四丁基氯化铵半笼型水合物的相平衡模型

Modeling Phase Equilibria of Semiclathrate Hydrates Formed with Tetrabutylammonium Chloride Solutions

本文在范德瓦尔-普朗特理论的基础上,考虑了四丁基氯化铵(TBAC)水合物的结构特征,建立了TBAC半笼型水合物相平衡模型。模型确定了水在空水合物晶格的蒸汽压及兰格缪尔常数与TBAC浓度的关系,引用e-NRTL模型和PR气体状态方程分别计算液相组分活度系数和客体分子气相逸度。同时,本文在280.1 K^293.6 K温度范围和0.337 MPa^7.017 MPa压力范围内预测了TBAC质量浓度范围为4.34%~34%的溶液体系下TBAC+CH4、TBAC+CO2半笼型水合物的相平衡条件,预测压力与实验数据的平均绝对偏差分别为3.2637%和9.2258%。预测结果与实验数据吻合较好。

Based on the van der Waals-Platteeuw （vdW-P） theory and the hydrate structure of tetrabutylammonium chloride （TBAC）, a thermodynamic approach is proposed to determine the phase equilibrium conditions of TBAC semiclathrate hydrates in this work. Two modifications for evaluations of vapor pressure of water in the empty hydrate lattice and Langmuir constants relating to the salt concentration in aqueous solution and temperature are proposed. To obtain the activity coefficients of species in the aqueous phase and the fugacity of gaseous hydrate former in gas phase, the electrolyte-Non-Random Two-Liquid （e-NRTL） activity model and Peng-Robinson equation of state （PR-EoS） are employed, respectively. Additionally, the model predicted phase equilibrium conditions for hydrates of TBAC ＋ CH4 and TBAC ＋ CO2 over temperature, pressure, and salt concentration ranges from 280.1 K to 293.6 K, from 0.337 MPa to 7.017 MPa, and from 4.34% to 34%, respectively. It is shown that agreement of predicted data with experimental data is satisfactory, with average absolute pressure deviation 3.2637% and 9.2258% for hydrates of TBAC ＋ CH4 and TBAC ＋ CO2, respectively.