竖流沉淀池内流态及影响因素模拟分析

为了研究了城市污水处理厂沉淀池速度场和质量浓度场,利用改进的RNG(重整化群)k-e紊流模型和Mixture混合模型,FLUNENT15.0软件对沉淀池进行仿真。结果表明:1)在竖流沉淀池距池底2~3米处池壁位置和污泥斗上部会形成两个明显的涡流,已经沉淀的颗粒在涡流的作用下重新进入沉淀池中;2)中心筒的污水遇到锥形挡板以后会有一部分重新进入到中心筒中,减轻了下降的污水对沉淀区的冲击;3)通过改变入流速度进行模拟对比,发现入流速度由0.3m/s增加到0.8m/s,清水区深度由池深的五分之四减小为二分之一,继续增加到1m/s,清水区消失,出水浓度达到0.3%,失去了沉淀效果。在保证出水水质的前提下沉淀池能承受的最大入流速度为0.86m/s.入流密度由1050 kg/m^3增加到1250 kg/m^3,沉淀区厚度由2m减小为1.5m,沉淀效果增强。试验结果验证了上述仿真结果可靠,对竖流式沉淀池工程设计具有一定的指导意义。

Vertical flow Sedimentation Tank Used as Primary Settling Tank Flow Pattern and Influencing Factors Simulation Analysis

In order to study the velocity field and concentration field of sedimentation tank in urban sewage treatment plant,the improved renormalization group(RNG)k-e turbulence model and Mixture mixed model included in FLUNENT15.0 software were used for settling basin simulation.The results show that:1)There were two obvious eddies 2-3 meters above bottom of vertical flow sedimentation tank and sludge,respectively.The eddies made the particles which have been settled entry the sedimentation tank again;2)The sewage from the central cylinder will re-enter the center in the cylinder after meeting conical baffle part,which reduces the lash to precipitation zone in the sedimentation tank;3)By changing the inflow velocity simulation,it can be found that as the inflow rate increases from 0.3 m/s to 0.8 m/s,the depth of clear water reduces from 4/5 of the tank to 1/2,continuing increasing to 1 m/s,and the clear water area disappears,the particle concentration of the outflow is 0.3%,which meant that the sedimentation tank lost the precipitation effect.The maximum inflow velocity can be 0.86 m/s under the guarantees for the quality of output water.As increasing the inflow particle concentration from 1050 kg/m^3 to 1250 kg/m^3,the thickness of the precipitation area reduces from 2 m to 1.5 m which improves the precipitation effect.Contrasting the simulation results with experimental results indicates that the simulation result is reliable,and has more practical meaning to the engineering practice.