振动和搅拌对SiO2纳米颗粒聚团流化的影响对比研究

Comparative Study on the Effect of Vibration and Stirring on the Fluidization of SiO2 Nanoparticle Agglomerates

纳米颗粒聚团间的黏性力较强,通常需要一定的辅助方法才能实现稳定流化。本文对比了振动、搅拌、以及振动和搅拌组合方法对SiO2纳米颗粒聚团流化特性的影响。结果表明,振动能消除沟流和节涌,提高床层膨胀高度,但当振动强度超过15.7 m·s-2后,振动会对流化产生负面影响。搅拌能显著提高床层膨胀比,但当转速超过200r/min后,流化床的稳定性逐渐降低。振动和搅拌的复合作用能在单场辅助流化的基础上进一步提高纳米颗粒聚团的流化质量,提高床层膨胀比,降低临界流化速度,将聚团尺寸减小到50〜150μm之间.振动和搅拌分别在垂直和水平方向上作用于床层,对纳米颗粒聚团流化的改善存在协同作用,但搅拌对流化的影响比振动的影响更为明显。

Due to the strong cohesive force between the nanoparticle agglomerates,some assisted methods are usually used to improve the fluidization quality of nanoparticle agglomerates.In this paper,the effects on the fluidization of SiO2 nanoparticle agglomerates of vibration,stirring and the combination of vibration and stirring are compared.The results show that,vibration can eliminate the channel and slug,and increase the bed expansion height.But,when the vibration strength exceeds to 15.7 m-s-2,the vibration would have a negative effect on fluidization.Stirring can significantly increase the bed expansion ratio,but when the rotate speed is more than 200 r/min,the stability of the fluidized bed decreases gradually.Compared with the single field assistance,the combined effect of vibration and stirring can further improve the fluidization quality,increase the bed expansion ratio,decrease the minimum velocity and reduce the agglomerates size to 50~150 μm.Vibration and stirring act on the bed in vertical and horizonal directions respectively,and there is a synergistic effect to improve the fluidization of nanoparticle agglomerates between them.However,the effect of stirring is more obvious than vibration.