Tyres pyrolysis

Williams, P. T. Taylor, D. T. 1993. Aromatiza-tion of tyre pyrolysis oil to yield polycyclic aromatic hydrocarbons. Fuel, 72, 1469-1474. 

M. F. Laresgoiti et al, Characterization of the liquid products obtained in tyre pyrolysis. Journal of Analytical and Applied Pyrolysis, 71, 917-934 (2004). 

D. Y. C. Leung and C. L. Wang, Kinetic study of scrap tyre pyrolysis and combustion, Journal of Analytical and Applied Pyrolysis, 45, 153-169 (1998). 

P. T. Williams and A. J. Brindle, Temperature selective condensation of tyre pyrolysis oils to maximise the recovery of single ring aromatic compounds. Fuel, 82, 1023-1031 (2003). 

Various alternatives have recently been proposed for the valorization of the solid carbon residue of tyre pyrolysis. Napoli et al.ni have compared the properties of the char with those of coal. The calorific value of the char is slightly higher than that of coal due to the lower ash content of the former, while... 

The feasibility of using the char generated by tyre pyrolysis as a precursor in the manufacture of activated carbon has been studied by various authors.119,131 Merchant and Petrich131 have obtained carbons with surface areas above 500 m2 g 1 from tyre pyrolysis in batch reactors and subsequent activation of the chars by treatment with superheated steam at temperatures in the range 800-900 °C. Teng et a/.119 have obtained activated carbons with surface areas above 800 m2 g 1 by pyrolysis of tyres up to 900 °C, followed by activation of the resulting chars in C02 at the same temperature. These surface areas are... 

Figure 4.36 Comparison of the particle size distribution of a coal and a tyre pyrolysis char 127 (a) char, (b) coal.

The most commonly used rubber in tyre manufacture is styrene-butadiene copolymer containing about 25 wt% of styrene. The presence of a high concentration of double bonds in the rubber backbone makes the alternative of degrading rubber wastes by treatment in hydrogen atmospheres very attractive. Moreover, because used tyres contain significant amounts of sulfur, hydrogenation also favours the removal of this undesired element as H2S, which allows oils to be produced with lower S content than those derived from tyre pyrolysis. 

Likewise, Orr et al.29,30 have explored the possible use of tyre pyrolysis oil as a solvent for coal liquefaction. The potential of this alternative was demonstrated by the fact that coal-TPO mixtures were transformed with higher conversion than when coal was reacted directly with ground waste rubber tyres. It is proposed that the polyaromatic compounds present in the TPO favour coal dissolution during liquefaction. Treatment of coal-TPO mixtures (50/50%) at 430 °C under 68 atm of cold-hydrogen pressure in the presence of a Mo catalyst led to a high coal conversion in just 10 min of reaction. From electron probe microanalysis of the coal particles after the reaction, the authors conclude that TPO favours the catalyst dispersion and its contact with coal, which results in enhanced coal conversion. 

Aguado, R. Olazar, M. Velez, D. Arabiourrutia, M. Bilbao, J. Kinetics of scrap tyre pyrolysis under fast heating conditions. J. Anal. Appl. Pyrol. 2005, 73, 290-298. 

GC-MS and GC-AED techniques were used for the direct analysis of used tyre vacuum pyrolysis oil [255]. Antioxidants and antiwear additives (0.25-5 wt% DODPA, a-NPA, TCPs, TPP, IPPs) in lubricating synthetic oils, essentially esters of branched-chain alcohols such as pentaerythritol, neopentylglycol and trimethylolpropane, were determined by means of GC-SIM-MS using diphenylamine (DPA) as an internal standard [256] similarly, TCPs, TPP, IPPs, DPs and I2P were quantitatively analysed by GC-FPD using triethylphosphate (TEP) as an internal standard. RSD values of 3-6% were reported for GC-SIM-MS, and 7-9 % for GC-FPD. 

Carbon black is made by the vapour-phase incomplete pyrolysis of hydrocarbons to produce a fluffy fine powder. Worldwide, about 7 million tons a year are produced. It is used as a reinforcing agent in rubber products such as tyres (20-300 nm), as a black pigment (<20 nm) in printing inks, paints, and plastics, in photocopier toner, and in electrodes for batteries and brushes in motors. 

Yang and co-workers [82] have reported a mechanistic study carried out based on the simultaneous measurement of enthalpy and weight loss by TG-DTA on tyre rubbers NR, SBR and BR. The hyphenated technique allows to attribute the observed exothermic peak to chemical reactions and the endothermic peak to evaporation of pyrolysis products. 

Rubber has a structure intermediate between thermosets and thermoplastics, with molecular chains linked by sulphur bridges during vulcanization. In pyrolysis, the main material is tyre rubber, a compound of styrene- butadiene- and isoprene-based rubber (SBR), of carbon black, sulphur, vulcanization aids, and zinc oxide. 

Pyrolysis of tyres is a feasible, yet technically difficult operation. The handling of the remnants of the steel carcass, the carbon black, the zinc oxide, as well as the tendency to repolymerize of the major products are serious stumbling blocks. Various rubber pyrolysis technologies have been developed, using, e.g. fluid bed, rotary kiln (Sumitomo Cement), molten salts, or cross-flow shaft systems (WSL/Foster Wheeler). 

Pyrolysing waste tyres in TG, three weight loss stages are reported [34] 200-330°C, 330-400°C and 400-500°C. The first step corresponds to the thermal decomposition of the mixture of oils, moisture, plasticizers and other additives, the second one to that of NR and the third one to the decomposition of BR and SBR content of the tyre. The pyrolysis conditions influence strongly the resulting oil [35]. 

An oil of low flash point in the range 14-18°C, and of 41-43 MJ Kg gross calorific value has been obtained in batch pyrolysis [36] of automobile tyre waste. In a pilot plant with semi-continuous feeding [37] the liquid yield of tyre waste decreased seriously with increasing temperature, and it was always lower in an atmosphere containing oxygen that in nitrogen. 

O. Senneca, P. Salatino and R. Chirone, A fast heating-rate thermogravimetric study of the pyrolysis of scrap tyres. Fuel, 78, 1575-1581 (1999). 

J. F. Gonzalez, J. M. Encinar, J. L. Canito and J. J. Rodriguez, Pyrolysis of automobile tyre waste. Influence of operating variables and kinetics study. J. Anal. Appl. Pyrol., 58-59, 667-683 (2001). 

A. M. Cunliffe and P. T. Wilhams, Composition of oils derived from the batch pyrolysis of tyres. J. Anal. Appl. Pyrol, 44, 131-152 (1998). 

J. A. Conesa, 1. Martin-Gullon, R. Font and J. Jauhiainen, Complete study of the pyrolysis and gasification of scrap tyres in a pilot plant reactor. Environ. Sci. Tech-nol, 38, 3189-3194 (2004). 

W. Kaminsky and H. Sinn, Pyrolysis of plastic wastes and scrap tyres using a fluidised bed process.In J. L. Jones and S. B. Radding(eds) Thermal Conversion of Solid Wastes and Biomass.ACS Syposium Series 130, American Chemical Society, Washington,D.C (1980). 

Fluidized sand beds are surprisingly insensitive to the unit size of the feed material. Pieces of scrap tires up to a weight of 2.7 kg each were fed and quantitatively pyrolyzed. These results offer the perspective for a pyrolysis process for scrap tyres without prior size reduction. Most pyrolysis processes use feed crushed to a 200-20 nun size which involves considerable expense [9], Successful pyrolysis experiments in an indirectly heated rotary kiln have been conducted by Kobe Steel [3]. 

H. W. Schnecko, Pyrolysis of used tires, Chem. Ing. Techn., 48, 443-447 (1976). W. Kaminsky, Pyrolysis of plastic waste and scrap tyres in a fluid bed reactor. Resource Recovery Conserv., 5, 205-216 (1980). 

Li et al. [16] also stndied the influence of pyrolysis temperature on the pyrolysis products derived from solid waste in a rotary kiln reactor. They used an externally heated laboratory-scale rotary kiln pyrolyser (Figure 19.8). The length of the rotary kiln was 0.45 m with an internal diameter of 0.205 m. Kiln rotation speed can be adjusted from 0.5 to 10 rpm. The raw materials used in this study were polyethylene (PE), wood and waste tyres. The results obtained by Li et al. [16] reiterated that as the reaction temperature profile changes so does the product yield (Figure 19.9). 

Considerable attention has been paid over the last few years to the use of microwave pyrolysis for the processing of scrap tyres. Approximately 2.5 million tonnes in North America, 2.0 million tonnes in the European Union and 0.5 million tonnes in Japan, of scrap tyres are discarded per year. As much as 50% of this waste is landfilled which is clearly causing an increasing unsustainable and unacceptable situation. Other recycling... 

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