Preventing Clogging in Woven Bag Recycling: Optimizing Large-Pitch Feeding and Compacting Systems

In the field of Post-Consumer Recycling (PCR), pelletizing PP/PE woven bags, jumbo bags, and raffia materials has long been recognized as a technical challenge. These materials are characterized by extremely low bulk density, irregular shapes, and a tendency to entangle. The most common pain points in twin screw extruder operations are "bridging" at the feed throat or "clogging" within the screw flights, leading to output fluctuations or total downtime. The key to solving this lies in optimizing the feed zone geometry for lightweight materials.

Once shredded, woven bags become thin, lightweight flakes or fibers.

• Compression Imbalance: If the screw feed zone volume is insufficient, the material cannot be pre-compressed before reaching the melting zone, causing a backup at the feed port.
• Friction Limitations: Lightweight materials have a low coefficient of friction against metal surfaces, limiting the screw's ability to "grip" and convey the material effectively.
• Trapped Air: A vast amount of air enters with the fluffy material. If not vented promptly in the feed section, back-pressure builds up, obstructing the downward flow of material.

To enhance the processing efficiency of lightweight woven bag scraps, the screw and barrel configuration must be specifically selected:

• Design Advice: The feeding section should utilize large-pitch thread elements, typically with a pitch 1.5 to 2 times the screw diameter.
• Technical Advantage: A larger Free Volume acts like a funnel to capture more fluffy material and complete initial compaction within a short distance, significantly boosting throughput.

• Compacting Feeders: Utilize a vertical force-feeder with a compacting function to pre-compress the loose flakes before forcing them into the extruder screw flights.
• Side Venting: Coordinate with side venting in the first feeding stage to exhaust the trapped air, preventing "melt-back" or material overflow caused by air blockage.

Recycled materials often contain residual sand or inks, requiring high hardware durability:

• Wear-Resistant Materials: We recommend bimetallic barrels with a hardness of 58-64 HRC. The inner liner must possess extreme resistance to physical erosion from impurities.
• Surface Treatment: Feed zone screw elements should be mirror-polished (Ra < 0.4 um) to reduce material adhesion at the screw root, preventing localized carbonization and subsequent clogging. (Reference: Stability Report for Continuous Pelletizing - Ref: #TS-DATA-PAGE12)

In woven bag recycling, simply increasing the screw speed is not a sustainable solution. By selecting high-precision components with large-pitch designs, high torque capacity, and precision clearance, manufacturers can increase effective output by over 30%. For recycling plants aiming for stable operations, premium custom feeding components compatible with Coperion or Erema standards are the core guarantee for reducing manual intervention and boosting profit margins.