Patent Application
20140231268
The invention relates to aluminum production using igneous electrolysis by means of the Hall-Héroult process. It more particularly relates to pot tending modules used in aluminum production plants.
Aluminum is produced industrially by igneous electrolysis in electrolytic cells according to the well-known Hall-Héroult process. The plants contain a great number of electrolytic cells laid out in line, in buildings called electrolysis halls or rooms, and electrically connected in series using connecting conductors. The cells are generally laid out so as to form two or more parallel lines which are electrically linked to each other by end conductors.
When operating, an electrolysis plant requires work on the electrolytic cells, including replacement of spent anodes by new ones, sampling of molten metal in the cells and sampling or top-ups of electrolyte. In order to carry out this work, the most modern plants are equipped with one or more pot tending assemblies including an overhead traveling crane which can be translated above the series of electrolytic cells, and one or more pot tending machines each comprising a carriage and a pot tending module provided with handling and servicing devices (often called “tools”) such as shovels and hoists, able to be moved on the overhead traveling crane. These assemblies are often called “Pot Tending Assemblies” (PTA) or “Pot Tending Machines” (PTM).
In order to optimize the space in the electrolysis halls and reduce the cost of investment, the electrolytic cells are laid out as close as possible to each other and close to one of the lateral sides of the electrolysis halls and an aisle as narrow as possible is made close to the other lateral side of the halls. This layout requires that the distance between the walls of the electrolysis hall and the limits of the workspace of each pot tending machine tool is as small as possible, especially for access to the electrolytic cells. This distance is called the “tool approach” distance. The position of the cells in the electrolysis hall and the total area of the hall that results from this is greatly dependent on the volume occupied by the pot tending machines and the possibilities of approaching and moving their tools. However, known pot tending modules occupy a large volume that makes it impossible to get close to the sides of electrolysis halls, particularly the lateral sides, and which significantly reduces their movements close to these sides. The volume of the modules can be reduced by bringing the tools closer together. However, this solution may increase the risk of damaging the tools during maintenance operations.
European patent EP 1781839 by the applicant proposes a pot tending module comprising a frame able to be secured to a carriage and a turret mounted on said frame so as to pivot about a vertical axis, said turret being equipped with a plurality of handling and service members. This pot tending module includes a set of tools mounted on telescopic arms, each telescopic arm being fixed to the turret by an articulated support allowing pendular movements of said telescopic arm with respect to a determined point of articulation. In this pot tending module, the telescopic arms are interconnected by a mechanical connecting device to maintain, within a determined tolerance range, the relative angular difference between the pendular movements of said telescopic arms. Such a pot tending module makes it possible to bring the tools closer together, thus limiting the volume, especially the width, under the frame of said module. It also give the tools a limited independence of movement, while preventing them from colliding with each other and preventing any jolts undergone by one of the tools from having a direct impact on the other tools.
A technical problem with the pot tending module of prior art is to further minimize the volume under the frame of the module, including the height under the frame of the pot tending module, and the volume of space covered by the entire pot tending module during rotation of its rotary part.
One subject of the invention relates to a pot tending module for use in a plant for producing aluminum by igneous electrolysis, said module comprising a frame able to be secured to a carriage and a rotary part mounted on said frame so as to pivot about a substantially vertical axis, said rotary part being equipped with at least one tool mounted on a telescopic arm of said rotary part, said pot tending module further comprising a first bearing structure mounted on said frame and designed to bear a hopper, said pot tending module being characterized in that said first bearing structure and said hopper are included in said rotary part, said first bearing structure being designed to bear the entire said rotary part and being mounted on said frame so as to pivot about said substantially vertical axis, and in that said rotary part comprises a second bearing structure, a fixed member of said telescopic arm being mounted on said second bearing structure interdependent with said rotary part through attachment means allowing pendular movements of said telescopic arm, said attachment means being fixed to an attachment part of said fixed member placed at a distance from the ends of said fixed member.
Most often, the pot tending module is mounted on the carriage of a pot tending machine, said carriage being, in turn, mounted on the overhead traveling crane of a pot tending assembly which may be translated above the electrolytic cells. The rotary part of the pot tending module is therefore generally placed or suspended below the carriage, i.e. still under the frame of said pot tending module. More specifically, this rotary part is usually mounted rotatably on the frame so as to be able to rotate, most often around itself, about a substantially vertical axis. In the following, this rotary part can also be called a turret.
As the first bearing structure is designed to bear all of said rotary part and is mounted on said frame so as to pivot about said substantially vertical axis, this first bearing structure is therefore generally the upper part of said rotary part.
The rotary part is normally equipped with a determined set of tools, each tool element of said assembly being mounted on a telescopic arm attached to the second bearing structure. The telescopic arms on which the tools are mounted, the second bearing structure, and the attachment means placed between the second bearing structure and the telescopic arms are all included in the rotary part. This determined set of tools may typically comprise at least one tool selected from a crust shovel, an anode handling clamp and a crust breaker.
In one aspect of the invention, the hopper is within the rotary part or turret. The rotary part therefore comprises not only the tools and telescopic arms on which they are mounted, but also the hopper. This hopper, which supplies the electrolytic cell with products in powder form, generally has a large volume compared with the tools and telescopic arms on which they are mounted. The inclusion of this hopper in the rotary part makes it possible to minimize the volume under the frame of said module, or more precisely the volume of the area covered by the entire pot tending module during rotation of its rotary part, and in particular the radial extent relative to the substantially vertical axis about which said rotary part is pivotally mounted.
In the following, the volume of the area covered by the entire pot tending module during rotation of its rotary part, and in particular during a full 360° rotation of said rotary part, can be described as the spatial requirement. So in other words, the inclusion of the hopper in the rotary part optimizes the overall space required, under the frame, by the pot tending module, and in particular the radial spatial requirements relative to the substantially vertical axis about which said rotary part is pivotally mounted. If this is not so and the hopper is fixed relative to the tools, they and their respective telescopic arms should be arranged so that their rotation is not impeded by said hopper, i.e. the tools and their respective telescopic arms should be arranged in a space having a symmetry of revolution relative to the axis of rotation of the rotary part which is outside that occupied by the hopper. This choice of including the hopper in the rotary part makes it possible to arrange the hopper, the tools and the telescopic arms on which they are mounted in a space which is generally smaller, because all of these objects rotate, at the same time, around a same axis of rotation.
According to another aspect of the invention, the fixed members of the telescopic arms on which the tools are mounted are attached to the second bearing structure, the latter being interdependent with the rotary part of the pot tending module. A fixed member of a telescopic arm generally means the hollow shaft in which a movable member carrying the tool slides, said fixed member being in this case attached to the second bearing structure. This second bearing structure, which is distinct from the first bearing structure mounted on the frame, is placed under said frame and more precisely under said first bearing structure. This second bearing structure is generally placed beneath the hopper. The second bearing structure can be advantageously constituted by a walkway placed under the hopper. In the following, the second bearing structure may be described as a walkway or as an under-hopper walkway. The walkway may carry other components than the tools, such as, for example, a hydraulic unit and electrical cabinets. This configuration in which the tools are mounted on the walkway allows maintenance operators to access the tools and the various components of the pot tending module.
In addition, the tools being mounted on the second bearing structure, the forces exerted by said tools are transferred to said second bearing structure rather than to the first bearing structure bearing the entire rotary part. The use of the second bearing structure or walkway under the hopper to fix the tools means that it is possible not to use the first bearing structure bearing the entire rotary part or turret to take up the main loads exerted by said tools. This configuration in particular makes for an overall reduction in the mass of the first bearing structure bearing the entire turret. This configuration also simplifies the construction of the first bearing structure bearing the entire turret.
In yet another aspect of the invention, the attachment means allow pendular movements of the telescopic arms on which the tools are mounted. This other aspect of the invention makes it possible not only to confer independence of movement on the telescopic arms in relation to the movement of the rotary part, but also to prevent jolts sustained by a tool from directly affecting the entire the rotary part, and the other tools carried by this rotary part.
In yet another aspect of the invention, the attachment means are fixed to an attachment portion of said fixed member arranged at a distance from the ends of said fixed member. In other words, the fixed member of the telescopic arm is not attached to the second structure by one of its ends. This aspect of the invention improves accuracy in positioning the tool. This aspect of the invention also makes it possible to raise the upper end of the fixed member to an elevation close to that of the frame. The space required under the frame is thereby reduced without the need to reduce the length of the fixed member.
The different aspects of the invention presented above therefore contribute to minimizing the space required under the frame of the pot tending module even more significantly.
In a preferred embodiment of the invention, the fixed member of the telescopic arm is connected to the first bearing structure by a mechanical connecting device that limits the amplitude of the pendular movements of said telescopic arm. In this way, the amplitude tolerance range of the pendular movements of the telescopic arm(s) is even better controlled. This tolerance range is defined with respect to the rotary part, and particularly with respect to the first bearing structure of said rotary part. Unlike the module described in European patent EP 1781839, the amplitude tolerance range of the pendular movements of the telescopic arm of a tool is not defined relative to other tools of said rotary part. The amplitude tolerance range of the pendular movements of a telescopic arm is defined more deterministically than in prior art because it no longer depends on the pendular movements of other tools.
With this configuration of the pot tending module, the axial or vertical component of the forces exerted by a tool and the telescopic arm on which it is mounted is taken up by the second bearing or walkway structure under the frame, via attachment means. As for the radial or horizontal components of these forces, these are partly taken up by the first bearing structure carrying all of the rotary part or turret under the frame, through the mechanical connecting device.
In a preferred embodiment of the invention, the attachment portion of the fixed member of the telescopic arm is at a distance D from an upper end of said fixed member greater than one tenth of the length L of said fixed member. Preferably, the distance D between the attachment portion and the upper end of the fixed member is between one quarter of length L of said fixed member and two thirds of this same length. For example, the distance D between the attachment portion and the upper end of the fixed member is equal to a half the length L of said fixed member. In this way, the accuracy and robustness of the tool are improved.
Preferably, the mechanical connecting device is mounted to connect the upper end of the fixed member to the first bearing structure. Advantageously, the mechanical connecting device comprises at least one damping system for limiting the amplitude of the pendular movements of the telescopic arm in a horizontal direction. Advantageously, the mechanical connecting device comprises two damping systems to limit the amplitude of the pendular movements of the telescopic arm in two substantially perpendicular horizontal directions.
Preferably, the upper end of the fixed member of the telescopic arm has an elevation just below that of the frame. Preferably, the part of the fixed member between its upper end and its attachment portion extends through an opening in the first bearing structure. In this way, the fixed member of the telescopic arm can extend to the frame, which makes it possible to limit the spatial dimensions under the frame of the pot tending module.
Preferably, the attachment means are designed to prevent rotational movements of the telescopic arm about a longitudinal axis of said arm. This gives the tools positioning freedom without changing their basic orientation.
According to one embodiment, the attachment means of the telescopic arm on the second bearing structure comprises first fastening means interdependent with said second bearing structure bearing against an upper face of said second bearing structure. This upper face of the second bearing structure extends generally in a plane substantially perpendicular to a longitudinal axis of the telescopic arm, so that the telescopic arm, the tool mounted at the end of said telescopic arm and any load on said tool exert bearing forces on said upper face via the first fastening means.
Preferably, the first fastening means of the attachment means of the telescopic arm on the second bearing structure comprises an intermediate support designed to be fixed interdependently to the second bearing structure, said attachment means comprising at least one bearing part interdependent with said telescopic arm bearing on said intermediate support and allowing pendular movements of said telescopic arm. In this way, the attachment means can take up the lifting forces exerted on the second bearing structure through the telescopic arm while lifting the tool and its potential load.
It should be noted that the tools can be actuated by actuating means, generally hydraulic cylinders or cable lifting means, whose function is both to maintain the active tool at the desired level, and to lift this tool and any loads handled by this tool. Generally, the line of action of said actuation means is coincident with the longitudinal axis of the telescopic arm carrying the tool. The forces exerted by these actuating means are generally lifting forces, i.e. forces adding to the weight of the tool, the telescopic arm on which it is mounted and any load being handled by this tool. The descending forces exerted by the actuating means are usually minimized due to the weight of the tool itself and its telescopic arm. In this way, the presence of at least one bearing point on the upper face of the second bearing structure is theoretically sufficient to take up the lifting forces exerted by the tools.
Preferably, the at least one bearing part (in this case both bearing parts) includes a fuse designed to break when the amplitude of the pendular movements of the telescopic arm is outside a predetermined range of tolerance. The material and shape of this fuse element are chosen so as to limit the forces having a horizontal component transmitted to the second bearing structure. In other words, the fuse element is designed to be broken before risking damage to the fixed component of the telescopic arm or the second bearing structure.
Preferably, the attachment means of the telescopic arm onto the second bearing structure includes second fastening means interdependent with the attachment portion of the fixed member of said telescopic arm, said second fastening means comprising two uprights oriented substantially parallel to the longitudinal axis of the telescopic arm.
Preferably, the attachment means comprises two bearing parts interdependent with the telescopic arm bearing on the intermediate support and allowing pendular movements of said telescopic arm, the fuse element of each bearing part being fixed interdependently onto each upright of the second fastening means respectively.
Another subject of the invention is a pot tending machine comprising a carriage and a pot tending module as described above.
Yet another subject of the invention is a pot tending assembly for a plant producing aluminum by igneous electrolysis including an overhead traveling crane and at least one pot tending machine according to the invention.
Yet another subject of the invention is the use of a pot tending assembly according to the invention for work on electrolytic cells for the production of aluminum by igneous electrolysis.
Electrolysis plants for the production of aluminum include a liquid aluminum production area containing one or more electrolysis halls 1. As illustrated in
The pot tending assembly 5 comprises an overhead travelling crane 13 which may be translated above the electrolytic cells 3, and along them, and a pot tending machine 15 comprising a movable carriage 17 able to be moved on the overhead travelling crane 13 and a pot tending module 19 equipped with several handling and servicing components such as 21 tools (shovels, extraction keys, crust breakers, etc.). The overhead traveling crane (13) rests and circulates on gantry tracks 23, 24 laid out in parallel with each other and with the main axis of the hall (and the line of cells). The overhead traveling crane 13 can thus be moved along the electrolysis hall 1.
As illustrated in
The carriage 17 of the pot tending assembly 5 is mounted on roller devices 31, 32 designed to allow the carriage on the gantry track of the overhead travelling crane 13. The frame 25 of pot tending module 19 is attached to the carriage 17. The rotary part or turret 33 of pot tending module 19 is mounted on frame 25 so as to rotate around itself around the substantially vertical axis A shown in
As illustrated in
The rotary part 33 of the pot tending module 19 further includes a hopper 37 for supplying an electrolytic cell with products in powder form, said hopper being carried by the first supporting structure 35. As explained above, the inclusion of this hopper 37 in the rotary part 33 minimizes the volume under the frame 25 of the pot tending module, or more precisely the spatial dimensions of the pot tending module.
The rotary part 33 of the pot tending module 19 is equipped with several handling and servicing components generally comprising a set of tools mounted on telescopic arms. In the embodiment illustrated in
The telescopic arm on which each tool is mounted means any device comprising at least one fixed member, typically a hollow shaft or an elongated chassis, and a movable member, typically a stem or a hollow shaft, able to be moved relative to the fixed member along a predetermined axis, which is generally parallel to the main axis of the fixed member. The fixed member is fixed to the pot tending module, namely the rotary part 33 of the pot tending module 19. The tool is fixed to the movable member, generally at one end thereof. In the embodiment illustrated in
The fixed member of the telescopic arm of each of these tools 21, 22, i.e. the hollow shaft 39 in which a movable member of said telescopic arm slides, is mounted on a second bearing structure 41. This second bearing structure is interdependent with the rotary part 33 and separate from the first bearing structure 35. This second bearing structure 41 is arranged under the hopper 37. In this case, the second bearing structure 41 can also carry a walkway placed below the hopper which can be equipped with a hydraulic unit and electrical cabinets. The walkway allows maintenance operators access to tools and various components of the pot tending module.
Specifically, as can be seen in
Unlike the pot tending module of prior art, the hollow shaft 39 of each telescopic arm is not attached to the second bearing structure 41 by one of its ends. The attachment means 43 are in fact attached to an attachment part of hollow shaft 39 which is placed at a distance from the ends of said hollow shaft, i.e. at a distance from the upper end and the lower end of said hollow shaft. The upper ends of hollow shafts 39 of the telescopic arms carrying the anode handling clamp 22 and the bucket shovel 21 are shown in
As shown in
The attachment means 43 includes two bearing parts 61 fixed to the hollow shaft of the telescopic arm 39 and resting on the intermediate support 55 allowing pendular movement of said telescopic arm. Each bearing part 61 comprises a fuse element 63 designed to break when the forces exerted by the telescopic arm on the second bearing structure 41, in particular the horizontal component of these forces, is outside a predetermined tolerance range. The attachment means 43 of the telescopic arm on the second bearing structure 41 comprise second fastening means 65 interdependent with the attachment part of the hollow shaft 39 of this same telescopic arm. These second attachment means comprise, in this case, two uprights 67 oriented substantially parallel to the longitudinal axis of the telescopic arm.
Each tool 21, 22 is actuated by a hydraulic cylinder 62, shown in
As can be seen in
In the example shown in
As can be seen in
As can be seen in
With this damping system 75, 76, any movement of the hollow shaft 39 of a telescopic arm and the movable part 79 interdependent with said hollow shaft is accompanied by a deformation of the deformable part 81 by compressing the spring 85 via one or other annular part 89, 90 and the mobile stop 87, 88 on which said annular part slides. At the same time, the same mobile stop 87, 88 is separated from the wall 83, 84 interdependent with the first bearing structure 35, while the opposite mobile stop 88, 87 rests more heavily on the other wall 84, 83 interdependent with the same bearing structure. The mobile part 79 and the hollow shaft 39 of the telescopic arm are then returned to their initial position by a spring 85. In this way, the tolerance range of the amplitude of the pendular movement of hollow shaft 39 of each telescopic arm is better controlled.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1102938 | Sep 2011 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2012/000376 | 9/24/2012 | WO | 00 | 3/28/2014 |
