In order to design ITM-based oxy-combustion power cycles, various reactor engineering analyses must be conducted with detailed modeling and simulation. An intermediate-fidelity ITM model is used to explore the dependence of ITM performance on reactor geometric structure, flow configuration, operating conditions, membrane material properties, and uncertainty in key modeling assumptions, such as the dominant fuel conversion mechanism. Many operational constraints are presented that are usually overlooked by black-box modeling strategies, and the implications of these constraints are explored. Further, a comparison is made between reactive and separation-only ITMs to assess the relative merits and disadvantages of each. The results show that although a reactive ITM significantly improves the partial pressure driving force, practical reactor engineering considerations indicate that this concept is not superior to counter-current separation-only ITMs, mainly because of the stringent temperature limitations of the membrane material. A Second Law assessment of certain ITM configurations is performed to evaluate the potential of ITM technology to reduce the air separation penalty, and to provide insight for effective systems-level integration. Overall, the results of our analyses capture the essential characteristics of ITM air separation systems for power cycles, and enable detailed systems-level studies to be performed. (C) 2011 Elsevier Ltd. All rights reserved.