Study On Characteristics Of The Gas-Solid Two Phase Flow In Magnetically Fluidized Bed And Its Application

It is convenient to achieve stable fluidization instead of bubbling fluidization by utilizing magnetically fluidized bed because of its advantage of controlling and adjusting. Furthermore, in magnetically stabilized fluidized bed, not only it can greatly improve the contact between gas and solid as result of no gas bypassing and particles' backmixing, but also can it be with less pressure drop and higher gas velocity in the bed. And it will be widely come into use in many industrial fields, such as environmental protection, separation technology, biological or chemical reaction, and so on. Therefore, it is of great significance to study further and systematically on the characteristics of the gas-solid two phase flow in magnetically fluidized bed, and all results can also be used in the engineering design and operation.In this paper, a dynamic model of the gas-solid two phase flow in magnetically fluidized bed is established first. Because the gas-solid two phase flow in magnetically fluidized bed belongs to dense-phase flow with the influence of the magnetic force, the intercoupling between the two phase should be considered more carefully and completely. On the basis of two-fluid model, combining the kinetic theory of granular flow, the differential equations of describing the gas-solid two phase flow in magnetically fluidized bed are obtained. On one hand, it can effectively solve the interaction because of the particles' turbulent flow, such as collision, friction and so on, on the other hand, considering the interaction of turbulent kinetic energy among the particles, the dissipation energy is introduced into the transportation equation of particles, and it can reflect the effect of the turbulence between the two phase well.Numerical simulation of the gas-solid two phase flow in magnetically fluidized bed is carried out, using FLUENT, a kind of software of computational fluid dynamics. It focuses on investigating the influence on the two phase flow due to varying magnetic field intensity. In the paper, no magnetic field, weak intensity and moderate intensity are computed for two kinds of particle with different diameters and three different ratios between gas superficial velocity (U_g) and initial bubbling velocity (U_mf) , and some results showing the characteristics of the gas-solid two phase flow in magnetically fluidized bed are obtained, including the distribution of the solid phase, pressure drop of the bed. Compared with the experimental data, it demonstrates that the results of the numerical simulation based on the dynamic model coincide with the experimental data well.In order to understand the mechanism of the gas-solid two phase flow in magnetically fluidized bed further, an experimental research to reveal the characteristics of magnetically fluidized bed is also carried out. In the experiments, the bed pressure drop and its fluctuation are measured by using digital sensor of pressure. And the minimum bubbling velocity is determined on the basis of the bed pressure drop and its fluctuation. To be further, the stable zones on different operational conditions in magnetically stabilized fluidized bed are obtained. Finally, on the basis of all experimental research, a relationship calculating the stable zone using three dimensionless factors, Re, Ar and Er is put forward, and it is more convenient to provide the operational parameters in practice. Consequently it is very helpful to promote the application of magnetically stabilized fluidized bed.All study on the characteristics of the gas-solid two phase flow in magnetically fluidized bed is to develop the application of magnetically fluidized bed better. On the basis of the study discussed above, a facility removing the dust in gas stream is designed for industrial application. The key components, for instance, bed structure, air distributor, magnetic field generator, and particles-regenerating system are designed in detail in the paper. Then the facility's performance of collecting dust is verified by the experiment, and in the meantime, the operational parameters for high efficiency of the facility are also concluded.