Gasification of shredder residue

At present, disposal of shredder residue (SR) is most commonly based on landfilling in Europe. However, landfilling will not be favoured in the near future and alternative methods have to be sought. This is due to the tightening regulations related to the increased need to recover materials and energy, and to mandatory targets on reducing landfilling. SR contains a significant portion of inorganic material and metals, as well as plastic with a high energy content. Air-blown fluidised-bed gasification is a potential technology for the efficient utilisation of SR for energy production and for the improvement of metal recovery. The fluidised-bed gasification process does not significantly oxidise metals, which enables efficient metal recovery. However, SR material is a challenging feedstock with a high ash content, a wide range of heavy metals and usually a relatively high chlorine content. This project has focused on the assessment of the technical feasibility of air-blown fluidised-bed gasification for the thermal treatment of SR. The project's tasks were research and development of fluidised-bed gasification, gas cleaning, and metal recovery from solid residues, culminating in the evaluation of the economics of the process. The results of the project showed that air-blown fluidised-bed gasification is a very economic alternative when applied to the efficient thermal conversion of shredder residue. Efficient hot gas cleaning is capable of removing chlorine and heavy metals (excluding mercury) efficiently enough to meet the regulations regarding waste incineration. Mercury might need an additional cleaning stage after the gas combustion if the feedstock contains a significant concentration of mercury. Although the process concept seems very promising, some further development is still needed, especially to avoid deposit formation in the bottom of the gasifier. There might be a risk of deposits, especially when chlorine and calcium-rich SR is gasified. Most probably this can be avoided on a large scale by clever design of the air distributor. Additional metal recovery from the bottom ash was shown to be a realistic alternative for increasing the degree of material recovery, as well as for reducing the disposal costs of the ash. The feasibility of this additional metal recovery is most probably shredder dependent and this option has to be assessed case by case. Assessment of the economic feasibility showed that gasification of SR seems economically very suitable, especially for those countries in which landfilling is not allowed or is expensive ( 90...120/t). In addition, the feasibility always depends on local conditions and therefore no universal assessment can be done.