Experimental and kinetic study of N2O thermal decomposition in pressurized oxy-combustion

Abstract

Pressurized oxy-combustion is regarded as a promising carbon capture technology for mitigating global warming. In addition, N2O is a significant greenhouse gas in pressurized oxy-combustion at moderate temperatures, with a Global Warming Potential 310 times that of CO2. It is important to study the formation and control of N2O in pressurized oxy-combustion. In this paper, the effects of CO2 atmosphere, pressure, temperature, residence time, and O2 concentration on N2O decomposition were investigated in a pressurized plug flow reactor. The results show that CO2 atmosphere significantly promotes N2O decomposition compared to N2 atmosphere. Increasing temperature accelerates the decomposition of N2O, with 1023–1223 K being the main decomposition temperature range. The decomposition efficiency of N2O increases with increasing pressure, while its increase becomes slow at above 5 bar. N2O decomposition efficiency in CO2 atmosphere decreases slightly as O2 concentration increases. The experimental results were compared to the kinetic modeling results calculated using GRI3.0 and GLA2018 mechanism, respectively. The modeling results show that GRI3.0 mechanism accurately predicts the decomposition of N2O at 1 bar while overestimates the decomposition at elevated pressures, while GLA2018 mechanism significantly underestimates the decomposition at all tested pressures. Further Rate-of-production analysis shows that the main reaction of N2O decomposition is N2O(+M) = N2 + O + M, which becomes the dominant reaction especially at elevated pressures. An enhanced third-body efficiency of 3 for CO2 was incorporated into the reaction N2O(+M) = N2 + O(+M) in GLA2018, which could predict the decomposition of N2O at elevated pressure accurately. The above results indicate that the decomposition of N2O is significantly enhanced in pressurized oxy-combustion.