KREVOX European Environmental Centre
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FDS Fluid Dryer

FDS fluid dryer is a technology characterized by its low heat energy usage indicator, equal to approx. 0.78 kWh per kg of evaporated water. Such types of installations are used mainly for large efficiencies, where the building area is limited. Currently, there 39 examples of such installations implemented worldwide. This technology allows operation for over 8000 hours per year.

FDS dryer is a classic example of combining two types of heat exchange, via convection or conduction. The dried sludge is kept in suspension by hot fluidization air, at the same time the sludge is heated by heat exchangers in the device's intermediate section. The main advantage of this technology is its low heat energy usage and good product quality. The dried up granules up to the 92% d.m. content are characterized by their uniform shape, easy for handling and containing minimal amounts of dust.

Process description

The mechanically dehydrated sludge, stored prior to that in a silos or other type of storage container is delivered via sludge pumps from the top to the fluid dryer.

The delivered sludge is kept in suspension in the fluid layer thanks to the air injected from the bottom. In the fluid layer of the intermediate section there are also heat exchangers in the form of pipes. The heating medium filling the pipes can be either steam or heating oil.
Next, a schematics of a fluid heating installation, together with cleaning exhaust gases and sludge transporting equipment, is shown.

FDS fluid dryer is a technology guaranteeing process security. 


 Fluid dryer - Susteren / Holland


8.300 kg/h

Material amount

11.000 kg/h


24 h/d, 5 days a week

End product

dry granulate > 92% d.m.



 Fluid dryer - Beverwijk / Holland


2 x 6000 kg/h

Sludge from over 20 plants

Heat source

saturated operation


24 h/d, 7 days a week

End product

dry granulate > 90% d.m.



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