Recycling and utilization of plastic wastes
Pollution of the environment by plastic becomes one of the most actual ecological problems of the humanity. The number of countries, where simple plastic burial at the waste landfills is illegal or limited, increases. And, moreover, only from 5% to 25% of plastic wastes go to the processing today.
- burning with getting petrochemical wastes — 56%;
- mechanical manipulation — 28%;
- use as feedstock for chemical industry — 16%.
Plastic wrap is the most attractive from all the wastes, because of its huge volume, short period of use and slow decomposition.
From the experience of communication with customers "Technokomplex" company distinguished the three most important factors in plastic processing:
1. consistent feedstock supply, which includes continued gathering and assortment;
2. the process of feedstock recycling, which is economical, safe and contributory to the environmental conservation;
3. the final use of the processed polymer, getting from it the good with acceptable market-value.
The second factor, as a rule, is pyrolysis technology, as exactly this allows to get goods with acceptable market-value.
Classification of plastic wastes*
||Such plastic is mainly used in production of disposable tare for drinks. Typical PET wrap are mineral water bottles. This wrap can evolve toxic chemicals while its re-using even after thorough cleaning. Its re-using is strictly forbidden.|
||Low pressure polyethylene (high density) is used for semirigid containers production, it is one of the safest plastics, and it can be re-used.|
||Polyvinyl chloride is often used, for example, in wrapping film for foods production. PVC is dangerous for the health and can evolve toxins. Polyvinyl chloride produces very dangerous chemical compounds, which are known as dioxins, which are often more dangerous, than cyanide, while burning.|
||High pressure polyethylene (low density), which is used for production of many wrap types (for example, polyethylene bags), is considered acceptable for re-using, and it is safer than many other plastics, but not so safe, as plastics HDPE and PP.|
Re-usable polypropylene is often met as material for lunch boxes. It belongs to the group of the safest plastics along with material HDPE.
Polystyrol is well-known in the form of foam plastic. PS evolves toxins and shouldn't be used as food packing. Also, it is rarely used for this reason, because of the lower chemical resistance to polyethylene, but it is presented, for example, in the tops for one-use coffee cups.
* Ivanova O.A., Rekhovskaya E.O. Recycling and processing of plastic wastes // Young scientist. - 2015.
Recycling of plastic wastes
In the beginning of 90-s, mechanical way of plastics' processing prevailed, today more focused attention is paid to the new recycling technologies, such as, pyrolysis.
Also, accent of the recycling object moved. Even 10 years ago packaging was processed more often, than other plastic wastes. Now, the priority is given to solid plastic details: automobile (bumpers, trim parts), computer casing etc.
Despite, that legal framework of many countries, including Russia, develops towards recycling and processing of plastics wastes approval, secondary polymers market isn't fully developed yet. However, positive market dynamic became noticeable with the extension of pyrolysis technology (effective and energy-conservative plastic recycling).
Wastes recycling to energy feedstock excludes many restrictions, which are common to mechanical processing, such as, impurity and deteriorating of derivative products.
Technology's data include the following methods:
- pyrolysis (the process of disruption in cross-linked polymer in the absence of air),
- hydrogenization (the process of disruption in cross-linked polymer in the presence of hydrogen),
- gasification (the process of disruption in cross-linked polymer in the presence of controlled quantity of oxygen).
Pyrolysis of plastic wastes
By means of pyrolysis plant “Pirotex” you can solve the problem of fractions processing, which are left after the mechanical operation of plastics and achieved the value limit. Besides, you can pyrolyze contaminated, mixed and very expensive for separation plastic wastes.
- liquid fuel: from 40 to 70%;
- carbon residue: from 10 to 25%;
- gas: from 15 to 55%.
Pyrolysis methods have been using since 30-s in Germany for increasing the quality of wastes, which were got while coal liquefaction.
Pyrolysis is the best recycling method of mixed plastic wastes with their transformation to petrochemical feedstock. The flexibility of the process and relative simplicity of design specifies economical success of pyrolysis in industrial scales.
The advantages of plastic pyrolysis :
- very low energy demand in the process of reaction (max 10% of feedstock energy content goes to the keeping of the process);
- possibility of polymer wastes recycling, which can not be processed by alternative methods (automobile bits, electronics wastes, which contain antipyrenes and metals), they can be mixed and contaminated;
- pyrolysis reaction flows without air consumption, oxygen addition and doesn't need the increased pressure;
- the stage of feedstock cleaning is absent, that leads to the absence of waste water;
- dirts and contaminants stay as solid residual of the process;
- the reaction flows in closed system, that eliminates contaminants leakage, and also leads to real absence of polluting emissions;
- conversion process has high efficiency: more than 90% of feedstock transfers to the derivative products, that helps to save the primary natural resources.
Plastic pyrolysis in pyrolysis plant “Pirotex” is one of the most economically sound and profitable ways of plastic wastes processing, at least, for three reasons:
1. appropriation of government subsidy and payment for recycling of polymer wastes;
2. liquid fuel – the most liquid good occupies up to 70% of value in derivative products;
3. high reliability of pyrolysis equipment, which is proved on more than 30 objects** of exploitation in different geographic, climatic and economical conditions.
** The quantity of objects is current at February, 2017