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

abstractcts - 9911744 j。PrausnitzU。美国的天然气工业是一个每年数十亿美元的产业。天然气生产效率的小幅提高可以带来巨大的经济效益，并对有限的自然资源起到可观的保护作用。天然气井的高效生产需要定量地了解混合碳氢化合物在一定温度范围内的汽液平衡，以及广泛的成分和压力范围，包括关键区域。由于合成和天然气混合物的实验数据有限，所以对相行为有一个很好的现象学描述；但是，对于计算这些平衡，我们还没有一种令人满意的分子热力学方法，这种方法在所有实际感兴趣的区域都是可靠的，即靠近和远离（汽液）临界区域。这项研究的目的是利用应用统计力学的最新成果来产生这样一种方法：由Chapman、Radocz等人提出的Wertheim（短）链流体理论，以及由Lue和Prausnitz最近提出并扩展的White的重整化群（RG）理论。RG理论的本质是在“经典”方程中包含密度波动的状态修正，密度波动在远离临界条件时不重要，但在接近临界点时变得非常重要。White的方法（由Lue和Prausnitz扩展）以一种相对简单的方式做到了这一点，从而大大提高了计算临界区域附近和远离临界区域的相平衡的能力。这项工作的最终目标是提出一个基于理论的、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，使之具有重要的应用价值。

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.