INNOVATION | ODOUR REDUCTION
Right: Coperion offers odour solutions such as devolatilisa- tion of bulk materials within silos
extrusion. “Operating directly on the granule with no additives, it contributes to the removal of VOC residuals and odour in quick time,” he says. “Bandera exploits a microwave-based technology as the main vehicle to achieve an innovative extraction system able to reduce residual odours from different sources. As prolonged treatment times mean a reduction in productivity and energy efficiency, Bandera’s aim is to keep such times to a minimum.” He also stresses the advantages of using a
twin-screw extruder for odour reduction. “The best way to deal with odour is to properly process post-industrial and post-consumer materials from the very beginning.” The Bandera HVTSE co-rotat- ing twin-screw extrusion systems feature high vacuum, minimum shear stress, a large surface for degassing and shorter residence time, which contribute to “enhanced process performance from the very beginning and ensuring the extrusion of high-quality materials also in terms of VOC and odour removal,” he says. Other benefits of the twin-screw technology include: superior mixing performance, reduction in polymer degradation, controlled thermoregulation, dilution and integration of additives, minerals and fibres. HVTSE technology is available in both cascade and single systems and can be used with HDPE, LDPE and PP, as well as styrenic resins and polycarbonate. Coperion offers two series of twin screw compounders which it says are suited for recycling applications: the high-end ZSK type and the STS type. In both series, homogenisation and devolatili- sation of recyclates take place at the highest intensity, it says. This is particularly beneficial in reducing odours when processing recyclate. There are different technology options depend- ing on the specific plastics recycling application. Coperion equips the process section of the twin screw compounders with degassing units, or a separate twin screw side devolatilisation ZS-EG unit can be installed. The company says: “With its large free cross section for the devolatilisation, the ZS-EG keeps the melt reliably in the process section even at maximum specific torque. Odour is removed effectively and product quality is improved.” Odours and gases are drawn off through the ZS-EG’s axially open screw flights. Coperion equipped the plastics recycling plant
of Aurora Kunststoffe in Neuenstein, Germany, which was taken over by MOL last year, with ZSK extruders and ZS-EG side devolatilisation units when Aurora’s production area had been damaged by fire. Coperion delivered three ZSK 45 twin screw
32 PLASTICS RECYCLING WORLD | May/June 2020
extruders and strand pelletisers, and supported the company with the engineering necessary for production. Aurora achieves throughputs of up to 650 kg/h on the ZSK 45 extruders. Aurora purchases production waste in various engineering materials, including PA6, PA66, PA11, PA12, POM, PP, PC, and PC-ABS. The three ZSK 45 extruders were designed individually for Aurora’s requirements, which Coperion equipped with ZS-EG twin screw side devolatilisation units and special wear protection for product-contact parts. Norbert Büter, Coperion Sales Manager, says:
“When recycling plastics, it is necessary to adapt the process parameters and recipes to the various raw materials. With their flexibility and high torques, ZSK twin screw extruders are optimally suited for processing even the most difficult raw materials to very good product quality – and they do it at throughputs that are economical. By devolatilising using ZS-EGs, not only are unwanted gases removed, operational safety of the entire vacuum system is increased. This applies especially to even very volatile viscosities.” Coperion has devised other odour solutions, such as devolatilisation of bulk materials within silos. Recycled compounds are stored in a silo for an appropriate time and conditioned air is fed to the silo to reduce the volatiles content. This devola- tilisation process step further increases product quality which is required in many industries, such as automotive and packaging, says Coperion. In order to improve the process and shorten the deodorisation time inside the silos, Coperion also
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IMAGE: COPERION
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