Description

Traditional combustion controls packages are relatively simple and effective for responding to a variable process steam or hot water load. However, simultaneous technological advances on two fronts (low NOx burner operation, and digital controller standardization) have complicated the task of selecting and implementing new combustion controls for new or retrofit boiler applications.

Low NOx burners typically incorporate different fuel and air mixing patterns which lead to reduced boiler emissions. Additionally, these applications may incorporate controlled variables which are not present in traditional burner packages. The required band of control for a low NOx combustion control application can be narrower than that of a traditional burner application. As regional NOx requirements continue to trend lower, the required band of control for low NOx combustion control systems also narrows. With this requirement for a narrow band of control, coupled with additional controlled combustion variables, more precision is required from the combustion controls system.

Advances in digital controller technology have made it possible for the controller hardware to enhance the overall boiler performance, while also adding new safety features. For example, parallel positioning systems with position feedback monitoring simulate the rigid linkage operation of single point positioning applications. Also, real time fuel / air ratio monitoring in a full metering combustion control application can shut down a burner if the measured air flow is inadequate for the complete combustion of the measured fuel flow.

The boiler owner is ultimately responsible for the safe and reliable long term operation of his boiler. There are five primary factors which the owner or his representative must control for a successful long term boiler combustion control application. These are:

• Proper selection and engineering of the control scheme
• Proper selection of the controller hardware, final control elements, and field measuring devices
• Proper commissioning
• Proper operation (including operator training and staffing)
• Proper maintenance

The member companies of the ABMA feel that this publication will enhance the understanding of boiler owners and system designers in the complicated and dynamic field of combustion controls.