Research On Sedimentation Performance Of Vertical-Flow Sludge Settling Tank

Vertical flow sludge settling tank has been used in the sewage treatment plant to reduce water and sediment the original sludge whose moisture content up to97%-98%, which can achieve the substantial reduction of sludge in a very small footprint and greatly reduce the required subsequent mechanical dehydration energy. The solid-liquid movement of the vertical flow sludge settling tank is very complex, and relying solely on the experimental study not only the cost is high but also the cycle is long. In the paper, the vertical flow sedimentation tank in a sewage sludge plant has been taken as a object of study, establishing the sedimentation tank physical model and the sludge settling mathematical model, and the method of numerical simulation and experimental validation has been used to study the settlement performance of the vertical flow sludge settling tank.The SIMPLEC algorithm was used to numerical simulation the solid-liquid two-phase flow field、turbulence structure and the distribution of two-phase internal sedimentation tank, which has got the distribution of the velocity field、turbulence structure and solid-liquid two-phase state; reveals the distribution of sedimentation tank flow field in the microscopic field and analyzed the relationship between the flow field and the sludge settling characteristics.Under different structural parameters and operating parameters,the flow field of settling tank has been analyzed, the results show that:when the reflector plate was been installed in the bottom of the center tube,the sludge particles have a more rapid and uniform diffusion in a circular area of the next segment of the settling tank center tube, which significantly increased the deposition efficiency of the sedimentation tank sludge.For the present model, when the vertical distance between the edge of the central tube and the reflector in the130-150mm and the reflective plate top cone angle around146°,sedimentation tank flow with low turbulent kinetic energy and has the best settlement effect; the sidewall tilt angle of sludge hopper between55-60°, which conducive to the formation of sludge layer in the sludge hopper;the settling tank whose structural parameters in the aforementioned optimal range can work properly when the inlet velocity below0.03m/s and the sedimentation tank height greater than3.5m, and the corresponding flow is the settling tank maximum capacity; settling tank deposition efficiency increases with the increase of the sludge particle density.The methods and results of this study on the vertical flow of sludge settling tank design with some guidance significance.