Phosphogypsum crystallization in the decomposition process of fine-grained phosphate rock with sulfuric acid

In this paper,the Mabian phosphate concentrate with average particle size of 55-60 μm was selected as the representative sample to study the influence of reaction factors on phosphate rock decomposition and phosphogymsum crystallization by Orthogonal Experiments and range analysis method.The reaction factors include reaction temperature,reaction residence time,SO3 concentration,liquid-solid ratio.The results showed that the optimal conditions were reaction temperature at 85 ℃,SO3 concentration at 0.040 g/mL,liquid/solid at 3.0 and reaction time for 4.0 h.Under the optimal conditions,the extraction rate of phosphoric acid from phosphate rock could be 93.43% and the average particle size of phosphogymsum crystal could be 74.47 μm.Through the regression analysis of experimental results,the mathematical model of the phosphate rock decomposition and average particle size of phosphogymsum could be obtained and the dynamic equations could predict and optimize the decomposition process of the fine-grained phosphate rock and the crystallization process of phosphogypsum.