Numerical Simulation Of 670t/h Boiler Combined Denitration By Deep Air Stagingand SNCR

Coal is the major primary energy source in China.Coal-fired boilers generate a large amount of nitrogen oxides during operation.The resulted environmental pollution is already seriously affecting the environment in which human beings live.Therefore,it attracts more and more attention.The combined application of deep air staged combustion and selective non-catalytic reduction(SNCR)technology has the advantages of lower operating cost and shorter construction period,and it has broad prospects for engineering applications.In order to reduce the NO_x emission of a 670t/h four-corner tangentially-fired boiler,numerically simulation and analysis were performed.Firstly,numerical simulations were carried out under different OFA rate.The flow field,temperature distribution,O2 concentration distribution,CO concentration distribution,and NO concentration distribution in different cases were analyzed.The results show that with the application of deep air staged combustion technology,the speed distribution,temperature distribution and distribution of flue gas components in the furnace change distinctly.The generation and emission of NO have been greatly reduced.The lowest NO emission was 78.9 ?mol/mol,while the OFA rate is 0.35.This NO emission decreased by 63.33%,compared with the case of 0.15 OFA rate.On the basis of the calculation of low NO_x combustion,numerical simulation of SNCR denitrification was carried out.The influences of SNCR reaction process parameters such as reducing agent atomization angle and ammonia-nitrogen mole ratio on the denitrification were analyzed.According to the calculation results,the optimization design of air staged combustion combined SNCR denitrification is carried out.In all the studied cases in this work,the optimal condition is: the OFA rate was 0.35;the 3# arrangement scheme of spray gunsis adopted;the ammonia nitrogen ratio is 1.05;the atomization angle of the spray gun is 20 degrees.In this optimal case,the NO and NH3 concentrations at the outlet of the furnace are 63.51 ?mol/mol and 12.46 ?mol/mol,respectively.