Formation and Dissolution of Crust Upon Alumina Addition into Cryolite Electrolyte (II)

The crusting/agglomerating behavior and heat transfer process upon feeding of smelting-grade alumina into aluminum electrolyte were investigated using a suspended weighing device. The influence of several feeding conditions on agglomerate formation and the heat transfer process, including the operating temperature (1173 K and 1233 K), feeding amount (5 g or 10 g alumina into 500 g electrolyte), and alumina preheating temperature (293 K and 773 K), was also analyzed. The results revealed that the mass of agglomerate was largely dependent on the feeding quantity, while the alumina content in the agglomerate stabilized at approximately 35%. Higher electrolyte temperature benefits the dissolution process in several ways: increasing the proportion of fast dissolution alumina, inhibiting agglomerate formation, and enhancing the agglomerate dissolution rate. The properties of the agglomerate were characterized, and surface microscopy revealed further details about its formation process.