HIGH-PRESSURE PHASE-EQUILIBRIA FOR CARBON-DIOXIDE METHANOL-WATER SYSTEM - EXPERIMENTAL-DATA AND CRITICAL-EVALUATION OF MIXING RULES

Equilibrium phase compositions for the carbon dioxide-methanol-water s ystem were measured at 313.2 K and pressures of 70, 100, and 120 bar. Three-phase equilibria for this system were also measured at 305.15, 3 08.15, and 311.15 K, temperatures and pressures near the critical poin t of carbon dioxide. The two- and three-phase equilibrium data were co rrelated with the Soave-Redlich-Kwong and Patel-Teja equations of stat e incorporated with various types of the local composition and Huron-V idal mixing rules. The Huron-Vidal mixing rules were found to be super ior to the local composition models in predicting two-phase equilibria . Since the pressure range covering the three-phase region was very na rrow, the Huron-Vidal mixing rules could not accurately predict the ex perimental three-phase equilibria. However, if there were a slight cha nge of pressure in phase calculation, the Huron mixing models could co rrectly predict the experimental three-phase region and equilibrium co mpositions.