Experimental and kinetics study on SO catalytic formation by FeO in oxy-combustion.

Sulfur trioxide (SO) is corrosive and environmentally harmful. Under oxy-combustion mode, the formation of SO is aggravated due to flue gas recirculation, and should be more concerned than that under traditional air-combustion mode. In this paper, the catalytic formation of SO by iron oxide (FeO) under oxy-combustion mode was experimentally studied in a fixed-bed reactor, and effects of temperature (300-900 °C), atmosphere, catalyst particle size, SO, O, and HO concentrations were discussed. Results show that FeO promotes SO formation, and the yield of SO reaches a maximum at 700 °C under both air- and oxy-combustion modes. Increasing O concentration in a range of 5-20% promotes the catalytic formation of SO, whose effect is restricted at a higher O concentration. Both increases of SO concentration in a range of 500-3000 ppm and steam concentration in a range of 0-20% decrease the SO yield. A significant effect of FeO particle size on SO catalytic formation is observed. When the particle size decreases from 50-75 μm to 10-25 μm, the inflection temperature shifts from 700 °C to 600 °C, while the maximum SO yield increases by 33%. Kinetics analysis results show that in this case, the catalytic conversion from SO to SO by FeO has an apparent activation energy E of 18.9 kJ/mol and a pre-exponential factor A of 5.2 × 10. At 700 °C and with FeO particle size of 50-75 μm, the global reaction orders of SO and O for SO formation are 0.71 and 0.13, respectively.