Question 207Steam Plants - 1st Asst/Chief

You are correct, the answer is A) incomplete combustion. A lower than normal boiler stack gas temperature usually indicates incomplete combustion, which means the fuel is not burning fully or efficiently. This results in unburnt fuel particles in the exhaust gases, leading to a lower stack temperature compared to normal operating conditions. The other options are incorrect because: B) Dirty watersides would affect heat transfer, not stack temperature. C) Dirty firesides would restrict airflow, leading to higher stack temperatures. D) Fuel with high sulfur content does not directly affect stack gas temperature.