Optimization of scrap tire devulcanization process using Taguchi and DEAR method in a supercritical fluid extraction pilot scale setup

Abstract

Recycling of scrap tires is gaining more significance to ensure sustainable consumption and production on a commercial scale. The supercritical CO2 extraction technique has been classified as green technology under United Nation's sustainable development guidelines. Literature shows that research on scrap tire devulcanization using supercritical CO2 was performed on a laboratory-scale setup only. However, significant pilot-scale research needs to be conducted before commercial use and technology transfer. This study utilized a pilot-scale supercritical fluid extraction equipment to devulcanize waste tire-derived crumb rubber. Using Taguchi's design of experiment (DOE) model along with the Data Envelopment Analysis Based Ranking (DEAR) approach, the effect of the input process variables on response factors was examined. The input functions, devulcanizing agent's concentration, and pump pressure were discovered to be the most influential parameters in the devulcanization process. Further optimization was carried out via the DEAR-Taguchi technique. The optimal process parameters were determined to be a pump pressure of 350 bar, an extractor temperature of 80 °C, a holding time of 30 min in the extractor, a CO2 circulation of 120 min, and a devulcanizing agent concentration of 15 vol.%. Finally, a validation experiment was conducted at the optimum conditions to verify the acceptability of the model. It was noticed that the divergence for the confirmation experiment was within 10 %, indicating that the approach used for the devulcanization of crumb rubber is acceptable.