What is the primary purpose of supplying excess air during furnace combustion?

• A. To reduce the amount of carbon dioxide produced
• B. To increase the temperature of the furnace
• C. To ensure complete combustion of the fuel
• D. To prevent the formation of water vapor

Answer: (C)

Verified step by step guidance

1. Understand that combustion is a chemical reaction between a fuel and oxygen, producing heat, carbon dioxide, and water vapor when complete.
2. Recognize that 'excess air' means supplying more oxygen than the exact amount needed for the stoichiometric combustion reaction.
3. Know that the primary purpose of supplying excess air is to ensure that all the fuel molecules have enough oxygen to react completely, preventing unburned fuel or carbon monoxide formation.
4. Realize that while excess air can slightly lower the furnace temperature due to the extra nitrogen and oxygen absorbing heat, its main role is not to increase temperature or reduce carbon dioxide production.
5. Conclude that supplying excess air helps achieve complete combustion, which improves efficiency and reduces harmful emissions like carbon monoxide.