Oxygen transport membranes in a biomass/coal combined strategy for reducing CO2 emissions: Permeation study of selected membranes under different CO2-rich atmospheres

• Integration of O2 membrane in biomass gasification and combustion processes is revised.
• A series of membrane materials are tested under CO2-rich conditions.
• CO2 affects negatively the O2 permeation while the effect is reversible for stable materials.
• LSFC and NFO–CTO membranes show stable operation under CO2-rich environments.

This contribution introduces how the integration of biomass as fuel in power plants would balance CO2 emissions and the related role of oxygen transport membranes (OTM) on it. CO2 capture techniques could be introduced to minimize CO2 emissions at the cost of a substantial energy penalty in the overall process. Among the different approaches, the use of pure O2 and/or N2-free oxidation gases for combustion and/or for gasification leads to promising energy efficiencies. Ceramic OTM membranes could be successfully integrated in such thermal processes, which enable to increase the net plant efficiency when CO2 capture is implemented. Further, this work reviews how selected ceramic materials and membrane architectures behave under CO2 containing atmospheres at high temperatures above 700 °C. These conditions have been selected for checking the viability of these membrane compositions and configurations to fit in an oxy-co-gasification process, involving coal and biomass. The tested asymmetric membranes present competitive oxygen fluxes in the range 0.6–1.2 ml min−1 cm−2 when using CO2 as (inlet) sweep gas at 850 °C (optimal membrane operation conditions in oxy-fuel power plant) and stable oxygen production up to 100 h of continuous operation in similar conditions. Specifically, La0.6Sr0.4Co0.2Fe0.8O3−δ and NiFe2O4–Ce0.8Tb0.2O2−δ composite materials showed the best results for oxygen permeation and time stability under CO2-rich atmospheres.

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