Role of sulphur and chlorine in condensable particulate matter formation during coal combustion

Condensable particulate matter (CPM) is a major component of primary particulate matter emitted into the atmosphere from stationary sources. However, the factors affecting CPM generation remain unclear. In this study, we systematically investigated the role of sulphur and chlorine in CPM formation during coal combustion. To explore the influence of S, various concentrations of SO₂ (0-2000 ppm) were added to the combustion process of high-S coal. The role of Cl in the generation of CPM was revealed by burning coal with a significant difference in the Cl content (0.51-9.70 mg/g). The results show that addition of SO₂, especially in SO₄^2-, to the combustion process increases the CPM inorganic fraction content from 5.83 to 48.3 mg/m³. In addition, we speculated that the presence of SO₂ may have led post-break oxidation of long-chain alkanes to form esters, especially phthalates. At the same time, in experiments concerning Cl, the opposite trend was observed between S and Cl in the CPM inorganic fraction. As the Cl content in the fuel increased, the S content in the inorganic fraction of CPM gradually decreased. This is because Cl inhibits the conversion of SO₂ to SO₃, therefore, less S forms CPM as SO₃ or as sulphides.