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Numerical Simulation of Combustion and NO_X Exhaust in an Tangential Fired Boiler

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Tutor: YinHongChao
School: Dalian University of Technology
Course: Energy and Power Engineering
Keywords: Tangentially Fired Pulverized Coal Boiler,Combustion,NO_x exhaust,Numerical Simu
CLC: TK229.6
Type: Master's thesis
Year:  2009
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Using software FLUENT,Non-Premixed Combustion Model was employed to investigate numerically the flow field,heat transfer and combustion process in a tangentially fired furnace of some 350 MW pulverized coal boiler of Huaneng Dalian Power Plant.To reduce the influence of the numerical pseudo-diffusion on the computational results,a measure was taken to improve the grid system so that fluids enter the control unit in the direction of perpendicular to the unit’s border,not forty-five degree angle to the border.The meshes of boiler are all hexahedral meshes by simplify.In this paper,Mixture Fraction is used to calculate the continuous-phase turbulence chemistry interaction,Standard k-εModels is used to calculate species transport,The P-1 Radiation Model is used to calculate the radioactive heat transfer,and particle tracking is calculated by Stochastic Model,volatile evolution is calculated by Two Competing Rate Devolatilization Model and char combustion is calculated by Kinetics/diffusion-limited Rate Model。Five different actual conditions are simulated by turning off different nozzle in this paper, and then it is that turning off the rock-bottom nozzle is the optimal project the conclusion. Based on this,this paper stdudies that how do velocity of born-out wind affect NOx exhaust, and then the results show that when the velocity of born-out wind is 40m/s,the amount of NOx exhaust is the least.In the end,the combustion in boiler is analyzed,and the simulation results show that temperature drops with the increase of furnace height,and the highest temperature appears in the area of the burners;from bottom to top,the intensity of swirl firstly strengthens and then weakens in the furnace,but residual swirl still exists at the exit of furnace;the distributions of CO,and CO2 concentration are strongly related to the temperature field,that is,the high temperature area corresponds to the high CO and low CO2 concentration area;The highest NOx distributions area is the the highest temperature and the highest O2 area of the burners,than the highest NOx distributions area is the middle of the boiler.The simulation resunt also shows that born-out wind can reduce production of NO and HCN can be oxidated to NO in the top of the boiler.The particles’ trajectories in the furnace were also obtained the results can apply the reference to boiler’s running and improvement.
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