Ecology. Ecological and meteorological problems of cities and industrial
zones
Stolyarova N.À., Chekhlan N.À., Shustova D.V.
Automobile-Highway Institute of the State Higher Educational
Establishment «DonNTU», Ukraine
Tire Utilization
From year to year the number of cars increases and the
number of used tires increases as well. Worn-out tires are the source of the
long-term contamination of the environment; they are treated as the wastes of
danger class IV and are subject to the obligatory utilization / recycling.
There are about 25 million of tons of used tires in the world now. Their number
annually increases by 7 million of tons.
As it had been estimated by the Ministry of Environment of Ukraine the
problem of waste tire utilization in Ukraine has reached a wide scale: every
year about 180000 ton of used tires are thrown away. They are stored in the
forests, fields, along the roads or burned. About 270 kilograms of soot and 450
kg of toxic gases come into the atmosphere during the burning of 1 ton of used
tires as well as such dangerous substances as benzopyrene, soot, dioxins,
furans, polyaromatic hydrocarbons, polychlorinated biphenyls (PCBs), chromium,
arsenic, cadmium, etc.
That all shows big opportunities of waste utilization
for tire recycling by means of pyrolysis
and valuable materials recovering such as pyrolysis gas, synoil, carbon
black, metal cord.
Scheme of the tire recycling is shown on the
Fig.1
Used tires are collected and delivered to the raw
material storage. Tires are examined for the presence of metal disks, rings and
sent to the cutting. In order to provide denser piling of raw materials into
the retort the tires can be cut. At first tire bead is cut and then the tire is
carved with the help of special scissors for tire cutting.
Whole or cut pieces of tires are loaded into retort
(basket) after that the retort is put into the pyrolysis installation (reactor)
with the help of telpher or other lifting mechanism. There it is heated up to
500°C with no access of oxygen (pyrolysis process).
Fig.1
Initially the installation is heated with the help of
additional fuel; home-made products (carbon residue (semi-coke), liquid fuel
fraction, pyrolysis gas (methane)) can be used for this purpose. After the 2-3
hour mode is achieved additional fuel is not used, the gas jet, working on
non-condensed residues of pyrolysis products, is activated instead. In the
result of the pyrolysis process gas and steam mixture is obtained. The mixture
is directed into the condensation system (rectifying column). After
rectification the residues of gas and steam mixture are burned down in liquid
fuel gas jet which ensures the process maintenance. As a result of condensation
liquid fuel fraction called synoil is obtained.
As the pyrolysis process is exothermal reaction
followed by heat release, extra pyrolysis gas similar to methane is obtained.
It can also be used profitably. The duration of the process makes 10-11 hours
taking into account that 0, 5 t of tires are loaded into the retort. When the
process is over which is indicated by the control and measuring apparatus and
by termination of gas emission, the pyrolysis installation is opened with the
help of telpher and the retort is taken out, sealed and moved to cool down.
In its turn another retort with raw materials is
loaded into the vacant pyrolysis installation after that the process continues.
After the full cooling action (10-12 hours) carbon residue
and metal cord can be moved from the retort. Then metal cord should be
separated from carbon residue. It is possible to use the mechanized way of
separation. In order to do this the contents of the retort are loaded into a
cellular basket which is installed into the sieving machine, where the
separation of carbon from metal cord takes place. Fine pieces of metal are
removed with the help of magnet separation. After sieving machine we obtain
clean metal cord and also black carbon ready for the further processing.
Products obtained by recycling are subject to further
processing for additional profit. So carbon residue is ground and marketed as
carbon black. Liquid fuel fraction is subject to sublimation for fractionation
into diesel, bituminous, petrol and other ones.
Technology benefits:
- No harmful emissions are discharged into the atmosphere;
- Convenient way
of raw materials loading/unloading;
- Separation
system of metal cord from carbon black is automated;
- Carbon residue
can be used for further processing;
- High yield of
liquid fraction;
- Rectification
of liquid fuel fraction;
- Safe
construction of the installation;
- Continuous
process.
Economic benefit from 1 unit of our pyrolysis
installation (tank) is 170-440 USD per day.
1 ton of waste tires can be converted into: pyrolysis gas - 100 m³;
synoil- 350-400 kg; carbon black - 250-300 kg; metal cord - 200-250 kg.
Income items from installation
Carbon black, containing 92-99% of pure carbon, is
directed to the refining in the technological process. This results in
obtaining of carbon-carbon materials for metallurgy and/or electro conductive
carbon black. Consumption range: carbon-carbon materials for metallurgy,
manufacture of synthetic diamonds, stationery, alternator brushes, chemical
current sources, conductive screens of shaft cables, as a filler of the
rubber-containing products and etc.
Synoil is very similar to natural oil. The main components of it are:
diesel, petrol, bituminous fraction. It can be used as stove fuel or as black
oil; additive for DO - 37% (its price is 25% lower than the price of diesel gas
oil), additive for petroleum - 33%; its octane number is 130, primer
(rust-preventing agent) - 30%. The price for synoil in the Ukrainian market is
0,3-0, 4 USD/l. After distillation the obtained products are sold at the price
from 0,6 to 1,2 USD/l.
Gas is one of the strategic raw materials for Ukraine.
It can be used for the operation of mini boiler stations. 100 m³ of gas is
obtained from one boiler, but only 50 m³ of gas is used for the in-house
needs (operation of 80 kW gas jet within 9 work hours).
Metal cord is sold as scrap metal or as binding wire after burning. The
price for it makes 0, 15-0, 5 USD/kg.
Collection of tires for recycling. In average the
prices in Ukraine make 0, 3-0, 6 USD/pcs. for light tires, 0, 6-1,2 USD/pcs.
for trucks tires or 50 USD/t.
Literature:
1.
http://www.biodiesel-ua.com