Numerical study on NO_X/CO emissions in the diffusion flames of high-temperature off-gas of steelmaking converter

摘要

The combustion of high-temperature off-gas of steelmaking converter with periodical change of temperature and CO concentration always leads to CO and NO_X over-standard emissions. In the paper, high-temperature off-gas combustion is simulated by adopting counterflow diffusion flame model, and some influencing factors of CO and NO_x emissions are investigated by adopting a detailed chemistry GRI 3.0 mechanism. The emission index of NO_x (EINO_x) decreases 1.7-4.6% when air stoichiometric ratio (SR) increase from 0.6 to 1.4, and it dramatically increases with off-gas temperature at a given SR when the off-gas temperature is above 1500 K. High-concentration CO in off-gas can result in high NO, emissions, and NO* levels increase dramatically with CO concentration when off-gas temperature is above 1700 K. Both SR and off-gas temperature are important for the increase of CO burnout index (BI_(co)) when SR is less than 1.0, but Bl_(co) increase about % when off-gas temperature increases from 1100 K to 1900 K at SR >1.0. BI_(co) increases with CO concentration in off-gas, and the influence of off-gas temper ature on Bl_(co) is marginal. BI_(C0) increases with the relative humidity (RH) in air supplied, but it increases about 0.5% when RH is larger than 30%.