CO and NOxEmissions from a Controlled-Air Burner: Experimental Measurements and Exhaust Correlations

Abstract

ABSTRACT We present an experimental study of CO and NOx emissions from a controlled-air burner. Burners of this type are used throughout industry for direct heating of gas streams. A small scale research burner is used which emulates the key geometric features of a typical production burner. Exhaust measurements based on parametric variations of burner operating conditions are combined with insights gained from in situ measurements and from visual observations of flame structure to develop a description of the key mechanisms controlling pollutant production. Combustion within these burners occurs via an ensemble of inverse diffusion flames that stabilize on an array of air holes located on the side plates of the burner. Measurements indicate that the highest flames in the burner control CO emissions. In contrast, NOx emissions are controlled by the lowest rows of lit flames. Owing to this separation, CO emissions can be reduced without significantly affecting NOx emissions. Numerical correlations are developed to describe CO and NOx, emissions from the controlled-air burner. The forms of these correlations are based on the kinetic mechanisms controlling emissions from the burner when using characteristic temperatures and residence times. The resulting expressions for CO and NOx emission indices provide correlation coefficients of 97% and 95%, respectively. Examination of the expressions suggests that the controlled-air burner has a lower limit for COEI near 8.6 and for NOxEI near 0.5.