Simulation Research On Structure’s Influence To Inner Flow Field Of EGSB Reactor

Anaerobic biological treatment technology plays an extremely important role in urbanwastewater treatment, with low operation cost, less surplus sludge, achievable energyrecycling, and other advantages. In recent years, anaerobic biological treatment reactor hasbeen developed rapidly, and a variety of anaerobic biological treatment reactors appeared,including expanded granular sludge bed (EGSB). Last decade, for EGSB reactor, researchersat home and abroad put extra weight on the study of water distributor and three-phaseseparator, and their main research method was experiment research, but because of the longoperational cycle of anaerobic biological treatment reactor, results achieved slowly.Based on the existing experimental results,the changes of internal flow of the EGSBreactor after adding a guide tube was investigated in the present, from the computational fluidmechanics perspective. Based on fluid dynamics research and numerical simulation approach,simulation of the inner flow field of EGSB reactor was investigated. Pretreatment moduleGAMBIT was used for building geometric models and meshing, and FLUENT software usedfor numerical computation. When the EGSB reactor was in operation, there was two materialsof different physical properties within the reactor, waste water and granule sludge, sointerphase interactions should be taken into account, for this reason Euler multiphase flowmodel was used. The numerical computation was been done by using standard k-ε model asturbulence model, finite element method as discrete method, SIMPLE algorithm as solutionmethod. Specific studies are as follows:Changes of the inner flow field of the EGSB reactor before and after adding a guide tubeinside was simulated. Based on the inner flow field distributions and phase distributionscalculated, the distributions of waste water and granule sludge and the operating state wereestimated, merits and demerits of the EGSB reactor after adding a guide tube inside wereanalyzed. The influence of operating parameter, reflux ratio, to the inner flow field of theEGSB reactor adding a guide tube inside was studied, with setting the reflux ratio equal to30:1,20:1,10:1,3:1. Changes of the inner velocity field distributions and phase distributionswere simulated, and the optimal reflux ratio were retrieved by analysis and comparison. Theflow field and concentration field of the EGSB reactor when the reactor-to-guide tubediameter ratio equal to15:3,15:5and15:7.5was simulated, and the influence of the ratio on the inner flow field of the EGSB reactor were analyzed. The cases of the ratio of the guidetube-to-inlet distance to the height of the guide tube equal to40:1,30:1and20:1wassimulated, and the influence of the ratio on the inner flow field of the EGSB reactor wereanalyzed.Preferable structural parameters and operation parameters were got by above contentanalyses, thus the purpose of optimizing EGSB reactor design, intensive mixing of wastewater and granule sludge, were achieved. At last, the best treatment effect was achieved.