Thermodynamic Modeling and Experimental Investigation of the System Fe-Ti-O-K for Ilmenite Used as Fluidized Bed Oxygen Carrier

The capability of ilmenite for potassium uptake in a simulated oxygen carrier-aided combustion environment has been investigated. The maximum uptake of potassium and the effect of potassium inclusion on the Fe-Ti-O system was analyzed. Through laboratory experiments and thermodynamic calculations, it was found that a molar ratio of 1:1 can be formed spontaneously for both the K-Ti-system (where the formation of K2Ti2O5 was found) and the K-Fe-system (where KFeO2 was found). K2Ti2O5 was identified as an unstable phase, undergoing decomposition into K2Ti4O9. The study demonstrates that the maximum K uptake, through forming K2Ti4O9 and KFeO2, reaches 25 wt %─a notably higher value than ilmenite exposed to biomass in a fluidized bed. The research concludes that the lifetime of ilmenite is therefore rather dependent on its mechanical integrity than its maximum potassium uptake.