The effect of additives on the co-pelletization of sewage sludge and extraction residue on combustion behavior and off-gas emission reduction.

Co-combustion of biomass and sludge is a promising method for waste treatment and power generation. In this study, additives such as ammonium dihydrogen phosphate (ADP), calcium oxide (CaO), attapulgite (AT), and their combinations were added into the co-pelletization of semi-dry sludge (with approximately 50% water content) and extraction residue from vegetable oil processing. The objective of the studies was to examine the pelletization behavior, reduce off-gas emissions during the combustion, and investigate the mechanisms influenced by these additives through the thermogravimetric analysis and the tube furnace combustion experiment. The results of the analysis of variance (ANOVA) indicated an increase in pellet density due to the addition of additives. During the combustion, the addition of AT and compound additives generated more complex compounds with high melting temperatures, thereby mitigating the high slagging tendency. Meanwhile, additives facilitated the conversion of ultrafine particles (PM 0.1) to fine particles, leading to a reduction in PM 0.1 emissions by 15.60–42.40%. The additives exhibited efficacy in reducing SO 2 emissions, with a reduction range of 5.00–23.20%. However, the addition of ADP additives resulted in a 12.00% increase in NO emissions. Consequently, adding additives to pellets could address the slagging issue and reduce the emission of air pollutants during combustion. [Display omitted] • The additives enhanced the density of the pellets. • The AT and compound additives showed a low slagging tendency. • The additives reduced the combustion stability of the pellets. • The additives decreased the PM 0.1 emission by 15.62–45.48%. • The compound additives showed better reduction of SO 2 emission. [ABSTRACT FROM AUTHOR]