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SUMMARYFossil fuels provide a significant fraction of the global energy resources, and this is likely to remain so for several decades. Carbon dioxide (CO 2 ) emissions have been correlated with climate change, and carbon capture is essential to enable the continuing use of fossil fuels while reducing the emissions of CO 2 into the atmosphere thereby mitigating global climate changes. Among the proposed methods of CO 2 capture, oxyfuel combustion technology provides a promising option, which is applicable to power generation systems. This technology is based on combustion with pure oxygen (O 2 ) instead of air, resulting in flue gas that consists mainly of CO 2 and water (H 2 O), that latter can be separated easily via condensation, while removing other contaminants leaving pure CO 2 for storage. However, fuel combustion in pure O 2 results in intolerably high combustion temperatures. In order to provide the dilution effect of the absent nitrogen (N 2 ) and to moderate the furnace/combustor temperatures, part of the flue gas is recycled back into the combustion chamber. An efficient source of O 2 is required to make oxycombustion a competitive CO 2 capture technology. Conventional O 2 production utilizing the cryogenic distillation process is energetically expensive. Ceramic membranes made from mixed ion-electronic conducting oxides have received increasing attention because of their potential to mitigate the cost of O 2 production, thus helping to promote these clean energy technologies. Some effort has also been expended in using these membranes to improve the performance of the O 2 separation processes by combining air separation and high-temperature oxidation into a single chamber. This paper provides a review of the performance of combustors utilizing oxy-fuel combustion process, materials utilized in ion-transport membranes and the integration of such reactors in power cycles. The review is focused on carbon capture potential, developments of oxyfuel applications and O 2 separation and combustion in membrane reactors. The recent developments in oxyfuel power cycles are discussed focusing on the main concepts of manipulating exergy flows within each cycle and the reported thermal efficiencies.

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Summary The increased level of emissions of carbon dioxide into the atmosphere due to burning of fossil fuels represents one of the main barriers toward the reduction of greenhouse gases and the control of global warming. In the last decades, the use of renewable and clean sources of energies such as solar and wind energies has been increased extensively. However, due to the tremendously increasing world energy demand, fossil fuels would continue in use for decades which necessitates the integration of carbon capture technologies (CCTs) in power plants. These technologies include oxycombustion, pre‐combustion, and post‐combustion carbon capture. Oxycombustion technology is one of the most promising carbon capture technologies as it can be applied with slight modifications to existing power plants or to new power plants. In this technology, fuel is burned using an oxidizer mixture of pure oxygen plus recycled exhaust gases (consists mainly of CO2). The oxycombustion process results in highly CO2‐concentrated exhaust gases, which facilitates the capture process of CO2 after H2O condensation. The captured CO2 can be used for industrial applications or can be sequestrated. The current work reviews the current status of oxycombustion technology and its applications in existing conventional combustion systems (including gas turbines and boilers) and novel oxygen transport reactors (OTRs). The review starts with an introduction to the available CCTs with emphasis on their different applications and limitations of use, followed by a review on oxycombustion applications in different combustion systems utilizing gaseous, liquid, and coal fuels. The current status and technology readiness level of oxycombustion technology is discussed. The novel application of oxycombustion technology in OTRs is analyzed in some details. The analyses of OTRs include oxygen permeation technique, fabrication of oxygen transport membranes (OTMs), calculation of oxygen permeation flux, and coupling between oxygen separation and oxycombustion of fuel within the same unit called OTR. The oxycombustion process inside OTR is analyzed considering coal and gaseous fuels. The future trends of oxycombustion technology are itemized and discussed in details in the present study including: (i) ITMs for syngas production; (ii) combustion utilizing liquid fuels in OTRs; (iii) oxy‐combustion integrated power plants and (iv) third generation technologies for CO2 capture. Techno‐economic analysis of oxycombustion integrated systems is also discussed trying to assess the future prospects of this technology. Copyright © 2017 John Wiley & Sons, Ltd.

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For decreasing greenhouse gas (mainly CO 2 ) emissions, several approaches have been evaluated and reviewed for capturing CO 2 in the utility industry, namely, carbon capture and storage technology (CCS), including precombustion capture, oxy-fuel combustion, and postcombustion capture. As a promising CCS technology, oxy-fuel combustion can be used to existing and new power plants. In oxy-combustion, a fuel is oxidized in a nearly nitrogen-free, diluted mixture such that the products consist mainly of CO 2 and water vapor, enabling a relatively simple and inexpensive condensation separation process, and then, CO 2 could be captured easily. There are two main approaches available to utilize the oxy-combustion technology, one of them is through the use of air separation units to separate O 2 , which will be used in the combustion process, and the other application is the ion transport membrane (ITM) reactor technology. This membrane separates oxygen from oxygen containing upstream (typically air). The oxygen transports through the membrane to a downstream permeate side containing fuel, with CO 2 as inert carrier gas and the combustion starts in the permeate side of the membrane. In the present review paper, the oxy-fuel combustion technology status for clean power generation and carbon capture is introduced, starting with the available carbon capture technologies and comparison between them. This is followed by a detailed review of research work that considers the oxy-fuel combustion process itself, with a particular focus on the applications to this technology in ITM reactors and gas turbine combustors. This work also presents a detailed analysis for the most recent advancement in the ITM reactors technology with more analysis related to the membrane separation mechanism, the available permeation equations in the literature and the membrane performance regarding separation only and ITM reactor applications. The new coefficients oxygen permeation equation model is introduced in this work by fitting the experimental data available in the literature for a LSCF-1991 ion transport membrane. Because of new challenges presented by oxy-fuel combustion, as opposed to air-fuel combustion, research pertaining to the analysis of oxy-fuel combustion in real systems such as gas turbines is also discussed in the present work.