Fluidized Bed

The Wurster process is a unique “coating technology” well suited to uniformly encapsulate individual particulates. This technology is characterized by the location of a spray nozzle at the bottom of a fluidized bed. The nozzle atomizes the coating solution. The particles are suspended in the fluidizing air stream that is designed to induce a cyclic flow.

The atomized coating solution collides with the particles as they are carried away from the nozzle. The temperature of the fluidizing air is set to appropriately evaporate solution or suspension solvent or solidify the coating material shortly after colliding with the particles. This process is continued until each particle is coated uniformly to the desired coating thickness.

The technology can be used to encapsulate solid materials with diameters ranging from near 50µm to several centimeters. The process has a greater drying capacity than other coating systems due to a relatively high fluidizing air velocity. Coating possibilities are relatively unlimited including the ability to place a hydrophilic coat on a hydrophobic core, or a water-based coat on a water-soluble core. Coating properties can be optimized with coat formulation parameters & processing conditions.