Combustion and heat transfer characteristics of oxy-coal combustion in a 100 MW_e front-wall-fired furnace

Oxy-coal combustion exhibits different characteristics of combustion, flow and heat transfer from those of air-coal combustion, due to the high concentration of CO₂ and H₂O in the product gases. Using computational modeling, this study investigated the combustion and wall heat flux (WHF) of a 100 MW_e boiler under air- and oxy-coal combustion conditions. The boiler had 12 swirl burners installed on the front wall for thermal input of 284 MW_th. Flame temperatures and corresponding WHF in oxy-coal combustion increased linearly as O₂ concentration increased from 24% to 30%. The case with 28% O₂ achieved the same level of WHF with that of air-coal combustion, which had a similar adiabatic flame temperature. Due to the lower heat capacity, the gas temperature above the burner region lowered more rapidly in air-coal combustion than in oxy-coal combustion. The proportion of char converted by CO₂ and H ₂O increased from approximately 8% in air-coal combustion to 19-23% in oxy-coal combustion. The increased rates of endothermic gasification reactions by CO₂ and H₂O lowered the temperature in the internal recirculation zone during oxy-coal combustion. This retarded char oxidation upstream of the flames.