There are two recycling methods for PET beverage bottles: chemical recycling and physical recycling. Chemical recovery method is a method to depolymerize waste PET bottles under certain reaction conditions to generate useful chemicals, such as producing low-grade fuel gasoline. Physical recycling is a method of re-granulating waste PET bottles through separation, crushing, washing and drying. There are two main physical recovery methods: one is to cut the waste PET bottle into pieces, separate HDPE, aluminum, paper and adhesive from PET, and then wash, dry and granulate the PET pieces; Second, non-PET magazines such as caps, seats and labels on waste PET bottles are separated by mechanical methods, and then washed, crushed and granulated. The former process: removing plastic products such as stones and wood and colored PET bottles by hand. The recycled PET must not contain PVC impurities, because its existence is the key factor affecting the color of PET. When the mixing amount of PVC is small, it can be separated manually on the conveyor belt, that is, when PVC and PET bottles are twisted, different physical phenomena occur at the stressed parts, and PVC bottles show opaque traces, while PET bottles do not, so that they can be separated. Some companies also use the different melting points of PVC and PET to pass broken PET and PVC fragments through a conveyor belt equipped with a heater to control a certain temperature. After melting, PVC will adhere to the conveyor belt, so it can be separated from PET. Ferromagnetic separators are used to separate iron. Some PET bottles are only broken once, others are roughly broken first and then subdivided, and finally become fragments with the size of 1.0- 1.5cm. A sieve with the aperture of 1.0- 1.5cm is installed at the outlet of the crusher to control the size of the fragments. Cleaning and impurity separation technology are the key to obtain high quality recycled PET. Plastic PE or finger labels are usually used for beverage bottles, and paper labels can be stuck with adhesive or during bottle blow molding. When the PET bottle is broken, some labels are broken into pieces, and some are still stuck with PET pieces. Broken PET usually adopts a combined separation device of blower and cyclone separator, which can remove about 98% of loose label fragments, or can be separated by a suction tower separation device, and the broken PET fragments are vertically added from the top of the separation tower. Debris and updraft form a countercurrent. By using the specific gravity difference between PET and tag fragments, the tag is extracted and PET comes out from the bottom of the separator. In order to ensure the efficiency of label separation, more than two sets of separation devices can be used in production. The purpose of cleaning is to remove the adhesive, ash and residue from the original bottle. 80- 100oC hot water is used for washing to soften or dissolve EVA adhesives or other types of adhesives used for sticking labels and substrates. In order to prevent the falling adhesive from sticking to PET chips again, additives such as alkali, emulsifier or other special chemicals need to be added to the water. The formula composition and content of cleaning solution are generally determined by the manufacturer according to the source and adhesive characteristics of waste bottles. The cleaning solution can be reused after reheating, and the cleaning can be carried out in a special cleaning tank equipped with a stirrer. In order to ensure cleanliness, the base is separated by using the different densities of HDPE and PET. The separation is carried out in septic tank, HDPE debris overflows from the top of the tank, and the sunken PET debris goes out from the bottom of the tank. Others use hydrocyclone instead of flotation tank for separation, and its separation effect is better. The water content of PET chips is usually reduced to 2% by centrifugal dehydrator, and then dried by belt or tube dryer to reduce the water content to 0.5%. PET cannot contain aluminum impurities, even a small amount of aluminum impurities will affect the transparency of recycled PET, so the aluminum content of recycled PET should be less than 50? 10-6. The easiest way to separate aluminum is to manually remove the aluminum cover and aluminum ring before crushing or reduce the aluminum content to 100 by electrostatic separation. 10-6, and this separation can be carried out on the conveyor belt; If PET chips are further purified by metal detection and separation system, the aluminum content can be lower than 5? 10-6。 There is little difference between regenerated PET extrusion granulation and primary PET extrusion granulation except for different feed. Single-screw or twin-screw extruder can be used for extrusion granulation, but the feed pressure of traditional extruder must be considered when designing, and the screw with larger feed size should be used instead. If twin-screw extruder is used, the effect will be better. The latter process: the recycling method is to separate the non-PET components in the PET bottle first, and then crush and recycle them. First, separate stones, wood, other plastic products and colored beverage bottles manually. PVC bottles can be separated by manual selection or PVC separation equipment. Metallic iron can be separated by a magnetic separator. The beverage bottles enter the cleaning machine after passing through the conveyor, and the bottles enter the processing production line vertically. The bottle cap and the pull ring are removed by the ring removing machine and the cap removing machine, and the bottle is weighed to ensure that the bottle cap has been removed. After testing, a bottle was found to be overweight, so it was separated from the production line. Then inject 100ml boiling water into each waste PET bottle to dissolve the remaining beverages in the bottle. At the same time, clamp and hang the bottle, brush the bottle with high-pressure water, soften the adhesive with hot water, so that the base will fall off automatically and the plastic or paper label will fall off. After washing, cut off the bottom of the bottle and the water in the bottle will be released. Crushing is like the equipment in the first process method. The PET bottle fragments are dried by a continuous dryer until the water content is lower than 0.05%. Extrusion granulation is the same as recovery method. Both of the above two recycling technologies are adopted by factories. Each process has its own characteristics. The first recovery method is easy to form large-scale production, but the separation technology is more complicated, there are more separation equipment, and the investment is larger. The second method has higher product purity, less equipment and less investment, but it is only suitable for intact beverage bottles. Broken or damaged beverage bottles need to be separated and recycled by other methods. In fact, considering the economic rationality of transportation, waste plastic bottles should be crushed and wrapped before transportation. Secondly, the recycling of cut bottle bottom is basically carried out according to the first method, so the second recycling method has great limitations.