The Batch Pyrolysis of Tyre Waste—Fuel Properties of the Derived Pyrolytic Oil and Overall Plant Economics

Abstract

Estimates for the generation of scrap tyres in the European Community are of the order of 1.5 million tonnes per year, including approximately 0.4 million tonnes per year from the United Kingdom. The majority of the tyre waste is dumped in open or landfill sites but represents a large wasted energy potential. Incineration has been considered as an alternative to dumping in an effort to utilize the high calorific value of scrap tyres; however, this disposal route may not maximize the potential economic recovery of energy and chemical materials from the waste. Pyrolysis of tyres is currently receiving renewed attention, since the derived oils may be used directly as fuels or added to petroleum refinery feedstocks; they may also be an important source of refined chemicals. The derived gases are also useful as fuel and the solid char has the potential to be used either as smokeless fuel, carbon black or activated carbon. In this paper, halved and whole scrap tyres were pyrolysed in a commercial two tonne per day batch pyrolysis unit at furnace temperatures from 700 to 950°C. The proportion of derived products was dependent on pyrolysis conditions, with a maximum yield of 30 per cent oil. The fuel properties of the derived oils, including calorific value, flash point, carbon residue, viscosity, sulphur content, etc., were analysed and compared to refined petroleum products. In addition the benzene, xylene, toluene, limonene and styrene concentration of the oils was determined to assess the potential of the oils as a source of chemical feedstocks. The oils were also analysed in terms of their chemical composition via liquid chromatography and Fourier transform infra-red spectroscopy and molecular mass range. The pyrolytic oils derived from tyres showed properties that were dependent on pyrolytic conditions and showed fuel properties comparable to those of petroleum products.