1. What is plastic
Plastic is a kind of high molecular organic compound, which is the general name of thermoplastic forming materials such as filling, plasticizing and coloring. It belongs to a kind of high molecular organic polymer family.
2. What are the common plastics in life?
The common plastic product materials in living mainly include polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC) and polyester (PET).
3. Current situation of waste plastic recycling
Volume of waste plastics
In terms of increment, the data of relevant institutions such as the Ministry of housing and urban rural development, the Plastics Association and the Chinese Academy of engineering show that the average daily removal volume of domestic waste per capita in China is about 1.1kg, of which the quality of plastic waste accounts for 12.1%. Therefore, the total amount of new plastic waste in China in 2021 may reach about 70 million tons.
Recovery rate of waste plastics
According to the report released by the China Materials Recycling Association, in 2020, China produced about 60 million tons of waste plastics, 21 million tons of landfill, 22 million tons of incineration, and 1 million tons of abandoned plastics, which leaked into the environment and caused plastic pollution, while the recovery was only about 16 million tons, and the overall recovery rate of waste plastics was 26.7%.
Current weakness of domestic plastic recycling market
Public information shows that the profit margin of plastic recycling enterprises is only 9.5% - 14.3%. Some waste investors and recyclers have low enthusiasm, and recycling enterprises are unable to continue to recycle low-value waste in the state of loss, while some are waiting and waiting. In addition, the domestic plastic recycling industry has not yet established a relatively complete monitoring and data platform.
Market demand for high-performance recycled plastics will meet explosive growth
Gao Yang, consultant of the joint working group on green recycled plastic supply chain, said at the release of China material recycling association that green and low-carbon recycling is the key to solving plastic waste pollution and accelerating the upgrading of the plastic industry. Under the guidance of the national carbon peak, carbon neutralization goals and the "14th five year plan" for the development of circular economy, the market application demand of environmentally friendly high-performance recycled plastics will usher in explosive growth.
4. Waste plastic recycling analysis
Physical recycling refers to the method of granulating and forming waste plastics directly after cleaning and crushing without damaging the polymer structure of plastics.
The physical recycling process is relatively simple and generally can accept most of the common plastics on the market. However, the disadvantages are also obvious. The plastic produced after physical recovery is usually low value plastic, and the performance of plastic will be reduced after multiple physical recovery, so it is difficult to achieve unlimited physical recovery. The application scenario of physical recycling is subject to many restrictions.
2. Chemical recovery
Chemical recovery is mainly to convert the polymer carbon chain in plastics into small molecules to produce fuel oil, chemical products, electricity or other products. Common chemical recovery methods include:
Incineration power generation
Also known as peroxide method, it can treat all types of waste plastics. The method converts carbon and hydrogen in waste plastics into carbon dioxide and water, generates heat energy, and finally converts it into power input and transmission system.
Incineration power generation generally includes fermentation, incineration and waste treatment. Waste plastics are mixed with other wastes and sent to incinerator for incineration after simple fermentation treatment. The heat energy generated during incineration is used to heat the water in the boiler and produce steam, which drives the steam turbine to generate electricity. The slag generated in the process and the fly ash collected in the flue gas will be sent to the landfill or reused after treatment, and the flue gas will be discharged to the atmosphere after treatment.
It is suitable for polyolefin waste plastics. Unlike incineration, there is no excess oxygen involved in the reaction. A small amount of oxygen reacts with the feed to produce syngas (carbon monoxide and hydrogen mixture). The final product can be used in coal chemical industry to produce methanol and ammonia.
Partial oxidation generally includes separation, cleaning and drying, crushing, melting, and gasification. The processes of sorting, cleaning, drying and crushing are consistent with those of physical recovery. Other processes are mainly introduced below:
Applicable to polyolefin waste plastics, there are two main categories. The first category is liquefaction process, which mainly includes thermal cracking, catalytic cracking and hydrocracking. Generally speaking, the main products of thermal cracking are heavy oil and wax, and the main products of catalytic cracking are light oil. The products of both can be used for petrochemical fuel or chemical products (such as plastics). Hydrocracking requires hydrogen, which leads to high cost and poor economy, so it is less used; The second category is carbonization process. The products include coke, activated carbon and RDF. The products can be used for coking and chemical industry to produce functional carbon. The following mainly introduces thermal cracking and catalytic cracking in liquefaction process.
Thermal cracking: the principle of thermal cracking is to destroy the C-C bond in the polymer chain through high temperature and high pressure to produce a variety of hydrocarbons. The main processes in the thermal cracking process generally include sorting, crushing, cleaning and drying, anaerobic thermal cracking, dechlorination, condensation, phase separation and fractionation. Pyrolysis generally requires high temperature and high pressure. The light gas in the process can be changed into pyrolysis fuel. The oil produced by the fractionator can be changed into final products for sale after oil washing.
Catalytic cracking: the catalytic cracking process is similar to thermal cracking, but the only difference is that the catalyst is added in the thermal cracking process, which reduces the temperature and pressure required for the reaction and speeds up the reaction rate. In addition, different from the disordered decomposition of long polymer chains during thermal cracking, the presence of catalyst can make the waste plastics undergo directional decomposition. The main process flow of catalytic cracking process includes separation, crushing, cleaning and drying, catalytic thermal cracking, dechlorination, condensation, phase separation and fractionation. The gasoline, kerosene and diesel oil produced by the fractionator can produce products sold to customers after oil washing.
Unlike anaerobic cracking, which requires high temperature and high pressure to consume a lot of energy, extraction is mainly to crush and clean the waste plastics, extract the polymer long chain in the waste plastics once or multiple times with organic solvents, and finally extrude and granulate after centrifugation and crystallization to produce plastic particles for customers. The process generally includes sorting, crushing, cleaning and drying, extraction, crystallization and extrusion.
5. Policies related to recycled plastics
On January 19, 2020, the national development and Reform Commission and the Ministry of ecology and environment issued a new version of the plastic restriction order - opinions on Further Strengthening the control of plastic pollution. Compared with the old version, the new version plans the implementation objectives of plastic restriction in three time stages, And limit the use of plastics in four key areas (non degradable plastic bags, disposable plastic tableware, disposable articles for hotels and hotels, and fast plastic packaging).
In July 2020, the Ministry of ecological environment and the national development and Reform Commission issued the notice on Solidly Promoting the treatment of plastic pollution, requiring to strengthen the supervision and inspection of the prohibition of the production and sale of plastic products; Strengthen the supervision and management of plastic prohibition and restriction in retail catering and other fields; Promote the treatment of agricultural film; Standardize the collection and disposal of plastic waste; Carry out special cleaning of plastic waste.
In July 2021, the national development and Reform Commission and other departments issued the circular economy development plan for the 14th five year plan, which proposed that the special action for the whole chain treatment of plastic pollution should actively and steadily promote degradable plastics while "banning plastics"
On September 15, 2021, the national development and Reform Commission and the Ministry of ecological environment issued the action plan for plastic pollution control in the 14th five year plan. The plan further improved the whole chain control system of plastic pollution, and further refined the deployment of source reduction of plastic use, cleaning, recycling, recycling and scientific disposal of plastic waste.