The output of synthetic resin in the world has reached 200 million tons, and the disposal of large quantities of post-consumer plastics has become a hot spot for the protection of the earth today. At present, there are several ways to treat post-consumer plastics: 1. landfill; 2. incineration; 3. composting; 4. recycling and regeneration; 5. degradable plastics.
Section 1 Plastic Recycling Method
Recycling methods for plastic recycling include: melting regeneration, thermal cracking, energy recovery, recycling of chemical raw materials and other methods.
(1) Melt regeneration Melt regeneration is a method of re-thermoplasticizing waste plastics. From the sources of waste plastics, this method can be divided into two categories: First, the recycling of clean waste plastics recovered from the scraps of resin plants and processing plants; and second, the recycling of various plastic products mixed after use. . The former said that simple regeneration, can produce better performance of plastic products; the latter said that the compound regeneration, generally can only prepare relatively poor performance of plastic products, and the recycling process is more complicated.
(2) Thermal cracking The thermal cracking method is a method in which the selected waste plastics are pyrolyzed to produce burning oil and fuel gas.
(3) Energy recovery Energy recovery is a method that uses heat generated when waste plastic is burned.
(4) Recovery of chemical raw materials, some varieties of plastic, plus polyurethane can be obtained by hydrolysis of raw materials for synthesis. This is a method of using chemical decomposition of waste plastics into chemical raw materials for recycling.
(5) In addition to the above methods for recovering waste plastics, there are various methods for using waste plastics. For example, the waste polystyrene foam is crushed and mixed into the soil to improve the water retention, air permeability and drainage of the soil. Or as a filler mixed with cement made of lightweight concrete, or add adhesives pressed into mat material.
Recycling plastics and plastics and processing solid wastes from plastics The use of petroleum and coal as raw materials to produce plastics to replace natural polymer materials has undergone a difficult process. An entire generation of outstanding chemists have achieved excellent physics and chemistry at present. Characteristics and durability are hard work. Plastics, with its light weight, durability, aesthetics, and low cost, replaced a large number of traditional packaging materials and contributed to a revolution in the packaging industry. However, contrary to the expectations of the people, it is precisely these excellent properties of plastics that produce a lot of durable and non-corrupted plastic waste. The large amount of discarded plastic packaging after use has become a major environmental hazard. The main reason is that these plastic wastes are difficult to handle and cannot be decomposed and turned into dust. In the existing municipal solid waste, the proportion of plastics has reached 15%-20%, and most of them are disposable plastic packaging products. The disposal of plastic waste is not only a problem in the plastics industry, but it has now become a widespread concern in the international community of public hazards.
In order to meet the needs of protecting the global environment, the world plastics processing industry has developed many new environmental protection technologies. In terms of saving resources, it is mainly to improve the product's endurance performance, prolong its lifespan, multi-functionality, and proper product design. In the aspect of resource reuse, it mainly studies the efficient sorting of plastic waste, separation technology, and high-efficiency melting and recycling technology. Chemical recycling technology, completely biodegradable materials, water-soluble materials, and edible films; in terms of reduction technology, the research is mainly focused on the technology of compression and volume reduction of waste plastics and the technology of film-packed containers, and on the premise of ensuring application performance, The thinning technology of products; the development of CFC substitutes is mainly focused on carbon dioxide foaming technology; on the research of substitutes, PVC and PVDC substitutes are mainly developed.
For the treatment of solid waste in urban plastics, three methods are currently used for landfill, incineration and recycling. Because of different national conditions, different countries, the United States to landfill, Europe, Japan, mainly incineration. With landfill treatment, the quality of plastics is generally light, and it is not easy to rot. This will cause the landfill to become a soft foundation and it is difficult to use it in the future. The use of incineration processing, due to the heat of plastic, easy to damage the stove, plus the gas generated after incineration will promote the global warming, and some plastics will also emit harmful gases in the burning and pollute the atmosphere. The use of recycling methods, due to man-hours, high recycling costs, and the lack of appropriate recycling channels, the world's recycling and reuse accounted for only about 15% of the total plastic consumption. However, due to limited world oil resources, from the perspective of saving the earth's resources, the recycling of plastics is of great significance. To this end, all countries in the world have invested a lot of manpower and material resources to develop various key technologies for the recycling of waste plastics, and have devoted themselves to the development of suitable applications for reducing the cost of recycling plastics.
one. Recovered heat energy method
Most plastics use petroleum as raw material, and the main component is hydrocarbons, which can be burned. For example, polystyrene burns more calories than dye oil. Some experts believe that sending plastic waste to an incinerator can provide the heat for heating or power generation. Because 86% of petroleum dyes are burned directly, only 4% of them are made into plastic products. When the plastic is used up, it is sent as heat energy. Burning is normal, and the use of heat energy is one of the last methods for plastic recycling and should not be taken lightly. However, many environmental groups oppose the burning of plastics. They believe that the incineration method will concentrate all the chaos of chemicals and cause toxic gases. For example, half of the PVC components are chlorine. The chlorine released from combustion has a strong erosive effect, and it is the culprit that causes dioxin.
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