Due to their high energy density, carbon-containing eFuels and eChemicals represent a promising option for storing renewable electricity. In P2X applications, the use of oxygen from water electrolysis has hardly been considered to date. However, electrolysis oxygen can be used for the sustainable provision of CO2 from biomass in so-called BECCS / BECCU processes.
The OxyCO2 project funded by the BMWK as part of the 7th Energy Research Program (funding priority “Energetic use of biogenic residues and waste materials”) envisages the coupling of electrolysis with fluidized bed combustion. The oxygen from the electrolysis is to be used efficiently for the oxyfuel mono-combustion of sewage sludge. The combustion then produces carbon dioxide, which can be used together with electrolysis hydrogen to produce methanol. The oxyfuel mono-combustion of sewage sludge not only closes the carbon cycle, but also enables phosphorus to be recycled from the incineration ash produced.
Together with partners, both the partial and complete oxyfuel mono-combustion of sewage sludge in an existing fluidized bed pilot plant at ZSW are being investigated. The innovative fluidized bed process will also be evaluated with regard to phosphorus recovery. Furthermore, the processing of CO2 to synthesis quality from the oxyfuel flue gas stream will be demonstrated experimentally. Due to the high CO2 content in the oxyfuel flue gas produced, the effort required for CO2 separation (amine scrubbing) for the subsequent production of eMeOH can be significantly reduced. Further possibilities for increasing efficiency and heat integration will be determined by simulating the entire process chain.