Allothermal air-steam gasification of biomass with CO2 (carbon dioxide) sorption: Performance prediction based on a chemical kinetic model

This paper deals with the technical feasibility of calcium oxide as a sorbent for CO2 (carbon dioxide) in syngas for air-steam gasification of lignocellulosic biomass. The process is simulated through a kinetic approach incorporating rate equations for the component reactions. Using the kinetic simulation data, parametric performance analysis is carried out highlighting the significance of SBR (steam to biomass molar ratio) and SOBR (sorbent to biomass molar ratio) on product gas evolution and heating value. In the range of operating conditions simulated (ER: 0.2-0.5, SBR: 0.25-2.2, SOBR: 0-0.43, T: 873-1273 K), the study reveals that the H2 concentration and heating value LHV (Lower Heating Value) increase respectively, by 13.6-16.5% and 10.2-20.1% for air-steam gasification with the introduction of the sorbent. The optimum values of ER, SBR and SOBR for both H2 concentration and LHV are 0.2, 2.2 and 0.43, respectively. Meanwhile, H2 concentration and LHV are at their optimum values at temperature of 1273 and 1073 K, respectively. At this optimised condition, the producer gas mixture is rich in hydrogen by almost 50%. The predicted results are compared with the reported experimental results on sorbent-enhanced steam gasification. The comparison reveals the good predictive power of the chemical kinetics model which is accurate by 94%.