Simulation perspective of upgrading biomass producer gas through a shift-methanation reaction coupled with cyclic CO2 capture

Abstract

Reducing the CO content and improving the lower heating value (LHV) of biomass producer gas are essential for transforming it into a reliable energy source. The present work strives to provide a simulation perspective for a biomass producer gas upgrading process containing integrated shift-methanation and cyclic CO2 capture, where the CO2 by product from the shift-methanation reactor is separated by cyclic mono-ethanolamine (MEA) scrubbing. Equilibrium calculations via the Gibbs energy minimization method reveal that the appropriate temperature and pressure window for the shift-methanation reaction is 300–450 °C and 1–5 bar, respectively. The simulation results show that the optimal stage number for both the absorber and stripper is 10. The desired value of absorber and stripper efficiency can be obtained by balancing the MEA flow rate and reboiler duty. The original biomass producer gas with a 44.4% CO content and LHV of 9.45 MJ/Nm3 is upgraded to a CO content below 10% and LHV over 14 MJ/Nm3, reaching the national classification standard of Grade I gas. The preliminary engineering design in this work combines the shift-methanation reaction with CO2 absorption–desorption, demonstrating much potential for industrial-scale applications.