Study on the Effect of Reactor Scale on Hydrogen Generation from Aluminum Powder and Water via Stirring

Hydrogen is considered a promising solution for mitigating global warming due to its potential to provide CO₂-free power when used in fuel cells and power generation systems. Traditionally, hydrogen production relies heavily on fossil fuel reforming, which emits CO₂. This study investigates an alternative hydrogen generation method by stirring aluminum alloy powder in water. The aluminum alloy powder is derived from waste aluminum, and the process is powered by renewable energy, aiming to combine waste recycling with carbon-neutral hydrogen production. This approach explores the feasibility of establishing a sustainable hydrogen production plant.

Previous experiments using a small stirred reactor (100 mL) compared pure aluminum powder with Al-Sn alloy powders. The alloy powders produced significantly more hydrogen, likely because stirring causes particle fragmentation, increasing the powders’ specific surface area and enhancing the reaction rate.

To assess scalability for industrial application, experiments were conducted in a larger 500 mL reactor. Hydrogen generation was tested with pure aluminum and Al-Sn alloy powders of varying compositions. The results demonstrated that hydrogen production using alloy powders in the larger reactor was six times greater than in the smaller reactor—exceeding the expected increase based on volume scaling alone. This discrepancy was attributed to the increased power input from the stirrer in the larger reactor, which likely intensified particle fragmentation and reaction kinetics.

These findings offer valuable insights into the scale-dependent behavior of the reaction system, providing essential data for the design and practical implementation of a hydrogen production plant based on this stirring-induced aluminum–water reaction method.