Oxygen production using monolithic Ba0.5Sr0.5Co0.8Fe0.2O3-δ membranes and steam as sweep gas

A decentralized and thermal method for oxygen production is very beneficial for small- and medium-scale consumers, especially for industries that generate significant amounts of high-temperature waste heat, such as steel and glassworks. Currently, the majority of oxygen production is achieved with central cryogenic air sep aration units. Other fully developed decentralized methods, such as (vacuum) pressure swing adsorption, have a high electrical energy demand and achieve a maximum oxygen purity of 95 vol%. This study offers an alternative utilizing mixed ionic-electronic conductor membranes made of Ba0.5Sr0.5Co0.8Fe0.2O3-δ to separate oxygen from air using steam as a sweep gas. When heated above 700 ◦C, these membranes can separate high-purity oxygen using the oxygen partial pressure difference between air and steam.
To investigate the functionality of this method, an experimental setup utilizing nine monolithic membrane tubes was developed. During the 7-h-long experiments, the furnace temperature was varied in the range from 700 ◦C to 900 ◦C, the air flow rate from 0 L/min to 12 L/min and the mass flow rate of steam from 200 g/h to 500 g/h. Results exhibited an approximately linear increase in oxygen output with furnace temperature and a higher oxygen separation degree at elevated steam mass flow rates. Therefore, a maximum oxygen flow rate of 960 mL/min with a purity of 99 vol% was achieved at 900 ◦C and a steam mass flow of 500 g/h. The remaining impurities were mainly non-condensed water vapor. With implemented smart heat management, these results show a promising outlook for the process.