The Numerical Simulation Study On Optimization Of Grid Flocculation Tank

In water treatment, Flocculation is one of the most important processes, which affects the processing efficiency of the subsequent processes. The stand or fall of flocculation is effected mainly by raw water quality、coagulant、the effect of mixing and the hydraulic conditions of flocculation. Optimize the flocculation process from the flocculation conditions of hydraulic not only reduces dosing amount of coagulant, but also reduces the hidden effects of coagulant for drinking water quality, and more conducive to the quality of the output water security.In this thesis, the research object is one grid flocculation tank of the project entity, combined with the existing flocculation kinetics theory to establish a reasonable mathematical model, the numerical simulation software of computational fluid dynamics is used to simulated the flow field of grid flocculation tank in numerical simulation. In this simulation, the grid layer spacing, grid spacing and the height of the water hole’s position are as to the influence factors of the flocculation hydraulic conditions,with turbulent kinetic energy K, turbulent kinetic energy dissipation rate ε and vortex velocity gradient Go as the evaluation indexes. In addition, analyzed the best water conditions in grid flocculation tank, and then optimized design of the parameter of the grid flocculation tank.It choosed the flocculation tank which has two shaft of lateral water as the calculation model, the results indicated:1、The grid layouts with grid spacing of 50 mm is able to provide the better hydraulic conditions for preliminary flocculation; and grid spacing of 80 mm and 100mm is more suitable for the intermediate stage in the process of flocculation. According to the simulation result is in accordance with the specification, which is proved the the choice of the calculation model is reasonable.2、 Based on the simulation analysis of different grid layer spacing in flocculation tank, The best grid layouts with grid layer spacing is 600 mm, which is able to provide the better hydraulic conditions for preliminary flocculation.3、Based on the simulation analysis of different water hole’s position in flocculation tank, it is conducive to the flocculation hydraulic conditions with the raised settings of the water hole’s position in turn in the front、middle、and end of the process of flocculation, so much so that obtain the better effect of flocculation. In addition,The front should be set to 100～300 mm; the middle should be set to 300～500 mm;the end should be set to 500～700 mm.In addition, in this thesis, based on the obtained conclusions, it has certain practical guiding significance and reference value for engineering for the design of the grid flocculation tank.