How does ammonia react with NOx when injected into the furnace?

The reaction of ammonia with nitrogen oxides (NOx) is a crucial process in reducing harmful emissions, particularly in industrial applications such as power generation and chemical manufacturing. When ammonia is injected into the furnace, it acts as a reducing agent in the presence of NOx.

During this reaction, ammonia (NH3) interacts with NOx (which typically comprises nitric oxide (NO) and nitrogen dioxide (NO2)). The primary outcome of this interaction is the conversion of these nitrogen oxides into nitrogen gas (N2) and water (H2O). This reaction not only helps in lowering the concentration of harmful NOx emissions but also contributes to more efficient combustion processes. The formation of nitrogen gas is particularly important because it is a non-toxic, inert component of the atmosphere, thus making this reaction beneficial for air quality.

In contrast, while the other reactions presented may involve ammonia, they do not accurately represent the specific interaction between ammonia and NOx in a furnace environment. The reaction identified as the correct choice is foundational in the context of emissions control technologies such as selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR), which utilize ammonia to mitigate NOx output.