Experimental Study of Coating in a Bottom Sprayed Fluidized Bed

摘要

Several investigations have been devoted towards understanding the coating process in fluidized beds. Most of these studies focused on spraying liquid droplets over the bed. However, due to the complexity of these systems, more investigations are still required to quantify the effect of operating conditions on the coating criteria. The present work aims at fundamentally understanding and precisely determining the effect of different operating conditions on coating quality in a jetting fluidized bed where the coating agent is sprayed as liquid droplets into the bed. A 3-D fluidized bed with a spraying nozzle situated in the middle of a perforated distributor plate was used for the experimental study of the effect of the operating condition on the coating quality. Results from the experimental part showed that at maximum jet gas flow rate which the jet didn turn into a spout and turbulent stage of fluidization the coating quality improves, but there is a limitation for the binder flow rate(NAR=4.0E-5) which is recognized in this study and could be use for any fluidized bed coater in the same condition. Based on the experimental results, an empirical function was derived to predict the coating efficiency in different operating conditions and this function also could be used in the mathematical model.