Effects of burner tilt angle on the combustion and NOX emission characteristics of a 700 MWe deep-air-staged tangentially pulverized-coal-fired boiler

- Effects of burner tilt angle on temperature and species distribution were studied.
- Effects of burner tilt angle on char burnout and NOX emissions were studied.
- Mechanism of the CO reduction when tilting burner upward was revealed.
- Tilting burner upward is beneficial in aspects of steam temperature and CO emissions.

The burner tilt angle has a significant influence on the combustion characteristics of a furnace, but few studies have focused on this topic. In this study, a numerical model was developed and validated to investigate the effect of the burner tilt angle on the combustion and NOX emission characteristics of a 700 MWe pulverized-coal-fired boiler with deep-air-staging technology. The turbulence, heat transfer and chemical reactions in the furnace were reproduced in detail by the model. Deep insight into the effects of burner tilt angle on combustion and NOX emission characteristics was acquired. The results show that the turbulence intensity in the burnout zone of furnace increases as the burner tilt angle increases, leading to a significant increase in the reaction rate of CO combustion. Hence, the level of CO emission is continuously reduced. The char burnout rate changes little with increasing burner tilt angle since the kinetic reaction rate and oxygen diffusion rate increase while the particle residence time decreases. The NOX emission increases as the burner is tilted farther upward because of an enhancement in fuel NO formation and a decrease in NO reburning. This study provides useful guidelines for improving the performance of deep-air-staged tangentially coal-fired boilers.