The Simulation Study On Flow Field Analysis And Optimization Improvement Of Reciprocating Baffled Flocculation Tank Based On CFD

As a kind of relatively mature flocculation process,the reciprocating baffled flocculation tank is widely used in large and medium water plants with relatively stable water treatment capacity.But in the actual operation conditions indicated that the hydraulic reciprocating baffled flocculation tank is not ideal,inefficient flocculation larger areas of the pool,and in the flocculation process of ineffective energy consumption proportion is large,low efficiency caused by the flocculation process of a long time.This paper takes a reciprocating baffled flocculation tank as an example,the use of CFD technology in Fluent software technology,the Flocculation Ratio of 1:1 modeling and analysis of simulation results using the corresponding software for post processing,find out the reasons for these problems and find out the hydraulic conditions need to be improved where the proposed optimization scheme.The main research contents and results are as follows:(1)The reciprocating baffled flocculation tank is modeled and simulated by Fluent software with Gambit software,get the inner flow velocity distribution,velocity vector and turbulent kinetic energy distribution,and data processing using Tecplot software.According to the basic theory of Flocculation Combined with the simulation results of the hydraulic characteristics of flow field of traditional reciprocating baffled flocculation pool as well as the problems found in the flocculation basin only a certain region in the corridor at the corner of a larger velocity gradient value and turbulent kinetic energy and velocity gradient other about 2/3 corridor area value and the turbulent kinetic energy is very small that does not produce obvious turbulence caused the effective collision here called flocculation area between particles flocculation efficiency.So the efficiency of flocculation process is lower and the time is longer;(2)The design parameter,which has an important effect on the hydraulic distribution of the flow field in the flocculation tank of the reciprocating separator,is the area ratio A that is the area A1 of the overcurrent section at the corner and the area A2 of the cross section of the corridor(A=A1/A2).Through the simulation and analysis of the flocculation tank with different A values,the optimal reference range of the cross section area ratio of A is 1.2 ~ 1.4,and the water distribution of the flocculation pool is more reasonable.The floc particles have been formed not only because of the excessive sheer force of the water flow,but also at the turning point;(3)In the simulation of the reciprocating baffled flocculation tank based on analysis of results for the presence of large inefficient flocculation area,put forward an optimal scheme that set the bar in the corridor,with the increase of turbulence intensity of flow and the disturbance,improve the flocculation efficiency;and analyzes the effect of different space bar.Select three common grid bars: 50 mm,80mm and 100 mm bars.Through simulation analysis and data processing,it is found that when the water flows through the bars of 50 mm,80mm and 100 mm respectively,the flow velocity increases from the original 0.55m/s to 0.720m/s,0.705m/s and 0.693m/s respectively.Clearance for the effective distance of 50 mm bars is about 1.4m;clearance for the effective distance of 80 mm bars is about 1.2m;clearance for the effective distance of 100 mm bars is about 1.0m;the optimization in the traditional reciprocating baffled flocculation improved bar set interval width should be chosen according to the size of the gap of the bar to decide;(4)According to the above results,in the reciprocating partition flocculation tank width of 0.6m corridor set multilayer bar.The first and second corridors set up nine-layer 80 mm grid bar,which sets up five-layer 80 mm bar in the third and fourth corridors,and sets up a three-layer 80 mm bar in the fifth and sixth corridors.When the water passes through the grid,it produces large velocity gradient and turbulence intensity,and a large amount of vortex is formed in the corridor of a distance after the bar.This increases the contact between flocculation particles collision,is advantageous to the flocculation body to generate and the growth of the alum flowers,to improve the efficiency of flocculation,and the flocculation time shortened about 4 min.