Studies on the Hall-Heroult aluminum electrowinning process

Abstract

Estudos da eletrólise da criolita-alumina fundida mostraram que nas melhores condições de operação, a 960 o C, a eficiência energética é de apenas 33%. Encontrou-se que para o funcionamento estável da célula a 3% de alumina a relação NaF/AlF 3 , em peso-percentual, deve ser no mínimo 1,11. Encontrou-se ainda que a fileira de ânodos posicionada junto a "down-stream" está sujeita a uma turbulência mais intensa, de modo que elevando-se o nível desta fileira em 4 cm, resulta em uma diminuição no número de "burnoffs". A seleção cuidadosa do material de revestimento da célula aumentou sua vida útil. A estabilidade da interface alumínio-banho é um dos principais fatores que afetam a eficiência de corrente. Uma modificação na célula foi proposta para se ter uma melhor estabilidade na interface alumínio-banho. O novo desenho proposto para a célula permite uma redução da distância cátodo-ânodo, diminuindo a voltagem e consequentemente, melhorando a eficiência anódica.Studies on the electrolysis of cryolite-alumina melt showed that even the best equipped smelter, functioning at 960 o C, has only 33% energy efficiency. For stable functioning of the smelter at 3% alumina the minimum wt% ratio NaF/AlF 3 was found to be 1.11. The anodes located on down-stream row were found to face more turbulence; raising their level by 4 cm resulted in decreasing the number of burnoffs. A careful selection of potlining material improved the pot life. The stability of the aluminum-bath interface is one of the major factors affecting the current efficiency. An improved cell design has been proposed to achieve the ultimate aluminum-bath interface stability. The proposed cell design should allow a reduction of the cathode-to-anode distance producing a lower voltage and improving the power efficiency.

Zero-Direct-Carbon-Emission Aluminum Production by Solid Oxide Membrane-Based Electrolysis Process

“…Considering the side reactions and anode loss due to oxidation with air, the actual anode carbon consumption produces about 1.5 kg of CO2 per kilogram of aluminum [4].…”

Zero‐Direct‐Carbon‐Emission Aluminum Production by Solid Oxide Membrane‐Based Electrolysis Process

“…Liquid aluminum is produced continuously at the cathode and gathers as an aluminum pool on the bottom of the cell. The oxygen reacts with the carbon anodes to form CO2 [3], [4]. The 2 electrolysis process is also called the aluminum smelting process.…”

“…Hall-Héroult cell operates with minimum 3wt% alumina [4], which is a general guideline for molten flux selection. Increasing the alumina content may result in an increase of the molten salt viscosity and decrease of electrical conductivity.…”

“…In the Hall-Héroult cell, the alumina content is kept at 2-5wt% during electrolysis [4]. Although the solubility of the molten flux in this work satisfies the requirement of the Hall-Héroult cell, it is beneficial to explore possible additives in the flux to increase the alumina solubility.…”

Artificial Neural Network Modeling and Optimization of Hall-Heroult Process for Aluminum Production

“…The industrial production of pure aluminum is carried out electrochemically in the Hall-Heroult process, which was discovered in 1889 and it remains to date the only known viable method for the production of aluminum (Prasad, 2000). In this electrolysis process, pure alumina is dissolved in an electrolyte of molten cryolite (Haupin, 1995) in large electrolytic furnaces, called reduction cells (Keniry, 1994).…”