宽筛分流态化过程的强化与实验研究

发布时间：2018-06-22 02:34

  本文选题：宽筛分 + 冷模实验　； 参考：《青岛科技大学》2015年硕士论文

【摘要】：流态化多晶硅化学气相沉积(CVD)在连续操作时会形成比较宽的粒径分布,需研究宽筛分颗粒体系的强化特性；加热板内构件的加载同样会影响流化床内颗粒的流态化过程,需研究该内构件对宽筛分颗粒流化特性的强化作用,详细内容如下：(1)根据宽筛分颗粒流化特性,本文自制一套直径0.215 m、高1.5m的带有下椎体的流化床冷模实验装置,Set 1-3为窄筛分实验物料、Set 4-5为宽筛分实验物料。通过分析床层段压降研究轴向固含量分布规律,采用抽气取样法分析局部颗粒浓度分布,并通过筛分研究宽筛分颗粒粒径分布,根据床层的静止高度和流化高度研究床层平均空隙率的变化规律,通过采集流化床内压力脉动信号并计算其功率谱密度、标准方差的研究方法分析床内气泡行为规律。(2)以窄筛分颗粒为对比,研究气固流化床内宽筛分实验物料的气泡行为、轴向固含量分布、局部颗粒浓度分布、粒径分布、床层空隙率。实验结果证明：(Ⅰ)在0.155m/s表观气速下,Set 2功率谱主频值为3.667,Set 4为3.533,差别不大,Set 5与Set 1类似,均无明显主频,宽筛分实验物料中的细颗粒可提高气泡的聚并、破碎频率,抑制大气泡的产生；(Ⅱ)细颗粒的加入使宽筛分颗粒流化高度增加,轴向固含量分布更均匀,流化状态更稳定；(Ⅲ)局部颗粒密度随轴向高度的增加而降低。密相区径向方向上由中心线向边壁处浓度逐渐增大,以Set4进行分析,在0.155m/s表观气速下,轴向高度0.2m处的固相体积分数由中心线处45%增大到边壁处60%;(Ⅳ)以Set 4实验物料研究宽筛分颗粒粒径分布。颗粒粒径随轴向高度的增加而降低,在0.294m/s表观气速下,底部颗粒平均粒径为220gm,在1.0m处减小至115μm,界面处下降趋势比较明显,由0.2m处的210μm减小到0.4m处的165μm。在径向方向上没有明显变化,在0.232m/s表观气速下,0.6m高度不同径向位置的粒径均在150μm左右；(V)细颗粒的加入可提高床层空隙率,在操作条件下,Set 4空隙率范围为0.37～0.48,Set 5空隙率范围为0.36～0.46,较Set 3的0.38～0.44有一定的提高。(3)在流化床中加入18块加热板内构件,对床内颗粒流化特性产生积极的影响,本课题研究了加热板内构件对宽筛分颗粒流态化过程的强化作用。实验结果证明,加热板内构件使床层压降产生小幅度的增加,增加值低于400Pa；空隙率减小趋势不明显；加载内构件后,Set4实验物料在0.155m/s表观气速下的主频值由3.533增加到6.000,主频幅值由2.795减小到2.504,0.232m/s表观气速下的主频值由4.567增加到5.700,主频幅值由6.553减小到4.264,床内气泡聚并、破碎频率明显升高,抑制大气泡效果显著。
[Abstract]:Fluidized polysilicon chemical vapor deposition (CVD) will form a wider particle size distribution during continuous operation, so the strengthening characteristics of wide sieve particle system should be studied, and the fluidization process of fluidized bed particles will also be affected by the loading of heating plate components. It is necessary to study the enhancement effect of the inner member on the fluidization characteristics of wide sieve particles. The detailed contents are as follows: (1) according to the fluidization characteristics of wide sieve particles, In this paper, a set of 0.215 m diameter and 1.5m high fluidized bed cold model test device with lower vertebra is made. Set 1-3 is a narrow screening material and set 4-5 is a wide screening material. The distribution of axial solid content was studied by analyzing the pressure drop of the bed section, the local particle concentration distribution was analyzed by the method of air sampling, and the particle size distribution of the wide sieve particle was studied by sieving. According to the static height and fluidization height of the fluidized bed, the variation of the average voidage of the bed is studied. The pressure pulsation signal in the fluidized bed is collected and its power spectral density is calculated. The study method of standard variance was used to analyze the behavior of bubbles in the bed. (2) the bubble behavior, axial solid content distribution, local particle concentration distribution and particle size distribution were studied in a gas-solid fluidized bed with narrow sieve particles as a comparison. Bed void ratio. The experimental results show that: (I) under the apparent gas velocity of 0.155m/s, the main frequency of power spectrum of Set 2 is 3.667% set 4 is 3.533, the difference is similar to that of set 1, and there is no obvious main frequency. The fine particles in the wide sieving experiment material can increase the coalescence and breaking frequency of bubbles. (II) the addition of fine particles increased the fluidization height of the wide sieve particles, the distribution of axial solid content was more uniform, and the fluidization state was more stable; (III) the local particle density decreased with the increase of axial height. In the dense phase region, the concentration increases gradually from the center line to the side wall in the radial direction. The concentration is analyzed with Set4, and at the apparent gas velocity of 0.155m/s, The solid volume fraction at the axial height of 0.2m increases from 45% at the center line to 60% at the side wall. (鈪，

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