Research On Low Nitrogen Combustion And Denitrification Technology Of 350MW Coal Fired Boiler In Power Plant

In China,coal-fired power generation units occupy a large proportion in power production.With the rapid development of China’s total economy,the total demand for electricity is increasing,and the total coal consumption is also increasing significantly,which directly causes the total NOx emission of coal-fired boilers to increase.With the implementation of the national energy conservation and emission reduction policy,in order to actively respond to the green development of electric power,a low NOx emission transformation was carried out for the old boilers of a coal-fired unit in an electric power company.Considering the current situation of domestic and foreign unit transformation,on the one hand,from the perspective of low nitrogen combustion,the original boiler combustion mode was adjusted to reduce the generation of nitrogen oxides from the source;on the other hand,in order to further reduce the nitrogen oxides discharged into the atmosphere,catalytic reduction reaction denitration process was added in the tail flue,so as to achieve ultra-low emission,The main work of this paper is as follows(1)The problems existing in the combustion of the original boiler are deeply analyzed.It is pointed out that the concentrated combustion of the boiler in the furnace results in the high temperature of the combustion area and the generation of more NOx.There is no classification in the air distribution,and the air volume is fully distributed in the combustion area at one time,so the oxygen content in the combustion area is larger,and the oxygen enriched combustion leads to more NOx generation.The original once through gap burner has no idea of reducing NOx,so it is relatively old.It is closely related to unstable combustion,high carbon content in fly ash and slagging in furnace.(2)In view of the problems existing in the combustion of the original boiler,the low nitrogen burner is selected,and the fuel is separated from the rich and the lean.The graded air distribution is arranged in the overall air distribution,and the C-type air is arranged in the burner.After the redesign,the main fuel combustion area,NOx reduction area and burnout area are formed in the boiler combustion area,which effectively reduces the temperature of the main combustion area of the boiler,The reasonable distribution of oxygen supply in the combustion area solves the problems of combustion stability,efficiency and slagging under the condition of low nitrogen combustion.(3)The combustion conditions before and after the transformation were simulated and compared by using FLUENT software.It can be clearly seen from the cloud picture that the concentration of NOx generated in the combustion process is greatly reduced after the staged air distribution and concentration separation combustion.The data of nitrogen oxides and oxygen after combustion in different operating conditions of the boiler after transformation are collected and sorted out.The data show that the content of nitrogen oxides in different operating conditions is basically in line with the expectation.In the low load stage,the oxygen content changes greatly,which has a great impact.After the load is higher,the influence of furnace temperature on nitrogen oxides is obvious,which has a certain reference significance for unit operation.(4)At the beginning of the design,the unit did not consider the problem of low emission of nitrogen oxides.In order to further reduce the concentration of nitrogen oxides in flue gas,the catalytic reduction process of nitrogen oxides was added in the tail flue.In this paper,the SCR denitration process was compared and selected,the urea pyrolysis process and SCR reactor were designed and calculated,and the catalyst was selected.Finally,the operation parameters of the reactor outlet were collected and analyzed,which showed that the transformation could achieve the expected goal of ultra-low emission.