EP0814181B1 - Procédé de régulation de la teneur en alumine du bain des cuves d'électrolyse pour la production d'aluminium - Google Patents

Procédé de régulation de la teneur en alumine du bain des cuves d'électrolyse pour la production d'aluminium Download PDF

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Publication number
EP0814181B1
EP0814181B1 EP97420090A EP97420090A EP0814181B1 EP 0814181 B1 EP0814181 B1 EP 0814181B1 EP 97420090 A EP97420090 A EP 97420090A EP 97420090 A EP97420090 A EP 97420090A EP 0814181 B1 EP0814181 B1 EP 0814181B1
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EP
European Patent Office
Prior art keywords
slope
alumina
phase
resistance
process according
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
EP97420090A
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German (de)
English (en)
French (fr)
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EP0814181A1 (fr
Inventor
Olivier Bonnardel
Pierre Marcellin
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.)
Rio Tinto France SAS
Original Assignee
Aluminium Pechiney SA
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Publication date
Application filed by Aluminium Pechiney SA filed Critical Aluminium Pechiney SA
Publication of EP0814181A1 publication Critical patent/EP0814181A1/fr
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    • 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
    • C25C3/20—Automatic control or regulation of cells

Definitions

  • the present invention relates to a method for precise regulation of the content alumina in igneous electrolysis tanks for the production of aluminum according to the Hall-Héroult process, in order not only to maintain the Faraday performance at a high level, but also to reduce emissions from fluorocarbon gases which are particularly harmful and polluting for the environment and that following the anomalies of operation of the tanks electrolysis known as the anode effect.
  • an excess of alumina creates a risk of fouling of the bottom of the tank by undissolved alumina deposits that can turn into plaques hard electrically insulating part of the cathode. This then promotes formation in metal of very horizontal electrical currents strong which, by interaction with magnetic fields stir the sheet of metal and cause instability of the bath-metal interface.
  • an alumina defect causes the appearance of the anode effect, resulting in a loss of production and a sharp increase in the voltage across the tank, which can increase from 4 to 30 or 40 volts.
  • This overconsumption of energy also has the effect of degrading the energy efficiency of the tank but also the Faraday yield following the redissolution of aluminum in the bath and the elevation temperature of the electrolysis bath.
  • the range of alumina contents to be respected is between 2 and 8%.
  • the concentration of alumina in the bath can vary during a cycle of 3 to 8%, which is still insufficient to regulate the alumina content of an acid bath in a range as low and narrow as 1 to 3 or 4%.
  • EP 044794 US 4431491
  • the slope P dR / dt representative of the change in resistance R caused by a change voluntary alumina diet for a period of time determined.
  • This mode of regulation therefore makes it possible to maintain the alumina content of the bath in a narrow and weak range and thus obtain yields Faraday of around 95% with acid baths, simultaneously reducing and notably the quantity (or frequency) of the anode effects on the tanks that are counted in number of anode effects per tank and per day (EA / tank / day) under the name "anode effect rate”.
  • the anode effect is a phenomenon of ion electrolysis fluorides which occurs when there is a lack of oxygen ions in contact with anodes due in particular to a lack of alumina.
  • the tank produces fluorocarbon gases whose trapping by the usual means is impossible due to their chemical inertness and high stability.
  • the method according to the invention makes it possible to solve this pollution problem by lowering the anode effect rate on average to 0.02 EA / tank / day, that is to say well below the target rate of 0.05 EA / tank / day and a fortiori rate of 0.2 to 0.5 EA / tank / day of the prior art; this even improving the Faraday yield over 95%.
  • the Applicant was able to observe that it was possible to dramatically reduce the rate of anode effect by switching to a fast-rate feeding regime without waiting that the resistance R has left the setpoint range according to the prior art previously described as soon as the resistance slope P becomes very high, an indication of a very low alumina content in the bath (1 to 2%) and a very high risk of appearance of anode effect.
  • Figure 1 in the appendix which represents the variation of the resistance R at the terminals of an electrolytic cell as a function of the alumina content of the bath for different increasing anode-metal distances DAM 1 to DAM 3 , clearly shows that regulating the alumina content of the bath between 1 and 3.5% we are in the best possible conditions, on the one hand to use acid electrolysis baths at lowered temperature guaranteeing excellent Faraday yields, on the other hand for detect the slightest variation in resistance since we place our in the zone with the steepest slope of variation of R, that is to say in the zone with the greatest sensitivity.
  • the counterpart of this double advantage implies a very rapid and quantitatively significant reaction capacity in terms of the alumina bath supply regime to prevent the very significant risks of triggering an anode effect which appear as soon as the alumina content of the bath is around 1%.
  • This new procedure for regulating the alumina content does not exclude the implementation of additional safety procedures.
  • the regulation procedure is initiated only when the tank is in normal operating conditions (that is to say correctly adjusted, stable and excluding disturbing operations of operation or adjustment such as change of anode, casting of metal or specific regulation procedures) authorizing the transition to phase 1.
  • the supply of alumina is at theoretical rate CT or waiting phase until what it finds normal operating conditions to go to phase 1.
  • phase 2 is started whatever the values of the resistance slope and the extrapolated slope.
  • the average resistance r (k) of this elementary cycle is also calculated at the end of each elementary cycle k of duration t.
  • These values r (k) are stored during the entire supply phase 1 for the calculation of the slope P (i) while keeping the last N values (N being a predetermined number).
  • the resistance slope P (i), the extrapolated slope PX (i) and the curvature C (i) determined at the end of each regulation cycle i of duration T are calculated from the history of average resistances r (k) of the elementary cycles stored since the start of phase 1 of undernourishment within the limit of the last N values and this by any calculation method implementing a smoothing of the raw data r (k) with elimination of the variations of resistance due to adjustment orders of the anode frame.
  • the computation of the resistance slope and of the auxiliary parameters can be carried out by parabolic regression on the resistances, or by linear regression on the resistance variations, or by any other method equivalent to a nonlinear regression on the resistances.
  • This linear regression on instantaneous slopes dr (k) is equivalent to a parabolic regression on the resistances r (k) after elimination of the variations resistance due to adjustment orders of the anode frame.
  • the new slope calculation method used in the implementation of the present invention is based on the principle of parabolic regression, which allows a much better approach to the actual rise curve resistance that a classic linear regression as shown in the diagram of Figure 3. If for considerations of complexity and means of calculation outside the scope of the invention, the applicant has not implemented exactly this type of regression for the slope calculation it nevertheless uses a method akin to a parabolic regression of calculating a linear regression line on the slopes instantaneous, and the value of the resistance slope P (i) is provided by the ordinate at time t (i) of the linear regression line on the slopes instant.
  • This new slope calculation procedure also provides additional and new information that is used as auxiliary adjustment parameters for optimizing content regulation alumina.
  • reference thresholds Po, PXo and Co can take different predetermined or calculated values according to the operating conditions of the tank (acidity of the bath, temperature, resistance for example).
  • the value of the reference slope Po is between 10 and 150 p ⁇ / s
  • that of the extrapolated slope of reference PXo is between 10 and 200 p ⁇ / s
  • that of the reference curvature Co is between 0.010 and 0.200 p ⁇ / s 2 ..
  • the method according to the invention was implemented for several months on prototypes of electrolytic cell with precooked anodes fed under 400,000 Amps under the following conditions:
  • Alumina is introduced directly into the molten electrolysis bath in doses successive of constant mass by several insertion orifices, maintained permanently open by a crust breaker.

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  • 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)
EP97420090A 1996-06-17 1997-06-16 Procédé de régulation de la teneur en alumine du bain des cuves d'électrolyse pour la production d'aluminium Expired - Lifetime EP0814181B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9607712 1996-06-17
FR9607712A FR2749858B1 (fr) 1996-06-17 1996-06-17 Procede de regulation de la teneur en alumine du bain des cuves d'electrolyse pour la production d'aluminium

Publications (2)

Publication Number Publication Date
EP0814181A1 EP0814181A1 (fr) 1997-12-29
EP0814181B1 true EP0814181B1 (fr) 2001-11-28

Family

ID=9493272

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97420090A Expired - Lifetime EP0814181B1 (fr) 1996-06-17 1997-06-16 Procédé de régulation de la teneur en alumine du bain des cuves d'électrolyse pour la production d'aluminium

Country Status (15)

Country Link
US (1) US6033550A (no)
EP (1) EP0814181B1 (no)
AR (1) AR007606A1 (no)
BR (1) BR9703604A (no)
CA (1) CA2208913C (no)
DE (1) DE69708513T2 (no)
ES (1) ES2165010T3 (no)
FR (1) FR2749858B1 (no)
IN (1) IN192205B (no)
NO (1) NO317186B1 (no)
NZ (1) NZ328095A (no)
RO (1) RO119240B1 (no)
SA (1) SA97180273B1 (no)
SI (1) SI9700163A (no)
ZA (1) ZA975324B (no)

Families Citing this family (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NO311623B1 (no) * 1998-03-23 2001-12-17 Norsk Hydro As Fremgangsmåte for styring av aluminiumoksidtilförsel til elektrolyseceller for fremstilling av aluminium
FR2830875B1 (fr) * 2001-10-15 2004-05-28 Pechiney Aluminium Procede de regulation d'une cellule d'electrolyse pour la production d'aluminium
FR2833274B1 (fr) 2001-12-07 2004-01-23 Pechiney Aluminium Procede et dispositif de detection des effets d'anode d'une cellule d'electrolyse pour la fabrication d'aluminium
US6866767B2 (en) * 2002-10-23 2005-03-15 Alcan International Limited Process for controlling anode effects during the production of aluminum
RU2303658C1 (ru) * 2005-11-02 2007-07-27 Общество с ограниченной ответственностью "Русская инжиниринговая компания" Способ управления технологическим процессом в алюминиевом электролизере с обожженными анодами
NO328080B1 (no) * 2007-11-19 2009-11-30 Norsk Hydro As Fremgangsmate og anordning for styring av en elektrolysecelle
CN101275249B (zh) * 2007-12-20 2010-06-02 中国铝业股份有限公司 一种实时预测铝电解槽内氧化铝浓度的方法
EP2135975A1 (en) * 2008-06-16 2009-12-23 Alcan International Limited Method of producing aluminium in an electrolysis cell
US10472725B2 (en) 2014-06-19 2019-11-12 United Company RUSAL Engineering and Technology Centre LLC Method for controlling an alumina feed to electrolytic cells for producing aluminum
CN113089029A (zh) * 2021-04-02 2021-07-09 贵州创新轻金属工艺装备工程技术研究中心有限公司 一种铝电解生产过程中的智能控料方法

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2487386A1 (fr) * 1980-07-23 1982-01-29 Pechiney Aluminium Procede et appareillage pour reguler de facon precise la cadence d'introduction et la teneur en alumine d'une cuve d'electrolyse ignee, et application a la production d'aluminium
US4425201A (en) * 1982-01-27 1984-01-10 Reynolds Metals Company Method for improved alumina control in aluminum electrolytic cells
NO166821C (no) * 1985-02-21 1991-09-04 Aardal & Sunndal Verk As Fremgangsmaate for styring av aluminiumoksyd-tilfoerselen til elektrolyseovner for fremstilling av aluminium.
FR2581660B1 (fr) * 1985-05-07 1987-06-05 Pechiney Aluminium Procede de regulation precise d'une faible teneur en alumine dans une cuve d'electrolyse ignee pour la production d'aluminium
US4654130A (en) * 1986-05-15 1987-03-31 Reynolds Metals Company Method for improved alumina control in aluminum electrolytic cells employing point feeders
NZ232580A (en) * 1989-02-24 1992-12-23 Comalco Alu Aluminium smelting process control

Also Published As

Publication number Publication date
AU719053B2 (en) 2000-05-04
RO119240B1 (ro) 2004-06-30
CA2208913A1 (fr) 1997-12-17
EP0814181A1 (fr) 1997-12-29
NZ328095A (en) 1998-11-25
BR9703604A (pt) 1998-10-27
AR007606A1 (es) 1999-11-10
DE69708513D1 (de) 2002-01-10
FR2749858A1 (fr) 1997-12-19
US6033550A (en) 2000-03-07
AU2495097A (en) 1998-01-08
IN192205B (no) 2004-03-13
CA2208913C (fr) 2004-02-10
SA97180273B1 (ar) 2005-11-12
DE69708513T2 (de) 2002-07-18
NO317186B1 (no) 2004-09-13
SI9700163A (en) 1997-12-31
ES2165010T3 (es) 2002-03-01
FR2749858B1 (fr) 1998-07-24
NO972723L (no) 1997-12-18
NO972723D0 (no) 1997-06-13
ZA975324B (en) 1998-06-25

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