Study On NO_x Conversion Mechanism Under O₂/CO₂ Combustion With High Concentration Of CO₂

China is a major coal consumer,and coal is also the main energy resource in China.The massive combustion of coal will discharge large amounts of pollutants such as NO_x,SO_x,and particulate dust,which will cause environmental problems such as acid rain,photochemical smog,fog and haze.These environmental problems are great harmful to human health and ecological environment.At present,China's desulfurization technology is a comparatively ripe craft,but there are still a series of problems that need to be solved in the denitration technology,especially the formation mechanism and the conversion ways of NO_x still exists many loopholes.Therefore further study of the nitrogen conversion mechanism during the coal combustion process to providing a theoretical basis for the development of denitration technology has become a key.Effects of Shenmu volatile,Shenmu char,coal-based activated carbon,graphite powder,atmosphere,temperature and interactive combustion with volatile on conversion characteristics from fuel nitrogen to NO_x along the reactor during oxyfuel combustion were investigated by pyrolysis tube furnace and entrained flow reactor.When the four samples combust alone,the volatile's trend of NO_x conversion characteristics emissions maintained a stable status,and the other three samples' trend were gradually increasing.All four samples emit more NO at the exit in higher combustion temperatures and O₂/N₂ combustion atmosphere.Under the condition that the three samples interacted combustion with Shenmu volatile,the regularities of NO emission of Shenmu char was similar to that of the single combustion,but the NO emission concentration decreased along the whole;the regularities of NO emission of activated carbon changed to increased first and then decreased,the NO emission concentration increased along the whole;the regularities of NO emission of graphite powder was similar to that of the single combustion,the NO emission concentration increased along the whole.Effects of Shenmu char,coal-based activated carbon,graphite powder,atmosphere and interactive combustion with volatile on the reduction law of NO during oxyfuel combustion with introduction of initial NO were investigated by pyrolysis tube furnace and entrained flow reactor.The introduction of initial NO enhances the reduction of NO by coal char,and the introduction of volatiles further enhances the reduction of NO by coal char;the conversion rate of char nitrogen to NO in O₂/CO₂/NO atmosphere is lower than that in O₂/CO₂/NO atmosphere,and NO is more reducible in O₂/CO₂/NO atmosphere;the introduction of initial NO significantly reduces the conversion rate of nitrogen to NO during combustion of activated carbon,and promotes the reduction of NO by activated carbon.The introduction of volatile speeds up the reaction speed,and further strengthens the reducibility of the mid-and late-reaction;the introduction of initial NO does not significantly reduce the conversion rate of nitrogen to NO during combustion of graphite powder,and does not enhance the reducibility of the combustion of graphite powder.The introduction of volatiles makes the change of the NO emission concentration along the whole more gradual;overall,the introduction of initial NO is not conducive to the reduction of NO emission.In this paper,the three heterogeneous reaction path of the coal char model with pyrrole nitrogen at the edge was optimized by Gaussian09 quantum chemistry calculation software.The intermediates,transition states,product and their configuration,energy and activation energy during the reaction pathways were obtained.The heterogeneous reaction mechanism of char nitrogen was achieved by analyzing each step of the elementary reaction from the microscopic molecular.The N in char combines with the 0 in O₂ and precipitated as NO during the heterogeneous oxidation reaction between nitrogen-containing char model and O₂;The N in char combines with the N in NO and precipitates in the form of N₂ during the heterogeneous reduction reaction between nitrogen-containing char model and NO;With the influence of CO,the O in NO combines with the CO and precipitates in the form of CO₂ during the heterogeneous reduction reaction between nitrogen-containing char model and NO.