Ingetecsa’s fluidised bed dryer excels in careful processing. Products that require longer drying times are ideal to process in a fluid bed. The drying air acts as a cushion for the particles to bounce on. This minimises product erosion as well as dust formation.
A blower pushes filtered air through a heater to the wind box. The wind box is a large space at the bottom of the fluidised bed dryer. From here the air distributes itself uniformly. It then flows upwards through the fluidisation plate. The nozzles of the nozzle plate are oriented towards the discharge end. Product enters the unit at the feed side. It drops on the fluidisation plate. At the opposite end is the weir. This overflow plate maintains the product level. It controls the residence time of the product in the machine. The feed rate, density of the product bed and the weir height determine the residence time of the product in the dryer. Emptying of the unit is by lowering or opening of the weir. As the product fluidises like a boiling liquid, it empties in a matter of only seconds.
Although the fluidised bed is normally continuously operated, batch operation is possible too.
Despite the high turbulence around the particles, the particle treatment is very gentle. Both from a mechanical and from a thermal viewpoint. That is because particles are gently lifted by the air and float on air cushions. Product travels through the machine in a plug flow motion. Fluidisation is entirely based on the product lift by the air flow through the product layer. Since there is no vibration used for the fluidisation, there is virtually no dust formation. So, any dust or fine particles that travel with the product feed, evacuate to a dust collector, like a set of high efficiency cyclones or a bag filter house.
Lastly, nozzle plates don’t break or tear apart in a static fluidised bed, which is a common problem of vibrating technology.
Large ports and hatches allow ample access to the interior for cleaning or for inspection.
Multiple temperature zones in the unit are possible by segregating the wind box. For that, each section receives air at different conditions. This way, drying and cooling of particles is possible in the same unit. The exhausted air flows leave the unit either combined or separately.
Other combinations are for example explosion tight versions, internal heat exchangers, self-emptying units, and an expanded bed version. But also solvent recovery, multi-stages, and hinged versions to open the entire dryer, are possible.
Other drying technologies
≡ The fluid bed dryer is ideal for gentle, slow paced drying of the granule. For the fluidised bed technology, particles should be relatively uniform in dimension.
≡ When the particle size distribution (PSD) is wider, the Spiral Flash Dryer is likely the better choice. It is a combination of a fluidised bed and a flash dryer. The Spiral Flash Dryer is also static technology. It is better suitable for products that consist of a range of smaller and larger particles.
≡ The conventional Flash Dryer is probably the best choice when the product is very fine. The fluidised bed would otherwise blow these fine particles out of the drying room. Furthermore, with smaller particles you won’t see much abrasion occurring.