Numerical Simulation Research On The Optimized Particles Distributor And Flow Behavior Of Solid And Liquid Phases In Fluidized Bed

Water pollution is one of the main environmental problems in our country, with the development of industry and city of our country, industrial wastewater and domestic sewage emissions increase, sewage without the emission standards discharged into the water. When the sewage discharged into the water body is not up to the discharge standard, it will pollute the surface water and groundwater. China's water resources are not rich, if the average occupancy calculated by the entrance flow, equivalent to only 1/4 of the world's per capita value.The pollution of surface water and groundwater will further reduce the number of available water resources, which will inevitably affect the industry ? agriculture and fishery production and harm to people's lives and health. So the sewage treatment is becoming an urgent affair which should be implemented soon. Implementations of the water resource and sewage treatment measures,advanced treatment and reuse of treated wastewater have become the inevitable requirements of the sewage career development. Biofilm process is an important method of treating sewage, and the fluidized bed is the crucial equipment in an activated sludge wastewater treatment process.This article combines the Euler-Euler multiphase flow model with the RNG k-? turbulence model which was used numerically to simulate the typical fluid dynamic fluidized bed,compares a number of physical quantities under the different particle distributors to analyze a reasonable form of distributors, and analyzes the different particle properties and operating conditions, including the particle volume fraction, flow field structure, turbulent kinetic energy and its dissipation rate ,to optimize the operating parameters of the fluidized bed, and study the advantages and disadvantages of different operating conditions, so that users can choose according to their own conditions for the distributor and operating parameters. The research mainly includes the following conclusions:(1) Through the validation of first model, it is known that the Euler - Euler multiphase flow model combined with the RNG k-? turbulence model was an effective way to simulate the solid-liquid two-phase flow in fluidized bed. Through the validation of second model we found that the selected multiphase flow model ,turbulence model, solving method and boundary conditions are in good agreement with the experimental data.. It can concluded that the selected numerical method, mathematical model and boundary conditions can well simulate the flow characteristics of the solid-liquid two-phase flow in fluidized bed.(2) By comparing different distributors, It is concluded that when particle distributor A was installed particles was completely fluidized and formed a uniform flow layer, no local high concentration area, axial concentration fluctuations but not much, and had the most uniform concentration compared others distributors in fluidized bed. When the distribution plate A is set the axial velocity distribution in the fluidized bed is more uniform, and the radial velocity distribution range of the particles is obviously much than that of other distributions, the maximum radial velocity is 0.17m/s, and the collision and friction between the particles is more intense.(3) In the same initial conditions, with the increase of the size of the carrier, the particles volume fraction, axial velocity, and expansion height of the bed decreases reduced the flow rate,the variation of uniformity and flow pattern become severe. With the increase of particles density, the volume fraction of the particle increases, but the expansion height of the bed and axial velocity decreases,the uniformity of velocity and flow pattern becomes worse. With the increase of the initial filling height of the particle, the volume fraction of the particles in the fluidized bed increases, the axial velocity decreases, and the bed expansion rate has a slight fluctuation. With the increase of the liquid velocity at the entrance of the fluidized bed, the volume fraction of the particle in the fluidized bed decreases, and the bed expansion rate and the axial velocity increase obviously.(4) The volume fraction, axial velocity distribution and non-uniform coefficient of velocity of the particles are compared when the different conditions, that found the particle density is 1500 kg/m3, the particle size of 1mm, initial filling height is 0.3m, the liquid velocity at the entrance of the fluidized bed is 0.15m/s was the optimal particle properties and running parameters for the given biological fluidized bed, it can improve the sewage treatment efficiency of fluidized bed..