PET beverage bottle recycling methods include chemical recycling and physical recycling. The chemical recycling method is a method of depolymerizing PET waste bottles under certain reaction conditions to generate useful chemicals, such as producing low-grade fuel gasoline. The physical recycling method is a method of re-granulating waste PET bottles through separation, crushing, washing and drying. There are two main physical recycling methods: one is to chop waste PET bottles into pieces, separate HDPE, aluminum, paper and adhesives from PET, and then wash, dry and granulate the PET fragments; the other is to first The non-PET bottle caps, bottoms, labels and other materials on the waste PET bottles are separated mechanically, and then washed, crushed and granulated. The former process: use manual methods to remove stones, wood and other plastic products and colored PET bottles. Recycled PET must not contain PVC impurities because its presence is a key factor affecting the color of PET. When the amount of PVC mixed is small, it can be separated manually on the conveyor belt. That is, when subjected to torsion, PVC and PET bottles will produce different physical phenomena in the stressed part. If there are opaque traces on the PVC bottle but not on the PET bottle, 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. The PVC is melted and adheres to the conveyor belt, so that it can be separated from PET. The separation of iron uses a ferromagnetic separator. Some PET bottles are broken only once, and some are coarsely broken first and then broken into subdivided pieces, eventually becoming fragments of 1.0-1.5cm in size. A screen with an 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 keys to obtaining high-quality recycled PET. Beverage bottles usually use plastic PE or finger labels. Paper labels can be glued with adhesive or during the bottle blow molding process. When the PET bottle is broken, some of the labels are broken into pieces, and some are still adhered to the PET fragments. , the subsequent broken PET usually uses a combined separation device of a blower and a cyclone separator, which can remove about 98% of the loose label fragments. It can also be separated by an air extraction tower separation device. The broken PET fragments are added vertically from the top of the separation tower, and the fragments are formed with the updraft. Counter flow uses the difference in specific gravity between PET and label fragments to remove the label and PET comes out from the bottom of the separator. In order to ensure label separation efficiency, more than two sets of separation devices can be used in production. The purpose of washing is to remove adhesives, dust and residues from the original bottle. For washing, use 80-100oC hot water to soften or dissolve the EVA adhesive or other types of adhesives attached to the label and base. To prevent the peeled adhesive from adhering to PET fragments, additives such as alkali and emulsification need to be added to the water. Agent or other special chemical agent. The formula composition and content of the cleaning liquid are generally determined by the factory based on the source and bonding characteristics of the waste bottles. The cleaning liquid can filter out impurities and reheat for recycling. Washing can be done in a special cleaning machine equipped with a stirrer. It is carried out in the selection tank. In order to ensure the cleaning effect, the washing can use a two-level washing process. The separation of the base is to use the different density characteristics of the base HDPE and PET to separate them. The separation is carried out in the corrosion cleaning tank, the HDPE fragments overflow from the top of the tank, and the sinking PET fragments go out from the bottom of the tank. Some use hydrocyclone separation instead of flotation tanks, and the separation effect is better. PET chips usually use a centrifugal dehydrator to reduce the moisture content of the chips to 2, and then dry them with a belt or tube dryer to reduce the moisture content to 0.5. PET cannot contain aluminum impurities. Even trace amounts of aluminum impurities will affect the transparency of recycled PET. Therefore, the aluminum content in recycled PET should be less than 50?10-6. The simplest way to separate aluminum is to manually remove the aluminum cover and aluminum before crushing. Rings or electrostatic separation methods can be used to reduce the aluminum content to 100?10-6. This separation can be performed on a conveyor belt; if the PET fragments are further purified through a metal detection separation system, the aluminum content can be lower than 5?10-6. Except for the difference in feed materials, there is not much difference between recycled PET extrusion and granulation and virgin PET extrusion and granulation.

Extrusion granulation can use a single-screw or twin-screw extruder, but when designing, it must be considered that the feed pressure of the traditional extruder is too large. Instead, use a screw with a larger feed part size. If a twin-screw extruder is used, Better results. The latter process flow: This recycling method is to first separate the non-PET components in the PET bottles and then crush them for recycling. It first uses manual methods to separate stones, wood and other plastic products as well as colored beverage bottles. The separation of PVC bottles can be carried out by manual selection method or PVC separation equipment. Metallic iron can be separated using a magnet separator. Beverage bottles enter the cleaning machine after passing through the conveyor. The bottles enter the processing production line vertically. The bottle caps and tabs are removed through the ring removal machine and the cap removal machine. The bottle caps are weighed to ensure that the bottle caps have been removed. The test found that the weight of a bottle exceeds the standard. Separate it from the production line. Then inject 100ml boiling water into each waste PET bottle to dissolve the remaining beverage in the bottle. At the same time, clamp the bottle and hang it up. Use high-pressure water to scrub the outside of the bottle and use hot water to soften the adhesive so that the base will fall off by itself and the plastic or paper label will be removed. come out. After washing, cut off the bottom of the bottle and release the water in the bottle. The crushing equipment can be used as in the first process method, and the PET bottle fragments are dried through a continuous dryer until the moisture content is less than 0.05. Extrusion granulation is the same as the recycling method. Both of the above recycling technologies are used by factories. Each of its craftsmanship has its own characteristics. The first recycling method is easier to achieve large-scale production, but the separation technology is more complex, requires more separation equipment, and requires larger investment. The second method has higher product purity, uses less equipment, and saves investment, but it is only suitable for complete beverage bottles without damage. Flattened 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 flattened and bandaged before transportation. Secondly, the recycling of the cut bottle base is basically carried out according to the first method, so the second recycling method has greater limitations.