Why Traditional Fiber Recycling Fails

PP multifilament yarn waste defeats conventional “agglomerator + water-ring pelletizing” lines on three fronts.

First, PP fibers possess extreme tensile strength that agglomerators cannot cut — overfeeding triggers overload shutdowns while underfeeding produces uneven plasticization and chronic die blockage, and pre-crushers fail equally because shredded fiber becomes too fluffy to discharge.

Second, PP’s excellent melt flowability causes water-ring pellets to stick together, forcing production stops every few hours.

Third, the energy cost is severe: a 500 kg/h agglomerator line demands ~160 kW for feeding alone. These failures share one root cause — a fundamentally wrong process route where shredding, feeding, and pelletizing methods were all selected without regard for high-strength, fluffy, high-flow fiber properties.

The WANROOETECH Process Route

WANROOETECH engineers a complete 15-station line rethought around PP fiber properties: Feeding Conveyor → Metal Detector → Single Shaft Shredder → Discharge Conveyor → Buffer Silo → Feeding Conveyor → Metal Detector → Screw Compaction Feeder → Extruder ① → Single-Plate Dual-Position Screen Changer → Extruder ② → Large-Area Dual-Column Screen Changer → Water-Strand Pelletizing → Vibrating Sieve → Finished Product Silo. The transformation rests on three critical substitutions — low-speed high-torque shredding replaces high-speed agglomeration, screw forced-feeding replaces friction compaction, and water-strand pelletizing replaces water-ring cutting — each matched to PP multifilament’s unique material behavior.

Four Core Design Innovations

The Single Shaft Shredder (PNDS-1000D) is upgraded from standard 45+45 kW to 55+55 kW with a #7 gearbox to handle fiber bales without overloads. DC53 die steel blades feature four-edge rotary cutters that reduce maintenance by over 80% through corner rotation, plus symmetrical fixed blades that lower blade costs by over 75% through four-sided regrind. The CNC-precision machined shaft maintains minimal blade gap to prevent fiber wrapping — the defining feature of a fiber shredder — while circulating cooling water stabilizes shaft temperature at 30-40°C to stop PP fibers from melting and binding, ensuring continuous full-load performance with 30-80 mm output ideal for downstream feeding.

The second innovation solves feeding and energy simultaneously. Where agglomerators consume ~160 kW for 500 kg/h fiber output, WANROOETECH’s 5.5 kW screw compaction feeder forces shredded 30-80 mm material into Extruder ①, whose screw is enlarged from Φ150 mm to Φ180 mm to create the groove volume for fluffy feedstock. This eliminates both the power hunger of agglomerators and the poor feeding efficiency of standard single-screw extruders with bulky material.

The third innovation ensures strand continuity during screen changes. PP’s high flowability mandates strand pelletizing, yet strand processes are vulnerable to screen-change interruptions that break strands and require manual rethreading. The dual-column filter after Extruder ② maintains continuous melt flow through its alternate column during changeover, eliminating pressure fluctuations and keeping strands intact. Combined with the single-plate dual-position changer after Extruder ①, this two-stage 80-120 mesh filtration ensures pellet purity for direct re-use in polypropylene yarn spinning.

The fourth innovation completes the system with water-strand pelletizing that overcomes both water-ring adhesion and traditional strand labor dependency. Guided water flow automatically pulls strands into the pelletizer with self-recovery on breakage, the vibrating sieve removes connected pellets and oversize particles, and the final product is standard 3×3 mm cylindrical pellets ready for remanufacturing.

South Africa Case: From Challenge to Stable Production

WANROOETECH’s decade-long partnership with Multifilament Yarn PTY LTD. began in 2016 with a PNMF-600 pulverizer and SRL-500/1000 mixer for masterbatch production, expanding through 2020-2023 as the customer added three more pulverizers and another mixer. By late 2024, rising oil prices and over 1,000 tons of accumulated production waste prompted an on-site survey in December and this complete recycling solution. A 3-ton trial in early 2025 validated the design with output reaching ~600 kg/h — 20% above the 500 kg/h design — with stable operation and uniform 3×3 mm pellets. Following deposit in June 2025, production completed in October with one month of in-factory testing, shipment in December, arrival in February 2026, and final on-site installation and training in July 2026.

Performance Comparison

Key Specifications

Design capacity: 500 kg/h | Measured output: ~600 kg/h

Total power: ~430 kW | Specific energy: ~0.35-0.45 kWh/kg (25-30% lower)

Pellet size: 3×3 mm | Shredder output: 30-80 mm

Shaft cooling: 30-40°C | Filtration: 80-120 mesh

Extruder ① : Φ180 mm screw | Extruder ② : Φ160 mm / 55 kW + 24 kW heating

Recycling Case Video

Frequently Asked Questions

Can PP fiber waste be recycled with an agglomerator?

Not recommended. PP multifilament’s extreme tensile strength causes agglomerators to overload or underfeed, producing unstable plasticization and die blockage, while consuming ~160 kW for 500 kg/h output. The proven route is low-speed shredding with forced screw feeding.

Why can’t water-ring pelletizing be used for PP fiber?

PP melt flowability is too high. Water-ring pellets adhere inside the cutting chamber, typically forcing stops after half a day. PP fiber recycling requires strand pelletizing with water-flow conveying and dual-column continuous screen changing for non-stop production.

Can this solution handle PET or nylon fiber waste?

Yes, with material-specific customization. The core route — shred, forced feeding, strand pelletizing — applies across fiber types, but screw L/D ratio, temperature profiles, and filtration require reselection. WANROOETECH provides customized design and trial validation for specific materials.