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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.

 

            References

1.                 Suat Uçar, Selhan Karagöz, Jale Yanik, Mehmet Saglam, Mithat Yuksel Copyrolysis of scrap tires with waste lubricant oil. Fuel Processing Technology 2005; 87:53-58.

2.                 Rubber Manufacturers Association (RMA), Scrap Tire Markets in the United States 2005, November 2006.

3.                 J.I. Riesman, Air Emissions from Scrap Tire Combustion, EPA-600/R-97–115, October 1997.

4.                 Adetoyese Oyedun, Ka-Leung Lam, Malte Fittkau, Chi-Wai Hui Optimisation of particle size in waste tyre pyrolysis. Fuel 2012; 95:417–424.

5.                 E.P. Volynkina, S.A. Kudashkina, A.V. Nezamaev, N.V. Zhuravleva "The use of waste tires" Ecology and Industry of Russia " 2001. ¹ 1. - P. 40-44.

6.                 A.E. Aubakirov, Zh.Kh. Tashmukhambetova, K.E. Burkhanbekov Identification liquid products of the thermal and thermocatalytic recycling of worn out tires // Eurasian Union of Scientists (ESU), ¹ VII, 2014. Chemical sciences. – P. 59-61.

7.                 A.E. Aubakirov, K.E. Burkhanbekov, E.B. Serikov Secondary catalytic recycling of used automobile tires // Materials IX-international scientific-practical conference "STRATEGICZNE PYTANIA SWIATOWEJ NAUKI -2013", 07-15 lutego 2013 roku, ", Przemysl, Polska. -P.54-57.

8.                 Zh.K. Kairbekov, E.A. Aubakirov, Zh.Kh. Tashmukhambetova,
M.F. Fayzullaeva, Zh.K. Shomanova, K.E. Burkhanbekov Catalytic Hydrogenation of Rubber Wastes // Bulletin of KazNU, Chemical Series, ¹ 5, 2014.

9.                 G.K. Vasilina, R.M. Moise, A.I. Kupchishin Influence of irradiation on the activity of natural zeolite in the process of toluene hydrogenation // International scientific and practical conference dedicated to the 70th anniversary of professor Zh.K. Kairbekov «Technology of hydrocarbon raw material complex processing», October 15-16, 2014. -P. 282-285.

10.             Gao N., Li A., Li W. Research into fine powder and large particle tire pyrolysis. Waste Manage. Res. 2009;27:242–50.