# Generation and Inhibition of SO\({}_{3}\) in Lead Smelting Flue Gas
## 3 Results and Discussion
### Generation of SO\({}_{3}\) in Experimentally Simulated Lead Smelting Flue Gas
#### 3.2.3 The Effect of Initial SO2 Content on SO3 Generation in Experimental Simulations  
Experimental investigations at 600 \({}^{\circ}\)C with a fixed gas flow rate (200 mL/min) reveal the limited sensitivity of SO3 conversion to SO2 concentration variations (10-30 vol%), as shown in Figure 6.  
Under homogeneous conditions, the SO3 conversion rates remain consistently low (0.5-1.8%) with minimal fluctuations, demonstrating a weak dependence on SO2 levels. In contrast, lead dust catalysis elevates the conversion rates to 12-14%, about an 8-fold enhancement over gas-phase reactions, though still exhibiting limited responsiveness to SO2 increases (<2% change across tested concentrations). These findings align with thermodynamic simulations showing decreasing SO3 concentrations at elevated temperatures despite the rising SO2/O2 levels. The weak correlation between SO2 content and SO3 generation stems from oxygen availability being the dominant controlling factor: every 1% increase in the initial O2 concentration boosts the conversion rates by 0.8%, whereas SO2 variations show a negligible impact. The experimental conversion rates lag theoretical predictions by 15-22% due to kinetic limitations preventing a full thermodynamic equilibrium. Lead ash catalysis operates through three synergistic mechanisms: (1) surface-mediated oxidation pathways that lower the activation energy, (2) oxygen activation at metal oxide sites, and (3) the stabilization of intermediate sulfur species. This catalytic system demonstrates remarkable robustness, maintaining a stable performance across wide SO2 ranges (10-30%) and temperature fluctuations (\(\pm\)50 \({}^{\circ}\)C), suggesting adaptability to variable smelting feedstocks. Practical implications emphasize oxygen optimization (>18 vol%) over SO2 adjustments for effective SO3 control. The catalytic approach reduces sensitivity to the feedstock  
Figure 6: SO3 conversion rate for different SO2 contents in homogeneous and heterogeneous conditions. sulfur content while providing consistent and critical advantages for emission mitigation in industrial applications. These insights establish catalytic modification as a superior strategy compared to gas-phase oxidation for SO\({}_{3}\) management in lead smelting operations. Effect of SO\({}_{3}\) Inhibition on the Oxidation Behavior of PbS in a Simulation of Lead Smelting Flue Gas  
By investigating the influence of O\({}_{2}\) content on the conversion of SO\({}_{2}\) to SO\({}_{3}\), as well as the thermodynamics and kinetics of PbS decomposition and oxidation behavior under flue gas system conditions, it was found that PbS and its decomposition products exhibit a significantly stronger binding affinity with O\({}_{2}\) compared to SO\({}_{2}\) within the temperature range of 100-1300 \({}^{\circ}\)C. Under flue reaction conditions, O\({}_{2}\) is preferentially consumed through chemical reactions with PbS and its decomposition products rather than by reacting with SO\({}_{2}\) to form SO\({}_{3}\). By injecting PbS particles of specific sizes into the flue gas, the decomposition and oxidation reactions of PbS can be utilized to consume oxygen, thereby controlling the reaction direction, extent, and SO\({}_{3}\) partial pressure at equilibrium (2 SO\({}_{2}\) + O\({}_{2}\)\(\leftrightarrow\) 2 SO\({}_{3}\)). This approach effectively reduces the SO\({}_{3}\) content in lead smelting flue gas [28]. Experimental verification was conducted using a simulated flue gas platform designed and established by the research team. Under the simulated flue system conditions, the effects of varying initial O\({}_{2}\) and SO\({}_{2}\) contents on PbS decomposition/oxidation behavior and SO\({}_{3}\) generation were studied. The following flue gas composition was maintained in the laboratory simulation: a baseline gas composition of SO\({}_{2}\) (18%), O\({}_{2}\) (4%), and N\({}_{2}\) (78%).