Thermodynamic Models for Vapor-Liquid Equilibria of Nitrogen+Oxygen+Carbon Dioxide at Low Temperatures

TL;DR

This paper develops and validates thermodynamic models, including Peng-Robinson EOS and Henry's law-based models, for predicting vapor-liquid equilibria of nitrogen, oxygen, and carbon dioxide at low temperatures, aiding CO2 recovery processes.

Contribution

It introduces a combined approach using Peng-Robinson EOS and molecular simulation to accurately model VLE of N2+O2+CO2, especially in CO2-rich regions.

Findings

Peng-Robinson EOS fits experimental data well except near critical points.

Molecular simulation predicts Henry's law constants for N2 and O2 in CO2.

Henry's law-based model reliably describes VLE in CO2-rich conditions.

Abstract

For the design and optimization of CO2 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 N2+O2+CO2. 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 N2 and O2 in CO2 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 CO2-rich region.