Analysis and modelling of a constant-flow hydrogen generator based on water dripping onto an activated bed of recycled aluminum

This work presents a novel hydrogen generator whose flow rate is controlled by the dripping frequency of water onto aluminum sawdust or recycled aluminum powder activated with small amounts of NaOH (20–26% NaOH-to-aluminum mass ratio). Controlled dripping maintains high local alkalinity by transiently diluting the medium and regenerating NaOH, reducing alkali consumption by more than eightfold compared with 6 M solutions. Experiments demonstrate stable hydrogen production at representative dripping conditions such as 7 mL min −1 , producing 1.1 L min −1 of hydrogen. A thermo-kinetic model estimates how long the hydrogen flow remains constant based on the available aluminum mass and the final reactor temperature. Higher final temperatures, sometimes achieved through insulation, increased aluminum mass, or elevating the NaOH content up to a 26% NaOH-to-aluminum mass ratio, enhance the hydrogen yield, which remains above 80%. The reactor self-heats through NaOH dissolution and operates safely under the intended conditions, as reactants remain confined and pressure stays low.