Correlation between chemical composition, wettability and carbon anode performance: Exploration of high quality carbon anode preparation for aluminum electrolysis

Abstract

The chemical composition of coal tar pitch has a significant effect on its wettability and the performance of carbon anode for aluminum electrolysis. This study aimed to reveal the correlation among chemical composition, wettability, and carbon anode performance, as well as provide strategies for reducing energy consumption, greenhouse gases, and hazardous waste emissions during aluminum electrolysis processes. First, the chemical composition of modified coal tar pitch was regulated by adding low-temperature coal tar pitch. The effects of low-temperature coal tar pitch mixing amount on the chemical composition, basic properties, contact angle, static wettability, functional groups, and coke microstructure were studied. In particular, electron paramagnetic resonance (EPR) and atomic force microscopy (AFM) were performed to qualitatively and quantitatively analyze radical emissions and surface structure of coal tar pitch at the microscopic scale. Subsequently, the correlation of chemical composition, wettability, and performance was discussed according to the effect of low-temperature coal tar pitch on the performance of carbon anode. Results showed that the incorporation of low-temperature coal tar pitch reduced the softening point and viscosity, and the increase in fluidity improved the contact angle and static wettability. Meanwhile, the increase in volatile content and the decrease in coking value, surface roughness, nanoscale adhesion, and free radical release concentration jointly weakened the bonding strength between coal tar pitch and calcined petroleum coke. The performance of the carbon anode prepared by blending low-temperature coal tar pitch weakened, except for the ash content. Consequently, the balance between the wettability and bonding strength of coal tar pitch is essential for the preparation of high-quality anode for aluminum electrolysis.