Title of Invention

DEVICE FOR HANDLING AN ELECTROLYTIC POT FOR PRODUCING ALUMINIUM

Abstract

The invention relates to a device for handling (300) an electrolytic cell (11) which is intended for the production of aluminium by means of fused-salt electrolysis. According to the invention, the cell is rectangular and comprises a metal casing (12) which is equipped with a rim (14a, 14b) along at least the long sides (17a, 17b) thereof. The inventive handling device (300) consists of at least one hook means (301, 301") which enables same to be gripped by a lifting and handling unit (20) and a frame (310) comprising a plurality of fixing means (320) which are distributed such as to enable the frame (310) to be fixed securely to the casing (12) at a plurality of determined locations. According to the invention, the handling device (300) can be used to maintain the deformation of the casing (12) of the cell (11) within a determined tolerance range when it is suspended by a lifting and handling unit (20).

Full Text

DEVICE FOR HANDLING AN ELECTROLYTIC POT FOR PRODUCING ALUMINIUM DESCRIPTION Domain of the invention The invention relates to aluminium reduction plants by fused bath electrolysis using the Hall-Heroult process. More specifically, the invention relates to handling devices used in the said plants. State of the art Aluminium metal is produced industrially by fused bath electrolysis, namely by electrolysis of alumina in solution in a molten cryolite bath called an electrolytic bath using the well-known Hall-Heroult process. Electrolytic cells intended for production of aluminium comprise a pot provided with cathodes and anodes made of a carbonaceous material that are partially immersed in the electrolytic bath. The pot comprises a steel shell, lining elements made of refractory materials and a cathode assembly located in the bottom of the pot. French patent application FR 2 806 742 (corresponding to American patent US 6 409 894) describes the typical structure of aluminium reduction plants and cells that they contain, in more detail. During operation, an aluminium reduction plant requires work on electrolytic cells, such as anode changes and the repair of pots. To perform these operations, the most modern plants are equipped with lifting and handling units comprising a travelling crane that may be translated above and along electrolytic cells, and at least one trolley provided with handling and work devices. Repair of a pot includes "lining removal" and "lining replacement" operations on the pots - These operations are designed to renovate crucible, formed by the inner lining and cathode elements of the pot. These operations may be done in place, in other words without removing the pot from the corresponding cell, but they can be damaging to the operation of cells and maintenance of electrolysis rooms. These operations produce dust, cause forward - return movement s of new and us ed materials in the electrolysis rooms and reduce the production of a series of cells by shutting down the corresponding cell during the work. It is preferable to repair pots in a special room designed for pot repair and located outside the electrolysis room, in order to avoid these disadvantages. Lifting and handling units used for the transport of electrolytic pots between the repair room and the electrolysis room(s) usually comprise one or two trolleys provided with lifting means. During repair operations, one or several lifting beams are usually fixed to the pot shell and is (are) used for handling the pot. However, the known means have the di s advantage that it is impossible to control deformation of the pot under the effect of its self-weight, which could cause deterioration of the "linings" that could significantly reduce the working life of the pot. Therefore, the inventors sought means of avoiding these disadvantages. Description of the invention An object of the invention is a device for handling an electrolytic cell pot designed for the production of aluminium by fused bath electrolysis, the said pot being rectangular, with a main X axis and comprising a steel shell with a deck at least over the long sides of the pot, the said device comprising at least one attachment means intended to enable gripping by a lifting and handl ing uni t and be ing char ac t er i s ed in tha t it comprises a frame provided with a plurality of rigid fastening means distributed so as to enable rigid fastening of the frame to the pot shell at a plurality of determined locations. The inventors had the idea of making the pot stiffer using at least one rigid element, namely the said frame, inserted between the pot and the lifting and handling unit and rigidly fixed at several locations of the pot shell. The frame enables the deformation of the pot shell - particularly due to longitudinal bending (in other words in the longitudinal direction of the pot) - to be kept within a determined tolerance range when it is suspended by a lifting and handling unit and thus avoids damage to the inner lining of the pot during pot handling operations. Distribution of the plurality of fastening means on the frame distributes the load on the frame, particularly along the length of the pot, thus minimising deformation of the shell under the effect of the self-weight of the assembly, by making this deformation similar to the deformation of the device. The determined fastening locations are typically distributed on a determined portion around the periphery of the pot shell. This portion typically covers at least 70% of the long sides of the pot, in order to minimise the "floating" (unfixed) part of the pot. The deformation deflection of the frame, under the action of its self-weight and the weight of the pot to which the device is fixed, is preferably less than + 5 MI over the entire length of the frame (along the longitudinal direction of the pot) and preferably less than or equal to + 2 mm. Preferably, the frame comprises one or two longitudinal beams designed to be arranged along the length of the pot. In the first case, the beam is typically provided with arms and the fastening means are located at the ends of these arms. In the second case, the beams are preferably parallel to each other and are connected by at least one cross-piece, and the fastening means are preferably distributed on the beams, possibly at the ends of the arms, so as to enable fastening of each beam to the corresponding long side of the pot. In one preferred embodiment of the invention, the handling device also comprises adjustable spacers designed to compensate for any geometry defects of the frame and / or the pot shell. Another object of the invention is the use of a device according to the invention in a fused bath electrolysis aluminium reduction plant. Another object of the invention is a method for handling an electrolytic cell pot designed for the production of aluminium by fused bath electrolysis, that can be implemented with a handling device according to the invention. The invention is described in detail with reference to the appended figures. Figure 1 illustrates a typical electrolysis room designed for the production of aluminium and equipped with a lifting and handling unit. Figure 2 diagrammatically illustrates a top view of possible variants of the frame of the handling device according to the invention. Figures 3 to 5 illustrate a preferred embodiment of the handling device according to the invention. Figure 3 represents the device in a transverse view (A) and a side view (B) . Figure 3 (A) corresponds to the plane of section A-A in Figure 3 (B) , Figure 3 (B) corresponds to the plane of section B-B in Figure 3 (A) . Figure 3(B) also diagrammatically illustrates an electrolytic cell (2) and a lifting and handling unit (20) while the pot (11) is being handled. Figure 4 shows the device in a partial transverse view. Figure 4(B) illustrates part of a means for fastening the pot to the handling device, in more detail. Figure 5 illustrates a side view showing the embodiment of the handling device illustrated in Figures 3 and 4, in more detail. Figure 4 corresponds to the plane of section C-C in Figure 5. Figure 5 corresponds to the plane of section D-D in Figure 4. In Figures 2 to 5, the handling device (300) is fixed to a pot (11) to illustrate the relative positioning of these elements. The aluminium reduction plants designed for aluminium production comprise one or several electrolysis rooms (1) comprising a large number of electrolytic cells (2) (typically several hundred cells), each electrolytic cell (2) comprising a pot (11) and anodes (10) . As illustrated in Figure 1, the pots (11) generally have an elongated rectangular shape with a main X axis; the length Lo of the pots (11) is usually more than three times their width Wo. The main X axis of a pot (11) is along the direction of its length. As illustrated in the figures, and particularly Figures 3 to 5, each pot (11) comprises a steel shell (12) that includes a box (13), a deck (14) and stiffeners (15) distributed along the box. The deck (14) typically comprises at least side decks (14a, 14b) on the long sides (17a, 17b) of the pot and end decks (14c, 14d) on the short sides (17c, 17d) of the pot. The stiffeners (15) usually comprise reinforcing members (16) arranged perpendicular to the external surface of the box (13) . The shell (12) is lined on the inside with lining elements made of refractory materials (not shown) and includes a cathode assembly (not shown). The pot (11) may be placed or removed using a lifting and handling unit (20) that can be moved along the electrolytic cells on running tracks (3, 3') using running means (23, 23'). Figure 1 shows a typical lifting and handling unit, seen in a side view (Figure 1(A)), and seen along the main axis (Figure 1(B)). The said unit (20) typically comprises a travelling crane (21), at least one trolley (22, 22') that can be moved along the travelling crane (21) and handling members (24, 24') that typically comprise at least one lifting device (25, 25') such as a pulley block. The pot (11) is connected to the lifting device (25, 251) by removable connection means (30, 301) that usually include distinct lifting beams (31, 31'), and articulated fixing means (32, 32') such as connecting rods or articulated levers, that enable an oscillation movement around the connecting points. The lifting beams (31, 31') are arranged transverse to the pot (11) and fixed to the lifting device (25, 251) by attachment means (33, 33'). The fixing means (32, 32') provide a statically determinate connection between the lifting device(s) (25, 25') and the pot (11). Known connection means (30, 30') enable longitudinal and transverse deformations of the pot. According to the invention, the pot (11) is fixed to the lifting device (25, 25') through a handling device (300) designed to make the shell rigid and to limit its deformation. The assembly formed by the pot (11) and the handling device (300) can then be manipulated as a single unit by the lifting and handling unit (20). The handling device (300) according to the invention comprises: - at least one attachment means (301, 3011) designed to enable gripping by a lifting and handling unit (20); a frame (310) provided with a plurality of rigid fastening means (320) distributed so as to enable rigid fastening of the frame (310) to the pot shell (20) at several determined locations. The rigid fastening means (320) enable a statically indeterminate link between the lifting devices (25, 25 ■) and the pot (11) . The attachment means (301, 301') are normally capable of being connected to lifting devices (25, 25 •) on the lifting and handling unit (20). They are typically chosen from among through holes, bolt systems and hooks. The handling device (300) advantageously comprises at least two attachment means (301, 301'). These attachment means are preferably sufficiently far from each other to prevent yaw of the shell during handling. This variant can also limit deformation of the frame (310) under the effect of the combined weight of the pot and the handling device. As illustrated in Figure 2, the frame (310) preferably comprises at least one longitudinal beam (311, 311a, 311b) and a plurality of rigid fastening means (320) distributed along each beam (311, 311a, 311b) so as to enable rigid fastening of the frame (310) at least on the long sides (17a, 17b) of the pot shell (12) . These beams (311, 3lla, 3l1b) will be arranged along the longitudinal direction of the pot. The fastening means (320) may be located at the end of arms (313) fixed to the beam or to each beam (311, 311a, 311b) . Each longitudinal beam (311, 311a, 311b) has a 1 ength L that is advantageously greater than 70% of the length Lo of the pot (11) and preferably greater than 80% of Lo. In a first embodiment of the invention, the frame (310) comprises a longitudinal beam (311), preferably a single beam, that will be placed parallel to the main X axis of the pot (11) and above this main axis. In the variant illustrated in Figure 2(A), the longitudinal beam (311) is provided with arms (313) distributed along the beam, typically at uniform spacings, and fastening means (320) are located at the end of these arms. In this embodiment, the attachment mean(s) (301, 301') is (are) typically provided on the beam (311) . In another embodiment of the invention, two variants of which are illustrated in Figures 2 (B) and 2 (C) , the frame (310) comprises two longitudinal beams (311a, 311b) that are parallel to each other and connected to each other by at least one transverse or "cross" bar (315, 315') and that will be placed parallel to the main X axis of the pot (11) and fixed to a corresponding long side (17a, 17b) of the shell (12). The fastening means (320) are distributed on the beams, possibly at the end of the arms (313) . The lengths L of the longitudinal beams (311a, 3l1b) are typically the same. In this embodiment, the attachment mean(s) (301, 301') is (are) advantageously provided on the cross piece(s) (315, 315'). In the variant illustrated in Figure 2 (C) , the two longitudinal beams (311a, 311b) are arranged so that they can be partly or entirely placed above each of the corresponding decks (14a, 14b) of the shell (12) located on the long sides (17a, 17b) of the shell. This variant has the advantage that it enables a significant reduction of the weight of the frame (310) . It also has the advantage that it is simpler to make. Figures 3 to 5 non-limitatively illustrate a particular variant of the embodiment of the invention in Figure 2(C). The cross-piece(s) (315, 315') can limit lateral deformations of the frame (310) . They may be removable, but they are preferably fixed to the longitudinal beams (311a, 311b) in order to make the device more rigid. The frame (310) advantageously comprises at least two cross pieces (315, 315') each provided with a attachment means (301, 301'). This variant limits the deflection of longitudinal beams (311a, 311b) under the effect of the combined weights of the pot and the handling device. The beam(s) (311, 311a, 311b) may possibly comprise stiffeners (312) to make them stronger and stiffer; these stiffeners are typically plates arranged transverse to the main axis of the beams. The beams (311, 311a, 311b) are typically formed from an elongated shell with a large section and a large bending inertia. The number of distinct fastening means (320) depends on the dimensions of the pot. It is typically more than 10. The maximum distance between the fastening means on the long sides of the pot is typically about 2 meters. The fastening means are typically distributed uniformly in order to simplify the design and use of the device. The average distance between the fastening means is typically between 0-5 and 2 meters. The fastening means (320) are preferably chosen among the means that enable the shell (12) to be fixed firmly but removably to the frame (310), such as bolt and nut systems. The fastening means (320) advantageously comprise tie-rods (321) that can be supported on the handling device (300) - typically on each longitudinal beam (311a, 311b) of the device at one end, and on the shell (12) at the other end. Consequently, the tie-rods (321) advantageously comprise a rod (322) that is typically threaded - at least at its two ends - so as to enable its fastening using nuts (323, 324). In practice, the rod (322) can pass through openings (19, 19') formed in the decks (14) of the shell. Fastening means (320) may comprise support bars (325) capable of being supported on stiffeners (15) of the pot shell, to distribute the load onto the stiffeners (15). This variant of the invention is advantageously implemented with pot shells in which the stiffeners (15) comprise openings (18) through which the said support bars (325) can be inserted (see Figures 4 and 5) . The support bars (325) may be formed of several elements (for example two distinct bars (325, 325') arranged in parallel and separated by spacers (326)). The openings (18) are advantageously reinforced using stiffeners that are typically in the form of a tube section. In one preferred embodiment of the invention, the handling device (300) also comprises a plurality of spacers (330) or "adjustable jacks" that can be used to adjust the spacing E between the pot shell (12) and the handling device (300) (typically between the decks (14) of the pot shell (12) and the longitudinal beams (3lla, 311b)). The spacers also provide determined support points between the pot shell (12) and the handling device (300). The spacers (330) are used to precisely adapt the handling device (300) to the pot shell (12) to avoid the need to add an additional deformation to the pot shell. The inventors have observed that the pot shells are often slightly deformed and that applying pressure from the longitudinal beams onto the pot shell without complementary adjustment elements could cause an additional deformation of the shell. The spacers (330) are preferably placed so as to apply pressure on the stiffer parts of the shell (12) (particularly the decks (14) of the pot shell, and typically at the reinforcing members (14') ) . The spacers (330) are typically in line with the support points of the tie-rods on the pot shell, as illustrated in Figure 5- The spacers (330) are typically chosen from among screw jacks. Another obj ect of the invention is a method of handling an electrolytic cell pot designed to produce aluminium by fused bath electrolysis comprising: - supply of a handling device (300) according to the invention; - placement of the handling device (300) on the shell (12) of a pot (11); - fastening of the handling device (300) on the pot shell using fastening means; - fastening of the handling device (300) to a lifting and handling unit (20) - typically to handling members (24, 24') of such a unit (20) - using at least one attachment means (301, 301'). The pot can then lifted, transported and put down. When the handling device (300) comprises spacers (330) , the method also comprises adjustment of a spacing E between the pot shell (12) and the handling device (300) using the said spacers (330) . When the frame (310) of the handling device (300) comprises at least two longitudinal beams (311a, 311b), placement of the handling device (300) on the shell (12) of a pot (11) typically includes alignment of these longitudinal beams (311a, 311b) with the lateral decks (14a, 14b) of the pot shell (12) located on its long sides (17a, 17b). When the handling device (300) comprises tie-rods (321), the beams (311a, 311b) are fixed to the shell (12) by clamping until the shell bears in contact with the said beams or, if applicable, in contact with the spacers (330). When spacers (330) are used, they are preferably adjusted before final clamping of the tie-rods (321) The spacers (330) are preferably integrated into the handling device (300) to simplify use of the handling device (300) or implementation of the method according to the invention. The spacers (330) may possibly be wholly or partly distinct from the device or they may be removable. When the spacers (330) are separated from the handling device at the time that it is put into place, the method also includes placement of a plurality of spacers (330), typically by insertion, between the frame (310) and the pot shell (12). CLAIMS 1. Device (300) for handling a pot (11) of an electrolytic cell (2) designed for the production of aluminium by fused bath electrolysis, the said pot being rectangular, with a main X axis and comprising a steel shell (12) with a deck (14) at least over the long sides (17a, 17b) of the pot (11), the said device (300) comprising at least one attachment means (301, 301') intended to enable gripping by a lifting and handling unit (20) and being characterised in that it comprises a frame (310) provided with a plurality of rigid fastening means (320) distributed so as to enable rigid fastening of the frame (310) to the pot shell (12) at a plurality of determined locations. 2. Handling device (300) according to claim 1, characterised in that it comprises at least two attachment means (301, 301')- 3. Handling device (300) according to either claim 1 or 2, characterised in that the frame (310) comprises at least one longitudinal beam (311, 3 lla, 311b) and a plurality of rigid fastening means (320) distributed along each beam (311, 311a, 311b) so as to enable rigid fastening of the frame (310) at least on the long sides (17a, 17b) of the pot shell (12). 4. Handling device (300) according to claim 3, characterised in that the fastening means (320) are located at the end of arms (313) fixed to the beam or to each beam (311, 311a, 311b). 5. Handling device (300) according to either claim 3 or 4, characterised in that the frame (310) comprises a longitudinal beam (311), that will be placed parallel to the main X axis of the pot (11) and above this main axis. 6. Handling device (300) according to claim 5, characterised in that the attachment means (301, 301') is (are) provided on the said beam (311). 7. Handling device (300) according to either claim 3 or 4, characterised in that the frame (310) comprises two longitudinal beams (311a, 311b) parallel to each other and connected to each other by at least one cross-piece (315, 315'), and designed to be placed parallel to the main X axis of the pot (11) and each to be fixed to a corresponding long side (17a, 17b) of the shell (12) . 8. Handling device (300) according to claim 7, characterised in that the attachment mean(s) (301, 301• ) are fitted on the cross piece(s) (315, 315'). 9. Handling device (300) according to either claim 7 or 8, characterised in that the frame (310) advantageously comprises at least two cross pieces (315, 315')/ each fitted with a attachment means (301, 301'). 10. Handling device (300) according to either claim 7 or 9, characterised in that each cross piece (315, 315') is fixed to the longitudinal beams (311a, 311b). 11. Handling device (300) according to either claim 7 or 10' characterised in that the longitudinal beams (311a, 311b) are arranged so that they can be partly or entirely placed above each of the corresponding decks (14a, 14b) of the shell (12) located on the longitudinal sides (17a, 17b) of the shell. 12. Handling device (300) according to any one of claims 1 to 11, characterised in that the fastening means (320) comprise tie-rods (321) that can be supported on the handl ing devi ce (300) at one end and on the shel 1 (12) at the other end. 13. Handling device (300) according to any one of claims 1 to 12, characterised in that it also comprises a plurality of spacers (330) that can be used to adjust the spacing E between the pot shell (12) and the handling device (300). 14. Handling device (300) according to claim 13, characterised in that the spacers (330) are chosen from among screw jacks. 15. Use of a handling device (300) according to any one of claims 1 to 14 in a fused bath aluminium reduction plant. 16. Method of handling an electrolytic cell pot (11) designed for the production of aluminium by fused bath electrolysis comprising: - supply of a handling device (300) according to any one of claims 1 to 14; - placement of a handling device (300) on the shell (12) of a pot (11); - fastening of the handling device (300) on the pot shell using fastening means (320); - fastening of the handling device (300) to a lifting and handling unit (20) using at least one attachment means (301, 301'). 17. Handling method according to claim 16, also comprising placement of a plurality of spacers (330) between the frame (310) and the shell (12). 18. Method of handling an electrolytic cell pot (11) designed for the production of aluminium by fused bath electrolysis, comprising: - supply of a handling device (300) according to either claim 13 or 14; - placement of a handling device (300) on the shell (12) of a pot (11); - adjustment of a spacing E between the shell (12) and the handling device (300) using the said spacers (330); - fastening of the handling device (300) on the pot shell using fastening means (320); - fastening of the handling device (300) to a lifting and handling unit (20) using at least one attachment means (301, 301'). Dated this 23 day of June 2006

Documents:

2287-CHENP-2006 AMENDED PAGES OF SPECIFICATION 22-11-2011.pdf

2287-CHENP-2006 AMENDED CLAIMS 22-11-2011.pdf

2287-CHENP-2006 CORRESPONDENCE OTHERS 23-03-2011.pdf

2287-CHENP-2006 EXAMINATION REPORT REPLY RECEIVED 22-11-2011.pdf

2287-CHENP-2006 FORM-3 22-11-2011.pdf

2287-CHENP-2006 OTHER PATENT DOCUMENT 22-11-2011.pdf

2287-CHENP-2006 POWER OF ATTORNEY 22-11-2011.pdf

2287-CHENP-2006 CORRESPONDENCE PO.pdf

2287-CHENP-2006 FORM-18.pdf

2287-chenp-2006-abstract.image.jpg

2287-chenp-2006-abstract.pdf

2287-chenp-2006-claims.pdf

2287-chenp-2006-correspondnece-others.pdf

2287-chenp-2006-description(complete).pdf

2287-chenp-2006-drawings.pdf

2287-chenp-2006-form 1.pdf

2287-chenp-2006-form 3.pdf

2287-chenp-2006-form 5.pdf

2287-chenp-2006-pct.pdf

2287-chenp-2006-sequence-listing.pdf