High temperature sorption separation of air for producing oxygen-enriched CO ₂ stream

A new high temperature sorption process for production of oxygen-enriched carbon dioxide stream through air separation with carbon dioxide as the purge gas is reported. The process is based on a fixed-bed packed with a perovskite-type strontium-iron doped lanthanum cobaltite, as the sorbent, operated in 500-900°C. Oxygen is adsorbed by the perovskite-type sorbent with air being fed. An oxygen-enriched carbon dioxide stream is obtained when the fixed-bed is regenerated with carbon dioxide as the desorption gas. A specific carbonation-reaction mechanism for the O ₂-desorption process and a complete reverse reaction during the O ₂-sorption process are identified with the evidences of XRD and TGA analysis. A study of the sorption process kinetics over a temperature range of 600-800°C was conducted by fixed-bed sorption/desorption and TGA experiments. Both desorption and sorption processes exhibit a high reaction rate in an initial stage followed by a slower rate in a second stage. A remarkable separation efficiency was observed at 800°C. The new process offers potential for applications in a number of processes including in the efficient and environmentally benign oxyfuel coal combustion process for power generation.