US3294656A - Method of producing aluminium - Google Patents

Method of producing aluminium Download PDF

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Publication number
US3294656A
US3294656A US230855A US23085562A US3294656A US 3294656 A US3294656 A US 3294656A US 230855 A US230855 A US 230855A US 23085562 A US23085562 A US 23085562A US 3294656 A US3294656 A US 3294656A
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Prior art keywords
electrolyte
alumina
concentration
excess
current
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Expired - Lifetime
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US230855A
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English (en)
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Schmitt Johannes
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Rio Tinto Switzerland AG
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Alusuisse Holdings AG
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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 process of producing aluminium in an electrolytic furnace from a fused iluoride (cryolite or chiolite) electrolyte containing alumina.
  • the current eiciency at any moment can be calculated by a newly-developed and rapid method based on the concentration of carbon dioxide and carbon monoxide in the gases escaping from the anodes (the anode gases) at that moment according to the formula:
  • the electrode distance the inuence of the distance of the lower surface of the anode from the separated aluminium (referred to hereinafter as the electrode distance), the electrolyte temperature, the concentration of alumina in the electrolyte and its acidity (the excess of aluminium fluoride over that amount which is combined in the cryolite as 3NaF.AlF3), on the current efciency, as Well as its course between two anode effects has been determined.
  • the influence of one of these variables on the current efliciency while the remaining variables were maintained substantially constant was tested.
  • FIGURES 1 to 4 of the accompanying Edrawings illustrate the results obtained. All precentages are percentages by weight.
  • FIGURE 1 shows the inuence of the electrode distance (the distance of the lower surface of the anode from the separated aluminium) and the associated furnace Voltage (voltage drop between the anode and cathode current leads outside the electrolytic furnace) on the current efiiciency.
  • the measurements were carried out at a temperature of 970 C, with a cryolite electrolyte which contained 'an excess of AlF3 of about 3% and a concentration -of alumina of about 4.7%. From the curve shown, which was obtained from 143 separate measurements, it surprisingly appears that the electrode distance has a practically immaterial influence on the current ethciency. 0n increasing the electrode distance from 4 to 6 cm., the current eiciency remained practically constant. With a greater distance, it increased slightly.
  • FIGURE 2 shows the influence of the electrolyte ternperature on the current efficiency.
  • the experiments were carried out with a cryolite electrolyte which contained an excess of A1F3 of about 1.5% and an A1203 content of about 6.7%.
  • the curve which was obtained from 94 individual measurements, shows that the current efficiency decreased rapidly with increasing temperature to a surprising extent. At 950 C., the current efficiency was found to be about 86.5%, while at 1000 C. it was only 80.5%.
  • FIGURE 3 shows the inuence of the concentration of alumina in the electrolyte on the current efciency.
  • the measurements were carried out in a cryolite electrolyte at 970 C. with an excess of AlF3 of about 3.3%. From the curve, which was obtained from separate measurements, it can be seen that the current efliciency increased rapidly with increasing A1203 concentration.
  • FIGURE 4 shows the iniuence of the A1F3 excess in the cryolite electrolyte on the current eiiiciency.
  • the measurements were carried out in an electrolyte at 965 C. which had ian A1202 concentration of about 5.2%. From the curve, which was obtained from 176 separate measurements, it can be seen that the current eiciency first decreased sharply with Ian increasing excess of AlF3 up to about 4%, and then increasedsharply again from about 5%.
  • the solidification temperature of the electrolyte depending upon its composition (amounts to CaF2, MgF2, as well as impurities such as P205), is generally from 910 to 930 C. Too high a temperature (higher than 960 C.) reduces the current efficiency and must therefore be avoided.
  • the excess of aluminium fluoride should be maintained constant as far as possible between 5 and 7% by frequent adjustment of the electrolyte composition, so that the minimum current eiciency at a 4% excess of AlF3 is avoided.
  • the eiciency increases again when the excess of aluminium iluoride falls below 4%, working under these conditions is undesirable, since the walls of the pot may become worn because the alumina becomes too soluble in the electrotyte, and in consequence i-t may not be possible to produce aluminium having a low silicon content.
  • an aluminium iluoride excess of above 7% is undesirable because the solubility of A1203 becomes greatly reduced and the furnace may become more difficult to operate.
  • the so-called furnace service includes in particular the breaking of the crust and the supply of alumina as Well as aluminium fluoride. To -avoid supersaturation of the electrolyte with A1203, it may be advantageous to break only parts of the crust instead of the whole crust.
  • FIGURE 5 shows the dependence of the A1203 concentration during the anode effect on the electrolyte ternperature (the curve was obtained from 51 individual measurements).
  • the occurrence of the anode effect is favored by a reduction in the temperature in that it begins at -a higher A1203 content. For example, at an electrolyte temperature of 995 C., the anode effect occurred only at an A1203 concentration of about 0.6%, while it took place at 960 C. with an A1203 concentration of as much as 2.5%. It was found that the furnace lmust be operated as cold as possible in order that the anode effect should take place with a relatively high content of alumina, which is necessary to achieve a satisfactory current efficiency.
  • l prefer not to wait simply for anode effects, for the electrolyte temperature may increase too much.
  • I prefer to break the crust periodically and so throttle the addition o-f A1203 in order to produce an anode effect.
  • I allow the concentration of A1203 to drop to -a level between 3 and 2.5% at least once every 48 ho-urs and at the most twice every 24 hours.
  • alumina is preferably added mechanically at intervals of 1A to 3 hours.
  • the method of operating -an electrolytic furnace either with prebaked anodes or with selfbaking Sderberg carbon anodes for the production of aluminum by passing direct electric current through a fluoride electrolyte composed mainly of molten cryolite 3NaF.AlF3 and containing an excess of aluminum fluoride AlF3 above that amount which is combined in the cryolite as Well as dissolved alumina Al203, comprising maintaining during a period of at least 12 hours and at most 48 hours the electrolyte temperature between 940 and 960 C., the concentration of alumina between 5 and 7% by weight and of aluminum fluoride excess between 5 and 7% by weight, and preventing the concentration of alumina and of excess aluminum fluoride from dropping below 5% during said period by frequent additions of alumina and aluminum fluoride to the electrolyte.

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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)
US230855A 1961-10-17 1962-10-16 Method of producing aluminium Expired - Lifetime US3294656A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1203061A CH412351A (de) 1961-10-17 1961-10-17 Verfahren zum Betrieb eines Aluminium-Elektrolyse-Ofens

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US3294656A true US3294656A (en) 1966-12-27

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US (1) US3294656A (de)
CH (1) CH412351A (de)
DE (1) DE1181431B (de)
FR (1) FR1335410A (de)
GB (1) GB970798A (de)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3380897A (en) * 1964-11-16 1968-04-30 Reynolds Metals Co Method of determining ore concentration
US3400062A (en) * 1965-05-28 1968-09-03 Aluminum Co Of America Method of controlling aluminum content during aluminumg electrolysis
US3485727A (en) * 1968-07-17 1969-12-23 Reynolds Metals Co Voltage control in aluminum electrolysis cells during flex-raise period
US3622475A (en) * 1968-08-21 1971-11-23 Reynolds Metals Co Reduction cell control system
US3625842A (en) * 1968-05-24 1971-12-07 Kaiser Aluminium Chem Corp Alumina feed control
US3839167A (en) * 1973-06-28 1974-10-01 Aluminum Co Of America Novel alumina feed for aluminum cell
US3852173A (en) * 1973-06-28 1974-12-03 Aluminum Co Of America Alumina reduction process
JPS52106309A (en) * 1976-03-04 1977-09-06 Mitsubishi Chem Ind Ltd Control of alumina supplying for aluminum electrolytic cell
JPS548109A (en) * 1977-06-22 1979-01-22 Mitsubishi Keikinzoku Kogyo Controlling method of feeding alumina into aluminum electrolytic bath
CN105568319A (zh) * 2016-01-19 2016-05-11 中国铝业股份有限公司 一种铝电解槽瞬时电流效率测试方法

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH560765A5 (de) * 1972-07-18 1975-04-15 Alusuisse
CN104451776B (zh) * 2013-09-13 2017-02-01 湖南创元铝业有限公司 阳极伸腿消化剂及其使用方法
CN103710730B (zh) * 2013-12-11 2016-05-11 中国铝业股份有限公司 一种铝电解槽中氧化铝浓度测定装置及方法
CN104911634B (zh) * 2015-05-07 2017-07-25 北方工业大学 一种根据阳极导电能力评价电解槽阳极电流分布的方法
CN113026057B (zh) * 2021-03-05 2022-06-24 浙江捷创智能技术有限公司 一种铝电解槽电流效率在线软测量方法
CN114965879B (zh) * 2022-05-12 2023-10-24 中国铝业股份有限公司 一种铝电解过程二氧化碳排放量的确定方法及相关设备

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2933440A (en) * 1956-10-09 1960-04-19 Kaiser Aluminium Chem Corp Method and apparatus for detection of anode effect
US3029194A (en) * 1954-01-19 1962-04-10 Varda Giuseppe De Furnace and process for the electrolysis of aluminum
US3034972A (en) * 1958-03-28 1962-05-15 Kaiser Aluminium Chem Corp Electrolytic production of aluminum

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3029194A (en) * 1954-01-19 1962-04-10 Varda Giuseppe De Furnace and process for the electrolysis of aluminum
US2933440A (en) * 1956-10-09 1960-04-19 Kaiser Aluminium Chem Corp Method and apparatus for detection of anode effect
US3034972A (en) * 1958-03-28 1962-05-15 Kaiser Aluminium Chem Corp Electrolytic production of aluminum

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3380897A (en) * 1964-11-16 1968-04-30 Reynolds Metals Co Method of determining ore concentration
US3400062A (en) * 1965-05-28 1968-09-03 Aluminum Co Of America Method of controlling aluminum content during aluminumg electrolysis
US3625842A (en) * 1968-05-24 1971-12-07 Kaiser Aluminium Chem Corp Alumina feed control
US3485727A (en) * 1968-07-17 1969-12-23 Reynolds Metals Co Voltage control in aluminum electrolysis cells during flex-raise period
US3622475A (en) * 1968-08-21 1971-11-23 Reynolds Metals Co Reduction cell control system
US3839167A (en) * 1973-06-28 1974-10-01 Aluminum Co Of America Novel alumina feed for aluminum cell
US3852173A (en) * 1973-06-28 1974-12-03 Aluminum Co Of America Alumina reduction process
JPS52106309A (en) * 1976-03-04 1977-09-06 Mitsubishi Chem Ind Ltd Control of alumina supplying for aluminum electrolytic cell
JPS548109A (en) * 1977-06-22 1979-01-22 Mitsubishi Keikinzoku Kogyo Controlling method of feeding alumina into aluminum electrolytic bath
CN105568319A (zh) * 2016-01-19 2016-05-11 中国铝业股份有限公司 一种铝电解槽瞬时电流效率测试方法

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Publication number Publication date
DE1181431B (de) 1964-11-12
CH412351A (de) 1966-04-30
GB970798A (en) 1964-09-23
FR1335410A (fr) 1963-08-16

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