A viscosity model for the (NaF + AlF3+ CaF2+ Al2O3) electrolyte

Robelin, Christian; Chartrand, Patrice

doi:10.1016/j.jct.2010.12.017

Cited by 26 publications

(12 citation statements)

References 31 publications

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“…Units are as follows: density is in g·cm –3 , conductivity is in S·m –1 , diffusivity is in 10 –9 m 2 ·s –1 , and viscosity is in 10 –3 Pa·s. The calculated density, total conductivity, and viscosity are compared to the critically assessed value (given in bracket next to the properties) of Robelin and Chartrand for density and viscosity and Wang et al for electrical conductivity. , …”

Section: Resultsmentioning

confidence: 99%

“…Pairwise relationship between EMD calculations and critical assessments for density (a), ionic conductivity (b), and viscosity (c) for the 11 studied cryolitic melts at 1260 K. The critically assessed data are from refs, − respectively, for density, ionic conductivity, and viscosity. The errors on the EMD data were obtained with the error block averaging method, , whereas the error bars on the critically assessed properties represent the average discrepancy between the different experimental datasets considered in the given assessment …”

Section: Resultsmentioning

confidence: 99%

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First-Principles Determination of Transference Numbers in Cryolitic Melts

Gheribi

Salanne

Zanghi

et al. 2020

Ind. Eng. Chem. Res.

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The charge and electron transport properties of molten ionic systems are among the most relevant properties to consider in the control of several electrochemical processes.First-principles-based equilibrium molecular dynamics (EMD) can provide reliable predictions of both the total and partial charge transport properties. In this work we calculate the charge transport properties of the electrolytic bath (Na 3 AlF 6 -AlF 3 -Al 2 O 3 ) of the Hall-Héroult electrolysis cells. We predict both the individual and collective charge transport properties (total, partial conductivity and self diffusion coefficients) for 11 different compositions typical of industrial conditions via a series of EMD simulations.The predicted total and partial ionic conductivities and their composition dependence are compared to available experimental data. A good agreement is obtained for all studied compositions. From a more fundamental point of view, the microscopic aspect of the charge transport properties of cryolitic melts is discussed through its correlation to the local structure of different melts. Deviations between the calculated partial conductivities and those derived via the Nernst-Einstein approximation can be explained by the presence of strong short-range ordering within the melts.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

First-Principles Determination of Transference Numbers in Cryolitic Melts

Gheribi

Salanne

Zanghi

et al. 2020

Ind. Eng. Chem. Res.

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“…Note that data for LiF-CaF 2 viscosity at operating temperatures are not available in literature. Then, viscosity was extrapolated from the work of Robelin et al as the sum of the fluorides compounds viscosities balanced by their molar fractions in the eutectic mixture [30]. These values are gathered in Table 1.…”

Section: Diffusion Coefficients and Mass Transport Approachmentioning

confidence: 99%

Generalized method for determining fluoroacidity by electrochemical diffusion coefficient measurement (application to HfF4)

Kergoat

Gibilaro

Massot

et al. 2015

Electrochimica Acta

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A B S T R A C TA universal method for fluoroacidity evaluation was developed and based on a mass transport approach: it simply consists in measuring the diffusion coefficient of an electroactive species in various molten media. The reduction behaviour of Hf(IV) ions was investigated in molten fluorides and diffusion coefficients of Hf(IV) ions were measured. Results showed that diffusion coefficients decrease with fluoroacidity, due to the effect of solvent viscosity (which is linked to bridged fluorines). A global approach of mass transport in solution was then proposed, taking into account both solute and solvent. The Schmidt number (Sc) defined as the ratio between solvent viscosity and solute diffusivity was calculated in order to take into account these two parameters. Results showed that Sc increases with fluoroacidity, in a much more sensitive way than D. This universal method can extended to all electroactive species and to all bath fluoroacidity.

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“…In paper [10] a thermodynamic model was suggested for calculating the viscosity of multicomponent fluoride systems. The authors used the thermochemical program FactSage [11].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, despite the importance of viscosity for the technological process, the viscosity of cryolite melts of conventional electrolytes has not been properly studied yet. According to various authors, the viscosity of the conventional electrolyte NaF-AlF 3 -CaF 2 -Al 2 O 3 in the CR range from 1.8 to 2.6 and 945-970 °С varies in the range from 1 to 5 mPa•s [10,12].…”

Section: Introductionmentioning

confidence: 99%

Effect of Al₂O₃ and CaF₂ additives on the viscosity of conventional cryolite melts

2021

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The viscosity of cryolite melts of conventional composition NaF–AlF3–CaF2–Al2O3 was studied by rotational viscometry using the FRS 1600 high-temperature rheometer. The cryolite ratio of the NaF–AlF3 melt was 2.1, 2.3, and 2.5; the Al2O3 content varied from 2 to 6.6, and CaF2 – from 0 to 8 wt%. The measurements were carried out in the temperature range from liquidus to 1200 °C. The conditions for the laminar flow of the investigated melts were determined, based on the measurements of the cryolite melts viscosity as a function of the shear rate at a constant temperature. A shear rate of 12 ± 1 s–1 was chosen for studying the viscosity temperature dependence for all samples. The viscosity temperature dependence of cryolite melts is described by a linear equation. The temperature coefficient b in this equation has negative values and varies in the range of (–0.01)–(–0.06) mPa·s/deg. It was found that the viscosity of cryolite melts of conventional composition in the range of operating temperatures of aluminum electrolysis (950–970 °C) varies from 2.5 to 3.7 mPa·s (depending on the composition and temperature). The viscosity of cryolite-alumina melts increases with the rise of alumina content: 1 wt% Al2O3 increases the viscosity, on average, by 1%. However, the influence of CaF2 is more significant: the addition of 1 wt% CaF2 leads to an increase in viscosity by 3%. A decrease in the CR of the melt by 0.1 (in the range of 2.1–2.5) leads to a decrease in the viscosity of cryolite melts by 2.3%. A viscosity regression equation for the cryolite melts of conventional composition as a function of several independent parameters (temperature, CR, CaF2 and Al2O3 content) is obtained by the multivariable approximation of experimental data. The equation satisfactorily (within 1.5%) describes the viscosity of conventional industrial electrolytes and can be used for estimation of their viscosity.

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A viscosity model for the (NaF + AlF3+ CaF2+ Al2O3) electrolyte

Cited by 26 publications

References 31 publications

First-Principles Determination of Transference Numbers in Cryolitic Melts

First-Principles Determination of Transference Numbers in Cryolitic Melts

Generalized method for determining fluoroacidity by electrochemical diffusion coefficient measurement (application to HfF4)

Effect of Al₂O₃ and CaF₂ additives on the viscosity of conventional cryolite melts

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A viscosity model for the (NaF + AlF3+ CaF2+ Al2O3) electrolyte

Cited by 26 publications

References 31 publications

First-Principles Determination of Transference Numbers in Cryolitic Melts

First-Principles Determination of Transference Numbers in Cryolitic Melts

Generalized method for determining fluoroacidity by electrochemical diffusion coefficient measurement (application to HfF4)

Effect of Al2O3 and CaF2 additives on the viscosity of conventional cryolite melts

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Effect of Al₂O₃ and CaF₂ additives on the viscosity of conventional cryolite melts