Calculation of vapor–liquid equilibrium and PVTx properties of geological fluid system with SAFT-LJ EOS including multi-polar contribution. Part III. Extension to water–light hydrocarbons systems
Calculation of vapor–liquid equilibrium and PVTx properties of geological fluid system with SAFT-LJ EOS including multi-polar contribution. Part III. Extension to water–light hydrocarbons systems
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DOI：
10.1016/j.gca.2013.10.027
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发表时间：
2014-01
影响因子：
5
通讯作者：
Rui Sun;Shaocong Lai;J. Dubessy
中科院分区：
文献类型：
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作者：
Rui Sun;Shaocong Lai;J. Dubessy
将Sun和Dubessy（2010，2012）改进的SAFT-LJ状态方程扩展到水轻烃体系。轻烃（包括CH_4、C_2 H_6、C_3 H_8和nC_4 H_（10））被模拟为无多极矩的链状分子。该状态方程考虑了水-轻烃体系中存在的分子形状和主要的分子间相互作用（包括Lennard-Jones链段间的排斥力和吸引力、氢键力和水分子间的多极相互作用）对剩余Helmholtz能的贡献。根据水-烃二元体系在汽液平衡下的互溶度数据，计算了H_2 O-CH_4、H_2 O-C_2 H_6、H_2 O-C_3 H_8和H_2 O-nC_4 H_（10）相互作用的可调参数。与实验数据的比较表明，SAFT-LJ状态方程能较好地描述水-轻烃二元体系在较宽的P-T范围内的汽液（和液液）平衡。该方程对甲烷、乙烷、丙烷和水互溶度的计算精度一般在实验不确定度范围内。此外，该模型能够准确地预测由水、轻烃和CO2组成的多组分体系的汽液平衡和PVTx性质。该状态方程是SAFT型状态方程中第一个在宽的P-T范围内定量计算水和轻烃互溶度的状态方程。研究结果表明，基于分子的状态方程结合传统的混合规则可以很好地描述水-轻烃混合物等高度非理想体系的热力学行为，但在临界区，该分析模型不能考虑长程密度波动。
The SAFT-LJ EOS improved by Sun and Dubessy (2010, 2012) is extended to water–light hydrocarbon systems. Light hydrocarbons (including CH4, C2H6, C3H8andnC4H10) are modeled as chain molecules without multi-polar moments. The contributions of the shape of molecules and main intermolecular interactions existing in water–light hydrocarbon systems (including repulsive and attractive forces between Lennard-Jones segments, the hydrogen-bonding force and the multi-polar interaction between water molecules) to the residual Helmholtz energy were accounted for by this EOS. The adjustable parameters for the interactions of H2O–CH4, H2O–C2H6, H2O–C3H8, and H2O–nC4H10pairs were evaluated from mutual solubility data of binary water–hydrocarbon systems at vapor–liquid equilibria. Comparison with the experimental data shows this SAFT-LJ EOS can represent well vapor–liquid (and liquid–liquid) equilibria of binary water–light hydrocarbon systems over a wideP–Trange. The accuracy of this EOS for mutual solubilities of methane, ethane, propane and water is within the experimental uncertainty generally. Moreover, the model is able to accurately predict the vapor–liquid equilibria andPVTxproperties of multi-component systems composed of water, light hydrocarbon as well as CO2. As we know, this EOS is the first one allowing quantitative calculation of the mutual solubilities of water and light hydrocarbons over a wideP–Trange among SAFT-type EOSs. This work indicates that the molecular-based EOS combined with conventional mixing rule can well describe the thermodynamic behavior of highly non-ideal systems such as water–light hydrocarbons mixtures except in the critical region for which long range density fluctuations cannot be taken into account by this analytical model.