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    磷酸二氢铵结晶介稳区预测模型构建及工艺优化

    Construction of metastable zone width prediction models and process optimization for ammonium dihydrogen phosphate crystallization

    • 摘要: 为精准调控磷酸二氢铵(NH4H2PO4)工业结晶过程,提高产品品质与生产效率,本研究首先系统地测定了其在308.15~338.15 K温度范围内的水溶液溶解度及饱和溶液密度,并采用Apelblat方程、Van′t Hoff方程和多项式方程进行溶解度热力学关联。结果表明:Apelblat方程拟合系数达到0.999 64,误差最小,精度最优,计算得到溶解焓为11.265 0 kJ·mol−1、溶解熵为14.872 6 J·mol−1·K−1,表明溶解过程为吸热非自发过程。其次,考察了降温速率与搅拌速率对介稳区宽度(MSZW)的影响规律,应用Nývlt理论、自洽类Nývlt理论及3D成核理论模型对MSZW进行预测与对比分析。研究发现:升温、降低降温速率或提高搅拌速率均显著减小MSZW,自洽类Nývlt理论模型的拟合系数达到0.9,具有最佳预测效果和适用性。最后,基于该模型构建了MSZW与饱和温度、冷却速率的定量关联式,为工业结晶工艺参数(如降温程序、搅拌强度)的优化设计提供了关键理论依据和数据支撑。

       

      Abstract: To achieve precise control of industrial crystallization processes and enhance product quality and production efficiency, in this study, the aqueous solubility and saturated solution density of the target substance were first systematically determined within 308.15-338.15 K, and the Apelblat equation, Van′t Hoff equation, and polynomial equation were employed for thermodynamic correlation of the solubility data. The results showed that the Apelblat equation had the smallest error and optimal precision (fitting coefficient: 0.999 64); the calculated dissolution enthalpy and entropy were 11.265 0 kJ·mol−1 and 14.872 6 J·mol−1·K−1, respectively, confirming the dissolution process as endothermic and non-spontaneous. Subsequently, the effects of cooling rate and stirring rate on the metastable zone width (MSZW) were investigated, and the Nývlt theory, self-consistent Nývlt-like theory, and 3D nucleation theory model were applied for MSZW prediction and comparative analysis. It was found that increasing temperature, decreasing cooling rate, or increasing stirring rate significantly narrowed the MSZW, and the self-consistent Nývlt-like theory model exhibited the best predictive performance and applicability (fitting coefficient: 0.9). Finally, a quantitative correlation between MSZW, saturation temperature, and cooling rate was constructed based on this model, providing critical theoretical basis and data support for the optimal design of industrial crystallization process parameters (e.g., cooling program, stirring intensity).

       

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