Working Principle

Dense rows of wedge-shaped hollow blades are mounted on a hollow shaft, through which the thermal medium circulates into the blades. This design delivers an extremely large heat transfer area per unit effective volume, and the applicable temperature range of the heating medium spans from -40℃ to 320℃. The medium can be steam or liquid media such as hot water and thermal oil.
Heating is realized via indirect heat conduction, with no air carrying away heat to waste; all heat is utilized to heat the materials. Heat loss is limited to minor ambient heat dissipation through the thermal insulation layer only.
The heat transfer surfaces of the wedge blades feature a self-cleaning function. Relative friction between material particles and the wedge surfaces creates a scouring effect that strips adhered materials off the blade surfaces, maintaining clean heat transfer surfaces during continuous operation.
The housing of the blade dryer is generally fitted with two to four hollow stirring shafts. Sealed end caps and a top cover are installed on the housing to prevent material dust leakage and ensure full equipment performance. The heat transfer medium flows through the housing jacket and hollow stirring shafts via rotary joints. The internal structure of each hollow stirring shaft varies based on the type of heat medium, to maximize heat transfer efficiency.

Application Scope

The paddle blade dryer has been successfully applied in food, chemical, petrochemical, dyestuff and industrial sludge industries.
It features integrated heat transfer, cooling and stirring functions, which support the following unit operations: low-temperature calcination, cooling, drying (solvent recovery), heating (melting), reaction and sterilization.
The stirring paddles themselves serve as heat transfer surfaces, which greatly expand the heat transfer area per unit effective volume and shorten processing time.
The wedge-shaped heat transfer surfaces are equipped with a self-cleaning function. Compression and tumbling stirring actions ensure uniform mixing of materials. Materials move in a piston flow pattern along the axial direction. The differences in material temperature, humidity and mixing degree across axial sections are minimal.
When thermal oil is used as the heating medium, the equipment can realize low-temperature calcination. Typical examples include the dehydration of calcium sulfate dihydrate () into calcium sulfate hemihydrate (), and the calcination of sodium bicarbonate () into sodium carbonate (), among others.
It also supports cooling processes using cooling water, chilled brine and other media. For instance, it can replace traditional alkali air coolers as alkali cooling equipment in sodium carbonate production lines. This design cuts power consumption and eliminates auxiliary air treatment facilities, significantly lowering operating costs.
Drying is the core function of this equipment. The air-free indirect drying process delivers ideal performance in solvent recycling, reduces energy consumption and simplifies environmental control and testing operations. It is especially suitable for solvent recovery and the treatment of heat-sensitive materials prone to combustion or oxidation, and is widely adopted in fine chemical, petrochemical and dyestuff sectors.
The consistent temperature, humidity and mixing conditions along the axial direction enable the equipment to perform heating, melting and solid-phase material reactions. It has achieved successful applications in compound fertilizer and modified starch production.
The paddle dryer can also be used for food and starch sterilization. Its large heat transfer area per unit volume rapidly raises materials to sterilization temperatures, effectively preventing product quality deterioration caused by prolonged heating exposure.
Double-shaft paddle dryers can be customized with a maximum heat exchange area of 300 m², and vacuum-type configurations are available upon request.

Schematic of Structure

Technical Parameter

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