ИСТИНА

Reftinskaya TPP is the largest coal-fired power plant in Russia. It annually generates more than 4 million tons of coal fly ash (CFA), while over 180 million tons have been accumulated in the landfill. The alumina (Al2O3) content makes up to 27 wt% that allows this type of raw material to be considered for alumina refining. Due to the high silica (SiO2) content (up to 65 wt%), traditional alkali methods cannot be used. In this research, we studied the acidic method using mixture of ammonium bisulfate (NH4HSO4) and sulfuric acid (H2SO4) as a leaching agent. A high-pressure reactor was used to intensify the leaching process. The effect of temperature, leaching time, solid to liquid ratio on the Al extraction degree was studied. The behavior of macro and micro impurities has been investigated. The samples of the solid residue after leaching were analyzed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and laser diffraction (LD) methods.