Influence of catalysts on co-combustion of sewage sludge and water hyacinth blends as determined by TG-MS analysis

Abstract

Effects of the three metal carbonates (K₂CO₃, Na₂CO₃, and MgCO₃) were quantified on catalytic co-combustion of the sewage sludge and water hyacinth (SW) blend using a thermogravimetric-mass spectrometric (TG-MS) analysis and kinetics modeling. The main dominating steps of the catalysts were the organic volatile matter release and combustion stage. Weighted mean values of activation energy (E_m) were estimated at 181.18KJ·mol^-1, 199.76KJ·mol^-1, 138.76KJ·mol^-1, and 177.88KJ·mol^-1 for SW, SW+5% K₂CO₃, SW+5% Na₂CO₃, and SW+5% MgCO₃, respectively. The lowest E_m occurred with SW+5% Na₂CO₃. Overall, catalyst effect on co-combustion appeared to be negligible as indicated by Gibbs free energy (ΔG). The normalized intensities of SW+MgCO₃ were strongest. The addition of Na₂CO₃ and MgCO₃ to SW increased flue gases emissions (CO₂, NO₂, SO₂, HCN, and NH₃) of SW, whereas the addition of K₂CO₃ to SW reduced flue gases emissions from the entire combustion process.

Keywords: Catalysts; Co-combustion; Sewage sludge; TG-MS; Water hyacinth.