TECHNOLOGY | MELT FILTRATION
the process – regularly find their way into the recycled material. The resulting scrap pushes up the cost. This also has negative impacts on the downstream extrusion process because the build-up of a filter cake on woven steel mesh screens accompanied by strong pressure fluctua- tions and the need for frequent screen changes creates extra work, as does cleaning with a reverse melt flow (backflush). Ettlinger says that in comparison with these
Below:Fimic melt filters are known for their high efficiency, low operating costs, inexpen- sive spare parts and user
friendly set-up, says the company
traditional woven steel mesh screens, laser-drilled microperforation provides much better separation efficiency. The woven steel mesh screens have a mesh size corresponding to the cross section of the conical holes in the filter screen, which are tapered in the direction of the melt flow. When melt flows through the screens, all contaminants larger than the hole diameter are retained on the filter surface. Due to the new 60 micron filtration fineness, the few residual contaminants are no longer visible to the human eye. The PET recycling process also has the basic ability to convert recycled material into new products with visual, mechanical and organo- leptic properties that are indistinguishable from virgin material. The significantly reduced occur- rence of black specks and other particles helps make the line more efficient because there are virtually no torn tapes or fibres; ultimately leading to substantial savings. Ettlinger adds that its melt filters can maintain continuous, constant filtration efficiency over several weeks or months without any process interruptions. Contaminants are removed from the microperforated filter screen by a scraper, and immediately discharged, with every rotation. The filtration surface remains absolutely clean as a result and the melt filter works with a constant pressure for long periods. Contaminants such as small elastic particles like silicone, which could otherwise be forced through the screen after a while, are unable to collect on the surface.
Ettlinger says that its continuous melt filters now open up new recycling possibilities for materials that have traditionally been considered too heavily contaminated or that contain extremely problem- atic contaminants. The new 60 micron filter screen makes the use of PET fines from recycled bottles an even more commercially attractive option. These fines occur during the sorting, grinding and washing processes and tend to be contaminated with large amounts of paper and aluminium. Although up to 20 tonnes of fines per month are generated even in small PET bottle recycling plants, this material is sold at a low price for lack of an alternative. Ettlinger adds that the continuous, high speed ECO melt filter will let recyclers convert their PET material flows into an even higher quality and more profitable end product. Italian company Fimic says that its filters for the
recycling market are renowned for high efficiency, low operating costs, inexpensive spare parts and user friendly set-up. Filters are designed to be replaced by a single operator in a maximum of 30 minutes and can be operated remotely. The company offers three types of changers – manual, automatic backflush filter and automatic scraper filter. Fimic adds that its automatic scraper and backflush changers allow filtering at low tempera- tures and low pressures. The RAS + REF model is a scraper or backflush filter changer that uses both a punched steel screen, which is extremely economical, and a laser screen, which is highly efficient in cases of signifi- cant contamination. In both cases, Fimic’s filter allows continuous working for days without any interruption of flow. The ERA is the company’s latest model for recycling. This new family of automatic filter changers has a double filtering and scraping system. ERA has two distinguishing filtration chambers. The first one has a punched screen to filter the most aggressive and largest contaminants, while a second one has a laser screen for the highest filtration level possible in total safety. The company says that advantages of these filters include the possibility of obtaining several consecutive filtration days due to the self-cleaning technique, a reduction of the amount of mesh change and downtime, reduced operator interven- tion, and an increase in extruder productivity due to a larger filter surface. Fimic says it is developing a new melt filter technology which it plans to launch at K 2019. BritAS Recycling-Anlagen has increased the filter surface of the automated belt melt filter ABMF 1600 by 50%. The company says that the increased filter surface both improves total output and
22 PLASTICS RECYCLING WORLD | March/April 2019
www.plasticsrecyclingworld.com
PHOTO: FIMIC
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