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The influence of interparticle forces (IPFs) on the hydrodynamics of a gas-solid fluidized bed was experimentally investigated with the help of a polymer coating approach. The results showed that the presence of IPFs in the bed can considerably change the hydrodynamic parameters. The tendency of the fluidizing gas passing through the bed in the emulsion phase increased with IPFs in the bubbling regime. The performance of a fluidized bed reactor was then studied through simulation of a reactive catalytic system using three different hydrodynamic models: (a) a simple two-phase flow model, (b) a dynamic two-phase flow model, and (c) a dynamic two-phase flow model, integrating the effects of superficial gas velocity and IPFs. The simple two-phase flow model was found to underestimate the reactor performance for catalytic reaction most likely due to the oversimplified assumptions involved in this model. Also, the simulation results showed that modification of the bed hydrodynamics due to IPFs resulted in a better performance for a bubbling fluidized bed reactor. This suggests that the hydrodynamic models should take into account the effects of superficial gas velocity and variation in the ratio of the magnitude of IPFs/hydrodynamic forces, due to any operational reason, to yield a more reliable evaluation of the performance of the fluidized bed reactor. [ABSTRACT FROM AUTHOR]

Due to their unique properties arising from their very small primary particle size and very large surface area per unit mass, ultrafine powders are applied in a wide range of processes and their application continues to increase. Gas fluidization is one the best techniques available for dispersing and processing these particles. However, they cannot be fluidized separately and, in fact, tend to fluidize as large sized very porous aggregates. In order to achieve a proper fluidization, appropriate assisting method is required. This contribution reviews experimental and theoretical studies on gas fluidization of ultrafine particles. It includes introduction of different forces playing role on the fluidization of these powders, phenomenological discussion on how they can be fluidized, a summary of various assisting methods and their impacts for improving the fluidization quality of these powders, a summary of different experimental methods for measuring the agglomerate size followed by different modeling approaches for the prediction of this important parameter, a brief review on different applications of these particles and their bed expansion behavior. With respect to the current and upcoming applications of ultrafine powders in industrial sectors, considerable theoretical and experimental work is left for mining new opportunities in chemical engineering on the subject of fluidization of ultrafine particles [ABSTRACT FROM AUTHOR]