Investigations on the iron-rich textile dyeing sludge pyrolysis characteristics: Thermal decomposition behaviors, products, potential mechanisms

The pyrolysis characteristics of iron-rich textile dyeing sludge (TDS) was investigated by combining TG-MS analysis, In-situ-FTIR analysis, Py-GC/MS analysis and bench-scale experiments. The thermal conversion of TDS could be characterized via two main stages, namely primary decomposition and secondary cracking. Primary decomposition occurred in the temperature range of around 150–550 ℃ and it was attributed to the breaking of aliphatic chain and functional groups, producing H2, CO, CH4, H2O, CO2, long carbon chain and residues. With temperature increasing, the reaction was defined as secondary cracking, including dehydrocyclization of aliphatics and carbon reduction of iron oxides. The final products were CO-rich gas, bio-oil and Fe-rich residues, respectively. Noted that when the temperature was 1000 ℃, the gas yield went up to 43.66 wt% and solid yield declined to 47.42 wt%, while liquid yield was only 8.92 wt%, implying that most of organics in TDS has been converted to gas. [Display omitted] •Potential mechanism of iron-rich TDS pyrolysis was studied.•Iron-rich TDS pyrolysis process could be characterized by two main stages.•Primary decomposition was due to the breaking of macromolecule and functional groups.•Secondary cracking mainly included dehydrocyclization and reduction of iron oxides.•Iron oxides in ash greatly promoted the conversion of TDS to gas (especially for CO).