Abstract
The enthalpies related to the dissolution of smelter-grade primary and secondary alumina in aluminium cells were calculated. The following was considered: (i) the heat content of alumina containing fluorides and other impurities, (ii) the heat of dissolution, (iii) enthalpies for bath evaporation and hydrolysis, (iv) enthalpies for desorption of H2O, HF, and SO2, (v) enthalpies for melting of solid fluorides, vi) enthalpies for fluorination of Na2O and CaO, and (vii) alumina production from fluorination of Na2O and CaO and hydrolysis of bath. A typical secondary alumina showed 0.022 kWh/kg Al higher energy consumption than the corresponding primary alumina, and 0.055 kWh/kg Al higher energy consumption than a hypothetical dry alumina without impurities. It is recommended that the enthalpy terms are considered by detailed calculation, or simply by adding a fixed term to the cell reaction.