Thermodynamic models for vapor–liquid equilibria of nitrogen + oxygen + carbon dioxide at low temperatures

Abstract

For the design and optimization of CO 2 recovery from alcoholic fermentation processes by distillation, models for vapor–liquid equilibria (VLE) are needed. Two such thermodynamic models, the Peng–Robinson equation of state (EOS) and a model based on Henry’s law constants, are proposed for the ternary mixture N 2 + O 2 + CO 2. Pure substance parameters of the Peng–Robinson EOS are taken from the literature, whereas the binary parameters of the Van der Waals one-fluid mixing rule are adjusted to experimental binary VLE data. The Peng–Robinson EOS describes both binary and ternary experimental data well, except at high pressures approaching the critical region. A molecular model is validated by simulation using binary and ternary experimental VLE data. On the basis of this model, the Henry’s law constants of N 2 and O 2 in CO 2 are predicted by molecular simulation. An easy-to-use thermodynamic model, based on those Henry’s law constants, is developed to reliably describe the VLE in the CO 2-rich region.