Reaction Mechanism of De-NOx by Activated Ammonia Generated by Dielectric Barrier Discharge
Y. Hayakawa, Y. Inoue, A. Takeyama, and S. Kambara
Environmental and Renewable Energy Systems Division, Graduate School of Engineering, Gifu University, Japan
Abstract- Selective non-catalytic reduction of NOx by activated ammonia generated by an intermittent dielectric barrier discharge has been developed to broaden and lower the narrow temperature window for de-NOx. A temperature window enlargement of 150°C was achieved at the lower boundary of the window using activated ammonia injection. In this study, the reaction mechanism for de-NOx was considered by the measurements of the chemical composition of activated ammonia, the verification de-NOx experiments, and the detailed kinetics simulation. A major chemical species of activated ammonia is molecular hydrogen. The effect of molecular hydrogen on de-NOx reactions was investigated by using an NH3/H2 gas mixture in the temperature range of 500°C-850°C. This clearly indicated that hydrogen played a key role in the expansion of the temperature window. The reaction mechanism of de-NOx was described using a detailed elemental kinetic model. This model suggested that molecular hydrogen produced key radical species for de-NOx reactions, such as HNO, NNH, and NH above 600°C, which were promoted NOx reduction at lower temperatures.
Keywords-SNCR, deNOx, dielectric barrier discharge, nitrogen oxide, ammonia, hydrogen