Numerical Simulation Of Redusing NO_X Emission In Vertical Staged Horizontal Bias Combustion Burner

As the problems of environment protection become serious, the emission ofcontamination is regarded more and more. So thenumber 2 boiler in GaoJing powerplant was retrofitted for the second time. OFA was equipped on the upside of theburner, and Horizontal Bias Combustion burner (HBC burner) became main burners.The method of changing secondary air proportion was adopted to lower the NOXemission.This thesis numerically simulates flow, heat transfer, combustion and NOemissionprocessina220t/htangentiallyfiredboilerusingaCFDsoftware FLUENT6.2.Two operation cases are simulated.The first case is under uniform secondaryairdistribution.The other case is under staged secondaryair distribution.The numericalresults showed the temperature field and the concentration distributions of thecombustion species in the furnace. In the numerical simulation of furnace process,the turbulence is accounted for Realizable k-εtwo equations turbulent model. Thestochastic tracking model is applied to analyze the gas-solid flow field. Radiationuses the P-1 model. The devolatilization process is modeled by two competingreaction model. The combustion of volatiles is modeled by the Probability DensityFunction (PDF). Char combustion is modeled by diffusion-kinetics model. Thegoverningequations are discreted over a non-uniform staggered grid in the Cartesiancoordinate using the finite difference method and the equations are solved bySIMPLEC algorithm. The simulation and the measurement of hot test are comparedand they agree with the other fundamentally. It shows that the technology whichcombined the Horizontal Bias Combustion burner (HBC burner) with Air stagecombustiontechnologycanhelptoHBCburnerplayingitsadvantagesasgoodflamestabilityandlowNOemission.Bythe way of numerical simulation and experiment, after air staging, when thepulverized coal is fed into the furnace, it is burned in reductive atmosphere and agreatdealofCOisproduced,whichcanrestraintheproductionofNOXeffectively.The inverse-tower air supply manner of secondary air is more helpful inreducing the emission of NOX, and the reduction amplitude is larger. The content ofO2 at the furnace exit influence a lot on the emission of NOX; the emission of nitrogen oxide reduces when the content of O2 at the furnace exit reduces.Meanwhile, both experiment and calculation results indicated that the calculatedburnout of coal particles kept in a low level all the time, and a high combustionefficiency was kept, which brings none bad influence on the economic character oftheboiler.