Based On The CFD Simulation Of Sewage Sludge Pipe Velocity,Concentration And Density Distribution

Sludge pipeline transportation technology of sewage treatment plant provides an effective way to solve the problem of sludge disposal in sewage treatment plant,which is a major demand of national production development and has become an important technical means of sludge treatment and disposal in sewage treatment plant.In this paper,CFD numerical simulation method is applied to simulate the sludge pipeline in the municipal sewage treatment plant,and the distribution characteristics and influencing factors of velocity field,concentration field and density field are mainly analyzed.The main research results are as follows:When sludge is transported in the pipeline,the velocity is symmetrical in the transverse axis direction of the pipeline,but it is no longer symmetrical in the vertical direction.The maximum point of the velocity is located in the center of the pipeline and gradually decreases towards the wall.As the inlet flow rate increases,the sludge reaches a stable flow position and moves back from the inlet of the pipeline.When the inlet flow rate v=0.25m/s and 1 m/s,the diameter of the sludge solid particles is 200um,the sludge concentration is 5%,and the pipe diameter is 300mm,The fluid in the tube is stable at x=2 m and 4 m,and the longitudinal section velocity reaches the maximum vmax=0.283 m/s and 1.287 m/s.When the size of the sludge particles,the concentration of the sludge and the diameter of the pipeline become smaller,the asymmetry of the fluid velocity in the pipeline will become stronger,and the maximum velocity point will gradually move upward to the center of the pipeline.When the sludge solid particle diameter is 50 um and 400 um,the inlet flow rate v=0.5 m/s,the sludge concentration is 5%,and the pipe diameter is 300 mm,the longitudinal cross section velocity of the fluid in the pipe at x=4 m and 6 m reaches the maximum vmax=1.244 m/s and 1.293 m/s and reaches stability.When the volume concentration of sludge is 2%and 8%,the inlet flow rate v=0.5m/s,the diameter of sludge solid particles is 200 um,and the diameter of pipe is 300 mm,the longitudinal cross section velocity of the fluid in the pipe at x=6 m and 10 m reaches the maximum value vmax=1.128 m/s and 1.294 m/s.When the diameter of the pipeline is 150 mm,the volume concentration of the sludge is 5%,the inlet flow rate v=0.5 m/s,and the diameter of the sludge solid particles is 200 um,the longitudinal cross section velocity of the fluid in the pipeline at x=2 m and 8 m reaches the maximum vmax=1.263 m/s and 1.291 m/s.In the vertical direction,the sludge particles mainly concentrated in the lower part of the pipeline,and the fluid was lower in the upper part of the pipeline,and higher in the lower part of the pipeline with a larger gradient.When the sludge particle size is 50 um,the inlet flow rate v=0.5m/s,the sludge concentration is 5%,and the pipe diameter is 300 mm,the particles are suspended in the pipe with little difference in distribution.The maximum concentration Cmax=0.102 and the maximum density ρmax=1740 kg/m3 appear at the upper end of the pipe bottom at the outlet of the pipeline.With the increase of sludge solid particle size,the position of the fixed bed is moved forward.When the sludge particle diameter is 200 um and 400 um,the inlet flow rate v=0.5m/s,the sludge concentration is 5%,and the pipe diameter is 300 mm,the stable bed is formed at x=8 m and 2 m,respectively.The maximum concentration appears at the upper position of the bottom of the pipe,Cmax=0.213 and 0.551.Maximum density ρmax=1860 kg/m3 and 1970 kg/m3.When the sludge concentration is 2%,the inlet flow rate v=0.5m/s,the diameter of sludge particles is 200um,and the diameter of pipe is 300mm,the drag force of liquid phase water plays a dominant role in influencing the sludge particles.The maximum concentration Cmax=O.113 and the maximum density ρmax=1310 kg/m3 appear at the bottom of the pipe.When the sludge concentration is 8%,the inlet flow rate v=0.5m/s,the diameter of the sludge particles is 200um,and the diameter of the pipe is 300mm,the interaction between the particles is strong,which promotes the suspension of particles in the liquid.The maximum concentration Cmax=0.128 appears at the exit position of the pipe.Maximum density ρmax=1670 kg/m3.When the diameter of the pipe is 450 mm,the inlet flow rate v=0.5m/s,and the diameter of the sludge solid particles is 200 um,when the volume concentration of the sludge is 5%,the particles in the pipe are less affected by turbulence under the condition of larger pipe diameter,and the influence of gravity on the fluid is greater,a stable fixed bed is formed at the position x=6 m.The maximum concentration Cmax=0.247 and the maximum density ρmax=1950 kg/m3 appear at the upper position of the bottom of the pipeline.