Final Report: An Economical Alternative for Sorting Polymers on the Small Materials Recovery Facility (MRF) LevelEPA Contract Number: 68D99061
Title: An Economical Alternative for Sorting Polymers on the Small Materials Recovery Facility (MRF) Level
Investigators: Sommer, Edward J.
Small Business: National Recovery Technologies Inc.
Project Period: September 1, 1999 through March 1, 2000
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (1999) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , SBIR - Waste , Small Business Innovation Research (SBIR)
Summary/Accomplishments (Outputs/Outcomes):It is well known that post-consumer plastics have become a tremendous burden upon our waste disposal system. Although plastics constitute only about 9% by weight of municipal solid waste they occupy approximately 1/4 the volume of the waste stream. The transport of plastics to landfill and their disposal in landfill is very expensive due to their light weight and large volume. The U.S. EPA has recommended recycling as being preferred over incineration and landfilling in its hierarchy of waste treatment alternatives.
It is generally felt that for plastics recycling to be economically viable in the long term the recycled resins must be competitive with virgin resins. In order to produce high quality recycled resins which can displace virgin resins in the marketplace it is necessary that the recycled resins be sorted to high purity specifications. Current processing technology first sorts post-consumer plastic containers, such as PET and HDPE, on the bottle level using hand sorting or automated bottle sorting technology. The bottle streams are then sent to grinders where they are reduced in size to "flake", normally about ? to ? inch in size. The flakes then are sent through a washing process to remove product residues, dirt, grime, glue, label pieces, and other contaminants. The cleaned flake is then dried and either boxed for shipping or sent to extruders for pelletizing in preparation for shipping or use in a new product.
In order to pelletize the flakes or use the flakes directly in a new product it is extremely important that the flake product be as pure and as clean as possible. Modern plastics extruding equipment is highly sensitive to impurities in the polymer feedstock. Automated flake sorting systems are becoming an essential tool for the processor in removing foreign contaminants and cross contamination from other polymers in the flake stream after the washing and drying process. Existing technologies rely either on optical color separation or opacity to x-ray absorption. However these systems are unable to distinguish polymers by chemistry to remove, for instance, polystyrene (PS) from PET or polypropylene (PP) from HDPE. In other words, x-ray or optical identification works well for contaminants which have different x-ray absorptive properties or are optically different but are useless for cross contamination of polymers which react to x-rays similarly or are optically similar.
The Phase I and Phase II research established feasibility for developing a new breakthrough infrared technology using newly developed sensors for spectroscopic sensing and high speed precision air jet ejection for rapid high accuracy sorting of polymers in their flake form. This new technology distinguishes polymer flake particles at high speed according to their chemistry and can provide a cost effective means for recyclers to sort streams of mixed polymers to high purity specifications. During Phase II a prototype flake sorting system was designed, constructed, and tested. The unit was installed in an operating plastics recycling facility for extensive field testing. These tests were highly successful and led to the sale and permanent installation of a commercial scale flake sorting system at the recycling facility. The infrared sorting system is capable of individually measuring, identifying, and sorting over 15,000 plastic flakes per second at feed rates of up to 5000 pounds per hour. The technology is unique in that it enables detection and removal of small polymer contaminant particles from materials streams at high throughput rates. A significant advantage of the new technology is the ability to detect and remove small polymer contaminants down to 1/16 inch in size. The sorter performs at high efficiency for contaminant removal and sets a new standard in the industry for minimal product loss (< 0.5%). Based upon performance levels and industry needs, National Recovery Technologies, Inc. (NRT), expects significant worldwide sales of the new technology.
Features of the new FlakeSortTM sorting technology include:
- Polymer Specific Identifications by Infrared Spectroscopy
- Sorting Independent of Particle Thickness
- Throughput Rates Up To 5000 lb/hr (2270 kg/hr)
- High Accuracy Precision Sorting
- Ultra-Low Product Loss
- Low Maintenance Requirements
- Easy Use Graphics Oriented Operator Interface (Color Touch Screen)
- Factory Diagnostics/Troubleshooting via Modem Connection
During the Phase II project NRT applied Phase II Option funding to adapt the new technology to development of a second commercial product, a laboratory instrument for measuring polymer contaminants in a stream of polymer product flakes. The instrument is useful to recyclers in conducting quality control analysis of their polymer products. Initial applications of this instrument have been for the measurement of PVC contamination in PET flakes after processing. Current techniques involve manual baking of PET samples in ovens to blacken PVC particles and then tedious hand sorting through the baked samples to remove and weigh the blackened PVC pieces. Thus the new Flake Analyzer instrument results in considerable labor savings and allows analysis of much larger samples thereby increasing the statistical validity of the process.
Features of the new Flake Analyzer technology include:
- Fast Accurate IR Spectroscopy
- Reports Contaminant Level in ppm
- Analysis Rates Up To 100 lb/hr
- Enables Testing of Large Samples to Improve Sampling Statistics
- No Oven Baking or Sizing
- Eliminates Wait for Critical Quality Control Information
- Custom Process Control Slipstream Applications
- Easy Use Graphics Oriented Operator Interface