Phase Equilibria for Natural-Gas Production. Calculation of Multicomponent Thermodynamic Properties Near-to and Far-From Critical

摘要：9911744J。普鲁斯尼茨。在美国，天然气行业是一个每年数十亿美元的行业。天然气生产效率的小幅提高可以带来非常大的经济优势，并显著节约有限的自然资源。从天然气井高效生产需要在相当范围的温度和广泛的组成和压力范围(包括临界区)上定量了解混合烃类汽液平衡。由于有限种类的合成AN天然气混合物的实验数据，有一个很好的相行为的唯象图景；但是，为了计算这些平衡，我们没有一个令人满意的分子热力学方法，它在所有实际感兴趣的区域都是可靠的，即在接近和远离(汽液)临界区。这项研究旨在利用应用统计力学的最新结果来产生这样一种方法：Chapman，Radocz等人发展的(短)链流体的Wertheim理论，以及Lue和Prausnitz最近发展和扩展的White顶部混合物的重整化群(RG)理论。RG理论的本质是将密度涨落的状态修正包括在“经典”状态方程中，这些修正在远离临界点的条件下不重要，但在临界点附近变得非常重要。怀特的方法(由Lue和Prausnitz推广)以一种相对简单的方式实现了这一点，从而大大提高了计算接近和远离临界区的相平衡的能力。这项工作的最终目标是提出一种基于理论的、面向工程的计算机化程序，供化石燃料行业的设计工程师直接使用。这项研究将产生新的工程科学知识。它将扩展、修改和综合统计力学的最新进展，走向重要的应用。

ABSTRACTCTS-9911744J. PrausnitzU. of California @ BerkeleyThe natural-gas industry in the US is a multibillion-dollar per year industry. Small increases in efficiency in natural-gas production can bring very large financial advantages and appreciable conservation of a finite natural resource.Efficient production from natural-gas wells requires a quantitative understanding of mixed-hydrocarbon vapor-liquid equilibria over a fair range of temperature and a wide range of composition and pressure, including the critical region. Because experimental data are available for limited variety of synthetic an natural gas mixtures, there is a good phenomenological picture of phase behavior; but, for calculating these equilibria, we do not have a satisfactory molecular-thermodynamics method that is reliable in all regions of practical interest, that is, near-to and far-from the (vapor-liquid) critical region. This research is directed at producing such a method using recent results from applied statistical mechanics: Wertheim's theory for (short) chain fluids as developed by Chapman, Radocz and others, coupled with renormalized-group (RG) theory of White recently developed and extended top mixtures by Lue and Prausnitz.The essence of RG theory is to include in a "classical" equation of state corrections for density fluctuations that are not important at conditions remote from critical but become very important near the critical point. White's method (as extended by Lue and Prausnitz) does that in a relatively simple way, thereby much improving the ability to calculate phase equilibria near to and far from the critical region.The ultimate goal of this work is to present a theoretically based, engineering-oriented computerized procedure for direct use by design engineers in the fossil-fuel industries. This research will produce new engineering-science knowledge. It will extend, modify and synthesized recent advances in statistical mechanics toward significant application.