Abstract
Selective non-catalytic reduction of NO_X by activated ammonia injection has been developed to broaden and lower the narrow temperature window for de-NO_X. A temperature window enlargement of 150℃ was achieved at the lower boundary of the window using activated ammonia injection. In this study, the reaction mechanism for de-NO_X was considered by the measurements of the chemical composition of activated ammonia, the verification de-NO_X experiments, and the detailed kinetics simulation. A major chemical species of activated ammonia is molecular hydrogen. The effect of molecular hydrogen on de-NO_X reactions was investigated by using an NH_3/H_2 gas mixture in the temperature range of 500℃-850℃. This clearly indicated that hydrogen played a key role in the expansion of the temperature window. The reaction mechanism of de-NO_X was described using a detailed elemental kinetic model. This model suggested that molecular hydrogen produced key radical species for de-NO_X reactions, such as HNO, NNH, and NH above 600℃, which were promoted NO_X reduction at lower temperatures.
