WO2016128652A1 - Method for detaching a spent anode assembly from a vessel of an aluminum production plant - Google Patents

Abstract

The method of the invention is carried out in order to detach a spent anode assembly (15) comprising at least one spent anode (16b) around which a crust has formed during electrolysis. The disclosed method involves a step in which a tool is used to break off the crust and the tool is moved along at least one section of the periphery of the spent anode so as to form a breaking line that is sufficient to allow the anode assembly to then be removed from the vessel (6). According to the invention, at least one tool used comprises a rotary disk (220) that has a substantially horizontal axis (221), the rotary disk being made to rotate about the axis thereof and being able to cut the crust.

Description

 Method for disengaging a spent anode assembly from a tank of an aluminum production plant

The present invention relates to a method for disengaging a spent anode assembly from a tank of an aluminum production plant by igneous electrolysis. The invention further relates to a device for disengaging a spent anode assembly from a tank of such an installation. The invention also relates to a service module for operating such an installation, a service machine comprising such a service module mounted on a trolley, a unit comprising a traveling crane and such a service machine, as well as an igneous electrolysis aluminum production plant comprising such a unit.

 Aluminum is conventionally produced in a plant called an aluminum smelter, by igneous electrolysis, according to the Hall-Héroult process.

 An aluminum smelter traditionally comprises, in a building, several hundred electrolysis cells connected in series and traversed by an electrolysis current. The electrolysis cells extend in a transverse direction and are arranged next to each other in a longitudinal direction. Thus, on the one hand, there is a transverse access path between two adjacent cells, and on the other hand a wider longitudinal operating aisle at the end of all the cells. The driveway allows the movement of vehicles and personnel on foot.

 An electrolysis cell conventionally comprises a steel tank having an inner lining of refractory materials, and containing a cathode of carbon material and an electrolytic bath in which is dissolved alumina. The cell also includes several anode assemblies. Each anode assembly comprises at least one anode immersed in this electrolytic bath and an anode rod sealed in the anode and mounted on an anode support. The anodes are generally made from carbonaceous blocks cooked prior to their introduction into the electrolysis cell. In addition, electrical conductors allow the routing of the electrolysis current between the cells of the installation.

The vessel has an opening through which the anode assemblies are introduced. In order to limit the thermal losses and to prevent the diffusion of harmful gases generated during the electrolysis reaction from the electrolysis cell, it is planned to close the opening of the tank with a set of removable covers, generally placed one at a time. next to the others in a longitudinal direction of the electrolysis cell, that is to say along the transverse direction, so as to form a closed chamber. Since the anode assemblies are consumed during the electrolysis reaction, they must therefore be replaced by new anode assemblies. During an anode assembly change, some of the covers are removed to open an access window inside the tank.

The spent anode assembly is removed from the electrolysis cell through this access window and deposited on a support, where it is stored temporarily before it can be taken to a revaluation zone. Then the crusts formed by the cover products periodically introduced into the electrolytic bath are removed and deposited in a scallop collection device with a cleaning tool also called scallop. This tool is inserted into the electrolysis cell through the access window. A new anode assembly is then introduced into the electrolysis cell, via the access window, in place of the spent anode assembly. Finally, the removable covers initially removed are replaced to close the access window.

 These operations are performed largely by means of a service unit comprising:

 a traveling crane which has two transverse beams and which is mounted longitudinally movable in the building above the electrolysis cells;

 a carriage mounted on the two girders of the traveling crane movably in the transverse direction, and carrying handling and intervention tools.

During the electrolysis, a crust is formed on the surface of the molten bath located in the electrolytic cell. This crust is thus formed around the anode and, when the anode is worn and must be replaced, it is taken in this crust. Thus, in order to be able to remove the spent anode assembly, it is first necessary to break the crust formed around the spent anode.

The characteristics of the crust are poorly known and / or poorly controlled. Indeed, its thickness is not controlled. Similarly, its hardness can vary on its thickness and according to its position in the tank. For this purpose, in order to be able to break it without taking into account its characteristics, it is known to use biting tools, which are mounted on one arm and driven by a vertical reciprocating movement, in particular by means of an actuator pneumatic. The arm, which can be mounted on the aforementioned carriage or on a vehicle on the ground of the installation, is moved so that the breaker moves on at least a part of the periphery of the spent anode. The piercer thus performs a series of point breaks of the crust, typically along a break line, and this sufficiently to allow the subsequent removal of the anode assembly from the tank, by a gripper assembly anodic. It is also known to use wheel-type tools, which are mounted free to rotate at the end of an arm, and whose rotation is caused by the friction of the wheel on the crust and the movement of the arm in the sense of the desired break line.

These solutions make it possible to break the crust while avoiding the knowledge of the characteristics of the crust.

 However, these crust breaking techniques have a number of disadvantages.

 Thus, the break line made by the breaker, formed of a series of point breaks, may be insufficient for the anodic assembly gripper can easily tear the spent anode assembly out of the bath. It is therefore necessary either to exert a greater pulling force, or to implement the breaker over a greater distance to the periphery of the anode, to obtain a zone of sufficient fragility.

Moreover, insofar as the rupture line is formed of a series of point breaks, tearing of the anode assembly causes the formation of large crustal blocks which break off and fall to the bottom of the tank. This leads to a significant loss of bath, and requires longer cleaning operations of the tank, thus increasing the cycle time and production costs.

The fact that the break line does not have a clean configuration can also make it difficult to set up and correctly position a new anode assembly in the vessel.

 In addition, the crust thus broken is pressed into the electrolytic bath, creating solid blocks in the liquid bath, which can change the composition of the electrolytic bath and reduce the efficiency of the electrolysis. These solid blocks also prevent the cleaning tool from properly dipping into the electrolytic bath. The placing of new anodes can also be hindered by such blocks.

 The present invention aims to overcome the disadvantages mentioned above.

For this purpose, and according to a first aspect, the invention relates to a method for disengaging a spent anode assembly from a tank of an igneous electrolysis aluminum production plant, the installation comprising cells extending in accordance with a transverse direction, the spent anode assembly comprising at least one used anode. The method uses here a unit comprising a structure comprising: a traveling crane extending in a transverse direction and adapted to move in a longitudinal direction above the cells;

 and a service machine comprising:

 A carriage mounted on the traveling crane and arranged to be able to move relative to the crane in the transverse direction and to be positioned above and to the right of each of the hoods of the cells;

A service module mounted on the carriage and comprising handling and intervention tools including at least one rotating disc disposed in a substantially vertical plane;

During the electrolysis, a crust has formed around the anode. The method then comprises a step of using a tool to break the crust on at least a portion of the periphery of the spent anode to realize a breaking line sufficient to allow subsequent removal of the anode assembly from the vessel.

 According to a general definition of the method according to the invention, at least one tool is used comprising a rotating disc having an axis extending substantially horizontally, the rotating disc being rotated about its axis and being able to cut the crust, and the method comprises at least the following steps:

 moving the carriage so that the rotating disk is located at a portion of a cell; moving the rotating disc relative to the crust, substantially vertically downwards, to bring the rotating disc into contact with the crust and to penetrate it at least partially into the crust over a penetration height; moving the rotating disk substantially in its plane relative to the crust, in a substantially horizontal translation of its axis with a feed rate, the rotating disk being rotated, to produce a breaking line along at least one vertical side of the used anode,

Therefore, at least the penetration height and the feed speed of the tool are adjusted to maintain the power developed by the motor below a threshold value.

Thus, the invention proposes to make the breaking line not with a biting tool but with a circular saw type tool. As a result, the crust is cut rather than broken. The line of rupture is therefore much sharper, which limits the formation of crustal blocks falling to the bottom of the tank and facilitates the insertion of a cleaning tool of the tank, for example a shovel bucket, and the establishment of a new anode assembly.

 This is even more advantageous if it is a change of anode in automatic mode, as this limits the risks of interruption of the automatic cycle.

In addition, the breaking line being at least partly continuous, and not formed of a succession of distinct points, it constitutes a zone of weakness greater than in the prior art. Therefore, thanks to the invention, it is conceivable to achieve a breaking line on a smaller distance to the periphery of the spent anode, without making it more difficult to tear the worn anode assembly. The time required for these operations is therefore reduced.

 It can be provided to use a rotating disk which is moved over at least a portion of the periphery of the spent anode, so that the break line forms a continuous cut. Alternatively, it may be provided to use a plurality of substantially aligned and adjacent rotating discs, which are moved downwardly to engage the crust but are not then moved horizontally. The rupture line is then formed of a succession of substantially contiguous continuous portions possibly separated by a bridge of material of very short length. These continuous portions have a length greater than the footprint or breakage made by a breaker.

 The method may comprise producing, by means of the rotating disk, a break line along at least one vertical side of the spent anode, for example along each of two parallel vertical sides of the spent anode. , and for example the realization of a line of rupture only along each of two parallel vertical sides of the worn anode.

 These two rupture lines can indeed suffice to allow sufficient disengagement of the spent anode to allow tearing without particular difficulties of the spent anode assembly.

 The method may include the simultaneous use of two rotary discs rotated about their respective axes, each of the rotating discs forming one of the break lines. Alternatively, one can provide the use of a single rotating disk which is moved to make a first line of rupture and a second.

 The rotating disk can moreover be cooled by blowing compressed air.

According to a possible embodiment, the installation comprises cells extending in a transverse direction (Y), the cells being arranged next to each other in a longitudinal direction (X), each cell comprising a tank which can contain a plurality of anode assemblies, for example substantially all, an anode assembly each including at least one anode and an anode rod, each cell having an upper opening, located in a substantially horizontal plane, which can be closed by a succession of removable covers, each of the covers being located at the right of an anode assembly contained in the cell. In addition, the method uses a unit comprising a structure comprising:

 a traveling crane extending in a transverse direction (Y) and adapted to move in a longitudinal direction (X) above the cells;

 and a service machine comprising:

 A carriage mounted on the traveling crane and arranged to be able to move relative to the traveling crane in the transverse direction (Y) and to be positioned above and to the right of each of the hoods of the cells;

 • A service module mounted on the carriage and comprising handling and intervention tools including at least one rotating disc disposed in a substantially vertical plane.

 The method then comprises the steps of:

 moving the carriage so that the rotating disk is located in line with a part of a cell hereinafter called the intervention zone;

 moving the rotating disc relative to the carriage, substantially vertically downwards, to bring the rotating disc into contact with the crust and to penetrate at least partially into the crust, the rotating disc being rotated;

 moving the rotating disk substantially in its plane, in a substantially horizontal translation of its axis, the rotating disk being rotated, to achieve a breaking line along at least one vertical side of the spent anode.

The method may comprise the use of two rotating discs arranged facing each other in substantially parallel planes, the two rotating discs being spaced apart from one another by a distance greater than the dimension of an anode according to the longitudinal direction (X) or the transverse direction (Y), so as to simultaneously achieve two lines of rupture on either side of the anode. Said two rupture lines are for example parallel to the longitudinal direction (X). It can be expected that the two rotating discs are linked in their movement of substantially horizontal translation of their axis, this being however not limiting.

With a service module further comprising an anode assembly gripper mounted on the same support as the rotating disk, the method may comprise the step comprising gripping the anode assembly by means of the anode assembly gripper prior to contacting the rotating disk with the crust. This ensures a good positioning of the rotating disc relative to the anode to disengage.

 With a service module further comprising a clamping / loosening member mounted on the same support as the rotary disc, the method may comprise the step of, by means of said clamping / loosening member, detaching the anode assembly from an anode receiver fixed on the cell, once the breaking line achieved by the rotating disc. The carrier carrying the anode assembly gripper can then be actuated to extract the anode assembly from the cell vessel.

According to a second aspect, the invention relates to a device for disengaging a spent anode assembly from a tank of an igneous electrolysis aluminum production plant, the spent anode assembly comprising at least one spent anode, a crust of being formed around the anode during electrolysis, said device being intended to be carried by a mobile equipment of the installation and comprising a tool for breaking the crust and a support of said tool.

 According to a general definition of the device according to the invention, the tool comprises at least one rotating disc having an axis extending substantially horizontally, the rotating disc being able to cut the crust when it is rotated about its axis. In addition, the device comprises a connection system between the rotating disk and the equipment, said linkage system comprising:

 means for rotating the rotating disk about its axis;

 means for moving the axis of the rotating disk in a translation substantially horizontal and orthogonal to said axis;

 and shaped guiding means for guiding said displacement in translation of the axis of the rotating disk,

so that the rotating disk can realize, on at least a part of the periphery of the spent anode, a sufficient breaking line to allow the subsequent removal of the anode assembly from the tank

The device then comprises a speed sensor for advancing the rotating disk and a height sensor for penetrating the rotating disk into the crust, the device further comprising a system for regulating the speed of advance and the penetration height of the rotating disc. The operating parameters of the rotary disk can thus be adjusted by the control system so as to maintain the power developed by the motor below a threshold value. The mobile equipment may comprise a carriage of a service machine mounted on a traveling crane. Alternatively, it could be a vehicle moving on the ground of the installation.

 The rotating disc may comprise at its periphery a plurality of rigid teeth, preferably substantially regularly spaced apart, said teeth having diamond elements reported and welded to the laser.

 Advantageously, the means for rotating the rotating disk about its axis comprise a motor located at a distance from the rotating disk, and a transmission system. The engine is thus remote from the cutting zone, that is to say at a distance from the tank. This is advantageous in terms of arrangement. Indeed, the power to be provided for the cutting operation is relatively high, for example of the order of 15 to 30 kW. An engine of such power has a significant size and is therefore difficult to accommodate in the available internal volume of the tank. It can for example be an electric motor or a hydraulic motor. The transmission system includes, for example, angle deflectors and rigid or flexible transmission shafts.

 It can be provided that the connecting system comprises a clamping jaw of a central portion of the rotary disc, the central portion covering a large enough surface, for example having a radius greater than one quarter of the radius of the rotary disc. The fact of providing such a coupling device between the drive means and the rotating disc, via a pinch on a large surface of the rotating disc, makes it possible to obtain a better maintenance of the rotating disc and to considerably reduce the risks that the disc rotating is deformed, especially is sailing.

 In addition, the connection system may comprise a compressed air blowing ramp to cool the rotating disc during cutting of the crust.

 The rotating disc may have a thickness greater than 6 mm, for example of the order of 7 mm. By this thick core, one increases the mechanical resistance to deformations, in particular to the veiling of the rotating disc.

According to a third aspect, the invention relates to a service module for operating an igneous electrolysis aluminum production facility, the installation comprising cells which contain anode assemblies and which are closed by covers, the service module being intended to be mounted on a carriage arranged to be able to move in a transverse direction (Y) with respect to a traveling crane which extends in a transverse direction (Y) and which is designed to move in one direction longitudinal axis (X) above the cells, the carriage forming a mobile equipment of the installation. According to a general definition, the service module also comprises at least one device as previously described, the connection system between the rotating disk and the equipment comprising an elevation system which is fixed to the carriage and which carries handling and intervention including said rotating disc.

 The service module may further comprise an anode assembly gripper mounted on said elevation system, and / or a clamping / loosening member mounted on said elevating system, said clamping / loosening member being shaped to be able to disengage. the anode assembly of an anode receiver fixed on the cell.

According to a fourth aspect, the invention relates to a service machine for operating an igneous electrolysis aluminum production plant, the installation comprising cells which contain anode assemblies and which are closed by covers, the service machine comprising:

 a carriage for mounting on a traveling crane, the traveling crane extending in a transverse direction (Y) and being adapted to move in a longitudinal direction (X) above the cells, the carriage being arranged to be able to moving relative to the crane in the transverse direction (Y) and to be positioned above and to the right of each of the hoods of the cells;

 and a service module as previously described, the service module being mounted on the carriage.

 According to a fifth aspect, the invention relates to a unit for operating an igneous electrolysis aluminum production plant, the installation comprising cells which contain anode assemblies and which are closed by covers, the unit comprising a structure comprising:

- a traveling crane which comprises two beams extending in a transverse direction (Y) and which is designed to move in a longitudinal direction (X) above the cells;

 and a service machine as previously described.

 According to a sixth aspect, the invention relates to an aluminum production plant by igneous electrolysis, comprising:

a building in which several cells are located; each cell extending in a transverse direction (Y), the cells being arranged next to each other in a longitudinal direction (X) by providing at one of their ends a longitudinal operating aisle; each cell can contain several anode assemblies each including at least one anode and anode rod; each cell having an opening that can be closed by a succession of removable covers;

 a unit as previously described, the traveling crane being mounted longitudinally movable on longitudinal rails formed in the vicinity of two transverse end walls of the building.

 According to a possible embodiment, each cell may contain several anode assemblies, for example substantially in their entirety, and the opening is an upper opening of the cell, located in a substantially horizontal plane, each of the covers being located at the right of a set. anodic content in the cell.

 In this case, the device may comprise two rotating discs arranged facing each other in substantially parallel planes, the two rotating discs being spaced from one another by a distance greater than the dimension of an anode according to the longitudinal direction (X) or the transverse direction (Y), so as to simultaneously achieve two lines of rupture on either side of the anode. It can be expected that the two rotating discs are linked in their movement of substantially horizontal translation of their axis, this being however not limiting.

 Several possible embodiments of the invention are now described by way of nonlimiting examples, with reference to the appended figures:

Figure 1 is a schematic perspective view of an aluminum production plant according to one embodiment of the invention, showing a unit including a carriage carrying tools including a rotating disk;

 Figure 2 is a schematic side and partial view of an aluminum production plant according to another embodiment of the invention, showing a device including a rotating disk;

 Figure 3 is a detail view in perspective of a rotating disk;

 Figure 4 is a detail view in cross section of a rotating disc;

 Figures 5a and 5b illustrate an embodiment of a device including a rotating disk, in two different orientations;

FIGS. 6a to 9b illustrate successive steps of a method for disengaging a spent anode assembly from a tank of an installation, by means of the device illustrated in FIGS. 5a and 5b; FIG. 10 schematically represents a tank of the installation, viewed from above, and shows two rupture lines made on either side of a spent anode assembly by means of a rotating disc.

 FIG. 1 schematically represents a plant 1 for producing aluminum by electrolysis, and more particularly an electrolysis room of such an installation 1.

 The installation 1 comprises a building in which are located several electrolysis cells 2. Each cell 2 extends in a transverse direction Y, and the cells 2 are arranged next to each other in a longitudinal direction X. Between two adjacent cells 2 is provided a transverse access path 4, and to one ends of the cells 2 is formed a longitudinal operating aisle 5 along the installation 1.

 Each cell comprises a tank 6 having two longitudinal walls 7 and two transverse walls 8, and containing a cathode and an electrolytic bath. The tank 6 has an upper opening 9 located in a substantially horizontal plane. Caps 10 are provided to seal the opening 9 removably. In the embodiment shown, the covers 10 are substantially planar and rectangular. Each cover 10 extends substantially in a horizontal plane, from a transverse wall 8 of the tank 6 to the opposite transverse wall 8, several covers 10 being juxtaposed along the direction Y to allow, together, to seal 9. Each cover 10 is provided with parts 11 that can be grasped in order to remove the cover 10. It should be noted that the arrangement of the parts 1 1 on the covers 10 as shown in FIG. 1 should not be considered as limiting.

 In the tank 6 are placed several anode assemblies 15. An anode assembly 15 comprises at least one anode 16 in the form of a precooked carbon block, which will be immersed in the electrolytic bath. An anode rod 17 is sealed in the anode 16, all the rods 17 being fixed on the same anodic support 18. In the embodiment shown, an anode assembly 15 comprises four anodes 16 and has a rectangular parallelepipedal shape, which is placed in the tank so as to extend substantially to the right of a single cover 10. The tank 6 and the anode assembly 15 are configured so that the anode assembly 15 can be housed substantially in its entirety in the tank 6, at least so that it does not protrude above the opening 9.

The tank 6 receives new anode assemblies 15, that is to say carrying new anodes 16a. During electrolysis, the anodes are gradually consumed and become used anodes 16b or butts (see Figure 6b in particular). A set Anode 15 worn, that is to say carrying a used anode 16b, must be removed from the tank 6 to be replaced by a new anode assembly 15.

 In particular, to carry out the anode assembly change operations 15, the installation 1 comprises a unit 30, or service unit.

The unit 30 comprises a crane 31 which comprises two beams 32 extending in the transverse direction Y. The crane 31 is mounted longitudinally movable on longitudinal rails formed in the vicinity of two transverse end walls 3 of the building. The crane 31 is thus designed to move in the longitudinal direction X above the cells 2 and the operating aisle 5.

The unit 30 also comprises a service machine 33. The service machine 33 comprises a carriage 35 mounted on the two beams 32 of the traveling crane 31, movable in the transverse direction Y. The carriage 35 is thus arranged to be able to be positioned above and to the right of each of the hoods 10 of the cells 2. The service machine 33 further comprises a service module 36 mounted on the carriage 35 and having handling and intervention tools. It is specified that, in Figure 1, these tools are shown very schematically.

 In the embodiment shown, the tools carried by the service module 36 are distributed in a first tool block 100 and a second tool block 200.

 The first tool block 100 comprises at least a first mast 1 1 1 which, in a non-limiting embodiment, is telescopic in the vertical direction Z. At its upper part, the first mast 1 1 1 is fixed on the carriage 35 and at its lower part, it carries one or more tools, including at least one hood gripper 101 and at least one cleaning tool 120 of the cell 2. The cleaning tool 120 is for example in the form of a bucket bucket.

The second tool block 200 comprises at least one elevation system in the form of a second mast 21 1, and for example two second poles 21 1 a, 21 1 b (see in particular in FIG. 5 a) which are, in a non-limiting embodiment, telescopic in the vertical direction Z. At its upper part, the second mast 21 1 - or each of the second masts 21 1 a, 21 1 b - is fixed on the carriage 35 and, at its lower part, it carries one or more tools, including at least one anode assembly gripper 201. The anode assembly gripper 201 may also be shaped to be able to grasp a containment bell. The second tool block 200 also includes at least one tool 220 for cutting the crust that forms during the electrolysis. According to the invention, this tool comprises a rotating disc 220 forming a blade, able to cut the crust at the way of a circular saw. The mast 21 1 forms a support of the rotating disc 220 which is mounted on the carriage 35 forming a mobile equipment installation 1.

 The fact that the first mast (and the second mast) is fixed on the carriage does not exclude that is provided at the interface of the mast and the carriage a device allowing a small degree of freedom in rotation about the axis X and / or the Y axis of the mast relative to the carriage. Such limited flexibility can reduce damage in the event of an impact, for example.

 Figure 2 illustrates an installation 1 according to another embodiment, wherein the opening 9 of the tank 6, and the covers 10 which seal, are arranged laterally. In addition, the anode assemblies 15 protrude above the opening 9.

In this embodiment, the tool for breaking the crust comprises a rotating disc 220, and an arm 450 which forms a support of the rotating disc 220 and which is mounted on a mobile equipment 550 of the installation 1 which may for example be a vehicle capable of moving on the floor of the installation 1.

 Figures 3 and 4 show in more detail one possible embodiment of the rotary disc 220.

 The rotating disc 220 has an axis 221 extending substantially horizontally, more precisely in the transverse direction (Y), the rotating disc 220 being disposed in a vertical plane (X, Z).

 The rotating disc 220 may be made of metal and have a thickness greater than 6 mm, for example of the order of 7 mm. As seen in Figure 3, the rotating disc 220 may comprise at its periphery a plurality of rigid teeth 222, preferably substantially regularly spaced, said teeth 222 having diamond elements reported and welded laser. In addition, there can be provided a protective device 223, in the form of a cap of the upper part of the rotary disc 220, to prevent projections during the implementation of the rotary disc 220.

 In operation, the rotating disc 220 is rotated about its axis 221, in order to cut the crust. The means for rotating the rotating disk 220 about its axis 221 comprise a motor 224 located at a distance from the rotary disk 220 and a transmission system (not shown).

However, the characteristics of the crust, such as its thickness and hardness, are not known, or are poorly controlled in the tank. Therefore, in order not to bias the motor 224 beyond a power threshold, acceptable in relation to the rated power of the motor, the vertical displacement and the horizontal displacement of the rotating disk 220 relative to the crust are adjusted. More specifically, displacements of the rotary disk 220 are determined in particular by the following operating parameters:

- the penetration height, that is to say the depth at which the rotating disk 220 enters the crust, by the vertical displacement of the rotating disk 220; the speed of advance, that is to say the speed at which the axis 221 of the rotary disk 220 moves horizontally with respect to the crust;

- The cutting speed, that is to say the speed at which the periphery of the rotating disk 220 comes into contact with the crust.

 Therefore, the system comprising the disk 220 and the motor 224 is slaved so that the power of the motor 224 does not exceed a threshold value by adjusting the penetration height and the cutting speed of the rotary disk 220.

 For this purpose, there is provided a speed sensor of the rotating disk 220 and a penetration height sensor of the rotating disk 220 in the crust. A system for regulating the feed rate and the penetration height of the rotating disk 220 receives the data from the sensors and acts accordingly on the rotating disk 220 to adapt its penetration height and its cutting speed.

 The cutting speed is typically indicated by a setpoint, but can also be regulated.

 As illustrated in FIG. 4, the connection system between the rotary disc 220 and the equipment that carries it (trolley 35 or equipment 550) may comprise a clamping jaw 225 of the central portion 226 of the rotary disc 220. Preferably, for better mechanical strength, the nip is at a central portion 226 of relatively large area, for example having a radius greater than one quarter of the radius of the rotary disc 220.

In addition, the connection system may comprise a ramp 227 for blowing compressed air to cool the rotating disc 220 during cutting of the crust.

 Reference will now be made to FIGS. 5a to 5b, which show in greater detail an embodiment of the device according to the invention, and more specifically the embodiment illustrated schematically in FIG. 1.

Each of the second masts 21 1 a, 21 1 b comprises:

an upper portion 212 fixed to the carriage 35; an intermediate portion 213 movable relative to the upper portion 212 along a substantially vertical upper guide axis 214, between a high position and a low position, sliding inside the upper portion 212;

 a lower portion 215 movable relative to the intermediate portion 213 along a substantially vertical lower guide axis 216 and distinct from the upper guide axis 214, that is to say shifted relative thereto. In the embodiment shown, the axes 214 and 216 are offset in the direction X and in the direction Y. The lower portion 215 is slidably mounted relative to the intermediate portion 213 outside the intermediate portion 213, between a high position. and a low position.

 In the embodiment shown, the upper 212, intermediate 213 and lower 215 portions are cylindrical, of polygonal section (for example substantially square), or round. Alternatively, they could be formed of an open profile, for example a U-shaped profile.

Guiding devices 231, 232, 233, 234 of the different portions 212, 213, 215 are provided relative to one another in their relative z-sliding movement, for example in the form of rollers and / or inner or outer guide pads.

 The intermediate portion 213 carries the anodic assembly gripper 201, also known as the tear-off tool, and more precisely in the embodiment shown two anodic assembly grippers 201.

 In addition, the lower portion 215 carries at least one rotating disc 220, used to disengage the spent anode assembly from the crust and then extract it from the vessel 6. In the embodiment shown, the rotary disc 220 is disposed substantially in the axis of the lower portion 215, and extends in a vertical plane (X, Z), with its axis 221 oriented along the axis (Y).

 In the embodiment shown, the lower portion 215 carries, as seen in Figure 5b, the two rotating discs 220 disposed substantially parallel, vis-à-vis their axes 221 being substantially merged. In addition, the two rotary disks 220 are arranged on either side along Y of the upper guide axis 214, being spaced from each other by a distance DY greater than the dimension dY of anode. 16 - or anodes 16 of the same anode assembly 15 - in the transverse direction (Y) (see Figure 6b).

A first actuator 235 allows the displacement of the intermediate portion 213 relative to the upper portion 212, and a second actuator 236 allows the movement of the lower portion 215 relative to the intermediate portion 213. It can be hydraulic cylinders, pneumatic or electric. The movements of the intermediate portion 213 and the lower portion 215 allow to adjust the penetration height of the rotating disc 220 in the crust.

According to the invention, there is further provided means for moving the axis 221 of the rotary disk 220 in a substantially horizontal translation and orthogonal to said axis 221, and guide means shaped to guide said displacement in translation of the axis. 221 of the rotary disk 220. Thus, the speed of advance is adjusted by adjusting the horizontal displacement of the axis 221 of the rotary disk 220.

According to an embodiment illustrated in Figures 5a and 5b, the translation is performed in the longitudinal direction (X). For this purpose are provided two longitudinal guide rails 230 fixed on the intermediate portion 213 and receiving integral members of the lower portion 215. In the embodiment shown, the two rotary discs 220 can be linked in their translational movement, this is not necessary. being not limiting. The two rotating discs 220 can act simultaneously to each perform a cut of the crust.

 In FIGS. 6a to 9b, steps of an operation of removal of a spent anode assembly 15, that is to say having at least one used anode 16b, prior to its replacement by an anode assembly, are represented. 15 nine. This used anode assembly is in the tank 6, in an intervention zone 600 of the cell 2.

 In FIGS. 6a and 6b, the carriage 35 is placed so that the second tool block 200 is in line with the intervention zone 600. More precisely, the anodic assembly grippers 201 are at the right of the corresponding gripping formed on the anodic support 18, and the rotating discs 220 are in line with the 240 transverse spaces existing between the anode assembly 15 located in the intervention zone 600 and adjacent anode assemblies 15 (Figure 6b). In addition, the rotating discs 220 are located substantially at a longitudinal end of the guide rails 230, which substantially corresponds to a longitudinal end of the spent anode assembly.

In addition, in FIGS. 6a and 6b, the intermediate portion 213 of the second masts 21 1 a, 21 1 b is in the lower position, but the lower portion 215 is in the high position, the rotating disc 220 not being in contact with the crust. The anodic assembly gripper 201 is thus in a position such that it can come to grip the anodic support 18. allows to correctly position, in the transverse direction Y, the rotating discs 220 to the right spaces 240.

 The lower portion 215 is then lowered, as illustrated in FIGS. 7a and 7b, and the rotating disk 220 - or each of the two rotating disks 220 - is rotated about its axis 221. Thus, the rotary disk 220 is brought into position. contact with the crust and may at least partially penetrate the crust.

 Then, the rotating disk 220 - or each of the two rotating disks 220 - is moved along the longitudinal axis (X), being guided in the guide rails 230, having the set advance speed, remaining substantially in its plane, and being always rotated, until substantially reaching the other longitudinal end of the guide rails 230, which corresponds substantially to the other longitudinal end of the spent anode assembly 15 (FIGS. 8a and 8b) ).

 The rotating disk 220 thus makes a break line 380 along a vertical side of the used anode 16b, the break line 380 extending in the longitudinal direction (X). More precisely, the two rotating discs 220 simultaneously produce two rupture lines 380 on either side of the used anode (s) 16b, as illustrated in FIG.

 In this configuration, the rotary disc (s) 220 have produced a rupture line 380 sufficient to allow the spent anode assembly 15 to be disengaged from the tank 6, by means of the anodic assembly gripper 201 raised by means of the mast 21 (FIG. Figures 9a and 9b). Due to the quality of this break line 380, and also its continuous character on both sides of the spent anode 16b, it is not necessary, in order to disengage the spent anode assembly, to make a break line. on at least one of the other sides of the anode 16b.

Prior to tearing and lifting the spent anode assembly, it may be necessary to separate the anode assembly 15 from an anode receiver 14 fixed to the cell 2 by means of a clamping member. loosening 245 mounted on the service module 36, on the lower portion 215. As illustrated in Figures 8a and 8b, this clamping / loosening member 245 can be deployed when used, and retracted the rest of the time (Figure 6a especially).

 Once the anode assembly 15 has been removed, the rotating disk 220 can be moved in translation to be returned to its initial position for use in a subsequent disengagement operation of another spent anode assembly.

The use of the rotating disk 220 in the manner of a rotary saw allows the crust to be cut along the rupture line, and no longer to penetrate it into the electrolytic bath. as in the state of the art. Thus, the pollution of the electrolytic bath by crust blocks is avoided, to maintain optimal conditions of the electrolytic bath. The lack of knowledge of the characteristics of the crust to cut it is bypassed is ensuring an adjustment of the penetration height in the crust and the speed of advance. The risks of blocking the rotating disc 220 and abnormal biasing of the motor 224 are thus reduced.

 The invention provides a decisive improvement to the prior art, and has many other advantages among which may be mentioned:

 reducing the cycle time of the anode change, in particular because certain steps can be performed simultaneously and not sequentially; minimizing the opening time of the tank, that is to say "bare" bath, also due to the completion of steps simultaneously and not sequentially;

 the compactness of the service unit, by a configuration of the "two tools in one" type, which allows the lightening and simplification of the unit, but also to limit the envelope of the electrolysis building;

 the correct positioning of the cutting discs around the anode, resulting in a gain in the reliability and repeatability of the automation of operations (including the ease of introduction of the new anode between the two adjacent anodes) and the securing of automatic operations (an offset of the disc (s) could lead to damage to the anode or equipment on the tank);

 reducing the effort required to extract the spent anode, thus generating less mechanical stress, especially for the gripping tool.

 It goes without saying that the invention is not limited to the embodiments described above as examples but that it includes all the technical equivalents and variants of the means described as well as their combinations.

Claims

A method for disengaging a spent anode assembly (15) from a vessel (6) of an igneous electrolysis plant (1) for aluminum production, the plant comprising cells (2) extending in one direction cross-section (Y), the spent anode assembly (15) having at least one spent anode (16b), a crust having formed around the anode during electrolysis, the method using a unit (30) comprising a structure comprising:  a traveling crane (31) extending in a transverse direction (Y) and adapted to move in a longitudinal direction (X) above the cells (2);  and a service machine (33) comprising:  A carriage (35) mounted on the traveling crane (31) and arranged to be able to move relative to the traveling crane (31) in the transverse direction (Y) and to be positioned above and to the right of each of the covers (10) of the cells (2); • a service module (36) mounted on the carriage (35) and comprising handling and intervention tools including at least one rotating disc (220) disposed in a substantially vertical plane; the method comprising a step of using a crust breaking tool on at least a portion of the periphery of the spent anode (16b) to provide a break line (380) sufficient to allow subsequent removal of the assembly anode (15) out of the tank (6), characterized in that at least one tool comprising a rotating disc (220) having an axis (221) extending substantially horizontally, the rotating disk (220) being driven in rotation about its axis (221) by a motor (224) and being able to cut the crust, the method comprising the following steps: moving the carriage (35) so that the rotating disk (220) is located at right a part of a cell (2); moving the rotating disc (220) relative to the crust, substantially vertically downward, to cause the rotating disc (220) to contact the crust and to penetrate at least partially into the crust over a penetration height; moving the rotating disc (220) substantially in its plane relative to the crust, in a substantially horizontal translation of its axis (221) with a speed in advance, the rotating disk (220) being rotated, for producing a break line (380) along at least one vertical side of the spent anode (16b), and in that at least one Penetration height and tool feed speed are adjusted to maintain the power output of the motor below a threshold value. 2. Method according to claim 1, comprising the production, by means of the rotating disk (220), of a breaking line (380) along at least one vertical side of the spent anode (16b), for example along each of two parallel vertical sides of the worn anode (16b). 3. The method of claim 2, comprising producing, by means of the rotating disc (220), a breaking line (380) only along each of two parallel vertical sides of the worn anode (16b). 4. The method of claim 2 or 3, comprising the simultaneous use of two rotating discs (220) rotated about their respective axis (221), each of the rotating discs (220) forming one of the rupture lines ( 380). 5. Method according to any one of the preceding claims, comprising the use of two rotating discs (220) arranged facing each other in substantially parallel planes, the two rotating discs (220) being spaced apart from each other. other than a distance (DY) greater than the dimension (dY) of an anode in the longitudinal direction (X) or the transverse direction (Y), so as to simultaneously produce two rupture lines (380) on each side; other of the anode (16b). The method of claim 5, wherein said two break lines (380) are parallel to the longitudinal direction (X). 7. Method according to any one of the preceding claims, wherein the service module (36) further comprises an anode assembly gripper (201) mounted on the same support (21 1) as the rotating disc (220), and in that the method comprises the step of gripping the anode assembly (15) by means of the anode assembly gripper (201) before placing the rotating disk (220) in contact with the crust, so as to ensure a good positioning of the rotating disk (220) relative to the anode (16b) to be disengaged. The method of any of the preceding claims, wherein the service module (36) further comprises a clamping / unclamping member (245) mounted on the same support (21 1) as the rotary disc (220), and in that the method comprises the step of, by means of said clamping / loosening member (245), separating the anode assembly (15) from an anode receiver (14) fixed on the cell (2), once the breaking line (380) made by the rotating disc (220). 9. Device for disengaging an anode assembly (15) used from a tank of an installation (1) for producing aluminum by igneous electrolysis, the spent anode assembly (15) comprising at least one spent anode (16b), a crust having formed around the anode during electrolysis, said device being intended to be carried by a mobile equipment (35, 550) of the installation (1) and comprising a tool for breaking the crust and a support (21 1, 450) of said tool, characterized in that the tool comprises a rotary disk (220) having an axis (221) extending substantially horizontally, the rotary disk (220) being able to cut the crust when it is rotated about its axis (221), and in that the device comprises a connection system between the rotary disc (220) and the equipment, said connection system comprising:  a motor (224) for rotating the rotating disc (220) about its axis (221);  means for moving the axis (221) of the rotary disk (220) in a translation substantially horizontal and orthogonal to said axis (221);  and guiding means (230) shaped to guide said translation displacement of the axis (221) of the rotating disk (220), so that the rotating disk (220) can provide, over at least a portion of the periphery of the spent anode (16b), a breaking line (380) sufficient to allow subsequent removal of the anode assembly (15). ) out of the tank (6). Apparatus according to claim 9, comprising a rotational disk feed speed sensor (220) and a crust disk penetration height sensor (220), the device further comprising a crane control system (220). speed of advance and the penetration height of the rotating disk (220). 1 1. Device according to claim 9 or claim 10, wherein the rotary disk (220) has at its periphery a plurality of rigid teeth (222), preferably substantially regularly spaced, said teeth (222) having diamond elements reported and welded to the laser. 12. Device according to any one of claims 9 to 1 1, wherein the connecting system comprises a jaw (225) for clamping a central portion (226) of the rotating disc (220), the central portion (226) having a radius greater than one quarter of the radius of the rotating disc (220). 13. Device according to one of claims 9 to 12, wherein the connecting system comprises a ramp (227) for blowing compressed air to cool the rotating disc (220) during the cutting of the crust. 14. Device according to one of claims 9 to 13, wherein the rotary disk (220) has a thickness greater than 6 mm, for example of the order of 7 mm. 15. Service module for operating an igneous electrolysis plant (1) for aluminum production, the plant (1) comprising cells (2) which contain anode assemblies (15) and which are closed by hoods (10), the service module (33) being intended to be mounted on a carriage (35) arranged to be able to move in a transverse direction (Y) with respect to a traveling crane (31) which extends along a transverse direction (Y) and which is adapted to move in a longitudinal direction (X) above the cells (2), the carriage (35) forming a movable equipment of the installation, characterized in that the service (36) further comprises at least one device according to one of claims 9 to 14, the connection system between the rotating disc (220) and the equipment (35) comprising an elevation system (21 1) which is attached to the carriage (35) and which carries handling and intervention tools of which the edit rotating disk (220). The service module of claim 15, further comprising an anode assembly gripper (201) mounted on said elevation system (21 1). The service module according to claim 15 or claim 16, further comprising a clamping / loosening member (245) mounted on said elevating system (21 1), said clamping / unclamping member (245) being shaped to be able to separate the anode assembly (15) from an anode receiver (14) fixed on the cell (2). 18. Service machine for operating an installation (1) for producing aluminum by igneous electrolysis, the plant (1) comprising cells (2) which contain anode assemblies (15) and which are closed by hoods (10), the service machine (33) comprising: a carriage (35) for mounting on a traveling crane (31), the traveling crane (31) extending in a transverse direction (Y) and being adapted to move in a longitudinal direction (X) above cells (2), the carriage (35) being arranged to move relative to the traveling crane (31) in the transverse direction (Y) and to be positioned above and to the right of each of the hoods (10) of the cells (2);  and a service module (36) according to one of claims 15 to 17, the service module being mounted on the carriage (35). 19. Unit for operating an installation (1) for the production of aluminum by igneous electrolysis, the plant (1) comprising cells (2) which contain anode assemblies (15) and which are closed by covers (10), the unit (30) comprising a structure comprising:  a crane (31) which has two beams (32) extending in a transverse direction (Y) and which is adapted to move in a longitudinal direction (X) above the cells (2);  and a service machine (33) according to claim 18.  20. Aluminum production plant by igneous electrolysis, comprising:  a building in which several cells (2) are located; each cell (2) extending in a transverse direction (Y), the cells (2) being arranged next to each other in a longitudinal direction (X) by providing at one of their ends an operating aisle (5) longitudinal; each cell (2) being able to contain a plurality of anode assemblies (15) each including at least one anode (16, 16a, 16b) and an anode rod (17); each cell (2) having an opening (9) closable by a succession of removable covers (10);  a unit (30) according to claim 19, the crane (31) being mounted longitudinally movable on longitudinal rails formed in the vicinity of two transverse end walls (3) of the building.  21. Plant according to claim 20, in which each cell (2) can contain several anode assemblies (15), and in that the opening (9) is an upper opening of the cell (2) situated in a substantially horizontal plane, each of the covers (10) being located at the right of an anode assembly (15) contained in the cell (2). 22. Installation according to claim 21, wherein the device comprises two rotating discs (220) arranged vis-a-vis in substantially parallel planes, the two rotating discs (220) being spaced apart from each other. a distance (DY) greater than the dimension (dY) of an anode (16) in the longitudinal direction (X) or the transverse direction (Y), so as to simultaneously realize two break lines (380) of other of the anode (16b).