Alexander Dedyukhin

Physicochemical properties of KF-NaF-AlF3 molten electrolytes

Conductivity of molten mixtures KF-NaF-AlF3 is measured in the whole concentration range of the [NaF]/([KF] + [NaF]) ratio at the cryolite ratio CR = 1.3 and 1.5 in the temperature range from 800°C to liquidus temperature. Replacement of K+ cations by Na+ ones results in a considerable conductivity increase. Alumina solubility rises with temperature and cryolite ratio ([KF] + [NaF])/[AlF3] in the KF-NaF-AlF3 system, and decreases with sodium fluoride content. Regression equations obtained allow calculating alumina solubility and electrical conductivity in the KF-NaF-AlF3 system in the CR range from 1.3 to 3.0 depending on the concentration of the components and temperature.

The electrical conductivity of chloride melts

The interrelationship between electrical conductivity, molar volume and enthalpy of mixing was studied for molten chlorides and their mixtures. The dependence of electrical conductivity and activation energy on the molar volume is different for various groups of salts. The dependence of specific conductivity on molar volume obtained for molten alkali chlorides was found to be similar to other chloride salts. The specific conductivity of binary mixtures that lack strong chemical interactions between the components can also be described by the proposed empirical equation. The enthalpy of mixing should be taken into consideration for these chemical interactions.

Electrical Conductivity of the KF‐NaF‐ AlF3 Molten System at Low Cryolite Ratio with CaF2 Additions

The effect of calcium fluoride on the electrical conductivity of low temperature electrolytes for aluminum electrolysis has been investigated. Calcium fluoride addition was found to decrease the electrical conductivity of the molten mixtures of potassium and sodium cryolite melts.

The calcium fluoride effect on properties of cryolite melts feasible for low-temperature production of aluminum and its alloys

The CaF2 effect on the liquidus temperature, electrical conductivity and alumina solubility in the potassium-sodium and potassium-lithium cryolite melts with cryolite ratio (CR = (nKF+nMF)/nAlF3, M = Li, Na) 1.3 was studied. The liquidus temperature in the quisi-binary system [KF-LiF-AlF3]-CaF2 changes with the same manner as in the [KF-NaF-AlF3]-CaF2. The electrical conductivity in the KF-NaF-AlF3-CaF2 melt decreases with increasing the CaF2 content, but it slightly raises with the first small addition of CaF2 into the KF-LiF-AlF3-CaF2 melts, enriched with KF, which was explained by the increased K+ ions mobility due to their relatively low ionic potential. The contribution of the Li+ cations in conductivity of the KF-LiF-AlF3-CaF2 electrolyte is not noteworthy. The Al2O3 solubility in the KF-NaF-AlF3 electrolyte rises with the increasing KF content, but the opposite tendency is observed in the cryolite mixtures containing CaF2. The insoluble compounds - KCaAl2F9 or KCaF3 - formed in the molten mixtures containing potassium and calcium ions endorse the increase of the liquidus temperature. The calcium fluoride effect on the side ledge formation in the electrolytic cell during low-temperature aluminum electrolysis is discussed.The CaF2 effect on the liquidus temperature, electrical conductivity and alumina solubility in the potassium-sodium and potassium-lithium cryolite melts with cryolite ratio (CR = (nKF+nMF)/nAlF3, M = Li, Na) 1.3 was studied. The liquidus temperature in the quisi-binary system [KF-LiF-AlF3]-CaF2 changes with the same manner as in the [KF-NaF-AlF3]-CaF2. The electrical conductivity in the KF-NaF-AlF3-CaF2 melt decreases with increasing the CaF2 content, but it slightly raises with the first small addition of CaF2 into the KF-LiF-AlF3-CaF2 melts, enriched with KF, which was explained by the increased K+ ions mobility due to their relatively low ionic potential. The contribution of the Li+ cations in conductivity of the KF-LiF-AlF3-CaF2 electrolyte is not noteworthy. The Al2O3 solubility in the KF-NaF-AlF3 electrolyte rises with the increasing KF content, but the opposite tendency is observed in the cryolite mixtures containing CaF2. The insoluble compounds - KCaAl2F9 or KCaF3 - formed in the molten mixtures ...

Reduction of the Operating Temperature of Aluminum Electrolysis: Low Temperature Electrolyte

Potassium Aluminum Fluoride obtained as a byproduct in the aluminum grain refiners and master alloys production may be used as an additive to the aluminum reduction process. The component leads to a considerable reduction in the liquidus temperature, and maintains other important parameters such as electrolyte conductivity and solubility of alumina. Both, laboratory tests and semi industrial trials in a 100A cell have been conducted in order to test the suitability of this new additive to the electrolytic process, with positive results. Potassium Aluminum Fluoride can be also used as a basic component of the low-temperature electrolyte for aluminum electrolysis.