Experimental And Simulation Study On Fixed Bed Reactors With Heterogeneous Photocatalysis For Water Treatment

Photocatalytic technology,as a new type of water treatment technology,has got more and more attention because it can efficiently remove the refractory organic pollutants and no secondary pollutant was produced.One of the important research directions is the application of photocatalytic technology in the treatment of printing and dyeing wastewater.However,the influence of various factors has limited its popularization and application in industry.The existing research also tend to improve the performance of the catalyst.The study of photocatalytic reactor is relatively small,used in the pilot plant is less.Aim at this problem,this study proposes the use of O3,UV and TiO2 combination method as the foundation to study and improve the fixed bed photocatalytic reactor,in order to get an efficient photocatalytic reactor and to enlarge it for pilot test.The main work of this thesis is as followed:1.An experimental study on circulation treatment of the Rhodamine B(RhB)simulated wastewater with specific concentration and specific volume was conducted by a lab-scale fixed bed photocatalytic reactor.The internal carrier structureof the fixed bed is multi surface hollow ball.The RhB's degradation rule was studied by changing the flow rate of simulated wastewater,pH,initial concentration and air intake quantity.It was found that the degradation of RhB simulated wastewater was in accordance with the first order reaction kinetics,and the effect of pH on the degradation of RhB was more complicated.The synergistic effect between UV and O3 was studied,and the experimental results showed that UV and O3 had obvious synergistic effect.2.On the basis of the above research,the carrier structure of the photocatalytic fixed bed reactor was redesigned and optimized.A new type of carrier for corrugated-baffle plate carrier structure was designed.The comparing experiment was conducted by the second fixed bed photocatalytic reactor which was composed by the redesigned carrier structure and the initial design fixed bed photocatalytic reactor which was composed by multi surface hollow balls.A comparable experiment was carried out when the mass flux of ozone was reduced to 26.499 mg/min(the oxygen flow rate was 0.2 L/min),the RhB simulated wastewater was changed from the recycling process to the one way process.Compared with the experimental results,it was found that the degradation rate of RhB in the fixed bed reactor with corrugated-baffle plate was much faster,and the degradation rate of RhB in the same residence time could be increased by at least 10%.3.The corrugated-baffle-glass-spring carrier structure was designed by adding glass springs in corrugated-baffle carrier structure.Under the same experimental conditions,through comparative experiment of RhB simulated wastewater that conducted by one way treatment,it was found that the photocatalytic fixed bed reactor with corrugated-baffle-glass-spring carrier structure could further improve the degradation rate of RhB.The degradation rate of RhB was increased at least 15%compared with the initial experimental device at the same residence time.4.Finally,after the analysis the pilot plant was designed based on the fixed bed reactor with its internal structure was corrugated-baffle plate carrier structure.The specific size of the pilot plant was got from design;the pilot plant would operated in a sealed and pressurized way;the sealing structure between the quartz tubes and the fixed tube plate was designed;the specific structure and the size of pilot carrier were got based on the test designed corrugated-baffle plate carrier structure;the material of the new carrier structure is made of titanium dioxide,which can be directly oxidized on the surface of TiO2 catalyst through high temperature treatment.5.Using numerical simulation software COMSOL as a tool to study the flow field of the design of pilot reactor,it was found that opening holes on the designed carrier was beneficial to the uniform distribution of the flow.Then,the effect of the opening size and the number of holes on the distribution of the fluid was studied.The numerical simulation results showed that the fluid distribution of one hole is better than the fluid distribution of open porous under the condition of same total opening diameter;the distribution of fluid of larger opening diameter was better than the distribution of fluid of small opening diameter,under the condition of same number of holes.The final decision was to open holes on two slopes of the new carriers,one opening at the same height on each side,and the opening diameter is 45 mm.At the end,the selection of the main devices involved in the pilot process were carrried out,the selection of feed pump was mainly carried out.