Fluid Bed Wurster HS Coating Systems from Glatt Air Techniques

The Wurster HS processing insert, patented by Glatt in 1992, provides significant improvements over conventional Wurster coating technologies through increased productivity, high spray rates, increased yields and applications with fine particles.

The Wurster HS consists of a conical product container with open-ended cylindrical inner partition. An air distribution plate is located at the lower end of the product container to distribute fluidizing air between the inner and outer partitions. The majority of air is directed through the inner partition. Particles are drawn into the inner partition by the pressure differential created by the difference in air velocities between the two partitions. The particles are conveyed through the inner partition and into the expansion chamber by the fluidizing air. As gravity overcomes the force of the fluidized air, the particles fall back into the outer partition where they are suspended in a slow moving "down bed". An air-atomizing nozzle in the center of the distribution plate introduces the coating solution. The nozzle sprays upward providing concurrent application of coating to the particles. As the particles travel upward, excess moisture is evaporated and removed from the process.

Applications for the Wurster HS include: