Experimental Study And Quantum Chemistry Calculation On Fuel Nitrogen Conversion Mechanism Under O₂/CO₂ Combustion

China is a major energy consumer,and has become the world's largest energy consuming country since 2010.Coal,as one of the most important energy sources in China,will still be the main energy resource in China in the future.About 2/3 of the consumption of coal in China is used for combustion.The polluting gases like CO₂,NOx and so on are increasing persistently.What' s more,the environmental problems such as greenhouse effect and acid rain have became seriously.Carbon capture and sequestration technologies is an effective way to reducing CO₂ emissions.Meanwhile,O₂/CO₂ combustion technology can significantly reduce the cost of CO₂ capture,and efficiently reduce the emissions of NOx and SOx,and it has sparked off an intense research on this field.Effects of atmosphere,temperature and particle size on conversion characteristics from fuel nitrogen to NOx along the reactor during oxyfuel combustion were investigated using an entrained flow reactor.Results indicate that the fuel nitrogen conversion ratio from fuel nitrogen to NOx?FN-CR?profile along the reactor axis under O₂/CO₂ atmosphere is similar with that under 02/N2 atmosphere.FN-CR increases rapidly initially and decreases slowly later,and a maximum value exists.As the temperature rises,the length of initial conversion stage of increases,and the FN-CR at the reactor exit increases but the peak is delayed.The FN-CR profiles of coals with different particle sizes show different trends.The FN-CR of smaller particles increases first and then decreases along the reactor axis while that of coarser particles monotonously increases,and that of the medium-sized particles is found between the two.The reason may be that the coals of different sizes have different combustion performance and NO reduction activities.As stoichiometric ratio increases,FN-CR increases and the position of the maximum value is delayed.FN-CR increases at first and then decreases along the reactor axis at the stoichiometric ratioo ??1.2,while it keeps going up at ?>1.2.The research of effects coal variety,temperature and conversion characteristics from fuel nitrogen to NOx along the reactor during oxyfuel combustion were investigated by pyrolysis tube furnace and entrained flow reactor.Combustion temperature and atmosphere have significant effects on the emission of NOx,which volatile combustion in O₂/CO₂ mode,and the trend of NOx conversion characteristics emissions in the three different conditions maintained a stable status.The regularities of NOx emission of char are diverse because of various kinds of coal as well as reactor during oxyfuel combustion and coking temperature.The amount of NOx of Shenmu char combustion show a considerable rise at first,which followed by a stable status.While that of Yangquan char increased firstly and then decreased slightly.It is interesting to note that NOx emissions of Char prepared by temperature of 1073K combustion shows a similar picture that the amount of NOx rises firstly and then keep stable,while the temperature of 1273K is increased slightly after a slow downward trend.NOx emissions of interaction between Shenmu char and volatile along the reactor axis increases at first followed by a constant interval,but the overall concentration of NO along the reactor axis is lower than only using Shenmu char to burn.NOx emissions of interaction between Yangqun char and volatile along the reactor axis increases first and then decreases slightly.NOx emissions of interactive combustion between Char and volatile prepared by 1073K temperature along the reactor axis increases first and then keep invariant,while the higher temperature of 1273K is decreased along the axis.The structures of pyridine nitrogen,pyrrolic nitrogen,pyridone and quaternary nitrogen were optimized by Gaussian 09 quantum chemical calculation software,which is used to search the transition state of the first step pyrolysis reaction for the energy of reactants and transition state,to calculate the activation energy of the first step pyrolysis reaction,and to compare the stability of four kinds of nitrogen.The precipitation reaction path of nitrogen in pyrolysis reaction was analyzed from the molecular perspective.Pyridine nitrogen and quaternary nitrogen were precipitated in the form of HCN,while pyrrolic nitrogen was precipitated as NHi free radical.The first step roll ring crack of pyridine nitrogen needs to break the largest energy barrier,and that of pyridone needs to break the smallest energy barrier.Pyridine nitrogen is the most stable,while the stability of pyrrolic nitrogen,quaternary nitrogen and pyridone decreases in turn.