Nitrogen Conversion Mechanism And Experimental Study During The Reaction Process Of Char-NO

Nitrogen oxide (NOx) is not only one of the major components of air pollution in China, but also the important composition of the haze occuring in China recent years. However, the major sources of the NOx emission are coal-fired power plants in China. Thus, it is important to research the formation and transformation mechanism as well as the control measures of NOx.Fuel-N is the major type of the NOx emission during the coal combustion. The conversion reaction of fuel-N in coal is composed of devolatilization and char reaction. The homophase reaction mechanism between volatiles and NOx is confirmed in previous studies. But the heterophase reaction mechanism between char and NOx has not been reached to an agreement. Especially little is known about the study on the mechanism of influence for the doped metallic compounds in the reaction of char-NO.The research technical route is as follows:the combined forms of nitrogen in the blended coal and char respectively; the transformation path of the type pyridine nitrogen/pyrrole nitrogen into the main precursor (HCN/NH3); the rule of the blended coal char to release coke nitrogen during the oxidation process; using Mayer bond order theory and transition state theory to reveal the transformation path of heterogeneous reduction NO by char; factorial experimental and mechanism study of the char-NO reaction intensified by doped metallic compounds. The research methods and results in this paper can be regarded as the theoretical basis and technical reference for the development of a partial denitration technology used by Char. The key findings of dissertation are as follows:Pyrrole nitrogen (N-5) in the blended coal is instability by the analysis of X-ray Photoelectron Spectrometer (XPS). The forms of nitrogen in the blended coal and corresponding char were researched by XPS. The results show that N-5 is transformed into the form of volatile gas or pyridine nitrogen (N-6) or quaternary nitrogen (N-Q).HCN is released relatively easily for pyridine type (N-6) coal edge model, while NH3 is released relatively easily for pyrrole type (N-5) coal edge model. The total activation energy for N-6 to release HCN is 451.67kJ/mol, but to release NH3, the total activation energy is 561.18kJ/mol. The formation of NH3 is possible in both char edge models containing 2-pyridone in zigzag and armchair configurations (N-5). However, NH3 is released relatively easily in the Armchair configuration containing 2-pyridone.The main gases produced in the combustion of the test char in air atmosphere include CO2, CO, N2O, HNCO and HCN in the study for the test mix coal char oxidation reaction process. The results of TG-FTIR indicate that the yield of CO2 is the most, while the productions of NO and NO2 are little. The formation trend of HCN, HNCO and N2O is basically the same and NH3 is not detected in this experiment.The theory of Mayer bond order can be effectively used to research the heterogeneous reduction reaction mechanism of NO on the char edge models surface at the molecular level. The key point which is more easily broken has also smaller Mayer bond order. The results indicate that N2 and CO are released in the process of heterogeneous reduction reaction of NO on the char edge model surface in armchair configuration, while only N2 is released in the process of heterogeneous reduction reaction between the char edge model in Zigzag configuration and two NO molecules.The total activation energy of char-NO can be reduced by doped metal compounds, thus the NO reduction rate is increased. Factorial experiment results show that the effect of the catalyst on NO heterogeneous reduction is affected by temperature, the kind of char and catalyst with more and more significant influence. A coupling model to predict NO reduction according to the parameters mentioned above is established based on a factorial experiment design. The catalytic effect of composite metallic compounds blended by calcium-based and iron-based in the same ratio is synergy for char-NO. The results from quantum chemistry study show that the total adsorption energy of char-NO can be enhanced by doped CaO in the system and the overall reaction activation energy of char-NO can be reduced by doped CaO than that without CaO.