Effects of flue gases (CO/CO₂/SO₂/H₂O/O₂) on NO-Char interaction at high temperatures

The effects of major flue gases (CO/CO₂/SO₂/H₂O/O₂) on the NO–char interaction at realistic high temperatures in the reburning zone of boiler are investigated, through the HEFR and HDTF at 1200–1500 °C. The results indicates that CO could significantly promote the NO–char interaction, with its temperature-sensitive region at 3%–5% CO. CO₂ (<5%) would promote NO reduction rate by 5–16%, while CO₂ in larger concentration has little effect on NO–char interaction. The effect of SO₂ on the NO–char interaction is limited. H₂O from 0 to 20% would make an increase of NO reduction rate by approximately 18%, with the formation of CO and HCN. 0.8% is the optimal O₂ concentration promoting the NO–char reduction. Even with a small amount of oxygen (0.8% O₂), the addition of H₂O could promote NO reduction at 1200 °C. With O₂ from 0.8% to 4% with 10% H₂O, the temperature-depending effects of H₂O and O₂ on NO–char interaction is advanced from 1.0 s to 0.5 s, even earlier. With CO₂ from 5% to 11% with 0.8% O₂, the temperature-depending effects of CO₂ and O₂ on NO–char interaction could be advanced from 1.5 s to 0.5 s.