Competition between NH3-O2 reaction and char-O2 reaction and its influence on NO generation and reduction during char/NH3 co-combustion: Reactive molecular dynamic simulations
Competition between NH3-O2 reaction and char-O2 reaction and its influence on NO generation and reduction during char/NH3 co-combustion: Reactive molecular dynamic simulations
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DOI：
10.1016/j.fuel.2022.124666
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发表时间：
2022
期刊：
影响因子：
7.4
通讯作者：
Dikun Hong;Lin Yuan;Chunbo Wang
中科院分区：
文献类型：
--
作者：
Dikun Hong;Lin Yuan;Chunbo Wang
To reduce CO2emissions in power plants, the co-firing of ammonia (NH3) and coal in boiler has received increasing attention in industry and academia. In this work, char/NH3co-combustion behaviors and NO generation and reduction characteristics under different temperatures, O2equivalence ratios and NH3co-combustion ratios are studied via the reactive molecular dynamic (ReaxFF MD) simulations. The initial reaction mechanisms of char oxidation and NH3oxidation revealed by ReaxFF MD simulations conform to the models that have been proposed, which proves the accuracy of ReaxFF MD method in studying char/NH3co-combustion. The char/NH3co-combustion simulation results show that NH3will compete with coal char for O2, resulting in an increase of NH3oxidation rate and a decrease of char oxidation rate. The competition between NH3-O2reaction and char-O2reaction during char/NH3co-combustion are largely depended on temperature, O2equivalence ratio and NH3co-combustion ratio. Compared to NH3combustion, the concentration of O and OH radicals are higher while the concentration of NH2, NH and NNH intermediates are lower during char/NH3co-combustion due to the competition between NH3-O2reaction and char-O2reaction, which enhances the NO generation reactions but weakens the NO homogeneous reduction reactions. Under oxygen-lean conditions, the homogeneous reduction of NO by NNH and the heterogeneous reduction of NO by unburnt char play an important role in reducing NO emissions, especially at high NH3co-combustion ratios. The reaction paths of NO reduction by char during char/NH3co-combustion are revealed. The results indicate that both the carbon atoms and the nitrogen atoms in char are responsible for NO reduction.
