Shahrood University of Technology Journal of Mining and Environment 2251-8592 10 3 2019 07 01 Modelling and optimization of digestion efficiency of bauxite in Bayer process: Iran Alumina company 799 809 1496 10.22044/jme.2019.8398.1720 EN M. R. Khani Faculty of Mining, Petroleum & Geophysics Engineering, Shahrood University of Technology, Shahrood, Iran M. Karamoozian Faculty of Mining, Petroleum & Geophysics Engineering, Shahrood University of Technology, Shahrood, Iran Journal Article 2019 05 06 In the present work, we investigated and optimized the digestion efficiency, A/S (Al₂O₃/SiO₂ in red mud)_, and N/S (Na₂O/SiO₂ in red mud) of mixed bauxite in Iran Alumina Company using the Bayer process. Digestion experiments were carried out in an induction rotary autoclave on a mix of Jajarm, Yazd, Tash, and Shirin Cheshmeh bauxites. A 4-factor 3-level response surface methodology was applied for the design and analysis of the experiment with the optimization of Na₂O concentration, digestion temperature, residence time, and amount of lime addition. Towquadratics and one linear model were derived for the prediction of digestion efficiency, and A/S and N/S responses. The results obtained showed that the optimum amounts for Na₂O concentration, temperature, amount of lime addition and residence time were 180 g/L, 275°C, 7.73%, and 50 minutes, respectively, in which the digestion efficiency, A/S, and N/S reached 72.05%, 1.169, and 0.27, respectively. Validation experiment showed that the digestion efficiency, A/S, and N/S were 72.24%, 1.162, and 0.28% respectively, which meant a 2% increase in digestion efficiency and a 0.09 and 0.02 decrease in A/S and N/S, respectively, compared to the current operating condition. https://jme.shahroodut.ac.ir/article_1496_6005b00058cf6a216fd141504ccd388a.pdf