A DIVERSE APPROACH FOR THE SOLUTION OF THE ISOTHERMAL MULTIPHASE FLASH PROBLEM - APPLICATION TO VAPOR-LIQUID-LIQUID SYSTEMS

The paper presents a novel approach for the solution of the isothermal multiphase flash problem with particular application to systems exhib iting liquid-liquid-vapor equilibria. The approach includes a rigorous method for thermodynamic stability analysis as a first step and an ef ficient phase identification procedure. The stability analysis, exerci sed only once, uses a modification of the Gibbs tangent plane criterio n. The identification procedure implements the results of the stabilit y test in a sequence of Liquid-liquid and liquid-vapor calculations on ly till the phase configuration with a minimum Gibbs energy is determi ned. The efficiency and reliability of the proposed new method is illu strated by solving three typical problems encountered in enhanced oil recovery, natural gas processing and petrochemical industry.