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The present work investigates reburning reduction of nitrogen oxides in oxy-fuel combustion by means of a detailed reaction mechanism applied to a plug-flow reactor. Reburning reactions, which are known to convert NOx into N2, are of special interest in oxy-fuel combustion because of extensive recirculation of flue gases, including NOx, to the flame. Furthermore, the high concentration of carbon dioxide in oxy-fuel combustion is known to influence the radical pool (H/O/OH), which is critical to the combustion chemistry. In the present work, it is shown how the changes in the radical pool alter the nitrogen chemistry both directly and indirectly by influencing the formation and oxidation of hydrocarbon radicals. It is shown that reburning is more sensitive to the combustion temperature but is less affected by the combustion stoichiometry under oxy-fuel compared to air conditions. The main reasons are the impact of increased CO2 concentration on hydrocarbon oxidation and the increased importance of CH3 as a reactant in oxy-fuel combustion.
Normann et al. (Thu,) studied this question.