EP0322326B1 - Schutzbeschichtung für Zapfen und herausragende Teile von vorgebrannten Anoden - Google Patents

Schutzbeschichtung für Zapfen und herausragende Teile von vorgebrannten Anoden Download PDF

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Publication number
EP0322326B1
EP0322326B1 EP19880420430 EP88420430A EP0322326B1 EP 0322326 B1 EP0322326 B1 EP 0322326B1 EP 19880420430 EP19880420430 EP 19880420430 EP 88420430 A EP88420430 A EP 88420430A EP 0322326 B1 EP0322326 B1 EP 0322326B1
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EP
European Patent Office
Prior art keywords
anodes
alumina
anode
logs
protective coating
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.)
Expired - Lifetime
Application number
EP19880420430
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English (en)
French (fr)
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EP0322326A1 (de
Inventor
Gabriel Audras
Bernard Samanos
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.)
Carbone Savoie SAS
Original Assignee
Societe des Electrodes et Refractaires Savoie SA
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Publication date
Priority claimed from FR878718452A external-priority patent/FR2624886B2/fr
Application filed by Societe des Electrodes et Refractaires Savoie SA filed Critical Societe des Electrodes et Refractaires Savoie SA
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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
    • C25C3/12—Anodes
    • C25C3/125—Anodes based on carbon
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/02—Electrodes; Connections thereof
    • C25C7/025—Electrodes; Connections thereof used in cells for the electrolysis of melts

Definitions

  • the invention relates to a coating for protection against corrosion and hot oxidation for pre-baked anode logs and the emerging carbonaceous part of these anodes used in aluminum production tanks by electrolysis of alumina dissolved in the cryolite melted using the Hall-Héroult process.
  • anode plugs are introduced into the upper part of the anode, into which logs (or steel plates) will be introduced and sealed. ) which will serve both to suspend the anode from the anode frame and to supply it with current.
  • the sealing is carried out by casting iron or more rarely by means of a carbonaceous paste of special composition.
  • the steel logs are subjected both to a high temperature and to the corrosive effect of the fluorinated effluents emitted by the tank in operation.
  • the molten cryolithic bath can come into contact with the base. steel logs.
  • the emerging part of the anodes that is to say the upper part which, in normal operation of the electrolytic cell, is not immersed in the molten electrolyte, undergoes degradation by combustion, that l 'It is sought to avoid by covering a solidified and ground electrolysis bath, possibly mixed with alumina, or by metallization obtained by spraying liquid aluminum.
  • SERS European patent application EP 0 269 534
  • This composition is essentially characterized by a carbon aggregate such as coke, artificial graphite, waste anodes or semi-graphite electrodes with a low ash content (preferably ⁇ 2%) bound by a lime aluminate cement, to low content of annoying impurities (SiO2, Fe2O3, TiO2, K2O, Cr2O3, total content preferably less than 1%) having an alumina content at least equal to 70% and, preferably, at least equal to 80%, the together being linked by addition of water.
  • a carbon aggregate such as coke, artificial graphite, waste anodes or semi-graphite electrodes with a low ash content (preferably ⁇ 2%) bound by a lime aluminate cement, to low content of annoying impurities (SiO2, Fe2O3, TiO2, K2O, Cr2O3, total content preferably less than 1%) having an alumina content at least equal to 70% and, preferably, at least equal to 80%, the together being linked by addition of water.
  • a complementary addition of magnesium spinel (Al2O3, MgO), whose thermal conductivity is high, makes it possible to lower the temperature of the surface of the anode, thus delaying oxidation.
  • alumina for example alumina for electrolysis or globular alumina, at a content which can constitute up to 50% of the total weight of the aggregate.
  • the cement content by weight, expressed in weight percent of the aggregate (carbon product + additives) is between 10 and 60% and, preferably, from 15 to 50%. It is appropriate to denote by "dry matter” the whole of the aggregate (carbonaceous product, alumina, additives) and the cement.
  • the same compositions are suitable, but it is then preferable to apply them by spraying with a gun.
  • a gun it is necessary, depending on the type of gun used, to control the particle size of the aggregate and the cement (less than 1 mm and, preferably, less than 0.5 mm) and significantly increase the quantity of water.
  • This amount of water will be fixed, for example, between 10 and 70% by weight relative to the dry matter (as defined above) for use in the form of collar paste and, up to 60% by weight for use in the form of a fluid paste to be sprayed on with a spray gun.
  • the object of the present invention is a protective composition which does not have the drawbacks of carbonaceous pastes or comprising a carbonaceous aggregate, and which provides effective protection of the base of the steel logs and possibly of the carbonaceous part emerging from the anodes throughout the lifespan of the anodes (about twenty days on average).
  • This composition is characterized by a mixture of dry materials made up of lime aluminate cement, magnesium spinel, possibly fine powdered alumina and water.
  • the lime aluminate cement has an alumina content of at least 70% and preferably 80% by weight. It preferably contains less than 1% of annoying impurities (SiO2, Fe2O3, TiO2, K2O, Cr2O3)
  • composition of the dry matter mixture is located in the following ranges:
  • the amount of water is between 10 and 80% of the total weight of the dry matter, the contents between 10 and about 50% corresponding to a pasty composition, usable as flange paste, and the contents going up to 80% corresponding to a fluid paste usable by spraying with a gun, with, in this case, a particle size of the dry materials less than 1 mm and preferably less than 0.5 mm.
  • the protective coating of the emerging part of prebaked anodes was implemented according to three formulations for application by spraying with a spray gun, which is adapted - by reducing the water content - for the use of paste paste.
  • the carbon substrate for the tests consists of a core 30 mm in diameter and 120 mm high.
  • the different compositions A, B, C are applied to a group of samples and a certain number of controls are kept without coating. All the samples are treated for 1 hour at 1000 ° C. under nitrogen to remove all traces of water.
  • a 2 hour carboxyreactivity test is then carried out at 1000 ° C. under a CO2 flow rate of 50 liters / hour.
  • the samples are cooled under a stream of nitrogen and each carrot is weighed to determine its weight loss.
  • the results are expressed in milligrams related to an area of 1 cm2 and for a duration of 1 hour. The result is therefore given in mg.cm ⁇ 2.h ⁇ 1.
  • the following results were obtained:
  • the optimal compositions expressed in Secar Cement / Secar cement + Al2O3 + Spinel ratio being between 5 and 50%.
  • the percentage of water to be added depends on the cement content and the particle size of the alumina. It is between 30 and 50 and preferably between 35 and 45% by weight relative to dry matter (that is to say 35 to 45 grams of water per 100 grams of the mixture of Secar cement + alumina + magnesium spinel ).
  • the reduction in corrosion of the anode logs is evident from the first cycle and is accentuated during the following cycles. It can be estimated that the useful life of the anode logs is extended by at least 30%.
  • Secar cement based on calcium aluminate having an alumina content at least equal to 70% and preferably at least equal to 80%.
  • the composition of Secar 80 and 71 cements from the company LAFARGE FONDU INTERNATIONAL and Spinel of Magnesium, from PEM (PECHINEY ELECTROMETALLURGY) are recalled below:

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Prevention Of Electric Corrosion (AREA)
  • Furnace Housings, Linings, Walls, And Ceilings (AREA)
  • Preventing Corrosion Or Incrustation Of Metals (AREA)

Claims (2)

1. Beschichtung zum Schutz der Zapfen von vorgebrannten, für Elektrolysewannen zur Herstellung von Aluminium im Hall-Heroult-Verfahren vorgesehenen Anoden und des herausragenden Teils dieser Anoden gegen die Korrosion und die Oxidation in der Wärme, dadurch gekennzeichnet, daß sie aus einem Gemisch von trockenen Substanzen besteht, das aus Kalkaluminat mit einem Tonerdegehalt von mindestens 70 % und einem schwachen Gehalt an störenden Verunreinigungen, Magnesiumspinell und eventuell feinpulvriger Tonerde in den folgenden Gewichtsanteilen:
Kalkaluminat   : 10 bis 95 %
Pulvrige Tonerde   : 0 bis 80 %
Magnesiumspinell   : 5 bis 10 %
zusammengesetzt und mit Wasser in einem Anteil von 10 bis 80 % des Gesamtgewichis der trockenen Substanzen verbunden ist.
2. Schutzbeschichtung nach Anspruch 1, dadurch gekennzeichnet, daß die Zusammensetzung für die Aufbringung als Kragenpaste auf die Anodenzapfen vorzugsweise in den folgenden Grenzen liegt:
Figure imgb0006
EP19880420430 1987-12-22 1988-12-21 Schutzbeschichtung für Zapfen und herausragende Teile von vorgebrannten Anoden Expired - Lifetime EP0322326B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR878718452A FR2624886B2 (fr) 1986-11-14 1987-12-22 Perfectionnement aux revetements de protection des rondins d'anodes precuites et de la partie emergeante de ces anodes
FR8718452 1987-12-22

Publications (2)

Publication Number Publication Date
EP0322326A1 EP0322326A1 (de) 1989-06-28
EP0322326B1 true EP0322326B1 (de) 1992-08-12

Family

ID=9358501

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19880420430 Expired - Lifetime EP0322326B1 (de) 1987-12-22 1988-12-21 Schutzbeschichtung für Zapfen und herausragende Teile von vorgebrannten Anoden

Country Status (9)

Country Link
EP (1) EP0322326B1 (de)
AU (1) AU610964B2 (de)
BR (1) BR8806778A (de)
CA (1) CA1340408C (de)
DE (1) DE3873713T2 (de)
ES (1) ES2043877T3 (de)
IN (1) IN169360B (de)
IS (1) IS1465B6 (de)
NO (1) NO885645L (de)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2606796B1 (fr) * 1986-11-14 1989-02-03 Savoie Electrodes Refract Revetement de protection destine aux rondins d'anodes precuites
NO930957L (no) * 1993-03-17 1994-09-19 Norsk Hydro As Marterialkompositt for oksidasjons- og korrosjonsbeskyttelse av anodenipler
US6818106B2 (en) * 2002-01-25 2004-11-16 Alcoa Inc. Inert anode assembly
WO2004035870A1 (en) * 2002-10-18 2004-04-29 Moltech Invent S.A. Anode current feeding connection stem
ES2644864T3 (es) * 2002-11-25 2017-11-30 Alcoa Inc. Ensamblaje de ánodo inerte

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1365820A (en) * 1972-02-15 1974-09-04 Zirconal Processes Ltd Coating composition suitable for use at high temperatures
FR2411166A1 (fr) * 1977-12-12 1979-07-06 Lafarge Fondu Int Liant hydraulique refractaire a base d'aluminate de calcium et son procede de preparation
US4354918A (en) * 1981-01-14 1982-10-19 Martin Marietta Corporation Anode stud coatings for electrolytic cells
JPS61111983A (ja) * 1984-11-02 1986-05-30 ミサワホ−ム株式会社 気泡コンクリ−トの製造法
BR8500347A (pt) * 1985-01-25 1986-09-09 Ardal Og Sunndal Verk Anodo pre-cozido com perda de carbono reduzida para emprego na producao de aluminio por reducao por fusao eletrolitica e processo de produzir o mesmo

Also Published As

Publication number Publication date
NO885645L (no) 1989-06-23
DE3873713D1 (de) 1992-09-17
NO885645D0 (no) 1988-12-20
IN169360B (de) 1991-09-28
EP0322326A1 (de) 1989-06-28
CA1340408C (fr) 1999-02-23
BR8806778A (pt) 1989-08-29
IS1465B6 (is) 1991-03-26
AU610964B2 (en) 1991-05-30
ES2043877T3 (es) 1994-01-01
IS3424A7 (is) 1989-06-23
DE3873713T2 (de) 1993-02-11
AU2742988A (en) 1989-06-22

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