Self-Cleaning Screen Changer Helps Recycle Dirty Scrap

Two different recyclers have discovered a way to process highly contaminated scrap without substantial losses in economy and productivity.

Article From: 12/27/2011 Plastics Technology

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Two different recyclers have discovered a way to process highly contaminated scrap without substantial losses in economy and productivity. In both cases the solution was a Fimic continuous, self-cleaning screen changer from Italy, available in North America exclusively from ADG Solutions, Fairfield, Conn.

ABC Polymers, Inc., Stone Mountain, Ga. (abcpolymers.com), and KW Plastics, Troy, Ala. (kwplastics.com), each reportedly reduced downtime by 30% following installation of the Fimic device. This has paved the way for both recyclers to run new types of materials that previously could not be processed because of their high level of contaminants—particularly paper and paperboard—which required constant operator intervention.

In a reprocessing line with the Fimic screen changer, ABC chiefly runs chiefly LDPE and LLDPE. Typical source material is stretch wrap, bubble wrap, and foam with up to 3% contaminants —labels, paperboard, and nylon cords or PET strands, whose higher melt temperatures result in filter-clogging “unmelts.”

“Previously it was not economical to run this type of material, given the need to wash and dry it before processing, clean away buildup from a conventional screen changer every few minutes, and lose a significant amount of good material with every purging,” notes Jeramy Daniels, president of ABC Polymers. “The Fimic system has reduced our total cost for using the material by 25% to 30%.”

In four reprocessing lines with the Fimic system installed, KW Plastics runs primarily PP scrap, including rigid parts, woven and nonwoven fabrics, fibers, and film. Typical contaminants are labels, paper, cardboard, and non-PP unmelts, such as nylon and PET.

“We wash all materials before processing them, but some materials are virtually impossible to get clean enough for conventional screen changers,” said KW co-owner Kenneth Campbell. “The Fimic system has opened the door to new source materials for us. The beauty of the system is that it has a huge 24-in.-diam. screen and its operation is completely automatic.”

The Fimic screen changer can handle scrap with up to 3% loadings of contaminants without slowing or stopping the process, and even contaminants close to an inch in diameter do not pose a problem, says ADG president Sandy Guthrie. “The self-cleaning action is very efficient, with purgings averaging less than 2.5 lb per cleaning cycle and minimal discharge of good material along with contaminants.”

Self-cleaning cycles are under automatic PLC control. Contaminants build up on the screen plate until backpressure reaches a preset level. That actuates a rotating blade, which sweeps the screen and purges the contaminant through a central discharge port. Typically, the screen does not need to be touched or changed more often than every week or two.

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