內通式流體化床中粒子循環速率之量測

Measurement of the Solid Circulation Rate in an Interconnected Fluidized Bed

葉文鈞(Wen-Chun Yeh)

指導教授 ： 錢建嵩

中原大學/工學院/化學工程研究所/碩士(2002年)

https://doi.org/10.6840/cycu200200249

摘要

中文摘要
因為具有較高之粒子循環率及較少之粒子損耗，內通式流體化床已被應用在有關物理及化學之操作上。為瞭解內通式流體化床粒子之流力行為，本研究係於由四個15公分見方之床體所組成及二個15公分見方床體組成之內通式流體化床中進行，實驗所使用的流體化粒子為密度2.42 g/cm3之透明玻璃珠兩種，其中A群粒子平均粒徑為68.66 慆，最小流體化速度（Umf）為0.75 cm/s；B群粒子平均粒徑為495.43 慆，最小流體化速度（Umf）為23.2 cm/s，A群粒子之操作氣速再3至6倍之最小流體化速度而B群粒子則操作在2至3倍最小流體化速度。
在四格床實驗數據方面藉由量測孔口之壓差計算床內粒子循環速率，二格床則由床體堰堤(weir)出口處直接承接粒子以計算粒子循環速率，並將兩床體之實驗結果相互比較，初步結果除發現粒子循環速率隨稀疏床之操作氣速及床重之增加而增加外，兩床間粒子循環率之分佈趨勢不盡相同，甚至A群粒子與B群粒子之粒子循環率分布趨勢也不盡相同。因此針對計算式中之排放係數(discharge coefficient, CD)做探討，發現CD並非常數，需考量其他之操作變數，而經由修正後之粒子循環率與實際量測值間之相關係數(correlation coefficient, R)為0.98以上，顯示修正後之公式之回歸效果相當良好。另外本研究亦探討粒子於床內之運動機構，藉由所拍攝之畫面說明粒子越過堰堤之模式。

關鍵字

內通式流體化床 ； 孔口 ； 粒子循環速率 ； 堰部

並列摘要

Abstract:
With higher solid circulating rates and less particle attrition, the interconnected fluidized bed (IFB) has been developed as a new application for many particle operations on physical and chemical processes. To understand the hydrodynamic behavior of particles in the IFB systems, all measurements of CRS were conducted in a four 15 cm e 15 cm compartments IFB and a two 15 cm e 15 cm compartments IFB. The density of the fluidized particles is 2.42 g/cm3. Two kinds of particles are used in this study, the average diameter of A group particles is 68.66μm and the minimum fluidized velocity (Umf) is 0.75 cm/s, average diameter of B group particles is 495.43 μm and the minimum fluidized velocity is 23.2 cm/s. The air velocity of A group particles is 3 Umf to 6Umf and the air velocity of B group particles is 2Umf to 3 Umf.
The CRS is calculated by means of acquisition of the pressure drop between orifices in 4-compartment IFB and measured directly from the outlet of the weir in 2-comparment IFB and compare these experimental results between 4-compartment IFB and 2-compartment IFB. The results show that the CRS a linear function of the operating velocity of the lean-phase bed and the CRS also increases with increasing the bed load. The linear trends of CRS between 2-comparment IFB and 2-comparment IFB do not mesh well and the linear trends of CRS between A group particles and B group particles do not accord well. By means of the discussion of the equation of CRS, the discharge coefficient (CD) is not a constant and other control parameters might be considered. After the correction of discharge coefficient, the correlation coefficients (R) between calculated values and experimental data are above 98%. The agreement between the calculated values and the experimental data is generally favorable. The particle moving mechanisms within the IFB are also discussed in this investigation.

並列關鍵字

Orifice ； Circulation rate of solid ； Interconnected fluidized bed ； Weir

參考文獻

Abellon, R. D., Z. I. Kolar, W. den Hollander, J. J. M de Goeij, J. C. Schouten and van den Bleek, “A single Radiotracer Particle Method for the Determination of Solids Circulation Rate in Interconnected Fluidized Beds”, Powder Technol., 92, 52-60 (1997).

Al-Zahrani, A. A. and M. A. Daous, “Bed expansion and average bubble rise velocity in a gas-solid fluidized bed”, Powder Technol., 87, 255-257(1996).

Beverloo, W. A., H. A. Leniger and J. Velde van de, “The Flow of Granular Solids through Orifices”, Chem. Eng. Sci., 260-269 (1961).

Bolton, L. W. and J. F. Davidson, “Dense Phase Circulating Fluidized Beds”, Chem. Eng. Commun., 62, 31-51 (1987).

Clift, R. and S. Rafailidis, “Interparticle Stress, Fluid Pressure and Bubble Motion in Gas-Fluidized Beds”, Chem. Eng. Sci., 48(9), 1575-1582 (1993).