The "Wurster bottom spray" invented by Professor Uster was a revolution in industrial coating. Fluidized bed coating machines are mainly used for coating small particles, such as powder coating, particle coating, and pellet coating. Due to the intense and highly dispersed movement of particles in a fluidized bed, it is particularly suitable for coating small particles. Therefore, fluidized bed coating machines are generally not used for tablet coating, as tablets are prone to breakage and wear during intense movement in the fluidized bed.

The fluidized bed coating machine controls the movement of materials to form an orderly fluidized state by adding a spacer with upper and lower openings and corresponding sieve plates with different aperture ratios in the hopper. Spray liquid is added to the system through a pneumatic nozzle installed at the center of the sieve plate, with the nozzle head facing upwards and spraying liquid from bottom to top, in the same direction as the material movement. There is a certain distance between the separator and the sieve plate to ensure that the material can flow smoothly from the outside of the separator to the inside, forming a cyclic flow state.

In the bottom spray device, the fluidization state of particles is very regular, and the time interval for particles to pass through the spray liquid mist is very regular. The coating liquid is sprayed on the surface of particles that move in an orderly manner near the nozzle, and the spread of the liquid mist is also very uniform, forming a uniform thickness of the coating film without pores, which will not cause poor coating performance due to disorderly movement like in top spray.

Bottom spray is mainly used in the field of coating

Can be used for both water-soluble coating and organic coating

Dispersion coating of high molecular weight polymers

Slow release and controlled release coating

enteric coating

Fine particle coating

Layered coating between different active ingredients

Main technical parameters

installation diagram