An experimental and modeling study of NOx and CO emission behaviors of dimethyl ether (DME) in a boiler furnace

Abstract

NOx and CO emission behaviors of dimethyl ether/air premixed flame in a boiler furnace were studied by experimental and modeling approaches in this paper. Five excess air ratios (1.05, 1.15, 1.30, 1.45 and 1.60) and two thermal loads (high load (about 270kW) and low load (about 130kW)) were involved to investigate their effects on the emission behaviors. Besides, a chemical reactor network was constructed on the basis of CFD solutions to calculate NO and CO emissions. A detailed chemical mechanism of dimethyl ether combined with the San Diego NOx chemistry which includes thermal, prompt, N2O and NO2 pathways was used. The research indicated that NO in the flame base was formed via a combination of thermal, prompt and N2O pathways. The thermal pathway dominated in the high-temperature (above 1800K) flame zone. NO in intermediate-temperature (1000–1600K) regions was generated via the NO2 pathway. Besides, a considerable amount of NO was converted to NO2 in the low-temperature (below 1000K) zones. Emission indices of NO and CO both decreased with the increment of excess air ratio. They became rather small if the excess air ratio was maintained above 1.30 and 1.15 respectively. The effect of thermal load on the NO emission index was insignificant. The CO emission index increased considerably under the high load.