The Research On Low Nitrogen Emission For Concentrated XCL Swirl Burners Used For A 600MW Boler Burning Lignite Coal

At present,China's air pollution presents complex in haze and photochemical smog,both of which are related to vast NOx emission.Coal combustion from thermal power plant will generate a grate amount of NOx,NOx emission is an important factor to cause air pollution.Therefore,how to reduce the generation of NOx in thermal power plant has been the key point to solve the problem of air pollution.The lignite coal is an important fuel source for thermal power plant,it is urgent to develop a technology to reduce the NOx emission for thermal power plant burning lignite coal.This thesis does the research on how to reduce the generation of NOx for a 600 MW lignite boiler.The thesis studies the mechanism of NOx generation from coal combustion and the schemes of reducing the NOx generation from domestic and international.Then a plan to reduce NOx emission was proposed which was based on the actual situation of the power plant.The plan is using concentrated XCL swirl burner to reduce the NOx emission by adjusting the ratio of primary air and secondary air.When the secondary air ratio is down,meanwhile the combustion is kept as usual,because the secondary air ratio is turn down and the over-fired air ratio is increased,a reductive air field will be created around main combustion zone.Therefore,NOx reducing can be expected.A numerical simulation was made for the retrofit,the numerical simulation does the research on gas velocity field,temperature field,oxygen content distribution,CO concentration distribution and NOx concentration distribution for a 600 MW lignite boiler both before and after the retrofit.Based on the analysis,it shows effectively reducing the formation of NOx could be accomplished through the optimization of secondary air and over-fire air ratio.This result is coincided with the theoretical analysis of the previous retrofit scheme,it proves the retrofit scheme is feasible.Through the combustion adjustment test,we get the relationships between the boiler efficiency,NOx emission,unburnt carbon content,CO emission and the boiler operation oxygen content,staged air flow ratio,the swirl intensity of burners.Finally the optimized operating parameters of the boiler are obtained.After retrofit,the NOx emission of the boiler can be significantly reduced to 283.4mg/m3 without any interference with boiler efficiency.