Technology | melt filtration
Technology companies are trying new ideas for melt filter systems to deal with the varying levels of contamination in plastics recycling. David Eldridge reports on recent developments
Continuing innovation in continuous melt filters
The need to remove contaminants from the melt flow has been a major issue in plastics recycling since the early days of the industry, when manual screen changers were the only option. There have been many advances in melt filtration since then – from semi- continuous to continuous systems, and with various solutions from different companies, such as belt systems and rotating screens – which automate the job of decontamination. Many companies now offer backflushing technology to deal with more heavily contaminated plastics waste, while not interrupting the all-important flow of melt to the compounding extruder. Even with these advances, technology companies are not slowing their rate of innovation, judging from the new melt filtration products they are developing for plastics recyclers. Nordson Corporation launched a new melt filtration
system at K 2016 that has a quite different design to other systems. The BKG HiCon R-Type system was developed to handle highly contaminated polyolefin or styrenic plastics and exhibits less melt loss than traditional backflush systems for highly contaminated plastics, the company says. Nordson says the system employs a unique design that uses a cylindri- cal ‘separating head’ with knives arranged on its surface in a helical
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pattern that move contaminant particles forward as the head rotates. Enclosing the head is a stationary filter ‘strainer tube’ element. When contaminated melt from an entry port flows into the cylindrical space between the rotating head and the strainer tube, the knives capture the contaminant and the contaminant-free melt moves through the strainer into flow channels that lead to an exit port. At the same time, the rotating head turns a screw which guides the contaminated material through cooling sections and discharges it into collecting bins. The steel strainer tubes are available with micro-
holes ranging from 120 to 750 microns. The holes are conical in shape, permitting passage of molten polymer while preventing blockage. This design and the symmetrically positioned knives in the drum contribute to the long working life of the tube, the company says. Once cleaned, the tube can be reused. To ensure uninterrupted production, it is possible to operate two HiCon R-type 250 systems in parallel. Christian Schroeder, Nordson’s Global Product Manager for Melt Delivery Products, says the BKG HiCon R-Type system has been purchased by
companies in Europe, Asia, and the US since its launch last year.
“The applications that the
R-Type system can support are extremely diverse,” says Schroeder. Examples of where
June 2017 | PLASTICS RECYCLING WORLD 27 Main image:
Nordson’s new technology
uses ‘strainer tubes’ with micro-holes
ranging from 120 to 750 microns
Left: Nordson’s BKG HiCon R-Type 250 melt filter
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