Numerical study on self-ignition temperature of biomass gasified gas for the application of MILD combustion

Abstract

Moderate and intense low-oxygen dilution (MILD) combustion of biomass gasified gas (BGG) has great potential. However, self-ignition temperature (Tsi) of BGG is not clear, which limits the establishment of BGG MILD combustion. In this study, Tsi of BGG was calculated in a perfectly stirred reactor using NUIG-NGM-2010 mechanism. Tsi of BGG/O2/N2 mixture was identified by the S-shape curve. Very wide ranges of the residence time τ (10−5 s–10 s), oxygen concentration XO2 (0.1%–35%) and equivalence ratio Φ (0.4–2.8) were considered. Results show that τ = 1 s was reasonable for MILD combustion. Tsi decreased with the increase of XO2. Tsi first decreases and then increases with the increases of Φ. BGG is easier to establish MILD combustion than CH4 because the critical XO2 is 11.7%, which is larger than CH4 (9.7%). Sensitivity analysis shows that R1 (H + O2 = O + OH) and R4 (O + H2O = OH + OH) are the most sensitive reaction for promoting ignition. R3 (OH + H2 = H + H2O), R21 (H2O2 + OH = H2O + HO2) and R13 (HO2 + OH = H2O + O2) were key reactions for prohibiting ignition under designed conditions.