Integrating O{sub 2} production with power systems to capture CO{sub 2}

Chemical cycles for separating oxygen (O{sub 2}) from air were developed many years ago. These cycles involve initiating a reaction to capture O{sub 2} from the air and changing the operating conditions to effect a controlled breakdown of the newly formed product to release the O{sub 2} and regenerate the original species. Two such O{sub 2} separation cycles are the Moltox{trademark} and the barium oxide/peroxide cycles. These cycles are generally more expensive than more conventional methods--such as cryogenic separation of air--partly because they consume high-temperature thermal energy (500--850 C). Conventional air separation to produce O{sub 2}, though more economical than these cycles, is still too expensive when applied to combustion of fossil fuels. The nitrogen content of the combustion air results in a flue gas stream that is low in carbon dioxide (CO{sub 2}); this increases the complexity and cost of capturing the CO{sub 2} from the flue gas. These chemical cycles can be integrated with power cycles, such as the high-temperature gas turbine (1,300--1,500 C), to provide efficient heat cascading and recovery. The heat cascading process can also be arranged to minimize the overall exergy loss in the integrated system. The enriched O{sub 2} stream produced can be used in the combustion process to generate a CO{sub 2}-rich stream that is more readily separable for production of commercial-grade CO{sub 2}. This paper presents a discussion of air and water separation techniques integrated with power cycles