Pollutant emission characteristics of staged combustion with hydrogen-enriched methane for gas-fired boiler based on Taguchi design

Hydrogen-enriched methane (HEM) combustion is an effective method to reduce the consumption of CH 4 . A Taguchi orthogonal method was proposed to investigate the effects of the H 2 -doping ratio X H2 , air preheating temperature T air , and excess air coefficient of burners arranged at the bottom E x,b on the NO x and CO emissions from HEM combustion in a gas-fired boiler. According to the analyses, the significant order of the three parameters for NO x emissions is T air > X H2 > E x,b . The optimal combination was X H2 = 0, T air = 300 K, and E x,b = 0.8, and the corresponding NO x emissions were 20.59 mg/m 3 . For CO emissions, the significant order of the three parameters is X H2 > T air > E x,b , and the optimal combination was X H2 = 0, T air = 400 K, and E x,b = 0.9 where the corresponding CO emissions were 5.47 mg/m 3 . An entropy weight method was used to obtain the optimal combination of X H2 , T air , and E x,b for the total NO x and CO emissions, and an index of comprehensive pollutant emissions (CPE) was proposed. Further investigation of the CPE in 25 trials showed that for the total emissions, the significance order of the three parameters was X H2 > T air > E x,b . The optimal combination was X H2 = 0.4, T air = 400 K, and E x,b = 0.8, and the corresponding NO x and CO emissions were 33.68 mg/m 3 and 6.53 mg/m 3 respectively. These results provide guidance on the operating conditions of HEM combustion for emissions control. • Pollutant emissions for hydrogen-enriched methane combustion were investigated. • Taguchi design method was adopted to study the signal-to-noise ratio of pollutants. • Significance order of impact parameters for pollutant emissions was determined. • Entropy weight method was used to obtain the optimal combination for emissions. • An index of comprehensive pollutant emissions was proposed for less emissions.