Magnetic Field To Assist The Fluidization Of The Role Of Non-magnetic Nanoparticles

The fluidization behavior of non-magnetic SiO2, ZnO and TiO2 nanoparticles in plexiglass column with the diameter of 5 cm is investigated. Plug and channeling in the traditional fluidized bed were observed in the lower superficial gas velocities. The pressure drop fluctuated extensively. Bubbling enlarged with increasing gas velocity. Defluidization, elutriation and large agglomerate appeared. The bed expansion ratio was small. So the fluidization performance of nanoparticles was poor in the traditional fluidized bed. Due to introduction of magnetic field energy, the slugging of bed was disappeared, the measured agglomerate size was decreased and fluidization quality was significantly improved.At the same time the influence of parameters such as fluidization time, superficial gas velocity, magnetic intensity and adding amount of the coarse magnets on size of agglomerates was studied. The results showed that more stable agglomerates could be got through a certain fluidization time. The fluidization time of SiO2 was 10 min, and ZnO and TiO2 nanoparticles were both 5min in the experiment. Both the experimental and theoretical results showed that the higher gas velocity leaded to a smaller agglomerate size. If the coarse magnets do not happen condensing, larger magnetic intensity and adding amount of the coarse magnets may leads to a decreasing of the agglomerate size.A mathematical model for the prediction of agglomerate sizes is established on the basis of energy balance of the agglomerate collision energy, magnetic field energy, energy generated by hydrodynamics shear and cohesive energy in MFB. The size of agglomerate of cohesive particles is calculated with this model. The equilibrium agglomerate sizes calculated by this model are in reasonable agreement with the experimental values.Agglomerating and breaking criteria are obtained based on the analysis of the solution of the energy balance model. The experimental results and theoretical analysis show that higher superficial gas velocity, lower cohesion of particles, lager magnetic intensity and adding amount of the coarse magnets are advantageous to the agglomerate fluidization of cohesive particles.