天然气主要组分流体混合物的PVTx和V-L相平衡性质预测:一种通用Helmholtz状态方程的方法

发布时间：2018-05-27 20:12

本文选题：天然气 + 状态方程　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：天然气是自然界中一种重要的地质流体,主要组分有CH4、C2H6、C3H8、CO2和N2。其热力学性质,特别是温度-压力-体积-组成(PVTx)和气-液(V-L)相平衡性质,在油气包裹体研究中是确定捕获温度与捕获压力的基础。虽然前人做了大量的实验研究,但是这方面的热力学性质数据仍然不多,覆盖的温度-压力-组成范围有限,而在实验数据基础上的有良好预测性的状态方程可以很好地计算这些性质,弥补这方面的不足。本文在Sun and Ely(2004)和Lemmon and Jacobsen(1999)热力学模型的基础上,建立了一个通用的天然气流体混合物(CH4-C2H6-C3H8-CO2-N2)Helmholtz自由能状态方程。该方程形式简单统一,精度高,适用范围广。方程中的参数通过对大量PVTx和V-L相平衡实验数据拟合而得,对于混合物,仅仅需要二元体系的实验数据拟合混合参数。结果表明,该方程不仅可以用来预测天然气主要组分流体混合物(CH4-C2H6-C3H8-CO2-N2)的PVTx性质,还可以计算V-L相平衡性质,适用于从三相点温度到650 K,压力小于2000 bar的温压空间。方程的精度高于Sun and Ely(2004)Helmholtz自由能状态方程,与Kunz et al.(2007)的GERG-2004状态方程的精度相当,但是比后者简单,因而可以很好地满足地质和化工等行业的应用需要。在该方程中,如果结合理想Helmholtz自由能部分,还可以精确地预测该混合物的其他热力学性质,如:熵、焓、热容、化学势、活度、逸度、吉布斯自由能、声速等。整个状态方程的计算程序采用国际上流行的计算语言Fortran95编写,结构简单,可以方便相关研究的需要。
[Abstract]:Natural gas is an important geological fluid in nature. The main components are Ch _ 4C _ 2H _ 6C _ 3H _ 8 CO _ 2 and N _ 2. The thermodynamic properties, especially the phase equilibrium properties of temperature-pressure-volume-composition PVTx and gas-liquid V-L), are the basis for determining the capture temperature and pressure in the study of hydrocarbon inclusions. Although a lot of experimental studies have been done, the thermodynamic properties are still limited, and the range of temperature-pressure-composition is limited. On the basis of experimental data, the state equation with good predictability can well calculate these properties and make up for these shortcomings. Based on the thermodynamic model of Sun and Elycan 2004) and Lemmon and Jacobsen 1999), a general free energy equation of state for natural gas mixture Ch _ 4-C _ 2H _ 6-C _ 3H _ 8-CO _ 2-N _ 2 (Helmholtz) has been established. The equation is simple and uniform, with high precision and wide range of application. The parameters in the equation are obtained by fitting a large number of PVTx and V-L phase equilibrium experimental data. For the mixture, only the binary system experimental data are required to fit the mixing parameters. The results show that the equation can not only be used to predict the PVTx properties of CH4-C2H6-C3H8-CO2-N2], but also can be used to calculate the V-L phase equilibrium, which is suitable for the temperature and pressure space from three-phase temperature to 650K and pressure less than 2000 bar. The accuracy of the equation is higher than that of the Sun and Ely(2004)Helmholtz free energy equation of state, which is similar to that of the GERG-2004 equation of state of Kunz et al. 2007, but simpler than that of the latter, so it can meet the needs of geology and chemical industry. The other thermodynamic properties of the mixture, such as entropy, enthalpy, heat capacity, chemical potential, activity, fugacity, Gibbs free energy, sound velocity and so on, can also be accurately predicted by combining the ideal Helmholtz free energy. The calculation program of the whole equation of state is compiled by the international popular computing language Fortran95, which is simple in structure and can be used to meet the needs of related research.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.13

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