The presence of a stable layer of frozen electrolyte is very important to ensure a long life of the aluminium electrolysis cells. Generally, in an operating cell, the freeze profile is determined by using mechanical probes. Temperature and heat flux measurements on the external surfaces of the pot have also been used to verify indirectly the presence and the thickness of the freeze, but the sensitivity of these measurements is limited. The present paper examines the possibility of using the signals from a number of temperature sensors implanted into the sidewall to identify the thickness - and potentially the shape - of the freeze. Numerical and laboratory experiments were carried out in order to determine the necessary number of sensors, the effect of their position and spatial arrangement that gives an appropriate sensitivity to follow the variations of the freeze-bath interface. In the experimental set-up the thermocouples were implanted into a carbon block, whereas the freeze layer was modelled physically by a variable thickness and shape sand layer. in the numerical simulation, parameters from both the laboratory set-up and from industrial cells were used to test the identification procedure.
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