Concluding Remarks

Aluminum smelters utilize calcined petroleum coke to make anodes for large-scale conversion of alumina into aluminum. The industry faces ongoing coke quality deterioration, such as increasing impurity content (sulfur and heavy metals), decreasing bulk density, and increasing concentrations of undesired textures. Furthermore, it is desirable to reduce SO₂ and CO₂ emissions.

Renewable alternatives to petroleum coke have been explored by several groups. Nevertheless, up to now it is not possible to produce coke with the required quality for aluminum smelting. Biomass-derived cokes usually have the desired low concentrations of sulfur and metals. However, bulk densities are much too low, and the cokes do not have the required anisotropic texture.

This talk will illustrate a process for production of renewable calcined coke from various fast pyrolysis bio-oils. Biomass is inherently low in undesired impurities. Coke manufacture by coking of biomass oil (as opposed to biomass carbonization) allows production of high-density coke. Finally, coke texture depends on the oxygen content of the coker feed. The desired anisotropic texture is favored by a low oxygen content. A modified pyrolysis process and bio-oil distillation procedure were used. This considerably reduced the oxygen content of the coker feed and yielded coke with the desired texture. Nickel and vanadium concentrations fell below 10 ppm. Sulfur was below 500 ppm. Other metals concentrations can vary, depending on the biomass source.