Technology | melt filtration
the plastic waste, for instance contamination by paper. Further development work on the ABMF systems
has involved Britas increasing motor capacity of the belt take-off and belt magazine. Italian company Cofit International has 40 years’
experience of developing and supplying screen changer technology. Its expertise with belt technology is epitomised in its flagship product called Gorilla Belt, an automatic screen changer designed for highly contami- nated waste which the company says has gained “significant acceptance” in the market. Alessandro Fabbri, president of Cofit, says annual
production is currently 20 Gorilla Belt units. These have been sold to Cofit customers both in compounding and recycling that produce granules. Explaining its unusual choice of product name, Cofit says: “The name Gorilla Belt has been conceived to give the idea of strength: it is equipped with two wedge blocks, like two big hands, to hold the screen, while a motor downstream displaces the screen by pulling it.” In an automatic operation, screen changing is
triggered by contaminants building up on the screen surface and increasing the pressure on it. When the differential between inlet and outlet melt pressure exceeds the set threshold (or alternatively when the preset timer value has elapsed) the screen changing cycle starts and a clean screen is pulled into position from the belt roll. Cofit says screen changing is carried out in about 15
seconds. The extruder does not need to stop during screen changes, as the melt is fed temporarily into an accumulator cylinder. Once the new screen section is properly positioned, the sealing cylinders close and the unit is airtight sealed. The entry valve opens and the accumulator cylinder slowly pushes forward, redeliver- ing the accumulated melt into the flow channel. The key strength of Gorila
Belt, according to Cofit, lies in its automatic operation. Using program- mable setups, the only time operator intervention is needed is for replacement of the 50 m long screen belt. Duration of the belt replacement depends on the level of contamination contained in the filtered material, but Cofit gives an indicative time of about 10 minutes. Each 50 m roll provides 125 screen changes and rolls butt weld together to allow continu- ing operation.
Gorilla Belt is intended for filtering highly contami- nated plastic materials, such as agricultural and
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building films and other post-consumer materials. Fabbri says: “Waste sources are the most different – being mainly post-consumer, it is a highly polluted material because it comes from sorted waste collection, characterized by a strong presence of wood, sand, metal, paper, chemical compounds, inks, etc.” Gorilla Belt is offered in different sizes,
according to accumulator cylinder dimensioning, with output ranging from 500 to 3,000 kg/h. The maximum filtration level is 80 microns. “As a matter of fact we
can satisfy any customer needs,” says Fabbri. “For example, within the re-com- pound sector, production peaks of 4,000 kg/h can be reached, by adding a 10% calcium carbonate and thus increasing the specific weight.” At K 2016, Gneuss showed its various rotary melt
filtration technologies. Taking centre stage was a PET post-consumer and industrial waste recycling line, based on a MRS 90i extruder fitted with a RSFgenius filtration system and the company’s new intrinsic viscosity (IV) booster system called Jump. The RSFgenius filters operate fully automatically, with process and pressure consistency, and have a back-flushing system and integrated self-cleaning. Gneuss says screen changes take approximately 20-30 minutes and need to be carried out every one to 16 weeks, depending on the level of contamination. RSFgenius filters are
intended for ultra-fine filtration, the filtration of
thermally sensitive melts and of materials with a high level of
contamination. On display at K 2016 was the RSFgenius 330, which is the second largest
filtration system in the Gneuss range. The company said the unit was destined for a BOPET line in Asia where it would operate with a filtration fineness of 20 microns.
Also shown at K 2016 was an RSFgenius 175, together
with a process-constant automatic filtration system SFXmagnus 150 and an SFXmagnus 90 R with integrated back-flushing. The R designation is for models designed to handle contamination surges on recycling lines.
June 2017 | PLASTICS RECYCLING WORLD 29
Above:
Cofit’s Gorilla Belt system
Left: Gneuss RSFgenius filters are intended for ultra-fine filtration
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