EP4174216A1 - Protection device for anodes of an electrolytic cell, comprising movable panels, and its implementation method - Google Patents
Protection device for anodes of an electrolytic cell, comprising movable panels, and its implementation method Download PDFInfo
- Publication number
- EP4174216A1 EP4174216A1 EP21204982.9A EP21204982A EP4174216A1 EP 4174216 A1 EP4174216 A1 EP 4174216A1 EP 21204982 A EP21204982 A EP 21204982A EP 4174216 A1 EP4174216 A1 EP 4174216A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- panel
- panels
- protection device
- anodes
- anode
- Prior art date
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Links
- 238000000034 method Methods 0.000 title claims description 21
- 239000004411 aluminium Substances 0.000 claims description 17
- 229910052782 aluminium Inorganic materials 0.000 claims description 17
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 17
- 238000005868 electrolysis reaction Methods 0.000 claims description 15
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- 238000009626 Hall-Héroult process Methods 0.000 description 9
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 7
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/22—Collecting emitted gases
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
- C25C3/00—Electrolytic production, recovery or refining of metals by electrolysis of melts
- C25C3/06—Electrolytic production, recovery or refining of metals by electrolysis of melts of aluminium
- C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
- C25C3/10—External supporting frames or structures
Definitions
- the invention relates to the field of fused salt electrolysis, and more precisely to an anodic assembly which is part of an electrolytic cell suitable for the Hall-Heroult process.
- the invention relates to a device which is adapted to protect the environment from the emission of anodes, which belong to this anode assembly.
- the Hall-Heroult process is the only continuous industrial process for producing metallic aluminium from aluminium oxide.
- Aluminium oxide Al 2 O 3
- molten cryolite Na 3 AlF 6
- the resulting mixture typically at a temperature comprised between 940 °C and 970 °C
- acts as a liquid electrolyte (usually called "electrolytic bath") in an electrolytic cell.
- An electrolytic cell also called “pot" used for the Hall-Héroult process typically comprises a steel shell (so-called potshell), a lining (comprising refractory bricks protecting said steel potshell against heat, and cathode blocks usually made from graphite, anthracite or a mixture of both).
- This cell is also provided with so-called anodic assemblies, which are formed by an anode hanger and at least one anode (usually made from carbon) that plunges into the liquid electrolyte.
- Anodes and cathodes are connected to external busbars.
- An electrical current is passed through the cell (typically at a voltage between 3.5 V and 5 V) which electrochemically reduces the aluminium oxide, split by the electrolyte into aluminium and oxygen ions, into aluminium at the cathode and oxygen at the anode; said oxygen reacting with the carbon of the anode to form carbon dioxide.
- the resulting metallic aluminium is not miscible with the liquid electrolyte, has a higher density than the liquid electrolyte and will thus accumulate as a liquid metal pad on the cathode surface from where it needs to be removed from time to time, usually by suction into a crucible.
- Industrial electrolytic cells used for the Hall-Heroult process are generally rectangular in shape and connected electrically in series, the ends of the series being connected to the positive and negative poles of an electrical rectification and control substation.
- the general outline of these cells is known to a person skilled in the art and will not be repeated here in detail. They have a length usually comprised between 8 and 25 meters and a width usually comprised between 3 and 5 meters.
- the cells also called “pots” are always operated in series of several tens (up to more than a hundred) pots (such a series being also called a "potline”); within each series DC currents flow from one cell to the neighbouring cell.
- the cells are arranged in a building, with the cells arranged in rows either side-by-side, that is to say that the long side of each cell is perpendicular to the axis of the series, or end-to-end, that is to say that the long side of each cell is parallel to the axis of the series. It is customary to designate the sides for side-by-side cells (or ends for end-to end cells) of the cells by the terms "upstream” and "downstream” with reference to the current orientation in the series. The current enters the upstream and exits downstream of the cell.
- the electrical currents in most modern electrolytic cells using the Hall-Héroult process exceed 200 kA and can reach 400 kA, 450 kA or even more; in these potlines the pots are arranged side by side. Most newly installed pots operate at a current comprised between about 350 kA and 600 kA, and more often in the order of 400 kA to 500 kA.
- the superstructure of the cell comprises a fixed frame and a mobile metallic anode busbar, also called “anode beam", which extends at the outer periphery of the fixed frame.
- Each anode is equipped with a metallic rod, for mechanical attachment and electrical connection to said anode beam.
- Anodes are provided along at least one line, typically along two lines on either side of the superstructure.
- anodes in the Hall-Heroult process are prebaked cuboids made from a carbonaceous material.
- the anode blocks are fixedly connected to so-called anode hangers. They serve two different purposes, namely to keep the carbon anodes at a predetermined distance from the cathode, and to carry the electrical current from an anode busbar (also called “anode beam”) down to the carbon anodes.
- Anode hangers are fixed to the overhanging anode beam in a detachable manner using clamps. They comprise an upper part called “anode rod” or “anode stem”, which is connected to the anode beam, and a lower part, called “anode yoke”.
- the anode yoke has a number of arms each of which terminates in a cylindrical stub that is embedded in preformed stubholes of the carbon anode blocks and fixed with cast iron acting as temperature-resistant, electrically conductive glue; this process is called “anode rodding” or “anode casting”.
- anode rod plus anode yoke is sometimes called “anode hanger”
- anode hanger plus anode block is called “anode assembly”.
- Anodes are subject to oxidative consumption during the electrolysis process, the carbon being oxidized into carbon dioxide. More generally, the Hall-Heroult electrolytic process leads to gaseous emissions, which, in addition to CO 2 , mainly comprise fluorine compounds such as hydrogen fluoride, originating from the electrolytic bath, as well as minor amounts of SO 2 . These fluorine compounds are noxious to workers and to the environment. Concerning environmental damage, it has been observed over the decades, as the production of smelters has increased, that fluorine compounds can damage the neighbouring vegetation, and can also cause damage (so-called fluorosis) to the cattle raised near aluminium smelters. Therefore, since the 1970s, gaseous emissions of Hall-Heroult cells are no longer released into the environment but undergo a purification.
- fluorine compounds such as hydrogen fluoride
- gaseous emissions from electrolytic pots are collected using protection devices such as hooding systems, and treated in gas treatment stations to remove fluorine compounds and other noxious compounds before releasing the collected air into the environment.
- Said gas treatment usually comprises a dry absorption of said noxious compounds on fresh alumina that is subsequently introduced into the electrolytivc pot.
- each protection (hooding) device is intended to cover at least one line of anodes.
- this device comprises first an elongated frame which extends, in use, substantially parallel to the line of anodes.
- This frame supports two fixed end walls, located at the opposite extremities of the anodes line.
- several panels are provided between these end walls.
- These panels are typically curved, in particular shaped as a quarter of a circle, so as to ensure an optimal protection.
- Said hood panels also act as heat shields, thereby limiting thermal losses of the electrolytic cell and protecting the workers.
- the panels need to be movable between two main configurations. In a first so-called protection configuration, these panels are located side by side to define a shield, with a close lateral contact for sealing matters. Moreover in a second so-called access configuration, these panels must be mutually separated so as to define a passage towards the anodes for the operators.
- a typical industrial electrolytic pot (known as DX+ TM or DX+ Ultra TM technology, commercialized by Emirates Global Aluminium) has 18 anodes on each side, arranged along a longitudinal axis (called here also "anode line") of the cell, and there are 19 hood panels on each side.
- anodes are changed by pairs, and for changing a pair of anodes three adjacent hoods need to be removed to gain access to the pair of anodes to be changed; eventually these three hood panels need to be put back in place.
- hood panels can be removed from the frame by lifting. Such a lifting operation may first be carried out manually. In this case, there are risks of premature mechanical damage of the panels, due to potential mishandling of the operators. In practice, these hoods need to be replaced when they exhibit a deformation such that they do no longer guarantee sufficient tightness. Repair and replacement of hood panels represent a rather significant cost in a smelting plant. Moreover, due to the substantial weight of the panels (typically around 17 kg per panel for DX+ TM or DX+ Ultra TM technology), their manual handling by an operator may cause injuries. As these panels are also very hot, their manual handling may lead to accidental burns, too.
- one goal of the invention is first to provide a device adapted to reliably protect environment from the emissions of the anodes of an electrolytic cell, which can be implemented by operators without any excessive physical strength.
- One other goal of the invention is to provide such a device which can bring about an improved sealing, in particular with respect to gaseous emissions of the anodes, compared to prior art solutions.
- One other goal of the invention is to provide such a device, which has a relatively simple structure and a satisfactory compactness.
- a protection device (100) for an anodic assembly of an electrolytic cell suitable for the Hall-Héroult electrolysis process, said assembly comprising a superstructure (102) as well as a plurality of anodes (A1-A8) arranged along at least one line (L1, L2), said superstructure (102) comprising a fixed frame (104) of substantially rectangular shape and an anode beam (106) adapted to support anode rods (108),
- Another object of the invention is an electrolytic cell suitable for the Hall-Heroult electrolysis process, comprising a protection device (100) as above.
- Another object of the invention is a method for changing a spent anode assembly in an electrolytic cell as above, comprising the steps of:
- Another object of the invention is an aluminium electrolysis plant comprising at least one line of electrolytic cells of substantially rectangular shape, said cells being arranged side by side, and said plant further comprising means for electrically connecting said cells in series and for connecting the cathodic busbar of a cell to the anode beam of a downstream cell, characterized in that more than 80% of the electrolytic cells in at least one of said line, and preferably each electrolytic cell of said line, is an electrolytic cell as above.
- Another object of the invention is a method for making aluminium by the Hall-Heroult electrolysis process using electrolytic cells of substantially rectangular shape, characterized in that said method is carried out in an aluminium electrolysis plant as above.
- An aluminium smelter comprises a plurality of electrolytic cells arranged the one behind the other (and side by side), typically along two parallel lines. These cells are electrically connected in series by means of conductors, so that electrolysis current passes from one cell to the next.
- the number of cells in a series is typically comprised between several tens up to more than four hundred, but this figure is not substantial for the present invention.
- the cells are arranged transversally in reference of main direction of the line they constitute. In other words the main dimension, or length, of each cell is substantially orthogonal to the main direction of a respective line, i.e. the circulation direction of current.
- an electrolytic cell used for the Hall-Heroult process typically comprises first a potshell and a lining, which are not illustrated on the figures.
- This cell also comprises a plurality of anode assemblies, each of which is formed by a metallic rod (so-called “anode rod”) and at least one anode fixed to it by means of an anode yoke.
- This anodic assembly known as such, is not part of the invention, so that it will not be described in detail.
- superstructure 102 comprises a fixed frame 104 and a mobile metallic anode frame 106 , hereafter called “anode beam", which extends at the outer periphery of the fixed frame.
- each anode is provided with a metallic anode rod 108 for mechanical attachment and electrical connection to the anode beam.
- These anodes are not shown on figure 1 , but their positioning is illustrated in particular on figure 4 .
- anode beam 106 is provided with pairs of hooks 110 , adapted to facilitate the attachment of the anode rods 108 to the anode beam 106 in the usual way.
- Two lines L1 and L2 are provided, on either side of superstructure 102 .
- Hall-Heroult electrolysis pot The general structure of a Hall-Heroult electrolysis pot is known per se and will not be explained here. It is sufficient to explain that the current is fed into the anode beam, flows from the anode beam to the plurality of anode rods and to the anodes in contact with the liquid electrolyte where the electrolytic reaction takes place. Then the current crosses the liquid metal pad resulting from the process and eventually will be collected at the cathode block.
- the present invention is more particularly directed to a protection device 100 , which is adapted to cooperate with one anode line.
- a protection device 100 which is adapted to cooperate with one anode line.
- two such devices referenced I and II as a whole, cooperate with respective anodes lines L1 and L2.
- Each of said devices forms a hood which separates the content of the electrolytic cell, as well as any off-gases generated by the electrolysis process, from the environmental atmosphere. Said off-gases are sucked through the superstructure into a gas treatment station, as mentioned above; this is known as such and will not be explained here in more detail.
- Device I will now be described, bearing in mind that the structure of device II is similar.
- Said device of the invention comprises an elongated frame 1 , which includes longitudinal beams 10 , 11 and 12 . Respective inner and outer beams 10 and 11 are positioned at the bottom of the frame, whereas upper beam 12 is positioned substantially above central beam 10 .
- Longitudinal beams 10 and 11 are mutually linked by horizontal cross pieces, namely a middle cross piece 13 as well as two opposite cross pieces 14 and 15 .
- longitudinal beams 10 and 12 are mutually linked by vertical posts, namely a middle post 16 as well as two opposite end posts 17 and 18.
- Several oblique bars 19 are also provided, so as to stiffen this frame.
- two plain walls 20 and 21 each having substantially the shape of a quarter of a disc, are fixed at the opposite ends of said longitudinal beams 10 , 11 and 12 .
- longitudinal beam 10 supports two mutually parallel brackets 22 and 23 , each being V shaped and positioned side-by-side.
- the upper surface of these brackets defines respective inner and outer tracks 24 and 25 .
- upper beam 12 is equipped with two further parallel brackets 26 and 27 , schematically illustrated on figure 7 , which are positioned the one under the other.
- the outer surface of these brackets defines further respective lower and upper tracks 28 and 29 , also schematically illustrated.
- these different tracks are adapted to cooperate with sliders, provided on panels which are part of the device I.
- the device I comprises two sets of panels, namely a first set of inner panels 3 , as well as a second set of outer panels 7 .
- the two sets comprise the same number, namely four inner panels 3a to 3d and four outer panels 6a to 6d in the illustrated example (see in particular figure 3 ).
- a different number of panel can be considered.
- Panel 3 comprises an inner skin 31 and an outer skin 32 , which are mutually distant over part of the panel, so that the latter partly forms a hollow body.
- inner skin may be a stainless steel sheet
- outer skin may be a sheet of aluminium. This stainless steel sheet is adapted to be exposed to flames and high temperatures, while also reinforcing the aluminium sheet.
- said skins are separated on longitudinal ends of the panel, so as to define longitudinal walls 33 and 34.
- outer skin 32 is designed to form some recesses, namely regions where this skin 32 extends close to inner skin 31 .
- outer skin 32 is first equipped with so-called long recesses, namely which extend over substantially its whole length : an inner recess 320 , an opposite outer recess 321 and an intermediate recess 322 .
- three further so-called recesses are provided side-by-side, between long recesses 323 and 324 : end recesses 325 and 326 , as well as a median recess 327 .
- U shaped elements 41 and 43 are fixed on the inner and outer edges of each recess 325 and 326 . These U shaped elements form handles, which enable operators to move the panel, as will be described hereafter. Since these handles are positioned in recesses, they do not protrude outside the global surface of outer skin, as shown on figure 10 .
- the two skins 31 and 32 contact each other and are mutually fixed by any appropriate means, such as rivets.
- any appropriate means such as rivets.
- skins are mutually fixed by a longitudinal line 330 of rivets.
- a rim 34 is interposed between these skins, so as to protrude outside with respect to these skins. This rim extends substantially over the whole length of the panel, namely along XX axis.
- the panel 3 is equipped with some outside rollers 36 , which form sliders.
- the shape of each roller is designed so as to cooperate with the above described inner track 24 .
- said roller is provided with a V-shaped groove 37 .
- two rollers are provided close to opposite longitudinal ends of the panel, bearing in mind that a superior number of rollers may be provided.
- one single roller may be considered: however this is not a preferred variant, due to its lack of stability.
- roller 36 The attachment of the roller on the skins is achieved by a fixing piece 38 , which is substantially S shaped. This latter is attached on the inner skin by one of the above described rivet 330 , as well as a further rivet 331 .
- a physical axis 40 is mounted on facing walls of rim 34 and piece 38 , with interposition of a U shaped element 42 . This makes it possible to rotate roller 36 around a geometric axis A36, which extends along transverse axis YY.
- a housing 44 is attached on the inner wall of rim 34 , in particular by welding.
- a locking rod 46 is slidably mounted in this housing, through opposite top 440 and bottom 442 walls thereof.
- a horizontal pin 47 protruding from said rod, is adapted to slide along a vertical notch 444 in the housing.
- a compression spring 48 is wrapped around rod 46 , so as to push said rod downwards, until pin 47 abuts against bottom wall of notch 444 .
- a ring 49 allows activation by an operator, so that the latter may pull rod 46 upwards, against compression action of the spring 48 .
- locking rod 46 is adapted to engage a so-called locking hole 112 , provided in the upper face of longitudinal beam 11 as shown by figure 27 .
- the inner longitudinal side of skins 31 and 32 are mutually fixed by a supplementary line 335 of rivets. As shown more in detail on figure 16 , some of these rivets 335 ensure the attachment of a further slider 50 , which is adapted to cooperate with the lower track 28 . To this end, slider 50 is accommodated in a housing 35 , which is mounted on the ends of skins 31 and 32 . Moreover member 351 is intended to reinforcement purpose, whereas 352 denotes a structural frame module, for holding the slider tip 51 .
- each outer panel 6 is to be compared with that of each inner panel 3 , as above described.
- said outer panel is formed by an inner skin 61 and an outer skin 62.
- outer panel 6 has substantially the same curved shape as inner panel 3 . Due to its position outside panel 3 , said outer panel 6 has a slightly superior radius of curvature. In use, the two panels 3 and 6 are positioned in close proximity, so as to strengthen the sealing effect.
- D36 the closest distance between outer skin 32 of inner panel 3 and inner skin 61 of outer panel 6 .
- this distance D36 is very little, in particular inferior to the thickness of hollow bodies.
- Figures 18 to 20 , as well as 22 to 26 show structural elements of panel 6 , that are substantially identical to those of panel 3 , which are illustrated on figures 8 to 10 , as well as 12 to 16.
- panel 6 is provided with several recesses, similar to those of panel 3 .
- Panel 6 is also equipped with a rim 64 , identical to that 34 (see figure 22 ).
- panel 6 comprises rollers 66 , analogous to those 36 .
- the inner wall of said rim 64 is provided with a housing 74 , adapted to cooperate with a locking rod 76 (see figure 24 ).
- panel 6 is equipped with a slider 80 .
- several lines of rivets 630 to 635 are also provided in several locations of panel 6 , in a similar way as rivets 330 to 335 of panel 3 .
- the protection device is in its closing configuration illustrated in particular on figure 4 .
- the different panels define a sort of shield in front of the side-by-side anodes. More in detail, inner panels 3a and 3b are in mutual contact, while panel 3a abuts against wall 21.
- outer panels 6a and 6b are in mutual contact, while panel 6a advantageously overlaps panel 3b.
- outer panels 6c and 6d are in mutual contact, while panel 6d abuts against opposite wall 20, and inner panels 3c and 3d are in mutual contact.
- outer panel 6c overlaps inner panel 3d whereas, on the other hand, outer panel 6b of overlaps inner panel 3c.
- These different overlap zones which are referenced OV on figure 4 , advantageously have a length ensuring a thermal insulation effect.
- locking rod 46 extends into facing hole 112: this cooperation between rod and hole applies at least for some of the above panels.
- the operator will move at least panel 6a which is initially located in front of target anode A3. To this end, he first pulls upwards ring 49, so as to disengage rod 46 out of initial hole 112 (see arrow F49 on figure 27 ). Under these circumstances, panel 6a can then be pushed manually by the operator using handles 71 and 73. More in detail this panel will slide with respect to the frame due to the cooperation, first between rollers 36 66 and tracks 25 24, in addition between sliders 50 80 and tracks 28 29. During this sliding motion.
- panel 6a is pushed towards the left according to arrow F6a, bearing in mind that it may be pushed towards the right according to arrow f6a.
- this outer panel is maintained in position, since spring 48 pushes locking rod 46 into another hole, located at the left with respect to the above mentioned initial hole (see arrow F48 on figure 27 ).
- Said panel 6a extends now in front of inner panel 3b namely, in other words, the latter is retracted behind this outer panel.
- the width of the above passage P3 may not be sufficient.
- the operator pushes, not only panel 6a as described above, but also adjacent panel 6b. As shown on figure 29 , it is in general more convenient to slide this adjacent panel 6b towards the right along arrow F6b, namely away from panel 6a. At the end of these two motions, panels 6a and 6b are located in front of respectively inner panels 3b and 3c.
- both panels 6a and 6b may be displaced towards the left, so as to cover inner panels 3a and 3b in view of the creation of passage P'3.
- only single panel 6b may be displaced so as to create a narrow passage, analogous to P3.
- steps analogous to those of the last two paragraphs may be carried out, in case of interventions on either anodes A7 or A8.
- the width of the above passage P2 may not be sufficient.
- the operator needs to push towards the right, not only panel 3a as described above, but also adjacent panel 3b.
- both outer panels 6a and 6b need to be moved in a preliminary step, so that the operators might easily displace above mentioned inner panels.
- These different motions illustrated on figure 31 by arrows F6a, F6b for outer panels, and by arrows F3a and F3b for inner panels, have a greater amplitude than motions of figure 30 .
- panels 3a and 3b are away from extremity wall 21, so as to create a larger passage P'2 towards anode A2. It is to be noted that this large passage also enables access to adjacent anode A1. In case of an intervention on this anode A1, it is also possible to move towards the right panel 3a, from the configuration illustrated in figure 30 . Moreover steps analogous to those described in the last two paragraphs may be carried out, in case of interventions on either anodes A5 or A6. In this last situation, it is preferred to move towards the left, first the outer panels 6a and 6b, and then the inner panels 3c and 3d.
- FIGS 33 to 36 illustrate other possibilities, for what concerns access configurations of the device according to the invention. These figures represent the basic elements of the frame, as well as the different panels.
- panel 3c is retracted behind panel 6b, so as to create a narrow passage P5, similar to P2 and P3, towards not shown anode A5.
- panels 3c and 3d are retracted behind respective panels 6b and 6c, so as to create a wider passage P'5, similar to P'2 and P'3.
- panels 3a to 3c are retracted behind respective panels 6a to 6c, so as to create a still wider passage P7.
- figure 36 all the inner panels 3a to 3d are retracted behind outer panels 6a to 6d, so as to create a maximal width passage P8.
- the device according to the invention can be made in various other embodiments.
- eight hood panels are provided on each side.
- the hooding device according to the present invention advantageously comprises approximately ten hood panels on each side. It is to be compared to the conventional hooding devices of a DX+ TM or DX+ Ultra TM electrolytic pot, which comprise 19 hood panels on each side.
- the device according to the invention has many advantages over prior art devices. Operator work is easier and safer, with less effort being required to slide the hood panels instead of removing them, reducing the risk of back injuries. Moreover, sliding hood panels are less subject to mishandling and damage than prior art panels. Sliding one or two hood panels for an anode change or other purpose requiring access to the anodes reduces emission of noxious gases into the potroom, as there is no need to slide the hood panel totally if convenient access is possible with a partially slid panel.
- the device according to the invention can be used in a process for changing a spent anode assembly, comprising the steps of
- This process can be carried out manually, or it can be carried using a pot tending machine; the sliding facility of the hood panel simplifies the operation of said pot tending machine for opening and closing the access to the anode assembly.
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- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrolytic Production Of Metals (AREA)
Abstract
This protection device, which is adapted to be placed in front of the anodes, comprises a frame (1) and a plurality of panels (3,6) which are mounted on the frame and are adapted to be displaced with respect to this frame, so as to allow access to said anodes for an operator.According to the invention panels (3,6) comprise a first set of inner panels (3a-3d), as well as a second set of so-called outer panels (6a-6d), said panels being adapted to slide with respect to said frame (1) along a longitudinal direction (XX) of anodes line(s) so that:- in a so-called closing configuration, panels (3,6) form a substantially continuous shield (S) in front of the line of anodes; and- in a so-called access configuration, at least one panel of inner set is at least partially retracted behind at least one panel of outer set, so as to define one passage (P5) for access to at least one of the anodes which are part of said line.
Description
- The invention relates to the field of fused salt electrolysis, and more precisely to an anodic assembly which is part of an electrolytic cell suitable for the Hall-Heroult process. In particular, the invention relates to a device which is adapted to protect the environment from the emission of anodes, which belong to this anode assembly.
- The Hall-Heroult process is the only continuous industrial process for producing metallic aluminium from aluminium oxide. Aluminium oxide (Al2O3) is dissolved in molten cryolite (Na3AlF6), and the resulting mixture (typically at a temperature comprised between 940 °C and 970 °C) acts as a liquid electrolyte (usually called "electrolytic bath") in an electrolytic cell. An electrolytic cell (also called "pot") used for the Hall-Héroult process typically comprises a steel shell (so-called potshell), a lining (comprising refractory bricks protecting said steel potshell against heat, and cathode blocks usually made from graphite, anthracite or a mixture of both).
- This cell is also provided with so-called anodic assemblies, which are formed by an anode hanger and at least one anode (usually made from carbon) that plunges into the liquid electrolyte. Anodes and cathodes are connected to external busbars. An electrical current is passed through the cell (typically at a voltage between 3.5 V and 5 V) which electrochemically reduces the aluminium oxide, split by the electrolyte into aluminium and oxygen ions, into aluminium at the cathode and oxygen at the anode; said oxygen reacting with the carbon of the anode to form carbon dioxide. The resulting metallic aluminium is not miscible with the liquid electrolyte, has a higher density than the liquid electrolyte and will thus accumulate as a liquid metal pad on the cathode surface from where it needs to be removed from time to time, usually by suction into a crucible.
- The electrical energy is a major operational cost in the Hall-Heroult process. Capital cost is an important issue, too. Ever since the invention of the process at the end of the 19th century much effort has been undertaken to improve the energy efficiency (expressed in kW/h per kg or ton of aluminium), and there has also been a trend to increase the size of the pots and the current intensity at which they are operated in order to increase the plant productivity and bring down the capital cost per unit of aluminium produced in the plant.
- Industrial electrolytic cells used for the Hall-Heroult process are generally rectangular in shape and connected electrically in series, the ends of the series being connected to the positive and negative poles of an electrical rectification and control substation. The general outline of these cells is known to a person skilled in the art and will not be repeated here in detail. They have a length usually comprised between 8 and 25 meters and a width usually comprised between 3 and 5 meters. The cells (also called "pots") are always operated in series of several tens (up to more than a hundred) pots (such a series being also called a "potline"); within each series DC currents flow from one cell to the neighbouring cell. For protection the cells are arranged in a building, with the cells arranged in rows either side-by-side, that is to say that the long side of each cell is perpendicular to the axis of the series, or end-to-end, that is to say that the long side of each cell is parallel to the axis of the series. It is customary to designate the sides for side-by-side cells (or ends for end-to end cells) of the cells by the terms "upstream" and "downstream" with reference to the current orientation in the series. The current enters the upstream and exits downstream of the cell. The electrical currents in most modern electrolytic cells using the Hall-Héroult process exceed 200 kA and can reach 400 kA, 450 kA or even more; in these potlines the pots are arranged side by side. Most newly installed pots operate at a current comprised between about 350 kA and 600 kA, and more often in the order of 400 kA to 500 kA.
- The superstructure of the cell comprises a fixed frame and a mobile metallic anode busbar, also called "anode beam", which extends at the outer periphery of the fixed frame. Each anode is equipped with a metallic rod, for mechanical attachment and electrical connection to said anode beam. Anodes are provided along at least one line, typically along two lines on either side of the superstructure.
- More precisely, anodes (also called "anode blocks") in the Hall-Heroult process are prebaked cuboids made from a carbonaceous material. The anode blocks are fixedly connected to so-called anode hangers. They serve two different purposes, namely to keep the carbon anodes at a predetermined distance from the cathode, and to carry the electrical current from an anode busbar (also called "anode beam") down to the carbon anodes. Anode hangers are fixed to the overhanging anode beam in a detachable manner using clamps. They comprise an upper part called "anode rod" or "anode stem", which is connected to the anode beam, and a lower part, called "anode yoke". The anode yoke has a number of arms each of which terminates in a cylindrical stub that is embedded in preformed stubholes of the carbon anode blocks and fixed with cast iron acting as temperature-resistant, electrically conductive glue; this process is called "anode rodding" or "anode casting".
- The entity "anode rod plus anode yoke" is sometimes called "anode hanger", and the entity "anode hanger plus anode block" is called "anode assembly".
- Anodes are subject to oxidative consumption during the electrolysis process, the carbon being oxidized into carbon dioxide. More generally, the Hall-Heroult electrolytic process leads to gaseous emissions, which, in addition to CO2, mainly comprise fluorine compounds such as hydrogen fluoride, originating from the electrolytic bath, as well as minor amounts of SO2. These fluorine compounds are noxious to workers and to the environment. Concerning environmental damage, it has been observed over the decades, as the production of smelters has increased, that fluorine compounds can damage the neighbouring vegetation, and can also cause damage (so-called fluorosis) to the cattle raised near aluminium smelters. Therefore, since the 1970s, gaseous emissions of Hall-Heroult cells are no longer released into the environment but undergo a purification.
- More precisely, gaseous emissions from electrolytic pots are collected using protection devices such as hooding systems, and treated in gas treatment stations to remove fluorine compounds and other noxious compounds before releasing the collected air into the environment. Said gas treatment usually comprises a dry absorption of said noxious compounds on fresh alumina that is subsequently introduced into the electrolytivc pot.
- In practice, each protection (hooding) device is intended to cover at least one line of anodes. In this respect, this device comprises first an elongated frame which extends, in use, substantially parallel to the line of anodes. This frame supports two fixed end walls, located at the opposite extremities of the anodes line. Moreover, facing the front side of the anodes, several panels (so-called "hood panels") are provided between these end walls. These panels are typically curved, in particular shaped as a quarter of a circle, so as to ensure an optimal protection. Said hood panels also act as heat shields, thereby limiting thermal losses of the electrolytic cell and protecting the workers.
- During the use of the cell, operators need to have access to the anode assemblies, in particular in view of their maintenance or the replacement of spent anode assemblies by new anode assemblies, or in emergency situations such as so-called anode effects. In this respect, the panels need to be movable between two main configurations. In a first so-called protection configuration, these panels are located side by side to define a shield, with a close lateral contact for sealing matters. Moreover in a second so-called access configuration, these panels must be mutually separated so as to define a passage towards the anodes for the operators.
- More precisely, a typical industrial electrolytic pot (known as DX+™ or DX+ Ultra™ technology, commercialized by Emirates Global Aluminium) has 18 anodes on each side, arranged along a longitudinal axis (called here also "anode line") of the cell, and there are 19 hood panels on each side. In these pots anodes are changed by pairs, and for changing a pair of anodes three adjacent hoods need to be removed to gain access to the pair of anodes to be changed; eventually these three hood panels need to be put back in place.
- In known solutions, hood panels can be removed from the frame by lifting. Such a lifting operation may first be carried out manually. In this case, there are risks of premature mechanical damage of the panels, due to potential mishandling of the operators. In practice, these hoods need to be replaced when they exhibit a deformation such that they do no longer guarantee sufficient tightness. Repair and replacement of hood panels represent a rather significant cost in a smelting plant. Moreover, due to the substantial weight of the panels (typically around 17 kg per panel for DX+™ or DX+ Ultra™ technology), their manual handling by an operator may cause injuries. As these panels are also very hot, their manual handling may lead to accidental burns, too.
- Under these circumstances, it has been considered to develop specific devices which are adapted to mechanically lift to the panels. Specific pot tending machines for handling hood panels have been patented (see for instance
WO 2015/132479 assigned to E.C.L. ) and are commercially available. However, this implies extra costs. In addition, such a mechanical lifting is not a very convenient operation, so that it does not avoid accidental deformation of the hood panels. - In view of the above, one goal of the invention is first to provide a device adapted to reliably protect environment from the emissions of the anodes of an electrolytic cell, which can be implemented by operators without any excessive physical strength.
- One other goal of the invention is to provide such a device which can bring about an improved sealing, in particular with respect to gaseous emissions of the anodes, compared to prior art solutions.
- One other goal of the invention is to provide such a device, which has a relatively simple structure and a satisfactory compactness.
- According to the invention, at least one of the aforementioned goals is achieved by a protection device (100) for an anodic assembly of an electrolytic cell, suitable for the Hall-Héroult electrolysis process, said assembly comprising a superstructure (102) as well as a plurality of anodes (A1-A8) arranged along at least one line (L1, L2), said superstructure (102) comprising a fixed frame (104) of substantially rectangular shape and an anode beam (106) adapted to support anode rods (108),
- said protection device, which is adapted to be placed in front of said anodes, comprising a frame (1) and a plurality of panels (3,6) which are mounted on the frame and are adapted to be displaced with respect to this frame, so as to allow access to said anodes for an operator,
- characterized in that
- said panels (3,6) comprise a first set of so-called inner panels (3a-3d), adjacent to anodes in use, as well as a second set of so-called outer panels (6a-6d), away from anodes in use, at least part of said panels and, preferably, all of these said panels being adapted to slide with respect to said frame (1) along a longitudinal direction (XX) of anodes line(s) so that
- in a so-called closing configuration, panels (3,6) form a substantially continuous shield (S) in front of the line of anodes; and
- in a so-called access configuration, at least one panel of inner set is at least partially retracted behind at least one panel of outer set, so as to define one passage (P2, P'2, P3, P'3) for access to at least one of the anodes which are part of said line.
- According to some embodiments of this protection device:
- said first set of inner panels (3a-3d) and said second set of outer panels (6a-6d) comprise the same number of panels.
- said frame defines at least a first track (24 28) and at least a second track (25, 29), which are mutually parallel, each inner panel (3) comprising at least a first slider (36,50) adapted to cooperate with said first track and each outer panel comprising at least a second slider (66, 80) adapted to cooperate with said second track.
- said frame comprises three longitudinal beams, namely a first so-called central beam (10), a second so-called outer beam (11) and a third so-called upper beam (12), as well as cross pieces (13-15) extending between central beam and outer beam, and posts 16-18) extending between central beam and upper beam.
- a pair of first (24) and second (25) tracks are provided on outer beam, whereas another pair of first (28) and second (29) tracks are provided on the upper beam.
- each panel (3, 6) comprises an inner skin (31, 61) and an outer skin (32, 62), said skins being at least partly distant so as to define a hollow body.
- said outer skin is provided with at least one recess, said recess being in particular provided with one handle (41, 43, 71, 73), said handle being either integrated into the global volume of the hollow body, or protruding out of said volume.
- in closing configuration, at least one inner panel and at least one outer panel define an overlap zone (OV) in front view.
- said device comprises locking means (46), movable between a locking position wherein they are adapted to lock said panel (3, 6) with respect to said frame in a predefined position, and a release position, said locking means comprising in particular a locking rod (46) mounted on said panel, as well as a hole (110) provided in said frame.
- said protection device comprises a compression spring (46) adapted to move said rod into said hole, as well as a release ring (49) adapted to remove said rod out of said hole.
- said device comprises insulation means, which are provided over part of said panel, in particular over opposite end walls of said panel.
- Another object of the invention is an electrolytic cell suitable for the Hall-Heroult electrolysis process, comprising a protection device (100) as above.
- Another object of the invention is a method for changing a spent anode assembly in an electrolytic cell as above, comprising the steps of:
- opening said protection device (100) by sliding at least one panel from a closed position into an open position, such as to open an access to an anode assembly,
- replacing said spend anode assembly by a new anode assembly,
- closing said protection device (100) by sliding back said at least one panel from said open position into said closed position.
- Another object of the invention is an aluminium electrolysis plant comprising at least one line of electrolytic cells of substantially rectangular shape, said cells being arranged side by side, and said plant further comprising means for electrically connecting said cells in series and for connecting the cathodic busbar of a cell to the anode beam of a downstream cell, characterized in that more than 80% of the electrolytic cells in at least one of said line, and preferably each electrolytic cell of said line, is an electrolytic cell as above.
- Another object of the invention is a method for making aluminium by the Hall-Heroult electrolysis process using electrolytic cells of substantially rectangular shape, characterized in that said method is carried out in an aluminium electrolysis plant as above.
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Figures 1 to 36 illustrate various aspects and embodiments of the invention. They are given here for illustration only and are not intended to limit the scope of the invention. -
Figure 1 is a perspective view, showing an anodic assembly of an electrolytic Hall-Heroult electrolytic cell, which is equipped with protection devices according to the invention. -
Figures 2 and 3 are perspective views, illustrating under different angles one of the protection devices shown onfigure 1 . -
Figures 4 and5 are respectively front and side views of the protection device shown onfigure 1 , in its closing configuration. -
Figures 6 and 7 are views of details VI and VII onfigure 5 , showing at a much larger scale different tracks that are provided on the frame, which is part of said protection device. -
Figures 8 to 10 are respectively perspective, front and side views of an inner panel, provided on said protection device. -
Figures 11 to 16 are cross-section views, along lines XI-XI to XVI-XVI onfigure 9 . -
Figure 17 is a front view, showing under another angle locking means which are also illustrated onfigure 14 . -
Figures 18 to 20 are respectively perspective, front and side views of an outer panel, provided on said protection device. -
Figures 21 to 26 are cross-section views, along lines XXI-XXI to XXVI-XXVI onfigure 19 . -
Figure 27 is a view of detail XVII onfigure 4 , showing the cooperation between locking means offigures 14 and 17 and the frame of the device according to the invention. -
Figures 28 to 31 are schematic front views, illustrating several possibilities with regard to the implementation of the protection device according to the invention. -
Figure 32 is a front view, analogous tofigure 4 , showing in greater detail the access configuration illustrated onfigure 29 , of the protection device according to the invention. -
Figures 33 to 36 are perspective views, illustrating other possible access configurations of the protection device according to the invention- 1
- Frame
- 10,11,12
- Longitudinal beams
- 13,14,15
- Cross pieces
- 16,15,16
- Posts
- 19
- Oblique bar
- 20,21
- Plain walls
- 22,23
- Brackets
- 24,25
- Inner and outer tracks
- 26,27
- Brackets
- 28,29
- Lower and upper tracks
- 3
- Inner panel
- 31,32
- Inner and outer skin of 3
- 320,321,322
- Inner, intermediate and outer recess of
panel 3 - 323,324,325,326,327
- Long (323,324), end (325,326) and median (327) recess of 3
- 33,34
- Longitudinal walls
- 330,331
- Rivets
- 332,333,334,335
- Lines of rivets
- 35
- Housing
- 351
- Reinforcement member
- 352
- Structural support frame
- 36
- Outside rollers
- 37
- Groove
- 38
- Fixing piece
- 40
- Physical axis
- 41,43
- Handles
- 42
- U-shaped element
- 44
- Housing
- 440,442
- Walls
- 444
- Notch
- 46
- Locking rod
- 47
- Pin
- 48
- Compression spring
- 49
- Ring
- 50
- Slider
- 51
- Tip of 50
- 6
- Outer panel
- 61,62
- Inner and outer skin of 6
- 620 to 652
- Same elements as those 320 to 327, 330 to 335, 351 and 352 for
panel 6 - 64
- Rim of 6
- 66
- Rollers
- 71,73
- Handles
- 74
- Housing
- 76
- Rod
- 80
- Slider
- 81
- Tip of 80
- 100
- Protection device according to the invention
- 102
- Superstructure
- 104
- Fixed frame
- A1-A8
- Anodes
- 106
- Anode beam (mobile)
- 108
- Anode rod
- 110
- Hook
- 112
- Hole
- OV
- overlap zones
- F3x, F6x
- Motions of panels 3x and 6x
- P2, P'2, P3, P'3, P5, P'5, P6, P7
- Passages towards anodes
- An aluminium smelter comprises a plurality of electrolytic cells arranged the one behind the other (and side by side), typically along two parallel lines. These cells are electrically connected in series by means of conductors, so that electrolysis current passes from one cell to the next. The number of cells in a series is typically comprised between several tens up to more than four hundred, but this figure is not substantial for the present invention. The cells are arranged transversally in reference of main direction of the line they constitute. In other words the main dimension, or length, of each cell is substantially orthogonal to the main direction of a respective line, i.e. the circulation direction of current.
- The Hall-Heroult process as such, the way to operate the latter, as well as the cell arrangement are known to a person skilled in the art and will not be described here in more detail. In the present description, the terms "upper" and "lower" refer to mechanical elements in use, with respect to a horizontal ground surface. Moreover, unless otherwise specifically mentioned, "conductive" means "electrically conductive".
- As aforementioned an electrolytic cell used for the Hall-Heroult process typically comprises first a potshell and a lining, which are not illustrated on the figures. This cell also comprises a plurality of anode assemblies, each of which is formed by a metallic rod (so-called "anode rod") and at least one anode fixed to it by means of an anode yoke. This anodic assembly, known as such, is not part of the invention, so that it will not be described in detail. As shown on
figure 1 ,superstructure 102 comprises a fixedframe 104 and a mobilemetallic anode frame 106, hereafter called "anode beam", which extends at the outer periphery of the fixed frame. - In an usual way each anode is provided with a
metallic anode rod 108 for mechanical attachment and electrical connection to the anode beam. These anodes are not shown onfigure 1 , but their positioning is illustrated in particular onfigure 4 . On thisfigure 1 ,anode beam 106 is provided with pairs ofhooks 110, adapted to facilitate the attachment of theanode rods 108 to theanode beam 106 in the usual way. Two lines L1 and L2 are provided, on either side ofsuperstructure 102. - The general structure of a Hall-Heroult electrolysis pot is known per se and will not be explained here. It is sufficient to explain that the current is fed into the anode beam, flows from the anode beam to the plurality of anode rods and to the anodes in contact with the liquid electrolyte where the electrolytic reaction takes place. Then the current crosses the liquid metal pad resulting from the process and eventually will be collected at the cathode block.
- The present invention is more particularly directed to a protection device 100, which is adapted to cooperate with one anode line. On
figure 1 , two such devices, referenced I and II as a whole, cooperate with respective anodes lines L1 and L2. Each of said devices forms a hood which separates the content of the electrolytic cell, as well as any off-gases generated by the electrolysis process, from the environmental atmosphere. Said off-gases are sucked through the superstructure into a gas treatment station, as mentioned above; this is known as such and will not be explained here in more detail. Device I will now be described, bearing in mind that the structure of device II is similar. - On
figure 2 , let us note XX the longitudinal axis of this device I, which is parallel in use to one anodes line, YY the transversal axis and ZZ the horizontal axis. "Inner" and "outer" refer to positions respectively close and away from the anodes in use, along YY axis. Said device of the invention comprises anelongated frame 1, which includeslongitudinal beams outer beams upper beam 12 is positioned substantially abovecentral beam 10. -
Longitudinal beams middle cross piece 13 as well as twoopposite cross pieces longitudinal beams middle post 16 as well as two opposite end posts 17 and 18. Several oblique bars 19 are also provided, so as to stiffen this frame. In addition twoplain walls longitudinal beams - As shown on
figure 6 ,longitudinal beam 10 supports two mutuallyparallel brackets outer tracks upper beam 12 is equipped with two further parallel brackets 26 and 27, schematically illustrated onfigure 7 , which are positioned the one under the other. The outer surface of these brackets defines further respective lower and upper tracks 28 and 29, also schematically illustrated. As will be described in further details, these different tracks are adapted to cooperate with sliders, provided on panels which are part of the device I. - According to an essential feature of the invention, the device I comprises two sets of panels, namely a first set of
inner panels 3, as well as a second set of outer panels 7. Advantageously the two sets comprise the same number, namely fourinner panels 3a to 3d and fourouter panels 6a to 6d in the illustrated example (see in particularfigure 3 ). However a different number of panel can be considered. - Let us now describe one
inner panel 3, with reference in particular tofigures 8 to 17 , bearing in mind that the structures of all inner panels are substantially identical. Viewed from the side, as shown onfigure 10 , this panel is bent so as to have substantially the shape of a quarter of the circle, with a diameter which is slightly inferior to that of eachaforementioned wall -
Panel 3 comprises aninner skin 31 and anouter skin 32, which are mutually distant over part of the panel, so that the latter partly forms a hollow body. By way of an advantageous example, inner skin may be a stainless steel sheet, whereas outer skin may be a sheet of aluminium. This stainless steel sheet is adapted to be exposed to flames and high temperatures, while also reinforcing the aluminium sheet. In particular, said skins are separated on longitudinal ends of the panel, so as to definelongitudinal walls outer skin 32 is designed to form some recesses, namely regions where thisskin 32 extends close toinner skin 31. - More in detail, as shown on
figures 8 to 10 ,outer skin 32 is first equipped with so-called long recesses, namely which extend over substantially its whole length : aninner recess 320, an oppositeouter recess 321 and anintermediate recess 322. In addition three further so-called recesses are provided side-by-side, between long recesses 323 and 324: end recesses 325 and 326, as well as amedian recess 327. As illustrated more in detail onfigure 11 , U shapedelements recess figure 10 . - In addition, over some other regions of the panel, the two
skins longitudinal line 330 of rivets. In this region, as shown onfigure 12 , arim 34 is interposed between these skins, so as to protrude outside with respect to these skins. This rim extends substantially over the whole length of the panel, namely along XX axis. - As represented on
figure 13 , thepanel 3 is equipped with someoutside rollers 36, which form sliders. The shape of each roller is designed so as to cooperate with the above describedinner track 24. Indeed said roller is provided with a V-shapedgroove 37. In the present embodiment, two rollers are provided close to opposite longitudinal ends of the panel, bearing in mind that a superior number of rollers may be provided. In theory, one single roller may be considered: however this is not a preferred variant, due to its lack of stability. - The attachment of the roller on the skins is achieved by a fixing
piece 38, which is substantially S shaped. This latter is attached on the inner skin by one of the above describedrivet 330, as well as afurther rivet 331. Aphysical axis 40 is mounted on facing walls ofrim 34 andpiece 38, with interposition of a U shapedelement 42. This makes it possible to rotateroller 36 around a geometric axis A36, which extends along transverse axis YY. - Referring now to
figures 14 and 17 , ahousing 44 is attached on the inner wall ofrim 34, in particular by welding. A lockingrod 46 is slidably mounted in this housing, through opposite top 440 and bottom 442 walls thereof. Moreover ahorizontal pin 47, protruding from said rod, is adapted to slide along avertical notch 444 in the housing. Acompression spring 48 is wrapped aroundrod 46, so as to push said rod downwards, untilpin 47 abuts against bottom wall ofnotch 444. Finally aring 49 allows activation by an operator, so that the latter may pullrod 46 upwards, against compression action of thespring 48. As will be further described, lockingrod 46 is adapted to engage a so-calledlocking hole 112, provided in the upper face oflongitudinal beam 11 as shown byfigure 27 . - Turning now to
figure 15 transversal edges ofrecess 321, namely parallel to YY axis, are mutually attached byopposite lines further line 334 of rivets, extending parallel to XX axis as shown onfigure 8 , is provided betweenadjacent recesses - With reference again to
figure 8 , the inner longitudinal side ofskins supplementary line 335 of rivets. As shown more in detail onfigure 16 , some of theserivets 335 ensure the attachment of afurther slider 50, which is adapted to cooperate with the lower track 28. To this end,slider 50 is accommodated in ahousing 35, which is mounted on the ends ofskins member 351 is intended to reinforcement purpose, whereas 352 denotes a structural frame module, for holding theslider tip 51.
Let us now describe oneouter panel 6, with reference in particular tofigures 18 to 26 , bearing in mind that the structures of all outer panels are substantially identical. The structure of eachouter panel 6 is to be compared with that of eachinner panel 3, as above described. In particular, said outer panel is formed by aninner skin 61 and anouter skin 62. Onfigures 18 to 26 the mechanical elements of saidouter panel 6, which are analogous to those ofinner panel 3 as shown onfigures 8 to 17 , are given the same references added by numbers respectively 30 and 300. - As can be seen on side view of
figure 5 ,outer panel 6 has substantially the same curved shape asinner panel 3. Due to its position outsidepanel 3, saidouter panel 6 has a slightly superior radius of curvature. In use, the twopanels figure 5 let us note D36 the closest distance betweenouter skin 32 ofinner panel 3 andinner skin 61 ofouter panel 6. Advantageously this distance D36 is very little, in particular inferior to the thickness of hollow bodies. -
Figures 18 to 20 , as well as 22 to 26 show structural elements ofpanel 6, that are substantially identical to those ofpanel 3, which are illustrated onfigures 8 to 10 , as well as 12 to 16. As shown onfigures 18 to 20 ,panel 6 is provided with several recesses, similar to those ofpanel 3.Panel 6 is also equipped with arim 64, identical to that 34 (seefigure 22 ). As illustrated onfigure 23 ,panel 6 comprisesrollers 66, analogous to those 36. The inner wall of saidrim 64 is provided with ahousing 74, adapted to cooperate with a locking rod 76 (seefigure 24 ). Further, as shown onfigure 26 ,panel 6 is equipped with aslider 80. It shall also be noted that several lines ofrivets 630 to 635 are also provided in several locations ofpanel 6, in a similar way asrivets 330 to 335 ofpanel 3. - The most significant difference between
panels figure 11 .Recesses panel 6 are also provided withhandles 71 and 73: however, contrary tohandles handles outer skin 62. Indeed, due to the outer position ofpanel 6, handles 71 and 73 do not need to be integrated in the volume of the hollow body forming this panel. Moreover an outside protruding configuration is more convenient, in view of implementation by the operators. - Several examples of implementation, regarding the protection device according to the invention, will now be given.
- Let us suppose first that anodes are in a normal use situation. Under these circumstances, the protection device is in its closing configuration illustrated in particular on
figure 4 . As shown on this figure, the different panels define a sort of shield in front of the side-by-side anodes. More in detail,inner panels panel 3a abuts againstwall 21. In additionouter panels panel 6a advantageously overlapspanel 3b. Moreoverouter panels panel 6d abuts againstopposite wall 20, andinner panels outer panel 6c overlapsinner panel 3d whereas, on the other hand,outer panel 6b of overlapsinner panel 3c. These different overlap zones, which are referenced OV onfigure 4 , advantageously have a length ensuring a thermal insulation effect. In this closing configuration, lockingrod 46 extends into facing hole 112: this cooperation between rod and hole applies at least for some of the above panels. - Let us suppose now that operators need to access to one of the anodes, for example the one A3 located behind
outer panel 6a. This situation may in particular occur this anode needs maintenance, or even needs to be replaced. Several possibilities can be considered. - In any case, the operator will move at least
panel 6a which is initially located in front of target anode A3. To this end, he first pulls upwardsring 49, so as to disengagerod 46 out of initial hole 112 (see arrow F49 onfigure 27 ). Under these circumstances,panel 6a can then be pushed manually by theoperator using handles rollers 36 66 and tracks 25 24, in addition betweensliders 50 80 and tracks 28 29. During this sliding motion. - In the example illustrated on
figure 28 ,panel 6a is pushed towards the left according to arrow F6a, bearing in mind that it may be pushed towards the right according to arrow f6a. At the end of this motion, this outer panel is maintained in position, sincespring 48pushes locking rod 46 into another hole, located at the left with respect to the above mentioned initial hole (see arrow F48 onfigure 27 ). Saidpanel 6a extends now in front ofinner panel 3b namely, in other words, the latter is retracted behind this outer panel. - This sliding motion makes it possible to create a passage referenced P3, which allows access to the operator towards target anode A3. Once the operator has carried out its intended work on this anode, he disengages the locking rod and pushes
panel 6a towards the right according to arrow G6a, so as to place this panel back in its initial position. At the end of these operations, panels are back in their initial shield configuration illustrated onfigure 4 . - In some cases, the width of the above passage P3 may not be sufficient. In this respect the operator pushes, not
only panel 6a as described above, but alsoadjacent panel 6b. As shown onfigure 29 , it is in general more convenient to slide thisadjacent panel 6b towards the right along arrow F6b, namely away frompanel 6a. At the end of these two motions,panels inner panels - Under these circumstances, this makes it possible to create a larger passage P'3 towards anode A3. It is to be noted that this large passage also enables access to adjacent anode A4. This passage P'3, which is schematically shown on
figure 29 , is also illustrated more in detail onfigure 32 . The latter is placed on the same sheet asfigure 4 so as to show, the one above the other, the respective closing and access configurations of the protecting device according to the invention. - As a variant, both
panels inner panels single panel 6b may be displaced so as to create a narrow passage, analogous to P3. Moreover steps analogous to those of the last two paragraphs may be carried out, in case of interventions on either anodes A7 or A8. - Let us suppose now that operators need to access to one of the anodes located behind an inner panel, for example the one A2 located behind
inner panel 3b. In such an event different possibilities can also be considered, bearing in mind that they are slightly different from the one described above with respect to anode located behind outer panels. - In any case, the operator will move at least
inner panel 3b towards the right according to arrow F3b onfigure 30 . After release of lockingrod 46, the operator pushes manually thispanel using handles right handle 43 cannot be easily used at the end of the motion. Therefore it may be convenient to also displaceouter panels Figure 30 illustrates the final position, as well as the arrows mentioned in the present paragraph. In this access configuration offigure 30 ,panel 6b is in front ofinner panel 3c, whereasinner panels - In some cases, the width of the above passage P2 may not be sufficient. In this respect, as shown on
figure 31 , the operator needs to push towards the right, notonly panel 3a as described above, but alsoadjacent panel 3b. Under these circumstances, bothouter panels figure 31 by arrows F6a, F6b for outer panels, and by arrows F3a and F3b for inner panels, have a greater amplitude than motions offigure 30 . - At the end of these motions, still with reference to
figure 31 ,panels extremity wall 21, so as to create a larger passage P'2 towards anode A2. It is to be noted that this large passage also enables access to adjacent anode A1. In case of an intervention on this anode A1, it is also possible to move towards theright panel 3a, from the configuration illustrated infigure 30 . Moreover steps analogous to those described in the last two paragraphs may be carried out, in case of interventions on either anodes A5 or A6. In this last situation, it is preferred to move towards the left, first theouter panels inner panels -
Figures 33 to 36 illustrate other possibilities, for what concerns access configurations of the device according to the invention. These figures represent the basic elements of the frame, as well as the different panels. - On
figure 33 panel 3c is retracted behindpanel 6b, so as to create a narrow passage P5, similar to P2 and P3, towards not shown anode A5. Onfigure 34 panels respective panels figure 35 panels 3a to 3c are retracted behindrespective panels 6a to 6c, so as to create a still wider passage P7. Finally,figure 36 , all theinner panels 3a to 3d are retracted behindouter panels 6a to 6d, so as to create a maximal width passage P8. - The device according to the invention can be made in various other embodiments. In the present embodiment, eight hood panels are provided on each side. More generally, the hooding device according to the present invention advantageously comprises approximately ten hood panels on each side. It is to be compared to the conventional hooding devices of a DX+ ™ or DX+ Ultra ™ electrolytic pot, which comprise 19 hood panels on each side.
- The device according to the invention has many advantages over prior art devices. Operator work is easier and safer, with less effort being required to slide the hood panels instead of removing them, reducing the risk of back injuries. Moreover, sliding hood panels are less subject to mishandling and damage than prior art panels. Sliding one or two hood panels for an anode change or other purpose requiring access to the anodes reduces emission of noxious gases into the potroom, as there is no need to slide the hood panel totally if convenient access is possible with a partially slid panel.
- As adjacent hood panels partially overlap, gas sealing is better than with conventional hood panels. Their function as a heat shield is at least as efficient as for conventional hood panels. The electrical insulation concept remains the same as for conventional hoods.
- Good cleaning of the sliding parts, in particular of
rollers 36 and tracks 24,25, is desirable after each anode change, in order to avoid accumulation of dust and crushed bath.
The device according to the invention can be used in a process for changing a spent anode assembly, comprising the steps of - opening said protection device 100 by sliding at least one
panel 3 from a closed position into an open position, such as to open an access to an anode assembly, - replacing said spend anode assembly by a new anode assembly,
- closing said protection device 100 by sliding back said at least one
panel 3 from said open position into said closed position. - This process can be carried out manually, or it can be carried using a pot tending machine; the sliding facility of the hood panel simplifies the operation of said pot tending machine for opening and closing the access to the anode assembly.
Claims (15)
- A protection device (100) for an anodic assembly of an electrolytic cell, suitable for the Hall-Heroult electrolysis process, said assembly comprising a superstructure (102) as well as a plurality of anodes (A1-A8) arranged along at least one line (L1, L2), said superstructure (102) comprising a fixed frame (104) of substantially rectangular shape and an anode beam (106) adapted to support anode rods (108),said protection device, which is adapted to be placed in front of said anodes, comprising a frame (1) and a plurality of panels (3,6) which are mounted on the frame and are adapted to be displaced with respect to this frame, so as to allow access to said anodes for an operator,characterized in thatsaid panels (3,6) comprise a first set of so-called inner panels (3a-3d), adjacent to anodes in use, as well as a second set of so-called outer panels (6a-6d), away from anodes in use, at least part of said panels and, preferably, all of these said panels being adapted to slide with respect to said frame (1) along a longitudinal direction (XX) of anodes line(s) so that- in a so-called closing configuration, panels (3,6) form a substantially continuous shield (S) in front of the line of anodes; and- in a so-called access configuration, at least one panel of inner set is at least partially retracted behind at least one panel of outer set, so as to define one passage (P2, P'2, P3, P'3) for access to at least one of the anodes which are part of said line.
- A protection device (100) according to claim 1, characterized in that said first set of inner panels (3a-3d) and said second set of outer panels (6a-6d) comprise the same number of panels.
- A protection device (100) according to claim 1 or 2, characterized in that said frame defines at least a first track (24 28) and at least a second track (25, 29), which are mutually parallel, each inner panel (3) comprising at least a first slider (36, 50) adapted to cooperate with said first track and each outer panel comprising at least a second slider (66, 80) adapted to cooperate with said second track.
- A protection device (100) according to any of claims 1 to 3, characterized in that said frame comprises three longitudinal beams, namely a first so-called central beam (10), a second so-called outer beam (11) and a third so-called upper beam (12), as well as cross pieces (13-15) extending between central beam and outer beam, and posts 16-18) extending between central beam and upper beam.
- A protection device (100) according to claim 4, characterized in that a pair of first (24) and second (25) tracks are provided on outer beam, whereas another pair of first (28) and second (29) tracks are provided on the upper beam.
- A protection device (100) according to any of claims 1 to 5, characterized in that each panel (3, 6) comprises an inner skin (31, 61) and an outer skin (32, 62), said skins being at least partly distant so as to define a hollow body.
- A protection device (100) according to claim 6, characterized in that said outer skin is provided with at least one recess, said recess being in particular provided with one handle (41, 43, 71, 73), said handle being either integrated into the global volume of the hollow body, or protruding out of said volume.
- A protection device (100) according to any preceding claim wherein, in closing configuration, at least one inner panel and at least one outer panel define an overlap zone (OV) in front view.
- A protection device (100) according to any preceding claim, wherein said device comprises locking means (46), movable between a locking position wherein they are adapted to lock said panel (3, 6) with respect to said frame in a predefined position, and a release position, said locking means comprising in particular a locking rod (46) mounted on said panel, as well as a hole (110) provided in said frame.
- A protection device (100) according to preceding claim, comprising a compression spring (46) adapted to move said rod into said hole, as well as a release ring (49) adapted to remove said rod out of said hole.
- A protection device (100) according to any preceding claim, wherein said device comprises insulation means, which are provided over part of said panel, in particular over opposite end walls of said panel.
- An electrolytic cell suitable for the Hall-Heroult electrolysis process, comprising a protection device (100) according to any of the previous claims.
- A method for changing a spent anode assembly in an electrolytic cell according to preceding claim, comprising the steps of:- opening said protection device (100) by sliding at least one panel from a closed position into an open position, such as to open an access to an anode assembly,- replacing said spend anode assembly by a new anode assembly,- closing said protection device (100) by sliding back said at least one panel from said open position into said closed position.
- An aluminium electrolysis plant comprising at least one line of electrolytic cells of substantially rectangular shape, said cells being arranged side by side, and said plant further comprising means for electrically connecting said cells in series and for connecting the cathodic busbar of a cell to the anode beam of a downstream cell,
characterized in that more than 80% of the electrolytic cells in at least one of said line, and preferably each electrolytic cell of said line, is an electrolytic cell according to claim 12. - A method for making aluminium by the Hall-Heroult electrolysis process using electrolytic cells of substantially rectangular shape, characterized in that said method is carried out in an aluminium electrolysis plant according to claim 14.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP21204982.9A EP4174216A1 (en) | 2021-10-27 | 2021-10-27 | Protection device for anodes of an electrolytic cell, comprising movable panels, and its implementation method |
PCT/IB2022/060142 WO2023073520A1 (en) | 2021-10-27 | 2022-10-21 | Protection device for anodes of an electrolytic cell, comprising movable panels, and its implementation method |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP21204982.9A EP4174216A1 (en) | 2021-10-27 | 2021-10-27 | Protection device for anodes of an electrolytic cell, comprising movable panels, and its implementation method |
Publications (1)
Publication Number | Publication Date |
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EP4174216A1 true EP4174216A1 (en) | 2023-05-03 |
Family
ID=78709191
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP21204982.9A Withdrawn EP4174216A1 (en) | 2021-10-27 | 2021-10-27 | Protection device for anodes of an electrolytic cell, comprising movable panels, and its implementation method |
Country Status (2)
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EP (1) | EP4174216A1 (en) |
WO (1) | WO2023073520A1 (en) |
Citations (6)
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SU134429A1 (en) * | 1960-04-18 | 1960-11-30 | Г.Г. Величко | Shelter for Aluminum Electrolyzers |
US4043892A (en) * | 1975-12-15 | 1977-08-23 | Reynolds Metals Company | Aluminum reduction cell having a lateral enclosure system |
NO154526B (en) * | 1979-04-23 | 1986-06-30 | Alusuisse | COVER FOR MELT ELECTRONIC CELLS FOR ALUMINUM MANUFACTURING. |
DE102011052543A1 (en) * | 2010-08-10 | 2012-02-16 | Solios Environnement | Method and device for enclosing the well gases in an aluminum electrolysis tank |
WO2015132479A2 (en) | 2014-03-05 | 2015-09-11 | E.C.L. | System for carrying out operations linked to the use of cells of a facility for producing aluminium by means of electrolysis |
AU2015208857A1 (en) * | 2014-01-27 | 2016-07-28 | Rio Tinto Alcan International Limited | Hooding system for an electrolytic cell |
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DE2263348A1 (en) * | 1972-12-23 | 1974-07-04 | Siemag Translift Gmbh | Aluminium electrolysis plant operating in fused salts - has segmented half hoods with individual drive for telescopic contraction |
US4002551A (en) * | 1975-04-17 | 1977-01-11 | Aluminium Pechiney | Process and apparatus for collecting the fumes given off during the production of aluminium in an electrolysis cell with a continuous anode |
DE2841459A1 (en) * | 1978-08-24 | 1980-03-06 | Alusuisse | COVER OF A MELTFLOW ELECTROLYSIS CELL |
CH648064A5 (en) * | 1981-09-08 | 1985-02-28 | Alusuisse | Encased molten-salt electrolytic cell for producing aluminium |
CN2576726Y (en) * | 2002-10-11 | 2003-10-01 | 杜荣华 | Alumium-electrolyzing prebaking anode electrolytic tank environment-protection tank-covering board |
US7282133B2 (en) * | 2004-03-08 | 2007-10-16 | Alcoa Inc. | Cermet inert anode assembly heat radiation shield |
CN206783783U (en) * | 2017-04-27 | 2017-12-22 | 甘肃东兴铝业有限公司 | A kind of aluminium electroloysis carbon anode changes protective cover |
CN207362344U (en) * | 2017-09-09 | 2018-05-15 | 聊城信源集团有限公司 | A kind of electrolytic cell with anode covering and heat insulating device |
CN110344082B (en) * | 2019-07-18 | 2020-12-08 | 国家电投集团远达环保工程有限公司重庆科技分公司 | Sliding mechanism for side cover plate of aluminum electrolysis cell |
-
2021
- 2021-10-27 EP EP21204982.9A patent/EP4174216A1/en not_active Withdrawn
-
2022
- 2022-10-21 WO PCT/IB2022/060142 patent/WO2023073520A1/en unknown
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
SU134429A1 (en) * | 1960-04-18 | 1960-11-30 | Г.Г. Величко | Shelter for Aluminum Electrolyzers |
US4043892A (en) * | 1975-12-15 | 1977-08-23 | Reynolds Metals Company | Aluminum reduction cell having a lateral enclosure system |
NO154526B (en) * | 1979-04-23 | 1986-06-30 | Alusuisse | COVER FOR MELT ELECTRONIC CELLS FOR ALUMINUM MANUFACTURING. |
DE102011052543A1 (en) * | 2010-08-10 | 2012-02-16 | Solios Environnement | Method and device for enclosing the well gases in an aluminum electrolysis tank |
AU2015208857A1 (en) * | 2014-01-27 | 2016-07-28 | Rio Tinto Alcan International Limited | Hooding system for an electrolytic cell |
WO2015132479A2 (en) | 2014-03-05 | 2015-09-11 | E.C.L. | System for carrying out operations linked to the use of cells of a facility for producing aluminium by means of electrolysis |
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WO2023073520A1 (en) | 2023-05-04 |
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