Which factors are necessary for complete combustion of a fuel?

Complete combustion of a fuel occurs when it reacts with enough oxygen, producing carbon dioxide and water as byproducts, without any unburned fuel remaining. For this process to be efficient, two critical conditions must be met: sufficient air (or oxygen) and an adequate temperature that allows the fuel to ignite and maintain combustion.

Having enough air is essential because it supplies the necessary oxygen for the chemical reaction. If there is insufficient oxygen, the combustion process will be incomplete, leading to the production of carbon monoxide and soot, which are indicative of incomplete combustion.

Additionally, a high furnace temperature is crucial because it ensures that the fuel reaches its ignition point and keeps the combustion reactions progressing continuously. If the temperature is too low, the fuel may not ignite properly or may not react completely with the available oxygen.

The other alternatives presented do not directly relate to the fundamental requirements of complete fuel combustion. Some may involve operational settings or conditions, but they do not address the core elements of adequate oxygen and heat that are necessary for full combustion efficiency.