Abstract
Sewage sludge odorous gas release is a key barrier to resource utilization, and conditioners can mitigate the release of sulfur-containing gases. The gas release characteristics and sulfur compound distribution in pyrolysis products under both single and composite conditioning strategies of CaO, Fe(2)O(3), and FeCl(3) were investigated. This study focused on the inhibition mechanisms of these conditioners on sulfur-containing gas emissions and compared the theoretical and experimental sulfur content in the products to evaluate the potential synergistic effects of the composite conditioners. The findings indicated that at 650 °C, CaO, Fe(2)O(3), and FeCl(3) inhibited H(2)S release by 35.8%, 23.2%, and 9.1%, respectively. Notably, the composite of CaO with FeCl(3) at temperatures ranging from 350 to 450 °C and the combination of Fe(2)O(3) with FeCl(3) at 650 °C were found to exert synergistic suppression on H(2)S emissions. The strongly alkaline CaO inhibited the metathesis reaction between HCl, a decomposition product of FeCl(3), and the sulfur-containing compounds within the sewage sludge, thereby exerting a synergistic suppression on the emission of H(2)S. Conversely, at temperatures exceeding 550 °C, the formation of Ca-Fe compounds, such as FeCa(2)O(4), appeared to diminish the sulfur-fixing capacity of the conditioners, resulting in increased H(2)S emissions. For instance, the combination of CaO and FeCl(3) at 450 °C was found to synergistically reduce H(2)S emissions by 56.3%, while the combination of CaO and Fe(2)O(3) at 650 °C synergistically enhances the release of H(2)S by 23.6%. The insights gained from this study are instrumental in optimizing the pyrolysis of sewage sludge, aiming to minimize its environmental footprint and enhance the efficiency of resource recovery.