A review of the alumina production from coal fly ash, with a focus in Russia

Abstract

Coal combustion used by the Combined heat and power plants (CHPs) generates solid wastes - coal fly ash (CFA). Up to 22% of the total electricity supply in Russian is coal-generated, this value is forecasted to not decrease until 2035, which in the next 14 years will translate into the accumulation of more than 260 Mt of CFA on the CHPs landfills. Following the Government recently presenting a roadmap towards the ramp-up of the CFA utilization from the current 8%–50% by 2035, the highly developed aluminum industry in Russia amidst the lack of its own bauxite sources is currently considering the utilization of CFA as an aluminum oxide-rich raw material for the alumina production. The present review localizes the largest sources of CFA in Russia, summarizes the annual CFA accumulation rates, and its stored volumes, and the chemical composition of the CFA generated in Russia. In this review, the actual acidic methods for alumina production (hydrochloric acid and ammonium bisulfate/sulfuric acid) were considered. Alumina powder obtained by acid methods was analyzed for the quality requirements of the Russian aluminum smelters to forward the case for the CFA's wide adoption as the raw material in both Russia's and worldwide aluminum industry. • Worldwide practices of the utilization of large volumes of CFA. • Localization of coal-fired power plants in Russia. • Characteristics of the chemical compositions of CFA formed in Russia. • Description of HCl and NH 4 HSO 4 + H 2 SO 4 for alumina production from CFA. • Characterization of alumina samples obtained by acidic methods.