Solar Assisted Production of MgAl2O4 from Bayer Process Electrofilter Fines as Source of Al2O3

Resumen

Compared with conventional high-temperature methods based on electricity and fossil fuels, concentrated solar energy route offers distinct advantages in terms of mitigating emissions of contaminants and shortening processing times. Nevertheless, solar-based route also encounters challenges in producing significant quantities of materials, although the deployment of this technology is still conditioned by the limited investigation in the field. This study presents a novel high-temperature process based on solar energy to produce MgAl2O4 spinel, which employs as source of Al2O3 a waste from the aluminum industry: waste alumina fines from the Bayer process. First, mixtures were prepared by mechanical mixing in a molar ratio 1:1 in agreement with the MgO-Al2O3 binary phase diagram. Then, synthesis of the MgAl2O4 spinel was conducted by static experiments (5 min) with direct application of concentrated solar energy (1150 W/cm(2)) at temperatures greatly exceeding 1800 degree celsius as reported by ANSYS software. Wastes from three Bayer process factories were studied, which exhibited after the synthesis process a good crystallinity. The carbon dioxide emissions avoidance would range from the 200 to 500 tons of CO2/year in the case of a small plant producing 1000 tons/year to 5000 to 12,000 tons of CO2/year in the case of a commercial plant producing 25,000 tons/year, thus contributing to mitigate climate change. The proposed process might lead to smaller volume of wastes in the aluminum industry, while the MgAl2O4 may be used as raw material in the numerous fields based on the chemical, thermal, dielectric, mechanical and optical properties.