含盐溶液汽液平衡预测

本文提出一种新的预测含盐溶液汽液平衡的方法。对Pitzer(1980年)模型进行扩展后,将其简化成单参数形式,推广至多元电解质溶液;经过适当假定,得到计算含盐挥发性强电解质和水体系及含盐水醇体系的活度系数公式,这些公式仅含有二元相互作用参数;由二元溶液的活度关联出参数后,可用于含盐体系各温度下汽液平衡的预测。关联了四十个二元电解质水溶液及七个电解质甲醇溶液298.15K时的简化Pitzer方程的单参数;用以推算六个水盐体系和二个甲醇盐体系在320-403K的蒸汽压,得到满意的结果,182个数据点的平均偏差小于0.65kPa;用以预测五个不同类型的含盐三元体系的等温、等压汽液平衡,所得的平均偏差对于汽相组成、沸点、压力分别为0.015、1K、1.92kPa。

PREDICTION OF VAPOR-LIQUID EQUILIBRIA IN SALT-CONTAINING SYSTEMS

A new method for the prediction of salt effects on VLE is proposed. The model of Pitzer(l980)is extended to aqueous multicomponent electrolyte systems and mixed solvent/salt systems. After reasonable simplification, the activity coefficient expressions with only one parameter for each binary electrolyte solvent action are derived for the solvent and volatile solute. It is possible to predict the VLE of salt containing systems by using these parameters which can be correlated with binary solution properties. The solvent activities of binary electrolyte solutions, including 40 sets of aqueous systems and 7 sets of methanol solution systems, are correlated to obtain the single parameter of the simplified Pitzer's model. Application of this model to estimate the vapor pressure depression in 320-403 K of LiCl, NaCl, KAc, HC1, CaCl_2, MgCl_2 binary aqueous solutions and LiCl, CaCl_2 binary methanol solutions has shown high accuracy. The total mean of absolute deviation of 182 data points is below 0.65 kPa. By the extended model and parameters correlated at 298.15K, the VLE of five different type of ternary salt-containing systems, H_2O+CaCl_2+MgCl_2, H_2O+KC1+HC1, H_2O+CaCl_2+HCl, H_2O+LiCl+CH_3OH, H_2O+CaCl_2+CH_3OH, are predicted with the total means of absolute deviation of 0.015 in vapor phase mole fraction, of 1K in the boiling point, and of 1.92 kPa in the vapor pressure.