Dedert’s Fluid Bed dryers provide for gentle yet efficient drying action, which is ideal for friable or soft agglomerated particles with a fairly narrow particle size distribution and medium size particles (200 – 400 Microns).
Product is fluidized by the process gas stream entering the dryer through the distributor plate. Dedert has a variety of distributor plates available, including static and vibrating fluid beds, used depending on the application.
Static fluid beds are used for powdered materials where all the particles are similar in diameter. This means that only a small amount of fine material is carried out of the fluid bed with the exhaust air leaving the bulk of the product suspended on the bed to be processed. Static fluid beds are very simple constructions with only the fluidizing plate requiring specialized design. Mechanically they are very simple.
Vibrating fluid beds handle material with a wide particle size range where the velocity required to fluidise the largest particles would carry away a significant proportion of the finer material in the exhaust. In these systems the airflow is reduced to suspend only the finer material and the larger product is suspended and propelled through the machine by vibration. The vibrating fluid beds have to be significantly stronger than static fluid beds to stand the high G forces and require a stiff lightweight mechanical design to withstand the forces generated. A sophisticated system must be used to isolate the vibration from the supporting structure.
Process drying air could be designed as multi-zone to enhance drying characteristics in different parts of the bed. Exhaust air leaves the dryer through a hood and is further cleaned in cyclones or bag filters to maximize product recovery while meeting emission guarantees.
Fluidised heating and cooling zones can be integrated into a single unit in a Fluid Bed dryer. Submerged extended surface heat exchangers can also be incorporated: this approach maximizes the heat transfer rate. Submerged heat transfer area can be retrofitted to existing Fluid Bed dryers to increase evaporative capacity.