ABSTRACT
This chapter gives a relatively short overview of combustion controls without going in depth on many of the design details extensively discussed in numerous specialized books1-4 with1 being a very good example on the subject. This chapter is primarily written to describe many practical issues related to the accuracy, reliability, and safety of the entire boiler control system that design engineers and users of the equipment need to be aware of when dening system requirements for specic conditions, comparing alternative solutions, and operating the systems. The importance of these issues is continuously increasing with more demand to operate combustion equipment with minimum possible NOx emissions-a goal that may be in potential conict with reliability and safety unless adequately addressed both in the system design and maintenance. The lowest NOx can be achieved when the ame is diluted with inert gases and/or heavily staged to the point that many deviations of the regime may result in combustion instabilities or a loss of ame. Minimizing these deviations in real systems whose operation is affected by many primary and secondary process variables (PVs) is the task of combustion controls. Some environmental regulations, like BACT (best available control technology) and MACT (maximum achievable control technology), by denition have become continuously moving targets for the combustion systems. These moving targets should be considered with the associated analysis of the costs to the industry and society that often is not properly completed. As a result, these moving targets have caused rising complexity of the combustion controls described here.
