Sewage Sludge Biosolids Dryer

Double shaft paddle dryer is a high-efficient, mechanically agitated, indirect-heating drying process. The dryer consists of a jacketed drying chamber/trough and two shafts welded with unique interemeshing hollow discs. Small paddles (or blades) are welded on the edge with different angle and quantity. Both drying chamber jacket and hollow discs are filled with heating medium, such as steam, hot thermal oil or hot water. In the drying process, counter-rotating shafts with discs completely mix and move wet mateial for uniform heat transfer. The evaporated moisture is sucked out by a draft fan after going through off-gas treatment system, which usually consists of a cyclone, tubular condenser and scrubber. 

Double shaft paddle dryer has been commonly used for drying sewage sludge, industrial sludge, animal manure and other biosolids etc for large scale production. Based on 30-year's experiences in manufacturing and operating paddle dryers, Our paddle dryer has been technically improved by the following aspects to better meet different working conditions: 

1. Hollow disc: The hollow disc is welded together by two halves of pressed disc steel plate on the edge. It has the following overwhelming advantages compared to traditional wedge-shaped paddle: 

1) More hollow discs can be installed to get more heating surface 

2) Because of more robust structure, much less weld and much weaker friction between wet material and hollow discs, hollow disc has much longer life-span. 

3) The paddles (or blades) welded on the disc edge with different angle and quantity can perfectly agitate, mix and move wet material for uniform and high-rate of heat transfer. It works just like a double-shaft " screw ". 

4) Hollow disc has self-cleaning function due to it's unique structure and the intermeshed blades can also help clean the disc surface for intimate heat transfer. 

5) Guide plates inside the discs can make sure heat medium reach every corner and forced to flow back into the shaft evenly without short-circuit. 

2. Tubular heating jacket: The tubular heating jacket on the drying chamber/trough can not only increase the working pressure, but also can make sure uniform heating. 

3. Off-gas treatment system: The off-gas treamtment system consists of cyclone, tubular condenser and two-stage scrubber that can reach very high emission standard. 

4. Low engergy consumption: The thermal efficiency can reach as high as 95%. And it just takes about 700 kcal heat to evaporate 1 kg water. 

Drying chamber inside

Hollow discs 

Tubular heating jacket

Off-gas treatment system 

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