Solution
Closed-Loop Plastic Micronization and Air-Classified Pulverizing System
Closed-loop airflow plastic micronization and vibratory classification system producing 20–80 mesh rotomolding powders with optimized bulk density and zero thermal smear.
- Solution scope
- Multi-Function System
- Flow and installation
- Continuous · Inline
- Capacity
- 200–1000 kg/h
This solution delivers an integrated, closed-loop cryogenic-assisted or ambient airflow micronization system engineered specifically for rotational molding (rotomolding), powder coating, and masterbatch carrier powder producers. Centered around a high-speed turbo or disc-type plastic pulverizer (Plastic Pulverizer), it integrates water-jacketed mill cooling, closed-loop negative-pressure pneumatic conveying, rotary airlock discharge, and precision multi-deck ultrasonic or linear screening with an automated coarse tailings regrind loop.
Rotational molding and powder coating demand strictly calibrated polymer micro-powders (typically 20 to 80 mesh / 180 to 850 µm) with high dry flowability, high bulk density, and smooth spherical morphology. Standard disc pulverizers frequently overheat heat-sensitive polyethylenes (LLDPE/HDPE), causing resin melting, disc smearing, tailing whiskers, and motor overload trips. Furthermore, uneven powder particle size distributions (PSD) lead to pinhole porosity, incomplete sinter fusion, and catastrophic brittle cracking in finished rotomolded water tanks, kayaks, and outdoor containers. This engineered solution continuously regulates milling zone temperatures while strictly separating on-spec powder from coarse fractions, producing free-flowing, defect-free micro-powders at high operational efficiency.
The problem
What the section changes
Delivers high-bulk-density, tail-free rotomolding powder with narrow particle size distribution and zero thermal smearing.
Dónde empieza el cliente
Rotational molders and compounding mills operate conventional disc pulverizers without active cooling jackets or closed-loop classifier circuits. Operators manually choke-feed pellets into the mill hopper, causing rapid temperature spikes exceeding 85°C inside the disc gap.
At these elevated temperatures, polyethylene pellets soften into sticky plastic smears on the grinding teeth, creating stringy tails, “popcorn” fluff, and severe motor stalls. Finished powder has low bulk density (< 0.28 kg/L) and poor dry flowability, causing massive bubble voids, mold sticking, and wall-thinning defects in rotomolded articles.
Por qué ocurre el problema
Pulverizing relies on high-speed kinetic impact and shearing between high-velocity rotating blades and stationary serrated stator discs. Up to 85% of electrical motor energy is converted directly into frictional heat within a confined micro-gap milling chamber.
Polyethylenes possess low melting points (115°C–130°C) and poor thermal conductivity. As heat accumulates, particles reach their softening threshold, causing them to smear across blade teeth, deform into elongated fibrous “tails” rather than rounded granules, and plug downstream screener meshes with static clinging.
Producción o estado objetivo
Spherical, highly fluid, tail-free polymer micro-powder with high bulk density and strict particle distribution, ensuring bubble-free sintering, fast cycle times, and zero cracking in finished rotomolded products.
Process
The steps, in the order the material flows
The equipment named here is maintained on the step it belongs to, so the list and the quotation cannot disagree.
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Pellet Intake and Tramp Metal Interception
RequiredRaw Material Preparation
Transfers virgin polymer pellets from storage bags into the pulverizer buffer hopper under automated level control.
Función del equipoVacuum loader maintains continuous pellet head in the machine hopper, fitted with high-strength magnetic grid to capture tramp iron.
Equipos Vacuum Loader
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Water-Cooled High-Shear Airflow Micronization
RequiredRaw Material Preparation
Micronizes polymer pellets into fine micro-particles through aerodynamic impact and high-speed mechanical shearing under active temperature control.
Función del equipoThe variable-speed vibratory feeder meters pellets into the high-speed turbo rotor. Dual cooling jackets circulate chilled water around the stator ring and door to maintain chamber temperature < 65°C, preventing particle softening.
Equipos Plastic Pulverizer
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Pneumatic Evacuation & Cyclone Separation
RequiredCooling
Pneumatically evacuates generated micro-powder instantly from the hot milling zone to halt thermal exposure and convey it to the cyclone.
Función del equipoHigh-pressure negative-pressure airflow carries powder through the cyclone collector, dropping particles through a rotary airlock while venting air through a pulse-jet baghouse filter.
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Vibratory Screening & Coarse Recirculation
RequiredPost-Pellet Treatment
Separates qualified rotomolding powder from oversized particles, automatically returning coarse fractions back to the mill intake.
Función del equipoPrecision vibrating screener classifies the powder stream. Coarse particles (> 35 mesh) drop into an automated venturi blower loop back to the pulverizer hopper; qualified powder drops into packaging bags.
Equipos Linear Vibrating Screen
Material
What goes in, what comes out
Condición y requisitos de alimentación
Standard rigid or semi-rigid thermoplastic granules: LLDPE (rotomolding grade), HDPE, LDPE, rigid PVC, ABS, PC, and masterbatch pellets. Granule size Ø2.5–4.0 mm, dry, non-tacky, ambient temperature, free of metal or abrasive mineral stones.
Condición y límites de salida
Free-flowing, spherical micro-powder with narrow Particle Size Distribution (PSD), 20 to 80 mesh (180–850 µm). High bulk density (≥ 0.35 kg/L for PE), smooth surface morphology, dry flow time ≤ 25 s, and exit temperature ≤ 45°C. Ready for direct rotomolding without mold venting issues.
200–1000 kg/h
Base de las cifras de capacidad
Based on a 600 mm or 800 mm rotor diameter turbo/disc pulverizer with 55 kW to 90 kW main drive motor, milling virgin LLDPE to 35 mesh (approx. 500 µm) under water-cooled jacket conditions, yielding 350 kg/h to 800 kg/h net qualified powder.
Fit
Where this section belongs — and where it does not
The boundaries are part of the solution: they keep a machine from being quoted into a case it cannot serve.
Adecuada cuando
Indispensable for rotational molders producing outdoor water storage tanks, kayaks, playground equipment, and intermediate bulk containers (IBCs) requiring high impact strength and smooth surface finish.
Ideal for masterbatch manufacturers producing ultrafine carrier powder for high-dispersion pigment and additive blending.
No adecuada cuando
Not suitable for low-hardness thermoplastic elastomers (TPE/TPU below Shore 75A) or tacky rubbers under ambient conditions, which instantly smear and fuse. Cryogenic pulverizing systems with liquid nitrogen must be specified for soft elastomeric grades.
Not suitable for mineral ores, glass, or highly abrasive ceramic powders (> 30% quartz/silica content) which cause rapid mechanical erosion of pulverizer grinding discs.
Condiciones pendientes de confirmar
Capacity specifications are based on standard virgin LLDPE/HDPE rotomolding pellets with bulk density ~0.55 kg/L, cylinder pellet dimensions Ø3×3 mm, and Shore D hardness 55–65. Feedstock must be virgin or clean un-degraded regrind with melt index between 2.0 and 8.0 g/10 min.
For engineering polymers (PA6, PA66, PC, PBT) or soft elastomers (EVA > 18% VA, TPU), a specialized liquid nitrogen (LN2) cryogenic injection dosing valve and thermal insulated milling chamber are required.
Site and connections
What the section assumes around it
Servicios auxiliares
- Suministro eléctrico
- 380 V / 415 V / 460 V, 50/60 Hz, 3-phase AC.
- Agua
- Chilled water loop: 8°C–15°C, flow rate 6–12 m³/h at 0.25–0.35 MPa.
- Aire comprimido
- 0.5–0.7 MPa clean, dry compressed air for baghouse pulse cleaning and pneumatic slide gates (approx. 0.3 m³/min).
- Extracción y ventilación
- Baghouse dust collector exhausts filtered clean air outdoors or back into plant (filter efficiency 99.9% down to 1 µm).
Total connected electrical power: 75 kW to 132 kW depending on model size and blower rating.
Limitaciones de la planta
- Superficie ocupada
- Linear footprint: approximately 18–25 m² including mill, cyclone, screener, and dust collector.
- Altura libre
- Vertical clearance of 4.2 m to 5.2 m required for cyclone receiver and screener elevation.
- Entorno
- Dry indoor manufacturing bay; dedicated dust collection zone with explosion relief venting recommended for combustible plastics.
Noise attenuation enclosure recommended around the main mill motor and blower housing (sound levels ~82–85 dBA).
Interfaces
- Mecánico
- DN100 / DN125 pneumatic powder conveying ducting with smooth-radius ceramic-backed or heavy-gauge stainless bends.
- Control
- PLC interlock: automatic feeder speed throttling based on main mill motor current draw (PID closed-loop load regulation).
- Aguas arriba y aguas abajo
- Upstream: pellet storage bin / vacuum loader. Downstream: rotary airlock discharging into bagger or powder silo.
Targets
What the section is judged on
The numbers are targets agreed per project, not a general promise.
- Powder Fineness (ASTM D1921 35 Mesh Pass Rate)
- ≥ 98.0% % Standard Ro-Tap mechanical sieve shaker analysis for 10 minutes
- Powder Bulk Density (LLDPE)
- ≥ 0.35 kg/L ASTM D1895 Method A graduated cylinder test
- Dry Powder Funnel Flowability
- ≤ 25 s / 100g Standard ASTM D1895 flow funnel test
Cómo se evalúa la aceptación
Commissioning verification requires a continuous 4-hour production run processing virgin rotational molding grade LLDPE pellets (MFI 3.0–5.0 g/10 min). Sieve classification per ASTM D1921 must show ≥ 98.0% passing through 35 mesh (500 µm) and zero retention on 20 mesh (850 µm).
Powder bulk density measured via ASTM D1895 Method A must exceed ≥ 0.35 kg/L (ensuring uniform mold packing), and dry flow time through a standard ASTM funnel must be ≤ 25 seconds for 100 g. Milling chamber exit temperature must remain continuously below 68°C without water spraying into the powder stream.
Scope of supply
What is in the delivery — and what is not
The confirmed scope is stated in the quotation; this is the boundary of the section as designed.
Incluido en el alcance del suministro
- High-Speed Turbo / Disc Plastic Pulverizer (Water-Jacketed) Precision dynamic balanced rotor, hardened SKD-11 / D2 serrated wear segments, dual-cooling water jackets on housing and stationary door.
- Automatic Load-Sensing Vibratory Feeder Electromagnetic vibratory tray with feed controller tied to main motor amperage to prevent mill choking and overload.
- High-Efficiency Cyclone Separator & Rotary Airlock Valve SUS304 cyclone receiver, heavy-duty drop-through rotary airlock feeder with wear-resistant tips, and anti-static grounding.
- Pulse-Jet Reverse Air Baghouse Dust Collector Continuous automatic pulse cleaning, antistatic polyester filter bags, centrifugal induced-draft fan, and collection hopper.
- Ultrasonic / Linear Vibratory Screen Classifier Double-deck screener separating overs for automatic pneumatic loop return back to the mill intake hopper.
No incluido en el alcance del suministro
- Cryogenic liquid nitrogen supply tanks and dosing valves LN2 cryogenic dosing manifold and vacuum-jacketed cryogenic piping unless explicitly contracted.
- Mains power electrical wiring to master control panel Cabling from plant substation to machine isolator switch is on customer side.
- External water chiller unit Refrigeration chiller unit supplying cold water to the mill jackets unless quoted in auxiliary package.
- Civil foundation work and dust room partition walls Factory architectural works, floor leveling, and building dust enclosures.
Before a price
What we confirm before this becomes a quotation
- 01 Polymer grade and target mesh specification Resin type (LLDPE, LDPE, HDPE, PVC, EVA), initial pellet dimensions, melt index, and required target sieve cut (e.g., 30, 35, 50, 80 mesh).
- 02 End-use application performance criteria Whether powder is intended for rotational molding, masterbatch carrier blending, carpet backing, or electrostatic powder coating.
- 03 Available process chilled water temperature and flow Cooling water temperature (≤ 15°C recommended, 5–10 m³/h at 0.3 MPa) to size the dual-jacket mill cooling circuit.
- 04 Finished product packaging format Whether finished powder discharges into 25 kg valve bags, open-mouth bags with sewing conveyor, or 1-tonne FIBC bulk bags.
Request a Quote Send these points with your inquiry; the section can then be quoted against your line, not against an assumption.
Photos
The section in the workshop
Photos go here once the section has been built and the material is cleared to publish.
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Placeholder · 1200 × 900 px (4:3)（占位图） Replace with an approved section photos, real workshop or installation views at this size.（按此尺寸替换为正式图片。） -
Placeholder · 1200 × 900 px (4:3)（占位图） Replace with an approved section photos, real workshop or installation views at this size.（按此尺寸替换为正式图片。）
Details
Further details
- Problema de producción principal
- Insufficient cooling
- Off-spec pellet size and fines
- Sticking and agglomeration