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Development of catalytic membrane reformer technology as a compact, energy efficient solution for on-site generation of hydrogen and ammonia/hydrogen fuel blends
Sitar, Rok
Sitar, Rok
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2023
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2024-11-29
Abstract
Ammonia is quickly becoming recognized beyond its role as a fertilizer but as both a leading hydrogen carrier and a zero-carbon fuel alternative. It is up to 25 times cheaper to store and transport hydrogen as ammonia relative to liquid hydrogen. To alleviate ammonia’s poor combustion characteristics, hydrogen can be added as a fuel promoter, leading to the formation of ammonia/hydrogen fuel mixtures whose combustion properties can be matched to those of conventional hydrocarbon fuels. This thesis builds upon this concept by describing the development of catalytic membrane reformer (CMR) technology as a compact, energy-efficient solution for the on-site generation of hydrogen and ammonia/hydrogen fuel blends. This work presents an entire development cycle of applying CMR technology for the generation of hydrogen and clean combustion fuels, by improving the CMR fabrication process, demonstrating the generation of ammonia/hydrogen fuel mixtures, and lastly evaluating technology for commercial deployment through a techno-economic analysis (TEA). First, an improved palladium membrane fabrication process was developed by augmenting the electroless plating process with sonication, tube rotation, and active temperature control. The upgraded fabrication process resulted in a 35% thinner Pd membrane, increased pure hydrogen permeance while also increasing membrane selectivity over nitrogen and ammonia. These improvements yielded a 71.5% increase in CMR volumetric hydrogen productivity. The improved CMR was then used for the generation of ammonia/hydrogen and hydrogen-enriched fuel mixtures. The simple addition of an ammonia sweep stream offered numerous benefits including enhanced volumetric productivity, complete hydrogen recovery, relaxation of membrane requirements, and isobaric operation which enabled a generation of high-pressure ammonia/hydrogen fuel mixtures without the need for capital and operating intensive compression. Complete ammonia conversion was observed at throughputs more than 10 times larger than the incumbent technology of packed bed reactors (PBR). A first-of-a-kind techno-economic analysis (TEA) was performed on the generation of ammonia/hydrogen fuel blends, comparing the CMR and PBR pathways. It was shown that the processing cost of transforming liquid ammonia into ammonia/hydrogen fuel blends with the CMR is 2.7 – 7.2 times lower than with the PBR, generating fuel blends for <0.5 $/kg-H2. Most importantly, it was demonstrated that ammonia/hydrogen fuels generated by the CMR are economically competitive with conventional liquid hydrocarbon fuels of gasoline, diesel, and jet A fuel, but remain approx. 50% more expensive than natural gas.
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