Effects of CO2 and N2 dilution on the characteristics and NOX emission of H2/CH4/CO/air partially premixed flame

Abstract

For the combustion of the mixture of blast furnace gas, natural gas, and coke oven gas in industrial burners, how to improve combustion efficiency and reduce pollutant emission are of significance. To accomplish this, an industrial partially premixed burner with a combustion diagnostic system is used to experimentally reveal the characteristics and NOX emission of H2/CH4/CO/air flame under CO2, N2, and CO2/N2 (replacing half of N2 with CO2) dilution. NOX emission and flame length, temperature profile, along with CO, CH4, and CO2 concentration profiles are analyzed with the three diluents in the fuel stream under different dilution rates (0–32% by volume). Experimental results show that for lean H2/CH4/CO combustion, greater proportions of CO2 in the diluent affect flame characteristics in various ways. These effects include longer flame length, lower highest flame temperature, the highest flame temperature being located farther away from the nozzle, and the highest CO2 concentration being located nearer the nozzle. Furthermore, results of CO, CH4, and CO2 concentrations indicate that chemical reactions in the flame are significantly affected by CO2 owing to the series reaction CH4⇌CH3→CO⇌CO2. Finally, increasing diluents or the ratio of CO2 in diluents has the benefit of reducing NOX emission.