Working Principle

Hollow wedge blades are arranged densely on the hollow shaft and the heat media flows through the hollow shaft to the blade. The heat transfer area in effective volume per unit is great and the temperature range of heat media is -40℃ to 320℃. The heat medium might be steam, or liquids such as hot water and thermal oil etc. Indirect heating does not carry air and take away the heat which is all used to dry the material except the heat loss of insulation layers by radiating. The heat transfer surface of the blade has self-cleaning function. The relative movements of the material granules and the wedge surface can wash off the material attached to the wedge surface so as to keep a clean heat transfer surface during operation. The Ω type shell of blade dryers usually has 2 to 4 pieces of hollow stirring shaft equipped inside. To avoid any leakage of material dust, there is sealed end closure and top cover for the shell. The heat transfer media flows through the rotating joint, shell's jacket and hollow stirring shaft. The hollow stirring shafts adopt different interior structures in accordance with different heat media to ensure the best transferring effect.

Characteristics

1. The blade dryer features low energy consumption due to the indirect heating with no heat taken away by the air and the insulation layer in the exterior wall of the dryer. It only consumes 1.2 kg of steam to evaporate 1kg of water for drying pulpous material. 

2. The blade dryer system is low in cost: Large heat transfer surface in effective volume per unit shortens the processing time and the size of the equipment. Therefore the building area and space are sharply decreased. 

3. The blade dryer can process a wide range of materials: Different heat media can be used to process heat-sensitive materials and materials that require high temperature as well. Commonly used media are steam, thermal oil, hot water and chill water. The dryer can perform continuous or batch operation in a variety of fields. 

4. The blade dryer produces low pollution: Without any carrying air, very little powder is carried out. The evaporation of solvents is low for easy handling. Sealed circulation can be used for materials that might cause pollution or materials whose solvents needs to be recovered. 

5. The operation cost is low: 1hour/day for each operator is enough for normal operation. The dryer features low-speed stirring and reasonable structure with low abrasion loss and maintenance cost. 

6. Steady operation: The material granules can fully contact the heat transfer surface because of the special compressing and swell-stirring effect of the wedge blade. The gradients of temperature, humidity and mixing are very small in different axial areas, which can ensure the stability of process.

Material to be dried

The blade dryer has been successfully applied in foodstuff, chemical industry, petrifaction, dyestuff, and industrial sludge etc. The characters of heat transfer, cooling and stirring enable it to perform the following unit operations: combustion (low temperature), cooling, drying (recovery of solvents), heating (melting), reacting and sterilizing. The stirring blade also acts as the heat transfer surface, which can increase heat transfer area in effective volume per unit and decrease processing time. The wedge heat transfer surface has self-cleaning function. Compressing and swell-stirring help the uniform mixing of the material which performs "piston flow" movement along the shaft. The gradients of temperature, humidity and mixing are very small in different axial areas. The blade dryer is able to perform low temperature combustion if using thermal oil as the heat medium, for instance, Ca2SO4·2H2O can be combusted into Ca2SO4·1/2H2O, NaHCO3 can be combusted into Na2CO3 and so on. It's capable of cooling with water and chill salted water etc as the cooling medium. For example, base cooling machine in soda industry replaces the old style base air cooler to save power and the processing equipment for tail air and thus reduce the operation cost. The equipment's main function of drying without hot air makes solvent recovery, energy consumption, environment control ideal for easy handling. It's particularly suitable for flammable, oxidizable and heat-sensitive materials and materials whose solvents need to be recovered. The dryer has been widely used in fine chemical industry, petrifaction, and dyestuff. The uniformity of temperature, humidity and mixing in axial areas makes the equipment capable of heating and melting, or reaction of solid materials. It has been successfully applied in mixed fertilizers and converted starch industries. The blade dryer is also used for sterilizing food and flour. The large heating area in effective volume per unit makes the material achieve sterilizing temperature very fast so as to avoid quality change caused by long time heating.

Technical Parameters