Process simulation and technical-economic evaluation for the design of an elastane recycling process from end-of-life stockings

The context for the work carried out during the thesis project was that of a mandated research by an industrial company who wished to implement a recycling process for the end-of-life of one of their products. Thus, the alternative routes to an industrialized recycling process for stockings, and, more specifically, their elastane component were studied. The aim was to evaluate the technical and economic feasibility, that is, the pros and cons, of the alternatives which were recognized in the use of: a selective dissolution-precipitation approach, an evaporation approach leading to high concentrations in the recycled component, an evaporation approach leading to a mixture suitable for dry-spinning. In particular, the analysis was carried out with the aid of the Software Tool Aspen PLUS which enabled the simulation and so quantitative assessment of the material and energy flows involved in each alternative process option. The implementation of the flowsheets on the Software also comprised the optimization of the overall operation of the single process alternatives, in particular in terms of energy recovery and integration. The results extrapolated from the final optimized configurations allowed for an economic analysis of the process alternatives, estimating capital and operative costs and comparing them among process options. Finally, the study allowed to highlight the critical aspects in technical and economic terms of each alternative solution, enabling to attain a relatively complete image of the issue. In particular, it was highlighted that the use of a hazardous component for the first process option was unnecessary for the operation, also from a thermodynamic and equilibria point of view and it was studied the possibility to exclude it from the process. In conclusion, instruments have been obtained and presented the company that shall help selecting and assessing future recycling strategies and investments to implement.