Alumina Sensors in Hall Heroult Electrol

This study investigates the performance of a sensor pair composed of the Cr/C O3 - Al/Mo couple for measuring electromotive force (emf) in Hall-Heroult electrolytes with varying alumina content. The objective is to assess the sensor's accuracy in predicting the theoretical emf values in electrolytes containing at least 3 wt-% alumina. The methodology involves experimental measurements of emf alongside theoretical calculations, focusing on high and low alumina concentrations in the molten salt electrolyte. Results indicate that the sensor provides reliable measurements with deviations within ±10 mV for higher alumina contents. However, in low alumina melts, measurement reproducibility deteriorates, leading to values consistently below theoretical predictions. This deviation is attributed to the corrosive properties of Hall-Heroult electrolytes, which increase the dissolution rate of yttria-stabilized zirconia and affect the sensor's interface activity. Furthermore, variations in convection patterns impact the diffusion of dissolved components, necessitating design improvements for effective sensor functionality. The findings suggest that in situ monitoring for alumina concentration can enhance operational control in aluminum electrolysis cells.