A METHOD FOR THE SIMULTANEOUS PHASE-EQUILIBRIA AND STABILITY CALCULATIONS FOR MULTIPHASE REACTING AND NONREACTING SYSTEMS

A development of the stability criterion for multiphase reacting/non-reacting systems is presented. This new development has led to a formulation of a set of coupled non-linear algebraic equations that describe both the stability and the isothermal-isobaric flash calculations of reacting and non-reacting systems. The formulation has been used to develop an algorithm for the simultaneous computation of stability and multiphase equilibria in reacting/non-reacting systems. The Newton-Raphson procedure is used to solve the stability and the summation equations for the phase fractions and the stability variables. The stability equation has been transformed to alleviate the problems associated with the ill-conditioning and the singularity of the Jacobian near the phase boundaries. The appearance or disappearance of a phase during the computations is handled easily. Simultaneous computation of the stability variables and the phase fractions is particularly suited near phase boundaries and for multiphase reactive systems. The effectiveness of the proposed algorithm is illustrated by examining a mixture of methane, carbon dioxide and hydrogen sulfide, and reacting mixtures typically encountered in methanol synthesis in the presence or absence of heavy oil.