Document Type : Case Study

Authors

School of Mining Engineering, College of Engineering, University of Tehran, Tehran, Iran

Abstract

The precipitation of aluminum hydroxide from a supersaturated sodium aluminate solution is known as an essential production step in the Bayer process. In this work, the real precipitation process in the Iran Alumina Plant was modeled by the historical data with the help of Design Expert. According to the results obtained, the recovery is significantly improved with decrease in the super-saturation factor (α) of the solution. However, this modification was found to be the most difficult change due to the operational problems. The results obtained indicated the significant impact of the seed size on the product size. The negligible effects of the other parameters involved on controlling the amount of fine grains (< 44 µm) and coarse grains (> 150 µm) in the product showed the significance of reactivating the classification and agglomeration sections. Ultimately, it was found that the recovery process could be enhanced from 46.32% to 47.86% at a constant α by increasing the seed concentration to 400 g/L, increasing the retention time by adding two precipitation tanks and reducing the temperature of the last precipitation tank by 2 ºC (by reducing the temperature of the inlet suspension), while preserving the quality of the product.

Keywords

[1]. Ruys, A. (2019). Alumina Ceramics: Biomedical and Clinical Applications, Woodhead Publishing, United Kingdom, 49-70.
[2]. Lumley, R. (2011). Fundamentals of aluminium metallurgy; Production, processing and applications, Woodhead Publishing, United Kingdom, 23-48.
[3]. Sonthalia, R., Behara, P., Kumaresan, T. and Thakre, S. (2013). Review on alumina trihydrate precipitation mechanisms and effect of Bayer impurities on hydrate particle growth rate. International Journal of Mineral Processing 137–148.
[4]. Zhang, Y., Zheng, S., Du, H., Xu, H., Wang, S. and Zhang, Y. (2009a). Improved precipitation of gibbsite from sodium aluminate solution by adding methanol. Hydrometallurgy 38–44.
[5]. Power, G. and Loh, J. (2011). Organic compounds in the processing of lateritic bauxites to alumina Part 1: origins and chemistry of organics in the Bayer process. Hydrometallurgy 105: 1–29.
[6]. Smeulders, D.E., Wilson, M.A. and Armstrong, L. (2001). Poisoning of Aluminum Hydroxide Precipitation by High-Molecular-Weight Fractions of Bayer Organics. Industrial & Engineering Chemistry Research 40 (25): 5901-5907.
[7]. Veesler S., Rource, S, and Boistelle, R. (1993). About super-saturation and growth rates of hydragillite Al(OH)3 in alumina caustic solutions. Journal of Crystal Growth 130 (3−4): 411−415.
[8]. Freij, S.J., Parkinson, G.M. and Reyhani, M.M. (2004). Direct observation of the growth of gibbsite crystals by atomic force microscopy. Journal of Crystal Growth 260 (1–2): 232–242.
[9]. Ilievski, D. and Livk, I. (2006). An agglomeration efficiency model for gibbsite precipitation in a turbulently stirred vessel. Chemical Engineering Science 61 (6): 2010–2022.
[10]. Bao-lin, L., Qi-yuan, C., Zhou-lan, Y. and Hui-ping, H. (2010). Effects of Na4EDTA and EDTA on seeded precipitation of sodium aluminate solution. Transactions of Nonferrous Metals Society of China 37-41.
[11]. Bhattacharya, I.N., Pradhan, J.K., Gochhayat, P.K. and Das, S.C. (2001). Factors controlling precipitation of finer size alumina trihydrate. International Journal of Mineral Processing 65: 109– 124.
[12]. Seyssiecq, I., Veesler, S., Boistelle, R. and Lamerant, J.M. (1998). Agglomeration of Gibbsite Al(OH)3 crystals in Bayer liquors. Influence of the process parameters. Chemical Engineering Science 5 (12): 2177—2185.
[13]. Seyssiecq, I., Veesler, S. and Boistelle, R. (1996). A non-immersed induction conductivity system for controlling super-saturation in corrosive media: the case of gibbsite crystals agglomeration in Bayer liquors. Journal of Crystal Growth 169: 124-128.
[14]. Ilewski, D. and White, E. T. (1994). Agglomeration mechanisms in Al(OH)3 crystallization from caustic aluminate solutions. Proceedings 1st International Technology Forum, Denver, CO, USA, American Institute of Chemical Engineers, New York, 305-310.
[15]. Guichardon, P., Falk, L. Fournier, M.C. and Villermaux, J. (1995). Study of micromixing in a liquid solid suspension in a stirred reactor. American Institute of Chemical Engineers & the Institution of Chemical Engineers 305 (91): 123-130.
[16]. Veesler, S. and Boistelle, R. (1993). About super-saturation and growth rates of hydrargillite Al(OH)3 in alumina caustic solutions. Journal of Crystal Growth 130: 411—415.
[17]. Li, T.S., Livk, I. and Ilievski, D. (2003). Super-saturation and temperature dependency of gibbsite growth in laminar and turbulent flows. Journal of Crystal Growth 358 (3–4): 409–419.
[18]. Bahrami, A., Nattaghi, E., Movahedirad, S., Ranjbarian, S. and Farhadi, F. (2012). The agglomeration kinetics of aluminum hydroxide in Bayer process. Powder Technology 351-355.
[19]. Addai-Mensah, J. (1997). Surface and structural characteristics of gibbsite precipitated from pure, synthetic Bayer liquor. Minerals Engineering 10 (1): 81–96.
[20]. Addai-Mensah, J. and Ralston, J. (1999). The influence of interfacial structuring on gibbsite interactions in synthetic Bayer liquors. Journal of Colloid and Interface Science 215 (1): 124–130.
[20]. Li, J., Prestidge, C.A. and Addai-Mensah, J. (2000). The influence of alkali metal ions on homogeneous nucleation of Al(OH)3 crystals from supersaturated caustic aluminate solutions. Journal of Colloid and Interface Science 224 (2): 317–324.
[21]. Chen, G.H., Chen, Q.Y., Yin, Z.L. and Yin, Z.M. (2006). Characterization of irregular seeds on gibbsites precipitated from caustic aluminate solutions. Transactions of Nonferrous Metals Society of China 16 (2): 483–487.
[22]. Li, X., Panias, D., Yan, L., Zhao, D., Zhou, Q., Liu, G., Peng, Z., Yang, S, and Qi, T. (2013). Relationship between Al(OH)3 solubility and particle size in synthetic Bayer liquors. Hydrometallurgy 57-68.
[23]. Gui-hua, L., Wen-bo, D., Tian-gui, Q., Qiu-sheng, Z., Zhi-hong, P. and Xiao-bin, L. (2017). Behavior of calcium oxalate in sodium aluminate solutions, Transactions of Nonferrous Metals Society of China 27: 1878−1887.
[24]. Li, X.B., Yan, L., Zhou, Q.S., Liu, J., Peng, Z., Liu, G. and Qi, T. (2019). Intensifying gibbsite precipitation from sodium aluminate solution by adding a mixed seed. Journal of Central South University 26 (2): 312-322.
[25]. Huang, W.Q, Liu, G.H, Ju, J.B., Li, X.B., Zhou, Q.S., Qi, T.G. and Peng, Z.H. (2019). Effect of lithium ion on seed precipitation from sodium aluminate solution. Transactions of Nonferrous Metals Society of China 29: 1323−1331.
[26]. PENG, Z.H., LIU, Y.T., ZHOU, Q. S., LIU, G.H. and Li, X. B. (2008). Effect of non-ionic surfactant on seeded precipitation of sodium aluminate solution. The Chinese Journal of Nonferrous Metals 18 (10): 1909 -1913.
[27]. Peng, Z.H., Liu, Y.T., Zhou, Q.S., Liu, G.H. and Li, X.B. (2011). Effect of ethers additive B35 on seeded precipitation of sodium aluminate solution. The Chinese Journal of Nonferrous Metals 21 (2): 459-464.
[28]. Li, X.B., Wang, D., Zhou, Q.S, Liu, G. and Peng, Z. (2012). Influence of magnetic field on the seeded precipitation of gibbsite from sodium aluminate solution. Minerals Engineering 32: 12–18.
[29]. Zhang, B., Li, J., Chen, Q. and Chen, G. (2009b). Precipitation of Al(OH)3 crystals from super-saturated sodium aluminate solution irradiated with ultrasonic sound. Minerals Engineering 22 (9–10): 853–858.
[30]. Patnaik, S.C., Satapathy, B.K. and Pradhan, B. (1995). Effect of process variables on the yield and strength of alumina hydrate precipitated from aluminate liquor. Indian Journal of Engineering and Materials Sciences 3: 73-78.