SCRAP TYRE PYROLYSIS - ARE THE EFFLUENTS VALUABLE PRODUCTS

Scrap tyre pyrolysis under nitrogen is studied at atmospheric pressure with the aim of producing a solid residue to be burned simultaneously with coal dust in a coal burning power plant. The experimental device maintains isothermal conditions. The temperatures of treatment are: 3 80, 450 and 550 degrees C. Three phases are obtained after pyrolysis: solid, liquid and gas and their composition is studied in relation to the temperature of the thermal treatment. The solid phase (char)-appro ximately 40% weight of the initial sample (steel free) mostly constitu ted of carbon, also contains the main mineral matter initially present in the used tyre. The char produced is brittle and has a high burning power which makes it suitable for burning when mixed with coal dust i n coal burning power plants. The steel weave is easily separated from the solid carbon residue after the thermal treatment and recovered wit hout physical or chemical change and can be recycled. The gas phase co ntains a mixture of light hydrocarbons, dihydrogen and carbon dioxide. The IRTF spectra of evolved gases shows a change in the ratio of ever y gas while the pyrolysis takes place. The liquid phase is a complex h ydrocarbon mixture in which some components have been identified. The chemical-valorization of the liquid phase is an alternative to a therm al valorization. The pyrolysis appears to be a technique which is able to reduce a bulky, high polluting industrial waste, while producing e nergy and/or valuable chemical compounds. (C) 1997 Elsevier Science B. V.