DISPOSAL OF PLASTIC WASTE

ABSTRACT

Plastic recycling is the process of converting plastic waste into secondary raw materials, energy, or products with certain consumer properties. The period of natural decomposition of plastics reaches several hundred years, so waste recycling is part of a global attempt to reduce the amount of harmful substances entering the environment. In total, there are three main processing methods: mechanical, chemical and thermal. Mechanical recycling (recycling) is the most common of them, when using it, the end result is the appearance of a new plastic material. The chemical method allows you to break down plastic waste into its constituent components. Subsequently, they are mixed and processed to create new materials. With the thermal method, the material is subjected to temperature treatment, as a result of which energy is generated.

Keywords: plastic recycling, disposal, mechanical methods, thermal methods, chemical methods, physico-chemical methods, secondary use of plastic.

Today, in all developed countries, garbage collection is carried out separately – plastic is separated from the main container and such waste is thrown into a separate container. This is the first stage in sorting, in which every person participates. This is how it is possible to separate the bulk of recyclable materials from non-recyclable garbage. In order to eliminate pollution of nature and reduce the amount of household garbage, it is better to buy products in disposable packaging and after using them, take the container for recycling, throwing it into special tanks. When buying reusable containers, pay attention to a special icon in the form of arrows, which means that this container can be given to the receiving point. Plastic is collected by companies that process and dispose of it. Further sorting takes place at enterprises, the contents are distributed into groups depending on the material.

Recycling and disposal

In order for the plastic to be reused, it must undergo appropriate processing, it is melted down for the manufacture of new containers, toys or products for domestic or professional use. After collection and sorting, the waste is sent for the production of new material.

Plastic recycling and recycling scheme

Recycling plants use several methods: mechanical grinding, thermal or chemical treatment. A physico-chemical method is also used. Thus, the integrity of the plastic structure is violated, and the basis for the manufacture of new products is obtained from it.

Mechanical methods

One of the simplest methods is grinding. The integrity of the products is violated without melting and chemical treatment of the base. First, the waste is sorted into soft and hard, which is necessary for further processing of garbage.

As a result of grinding , it is possible to obtain three types of raw materials:

- granules – when passing products through a crusher and shredder, solid waste is crushed on machines;

- flex – these materials are obtained from soft plastic under temperature fluctuations;

- pellets are also made of soft plastic, which is subjected to thermal effects during mechanical processing.

Grinding to small particles is a high–quality processing, as a result of which it is possible to increase the density of raw materials. Usually this method is used before further melting of plastic to obtain high-quality material. Often these operations are carried out separately and the raw materials are sent to other processing plants.

Thermal methods

Thermal processing is the most common – the material is loaded into the furnace, where it is affected by high temperature and accelerates its decomposition. As a result of such treatment, the volume of garbage is reduced by 90%, harmless ash remains, and toxic gases are captured by special filters. If household waste is disposed of by incineration, it is delivered without prior sorting. This method allows you to unload landfills at the landfill and dispose of a large amount of garbage.

Today, the second method of thermal processing is in demand – pyrolysis for fuel production. The difference of this method is that the combustion is carried out in oxygen-free furnaces with chemical reactions for the splitting of plastic.

The procedure can be carried out in three temperature modes:

- up to 350 °C is cracking, during which the octane number of fuel or new polymers is changed;

- 450-900 °C – complete combustion of the product with the release of a large amount of heat;

- more than 900 °C is a similar process, during which a minimum of solid sediment is formed.

Chemical methods

A method of processing plastic by chemical methods is used – the waste is placed in a pre-prepared tank in which chemical reactions take place. Liquids and catalysts are added to the container to accelerate the decomposition process. As a result of such a reaction, it is possible to obtain recycled products that are allowed to produce new plastics.

Methods of splitting materials:

- methanolysis is the splitting of plastic by exposure to methanol and high temperatures;

- hydrolysis – the material is exposed to thermal effects in contact with water and acids;

- glycolysis is an oxidation process in which a secondary product is obtained.

The first method is one of the most popular, but it is used only in large factories because of its explosiveness. The use of all chemical methods involves risks, so they are most often used in professional enterprises.

Physico-chemical methods

To increase the strength of the material, physico-chemical methods are suitable – because plastic, like metal, loses its strength over time and becomes more elastic or vice versa, brittle. Due to such "fatigue", the products cannot be used for their intended purpose, the container will leak quickly, and the part will not withstand the declared load.

First, the plastic is machined, crushed, the contents are thoroughly mixed. At the second stage, melting and addition of plasticizers are carried out, which restore the properties of the material. Thanks to this treatment, the products can be reused.

Recycling of plastic

Many citizens consciously take care of the environment and use household plastic repeatedly, without recycling. Household containers are adapted for storing water, some use plastic in construction and even for home or garden decoration. Today, you can find many ways to make something useful out of plastic products, giving them a "second life".

The main thing is not to throw plastic into a general landfill, where it will decompose for hundreds of years. It is almost impossible to burn plastic in domestic conditions, it will simply melt in a fire or in an oven. This is a serious environmental damage that nature will not be able to eliminate quickly. Plastic pollution is the scourge of our time (unfortunately). Every year there is more and more plastic on the planet. There is already so much of it that plastic particles are found even in fish. But they are trying to fight the problem in every possible way. Scientists have already come up with many ways to recycle plastic and continue to work on new ones. Zeleny told about them in more detail.

What are the types of plastic recycling?

Physical processing method

This is mechanical recycling. This method is the most common. First, plastic waste is sorted by type, degree of contamination and condition of the material. Then the plastic goes through the pre-crushing stage. The resulting mass is sorted again, washed and dried. After that, the plastic is melted in thermal installations to obtain a homogeneous melt (it is called a recycle). At this stage, crushers and granulation plants come into play. Molten material is sent to them, from which granules are obtained at the output. New bottles, containers and other plastic products are made from these pellets.

Chemical processing methods

This type of processing has advantages over mechanical processing. Mechanical processing is more expensive, as it requires more serious sorting of waste. Most often, the chemical method is used to process contaminated material.

There are two directions in chemical recycling. The first is called P2P (plastic-to-plastic). In this case, the waste is converted into finished recyclables (polymers), from which the final product will be obtained.

The second direction is P2F (plastic–in-raw materials). Here plastic waste is processed into petrochemical products (transport fuel, candle wax, synthetic oil). Chemical recycling also begins with the collection and sorting of the material. Then several technologies can be used (below).

1. Hydrolysis and glycolysis

During hydrolysis, plastic is split using high temperatures and an aqueous acid solution. At the output, granules are obtained that are maximally purified from toxic substances. This method requires quite a lot of time and is expensive. Glycolysis is the processing of plastic using glycol and temperatures above 210-250 degrees. The resulting raw materials cannot be used for the production of products used in the food industry.

2. Solvolysis

This processing method uses a wide range of solvents, pressures, temperatures and catalysts (alcohols and supercritical fluid). The result is reduced fiber and unsaturated polyester resins.

3. Methanolysis

Here, the splitting of plastic occurs with the help of methanol. The procedure is carried out under high pressure in a reactor where a high temperature is maintained. This method is explosive, so it is resorted to in special cases to obtain polyesters.

4. Thermocatalysis

This method turns plastic waste into liquid fuel. First, the waste is crushed, then heated at a temperature above 400 degrees in the presence of a catalyst. The resulting mass becomes ready-made boiler fuel. Gasoline, diesel or fuel oil can also be obtained from it.

Thermal processing methods

Thermal mechanisms differ in the reaction medium: oxygen and inert (without oxygen). There are several types:

1. Pyrolysis

This is one of the most effective, but expensive ways to recycle plastic. It implies the thermal decomposition of waste in the absence of oxygen. At temperatures up to 600 degrees, mainly liquid products are obtained, and at a higher temperature, gaseous products are obtained. Carbon black and metal compounds are formed in the solid residue. Pyrolysis makes it possible to recycle mixed and contaminated waste. With this method, 99% of the harmful substances that make up the plastic are destroyed. This makes pyrolysis one of the most environmentally friendly waste recycling options. But it requires a lot of energy.

2. Gasification

With this method, the waste is treated with a plasma stream at a temperature of 1200 degrees. This method avoids the formation of resin and helps to achieve the destruction of toxic substances. The waste turns into ash, which is often pressed into briquettes and laid in the foundation of buildings. Even during gasification, synthetic gas is obtained, which can be used to generate thermal and electrical energy. The main advantage of the method is that it is possible to process plastic without sorting among themselves, that is, different types of plastic products fall into one furnace.

Disposal at home

Using plastic bottles for decoration

Recycling of plastic waste at home – the use of bottles and containers made of plastic in the form of a source for the manufacture of decorative ornaments on the house plot.

Such processing allows you to:

- save minerals;

- reduce the amount of energy consumed;

- reduce the quantitative composition of solid waste;

- put the disposal of plastic waste on the industrial stream.

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