硝酸盐型卤水体系的综合热力学模型与多温相图预测

硝酸盐型卤水是盐湖卤水、 硝酸盐工业、 废水处理中普遍遇到的电解质溶液体系. 硝酸盐具有极高的溶解度, 实现硝酸盐型复杂电解质体系物性和相平衡的精准热力学表达依然具有挑战性. 以煤化工废水的典型体系Na⁺//NO₃^- , Cl^-, SO₄^{2 -} -H₂O为对象, 以改进的eNRTL模型为基础, 由活度系数模型、 溶液物性模型、 物种热力学模型和固液相平衡模型构成了电解质体系的综合热力学模型. 利用二元体系的冰点、 饱和蒸汽压、 等压摩尔热容、 活度系数和渗透压系数等物性数据和三元体系等温相平衡数据, 采用多目标优化方法, 获得了表达研究体系的多温特性的12组液相特征参数和7个固相物种的热力学参数. 据此完成了3个二元体系、 3个三元体系等温相平衡的准确计算和三元、 四元完整相图的预测, 适用温度达到实验所及的全部温度范围(254.65~543.15 K)； 适用浓度达到饱和程度, 其中NaNO₃的浓度高达226.88 mol/kg. 三元、 四元体系的多温相图预测结果与实验数据相吻合, 并给出了9个三元、 5个四元体系零变点的完整信息.

Comprehensive Thermodynamic Model and Polythermal Phase Diagram Prediction of Nitrate Type Brine Systems

Nitrate type aqueous electrolyte systems are encountered in salt lake brine， nitrate industries and wastewater treatment. Due to the high solubility of nitrate， it is still challenging to achieve accurate thermodynamic expression of physical properties and phase equilibrium of nitrate complex electrolyte system. The Na⁺//NO₃^-， Cl^-， SO₄^{2 -} -H₂O typical system of coal chemical wastewater was selected as the research object. Based on the improved eNRTL model， the comprehensive thermodynamic model of electrolyte system was composed of activity coefficient model， liquid properties model， species thermodynamic data model， and solid-liquid phase equilibrium model. Based on the freezing points， saturated vapor pressure， isobaric molar heat capacity， activity coefficients and osmotic pressure coefficients of binary systems and the isothermal phase equilibrium data of ternary systems， 12 sets of liquid parameters and thermodynamic parameters of 7 solid species were obtained by multi-objective fitting. The complete multi-temperature phase diagrams of 3 binary systems， 3 ternary systems and one quaternary system were calculated and predicted. The applicable temperature reached all the experimental temperature ranges， namely， 254.65—543.15 K， and the applicable concentration reached saturation， the concentration of NaNO₃ reached 226.88 mol/kg. The predicted results of multi temperature phase diagrams of ternary and quaternary systems are in good agreement with the experi- mental data. The results expand the expression ability of electrolyte model in ultra-concentrated and multi- temperature complex systems， and the model and parameters can be used in chemical process of nitrate- containing system， wastewater treatment， salt lake brine resource development and other processes.