Thermodynamic analysis of using CO2 as a co-gasification agent in supercritical water gasification of glycerol

Using CO2 as a co-gasification agent in supercritical water gasification (SCWG) of glycerol is one of the promising approaches for syngas production. In this study, a non-stoichiometric two-phase model (i.e., supercritical and solid phase) is used for thermodynamic analysis of supercritical H2O-CO2 co-gasification (SCWCG) of glycerol. The Gibbs free energy of the entire system is minimized to calculate the equilibrium compositions of gaseous and solid products. The chemical potentials of gaseous products are accurately predicted by using the PR-BM equation of state. The validity of the established model is initially confirmed through its fitting with experi-mental data. Subsequently, the model is used to investigate the effects of various single and combined operating conditions on product compositions. The findings indicate that temperature, CO2 addition and glycerol con-centration have significant influence on the process performance, whereas the pressure has a negligible effect. In addition, the theoretical maximum H2 molar fraction of 68.15% are obtained. Furthermore, the reaction heat duty and high heating value of gaseous products are analyzed. When the glycerol concentration is low, the SCWCG process turns out to be endothermic and can be energetically self-sufficient by adding a small amount of O2 at the expense of reducing the heating value of gaseous products. The study provides valuable insights on designing an optimal SCWCG process for syngas production from glycerol.

Automated summary

This study investigates the use of CO2 as a co-gasification agent in supercritical water gasification and provides valuable insights on designing an optimal process for syngas production.