A comparison of sulfur and chlorine gas species in pulverized-coal, air- and oxy-combustion

Gas phase measurements of sulfur species (SO2, H2S, SO3, and COS) and HCl were collected in the staged near-burner region and the post tertiary injection oxidizing region of a pulverized-coal flame under air- and oxy-fired conditions. The near burner region was characterized by a high CO region near the center of the reactor directly below the burner. This reducing region as indicated by high CO concentrations produced high H2S and COS and lower SO2 concentrations in comparison to the post tertiary injection oxidizing region for both air and oxy-fired conditions. The concentrations of HCl were in most cases insensitive to radial location. Concentrations of all measured sulfur gases were 2.4–2.9 times higher in oxy-fired conditions than air-fired conditions consistent with the increase expected by the removal of N2 from the oxidizer. The concentration of H2S were on average 5.8 times higher in oxy-fired reducing conditions than air-fired reducing conditions indicating that the oxy-fired near burner regions were higher in H2S and lower in SO2 than would be predicted by removal of N2 alone from an air-fired system. The concentrations of SO3 were less than 2% of the total sulfur for both air and oxy-fired conditions but the uncertainty of the measurement did not allow for a comparison between the two firing modes. The concentrations of HCl were 2.4–2.8 times higher in oxy-fired conditions consistent with the removal of N2 from the oxidizer. The total measured sulfur, HCl, SO3, and reducing zone H2S were all found to increase linearly with increasing sulfur and chlorine concentrations in the coal.