Sustainability metrics for coal power generation in Australia

The basis of this work was to investigate the relative environmental impacts of various power generators knowing that all plants are located in totally different environments and that different receptors will experience different impacts. Based on IChemE sustainability metrics paradigm, we calculated potential environmental indicators (P-EI) that represent the environmental burden of masses of potential pollutants discharged into different receiving media. However, a P-EI may not be of significance, as it may not be expressed at all in different conditions, so to try and include some receiver significance we developed a methodology to take into account some specific environmental indicators (S-EI) that refer to the environmental attributes of a specific site. In this context, we acquired site specific environmental data related to the airsheds and water catchment areas in different locations for a limited number of environmental indicators such as human health (carcinogenic) effects, atmospheric acidification, photochemical (ozone) smog and eutrophication. The S-EI results from this particular analysis show that atmospheric acidification has highest impact value while health risks due to fly ash emissions are considered not to be as significant. This is due to the fact that many coal power plants in Australia are located in low population density air sheds. The contribution of coal power plants to photochemical (ozone) smog and eutrophication were not significant. In this study, we have considered emission related data trends to reflect technology performance (e.g., P-EI indicators) while a real sustainability metric can be associated only with the specific environmental conditions of the relevant sites (e.g., S-EI indicators)

High performance yttrium-doped BSCF hollow fibre membranes

Oxygen production from BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3-delta) and yttrium-doped BSCF (Ba0.5Sr0.5Co0.8Fe0.175Y0.025O3-delta) hollow fibres was investigated, and the role of yttrium in the crystal structure was further explored using high-temperature X-ray diffraction. Yttrium substitution acted to increase the oxygen flux significantly, from 4.9 to 7.0 ml cm(-2) min(-1) at 900 degrees C for the BSCF and the BSCFY membranes, respectively. Permeation was particularly enhanced at lower temperatures, between 66% and 92% over the range 650-800 degrees C. The lattice expansion determined from high temperature X-ray diffraction measurements in air was similar for both compositions, suggesting that the higher oxygen fluxes obtained for BSCFY hollow fibres could be attributed to the higher non-stoichiometry due to yttrium addition to the BSCF crystal structure. In addition, the improvement of oxygen fluxes for small wall thickness (similar to 0.3 mm) hollow fibres operating below the critical length (i.e. limited surface kinetics regime) indicates that yttrium has enhanced the surface exchange rates. XRD patterns showed split peaks around 2 theta 31 degrees and 56 degrees above 200 degrees C, likely corresponding to a coexisting hexagonal perovskite phase. This peak-splitting was more pronounced for BSCFY, suggesting that the kinetics of the hexagonal phase formation may be faster for the yttrium-doped perovskite. The lattice volume of BSCFY expanded more than BSCF when exposed to nitrogen at 900 degrees C, confirming a higher release of oxygen and enhanced oxygen non-stoichiometry. (C) 2012 Elsevier B.V. All rights reserved

International Journal Of Nanotechnology: Editorial

[No abstract available]4545145

Nafion-MPMDMS nanocomposite membranes with low methanol permeability

In this work Nation nancomposite membranes have been synthesised using a directed sol-gel synthesis technique with (3-mercaptopropyl) methyldimethoxysilane as the silicon alkoxide precursor. The resulting membranes with 16.7 wt% inorganic content showed a 89% reduction in methanol permeability compared to Nafion 117 at 50 degrees C. Small angle X-ray scattering data profiles for the nanocomposite membranes were distinctly different to those of unmodified Nafion 117 and showed a distinct upturn at low q. The slope of the curves was approximately -3.5 over the range 0.01 < q < 0.015, suggesting the presence of scattering objects with a mass fractal structure in the range 40-60 nm. Such objects were directly observed by transmission electron microscopy, and indicate an interpenetrated network of inorganic agglomerates and the host Nafion polymer, which significantly decreases the methanol permeability. The membranes may be suitable candidates for use in direct methanol fuel cells. (c) 2006 Elsevier B.V. All rights reserved

Long-term flue gas exposure effects of silica membranes on porous steel substrate

In this work we investigate the long-term effects of exposing an inorganic membrane for 1100 h in a flue gas stream of a coal power plant. Of particular importance, from an industrial testing perspective, was the effect of fly ash deposition, water vapour and acid gases on the integrity of the membrane made of cobalt silica coated on a substrate of 316L steel, with interlayers of 310S steel, yttria-stabilized zirconia and gamma-alumina. Subsequent to the flue gas testing, the membrane was characterized for single gas permeance, SEM and EDX spectroscopy. Diffusion of nickel and chromium during sintering was observed at the interface of the 316L/310S steels, resulting in a reduced capacity to withstand corrosion in this area. Single gas permeation testing following flue gas exposure revealed a maximum permeation of 1.85 x 10(-8) mol m(-2) s(-1) Pa-1 and 2.13 x 10(-8) mol m(-2) s(-1) Pa-1 for helium and hydrogen respectively, and selectivity of 5.1 and 5.2 for He/N-2 and H-2/CO2 respectively, was achieved at a pressure difference of 2 x 10(5) Pa (2 bar) at 200 degrees C. The permeation behavior of the membrane appeared to be altered as a result of flue gas exposure with the membrane displaying a reduced H2 flux in contrast to an unexposed but otherwise identical membrane which displayed fluxes an order of magnitude higher than the membrane used in the power plant. This change in permeation behavior was thought to be the result of densification of the silica matrix following long-term exposure to flue gas containing water vapour. Micro-fractures in the surface of the cobalt silica gas separation layer were also observed, possibly the result of expansion due to corrosion. However, bulk diffusion was not observed suggesting that the layer was not completely compromised. (C) 2010 Elsevier B.V. All rights reserved

From chelating precursor to perovskite oxides and hollow fiber membranes

Perovskite Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) is a promising mixed-conducting ceramic membrane material in addition to being a good electrode catalyst for solid oxide fuel cells. In this study, BSCF powder was synthesized via a chelated water-soluble complex method at relatively low temperatures. The combined ethylenediaminetetraacetic acid and citric acid was used for the synthesis of a complex-based precursor, followed by thermal decomposition of the precursor at high temperatures. Thermal behavior, crystal phases, and structures of the prepared powders were characterized by thermogravimetric analysis/differential scanning calorimetry, XRD, and scanning electron microscopic (SEM) techniques, respectively. Pure and single-phase perovskite could be obtained after sintering at a temperature higher than 800 degrees C for 5 h. The soft precursor powder synthesized at lower temperatures, i.e., 600 degrees C, is water insoluble and more appropriate for use as a membrane material to prepare gas-tight tubular or hollow fiber ceramic membranes. By contrast, the hollow fibers prepared via the traditional techniques where the perovskite powder is used as the starting membrane materials display gas leakage. The fibers were characterized by SEM, XRD, and tested for air separation at ambient pressure and temperatures between 700 degrees and 950 degrees C. The oxygen flux measured in this work reached 3.90 mL.(min.cm(2))(-1) and compares favorably with any experimental values reported in the open literature

Characterization of hybrid organic and inorganic functionalised membranes for proton conduction

Titanium zirconium phosphate and organic polymer hybrid (poly-vinyl alcohol, (3-glycidoxypropyl)-trimethoxysilane and ethylene glycol) based membranes were investigated for their potential application as proton conductors. The hybrid materials were characterized by XRD, FTIR, SEM, TGA and impedance spectroscopy analysis. It was found that embedding of functionalised inorganic particles (TiZrP) into composite polymer matrix allowed for some crystallinity formation, and cross-linking of hydroxyl groups during annealing or reactions within the organic and inorganic phases during synthesis. A complex structure was formed, as many FTIR peaks were masked by more defined peaks assigned to P-O-R bonds. The high concentration of phosphorus in the TiZrP (1:1:9 molar ratio) samples resulted in more hydrophilic particles. This was further reflected in the hybrid membranes as the water losses increased from 13 to 25 wt.% as a function of the TiZrP content changing from 10 to 50 wt.% in the final hybrid membrane, respectively. As a result, proton conductivity increased by two to three orders of magnitude from blank (organic phase only) membranes (2.61 x 10(-5) S cm(-1)) to TiZrP hybrid membrane (2.41 x 10(-2) S cm(-1)) at 20 degrees C. Proton conduction changed as a function of temperature and the Ti1Zr1P9 particles content, mainly attributed to the membrane ability to retain water, thus complying with the Grotthus mechanism