Estimation of VLE phase compositions of binary systems containing gaseous components, from the feed composition and the cell volume

A procedure is presented for estimating the composition of the vapor and liquid phases formed by a given binary mixture in an equilibrium cell, at given temperature and pressure, so that the need of chromatographic analyses is overcome. It applies to any kind of components, including gaseous and/or polar ones. The method is based on a cubic equation of state and the execution of flash calculations, with the constraint of reproducing the total cell volume. It requires for each component the critical constants and the liquid density and vapor pressure, or, if the component is gaseous, its acentric factor only. Experimental data was used to optimize the accuracy of the method. Experimental phase compositions, mainly of the liquid phase, are normally reproduced within 1%.