Combustion Characteristics of a 3 MW Class Oxy-fuel FGR Combustion Boiler for CO2 Capturing

In this study, a coaxial type burner capable of applying air combustion, oxy-fuel combustion, and oxy-fuel oxygen combustion with FGR (flue gas recirculation) was developed and tested for combustion and exhaust gas characteristics by installing it in a 3 MW class flame-tube type boiler. Compared with the results obtained from a 0.5 MW class boiler with a similar burner, the scaled-up characteristics were verified and the recirculation rates for a stable flame were compared. Combustion characteristics were investigated by varying fuel supply rate and fuel-to-oxidizer ratio, and the flue gas was analyzed under each condition. Consequently, it was confirmed that carbon dioxide can be separated, and NOx emissions can be reduced by applying oxy-fuel combustion to industrial boilers. However, it was discovered that it is difficult to obtain a stable flame under partial load conditions when oxy-fuel combustion is applied and that this changes the recirculation rate that can yield a stable flame for a burner with a different capacity.