What is the excess air range associated with a safe operation range of 6-9% O2 after combustion?

To determine the excess air range associated with a safe operation range of 6-9% O2 after combustion, it's essential to understand the relationship between oxygen levels in flue gas and excess air in the combustion process.

When combustion occurs, the ideal combustion process uses a specific amount of air. However, to ensure complete combustion and prevent the production of harmful emissions, additional air, referred to as excess air, is usually provided. The excess air allows for more complete burning of the fuel, helping to maintain adequate oxygen levels in the flue gas.

In the specified range of O2 being 6-9%, this indicates a proper level of excess air relative to the stoichiometric requirements of the fuel being burned. Typically, an O2 concentration in that range corresponds to a significant amount of excess air, which is usually estimated at around 35-65%. This relationship helps in optimizing combustion efficiency while ensuring environmental compliance by minimizing pollutants.

Therefore, the choice that corresponds to the excess air range aligned with a 6-9% O2 level is within the 35-65% range, making it the most accurate response related to maintaining optimal combustion conditions. Understanding this relationship is crucial for operations to ensure safety and efficiency in combustion systems.