Experimental Study Of Nitrogen Migration Regularity During Char-NO Reaction

Nitrogen oxide （NO_x） is a well-known pollutant causing environmental problems. In China, coal-fired power plants are the main sources of nitrogen oxide. Thus investigation of nitrogen conversion regularity during coal combustion is of great significance to NO_x control in power plant and environmental improvement.Nitrogen in coal will generate NO_x during combustion. The generation process is composed of devolatilization and char reaction. The reaction mechanism between volatiles and NO_x is confirmed in previous studies. But the study in the reaction between char and NO_x is insufficient, especially the effect of the doped metallic compounds in the reaction of char-NO.A kind of anthracite char and a kind of bituminous char were chosen in this article. And two kinds of metallic compounds were doped into the char according to incipient-wetness impregnation method. A experiment based on thermo-gravimetric （TG） analysis coupled with fourier transform infrared spectroscopy （FTIR） and a factorial experiment of char-NO were done for the char samples. The combustion characteristics of the char and the nitrogen migration regularity during the generation of NO_x were studied in TG-FTIR experiment. And the nitrogen migration regularity in the reaction of char-NO with doped metallic compounds was studied in the factorial experiment.The main results of these experiments are as follows:（1）Both total active specific area and its increase rate of anthracite char are bigger than those of bituminous char. And the activation energy of anthracite char during combustion reaction is lower than bituminous char, indicating the former char is easier to react. （2）The results of FTIR experiment indicate the main nitrogenous gases generated during the combustion in air atmosphere include N₂O、HNCO and HCN. The formation trend of HNCO and N₂O is basically the same. And NO and NO2 is barely not detected while NH3 is not detected at all in this experiment. （3） Factorial experiment results show that the effect of the catalyst on NO heterogeneous reduction is affected obviously by temperature, calcium-based metallic compounds and iron-based metallic compounds with more and more significant influence. The catalytic effect of composite metallic compounds is synergy for char-NO. A coupling model of good fit to predict NO reduction according to the parameters mentioned above was established based on a factorial experiment design.