Study On Mixing Of Multi-Streams Of Gas-Solid In Fluidized Beds

In this thesis, the solid mixing of similar materials and dissimilar materials in fluidized beds were reviewed. The mechanisms of solid mixing and segregation, affecting factors and mathematical models, et al., were discussed in detail.Experiments were carried out to study the method for measuring solid mixing in fluidized beds. The fiber optic probes could be used to measure the solids concentration in the lean phase and the fine particles RTD in the dense phase. But the signals were difficult to be calibrated to the true concentrations, so only qualitative results were obtained. On view of the fact that different colored particles could adsorb different lights, it became possible to use the fiber optic probe to measure the fines concentration in the dense phase in the coarse particles fluidized bed, if the fines and coarse particles are of different colors and suitable light source and filter are used. Since the bubbles and the coarse particles have significant influence on the signals, the practical use of this quantitatively is still of some difficulty.Experiments were carried out to study the residence time distribution of the fine particles in a coarse particles fluidized bed. The effects of the injecting fines quantity, gas velocity, the locations of the fines injection, and the fluidized bed height on the fines RTD were investigated. Because of the interaction between the fines and coarse particles in the bed, the residence time of fines was found substantially longer than the gas residence time, and had a widely distribution. The fines RTD is dominantly determined by the gas velocity, especially at the low gas velocity. The fines residence time decreases with the increases of gas velocity and the quantity of injecting fines. The location of the fines injection point unsubstantially influences on the fines residence time. There exits a specific bed height, at which the fines residence time is the shortest. On the mechanism of the interactions between the fines and coarse particles, a theoretical model was proposed to describe the...