The aviation industry is constantly evolving so that it can design lighter aircrafts, reduce consumption/emissions and put in place more efficient recycling systems that allow reusing the valuable materials used in their construction.
The European project SENTRY is part of the ambitious “Clean Sky” program. An outstanding public-private partnership between the European Commission (EC) and the aircraft industry, established to bring significant step changes and improve the environmental impacts of aviation.
In this project, the “End of Life Analysis” of three panels of aircraft fuselage has been conducted. The fuselage is produced by different new generation aluminum alloys which are rich in specific alloying elements, such as lithium or silver, and covered by different defensive layers that protect them against corrosion and other types of external aggressions.
Lithium is the lightest metal existing element in nature and its cost is about 30 times higher than aluminum. It is a highly oxidizable and volatile element so it is necessary to follow strict guidelines on recycling, which are not common in other aluminum alloys. The SENTRY project proposes the development of an efficient recycling technology of these alloys, trying to accomplish an integral exploitation of all the lithium content from them.
Furthermore, the elimination of the protective layers, which is the 4% by weight on the metallic material, must be accomplished through environmentally sustainable methods, avoiding the addition of impurities that reduce the quality of the recycled aluminum obtained.
The current recycling scenario used as a reference in the SENTRY project, involves the indiscriminate mixing of alloys. This generates a dilution of alloying elements (Li, Ag, etc) in the aluminum, preventing possible re-use with its initial concentration value. Under these conditions the reuse can only be done at low dilutions and as very poor quality aluminum.
The SENTRY project is aimed to carry out a specific recycling process of alloys used to manufacture aircraft panels from the fuselage, so that the materials used do not get diverted towards products of lower value and are liable to be used again in manufacturing of high quality aeronautic alloys and reincorporated into the original application. To reach these ambitious objectives a new scenario of dismantling, compatible alloy sorting, coating removal and recycling is proposed.
IK4-Azterlan has taken an active role in optimizing processes, both from the removal of protective coatings and from the efficient recycling of metal alloys, especially the ones alloyed with lithium.
The project, already in the final stage of implementation, has successfully fulfilled the main objectives set out previously:
- The panels have been dismantled effectively, sorting materials according their alloys.
- Coatings have been removed successfully minimizing to the maximum the environmental impact of these operations.
- Finally, the alloys have been recovered and especially lithium alloys, with high recycled yields and minimal losses of critical elements.