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| Conference Presentation (After Call) | FZJ-2023-03749 |
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2023
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Please use a persistent id in citations: doi:10.34734/FZJ-2023-03749
Abstract: Fuel cell and hydrogen applications will be key to enable the transition towards decarbonization and achieving the EU's targets of zero net greenhouse gas emissions by 2050. In the next years, priority will be set on the expansion of suitable hydrogen electrolyzers, such as solid oxide electrolysis cells (SOECs). Compared to other types of electrolyzers, the SOEC has a moderate technology readiness level (TRL 5-7). In order to facilitate the market entry and at the same time recover valuable raw materials, recycling concepts have to be developed and implemented at an early stage.The task of reusing or recovering high-temperature electrolyzer components is being addressed and focusses on the reprocessing of ceramic components of End-of-Life SOECs. Recycling in a closed-loop is particularly desirable, while the process is designed to be as scalable as possible. The biggest challenge for SOC recycling arises from the fact that no standardized manufacturing process for hydrogen electrolysis stacks/cells is currently existing. As a result, several cell types are available, sometimes differing significantly in their structures, materials and materials shares used. The cell designs can be divided into metal-supported cells (MSCs), electrolyte-supported cells (ESCs), and fuel electrode-supported cells (FESCs). Even within one cell type, differences can occur depending on the manufacturer. Therefore, it is likely that a classification and separation according to comparable cell types will be needed in the future.We focus mainly on the recycling of FESC-type cells. After separation from the stack, the cell will undergo different stages within the recycling process, illustrated in Figure 1. After re-oxidizing the whole cell, the air electrode and contact layer (~15 wt%) are removed by acid treatment, however most parts of the cell remain stable (~85 wt%). This solid fraction is further milled down and reprocessed to substrate slurry. Defined portions of the recycled slurry are admixed with standard slurry. The resulting green tapes and sintered bodies are investigated in terms of microstructure and mechanical stability.Parts of the liquid fraction of the cell, according to ~15 wt% of the cell, are recovered by oxalate precipitation of lanthanum. It was possible to recover ~95% of the lanthanum contained, which corresponds to about 60 wt% of the total dissolved load.
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