化工学报 ›› 2023, Vol. 74 ›› Issue (8): 3256-3265.DOI: 10.11949/0438-1157.20230470

• 热力学 • 上一篇    下一篇

三元体系KCl + CaCl2 + H2O 298.2、323.2及348.2 K相平衡研究及计算

于旭东(), 李琪, 陈念粗, 杜理, 任思颖, 曾英()   

  1. 成都理工大学材料与化学化工学院,四川 成都 610059
  • 收稿日期:2023-05-12 修回日期:2023-06-28 出版日期:2023-08-25 发布日期:2023-10-18
  • 通讯作者: 曾英
  • 作者简介:于旭东(1985—),男,博士,副教授,xwdlyxd@126.com
  • 基金资助:
    国家自然科学基金项目(U21A2017)

Phase equilibria and calculation of aqueous ternary system KCl + CaCl2 + H2O at 298.2, 323.2, and 348.2 K

Xudong YU(), Qi LI, Niancu CHEN, Li DU, Siying REN, Ying ZENG()   

  1. College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059, Sichuan, China
  • Received:2023-05-12 Revised:2023-06-28 Online:2023-08-25 Published:2023-10-18
  • Contact: Ying ZENG

摘要:

采用等温溶解平衡法开展了298.2、323.2、348.2 K三元体系KCl + CaCl2 + H2O相平衡研究,测定了平衡液相组成及密度,采用Schreinemakers湿渣法和X射线粉晶衍射法确定了平衡固相组成。研究发现:298.2 K时,该体系为简单三元体系,无复盐形成,相图由1个三元共饱点、2条单变量曲线和2个结晶相区组成;323.2和348.2 K时,该体系为复杂三元体系,有复盐氯钾钙石(KCl·CaCl2)形成,相图均由2个三元共饱点、3条单变量曲线和3个结晶相区组成。对比该三元体系278.2、298.2、308.2、323.2、348.2 K相图可知:随温度升高,CaCl2结晶形式发生变化,CaCl2·6H2O(278.2、298.2 K)→CaCl2·4H2O(308.2 K)→CaCl2·2H2O(323.2、348.2 K);KCl结晶面积在323.2 K时最大,氯钾钙石结晶面积随温度升高而增大。采用Pitzer-Simonson-Clegg模型进行了三元体系KCl + CaCl2 + H2O(298.2、323.2、348.2 K)热力学计算,理论计算值与实验值吻合较好。

关键词: 相平衡, 溶解性, 水合物, PSC模型, 氯钾钙石

Abstract:

The composition of equilibrium liquid of the ternary system KCl + CaCl2 + H2O were determined by isothermal dissolution method at 298.2, 323.2, and 348.2 K. The density and composition of the equilibirum liquid phase were measured experimentally. The equilibirum solid phase composition was determined by Schreinemakers wet residue method and X-ray diffraction method. It is found that at 298.2 K, the system is a simple ternary system without double salt formation, and the phase diagram consists of one ternary invariant point, two univariate curves and two crystalline phase regions. The ternary system belongs to complex type system with the formation of double salt chlorocalcite (KCl·CaCl2) at 323.2 and 348.2 K. And the phase diagrams consist of two invariant points, three univariate curves and three crystallization regions. By comparing the phase diagrams of the ternary system at 278.2, 298.2, 308.2, 323.2, and 348.2 K, it can be found that with the temperature increasing, the crystallization form of CaCl2 changes from CaCl2·6H2O (278.2, 298.2 K), CaCl2·4H2O (308.2 K) to CaCl2·2H2O (323.2, 348.2 K). The crystallization area of KCl is the largest at 323.2 K, and the size of the double salt chlorocalcite crystallization region increases with the temperature increasing. The thermodynamics calculations of KCl + CaCl2 + H2O at 298.2, 323.2, and 348.2 K were carried out by Pitzer-Simonson-Clegg model, and the calculation values agree well with the experimental values.

Key words: phase equilibria, solubility, hydrate, PSC model, chlorocalcite

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