Thermal performance and heat transfer characteristics analyses of oxy-biogas combustion in a swirl stabilized boiler under various oxidizing environments

Abstract

The present study deals with the numerical simulation of biogas diffusion flame in swirl stabilized boiler under different oxy-combustion conditions. The current study aims to investigate the impacts of O2/CO2 and O2/H2O oxidizer mixtures on the thermal and combustion characteristics of biogas flame in the boiler. Accordingly, the combustion simulation process is performed by the k-ω SST turbulence, DO radiation, and Flamelet Generated Manifold (FGM) combustion models. Results showed that by the increasing swirl angle, heat flux uniformity factor (UF) enhances by 26.8% and 129.9% for O2/CO2 and O2/H2O combustion modes, respectively. Also, by raising O2%, the flame peak temperature increases from 1832 K to 2171 K in O2/CO2 mode and from 2053 K to 2283 K in O2/H2O case. It was observed that the maximum of UF on the boiler wall could be achieved to be 0.81 at SA 60° in oxy-steam mode. Moreover, the UF value significantly increases by 39.42% on the boiler wall by transitioning from O2/CO2 to O2/H2O combustion mode at higher O2 content. Finally, results imply that there is no need to increase O2 content beyond 50% to reach higher heat transfer rate in O2/H2O mode because this would result in additional costs.