Process simulation and technical-economic evaluation of the recycling process of motorcycle helmets

The objective of this thesis was to evaluate two process alternatives for recycling multi-material helmets, focusing on economic sustainability and technical feasibility. Helmets, composed mainly of EPS and ABS, were recycled using a selective dissolution-precipitation/evaporation technique. In the first part of the plant, which remained constant across both configurations, EPS was recycled through dissolution with limonene and precipitation with ethanol, followed by solvent recovery via distillation. For ABS recycling, two configurations were assessed: 1. Selective dissolution with ethyl acetate and precipitation with butanol. 2. Dissolution in ethyl acetate followed by evaporation of the residual solvent from the ABS-ethyl acetate mixture. The simulations for these processes were conducted using ASPEN PLUS software, which is highly suitable for chemical and process engineering simulations. The aim was to optimize the configurations, focusing on effective distillation strategies for solvent and heat recovery to minimize plant costs. The simulations and optimizations led to significant findings. The polymer recovery was high, with nearly pure polymers being retrieved, and the solvent recovered exceeded 90% purity, enabling recycling back into the process and reducing external solvent requirements. Economically, the ABS processing configuration involving only ethyl acetate evaporation proved superior performances due to lower costs and fewer steps compared to the precipitation method. Despite the successes in simulation, the plant small scale presented challenges. The distillation columns and other equipment sizes were impractically small for continuous operation, limiting the plant's viability. With a capacity to process up to 50,000 helmets annually, the plant would operate for only three months per year. To address this, a semi-batch process or a multi-purpose recycling plant could be considered for better efficiency and continuous operation throughout the year.