INFLUENCE OF TEMPERATURE IN THE CONTINUOUS PYROLYSIS OF WASTE TYRES IN A CONICAL SPOUTED BED REACTOR
Sustainable process-product development & green chemistry
Environmental Engineering & Management (T1-3)
Keywords: Pyrolysis, waste tyres, spouted bed
Waste tyres are a serious environmental problem due to the potential risk involved in their stockpiling. At present, 2.5 million tonnes per year of waste tyres are generated in Europe, a similar amount in USA and approximately 1 million tonnes in Japan [1]. Pyrolysis is considered to be one of the more feasible solutions that may be economically profitable at large scale. The interest is centred on the fact that the products obtained by this process may be easily handled, stored and transported and they may be transformed in other units that are not near the recycling one [2]. The pyrolysis liquid product may be used directly as fuel or may be added to a refinery feed. Furthermore, interesting chemical products, such as benzene, toluene, xylenes and limonene [3] are obtained.
In this work, the pyrolysis of scrap tyres has been studied in the 425-600ºC temperature range. The experimental runs have been carried out in a pilot plant conical spouted bed reactor provided with a system for continuous feeding of scrap tyres. The feeding rate was 3 g/min and the mass fed in each run was 100 g.
The main components of the tyre material studied are (in %wt): natural rubber (SMR 5CV), 29.59; styrene-butadiene rubber (SBR 1507), 29.59; carbon black (ISAF N220), 29.59; zinc oxide, 2.96; phenolic resin, 2.37; sulphur, 0.89 and other less important components.
The products obtained in this process can be divided into five different fractions:
Gases containing C1-C4 hydrocarbons whose yield varies from only 1.8% at 425ºC to more than 8% at 600ºC. The gases can be burnt to provide energy for the endothermal pyrolysis process.
The non-aromatic liquid fraction consists of hydrocarbons in the C5-C10 range and decreases from 36% at 425ºC to 13% at 600ºC. Nevertheless the C5-C10 aromatic hydrocarbons increases from 13% to 23%. The C5-C10 fraction contains valuable tyre monomers, such as isoprene, limonene (isoprene dimer) and styrene.
The tar fraction is made up of hydrocarbons heavier than C10, this fraction does not have a clear tendency in the studied range of temperatures and its yield varies from 9% to 11%.
Finally the char yield increases from 33.9 at 425ºC to 35.8% at 600ºC. These values are slightly higher than that corresponding to the carbon black and other solids in the original tyre. This carbonaceous material may be used as a quality fuel, or a suitable raw material for carbon black or active carbon once activation has been carried out.
Literature cited
1 Larsen, M.B., Schultz, L., Glarborg, P., Skaarup-Jensen, L., Dam-Johansen, K., Frandsen, F., Herriksen, U., Fuel, 85, (2006) 1335.
2 J.M. Lee, J.S. Lee, J.R. Kim and S.D. Kim, Energy, 20 (1995) 969.
3 P.T. Williams and A.J. Brindle, Fuel, 83 (2003) 1023.
Presented Tuesday 18, 15:20 to 15:40, in session Environmental Engineering & Management (T1-3).
