| Gas distribution uniformity of fluidized bed played an important role for hydrodynamic behavior, chemical reactions, heat transfer and mass transfer and was one of the important factors for the fluidized bed. Inlet ways of gas and the structure of air distribution plate had many forms for fluidized bed, but all of them should meet the basic conditions for air flow. If the gas distributed uniform, it would lead to the irrational distribution of particles, and could cause uneven distribution of solid particles, which affected the Overall fluidized of solid particles on the fluidized bed. Therefore,it was of vital importance to study the behavior of fluid flow for fluidized bed, which had a very important practical significance.This paper used the computational fluid dynamics to simulate the gas-solid flow for the fluidized bed and bubble motion characteristics for four kinds of plates for fluidized bed, which were flat shape, ∧ shape, ∨ shape and inclined shape, were compared with each other, and the influence of varied inclined angles on solids concentration and velocity distribution for ∧ shape, ∨ shape and inclined shape plates were analyzed. Furthermore, the impact of the opening rate and diameter of hole for the flow characteristics were also studied. Main research results are summarized as follows:(1) Setting up a gas-solid flow model for the single nozzle fluidized bed based on Euler-Euler two-fluid model and Gidaspow model. Adopting standard k-ε, RNG k-ε and Realizable k-ε turbulence model for the single nozzle fluidized bed to conduct numerical simulation, and the motion characteristics of bubbles were got. A more suitable numerical model for fluidized bed of gas-solid flows was determined by comparing the results of both the experiment and the numerical simulations.(2) Bubbles motion characteristics were numerical simulated for four plates distribution structure fluidized bed of flat shape, ∧ shape, ∨ shaped and inclined shape, and result showed that the bubbles had the same motion characteristics. When using the non-uniform way for distributing the wind along the radial, it observed that gas carrying solid particles went upward in high speed zone of wind, because of the smaller bed resistance in low speed area of wind, and the solid particles went downward under gravity, circular motion of the fluidized bed then formed.(3) Distribution curves of solid particles in the radial direction of fluidized bed for four air distribution plates as flat shape, ∧ shape, ∨ shape and inclined shape were compared, and the results showed that the average volume fraction of solid particles for the flat shape fluidized bed had the most volatility, but the last three kinds of distribution plates was less volatile, and the distribution curves of the latter three closed to each other.(4) Solid particle volume fraction and velocity distributions for the ∧ and ∨ shape air distribution plates at different angles of the fluidized bed were analyzed, and the result showed that the solid particles was more evenly distributed within angle from 20°~30°, the velocity gradient in radial was large and the mixing characteristics of gas-solid was better.(5) Solid particle volume fraction and the velocity distributions for the inclined shape plate bed at different angle of fluidized bed were analyzed and the result showed that the solid particles distribution were basically the same at different angles of the fluidized bed. When the inclined angle was 30°, the solid particles had a large velocity gradient in radial direction, so the mixing characteristics of gas-solid were good.(6) Numerical simulation of flow characteristics of the fluidized beds in shape of ∧, ∨ and inclined one air distribution plates were conducted under different opening rates and hole diameters, the result showed that at the inclined angle of 30°, the mixing characteristics of gas-solid were better for three distribution plates when the opening rate was 0.8% and hole diameter was 2 millimeters. |
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