A Summary of the Sorting Technology and Resource Technology of Waste Plastics in Domestic Waste
This paper briefly introduces the domestic and foreign domestic waste plastics sorting technology and resource technology, and proposes three optimized combination technologies of waste plastics recycling and sorting technology. It is recommended that environmental protection enterprises need to integrate the characteristics of domestic domestic garbage, rationally organize the recycling of domestic waste plastics, and use the combination of sorting process and equipment to obtain the best products and the largest resources.
With the rapid development of the social economy, the output of human urban domestic waste has increased year by year, and the proportion of waste plastics has also increased year by year. At present, the proportion of recyclables in urban domestic waste in China has exceeded 30%, mainly in plastics, paper, rubber, metal and glass, of which the proportion of waste plastics is quite large.
The impact of waste plastics on the ecological environment cannot be ignored. For example, because of its difficult degradation, it can cause "white pollution" problems. Domestically, the sorting methods for domestic waste and landfill waste plastics are mostly classified by sorting equipment. The sorted waste plastics seek a way out according to local market demand or government requirements.
The sorting method mainly utilizes the physicochemical properties of the waste plastics, and the waste plastics are separated from the domestic garbage by the corresponding sorting equipment. In terms of resource utilization, waste plastics can be directly regenerated, modified and regenerated, incinerated, catalytically cracked, hydrocracked, and the like.
At present, there is still no relatively complete technical system for sorting and supporting the use of waste plastics and resource utilization in China. There is no scientific research basis for the separation or disposal of waste plastics. The research is even weaker. Due to different national conditions, the classification of sources in developed countries such as Europe, Japan, and the United States is more meticulous, resulting in a more perfect post-pretreatment and resource utilization system. This work in China will take several years to reach. For example, in the United States in the recycling of waste plastics according to the constitution of waste sorting and resource utilization, Japan, the United States related units through the development of a hydrocyclone for the separation of plastics in the garbage; a United States Institute of Technology developed a selective separation of waste using solvents Plastic technology. For foreign waste treatment and resource utilization technology, China can only learn from the package.
Although there are many methods for resource utilization of waste plastics, some waste plastics recycling processes have higher requirements on the characteristics and purity of raw materials. For example, waste plastics are only deposited by single-function drum screens and gravity air sorters. There are many sundries. If it is used for granulation, equipment should be optimized and combined from the sorting process, and reasonable equipment combination and optimization should be used to meet the requirements of subsequent resource processing.
It can be seen that in order to keep up with the national environmental protection policy and meet the market demand, if the waste plastics treatment is truly "harmless, reduced, and resource-oriented", the domestic waste plastics sorting technology and its resources are in line with national conditions. Research and analysis of the linkages between technologies and technologies is imperative.
This paper briefly introduces the proportion and characteristics of waste plastics in domestic garbage, as well as the separation process and resource utilization of waste plastics, and comprehensively analyzes the links between several people, and draws the sorting of waste plastics to adapt to China's national conditions. And three sets of processes for resource utilization.
First, the proportion and characteristics of waste plastics in garbage
Since the organic matter in the landfill waste will degrade over time, there are some differences in the waste components in the landfills in various regions of China. For example, Qian Qianchun studied the waste plastics in a landfill that has been landfilled for 14 years and occupied a large proportion of waste components. Fang Wenjun's research on the old landfill in Jingmen, Hubei Province, shows that all the landfill wastes account for a large proportion of humus, plastics account for about 10%, humus accounts for 75.7%, plastics account for 10.1%, and stones account for 10.1%. 8.7%, wood bamboo, fabric, glass, metal, paper accounted for a small proportion, respectively 2.2%, 1.4%, 0.6%, 0.3%, 0.1%, other small or difficult to identify garbage (including shells , rubber, bones, diapers, leather, etc.) accounted for 0.9%.
Plastic is a polymer material formed by polymerization of monomers, which is divided into thermoplastic and thermosetting plastics. After the thermosetting plastic is formed by heat curing, it is infusible and insoluble, such as phenolic resin, epoxy resin, amino resin and the like. Plastics of this nature cannot be recycled by thermoplastics. Thermoplastics are widely used and can be repeatedly heated to soften melt flow molding and cooling hardening over a range of temperatures. Polyethylene, polypropylene, polyvinyl chloride, polystyrene, etc. are commonly used in thermoplastic household waste, and can be recycled.
In the past five years, through engineering practice and experimental analysis, it is known that the landfill waste sorting materials are the largest, and the film plastic bags account for the largest proportion of total waste plastics, with an average of over 70%. Among them, white plastic film (PE) and color film plastic (PE) were 24.5% and 39.7%, respectively. Most of the bottled plastics are recycled by the scavengers before landfill, and the film plastics are basically directly mixed with other wastes due to their low utilization value.
There are also some differences in the composition of waste plastics in landfills and domestic garbage, mainly C, N, O, S, Cl, Si, Al, etc. Studies have shown that the C content of waste plastics in landfills is newer than life. The waste plastics in the garbage are low, while the N, O, Si and Al are higher, and the difference in S and Cl contents is small.
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