Simulation On Heterogeneous Photocatalytic Fixed Bed Reactor For Wastewater Treatment

Photocatalytic technology,as a new type of advanced oxidation technology,has got widely attention in recent years because it can efficiently remove the refractory organic pollutants and no secondary pollutant is produced.One of the important research directions is its application in the treatment of wastewater,especially which is difficult to degrade.But for now the photocatalytic technology is still in the laboratory scale,and it is mainly focused on improving the performance of the catalyst,The existing research also tends to improve the performance of the catalyst.The study of photocatalytic reactor is relatively few,especially its use in the pilot plant.The existing reactors still have many drawbacks such as:the small photocatalytic area,the low light efficiency,the poor mass transfer,and all these have limited to popularize photocatalytic technology in industrial.Numerical simulation has the advantages of low cost,short period and could reveal the process of fluid moving in a visualized way,which is pretty helpful on observation of some phenomena.A precise numerical model is crucial for simulation.There isn't the suitable numerical model to be used in designing heterogeneous reactor since the complexity of the photocatalytic system.It turns out that the photocatalytic technology to be scale applied is still behind schedule.Aiming at these problems,by analyzing the mechanism of photocatalytic reaction,fixed bed photocatalytic reactor is studied to be based on TiO2/O3/UV method by numerical simulation,which is expected to get an efficient photocatalytic reactor and to enlarge it for pilot test.The main work of this thesis can be concluded as followed:1.In order to brought up a new fixed bed photocatalytic reactor which can be with good mass transfer,big reaction area and high light efficiency in theory,the existing photocatalytic reactors are studied by deeply analyzing the reactive mechanism and mutual influence between factors.This fixed bed reactor is composed of a column body,some wave baffles and UV tubes,and the wave baffles are covered by thin layer of TiO2.2.The new numerical model is formed to simulate the degradation process,particularly,there are three parts of reactions can be responsible for the pollutants degradation,one is that pollutants can be directly oxidized by O3,the second is that generating the hydroxyl radical when O3 is irradiated by UV light can degrade the pollutants,and the last is that hydroxyl radical can be generated when O2.O3 are irradiated by UV light with TiO2,and the generating hydroxyl radical can react with pollutants in water.3.Taking Rhodamine B as the model pollutant,the numerical simulation software COMSOL was used to study the degradation rate at different RhB flow with the governing equations,which are laminar flow equation,Helmholtz equation and mass transfer equation.And the result shows that the errors between simulated and experimental values are all under 10%,which verifies the accuracy of the numerical model.4.On the basis of the above mathematical models,the simulation and design of photocatalytic oxidation reactor with a capacity of 10t/h was carried out.And this will be the theoretical support for industrialization.