High-pressure aluminum-water reactions: Hydrogen generation, oxide evolution-aluminum regeneration, and exotherm optimization

Hydrogen production, power generation and energy storage via aluminum-water reactions offer high energy density and long cycle life. However, reliance on intermittent high-pressure experiments has hindered detailed investigations of reaction exotherms and environmental influences. The coupling between energy release and the high energy demands of aluminum electrolysis remains largely unexplored. In this work, the influence of water phase state, water-recycle number, heating rate, and residence time on hydrogen yield and solid product evolution was systematically examined across aluminum particle sizes (4.5–7 μm to 8 mm). Aspen Plus modeling was employed to quantify the exothermic and heat-utilization characteristics of reaction, leading to the development of an energy consumption model. Results indicate that below 264–312 °C, smaller particles exhibit a marked advantage in hydrogen generation. Above this temperature range, the formation of a porous AlO(OH) layer reduces mass transfer resistance, thereby eliminating particle-size differences. The Extended residence time compensated for differences in temperature, pressure, and aqueous state. The heating rate modulated thermal disturbance and mass transfer. Simulations showed that 4.5–7 μm aluminum released 0.007 MW mol−1 more heat than 8 mm particles under full conversion. The energy required to regenerate aluminum from electrolytic alumina was 32 % lower than that for primary aluminum production.