Mechanochemical regeneration of sodium borohydride (NaBH4) offers a promising route towards more sustainable hydrogen storage, yet the translation of laboratory-scale processes to industrially relevant scales remains a major challenge. In this work, a horizontal attritor is investigated as a potential scale-up platform for the regeneration of NaBH4 from hydrated sodium metaborate and magnesium hydride.

Using Discrete Element Method (DEM) simulations, the influence of key machine-design and operating parameters on collision behavior and energy dissipation is analyzed. Particular attention is given to the balance between tangential and normal dissipation, motivated by previous studies that identified tangential interactions as highly beneficial for regeneration yield. A fractional factorial design is employed to quantify the effects of impeller spacing, relative impeller angle, chamber clearance, fill ratio, and rotational speed on a set of normalized and absolute key performance indicators (KPIs), including collision frequency, power dissipation per ball, and the tangential-to-normal dissipation ratio.

The results show that fill ratio is the dominant factor governing most KPIs, while impeller geometry can substantially alter dissipation behavior. Operating conditions that promote tangential dissipation are identified and subsequently used in a preliminary scale-up investigation. The scaled horizontal attritor achieves dissipation characteristics comparable to those reported for the laboratory-scale high-energy ball mill (HEBM) used by Garrido et al., while substantially exceeding its tangential-to-normal dissipation ratio. Furthermore, the scale-up cases maintain favorable collision frequencies and power dissipation levels, indicating strong potential for industrial implementation.

Overall, the horizontal attritor emerges as a promising and energy-efficient candidate for scaling up the mechanochemical regeneration of sodium borohydride and potentially other mechanochemical processes. ... Read more