Numerical Simulation And Optimization Of Gas Distributor Structure In Sintering Flue Gas Ozone Denitrification System

In order to control the emission of NOx in steel industry and other industries and protect the environment,more and more attention has been paid to denitrification technology in China.Compared to Selective Catalytic Technology(SCR)and Selective Non-Catalytic Reduction(SNCR),ozone denitrification technology can be applied to low temperature denitrification.Meanwhile,due to its instability,ozone can decompose slowly into oxygen at room temperature so that the environment pollution caused by ozone can be avoided.It is known to us all that mixing uniformity of NOx and gas(reducing agent of SCR and SNCR,oxidant ozone in ozone denitrification process)will have a great impact on the efficiency of a denitrification system.Since gas distributors are often used in denitrification process to enhance the mixing uniformity,therefore,this paper focused on the optimization of distributor structures and obtained the optimal solutions.The research is including main parts as follows:Firstly,based on the ozone denitrification design for sintered flue gas from a 200m~2Sintering flue gas machine,we calculated the amount of ozone needed.After that,the structures of the gas distributor and flue pipe were optimized,and the components of mixed gas as well as boundary conditions were determined for subsequent simulation of flow field.By a commercial CFD simulator,FLUENT 14.0,the gas flowing in the pipe was characterized.And,the effects of nozzle injection angle,the number of branch nozzles and the mixing distance on gas mixing were analyzed.It is shown that if the number of nozzles stays unchanged,the gas disturbance will go up while the relative standard deviation of ozone concentration and ozone flowing velocity will decline a long with a larger nozzle injection angle.When the injection angle stays the same,the effect of gas mixing will be improved with the increase of nozzle number.No matter what kind of gas distributor structure it is,with mixing distance increases,the relative standard deviation of gas velocity will decline at first,then increase but finally decline again.The pressure drop at inlet and outlet will rise with the increase of the nozzle number and spray angle.In a word,when the number of branch pipe nozzle per unit is 10 whilst the nozzle spray angle is 45°and the mixing distance reaches 4m,the gases mix best.Finally,the difference between single-layer gas distributor scheme and two-layer staggered gas distributor scheme was studied.The results show that at inlet and outlet of the distributor,even though the pressure drop of the latter scheme is slightly lower than that of the former scheme,the mixing efficiency of the former scheme is obviously higher than that of the latter scheme.It is concluded that the gas mixing efficiency will be highest in a single-layer gas distributor with 10 nozzles per unit,nozzle angle 45°and 4m for mixing distance.