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June 1, 2008

6 Min Read
Product Focus: Pelletizers

Pelletizer equipment producers in their latest offerings are looking at ways to help compounders and masterbatchers concentrate on other processing details than dust generation, uniformity and smoothness of the granules, and lost production time due to maintenance. Volker Reichert, project manager at C.F. Sheer (Stuttgart, Germany), says what really counts today is easy cleaning in short order to keep equipment up and productive.Last year his company unveiled a new underwater pelletizing series, S-UWG, that is designed and sized for processing a range of polyolefins, engineering resins, elastomers, and hot-melt adhesives. This unit helps optimize compounding and recycling businesses with its throughput of 7.5 tonnes/hr.

Sheer’s S-UWG underwater pelletizer

Coperion Werner & Pfleiderer water ring pelletizer WRG280

Reduction Engineering’s 800 series

To reduce maintenance and cross-contamination, design geometries of the pelletizing unit are of key importance, says Chris Case, managing director at Reduction Engineering (Kent, OH). His firm’s 800 series pelletizer design helps safeguard against stray pellets from previous production runs fouling compounds, a concern for color masterbatchers. “Just a few black pellets, for example, in a gaylord-full of beige compound can yield molded or extruded products with obvious defects,” Case says. “In designing the Reduction 800 series, we eliminated the hang-ups and hiding places often found in conventional equipment that can cause such pellets to find their way into the discharge stream for the next production run.”An underwater pelletizer that differs from competitive systems in its thermal isolation of the die plate from the die head has been introduced by ECON Maschinenbau & Steurungstechnik (Weißkirchen, Austria). The ECON technology is said to eliminate freezing of the die holes, lower head pressure, and minimizes heat loss to the cooling water. ECON claims energy savings as great as 95% can be achieved. The unit’s built-in treatment and re-circulating system for process water eliminates the need for a water bypass required in competitive pelletizers. To accommodate abrasive fiber- or mineral-filled polymers, ECON’s Ceconid die plate is available with high-hardness knives.Kneader equipment builder Buss (Pratteln, Switzerland) has come out with a modular pelletizing unit for its recently debuted MX kneader. Colin Richardson, technical marketing manager at the company, says the unit is designed so the pellets drop directly into a fast-flowing water bath that also conveys them away from the pelletizer. He says the aerodynamically optimized cutting rotor as well as the re-design of the unit’s hood, from sheet steel to aluminum casting, make a major contribution in reducing dBA levels, a concern because of stringent noise regulations being passed by the EU.For big output, Coperion Werner & Pfleiderer (Stuttgart, Germany) developed its UG925 underwater pelletizer. Equipped with a heated pelletizing die, it copes with an output rate of 72 tonnes/hr. The first such installation went into service in Plock, Poland at a polypropylene compounding plant late last year.The patent-pending underwater pelletizer from Crown/CDL Technology (Addison, IL) is designed to produce consistent, exact-shaped pellets and at the same time eliminate die-hole freeze-off, thanks to the company’s hydraulic polymer diverter valve. An improvement in residence time can be achieved when the hot melt reaches the die face. Fast startup is possible since the operator pushes a single button to start the underwater pelletizing process by diverting the melt into the Anti-Freeze die.BKG Bruckmann & Kreyenborg Granuliertechnik, part of the Kreyenborg Group (Munster, Germany), has just signed a deal to supply two turnkey underwater pelletitzing systems for a nylon 6 line at Rayong, Thailand operated by UBE Nylon. The equipment has a throughput of 150 tonnes/24 hr and should be in operation by September next year. BKG has also updated its Crystallcut underwater pelletizer system, which utilizes the heat inherently within the polymer melt to crystallize pellets during pelletizing. The melt is cut underwater directly at the pelletizer die face, then it is transported to a centrifugal dryer where moisture is separated from the granules. From there the pellets are moved on a specially designed vibrator conveyor where the material transforms from amorphous to crystalline, using the inherent heat trapped within each pellet.Rieter Automatik (Großostheim, Germany) premiered a unique method to produce either spherical or cylindrical shaped micropellets on the same line at the switch of a button at K2007. The production components are installed on a single, common platform of the compact line. As the melt flow leaves the extruder, it is directed either into a PRIMO strand pelletizing line with cooling trough and air knife or into a SPHERO underwater pelletizing unit. Switchover occurs using a pneumatic 3/2-way valve. Also new from Rieter is its BAOLI strand pelletizing series in operating widths of 100, 200, and 300 mm, as well as custom for North American needs. It offers a throughput of up to 3000 kg/hr for PET and PBT compounds or masterbatches.

Rieter Automatik’s BAOLI series with cutting head open

Crown/CDL Technology’s underwater pelletizer

ECON underwater pelletizer with throughput from 5-6500 kg/hr.

Competitor Gala Kunststoff und Kautschukmaschinen (Xanten, Germany) sees a big future with its “i-heat process” (April 2008 MPW pg. 30) designed especially for cutting and drying wood-plastics composites (WPC) granules. Despite the fact that wood-flour elements in the melt are highly moisture absorbent, which in the past made underwater pelletizing almost prohibitive, Gala has found a way to utilize the inherent heat in the pellets to strip off unwanted moisture.In the first stage of a two-phase flow directly following pellet cutting, the granule’s surface is cooled in a fully water-filled cutting chamber that helps prevent agglomeration. In the next phase, air or a gas is injected into the slurry pipe, which produces a mist on the tubing wall and a gas phase in the center of the tube. This gas not only cools but also transports the pellets forward to a centrifugal dryer. Gala Technical Director Michael Ello says following the process, pellet moisture count is less than 0.05%.New from Coperion Werner & Pfleiderer is a water ring granulator, WRG320, for polystyrene with a throughput of 5 tonnes/hr. Delivery and startup occurred in Italy at the beginning of last year and a second unit, WRG400, with an output of 7 tonnes/hr, has been ordered by the same customer. This compact unit features reduced energy use. Quick and easy startup, low pressure on the die plate, and an even temperature over the entire surface of the cutting plate provides uniform-sized granulate to ensure no bridging during processing.BKG Bruckmann & Kreyenborg Granuliertechnik GmbH www.kreyenborg.comBuss AG www.busscorp.comC.F. Scheer www.cf-scheer.deCoperion Werner & Pfleiderer www.coperion.comCrown/CDL Technology Inc. www.crown-cdl.comECON GmbH www.econ.co.atGala Kusntstoff-und Kautschukmaschinen GmbH www.gala-europe.deReduction Engineering Inc. www.reductionengineering.comRieter Automatik GmbH www.rieter-automatik.com

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