Fuel Nitrogen Conversion Kinetics Of C1 At High CO₂ Concentrations In A Jet Stirred Reactor

Fuel nitrogen is the main source of NO_x emissions from nitrogen-containing fuel such as coal,as well as in oxy-fuel combustion technology that can achieve large-scale carbon capture.The high CO₂concentration under oxy-fuel combustion changes the fuel-NO_x conversion path.At present,there are relatively few studies on the conversion of fuel-nitrogen under high CO₂concentration atmosphere,especially the lack of systematic research in a wide range of equivalence ratios.To develop new low NO_x oxy-fuel combustion technology,it is needed to deeply explore the fuel-nitrogen mechanism under high CO₂ concentration atmosphere.Based on the house-made jet stirred reactor bench,the nitrogen conversion characteristics of C1（CH₄ and syngas）doped with NH₃ under high CO₂ concentration are experimentally and numerically researched.The effects of different conditions such as temperature,equivalent ratio and CO₂ concentration are systematically investigated.By systematically evaluating the five detailed mechanisms about fuel nitrogen conversions,PG2018 mechanism developed by Glarborg et al.performs best in predicting the experimental data of the jet stirred reactor in the present work.Then,based on the above reactor experiment and PG2018 mechanism simulation,the present work researches the C1 fuel nitrogen conversion characteristics.Under fuel-lean conditions,as CO₂ concentration increases from 0 to 60%,residence time increases from 0.5 s to 10 s,and temperature decreases from 1400 K to 800 K,NO production gradually decreases;while under fuel-rich conditions and at temperatures higher than 1200 K,the amount of NO produced is higher under high CO₂concentration atmosphere,relative to that under O₂/N₂atmosphere.In addition,as the equivalence ratio increases from 0.5 to 1.6,the amount of NO produced gradually decreases;but when the equivalence ratio is greater than 0.9,as the equivalence ratio increases,the amount of CO produced under high CO₂ concentration atmosphere increases significantly.For N₂O,the generation of N₂O is basically insensitive to CO₂ concentration.Based on the conversion rule of fuel nitrogen,the present work suggests that in addition to reducing the fuel nitrogen content,the equivalence ratio can be controlled near 0.9,and the residence time can be controlled as much as possible for more than 3 s,for the control of fuel-NO_x emissions under high CO₂ concentration.Finally,the present work further analyzes the C1 fuel nitrogen conversion path.With NH₃as the nitrogen source,the main path of fuel-NO generation is NH₃→NH₂→HNO→NO.Under fuel-lean conditions,as the CO₂ concentration increases from 0 to 60%,the path gradually weakens.NO reduction reactions（eg NH₂+NO?N₂+H₂O,NH₂+NO?NNH+OH and N+NO?N₂+O）are also important.Under fuel-rich conditions,the NO reduction reaction will reduce a large amount of NO emissions,but under the condition,the NO reduction reaction will be suppressed by high concentration CO₂.The key reactions that control the formation of N₂O are NH+NO?N₂O+H,N₂O+H?N₂+OH and N₂O（+M）?N₂+O（+M）are not sensitive to variation of CO₂ concentration.