Robust calculations of critical end lines of ternary systems

PISONI, G. O.; CISMONDI DUARTE, MARTIN; ZABALOY, M.

Conferencia; IX Iberoamerican Conference on Phase Equilibria and Fluid Properties for Process Design; 2012

A ternary critical end line (T-CEL) is a line of Ternary critical end points (T-CEP). T-CELs provide key information on the phase behavior of ternary systems. A ternary system may have several T-CELs. It is desirable to have available a robust algorithm for computing complete ternary CELs, thus minimizing the need for user intervention. It is also important to reliably detect the key points where T-CELs originate or terminate. In this work, we propose to apply a numerical continuation method (NCM) for the fast and robust computation of T-CELs. As in other recent works, the present NCM makes use of a sensitivity vector for predicting the solution of the T-CEP system of equations and for identifying the optimum variable to be specified for calculating the next point belonging to the T-CEL being built. We present calculated T-CELs for a couple of highly asymmetric systems showing the topologies that these lines define. We consider a model of the equation of state (EOS) type and use it over wide ranges of conditions.