Flame behavior and emission characteristics of methane and ammonia fueled high-temperature flame in a bench-scale furnace

In this study, an attempt has been made to apply ammonia to the heating furnaces, which is the current major CO2 source in the industrial division. The use of the highly preheated air around 1000℃ differs the combustion field of the heating furnaces from the others, and NH3 application with such highly preheated air has hardly been reported. Then, in this study, a bench-scale furnace capable of creating a combustion environment at elevated inlet and in-furnace gas temperature has been designed and constructed. With a fuel of 30% ammonia and 70% methane based on the lower heating value (55% ammonia and 45% methane based on volumetric flow rate), radical profiles, exhaust gas compositions, and gaseous distributions inside the furnace have been measured. Fuel injection configurations are changed by using 4 “side nozzles” and 1 “center nozzle”. The former is located just inside the annular air nozzle, while the latter is further inside. The results show that the addition of NH3 to CH4 drastically changes the profiles of OH, NH, and CN radicals and, thus, the structure of the reaction zone. Then, the peaks of radical chemi-luminescence are higher in the case of side-CH4 injection than side-NH3. The higher peak indicates the formation of the hot spot for the side-CH4 case, and thus, exhaust NO concentration is found to be high (over 1000ppm) for the side-CH4 case. The results of the gaseous measurements inside the furnace indicate elevated NO concentrations at all points, which is in accordance with high NO at the exhaust. Besides its high NO concentration, NH3 and N2O have hardly been detected due to the high-temperature inlet air and atmosphere.