【作者】 许凯；

【导师】 王伟文；

【作者基本信息】 青岛科技大学 ， 化学工程， 2009， 硕士

【摘要】 本文针对大型流化床反应器存在进气不均、易产生大气泡和颗粒团聚体,对于强放热或吸热反应须在流化床内设置管式内构件以及时取热或加热,出口气体带出的固体颗粒量较大等弊端,进行了流场模拟与实验研究。内容包括:设计了双锥导流式进气分布器,并利用FUENT软件对不同结构参数下分布器的流场进行了数值模拟。模拟结果表明:外锥的设立,避免了不能使气体均布的弊端;合理调整导流口的位置与尺寸能确保流体沿分布器内锥表面压力均布;分布器内气体分布不均匀度随内锥开孔率的增加先减小后增大,并沿流体的流动方向有降低的趋势;当内锥开孔率为0.8~1%,锥角采用60°时气体分布器的不均匀度小、压降低。并且利用实验验证了上述模拟结果。对三种不同外形的流化床进行了模拟。结果显示,流化床的扩大段对床内部流场的影响显著。三种拥有扩大段的床形在降低密相床层高度、颗粒速度方面要好于普通圆筒形流化床。圆锥形流化床,降低了颗粒扬析,但容易出现沟流;当静床床面低于扩大段下端的流化床时,不适宜的结构尺寸会造成内部气泡尺寸较大、易聚并发生节涌;对静床床面位于扩大段下端,床层尺寸比例设计合理时,密相床层高度低,内部气泡尺寸较小、颗粒的扬析量少、流场稳定,与实验结果吻合。作者对加入垂直与水平两种沉浸管的流化床内部流场进行了研究。对垂直沉浸管式流化床的模拟表明:垂直管上方与下方床层内的颗粒有从流化中心向边壁运动的趋势,而垂直管区域内的颗粒沿轴向向上运动;垂直管的加入破碎了流化床内的大气泡、减缓了气泡上升速度、减弱了气泡聚并;降低了垂直管上方床层区域内的颗粒固含率,减少了颗粒的扬析;适当加大垂直管间距可以有效降低壁面处的颗粒固含率及密相床层高度。对水平沉浸管式流化床的模拟发现:床内一定数量的管道被“气穴”包围,且管间距减小后,“气穴”增多;床内管束采用正三角与正方形两种排列方式均能降低管束上方区域内的颗粒固含率;管束呈三角形排列时密相床层高度较低,且颗粒在中心区域具有较高的轴向速度,有助于减少“气穴”现象。更多还原

【Abstract】 In this paper, a flow field simulation and experimental study were researched because of uneven intake and easy to have a big bubble and particle aggregates, setting up baffle for transferring heat and heating in strong exothermic or endothermic reaction, bringing out a larger number of solid particles by air-out in the industrial synthesis of organic silicon monomer reaction. To solve the above problem, the specific research as follow:The writer designed the double cone diversion inlet distributor and simulated various structural parameters of the flow field distribution with CFD simulation software. Simulation results show that outside cone could avoid the drawbacks of asymmetric gas distribution; Reasonable adjustments to diversion trench location and size could ensure the uniform pressure distribution along the inner surface of inner cone. While the ratios of aperture in inner cone increased, gas distribution uneven distribution increased after the first decrease; When the value of ratios of aperture and inside cone angle was 0.8~1% and 60°,pressure drop and uniform gas distribution reached perfect. Above all analog value corresponded with the experimental data.The flow field distribution of three different external shape fluidized bed was simulated. According to the simulation results, conical fluidized bed was prone to channeling flow, reducing gas utilization; The fluidized bed that static bed height is lower than the bottom of the expanding section that internal flow field was volatile, When inappropriate size of it was easy to grow large bubble and had slugging phenomenon; The fluidized bed that static bed height at the bottom of the expanding section had lower dense bed height, smaller bubble size, less elutriation. The simulation results corresponded with experimental results. Author studied the flow field of fluidized bed joined the vertical and horizontal immersed tubes. Simulating vertical immersed tube fluidized bed showed: particles flowed from the center to the edge of wall in the top and bottom of vertical tubes, and particles in the vertical tubes bank flowed along the axial upward; Vertical tubes broken the large bubbles in fluidized bed, reduced the bubble rise velocity, weakened bubble coalescence, reduced particle concentration above the vertical pipe region, so particle elutriation decreased; Appropriate to increase the spacing can effectively reduce particle concentration along the wall and the height of dense phase bed. Simulating horizontal tube fluidized bed showed: a certain number of channels were surrounded by“cavitations”, When decreasing the tubes spacing, the number of cavitations increased; The tubes that arranged by triangular and square could reduce particle concentration at the top of the tube band; The bed that tubes were arranged by triangular had the lower bed height, and the particles in the central region had a higher axial velocity, which could reduce the“cavitations”phenomenon.更多还原