Dependence of N2O/NO Decomposition and Formation on Temperature and Residence Time in Thermal Reactor

Abstract

Nitrogen dioxide (N2O) is a greenhouse gas that is harmful to the ozone layer and contributes to global warming. Many other nitrogen oxide emissions are controlled using the selective non-catalytic reaction (SNCR) process, but N2O reduction methods are few. To avoid future air pollution problems, N2O reduction from industrial sources is essential. In this study, a N2O decomposition and NO formation under an argon atmospheric N2O gas mixture were observed in a lab-scale SNCR system. The reaction rate and mechanism of N2O were calculated using a reaction path analyzer (CHEMKIN-PRO). The residence time of the gas mixture and the temperature in the reactor were set as experimental variables. The results confirmed that most of the N2O was converted to N2 and NO. The change in the N2O reduction rate increased with the residence time at 1013 and 1113 K, but decreased at 1213 K due to the inverse reaction. NO concentration increased with the residence time at 1013 and 1113 K, but decreased at 1213 K owing to the conversion of NO back to N2O.

Effect of the Oxygen Concentration and Temperature on Thermal Decomposition of N2O in an Inert Gas

“…The temperature of the reactor was measured using R-type thermocouples. 20 Here, the concentration of the exhaust gas after the reaction was measured using a nondispersive infrared (NDIR) gas meter (NOVA IR-Pro). The measurement error of the gas meter was below 2% (electrochemical sensor).…”

“…An insulator surrounds the reactor to prevent heat loss and maintain the temperature of the experiment. The temperature of the reactor was measured using R-type thermocouples . Here, the concentration of the exhaust gas after the reaction was measured using a nondispersive infrared (NDIR) gas meter (NOVA IR-Pro).…”

Full-Scale Investigation of Dry Sorbent Injection for NOx Emission Control and Mercury Retention

“…Ports 1-4 were used for in-furnace temperature measurement to determine the optimal sorbent injection zone. According to the most recent knowledge [28][29][30] an optimal temperature window for a selective non-catalytic reduction of nitrogen oxides with urea ranges from 950 to 1050 °C. Injection into a higher temperature zone leads to increased NOx formation, and into a temperature lower than 950 °C leads to ammonia slip formation.…”

“…The measurement error resulting from the radiation, which may reach 20%, is reduced to approx. 10% by using a According to the most recent knowledge [28][29][30] an optimal temperature window for a selective non-catalytic reduction of nitrogen oxides with urea ranges from 950 to 1050 • C. Injection into a higher temperature zone leads to increased NO x formation, and into a temperature lower than 950 • C leads to ammonia slip formation. In the case of urea injection in the right temperature zone, it is possible to significantly improve the reduction process; therefore, every full-scale research should be preceded by in-furnace temperature measurement in the combustion chamber to determine the appropriate temperature window.…”

Combined NOx and NH3 Slip Reduction in a Stoker Boiler Equipped with the Hybrid SNCR + SCR System FJBS+

“…In fact, the reaction mechanism is very complex: 31 compounds and 173 reactions that occurred during the NO x reduction process were identified [5]. The most efficient NO x conversion in the non-catalytic process can be reached in a temperature range of 870-1100 • C [6,7] while in catalytic conversion in 180-450 • C, for most catalysts 300-350 • C [8,9]. SCR technology is possible to be applied in waste-to-energy units, including combustion of medical and hazardous waste [10,11].…”