A. Redkin

Heat of fusion of halide salts and their eutectics

The heat of fusion of eutectic mixtures LiCl–CsCl, LiCl–KCl–CsCl, LiBr–KBr–LiF, LiBr–CsBr, and LiBr–KBr–CsBr was measured using differential scanning calorimetry. The molar heat of fusion of all mixtures under study was found to be dependent on melting temperature. Two different statistical methods were used to obtain the correlation for all the alkali and alkaline-earth halide salts.

Electrical conductance, density, and the liquidus temperature of the KCl–PbCl2 equimolar mixture with lead oxide additives

The influence of the PbO additive (up to 8.1 mol %) on the physicochemical properties of the KCl–PbCl2 molten system is investigated. The primary crystallization temperatures of selected electrolyte compositions are determined. The temperature and PbO-content dependences of the conductance of electrolytes in cells with parallel electrodes are found by the impedance measurement method. The temperature dependence of density of the KCl–PbCl2 equimolar melt containing up to 8.1 mol % lead oxide is measured by the Archimedean method, and the molar volumes are calculated. It is shown that the concentration dependence of the molar volume has an extreme form.

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.

INFLUENCE OF ELECTROLYTE COMPOSITION AND OVERHEATING ON THE SIDELEDGE IN THE ALUMINUM CELL

The paper presents a theoretical study conducted to investigate the effect that the chemical composition of electrolyte and its overheating have on the size of sideledge formed in an aluminum smelting bath. Three electrolyte compositions were chosen: (1) sodium cryolite with the cryolite ratio CR = 2,7; (2) cryolite CR = 2,7 + 5 wt.% CaF2; (3) cryolite CR = 2,7 + 5 wt.% CaF2 + 5 wt.% Al2О3. The electrolyte liquidus overheating temperatures were 5, 10, 15 and 20 °C. Calculations were performed using the finite element method. A simplified design of an aluminum cell was used with a prebaked anode. The temperature field was calculated using a mathematical model based on the Boussinesq approximation, which contains the Navier–Stokes equation as well as thermal conductivity and incompressibility equations. The key role of electrolyte overheating in sideledge formation was established. The resulting sideledge profile depends on the heat transfer coefficients and thermophysical properties of materials. The smallest sideledge thickness with the same electrolyte overheating was observed in cryolite composition 3, and the profiles of the formed sideledge for samples 1 and 2 were nearly the same. The thickness of the sideledge formed with a 5 degree overheating exceeded 7 cm and the difference in temperature between the sideledge in contact with electrolyte and the side block wall was 20–25 degrees. It was found that the virtually total disappearance of the sideledge occurs at electrolyte liquidus overheating by 20 degrees.

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 ...

Electrical conductivity of molten mixtures of potassium and sodium fluorides with calcium fluoride

The electrical conductivity of molten mixtures of calcium fluoride with sodium and potassium fluorides was investigated by impedance spectroscopy. The calcium fluoride additions to alkali metal fluoride melts decrease their electrical conductivity. Small additions of potassium and sodium fluorides to CaF2 do not change its conductivity essentially.