Downloaded from orbit.dtu.dk on: Oct 05, 2021 Electrically heated steam methane reforming Wismann, Sebastian Thor Publication date: 2019 Document Version Publisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Wismann, S. T. (2019). Electrically heated steam methane reforming. Technical University of Denmark. General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Users may download and print one copy of any publication from the public portal for the purpose of private study or research. You may not further distribute the material or use it for any profit-making activity or commercial gain You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Ph.D. Thesis Electrically heated steam methane reforming Sebastian Thor Wismann Supervisor: Professor Ib Chorkendorff Co-supervisors: Professor Cathrine Frandsen Research Engineer Peter M. Mortensen Technical University of Denmark Department of Physics Surface Science and Catalysis (SurfCat) August 2019 Preface This thesis is submitted as part of the requirement for obtaining a PhD degree at the Technical University of Denmark. The presented research is supported by Innovation Fund Denmark (File No. 5160-00004B) and the Villum Foundation (Grant 9455). The work presented herein was performed from September 1st 2016 to August 31st 2019, in the Surface Science and Catalysis group (Surfcat) under supervision of Professor Ib Chorkendorff, Professor Cathrine Frandsen, and Research Engineer at Haldor Topsoe, Peter M. Mortensen. Most of the experimental work detailed within was performed in collaboration with Haldor Topsoe A/S (Preparation/Characterization) and Danish Technological Institute (Reactor tests). I would sincerely like to thank my supervisors for setting the framework of the project, being supportive of alternative approaches, and their insight and comments from individual areas of expertise when my “compact illustration” of results got a little too carried away. I would also like to thank Jakob S. Engbæk and Søren B. Vendelbo for their extensive insight, ranging from applied practical experience to detailed theoretical physics. I would like to thank my colleagues Mads R. Almind, Nikolaj Langemark, and Miriam Varón for their assistance and insight regarding synthesis, characterization, and discussion of - at the time - inexplicable phenomena. I would like to express my gratitude to all my wonderful colleagues at SurfCat, who creates the environment of engaged and helpful researchers, always ready to discuss vexing results or troubleshoot an experiment. Finally I would like to thank my family and friends, for enduring being subjected to my extremely interesting explanation of obscure details, that at the time seemed very important (at least to me). I dedicate this work to Sofie, who not only endured, but at times showed actual interest, and who always supported me. i Abstract Increasing focus on sustainability has driven a growing implementation of renewable energy in recent years, resulting in economically competitive costs of renewable electricity compared to electricity generated from fossil fuels. However, the lack of solutions for efficient storage of excess renewable energy creates a demand for technologies compatible with the intermittent nature of renewable energy production. Production of synthesis gas by steam methane reforming (SMR) is a strongly endothermic reaction, today heated by combustion of fossil fuel. Global production of syngas accounts for ca. 3% of all CO2 emissions. Electrification of the SMR process can supplant the combustion as heat source, reducing emissions by a third. This thesis describes the research into two types of electrical heating: induction and resistance heating. The work is based on experimental results at laboratory scale, elucidated by computational fluid dynamics modelling, which is further used to extrapolate to industrial relevant conditions, to gauge the potential of the respective technologies. Electrification of the SMR process provides several substantial benefits compared to current industry. In this thesis, we show that thermal gradients are practically eliminated, providing a substantial increase in catalyst effectiveness. Additionally, it is found that integrated heating enables reactors at industrial capacity two orders of magnitude smaller than current fired reformers. The lower thermal mass enables start-up within minutes, potentially compatible with the intermittent nature of renewable energy. Moreover, electrically heated SMR significantly reduce flue gas from combustion, enabling changes to current plant designs. With compact reactors and less heat recovery, electrically heated SMR is less susceptible to economy of scale, and offers a flexible and scalable platform. Induction-heated reforming by magnetic hysteresis of a ferromagnetic catalyst or susceptor for high temperature endothermic reactions presents a paradigm shift for direct heating of endothermic processes, supplying heat directly to the catalytic sites. Here, it is demonstrated how the traditional temperature profile is inverted by hysteresis heating, effectively removing all limitations of thermal conductivity within the catalytic bed. It is shown how ii the Curie temperature can serve as a safety limit, but at the same time limits application at industrial conditions. Adding layers of increasing Co/Ni ratio to increase the effective Curie temperature can extend the operational temperature range. It is shown how resistance-heated reforming enables improved reaction control, and supports operation at harsher conditions and higher methane conversion than conventional fired reformers. Moreover, paths for significant improvement in reactor capacity per volume is predicted by optimizing reactor dimensions and geometry, tailoring the effectiveness factor up to 75%, potentially reducing the required amount of catalyst by 2 orders of magnitude. In summary, electrically heated SMR provides a new, flexible, and competitive, platform for greener production of syngas. Electrification of SMR could reduce CO2 emissions by nearly 1% if implemented on a global scale. Flexible operation capacity, and fast transient behavior, shows promise considering compatibility with the intermittent nature of renewable energy production. Significant reduction in reactor volume and improvements in catalyst efficiency enables simplification in current industrial plants, and enables efficient operation at smaller scales. Electrification of endothermic processes is an important step towards a sustainable society. iii Resumé Et stigende fokus på bæredygtighed har i løbet af de seneste år medført en hurtigt voksende implementering af vedvarende energi, hvilket har resulteret i faldende priser på grøn elektricitet, nu sammenlignelige med elproduktion fra fossile brændsler. Den primære udfordring for vedvarende energikilder er den varierende produktion, kombineret med en udpræget mangel på effektive løsninger til opbevaring af overproduktion i stor skala. Der er derfor stor interesse for teknologier som er kompatible med den varierende produktion af grøn strøm. Produktion via dampreformering af naturgas (Steam methane reforming) er en stærkt endotherm proces, der i dag opvarmes ved afbrænding af yderligere fossile brændstoffer. Den samlede produktion af syntesegas svarer til næsten 3% af globale CO2 udledninger. Ved i stedet at anvende vedvarende elektricitet til opvarmning er det muligt at reducerer udledningen af CO2 med omkring en tredjedel. Denne afhandling beskriver undersøgelser af to typer elektrisk opvarmning; induktion og modstands opvarmning. Projektet er baseret på eksperimentelt arbejde i laboratorie skala, med henblik på at belyse relevante fænomener igennem CFD modellering (Computational Fluid Dynamics). Med udgangspunkt i de implementerede CFD modeller er det muligt at kvantificere problemstillinger, samt potentialet for skalering til industrielle betingelser. Anvendelse af elektrisk opvarmning tilbyder nye fordele i forhold til nuværende industrielle processer. Igennem denne afhandling illustreres det hvordan begrænsende temperatur gradienter kan omgås, hvilket resulterer i betydeligt mere effektiv anvendelse af katalysatoren. Ved at integrere varmekilden er det muligt reducere størrelsen af en reaktor med op til to størrelsesordner i forhold til opvarmning med fossile brændsler. Den resulterende lavere termiske masse giver muligheden for at starte en reaktor indenfor få minutter, hvilket skaber et grundlag for implementering kompatibel med den fluktuerende produktion af vedvarende energi. Derudover begrænses mængden af røggas drastisk, hvilket begrænser mængden af nødvendige varmevekslere. Elektrisk opvarmede reaktorer er mindre afhængige af total kapacitet end nuværende industrielle anlæg, og giver en mulighed for implementering i mindre skala. iv Med induktionsopvarmning via magnetisk hysterese er det muligt at opvarme en ferromagnetisk katalysator direkte, hvilket løser de primære begrænsninger for den industrielle proces i dag. Ved direkte at varme de katalytiske partikler fjernes begrænsende varmetransport, og den