What is the Paddle Dryer？

The paddle dryer is an industrial drying apparatus specifically designed for drying moist, viscous slurry-like materials such as sludge or pastes. It is a horizontally positioned, hollow-structured cylindrical unit equipped with agitation blades, heating elements, and a rotating shaft to achieve efficient drying. You may utilise it in industries such as the chemical and pharmaceutical industry, food production, and industrial wastewater treatment.

How does the Paddle Dryer work？

• Feeding the Material: Prior to commencing the drying process, you must place the moist material into the chamber of the paddle dryer.
• Agitating the Material: The rotating shaft drives the paddles to continuously stir the material, preventing the moist material from clumping or sticking together. Furthermore, during the heating process, the paddles continue to rotate to ensure more uniform heating.
• Heat Transfer: Heat transfer methods vary depending on the paddle dryer type. One method involves direct heat transfer, where hot gas contacts the material directly. The other employs indirect heat transfer, where hot gas transfers heat through a jacket and hollow paddles.
• Discharge of Finished Product: The material is continuously stirred to ensure even cooling. The paddle dryer discharges the dried material after complete drying.

Components of the Paddle Dryer

Heat Transfer and Agitation System

• Rotary shaft: The rotating shaft of the paddle dryer drives the paddles to agitate the material during the drying process. It is typically hollow, allowing hot gas or other heat transfer media to pass through the shaft, thereby transferring heat to the material.
• Paddles: The paddles come into direct contact with the material during stirring. Consequently, they are also designed with a hollow structure to facilitate the flow of hot gas, enhancing drying efficiency. The rotation of the paddles ensures uniform drying of the material. Additionally, their wedge-shaped design achieves a self-cleaning effect, preventing material adhesion and clumping on the blades.
• Housing: The casing of the paddle dryer protects the internal components.  It contains the material and features a sealed design. It is also hollow to increase the heat contact area and prevent direct thermal damage to the material.

Power and Fuel

• Motor: The motor serves as the primary power source for the paddle dryer, enabling high-torque rotation of the paddles to ensure efficient drying.
• Fuel: Heat for paddle dryers is primarily generated through thermal oil, hot water or steam. Additionally, to support environmental sustainability, some paddle dryers utilise biomass for heating.

Sealing Structure

To prevent heat and material leakage, paddle dryers incorporate sealing mechanisms. Furthermore, sealing is essential for vacuum paddle dryers to prevent disruption of the vacuum environment.

Emissions Control

Moisture emitted within the paddle dryer must be promptly discharged; otherwise, drying efficiency will diminish. The discharge system incorporates a condenser and cyclone separator to prevent material wastage and achieve efficient emissions, thereby ensuring stable equipment performance.

Feed and Discharge Apparatus

Material may be introduced into the paddle dryer via its hopper, with the dried product discharged from the rear end of the unit. This is typically equipped with a rotary airlock valve or other separation device to ensure stable discharge.

Types of Paddle Dryer

Direct and Indirect Paddle Dryers

• Direct Paddle Dryer: The heated gas produced by the direct paddle dryer’s heating system enters the chamber directly to contact the moist material, evaporating the moisture within for drying.
• Indirect Paddle Dryer: The vessel walls and paddles of an indirect paddle dryer are hollow. The hot gas heats these components, which then transfer their temperature to the moist material to achieve heat dissipation. Consequently, this permits the use of indirect paddle dryers for temperature-sensitive materials such as foodstuffs and pharmaceuticals.

Batch and Continuous Paddle Dryers

• Batch Paddle Dryer: A batch paddle dryer can only process a fixed quantity of wet material per operation. It is typically employed for small-batch drying projects and can provide more precise time control.
• Continuous Paddle Dryer: The continuous paddle dryer is the ideal drying equipment for large-scale drying projects. It permits continuous feeding of material into the unit during operation, enabling uninterrupted drying and discharge for non-stop processing.

Vacuum and Dual-Zone Paddle Dryers

• Vacuum Paddle Dryer: The vacuum paddle dryer operates within a complete vacuum environment. This vacuum reduces the boiling point of moisture within the wet material, enabling drying at lower temperatures. This effectively protects heat-sensitive materials from damage while achieving superior drying efficiency.
• Dual-Zone Paddle Dryer: The dual-zone paddle dryer is also frequently employed for drying heat-sensitive materials. In addition to its heating system, it incorporates an independent cooling zone to regulate temperatures throughout the drying process.

Advantages of Paddle Dryers

Exceptional Drying Performance 

Firstly, the paddle dryer maximises heat transfer efficiency through both direct and indirect drying methods, yielding satisfactory drying performance for both viscous and powdered materials. Also, its drive shaft powers the paddles to rotate efficiently, ensuring uniform heating and preventing localised overheating or incomplete drying.

Friendly for Temperature Sensitive Materials

For drying sensitive materials, paddle dryers deliver outstanding performance. Unlike conventional drying methods, paddle dryers do not utilise thermal convection for drying. Instead, they employ indirect heating or achieve low-temperature drying through vacuum environments and cooling systems, thereby preventing damage to your heat-sensitive materials.

High Cost Effectiveness

Although paddle dryers entail a higher initial investment, they deliver superior drying efficiency while consuming less energy (achieving energy savings of 20% to 40%). Furthermore, paddle dryers provide stable drying performance for large-scale drying projects. Consequently, they generate greater overall benefits, despite the higher purchase cost.

Scalability

Paddle dryers are a highly flexible and scalable drying system. As drying requirements evolve, you may expand the system to enhance its overall drying capacity and capability without replacing existing equipment. This flexible scalability eliminates the need for substantial initial investment, energy consumption, and maintenance costs.

Low Maintenance Costs

The paddle dryer features a simple structure with few moving parts during operation, resulting in enhanced durability. This extends its service life while reducing maintenance requirements and minimising downtime and damage.

Applications of Paddle Dryers

Environmental Protection

You can use the paddle dryer to treat sludge. Consequently, they deliver highly efficient drying performance, enabling their use in industrial, municipal, and agricultural applications to treat industrial waste, municipal sludge, animal manure, and similar materials.

Chemical and Pharmaceutical Industries

Certain chemical products (such as polymers and catalysts) are also highly suitable for processing using your paddle dryer. They permit precise temperature control and ensure stable, round-the-clock operation for consistent drying. Certain pharmaceuticals are highly temperature-sensitive; employing paddle dryers enables low-temperature drying, preventing damage to your drugs and associated cost losses.

Food Processing

You can also use paddle dryers in food drying applications. Their enclosed design and cleaning protocols guarantee food hygiene and safety. Opting for a vacuum paddle dryer further isolates the process from external air, enabling low-temperature drying to prevent spoilage caused by excessive heat.

Jiangsu Fanqun Drying Equipment Factory possesses over 25 years of production expertise within the drying industry, with products exported to the United States, Japan, and numerous other countries worldwide. Should you be seeking high-quality drying solutions, our paddle dryers are well-suited to meet your requirements.