The use of statistical associating fluid theory to improve the BACK equation of state I. Pure fluids

In this paper, statistical associating fluid theory (SAFT) equation of stat e (EOS) is incorporated into the Boublik-Alder-Chen-Kreglewski (BACK) EOS. The adjustable parameters for 16 pure non-associating fluids are compiled f rom references and those for 25 pure non associating fluids are regressed w ith VLE data in this work. A new equation of state called SAFT-BACK equatio n is proposed by combining the hard convex body term and dispersion term of BACK equation with the associating term of SAFT equation so that it can de scribe phase equilibrium behavior for pure associating fluids. In this mode l, an associating molecule is treated as a convex body with associating sit es on it. The adjustable parameters for 13 pure associating fluids are regr essed. When compared to the original SAFT, the SAFT-BACK EOS can give more accurate description in the near critical region. (C) 2000 Elsevier Science B.V. All rights reserved.