Alternatives for oxygen-selective membrane systems and their integration into the oxy-fuel combustion process: A review

Coal-fired power plants are considered to be one of the industrial technologies with a substantial contribution to climate change. In order to reduce their environmental impact, carbon capture and storage have acquired importance as a future clean coal technology in short and medium term. Concerning the closer-to-market options for CO2 capture, oxy-combustion is seen as one of the promising zero-emission plants due to the possibility of its suitability in existing boilers. This technology uses oxygen as the oxidant for combustion, providing a raw CO2 product which contains mainly water vapor, oxygen and nitrogen. Currently, cryogenic air separation is the only available mature option on a commercial scale. However, this system involves a high capital investment and an energy penalty in the oxy-fuel process, thus hindering its full-scale commercialization. As oxygen transport membranes offer significant advantages compared to the previous alternative, this option is foreseen as a candidate for its replacement. This work includes a review of this system and focuses on the study of the possible alternatives for integration into the oxy-fuel combustion process. As a result of this research, the compiled information has been homogenized, providing a completed base data related to operating parameters, required equipment and location of the combustion process for each studied alternative.