振动辅助纳米颗粒聚团流化实验研究

Experimental study on fluidization of nanoparticle agglomerates with the assistance of vibration

在内径40mm的流化床实验台上,研究SiO2、Al2O3和TiO23种纳米颗粒在振动辅助流化时不同振幅、频率下的流化特性,比较振动对不同黏性纳米颗粒流化的改善程度及原因。结果表明,在无振动条件下,SiO2纳米颗粒达到稳定状态时表现为散式流态化;Al2O3和TiO2纳米颗粒在流化床底部形成较大的聚团,导致明显的流化分层现象。在振动条件下,SiO2纳米颗粒的临界流化速度降低,床层膨胀高度随着振幅和频率的增加而降低;而对于Al2O3和TiO2颗粒,随着振幅和频率的增加,临界流化速度降低,床层膨胀高度增加,流化床底部的聚团尺寸减小,但当频率和振幅较低时,振动对其流化行为无明显改善。振动强化了纳米颗粒聚团的碰撞,具有促进聚团破碎和密实化的双重作用。针对不同黏性的纳米颗粒,若要达到最优的流化质量,需要探索不同的振动参数。

The fluidization characteristics of SiO2,Al2O3,and TiO2 nanoparticles with the assistance of vibration at different frequencies and amplitudes are studied in a plexiglass fluidized bed with the inner diameter of 40 mm.The effects of vibration on fluidization of nanoparticles with different cohesiveness are compared.The results show that,without vibration,the SiO2 nanoparticle agglomerates are fluidized smoothly while the Al2O3 and TiO2 nanoparticle agglomerates are fluidized with segregation because there are large agglomerates at the bottom of the fluidized bed.When the vibration is introduced,the minimum fluidization velocity of SiO2 decreases,and the bed expansion ratio of SiO2 decreases with the increase of amplitude and frequency.For the Al2O3 and TiO2 nanoparticles,as the amplitude and frequency increase,the minimum fluidization velocity decreases,the bed expansion ratio increases,and the agglomerate size decreases at the bottom of the fluidized bed.However,the vibration makes no significant improvement in fluidization at low frequency and low amplitude for the Al2O3 and TiO2 nanoparticles.Vibration enhances the collision of nanoparticle agglomerates and has the dual effect of promoting the breakage and compaction of the agglomerates.The optimal vibration parameters need to be explored to achieve the optima fluidization quality of different nanoparticles.