Numerical study on NOx reduction in a large-scale heavy fuel oil-fired boiler using suitable burner adjustments

A numerical framework was carefully developed to simulate the combustion of heavy-fuel-oil (HFO) in a large-scale boiler. The present numerical solutions were compared with the measured data of a laboratory benchmark test and on-site operational data of the chosen HFO-fired boiler. Next, the developed framework was used to perform the sensitivity analyses aiming to reduce the NO emission from the HFO-fired boiler without any adverse effect on its combustion performance. Practically, this study focused on re-adjustments of 24 working burners, which could control the combustion in the HFO-fired boiler. The early outcome showed that the boiler NO emission and its combustion performance could be controlled via the proper adjustments of air distributions within the three burners’ stages and the swirl intensity. Although bigger mean droplet sizes and higher injection velocities reduced the NO emission considerably, it adversely led to much lower boiler’s combustion efficiency. The present study eventually arrived at an optimal adjustment for the burners by reconsideration of the air distributions within the three burners’ stages, the flame swirl intensity magnitude, and the fuel injection quality. The achieved optimal adjustment reduced the amount of NO emission by 30%, while the combustion efficiency would remain unaffected.