Given below are two statements:
Statement I: Fuel oxides of nitrogen (NOx) is created when nitrogen and oxygen in the combustion chamber are heated to as high as 1000° C temperature.
Statement II: Thermal NOx is often the dominant source in the total NOx emissions.
In the light of the above statements, choose the most appropriate answer from the options given below:
Both Statement I and Statement II are false
Both statements describe sources of oxides of nitrogen (NOx) formed during combustion, but need to be checked against correct combustion chemistry.
Statement I claims that heating nitrogen and oxygen together in the combustion chamber to about 1000°C produces 'fuel NOx'. This is incorrect on two counts: first, NOx formed from atmospheric nitrogen (N2) and oxygen (O2) reacting at high flame temperatures is called thermal NOx, not fuel NOx — fuel NOx instead originates from nitrogen chemically bound within the fuel itself, which oxidises during combustion largely independent of flame temperature. Second, thermal NOx formation only becomes significant at much higher temperatures, typically above about 1300°C and rising sharply above 1600°C; at around 1000°C the thermal pathway contributes very little. So Statement I is false.
Statement II claims thermal NOx is often the dominant source of total NOx emissions. While thermal NOx can dominate in very high-temperature processes such as gas turbines, in many common combustion sources, particularly coal and other nitrogen-rich fuel combustion, fuel NOx arising from nitrogen already present in the fuel is typically the larger contributor to total NOx emissions. As a general statement about total NOx emissions this is therefore not correct, making Statement II false as well.
Hence both statements are false.
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