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Plastics Recycling: An End to Unpleasant Odors

Recycled plastics often carry unpleasant odors caused by surface contaminants, solvent residue, additives and/or foreign materials. Disruptive smells may also stem from packaging that has absorbed the odor of its original contents. Such transferred odorants are particularly hard to remove.

Coperion and Herbold Meckesheim: Deodorization of Recycled Plastics

Recycled plastics require deodorization at several points along the recycling process chain. Only in this manner can one be certain that the recyclate will meet very high mechanical and sensory demands, will not exhibit undesired odors, and will achieve the quality needed for the intended application.

Coperion and Herbold Meckesheim offer a variety of solutions all along the recycling process to remove unpleasant odors from plastic. These technologies excel due to their especially reliable and energy-efficient operation. 

In a first step, odors are eliminated as the waste plastic undergoes mechanical pretreatment during shredding, washing and drying. Further odors can be removed from the shredded plastic in a silo using fresh air circulation.

The next, intensive devolatilization step, which markedly improves the recompound’s sensory quality, takes place during compounding in a ZSK twin screw extruder. Following melting and intensive homogenization of the waste plastic in the ZSK extruder’s process section, volatile particles are degassed from the plastic melt in a highly energy efficient process. Using various technologies such vacuum devolatilizations, these dissolved gases are reliably removed from the product. This effect can be significantly intensified with the addition of liquid stripping agents. Use of a ZS-EG side devolatilization unit provides a particularly effective and stable degassing process in the ZSK twin screw extruder, maximizing its deodorizing capabilities when high quantities of gas are present. 

Coperion: Mobile Desodorization Unit
Using the mobile deodorizing unit, specific odor reduction potential can be tested at your location on freshly produced product under actual production conditions.

Coperion also offers post extrusion and pelletizing deodorization systems that play a further key role in improving waste plastic to the qualitative level of new plastic. They reliably remove any residual unpleasant odors from recycled plastic compounds. Hot air flows through the pellets in silos, diffusing even particularly stubborn, long-chain molecules from the compounds. For this step, Coperion 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 deodorize the granulate and another to cool the granulate with cold air. In this process, comparatively little energy is needed to warm the product to the desired devolatilization temperature. Moreover, the cooler’s process heat can be used to pre-warm the pellets, increasing energy efficiency. 

Alternatively, 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.

Coperion’s experts will help you to identify the optimal degassing methods for your recycling process and achieve the product quality you desire, always keeping investment and subsequent operational costs of the individual process steps in mind. A variety of technologies are at your disposal in Coperion and Herbold Meckesheim Test Centers worldwide to test potential deodorization methods in advance.

For silo devolatilization, Coperion offers a mobile test unit to determine your specific needs on site. Using freshly produced product under actual production conditions, the options for odor reduction can be thoroughly investigated in situ, defining machine parameters to achieve the desired product quality.

Advantages at A Glance

  • Versatile scope of application for recyclate and highest product quality
  • Highly efficient Coperion and Herbold Meckesheim solutions with maximum throughputs and reliability
  • Optimal solution for your application, taking investment and operating costs into account
  • Low maintenance and operating costs
  • Test Centers for recycling applications and mobile deodorization unit for tests at your location

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