Kinetics Study of Magnesium Impurity Removal from Phosphate Rock by Mixture of Phosphoric and Sulfuric Acid
1. Anhui Key Laboratory of Controllable Chemical Reaction & Material Chemical Engineering, School of Chemical Engineering, Hefei University of Technology, Hefei 230009, China; 2. Anhui Liuguo Chemical Industry Corporation, LTD, Tongling 244000, China
Abstract：For increasing efficiency of MgO removal, the process of remove magnesium impurities from phosphate rock by the mixture of phosphoric and sulfuric acid was investigated to understand the reaction mechanism of magnesium removal via the mixed acid. Scanning electronic microscopy and energy dispersive X-ray spectroscopy were utilized to characterize the intermediate and final products. And semi-empirical model was suggested to analyze the experimental data. It was found that the ratio of magnesium removal was controlled by the chemical reaction step. The apparent activation energy for this process was found to be 41.78 kJ/mol. It also turned out that both CaCO3·MgCO3 and Ca5(PO4)3F in phosphate ore first reacted with H3PO4, then the generated product Ca(H2PO4)2 reacted further with H2SO4. A large number of solid phase, alternate accumulation of permeable Ca(H2PO4)2 and CaSO4·2H2O were obtained due to the application of mixed acids. Existence of Ca(H2PO4)2 in the solid layer can change the shape of CaSO4·2H2O from needle-like, long and thin corrugated shape, or sheet structure into rod-like shape or rhombohedron shape, reducing the diffusion resistance of ore surface for H+ permeation and promoting the reaction of magnesium removal efficiently. At the same time, the loss of P2O5 was decreased obviously using the mixed acids.
Chen Yu 1,Jin Mengyuan 1,Wang Ye 1 et al. Kinetics Study of Magnesium Impurity Removal from Phosphate Rock by Mixture of Phosphoric and Sulfuric Acid[J]. 化学反应工程与工艺, 2013, 29(4): 372-378.
