Application of Regular Solution Theory to Vapor-Liquid Equilibria of Cryogenic Fluids

Abstract

The regular solution theory was applied to predict the vapor-liquid equilibria of cryogenic fluids, such as argon, nitrogen, oxygen, carbon monoxide, carbon dioxide, methane, ethylene, ethane and propane. Whenthe system temperature is sufficiently below the critical temperature of each component, the vapor-liquid equilibria were well predicted by using the liquid properties at the saturation line of pure component. When the system temperature is close to the critical temperature of light component, good results were obtained by adjusting the liquid volume of the light component only. This liquid volume was determined by fitting calculated vapor-liquid equilibrium relations to the experimental results and was generalized as a smoothed curve. This generalized curvewasalso useful in estimating the hypothetical liquid volume.Vapor-liquid equilibria involving a supercritical component were predictable by using the hypothetical liquid fugacity and the solubility parameter obtained based on the generalized curve for the adjusted liquid volume.