Steam generated from boilers is used in many industrial processes, including manufacturing, refining, chemical processing and power generation. The burner is the heart of a boiler system, providing the necessary combustion of fossil fuels. Yet, if the burner is the heart, then the combustion controls — which manage air and fuel flow to the burner — are the brains of the boiler system. Airflow must be controlled and balanced, and sufficient quantity must be provided to ensure complete fuel combustion with minimal unburned hydrocarbons. At the same time, too much airflow can decrease boiler efficiency. This balance is determined by the combustion control scheme.
This article will discuss the typical combustion control schemes that are used on watertube and firetube boilers and present advantages and disadvantages for each scheme. For the purpose of discussion, it is assumed that the burner fuel is either gaseous or liquid (oil), not a solid fuel. Also, it is assumed that there is one burner per boiler and that there is a combustion-air fan (the burner is not a natural-draft design).