World production of synthetic resin reached 200 million t, a large number of post-consumer plastic processing has become a hot spot of today's global environment. Currently, post-consumer plastic processing has the following several ways: 1 landfill: 2 burning: 3 composting; 4 Recycling; 5 using biodegradable plastic.
Plastic recycling method
Plastic recycling regeneration method: melt regeneration, pyrolysis, energy recovery, recycling and other methods such as chemical raw materials.
(1) melting recycled waste plastic melt is re-recycled plastics and to use the heating method. Plastics from the waste source, this method can be divided into two categories: First, by resin plant, processing plant clean scrap recycling waste plastics recycling; the second is through a variety of mixed use, recycling of plastic products . The former says simply recycled, can be obtained better performance plastic products; which said compound regeneration, generally only the preparation of relatively poor performance plastics, and recycling process is more complex.
(2) pyrolysis pyrolysis method is to pick through the waste plastic pyrolysis obtained by burning fuel oil, fuel gas method.
(3) Energy recovery Energy recovery is the use of plastic waste heat generated by combustion method.
(4) recovery of chemicals, some of the varieties of plastic, plus the polyurethane synthesis can be obtained by hydrolysis of the raw material monomer. This is a use of chemical decomposition of waste plastics into chemical raw materials for recycling methods.
(5) other, in addition to the above method of recycling waste plastics, there are various ways to use waste plastics, such as polystyrene foam waste mixed with soil after grinding to improve moisture retention, aeration and drainage, or as a filler made of lightweight concrete with cement, pressed into mats or by adding adhesive materials.
Plastic and plastic for recycling solid waste treatment
With oil and coal as raw material to replace natural production of plastic polymer materials, has experienced a difficult course, a whole generation of outstanding chemists to achieve the current plastic has the excellent physical and chemical properties and durability of hard work paid. Plastic for its light weight, durable, beautiful, cheap, etc., to replace a large number of traditional packaging materials, led to a revolution in the packaging industry. Than anyone expected, but plastic is just plastic, these excellent properties of a large number of manufacturing durable plastic garbage does not rot. After using a large number of discarded plastic packaging has become a major scourge of harm to the environment, the main reason is that these difficult to deal with plastic waste, not to break down and dust. The existing municipal solid waste, the proportion of plastic has reached 15% -20%, most of which are single-use plastic packaging products in the name of class. Plastic waste disposal has not only the plastics industry, is now become a public nuisance of the international community's attention.
Protect the global environment in order to meet the needs of the world's plastics processing industry developed a number of new environmental protection technologies. To save resources, mainly to improve product performance, resistance to older, longer life, multi-functional, product amount of design; re-use of resources, is to study the efficient sorting of plastic waste, separation technology, high-melting recycling technology, chemical recycling technology, a fully biodegradable materials, water-soluble materials, edible film; in reduction technology, is to study the volume reduction of waste plastic compression technology, thin film bag container technology, to ensure application performance under the premise, as far as possible Thin technology products; in the development of CFC substitutes, mainly carbon dioxide, foam technology research; research in alternatives, mainly PVC and PVDC develop substitutes.
Plastic solid waste disposal in the city, at present mainly landfill, incineration and recycling are three ways. Due to different national conditions, countries vary, the United States-based landfill, Europe, Japan, mainly by burning. The use of landfill, largely due to the quality of light plastic, and non-perishable, will lead to a soft texture landfill base, the future is difficult to use. The use of incineration, due to plastic heat capacity, easy to damage the stove, with gas produced by incineration will lead to global warming, some plastic in the incineration will release harmful gases and pollution of the atmosphere. The use of recycling methods, because labor-intensive, high cost of recycling, recovery and the lack of appropriate channels, the world's recycling plastics consumption accounts for about 15%. But the world's oil resources are limited, from the perspective of saving the earth's resources, plastic recycling is of great significance. To this end, the world's countries have a lot of manpower, material resources, development of various waste plastics recycling key technology, is committed to reducing the cost of recycling plastic development of the appropriate applications.
Heat recovery method
Most petroleum-based plastic materials, the main components of hydrocarbons, can burn, such as polystyrene calories burned oil is higher than the dye. Some experts believe that the burning of plastic waste into the incinerator, heating or power generation can provide the heat, because 86 percent of oil dyes are directly burned, of which only 4% made of plastic, plastic exhausted and then sent when the heat burning is normal, heat use is the last one of the methods of plastic recycling, can not be ignored. But many environmental groups oppose the burning of plastic, they believe that incineration of the mess all the concentrated chemical combustion, will produce toxic gases. Half of ingredients such as PVC is chlorine, chlorine released when burning the erosion of strong destructive, and is the culprit causing dioxin.
At present, Germany has 20 million tons of PVC per year waste, of which 30% is burned in incinerators, burn panic, the law compelled to develop countermeasures. German Federal Environment has provided all of the incinerators must comply with every cubic meter of gas is lower than 0.1ng (ng) is limited. German incinerator air pollution standard Although the high standards are recognized worldwide, but still did not dare burn method does not release harmful substances due to mechanical failure, it can be expected, national environmental groups will continue to vigorously oppose the incineration of recovery of thermal energy.
Separation and recovery method
As plastic recycling, the most important thing is to classify. Common plastics are polystyrene, polypropylene, low density polyethylene, high density polyethylene, polycarbonate, polyvinyl chloride, polyamide, polyurethane, etc., these plastics is generally difficult to distinguish the difference. Now most of the plastic classification done by hand. Recently the machine has a new classification of research, the German Association of the invention to a chemical infrared technology to identify categories, both quickly and accurately, but the high cost of sorting.
Researchers began trying to extract the chemical composition of plastics for recycling. The process is used to cut long-chain polymers, to restore its original character, pyrolysis of the raw materials used to make new plastic. Some of these methods is by adding a combination of chemical elements to promote chemical cleavage of carbon atoms, or by adding energy to promote thermal cracking.
Germany's Bayer AG has developed a type of chemical reduction method to the hydrolysis cleavage PUC sponge. Tests show that chemical reduction is technically feasible, but it can only be used to clean plastic processing, such as manufacturing process resulting corner powder and other plastic waste. The family used the contaminated dirt on the other plastic, it is difficult to deal with chemical decomposition. The application of this reduction to the 21st century will be a lot of use of hydrolysis processing waste. Some new chemical process of decomposition is still under study, Ford Motor Company is currently used in the ester solution processing waste plastic car parts.
U.S. Lunse Institute of Technology have developed a biodegradable plastic waste solution, this kind of solution has been patented and 6 mixed with different types of plastic heating. At different temperatures can be extracted from six kinds of polymers. Experiment, the polystyrene plastic debris and the solution at room temperature, dissolved into the mixture, to a sealed container into the heating, and then into the low pressure "flash chamber", the rapid evaporation of the solution (which can recycling hand), and the rest is pure polystyrene can be used again.
Allegedly, the purification unit with the Institute, 1kg per hour purified polymer. New York State and Niagara. Mohawk Power Company is planning to jointly build a small-scale pilot plant. Investors claim that the plant is completed, 4t h recyclable polymer materials. The cost is only 30% of raw materials, has a very clear commercial value.
Hydrogenated analysis solution
Many experts believe that the hydrogenation process can be used for mixed plastics. The mixed plastic debris into the hydrogen reactor, the pressure to present a specific temperature, will be able to produce synthetic crude oil and gas and other raw materials. This approach can be used for processing of PVC waste, the advantage does not produce toxic dioxins and chlorine. Using this approach to mixed plastic materials, depending on the plastic components, which can be 60% -80 & ingredients to Make synthetic crude oil. German chemical company BASF and other countries in the three joint research report that the hydrogenation of pyrolysis law, the best way analysis of solutions of a good quality synthetic crude oil products can be used to oil refining.
American University of Lexington Dunkentaji invented a plastic fuel oil, waste plastics into high-quality process approach. In this way the production of fuels like crude oil, even lighter than crude oil, more easily refined into high-octane fuel. This production of fuel oil from waste plastic does not contain sulfur impurities are rare. Using a similar approach with the plastic and coal liquefaction. Can also produce high-quality fuel oil.
Researchers in the Shower in the various plastic and zeolite catalyst, TETRALIN mixed together and then into a technique called "pipe bomb" reactor, the hydrogen pressure and heated to promote macromolecular plastic down into smaller molecular weight compounds, this process is similar to crude oil processing in the compound. After this treatment, waste plastic oil production rate is high, polyethylene plastic bottles of oil yield up to 88%. When the waste plastics and coal mixed with roughly a 1:1 ratio and liquefaction, you can get more high-quality fuel oil. After this process the economic benefits of the method is expected after the use of fuel oil, waste plastics has become transformed in 5-10 years with blast furnace efficiency. At present, Germany has begun to build a promising Bote Pu Nissan 200t plastic fuel reactor.
Class design method by
Research and development departments in the design of the product recovery and disassembly in mind the need to deal with the United States suitable for recycled materials, the focus is not to consider the individual parts should be made of a plastic which is ideal, but considering the material can be widely used This is the idea of revolutionary change.
In order to facilitate recycling, designers began to design products to avoid the use of a variety of plastics, the United States BMW plans to design its new vehicles by 40 percent of the plastic kind, is to facilitate the recycling of waste plastics. The reason why the automotive industry to reduce plastic use types, and the subject of design considerations, the main emphasis on environmental protection is expected to win the good image of the appreciation by consumers. Currently, this design concept is gradually infected the entire plastics processing industry.
But all the efforts are still unable to access the market on 20 kinds of plastic in any of the disappeared. After all, diversity has led to plastic products to listen to the ever-changing variety of categories, such as computer manufacturing and production of plastics used in car use of plastic is not the same.
To this end, the experts recommended the development of the recycling standards that the industry can only use the specified special materials, or can not control the efficient recycling, electronics and automotive industries have begun to develop such standards.
The world market for waste electrical and electronic plastics recycling has attracted attention, International Business Machines Corporation (IBM) has started the computer and business machine plastic parts standard code, and in the development of plastics for recycling electronic components and simplify the removal of equipment product structure, and also consider removing components of surface shading, control the external adhesive plastic additives to reduce the amount of use of non-use of recycled process components and external components.
Recycling of discarded auto parts has also been much progress, many countries are in a vehicle with easy recovery of recyclable plastic material selection and product design premise. Some countries have developed standards for effective recovery of a number of automotive plastic parts and recycling programs, and consider the development of automotive plastics contribute to dismantling and sorting the unified sign system. Europe and other countries are still studying chemical depolymerization recovery of automotive plastics.
On the positive development of plastic recycling technology, research and development of biodegradable become the world's plastics processing industry research focus. Researchers hope to develop a microbial environment in the degradation of plastics, to handle a large number of single-use plastic, especially plastic film and packaging waste more farmland, forests, marine pollution. Research goal is to develop a process to ensure the use of its name item performance, and once used up abandoned, can be broken down by microorganisms in the environment, and thus full access to the ecological cycle of plastic. At the same time, the plastic of lower production costs, with corresponding economy. If this is the biodegradable plastics after use can be composted along with the normal biological waste, without having to spend a very high price for the collection, sorting and recycling process. Moreover, the decomposition products into the ecological cycle, no waste of resources problem.
In research and development of biodegradable plastics in the world have invested a lot of financial and human resources cost a lot of energy research. Plastics processing industry generally believe that biodegradable plastic is the 21st century, new technology issues.
The late 1980s, in order to solve the problem of degradation of garbage bags in the U.S. corn business to promote, add starch, polyethylene bags as biodegradable plastics in Europe and America all the rage. However, due to which the polyethylene is not biodegradable, so its application research has significantly cooled. Only because of starch rich source of raw materials, and cheap, there are still many researchers engaged in research in this area and hope through a variety of formulations technology, a breakthrough in terms of degradation.
Currently the main technologies developed fermentation route synthesis, the use of natural polymers (cellulose, lignin, chitin) synthesis of chemical synthesis, and has developed some biodegradable plastic water-soluble resin, but the overall to say, failed to meet its cost of production requirements of industrial mass production.
Germany's Bayer experts in fiber products after several years of research, made of a completely broken down into humus plastic. With this plastic packaging film, you can break down quickly in the soil, "disintegrating", within 10 days can return to nature. According to the identification of environmental organizations, and the decomposition of this plastic in the environment and human and material are secure. The company successfully developed this new type of plastic is hard and difficult to extend the cellulose mixed with the polyurethane system. To this new type of plastic in the earth, the soil microorganisms can be delicious food, microorganisms multiply rapidly soon be able to fully digest the material into humus hair.
Such material will be a household plastic wrap, and 14 days to complete a powder, after 8 weeks will lose 80% of the weight. Material culture in this bowl of nutrition, several weeks after implantation of the soil are turned into humus, compost served as role As this new technology of production costs are too high. Is several times more than ordinary plastic, so it is difficult to achieve commercial production.
Experiments in the application, after years of efforts, China biodegradable polyethylene film on the research project has achieved initial success, developed a biodegradable plastic film samples, and conducted a small area of the trial, it seems in terms of its technical maturity , has not yet reached large scale application level. China's light-degradable plastic additive has not been involved in the field. United States light-degradable plastics for bottled beverages to mention ring for many years, Israel and Canada have a trial of light degradation of film, but no reports of large-scale applications.
According to the forecast, such as biodegradable plastics industrial research counted as 100 words, the current research and development only in the relative phase of 30 is expected after 2000, is expected to realize industrialization. Currently, the U.S. research and development of this technology in a leading position in Europe comes second, Japan's third.
In general, biodegradable plastics research and development there are many problems to be overcome. First, the definition of plastic degradation is no uniform understanding that biodegradable really mean? That is the decomposition of biodegradable plastics to determine what time period? In addition, the decomposition products should be on what? What is the end product of carbon dioxide and water, or the practical application of any form of harmless residues? Secondly, the evaluation test of biodegradable plastics is no unified approach to the world recognized. The U.S. Society for Testing and Materials, Japanese Industrial Standards Institute and the International Organization for Standardization are active in this area, although the ASTM has formally issued a number of results can not be applied to the actual plastic waste processing.
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