Numerical Simulation Of Combustion Characteristics Of 660MW Ultra-Supercritical Four-Wall Tangentially Fired Boiler

In this paper,a power plant HG-1968/29.3-YM5 type 660MW ultra-supercritical four-wall tangential-fired pulverized coal fired boiler is studied by using the commercial software ANSYS ICEM to establish engineering model and mesh,and using ANSYS FLUENT to study the performance characteristics of the boiler through numerical simulation,aiming at providing theoretical guidance and reference for the economic,safe operation of the boiler.This paper first introduced the basic situation of the boiler,and briefly introduced the mathematical model of numerical simulation.According to the characteristics of each model,combined with the actual situation of the research object,the appropriate mathematical model was selected based on the work of others.Then,according to the actual size and structural characteristics of the boiler,after the1:1 entity modeling and grid division,the numerical calculation of the boiler rated working condition is carried out to determine the rationality of mesh generation and mathematical model selection.On this basis,the effects of excess air coefficient,SOFA damper opening,coal mill combination and load variation on combustion and NO_x generation characteristics of the boiler were studied respectively.The flow characteristics,combustion characteristics,component distribution and NO_x emission characteristics of various working conditions were analyzed.The results show that increasing the amount of air in the furnace to a certain extent can make the combustion more fully,reduce the carbon content in fly ash,but increase NO_x emissions.The excess air coefficient in the furnace can achieve low NOx emissions and high combustion efficiency from 1.1 to 1.15.Under the premise that the SOFA wind rate is 30%,reducing the SOFA damper opening will make the actual tangent circle diameter become larger.Although the main combustion zone is more fully burned,it will increase the NO_x generation amount.Under all operating conditions of the six-layer burner,the boiler has poor combustion effect and generates more NO_x.When the five-layer burner is put into operation,the coal mill combination method is ABCDE to achieve the lowest NO_x emission when the combination method is BCDEF.The highest concentration of NO_x emissions.The reduction of the load causes the temperature level in the furnace to drop and the NO_x emissions to decrease,but the air flow organization and degree of burn-up are poor.Based on the four wall tangentially fired boiler was studied systematically,through the arrangement of position change of the main burner to form four corner tangential combustion model,in which other conditions are same to the numerical simulation,and compared the four wall tangentially fired combustion model.The results show that the performance of the four wall tangential firing mode is better than the four corner tangential firing mode,no matter in air distribution,combustion quality and NO_x emission performance,which provides a reference for the selection of tangential firing mode.