Transformation Characteristics And Mechanism Of Fuel Nitrogen During O₂/CO₂ Combustion

In these years, a large number of carbon dioxide has been produced by fossil fuel combustion, high levels of carbon dioxide in the air will cause the green house effect, which has great impact on people's daily life and threaten other creatures, it has been paid close attention by governments and scholars. Among these technologies O2/CO2 combustion is an economical and effective technology. The O2/CO2 combustion technology can significantly reduce the cost of CO2, and it has become a hot topic in recent years.Although many researchers have carried out many results by this kind of combustion, but has less understanding of the processes and mechanism of the conversion of fuel nitrogen This article based on a detailed analysis of the characteristic of the pulverized coal, experiments had been done in a fixed bed flow reactor and a pyrolysis reactor (gasification) and combustion tests under high CO2 concentration atmosphere, flue gas and the solid residue test conducted a deeper analyzes, in order to get the fuel nitrogen in O2/CO2 emission rules and transformation mechanism during combustion.In this paper, proximate analysis, Ultimate analysis and X-ray photoelectron spectroscopy (XPS) have been used for determination of element and functional groups of powdered coal. The results show the detail composition and elemental speciation distribution of the two pulverized, as well as their variation with particle size. Both the role of coal in different chemical mechanical force (reflected in the different size) beneath the coal composition trends the different.Pulverized static thermal and chemical processes are easy to control, It can be used from slow to fast heating rates, the reacting time can be handed flexible,and can get more detailed changes samples in pyrolysis and combustion process. And then have some researches on a fixed bed, gas analyzer was used for real-time monitoring during the experiment. It was found that under O2/CO2 atmosphere NOX emissions below the O2/N2 atmosphere. Improve the oxygen concentration can make the starting temperature NO emissions fall under two atmosphere. Add NO into the initial atmosphere tu simulate circulation NO reduction.In order to make a further understanding of the combustion and emission characteristics of coal in O2/CO2 atmosphere, we designed and assembled a vertical tubular furnace test bench to simulate the combustion process. By the result of experiments we concluded that the types of coal, furnace temperature, excess oxygen ratio, the initial NO concentration had influences on NO emissions, and then the influence mechanisms of these factors were analyzed. The results show that:the temperature has a great impact on Shenmu bituminous coal's NOx emissions, As the temperature rises NO emission concentration improved, but has less impact on Yangquan anthracite When the excess oxygen coefficient was 1.2, the minimum content of NO in the flue gas, coal combustion would incomplete or the NO emissions would too high when the peroxide coefficient too small or too large. After adding certain quantity of NO in the initial atmosphere volatile has a reducing action on the NO, NOX can be reduced to N2.Finally, we carried out a systematic analysis of pulverized coal, char and ash after combustion using XPS and elemental analysis; then we carried out a further analysis of steps of the heterogeneous mechanism based on the element content and surface functional group content analysis, which can be used to determine the possible heterogeneous mechanism of NO and provide a reference to the transformation mechanism of NOX of pulverized coal combustion in O2/CO2 atmosphere.