Thermal chemical and microstructural cha

The anode cover material (ACM) of aluminum electrolysis cells reacts with the liquid bath and vapor penetrating inside this powdered material to form a denser material, called the anode crust. The thermal property of the anode crust affects the top heat losses of aluminum electrolysis cells. The operation and design of electrolysis cells can be controlled through a better understanding of the thermochemical evolution of the anode crust. The typical anode crust is found either in the solid state up to 696°C or in the solid-liquid state at higher temperatures. Its thermal conductivity is determined from 100°C up to 950°C on the samples extracted from an industrial electrolysis cell. For example, the thermal conductivity of the lower part of the anode crust decreases from 1.38 W m−1 °C−1 at 100°C to 0.89 W m−1 °C−1 at 950°C. The specific heat capacity, enthalpy, bulk density, and thermal diffusivity are also determined from experimental measurements. The crystalline phases composing the anode crust are quantified using a Rietveld method performed on X-ray diffraction patterns. The thermochemical behavior of the industrial anode crust is investigated with differential scanning calorimetry and thermodynamic equilibrium calculations.