PYROLYSIS OF SCRAP TYRES: KINETIC MODELING AND COLD PHASE STUDIES WITH SAND IN ROTATING CONE REACTOR

Abstract

With the faster depletion of fossil fuel resources and globally increasing use of energy, there is a dire need to come up with alternate sources of energy. One such source of energy can be a waste tyre. Tire dumps are fire hazards and are also breeding sites for mosquitoes. The management of scrap tires has become a serious problem in recent years and thus gives motivation to search methods for its proper disposal. Pyrolysis has been proposed as a feasible recycling technology to treat tonnages of scrap tyres produced throughout the world. Pyrolysis, the thermal breakdown of the tyre in the absence of oxygen, generates HCV oil, char and HCV gas, all of which have the potential to be recycled. Thermogravimetric analysis and Derivative thermogravimetric analysis characteristic curves of two tyre samples (Bicycle tyre & Moped tyre) of known composition has been utilized to analyze the thermal degradation behavior of the two tyre samples in nitrogen purging and data from the same was used to calculate the kinetic parameters of thermal degradation of two tyre samples at different heating rates by fitting basic solid state degradation models available in literature. Both tyre samples showed two distinct zones of thermal degradation representing lower and higher temperature degradation. An increase in heating rate produced a shift to higher temperatures of thermal degradation. For both the tyres, the decomposition zone width (temperature range of decomposition) at different heating rates was approximately same in degradation zone 1 but not in zone 2. Also, as heating rate was increased, percentage sample pyrolyzed (up to a particular temperature) decreased. Though, this trend is more prevalent at lower heating rates than higher heating rates. It was observed that for both the tyres, in the degradation zone 1, mode of degradation was always first order chemical reaction irrespective of heating rates. However in zone 2, the mechanism of degradation was found to be 3-dimensional diffusion at all heating rates. For bicycle tyre, the activation energy was almost constant in zone 1 but it decreased in zone 2 on increasing the heating rate. For moped tyre, the activation energy increased in zone 1 but it decreased in zone 2 on increasing the heating rate. For bicycle tyre, activation energy was found in the range of 115.15–124.87 kJ/mol and 97.85–171.19 kJ/mol, and the pre-exponential factor was found in the range of 29600–152836 min-1 and 33794-75821 min 1, in zone 1 and zone 2, respectively in nitrogen purging for heating rates between 5-25 K/min. For moped tyre, activation energy was found in the range of 58.28–137.09 kJ/mol and 75.92– 308.94 kJ/mol, and the pre-exponential factor was found in the range of 11221–167816 min-1 and v 55401-86663 min-1, in zone 1 and zone 2, respectively in nitrogen purging for heating rates between 5-25 K/min. Experimental study was