An integrated system that uses the thermal energy of the molten polymer in PET pelletizing for subsequent crystallization eliminates problems caused by the agglomeration of amorphous material and substantially reduces energy costs for compounding or recycling, according to Nordson BKG™. Called CrystallCut®, the patented* process avoids the need to cool PET after pelletizing and then reheat it for crystallization. As an integrated network that incorporates underwater pelletizing, drying and crystallizing, it is designed for precise control of material temperatures throughout the process, preventing production and quality problems caused by insufficient crystallization and excess levels of amorphous material. The energy efficiency of the system can save more than € 3,000,000 in annual energy costs for a typical PET resin plant and nearly € 200,000 for an extrusion line recycling PET bottle flakes, according to examples cited by Nordson BKG™ based on actual commercial installations (see graph for an example relating to polymerization). “The CrystallCut system provides substantial relief to the cost pressure on PET polymerization and recycling, particularly as prices for PET fall,” said Ralf Simon, managing director of Nordson BKG™. “In addition, because the system utilizes residual thermal energy within the material to crystallize pellets from the inside out, it yields an enhanced crystalline structure that results in lower energy costs for re-melting the material.” In the system, the hot PET granulate produced by the face cutter of the underwater pelletizer is transported rapidly to the pellet dryer in hot water (up to 95 °C) through closed conveying pipes, where pellet cooling and solidifying takes place. This conveying medium and the short distance between die head and dryer are keys to conserving the heat from melt processing. The pellets are at a temperature in the 150 to 160 °C range when they exit the dryer onto a vibrating conveyor. This keeps the pellets in constant motion, generates a uniform distribution of thermal energy, and prevents pellets from sticking together. At the completion of the process, the pellets have a temperature of approximately 180 °C, have achieved up to 40% crystallinity, and may be transferred directly to solid state polycondensation (SSP). In addition to saving energy costs and preventing amorphous PET clumping, the CrystallCut system yields an almost dust-free product and increases bulk density by 8% in comparison with a conventional process.
 Assuming an average energy cost of 12 cents/kWh, Nordson BKG™ estimates that the system yields energy savings of up to 125 kWh or €15/ton of PET in a modern PET polymerization plant. Since such a plant can achieve a production capacity of 600 tons/day, these savings amount to €9,000 daily and €3,200,000 pa. This represents an annual energy saving of more than 26 gigawatt hours, or 26,000 megawatt hours. Another example cited is that of an extrusion line which recycles PET bottle flakes at a rate of 1,500 kg/hr. The savings achievable with the CrystallCut system exceed 180 kWh, or more than 1.4 cents/kg. In a 365/24 operation this equates to €190,000 pa.   (* U.S. Patent No. 8,324,339 B2)

Automatik Plastics Machinery's SPHERO® is an underwater pelletizing system designed for all kinds of thermoplastic materials, characterized by high flexibility and a small footprint. The system produces spherical pellets of superb quality, ideally suited for further processing with throughputs up to 36,000 kg/hr. The system is applicable for compounding, recycling and raw material manufacturing, depending on size and technical features. With a capacity range of a few 100 kg/hr to several t/hr this system is basically applicable for all materials with thermoplastic behavior, such as Polyolefins - LDPE, HDPE, PP, Styrene polymers- PS, SAN, ABS, Acrylic resins-PMMA, PAN, Polyacetals - POM, Polycarbonates, Polyesters-  PET, PBT, PEN, Polyamides- PA 6, PA 6.6, PA 11, Thermoplastic elastomers- TPE-S, TPE-O, TPE-E, Polyurethane, Hot melt adhesives. A unique knife head design and optimized flow conditions within the cutting chamber ensure perfectly spherical pellets which are ideally suited for further processing. Through axial movement of the motor shaft, the main drive motor continuously grinds the knife edges during operation, increasing equipment availability and thus reducing costs. A further highlight is the liquid-heated die plate. The design of the die plate as well as the arrangement of heating pipes and valves assures a simple, rapid exchange. Compared with conventional electrically heated die plates the new design produces pellets with consistently narrow size distribution, a feature heretofore not attained.

Benefits

• Rugged design – all components are arranged on a common supporting frame
• Excellent pellet quality – optimum water flow within the cutting chamber combined with an unique knife head design
• Quick product change – cleaning, assembly and start-up are kept to a minimum
• Optimized lifetime of the cutting tools
• Single-handed opening and closing of cutting chamber for quick, convenient and safe operation
• Various die plate options available: electrical-heated, liquid-heated and thermally insulating SuperFlow die plate
• Integration into Combi-Crystal-PET® guarantees an innovative PET production with high potential of energy savings
• Reduced energy consumption with no additional heating required