Sorting plastic flakes in recycling.

13 November, 2018

Plastics are materials without which it would be difficult to imagine life today. Bottles, packaging, window frames, toys … an infinite number of products. All these things will one day end their exploitation period, eventually ending up in landfills and to utilization sites. Polymeric materials decompose for thousands of years, disrupting the natural physical and chemical processes that regulate the environment. One of the ways to change this is recycling. Although for most people this process begins and ends with throwing a plastic bottle into a correct container, in fact it is actually only the beginning of a long and complicated path that unnecessary plastic has to take in order to be reusable.
Plastic waste goes to recycling plants as it was collected – without distinction between color and type of material. In order for plastics to be reused, they have to be sorted according to these two criteria. In many places this work is done manually, although this is changing. The development of high-resolution digital cameras, as well increasingly powerful computers, have made it possible to use of optical sorters for this purpose. Because in the sorters, the rejection of material usually is realized with using compressed air, the sorted objects have to be small in size. To meet this requirement, the mixture of pre-cleaned waste, unlike manual sorting, is first cut into plastic flakes and then sorted by optical sorters.

How does the sorting of plastic flakes work?
Plastic flake sorting systems have to meet very high requirements because the differences detected are very small and the flakes themselves are small. In order for the recovered granulate to be allowed to be used again, e.g. in the chemical or textile industry, it has to meet high standards, comparable to the specifications of the original material.
How does an optical sorter work? The material in the form of flakes is fed into the hopper, from where it goes to the vibrating feeder. To create a single layer of material, in the next step the flakes are accelerated using a free fall. Then, when the material is below the edge of the chute, it’s observed by a high-resolution camera from which the image is analyzed by the computer. Depending on the results, the flakes continue free fall or, if they don’t meet the requirements, are rejected by compressed air valves.
Depending on the requirements, optical sorters allow you to sort plastic flakes by color or material. For applications where only the first option is required, the sorter is equipped with a monochrome or color camera, operating in visible light. Such configuration is enough to efficiently recognize the color of the objects, and at the same time cost-efficient.
In addition to sorting plastic flakes by colour and material, optical sorters have another function. We are talking about detecting impurities and other foreign bodies such as stones, sticks, pieces of labels, etc. Although plastic flakes are not the first step in the reprocessing of plastics, they may still contain certain contaminants that are as dangerous as foreign plastic inclusions for further processing steps. This example shows that investment in optical sorter is not only investment in greater efficiency, but also in production safety to avoid long-term and expensive downtime.

Why we need to recycle plastic?
There are several reasons for recycling. Plastic granules can be used to re-produce bottles, fleece clothing and other types of sports clothing with good thermal properties. Plastic flakes are also used to make various types of films and packaging strips, as well as packaging that is suitable for contact with food – all in harmony with environment. Recycling not only saves natural resources, but also allows the re-use of materials that would decompose over hundreds of years, or would have been incinerated, poisoning the natural ecosystem.
Recycling is not only ecology, but also business. Recycling is based on maximising the use of available secondary raw materials with minimum energy input This is what the technology of converting plastics into plastic flakes makes possible. Modern sorting machines, such as AVISCAN, make it possible to re-use the available material at a low cost of operation.
The energy required for recycling is less than that required to produce completely new materials. According to various sources, the difference is from a few to several dozen percent, depending on the type of material. Thanks to optical sorters, the quality of the recovered raw materials is as high as the original ones and meets the production requirements.

AVISCAN is device dedicated to sorting loose products, such as plastic flakes. A special feature of our devices is the high precision. Thanks to it, AVISCAN optical sorters ensure almost 100% accuracy in rejecting unwanted materials and a small loss of good material. The patented speed equalization technology ensures that the compressed air goes precisely into the unwanted object. As a result, the use of secondary raw materials is even better. High resolution cameras combined with powerful computers guarantee high performance of sorting system. AVISCAN sorters can work with all types of plastics, such as: PET, HDPE, PVC, PVC or LDPE.

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