Fluidization of nanoagglomerates in a rotating fluidized bed
Fluidization of nanoagglomerates in a rotating fluidized bed
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DOI：
10.1002/aic.10826
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发表时间：
2006-07
期刊：
影响因子：
3.7
通讯作者：
J. Quevedo;R. Pfeffer;Yueyang Shen;R. Davé;Hideya Nakamura;S. Watano
中科院分区：
文献类型：
--
作者：
J. Quevedo;R. Pfeffer;Yueyang Shen;R. Davé;Hideya Nakamura;S. Watano
在旋转流化床（RFB）系统中以对应于10、20、30和40倍重力（9.8m/s2）的不同旋转速度流化纳米颗粒的团聚体。初级粒度分别为12、16和21 nm的粉末（气相二氧化硅Aerosil® R974、Aerosil® R972和Aeroxide® TiO 2 P25）形成微米级纳米团聚体，气相二氧化硅具有约30 kg/m3的非常低的堆积密度，而Aeroxide® TiO 2 P25具有约90 kg/m3的略高的堆积密度。用床层膨胀、压降和最小流化速度（Umf）来描述它们的流化行为。结果发现，气相二氧化硅团聚体膨胀相当大，而TiO 2团聚体显示出非常小的床膨胀。Aerosil® R974和R972的最小流化速度范围为0.02至0.07 m/s，Aeroxide® TiO 2 P25的最小流化速度范围为0.13至0.20 m/s;所有粉末的Umf均在较高转速下增加。在高于Umf的气体速度下，气相二氧化硅附聚物的流化床压降高于文献中发现的数学模型的理论估计。因此，人们认为，对于这些轻颗粒附加的切向动量效应可能会增加床层压降，并提出了一个修正的模型。此外，团聚体尺寸和床层的外部空隙率通过使用分形分析结合使用Aerosil® R972获得的数据的修改的Richardson-Zaki方程来预测。© 2006美国化学工程师学会AIChE J，2006
Agglomerates of nanoparticles were fluidized in a rotating fluidized bed (RFB) system at different rotating speeds corresponding to 10, 20, 30 and 40 times the gravity force (9.8 m/s2). The powders, fumed silica Aerosil® R974, Aerosil® R972 and Aeroxide® TiO2 P25, with a primary particle size of 12, 16 and 21 nm, respectively, form micron sized nanoagglomerates having a very low bulk density of around 30 kg/m3 for the fumed silicas, and a somewhat higher bulk density of about 90 kg/m3 for Aeroxide® TiO2 P25. Their fluidization behaviors are described by the fluidized bed expansion, pressure drop and minimum fluidization velocity (Umf). It was found that the fumed silica agglomerates expanded considerably while the TiO2 agglomerates showed very little bed expansion. The minimum fluidization velocities for Aerosil® R974 and R972 ranged from 0.02 to 0.07 m/s and from 0.13 to 0.20 m/s for Aeroxide® TiO2 P25; Umf increased at higher rotating speeds for all powders. At gas velocities above Umf, the fluidized bed pressure drop of fumed silica agglomerates was higher than theoretically estimated by mathematical models found in the literature. Thus, it is believed that for these light particles additional tangential momentum effects may increase the bed pressure drop and a revised model is proposed. In addition, the agglomerate size and external void fraction of the bed are predicted by using a fractal analysis coupled with a modified Richardson-Zaki equation for data obtained with Aerosil® R972. © 2006 American Institute of Chemical Engineers AIChE J, 2006