Kinetics of sulphur compounds in waste tyres pyrolysis

Liquid phase pyrolysis of scrap tyres was carried out in a lab scale autoclave (300 cc) in the presence of 1,2,3,4-tetrahydronaphtalene (tetralin) as hydrogen donor. Experimental runs were carried out at T=380 and T=400°C and at 50 bar inert gas pressure. Liquid phase samples, withdrawn during the reaction runs, were analysed by GC–FPD technique to follow the fate of sulphur compounds. Gas phase was withdrawn at the end of each run and analysed by GC–FPD and GC–TCD. During the pyrolysis process, sulphur compounds undergo formation and consumption reactions. The fate of sulphur compounds has been modelled on the basis of a two-step reaction mechanism. Kinetic constants of sulphur compound reactions were evaluated lumping all sulphur compounds in a single group. Only about 1% of sulphur present in the loaded tyre was detected in the liquid phase, the remaining being released as H2S in the gas phase.