A new approach for improving the quality of the carbon anode for aluminum electrolysis – An impregnation-baking process

Prebaked carbon anode is the primary consumable material in the aluminum reduction cell, and its quality directly affects the energy consumption of aluminum production. An impregnation-baking process of the anode was proposed to reduce the anode porosity, improve the quality of the anodes, and reduce additional carbon consumption. The theoretical analysis and industrial testing on the impregnation-baking process were carried out. Firstly, the coal tar pitch was immersed into the anode carbon block through the impregnation process. An anode impregnation model was developed and used for theoretical calculations to analyze the effects of pressure and temperature on the impregnation process. The accuracy of the model was verified experimentally. Secondly, the impregnated anodes were placed in an electromagnetic induction heating furnace for baking to carbonize the immersed pitch. The thermogravimetric and pyrolysis kinetics methods were used to analyze the baking process of the impregnated anodes. Finally, the impregnated-baked anodes were compared with common anodes regarding their impact on the technical and economic indicators of the aluminum electrolysis process in industrial tests. The results showed that the physicochemical properties of the impregnated-baked anodes were significantly improved, with the bulk density increase of 0.1 g/cm3, air permeability reduction of 0.54 nPm, compressive strength enhancement of 9.43 MPa, and electrical resistivity decrease of 10 uΩ·m. The anode service life was increased from 31 to 35 days, the current efficiency was increased by 0.44 %, and the operating voltage was reduced by 17 mV, which improved economic benefit significantly.