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• Proven technology

Radiation safety issues

Automated—Flakes Can be used for colors today, and potentially for some material ID in the future; usually limited to removing one material present in small quantity from major material

Figure 14.8 shows a mixed plastic bottle sorting line that employs a combination of near-infrared, visible, and X-ray methods to separate PET, HDPE, and PVC bottles. Throughputs above 1500 pounds per hour per line are possible and sorting accuracy and yields are excellent. In bottle sorting, achieving a singulated

stream of bottles for presentation to the detector and air ejectors (a blast of air is usually used to eject an identified bottle off of a moving belt downstream from the detector) is an important part of the overall ID and sorting technology.

The ability to ID black plastics is of secondary importance in the case of bottles but becomes more important for some electrical and electronic plastics and for many automotive plastics. Mid-infrared (MIR) can identify many black plastics but not near-infrared (NIR), where the carbon black interferes [19, 64, 65]. Recently, a company has reported success in applying laser Raman techniques to the rapid identification of black plastics [66].

Many companies have been instrumental in the development of technology and equipment for the rapid identification of plastic bottles [54] and durable plastic parts [10, 19, 63] for the purpose of recycling. Three companies that market plastics ID and related sorting equipment internationally are referenced here:

Magnetic Separation

Systems, Inc. (MSS) 3738 Keystone Avenue Nashville, TN 37211 Tel +1 (615) 781 2669 Fax +1 (615) 781 2923 [email protected] www.magsep.com

National Recovery

Technologies, Inc. (NRT) 566 Mainstream Drive Suite 300

Nashville, TN 37228 Tel +1 (615) 734 6400 Fax +1 (615) 734 6410 [email protected] www.nrt-inc.com

LLA Instruments GmbH

Schwarzschildsr. 10 D-12489 Berlin-Adlershof Germany

Tel +49 30 6719 8376 Fax +49 30 6392 4766 [email protected] www.lla.de

In some situations, manual sortation of plastics recovered from durable goods is feasible because of the size and value of each item and compatibility with present disassembly practices. Figure 14.9 shows the use of an MIR instrument to ID dismantled plastics parts from E&E equipment or automobiles. If the durable plastic part has been painted, the identification needs to employ an unpainted surface if available or the paint film must be physically removed first.

In most situations, the manual identification and sorting of plastics parts from automobiles or computer and business equipment housings using fast infrared techniques has significant throughput limitations. Overall ID and sorting rates of

Figure 14.9. Use of bench-top mid-infrared rapid plastics identification equipment. Photo courtesy of MBA Polymers, Inc.

about 250 lb per hour for automobile interior trim plastics and near 900 lb per hour for computer and business equipment housings can be expected [49, 67]. This is not very impressive when compared to the fully automated flake-sorting rates near 10,000 lb per hour achieved using state-of-the-art density separation methods as discussed later in this chapter.

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