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Selected aspects of regional interfuel competition the role of natural gas /Lindberg, James B. January 1963 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1963. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 262-271).
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Novel heterogeneous catalyst anodes for high-performance natural gas-fueled solid oxide fuel cellsYoon, Daeil 16 January 2015 (has links)
Solid oxide fuel cells (SOFCs) are electrochemical energy conversion devices that directly transform the chemical energy of fuel into electrical energy. They generate electricity far more efficiently and with fewer emissions per megawatt-hour compared to any combustion-based power generation system. More remarkably, SOFCs can directly use hydrocarbon fuels without requiring external fuel reforming, employing low-cost Ni catalyst instead of noble-metal catalysts used for low-temperature fuel cells. However, the conventional SOFCs using Ni-based anodes fed with carbon-containing fuels have one pitfall; the carbon produced by hydrocarbon cracking is deposited on the Ni surface, thereby precluding the surface of the Ni-based anodes from being available for further fuel oxidation and consequently impeding SOFC operation. This dissertation focuses on overcoming this critical drawback to allow for the simultaneous use of Ni-based anodes and hydrocarbon fuels. Further work focuses on improving SOFC performance to provide the highest efficiencies possible. To boost the power densities of SOFCs, a novel, facile approach to modify the surface structure of anode powders and thereby enlarge the three-phase boundary (TPB) regions of anodes is presented. One such powder preparation method based on the electric charge variation of oxides depending upon the pH of the solution results in significantly extended TPB regions and thus a remarkable increase in power densities of SOFCs. Another method involves the formation of Ce₁₋[subscript x]Gd₁₋[subscript y]Ni[subscript x+y]VO₄₋[subscript delta] at the phase boundaries between NiO and Ce₀.₈Gd₀.₂O₁.₉ (GDC) by V⁵⁺-incorporation onto NiO surface; this method improves the microstructure of Ni-GDC-based anodes and considerably lowers GDC electrolyte sintering temperature, thereby enhancing the SOFC performance. With these high performance anodes, natural gas-fueled SOFCs are studied through two strategies to alleviate coking: incorporation of catalytic materials onto the Ni surface and the introduction of catalytic functional layers (CFLs) to the outer surface of an anode-supported single cell. Hydrogen tungsten bronze and hydroxylated Sn formed on the Ni surface provide hydroxyls for the deposited solid carbon, removing it from the anodes as CO₂. Moreover, the use of hydrophilic Sn or Sb-incorporated Ni-GDC CFLs prevents the anode from being exposed directly to hydrocarbon fuels and controls the solid carbon accumulation similarly to the former strategy. / text
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Ein Beitrag zur Modellierung von Dampfreformern für erdgasbetriebene BrennstoffzellenheizgeräteNitzsche, Jörg 29 October 2010 (has links)
Eine kompakte und effiziente Wasserstofferzeugung aus verfügbaren Energieträgern ist für die Marktfähigkeit von Brennstoffzellenheizgeräten essentiell. Der Auslegung von Reformern für PEM-Brennstoffzellen kommt eine große Bedeutung zu, da bei diesem Brennstoffzellentyp keine interne Reformierung möglich ist. In dieser Arbeit werden die mathematische Modellierung der Dampfreformierung von Erdgas, die Rolle der eingesetzten Katalysatoren und die Problematik von Wärme- und Stofftransportprozessen untersucht. Für fünf kommerzielle Nickel- und einen Rhodiumkatalysator werden die Kinetik, die effektive Wärmeleitfähigkeit und der Diffusionskoeffizient ermittelt. Unter Verwendung dieser Werte wird in einem Einzelpartikelmodell die Existenz und Signifikanz von intra- und extrapartikulären Stoff- und Temperaturgradienten evaluiert. Daraus werden für ein quasihomogenes Reaktormodell Modellparameter abgeleitet, die eine exakte Simulation unter Berücksichtigung der relevanten Phänomene zulassen. Schließlich wird ein Reaktormodell erstellt, welches mit Messwerten aus einem Versuchsreaktor validiert und für eine Sensitivitätsanalyse verwendet wird.
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