What reaction produces sulfur dioxide during fuel combustion?

The production of sulfur dioxide during fuel combustion specifically occurs when sulfur reacts with oxygen. This reaction is a chemical process where sulfur, often present in fossil fuels, combines with oxygen to form sulfur dioxide (SO₂). This is particularly relevant in the context of burning fossil fuels like coal and oil, which may contain sulfur impurities.

In the case of hydrocarbons reacting with oxygen, while this reaction produces carbon dioxide and water, it does not produce sulfur dioxide unless sulfur is also present in the fuel. Carbon reacting with oxygen produces carbon dioxide, and nitrogen reacting with sulfur is not directly related to the combustion process of fuels but rather to reactions that can occur in specific conditions. Hence, the reaction of sulfur with oxygen is the mechanism that leads directly to the formation of sulfur dioxide during combustion.