APPLICATION OF CONTINUATION METHODS TO THE CALCULATION OF SOLID -FLUID -FLUID AND RELATED SOLID -FLUID EQUILIBRIA OF BINARY ASYMMETRIC MIXTURES IN WIDE RANGES OF CONDITIONS

S.B. RODRIGUEZ-REARTES; M. CISMONDI; M.S. ZABALOY

Arcachon, France

Simposio; 9th International Symposium on SuperCritical Fluids (ISSF 2009); 2009

I.S.A.S.F – E.N.S.I.C

The efficient calculation of the global phase equilibrium behavior of asymmetric n-alkane / n-alkane binary mixtures, in wide ranges of conditions, is relevant for understanding wax deposition phenomena. In this work, we propose and explore the use of path-following methods for tracking entire solid-fluid (SF) and solid-fluid-fluid (SFF) equilibrium curves for binary asymmetric mixtures. Our case studies are the highly asymmetric systems: Methane (C1) / n-Eicosane (C20) [1], Methane (C1) / n-Tetracosane (C24) [2] and Methane (C1) / n-Triacontane (C30) [3]. We obtained complete SFF equilibrium lines and SF equilibrium isopleths, isobars and isotherms, in single runs, by using the continuation approach, which makes possible to define robust calculation algorithms. The construction of SF lines takes advantage of information corresponding to SFF lines, generated previously. We also introduce in this work a modeling approach which pays close attention to the limit where the pure heavy component is under solid-liquid equilibrium conditions. The model assumes that the solid phase is only formed by the pure heavy component, and does not consider polymorphic transformations. For describing the fluid phases we use the Peng-Robinson equation of state (PR-EOS). Although the model is relatively simple, it is able to grasp the complex observed behavior for the studied systems.  Keywords: Solid-Fluid Equilibrium, Solid-Fluid-Fluid Equilibrium, Continuation Method, binary n-alkane systems.