Nitrogen oxides (NOx) are formed during combustion primarily through two main mechanisms, as noted in the reference provided.
NOx formation in combustion engines and industrial furnaces is a significant environmental concern. Understanding how these pollutants are generated is key to developing strategies for their control and reduction.
Main Ways Nitrogen Oxides are Formed in Combustion
The formation of nitrogen oxides during combustion is linked to the presence of nitrogen and oxygen at high temperatures. Based on the provided reference, the two primary sources are:
- Fuel-Bound Nitrogen: NOx can be formed partly from nitrogen compounds in the fuel. Some fuels, particularly heavier oils and solid fuels like coal, contain nitrogen as part of their chemical structure. When these fuels burn, this fuel-bound nitrogen can react to form NOx.
- Thermal NOx (Atmospheric N₂ and O₂ Reaction): This is the dominant pathway, accounting for mostly of the NOx produced. It occurs by the direct combination of atmospheric oxygen and nitrogen in flames. At the very high temperatures found in the flame zone during combustion, the strong triple bond in diatomic nitrogen (N₂) and the double bond in diatomic oxygen (O₂) can break, allowing these atoms to react and form various nitrogen oxides, predominantly nitric oxide (NO). The rate of this reaction increases sharply with temperature.
While nitrogen oxides also occur naturally from sources like lightning and microbial processes in soils, the formation discussed above specifically pertains to human-caused combustion activities.
Understanding these formation pathways is crucial for implementing emission control technologies, such as optimizing combustion conditions or treating exhaust gases.
