Fluctuating energy sources require enhanced energy storage demand, in order to ensure safe energy supply. Power to gas offers a promising pathway for energy storage in existing natural gas infrastructure, if valid regulations are met. To improve interaction between energy supply and storage, a flexible power to gas process is necessary. An innovative multibed methanation concept, based on ceramic honeycomb catalysts combined with polyimide membrane gas upgrading, is presented in this study. Cordierite monoliths are coated with γ-Al 2 O 3 and catalytically active nickel, and used in a two-stage methanation process at different operation conditions (p = 6-14 bar, GHSV = 3000-6000 h −1 ). To fulfill the requirements of the Austrian natural gas network, the product gas must achieve a CH 4 content of ≥96 vol %. Hence, CH 4 rich gas from methanation is fed to the subsequent gas upgrading unit, to separate remaining H 2 and CO 2 . In the present study, two different membrane modules were investigated. The results of methanation and gas separation clearly indicate the high potential of the presented process. At preferred operation conditions, target concentration of 96 vol % CH 4 can be achieved.
The steel industry is one of the most important industry sectors, but also one of the largest greenhouse gas emitters. The process gases produced in an integrated steel plant, blast furnace gas (BFG), basic oxygen furnace gas (BOFG) and coke oven gas (COG), are due to high shares of inert gas (N2) in large part energy poor but also providing a potential carbon source (CO and CO2) for the catalytic hydrogenation to methane by integration of a Power-to-Gas (PtG) plant. Furthermore, by interconnecting a biomass gasification, an additional biogenic H2 source is provided. Three possible implementation scenarios for a PtG and a biomass gasification plant, including mass and energy balances were analysed. The scenarios stipulate a direct conversion of BFG and BOFG resulting in high shares of N2 in the feed gas of the methanation. Laboratory experimental tests have shown that the methanation of BFG and BOFG is technically possible without prior separation of CO2. The methane-rich product gas can be utilised in the steel plant and substitutes for natural gas. The implementation of these renewable energy sources results in a significant reduction of CO2 emissions between 0.81 and 4.6 Mio tCO2,eq/a. However, the scenarios are significantly limited in terms of available electrolysis plant size, renewable electricity and biomass.
The by-product gases from the blast furnace and converter of an integrated steelworks highly contribute to today’s global CO2 emissions. Therefore, the steel industry is working on solutions to utilise these gases as a carbon source for product synthesis in order to reduce the amount of CO2 that is released into the environment. One possibility is the conversion of CO2 and CO to synthetic natural gas through methanation. This process is currently extensively researched, as the synthetic natural gas can be directly utilised in the integrated steelworks again, substituting for natural gas. This work addresses the in situ methanation of real steelworks gases in a lab-scaled, three-stage reactor setup, whereby the by-product gases are directly bottled at an integrated steel plant during normal operation, and are not further treated, i.e., by a CO2 separation step. Therefore, high shares of nitrogen are present in the feed gas for the methanation. Furthermore, due to the catalyst poisons present in the only pre-cleaned steelworks gases, an additional gas-cleaning step based on CuO-coated activated carbon is implemented to prevent an instant catalyst deactivation. Results show that, with the filter included, the steady state methanation of real blast furnace and converter gases can be performed without any noticeable deactivation in the catalyst performance.
Die Umstellung der Energieversorgung auf erneuerbare Quellen (Wind, Photovoltaik) wird in Zukunft verstärkt die Volatilität in der Stromerzeugung erhöhen. Um eine ausgeglichene Leistungsbilanz im Stromnetz sicherzustellen, werden Speicher benötigt -nicht nur kurzzeitig, sondern auch saisonal. Die bidirektionale Kopplung bestehender Energieinfrastruktur mit dem Stromnetz kann hier Abhilfe schaffen, indem der Strom in Elektrolyseanlagen zur Wasserstofferzeugung genutzt wird. Der Wasserstoff kann Erdgas in der vorhandenen Infrastruktur (Gasspeicher, Pipelines) in begrenztem Umfang beigemischt werden oder in einer gaskatalytischen Reaktion, der Methanisierung, mit Kohlendioxid und/oder Kohlenmonoxid direkt zu Methan umgesetzt werden. Durch den Rückgriff auf die Erdgasinfrastruktur wird eine Entlastung der Stromnetze erreicht und eine Speicherung der erneuerbaren Energien auch über lange Zeiträume ermöglicht. Ein weiterer Vorteil dieser als "Power-to-Gas" bezeichneten Technologie ist, dass das so erzeugte Methan eine Senke für CO 2 -Emissionen darstellt, da damit fossile Quellen substituiert werden und so CO 2 in einem geschlossenen Kreislauf geführt wird.Die Forschung im Bereich der Power-to-Gas-Technologie adressiert derzeit technologische Fortschritte sowohl im Bereich der Elektrolyse als auch für die nachfolgende Methanisierung, insbesondere, um Investitionskosten zu senken. Im Bereich der Methanisierung sind lastflexible Verfahren zu entwickeln, die der fluktuierenden Wasserstoffbereitstellung angepasst sind. Die Wirtschaftlichkeit der Power-to-Gas-Prozesskette kann durch eine synergetische Einbindung in bestehende Industrieprozesse erhöht werden. Beispielsweise bietet ein integriertes Hüttenwerk ein vielversprechendes infrastrukturelles Umfeld, da zum einen kohlenstoffhaltige Prozessgase in großen Mengen anfallen, zum anderen der Sauerstoff als Nebenprodukt aus der Wasserelektrolyse einer direkten Nutzung zugeführt werden kann. Derartige Konzepte lassen einen wirtschaftlichen Einsatz der Power-to-Gas-Technologie in naher Zukunft erwarten.Schlüsselwörter: Power-to-Gas; Methanisierung; erneuerbare Energie; Speicher Power-to-Gas: the significance of chemical storage in an energy system containing high shares of renewable energy. The restructuring of the energy supply towards renewable sources (wind, photovoltaics) will increase the volatility in power generation
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