Optimization of parameters during phosphoric acid production using response surface methodology: toward a biomimetic process†

In order to improve the performance and efficiency of a process, understanding the influence of various variables on a desired output or response is a common task in engineering challenges. This paper aims to investigate the effect of three parameters – namely the free H₂SO₄ rate, the solid rate, and the percentage of P₂O₅ in the ranges of 2.4–5.8%, 32–37%, and 28–32%, respectively – on the reactive crystallization phase during the phosphoric acid production. The experiments were carried out using a filterability workbench and a semi-continuous reactor that replicated the operating conditions of the dihydrate process. The investigation conducted using the factorial and Box–Behnken methods enabled the optimization and determination of operational significant conditions affecting the filterability of the phosphoric slurry to be thoroughly evaluated and controlled. Overall, response surface methodology (RSM) has several advantages over classical one-variable-at-a-time optimization, including the ability to assess the interaction effect between variables on the response of interest and the ability to generate large amounts of data from a limited number of experiments. Furthermore, the desirability function approach has been successfully implemented for the identification of the optimal conditions, and phosphogypsum crystals offering high and low filterabilities were characterized and compared. Finally, we anticipate that our paper will serve as a foundation for the explanation of how the natural giant gypsum crystals of Naica and Pulpí were formed.