Phase equilibria of non-ideal solutions.

Abstract

In this investigation new and more efficient means for obtaining, processing and screening the urgently needed vapor-liquid equilibrium data were proposed. Experimental vapor-liquid equilibrium data for the binary and ternary mixtures of the components nitrogen, methane and ethane were obtained at -240°F by means of a modified forced recirculation apparatus. Liquid-liquid-vapor equilibrium data of the ternary system were also obtained at the same temperature. Two methods were proposed for computing vapor phase compositions from total pressure and liquid composition data. One was for low and medium pressure conditions, in which a hypothetical component concept was employed and thus extended the method for binary systems to ternary systems at isothermal condition. The proposed method was successfully applied to the ternary system nitrogen-argon-oxygen. The other was proposed for high pressure systems in which an adjusted activity coefficient was introduced in conjunction with the appropriate symmetric and unsymmetric conventions. As a result, the indirect method was generalized and extended to the high pressure and multicomponent systems. Moreover a nonlinear regression technique was introduced making possible the evaluation of the adjustable parameters. Three binary systems were used to illustrate the proposed method with good results. A general thermodynamic consistency test method which permits a point-by-point evaluation of the vapor-liquid equilibrium data was proposed and the maximum experimental error bounds were also established analytically. Vapor-liquid equilibrium data of one ternary and five binary systems were effectively evaluated by the proposed method. In addition, the total pressure method of Barker was generalized, the composition resolution method of Van Ness was extended to the ternary systems and a five-junction copper-constantan thermopile was built and its calibration table was also prepared.