“Wurster Accelerator” Coating Technology

Pellet/Fine Particle Coating

When is a Wurster system used?

The Wurster coating system is ideally suited for the coating of particles ranging from fine powders (~10 micron) up to small pellets (2-3 mm). It consists of a processing insert that is placed inside a fluid bed processor.

FC-200M Fluid Bed showing the 46″ Wurster Coating processing insert.

What is the Wurster Accelerator?


FREUND’s patented Wurster Accelerator System provides the fastest possible spray rates for Wurster coating processes. Compressed air diverts product away from the spray nozzle tip, optimizing product movement through the spray zone and minimizing agglomeration.

FREUND’s patented Wurster Accelerator System.

What are the results?

Diverting the particles around the spray nozzle allows for a much faster spray rate to be achieved, lowering process times and decreasing the attrition normally found in longer Wurster coating processes. In the case study below, improvements of spray rate up to 600% were achieved when using the Wurster Accelerator coating system.

The graphs above show conventional spray rates (red) compared to spray rates achieved with the Wurster Accelerator (blue).

Adjustable Height Partitions

Scale-up is easily achieved by including multiple partitions within the Wurster processing insert. Each partition contains its own Wurster Accelerator spray gun and diverting system. The partitions move in unison through the use of a center lift device. The distance between the air distribution plate and the bottom of the partition is tightly controlled.

46″ Wurster Insert with six Wurster Accelerator partitions. All partitions are connected together by a center lifting column.

In Process Removable Spray Guns

While the process is in operation, it may become necessary to remove the spray guns for manual cleaning. FREUND’s removable spray gun design allows for the guns to be removed without affecting the process in the other Wurster Accelerator partitions. Without the use of tools, each spray gun can be removed and replaced within a matter of minutes.


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