Evaluation of Candidate Materials for Chemical Looping Combustion Fuel Reactor Superheaters

Sammanfattning

Chemical looping combustion (CLC) is a promising technology, enabling effectivecarbon capture and storage while reducing the energy penalty associated with carbon capture and storage in conventional waste-to-energy systems. The fuel reactor(FR) side of a waste-fired CLC system exhibits a harsh oxidizing environment; consequently, the material selection is essential for achieving reliable long term operation.This thesis has evaluated the corrosion resistance of six candidate superheater materials for use in the FR of a CLC system. The investigated alloys were Sanicro 28,Sanicro 35, Sanicro 60, TP347, EF101, and a low-alloyed reference steel T22, alsoused for method development. The samples were exposed for 168 hours at 400◦Cin an atmosphere containing 5% O2, 20% H2O and CO2 bal. Potassium chloridewas deposited on the sample surfaces to simulate the alkali chloride-containing environment associated with the combustion of waste-derived fuels. Using gravimetricanalysis combined with scanning electron microscopy (SEM) and energy dispersivespectroscopy (EDS) the corrosion behavior was analyzed.Results show that Sanicro 28, 35, and 60 exhibit the lowest mass gains and formedthin protective scales with no visible sign of internal oxidation. TP347 also demonstrated good corrosion resistance, although evidence of internal oxidation was observed. EF101 experienced breakaway corrosion along with T22 although spallation was not observed to the same degree. Cross-sectional analysis showed thatthe Ni-containing alloys were able to form a thin and protective oxide scale whichis likely composed of a chromium-rich oxide, while EF101 failed to establish andmaintain a continuous protective Al-rich oxide scale, resulting in the formation ofFe- and Cr-rich corrosion products. Chlorine enrichment within the oxide scales alsosuggest that chlorine induced degradation through the electrochemical mechanismcontributed to higher degradation of the metals.The results indicate that all Sanicro samples along with TP347 are viable candidate materials for use in superheaters in CLC systems. Considering both corrosionperformance and alloy composition, TP347 emerges as the most economical alternative due to its lower Ni content, providing a significant improvement in corrosionresistance compared to T22.