1 Pelletizing System Options Types of Pelletizing Systems for Extrusion . Strand Water Bath by Strand Water Slide Dana Darley Extrusion Auxiliary Serv ices Dacula, GA Hot Die Face Air Cooled (678) 714-5218. www . Die Face Water Ring Die Face Under Water Drop Pelletizing Strand Water Bath - Strengths Strand Water Bath - Weaknesses Low cost Very little automation Simple to use Limited pellet size Easy to clean and High cutter changeover wear/maintenance Sensitive to process variations Strand Water Slide - Strengths Strand Water Slide - Weaknesses Higher level of Higher cost automation High cutter wear and Self stranding maintenance, but less Variable cooling then water bath Higher process rates Difficult to setup More com pact 1.
2 Hot Die Face Air Cooled - Strengths Hot Die Face Air Cooled - Weaknesses Very limited cooling Very simple design capability No contact with water Low outputs High blade Wear Compact layout High dust levels Easy to s etup and operate Die Face Water Ring - Strengths Die Face Water Ring - Weaknesses Relatively low cost Limited to Olefins Compact design Poor performance on high Better cooling capabilities heat and sticky materials No die freezing Limited application range Die Face Under Water - Strengths Die Face Under Water - Weaknesses Highest automation Relatively high System cost Complicated auxiliary and Very versatile can process water/drying systems most any polymer Die freeze issues on high heat High blade life products Production of micro pellets 2.
3 Drop Pelletizing - Strengths Drop Pelletizing - Weaknesses Specialty System for low High cost and complexity viscosity polymers and waxes Strand Pelletizing , with manual feed Extrusion Die Discharge angle between 45 & 90 degrees Die holes between 2 & 7 mm Normally, strand Pelletizing with manual strand feed consists of the following components: Strand Die Cooling trough Strand dryer Strand pelletizer Maxim um number of holes around 250. Die width approximately 1500 mm Electric or oil heated .. Die body Flow channel Die plate Diagram to show machine structure.
4 Extrusion Die . Cooling Trough Strand Drying Up to 2 m wide and 12 m long Blowing, vacuum or a combination to remove water Two or more spreader bars Water flows opposite strand flow Vary temperature control Multiple partitions or baths in series . Blowing nozzle Suction nozzles Water bath Strand drying 3. Strand Pelletizer Features Strand Pelletizer, cont. Working widths 25 to 1000 mm Compact design, with easy access Belt driven for speed range adjustment Easily replaceable wear parts Most universal Pelletizing System available Strand is not suitable for: Processes with frequent strand breaks Frequent starts, with high throughput rates Strand pelletizer Automatic Strand Feed Dry Cut Water Trough Automatic Feed Water supply table.
5 Starts and stops without manual intervention Water trough . Broken strands are automatically re-threaded Spray nozzles . Vertical trough adjustment . No water between strands or on surface Horizontal trough adjustment . Water manifold .. Diagram to show dry cut .. Extrusion Die Water trough Diagram to show water trough Strand drying Pelletizer Automatic Strand Components Automatic Strand Components, cont. Water supply table Strand drying Laminar water flow defines thickness of the water layer Water separated by gravity Table can be smooth or grooved Water removed through slots by vacuum.
6 Blowing or both Swivel table to vertical plane Residual moisture levels of approximately For startup increase water flow by 30% Strand speed should not exceed 100 m/min Water trough Airspeeds of 25 to 35 m/s Slopes from 2 to 10 degrees Pelletizer is basically the same as for manual s ystem 2 to 7 m in length Typical applic ations Bottom must be smooth and can be covered Working widths from 100 to 1000 mm Spray nozzles Rates up to 800 kg/h pellet temperatures 70 to 120 C. Adjusted from mist to spray . 4. Strand Conditioning Cooling Belts Homogenizes the tem perature of strand cross section.
7 Clean pellet c ut for glass filled materials. Diagram to show cooling belts Pellet tem perature reduc ed by 10 30 C.. Lower residual moisture.. Die head .. Diagram to show strand conditioning Cooling belts Strand drying Die head Pelletizer Water trough . Strand drying . Temperature compensation section (strand conditioning) . Pelletizer . Water-Free Pelletizing Strand, Wet Cut - Horizontal .. Guide plate Guide plate channel Diagram to show wet cut, horizontal design Diagram to show water-free Pelletizing Pelletizer Water trough . Pneumatic pellet transport Pelletizer.
8 Pelletizer after-cooling section with agglomerate trap or start-up filter and water separator . Pellet dryer . Horizontal Strand Pelletizing Horizontal Pelletizing , cont. Water trough similar to dry cut, to 7 m long Pellet dryer Water Separation Accelerate pellets mechanically onto sieves or rings Water separated by gravity before entering pelletizer Centrifugal dryers and impact ring centrifuges Water conveyed from dryer to coolant circuit Fluidized bed dryers Pelletizer Applications Housing must be waterproof bearings should be sealed Working widths from 200 1000 mm Cutting tools abrasion proof & corrosion resistant Strand speeds up to 250 m/min Spray the cutting rotor to prevent pellet adhesion Throughputs up to 12.
9 000 kg/h Pelletizer c ooling section PET, PBT, PA, PC, ABS, PP. Pipe kept half full pre-drainage before the dryer 5. Vertical Strand Pelletizing Wet Cut Vertical Pelletizing , cont. Strand guide and pelletiz er form unit. Di e he ad Stran d gu id e Each strand has own guide groove. Pel leti zer Re-c o oli ng s ecti on Pel let dr yer Normal heights between 2000 and 3600 mm. Working widths from 300 to 900 mm. Throughput rates up to 7500 kg/h. Brittle plastics, requiring short c ooling sections. GPPS, HIPS, PMMA, SAN. Diagram to show a wet cut System , vertical type Water Ring Pelletizing Water Ring Pelletizing , cont.
10 No water at the die face no die freeze Polymer cut in air quenched in a ring of water Polymer must release from metal olefins Pellets submerged in slurry transported to dryer Die facing straight down or horizontal Water Ring Pelletizing , cont. Underwater Pelletizing System Vortex Pelletizer from Conair S h o r t cu t t o A NI M A T ~ 1 . ln k 6. Why are chips spherical, when an underwater P&I of Underwater Pelletizing System Pelletizing process is used ? S h o r t cu t t o S C HNE I ~ 1 . ln k The molten polymer is cut into drops by the fast rotating blades of the pelletizer just when leaving the die holes and emerging into the process water.