Upgrading of automobile shredder residue via innovative granulation process ‘ReGran’

Stricter regulatory requirements concerning end-of-life vehicles and rising disposal costs necessitate new ways for automobile shredder residue utilisation. The shredder granulate and fibres, produced by the VW-SICON-Process, have a high energy content of more than 20 MJ kg−1, which makes energy recovery an interesting possibility. Shredder fibres have a low bulk density of 60 kg m−3, which prevents efficient storing and utilisation as a refuse-derived fuel. By mixing fibres with plastic-rich shredder granulate and heating the mixture, defined granules can be produced. With this ‘ReGran’ process, the bulk density can be enhanced by a factor of seven by embedding shredder fibres in the partially melted plastic mass. A minimum of 26–33 wt% granulate is necessary to create enough melted plastic. The process temperature should be between 240 °C and 250 °C to assure fast melting while preventing extensive outgassing. A rotational frequency of the mixing tool of 1000 r min−1 during heating and mixing ensures a homogenous composition of the granules. During cooling, lower rotational frequencies generate bigger granules with particles sizes of up to 60 mm at 300 r min−1. To keep outgassing to a minimum, it is suggested to melt shredder granulate first and then add shredder fibres. Adding coal, wood or tyre fluff as a third component reduces chlorine levels to less than 1 wt%. The best results can be achieved with tyre fluff. In combination with the VW-SICON-Process, ReGran produces a solid recovered fuel or ‘design fuel’ tailored to the requirements of specific thermal processes.