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

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 m...

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Autores principales:	A. S. Lyutina, A. A. Kataev, A. V. Rudenko, O. Yu. Tkacheva
Formato:	article
Lenguaje:	EN RU
Publicado:	Uralʹskij federalʹnyj universitet imeni pervogo Prezidenta Rossii B.N. Elʹcina 2021
Materias:	molten cryolite alumina calcium fluoride viscosity rotary method Chemistry QD1-999
Acceso en línea:	https://doaj.org/article/c2b9afab6bc540ed9bb4af220f517560
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spelling	oai:doaj.org-article:c2b9afab6bc540ed9bb4af220f5175602021-12-01T05:53:11ZEffect of Al2O3 and CaF2 additives on the viscosity of conventional cryolite melts2411-141410.15826/chimtech.2021.8.3.06https://doaj.org/article/c2b9afab6bc540ed9bb4af220f5175602021-09-01T00:00:00Zhttps://journals.urfu.ru/index.php/chimtech/article/view/5216https://doaj.org/toc/2411-1414The 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.A. S. LyutinaA. A. KataevA. V. RudenkoO. Yu. TkachevaUralʹskij federalʹnyj universitet imeni pervogo Prezidenta Rossii B.N. Elʹcina articlemolten cryolitealuminacalcium fluorideviscosityrotary methodChemistryQD1-999ENRUChimica Techno Acta, Vol 8, Iss 3 (2021)
institution	DOAJ
collection	DOAJ
language	EN RU
topic	molten cryolite alumina calcium fluoride viscosity rotary method Chemistry QD1-999
spellingShingle	molten cryolite alumina calcium fluoride viscosity rotary method Chemistry QD1-999 A. S. Lyutina A. A. Kataev A. V. Rudenko O. Yu. Tkacheva Effect of Al2O3 and CaF2 additives on the viscosity of conventional cryolite melts
description	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.
format	article
author	A. S. Lyutina A. A. Kataev A. V. Rudenko O. Yu. Tkacheva
author_facet	A. S. Lyutina A. A. Kataev A. V. Rudenko O. Yu. Tkacheva
author_sort	A. S. Lyutina
title	Effect of Al2O3 and CaF2 additives on the viscosity of conventional cryolite melts
title_short	Effect of Al2O3 and CaF2 additives on the viscosity of conventional cryolite melts
title_full	Effect of Al2O3 and CaF2 additives on the viscosity of conventional cryolite melts
title_fullStr	Effect of Al2O3 and CaF2 additives on the viscosity of conventional cryolite melts
title_full_unstemmed	Effect of Al2O3 and CaF2 additives on the viscosity of conventional cryolite melts
title_sort	effect of al2o3 and caf2 additives on the viscosity of conventional cryolite melts
publisher	Uralʹskij federalʹnyj universitet imeni pervogo Prezidenta Rossii B.N. Elʹcina
publishDate	2021
url	https://doaj.org/article/c2b9afab6bc540ed9bb4af220f517560
work_keys_str_mv	AT aslyutina effectofal2o3andcaf2additivesontheviscosityofconventionalcryolitemelts AT aakataev effectofal2o3andcaf2additivesontheviscosityofconventionalcryolitemelts AT avrudenko effectofal2o3andcaf2additivesontheviscosityofconventionalcryolitemelts AT oyutkacheva effectofal2o3andcaf2additivesontheviscosityofconventionalcryolitemelts
_version_	1718405502759600128

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

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