| With the development of energy and chemical industry,the proportion of high concentration and refractory wastewater is increasing,and such wastewater needs to be pretreated before biochemical treatment.As an ideal wastewater pretreatment technology,iron-carbon(Fe-C)micro-electrolysis can effectively improve the biodegradability and reduce the color and toxicity of wastewater.However,Fe-C filler gets passivation and hardening during long-term operation,which will reduce the process efficiency.In order to solve this problem,a novel internal circulation Fe-C micro-electrolysis(ICE)reactor was developed by combining the internal loop airlift reactors(ILAR)with Fe-C micro-electrolysis.The research of the internal loop airlift reactor stays at the laboratory level,because structure parameters and operation parameters have great influence on the multiphase flow,and the design theory of the system has not been formed.Hence,the reactor has been limited the application in industry.The structure optimization and performance of ICE reactor is studied in this paper.Firstly,the gas-liquid two-phase and gas-liquid-solid three-phase model was used to optimized the ICE reactor by computational fluid dynamics(CFD)method.The gas-liquid two-phase simulation employs VOF model,and liquid velocity and gas holdup radial distribution parameters is indicators to study the effects of structural parameters(height-diameter ratio,diameter ratio,bottom gap height and the number of water pipes)on the gas-liquid flow in the two-phase system,The Euler-Euler-Euler model is used for gas-liquid-solid three-phase simulation,and Schiller-naumannl model is used for gas-liquid drag force,and Gidspow model is used for gas-solid and liquid-solid.Structural parameters of ICE reactor are optimized by taking the hydrodynamic parameters such as radial distribution of solid phase and gas holdup as indicators.Secondly,the correlation between gas holdup and dissolved oxygen was discussed by simulating the distribution of dissolved oxygen concentration field,and the simultaneous oxidation and reduction performance of the reactor is verified.Finally,the optimum structural parameters are obtained by simulation:the ratio of height to diameter(H/D)is 4:1,the ratio of diameter(D/D_r)is 7:1,the bottom gap height(H_d)is 90 mm,uniform water distribution and the number of water distribution pipes is 4.The experimental scale ICE reactor that has optimized above is applied to treat a simulated wastewater(aniline solution)and an industrial wastewater(coking wastewater).Firstly,the Chemical Oxygen Demand(COD)and aniline removal rate were selected as evaluation indexes to evaluate the effects of aeration,treatment time,pH and Fe-C ratio in the simulated wastewater treatment.On the basis of the single factor experiment results,the response surface method(RSM)is used to optimize the technological conditions for the treatment of simulated wastewater by the ICE reactor.With the optimal conditions,the degradation mechanism of aniline pollutants is analyzed by means of liquid chromatography,FTIR spectrometry,ion chromatography and Gas Chromatography-Mass Spectrometer(GC-MS).Secondly,using the same experimental method,the coking wastewater is treated.The optimum process as follows:aeration is 0.13 m~3/h,Fe-C ratio is1:1,pH is 2.3,average COD removal rate is 67.77%,chromaticity removal rate is 93.75%and reaction time is 90 min.The COD concentration of treated wastewater is below 80 mg/L,which is satisfied with the standard of coking wastewater.The dynamic continuous experiment is carried out under the optimum process conditions,and the reactor is continuously operated for 4 months without passivation of the filler.Finally,an ideal ICE reactor for industrial wastewater treatment is designed based on the simulation optimization parameters and experimental results. |
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