Flamelet LES of pulverized coal combustion and NO formation characteristics in a supercritical CO2 boiler

In the present study, LESs of a modeled typical combustion zone of a 1000 MW S-CO₂ coal-fired boiler using a hybrid flamelet/progress variable model are conducted for the first time. In the hybrid model, both the fuel-N from volatiles and char are considered, and two progress variables are used for major species and NO, respectively. The combustion and NO formation characteristics at different regions are qualitatively and quantitatively investigated. The results indicate that the mixture of primary air and secondary air, the high-temperature wall as well as the adjacent flame can promote the pulverized coal combustion (PCC) and NO formation. In addition, the effects of wall temperature and flue gas recirculation on PCC and NO formation are investigated. The results show that compared with the supercritical H₂O boiler, a slight rise of 2.08% and 3.05% for temperature and NO production can be observed in the supercritical CO₂ boiler due to a higher wall temperature; flue gas recirculation with a recirculation rate of 27% can effectively reduce the production of NO by 57.6% in the supercritical CO₂ boiler.