The use of oxygen-enriched air, instead of ambient air, can significantly improve the energy efficiency of combustion processes and reduce the cost of CO 2 capture from flue gases throughout manufacturing industries. This study examines the overall energy savings and economic benefits that can be obtained using oxygen-enriched combustion based on novel membranes and processes to produce oxygen-enriched air. Membrane processes using low-pressure air as a countercurrent sweep in the permeate were used to minimize the energy cost of producing oxygen-enriched air. High-performance thin film composite membranes based on a series of perfluoropolymers and bench-scale spiral-wound modules were prepared, and showed oxygen permeance as high as 1200 gpu (1 gpu = 10 −6 cm 3 (STP)/cm 2 •s•cmHg) combined with O 2 /N 2 selectivity of 3.0. The membrane-based oxygen-enriched combustion processes show good energy savings (defined as the fuel savings less the energy consumption of producing oxygen-enriched air) and economic benefits (defined as the value of fuel saved less the operating cost of producing oxygen-enriched air), especially at flue gas temperatures higher than 1090 °C (or 2000 °F). For example, at a flue gas temperature of 1649 °C (or 3000 °F), membrane-based oxygen-enriched combustion shows a net energy savings of 35% and a net economic benefit of 29%, compared to the combustion process with air. The effect of oxygen-enriched air on NO x emissions in a natural gas furnace was also experimentally investigated.

We report results on the processing and characterization of tellurite-based glass in the TeO 2 -Bi 2 O 3 -ZnO (TBZ) glass family and efforts to reduce their absorption loss due to residual hydroxyl (OH) content. We show that the introduction of alkaline or alkaline earth in the glass network, drying of the batch with fluorine-based raw materials before melting, and melting of the glass in O 2 -rich atmosphere can lead to a significant reduction in OH content. Employing these steps in TBZ glass processing resulted in a 93% reduction of OH content as compared with a reference composition. The reduction in OH content was verified by a decrease of the absorption band center at 3000 cm À1 as well as a decrease of the free volume in the glass. The addition of F in the glass network was found to reduce the fraction of nonbridging oxygen associated with OH. X-ray fluorescence spectrometry was used to determine the amount of remaining F.

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Perfluorocyclobutyl (PFCB) polymers are a new class of materials that show promise as selective layer materials in the development of composite membranes for gas separations, such as carbon dioxide/methane (a pure gas ¼ 38.6) and oxygen/nitrogen (a pure gas ¼ 4.8) separations. In many of the flat sheet applications, a thin film of the selective layer that is free of major defects must be coated onto a support membrane. A focus of this study was to elucidate the impacts of solvents, polymer concentration, and dipcoating withdrawal speed on PFCB thin film thickness and uniformity. An extension was proposed to the Landau-Levich model to estimate the polymer film thickness. The results show that the extended model fits the thickness-withdrawal speed data well above about 55 mm/min, but, at lower withdrawal speeds, the data deviated from the model. This deviation could be explained by the phenomenon of polymer surface excess. Static surface excesses of polymer solutions were estimated by applying the Gibbs adsorption equation using measured surface tension data. Prepared films were characterized by ellipsometry. Refractive index was found to increase with decreasing film thickness below about 50 nm, indicating densification of ultrathin films prepared from PFCB solutions below the overlap concentration. Atomic force microscopy was used to characterize surface morphologies. Films prepared from tetrahydrofuran and chloroform yielded uniform nanolayers. However, films prepared using acetone as solvent yielded a partial dewetting pattern, which could be explained by a surface depletion layer of pure solvent between the bulk PFCB/acetone solution and the substrate.