CIESC Journal ›› 2020, Vol. 71 ›› Issue (1): 209-215.DOI: 10.11949/0438-1157.20191148

• Thermodynamics • Previous Articles     Next Articles

Phase equilibria of quaternary system CaCl2-CaSO4-CaB6O10-H2O at 308.15 K

Fei YUAN(),Jiangtao SONG,Jiayin HU,Yafei GUO,Shiqiang WANG,Tianlong DENG()   

  1. College of Chemical Engineering and Materials Science, Tianjin University of Science and Technology, Tianjin 300457, China
  • Received:2019-10-09 Revised:2019-11-09 Online:2020-01-05 Published:2020-01-05
  • Contact: Tianlong DENG

四元体系CaCl2-CaSO4-CaB6O10-H2O 308.15 K相平衡研究

袁菲(),宋江涛,胡佳音,郭亚飞,王士强,邓天龙()   

  1. 天津科技大学化工与材料学院,天津 300457
  • 通讯作者: 邓天龙
  • 作者简介:袁菲(1994—),女,博士研究生,987632955@qq.com
  • 基金资助:
    国家自然科学基金项目(21773170);湖北省技术创新专项重大项目(2019ACA149);教育部创新团队资助计划(IRT_17R81)

Abstract:

In this work, an isothermal dissolution method was used to study the phase equilibria for the quaternary system (CaCl2-CaSO4-CaB6O10-H2O) at 308.15 K. The solubilities, densities, refractive indices and pH were investigated experimentally. According to the experimental data, the phase diagram, water-phase diagram and the diagrams on physicochemical properties including density, refractive index and pH against composition were plotted. The phase diagrams for the quaternary system at 308.15 K include one invariant point, three univariate solubility curves and three crystalline regions corresponding to CaCl2·4H2O, gypsum (CaSO4·2H2O) and gowerite (CaB6O10·5H2O). The crystallizing area of gypsum (CaSO4·2H2O) is the largest, the gowerite (CaB6O10·5H2O) is the second, and the CaCl2·4H2O is the smallest, indicating that the gypsum is most easily crystallized. In addition, the quaternary system was of the hydrate type I, neither double salt nor solid solution were formed. The physicochemical properties change regularly with the increasing of CaCl2 concentration and appeared a turning point at invariant point. The distributive behaviors of density and refractive index against the concentration of calcium chloride in the equilibrium solution are similar. On the contrary, the change law of pH is opposite. The phase equilibrium study of quaternary system (CaCl2-CaSO4-CaB6O10-H2O) will provide a theoretical basis for the development and utilization of calcium and boron resources in oilfield brines.

Key words: salt-water system, phase equilibria, the method of isothermal dissolution equilibrium, calcium borate

摘要:

采用等温溶解平衡法研究了四元体系CaCl2-CaSO4-CaB6O10-H2O在308.15 K下的稳定相平衡。测定了该体系的溶解度及平衡溶液的物化性质(包括折射率、密度和pH)。根据实验数据,分别绘制了该四元体系的干基图、水图以及相应的物化性质–组成图。研究结果表明:该体系在308.15 K时有1个共饱点(CaCl2·4H2O + CaSO4·2H2O + CaB6O10·5H2O),3条单变量溶解度曲线,3个单盐结晶区,分别对应于CaCl2·4H2O、硬石膏(CaSO4·2H2O)和高硼钙石(CaB6O10·5H2O)。其中,硬石膏CaSO4·2H2O结晶区最大、高硼钙石CaB6O10·5H2O结晶区次之,而CaCl2·4H2O结晶区最小,表明硬石膏最易于结晶析出。此外,该四元体系在308.15 K下没有复盐和固溶体生成,属于简单水合物I型。平衡液相的物化性质随着CaCl2浓度的增大呈规律性变化,并在共饱点处发生转折。其中,折射率和密度的变化规律相近,而pH的变化规律则与之相反。对该四元体系的稳定相平衡进行研究,将为综合开发利用油田卤水中的钙、硼等资源提供理论依据。

关键词: 水盐体系, 相平衡, 等温溶解平衡法, 钙硼酸盐

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