| This study evaluated the pitch wetting and penetration behavior of petroleum coke and recycled anode butts used in the production of anodes for alumina smelting. The parameters relevant to wetting and capillary infiltration into porous media were determined. The pore entrance radius and length of the filler materials, the surface tension and viscosity of the binder material, and the contact angle of wetting between the filler, binder, and air were determined for the raw materials used in the production of carbon anodes. The raw materials were penetrated with pitch at a range of temperature-time conditions, and the amount of pitch that coated and penetrated the particles was measured.; The amount of pitch that coated and penetrated the filler materials was correlated to filler and binder properties and operational parameters using linear regression and multiple linear regression analyses. The factors that had the greatest influence on the pitch coating and penetration volume were the average pore entrance radius of the carbon and the time of penetration. Pitch coating and penetration volume increased with both parameters. The surface tension of the pitch and the contact angle of wetting were not found to be significant for the time and temperature conditions utilized in this study.; Raw materials were modified to enhance property differences observed between the as-received coke and butts samples. Coke was oxidized by nitric acid to increase the quantity of surface oxygen functional groups. Anodes were subjected to reverse polarity tests to produce butts samples with increased concentrations of bath constituents. The presence of oxygen on the surface of the materials increased the pitch coating and penetration volume compared to as-received coke. The results also suggest that the presence of impurities also caused and increase in the pitch coating and penetration volume, although there was some ambiguity present in those data.; Overall, petroleum coke and recycled anode butts were found to have different pitch wetting and penetration behavior due to differences in porosity and chemical surface properties. These physical and chemical properties play a significant role in green mix formulation and affect the amount of pitch needed to optimize a given aggregate size distribution. |
