Pyrolysis of natural, butadiene, styrene-butadiene rubber and tyre components: Modelling kinetics and transport phenomena at different heating rates and formulations

A model acknowledging reaction kinetics and thermal conduction during waste end-of-life (ELT) tyre pyrolysis was developed based on the individual consideration of elastomers, namely natural (NR), butadiene (BR) and styrene-butadiene (SBR) rubber; fabric, that is rayon, nylon and aramid; and wire. External diffusional and thermal film resistances proved to be negligible during the thermal cracking. An algorithm was developed to extract pre-exponential factors, activation energies, the orders of reactions, the enthalpies of reactions, and transport parameters. The pyrolysis of various formulations at different volumetric flow rates and heating rates was monitored by thermogravimetry (TG) and differential scanning calorimetry (DSC), whereas the pertinent thermodynamic properties (density, specific heat capacity, and thermal conductivity and diffusivity) were determined separately. The un-decomposable weight fraction containing carbon black, char and ash was 39% for the investigated rubber and 13% for the fabric formulation. The sensitivity analysis of the pyrolysis on compound and process (operating) conditions was performed. The obtained results (taking into account their drawbacks) with the additional measurements and modelling may be used for the thermochemical treatment reactor scale-up and optimization, and consequently, a suitable design of energy and products recovery instead of disposal or landfilling, thus minimizing hazardous waste and contamination to soil and water resources. (c) 2012 Elsevier Ltd. All rights reserved.