Yang Yafan, Narayanan Nair Arun Kumar, Sun Shuyu
Physical Science and Engineering Division (PSE), Computational Transport Phenomena Laboratory, King Abdullah University of Science and Technology (KAUST) , Thuwal, Jeddah 23955-6900, Saudi Arabia.
J Phys Chem B. 2017 Oct 19;121(41):9688-9698. doi: 10.1021/acs.jpcb.7b08118. Epub 2017 Oct 10.
We perform molecular dynamics simulation study of CO, methane, and their mixture in the presence of brine over a broad range of temperature (311-473 K), pressure (up to about 100 MPa), and NaCl concentration (up to about 14 wt %). The general decrease in the interfacial tension (IFT) values of the CH-brine system with pressure and temperature is similar to that obtained for the corresponding CH-water system. The IFT of methane and brine is a linearly increasing function of salt concentration, and the resulting slopes are dependent on the pressure. A similar behavior as methane is observed for such systems containing CO and CO-CH mixture. The IFT of CO and brine increases linearly with increasing salt content; however, the resulting slopes are independent of pressure. The simulations show that the presence of CO decreases the IFT values of the CH-water and CH-brine systems, but the degree of reduction depends on the amount of CO in each sample, which is consistent with experimental evidence. These IFT values show a linear correlation with the amount of CO, and the resulting slopes are dependent on the temperature and pressure. Furthermore, our results for the mole fractions of the different species in the CO-CH-water system at 323 K and 9 MPa are in agreement with those of experiments. The mole fractions of methane and CO in the water-rich phase decrease with increasing salt concentration, whereas that of HO in the methane- or CO-rich phases remains almost unaffected in all of the studied cases. Our results could be useful because of the importance of carbon dioxide sequestration and shale gas production.
我们对一氧化碳、甲烷及其混合物在盐水存在下，在广泛的温度范围（311 - 473K）、压力（高达约100MPa）和氯化钠浓度（高达约14wt%）下进行了分子动力学模拟研究。CH - 盐水体系的界面张力（IFT）值随压力和温度的总体降低与相应的CH - 水体系相似。甲烷与盐水的IFT是盐浓度的线性递增函数，所得斜率取决于压力。对于含有一氧化碳和一氧化碳 - 甲烷混合物的此类体系，观察到与甲烷类似的行为。一氧化碳与盐水的IFT随盐含量增加而线性增加；然而，所得斜率与压力无关。模拟结果表明，一氧化碳的存在会降低CH - 水和CH - 盐水体系的IFT值，但降低程度取决于每个样品中一氧化碳的含量，这与实验证据一致。这些IFT值与一氧化碳的含量呈线性相关，所得斜率取决于温度和压力。此外，我们在323K和9MPa下对一氧化碳 - 甲烷 - 水体系中不同物种摩尔分数的研究结果与实验结果一致。富水相中甲烷和一氧化碳的摩尔分数随盐浓度增加而降低，而在富甲烷或富一氧化碳相中HO的摩尔分数在所有研究情况下几乎不受影响。由于二氧化碳封存和页岩气生产的重要性，我们的结果可能会有所帮助。
