Economic recycling is defined by recovering high quality products from contaminated material. After successful trials at a South American food packaging film producer, KREYENBORG GmbH has equipped eight of the film producer’s recycling lines with backflush screen changers. Through the filtration process, PET flakes can be processed at a throughput rate of 500 kg/h. Thereby, different qualities of material and varying degrees of contamination pose a challenge for the screen changers.
The backflush screen changer has a self-cleaning function; this backflush procedure is initiated after achieving a certain pressure limit. In this process, a filter screen is automatically moved out of the production position and backflushed by the redirected melt stream. As a result, the contamination is removed from the screen cavity and ejected via the drain channels. This is referred to as “the material lost due to the backflushing operation”. Following this, the filtration screen is moved back in the production position.
To give an estimate of the running costs (loss of material due to backflushing, wire screen cloth, etc.), eight of the KREYENBORG screen changers were compared to a currently available screen wheel filter which was in use on an identical extrusion line. During the processing of various different materials, the amount of material lost hourly due to the backflushing operation using the KREYENBORG backflush filter was reduced by half when compared to the screen wheel filter. Furthermore it was possible to increase the fineness of the filter mesh. The key to success of the system lies in the experience and technology used in the
design procedure together with the compatibility of the various components.
The customer is completely satisfied with the performance of the KREYENBORG screen changers which have been installed. Therefore, the food packaging film producer plans to install two more KREYENBORG backflush screen changers during the coming year.