市政污泥化学调理装置CFD模拟

CFD simulation of chemical conditioning unit of municipal sludge

市政污泥机械脱水前多采用化学调理,调理装置搅拌过程中的流场分布直接影响调理效果。采用多重参考系-流体体积模型对实验室污泥调理罐(内径为40 cm)的流场特性进行计算流体力学(computational fluid dynamics,CFD)模拟研究,验证了实验室调理罐模型气液两相分布情况。实验室调理罐的模拟结果表明:单层直桨叶调理罐的搅拌桨直径与调理罐内径比优化值为1:1.75,挡流板宽度与调理罐内径比优化值为1:20,可有效消除流体旋涡,增强湍动作用。在此基础上,对中试调理罐(内径为110 cm)的流场特性进行模拟并与实际测量值校验。该研究采用的多重参考系-流体体积模型可为同类污泥调理罐设计与优化提供参考。

Chemical conditioning is commonly used before the mechanically dewatering process for sewage sludge. The flow field distribution of conditioning tank has a significant effect on conditioning when paddles are operating. Moving reference frame-volume of fluid model was used for simulating flow field distribution of a sludge conditioning tank with the inner diameter of 40 cm by CFD （computational fluid dynamics） technology, and the gas-liquid two-phase distribution was verified. The results showed that in the single straight blade paddle conditioning tank, the optimium ratio of paddle diameter to tank diameter was 1：1.75 and the optimum ratio of baffle width to tank diameter was 1：20. Under these optimum conditions, the fluid swirl could be effectively eliminated and the turbulent action could be enhanced. Furthermore, the flow field distribution simulation was conducted for pilot-scale conditioning tank with the inner diameter of 110 cm and the simulation results were compared with test results. Moving reference frame-volume of fluid model used in this study can provide references for design and optimization of similar sludge conditioning tank.