Pyrolysis of predried dyeing sludge: Weight loss characteristics, surface morphology, functional groups and kinetic analysis

The weight loss characteristics, surface morphology, functional group, and kinetic parameters of predried dyeing sludge (PDS) pyrolysis was studied for the first time in this paper. The contents of both volatile matter and organic matter in PDS char both decreased with the increase of pyrolysis temperature. The PDS pyrolysis process can be divided into four stages: S-1 (30 degrees C-180 degrees C)-water evaporation, S-2 (180 degrees C-500 degrees C)-decomposition of organic compounds such as aliphatic compounds and biomass fibres, S-3 (500 degrees C-900 degrees C)-decomposition of the former stage residues, and S-4(900 degrees C-1350 degrees C)-decomposition of carbonaceous material remaining in the char and vaporization of partial ash. With the increase of pyrolysis temperature, the number density of small spherical particles on the PDS particle surface increased. The decomposition of aliphatic hydrocarbon was basically completed at 700 degrees C. The average activation energy of PDS in S-2-S-4 stages were 172.93, 445.65, and 301.76 kJ/mol, respectively. The pyrolysis reaction of PDS samples could be described by nth-order reaction mechanism function.