US3539461A - Anode effect termination - Google Patents

Anode effect termination Download PDF

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Publication number
US3539461A
US3539461A US676500A US3539461DA US3539461A US 3539461 A US3539461 A US 3539461A US 676500 A US676500 A US 676500A US 3539461D A US3539461D A US 3539461DA US 3539461 A US3539461 A US 3539461A
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anode
cell
alumina
percent
electrolyte
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US676500A
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English (en)
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Leon S Newman
Jack E Griffin
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Kaiser Aluminum and Chemical Corp
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Kaiser Aluminum and Chemical Corp
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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

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  • the instant invention relates to a process for terminating an anode effect in an electrolytic cell for the production of aluminum and a system useable in carrying out the process.
  • the process involves determining when the voltage drop across the cell exceeds about 150 percent of the normal operating value and lowering the cell anode so as to reduce the anode-cathode distance in the cell to from about 30 to about 60 percent of the normal operating distance.
  • the available alumina concentration in the bath or electrolyte is adjusted to from about 2 percent to about 6 percent by weight.
  • the anode is raised so as to restore the normal anode-cathode distance and the anode effect is terminated.
  • the metal aluminum is extracted from aluminum-bearing compounds such as alumina (A1 by electrolysis from a molten salt bath or electrolyte.
  • the electrolytic cell comprises in general a steel shell having disposed therein a carbon lining.
  • One or more consummable carbon electrodes is disposed from the top of the cell and is immersed at its lower extremity into a layer of molten electrolyte which is disposed in the cell.
  • the electrolyte or bath which is a mixture of alumina and cryolite is charged to the cell and an electric current is passed through the cell from the anode to the cathode via the layer of molten electrolyte.
  • the alumina is dissociated by the current so that aluminum is deposited on the liquid aluminum cathode and oxygen is liberated at the carbon anode, forming carbon monoxide and carbon dioxide gas.
  • a crust of solidified electrolyte and alumina forms on the surface of the bath, and this is usually covered over with additional alumina.
  • the reduction process involves precisely the same chemical reactions.
  • the principal difference is one of structure.
  • the prebake cell the carbon anodes are prebaked before being installed in the cell, while in the Soderberg, or self-baking anode cell, the anode is baked in situ, that is, it is baked during operation of the electrolytic cell, thereby utilizing part of the heat generated by the reduction process.
  • the instant invention is applicable to either cell.
  • a typical aluminum electrolytic bath used in commercial installations might have the following composition: 1 to 10 percent alumina, 0 to 10 percent aluminum trifluoride, 5 to 12 percent calcium fluoride, and to percent cryolite.
  • alumina is consumed in direct proportion to the metal production.
  • a troublesome phenomenon known as an anode effect occurs.
  • the voltage drop across the cell can increase, for example, from around 4 volts to as much as 40 volts and even higher. This effect is generally attributed to too low a concentration of alumina in the reduction cell bath or electrolyte.
  • the actual concentration of alumina in the electrolyte at which this effect occurs seems to depend upon the temperature, the composition of the electrolyte and the anode current density.
  • the occurrence of the anode effect is the signal for the addition of more alumina. The attendant does this by breaking the frozen crust on top of which he has previously distributed a layer of alumina.
  • the addition of the alumina, as well as a vigorous stirring of the electrolyte, causes the anode effect to disappear, after which the electrolysis continues its normal course until the next anode effect occurs.
  • British Pat. 853,056 describes a procedure utilizing a sonic vibrator to terminate anode effects. How this procedure terminates the anode effect is not stated.
  • Louis Ferrand in US Pat. 2,560,854, describes a procedure for terminating an anode effect which involves slowly oscillating the anodes from a lean region in the electrolyte to a richer region (richer in alumina). Allegedly, this mixes the alumina in the bath more thoroughly and assists 3 in terminating an anode effect. The cumbersome equipment involved to carry out this procedure is easily imagined. Presumably the oscillatory action of the anode facilitates the escape of gaseous bubbles from beneath them. More even current density for the cell is also alleged to be a result of this interesting operation.
  • Robert J. Cooper in U.S. Pat. 2,930,746, discusses the manual procedure mentioned above and notes other practices which can be used, include raking the metal in the aluminum pot below the anodes vigorously to cause temporarary short-circuits from the anode to the aluminum. This cools the gases and disturbs them so they escape more readily. Lowering of the anodes closer to the molten aluminum pad is also used to stop the anode effect. He then proposes a voltage, current and temperature responsive control system which will raise and lower the anode as needed to maintain these variables at predetermined operating levels. According to the patent, this procedure will also terminate anode effects.
  • the instant invention provides a simple yet effective procedure for rapidly terminating anode effects. If the practices of this invention are adhered to, better than 90 percent of all anode effects can be rapidly terminated.
  • the process involves determining when the voltage drop across the cell exceeds about 150 percent of the normal operating value and when that level has been reached, lowering the cell anode so as to reduce the anode-cathode distance in the cell to from about to about 60 percent of the normal operating distance and desirably to not more than about 51 percent.
  • the available alumina concentration in the bath is adjusted to from about 2 percent to about 6 percent by weight of the bath.
  • the anode is raised so as to restore the normal anode-cathode distance and when raised the anode effect is terminated and normal operating conditions are restored.
  • the available alumina concentration in the bath or electrolyte may be adjusted by placing a quantity of alumina on the crust over the cell electrolyte and breaking the crust on the cell electrolyte so as to cause the alumina placed thereon to feed into the electrolyte.
  • Various procedures may be used for the alumina addition.
  • the alumina may be fed into the electrolyte prior to the lowering of the cell anode, during the lowering of the cell anode, after the lowering of the cell anode, or even after the raising of the cell anode.
  • a desirable procedure is to feed the alumina into the electrolyte in increments so as to gradually introduce the alumina into the bath and thereby facilitate dissolution thereof and prevent formation of muck on the cathode, in which case at least one of the increments of alumina is fed into the electrolyte after the lowering of the cell anode.
  • muck is meant an accumulation of alumina and other bath constituents which can collect between the carbon lining and molten aluminum pad and interfere with the operation of the cell and the purity of the metal produced.
  • An appropriate system for terminating an anode effect in accordance with the instant invention involves first of all, suitable means such as a voltmeter for measuring the voltage drop across the cell and signalling when the voltage drop across the cell exceeds about 150 percent of the normal operating value. This signal then triggers the system into action.
  • suitable means such as a voltmeter for measuring the voltage drop across the cell and signalling when the voltage drop across the cell exceeds about 150 percent of the normal operating value. This signal then triggers the system into action.
  • Means such as an anode jacking motor, in response to the voltage signal lower the cell anode or anodes so as to reduce the anode-cathode distance in the cell to from about 30 to about 60 percent of the normal operating distance.
  • the available alumina concentration in the cell is adjusted by other means responsive to the voltage signal to from about 2 percent to about 6 percent b weight.
  • means are provided for raising the anode so as to restore the normal anode-cathode distance.
  • FIG. 1 is a graph of the cumulative percent of anode effects terminated versus the remaining percent of normal anode-cathode distance after anode lowerin
  • FIG. 2 is a schematic circuit diagram of a possible anode effect terminator system.
  • FIG. 3 shows the cam timer sequence for the anode effect terminator system shown in FIG. 2.
  • Feeders were operated six times at IO-second intervals for the onset of the anode effect to feed approximately 30 pounds of alumina to the cell, increasing the concentration to from about 2% to about 6% by weight, with the anodes having been lowered within 19 seconds after the anode effect occurred.
  • a puncher bar was operated after the alumina was added to feed the alumina, which had been placed on the crust over the cell electrolyte by the feeders, into the electrolyte or bath.
  • the anode jack motor was then operated to raise the anode and bring the anode-cathode distance to near normal adjustment. This result is shown at point A in FIG. 1.
  • the anode jack motor was operated so as to lower the cell anode to reduce the anode-cathode distance in the cell to not more than about percent of the normal operating distance. This was done within 15 seconds after the signal that the voltage drop across the cell had exceeded about percent of the normal operating value.
  • the feeders were operated 12 times after the start of the anode effect in 10-second intervals so as to place a measured quantity of alumina (approximately 60 pounds) on the crust over the cell electrolyte.
  • the crust breaker puncher 'bars were operated after 6 feeder operations and again after 12 feeder operations, breaking the crust on the cell electrolyte so as to cause the alumina placed thereon to feed into the electrolyte.
  • the anode jack shaft motor was operated 100 seconds after the start of the anode effect to raise the anodes so as to substantially restore the normal anode-cathode distance. Of 333 recorded anode effects, 74 percent were successfully terminated, as shown at point B in FIG. 1.
  • the anode-cathode distance reduction was increased so that the anode-cathode distance was reduced to not more than about 41 percent of the normal operating distance.
  • the crust breaker puncher bar was operated once after each three feeder operations.
  • the anode-cathode distance was left at the reduced value for about 155 seconds before the anode was raised so as to substantially restore the normal anode-cathode distance.
  • the system was actuated when the voltage drop across the cell exceeded about percent of the normal operating value. Of 81 recorded anode effects, 77 or about 95 percent were successfully terminated. This is recorded at point C in FIG. 1.
  • Tests B were operated 17 times to feed 85 pounds of alumina.
  • the crust breaker puncher bar was operated 5 times and the anode-cathode distance was left at the reduced value for seconds.
  • 84 or about 93 percent were successfully terminated as recorded at Point B in FIG. 1.
  • Tests E duplicated the features of Tests C, except that the anode jack shaft motor was operated so as to reduce the anode-cathode distance to about 51 percent of the normal anode-cathode distance and the crust breaker puncher bar was operated 5 times. This procedure successfully terminated over 95 percent of all anode effects experienced as recorded at point B in FIG. 1.
  • FIG. 2 and FIG. 3 shows the cam timer sequence for the system.
  • This system will lower the cell anode so as to reduce the anode-cathode distance in the cell to from about 30 to about 60 percent of the normal operating distance and desirably to not more than about 51% of the normal operating distance.
  • the available alumina concentration in the bath is adjusted to the desired value in the range of from about 2 percent to about 6 percent by weight by feeding the alumina in increments, shown in the example as 17 five-pound increments in which the first increment of alumina is placed on the crust almost simultaneously with the lowering of the anode and the last increment being added as the anode is raised.
  • the crust on the cell electrolyte is broken by the crust breaker puncher bar 5 times during this sequence of incremental feeding of alumina.
  • the system is designed to be actuated when the voltage drop across the cell exceeds about 150 percent of the normal operating value.
  • the timer motor is actuated and the sequence of operations described and shown in the schematic and cam timer sequence takes place. This procedure at the S 1% of normal anode-cathode distance setting will extinguish at least 95 percent of all anode effects incurred in normal reduction cell or pot operation.
  • the signficant factor in terminating anode effects by reducing anode-cathode distance is that the final anode-cathode distance is reduced enough to cause the effect to cease. Reducing the anode-cathode distance to not more than about 51 percent of the normal operating distance has been found to do this in 95 percent of the cases.
  • the minimum anode-cathode distance reduction that provides acceptable reliability, i.e., 95 percent, is preferred to minimize the disturbance of the bath level.
  • the addition of alumina to the bath as part of the terminating procedure aids in anode effect terminations. The added alumina, if it is dissolved in the bath, favors return of the cell to normal electrolysis.
  • the amount of alumina added to the bath should be no more than the bath can dissolve to prevent formation of muck on the cathode.
  • the anode effect terminator system and the process de scribed herein charged only enough alumina during terminating procedures to prevent recurring anode effects.
  • the improved alumina regulation provides the means to keep the cathode free of muck. The elimination of muck on the cathode results in improved operating efficiency.
  • Prompt successful anode effect termination in accordance with this invention saves hard physical effort normally required from pot men. This reduction in the need for hard work reduces the amount of manpower required to operate a potline.
  • the work assignment of the pot men can be carried out without unscheduled interruptions to terminate anode effects. Less than 1 anode effect out of 20 will require manual termination. Only a few of the manually terminated anode effects require more than a small amount of the raking procedure mentioned above in the discussion of the Cooper patent. Pot men will be able to work at other duties without stopping to terminate an anode effect.
  • a system for terminating an anode efiect in an electrolytic cell for the production of alumina which comprises:
  • (b) means responsive to the voltage signal for lowering the cell anode so as to reduce the anode-cathode distance in the cell from normal operating distance to from about 30 to about 60 percent of the normal operating distance;
  • () means responsive to the voltage signal for adjusting the available alumina concentration in the cell to from about 2 percent to about 6 percent by weight;
  • (d) means for raising the anode so as to restore the normal anode-cathode distance, whereby the anode effect is terminated.

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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)
  • Control Of Non-Electrical Variables (AREA)
US676500A 1967-10-19 1967-10-19 Anode effect termination Expired - Lifetime US3539461A (en)

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US (1) US3539461A (enrdf_load_stackoverflow)
JP (1) JPS505128B1 (enrdf_load_stackoverflow)
BR (1) BR6803211D0 (enrdf_load_stackoverflow)
CH (1) CH516645A (enrdf_load_stackoverflow)
DE (1) DE1802787A1 (enrdf_load_stackoverflow)
FR (1) FR1589563A (enrdf_load_stackoverflow)
GB (1) GB1243810A (enrdf_load_stackoverflow)
NL (1) NL6815045A (enrdf_load_stackoverflow)
NO (1) NO123318B (enrdf_load_stackoverflow)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3674674A (en) * 1968-12-27 1972-07-04 Delfzijl Aluminium Apparatus for controlling electrode adjustment during aluminum oxide reduction
JPS4975402A (enrdf_load_stackoverflow) * 1972-10-18 1974-07-22
JPS4979308A (enrdf_load_stackoverflow) * 1972-12-07 1974-07-31
US4675081A (en) * 1985-03-18 1987-06-23 Alcan International Limited Controlling aluminium reduction cell operation
US20040079649A1 (en) * 2002-10-23 2004-04-29 Renaud Santerre Process for controlling anode effects during the production of aluminium
RU2285755C1 (ru) * 2005-04-05 2006-10-20 Общество с ограниченной ответственностью "Инженерно-технологический центр" Способ автоматического устранения анодных эффектов
WO2012146060A1 (zh) * 2011-04-29 2012-11-01 中铝国际工程股份有限公司 阳极效应抑制与熄灭的方法和设备
RU2659512C1 (ru) * 2017-06-05 2018-07-02 Федеральное государственное автономное образовательное учреждение высшего образования "Сибирский федеральный университет" Способ гашения анодного эффекта в алюминиевом электролизере
WO2019171235A1 (en) * 2018-03-07 2019-09-12 Dubai Aluminium Pjsc Method for early detection of certain abnormal operating conditions in hall-héroult electrolysis cells

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2032773C1 (ru) * 1992-06-30 1995-04-10 Товарищество с ограниченной ответственностью "Межотраслевой центр проблем экологии и эффективности производства алюминия" Способ получения алюминия
EP0604664A4 (en) * 1992-06-30 1995-01-25 Tovarischestvo S Ogranichennoi METHOD FOR PRODUCING ALUMINUM AND OTHER METALS.

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1397946A (fr) * 1964-01-14 1965-05-07 Pechiney Procédé pour la prévision des brûlures, l'alimentation systématique et la régulation automatique du système anodique des cuves pour l'électrolyse ignée de l'alumine
US3317413A (en) * 1963-09-23 1967-05-02 Pechiney Cie De Produits Control of alumina content during igneous electrolysis
US3329592A (en) * 1963-08-30 1967-07-04 Reynolds Metals Co Method of and apparatus for controlling aluminum reduction pots
US3400062A (en) * 1965-05-28 1968-09-03 Aluminum Co Of America Method of controlling aluminum content during aluminumg electrolysis
US3434945A (en) * 1963-08-30 1969-03-25 Alusuisse Terminal voltage regulation in electrolytic aluminum production

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3329592A (en) * 1963-08-30 1967-07-04 Reynolds Metals Co Method of and apparatus for controlling aluminum reduction pots
US3434945A (en) * 1963-08-30 1969-03-25 Alusuisse Terminal voltage regulation in electrolytic aluminum production
US3317413A (en) * 1963-09-23 1967-05-02 Pechiney Cie De Produits Control of alumina content during igneous electrolysis
FR1397946A (fr) * 1964-01-14 1965-05-07 Pechiney Procédé pour la prévision des brûlures, l'alimentation systématique et la régulation automatique du système anodique des cuves pour l'électrolyse ignée de l'alumine
US3455795A (en) * 1964-01-14 1969-07-15 Pechiney Prod Chimiques Sa Apparatus and method for the operation of cells for the igneous electrolysis of alumina
US3400062A (en) * 1965-05-28 1968-09-03 Aluminum Co Of America Method of controlling aluminum content during aluminumg electrolysis

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3674674A (en) * 1968-12-27 1972-07-04 Delfzijl Aluminium Apparatus for controlling electrode adjustment during aluminum oxide reduction
JPS4975402A (enrdf_load_stackoverflow) * 1972-10-18 1974-07-22
US3888747A (en) * 1972-10-18 1975-06-10 Nat Southwire Aluminum Method of and apparatus for producing metal
JPS4979308A (enrdf_load_stackoverflow) * 1972-12-07 1974-07-31
US4675081A (en) * 1985-03-18 1987-06-23 Alcan International Limited Controlling aluminium reduction cell operation
AU576142B2 (en) * 1985-03-18 1988-08-11 Alcan International Limited Monitoring depth of electrolyte by raising anode and measuring current drop
US20040079649A1 (en) * 2002-10-23 2004-04-29 Renaud Santerre Process for controlling anode effects during the production of aluminium
US6866767B2 (en) 2002-10-23 2005-03-15 Alcan International Limited Process for controlling anode effects during the production of aluminum
RU2285755C1 (ru) * 2005-04-05 2006-10-20 Общество с ограниченной ответственностью "Инженерно-технологический центр" Способ автоматического устранения анодных эффектов
WO2012146060A1 (zh) * 2011-04-29 2012-11-01 中铝国际工程股份有限公司 阳极效应抑制与熄灭的方法和设备
RU2659512C1 (ru) * 2017-06-05 2018-07-02 Федеральное государственное автономное образовательное учреждение высшего образования "Сибирский федеральный университет" Способ гашения анодного эффекта в алюминиевом электролизере
WO2019171235A1 (en) * 2018-03-07 2019-09-12 Dubai Aluminium Pjsc Method for early detection of certain abnormal operating conditions in hall-héroult electrolysis cells

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Publication number Publication date
DE1802787A1 (de) 1969-05-08
CH516645A (de) 1971-12-15
JPS505128B1 (enrdf_load_stackoverflow) 1975-02-28
GB1243810A (en) 1971-08-25
NL6815045A (enrdf_load_stackoverflow) 1969-04-22
BR6803211D0 (pt) 1973-01-09
FR1589563A (enrdf_load_stackoverflow) 1970-03-31
NO123318B (enrdf_load_stackoverflow) 1971-10-25

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