Integrated adsorber concepts for use in direct air capture and power-to-gas applications
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Date
2021
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Abstract
Die Anwendung technologischer Konzepte zur direkten Abtrennung des Treibhausgases
Kohlenstoffdioxid (CO2) aus atmosphärischer Luft (Direct Air Capture, DAC) wird als
einer der vielversprechendsten Ansätze zur Abschwächung des anthropogenen Treibhauseffekts betrachtet. Deren großtechnischer Einsatz wird jedoch durch verschiedene intrinsische Limitierungen erschwert, welche sich insbesondere aus dem stark verdünnten Zustand
von CO2 in der Atmosphäre ergeben und in einen unzulässig hohen CO2-spezifischen Energiebedarf des Abtrennungsprozesses resultieren können.
Durch Detailmodellierung und Simulationsstudien wird gezeigt, dass die in dieser Arbeit entwickelten Wärmeintegrationsstrategien und deren technische Realisierungen inner halb neuartiger Band- (MBtA) und Wanderbettadsorberkonzepte (MBdA) eine signifikante
Reduktion des CO2-spezifischen Wärmebedarfs von thermischen Sorbentregenerationskonzepten ermöglichen. Die Problematik von Wasserkoadsorption auf DAC-Sorbentien,
welche im Rahmen ausführlicher experimenteller Studien innerhalb dieser Arbeit bestätigt
wird, kann jedoch zu einem zusätzlichen, signifikanten CO2-spezifischen Wärmebedarf innerhalb des Regenerationszyklus des Sorbents führen. Insbesondere eine Rückgewinnung
der im desorbierten Wasserdampf gespeicherten Latentwärme durch mechanische Brüden-
kompression (MVR) wird innerhalb dieser Arbeit als ein vielversprechender ingenieurtechnischer Ansatz zur Reduzierung der H2O-Koadsorption bedingten Energiestrafe identifiziert.
Die entwickelten Konzepte werden innerhalb eines Power-to-Gas (PtG) Prozesses als
wärmeeffiziente CO2-Quelle integriert. In diesem Zusammenhang zeigen durchgeführte
Detailsimulationen und Pinchanalysen, dass durch eine gezielte Ausnutzung der Synergien
innerhalb der Prozessstruktur ein hoch-ressourceneffizenter DAC-PtG Prozess realisiert
werden kann. Dieser ermöglicht eine autotherme Produktion von Methan ausschließlich
auf der Basis von erneuerbaren Energien und den Edukten Kohlenstoffdioxid und Wasser,
welche aus atmosphärischer Luft gewonnen werden.
The application of technological concepts for removal of the greenhouse gas carbon dioxide (CO2) from the atmosphere (direct air capture, DAC ) is considered to be one of the most promising approaches to mitigate the anthropogenic greenhouse effect. But its large-scale application is hampered by several intrinsic limitations. These result in particular from the highly diluted state of CO2 in the atmosphere and can lead to an impedingly high CO2-specific energy demand of the capture process. In-depth modeling and simulation show that the heat integration strategies developed in this work and their technical realization within novel belt (MBtA) and moving bed adsorber (MBdA) concepts allow for a significant reduction of the CO2-specific heat demand of thermal sorbent regeneration concepts. However, the problem of water co-adsorption on DAC sorbents, which is confirmed by experimental studies within the framework of this contribution, can lead to an additional, significant CO2-specific heat demand within the sorbent regeneration cycle. Recovery of the latent heat stored in the desorbed water vapor by mechanical vapor compression (MVR) is identified as a promising engineering approach to reduce the energy penalty attributed to H2O co-adsorption. The concepts developed are integrated as heat-efficient CO2 sources within a power-to-gas (PtG) process. Detailed modeling and pinch analysis reveal that a highly resource efficient DAC-PtG process can be realized by targeted utilization of the synergies within the process structure. Autothermal production of methane solely based on renewable energy supply and on the educts carbon dioxide and water, captured from ambient air, seems feasible.
The application of technological concepts for removal of the greenhouse gas carbon dioxide (CO2) from the atmosphere (direct air capture, DAC ) is considered to be one of the most promising approaches to mitigate the anthropogenic greenhouse effect. But its large-scale application is hampered by several intrinsic limitations. These result in particular from the highly diluted state of CO2 in the atmosphere and can lead to an impedingly high CO2-specific energy demand of the capture process. In-depth modeling and simulation show that the heat integration strategies developed in this work and their technical realization within novel belt (MBtA) and moving bed adsorber (MBdA) concepts allow for a significant reduction of the CO2-specific heat demand of thermal sorbent regeneration concepts. However, the problem of water co-adsorption on DAC sorbents, which is confirmed by experimental studies within the framework of this contribution, can lead to an additional, significant CO2-specific heat demand within the sorbent regeneration cycle. Recovery of the latent heat stored in the desorbed water vapor by mechanical vapor compression (MVR) is identified as a promising engineering approach to reduce the energy penalty attributed to H2O co-adsorption. The concepts developed are integrated as heat-efficient CO2 sources within a power-to-gas (PtG) process. Detailed modeling and pinch analysis reveal that a highly resource efficient DAC-PtG process can be realized by targeted utilization of the synergies within the process structure. Autothermal production of methane solely based on renewable energy supply and on the educts carbon dioxide and water, captured from ambient air, seems feasible.
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Keywords
Direct air capture (DAC), Power-to-gas (PtG), Carbon dioxide (CO2), Adsorption, Methanation