Dedert Flash dryers are simple yet versatile in their design. Flash dryers can be used for drying a variety of products, usually filter cakes. Slurries, when preconditioned, will also dry well on Flash dryers. In a Flash dryer wet material is dispersed into the drying air stream via one of many types of feeding devices provided by Dedert. Drying takes place in a matter of seconds as heat is transferred from the airstream to the particle. Since Flash dryers only remove surface moisture, the drying rate is constant throughout the drying phase.
Once dried the product is separated from the airstream by using high efficiency cyclones or in the case of fine products, a bag filter. Secondary air cleaning devices such as wet scrubbers or thermal oxidizers guarantee the mandatory emission levels required for permitting.
To improve efficiency Dedert Flash dryers are often designed in a partially-closed circuit mode where exhaust gases are recycled back to the furnace. Alternate heat sources such as turbine exhaust gases can be used to increase energy efficiency in open-circuit dryers.
Flash dryers can be designed with inlet temperatures as high as 800° C (1470°F).
Dedert Ring dryers are used when products cannot be dried efficiently in single pass Flash Dryers. The Dedert Ring dryer is the solution in cases where particular powders, pastes, cakes or slurries require extended drying times.
The differentiating technology between the Flash dryer and the Ring dryer is the incorporation of a classifier (manifold), which enables the recirculation of semi-dried product back to the initial heat zone for additional drying and dispersion. The classifier achieves this by the adjustment of blades which cut into the layer of material that has been centrifugally classified. The splitter blades are adjusted and set by qualified Dedert engineers during the commissioning of the Ring Dryer and need not be adjusted once set.
The recycled material on the Ring dryer allows a comparatively lower exhaust temperature to be used while achieving the desired final moisture content. Drying efficiency is improved and variations in product quality are limited.
Ring dryers are used for many heat sensitive material some of which cannot be processed on any other equipment.
Very large evaporations are possible up to 40 tonnes per hour. With certain products the dryer exhaust gas can be recycled to save energy and reduce the oxygen content circulating in the dryer. The bleed off from this type of system can be used to provide waste heat for other processes.