In the industrial production of polyamide 6 (PA6, commonly nylon-6), the extraction and drying of chips is the process step that decides final product quality. Wet chips just out of underwater pelletizing or water conveying carry a large amount of surface water. If this surface water is not removed efficiently before entering the continuous drying tower, it sharply increases the energy load of subsequent hot-air or nitrogen drying — and can even cause chip caking and degradation.
Addressing this industry pain point, Germany’s APRO — with its refined stainless-steel equipment craftsmanship — has launched a new generation of mechanical drum centrifugal dewatering/drying machine (Granulattrockner). As a deep extension of established centrifugal-dewatering patent technology, it brings several major innovations for modern high-throughput, high-quality PA6 chip lines.
APRO mechanical drum centrifugal dewatering/drying machine — designed to strip surface water from PA6 chips efficiently
Why does it fit the PA6 process so well?
1. The TORQUE coaxial direct-drive system: no “power anxiety”
Conventional centrifugal dryers usually place the motor to the side with belt drive, which adds mechanical wear and energy loss at high speed.
- Axis alignment: APRO uses the new TORQUE drive with a Siemens Sinamics 120 inverter, placing the motor symmetrically on the vertical centre axis of the machine.
- Energy efficiency: this direct-drive structure delivers lower drive power input and constant torque output.
- Variable speed: stepless adjustment of 50%–100% rated speed, so operators can optimise speed for PA6 chips of different viscosity (film grade, textile grade or engineering-plastic grade).
2. Versatile feeding options
After leaving the underwater pelletizer, PA6 chips place different demands on the dewatering inlet depending on throughput and layout. APRO offers a highly flexible modular system:
- Static siphon feed (Siphoneintrag): automatic overflow feeding by liquid-level head; chips travel wrapped in water for even loading, minimising mechanical impact at the start of feeding.
- Screw feed (Schnecken-Eintrag) with automatic screen cleaning: for special processes or high-concentration chip flow, a dedicated feed screw ensures continuous, even feeding; an integrated screen back-flush/self-cleaning system prevents fines and oligomers from clogging the mesh.
- Pump feed: connects directly to the upstream conveying pump for flexible layout.
3. Customisable rotor and screen geometry
Chip shape, particle size and throughput (APRO single-unit capacity covers 150 – 5000 kg/h) directly affect dewatering efficiency. APRO’s modular design lets you choose between cylindrical (zylindrisch), conical (konisch) and stepped (Stufen Form) rotor/screen geometries. This precisely controls residence time and the climbing path of chips inside the centrifuge, achieving lower frictional particle abrasion (Minderung des Abriebs) and excellent residual surface moisture (optimale Restfeuchte).
Process-safety core: open vs gas-tight system
In PA6 production, protecting chips from oxidation and contamination is critical. Freshly pelletized chips are hot, and on contact with abundant oxygen they yellow easily. APRO addresses this sensitivity with two system options:
| System type | Sealing | Typical PA6 application |
|---|---|---|
| Open system (Offenes System) | No mechanical seal (ohne Gleitringdichtung) | Fast mechanical dewatering of standard chips, PA6 compounding pellets and downstream recyclate. |
| Gas-tight system (Gasdichtes System) | High-end mechanical seal (mit Gleitringdichtung) | Continuous dewatering of high-quality virgin chips on polymerization lines; can be inerted (e.g. nitrogen) to fully exclude oxygen and prevent hot chips from oxidising/yellowing. |
Overall benefits of the APRO centrifugal dryer
- Lower downstream energy: mechanical centrifugal dewatering is the lowest-energy way to remove surface water. After APRO, residual surface moisture is very low, greatly easing the load on the downstream continuous drying tower (hot-nitrogen loop).
- Higher chip grade: a smooth material path and adjustable variable speed avoid excess dust and burrs (Abrieb) from violent collisions in the drum, keeping chip appearance uniform.
- Stable continuous production: all-stainless-steel (Edelstahl) construction resists wear and corrosion, and efficient screen self-cleaning meets the demands of high-uptime, long-campaign PA6 plants.
Conclusion
In modern PA6 polymerization and compounding plants pursuing energy savings and quality upgrades, optimising every unit operation matters for competitiveness. With its direct-drive technology, modular design and rigorous gas-tight anti-oxidation options, Germany’s APRO drum centrifugal dryer is becoming an efficient tool that high-standard nylon-6 lines cannot ignore at the chip-dewatering stage. For standard specifications and tailored selection of APRO mechanical dryers, please get in touch.