3-PHASE FLASH CALCULATIONS FOR MULTICOMPONENT SYSTEMS

A three-phase flash algorithm (Nelson, Computers chem. Engng 11, 581, 1987) has been incorporated into a program for calculating high-pressure phase equilibria (Dohrn and Brunner, Chem. Technik 41, 65; 1989a). The method presented here includes the a priori determination of the number of phases present and the solution of the flash equations once the number of phases has been determined. Although an extension to more than three coexisting phases is possible, the method given here is restricted to multicomponent systems with a maximum of three phases in equilibrium. To illustrate the method, phase-equilibrium calculations are shown for the ternary systems hexadecane-water-hydrogen and toluene-water-hydrogen at elevated pressures and temperatures.