After nearly 30 years of development, China's waste plastics recycling industry, especially due to the implementation of “supply-side†reforms, environmental protection, and prohibition of import of waste plastics, has emerged from family-style, decentralized to standardized, large-scale, large The trend of capital investment and other development. Compared with other renewable resources such as steel, glass, wood, paper, etc., waste plastics are various in variety, different in shape, difficult to distinguish, and the residue is diversified after use. Most of the mixed plastics have extremely low application value, resulting in a recycling process. Complexity and diversity. This paper tries to find the corresponding countermeasures from the difficult points of the waste plastics recycling industry.
Difficult analysis and breaking measures
1. Classification criteria
At present, there is no uniform industry standard for the recycling of waste plastics in China. The lack of standards is not conducive to the establishment of a unified market system, clear access conditions, and promote technological progress. The development of primary plastics and modified plastics is rapid, plastic products are changing with each passing day, and product standards are not perfect relative to other industries. The current popular classification is the plastic type marking code used by the American Plastics Industry Association (spi). This mark code is also used in many countries around the world, including China.
Compared to virgin plastics, the criteria for recycling plastics are more complex and complex, such as the type of plastic or modification, the residue of the previous application, the shape before regeneration, the degree of degradation, the miscibility with other types of plastics, and the color. and many more. The spi logo code is far from meeting the requirements for recycling and recycling of waste plastics.
People of insight in the recycled plastics industry have realized the necessity of setting standards. Relevant departments and industry organizations have begun to pay attention to this work. The relevant standards are in the process of being started. For example, there are related standards for individual types such as pet, but most others. There is still a gap, and there is an urgent need for overall planning and strengthening formulation. After years of exploration, Guangdong Zhishun Company has developed a set of practical classification standards for common pp/pe and other waste plastics.
2, sorting (separation) technology
There are many kinds of plastics. The current sorting methods are mainly manual sorting, which has problems such as low efficiency, great dependence on people's subjective judgment and poor working environment.
In recent years, many companies at home and abroad have been committed to the development of sorting technology, mainly using light refraction, light transmittance, density, thickness and other characteristics of the classification, but with the application of modified materials in a large number of plastic products, still need to overcome the following problems: 1) The difference in density of different kinds of plastics is not obvious, or the difference in density of modified plastics of the same kind is large, leading to misclassification; (2) different plastics are colored to cause folding (transparent) light to be invalid; (3) the same The type of plastic can be made into a film, a blow bottle, a press plate, etc., and the shape of the product is also difficult to distinguish.
Practice has proved that by formulating a unique classification standard system and method, improving the sorting equipment, and strengthening personnel training during the project copying process, the sorting problem can be better solved and the sorting quality can be improved.
3, cleaning technology
The use of water as a cleaning medium is still the primary means of removing impurities from waste plastics. Difficulties in cleaning technology: (1) The same type of plastic is a film and a certain thickness of plastic can not be cleaned with the same set of equipment; (2) different types of plastics before the application of different things to the residue, which often requires different cleaning Process and equipment; (3) Single plastic cleaning equipment is difficult to meet the requirements of different density plastic cleaning; (4) The same cleaning process must achieve sufficient cleanliness, and can not consume a lot of water, cleaning sewage should be easy to handle.
In the process and technology of waste plastic cleaning, it is necessary to develop different series of equipment for different types of waste plastics, which is conducive to grasping the characteristics of materials and impurities and solving major technical problems.
4. Modified granulation technology
Recycled plastics can be recycled and reused, and there is a downstream market, which is a key link to realize the recycling of waste plastics. Recycled plastics tend to be miscellaneous, and the previous application residues are complex; while downstream users use raw materials to require good quality stability of recycled plastics. Therefore, the plastic recycling process often needs to adjust the performance of recycled plastics, which requires modification. The modification technology of recycled plastics is different from the modification of virgin plastics, because the performance index of virgin plastics is very stable, and recycled plastics are unpredictable. How to use this poorly stable raw material to produce a stable product is a difficult problem to be solved.
To this end, the following two methods can be used in combination: one is to develop modified masterbatch for common defects in the recycling process of waste plastics, and to add as needed; the other is to combine the stylized connection of the process to reduce system errors and operator skills, The requirements of skills, so as to achieve the goal of maintaining product quality and reducing manufacturing costs.
5. Supporting environmental protection technology
The waste plastics recycling industry started in China with low threshold, high pollution, workshop type and point dispersion. The early employees were of low quality and the working environment was bad. The sewage waste gas and residual waste were discharged at will, and the imported waste plastics were entrained with “foreign garbageâ€. "Whether, leading to standardized enterprises are unprofitable, few large enterprises have entered the waste plastics recycling industry, so the industry is often criticized by the Chinese.
Environmental protection issues in the waste plastics recycling industry include: wastewater, waste gas, noise, dust, solid waste, hazardous waste, etc. Different types of waste plastics and different treatment processes produce different environmental pollutants, so environmental protection measures should be targeted.
One of the solutions is to develop the main process equipment and the supporting equipment that meets the environmental protection requirements according to the types and states of different waste plastics, and effectively combine them to form a “technology + equipment†module to provide one-stop solution for enterprises. Program. Such as "Zhishun?mcb?500 type pp/pe waste plastics regeneration module" and "Zhishun?mcb? waste plastic film regeneration module", have been selected by the Ministry of Industry and Information Technology 2017 "Industrial Resources Comprehensive Utilization Advanced Applicable Equipment Catalogue" and The catalogue of major environmental protection technology equipment encouraged by the state is valuable in that both can use the same sewage treatment unit facilities.
6. The contradiction between the dispersion of waste plastic resources and the scale of recycling production
Waste plastics have the characteristics of scattered resources, light weight and large volume. They are more suitable for storage and transportation than other renewable resources, especially foamed plastics. The long-distance transportation cost is too high. For example, large enterprises or industry organizations can establish data analysis systems for national waste plastics production and composition, and market demand for recycled plastics, and manage and mine big data to realize information sharing, industry and other resource sharing, and industry linkage. The country will rationally arrange different types of waste plastics recycling, sorting, cleaning and recycling production lines, arrange for local disposal or grading and transportation.
The comprehensive and perfect solution is to develop a complete set of special equipment for recycling stations to achieve the near-crushing and cleaning of waste plastics, high compression ratio packaging, etc. Second, the development of a "technical + equipment" standardized module that is easy to copy. Taking the 500-type pe/pp waste plastics regeneration module as an example, the capacity of a single module is suitable for the disposal of waste plastics in the domestic garbage of the prefecture-level city with a population of about 300 km or less. For areas with large capacity demand, superposition Multiple modules are available. The series of solutions solves the problem of distributed collection, pooling, centralized disposal and production scale as a whole.
to sum up
The difficulties in the waste plastics recycling industry are interlocking and affecting each other. Enterprises in different links in the industrial chain need to break through the bottleneck of funds, promote technological innovation, expand the supply of waste plastics and sales channels, and foster a new mode of cooperation, from low quality, high energy consumption to high quality, low energy consumption, multi-variety, fine classification, high technology. The direction of application is developed, and after seeking a breakthrough, the “three unifications†of economic, social and environmental benefits will be achieved with all parties.
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