Aluminum Steam Oxidation in the Framework of Long‐Term Energy Storage: Experimental Analysis of the Reaction Parameters Effect on Metal Conversion Rate

Abstract

Aluminum is a promising material as an alternative green energy carrier thanks to its very high volumetric energy density and full recyclability. Aluminum oxidation with steam in the temperature range of 600–900 °C is investigated as an innovative and promising methodology for aluminum conversion resulting in hydrogen and heat production. Reaction times, hydrogen production rate and yield are assessed varying operational parameters such as temperature, steam to aluminum ratio, and gas hourly space velocity within the reactor. The conversion yield of aluminum is assessed at 73.13% at 900 °C and ambient pressure, with reaction times comparable with the one reported in the literature for water oxidation in batch‐pressurized reactors. Moreover, over 750 °C, alumina is produced in microparticles, allowing reactor operating times up to 1 h without incurring in the clogging effect. The obtained results are promising for the continuous operating condition of a future full‐scale reactor.

Potential of Aluminum as a Metal Fuel for Supporting EU Long‐Term Energy Storage Needs

“…Reaction 3 mechanism oxidizes Al in steam at temperatures above 1600 °C, but several issues arise due to the clumping of Al 2 O 3 . [16][17][18][19] Moreover, a previous study [9] proved the feasibility of Al oxidation in steam, according to Reaction 3, at temperatures ≈900 °C. Such innovative process at 800-1000 °C prevent the clumping of Al 2 O 3 without requiring catalysts or additives.…”

“…However, the named studies as well as the scenario assessment are based on theoretical assumptions, which must be proven. Consequently, after a preliminary experimental assessment, [9] the Al-steam oxidation is herein tested at the lab-scale to prove the technical feasibility of avoiding clogging of the rector and enabling the direct recycling of the produced Al 2 O 3 in the Hall-Héroult process. This allows to derive major theoretical and experimental implications and to define next steps.…”

“…[15] The Metal-to-X path is carried out using an innovative Alsteam oxidation process previously proposed and preliminary demonstrated experimentally. [9] The oxidation reaction shows variabilities depending on stoichiometric ratio of steam, and ambient conditions (e.g., pressure and temperature):…”

“…Therefore, emerging concepts using metals as energy carriers for long-term(duration) energy storage demonstrate features to solve the challenges regarding volumetric energy density, material availability, ease of storage and transportation, as well as low cost and integration with industrial processes. [7,8] Several reactive metals have been recently proposed by the authors, [2,9,10] highlighting Al, which is non-critical, non-toxic, and widely available, offering volumetric energy density of 23.5 kWh L −1 , RTEs competitive or even higher than H 2based storage applications using low temperature electrolysis and fuel cells, and a fully circular process. [2] Model-based results show promising techno-economic feasibility and potentially improved environmental sustainability performance, [11][12][13] However, the absence of experimental demonstrations was previously identified as a research gap for such emerging concepts.…”

“…On the other hand, steam combustion at temperatures above 1600 °C is affected by clogging issues generated by Al 2 O 3 clumping. Thus, following the preliminary experimental demonstration of the process at intermediate temperatures (600-900 °C), [9] the feasibility of the process without technical impediments (clogging of the rector) and enabling the direct recycling of the produced Al 2 O 3 in the Hall-Héroult process is a must be condition.…”