DAVOS, SWITZERLAND - Sorting plastic waste is one of the pithiest problems confronting recyclers. Manual sorting is expensive, labor-intensive and inexact, and automated sorting has limitations as to the types of materials that can be sorted.
Attendees at the Recycle '95 Worldwide Recycling Conference, held May 15-19 in Davos, heard descriptions of two advanced infrared sorting systems that aim to solve those problems.
TOA Electronics Ltd. of Tokyo has developed a new automated sorting system that works using short infrared waves to scan and identify resin types in waste specimens.
Toshio Amano, managing director of the Tokyo control and electronic equipment manufacturer, said that his company's system can identify most plastic with 99.9 percent accuracy.
``The spectrometer has been shown capable of identifying any types of plastic, regardless of how dirty the material is, using the accompanying software,'' Amano said. ``Each plastic type has a distinctive molecular identity, which can be detected using short-range infrared waves of 1-2 micrometers. This is as individual as a fingerprint.''
Developed in conjunction with the Plastic Waste Management Institute in Tokyo, the system can be adapted to conveyor-fed bottle-sorting lines, and can discriminate bottles of any thickness and any size from 200-2,000 milliliters, regardless of color or clarity.
The system can be adapted for film and sheet, pigmented or mineral-loaded resins, and for all shapes and sizes of waste.
The identification process takes about two seconds per bottle or piece.
Amano admitted that the largest problem left to solve is the speed of his system.
``We currently can operate at about 200 kilograms [440 pounds] per hour,'' he said. ``We recognize that that is not fast enough for a commercialization. I am confident that we can improve that and we are aiming at being able to do 1 ton per hour.''
Amano envisions the equipment's use in package equipment designed to help consumers identify plastics, so that they may sort them properly at the point of purchase or return.
Placed at the supermarket or other retail outlet, the system would take in the bottle, identify it, and deposit it inside the machine. Linked to machinery to compress or crush the material and to return bottle deposits to the customer, it could provide an accurate presort.
The machinery, depending on the size and linked systems, could sell for about $25,000, Amano said.
The system was similar to another identification device shown at the conference by Bruker Analytische Messtechnik GmbH, a control maker based in Karlsruhe, Germany.
Gunter Zachmann, physicist for Bruker, said the company's machine uses midrange infrared light [2-20 micrometers] to identify resin types in three to four seconds.
``It can identify 30 different resin types and has been used for about two years,'' he said. ``We installed one at BMW's dismantling plant in Munich, and improved the accuracy and volume of their sorting there dramatically.''
He said the American Plastics Council and several U.S. companies, including General Motors Corp., are evaluating the Bruker system.