气液固三相流化床流动特性研究

发布时间：2018-04-18 18:20

本文选题：气液固三相流化床 + 局部相含率　；参考：《浙江工业大学》2015年硕士论文

【摘要】：随着好氧生物流化床在城市污水处理中越来越多的应用,对其中的流动特性研究也受到越发的重视。本文在以焦末为固相、空气为气相、水为液相的三相流化床中结合实验和CFD模拟研究了局部气含率和局部固含率的分布。实验用流化床内径100 mm,高1.7 m,焦末粒度1.07 mm。分别采用电导探针法和光纤法测定局部气含率和局部固含率。同时采用E-E-E模型模拟三相流化床,应用计算流体力学进行模拟,并通过实验结果进行了验证,表明RNG湍流模型较standard模型和laminar模型更好的预测了局部相含率,3D模拟较2D模拟更为贴近实际,气泡直径敏感性分析表明选取一个合适的气泡直径对模拟有较大的帮助。气含率在距分布板较近的位置径向分布较均匀而在距分布板较远处有明显的沿径向从中心处往壁面处减小的趋势。在靠近入口的位置,固含率在靠近壁面时有所上升,而在距入口较远的位置,固含率在靠近壁面时有所下降。实验结果表明,表观气速为0.35~0.71 cm/s,表观液速为2.12~3.54 cm/s时,局部气含率在流化床中沿径向r/R=0~0.8处分布较均匀,在靠壁面处下降至约0.5%,且随表观液速增加而减小,随表观气速增加而增大,且在距分布板轴向高度分别为370 mm和470 mm时趋势一致,大小沿轴向增加,在表观气速一定时,液速小于2.12 cm/s时,气含率沿径向减小的趋势较明显。局部固含率沿径向分布较均匀,基本不随表观气速变化而变化,随表观液速增大而增大,且在距分布板轴向高度分别为370 mm和470 mm时趋势一致,大小沿轴向减小。
[Abstract]:With the increasing application of aerobic biological fluidized bed in municipal wastewater treatment, more and more attention has been paid to the study of flow characteristics.In this paper, the distribution of local gas holdup and local solid holdup was studied in a three-phase fluidized bed with coke powder as solid phase, air as gas phase and water as liquid phase.The diameter of fluidized bed is 100 mm, the height is 1.7 m, and the particle size of coke powder is 1.07 mm.The local gas holdup and local solid holdup were measured by conductance probe method and optical fiber method respectively.At the same time, the E-E-E model is used to simulate the three-phase fluidized bed, and the computational fluid dynamics is used to simulate the fluidized bed.The results show that the RNG turbulence model is better than the standard model and the laminar model in predicting the local phase holdup. The sensitivity analysis of bubble diameter shows that choosing a suitable bubble diameter is of great help to the simulation.The gas holdup distribution is more uniform in the near position from the distribution plate to the wall, but decreases obviously in the distance from the center to the wall in the distance from the distribution plate.Near the entrance, the solid holdup increases when it is near the wall, but decreases at the distance from the entrance.The experimental results show that when the apparent gas velocity is 0.35 ~ 0.71 cm / s and the apparent liquid velocity is 2.12 ~ 3.54 cm/s, the local gas holdup distributes evenly along the radial r/R=0~0.8 in the fluidized bed, and decreases to about 0.5% at the wall, and decreases with the increase of the apparent liquid velocity, and increases with the increase of the apparent gas velocity.When the axial height from the distribution plate is 370mm and 470mm, respectively, the trend is the same, and the size increases along the axial direction. When the apparent gas velocity is constant and the liquid velocity is less than 2.12 cm/s, the gas holdup decreases more obviously along the radial direction.The local solid holdup distributes uniformly along the radial direction, basically does not change with the apparent gas velocity, but increases with the increase of the apparent liquid velocity, and the trend is the same when the axial height of the distribution plate is 370 mm and 470 mm, respectively, and the size decreases along the axial direction.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ051.13

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