Tire Char Research Articles

Activation of pyrolytic tire char with CO 2: kinetic study

Chars from old tire pyrolysis have been activated with CO 2. The chars were obtained by pyrolysis of a waste tire sample in a fixed bed reactor at a temperature of 1000 °C for 3 h. The pyrolytic char, basically the original carbon black plus the tire mineral matter, was ground and sifted to an average particle size obtaining different fractions that were used as raw material in the activation experiments. These experiments were performed in a thermobalance at different temperatures (850, 900, 950 and 1000 °C) in order to determine the activation energy and pre-exponential factor, basic intrinsic kinetic parameters of the activation process. Experimental conditions were optimized to avoid internal and external mass transfer phenomena performing experiments with different particle sizes, at different flow rates and initial weights. Moreover, the tire char activation was found to be a first order reaction with respect to CO 2. A kinetic expression for tire activation, based on the random pore model and the structural parameters of the pyrolytic char, was deduced. In addition, with this kinetic model it can also be explained the maximum in reaction rate observed experimentally at conversions around 40%.

Mesoporous carbons from waste tire char and their application in wastewater discoloration

Waste tire char was employed as the precursor for the production of activated carbons with steam activation. Carbons with different porosities were obtained by activating the char to different extents of burn-off. Unlike commercial grade carbons that are generally microporous, the pores of the tire-char carbons are mainly composed of mesopores that have a mean size of 500 Å. Both the surface area and pore volume of the carbons increase with the extent of activation and pass through a maximum at a burn-off of 43%, above which the porosity decreases with further activation. Adsorption of methylene blue from aqueous solutions shows a monolayer coverage of the adsorbate on the carbon surface and a full access of the adsorbate to all the pores, which renders a high discoloration capability per unit area of the carbons. The methylene blue capacity of the carbons was found to increase with the adsorption temperature. Langmuir analysis shows that this increase in capacity with temperature can be attributed to an increase in the number of the adsorption sites as well as the endothermic nature of this specific adsorption.

Characterization and potential applications of pyrolytic char from ablative pyrolysis of used tires

Pyrolysis has the potential of transforming used tires into useful recyclable products. Pyrolytic char is one of the most important products of tire pyrolysis. The process economy depends strongly on its commercial value. A 2-year study was undertaken to examine the chemistry and commercial applications of pyrolytic char obtained from the commercialized process called Continuous Ablative Regenerator (CAR) system (Enervision Inc., Halifax, Canada). The pyrolysis temperature was 550°C, residence time 0.6 s, under N 2 flow and using ∼1 cm tire shreds. A small-scale unit, 0.25 ton day −1, was used in the study. The process is unique in design and features several operating parameters, which favor optimum tire pyrolysis (e.g. no heat transfer medium, fast pyrolysis and rapid product quenching). The physical properties (porosity, particle and aggregate size, surface area), chemical properties (elemental analysis, ash content and composition) and aqueous adsorption properties (for metals, phenols and methylene blue) of the pyrolytic char were examined. As well, laboratory-scale production of activated carbon from tire pyrolysis char was examined as a means of upgrading. The activated carbon was characterized in the same manner as the char. Results revealed that the char must be post- carbonized (600°C) to remove unwanted odor and trace oils. The resulting carbonized char has excellent adsorption capacity for phenol and metals (i.e. lead) from solution. It is believed that the high sulfur content in the char (2%) and the inherent composition of tire char is responsible for these properties. Activation using steam (900°C, 3 h) produced an activated carbon with good surface area (302 m 2 g −1), excellent adsorption for phenol and methylene blue, but showed no improvement for metal removal. Norit SA3 and commercial charcoal were used for comparison. Further studies will be conducted to examine the char performance for Hg removal from air and water and its use in wastewater treatment and as a stack gas scrubber medium.

Properties of Chars and Activated Carbons Derived from the Pyrolysis of Used Tyres

A nitrogen purged static-bed batch reactor was used to pyrolyse 3 kg batches of shredded scrap tyres at temperatures between 450 and 600 °C. The yield of char remained fairly constant at about 38 wt% irrespective of pyrolysis temperature; however, the yield of oil decreased from 58 wt% to 53 wt% and the gas yield increased from 4.5 wt% to 8.9 wt%. The derived tyre char was characterised for a range of properties, including: surface area, pore size distribution, ultimate and proximate analysis, calorific value and sulphur content and trace metal content. The tyre char was subsequently activated in a steam/nitrogen or carbon dioxide/nitrogen mixture at 835 to 935 °C. The activated carbons were then acid demineralised and the influence of activation process conditions on the surface area, micropore volume, mesopore volume, mesopore surface area and the mesopore size distribution was investigated. The maximum BET surface area generated was 640 m2 g−1 at 65 wt% burnoff. All the activated carbons had a considerably greater mesopore volume than micropore volume, which was due to the predominantly mesoporous structure of the initial tyre char. Examination of the Kelvin mesopore size distribution profiles indicated that activation of tyre char proceeded via the standard mechanism, i.e. micropore formation followed by pore widening and finally pore destruction. Carbon dioxide activation produced carbons with a lower BET surface area, absolute micropore volume and total pore volume, but narrower size distribution than when steam was the activating agent. The activation temperature had little apparent effect on the properties of the activated carbons. Overall, the activation process employed proved a viable means of producing carbons of comparable quality to low grade commercial activated carbons.

Influence of Process Conditions on the Rate of Activation of Chars Derived from Pyrolysis of Used Tires

Used tires were pyrolyzed in a nitrogen-purged 3 kg static bed, batch reactor. The char was subsequently activated in an equimolar mixture of either steam and nitrogen or carbon dioxide and nitrogen. Activation was a two-stage process, with an initial more rapid gasification of carbonized rubber deposits followed by less rapid gasification of carbon black. The activation energy in steam was 201 kJ mol-1. The burnoff achieved by carbon dioxide under otherwise identical conditions to that of steam was on average 72% of that found when steam was used. The reactivity of acid-demineralized char in steam was around 22% less than that of raw char. It was suggested that calcium ions in the raw tire char catalyzed the gasification reactions. The tire pyrolysis temperature had an unclear influence on the rate of activation of the derived chars. The influence of particle size on the rate of activation was also investigated, and the results are discussed in terms of ash content and distribution. The outflow gas composition and gross calorific value of the gas were also determined in relation to activation conditions. BET surface areas of the derived activated carbons reached a maximum of 640 m2 g-1.

5676775 Process for manufacturing corrosion resistant metal products: Cacace Antonino Giorgio; Clark Allan Douglas West Glamorgan SA3 3BU, United Kingdom

Pyrolysis has the potential of transforming used tires into useful recyclable products. Pyrolytic char is one of the most important products of tire pyrolysis. The process economy depends strongly on its commercial value. A 2-year study was undertaken to examine the chemistry and commercial applications of pyrolytic char obtained from the commercialized process called Continuous Ablative Regenerator (CAR) system (Enervision Inc., Halifax, Canada). The pyrolysis temperature was 550°C, residence time 0.6 s, under N2 flow and using ∼1 cm tire shreds. A small-scale unit, 0.25 ton day−1, was used in the study. The process is unique in design and features several operating parameters, which favor optimum tire pyrolysis (e.g. no heat transfer medium, fast pyrolysis and rapid product quenching). The physical properties (porosity, particle and aggregate size, surface area), chemical properties (elemental analysis, ash content and composition) and aqueous adsorption properties (for metals, phenols and methylene blue) of the pyrolytic char were examined. As well, laboratory-scale production of activated carbon from tire pyrolysis char was examined as a means of upgrading. The activated carbon was characterized in the same manner as the char. Results revealed that the char must be post- carbonized (600°C) to remove unwanted odor and trace oils. The resulting carbonized char has excellent adsorption capacity for phenol and metals (i.e. lead) from solution. It is believed that the high sulfur content in the char (2%) and the inherent composition of tire char is responsible for these properties. Activation using steam (900°C, 3 h) produced an activated carbon with good surface area (302 m2 g−1), excellent adsorption for phenol and methylene blue, but showed no improvement for metal removal. Norit SA3 and commercial charcoal were used for comparison. Further studies will be conducted to examine the char performance for Hg removal from air and water and its use in wastewater treatment and as a stack gas scrubber medium.

Advanced control for power plant profitability

Large number of waste automotive tyres are being disposed through landfill or illegally dumped and only small proportions are currently recycled. Waste tyres can be a source of health and environmental concerns and also represents a loss of potential valuable source. The ecofriendly and resource recovery approach is critically required to recycle waste automotive tyres. In this paper, an attempt to synthesis SiC/Si3N4 nanocomposite by in situ process using automotive waste tyres as resources has been reported. The synthesis was carried by using simultaneous carbothermal reduction and nitridation reaction at 1550 °C in nitrogen atmosphere using pyrolysed waste automotive tyre char as carbon source and silicon dioxide as silica source. The formation of SiC and Si3N4 particles was confirmed by FTIR and XRD techniques. Raman analysis signifies the major phases of β-SiC, α-Si3N4 and β-Si3N4. The particle size of synthesised SiC/Si3N4 nanocomposite was in the range of 20–100 nm and mainly composed of sphere shaped nanoparticles. This innovative approach of using automotive tyres as carbon source for synthesising SiC/Si3N4 nanocomposite will reduce the volume of wastes in landfills, decreases the risk of health concerns and also recovers valuable carbon resource.

Applications for activated carbons from waste tires: natural gas storage and air pollution control

Natural gas storage for natural gas vehicles and the separation and removal of gaseous contaminants from gas streams represent two emerging applications for carbon adsorbents. A possible precursor for such adsorbents is waste tires. In this study, activated carbon has been developed from waste tires and tested for its methane storage capacity and S0 2 removal from a simulated flue-gas. Tire-derived carbons exhibit methane adsorption capacities (g/g) within 10% of a relatively expensive commercial activated carbon; however, their methane storage capacities ( V m V s ) are almost 60% lower. The unactivated tire char exhibits SO 2 adsorption kinetics similar to a commercial carbon used for flue-gas clean-up.