Abstract The stable phase equilibrium data of Mg2+, NH4+//Cl−, SO42−−H2O quaternary interaction system and its four ternary subsystems at 363.15 K were determined by isothermal dissolution equilibrium method, and the corresponding stable phase diagrams of the above systems were plotted. According to the phase diagram, there are seven solid phase crystalline regions, which correspond to MgSO4·(NH4)2SO4·6H2O, MgSO4·6H2O, MgSO4·4H2O, MgCl2·6H2O, (NH4)2SO4, MgCl2·NH4Cl·6H2O and NH4Cl, respectively. MgSO4·(NH4)2SO4·6H2O has the largest crystalline region among these crystalline regions, which indicates that the double salt MgSO4·(NH4)2SO4·6H2O is the easiest to crystallize out. Based on the extended Pitzer model, the solubility data of the ternary subsystems and the quaternary system were calculated. The results showed that the calculated values were close to the experimental values. According to the comparison between the stable phase diagram of the quaternary system at 298.15 K and 363.15 K, a new process of preparing N–Mg compound fertilizer (MgSO4·(NH4)2SO4·6H2O) at 298.15 K and crystallizing NH4Cl at 363.15 K by using ammonium sulfate and magnesium chloride as raw materials was designed in this paper and the process route was verified by experiment.

中文翻译：

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Mg2+, NH4+//Cl−, SO42−−H2O四元体系在363.15 K的相平衡研究及其应用

摘要 采用等温溶解平衡法测定了Mg2+、NH4+//Cl−、SO42−−H2O四元相互作用体系及其四个三元子系统在363.15 K时的稳定相平衡数据，并绘制了上述体系对应的稳定相图. 根据相图，有七个固相晶区，分别对应于MgSO4·(NH4)2SO4·6H2O、MgSO4·6H2O、MgSO4·4H2O、MgCl2·6H2O、(NH4)2SO4、MgCl2·NH4Cl·6H2O和NH4Cl ， 分别。在这些晶区中，MgSO4·(NH4)2SO4·6H2O的晶区最大，说明复盐MgSO4·(NH4)2SO4·6H2O最容易结晶出来。基于扩展的Pitzer模型，计算了三元子系统和四元体系的溶解度数据。结果表明，计算值与实验值接近。根据 298.15 K 和 363.15 K 四元系稳定相图的比较，提出了一种在 298.15 K 制备 N-Mg 复合肥（MgSO4·(NH4)2SO4·6H2O）和在 363.15 K 结晶 NH4Cl本文设计了以硫酸铵和氯化镁为原料的工艺路线，并通过实验验证了该工艺路线。