Study On Performance Of Rotating Multielectrodes Electrochemical Reactor And Its Application

Electrochemical oxidation is considered to be a promising technology for wastewater treatment.The development of electrochemical oxidation reactors is an important research direction,because it is the indispensable place for electrochemical oxidation reactions.In the electrochemical oxidation reaction process,the mass transfer performance of the reactor becomes a key factor affecting the treatment effect of electrochemical oxidation process especially under the operating conditions with high current density.Moreover,the occurrence of oxygen evolution reaction in the reactor causes the adhesion of bubble curtain on the electrode surface,which will weaken the mass transfer performance and reduce effective reaction area of the electrode surface.Therefore,there is an urgent need to develop a novel electrochemical reactor that can effectively intensify the electrochemical oxidation process.In this thesis,a systematic experimental study on the rotation characteristics and reaction performance was explored against the novel rotating multielectrodes reactor(RMER)we proposed for the electrochemical oxidation process intensification,and its mass transfer enhancement effect were evaluated by quantitative analysis and visual study.Meanwhile,qualitative and quantitative evaluations of fluid flow characteristics were studied by pulse tracing technique and computational fluid dynamics(CFD)technique.Finally,the reactor with the optimized structure was applied to the application study of rhodamine B simulated wastewater coupled with ozone process.The main findings are as follows:1.A novel rotating multielectrodes electrochemical reactor(RMER)was proposed aiming to solve the key scientific problems that poor mass transfer performance and the adhesion of the bubble curtain on the electrode surface would seriously affect the conversion and energy efficiencies in the electrochemical reactor.Apart from the electro-oxidation function,the anodes in RMER act as a rotational disturbance promoter to deal with the problem of the bubble curtain.Experimental results in RMER showed that the phenol degradation rate of rotating anode at 300 rpm was 1.45 times that of static anode.Compared with static anode,the mass transfer coefficient of the RMER with rotational anode increased by 110%.Bubble behavior was investigated by a visualization method,showing that the increase of the anode effective area was one of the main factors to enhance the phenol degradation efficiency.Therefore,RMER displayed promising prospects on the application of wastewater treatment.2.The fluid flow characteristics of the reactor without bubbles existence were taken as blank experiments,and the fluid flow with bubbles existence after electrochemical reaction was compared with it.The comparison found that the bubbles adhesion on the electrode surface has a significant effect on the fluid flow in the reactor.The fluid flow within the reactor is significantly improved by the use of 3D printed spoilers.Meanwhile,through the quantitative analysis of the characteristic parameters in the process,the mixing and axial diffusion performances of each spoiler are evaluated reasonably.3.According to the four optimization schemes with different spoiler structures for improving fluid flow,CFD simulation technology was used to acquire and analyze the flow field in detail generated by different spoilers in the reactor.Based on the analysis of the flow field information in different structural spoilers,the addition of the spoiler could effectively increase the level of turbulent kinetic energy inside the reactor and typically improve the macromixing effect in reactor.This would provide a more favorable reaction environment for the electrochemical oxidation reaction process and realize the intensification idea in the process.Simultaneously,for the better comparison with the spoilers on its structure features,we further explored operating parameters affecting the turbulent kinetic energy and macroscopic mixing performances in the reactor.Studies have shown that higher rotational speed,lower feed ratio,and lower flow rate have a considerable effect on the turbulence increase,the enhancement of macroscopic mixing performance,and improve the fluid flow.4.The degradation of the simulated dye wastewater—Rhodamine B solution was carried out by electrochemical oxidation method coupled with ozone process.The degradation efficiencies of RhB in different treatment processes were also compared.Moreover,the key operating parameters were experimentally explored such as ozone concentration,gas velocity,pH,etc.The degradation efficiency of RhB significantly increased with time,and reached the peak value of 99.4%in 20 min.Compared with the electrochemical oxidation process,the degradation efficiency of the optimized process was improved by 49.3%.Experimental results showed that the high ozone concentration,large gas velocity,and low pH value were beneficial to the degradation process of RhB.Therefore,the coupling of the ozone process could better enhance the electrochemical degradation process.