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WO2024030044A1 - Procédé de production d'aluminium par électrolyse d'une solution d'alumine dans de la cryolite - Google Patents

Procédé de production d'aluminium par électrolyse d'une solution d'alumine dans de la cryolite Download PDF

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Publication number
WO2024030044A1
WO2024030044A1 PCT/RU2023/000023 RU2023000023W WO2024030044A1 WO 2024030044 A1 WO2024030044 A1 WO 2024030044A1 RU 2023000023 W RU2023000023 W RU 2023000023W WO 2024030044 A1 WO2024030044 A1 WO 2024030044A1
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WIPO (PCT)
Prior art keywords
electrolysis
melt
alumina
cryolite
temperature
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.)
Ceased
Application number
PCT/RU2023/000023
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English (en)
Russian (ru)
Inventor
Владислав Владимирович ФУРСЕНКО
Олег Владимирович АНИСИМОВ
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Individual
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Individual
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Publication date
Priority claimed from RU2022120991A external-priority patent/RU2812159C1/ru
Application filed by Individual filed Critical Individual
Publication of WO2024030044A1 publication Critical patent/WO2024030044A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • 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
    • C25C3/18—Electrolytes

Definitions

  • the present invention relates to non-ferrous metallurgy, in particular to the production of aluminum by electrolysis of molten salts.
  • This method is adopted as a prototype.
  • This method of electrolytic production of aluminum includes loading into the electrolyzer at the start-up stage an electrolyte containing a mixture of cryolite (NasAlFe) with aluminum fluoride (AIF3), and carrying out electrolysis in a molten electrolyte bath with electrolytic decomposition of alumina to metallic aluminum, while the content of aluminum fluoride in the loaded electrolyzer mixture of cryolite with aluminum fluoride is from 25 to 35 wt.%.
  • an electrolyzer was used, which was a graphite crucible shielded on the outside with graphite chips and a corundum container.
  • the electrolyzer is placed in a resistance furnace at a temperature of 25°C.
  • the graphite crucible was covered with a graphite lid in which a platinum-platinum-rhodium thermocouple simultaneously immersed in a salt mixture.
  • the furnace with electrolyzer is heated according to the program: heating from 25 to 1000°C for 120 minutes and holding at 1000°C for 120 minutes.
  • a thermostat and a master platinum-platinum-rhodium thermocouple are used.
  • the change in temperature of the mixture of cryolite and aluminum fluoride over time is monitored using a thermocouple lowered into the mixture. From the obtained temperature-time data, the solidus temperature of the salt mixture, the time of heating the mixture to the solidus temperature, and the heating time of the mixture from the solidus temperature to a temperature of 980°C are determined with an accuracy of ⁇ 2°C.
  • the main negative factor influencing the conditions of the electrolysis process is the presence of a forced compromise between the operating temperature of the electrolyte melt and other process parameters. It is known that with increasing temperature, the rate of electrolysis increases, the percentage of alumina solubility in the electrolyte melt increases, although the corrosion rate also increases, but the use of metal electrodes of the appropriate chemical composition largely eliminates this problem.
  • the forced current required to maintain the process includes the current required to maintain the given temperature (700-800°C) of the electrolyte, which leads to the need for a dramatic increase in energy costs (about 40%). The problem of starting the process is not solved here.
  • the present invention is aimed at achieving a technical result consisting in reducing the time for producing primary aluminum by electrolysis of an alumina solution in cryolite while reducing energy consumption for heating the electrolyzer and the source material loaded into it.
  • the specified technical result is achieved by the fact that the method of producing aluminum by electrolysis of a cryolite melt with the addition of 30% aluminum trifluoride and periodic supply of alumina to maintain the amount of alumina in a volume of 3-8% in the electrolyte melt is implemented in two stages, in the first of which the production of the specified melt and maintenance the temperature of this melt above the liquidus temperature is ensured by heating the electrolysis bath made of a molybdenum-containing alloy separately non-electric energy source, and in the second stage, the electrolysis process is carried out using an electric energy source at an electrolyte temperature of 900-1000°C and a direct current of 5 volts is supplied to the electrodes of the electrolysis bath with a current strength that ensures an anode current density of 1 A/cm 2 and a cathode current density current 0.9 A/cm 2 .
  • combustion of natural gas or diesel fuel is used as a separate non-electric energy source.
  • binary, low-consumable metal electrodes are used in the form of coaxially located and separated pipes, one of which is the cathode and the other the anode.
  • the selection of primary aluminum is carried out through a gate valve assembly in the bottom part of the electrolysis bath under the electrode space.
  • a new method is considered for producing aluminum by electrolysis of a solution of alumina in cryolite (NasAIK) with 30% aluminum trifluoride (ATF) with separate melting processes, maintaining a given temperature of the melt and the electrolysis process itself.
  • This method is a technology of SEFCO LLC.
  • Purified primary aluminum is drained for further use, and impurities removed from the electrodes are sent to process waste.
  • the technology has hardware. The method can be used for purification and production of other metals and alloys.
  • the main distinctive feature of the proposed invention is the separation of the processes of melting and maintaining the temperature above liquidus temperature of the electrolyte and the actual electrolysis of the melt.
  • This separation opens up the opportunity to use organic energy sources - natural gas, diesel fuel, etc. - to carry out the melting process and maintain a given temperature of the melt, and to spend electricity only on the process of electrolysis of the cryolite melt with alumina dissolved in it. It becomes possible to optimize the process as a whole by fixing the electrolyte temperature.
  • the multi-day process of starting up the electrolyzer is eliminated.
  • the starting period of a non-working electrolyzer is reduced to the time of melting of the charge materials (we do not consider accompanying processes, for example, replacing the lining, etc.)
  • cryolite melt by electrolysis with the addition of 30% aluminum trifluoride and periodic supply of alumina to maintain the amount of alumina in a volume of 3-8% in the electrolyte melt;
  • an electrical energy source at an electrolyte temperature of 900-1000°C and supplying 5 volts of direct current to the electrodes of the electrolysis bath with a current intensity that provides an anodic current density of 1 A/cm 2 and a cathode current density of 0.9 A/ cm 2 carry out the electrolysis process itself.
  • Molybdenum has an extremely low coefficient of thermal expansion. Molybdenum is a refractory metal with a melting point of 2620 °C and a boiling point of 4639 °C.
  • molybdenum as a metal, has increased thermal conductivity.
  • the thermal conductivity of this metal varies from 105 to 100 W/(m deg) (ten times higher than that of steel).
  • the heating of a molybdenum bath by any energy source is many times faster than that of steel baths with a lining. In this case, heating is uniform over the entire surface of the bath. Taking this property into account, it became possible to use natural gas or diesel fuel burners, which are located under the bottom of the bath. Such burners provide a high degree of heating in a short period of time and are economically cheap and therefore cost-effective.
  • molybdenum as a material for the electrolyzer bath makes it possible to eliminate the transfer of rough inclusions from the bath (during electrolysis in a lined bath, rough lining particles enter the melt. Also there is a chemical interaction between the chemical elements of the bath materials and the melt, which affects the purity of the resulting primary aluminum). Molybdenum or alloys based on it or alloys containing it are inert to the ingredients of the charge (neutral to the melt of Na Ali'e cryolite with a 30% addition of AIF3), from which the melt of aluminum-containing material is obtained, and do not react chemically with this melt. Molybdenum as a tool or structural material in alloys has high heat resistance and high chemical inertness.
  • molybdenum within the framework of this description is understood not as a pure chemical substance, but as a molybdenum-containing alloy or molybdenum-containing material (chrome-molybdenum steel X12M, structural alloy steel grade 18X2N4MA, complex alloy steel of the martensitic class grade 15X11 MF and other steels and alloys including molybdenum for ensuring high heat resistance).
  • the common features of the prototype and the claimed method are the electrolysis of cryolite melt (NaAIIA) with 20-40% AIF3 with periodic additional loading to maintain the level of alumina (AI2O3) in the melt undergoing electrolysis equal to 3-8%.
  • the installation contains a molybdenum bath 1, placed on supports, in the bottom zone of which burners 2 are located, to which organic fuel 3 (natural gas, diesel fuel, etc.) is supplied through channel 3.
  • the burner unit is equipped with means for regulating the fuel flow, means for remote ignition of the burners, means for combustion control and emergency shutdown, as well as associated automation necessary for the safe operation of this unit. These means are not described in detail as they are not related to the essence of the claimed invention.
  • Around the bath along the perimeter of its side wall there are electric heating elements 5 of the electrical energy supply system.
  • a heat-protective lining 6 is mounted along the entire surface of the side wall of the bath to reduce the transfer of heat from heating to the environment.
  • a channel 7 for draining primary aluminum In the lower bottom part of the bath there is a channel 7 for draining primary aluminum.
  • a gate valve 8 is installed in this channel.
  • the bath is enclosed by a casing 9, in the upper part of which above the bath there is an outlet 10 of gases 11 (gaseous products of electrolysis) into the recycling channel.
  • bipolar electrodes Inside the bath there is one or several bipolar (bipolar) electrodes connected in parallel and installed vertically.
  • the bipolar electrode consists of two large-diameter pipes separated by high-temperature dielectric washers. (anode) 13 and inner pipe (cathode) 14, which are made with holes across the entire surface for the passage of gases (mainly O and O2).
  • a large pipe is mounted through a heat-resistant insert 15 (type of bushing) and secured to the electrolyzer bath.
  • Experimental studies have shown. That the inter-pipe distance between the walls of coaxially located and separated pipes should be in the range of 2-4 cm.
  • Bipolar electrodes in tubular design differ in area into anode and cathode electrodes, and therefore have different values of the anode and cathode current densities. Electricity with a voltage of about 5 volts and a current of up to 1000 amperes with the possibility of smooth regulation from 0 to 1000 amperes is supplied to the upper part of the bipolar anodes, plus to the anodes of the bipolar electrodes connected in parallel, and to the summing cathode in the bottom part of the electrolyser.
  • the built-in resistance furnace has a system for measuring and automatically maintaining the set temperature (900-1000°C, preferably 950°C is optimal).
  • a thoroughly mixed mixture of cryolite with 30% aluminum trifluoride and 8% alumina (NasAIFe + 30% AIF3 + 8% AlgO3) is loaded into a cold electrolyzer bath.
  • the resulting charge mixture must be transferred and subsequently maintained in a molten state during the entire electrolysis process.
  • natural gas combustion is used in the first stage, which provides energy savings of approximately 40%.
  • the furnace automation switched to the mode of maintaining the melt temperature equal to 950° C. Subsequently, the temperature of the electrolyte melt was kept constant.
  • the required time was 3.0 hours, not counting 2 hours for heating the furnace and the loaded charge.
  • the source of electrolysis current was turned on.
  • the cathode area is 400 cm 2 , and the area anode 800 cm 2 . Therefore, the required anode current density of 1 A/cm 2 is achieved at a current from the electrolysis voltage unit of 800 amperes.
  • the cathode current was equal to 2 A/cm 2 .
  • Electrolysis under the given conditions was carried out for 4 hours. Every hour, the composition was adjusted by pouring a calculated measure of heated alumina powder into the bath.
  • the resulting aluminum was poured through the drain channel, by tilting the entire cell body, into a steel mold.
  • the resulting primary aluminum has the following chemical composition in comparison with compositions A995, A99, the requirements for which are specified in the current interstate standard GOST 11069-2001 (about grades of primary A1)
  • the present invention is industrially applicable and has undergone pilot tests, which have shown a significant acceleration of the process of obtaining primary aluminum and savings in energy consumption

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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)

Abstract

La présente invention se rapporte au domaine de la métallurgie des métaux non ferreux. L'invention concerne un procédé de production d'aluminium consistant en une électrolyse d'une solution d'alumine dans de la cryolite avec 30% de trifluorure d'aluminium, lors de processus distincts de fusion, de maintien du bain de fusion à une température donnée et du processus d'électrolyse proprement dit (technologie de la société SEFKO). Il est ainsi possible de réduire radicalement la consommation d'énergie électrique lors du processus de création d'un bain de fusion d'électrolyte et de maintenir une température donnée du bain de fusion d'électrolyte en remplaçant l'énergie électrique par l'énergie de combustion d'un combustible organique (comme du gaz naturel). On produit tout d'abord, dans un four à gaz ou autre combiné à un bain d'électrolyse, un bain de fusion de cryolite avec 30% de trifluorure d'aluminium et 8% d'alumine à une température de 900-1000°С, après quoi on envoie un courant, depuis une source de courant d'électrolyse vers des électrodes métalliques bipolaires verticales à faible usure, nécessaire pour créer un mode d'électrolyse voulu, et on maintient un rapport de cryolite de 1,1 à 1,9. On ajoute périodiquement de l'alumine à mesure de sa consommation. A mesure que l'aluminium primaire obtenu s'accumule, celui-ci est est déversé via une unité de fermeture à guillotine vers la partie de fond du bain d'électrolyse.
PCT/RU2023/000023 2022-08-02 2023-01-27 Procédé de production d'aluminium par électrolyse d'une solution d'alumine dans de la cryolite Ceased WO2024030044A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
RU2022120991 2022-08-02
RU2022120991A RU2812159C1 (ru) 2022-08-02 Способ получения алюминия электролизом раствора глинозема в криолите

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WO2024030044A1 true WO2024030044A1 (fr) 2024-02-08

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5114546A (en) * 1987-09-23 1992-05-19 Hoechst Aktiengesellschaft Process for the preparation of fluorinated acrylic acids and derivatives thereof
RU2318924C2 (ru) * 2002-10-18 2008-03-10 Мольтех Инвент С.А. Электролизеры для получения алюминия электролизом с анодами на основе металлов
US8936710B2 (en) * 2012-05-23 2015-01-20 Shenzhen Sunxing Light Alloys Materials Co., Ltd. Low-molecular-ratio cryolite for aluminium electrolytic industry and method for preparing the same
RU2651929C1 (ru) * 2017-04-05 2018-04-24 Федеральное государственное бюджетное учреждение науки Институт высокотемпературной электрохимии Уральского отделения Российской Академии наук Способ электролитического получения алюминия
RU2686408C1 (ru) * 2018-06-20 2019-04-25 Федеральное государственное бюджетное учреждение науки Институт высокотемпературной электрохимии Уральского отделения Российской Академии наук Способ электролитического получения алюминия

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5114546A (en) * 1987-09-23 1992-05-19 Hoechst Aktiengesellschaft Process for the preparation of fluorinated acrylic acids and derivatives thereof
RU2318924C2 (ru) * 2002-10-18 2008-03-10 Мольтех Инвент С.А. Электролизеры для получения алюминия электролизом с анодами на основе металлов
US8936710B2 (en) * 2012-05-23 2015-01-20 Shenzhen Sunxing Light Alloys Materials Co., Ltd. Low-molecular-ratio cryolite for aluminium electrolytic industry and method for preparing the same
RU2651929C1 (ru) * 2017-04-05 2018-04-24 Федеральное государственное бюджетное учреждение науки Институт высокотемпературной электрохимии Уральского отделения Российской Академии наук Способ электролитического получения алюминия
RU2686408C1 (ru) * 2018-06-20 2019-04-25 Федеральное государственное бюджетное учреждение науки Институт высокотемпературной электрохимии Уральского отделения Российской Академии наук Способ электролитического получения алюминия

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