Research On The Characteristics Of NO Ozonation Process And Gas Mixer Based On Numerical Simulation

Ozone-Based Low-Temperature Oxidation de-NOx Process can oxidize NO(>95%in flue gas)into the high valence NOx(such as NO2 and N2O5)which is removed by the followed desulfurization system.The process avoids the secondary pollution and has few influences on the existing units.This paper used sensitivity analysis method to analyze and simplify the oxidation reactions between O3 and NO in Ozone-Based Low-Temperature Oxidation de-NOx Process,and obtained the main elementary reactions and factors influencing N2O5 formation.In addition,a new type of gas mixer was developed according to the working principle of static mixer,and the effects of the geometry and process conditions of the mixer on the NO oxidation efficiency were analyzed based on the computational fluid dynamics(CFD)method.The 78-step oxidation mechanism of NO was concluded by summarizing the reactions between O3 and NO from the previous studies.After verified by experimental data,the reaction mechanism was analyzed and simplified by sensitivity analysis based on the verification by experimental data,and a 21-step reaction mechanism was obtained.In addition,the absolute value of the sensitivity coefficient of each elementary reaction showed that the main elementary reactions in the process of NO oxidation are O3+NO=NO2+O2,O3+NO2=O2+NO3,NO2+ NO3=N2O5,NO2+NO3=NO+NO2+O2,N2O5=NO3+NO2 and NO+NO3=NO2+ NO2.H2O promotes the consumption of NO,NO3 and N2O5 only at low temperature,and the decomposition of O3 has little effect on the reaction in a certain temperature range.The increase of reaction temperature merely increases the weight of O3+NO2=O2+NO3 and decomposition reaction of NO3.The weight of the decomposition reaction of O3 remain stable.As to the effect of operational conditions on the yield rate of N2O5,the increase of the molar ratio is benefit to the formation of N2O5 with the molar ratio of O3/NO greater than 1.00,and the recommended range for the molar ratio of O3/NO is 1.50-1.75.The increase of reaction temperature inhibits the formation of N2O5.In detail,N2O5 will not decompose basically when the reaction temperature is not higher than 373K.butN2O5 starts to decompose after 1.5 seconds when the reaction temperature is greater than 373K.The flow field distribution in the static mixer was studied by Reynolds-Averaged Navier-Stokes Equations which are closed by the Realizable k-ε turbulence model.The influence of structural parameters on mixer performance were analyzed,which based on the uniformity of flow field and pressure drop.Including angle θ of inclined deflector,dimensionless distance l between nozzle outlet and deflector and dimensionless height h between deflector.The results showed that θ has a greater influence on the uniformity of flow field and pressure drop,and the l and h merely affect pressure drop.The simulation results of process conditions showed that N2O5 conversion rate increases first and then decreases with the increase of flue gas temperature.The temperature range with the highest conversion rate is 363 K-373 K.The conversion rate of N2O5 decreases with the increase of flue gas velocity.When concentration of O3 remain stable,the molar ratio of O3/NO may decrease due to the load change,the N2O5 conversion first increases and then decreases.