Effects of oxidant distribution mode and burner configuration on oxy-fuel combustion characteristics in a 600 MWe utility boiler

The application of oxy-fuel combustion in utility boilers has drawn increasing attention in recent years. The previous numerical studies on oxy-fuel utility boilers mainly focused on effects of O2 concentration and flue gas recycle mode. In the present study, the effects of oxidant distribution mode and burner configuration on characteristics of oxy-fuel combustion were numerically investigated. The simulation results showed that a similar aerodynamic field and a higher char burnout compared with those of air-combustion were obtained by closing the separated over fire air (SOFA) nozzles under oxy-fuel condition. After the oxidant staging was employed in oxy-fuel combustion, the NOx emission was decreased to approximately half of that in air, but the momentum of second air (SA) suffered a remarkable reduction. The undesired reduction of second air momentum could result in some serious problems. A burner configuration and a new oxidant distribution mode were proposed to solve the problem of insufficient momentum of SA after the oxidant staging was adopted. The incomplete combustion heat loss could decrease to the same level as that of air combustion after the proposed burner configuration was employed. The present investigation is beneficial for offering guidance in both retrofitting and operation of oxy-fuel utility boiler.