Browsing by Author "Álvarez-Feijoo, Miguel A."

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    Assessment of Selected Alternative Fuels for Spanish Navy Ships According to Multi-Criteria Decision Analysis
    (Journal of Marine Science and Engineering, 2023-12) Álvarez-Feijoo, Miguel A.; Alfonsín, Víctor; Álvarez-Feijoo, Miguel A.; Llopis, Lara
    Climate change and environmental degradation are growing concerns in today’s society, which has led to greater awareness and responsibility regarding the need to adopt sustainable practices. The European Union has established the goal of achieving climate neutrality by 2050, which implies a significant reduction in greenhouse gas emissions in all sectors. To achieve this goal, renewable energies, the circular economy, and energy efficiency are being promoted. A major source of emissions is the use of fossil fuels in different types of ships (from transport ships to those used by national navies). Among these, it highlights the growing interest of the defense sector in trying to reduce these emissions. The Spanish Ministry of Defense is also involved in this effort and is taking steps to reduce the carbon footprint in military operations and improve sustainability in equipment acquisition and maintenance. The objective of this study is to identify the most promising alternative fuel among those under development for possible implementation on Spanish Navy ships in order to reduce greenhouse gas emissions and improve its capabilities. To achieve this, a multi-criteria decision-making method will be used to determine the most viable fuel option. The data provided by the officers of the Spanish Navy is of great importance, thanks to their long careers in front of the ships. The analysis revealed that hydrogen was the most suitable fuel with the highest priority, ahead of LNG, and scored the highest in most of the sections of the officials’ ratings. These fuels are less polluting and would allow a significant reduction in emissions during the navigation of ships. However, a further study would also have to be carried out on the costs of adapting to their use and the safety of their use.
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    Influence of Activated Carbon Granulometry on H2 Purification in Glycerol Reforming Syngas: Adsorption and Kinetic Analysis
    (Energies, 2024-11-29) Maceiras, Rocío; Feijoo, Jorge; Pérez-Rial, Leticia; Álvarez-Feijoo, Miguel A.; Eslami, Naser
    This study investigates the adsorption performance of granular activated carbon (GAC) and pelletized activated carbon (PAC) for the purification of syngas produced from glycerol reforming, focusing on the removal of CO2, CO, and CH4. The adsorption process was studied at two different flow rates (0.5 L/min and 1 L/min) to assess the impact of particle size and gas flow rate on adsorption capacity. The results indicate that GAC exhibits superior multi-gas adsorption, particularly at lower flow rates, effectively capturing CO2, CO, and CH4, while PAC exhibits lower adsorption performance. Kinetic analysis revealed that the pseudo-second-order and Avrami models fit well with both adsorbents, though GAC aligns more closely with the Avrami model, reflecting its multi-step adsorption mechanism and greater pore diffusion efficiency. These findings highlight the importance of adsorbent size and flow rate in optimizing hydrogen purification processes, with GAC emerging as a highly efficient adsorbent for industrial-scale syngas treatment.
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    Influence of alumina fixed-bed in steam reforming of glycerol for hydrogen production (7th International Conference on Renewable Energy and Conservation, ICREC 2022 November 18–20, 2022, Paris, France)
    (Energy Reports, 2023) Maceiras, Rocío; Feijoo Conde, Jorge; Alfonsín, Víctor; Pérez, Leticia; Álvarez-Feijoo, Miguel A.; Falcón, Pablo; Vallejo, Javier P.
    In this study, hydrogen production by steam reforming was carried out in a tubular fixed-bed reactor. The influence of some operating variables such as temperature, flow rate of the feeding glycerol solution and space velocity on hydrogen production under a non-catalyzed reaction was analyzed. The results showed that the hydrogen yield increased with temperature and decreased with the space velocity. As the feedstock flow rate increased, the hydrogen yield decreased rapidly. Compared with a reference experiment without fixed-bed, the use of non-porous alumina fixed-bed showed better results. Under the best reaction conditions (900 ◦C and a feedstock flow rate of 0.85 g/min), 17 L/h of syngas were obtained, with a purity of about 55% of hydrogen and a production of 2.7 moles of hydrogen by mol of glycerol.