Effect of Swirl Blade Deflection Angle on Combustion and Emission Characteristics of By-Product Gas Boiler

Abstract Swirl burner is widely used in boilers due to its high combustion efficiency. The swirl blade deflection angle affects the combustion and emission characteristics of the boiler. In this study, based on the experimental data and numerical simulation, a method for adjusting the outlet flow direction of the swirl burner is proposed through a self-defined angle. The numerical simulation is focused on the combustion process of a 330 t/h subcritical boiler. The results indicate that increasing β angle raises the overall furnace temperature when α angle = 30 deg, the average maximum temperature reaches 1611 K, and the average NOx concentration is stable at about 8 mg/m3, though this setup is less effective for gas mixing. When α = 0 deg, the temperature distribution is uniform and lower than the temperature distribution when α = 30 deg. Adjusting β angle has minimal impact on the temperature, but as β angle increases, the NOx concentration decreases, dropping to 6.5 mg/m3 at α = 30 deg. When β angle exceeds 45 deg, its influence on NOx generation is weakened. Conversely, at α = −30 deg, the high-temperature region is concentrated, resulting in an overall temperature below α = 0 deg. This results in an uneven heat load on the furnace wall and a stable average NOx concentration of about 4 mg/m3.