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E.A. Aubakirov1, Zh.Kh. Tashmukhambetova2, K.E. Burkhanbekov3
1Doctor of Chemical Sciences, Professor, 2Candidate
of Chemical Sciences, Associate Professor, 3Candidate for a Doctor's
Degree
Al-Farabi Kazakh National University (Almaty), Kazakhstan
Pretreating waste tire with liquid nitrogen and
radiation exposure for the catalytic process
Nontraditional methods of pretreating waste tires such as radiation
exposure and processing with liquid nitrogen were
investigated for the aim of influencing to the yield of
liquid products of the catalytic hydrogenation.
Treatment waste tire with liquid nitrogen gave
possibility to the mechanical separation of the polymer mass from the tire cord and were divided into particle size types: 0.4-0.6, 0.8-1.0, 8.0-10.0
mm respectively. The
0.4-0.6 mm particle size of tire had
given a high yield of liquid
product in catalytic thermal
processing. After, the tire crumbs with particle size 0.4-0.6 mm was
subjected under dose of radiation exposure in the ranged
of 100-500 kGy. At a dose of 300 kGy
was observed the highest yield of
liquid product.
Key words:
waste tire, catalytic recycling, radiation exposure, particle size, waste
ferroalloy.
Introduction
In our modern world with a
civilization of mankind the production of industrial and household materials grows. Therefore, the number of hard utilizing wastes
increases. But the main problem wastes
such as rubber, plastic etc. are not
biodegradable [1-3]. Annually
Japan generates about 1 million tonne, and China had produced 5.2
million tonnes of waste tires in
2010 [4]. Due to the lack of appropriate
processes and technologies worn out
automobile tires are accumulated and stored in the territories of enterprises and organizations. Infinitely accumulate
and store waste tires
are impossible, because it requires
large areas of land.
Mostly
using methods to utilize waste tires are their storage in landfills and incineration. However, these methods do not solve the problem of environmental pollution.
The worn out automobile tires by the influence of microorganisms can be converted into environmentally
hazardous substances. Also, when burning these wastes
they emit a significant amount of gaseous and solid wastes which are
needed to be utilized [5].
In this regard, it is
necessary to develop effective utilizing methods for
automobile tires, rubber wastes,
which can simultaneously solve the problem
of reusing and environmental protection. Moreover, if
solve these problems this can give additional types of energy
sources. Nowadays, the preferable methods of recycling waste tires are their thermal and thermocatalytic processing to liquid products,
which can be used as high-quality motor
fuels after appropriate treatment [6].
Experimental
As a raw
material of the experiments was used tire crumbs with different particle sizes
taken by liquid nitrogen. As a catalyst had been used
composite catalyst based on ferroalloy production wastes (FAP) and natural zeolite from Taizhuzgen deposit
enriched with heulandite and clinoptilolite [8]. The FAP wastes
in its composition consists transition metals such as iron and manganese. As a source of hydrogen, also a binder component both raw materials and catalyst was taken a paste agent (PA) based
on heavy oil residue from "Kumkol"
deposit, with an initial boiling
point above 500 °C.
The experiments were performed
in batch-type installation under 5
MPa pressure and with 400 °C temperature
by continuous stirring. Time of
the experiment was 60 min.
The ratio of tire crumbs - paste agent (TC-PA) is 1-1
[7].
Radiation treatment of tire
crumbs was carried out on a linear
electron accelerator ELA-6 with
energy 6-MeV in an inert environment
[9]. The irradiation was performed
with a flux density of electrons 2 uA/cm2 and the dose ranged from 100 to
500 kGy.
Results and Discussion
Nontraditional
pretreating methods were investigated for the purpose to increase the yield
of liquid product of the catalytic
processing of waste tire. One of
the important factors of catalysis is the specific surface area of the feedstock. Therefore, in our case studying
the specific surface area of waste
tire is very important [10].
Thus, the sample of worn out automobile
tire was subjected to the liquid nitrogen treatment.
Treatment waste
tire with liquid nitrogen leads not just to the grinding of the tire, also to its activation, likely,
accompanied by significant structural
changes in the organic portion of the waste. By treating waste tire with liquid nitrogen was observed a
separation of polymer cord
which further was divided to the rubber
and polymer fibers. After, rubber
crumbs sorted out to the particle size types: 0.4-0.6, 0.8-1.0, 8.0-10.0
mm respectively.
The
particle size types of the tire crumbs
obtained from the treating of worn out
automobile tire with liquid nitrogen are presented in Table 1.
Table
1
Particle
size types of the tire crumbs
after treating with liquid nitrogen
Size types |
Polymer fiber |
Particle size of tire crumbs, mm |
||
0.4-0.6 |
0.8-1.0 |
8-10 |
||
Wt. % |
46.9 |
25.5 |
18.9 |
8.7 |
After
treating waste tire with
liquid nitrogen, we carried out experiments both with a
catalyst FAP-zeolite in a ratio of 80-20 [8]
and without catalyst. The
influence of particle sizes of waste tire to the yield of
liquid product has shown in Figure
1.
Fig. 1. Influence of particle sizes of tire to the yield of liquid product
Thermal
recycling of waste tire with
particle size 0.4-0.6 mm obtained by treating with liquid nitrogen has shown a
high yield of liquid product in presence of FAP-zeolite
catalyst (80-20) in comparison with other particle
sizes of tire crumbs.
This suggests that the large particle sizes of waste tire have a small
surface area, so they form large clumps. These clumps impede on
the high yield of liquid product and to the work of transition
metals of the catalyst. Because,
the work of these metals are inhibited by large clumps and this leads to
coking [6].
Treating
waste tire with liquid
nitrogen increased the yield of liquid product of
the catalytic process up to 60-65% comparing with the
process without catalyst. The maximum yield was 57.90
wt.%.
Also,
other non-traditional methods
were investigated such as treating of waste tire with radiation
exposure. The waste tire with particle size 0.4-0.6
mm was exposed to
the radiation dose in the range of 100-500 kGy.
The
dependence of the yield of liquid
product from irradiation of waste tire has shown in Figure 2.
Fig. 2. The dependence of the yield of liquid product from dose irradiation
As
seen in Figure 2, the
irradiated waste tire at a dose of 300 kGy increases the yield of liquid product up
to 66.2 wt.%. This proves that, prior radiation exposure of feedstock leads to their activation and increasing
the yield of liquid product.
Thus, using preliminary radiation
exposure and treatment with liquid
nitrogen of waste tires in catalytic hydrogenation in
the presence of composite catalysts
can significantly affect to the organic
mass structure of feedstock and increase
the yield of liquid product.
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