Fluid Bed Coater

The bottom spray fluid bed granulation system, also known as the Wurster system, is the primary application of fluidized bed coating technology. It has been widely used for coating microspheres, granules, and even powders with particle sizes below 50μm.

The material tank of the bottom spray device features a Wurster column at its center, with an air distribution plate at the base containing numerous circular perforations. The differential opening rates between the inner and outer sections of the Wurster column create varying airflow intensities, enabling particles to undergo regular circulation within the column. The spray gun is installed inside the partition ring, with the liquid spray direction aligned with the material’s movement. This configuration designates the inner Wurster column as the primary coating zone while the outer section serves as the main drying area. Particles pass through the coating zone every few seconds, completing one full coating-drying cycle. Since all particles have equal probability of passing through the coating zone, the resulting coating film is uniformly dense and consistent.