基于PC-SAFT方程研究多孔介质中水合物相平衡的预测模型

Hydrate Formation Phase Equilibrium Model in the Porous Media Based on PC-SAFT Equation of State

对多孔介质中水合物的形成条件预测模型进行了研究.利用微扰链-统计缔合流体理论状态方程(PC-SAFT)结合van der Waals-Platteuw模型和毛细管Kelvin模型,建立了用于多孔介质水合物体系的相平衡预测模型.在此模型基础上,针对甲烷水合物和CO2水合物对界面张力作了进一步的研究.根据多孔介质水合物相平衡实验数据回归得到不同条件下的界面张力值,结果发现,界面张力随温度升高而单调升高,随孔径的增大而单调减小,并且具有较好的线性关系.提出了界面张力与温度和孔径的关联计算公式,并采用遗传算法优化回归了公式的参数.以此关联公式为基础使改进后的模型具有良好的计算精度,在所考察温度和孔径范围内,对于甲烷水合物和CO2水合物的相平衡预测压力与实验数据的绝对平均偏差分别为1.66%和2.76%.

The thermodynamic model of hydrate equilibrium formation conditions in the porous media was studied.Based on the penturbed chain-statistical associating fluid theory（PC-SAFT） equation of state（EOS）,combining with van der Waals-Platteuw model of hydrate and Kelvin equation of capillary,a phase equilibrium computational model was built.Based on this model,the surface tension was further studied for methane and CO2 hydrate.Firstly,values of surface tension were regressed from experimental equilibrium formation conditions.It is shown that the surface tension increases with the temperature increasing and decreases with the pore radius increasing,moreover,it shows a near-line trend.Thus,the surface tension function of temperature and pore radius was proposed.Parameters of the function were optimized from experimental data with genetic algorithm.The result shows that the revised model with the correlated surface tension has a distinct improvement in the predicting the hydrate equilibrium formation conditions,average absolute deviations are 1.66% and 2.76% for methane and CO2 hydrates,respectively.