Coperion is supplying an extrusion system to Ghent University in Belgium for comprehensive research and development tasks in chemical recycling of mixed plastic waste. Coperion designed this laboratory system, built upon a ZSK 18 MEGAlab twin screw extruder, especially for chemical recycling of post-consumer waste within a throughput range of 1-10 kg per hour. Along with the extruder, it includes a feeder from Coperion K-Tron as well as a vacuum unit.
Plastic waste, especially packaging waste, is generally a mixture of materials with a high degree of contamination. Recycling this raw material is usually difficult, as sorting and cleaning of waste is in many cases neither economically viable nor technically feasible. Chemical recycling is a promising process to recycle these material streams into chemicals, waxes or liquid energy carriers.
As a trailblazer in the development of chemical recycling of plastic waste, Ghent University has laid the foundation for many forward-looking developments in the field that are paving the way to more sustainability in the plastics industry. Chemical reaction engineering in general and the kinetics of chemical reactions are major axes of the research done at the Laboratory for Chemical Technology (LCT) of Ghent University. These include, among other applications, optimization of existing industrial processes and development, intensification and scale-up of novel technologies aimed at minimizing waste streams and energy consumption.
Twin Screw Extrusion for Efficient Energy Addition
Coperion’s twin screw extruder technology is particularly well suited for chemical recycling of plastics. After post-consumer waste, either shredded or compacted, is reliably added to the extruder’s process section by the Coperion K-Tron feeder, a great deal of mechanical energy is introduced into the material in shortest time thanks to the continuous surface renewal as well as intensive dispersion and shearing along the twin screws.
Within about 30 seconds, a homogeneous, highly devolatilized melt with a temperature of up to 350°C is produced, into which the energy has been introduced very efficiently.
Further materials, such as catalysts, can be added and mixed in as needed. In some cases, residual water or chlorides from PVC are introduced into the extruder in minute quantities along with the plastic waste. Both are reliably extracted via vacuum devolatilization on the extruder's process section.
Twin screw extruders possess numerous advantages that are especially beneficial in chemical recycling. The technology covers a broad range of throughputs. On larger ZSK extrusion machines, throughputs of up to 20 t/h can be realized using this process. Polymers of various viscosities are reliably plastified thanks to the highly effective mode of operation of the twin screws. Plastic energy dissipation takes place in no time. When needed, corrosion and wear protection of all product-contact parts within the process section can assure long extruder lifetime even when processing very aggressive materials.