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

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