LAUSR

Abstract High NOx emission level exists in conventional heavy fuel oil (HFO) boiler due to its high-temperature region in the downstream. In this study, separation plates are installed near the spray nozzle to reduce the NOx emission of the burner. However, this geometry modification of burner can cause strong vibration in 660 MWe HFO boiler. The NOx emissions of zero, two, four and six separation plates are predicted using three-dimensional numerical simulations and compared to the experimental data. The NOx emission level is predicted at 473, 437, 422 mg/m3 at 3% O2 with two, four and six separation plates respectively. While significant NOx emission reduction achieved in the case of six separation plates, its effect on combustion instability is also revealed by using three-dimensional finite element method (FEM). The time delay is calculated by tracking the droplets convective time before combustion and the steady simulation results of the boiler with zero and six separation plates are fed into the acoustic solver. The installation of six separation plates leads the mean time delay at 52.5 ms and positive linear growth rate. The conclusions indicate that the method of installation of six separation plates to reduce NOx emission can cause combustion instability in HFO boiler.