Interval Methods for Reliable Computations of Phase Equilibrium From Equation of State Models
We have addressed the phase split problem with the Gibbs energy minimization approach. INTSTAB is first used to obtain all the stationary points. They provide extremely good initial estimates for the equilibrium phase compositions. An enhanced Han-Powell method for successive quadratic programming (SQP) is then used to perform a local minimization of Gibbs free energy to locate prospective global minima. INTSTAB is again used to verify if a global minimum has been reached. By combining the speed of this local SQP solver with the reliability of INTSTAB, we have developed an efficient and completely reliable approach for computing multi-phase equilibria. This method was implemented in the package INTFLASH.
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign