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An experimental survey of waste tyre gasification with steam as oxidizing agent has been conducted in a continuous bench scale reactor, with the aim of studying the influence of the process temperature on the yield and the composition of the products; the tests have been performed at three different temperatures, in the range of 850-1000°C, holding all the other operational parameters (pressure, carrier gas flow, solid residence time). The experimental results show that the process seems promising in view of obtaining a good quality syngas, indicating that a higher temperature results in a higher syngas production (86 wt%) and a lower char yield, due to an enhancement of the solid-gas phase reactions with the temperature. Higher temperatures clearly result in higher hydrogen concentrations: the hydrogen content rapidly increases, attaining values higher than 65% v/v, while methane and ethylene gradually decrease over the range of the temperatures; carbon monoxide and dioxide instead, after an initial increase, show a nearly constant concentration at 1000°C. Furthermore, in regards to the elemental composition of the synthesis gas, as the temperature increases, the carbon content continuously decreases, while the oxygen content increases; the hydrogen, being the main component of the gas fraction and having a small atomic weight, is responsible for the progressive reduction of the gas density at higher temperature.

The disposal of waste tires represents a relevant problem within the waste management strategy of the European community: more than 300 000 000 tires are estimated to reach their end of life each year in the 27 member states of the European Union and comparable amounts are found in North America, Latin America, Asia, and the Middle East. The global total is ∼1 000 000 000 and rising each year. (Source: European Tyre Recycling Association (ETRA), 2006.) It is well-known that scrap tires possess high volatiles and low ash contents, together with a heating value that is higher than coal and biomass. These properties make them an ideal material for alternative thermal processes, such as pyrolysis and gasification, which can be finalized both to energy and material recovery. Within this frame, the present work is related to experimental tests and has obtained results of a combined process of scrap tire steam gasification and syngas catalytic reforming, with the aim of exploring the possible utilization of syngas for fuel cell applications. Four catalysts have been used for the experimental tests: two natural mineral products (olivine and dolomite) and two commercial nickel-based catalysts. Experimental data show that whether olivine or dolomite is used directly into the reactor to carry out the steam gasification, the char and gas yields increase with respect to the sole tire gasification (the char production varies from 41.2% w/w without catalysts to 59% w/w and 47.9% w/w, using olivine and dolomite, respectively; the gas production varies from 60.8% w/w for the sole tire gasification to 63.5% w/w with olivine and 84% w/w with dolomite). Then, while the olivine shows a stronger effect on the char production, the dolomite seems to be more effective on the gas yield. Moreover, both the catalysts promote a higher hydrogen production, which varies from 51.6 vol % for the sole tire gasification to 65.6 vol % and 57 vol % using, respectively, dolomite or olivine, basically because of the enhanced cracking of methane and the other hydrocarbons (the methane content decreases from 27.6 vol % for the sole tire gasification to 11.3 vol % and 20.8 vol %, using dolomite or olivine, respectively). Regarding both dry and steam reforming, the experimental tests show that the catalytic step, tested by varying the temperature, the catalytic substrates, and the reactive atmosphere, promote the production of a high hydrogen-rich gas, already at the lower tested temperature. It has been seen that the stronger effect for the increase of hydrogen content is for steam reforming condition and using a commercial nickel catalyst instead of Ni/olivine: under such conditions, the hydrogen content increases, from 51.6 vol % before the reforming up to 78 vol % at 650 °C. With regard to gas production, a strong increase of the flow, mostly due to the effect of the cracking reactions, is registered as well and, more in detail, the gas production increases from 0.8 m 3 kg À1 fed, before the reforming, up to 1.0 m 3 kg À1 fed and 1.5 m 3 kg À1 fed, re...

In this work, the steam gasification of scrap tires was investigated as a sustainable and cost-effective alternative to tire landfill disposal. Steam activation of the char derived from the tire residues of the gasification process was carried out at constant temperature and feeding ratio between gasifying agent and char, using different activation times (180 and 300 min). The complete characterization of all intermediate products of the processes, namely, raw material (tire), gasification products (char and syngas) and activation products (adsorbents, named Tirecarb), was performed. The adsorbents obtained from tire gasification were used to remove cadmium ions from aqueous solutions at 25 °C and pH 7. The experimental results showed that the higher the activation time, the higher the cadmium adsorption capacity. Experiments were carried out under the same conditions using a conventional activated carbon, and additional comparisons with other experimental results on Cd(II) adsorption on low-cost sorbents available in the relevant literature are also reported. In both cases, Tirecarb was found to show the highest cadmium adsorption capacity.

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