Numerical Simulation Of Low Nitrogen Combustion In 300 MW Tangential Boiler

Environmental pollution and energy shortage are major problems facing social development,and the emission control of NO_x pollutants has become an important problem to be solved in China's power industry.Therefore,studying the low-nitrogen combustion mode of boilers and optimizing the operation of the unit is of great significance for the development of China's power industry and the low-nitrogen operation of coal-fired units.At present,low nitrogen combustion in the furnace is realized mainly through two ways:one is to optimize the operating conditions of the unit by changing the combustion conditions;the other is to minimize the production of NO_x by changing the arrangement and position of the burner,so the full text work will be carried out based on these two aspects.In this paper,a 300 MW tangentially fired boiler is taken as the research object.Firstly,the velocity field,temperature field,component field and particle trajectory are simulated under the tangentially fired mode,and the combustion characteristics and NO_x emission law of the unit under different operating conditions are emphatically studied.Then,based on the 300 MW tangential boiler,the wall-type tangential mode is formed by changing the burner's layout.The distribution characteristics of velocity field,temperature field and component field in the furnace under three wall-type tangential modes are analyzed and compared in detail by numerical simulation,and compared with the four-corner tangential mode.The conclusions of the research are as follows:(1)The model chosen in the numerical simulation is reasonable and the calculation results are reliable.(2)The characteristics of low nitrogen combustion are different under different operating conditions:increasing excess air coefficient,increasing oxygen content in main combustion zone,decreasing CO content and increasing NO_x production in 1.25operating conditions are better;increasing SOFA air rate,reducing air volume in main combustion zone,intensifying incomplete combustion of pulverized coal,and decreasing NO_x emission.When the SOFA wind rate is 25%,the parameters are reasonable;with the increase of SOFA tilt angle,the NO_x concentration at furnace outlet decreases,but the emission reduction effect is not significant.(3)Compared with the four-corner tangential method,the SOFA wind wall arrangement has little effect on the flow field and temperature field in the lower part of the furnace,and the NOx emission value at the outlet of the furnace decreases by5.5%.The layout of SOFA wind and secondary wind wall improves the flow field,but the overall combustion temperature level of the furnace is higher and the furnace outlet is higher.The NO_x value increased by 3.4%.The wall layout of the burner makes the distribution of the aerodynamic field and temperature field in the furnace better,and the NO_x emission value decreased by 17%.This is the recommended low nitrogen arrangement of the burner.