Fluid-bed dryer for quasi-continuous batch operation

Vibration angle can be infinitely varied during operation from 30 to 90 degrees in and counter to the main conveying direction.

A three-stage, vibrating fluid-bed dryer for gentle drying of sensitive food ingredients was designed and delivered for an international manufacturer.

This machine type – which integrates all the advantages of batch operation while taking adequate account of the continuously operating preceding stage – was selected following intensive preliminary tests because it assures exact compliance with and reproducibility of the specified residence time for the complete product. The elaborated technical solution – the vibrating fluid-bed dryer illustrated below – has a fluidizing plate area of 6 m².

The dryer's three cascaded product chambers, separated from one another by pneumatically operated vertical weirs, are clearly visible. In the first step, the required product is conveyed to the first chamber, where it is predried with a defined quantity of hot air. When the permissible product temperature is reached, the first weir opens and the product enters the second chamber. At the same time, the first chamber is filled with moist product. The third chamber is filled in the same way, and the product discharge that follows the drying and cooling process is also based on this principle. The air flows, air temperature, and residence time are adapted to the defined product quality requirements in each of the three zones.

During the drying phase, the product bed can be homogenized with the electronically controlled VARIO motor by applying a vertical vibration or a vibrating motion counter to the main conveying direction. In addition, the conveying motion from one chamber to the next and the discharge from the dryer can be supported by optimizing the vibration angle.

The dryer is manufactured in line with strict hygienic standards to minimize the risk of germ formation in the sensitive product. The fluidizing plates, which are assembled from conveniently sized sections, are locked inside the dryer housing by pneumatically operated eccentric fasteners and can be easily removed on rollers for cleaning.