Wanted: low-cost recycle sortation.

Several companies are working on low-tech, low-cost ways to separate plastics using heat and light instead of x-rays or machine vision. Those firms include ChemKal Corp. in Buffalo, N.Y., and Resource Energy Ventures in Phoenix, Ariz. (both cited in a recent report in Plastics Recycling Update newsletter, published in Portland, Ore.), as well as Plastic Technologies Inc., an independent research lab in Toledo, Ohio. All have patents on their processes and have proven their ideas in bench-top trials. All are working on systems that potentially could cost under $10,000, but none appears close to a commercial-scale trial.

The Holy Grail for all their R&D efforts is to devise affordable, automated ways to separate PVC from PET and other plastics. Existing commercial approaches to PVC separation include x-ray fluorescence, which identifies chlorine atoms in PVC; infrared scanners; and uv "black-light," which makes PET fluoresce a different color from PVC so that hand sorters can pick out the PVC. X-ray fluorescence sold primarily by National Recovery Technologies Inc., Nashville, Tenn., is so far the dominant system in commercial use. But it can cost upwards of $100,000, so most of the current installations at recyclers were heavily subsidized by plastics industry trade groups. (CIRCLE 12)

WHAT'S IN R&D

Chemkal uses a "phase-contrast" enhanced light source that includes uv and other light frequencies. This illumination system causes PET to show up in one color (usually blue) while PVC appears in another (white, red, green or yellow). The system's special membrane-like light source needs to be replaced every six months and costs $100. A basic unit with the light source in a 4-ft enclosure will cost $5300 and process approximately 1200 lb/hr with two people sorting, Chemkal says. The modular enclosures can be built up to 16 ft long. (CIRCLE 13)

Resource Energy Ventures has patented a sequentially heated conveyor belt that separates plastic flake according to melt temperature tier of a three-tiered PTFE conveyor belt is heated to a different temperature, increasing from top to bottom. The top belt makes the lowest-melting flake tacky. That flake sticks to the conveyor and travels to the underside of the belt, where it's scraped off and removed on a separate conveyor. Higher-melting flake sticks to the next conveyor, and so on. A 4-ft conveyor was tested at the University of Mass. at Lowell and proved "99% accurate," Resource Energy says. The company expects a 1000-2000 lb/hr device to cost less than 0.005[cts.]/lb to operate. (CIRCLE 14)

Plastic Technologies is also developing sortation technologies using heat and light. A project for the National Association for Plastic Container Recovery (NAPCOR), a PET packaging trade group in Charlotte, N.C., aims at optimizing use of uv light to identify PVC in a stream of recycled PET containers in order to enhance manual sortation. (CIRCLE 15)

Plastic Technologies also has patented an agglomeration process to separate vinyl from other plastics and contaminants like rubber and thermosets--for example, separating shredded vinyl wire chop from other wire-insulating materials and contaminants. Heating and agitating the wire chop in an 8-lb-capacity Henschel intensive mixer made the PVC melt and clump together into large, nearly pure lumps, excluding the higher-melting plastics and contaminants so that the PVC could be screened off. (I. Waxman & Sons in Mississauga, Ont., and the Geon Co. in Akron, Ohio, use a similar process commercially.). (CIRCLE 16)

DARK/LIGHT FLAKE SORTING

Several recyclers are also using automatic scanning systems to remove dark-colored flake from PP caps in natural milk-jug resin. Union Carbide Chemicals & Plastics Co.'s recycling plant in Bound Brook, NJ., installed the first Opti-Sort light/dark sorter for flake from Simco/Ramic of Medford, Ore. (see PT, Sept. '92, p. 15), over six months ago. A second, larger Opti-Sort system just started up at KW Plastics in Troy, Ala., also culling colored cap flake from natural HDPE. (CIRCLE 17)