Quantitative analysis of crystallization processes remains challenging due to the complicated relationships among the multiple phases and their spectra. In this work, in situ Raman spectroscopy was chosen to quantitatively analyze the solution concentration and suspension density simultaneously in a crystallization process . A model based on support vector regression (SVR) was developed to separate the information of solution and solid from the Raman spectra. The simultaneous correlations of the spectra with solution concentration and suspension density were achieved and the results were evaluated. It demonstrated that the SVR-based method proposed in this work gave satisfactory fitting and prediction performance. Furthermore, the model was validated in the reactive crystallization of the ternary NaHCO 3 -Na 2 CO 3 -H 2 O system. It suggested that baseline removal is not necessary when using this model. The effect of bubbles should be included for the clear solution but could be neglected in solid suspensions. The results of this work provide a simple and rapid option for the quantitative analysis of crystallization processes and similar suspension systems.
Ammonium chloride (NH 4 CI) finds extensive applications across numerous sectors such as chemicals, pharmaceuticals, and agriculture, necessitating enhancement in the quality of crystal products and precision in designing the NH 4 CI crystallization process. In this paper, we conducted an investigation into the solubility and supersolubility of NH 4 CI in H 2 O-Ethylene Glycol(EG) binary system with various proportions via dynamic laser method. We utilized the Apelblat model, Van’t Hoff model, and Redlich-Kister model to correlate the experimental findings, and derived thermodynamic parameters through these correlations. Further, we determined the solid-liquid surface tension and crystal surface entropy factor of NH 4 CI in the system using the Mersmann equation and Barata equation, thereby providing essential input for understanding crystallization kinetics. Afterward, we meticulously examined the crystallization kinetics of NH₄Cl in the H₂O-EG solvent by utilizing the batch dynamic approach. We established equations that correlated the rates of crystal nucleation and growth obtained through regression analysis. Additionally, we explored in - depth the effects of supersaturation and suspension density on the crystallization kinetics of NH₄Cl. Our results reveal that the dissolution of NH 4 CI in the binary solvent system under different proportions takes place as a non-spontaneous endothermic process, and importantly, the Redlich-Kister model appears to offer a superior comprehension of the solubility of NH 4 CI. An increase in supersaturation and stirring rate augments both the growth and nucleation rates, while an increase in suspension density elevates the nucleation rate. These research findings are expected to be advantageous for those designers involved in the industrial crystallization process of NH₄Cl.
危险品化学品经营许可证（带存储）