Abstract
Fluidized bed coaters or granulators with spray nozzles are used to produce coating particles, granules and agglomerates in various industrial fields. When the binder liquid containing fine particles is sprayed into a hot fluidized bed, the fluidizing particles grow in size by agglomeration due to the particles colliding with the spray droplets that first form liquid and then solid bridges between particles. This phenomenon causes unstable coating or granulating and ill-balanced products. The question then arises about mono-core coating with finer particles. We investigated the characteristics of the mono-core coating using a draft-tube spouted-bed coater, applying the separation force due to the high-speed gas from the inlet nozzle. As a result, it is found that mono-core coating could be achieved due to the shear force and the external solid circulating system. It is shown that the coating ratio can be controlled by selecting the coating operation time and the concentration of binder liquid. Also, it is found that choking of the draft-tube can be delayed by increasing the inlet gas velocity and the bed temperature.
