TBAB水溶液体系中半笼型水合物的相平衡预测模型

Prediction of the phase equilibrium of semi-clathrate hydrate in TBAB aqueous solution

四丁基溴化铵(TBAB)是一种广泛使用的水合物促进剂,可以显著降低水合反应的形成条件。针对TBAB水溶液中离子与溶剂间较强的相互作用力,采用电解质NRTL方程确定液相组分的活度系数,结合含TBAB水合物的晶体结构特征和Chen-Guo水合物模型,建立了TBAB水溶液体系中水合物形成热力学条件的预测模型。与TBAB质量分数为5%~60%的221个实验数据点进行对比分析,结果显示温度平均相对误差为0.112%,预测值与实验数据具有较好的一致性。通过关联混合电解质体系下盐-溶剂间的交互作用参数,该模型还可进一步扩展到TBAB+NaCl复合盐体系下水合物相平衡条件的预测。在TBAB质量分数范围为5%~20%、NaCl质量分数为3.5%~10%的复合盐溶液体系中,CO_(2)形成半笼型水合物的相平衡条件的实验值与预测值的温度偏差范围为0.01~1.17 K,二者比较吻合。本模型可以为水合物法气体分离、气体储运等技术的实际应用和工艺包开发提供理论基础。

Tetrabutyl ammonium bromide(TBAB)is a widely used hydration promoter that can significantly reduce the formation conditions of hydration reactions.Considering the strongly interactive forces between ions and solvent in TBAB aqueous solution,the electrolyte NRTL equation was adopted for determining the activity coefficient in liquid phase.Coupled with the lattice structure of TBAB hydrate and the Chen-Guo hydrate model,a thermodynamic model for predicting the phase equilibrium conditions of TBAB semi-clathrate hydrate was proposed.The predictions were in good agreement with 221 experimental data points with concentrations of TBAB in the range of 5%—60%(mass).The average relative deviation for equilibrium temperatures is only 0.112%.In addition,the developed model could be further extended for predicting the phase equilibrium conditions of CO_(2)semi-clathrate hydrate with additives of TBAB and NaCl by correlating the interactive parameters of salts-solvent in mixed electrolytes systems.Using the proposed model,the phase equilibrium conditions of TBAB+NaCl+CO_(2)semi-clathrate were predicted over TBAB mass fraction ranging from 5%to 20%,and NaCl mass fraction ranging from 3.5%to 10%.The results show that a good agreement was reached between the predictions and experimental data,with the temperature deviations ranging from 0.01 to 1.17 K.This model can provide a theoretical basis for the practical application of hydrate gas separation,gas storage and transportation,and the development of process packages.