MINGHUNG
Wet chip feeding → Drum rotation + hot air inlet → Chips are tumbled and moved forward by lifting flights → Direct contact between hot air and chips for heat and mass transfer → Moisture evaporation → Dried chips discharge → Exhaust gas is dedusted and released
 | The working process of the three-channel drum dryer |
1. Feeding and Mixing
Wet wood chips (with high moisture content) are fed into the inlet of the dryer by conveying equipment such as belt scales or screw conveyors.
Simultaneously, high-temperature flue gas (or hot air) generated by the hot air furnace enters the drum from the same end (in a parallel-flow design) or the opposite end (in a counter-flow design).
In the parallel-flow design, the chips and hot air move in the same direction. The high-temperature air first contacts the wet chips, instantly removing surface moisture, effectively preventing heat damage to the material.
2. Tumbling and Forward Movement
The drum rotates slowly at a set speed. Different types of lifting flights (or lifters) are installed on the inner wall of the drum.
The lifting flights continuously pick up and scatter the chips, forming a uniform material curtain, ensuring that every chip is fully exposed to the hot airflow.
Under gravity, the chips move slowly forward along the axis of the drum, undergoing multiple cycles of “lifting and falling,” which ensures uniform drying.
3. Heat Exchange and Moisture Evaporation
The hot air comes into direct contact with the chips, transferring heat through convection, which heats the moisture inside the chips and causes it to vaporize.
Moisture in the chips (mainly free water and some bound water) turns into steam upon heating and quickly diffuses into the hot airflow.
Due to the large specific surface area and relatively thin thickness of the wood chips, the drying efficiency is much higher than that of bulk materials.
4. Multi-Stage Drying (Unique to Three-Pass Design)
In a three-pass rotary drum dryer, the structure consists of three concentric cylinders nested inside one another. The chips and hot air travel a longer path within the drum:
Inner cylinder: High-temperature zone for rapid evaporation of surface moisture.
Middle cylinder: The material turns back, with moderate temperature to continue drying internal moisture.
Outer cylinder: Low-temperature zone where the chips approach the target moisture content and undergo final moisture balancing before discharge.
This design reduces the equipment footprint and improves thermal efficiency, making it particularly suitable for large-scale continuous production.
5. Discharge and Exhaust Gas Treatment
The dried chips (with moisture content typically controlled at 2%–5%) are discharged from the outlet and sent to the subsequent gluing process.
The exhaust gas, containing dust and water vapor, is purified through equipment such as cyclone separators and baghouse filters before being released. Part of the exhaust gas can be recirculated to improve thermal efficiency.
The system uses PLC-based real-time monitoring of key parameters such as drum outlet temperature, air pressure, and chip moisture content, automatically adjusting the heat supply from the hot air furnace, drum speed, and feed rate to ensure stable output moisture content.
| Difference with Single-Pass Rotary Drum Dryer |
The single-pass dryer has a simpler structure with just one drum. The chips pass through the drum once to complete the drying process.
It is suitable for small to medium-sized production lines or applications with less stringent drying requirements.
The working principle is essentially the same—“tumbling + direct contact with hot air”—but its thermal efficiency and footprint are not as advantageous as the three-pass design.
1. High Thermal Efficiency
Equipped with an efficient hot air circulation system combined with flue gas waste heat recovery technology, significantly reducing fuel consumption. It supports various heat sources such as biomass, natural gas, and thermal oil.
2. Stable Drying Quality
Optimized lifting flights and adjustable drum speed ensure uniform heat transfer throughout the drying process, preventing issues such as surface dryness with internal moisture or localized overheating, providing stable moisture content for subsequent gluing and board forming.
3. High Capacity Design
A single system can meet the drying demands of particleboard production lines with an annual capacity of 100,000 to 500,000 cubic meters, suitable for large-scale continuous production.
4. Safety and Environmental Compliance
Equipped with explosion-proof and fire-prevention devices, along with dust collection and flue gas treatment systems, meeting international environmental emission standards.
5. Highly Automated
PLC-based centralized control enables real-time monitoring of key parameters such as temperature, moisture content, and airflow, with support for remote monitoring and fault diagnosis.
Drying Medium: Hot air / Flue gas
Operating Temperature: 120–200°C
Final Moisture Content: 2–5% (adjustable)
Production Capacity: 10–50 t/h (depending on raw material and model)
Equipment Material: High-temperature resistant, wear-resistant steel plate
We provide turnkey services including process design, equipment manufacturing, installation and commissioning, and personnel training. Customized designs based on customer-specific raw material characteristics and site conditions are also available.
Our contacts:
Whatsapp: +8618769900191 +8615589105786 +8618954906501
Email: osbmdfmachinery@gmail.com
