Detailed Production Process of Wood Sawdust Pellet Machine
The wood sawdust pellet machine converts waste wood into efficient biomass pellet fuel. Its production process involves several key steps to ensure that the final product has high density and stability. The detailed process is as follows:
1. Raw Material Crushing and Pretreatment
Crushing: First, a wood crusher is used to break waste wood, branches, and other raw materials into small particles, usually controlled to be under 5 millimeters in size to facilitate subsequent processing. If the raw material is already sawdust, this step can be skipped to reduce costs.
Screening: The crushed materials are passed through a screening machine to remove larger wood blocks, nails, and other impurities, ensuring the raw materials are clean and preventing equipment blockage.
2. Drying and Conditioning
Drying: The raw materials need to be dried to a moisture content of 10%-18%, using a airflow dryer or natural sun drying, with temperature controlled between 50-70°C. This evaporates excess moisture and enhances pellet formation. After drying, the materials pass through a cyclone separator to discharge moisture and maintain a dry environment.
Conditioning: The dried sawdust is sent into a conditioner, heated with steam or hot water to 70-100°C, to soften fibers and activate lignin (a natural binder), enhancing the pellet's binding strength and durability.
3. Granulation and Forming
Extrusion Forming: The conditioned wood chips enter the pellet mill (such as ring die or flat die types). In a ring die pellet mill, the rotating ring die and the fixed roller create a wedge zone, compressing the material and forcing it into the die holes at pressures of 100-200 MPa, raising the temperature to 90-120°C. In a flat die pellet mill, the material is compacted through the relative motion between the rollers and the flat die.
Cutting: The continuous cylindrical rods extruded from the die holes are immediately cut by knives to form pellets of specified length (usually 1.5-3 times their diameter).
4. Cooling and Post-treatment
Cooling: Freshly formed pellets have high temperatures (80-100°C) and soft texture, requiring rapid cooling to room temperature through a counterflow cooler with ambient air. This prevents breakage and reduces the moisture content to 10%-12%, allowing the lignin to solidify.
Screening: Cooled pellets pass through a vibrating screen to remove fine particles, ensuring product consistency. Non-conforming pellets are returned for re-pelletizing.
5. Packaging and Storage
Packaging: Qualified pellets are packed into bags or bulk bags via a packaging machine for easy transportation and storage. Storage should be kept away from moisture to prevent absorption that could affect combustion performance.
This process integrates crushing, drying, granulation, and cooling, optimizing resource utilization and providing an efficient solution for environmentally friendly energy production.