The development of the hottest plastics industry a

2022-08-04
  • Detail

Development of Plastics Industry & Protection of natural environment Abstract: plastics, together with steel, wood and cement, constitute the four basic materials of modern industry and play an important role in the working principle of digital sensors of electronic universal machines in the development of national economy. Plastics are widely used in industry, agriculture and people's daily life because of its excellent comprehensive properties, convenient processing, and significant energy saving in production and use. With the vigorous development of the plastic industry and its large-scale use, the environmental pollution caused by waste plastic products and plastic garbage is becoming more and more serious. The waste and disposal of plastic products has caused a series of environmental problems. "White pollution" has become a well-known synonym for environmental pollution caused by plastic materials, and has become a global environmental hazard. It is of great significance to correctly understand the impact of waste plastics on the environment and actively study their treatment and disposal processes for environmental protection and resource utilization

key words: white pollution waste plastics environmental recycling and utilization

1 definition of white pollution

plastics are widely used as packaging materials for various products because of their low price and convenient forming. With the development of modern plastic industry and the improvement of consumption level, most of them are disposable products, which are discarded after use, causing environmental pollution. For example, the white foamed polystyrene plastic used as packaging materials for electrical appliances, industrial instruments and meters, as well as fast-food boxes and beverage cups, is characterized by large volume, light weight, non decay and non decomposition. It is discarded by people after use, causing white foamed plastic products everywhere along the railway, river routes, cities and scenic spots, seriously affecting the environment and city appearance and health, and is called "white pollution" by people

plastics are a kind of polymer materials. Ethylene, propylene, vinyl chloride, styrene, etc. can be prepared from petroleum. Under certain conditions, the molecules of these substances can react with each other to produce compounds with large molecular weight (i.e., polymers): polyethylene, polypropylene, polyvinyl chloride, polystyrene. The plastics we usually use are the materials composed of the above four polymers (polyethylene and polypropylene films make a brittle sound when shaking, while PVC films are soft and do not make a brittle sound when shaking; foamed plastics are generally polystyrene and have thick smoke when burning). Since the 1960s, plastics have entered a stage of wide application. Because plastic has many advantages: it is easy to obtain materials, low price, convenient to process and light in texture, it is very popular in the world as soon as it comes out. It quickly infiltrates into all aspects of social life. Plastic is made into bowls, cups, bags, basins, barrels, tubes, etc. Plastic is listed as one of the greatest inventions in the 20th century. The popularity of plastic is known as the white revolution

with the rapid development of modern society, white pollution is becoming more and more serious, which has brought great harm to people: (1) caused "visual pollution": disposable plastic products discarded in the environment at random have caused people a sense of "dirty, disordered and poor" visually, which has damaged the landscape aesthetics of cities, rural areas and scenic spots, and even affected people's work and life emotions. It has also damaged the city's appearance and health, It has brought great difficulties to the establishment of a national health city. (2) Cause damage to the natural ecological environment: disposable plastic products are difficult to degrade in the natural environment due to the strong stability of its raw material - polymer resin. They can exist for hundreds of years or even thousands of years. Such a large number of long-term accumulation will cause damage to the natural ecological environment. Direct damage includes: mixing in the soil will affect the growth of crops, resulting in the reduction of crop production; Being eaten by poultry, livestock, wild animals (even endangered wild animals) will lead to their death. Indirect damage mainly refers to the damage to the environment caused by the disposal of disposable plastic products. If the landfill method is adopted, it will continue to occupy valuable land resources; If the incineration method is adopted, a large amount of toxic and harmful gases will be generated and the atmospheric environment will be damaged; In addition, the use of HCFCs as blowing agent in the production of foamed plastic lunch boxes and packaging materials will seriously damage the atmospheric ozone layer. (3) Impact on human health: recent studies have found that a certain amount of styrene monomer remains in the disposable foamed plastic lunch box with polystyrene PS as raw material, which is harmful to human health. Foreign developed countries have restricted the use of PS plastics in food packaging, or required coating treatment on its surface

according to literature reports, in 1995, China's total output of plastic products was nearly 7million tons, of which about 1.7 million tons were used as packaging materials. After these packaging materials were used, about 500000 tons were used as solid waste into the urban solid waste treatment system, and the other part was thrown away by users, forming plastic waste. These plastic wastes are discarded on the roadsides, greenbelts or shade trees of prosperous cities and tourist attractions, damaging the urban landscape and affecting the city appearance $in windy cities, the discarded plastic bags dance with the wind, posing a great threat to the urban power supply system. In 1996, there were more than ten short circuit accidents caused by wrapping plastic bags around overhead power supply lines in Tianjin electric power industry (plastic packaging for food and drink is a hotbed for mosquitoes, flies and bacteria to survive and reproduce, which is very easy to cause the spread of bacteria and affect environmental health and the health of the urban public.

as early as the early 1970s, industrial developed countries such as the United States, Italy, Germany, Japan and France had established sound urban waste collection and classification systems and used the method of actual landfill and incineration to treat solid waste, but It will bring pollution to the living environment such as underground water sources, rivers, lakes and the atmosphere. For example, three incineration sites in Paris, France, incinerate about 5kt of garbage every day, and use the steam generated by combustion heat to heat the area of 35000 people. As a new resource technology for direct energy recovery without secondary public hazards, a thermal decomposition plant has been established in Maryland near Washington, D.C., with an investment of 15million US dollars. It can process 1kt of garbage per day. In addition to producing 90t of steam per hour, it can also recover 70 t of iron, 170t of glass and 80t of carbon powder. In addition, there are microbial decomposition technology and the establishment of a comprehensive treatment system for the recycling of municipal solid waste. With the increasingly extensive application of plastics, the plastic waste in urban garbage in industrial developed countries has reached as high as 10%, so the recycling of waste plastics in urban garbage has been paid more and more attention. It is difficult to recycle plastics from household garbage. General garbage contains ordinary plastics of average quality, and different kinds of plastics are mixed together. The pollution is serious and the recycling cost is expensive. The main difficulty of recycling is collection and classification. The remanufactured product market is limited due to high processing costs

2 impact of treatment methods on the environment

at present, more than 800million plastic fast-food boxes are discarded along the railway in China every year. With the development of urban fast-food industry, the annual amount of discarded fast-food boxes is as much as 10billion, of which more than 80% are not recycled and scattered in the environment, weighing more than 80000 tons

at present, the plastic products widely used in China's market are non degradable plastics, with expanded polystyrene, polyethylene or polypropylene as raw materials, with a molecular weight of more than 20000. Only when the molecular weight is reduced below 2000 can it be used by microorganisms in the natural environment to turn into water and other organic matter. This process takes 200 years; If it is landfilled, it will affect the absorption of nutrients and water by crops, resulting in reduced production; Burning it will release a variety of chemical toxic gases, including dioxin, which is extremely toxic. Even if a small amount is ingested, it can cause deformity and death of birds and fish, damage the ecological environment and do great harm to people. At the same time, people are lack of awareness of environmental treatment, unable to recognize the importance of environmental treatment

at present, the most important method of urban waste disposal in China is landfill, accounting for more than 70% of the total disposal, followed by high-temperature composting, accounting for more than 20%. With the improvement of residents' living standards, the organic matter, combustible matter, recyclable matter and usable value of urban domestic waste have increased greatly. Therefore, it is very important to promote the classified collection of waste and the industrialization of waste treatment for the harmless treatment of waste. The three main waste treatment technologies, landfill, composting and incineration, commonly used internationally, are based on the classified collection of waste, while the main component of urban domestic waste is food waste. According to the statistics on the composition of garbage in various provinces, the proportion of food garbage in Beijing is 37%, that in Tianjin is 54%, that in Shanghai is 59%, and that in Shenyang is 62%. At present, the most commonly used way to deal with table garbage in the world is to use the food garbage processor, which smashes the food garbage into tiny particles and enters the drainage system with tap water. After a certain fermentation, it can be used as fertilizer to return to the soil, which is not only conducive to the harmless treatment of food garbage, but also conducive to the reuse of resources. Today, the popularity of this method in the United States is more than 95%, and that in Japan is more than 35%

urban garbage is not only our burden, but also a rich resource. The rational development and utilization of garbage is related to the sustainable development of China's urban environment. Purifying the urban environment and rebuilding a green home not only need our appeal, but also need our real action

2.1 impact of landfill treatment on the environment

landfill treatment is a physical facility to treat waste in the shallow layer of the earth's surface. Its design and construction quality should ensure to reduce the impact of the landfill waste on the environment and the surrounding human health. The fundamental difference from the historical waste landfilling (pit filling, ditch filling, pond filling, etc.) or uncontrolled stacking is that the planning, design and operation management of modern waste landfills involve many scientific, engineering and economic principles, and they need to be operated under the guidance of science from the beginning of their construction until they are put into operation. The contents involved include: consideration of landfill site selection, control of released gas, control of leachate, control of surface water, structural characteristics and stability of landfill. The experimental wastes such as tensile, contraction, zigzag and bending resistance of metal and non-metal materials can be filled in the city in the potholes, which can not only dispose the wastes, but also cover the earth to make land, so as to protect the environment. The main methods of municipal waste landfill are:

(1) sanitary landfill. Dump a layer of municipal waste (60cm thick), compact it, and cover it with 15cm thick soil, sand or fly ash. Repeat this process, and finally cover it with 90-120cm thick topsoil

(2) compressed landfill. After the waste is compressed and backfilled, it can prevent fire, prevent the breeding of mosquitoes, and decompose slowly

(3) broken waste landfill. It can prevent fire and is conducive to the propagation of aerobic bacteria. The lowest part of the landfill site for urban waste shall be more than 3m higher than the groundwater level, and anti-seepage and exhaust measures shall be taken for the landfill site. After the landfill is closed, it can be used as a green place, and permanent buildings cannot be built on it

as waste, it is the main method to treat waste plastics by sending it to the municipal waste landfill for landfilling. With the rapid development of plastic industry, the output of waste plastics is in direct proportion to it, and the resulting environmental problems are becoming increasingly prominent. First of all, landfilling encroaches on limited arable land, seriously wasting land and resources. Second, the plastic waste will not decay after landfilling

Copyright © 2011 JIN SHI