Prediction of the PVTx and VLE properties of natural gases with a general Helmholtz equation of state. Part I: Application to the CH 4 -C 2 H 6 -C 3 H 8 -CO 2 -N 2 system
Prediction of the PVTx and VLE properties of natural gases with a general Helmholtz equation of state. Part I: Application to the CH 4 -C 2 H 6 -C 3 H 8 -CO 2 -N 2 system
复制标题
DOI：
10.1016/j.gca.2017.09.025
复制
发表时间：
2017-12
影响因子：
5
通讯作者：
Shide Mao;Mengxin Lü;Zeming Shi
中科院分区：
文献类型：
--
作者：
Shide Mao;Mengxin Lü;Zeming Shi
建立了一个以Helmholtz自由能为显式变量的通用状态方程（EOS），用于预测天然气主要组分CH 4-C2 H6-C3 H8-CO2-N2流体混合物的压力-体积-温度-组成（PVTx）和汽液平衡（VLE）性质。该状态方程是基于Sun和伊利（2004）对纯组分（CH 4，C2 H6，C3 H8，CO2和N2）的改进状态方程，采用四个混合参数，并包含Lemmon和Jacobsen（1999）提出的简单广义偏离函数。与实验数据的比较表明，该方程能在623 K和1000 bar范围内计算CH 4-C2 H6-C3 H8-CO2-N2流体混合物的PVTx和汽液平衡性质，其误差小于或接近实验误差。根据该状态方程可直接计算出CH 4-C2 H6-C3 H8-CO2-N2体系的等容线，并据此解释相应的流体包裹体显微测温和拉曼分析数据。如果结合流体的理想亥姆霍兹自由能，通用状态方程可以计算其它热力学性质，也可以推广到包括仲烷烃（碳数大于3）和非烷烃组分（如H2S、SO2、O2、CO、Ar和H2O）在内的多组分天然气。这部分工作将在不久的将来完成。
A general equation of state (EOS) explicit in Helmholtz free energy has been developed to predict the pressure–volume-temperature-composition (PVTx) and vapor-liquid equilibrium (VLE) properties of the CH4–C2H6–C3H8–CO2–N2fluid mixtures (main components of natural gases). This EOS, which is a function of temperature, density and composition, with four mixing parameters used, is based on the improved EOS of Sun and Ely (2004) for the pure components (CH4, C2H6, C3H8, CO2and N2) and contains a simple generalized departure function presented by Lemmon and Jacobsen (1999). Comparison with the experimental data available indicates that the EOS can calculate thePVTxand VLE properties of the CH4–C2H6–C3H8–CO2–N2fluid mixtures within or close to experimental uncertainties up to 623 K and 1000 bar within full range of composition. Isochores of the CH4–C2H6–C3H8–CO2–N2system can be directly calculated from this EOS to interpret the corresponding microthermometric and Raman analysis data of fluid inclusions. The general EOS can calculate other thermodynamic properties if the ideal Helmholtz free energy of fluids is combined, and can also be extended to the multi-component natural gases including the secondary alkanes (carbon number above three) and none-alkane components such as H2S, SO2, O2, CO, Ar and H2O. This part of work will be finished in the near future.