Acid Demineralization and Characterization of Carbon Black Obtained From Pyrolysis of Waste Tyre Using Thermal Shock Process

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1 International Journal of Research in Chemistry and Environment Vol. 3 Issue 1 January 2013( ) ISSN Research Paper Acid Demineralization and Characterization of Carbon Black Obtained From Pyrolysis of Waste Tyre Using Thermal Shock Process *Ware Pundlik, Shukla Vikaskumar, Kushvah Avadhesh, Desai K. R. Department of Chemistry, Uka Tarsadia University, Bardoli, Gujarat , INDIA (Received 29 th October 2012, Accepted 6 th December 2012) Available online at: Abstract: Although, 1.5 billion scrap tyres / yr are produced and 41% of these amounts become waste in India and China, these waste tyres are not evaluated properly. One of the thermal processes is pyrolysis that waste tyres can be converted into gas, oil and solid product. Scrap tyres do not decompose easily in the nature and cause too many environmental problems. The carbon black obtained from pyrolysis of scrap tyres at a temperature of 500 C contains % ash. Due to the presence of high ash content limits its application in different products. The pyrolytic carbon black obtained (CB) was contaminated by various additives of the original tire. Contaminants were also produced by chemical reactions occurring in the pyrolysis reactor. A characterization and demineralization of the recovered carbon black was performed and a possible reduction of the ash content by H 2 SO 4, HCl, HNO 3 and NaOH treatment was investigated. The variables which were studied included the ratio of reactant to carbon black, the reactant concentration, the treatment temperature and the reaction time. As a conclusion, the improvement studies had a positive effect to decrease ash content of solid products. It was found that treatment of a mixture of acids is very effective than individual. Keyword: Acid, Ash, Demineralization, Pyrolytic carbon black, Reduction, Treatment. Introduction The increase in the awareness of waste management and environmental related Issues has led to substantial progress in the utilization of rubber waste [1]. Figure 1: World Carbon Black Market (+/-$9 Billion) Sources: Jim Blackman, Investor Relations, 208 The world generates about 1.5 billion waste tires annually, from fig. 1, 41 percent of them in emerging markets in India and China and rest is in another country. Carbon Black is the main product recycled by Pyrolysis technology. The amount of recycled carbon black is 30% to 35% (depending on the type of tyres) of the total amount of scrap tyres recycled in the system. Scrap tire rubber consists of about 60 wt. % volatile organics, 30 wt. % fixed carbon and 10 wt. % ash. Elemental analysis shows that the tire rubber contains approximately 80 wt. % C, 7 wt. H, 0.4 wt. % N, 1.5 wt. % S, 3 wt. % O and 8 wt. % ash. The main components of pyrolysis gases reported by various authors are: H 2, H 2 S, CO, CO 2, CH 4, C 2 H 4, C 3 H 6 and other light hydrocarbons [7]. With respect to the pyrolysis yields, 550 C was a high enough temperature for the pyrolysis of the tyres since decomposition was complete and no significant differences were found in the solid, liquid and gas yields at

2 higher temperature [2]. The carbon yield was found to decrease with the pyrolysis temperature, holding time, and KOH/tire ratio [6]. The photocatalytic desulfurization of waste tire pyrolysis oil was carried out using TiO 2 as the photocatalyst. It was found that the maximum % sulfur removal of 43.6% was achieved when 7 g of TiO 2 /L of waste tire pyrolysis oil was loaded into the system containing 1/4 (v/v) of waste tire pyrolysis oil/acetonitrile at 50 C for 7 h [14]. Activated carbon prepared from wood was found suitable adsorbent for removal of Ionic dyes [4]. The research findings of the studies show that fixed-bed fire-tube heating pyrolysis is a good option for production of bio-crude oils from solid tire wastes [8]. For tires that are scrapped, the study shows that less than 40% of the energy embedded in tires are recoverable as fuel energy [9]. Use of tires for some applications may not offset the energy use of any materials (i.e., Aggregates), but it does offset energy use when replacing polymers. As a fuel, tires are superior to coal in specific energy content and the environmental burden of residues. More than half the tires scrapped in the US are used for fuel [9]. According to India Carbon Black s Market Forecast and Opportunities, 2017 carbon black market in India is expected to grow at the compounded annual growth rate of around 9% between 2012 and 2017 which is anticipated to drive the market to new heights [10]. From figure 2, the question arises in each mind why the recycling of rubber is very much few as compared to others? Consist of solid products high ash and high sulfur are unsuitable for efficient use as a commercial carbon black. For instance, this study focuses on an understanding of the recovery of pyrolysis products and the removal of sulfur from pyrolytic CB during pyrolysis. Material and Methods The tyre material was shredded and crumbed to produce a size of 8-9mm without steel in it. The sample of Carbon Black was obtained by pyrolysis of used tires at a temperature of 500 C. The thermal shock pyrolysis process is shown in figure 3. This kind of carbon black is used in tires as a filling material. Treatment: The carbon black sample obtained from thermal shock pyrolysis was ground, dried at 120 C for 24 h and sieved. The particle size distribution was as follows: 0.25mm, 0.71mm, d>100mm, using ASTM standard sieves. The 5 g CB samples were mixed with different volumes of acid. The acids to CB ratios are shown in table 2, 3 and 4. The mixtures were heated at temperatures o C for different times (30-40 min) with vigorous stirring. The sample was filtered on a Whatman No. 42 filter paper to separate the CB which was washed with distilled water. Then, the sample was treated with sodium hydroxide in the same conditions as with the acid. The sample was filtered, washed with distilled water and dried at 120 C for 24 h. The reactant to CB ratio, the reactive concentration, the heating temperature and the reaction time were investigated. WHY? Figure 2: Industrial symbiosis and waste recovery in an Indian industrial area [10]. 209

3 Figure 3: Diagram for pyrolytic and thermal shock processes Table 1 Proximate Analysis of Carbon Black [CB] Parameter HAF N330 FEF N550 Printex U (Degussa) Initial CB CB + HCl+ HNO 3 + H 2 SO 4 +NaOH CB + HCl+ HNO 3 Moisture Ash Volatile matter Fixed carbon GCV, MJ/ kg Table 2 After sieving: Three different parts Using 60 and 20 mesh sieves Mixture 0.25 mm CB Mixed CB 0.71mm CB Course CB CB HCl HNO H 2 SO Aqua Ragia Aqua Ragia +H 2 SO Anti aqua Anti aqua +H 2 SO Figure 4: Variations of Ash content (in %) with different size of CB 210

4 Analysis: The carbon black sample was characterized using muffle furnace, hot air oven for moisture, ash and volatile matter. Gross calorific value (GCV) of CB was done in the Mantra Laboratory, Surat. Results and Discussion To enhance the commercial value of this CB so as to increase its potential usage, it is necessary to treat it. Common and low price reactants were chosen. Using HCl instead of sulfuric acid for the demineralization of the pyrolytic carbon black proved to be equivalent in terms of ash reduction [11]. Table l, summarizes the results of the initial and acid treatment of CB. The results show that the tyre had a typical volatile content of 2.9%, fixed carbon of 85.15%, ash content of 11.7% and moisture content of 0.25%. The treatment of HCl, H 2 SO 4, HNO 3 and NaOH on CB reduces ash content upto 5.59 while treatment with only HCl and HNO 3 ash was found 6.21%. This is because of sulfate and hydroxides formed in the presence of H 2 SO 4 and NaOH [3,12]. The mixed CB was separated by using 60 and 20 mesh sieve for different particle sizes. Concentration of the ash in the CB recovered was considerably higher than that of the commercial carbon black filler. This is due to the metalloorganic and inorganic components added to the elastomer during the formulation of the tire in order to improve its quality [3]. Table 2, shows the % of ash for the different combination of HCl, HNO 3 and H 2 SO 4 were used for demineralization by CB. From fig.4, the extent of demineralization increased with a decrease in size and presence of aqua ragia. The ash reached 2.9% in the presence of 0.25mm CB and Aqua Ragia +H 2 SO 4. Treatment of a mixture of sulfuric acid and aqua ragia resulting the formation of salts of sulfates (in solution) and chlorides and nitrates (deposits). These products can be recovered and used in specific applications. Table 3, Summarizes the different proportion of HCl and HNO 3 with CB, and indicates the 1:3 proportion of HCl:HNO 3 gives minimum ash content 3.84%. While from figure 5, the ash content decrease up to 1:3 ration of HCl:HNO 3 and again increases. The opposite result was found in the case of HNO 3 :HCl ratio. The increasing ash content as the ratio of acid mixture increases. The study expanded for different concentration of anti aqua ragia in Table 4 indicates the minimum ash content was found in S 2 and S 7 samples. No significant changes were observed by increasing the concentration of anti aqua ragia. This is because of regeneration of different salts in CB. Table 3 50g Course size Carbon Black + HCl : HNO ml H 2 O S. No. Ratio HCl:HNO 3 HNO 3 :HCl 1 HCl HNO : : : : : Figure 5: Variations of ash with different ratios of HCl : HNO 3 Conclusion The results found that ash reduced in pyrolytic CB up to 2.94% in the mixture of Aqua Ragia and H 2 SO 4. In case of anti aqua ragia, ash reduced more than aqua ragia and no effective changes found in ash content by changing the concentration of aqua ragia and anti aqua raga. Analyses of the results obtained show that the acid treatment is an efficient way to decrease the ash content of the pyrolytic carbon black obtained by pyrolysis of scrap tires. By reducing the ash content increases the surface area of the carbon black particles and expands the range of utilization of the CB. The soluble and non-soluble salts formed (sulfates and hydroxides, respectively) by mixing the spent sulfuric acid and can be used for other applications. Future work should be directed at optimizing the demineralization process. Table 4: At different Ratios of Anti Aqua Ragia + CB (0.71mm) S. No. S 1 S 2 S 3 S 4 S 5 S 6 S 7 Ratio (20 g CB) 2:6 4:12 6:18 8:24 10:30 12:36 15:

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