Magnetic Field To Assist The Role Of Nano-particle Fluidization

Nanoparticles in the size range of 0.1 nm to 100 nm belong to Geldart group C particles. These particles have many excellent physical and chemical characteristics so that they have been extensively applied in many industrial fields. However, their applications have been limited due to strong cohesiveness and aggregating. Fluidization can promote the contact of gas-solid and improve the flowability of nanoparticles.The fluidization behavior of non-magnetic SiO₂, ZnO, TiO₂, Al₂O₃ and magnetic Fe₃O₄,Fe,Ni nanoparticles in plexiglass column with diameter of 5 mm is investigated. Plug and channeling in the traditional fluidized bed can be observed in the low superficial gas velocity. The pressure drop fluctuates extensively. Bubbling enlarges with increasing gas velocity. Defluidization, elutriation and large agglomerate appeared. The bed expansion ratio is small. So the fluidization performance of nanoparticles is poor in the traditional fluidized bed.By adding coarse magnets with the average size of 2 mm into the fluidized bed, the large agglomerate, bubble and channeling can be broken up, the bubbling and elutriation were also restrained because of coarse magnets vibrating violently under an axial magnetic filed. The influence of the superficial gas velocity, the amount of coarse magnets and magnetic-field intensity on the fluidization quality of nanoparticles has been investigated in detail. The fluidization quality of SiO₂ is better than ZnO, TiO₂, Al₂O₃ and Fe₃O₄ in the magnetic fluidized bed. The size of agglomerate and the minimum fluidization velocity were decreased. The agglomerate particle fluidized (APF) can be achieved for SiO₂ nanoparticles.The fluidization ability of ZnO, TiO₂, Al₂O₃ and Fe₃O₄ nanoparticles was poor in a traditional fluidized bed or even in the magnetic fluidized bed with adding coarse magnets, so the fluidization of mixture of nanoparticles was researched. The non-magnetic and magnetic particles can be mixed uniformly and the fluidization quality was improved in the magnetic fluidized bed. The homogeneous fluidization was realized in the appropriate amount of coarse magnets, magnetic-field intensity and gas velocity. The mass fraction of nano-ZnO can reach 60% in the non-magnetic mixtures, but the mass fraction of additive TiO₂, Al₂O₃ is no more than 50%. The coordination of nanoparticles in the fluidization was analyzed.The Richardson-Zaki equation was used to validate the particulate fluidization of mixtures. Based on the analysis of bed mass and the Ergun equation, model for estimating the minimum fluidization velocity of the mixture formed by APF and ABF nanoparticles is proposed for further research in mixed nanoparticles and its application in the future.