Combustion Air Humidification for NOx Emissions Reduction in Gas Boiler: An Experimental Study

Abstract

NO x emission reduction from gas boilers has become a key issue in improving air quality. Combustion air humidification technology is gradually being used to reduce NO x emissions. However, the NO x emission reduction effect of gas boilers at a higher combustion air humidity has been studied less. A flue gas with low NO x emissions and a waste heat recovery system using combustion air humidification technology are proposed in this study. In the ultra-low NO x mode, the effect of high combustion air humidity on NO x emission reduction and efficiency of the gas boiler were studied experimentally. In the waste heat recovery mode, the effects of the heat network backwater temperature on the NO x emission reduction and system efficiency were studied experimentally. Results showed that an increase in air humidity can significantly reduce the NO x concentration formed by combustion. The ultra-low NO x mode reduces NO x emissions from 130 mg/m 3 to 23.3 mg/m 3 and affects the boiler efficiency slightly. In the waste heat recovery mode, NO x emissions can be reduced to 39.9 mg/m 3 when the backwater temperature of the heat network is 55 C. This condition improves the efficiency to 93.8%. The analysis results provide suggestions for the selection of the operation modes.