非对称烷烃体系气液相平衡预测模型的改进

Modification of vapor-liquid equilibrium prediction model for asymmetric alkane systems

针对高度非对称烷烃体系,对EOS-G^E气液相平衡预测模型加以改进,其中,状态方程采用考虑体积平移参数的PR-EOS,G^E通过UNIFAC溶液模型计算。针对基团贡献法中假设"溶液中所有基团各向同性"的不足,采用体积参数非线性加和的方式对UNIFAC模型中组合活度系数加以改进。通过对比原始UNIFAC模型和改进UNIFAC模型的预测误差发现,当体系中轻组分含量较低时,原始UNIFAC模型和改进UNIFAC模型对体系泡点预测精度相当;当体系中轻组分含量较高时,原始UNIFAC模型泡点预测值远远低于实验值,而改进UNIFAC模型泡点预测值与实验值高度吻合。模型的改进不仅提高了非对称烷烃体系气液相平衡的预测精度,而且拓展了EOS-G^E模型的应用范围。

In this paper, the EOS-G^E vapor-liquid equilibrium prediction model was modified so as to be suitable for highly asymmetric alkane systems. The volume translated PR-EOS is adopted as the equation of state, and GE is calculated by the UNIFAC solution model. In the group contribution method, it is assumed that all groups in the solution are isotropic. To eliminate the shortage of this assumption, the combined activity coefficient of UNIFAC model was modified by the nonlinear sum of volume parameters. The original and the modified UNIFAC model were compared in term of prediction error. It is indicated that when the content of light components in the systems is low, the prediction accuracy of bubble point by two models is about the same. When the content of light components in the systems is high, the predicted bubble point of the original UNIFAC model is much lower than the measured value, and that of the modified UNIFAC model is consistent with the measured value. Based on the modification of EOS-G^E vapor-liquid equilibrium prediction model, the prediction accuracy of vapor-liquid equilibrium of asymmetric alkane systems is improved, and the application range of EOS-G^E model is extended.