Numerical Simulation Of Radiation Field And Photocatalytic Surface Reaction In Photocatalytic Reactors

As a new indoor air pollutant removal method, photocatalytic air purification technology is considered to be a possible alternative of the conventional pollutant removal method because of its great application prospects. Its commercial application has been already on the initial stage. Photocatalytic reactor is the main equipment of the photocatalytic air purification technology. Study deeply on the light radiation field, photocatalytic reaction process and fluid dynamic behavior in the photocatalytic reactor can provide theoretical guidance for the reactor optimization and design. In this work, flat plate reactor, annular photocatalytic reactor, and honeycomb monolith reactor were selected as the research objects. These three typical photocatalytic reactors were systematically studied by the computational fluid dynamics method. The main research contents are as follows:Firstly, the flat plate photocatalytic reactor whose structure was relatively simple was taken as the research object, the photocatalytic decomposition in the flat plate reactor was modeled, and the feasibility of using CFD method to simulate the photocatalytic decomposition process was initially demonstrated. The model and approach for the numerical simulation of the photocatalytic reactor was clarified, and laid the foundation for the following research work.Secondly, take the annular photocatalytic reactor as the research object, the influence factors, such as the reflection of the quartz tube and reactor outer wall, on the light intensity distribution in the reactor were investigated. For the photocatalytic reactions, the effects of different reactor lengths and inlet flow rates on the conversions of the trichloroethylene were studied. Through comparing with the experimental data to validate the feasibility of the simulation method, the foundation for the subsequent reactor optimization was made.Based on the above annular reactor simulation method, the effects of different designs of the reactor configurations on the reactor performance were studied. The related designs of reactor configurations mainly involved the following three aspects: the relative position of the reactor inlet and outlet; the width of the annular; and the enhanced cell of the fluid flow disturbance(gasket). The study results showed that the parallel flow reactor inlet, the narrow annular width, and the mass transfer enhancement cell could improve the reactor performance significantly.Finally, the honeycomb monolith reactor was simulated. This paper presented a novel CFD simulation method for the honeycomb monolith reactor, through the reasonable simplification of the radiative transfer equation, by introducing the new model parameter-channel wall absorption coefficient-to simulate the local UV flux in the honeycomb channel. Then the simulation results of the light radiation were introduced into the simulation of formaldehyde photocatalytic degradation in the reactor, thus the simulation of the honeycomb monolith reactor was implemented. Based on the above simulation method, the optimization of the honeycomb monolith reactor was studied systematically. The effects of several reactor dimensionless geometric parameters(α、β and γ) were investigated and correlated in terms of "dimensionless uniformity of radiation distribution(η)", "honeycomb monolith photon absorption efficiency(φ)" and "overall monolith photonic efficiency(Ф = φη). And the conclusions were drawn: when the monolith-to-lamp height ratio was nearly equal to one(α = 1.0~1.1),the maximum values of the overall monolith photonic efficiency(Ф) were achieved; the optimal monolith-to-lamp distance ratio(βoptimum) was correlated in terms of the number of lamps(γ).In this paper, by investigating on the different types of the photocatalytic reactor, which is meaningful to the development of high performance photocatalytic reactor, some inspiration for the further photocatalytic reactor optimization was provided.