Overview of EPS Foam Recycling
EPS has been widely used in construction, packaging, electronic and electrical products, ships, vehicles and aircraft manufacturing, decoration materials, housing construction and other fields because of its excellent and lasting thermal insulation, unique cushioning shock resistance, aging resistance and waterproofness, which greatly facilitates our lives.
However, more than 50% of them are shock-absorbing packaging for electronic and electrical appliances, fresh-keeping packaging for fish boxes and agricultural products, which are abandoned after one-time use. Because EPS has bacterial resistance, weather resistance and corrosion resistance, it can be completely degraded in aerobic state for 300 years. A large number of waste foam plastics are scattered in the natural environment, which has become a “white pollution” affecting the earth’s living environment.
Since the 1980s, eight States in the United States, Japan, South Korea, Taiwan Province of China and other countries and regions have legislated to prohibit or restrict the use of polystyrene foam tableware. In 1999, the former State Economic and Trade Commission of China also issued Decree No.6 to prohibit production and use. However, various prohibition and restriction measures have not effectively improved the white foam pollution. Through continuous exploration and practice, technological progress and innovation, countries have gradually solved the problem of recycling waste foam plastics, making large-scale recycling of EPS foam waste possible.
At present, about 15 million tons of EPS foam plastics are produced annually in the world, of which about 2 million tons are produced in China. Except for a few developed countries, waste PS foam materials in most countries and regions have not been effectively recycled. According to incomplete statistics, the recycling rate of PS foam in Nordic countries and Japan is 72%, that in Korea is 64%, and that in other countries and regions is only 10-30%. In China, due to the imperfect recycling mechanism, 70% of them are buried or incinerated, and only 30% are recycled.
EPS foam recovery technology
1.EPS foam incineration to recover heat energy
Heat recovery by incineration is to burn waste polystyrene plastics in a special incinerator to recover heat to replace part of the fuel. The calorific value of polystyrene is as high as 4600 kJ/kg, which exceeds the average calorific value of fuel oil of 4400 kJ/kg, and can partially replace the fuel for ironmaking, power generation and combustion boilers.Although the combustion method can obtain energy, it needs to use a special combustion blast furnace, otherwise the insufficient combustion of polystyrene will produce harmful substances such as styrene and dioxins, which will cause secondary pollution to the environment. The cost of incineration recovery device is high, and the use value of materials has not been fully utilized.
2. EPS foam compression and granulation
EPS foam compression and granulation is the most widely used EPS foam recycling method at present. Polystyrene foam waste is compressed or melted by a professional foam compactor to form compact foam compression blocks, which are easier to sell than waste foam loose materials, and the price is about twice as high. The EPS foam compress block can be used for granulation to produce high-quality EPS regenerate particles, which can be applied to that production of new foam products.
3.Recovering styrene monomer by chemical pyrolysis
Polystyrene readily decomposes into aromatic compounds at high temperatures. The waste polystyrene foam can be cracked into gas phase products such as C1-C4 hydrocarbons and liquid phase products such as styrene and aromatic hydrocarbons by high temperature pyrolysis. At 580 ℃, 65% of styrene monomer and 10% of oligomer were obtained. Chemical thermal cracking method is one of the ways of high-quality recovery, but the disadvantage is that the energy consumption in the recovery process is large, and there are also problems of low recovery rate and easy carbonization on the recovery equipment in the industrial production process.