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Combustion Air Control
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The results of boiler control improvement projects may be disappointing due to unrealistic expectations and a failure to recognize the study and analysis required to ensure success. Early recognition of the need for data collection and boiler calibration is the first step to a successful project. Closed-loop control of flue gas oxygen content requires precise control of fuel-air ratios. This may be difficult on an industrial boiler which uses a variety of fuels, often with changing heating values. On older boilers the problem is further compounded by insufficient control hardware installed at a time when project costs were more important than efficient fuel utilization. Failure to identify and solve fuel-air ratio control problems will result in unsatisfactory flue gas oxygen control. Simple tests provide the data needed to evaluate the potential success of closed-loop oxygen control and to identify major control deficiencies. These tests: - Measure the effect that changing boiler load has on flue gas oxygen content while firing with the predominant fuel. - Measure the effect that changing the ratio of the predominant fuel to each of the auxi1iary fuels has on flue gas oxygen content. Additional testing is needed to calibrate and tune the revised system. Once satisfactory combustion air control has been achieved, the flue gas oxygen control loop may be closed.
Hughart, C. L. (1979). Combustion Air Control. Energy Systems Laboratory (http://esl.tamu.edu). Available electronically from