Reaction characteristics of no_x and n₂o in selective non-catalytic reduction using various reducing agents and additives

Artificial nitrogen oxide (NO_x ) emissions due to the combustion of fossil fuels constitute more than 75% of the total NO_x emissions. Given the continuous reinforcement of NO_x emission standards worldwide, the development of environmentally and economically friendly NO_x reduction techniques has attracted much attention. This study investigates the selective non-catalytic reduction (SNCR) of NO_x by methane, ammonia, and urea in the presence of sodium carbonate and methanol and the concomitant generation of N₂O. In addition, the SNCR mechanism is explored using a chemical modeling software (CHEMKIN III). Under optimal conditions, NO_x reduction efficiencies of 80–85%, 66–68%, and 32–34% are achieved for ammonia, urea, and methane, respectively. The N₂O levels generated using methane (18–21 ppm) were significantly lower than those generated using urea and ammonia. Addition of sodium carbonate and methanol increased the NO_x reduction efficiency by methane to ≥40% and 60%, respectively. For the former, the N₂O level and reaction temperature further decreased to 2–3 ppm and 850–900^◦C, respectively. The experimental results were well consistent with simulations, and the minor discrepancies were attributed to microscopic variables. Thus, our work provides essential guidelines for selecting the best available NO_x control technology.