In the current plastic recycling industry in China, the recycling of beverage bottles (PET) may be the most "money" and the most popular recycling project.
In post-consumer plastic recycling, there are two important factors that affect the quality of the final product: sorting and cleaning.
1. Sorting Most of the recycling companies in China currently use manual sorting when handling post-consumer bottles or other containers. In foreign countries, especially Europe and the United States, an automatic sorting device has been developed to accommodate large-scale materials. Processing requirements.
Principle: Sorting is the separation of doped PVC, other polymer bottles, and colored bottles from PET bottles. (Caps and labels cannot be removed during sorting.)
Almost all sorting systems are based on the same principle, that is, using different resins for different absorption of light. The raw material (the bottle after consumption) passes through a detector (infrared or X-ray) and the computer system identifies the type of the substance and determines whether the substance should be ejected from the material stream. To eject, the pneumatic valve behind the detector opens immediately and ejects the bottle from the material stream.
Maintenance: There is little maintenance on the separator. General maintenance is for conveyor belts, air valves, and compressed air. At the same time, the scale (setpoint) of the system needs to be updated when appropriate.
Computer Systems: All detectors are controlled by computer systems. In general separators, manufacturers provide network connections to diagnose and analyze problems in the production process and solve them.
Selection principle: Whether or not the separation system is selected is determined by the recycling company's throughput. The maximum output of the bottle separator has now reached 5000 KG/H. The choice of X-ray or infrared is generally determined by the user according to actual needs. Infrared can determine many new polymers and can remove impurities in PET very well.
Some very dirty bottles or liquids inside the bottle can cause the X-ray detector to misdetect. Many users choose the X-ray because its technology is very mature.
Bottle Chips and Color Separation Technology: In 1997, NRT (National Recovery Technologies) Corporation was commissioned by the U.S. Environmental Agency to develop a machine for separating PVC from PET bottle tablets. In the year 99, the machine (Flakesort) was put into use. It can achieve a 99+% effect when it is separated from clean, dry, 3mm or more bottle pieces. That is, if the raw material contains 1% of PVC, it can reach 0.01% after separation. (100PPM).
For color separation, when the visible light passes through the colored bottle, the bottle will appear shaded, so it is easy to separate the colored bottle from the transparent bottle. NRT also developed a combined separator to separate light blue, dark blue and black. Different color bottles [NRT company: email:]
The recycled PET is generally used to pull fibers, extrude plates, and remake bottles. For PVC fiber content of 100ppm will be able to meet the needs of the re-bottle PVC content is generally required to control below 20PPM. In the past several years when the author was engaged in the recycling of waste plastics, he had received samples from many domestic recycling factories and sent them to the United States or Europe for testing. As a result, the content of binders and PVC was very high, which also enabled us to recycle. The use and value of the material are much reduced.
2. Cleaning process A complete cleaning system generally includes: pre-washing, cleaning, rinsing, and other processes.
The pre-washing part generally uses the water at the back of the process to remove the abrasive contaminants on the surface of the material. The water used in this part comes from the cleaning process, otherwise the water will be discharged as waste water.
After the pre-wash part (heat), the glue of the adhesive label begins to melt and the PVC bottle begins to fade.
Cleaning (flakes): Residual glue and other contaminants can be separated by equipment such as cleaning tanks and horizontal separators. At the same time, in the cleaning process, continuous or intermittent cleaning can be selected according to whether the impurity content of the material is even or not. If the material impurity content is evenly selected for continuous cleaning, intermittent cleaning is selected for uneven content.
Rinsing process: It is possible to separate polymers with different densities and to wash the materials again and balance the pH.
Water treatment: Water treatment is important, not only for the function of the machine but also for the final product quality and disposal costs. A successful production line requires a filtration, treatment and recycling system with water.
Under normal circumstances, after such high-quality cleaning, the contents of various impurities are controlled at about 10PPM. (The content of PVC depends on the result of automatic or manual sorting)
Sorema, Italy has developed a new pre-wash method:
1) The possibility of automatic loading of equipment, thus minimizing the possibility of worker exposure to dirt.
2) The automation of the processing method and the possibility of using it on any washing equipment currently available.
3) The pre-wash system uses filtered drain water from subsequent washing equipment, so the use of water is only increased to some extent.
According to China Plastics Online, Sorema has developed Ekopet, a recycling technology specifically for PET bottles, which is accomplished by the following steps: hot washing and sorting of bottles; wet grinding; super cleaning; and Ekopet extrusion granulation.
Sorema claims that the PET pellets obtained using this technology can be reused in FDA-approved food packaging, and that after tackifying, the intrinsic viscosity has increased.
Sorema offers four types of systems with processing capacities of 500, 1 000, 2000 and 4000 kg/h.
[sorema email:]
It is reported that several domestic companies are currently discussing the possibility of bottle-to-bottle recycling with SOREMA. Perhaps China's plastic recycling companies will soon get rid of the small scale, disperse layout, and low quality of recycled processing products. The situation. In this way, a series of large-scale demonstration companies or demonstration bases have been established, scientific and reasonable resource recovery technology systems have been established, and high-quality recycling products have been produced. Recycled materials have been upgraded from the perspective of low-value fiber and plastic bags. Produce products with high value and profit.
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