Experimental study of volatile-N conversion at O2/CO2 atmosphere in a drop tube furnace

摘要

In coal combustion,NOx is largely formed from the oxidation of volatile nitrogen compounds such as HCN and NH3. The experiments on the volatile-N conversion to NO at O2/CO2 atmosphere were carried out in a drop tube furnace. The effects of the excess oxygen ratio X (0.6-1.4), temperature (1000-1300°C),O2/CO2 ratio,and as well as CH4/NH3 mole ratio were investigated. To further understand the importance of NO reburn during volatile combustion,experiments were also performed with different concentrations of background NO (0-950 ppm). The results show that volatile-N conversion to NO is sensitive to excess oxygen ratio X at strongly oxidizing atmosphere.For volatile combustion, there is an optimal temperature and inlet O2 concentration to minimize the volatile-N conversion to NO. The CH4/NH3 mole ratio plays an important role on the NO formation under oxidizing atmosphere.High levels of background NO prohibit the volatile-N conversion to NO significantly as the volatile-N conversion ratio decreases by 19-36%. The reburn fractions of recycle NO in fuel-rich and fuel-lean condition are 14.8% and 9.8% at 1200°C,respectively.