Numerical Simulation And Practical Parameters Optimization Of Micro Vortex Grid Flocculation Tank

Water purification process generally includes mixing, flocculation,sedimentation, filtration and disinfection. Flocculation is the key stage of the whole process, which directly determines the effect of water treatment. Micro vortex grid flocculation tank is one of the most widely used forms of flocculation tank, so it is very important to simulate design parameters and optimize the process of the grid flocculation tank. On the basis of flocculation kinetics, by using computational fluid dynamics(FLUENT), the issue focuses on simulating the grid flocculation tank, in order to determine the optimal design parameters and optimize the design of the project.In this paper, the design parameters of micro vortex grid flocculation tank are variable, including using Fluent software to realize numerical simulation,adopting standard k-ε model and Realizable k-ε model as the method of numerical simulation, using turbulent kinetic energy k and turbulent kinetic energy dissipation rate ε, velocity gradient G’ and eddy size λ as the flocculation effect indicators. The whole investigation is based on the analysis of the fluid state. The results of research show that:(1) placement of grid in the flocculation tank can greatly increase the energy utilization rate, improve the turbulent state of the flow and increase the number of micro vortex, and the grid should be suspended in the vertical water channel;(2) in two-dimensional numerical simulation of single grid micro vortex grid flocculation tank, single factor simulation was conducted when strip width is 5 mm-80 mm, grid space is 20mm-120 mm, inlet velocity is 0.06 m/s-0.3 m/s, and maximum turbulent kinetic energy and turbulent kinetic energy dissipation rate occurs when the strip width is80 mm, grid space is 20 mm, inlet velocity is 0.3 m/s. As excessive flow shear force will lead to the destruction of produced flocs, therefore it should be controlled in a certain range to ensure better flocculation effect;(3) reasonable grid plate space has a good effect on increasing the utilization rate of inputenergy;(4) four optimal groups design parameters with good flocculation effect are presented in the three-dimensional simulation of grid flocculation tank: strip width 50 mm, grid space 120 mm, inlet velocity 0.3 m/s, grid plate space 200 mm;strip width 50 mm, grid space 110 mm, inlet velocity 0.3 m/s, grid plate space700 mm; strip width 70 mm, grid space 40 mm, inlet velocity 0.2 m/s, grid plate space 300 mm; strip width 40 mm, grid space 20 mm, inlet velocity 0.08 m/s, grid plate space 700 mm.