Co-pyrolysis of sewage sludge and rice husk by TG–FTIR–MS: Pyrolysis behavior, kinetics, and condensable/non-condensable gases characteristics

Abstract

In this study, pyrolysis behavior, kinetics, and condensable/non-condensable gases characteristics during co-pyrolysis of sewage sludge (SS) and rice husk (RH) were evaluated using Thermogravimetric–Fourier transform infrared spectrometry–Mass spectrometry (TG–FTIR–MS). The mass loss was divided into two stages: the main devolatilization and the continuous slight decomposition of macromolecular substances. The pyrolysis behavior was improved during co-pyrolysis, and the interaction between SS and RH showed synergistic and inhibitive effects. The lowest average activation energy was obtained at 30% RH blending; the Diffusion 3D (Zhrualev–Lesokin–Tempelmen) reaction model can fit the pyrolysis process using the Coats–Redfern method. The functional groups and condensable/non-condensable gases (O-H, C=O, C-O, C-H benzene skeleton, CO, CO₂) were detected by FTIR, revealing the synergistic effect on the evolution of condensable/non-condensable gases in the promotion of C-O, C=O and CO₂ release in blends. The condensable and non-condensable products were detected via MS (including aliphatic and aromatic hydrocarbons, CO₂, NOx and SOx). The results showed that CO₂ was the main gaseous product and confirmed an enhancement of the CO₂ release during co-pyrolysis. The release of both hydrocarbons (C₂H₆, C₄H₇⁺, C₄H₈) and pollutants (SO, SO₂ and toluene) were significantly increased when dealing with pyrolysing the feedstock blend.