The Numerical Simulation Study Of The Horizontal Axis Mechanical Flocculation Tank

Flocculation is an important part in water treatment,the effect of flocculation directly affects the operation condition,treatment cost and final effluent quality of subsequent unit process,the hydraulic conditions have great influence on the flocculation effect.Mechanical flocculation tank is a common construction of water treatment,which has the advantages of small head loss and better adaptation to the change of water quantity and quality.Therefore,numerical simulation of mechanical flocculation tank from the point of view of flocculation hydraulic condition is necessary.The horizontal axis mechanical flocculation tank is taken as the numerical simulation research object,based on the method of CFD numerical simulation,using the Fluent software for different sizes of horizontal axis.The turbulent kinetic energy k,turbulent kinetic energy dissipation rate?,vortex velocity gradient G₀as flocculation effect evaluation index,the different agitators rotation direction and and water intake mode,size of inlet hole,shape of water hole,size of slurry plate of horizontal axis mechanical flocculation tank to carry on the numerical simulation,study the internal flow field and flow characteristics,to explore the best flocculation hydraulic conditions,to optimize the design and running of the horizontal axis mechanical flocculation tank,in order to improve the flocculation effect,improve water quality.The results show that:1、Through the simulation of different horizontal axis mechanical flocculation tank with the different agitators rotation direction and and water intake mode,It is found that horizontal axial mechanical flocculation tank with upper hole inlet and agitator rotating counterclockwise has the best flocculation effect.2、Through the simulation of the mechanical flocculation tank with different sizes of circular,square and rectangular holes,it is found that the use of circular holes can effectively improve the turbulence degree of the whole pool body and enhance the flocculation effect.3、Through the simulation of mechanical flocculation tanks with different sizes and sizes of inlet holes,it is found that reducing the size of inlet holes properly can improve the turbulence degree of each reaction cell in the mechanical flocculation tank,especially the turbulence degree of the first reaction cell,and appropriately reducing the size of inlet holes can enhance the flocculation effect.4、Water Supply and Drainage Design Manual（Volume 3）:The length-width ratio of horizontal axis mechanical flocculation tank is 10-15.Through the simulation of mechanical flocculation tank with different slurry plate length-width ratios,it is found that the flocculation effect is the best when the slurry plate length-width ratio is10.The simulation results can be used as reference for the practical engineering of horizontal axial mechanical flocculation tank.