Thermodynamic analysis of hydrogen-enriched syngas generation coupled with in situ CO₂ capture using chemical looping gasification method

The CaO-based chemical looping gasification (CaO-based CLG) of biomass was considered as a potential technology to improve hydrogen-enriched syngas production and capture in situ CO₂ effectively. Thermodynamic analysis with Gibbs free energy minimization through Lagrange multiplier method was performed for CaO-based CLG to produce hydrogen-enriched syngas. The analysis was conducted to investigate the effects of different operation parameters [including CaO/C ratio (0–3.0), pressure (0.1–5.0 MPa), gasification temperature (600–700 °C) and S/C ratio (0.5–3.0)] on hydrogen fraction, syngas yield, gas LHV and in situ CO₂ capture efficiency. The results suggested that the preferential conditions for producing hydrogen-enriched syngas in CaO-based CLG were achieved at 600 °C, atmospheric pressure, S/C ratio of 2.0 and CaO/C ratio of 2.0. CaO-based could capture in situ CO₂ effectively and the capture efficiency reached 92.6%. Under these optimal operation parameters, the hydrogen fraction, gas yield and gas LHV reached 98.5%, 1.87 mol mol_C⁻¹ and 10.7 MJ Nm⁻³, respectively. Ultimately, the heat and mass balance of gasification was obtained at the optimal operation conditions, and gasifier did not need any external heating except from the heat carried by CaO.