Numerical Simulation Of Fluid Dynamics And Photocatalytic Degradation Of Sodium Oxalate

ABSTRACT:As domestic and international environmental issues have become increasingly prominent, especially the continuing impact of the recent haze of domestic cities, environmental pollution has become a serious problem. A variety of means to effectively control pollution attracted the attention of the world. The most attracting advantage of semiconductor photocatalytic technology is the degradation of refractory organic pollutants among advantages such as mild reaction conditions, no secondary pollution, energy saving, etc. TiO2photocatalytic oxidation technology has been developing rapidly because it is cheap, non-toxic, chemical stable. However, there are two technical problems that should be solved before the widely application of this technology. The first is to improve the efficiency of the photocatalyst; the second is to the optimization of photocatalytic reactor. This thesis focuses on the second problem.Photocatalytic reactor is a complex reactor which combined gas-liquid-solid multiphase substances and optical radiation in a reactor. We call it four-phase reactor. Gas substance generally is oxygen or air, whose role is to consume the electrons in the pair of electron-hole generated by TiO2, which is essential in the reaction of photocatalytic; liquid phase generally is water, which contains the reactants, organic pollutants; solid phase is the catalyst (TiO2); optical radiation provide energy required for the reaction. In order to reach the highest utilization efficiency of quantum, the fastest rate of mass transfer and reaction, a photocatalytic reactor should be optimized to coordinate the matters among the three phases and optical radiation energy.Commercial application of photocatalytic technology has so far remained stagnant, which is mainly due to the lack of physical basis of mathematical models among other factors. This paper uses the concept of local volumetric rate of energy absorption (LVREA), and the linear relationship between the rate of radiation initiated and the LVREA, so that the equation of reaction rate is simplified. Equations of reaction rate and boundary conditions are compiled using the UDF. Photocatalytic degration sodium oxalate is simulated by CFD software FLUENT. Simulation results are compared with V.K.Pareek’s experimental data. Then we predicte the effect of photocatalytic degradation sodium oxalate when the retention time is105min and120min which don’t have the experimental date. The main conclusions are:(1) Using the concept of local volumetric rate of energy absorption, the simulation results fit well with V.K.Pareek’s experimental data as the different concentration of catalytic and hydraulic retention time.(2) The optimum hydraulic retention time is90min when the hydraulic retention time is different; correspondingly, the maximum removed loading of sodium oxalate is0.0669kg/(m3·min).(3) The optimum catalyst concentration is1.0g/L no matter how much the hydraulic retention time is.