Experiments And Modeling Of NO Reduction By C1 Fuels Under High CO₂ Concentration

Reburning is an inexpensive and effective NO_x reduction technology that has been adopted in many combustion systems.It can reduce NO_x emission by more than 50%under conventional air combustion system.For the oxy-fuel combustion,due to the effect of the flue gas cycle,part of the NO_x generated after combustion is taken back to the combustion area,so that the oxy-fuel combustion essentially has the possibility of low-nitrogen reconstruction through the reburning techonology.The atmosphere inside the furnace in the oxy-fuel combustion system is diluted by CO₂,so the mechanism of NO_x generation and reburning during the combustion process will be different from that in the conventional N₂ atmosphere.Therefore,it is necessary to conduct a more in-depth study on the reburning mechanism in a CO₂-rich atmosphere.In this paper,experiments of NO reduction by CH₄ and syngas in both N₂ and CO₂-rich atmospheres are conducted in a self-constructed jet-stirred reactor experimental bench.The CHEMKIN-PRO is used to perform kinetic modeling of experimental conditions.Moreover,a detailed mechanism（PG2018-mod mechanism）which is suitable for the reburning simulation in N₂ and CO₂-rich atmosphere is proposed in this work.The calculation results using this mechanism are in good agreement with the experimental data of methane and syngas reburning in this paper.When using methane as a reburning fuel,the maximum NO reduction in a CO₂-rich atmosphere is achieved at T=1300 K,Φ=1.25,and the CH₄/NO ratio=20 with a maximum reduction efficiency of 63%.Moreover,when the CH₄/NO ratio≤5,the NO reburning in the CO₂-rich atmosphere is reduced by 40%-60%at temperatures above 1100 K compared to that in the N₂ atmosphere.The inhibition of CH₄ oxidation under high CO₂ concentrations is responsible for the decrease in the NO reduction efficiency.When using syngas as a reburning fuel,the NO reduction efficiency of the syngas does not change significantly with T,Φand the H₂/CO ratio,and the maximum NO reduction efficiency is 7%if CH₄ is not included in the syngas composition.However,when X_CH4=10%,the maximum NO reduction efficiency is increased to 24%.Moreover,whether methane is present or not,the reduction efficiency of NO by syngas in the CO₂-rich atmosphere is reduced by20%-40%compared with that in the N₂ atmosphere when T>900 K.