For top-spraying fluidized bed granulation or coating , liquid sprayed down from the two-fluid atomizer located above the surface of the fluidized bed or immersed in the fluidized bed. The wetted part of the particle in the bed is the aim of this article. Firstly, using different method the wettability of the polypropylene particle with water or aqueous suspension was measured. It is resulted that the wetted part of the particle is very small, but it is affected by the processing variables such as the flow rate and the temperature of the air and the spraying rate. Secondly, a correlation of the wetting coefficient, expressing the wetted part, with the processing variables is obtained from experiments and data regression. Finally, the correlation is introduced to the mathematical model, the gas humidity and temperature profiles as well as the particle temperature profile can be obtained. Compared with the experimental results, the wetting coefficient and the mathematical model are verified.
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