolysis cell or between two neighbouring electrolysis cells of the plant; and positioning a first anode servicing assembly above a first electrolysis cell, located on a first side of the given electrolysis cell or the two neighbouring electrolysis cells, with respect to a main axis; positioning a second anode servicing assembly above a second electrolysis cell, located on a second side of the given electrolysis cell or the neighbouring electrolysis cells, with respect to the main axis; conducting at least one specific anode servicing function on the first electrolysis cell and/or on the second electrolysis cell.

Description

FIGURES

[0064] FIGS. 1 to 18 represent an embodiment of the present invention; they do not limit the scope of the invention.

[0065] FIG. 1 is a schematic view, showing the global arrangement of a series of cells in an electrolysis plant according to the invention.

[0066] FIG. 2 shows a schematic transverse cross-sectional view of an electrolytic cell which belongs to plant of FIG. 1.

[0067] FIG. 3 shows a schematic transverse cross-sectional view of plant of FIG. 1, illustrating more particularly a pot tending machine (PTM) facing a cell of said plant.

[0068] FIG. 4 shows a schematic transverse cross-sectional view of plant of FIG. 1, illustrating more particularly an anode servicing assembly facing a cell of said plant.

[0069] FIGS. 5 and 6 are schematic views analogous to FIG. 1, showing two stages of a monitoring process of said plant, according to the invention.

[0070] FIG. 7 is a perspective view, showing more in detail an anode servicing assembly which equips the plant of above figures.

[0071] FIG. 8 is a perspective view showing in particular a carrier, which is part of the anode servicing assembly of FIG. 7, as well as rails on which said carrier is mounted.

[0072] FIG. 9 is a perspective view showing carrier of FIG. 8, as well as a platform cooperating with said carrier.

[0073] FIG. 10 is a perspective view showing a first operating step of an anode servicing assembly, wherein the position of an anode rod is captured by a camera.

[0074] FIG. 11 is a perspective view showing another operating step of this anode servicing assembly, wherein the position of a lifted anode is captured by a camera.

[0075] FIG. 12 is a perspective view showing another operating step of this anode servicing assembly, wherein hood panels of the pot shell are removed.

[0076] FIG. 13 is a perspective view showing another operating step of this anode servicing assembly, wherein material surrounding an anode intended to be replaced is vacuum cleaned.

[0077] FIG. 14 is a perspective view showing another operating step of this anode servicing assembly, wherein crust surrounding anode of FIG. 13 is broken.

[0078] FIG. 15 is a perspective view showing another operating step of this anode servicing assembly, wherein anode of FIG. 13 is lifted.

[0079] FIG. 16 is a perspective view showing another operating step of this anode servicing assembly, wherein shape of lifted anode of FIG. 15 is captured.

[0080] FIG. 17 is a perspective view showing another operating step of this anode servicing assembly, wherein a replacement anode is put in place, instead of anode of FIGS. 13 to 16.

[0081] FIG. 18 is a perspective view showing another operating step of this anode servicing assembly, wherein some material is poured around replacement anode of FIG. 17.

DETAILED DESCRIPTION

[0082] The following reference numbers are used in the figures:

TABLE-US-00001 1 Electrolytic cell 2 Sidewalls of potshell (prior art) 4 Bottom of potshell 3 Lining 5 Anode assembly 6 Anode rod of 5 7 Anode of 5 5U Spent Anode assembly 6U Anode rod of 5U 7U Anode of 5U 8 Cathode block 9 Cathode collector bar 10 Anode frame 11 Electrolytic bath 12 Liquid aluminium pad 13 Hood panel 14 Clamps 15 Anode assembly 16, 16, Sheds (building) 17, 18 Side walls of shed 19 Top wall of sheds 20, 21 Running paths 25 Pot tending machine (PTM) 26 Body of 25 27 Lifting machine of PTM L31 Main axis of body 31 30 First anode servicing 31 Body of 30 assembly 32 Anode servicing machine 33, 33, Rails of 32 34, 34, Tracks of rails 35 Second anode servicing assembly 40 Carrier for 45 41, 42 Sidewalls of potshell 45 Hopper 50 Carrier for 55 55 Crust breaker 60 Carrier for 65 62 Platform for 65 65 Bucket shovel 70 Carrier for 75 72 Platform for 75 75 Multi-tool robot 750 Deck of 75 752 Proximal arm of 75 753 Intermediate arm of 75 754 Distal arm of 75 756 Rotator of 75 758 Head of 75 76 Camera of 75 77-79 Tools of 75 80, 81 Carriers for 85 82, 83 Platforms for 85 85 Lifting robot 90, 91 Carriers for 95 92, 93 Platforms for 95 95 Lifting robot C1-Cn; C1-Cn; Ci; Ci; Cj; Cj Electrolytic cells L1, L2 Lines of electrolytic ZZ Vertical axis cells XX Main axis of cell line YY Transverse axis of cell line

[0083] The present invention is directed to the arrangement of a plant, also called aluminium smelting plant or aluminium smelter, using the Hall-Hroult process. This plant comprises a plurality of electrolysis cells (potline) connected in series. The Hall-Hroult process as such, the way to operate the latter, as well as the general structure of above electrolysis cells are known to a person skilled in the art and will not be described here. In the present description, the terms upper and lower refer to mechanical elements in use, with respect to a horizontal working surface. Moreover, unless otherwise specifically mentioned, conductive means electrically conductive.

[0084] As schematically shown on FIG. 1, the aluminium smelter of the invention comprises a plurality of electrolytic cells, typically arranged along two parallel lines L1 and L2, each of which comprises n cells, i.e., C1 to Cn and C1 to Cn. The electrolysis current therefore passes in a cascade fashion from one cell to the next cell, along arrow DC. The number of cells in a series is typically comprised between 50 and over 250, even over 400 in the most recent smelters, but this figure is not substantial for the present invention.

[0085] The electrolytic cells are rectangular shaped and are arranged transversally (side by side), in reference to the line they constitute. In other words, the main dimension, or length, of each cell is substantially orthogonal to the main direction of the line, i.e., the circulation direction of current. The large sides of two adjacent cells are parallel. The electrolytic cells, or pots, can implement various technological variants that do not form a part of the present invention; such pots are known to a person skilled in the art. On the FIG. 1, only the contour of the external metal (steel) shell, or potshell, of the cells is shown.

[0086] The general structure of a Hall-Hroult electrolysis pot is known per se and will not be explained here in detail. It is sufficient to explain, in particular in relation with FIG. 2, that a typical cell 1 includes a potshell comprising a first longitudinal sidewall 2, a second longitudinal sidewall 2, first and second transversal end walls (not visible on FIG. 1) and a bottom 4. The potshell walls define a space lined on its bottom and sides with refractory materials 3 (maintaining the thermal balance during the electrolysis process) along with the cathode blocks 8, thereby defining a volume containing the molten metal and electrolyte. The side lining 3 comprises a layer of carbonaceous material (not shown on the figures) protected in steady state operation by solid electrolyte in contact with molten liquid material.

[0087] Said cathode blocks 8 comprise one or more cathode collector bars 9. They protrude out of the potshell. Several anode assemblies 5 are also provided, each comprising an anode rod 6 and an anode 7. Electrical current enters the cell through anodes 7 (suspended above the cell by anode rods 6 attached to an aluminium beam called anode beam, which is supported by the cell superstructure 10), passes through the molten electrolytic bath 11 and the molten aluminium pad 12, and then enters the carbon cathode block 8. The current is carried out of the cell by the cathode collector bar 9 connected to the cathode busbar not shown on FIG. 2. The cell 1 is closed by a set of hood panels 13. In a way known as such, clamps 14, which are schematically represented, ensure removable fixing of anode rods to anode beam.

[0088] Typically, all the cells of the plant have the same structure. Two sheds 16,16 are also provided, each covering a respective line. On FIG. 1, these sheds are illustrated in phantom lines. As shown on FIGS. 3 and 4, said shed 16,16 comprises sidewalls 17,18 as well as top walls 19. The shed 16,16 can be open or closed, at one or both longitudinal ends. With reference to these figures, each cell is arranged so as to leave running paths 20, 21 on internal faces of side walls 17,18 of said shed 16,16. These paths allow the displacement of anode servicing assemblies along main axis of each line, as will be explained here after. Each path is provided with appropriate means, such as rails, for cooperating with complementary means of anode servicing assembly, such as wheels.

[0089] The combination, according to the invention, between a heavy lifting assembly (often designated as a cathode transport crane, abridged CTC) and/or a pot tending assembly (abridged PTM) on the one hand, and at least one anode servicing assembly on the other hand, will now be described. In particular, the anode servicing assembly advantageously uses the same running paths as the heavy lifting assembly and/or the pot tending assembly. When the heavy lifting machine is not needed, it does not stay in the line but (usually) in the pot repair area (not shown on the figures), from where it is moved into the pot line with a transboarding machine (not shown on the figures) generally located in the central passage.

[0090] This description is made, first with reference to FIGS. 3 to 6 which are schematic. The structure of these anode servicing assemblies will be described more in detail with reference to FIGS. 7 and following.

[0091] A plant according to the invention is provided with a pot tending assembly 25, schematically shown on FIG. 3. The latter comprises an elongated body 26, such as a beam, which is equipped with above-mentioned complementarity means, so as to run along above-described paths. Moreover, said pot tending assembly is provided with a so called pot tending machine 27. In a way known as such, this lifting machine is adapted to carry out the function of raising an anode beam. In this respect, the lifting power of this lifting machine is sufficient to fulfil this lifting. Typically, this lifting machine is not adapted to fulfil some other functions, such as replacing a spent anode assembly by a new anode assembly; adding a specific anode changing machine to the pot tending machine is possible, but will add unnecessary cost, and will not provide sufficient flexibility of use.

[0092] A plant according to the invention is usually also provided with a heavy lifting assembly (not shown on the figures), which comprises an elongated body, such as a beam, which is equipped with above-mentioned complementarity means, so as to run along above-described paths. Moreover, said heavy lifting assembly is provided with a so called heavy lifting machine which, in a way known as such, is adapted to carry out the function of lifting a potshell and lifting a superstructure. In this respect, the lifting power of this lifting machine is sufficient to fulfil this lifting. Typically, this heavy lifting machine is not adapted to fulfil some other functions, such as pot tending functions (such as raising anode beams) or anode servicing functions.

[0093] A plant according to the invention is also provided with at least one so called anode servicing assembly. In the present embodiment as will be explained more in detail, two anode servicing assemblies 30,35 are provided. Each anode servicing assembly, schematically shown on FIG. 4, comprises an elongated body 31, such as a beam, which is equipped with above-mentioned complementarity means, so as to run along above-described paths. Moreover, said anode servicing assembly 30,35 is provided with a so-called anode servicing machine 32. The present invention is directed to said anode servicing assembly 30,35, and to said anode servicing machine 32.

[0094] This machine 32 is provided with several operating devices, which will be described more in detail hereafter. These operating devices are adapted to carry out a specific anode servicing function, such as replacing a spent anode assembly by a new anode assembly. These operating devices are not adapted to carry out the lifting of a cell or the raising of an anode beam. In this respect, the lifting power of each operating device is not sufficient to fulfil this lifting. Typically, the lifting power of each of those operating devices is inferior to 20 metric tons, and can be inferior to 10 metric tons. This will simplify its structure.

[0095] In other words, the heavy lifting machine is adapted to fulfil certain functions, such as lifting a whole cell, and a superstructure which cannot be fulfilled by the anode servicing machine 32 because the latter does not have enough lifting power. Likewise, the pot tending machine is adapted to fulfil certain pot tending operations, which cannot be carried out by the anode servicing machine 32 because the latter does not have enough lifting power. Moreover, the anode servicing machine 32 is adapted to fulfil at least one so called distinctive function, such as automatically (i.e., without a human operator) replacing a spent anode assembly, which cannot be fulfilled automatically by a pot tending machine. On the other hand, the heavy lifting machine of the heavy lifting assembly is not adapted to replace a spent anode assembly by a new one, because it is lacking specific tools.

[0096] An operating method of the global plant according to the invention will now be described, with reference to FIGS. 5 and 6. These do not however illustrate the operation of the anode servicing assembly 30 or 35, which will be described with reference to FIGS. 10 to 18.

[0097] It is advantageous to provide each line of the plant with a plurality of anode servicing assemblies, depending on the number of cells to be served. On FIGS. 5 and 6, a first anode servicing assembly 30, 30 and a second anode servicing assembly 35, 35 are shown to allow changing anodes simultaneously on different cells of the same line of cells.

[0098] With reference to FIG. 5, let us suppose that the pot tending assembly 25, 25 faces one first given cell Ci, Ci located close to the rectifier end of the line on said figure. As a variant, said pot tending assembly may be positioned between two neighboring cells. In particular, this pot tending assembly may carry out a first type of operation on said cell(s), such as a lifting of the latter. In this respect all the other cells may be dealt by the two anode servicing assemblies. Indeed, top cells C1 to Ci1, C1 to Ci1 may be dealt by first anode servicing assembly 35,35, whereas bottom cells Ci+1 to Cn, Ci+1 to Cn may be dealt by second anode servicing assembly 30,30.

[0099] With reference to FIG. 6, let us suppose now that pot tending assembly 25,25 has moved from its position of FIG. 5, so as to face one second given cell Cj, Cj located close to the non-rectifier end of the line on said figure. According to the invention all the other cells still may be dealt by the two anode servicing assemblies. Indeed, top cells C1 to Cj1 C1 to Cj1 may be dealt by first anode servicing assembly 35,35, whereas bottom cells Cj+1 to Cn, Cj+1 to Cn may be dealt by second anode servicing assembly 30,30.

[0100] Within the meaning of the invention, the first and second anode servicing assemblies 30, 30, 35 35 may carry out servicing operations on cells, which may be the same servicing operations or different servicing operations. In particular, they may proceed to the change of the spent anode, so as to replace it by a new one. With reference to FIGS. 7 to 18, one constructive embodiment of an anode servicing machine, capable of such a replacement, will now be given.

[0101] An overall view of anode servicing machine 30 according to an advantageous embodiment is given on FIG. 7. Elongated body 31 of said anode servicing machine 30 comprises in particular two parallel rails 33,33, extending along transversal axis YY. As a consequence, this axis is coincident with a so-called main axis L31 of elongated body 31, which is shown in particular on FIG. 8.

[0102] As shown on FIG. 8, each rail 33,33 has opposite top and bottom walls, as well as opposite inner and outer walls. So-called inner wall of one rail faces the other rail. Tracks 34, 34, 34 are provided on at least one side wall of at least one rail. Said track, the structure of which is of any appropriate type, permits the displacement of carriers which will be described here under. In the illustrated example, both inner and outer walls of first rail are provided with respective tracks, whereas outer wall of second rail is provided with a respective track.

[0103] Back to FIG. 7, each track 34,34,34 cooperates with at least one carrier 40,50,60,70,80,81,90,91 which is mounted on this track. Said carrier is mobile on said track, along main axis L31 of the elongated body 31. To this end, said carrier is equipped with appropriate running means, such as rolling means. Each carrier 40,50,60,70,80,81,90,91 is adapted to support one or more operating devices 45,55,65,75,85,95. In the example of FIG. 7, two carriers 90,91 are provided on outer wall of first rail 33, three more carriers 40,50,70 are provided on inner wall of first rail 33, whereas three further more carriers 60,80,81 are provided on outer wall of second rail 33.

[0104] Said carriers may cooperate with the above-mentioned operating devices, in two distinct modes. In a first mode, one carrier may directly form a support assembly for a respective operating device. In other words, it means that a given operating device is immobilized, at least in translation, with respect to said carrier. In the present embodiment, this applies for two carriers 40,50 which respectively support a hopper 45 and a nozzle 55, the functions of which will be detailed hereafter.

[0105] In this first mode, said operating devices 45,55 are independently movable, along only longitudinal axis L31 of the elongated body 31.

[0106] In a second mode, some carriers may support operating devices while allowing a further displacement of the latter. In this respect an intermediate platform is fixed on said carrier, said platform permitting the movement of device along the vertical axis ZZ; this axis is shown on FIG. 9. To this end said platform is equipped with appropriate driving means, such as a servo motor. A support assembly, within the meaning of the invention, is then formed by said carrier and said platform.

[0107] According to a first possibility of said second mode, single carrier 60 cooperates with single platform 62 which in turn supports an operating device, which is a bucket shovel 65. In a similar manner, single carrier 70 cooperates with single platform 72 which in turn supports an operating device, which is a first robot 75, the structure of which will be described in further detail below.

[0108] According to a second possibility of said second mode, two different carriers may be provided for one single operating device, in particular in case the latter is heavy and or has great dimensions. As shown on FIG. 7 two carriers 80 and 81 support two respective platforms 82 and 83, on which a first lifting robot 85 is mounted. In addition, two more carriers 90 and 91 support two respective platforms 92 and 93, on which a second lifting robot 95 is mounted. Lifting robots 85 and 95 are typically adapted to lift an anode, in a way known as such.

[0109] In this second mode, said operating devices 65, 75, 85, 95 are independently movable, along not only longitudinal axis L31 of the elongated body 31, but also vertical axis ZZ.

[0110] The functions of these mechanical elements will become clear, at reading the description of the following example of an operating method according to the present invention. This example is given with reference to further FIGS. 10 to 17. On the latter, all the mechanical elements of the anode servicing assembly according to the invention are not illustrated, for sake of clarity. In particular, these FIGS. 10 to 17 show only one 33 of the two rails, which form the elongated body.

[0111] These figures also illustrate robot 75, in further detail. With reference in particular to FIG. 12 this robot 75 first comprises, starting from platform 72, a deck 750 which is pivotably mounted on this platform around a vertical axis. Furthermore, three successive arms are provided, namely a proximal arm 752 pivotably mounted on deck 750 around horizontal axis A752, an intermediate arm 753 pivotably mounted on arm 752 around horizontal axis A753, as well as a distal arm 754 pivotably mounted on arm 753 around horizontal axis A754. A rotator 756 is further pivotably mounted on distal arm around longitudinal axis L754 of said arm.

[0112] Said rotator is provided with a multi-use head 758, which is pivotably mounted around horizontal axis A758. As illustrated in particular on FIGS. 13 and 14, this head is adapted to detachably receive specific tools 77, 78 and 79 which will be further described. In particular these tools may be detachably fixed on platform 72. Moreover, this head 758 is provided with a camera 76, which is of any appropriate type, in particular of the 3D type. Contrary to tools 77 to 79, this camera is preferably attached to this head in a permanent way.

[0113] Let us suppose that one anode assembly of a cell needs to be replaced, which is called here after spent anode assembly. The latter is referenced 5U, whereas its rod and its anode are respectively noted 6U and 7U. This task will be carried out either by first or second anode servicing assembly.

[0114] Let suppose that the chosen anode servicing assembly is the one referenced 30. The latter first picks up a so-called replacement anode assembly, intended to replace above-mentioned spent anode assembly. In this respect FIG. 10 illustrates end cell C1, as well as a group RG of replacement anode assemblies which are gathered in the vicinity of this cell C1. Then said anode servicing assembly 30 moves to the group of replacement anode assemblies, by running along paths 20, 21 which are shown on FIGS. 3 and 4. FIG. 10 shows rail 33 of anode servicing assembly 30, one 20 of these running paths, as well as robots 75 and 85.

[0115] Let us note 5R the chosen replacement anode assembly, as well as 6R and 7R respectively its rod and its anode. The 3-D camera 76 first localizes the position of the replacement anode rod 6R (see capture 76A). Then the lifting robot 85 is moved so as, first to pick up the replacement anode assembly, and then lift this picked up assembly as shown on FIG. 11 (see arrow L1). Once this replacement anode assembly has been lifted, the 3-D camera determines the position of this replacement anode (see capture 76B). After this determination step the anode servicing assembly 30, which carries the replacement anode assembly 5R, is driven back along the paths (see arrow F30 on this FIG. 11) until it reaches the location of the spent anode.

[0116] Robot 75 is then moved, so as to equip its head 758 with a U-shaped gripper 77 (see FIG. 12). This gripper 77, which is detachably fixed on platform 72 (see in particular FIG. 14 which shows this gripper on this platform), is adapted to cooperate with the hood panels 13. As shown on FIG. 12, each anode assembly of a given cell is associated with two adjacent hoods panels, i.e., it is necessary to remove two adjacent hood panels to access to a given anode assembly. In particular the spent anode assembly 5U is associated with hood panels 13A and 13B. The camera 76 first localizes right hood panel 13A, and thereafter gripper 77 lifts said hood panel and places it onto neighboring hood noted 13C as shown on this FIG. 12. The same operation (not shown on this FIG. 12) is carried out on the left hood panel 13B, which is localized, gripped and then placed onto neighboring hood panel 13D.

[0117] Robot 75 is then moved, so as to release back the gripper 77 on platform. Head 758 is then equipped with above-described nozzle 55. This nozzle makes it possible to aspirate hot material (crushed bath and alumina mixture) called hereafter ACRM (Anode Cover Recycled Material), from the vicinity of spent anode along arrow F55. This step is illustrated on FIG. 13. Said nozzle is then placed back on its carrier 50.

[0118] Thereafter said robot 75 further moves, so that its head might be equipped with a crust saw 78, which is detachably supported by platform 72 (see also FIG. 13 showing this saw mounted on this platform). The crust around spent anode is then broken, typically around four sides of said spent anode (see FIG. 14 with lines F78 showing the motion of the saw 78). So as to avoid any undue damage, the 3-D camera had previously determined the position of the neighboring anodes, namely those which are on either side of spent anode. Said crust saw 78 is then placed back on its platform 72.

[0119] Afterwards the position of the anode rod 6U of spent anode assembly 5U is checked, using said 3-D camera 76. This step, which is not shown on the figures, is analogous to above-described step carried out on replacement anode assembly 5R. Then the other lifting robot 95 is lowered, so as to come in the vicinity of spent anode assembly. Clamp 14 is unlocked, using an appropriate screw tool 96 which is provided on said lifting robot 95. Then the latter lifts then said spent anode, as shown by arrow L2 on FIG. 15.

[0120] 3-D camera 76 determines then the position of this spent anode, as shown on FIG. 16 (see capture 76C). Said FIG. 16 illustrates, on the one hand lifting robot 85 and replacement anode assembly 5R, on the other hand lifting robot 95 and spent anode assembly 5U. It shall be noted that providing two distinct lifting robots 85, 95 brings about specific advantages. Indeed, it makes it possible to operate two anode assemblies at the same time, without moving anode servicing assembly between spent anode assembly and the group of replacement anode assemblies. This makes it possible to save time, for what concerns the global processing of the plant.

[0121] Said camera 76 also checks the shape of spent anode assembly 5U as well as the position of the pot opening PO, created by the removal of hood panels 13A and 13B. On FIG. 17, only first removed panel 13A is illustrated above panel 13C, bearing in mind that other removed panel 13B is placed above panel 13D. Replacement anode assembly 5R is then put in place, into the above-mentioned pot opening. This step is illustrated on FIG. 17, the arrow D showing the downwards motion of both robot 85 and replacement anode assembly 5R. The final position of said replacement anode is adjusted on the basis of images, which have been captured by the above camera 76 as above described. Clamp 14R is locked by a tool 86, analogous to that 96, which is provided on robot 85.

[0122] As shown on FIG. 18 multi use head 758 of robot 75 grasps then the above-described nozzle 55. The latter contains a quantity of recycled hot ACRM, which is poured at the vicinity of replacement anode along arrow f55. Moreover, some cold ACRM is further poured on top of above poured ACRM, until right thickness is reached (said step is not illustrated). This further quantity of ACRM is fed to nozzle 55, from hopper 45.

[0123] As final steps, which are also not illustrated, multi-use head of robot 75 places back hood panels 13A and 13B in their original position, so as to close pot opening PO. Camera 76 checks then that the new anode is situated at the right height. As a further checking step, multi-use head grasp tool 79, which is adapted to measure the current intensity and to determine proper anode settings.

[0124] It should be noted that the embodiment of the anode servicing assembly according to the invention which comprises a camera configured to determine and control the anode height is particularly advantageous. Prior art devices use either external reference systems or laser height measurement devices.