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

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

ABSTRACT CTS-9911744 J. Prausnitz U. of California @ Berkeley The 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.