关键词: 铝电解, 生物沥青, 碳阳极, 润湿性, 焦化值

Abstract: The carbon anode is prepared by baking a mixture of petroleum coke aggregate and pitch at 180℃ for use in the aluminum industry. Due to its good wettability and environmental friendliness towards carbon anode aggregates, the biopitch is considered as a promising carbon anode binder. The biomass conversion technology, substituting traditional coal tar pitch with biopitch, partially or completely in the aluminum production, has recently received domestic and foreign researchers' attention. However, the biopitch typically has a lower coking value which may have a negative impact on its performance. In this work, alumina additives have been added to the biopitch anode to improve its performance. In order to understand the effect of alumina additives on the performance of biopitch anodes, biopitch anode materials were prepared by hot pressing and sintering in the laboratory with alumina as a catalyst. The CO2 reactivity of the anodes was tested with a thermogravimetric analyzer in laboratory. The influence of additives on the performance of the anodes and the CO2 reactivity as well as the wettability of biopitch on petroleum coke were studied by X-ray diffraction analysis, optical microscopy (OM) and high-resolution transmission electron microscopy (HRTEM). The results indicated that the biopitch exhibited better wettability than coal tar pitch with the same surface tension and viscosity. In addition, a transformation occurred from initially less well-ordered to ordered structure for the biopitch anode with alumina additives during baking, thereby increasing the coking value of the biopitch, reducing the CO2 reactivity of biopitch anodes and improving their antioxidant properties. Accompanied by an enhancement in the graphitization degree and an increase of carbon structural orders, the performance of biopitch anodes has been improved significantly with alumina as additives. The biopitch could be used to replace 100% of the coal tar pitch in a carbon anode recipe. This study has provided a theoretical guidance for the application of biopitch anodes and the reduction of energy consumption in aluminum electrolysis.

Key words: aluminum electrolysis, biopitch, carbon anode, wettability, coking value