TECHNOLOGY | ODOUR REDUCTION


Above: Coperion and Herbold Meckesheim offer a variety of solutions along the recycling process to remove unpleasant odours from plastic


extruder. [After the process section], volatile particles are degassed from the plastic melt.” Dissolved gas removal can be intensified with the addition of liquid stripping agents. For high quanti- ties of gas, a ZS-EG side devolatilisation unit can maximise the extruder’s deodourising capabilities.


Two processes Coperion also offers deodourisation systems for removing residual unpleasant odours post-extru- sion and pelletising. For this step, which involves hot air flowing through the pellets in silos, Coperi- on has developed two different process solutions, depending upon the desired end-product quality, the temperature it requires, residence time and quantity of air.


One method uses two silos (one to warm and deodourise the granulate and another to cool the granulate with cold air). “In this process, compara- tively little energy is needed to warm the product to the desired devolatilisation temperature. Moreover, the cooler’s process heat can be used to pre-warm the pellets, increasing energy efficiency,” Schofer reports. In an alternative method, warming, degassing and cooling can take place in one silo by using two Bulk-X-Change heat exchangers. “This solution is much more compact, requiring only one silo,” Schofer says. The company offers a mobile test unit to determine specific needs for silo devolatilisation on a customer’s site. “Using freshly produced product under actual production conditions, the options for odour reduction can be


Left: Using Coperion’s mobile deodourising unit, specific odour reduction potential can be tested on freshly produced product


under actual production conditions 38 PLASTICS RECYCLING WORLD | October 2024


thoroughly investigated in situ, defining machine parameters to achieve the desired product quality.” Zeppelin Systems offers deodourisation plants


that remove odour from plastic recycled materials by means of a physical thermal cleaning process. These include a batch system (Fresh-TEC Deo-B) and a continuous system (Fresh-TEC Deo-C). The systems are an adaptation from the company’s degassing technology that has been used in virgin polyolefin production for decades. Several of the new, scaled-down systems optimised to maximise efficiency in the recycling industry are in daily commercial operation, says Julian König, Head of Sales, Recycling Plants at Zeppelin. The systems can be used either after producing recycled granules or after a compounding extrusion and pelletising step. A compounding extruder can remove highly volatile contaminants, but complex contaminants require extended treatment time for efficient decontamination, König says. Both batch and continuous systems can be designed to reduce energy consumption through insulation as well as energy recovery. “Deodourisa- tion requires material treatment with a flow of gas at a high temperature for an extended time. The energy for that process is stored in the degassed granulate leaving the system as well as in the off-gas. We have developed recuperators to harvest that energy and feed it back to the system. That leads to a significant reduction of external energy use,” König reports. Batch systems offer lower capital expenditure,


but energy-efficient, continuous systems are typically chosen for higher throughputs or less frequent changeover, such as a continuous flow of one material for multiple days. Aimplas, the Technological Institute of Plastics


located in Valencia, Spain, has participated in multiple EU projects to develop solutions for recycled plastics. The group has optimised a single-screw extrusion line for the elimination of


www.plasticsrecyclingworld.com


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