Alberta Boilers Safety Association (ABSA) Practice Test

During combustion, what percentage of NOx formed is typically NO?

1. 90%

2. 75%

3. 50%

4. 25%

The correct answer is: 90%

During combustion, particularly in the context of fossil fuel combustion, a significant portion of the nitrogen oxides (NOx) produced is in the form of nitrogen monoxide (NO). Research and studies in the field of combustion engineering indicate that about 90% of the NOx formed during these processes is typically NO. This occurs because the high temperatures present during combustion facilitate the reaction between nitrogen (N2) in the air and oxygen (O2), primarily leading to the formation of NO. The formation of NO over other nitrogen oxides, such as nitrogen dioxide (NO2), is favored due to both kinetic and thermodynamic factors. At elevated combustion temperatures, the predominance of NO makes it the primary nitrogen oxide emitted from combustion sources, while the subsequent reactions that could convert NO to NO2 generally happen at lower temperatures or under specific conditions beyond the immediate combustion process. Understanding this relationship is crucial for developing strategies to manage NOx emissions effectively, as it allows for targeted approaches in combustion system design and emission control technologies. This knowledge is particularly important in the context of regulations aimed at reducing air pollution and improving environmental health.