As the consumption of plastic products increases, so does the waste of plastic. At present, the waste plastics in China are mainly plastic film, plastic silk and woven fabric, foam plastics, plastic packaging boxes and containers, daily plastic products, plastic bags and agricultural plastic film. In addition, the annual consumption of plastics for automobiles has reached 400,000 tons, and the annual consumption of plastics for electronics and appliances has reached more than 1 million tons. These products have become one of the important sources of waste plastics after being scrapped. It is understood that in 2011, China's waste plastic production volume of about 28 million tons, 2012 for 34.13 million tons. The storage, transportation and processing of these waste plastics will inevitably damage the environment and endanger people's health if the application and post-treatment of the waste plastic materials waiting for processing are not appropriate.
With the increase of global crude oil price, the price of plastic products, one of the petroleum derivatives, rises naturally, and the recycling of waste plastic is also mentioned as the primary position. Waste plastic recycling has been widely used by modern chemical enterprises. Waste plastic after manual screening and classification, but also through the crushing, granulation, modification and other processes, into a variety of transparent and opaque plastic particles, and then according to the classification phase, finally become re-use of raw materials.
At first, a large number of plastic recycling USES landfill or incineration methods, resulting in a huge waste of resources. Therefore, waste plastics are used in blast furnace injection instead of coal, oil and coke, in cement rotary kiln instead of coal to make cement, and in garbage solid fuel (RDF) for power generation.
RDF technology was originally developed in the United States. In recent years, in view of the shortage of landfills in Japan and the serious corrosion of boilers by HCI when waste plastics containing chlorine are treated by incinerators, and dioxins will be generated in the combustion process to pollute the environment, the use of waste plastics with high calorific value is mixed with various combustible waste to produce a calorific value of 20933kJ/kg and RDF with uniform particle size, even if chlorine is obtained
It is also convenient to store, transport and use substitute coal for other boilers and industrial kilns.
Blast furnace injection waste plastic technology is also a new method to treat waste plastic by using the high calorific value of waste plastic as raw material to make suitable particle size for injection into blast furnace instead of coke or pulverized coal. The application of waste plastics in blast furnace injection abroad shows that the utilization rate of waste plastics is up to 80%, the emission is 0.1% to 1.0% of the incineration amount, the harmful gas produced is less, and the treatment cost is lower. The technology of blast furnace injection of waste plastics opens up a new way for the comprehensive utilization of waste plastics and the treatment of "white pollution". Germany and Japan have had successful applications since 1995.
Solid fuel waste power generation was first used in the United States, and there are 37 RDF power plants, accounting for 21.6% of the total. Japan has recognised the huge potential of waste plastic for generating electricity. In Japan, some small waste incineration stations have been transformed into RDF production stations in order to realize continuous and efficient large-scale power generation after concentration. The steam parameters of waste power stations have been increased from 30012 to 45012, and the power generation efficiency has been increased from 15% to 20%-25%.
To facilitate plastic recycling, The Society of The Plastics Industry, Inc., USA, has proposed a plastic Identification Code, which USES plastic types to classify tags: Resin Identification Code. Recyclable plastic containers come with a triangular tag with three arrows around it, indicating the type of plastic.
China's national standard (gb18455-2001) stipulates that plastic packaging products or plastic containers with a volume/volume of more than 100 ml must be visually marked with plastic recycling labels:
Use of abbreviation name
PET polyethylene terephthalate, also known as polyester, is commonly found in bottles.
HDPE high density polyethylene is commonly found in lotion containers, milk bottles, supermarket plastic bags.
PVC is common in pipes, outdoor furniture, raincoats.
LDPE low density polyethylene (LDPE) is commonly found in toothpaste or facial cleanser hose packaging.
PP is commonly found in bottle tops, straws, and microwave food containers.
PS polystyrene is divided into unfoamed or foamed. Unfoamed polystyrene, commonly found in some beverage containers (such as yakult); Already foamed bubble is commonly known as foamed gum, commonly seen in packaging with gelatine, disposable heat preservation rubber cup, packaging frozen meat container, lunch box.
Other recyclable plastics include polymethyl methacrylate (PMMA), polycarbonate (PC), polylactic acid (PLA), Nylon and FRP, and bidirectional stretch polylactic acid film (BOPLA).