Abstract:The influence of aluminum electrolyte component on its temperature is an important issue within the field of aluminum reduction with pre-baked cells. The characteristic correlation between excess AlF₃ concentration and aluminum electrolyte temperature was explored through the modeling of heat and mass transfer processes in industrial pre-baked aluminum reduction cells. A coupled heat/mass-balance model was derived theoretically from the mass and energy balance of an electrolysis cell, and then was simplified properly into a practical expression. The model demonstrates that if environmental temperature and Al₂O₃ concentration keep constant, the excess AlF₃ concentration decreases with the aluminum electrolyte temperature linearly and its decrease rate is dependent on the heat transfer property of aluminum electrolyte, side wall and cell shell. Secondly, experiments were conducted on site with two industrial cells in an aluminum electrolysis plant. Excess AlF₃ concentration and aluminum electrolyte temperature were obtained simultaneously together with other parameters such as Al₂O₃, CaF₂, MgF₂ and LiF concentrations. Results show that the maximum absolute error between the tested value and the calculated value of excess AlF₃ concentration using the proposed model is less than 2%. This reveals that the coupled heat/mass-balance model can appropriately characterize the correlation between excess AlF₃ concentration and aluminum electrolyte temperature with good accuracy and practicability.

Key words: aluminum electrolysis; electrolyte temperature; excess AlF₃ concentration; energy balance; mass balance; coupled model