Abstract
Gasification experiments in this study were performed in a 2–4 MW indirect gasifier coupled to a semi-commercial CFB combustor at Chalmers University of Technology. Experiments were carried out during 13 days with automotive shredder residue (ASR), giving a unique opportunity to investigate the bed material under realistic conditions and with long residence times. The metal rich ash was accumulated in the bed, gaining some oxygen carrying capabilities, creating a chemical looping gasification (CLG) process. This study aims to expand the knowledge about the chemistry of zinc, copper, lead and antimony during CLG of ASR. Several experimental methods have been utilized, such as XRD, SEM-EDX and XPS along with detailed thermodynamic calculations to study chemical transformations that can occur in the system. Thermodynamic calculations showed that the reduction potential affect the phase distribution of these elements, where highly reduction conditions result in heavy metals dissolving in the slag phase. Copper and zinc ferrites, lead silicates and antimony oxides were identified at the particle surfaces in the bottom ash. The formation of an iron rich ash layer plays an important role, especially for copper and zinc speciation. The main pathways in the complex CLG system have been discussed in detail.
Highlights
In 2018 around 309 million motor vehicles were circulating in the EU [1]
This study aims to expand the knowledge about the chemistry of copper, lead, zinc and antimony in chemical looping gasification of Automotive Shredder Residue (ASR)
This paper has used several experimental methods and thermody namics to analyse the chemical transformations that can occur during chemical looping gasification of ASR waste
Summary
In 2018 around 309 million motor vehicles were circulating in the EU [1]. The same year, the number of produced motor vehicles was around 19.2 million units corresponding to 20% of the global production [1]. There are around 6–8 million end-of-life vehicles (ELV) in the EU which generate around 7–8 million ton of waste. ELVs are processed in three main phases: depollution, dismantling and shredding [2]. Around 75 wt% of a dismantled vehicle is ferrous scrap metals and materials which can be mechanically recycled. The remaining 25%, which cannot be further separated or recycled is called Automotive Shredder Residue (ASR) corresponding to an amount of around 2 million tons yearly. Due to its heterogenous nature and complex composition ASR is largely landfilled [2]
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