In 2010, European polymer producers generated some 104 billion euros in turnover (Plastics – the facts, 2011), about the same as for the European production of raw steel1. A major difference between the polymers and steel cases is that European recyclers contribute approximately 35 billion euros per year of secondary steel but only 2 billion euros per year of secondary polymer value to the raw material market (Earnings, jobs and innovation: the role of recycling in a green economy, 2011). The reason for this difference is that recycling processes for steel are relatively simple and cheap, whereas the recycling of polymers is generally complex and expensive. In order to improve the economy of plastics recycling, the European Commission granted an FP7 project (W2Plastics) to a consortium of research institutes and industries in 2009. This W2Plastics project (www.w2plastics.eu) focuses on the separation of polyolefins, and more specifically on packaging polyolefins, which represent approximately 30% of the total polymer production. The central goal of the project is to achieve an innovative process for the purification of polymers from mixtures of post-consumer polyolefin wastes. The W2Plastics process separates such mixtures into different grades of polyethylene (PE) and polypropylene (PP) using magnetic density separation assisted by online quality control by hyperspectral imaging.
Polymers and steel each represent about one fifth in value of all the raw materials needed for consumer products and constructions (i.e. excluding raw materials for energy production).
Urban Mining Delft
An important part of FP7 projects is to disseminate their successes to the European industry, so as to ensure widespread implementation. Urban Mining Delft (UMD) was set up by the Delft University of Technology (the coordinator of the W2Plastics project) to facilitate the transition of the technology from the research phase to industrial practice. UMD holds patents to part of the innovative technology involved in the process. A number of scientists involved in the W2Plastics project have a position in the Industry & Science Board of the company.
Shredded handpicked polyolefin mix (left) and four products produced by MDS (right).
Applications of the w2plastics technology
Important applications of the W2Plastics technology are the separation of the rigid fraction of shredded packaging waste, plastics mixes from E-waste recycling, and the purification of the major polymers from some mono-streams of shredded EOL products. The largest of these applications is rigid packaging waste, and the polyolefin fraction in particular. The technology most often applied on packaging waste separation in Western Europe is based on Near Infra-Red (NIR) sensing and ejection of the recognised polymer objects from the waste flow by compressed air. As this technology is expensive (approximately 170 euros per ton of input), it is typically performed on expensive separately collected packaging waste, not on raw household waste. One of the problems of NIR sorting is that it leaves a rather large mixed residue fraction with a negative value. After washing and shredding, the W2Plastics technology is able to extract individual polymer products from this residue.
A second source of polyolefin packaging waste is in Eastern Europe, where hand pickers take rigid plastic objects directly from the flow of household waste and classify them into different types of polymers at a cost of approximately 200 euros per ton of product. One of these polymer classes consists of mixed polyolefins. The W2Plastics technology can separate this mix into PP and PE products.
Details of the basic MDS technology.
Specifications of the technology
At the heart of the separation process, the Magnetic Density Separator (MDS) cuts the shredded mixed input waste into four different density ranges of polymer products and a fifth product, or residue, that is either much heavier than water (e.g. metals, glass etc.) or much lighter than water (e.g. foam, wood), depending on the type of application. The input typically has a particle/flake size between 1 mm and 10 mm, and a flake thickness of 0.3 mm to 3 mm. Capacity depends on the average flake thickness but is of the order of 3 tons per hour for an industrial unit with an investment cost of approximately 2 Million euros. Online quality control of the input and the polymer products is performed by Hyperspectral Imaging (HSI, see figure below). Further details of the technology are given in table above.
Analysis of a feed stream (above) by Hyperspectral Imaging (below). Red particsls = PE, Green particles = PP.
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