Chinese Journal of Chemical Engineering ›› 2020, Vol. 28 ›› Issue (9): 2391-2408.doi: 10.1016/j.cjche.2020.03.039

• Chemical Engineering Thermodynamics • Previous Articles     Next Articles

Thermodynamic modeling and phase diagram prediction of salt lake brine systems. I. Aqueous Mg2+-Ca2+-Cl- binary and ternary systems

Huan Zhou, Xiaolong Gu, Yaping Dai, Jingjing Tang, Jian Guo, Guangbi Li, Xiaoqin Bai   

  1. College of Chemical Engineering and Materials Science, Tianjin Key Laboratory of Marine Resources and Chemistry, Tianjin University of Science and Technology, Tianjin 300457, China
  • Received:2020-02-10 Revised:2020-03-25 Online:2020-09-28 Published:2020-10-21
  • Contact: Huan Zhou
  • Supported by:
    The authors gratefully thank the financial support of the National Natural Science Foundation of China (U1407204, U1707602) and also the Yangtze Scholars and Innovative Research Team in University of Education of China; the Innovative Research Team of Tianjin Municipal Education Commission (TD12-5004), and the Foundation of Tianjin Key Laboratory of Marine Resources and Chemistry (201602).

Abstract: Salt lake brine is a complex salt-water system under natural environment. Although many models can express the thermodynamic properties and phase equilibrium of electrolyte aqueous solution, the multi-temperature characteristics and predictability are still the goals of model development. In this study, a comprehensive thermodynamic model system is re-established based on the eNRTL model and some improvements: (1) new expression of long-range electrostatic term with symmetrical reference state is proposed to handle the electrolyte solution covering entire concentration range; (2) the temperature dependence of the binary interaction parameters is formulated with a Gibbs Helmholtz expression containing three temperature coefficients, the liquid parameters, which associated with Gibbs energy, enthalpy, and heat capacity contribution; and (3) liquid parameters and solid species data are regressed from properties and solubility data at full temperature range. Together the activity coefficient model, property models and parameters of liquid and solid offer a comprehensive thermodynamic model system for the typical bittern of MgCl2-CaCl2-H2O binary and ternary systems, and it shows excellent agreement with the literature data for the ternary and binary systems. The successful prediction of complete phase diagram of ternary system shows that the model has the ability to deal with high concentration and high non-ideality system, and the ability to extrapolate the temperature.

Key words: Aqueous electrolytes, Comprehensive thermodynamic model, MgCl2-CaCl2-H2O, Phase diagram, Thermodynamic properties