EP3347509A1 - Ensemble cathode pour cellule d'électrolyse approprié pour le procédé hall-héroult - Google Patents

Ensemble cathode pour cellule d'électrolyse approprié pour le procédé hall-héroult

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Publication number
EP3347509A1
EP3347509A1 EP16843770.5A EP16843770A EP3347509A1 EP 3347509 A1 EP3347509 A1 EP 3347509A1 EP 16843770 A EP16843770 A EP 16843770A EP 3347509 A1 EP3347509 A1 EP 3347509A1
Authority
EP
European Patent Office
Prior art keywords
cathode
insert
bar
slot
region
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP16843770.5A
Other languages
German (de)
English (en)
Other versions
EP3347509B1 (fr
EP3347509A4 (fr
Inventor
Bernard JONQUA
Abdalla ALZAROONI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dubai Aluminium PJSC
Original Assignee
Dubai Aluminium PJSC
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Publication date
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Publication of EP3347509A1 publication Critical patent/EP3347509A1/fr
Publication of EP3347509A4 publication Critical patent/EP3347509A4/fr
Application granted granted Critical
Publication of EP3347509B1 publication Critical patent/EP3347509B1/fr
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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
    • C25C3/08—Cell construction, e.g. bottoms, walls, cathodes
    • 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
    • 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
    • C25C3/16—Electric current supply devices, e.g. bus bars

Definitions

  • the invention relates to an improvement of an electrolysis cell (also called “pot") for producing aluminium by fused salt electrolysis using the Hall-Heroult-process. More precisely it relates to a cathode assembly for such electrolytic cell allowing to decrease the cathode voltage drop and modify the current distribution along the cathode assemblies in a desirable way.
  • the invention relates to a cathode assembly in which the electrical contact between the cathode material and the busbar to which the cathode is connected involves a copper bar.
  • the Hall-Heroult process is the only continuous industrial process for producing metallic aluminium form aluminium oxide.
  • Aluminium oxide Al 2 0 3
  • molten cryolite Na 3 AIF 6
  • the resulting mixture typically at a temperature comprised between 940°C and 970°C acts as a liquid electrolyte in an electrolytic cell.
  • An electrolytic cell used for the Hall-Heroult process typically comprises a steel shell (so-called “pot- shell”), a lining (comprising refractory bricks protecting said steel shell against heat, and cathode blocks usually made from graphite, anthracite or a mixture of both), and a plurality of anodes (usually made from carbon) that plunge 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 3.8 V to 5 V) which electrochemically reduces the aluminium oxide, split by the electrolyte into aluminium ions and oxygen ions, into aluminium at the cathode and oxygen at the anode, said oxygen reacting with the carbon of the anode.
  • 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 below the electrolyte, from where it needs to be removed from time to time, usually by suction into a crucible.
  • pots are always operated in series of several tens (up to several hundreds) pots (such a series being called a "potline"); within each series DC currents flow from one cell to the neighbouring cell. Much effort is still being made to optimise the process in order to increase its energy efficiency.
  • Aluminium conductors are used for the busbar systems for both anodes and cathodes.
  • aluminium cannot be used in direct contact with the cathode blocks due to its low melting point (about 660°C for pure aluminium).
  • steel bars are conventionally used for ensuring electrical contact with the cathode blocks; these so-called cathode bars are connected to cathode busbars (made from aluminium) by welded and/or bolted connectors.
  • Cathode bars are typically fitted into slots machined into the lower surface of the cathode block.
  • Typical solutions comprise a copper rod or bar that is inserted into a groove or slot machined into the steel cathode bar, over all or part of the length of said cathode bar.
  • the basic concept of a copper insert fitted into a slot or groove machined in a steel cathode bar is described in WO 2001/63014 (Comalco), WO 2005/098093 (Aluminium Pechiney) and WO 2009/055844 (BHB Billington).
  • FR 1 161 632 (Pechiney) discloses a copper insert fitted into a groove machined in a carbon cathode block using cast iron as a sealing material.
  • composition of cast iron used for sealing cathode bars into the grooves of carbon cathodes is known to be critical (see US 2,593,751 assigned to Pechiney), because the cast iron should not undergo any swelling due to structural transformations, as swelling could cause the carbon material to develop cracks.
  • a copper bar with circular cross section fitted into a steel bar with outer rectangular cross section and an inner "U” section, the "U” section being closed by a block see US 3,551 ,319 (Kaiser); a copper bar welded to a lateral face of a steel bar, see US 2,846,388 (Pechiney); a copper bar with rectangular cross section inserted into a steel tube with rectangular cross sections, see US 5,976,333 (Alcoa); a copper bar with circular cross section inserted into a steel tube with rectangular external cross section and a bore with circular cross section, see WO 2005/098093 (Aluminium Pechiney).
  • WO 2013/039893 (Alcoa) describes the use of a copper insert as a joint
  • WO 2007/071392 (SGL Carbon) describes the use of sheets made from expanded graphite
  • RU 2285754 describes the use of a carbonaceous paste.
  • Such a joint material may improve the electrical contact between the carbon block and the steel bar.
  • RU 2285754 proposes to secure the copper bar inserted into the slot of the steel bar by welded-on steel plates while allowing for a narrow cavity between the copper insert and the steel bar, i.e. the section of the copper insert is somewhat smaller than that of the groove into which it is fitted.
  • the copper inserts do not extend along the whole length of the steel cathode bar, but a spacer section is provided at each end of the cathode bar into which the copper insert does not extend.
  • the copper bar can be made in two pieces separated in the centre of the cathode by a steel plug and/or an air gap.
  • WO 2002/42525 Servico
  • a cathode bar comprising a steel bar into which at each end a copper bar is inserted, the copper insert extending beyond the end of the steel bar and ensuring the electrical contact with the connection to the aluminium busbar.
  • This peak current density causes local erosion of the cathode due to magnetohydrodynamic effects which are related to high magnetic fields and lead to stirring of the molten aluminium and generalized and/or localized wear on the cathode surface that is in contact with the molten metal pad; this is particularly marked when the block is rich in graphite. Such local erosion can limit the lifetime of the cathode.
  • WO 2005/98093 describes the presence of an unsealed zone at the extremity between the cathode bar and the cathode material.
  • a similar solution is proposed in WO 2004/031452 (ALCAN) using embedding spacers. Fine tuning of the electrical conductivity of cathode blocks parallel to their length by using specially designed cathode bars with copper inserts can therefore decrease the localised cathode erosion; some of the cited documents also address the influence of thermal losses though cathode bars on magnetohydrodynamic effects, knowing that the use of copper inserts tends to lead to an increase of the thermal conductivity of the cathode bar.
  • WO 2004/059039 describes cathode assembly in which a marginal zone of the cathode block facing the collector that has a higher electrical resistance parallel to the length of the cathode block than in the centre of the cathode block; this goal is obtained by using copper inserts or plates with different thickness over different portions of the length of the steel bar, in conjunction with electrically insulating layers between the copper bar and the steel bar.
  • These cathode structures are rather difficult to manufacture and to assemble.
  • a similar effect is achieved in a simpler way by a copper insert that ends at a specified distance from the outer face of the cathode block, as described in WO 2008/062318 (Rio Tinto Alcan).
  • WO 03/014423 (Alcoa): it uses several parallel steel cathode bars in conjunction with electrically insulating layers.
  • US 6,231 ,745 (Alcoa) describes a half-length copper insert that extends somewhat out of the cathode block, but does not extend outside the cell wall.
  • cathode bar systems allow some fine-tuning of electrical conductivity at the outer face of the cathode assembly, they are rather complex to manufacture, and do not offer much flexibility as to the conductivity profile than can be achieved over the length of the cathode block.
  • a cathode assembly suitable for a Hall-Heroult electrolysis cell comprising
  • cathode body made of a carbonaceous material
  • cathode bar made of a first conductive material, said cathode bar being fitted in a groove provided in said cathode body;
  • said insert has at least one first so-called electrically conductive region and at least one second so-called electrically non-conductive region, the electrically conductive contact peripheral length of said insert with said cathode body and/or said cathode bar being superior in the first region than in the second region.
  • This cathode assembly is the first object of the present invention.
  • peripheral walls of said insert define a functional clearance with the facing walls of said cathode body and/or said cathode bar, said functional clearance being filled with a solid non-conductive material or with air.
  • Said electrically non-conductive region is placed inside the groove in such a way that it starts at the edge of the front wall and/or rear wall of cathode body and extends towards the centre of the cathode body.
  • the non-conductive region extends over a part of the axial length of this insert, which is comprised between 6 and 20%, in particular between 9 and 15% of the whole axial length of this insert.
  • the slot or bore in cathode bar has a substantially constant cross section over its axial length and the non-conductive region is defined by a local restriction of the cross section of the insert.
  • the insert has a substantially constant cross section over its axial length and the non-conductive region is defined by a local widening of the cross section of the slot or bore of cathode bar.
  • both the slot or bore in the cathode bar and the insert have a polygonal cross section, and at least one peripheral wall of said insert is remote from facing walls of the slot or bore in the non-conductive region.
  • both the slot or bore in the cathode bar and the insert have a circular cross section, and peripheral wall of said insert is remote from facing wall of the slot or bore in the non-conductive region, so as to define an annular gap there between.
  • the axial length of said second so called non- conductive region is between 50 mm and 250 mm, in particular between 100 and 200 mm.
  • the insert and the slot are polygonal in cross-section, the number of walls of the insert, contacting the cathode bar, being superior in the conductive region(s) than in the non-conductive region(s).
  • Another object of the invention is a process for making a cathode assembly according to the invention, comprising the steps of
  • said insert has at least one first so-called electrically conductive region and at least one second so-called electrically non-conductive region, the electrically conductive contact length, in cross section, of said insert with said body and/or said cathode bar being superior in the first region than in the second region.
  • Yet another object of the invention is an electrolytic cell for the production of aluminium by the Hall-Heroult process, comprising at least one cathode assembly according to the invention.
  • a last object is a process for making aluminium by the Hall-Heroult process, using an electrolysis cell having cathodes assemblies according to the invention.
  • FIGS 1 to 26 represent various embodiments of the present invention.
  • Figure 1 is a perspective view, showing a first embodiment of a cathode assembly according to the invention, wherein the insert of this assembly is rectangular in cross section.
  • Figure 2 is a bottom view, showing the cathode assembly of figure 1.
  • Figure 3 is a cross section showing the cathode assembly of figure 1 , along line Ill-Ill of figure 2.
  • Figure 4 is a perspective view, showing a cathode bar which belongs to the cathode assembly of the figure 1.
  • Figure 5 is a cross section showing the cathode bar of figure 4, along line V-V of figure 4.
  • Figure 6 is a perspective view, showing an insert which belongs to the cathode assembly of the figure 1.
  • Figures 7 and 8 are cross sections showing the insert of figure 6, along lines respectively VII-VII and VIII-VIII of figure 6.
  • Figure 9 is a perspective view, showing the insert of figure 6 which is fitted in a slot of the cathode bar of figure 4.
  • Figures 10 and 11 are cross sections showing the insert fitted in the slot of the cathode bar, along lines respectively X-X and XI-XI of figure 9.
  • Figure 12 is a view at a larger scale, showing the detail XII of figure 10.
  • Figures 13 to 15 are cross sections analogous to figure 12, showing variants of this first embodiment the invention.
  • Figure 16 is a perspective view, analogous to figure 1 , showing a second embodiment of a cathode assembly according to the invention, wherein the insert of this assembly is circular in cross section.
  • Figure 17 is a bottom view, analogous to figure 2, showing the cathode assembly of figure 16.
  • Figure 18 is a cross section showing the cathode assembly of figure 1 , along line XVIII- XVIII of figure 17.
  • Figure 19 is a perspective view, analogous to figure 6, showing a cathode bar which belongs to the cathode assembly of the figure 16.
  • Figure 20 is a cross section showing the cathode bar of figure 19, along line XX-XX of figure 19.
  • Figure 21 is a perspective view, analogous to figure 6, showing an insert which belongs to the cathode assembly of the figure 16.
  • Figure 22 is a bottom view, showing the insert of figure 21 which is fitted in a hole of the cathode bar of figure 4.
  • Figures 23 and 24 are cross sections showing the insert fitted in the hole of the cathode bar, along line XXIII-XXIII and line XXIV-XXIV, respectively, of figure 22.
  • Figure 25 is an enlarged view, showing the detail XXV of figure 24.
  • Figure 26 is a cross section of a cathode assembly along a vertical longitudinal plane, showing more specifically the end regions of the insert and the cathode body.
  • WX Width of element W W1 , W3, W51 , W5A, W5B, W7, W17, W37 Description
  • a “cathode assembly” C comprises the cathode body 1 and the cathode bar 3.
  • the present invention applies to cathodes used in the Hall-Heroult process that form the bottom of an electrolysis cell, said cathodes being assembled from individual cathode assemblies C, each of which bears at least one cathode bar 3.
  • the Hall-Heroult process and the outline of an electrolysis cell (also called “pot") are known to a person skilled in the art and will not be described here in great detail.
  • the cathode assembly of the invention is designated as a whole by alphanumeric reference C. It is suitable for a Hall-Heroult electrolysis cell, but could be used in other electrolytic processes.
  • the cathode assembly C first comprises a cathode body 1 , of known type, which is made of a carbonaceous material, typically graphitized carbon or graphite.
  • This cathode body 1 which has an elongated shape, has opposite front 11 and rear 12 walls, as well as peripheral walls. The latter are formed by parallel upper and lower walls 13 and 14, as well as parallel side walls 15 and 16.
  • its length L1 (see figure 2), i.e. the distance between walls 11 and 12
  • its width W1 i.e. the distance between walls 15 and 16 is between about 400 mm and about 675 mm.
  • its height H1 (see figure 1), i.e. the distance between walls 13 and 14, is between about 420 mm and about 580 mm.
  • the lower wall 14 of cathode body 1 is provided with a longitudinal groove 17 extending from one cathode body end to the other (see in particular figure 2). The free end of the groove 17 leads to fronts 11 or rear 12 wall of body 1.
  • groove 17 Opposite side walls of groove 17 are referenced 171 and 172, whereas its upper wall is referenced 173 (see figure 3).
  • its width W17 i.e. the distance between walls 171 and 172, is between about 130 mm and about 280 mm.
  • its depth D17 i.e. the distance between upper wall 173 and the surface of lower wall 14, is between about 150 mm and about 240 mm.
  • the cathode assembly C also comprises two cathode bars 3 and 3', each of which is accommodated in groove 17.
  • Each cathode bar 3 or 3' is made of a first conductive material, typically steel.
  • the structure of bar 3 will now be described, bearing in mind that structure of the other bar 3' is identical.
  • This cathode bar 3, which has an elongated shape (see in particular figure 4), has opposite front 31 and rear 32 walls, as well as peripheral walls. The latter are formed by upper and lower walls 33 and 34, as well as side walls 35 and 36. Two adjacent walls form longitudinal chamfers or rounded corners 39, in a known manner.
  • upper and lower wall 33,34 and / or side walls 35,36 are parallel; in an advantageous variant of this embodiment the cathode bar is essentially rectangular in cross section.
  • the length L3 of cathode bar 3 is superior to that of length of half groove 17, so as to define a projection 38 (see in particular figure 2), which extends beyond front wall 11 of the cathode block body.
  • the length L38 of projection 38 is between about 350 mm and about 600 mm.
  • the width W3 of bar 3 i.e. the distance between walls 35 and 36, is slightly inferior to the width W17 of groove 17.
  • the height H3 of bar 3 i.e. the distance between walls 33 and 34, is slightly inferior to the height H17 of groove 17.
  • the gaps between facing walls of bar 3 and groove 17 are filled with cast iron, in a known way, and/or with an intermediate carbonaceous material (see figure 3) which will be described below.
  • the upper wall 33 of cathode bar 3 is provided with a housing formed by a longitudinal slot 37.
  • This slot 37 extends over only a part of the whole length of the cathode bar 3, i.e. it does not longitudinally lead to front and rear walls thereof.
  • this slot may be provided in another peripheral wall of cathode bar 3, in particular in side walls 15,16 ; in this (less preferred) case a symmetrical configuration is preferred.
  • Opposite side walls of slot 37 are referenced 371 and 372, whereas its bottom wall is referenced 373 (see figure 5).
  • its width W37 i.e. the distance between walls 371 and 372 is between about 50 mm and about 100 mm.
  • its depth D37 i.e. the distance between walls bottom wall 373 and the surface of upper wall 33, is between about 50 mm and about 80 mm.
  • the cathode assembly C also comprises two inserts 5 and 5', each of which is accommodated in a respective slot 37 and 37', see figure 9.
  • Each insert 5 or 5' is made of a second conductive material, having a higher electrical conductivity than that of said first conductive material, typically copper.
  • This insert 5 which has an elongated shape, has opposite front 51 and rear 52 walls, as well as peripheral walls. The latter are formed by upper and lower walls 53 and 54, as well as side walls 55 and 56. In one embodiment upper and lower wall 53,54 and / or side walls 55,56 are parallel; in an advantageous variant of this embodiment the insert 5 is essentially rectangular in cross section.
  • the above length L5 of insert 5 is called axial length, namely along main axis of this insert.
  • This term "axial length” also applies for above mentioned lengths L1 and L3.
  • the peripheral length of insert i.e. the sum of the lengths of its sides, in cross section like on figures 10 and 1 1.
  • the peripheral contact length of insert 5 is the sum of the lengths of its sides, which contact cathode bar 3.
  • the axial length L5 of insert 5 is slightly smaller to that of slot 37. Over its length, this insert comprises at least three regions, the cross-sections of which are different. In the illustrated example, this insert includes two end regions 5A and 5B, which have the same cross-section, as well as an intermediate region 5C, which has a different cross-section as will be further explained.
  • the ratio L5C/L5 between the axial length L5C of intermediate region 5C and the axial length L5 of whole insert 5 is between about 8 % and about 20 %, in particular between about 9 % and about 15 %.
  • the height H5 of insert i.e. the distance between walls 53 and 54, is slightly inferior to the height H37 of slot 37.
  • This height can differ over the whole length of insert 5, related to the longitudinal deformation of the collector bar.
  • the width and/or height of insert 5, i.e. the distance between walls 55 and 56, and/or between walls 53 and 54, may not be constant over this length, which defines the above mentioned different regions.
  • the width W5A or W5B of end regions 5A and 5B substantially corresponds to that of slot 37. Therefore, once the insert 5 is placed into slot 37, there is a fit, first, between side wall 371 of said slot 37 and side walls 55A, 55B of said insert 5 and, moreover, between side wall 372 of said slot 37 and side walls 56A, 56B of said insert 5.
  • This fit which is shown on figure 11 , makes it possible to create an electric contact between cathode bar 3 and regions 5A and 5B of the insert 5.
  • side walls 55C and 56C of intermediate region 5C define recesses with side walls 55A and 56A, as well as 55B and 56B, of adjacent end regions 5A and 5B.
  • these side walls 55C and 56C are distant from facing walls 371 and 372 of slot 37, in order to define two functional gaps or clearances 7 (see figure 10). These clearances are better shown on figure 12, where their scale is enlarged towards other mechanical elements, in view of clarity.
  • the width W7 of these clearances i.e. the closest distances between respective walls 371, 372 of slot 37 and intermediate region 5C, is enough to avoid any electric contact between bar 3 and insert 5, in this intermediate region. In an advantageous manner, this width is greater than about 0.5 mm, in particular greater than about 0.8 mm.
  • this width W7 is between about 0.5 mm and about 2 mm, in particular between about 0.5 mm and about 1 mm.
  • Figures 10 and 1 1 show cross sections of insert 5 accommodated in slot 37, respectively in intermediate region 5C and in end region 5B.
  • the electrically conductive contact peripheral length of insert can be defined by the length of this insert contacting cathode bar 3, in cross section like on figures 10 and 1 1.
  • This contact may be direct, like on figure 1 1 , or may be indirect, i.e. it is then ensured via a conductive material.
  • side walls 55A and 56A are in electrical contact with the cathode bar, which means that electrically conductive contact peripheral length is equal to the sum of the lengths of three sides of this end region 5A, i.e. H5 + W5A + H5.
  • the electrically conductive surface corresponds to the product between conductive peripheral length, as defined above, and axial length. For region 5A, this conductive surface is equal to (2*H5 + W5A)*L55A. In an analogous manner, for region 5B, electrically conductive peripheral length is equal to H5+W5B+H5, and conductive surface is equal to (2*H5 + W5B)*L55B.
  • the non-conductive region is placed inside the cathode block groove in such a way that it starts at the edge of the front wall 11 and/or rear wall 12 of cathode body 1 and extends towards the centre of the cathode body 1.
  • conductive ratio i.e. the ratio between, on the one hand, electrically conductive contact surface in non-conductive region and, on the other hand, electrically conductive contact surface in conductive region. In the shown example, this ratio is approximately equal to 10 %.
  • electrically conductive contact length in non- conductive region is equal to 0, since no part of region 5C contacts cathode bar 3. Facing walls respectively 54C and 373 define another clearance 7". The conductive ratio is therefore equal to 0.
  • electrically conductive contact length in non- conductive region is equal to (L54C+L56C).
  • the conductive ratio is by far inferior to 1.
  • the insert and the slot are rectangular in cross-section, i.e. they have four peripheral walls.
  • this insert and this slot may have different polygonal cross sections, with a different number of peripheral walls. In this case, the number of walls of the insert, contacting the cathode bar, is superior in the conductive region(s) than in the non-conductive region(s).
  • both the slot 37 and the insert 5 are non-polygonal, but define a portion of a circle in cross section, in particular a half circle.
  • the non shown conductive region has the same radial dimension as the slot, whereas the non-conductive region is defined by a portion 5C of the insert, the radial dimension of which is reduced.
  • the conductive ratio is equal to 0.
  • Figures 16 to 25 show another embodiment, wherein both the insert and the slot of cathode bar are circular in cross section.
  • cathode body cathode bar and insert.
  • the mechanical elements of cathode body 2 which are similar to those of cathode body 1 of first embodiment, will be given the same reference numerals, the first digit "2" being used instead of "1".
  • the mechanical elements of insert 6, which are similar to those of insert 5 of first embodiment, will be given the same reference numerals, the first digit "6" being used instead of "5".
  • cathode body 2 is substantially identical to that of cathode body 1.
  • the structure of each cathode bar 4 or 4' is globally similar to that of cathode bar 3 or 3'.
  • cathode bar 4 differs from cathode bar 3, essentially in that the housing 47 receiving the insert 6 is not formed by a slot 37, but by a bore 47. The latter does not transversally lead to a side wall of the bar 4, but longitudinally leads to the one single wall of this bar, namely rear wall 42, as can be seen on figures 19 and 22.
  • this bore 47 differs from slot 37, in that it is circular in cross-section.
  • its length L47 (see figure 22), i.e. the distance between its bottom 473 and front wall of bar 4
  • D47 is between about 30 mm and about 70 mm.
  • the cathode assembly C of this second embodiment also comprises two inserts 6 and 6', each of which is accommodated in a respective bore 47 and 47'.
  • this insert 6 has an elongated shape, as well as a circular cross-section. It has opposite front 61 and rear 62 walls, as well as a peripheral wall 63.
  • the axial length L6 of insert 6 can be equal to that of slot 47. Over its length, this insert comprises at least three regions, the cross-sections of which are different. In the illustrated example, this insert includes two end regions 6A and 6B, which have the same cross-section, as well as an intermediate region 6C, which has a different cross-section as will be further explained.
  • the ratio L6C/L6 between the axial length L6C of intermediate region and the axial length L6 of whole insert is between about 6 % and about 20 %, in particular between about 9 % and about 15 %.
  • the diameter D6A or D6B of end regions 6A and 6B substantially corresponds to that of bore 47. Therefore, once the insert 6 is placed into bore 47, there is a fit between side wall 471 of this bore and side walls 63A, 63C of the insert (as shown on figure 23 with side wall 63A). This makes it possible to create an electric contact between bar 4 and regions 6A and 6B of the insert 6.
  • the diameter D6C of intermediate region 6C is slightly inferior to the diameter D6A or D6B of end regions 6A and 6B.
  • peripheral walls 63C are distant from facing walls 471 of bore 47, in order to define an annular gap or clearance 9.
  • this clearance 9 is better shown on figure 25, where its scale is enlarged towards other mechanical elements, in view of clarity.
  • the conductive ratio as defined above, is equal to 0 since no region of tapered region 6C contacts the bar 4.
  • the cross section of the slot is constant and the insert has at least one local tapered region, the transversal dimension of which is smaller.
  • the cross section of the insert may be constant, whereas the slot has at least one local widened region, the transversal dimension of which is larger.
  • Each widened region of the slot defines a non-conductive region of the insert.
  • the electrically non-conductive region 7 of the copper insert 5 can be placed inside the cathode block groove in such a way that it starts at the edge of the front wall and/or rear wall of cathode body 1 and extends towards the centre of the cathode body.
  • the copper insert 5 can also extend until the outer end of the steel cathode bar 3.
  • the cathode assembly C according to the present invention can be of the same height or of different height, and/or can have a structured surface, and accordingly the cathode formed by these cathode assemblies can have a single flat upper surface (which is by far the most common cathode structure), or its upper surface can comprise regions of different heights or can be otherwise structured.
  • the gaps between facing walls of cathode bar 3 and groove 17 are filled with cast iron, in a known way, and/or with a carbonaceous intermediate material.
  • Said intermediate carbonaceous material in direct contact with the metallic connection bar 3 must be somewhat deformable, such as to accommodate the higher thermal expansion of the metallic connection bar 3, usually made from steel, with respect to the material of the cathode assembly C.
  • compressed expanded graphite most conveniently in the form of a sheet
  • carbonaceous sealing paste can be used, and/or carbonaceous sealing paste.
  • Compressed expanded graphite is available in the form of sheet of different densities and thickness from several manufacturers and under different tradenames (such as PapyexTM manufactured by Mersen, and SigraflexTM manufactured by SGL).
  • the sealing paste advantageously includes carbonaceous particles dispersed in a binder that has a high carbon yield after baking.
  • Said carbonaceous particles can be graphite particles.
  • Such sealing pastes are commercially available from different manufacturers and under various tradenames (Sealing paste HCF 80 from Carbone Savoie for example).
  • the thickness of the sealing paste is calculated according to the width of the collector bar, taking into consideration the differential of thermal expansions between the copper and the graphitized cathode assembly; a thickness comprised between 15 and 25 mm can be used.

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  • Electrolytic Production Of Metals (AREA)

Abstract

La présente invention concerne un ensemble cathode pour cellule d'électrolyse approprié pour le procédé de Hall-Héroult: cet ensemble cathode (C) comporte un corps de cathode (1 ) réalisé en un matériau carboné, au moins une barre de cathode (3) réalisée en un premier matériau conducteur, ladite barre de cathode étant ajustée dans une rainure (17) prévue dans ledit corps de cathode (1), au moins un insert réalisé en un second matériau conducteur, possédant une conductivité électrique supérieure à celle dudit premier matériau conducteur, ledit insert (5) étant ajusté dans une fente (37) ou un alésage prévu(e) dans ladite barre de cathode (3). Selon l'invention, ledit insert (5) comprend au moins une première région dite conductrice d'électricité (5A) et au moins une région dite non-conductrice d'électricité (5C), la longueur périphérique de contact conducteur d'électricité dudit insert avec ledit corps de cathode (1) et/ou ladite barre de cathode (3) étant plus grande dans la première région que dans la seconde région.
EP16843770.5A 2015-09-09 2016-09-07 Ensemble cathode pour cellule d'électrolyse approprié pour le procédé hall-héroult Active EP3347509B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1515963.5A GB2542150A (en) 2015-09-09 2015-09-09 Cathode assembly for electrolytic cell suitable for the Hall-Héroult process
PCT/IB2016/055324 WO2017042691A1 (fr) 2015-09-09 2016-09-07 Ensemble cathode pour cellule d'électrolyse approprié pour le procédé hall-héroult

Publications (3)

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EP3347509A1 true EP3347509A1 (fr) 2018-07-18
EP3347509A4 EP3347509A4 (fr) 2019-05-01
EP3347509B1 EP3347509B1 (fr) 2020-08-05

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EP (1) EP3347509B1 (fr)
GB (1) GB2542150A (fr)
WO (1) WO2017042691A1 (fr)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2554702A (en) * 2016-10-05 2018-04-11 Dubai Aluminium Pjsc Cathode assembly for electrolytic cell suitable for the Hall-Héroult process
GB2595460A (en) * 2020-05-26 2021-12-01 Dubai Aluminium Pjsc Cathode assembly with metallic collector bar systems for electrolytic cell suitable for the Hall-Héroult process

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0052577B1 (fr) * 1980-11-19 1984-02-15 Schweizerische Aluminium AG Ancrage pour une barre cathodique
CH657383A5 (de) * 1981-08-31 1986-08-29 Alusuisse Elektrolysewanne zur herstellung von aluminium mittels schmelzflusselektrolyse und verfahren zum einsetzen der eisenbarren.
FR2606428B1 (fr) * 1986-11-10 1989-02-03 Pechiney Aluminium Procede et dispositif de scellement, sous precontrainte, de barres cathodiques
US6231745B1 (en) * 1999-10-13 2001-05-15 Alcoa Inc. Cathode collector bar
AUPQ584800A0 (en) * 2000-02-25 2000-03-16 Comalco Aluminium Limited An electrical reduction cell
AU2003271461A1 (en) * 2002-10-02 2004-04-23 Alcan International Limited Collector bar providing discontinuous electrical connection to cathode block
FR2868435B1 (fr) * 2004-04-02 2006-05-26 Aluminium Pechiney Soc Par Act Element cathodique pour l'equipement d'une cellule d'electrolyse destinee a la production d'aluminium
EP2896081B1 (fr) * 2012-09-11 2019-04-10 Alcoa USA Corp. Appareil à barre de prélèvement de courant, système et procédé pour son utilisation

Also Published As

Publication number Publication date
GB201515963D0 (en) 2015-10-21
GB2542150A (en) 2017-03-15
EP3347509B1 (fr) 2020-08-05
WO2017042691A1 (fr) 2017-03-16
EP3347509A4 (fr) 2019-05-01

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