Multi-response optimization toward efficient and clean (co-)combustions of textile dyeing sludge and second-generation feedstock

Abstract

The rapid growth of textile dyeing sludge (TDS) necessitates feeding it back into a circular economy in an efficient and clean way. This study aimed to optimize the clean and efficient operational conditions to co-combust TDS and incense sticks (IS). The (co-)-combustions exhibited four distinctive stages of thermal degradation. According to the master-plots method, the reaction mechanisms of reaction order (F2.4 and F1.5), three-dimensional diffusion (D3), and nucleation growth (A1.5) best explained the four stages, respectively. The interaction between TDS and IS exerted an inhibition effect in the range of 400–500 °C and a facilitation effect in the range of 600–1000 °C. At 300 °C as the main reaction temperature, the main evolved gas and functional groups such as CO2, H2O, CH4, C˭O, C-O, and C-H were detected. The addition of IS improved the comprehensive combustion index, inhibited SO2, but enhanced CO2, HCN, and NOx emissions. CaO in IS enabled Fe to remain in TDS and fixed more S in ash. Multi-response optimizations based on the best-fit artificial neural networks revealed the range of 545–605 °C and the co-combustion of 25% TDS and 75% IS as the cleaner and more efficient operational conditions.