Pyrolysis of textile dyeing sludge in fluidized bed and microwave-assisted auger reactor: Comparison and characterization of pyrolysis products

This paper investigated fluidized bed pyrolysis (FBP) and microwave-assisted auger pyrolysis (MWAP) for treatment and disposal of textile dyeing sludge (DS), and the products were analyzed and compared. MWAP achieved higher yields of char and condensate, and lower non-condensable gas yields compared to FBP. The yields of CO2 from FBP were much higher than those from MWAP at 450–850 °C. Whereas the yields of H2, CO and CH4 from MWAP were greater than those from FBP at higher temperature (e.g. 850 °C). The maximum condensate yields of FBP and MWAP were observed at 650 °C. Pyrolysis oil of MWAP contained less of macromolecules compared to FBP. Pyridine, phenol, aniline and their derivatives were major components in MWAP oil. Pyridine was the dominant oil component at 850 °C for FBP. Most of nitrogen-, sulfur- and chlorine-containing compounds were retained in FC (FBP char) and MC (MWAP char), and higher relative proportion (RP) of nitrogen, sulfur and chlorine were observed in the condensate and non-condensable gas from MWAP in comparison with FBP. FBP and MWAP both decreased risk degrees of heavy metals compared to raw DS, and heavy metals in FC and MC posed slight risk to the environment based on national standards in China.