CFD Simulation Of Photocatalytic Degradation Of Volatile Organic Compounds

The photocatalysis has gained a lot of attention as a treatment process due to its strong oxidation and without secondary pollution.This technology has been developed in the practical application,however,the size of the reactor,the recycling and state of the catalyst and other problems inhibit the large-scale commercial applications.As the main equipment of photocatalytic reaction,photocatalytic reactor can affect the degradation efficiency of photocatalysis.In this dissertation,a small photocatalytic reactor with simple structure was studied.The velocity distribution of gas in the reactor and the degradation efficiency of the reactor were simulated using computational fluid dynamics(CFD).There are seven models used in this dissertation,including six kinds of low Reynolds turbulence models and Laminar model.Result shows that Laminar model can simulate the velocity distribution and the effect of degradation well,it has a good agreement with the experimental results.All the low Reynolds turbulence could not simulated velocity distribution simulation well but the degradation efficiency they simulated can match well with the by the experimental results in the low flow rate,a protion of low Reynolds turbulence models could simulate the velocity well due to the increase of flow rate,it could causes the increase of the Reynolds number.For larger reactors,the effects of inlet velocity,initial concentration,radiation intensity and internal structure on the flow field,turbulent viscosity,radiation field and concentration field distribution in the reactor were investigated.The change of these variables will affect the flow state of the fluid in the reactor,thus affecting the degradation of ethylene in different parts of the reactor.The results showed that the increase of flow rate and initial concentration would lead to the decrease of degradation efficiency and the increase of degradation amount per unit time,and there was an optimal value.The change of inlet velocity will affect the distribution of velocity field and the distribution of turbulent viscosity in the reactor,leading to different ethylene degradation amounts in different parts of the reactor.And the increase of initial concentration is conducive to the increase of ethylene adsorption on the catalyst surface per unit time,which leads to the increase of degradation amount in the same time.For the region with small turbulence viscosity,the degradation amount increased more obviously with the increase of initial concentration.In this dissertation,the increase of radiation intensity would promote the degradation of ethylene in the reactor,the effects of the increase of radiation intensity on different parts of the reactor were not consistent.The higher the turbulence viscosity,the lower the influence of radiation intensity on it.In this dissertation,decorate two cases of the baffle,they are the perpendicular to the direction of fluid flow and parallel to the direction of fluid flow,baffle inside the reactor can affects the flow field and turbulent viscosity.Parallel to the direction of fluid flow of the baffle can increase the movement path of fluid,but also can increase the turbulent viscosity of reactor,the two have opposite effects on ethylene degradation in the reactor.The baffle perpendicular to the flow direction can cause the fluid to form a backflow area,which can increase the contact time between the fluid and the catalyst surface,but the turbulent viscosity will also increase.By arrangement the baffles in the reactor to adjusting the turbulent viscosity ant movement path in the reactor,it can improve the degradation efficiency and the amount.In this dissertation,the overall simulation of the flow field,turbulent viscosity,radiation field and concentration field in the photocatalytic reactor has theoretical significance for the development of high-performance photocatalytic reactor in the future.