Pilot-Scale Pyrolysis of Scrap Tires in a Continuous Rotary Kiln Reactor

Abstract

The pilot-scale pyrolysis of scrap tires in a continuous rotary kiln reactor was investigated at temperatures between 450 and 650 °C. As the reactor temperature increased, the char yield remained constant with a mean of 39.8 wt %. The oil yield reached a maximum value of 45.1 wt % at 500 °C. The pyrolytic derived oils can be used as liquid fuels because of their high heating value (40−42 MJ/kg), excellent viscosity (1.6−3.7 cS), and reasonable sulfur content (0.97−1.54 wt %). The true-boiling-point distillation test showed that there was a 39.2−42.3 wt % light naphtha fraction in the pyrolytic oil. The volatile aromatics were quantified in the naphtha fraction using gas chromatography−mass spectrometry. The maximum concentrations of benzene, toluene, xylene, styrene, and limonene in the oil were 2.09 wt %, 7.24 wt %, 2.13 wt %, and 5.44 wt %, respectively. The abundant presence of aromatic groups was also confirmed by functional group Fourier transform infrared analysis. The concentration of polycyclic aromatic hydrocarbons such as fluorine, phenanthrene, and anthracene increased with increasing temperature. The pyrolytic char was composed of mesopores with a Brunauer−Emmett−Teller (BET) surface area of about 89.1 m2/g. The char after carbon dioxide activation had a high BET surface area of 306 m2/g at 51.3% burnoff. The relationship between the surface area and the carbon burnoff was almost linear. Both the original pyrolytic char and the activated char have good potential for use as adsorbents of relatively large molecular species.

Pyrolysis of waste tyres: A review

“…The caloric value of the tyre oils ranged between 38 to 42.66 MJ kg -1 and was comparable with that of the petroleum fuels shown in Table 5. Others have reported the calorific value of the tyre pyrolysis oil to be between 38 and 49.5 MJ -1 (Williams et al, 1998;Li et al, 2004;Murugan et al, 2008a;Banar et al, 2012;Rada et al, 2012). Kar (2011) used expanded perlite as a catalyst mixed with waste tyre in an attempt to improve the fuel properties of the product pyrolysis oil.…”

“…A maximum yield of product oil of 38.12 wt.% was obtained at 550°C and maximum gas yield of 10.75 wt.% at 680°C. Li et al (2004) also used a rotary kiln reactor to investigate tyre pyrolysis at different pyrolysis temperatures. The rotary kiln consisted of a 0.3 m diameter, 3 m long reactor rotating at between 0.45 and 0.9 r.p.m., externally heated by electrical furnaces corresponding to an effective heated length of 1.8 m. The highest oil yield of 45.1 wt.% was obtained at 500°C pyrolysis temperature with a gas yield of 13.6 wt.%.…”

“…Kaminsky et al (2009) have reported detailed analyses of tyre pyrolysis oils obtained from pyrolysis of tyres in fluidised beds ranging in throughputs from laboratory scale at 1 kg -3.8 wt.% respectively for a laboratory scale reactor at 740°C. Cunliffe and Williams (1998a) reported maximum concentrations of volatile aromatic compounds of toluene at 1.77 wt.%, decomposes to a range of products including benzene, xylene, toluene, trimethylbenzene, styrene and methylstyrene which occurs at pyrolysis temperatures above 500°C and/or with long hot zone residence times (Pakdel et al, 1992;Li et al, 2004).…”

“…Table 3 shows some of the PAH identified in tyre pyrolysis oil (Williams and Bottrill, 1995;Cunliffe and Williams, 1998a;Dai et al, 2001;Li et al, 2004;Conesa et al, 2004;Laresgoiti et al, 2004;Olazar et al, 2008;Kaminsky et al, 2009;Banar et al, 2012). Concentrations of total PAH in tyre pyrolysis oils are reported at 1.72 wt% for a fixed bed reactor at 500°C (Cunliffe and Williams, 1998a), however, higher concentrations of PAH totalling over 16 wt.% have been reported for the rotary kiln pyrolysis of waste tyres at the same temperature (Li et al, 2004). A wide range of PAH have been reported by Laresgoiti et al (2004), consisting of mainly naphthalene, fluorene and phenathrene and their alkylated homologues.…”

“…There was little influence of pyrolysis temperature on the trace metal or sulphur content of the chars over the temperature range investigated. Li et al (2004) also investigated the characteristics of chars produced from a rotary kiln reactor over a similar temperature range of 450 to 650°C. They also reported that the volatile content of the product chars decreased with increasing temperature, from 16.61 wt.% to 6.27 wt.%, with typical surface area~89 m 2 g -1 .…”