Recycling and utilization of plastic wastes and PET bottles
Plastics, hundred thousand tons of which are thrown by people daily, are, perhaps, the most evident trace of human civilization. That is why recycling of plastics becomes no less significant issue than the utilization of scrap tires.
Despite the fact the Customers of the Technokomplex equipment rarely purchase the Pirotex pyrolysis plant as a line for recycling and utilization of plastics bottles only or as the pyrolysis system for plastics recycling, the company has thoroughly studied the questions: what is meant by this certain type of feedstock and what methods of its recycling and utilization can be used.
Types of plastic wastes.
To start with we should take a look at different types of plastics. According to statistics about 50% of general waste consists of polymers. More than third of this polymers are represented by polyethylene, the most popular kind of plastic.
In general, plastic wastes include various wrapping, PET bottles and appliance plastic parts, that end up in landfills since they are refused due to manufacturing defect or expiration of working life.
First, let's find out why are plastic bottles so popular? The answer is they have a number of advantages in comparison with glass:
This material was patented by the DuPont company in 1941 in Great Britain. And the first plastic bottle came to life only in the 70s.
1) lightweight - facilitates bottles transportation;
2) high transparency - makes bottle filling with soda more efficient;
3) possibility to dye plastic material in any colour - expands the scope of its commercial use;
4) durability - reduces the risk of breakage during transportation.
On the other hand, PET package let the ultraviolet and oxygen through and releases carbon dioxide. It is called “the low barrier function” that worsen the condition of some products storage, for example, beer. According to European standards this drink should be stored in plastic bottles for not more than two weeks ( in Russia this timescale is increased up to three-four months). But anyway PET bottles are very popular and should be properly utilized when their useful life is over.
It should be noted that wrapping, which is another very important form of wastes, has one great shortcoming despite a number of advantages – the time of its decomposition is more than 100 years. The same may be said about appliance plastic parts.
Methods of polymer recycling and utilization.
In Russia the problem of plastics utilization differs from the same problem in other countries. For example, European manufacturers of plastic package and wrapping pay certain charge, in which the sum necessary for separation and utilization of produced products is already included. Automotive industry often use processed plastic for production of inner parts of doors and bumpers.
Unfortunately, the culture of wastes separation and processing is still not completely developed in Russia. This causes troubles for organizations who aim to process this particular wastes. But, definitely, the first steps are already taken in this direction.
The methods of plastic wastes processing include:
Hydrolysis - a decomposition of original substance by interaction between substance and water with formation of new components.
Glykolysis - a dissolution by catalytic agent under heating.
Pyrolysis - a thermal decomposition of organic and non-organic compounds.
- splitting by methanol, is a thermal method;
- splitting at extreme temperature and pressure - is a hydrolysis. As a result high-quality chemical products are obtained;
- decomposition at high temperature and pressure, by ethylene glycol and catalytic agent until the clean product is formed;
- thermal decomposition of substance in/without presence of oxygen is a pyrolysis;
- mechanical crumbing, at both low and normal temperatures with further washing, drying and granulating of plastics, preparing it for further use.
It should be mentioned that in case of plastic wastes we speak not only about recycling (the process of industrial wastes and garbage usage) but also about utilization (the process when resources that can not find direct implementation, secondary resources, production and consumption wastes are used).
Pyrolysis of plastics
Why is pyrolysis method interesting for plastic bottles recycling and utilization? This method allows obtaining not one but several marketable products at the same time.
Moreover, gas produced during the pyrolysis process can be then used to support the equipment operation allowing energy reduction. Another very interesting preference is that thorough sorting of plastic is not required as any plastic material can be completely processed.
Technokomplex has in its practice not many cases of the Pirotex pyrolysis plant usage as the equipment for recycling and utilization of plastic wastes. The company, however, has developed a special technological chart that allows obtaining maximum output (liquid fuel and carbon black) in course of plastics utilization.
Liquid fuel from plastics can be further processed in mini oil refinery just as the fuel from pyrolized mechanical rubber goods.