Optimization of Ammonium Sulfate Crystallization under the Action of Ammonium Chloride Using the Response Surface Method
Gaoyong Zi, Bangfu Huang, Liubin Luo, Zhe Shi, Linjing Yang
Abstract
This paper presents a comprehensive study conducted to investigate the influence of doped ammonium chloride on the solubility, metastable zone width, and crystallization of ammonium sulfate. Herein, the solubility and metastable zone width of a solution of ammonium sulfate under the action of ammonium chloride were determined by using the laser method. Furthermore, the response surface method was used to study the interaction of the seed crystal concentration, pH value, and stirring rate on the crystallization of ammonium sulfate under the action of ammonium chloride. The results showed that the solubility of ammonium sulfate decreased with increasing ammonium chloride concentration. Additionally, the metastable zone width changed with increasing ammonium chloride concentration. These three factors considerably influence the crystallization yield and average particle size, and the order of influence is the stirring rate > seed crystal concentration > pH value. The seed crystal concentration and stirring rate substantially influence the yield and average particle size. The stirring rate enhances solution supersaturation and improves the crystallization environment while concurrently inhibiting the formation of new crystal nuclei in the mixed solution; this effect is attributed to the stirring motion. When the seed crystal concentration, pH value, and stirring rate were 1%, 4.5, and 325 rpm, respectively, ammonium sulfate crystals with an experimental crystallization yield of 61.753 g and an average particle size of 835 μm were obtained, ammonium sulfate crystals with a theoretical crystallization yield of 61.538 g and an average particle size of 863 μm were obtained, and the errors between the experimental value and the predicted value of the model were 0.34 and 3.24%, respectively, indicating that the model was effective.