Alberta Boilers Safety Association (ABSA) Practice Test

What happens when excess air is reduced in a furnace?

1. Combustion efficiency increases

2. Emissions increase

3. Temperature decreases

4. Fuel consumption decreases

The correct answer is: Combustion efficiency increases

When excess air is reduced in a furnace, combustion efficiency increases because the air-to-fuel ratio becomes more optimal. In a furnace, excess air is necessary to ensure complete combustion of the fuel, but when too much air is present, it can lead to heat loss due to the need to heat the extra air that doesn’t contribute to the combustion process. Reducing the amount of excess air allows for a better balance between the fuel being burned and the air required for its combustion, leading to more complete combustion of the fuel. This optimal combustion means that more energy is derived from the fuel, enhancing the overall efficiency of the furnace. Additionally, fuel is utilized more effectively, potentially reducing fuel consumption over time while producing the same output. Hence, increasing combustion efficiency is directly linked to the appropriate management of air in the combustion process.