Application of calcium ferrites as oxygen carriers for microalgae chemical looping gasification

Calcium ferrites (CaFe2O4 and Ca2Fe2O5) are adopted as oxygen carriers for microalgae chemical looping gasification (CLG), and their reactivity is tested through TG-FTIR and fixed-bed reactor. Thermodynamics data show the ideal temperature for calcium ferrites, at which they can react with carbon but not with CO/H2. TG-FTIR tests indicate that calcium ferrites have lower oxidizability than Fe2O3, according to the higher reduction temperature, lower CO2 production and higher CO production. The great selectivity of calcium ferrites is also verified by fixed-bed tests. With steam, the efficiency can be elevated from 82.95% (with Fe2O3) to 92.49% (with Ca2Fe2O5) at 850 °C. In one typical cycle, the synthetic calcium ferrites can be oxidized into the initial state after air oxidation, and Ca2Fe2O5 keeps a better surface structure than CaFe2O4. In summary, calcium ferrites have great selectivity for synthesis gas production, and are suitable for microalgae CLG, especially for Ca2Fe2O5.