The 3D Numerical Simulation Of NOx Reduction By Natural Gas Reburning

NOx emission on the coal burning is one of the major pollutant sources for atmosphere. In order to resolve the pollutant problems of NOx emission,many technologies of controlling NOx emission have been proposed,such as air-staged combustion and reburning technology. Thereinto,Natural Gas Rebuming(NRG)is a technology of injecting natural gas in reburning zone to reduce the NOx emission.It has the advantage of low investment,low operating expenses and high NOx reduction efficiency.As the development of reburning technologies in China and foreign countries,it will have very important value of engineering application with NRG.This paper summarizes the principle and controlling technologies on NOx emission by coal combustion,especially emphasis on NRG.Furthermore,it is outlined that the relevant models on the process of coal combustion.Based on it,three dimensional numerical simulation of Natural Gas Rebuming is carried out.With the typical tangentially fired boilers in China as research object,it is set up that the pulverized coal combustion models and the NOx models.Through CFD method,the combustion process is simulated.All of these will promote the engineering applications of fuel reburning technology.The combustion characteristic is obtained by simulating the general combustion process and the NGR process.It shows the necessity of NGR.The influences of the main parameters on NOx emission are researched.The results show that for the boiler researched in this paper, comprehensive considering the NOx reduction efficiency and the combustion efficiency, optimal operating condition can be obtained:reburned zone's length being 800mm;the stoichiometric ratio in rebumed zone being 0.9;the stoichiometric ratio in primary combustion zone being 1.1;the injection place of rebuming fuel being 800mm;the natural gas ratio being 10%～15%.Compared the NGR with the general combustion,NGR technology can reduce NOx emission effectively.In comparison to the air-staged combustion,the efficiency of NGR technology is better that of air-staged.For all kinds of reburning technologies,with different rebuming fuel,the efficiency of reducing NOx emission is different.Using natural gas as reburing fuel can reduce NOx emission more effectively.By numerical simulation,the influences of the main parameters on NOx emission are researched in NGR technology.By comparing,the results can prove the effectiveness of NGR technology and provide a useful reference and instruction for theoretical research and industrial application.