Pyrolysis of automobile shredder residue in a bench scale rotary kiln

Automotive shredder residue or car fluff or is one of the main end-of-life vehicles by-products. In order to minimize environmental impacts due to demolition processes, the reduction of flows to be landfilled is required by the EU 2009/1 Directive. Thus, recycling and energy recovery are strongly encouraged. Pyrolysis is a thermal conversion process able to recovery energy from car fluff. Pyrolysis can be defined as a process in which a solid form of fuel is converted into a gas, an oil and a solid residue (char). Additionally, the char has a high-energy recovery potential. In this context, the aim of the study was to investigate the pyrolysis of car fluff by means of a bench scale rotary kiln. The activities included the following steps: (i) Chemical-physical characterization of the inlet fluff; (ii) Bench scale experimentations; (iii) Chemical-physical characterizations of char, oil and syngas (pyrolysis outputs). Two type of car fluff were investigated. The first one, indicated as Car fluff A, represents the oversize fraction of a screening process based on a sieve of 3 cm. While, the second one, the under screen fraction. Car fluff A presented a moisture content of 0.62%, a volatile organic compounds content of 76.6%, a carbon content of 5.8%, an ash content of 16.8% and an high and lower heating values of 19 MJ/kg and 17.2 MJ/kg, respectively. Instead, car fluff B presented a moisture content of 1.64%, a volatile organic compounds content of 78.4%, a carbon content of 4.7%, an ash content of 15.2% and an high and lower heating values of 21.7 MJ/kg and 19.9 MJ/kg, respectively. Tests were carried out in a bench scale rotary kiln with a volume of 7.79 dm3. Furthermore, several parameters such as kiln rotation speed, temperature, car fluff and nitrogen flow rate had varied. Results related to the experiment tests in which temperature varied in the range 450-650°C, are as follows: (i) The yield of syngas increases with the pyrolysis temperature; (ii) The syngas had a lower eating value in the range 18-26 MJ/Nm3 as a function of the content of light hydrocarbons; (iii) The maximum production of oils (approximately 35%) takes place at a temperature of 550 °C. The oil appear as a viscous liquid with a heating value in the range 12.5-14.5 MJ/kg and ash content negligible; (iv) The use of char as fuel requires standardization and an improvement in physical and chemical properties; (v) The char has a minimum of production at 550°C with a heating value of 12-18 MJ/kg and an ash content in the range of 48-58%. Finally, the SEM analysis showed that at higher temperature (650°C) the char structure becomes more porous.