Vapor-Liquid Equilibria Of A Methane-Condensate System Using Chromatographic Assays
Authors: Stuckey A. Nelson , Edmister Wayne C. 
Published: December 2007

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Abstract
Vapor-liquid equilibrium K-values and phase densities have been obtained experimentally for a Methane-Morrow condensate system at 150 and 250 degrees F and pressures from 100 psia to the dew or critical points of the system at these temperatures. Samples of the equilibrium vapor and liquid phases are taken from the Michels-design equilibrium cell into calibrated density traps, after reaching equilibrium by an experimental procedure that includes recirculation of the vapor phase by means of a magnetic pump. The material from the sample traps was withdrawn and its mass and composition were determined. The equilibrium densities and K-values were calculated from the mass and composition data of the individual phases.
An outstanding feature of this investigation is the use of a single chromatograph and set of operating conditions for the composition analysis of the equilibrium phases. Some 36 component peaks ranging from methane to C 20 were identified individually in the condensate and the chromatograph was calibrated for these components. Other peaks were grouped according to then known boiling point range.
The K-values and phase density data obtained in this investigation are summarized and the technique used for the composition assay of the equilibrium phases is described.

Introduction
There are relatively few systems whose equilibrium relations can be calculated from Raoult's and Dalton's laws. On the other hand there are a large number of industrially important systems whose equilibrium relations cannot be predicted from purely theoretical or empirical considerations and which must be obtained by direct experimental investigation.
The phase behavior of complex hydrocarbon systems is of both theoretical and practical interest; theoretical because of the need for the development of better correlations for the thermodynamic properties of coexisting gas-liquid phases; and practical because of the need for vapor-liquid K-values and phase densities for design calculations and economic studies.
During the past 30 years much effort has been devoted to the study of the volumetric and phase behavior of pure paraffin hydrocarbons and of binary and ternary mixtures of these compounds. The objective of many of these studies was to use this binary and ternary data to predict the behavior of more complex mixtures.