1. Description of Hollow Paddle Dryer
Hollow Paddle Dryer is a horizontal stirring and heat conduction type drying equipment that can work continuously. Its stirring blade is like ship paddle, so it is called paddle dryer. In foreign countries, it is also called slot dryer or stirring dryer.
Needed heat of the dryer relies on heat conduction to heat indirectly, so during the drying period it doesn't need air or little air to take the moisture away. It greatly reduces the heat loss that took away by air flow and the use ratio of heat is improved, so it is a kind energy saving type drying equipment. Paddle dryer is widely used in petrochemical, chemical, metallurgy, foodstuff, pharmaceutical, pesticide industrials and so on for drying powder, granules, filter cake and seriflux materials.
On the basis of a wide research, absorption and digestion of domestic and foreign advanced technology, our company  improved and optimal designed the wedge hollow paddle dryer. It can indirectly heat or cool paste shape, granules, powder and seriflux materials. It can achieve the operation of drying, cooling, heating, sterilization, reaction and low temperature calcinations, etc. In the equipment, the wedge-shape stirring and heat transfer paddle has high heat transfer efficiency and the heat transfer surface self-clean function.





2.  Features of  Hollow Paddle Dryer   

Low Operation Cost
- Easy to operate
- Requires minimal attention
- Simple instruments monitor the process
- High efficiency
- Low off-gas volume

Low Maintenance Cost
- Designed for high torque and low operating speed
- Simple durable design for easy and low maintenance
- No internal parts to adjust or maintain
- No metal to metal contact
- Shafts, pillow block bearings, and drive components are designed for long life under adverse conditions, insuring long term mechanical integrity
- Robust frame supports split pillow block bearings
- Grease-purged stuffing boxes. Alternate seal designs are available

Low Installation Cost

- Designed with compact structure
- Small off-gas system
- Vertical shaft removal reduces building size requirements

3. Working Principle of  Hollow Paddle Dryer

The Hollow Paddle Dryer has a metal wall which separates the process mass from the heat source (steam or hot oil). High thermal efficiency is obtained because the heat from the thermal medium goes directly into the process mass. As the material comes into contact with the heated through and agitators, the process mass is heated via conduction. With an insulated dryer, very little heat is lost. To evaporate 1kg of water only requires about 1.2kg of steam for slurry materials. Exhaust gas is minimal and at a low temperature. Therefore, the volume of non-condensable gas from the dryer, which might require treatment, is minimal.

The dryer is an indirect heat transfer device which utilizes a high degree of mechanical agitation to enhance contact with the product being dried. Evaporation rates per square foot of heat transfer surface are maximized through self-cleaning paddles and the mixing effect. Movement of the process material between the slanting surfaces of the revolving wedge-shaped paddles generates shearing forces, which clean the paddle surfaces and maximize conductivity. Counter rotating shafts move the material away from the walls, cleaning the walls by means of the tab on each paddle. This results in higher heat transfer rates than disc or single shaft designs.

The wedge-shaped paddles, and the intermeshing of the dual agitators, create a localized mixing effect around the paddle. This allows more individual particles in the bed to be exposed directly to the heat transfer surface, thereby increasing the heat transfer rate, allowing the use of smaller equipment.