Secondary and Recycled Aluminum as a Reactive Fuel: Feedstock, Processing, Combustion, and Energy Conversion

Aluminum is widely studied as a metal fuel, but most work uses high-purity commercial powders or specially prepared alloys. Recycled aluminum has been reviewed mainly as a metallurgical feedstock or as a source of hydrogen from the aluminum water reaction. This review focuses on the link between the origin of secondary aluminum and its behavior as a reactive material. Machining chips, industrial powder waste, foil, secondary alloys and metallic aluminum recovered from dross are compared in terms of active aluminum content, particle size, surface oxide, alloy composition and processing history. The effects of grinding, mechanical activation, metal recovery and surface modification on oxidation and ignition are discussed. Direct combustion and hydrogen generation are considered together, with shorter sections on pyrotechnic and aerosol applications. Available data show that selected waste streams, especially AlSi10Mg powder and aluminum foil, can retain useful chemical energy. The main gaps are direct comparison with commercial powders, batch reproducibility and reliable measurement of active aluminum. Reactive use is most reasonable for waste streams that are difficult to return to high-quality alloys or already exist as fine powder.