Study on comprehensive treatment of the hottest pl

2022-09-21
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Research on the comprehensive treatment of plastic packaging waste

(Guangzhou University) table 1 the annual per capita discharge of urban waste in some countries in the world name of the United States, Britain, France, Germany, Netherlands, Switzerland, China emissions (kg) table 2 the annual per capita discharge of urban domestic waste in Guangzhou table 3 the plastic content in urban domestic waste in some countries in the world project United States, Britain, France, Germany, Netherlands, Switzerland, China plastic content (PP) 52.543433 other packaging waste content other content 454 New materials are an important aspect of the technological revolution. Due to the development of plastics and its superior properties, plastic packaging is becoming more and more extensive. Considering the structure, plastic packaging containers can be divided into boxes, barrels, bottles, bags and large containers; Considering the molding method, it can be divided into injection, die-casting, hollow and vacuum molding containers. The cost of products is nearly 90% lower than that of traditional materials. Plastic packaging waste refers to the plastic packaging containers and materials that lose or complete the function of maintaining the original value and use value of the contents and become solid waste, The comprehensive treatment of plastic packaging waste refers to the treatment (i.e. reducing the volume of plastic packaging waste) and utilization (i.e. extracting from plastic packaging waste or converting it into usable resources and other raw materials through 'recycling, processing, etc.). 1、 The content of plastic packaging waste in urban life when plastic packaging container loses or completes the function of maintaining the original value and use value of its contents, it, like other packaging waste, becomes solid waste and joins the ranks of garbage. Data show that the United States produces 150 million tons of domestic waste every year; In recent years, the amount of urban domestic waste in China has reached 150 million tons, taking Shanghai and Guangzhou as examples. Shanghai has produced about 10000 tons of urban domestic waste per day; Guangzhou has a daily output of more than 5000 tons of urban domestic waste (see Table 1 and table 2 for details), and about 1/3 to 1/2 of these urban domestic waste are packaging waste, of which plastic packaging waste is about 35% For example, packaging waste in the United States accounts for about 33% of urban domestic waste, Japan accounts for about 40%, EU countries account for about 30% to 50%, and China accounts for about 30% to 40% (see Table 3, table 4 and table 4 for details. The content of plastic in Guangzhou urban domestic waste in the year of placement. The content of other packaging waste in other packaging materials 19865.09.185.9 table 5 the average content of plastic in world urban domestic waste and the total plastic content in several years. The total amount of plastic waste (106 tons) Table 6 plastic content and quantity of municipal solid waste in Guangzhou * II. Pollution status and harm of plastic packaging waste the annual output of plastic in the world has exceeded 100 million tons, of which about 30% is used for packaging. After one-time use, most of these packages have become solid waste. Due to its light weight, large volume and large quantity, it is difficult to degrade and cannot be incinerated at will. Most of it is discarded beside the railway, inland waters, urban streets and alleys. Over time, it has become a shocking "white pollution" zone. According to the investigation of relevant departments, the total amount of waste plastic discharged into the environment in Shanghai every year is 290000 tons, including 673million disposable foaming tableware, weighing 3363 tons; The daily output of garbage in Beijing is 12000 tons, and plastic waste accounts for 360 tons; The daily output of garbage in Guangzhou is about 5000 tons, and plastic garbage accounts for 755 tons. White pollution and serious harm are shown as follows: some plastic products contain harmful substances such as PVC and acrylonitrile, which will produce HCl when burned. HCl is one of the important reasons for acid rain. At present, acid rain areas in China account for 30% of the land area, and the frequency of acid rain in Central China is as high as 90%. The use of carbon oxychloride (CFC) and Freon (discontinued) in the production of foamed plastics will destroy the ozone layer in the atmosphere, lead to excessive ultraviolet radiation, aggravate the greenhouse effect and destroy the atmospheric ecological balance. Plastic garbage not only causes long-term visual pollution, but also provides breeding grounds for rats, mosquito ropes and bacteria. Plastic garbage will also release a variety of toxic chemical gases. It is conceivable that an increasing number of white garbage that is difficult to degrade will succeed in the world's * large toxic gas reservoir if no measures are taken. First of all, it destroys the ecological balance of soil and reduces the yield of crops. China is a big country in the use of agricultural mulching film, with an annual use of 800 ~ 900 thousand tons. According to the special investigation of the agricultural department, the residual activities in fields, soils and rivers all over the country every year, which hinder the absorption of water by plants and the growth of roots, degrade the quality of cultivated land and reduce the yield of crops. According to expert measurement, when the residual plastic products per mu reach 3.9kg, the output of various crops can be seen in Table 7 Table 7 the impact of plastic residue on crop output. Crop types corn wheat rice soybeans vegetables production reduction 11 the impact of pollution on land ecology. Many cities and towns in China use landfill method to treat garbage, while plastic garbage is large and difficult to degrade, which not only takes up a lot of land resources, but also pollutes groundwater. The land filled with garbage cannot grow crops and trees, which will make a large area of land lose its use value, If mulching film is used for a long time and effective measures are not taken, many cultivated land will not be harvested in 15 years. In recent years, the economic losses caused by environmental pollution and ecological damage in China have reached 200 billion yuan per year, including 100 billion yuan of ecological damage. Nearly 300million mu of cultivated land has been polluted by "three wastes" and pesticides. Due to pollution, grain production has been reduced by 25.6 billion jin. Endangering human health, a variety of animals and plants are on the brink of extinction. The hole in the ozone layer will destroy the human immune system and increase the chance of cancer and the incidence rate of white malaria. A variety of toxic chemical gases released by plastic waste will make people thin, liver dysfunction, nerve damage, and induce cancer. Styrene, the free unit of polystyrene products, will be harmful to health after it is heated and released into the human body with food. Climate change, population surge, and new diseases in Kangnai, the United States, including pollutants and chemical pollution * are serious. 3、 Separation technology of plastic packaging waste plastic packaging waste can be separated from other waste manually or mechanically (gravity method), and then adopt visual identification, combustion identification, specific gravity identification, solvent separation, wind screening, electrostatic separation, low-temperature powder crushing and other methods. For waste plastics in small quantities, the following methods can be adopted for classification: first, remove the sundries such as metal, glass, rope and waste plastics with serious pollution; Secondly, agricultural film, packaging film, foam plastic, plastic bottle box are classified; Third, classify the products according to the color depth; Base 4 uses simple methods such as visual inspection, hand feeling, specific gravity and combustion to classify commonly used PVC, polystyrene, polypropylene and other plastics. All kinds of plastics have different densities. Put different kinds of plastics in a specific solution, and classify and identify them according to the sinking and floating of plastics in the solution. Because plastics are non wetting, surfactants are often used for pretreatment, wetting and sorting. Commonly used plastic solutions include water, saturated salt solution, alcohol solution and calcium chloride solution. The separation of waste plastics is realized by using different solubility of various plastics in organic solution. The method is to add waste plastic fragments into a specific solution, control different temperatures, and selectively dissolve and sort various plastics. This technology has less solvent loss, and the recovered polymer can be reused after heating and granulation, with good performance. When there is a large amount of waste and sundries, wind screening technology can be used. This method is to throw the crushed waste plastic from the top in the re screening room, spray air from the horizontal, and screen it by using the self weight of the plastic and the different resistance to the air. Electrostatic separation technology originates from the dry separation method, which is characterized by the separation of granular substances with a diameter of less than 8mm, which has nothing to do with density. Its size and shape do not affect the separation, and it consumes low energy and has a large processing capacity. 4、 Recycling of plastic packaging waste is very harmful to the environment and society, so recycling it is particularly important. Generally, the following ways can be taken: first, manufacturing building materials, second, manufacturing daily necessities, and third, manufacturing chemical products; Its four cracking gas, oil and monomer; Fourth, it is burned together with other garbage for heat recovery (steam, hot gas and power generation). Recycling of waste polyethylene PVC accounts for more than 30% of plastic products in China. The recycling of waste PVC is mainly to directly recycle or supplement appropriate new materials, and re produce various products. When these recycled materials are too dirty to make other products, they can still be used as infrastructure and water conservancy products (pipes, grooves, belts, plates, etc.). The recycled products of waste PVC should be added with corresponding additives according to different varieties to meet the use requirements. The formula is shown in Table 8. The composition of PVC is complex. In addition to resin, there are certain auxiliary materials such as plasticizers, stabilizers, lubricants, pigments, etc. These additives will volatilize and lose in varying degrees due to the action of light and heat in the process of use. In the process of replication, an appropriate amount of additives must be added to make the PVC waste plastic maintain good physical mechanism performance after replication. Waste polyethylene plastic is reacted with coal tar in the reaction. In the presence of catalyst, less concentrated components such as naphthalene and anthracene in coal tar are easy to react with bonded PVC molecules to form a two-dimensional structure, Thus, the softening point of tar pitch modified by table 8 waste polyethylene recycling material formula material soft hard soft foam plastic waste PVC material dibutyl phthalate alkyl benzene sulfonate tribasic lead nitrate barium stearate or paraffin Azodicarbonamide can be raised. Its performance is better than that of general petroleum asphalt felt, tar asphalt felt and tar asphalt felt, especially with good low resistance and softness, which is especially suitable for construction in northern areas. Its specific operation: add asphalt in the enamel reactor, mix it electrically at 150 ~ 200r/rain, raise the temperature to 150~170, reverse apply it for 3h, add filler, and mix it for a moment to produce the modified tar asphalt. Basic formula: 100 parts of tar, 12-15 parts of waste PVC plastic, 29-32 parts of plasticizer and 30-50 parts of filler. Polystyrene can be divided into GPS and EPS. EPS is mainly used in the form of foamed plastic as shockproof packaging materials for household appliances such as televisions, refrigerators, washing machines, precision instruments and handicrafts. It is also used in food packaging such as fast food lunch boxes, and can also be used as thermal insulation materials. This improves the effect of vicious competition in the market. Most of the packaging materials are disposable and become waste when used up. There are two molding methods for polystyrene foamed plastics: one is direct foaming method, and the other is expandable bead method. These two methods are physical processes, which do not damage the polymer structure of polystyrene, so that it still retains its original properties, so it can be recycled. Taking the waste fast food box as an example, the process flow is: Waste fast food box washing drying crushing forced feeding pre plasticization extrusion plasticization (machine head with quick change filter) - molding cooling granulation bagging-75 extruder. The apparent density of waste polystyrene foam is 20 25kg/m3, and the wet density of concrete made after processing and mixing is 220270kg/m3, which is basically equivalent to expanded perlite. The density after drying can be greatly reduced, and there are no special requirements for the cement mixed with it. There are many ways to make light building materials from waste polystyrene foam. For example, polystyrene foam particles, cement as binder, crushed

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