Abstract
A novel method was developed for extracting alumina (Al2O3) from fly ash using an ammonium hydrogen sulfate (NH4HSO4) roasting process, and the thermodynamics and kinetics of this method were investigated. The thermodynamic results were verified experimentally. Thermodynamic calculations show that mullite present in the fly ash can react with NH4HSO4 in the 298–723 K range. Process optimization reveals that the extraction rate can reach up to 90.95% when the fly ash reacts with NH4HSO4 at a 1:8 mole ratio of Al2O3/NH4HSO4 at 673 K for 60 min. Kinetic analysis indicates that the NH4HSO4 roasting process follows the shrinking unreacted core model, and inner diffusion through the product layer is the rate-controlling step. The activation energy is calculated to be 16.627 kJ/mol; and the kinetic equation can be expressed as 1 − (2/3)α − (1 − α)2/3 = 0.0374t exp[−16627/(RT)], where α is the extraction rate and t is the roasting temperature.
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References
J.C. Swanepoel and C.A. Strydom, Utilisation of fly ash in a geopolymeric material, Appl. Geochem., 17(2002), p. 1143.
X. Querol, N. Moreno, J.C. Umaña, A. Alastuey, E. Hernández, A. López-Soler, and F. Plana, Synthesis of zeolites from coal fly ash: an overview, Int. J. Coal Geol., 50(2002), p. 413.
R.S. Iyer and J.A. Scott, Power station fly ash: a review of value-added utilization outside of the construction industry, Resour. Conserv. Recyl., 31(2001), p. 217.
P.M. Sun, G.M. Li, J.W. Tong, H.Y. Xu, and Z. Zhao, Study on sintering process of raw materials in extracting alumina from fly ash of coal industry power plate, J. China Coal Soc., 32(2007), No. 7, p. 744.
V.L. Rayzman, S.A. Shcherban, and R.S. Dworkin, Technology for chemical-metallurgical coal ash utilization, Energy Fuels, 11(1997), p. 761.
R. Padilla and H.Y. Sohn, Sodium aluminate leaching and desilication in lime soda sinter process for alumina from coal wastes, Metall. Trans. B, 16(1985), p. 707.
A. Seidel and Y. Zimmels, Mechanism and kinetics of aluminum and iron leaching from coal fly ash by sulfuric acid, Chem. Eng. Sci., 53(1998), No. 22, p. 3835.
B.K. Dutta, S. Khanra, and D. Mallick, Leaching of elements from coal fly ash: Assessment of its potential for use in filling abandoned coal mines, Fuel, 88(2009), p. 1314.
C.Y. Wu, H.F. Yu, and H.F. Zhang, Extraction of aluminum by pressure acid-leaching method from coal fly ash, Trans. Nonferrous Met. Soc. China, 22(2012), No. 9, p. 2282.
N. Nayak and C.R. Panda, Aluminium extraction and leaching characteristics of Talcher Thermal Power Station fly ash with sulphuric acid, Fuel, 89(2010), p. 53.
G.H. Bai, W. Teng, X.G. Wang, J.G. Qin, P. Xu, and P.C. Li, Alkali desilicated coal fly ash as substitute of bauxite in lime-soda sintering process for aluminum production, Trans. Nonferrous Met. Soc. China, 20(2010), p. s169.
A. Seidel, A. Sluszny, G. Shelef, and Y. Zimmels, Self inhibition of aluminum leaching from coal fly ash by sulfuric acid, Chem. Eng. J., 72(1999), No. 3, p. 195.
A.D. Kelmers, R.M. Canon, B.Z. Egan, L.K. Felker, T.M. Gilliam, G. Jones, G.D. Owen, F.G. Seeley, and J.S. Watson, Chemistry of the direct acid leach, calsinter, and pressure digestion-acid leach methods for the recovery of alumina from fly ash, Resour. Conserv., 9(1982), p. 271.
R.H. Matjie, J.R. Bunt, and J.H.P. van Heerden, Extraction of alumina from coal fly ash generated from a selected low rank bituminous South African coal, Miner. Eng., 18(2005), p. 299.
D.L. Ye and J.H. Hu, Practical Handbook of Thermodynamic Data for Inorganic Compounds, 2nd Ed., Metallurgical Industry Press, Beijing, 2002, p. 1.
X.C. Fu, W.X. Shen, and T.Y. Yao, Physical Chemistry, Higher Education Press, Beijing, 1990, p. 885.
J.A. Dean and J.F. Wei, Lange’s Handbook of Chemistry, Science Press, Beijing, 2003, p. 81.
G.Q. Liu, L.X. Ma, and J. Liu, Chemical Property Data Handbook (Inorganic Volume), Chemical Industry Press, Beijing, 2002, p. 410.
J.H. Li, G.E. Zhang, and J.C. Zhang, Thermoanalytical investigation of NH4HSO4-Na2SO4 system for chemical storage of energy: 1. Thermodynamic of the system, J. Henan Normal Univ. Nat. Sci., 20(1992), No. 2, p. 54.
H.G. Li, Metallurgical Principles, Science Press, Beijing, 2005, p. 291.
H.G. Li, Hydrometallurgy, Central South University Press, Changsha, 2002, p. 69.
Y.X. Hua, Introduction of Metallurgical Process Kinetics, Metallurgical Industry Press, Beijing, 2004, p. 191.
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Wang, Rc., Zhai, Yc. & Ning, Zq. Thermodynamics and kinetics of alumina extraction from fly ash using an ammonium hydrogen sulfate roasting method. Int J Miner Metall Mater 21, 144–149 (2014). https://doi.org/10.1007/s12613-014-0877-x
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DOI: https://doi.org/10.1007/s12613-014-0877-x