Extruder with a Hollow Cylinder
Novel Device for Processing Problematic Waste
The cylindrical extruder from VTT Technical Research Centre of Finland Ltd can be used, for example, to turn problematic plastics and textiles as well as food waste into pellets. The prototype has already exceeded the industrial steering group’s expectations during initial testing. The research center is currently looking for a partner to commercialize the technology.
Behind the idea for the novel extruder is VTT’s research scientist Hannu Minkkinen, who discovered that materials could rotate around the device’s hollow cylinder. “Commercializing the device would create completely new possibilities both in terms of waste processing and novel material combinations,” explains VTT’s principal scientist Tomi Erho.
30 cm Screw Diameter
The diameter of the extruder screw determines the size of the feed throat and also the kinds of materials that the device is capable of processing. The prototype has a screw diameter of 30 cm instead of the 3 to 4 cm typically found in conventional devices of the same output.
The large diameter combined with a shallow screw channel makes it possible to mix different components of problematic, porous and lightweight materials and to make the mixed mass compatible with the next stage of the production process.
Benefits Compared to Traditional Extruders
According to the Finnish research organization, benefits compared to traditional extruders are:
- Thanks to the simple design of the device, it is cheaper to make than traditional mixing twin-screw extruders.
- Thanks to its short length, the device can also be mounted upright if necessary. VTT’s prototype is less than two meters long and weighs 1.5 t.
- The compactness of the device makes it possible to transport to where it is needed.
- The design enables accurate temperature control combined with efficient mixing and, considering the size of the device, exceptionally long residence time. Long fibers can be processed without cutting them, which is useful when mixing fiber composites, for example, or when processing textiles.
VTT’s research scientists have been testing the prototype’s performance with, for example, pieces of plastic film, mixed plastic waste, various kinds of textiles and bread. In addition to recycling, the device has been used to produce long fiber composites.
Recycle Materials without Need to Separate Fibers or Components
"The new extruder opens up a revolutionary opportunity to recycle mixed textiles and materials without having to separate fibers or components. We have successfully tested the device, for example, for recycling pillows without removing the filling in the course of a project called Telaketju with funding from Business Finland”, says senior scientist Pirjo Heikkilä from VTT.
“Many textile recycling processes are only suitable for products containing homogeneous fibers. However, textiles are often made of a mix of fibers, and many products are comprised of different layers,” says senior scientist Pirjo Heikkilä from VTT.
The device was designed and the prototype built with funding from Business Finland’s and VTT’s funding instrument for commercialization of research results. (kk)