ANODIC GAS COMPOSITION AND CARBON CONSUMPTION DURING ELECTROLYSIS OF CRYOLITE-ALUMINA MELTS

摘要

The theoretical composition of the primary anodic gas - according to a proposed equation for the total process in an aluminum electrolyzer [1]: 3Al_2O_3 + 5C = 6Al + 4CO_2 + CO (1) - satisfactorily corresponds to known experimental data [2, 3]. Within temperatures of 915-940 deg C and current density at the anode of 0.64-1.43 A/cm~2 the gas contains - on average - 80.5 percent CO_2, 18.8 percent CO, and 0.6 percent O_2. The composition of secondary anodic gas can be calculated from the interaction between the carbon deposited on an anode and the CO_2 contained in the primary gas. The completeness of the secondary reaction according to the reaction CO_2 + C = 2CO (2) depends on the reaction capacity and the porosity of carbonaceous material being used, the temperature, and the structural features of the anode.