If not so long ago, the use of recyclable materials and recycling of waste associated with our fellow citizens with the past – the Soviet practice of voluntary and forced collection of scrap metal and waste paper, but today more and more often people associate these practices with the future. It is a kind of man-made analogue of the natural ecosystems with their “secrets” of maintaining a balance. But in fact, recycling is faced with a number of scientific, technological and even ethical issues.
Create demand
Before starting the treatment of waste in an industrial scale, they need to collect, and that’s the problem. The world is produced annually about 30 million tons of waste plastics only, and only about 10% of them are recycled. In Russia, too, there are companies such profile, but the “offer” their services often exceeds demand. “One of the major incidents, which tell the representatives of such companies in the media and at industry conferences – is that the number of facilities for the processing of polymers in Russia exceeds the volume of raw materials, which they can not find – told STRF.ru Alexander Tsygankov, Director development Charity Shop. – For example, a plant for the processing of PET “Plarus” from the Moscow region had to import recycled plastic from abroad to get their power. ”
But today most of the polymers “recycle” as a rule, it means “burning”, which leads to emissions of carbon dioxide and other oxides and unburned residue accumulation, all of this is not only a waste of useful materials, but also the pollution of the surrounding space.
Pyrolysis: temperature controlled
But no less important is the problem of maximizing the usefulness of the most recycling. If we talk about plastic waste, the “output” in theory it is possible to obtain a wide range of fuel fractions, as well as composite materials and energy.
Now one of the most common and effective processing of such complex areas as the rubber polymers is their fragmentation. The resulting rubber crumb used in enterprises as a reagent. But apart from the crumbs by crushing formed “by-product” – a polymer cord, which, together with the “entangled” in it baby, up to 30% of raw materials. To recycle and its mechanical action is not enough.
Scientists from the Tver State Technical University under the guidance of Doctor of Technical Sciences, Professor Yuri Kosivtsova confident that you can solve the problem by taking control of the processes taking place at high temperatures. In particular, this trend is developing in the framework of the project “Development of technology for environmentally friendly recycling of plastic waste by a low-temperature catalytic pyrolysis to produce a combustible gas, liquid fuel fractions and composite materials for various applications”, supported by the Federal Target Program “Research and Development” for 2014-2020.
Pyrolysis (suppuration), which rely scientists – is a chemical process in which under the influence of high temperatures and lack of oxygen decompose organic (and many inorganic) compounds.
“Pyrolysis – not the new technology – Kosivtsov said. – More people in the ancient caves used stone coal, and it is obtained by pyrolysis. We have improved and the process of adding special catalysts, and installation. ”
Indeed, the impact of high temperatures on the timber with a limited access of oxygen is known from ancient times. That charcoal fueled kiln times our ancestors Iron and Bronze Ages.
Old technology in new reading
Improvements of this ancient skill, produced a team of TSTU, led to the fact that in addition to the coal obtained from the reaction of hydrogen and more, which in its pure form, is likely to become the basis for future energy.
“In fact, the output we get two useful products – said the project manager. – This is the electrical energy that is produced directly in the installation and then fed into the grid. And carbon residue obtained after pyrolysis – low-grade coal, which can be used as an absorbent “.
In addition, scientists isolated, liquid and gaseous fuel fractions, with it their way they are trying to maximize, reducing the share of solid reaction products.
But one of the major disadvantages of this process is that the useful yield is obtained in the pyrolysis reaction only at very high temperature – about 1000 ° C. To adapt this method for the production, the research team from the TSTU improves installation, and most importantly, looking for effective and yet inexpensive catalysts that will significantly reduce the reaction temperature.
Volume of gaseous products of pyrolysis reactions as a function of temperature and the presence and type of catalyst. From the presentation of the scientific team TSTU
As catalysts for the pyrolysis of a variety of materials used – and metal chlorides and silica-alumina catalysts, special clays, which are widely used for cracking. The final preferred and scientists from TPGU, because such catalysts are not only highly effective but also available, and therefore inexpensive. Thanks to their use
pyrolysis temperature was reduced from 1100 ° C to 400-600 ° C, the useful output of the low-temperature pyrolysis increased by 10-30% depending on the kinds of catalysts and reaction time.
and temperature lowering means lowering the cost of the end product (it is possible to use less heat resistant materials in the installation, and the energy costs for heating are reduced), and thus, greater viability technology.
Pyrolysis takes place, so to speak, in three stages. First, the polymer (which may be, for example, old tires, and there may be other polymers – the optimal catalysts can pick up for any “of raw garbage”) breaks down into solid carbon residue, heavy and light hydrocarbons and gases: hydrogen, carbon monoxide gas, methane and others. Then successively decompose heavy hydrocarbons – in the lungs and gas, and light – on the gases. The high proportion of heavy and light gases react – the more useful the reaction yield.
By the way, generates heat setting also relatively cheap way – is used as fuel diesel easily accessible, however, the installation may not work on other fuels.