How to ensure that waste plastics are reborn as high-quality recycled particles?

The primary challenge of plastic recycling is the cleanliness of the raw materials. Waste plastics are often mixed with oil, dust, label paper, metal fragments and other impurities, which not only affect the quality of recycled plastics, but may also damage the production line. Therefore, cleaning becomes the primary task of the granulation extrusion production line.

In order to achieve efficient cleaning, the production line usually uses a variety of cleaning equipment, including vibrating screens, flotation tanks, and powerful washing machines. The vibrating screen uses the principle of vibration to screen out large impurities and foreign matter in the plastic raw materials; the flotation tank uses the density difference between plastic and water to float and remove light impurities (such as paper scraps and foam) through bubbles; the powerful washing machine uses high-pressure water flow and detergent to deeply clean the plastic and remove oil, dust and other attachments.

More advanced, some production lines are also equipped with ultrasonic cleaning equipment. When ultrasonic waves propagate in liquids, they will produce strong cavitation effects and microjets. These tiny energy waves can penetrate into the tiny pores inside the plastic and completely remove the oil and dirt that are difficult to clean. Ultrasonic cleaning not only improves cleaning efficiency, but also ensures the stability of cleaning quality.

The cleaning process is not static, but needs to be adjusted according to the type of raw materials, degree of pollution and subsequent processing requirements. For example, for plastics with heavy oil pollution, the amount of detergent and cleaning time can be increased; for plastics containing a large amount of metal fragments, magnetic separation equipment can be added to remove magnetic impurities. In addition, the production line is also equipped with a water quality monitoring system and a detergent concentration detection system to ensure the quality and stability of the cleaning fluid, thereby ensuring the cleaning effect.

Although most of the impurities have been removed from the cleaned plastic raw materials, they are still large or irregular in shape, which is not conducive to subsequent melting processing. Therefore, crushing becomes another important link in the production line.

Crusher is a key equipment in the process of plastic recycling and reuse. It can crush large pieces of plastic raw materials into smaller particles for easy melt extrusion. According to the crushing principle and purpose, crushers can be divided into many types, such as shear crusher, hammer crusher, extrusion crusher, etc.

The shearing crusher uses the shearing action of the blade to cut the plastic raw materials into smaller pieces; the hammer crusher uses the high-speed rotating hammer head to impact and tear the plastic to achieve the purpose of crushing; the extrusion crusher uses the extrusion action of the screw to crush the plastic raw materials and discharge them through the screen. Different types of crushers have different characteristics and applicable scopes. The production line usually selects suitable crushers for combination use according to the type of raw materials and crushing requirements.

The size of the crushed plastic particles directly affects the efficiency of subsequent melting processing and the quality of recycled plastics. Therefore, particle size control during the crushing process is crucial. The production line usually adopts a multi-stage crushing and screening system to ensure that the crushed plastic particles have a uniform particle size distribution. The first-stage crusher crushes large pieces of plastic into smaller pieces, and the second-stage crusher further refines the particle size and performs graded screening through the screen to remove particles that do not meet the particle size requirements.

The production line is also equipped with a particle size detection system and an automatic adjustment system to monitor the size of the crushed particles in real time and automatically adjust the crusher parameters according to the test results to ensure the stability and accuracy of particle size control.

As the primary link of the granulation extrusion production line, cleaning and crushing are of great importance. They not only ensure the cleanliness and appropriate particle size of the raw materials, but also lay a solid foundation for the subsequent melting process. In the melting process, clean and uniform plastic particles can melt faster and more fully, improving the melting efficiency and the quality of the recycled plastic. At the same time, the crushed plastic particles have a larger specific surface area, which is conducive to heat and mass transfer in the melting process, further improving the melting effect.