SO₃ formation and the effect of fly ash in a bubbling fluidised bed under oxy-fuel combustion conditions

This study investigates SO₃ formation under air-fired and oxy-fuel combustion environments in a bench-scale bubbling fluidised bed. Flue gas compositions typical of air-fired and oxy-fuel environments were simulated with synthetic gas mixtures. Parameters such as bed temperature and SO₂ and H₂O concentrations were varied to determine their effect on the formation of SO₃. Tests were also performed using three fly ashes produced from three different coals and combustion systems. Oxy-fuel combustion led to increased SO₃ concentration as compared to typical air-fired environments. SO₃ concentrations increased with combustion temperature and O₂ concentrations. SO₃ formation also depends on the chemical composition of the fly ash.