Chromatographic analysis of the gases obtained in tyre pyrolysis

Representative samples of a whole car tyre have been pyrolysed under nitrogen in a 3.5 dm(3) autoclave at 400, 500, 600 and 700 degrees C. The whole gas generated during each pyrolysis run was collected in several plastic bags all of which were analysed, and so the composition of tyre pyrolysis gas and its evolution during the process were determined reliably. Tyre pyrolysis gases are composed of CO, CO2, H2S, and hydrocarbons such as CH4, C2H4, C3H6, C4H8 etc. and its unsaturated derivatives. Multidimensional gas chromatography using three capillary columns installed in a sole furnace have been used, together with a Thermal Conductivity Detector (TCD) and a Flame Ionisation Detector (FID) connected on-line. The gas components have been quantified collecting and handling the data with an appropriate software system. This assembly (three columns + two detectors + software system) enables easy and automatic analysis of tyre pyrolysis gases with only one sample injection. No significant influence of temperature on tyre pyrolysis solid, liquid and gas yields was observed over 500 degrees C; however there was an influence of temperature on gas composition and its evolution. At higher temperatures, more COx (CO + CO2) was produced, derived from inorganic components, and more lighter gases were produced, generated in secondary reactions. (C) 2000 Elsevier Science B.V. All rights reserved.