Dynamics Mechanism Investigation on the Formation of SO₃ During Pressurized Oxy-fuel Combustion

The increase of pressure and enrichment of SO₂ due to gas flue recycle, significantly intensify the formation of SO₃ during pressurized oxy-fuel combustion. By using detailed chemical reaction mechanism and thermodynamic equilibrium calculation, investigation on the influence of key factors on the formation of SO₃ was carried out. Results show that, under pressurized oxy-fuel combustion the time reaching to equilibrium of the overall reaction (2SO₂+O₂ →2SO₃) significantly shortened, and the formation of SO₃ is promoted. With pressure increasing from 0.1 MPa to 1.5 MPa, the concentration and partial pressure of SO₃ increase to 4 times and 56 times relatively, and the acid due point (ADPT ) increased 71℃. In high temperature flame zone (T≥1473 K), the equilibrium time ranges within 1 and 100 ms and the ratio of SO₃ formed ranges within 0 and 6.5%. While in post-flame zone, the reaction rate is slow and the equilibrium time ranges within 1-10³ s. The evaluation of SO₃ in post-flame zone using thermodynamic equilibrium reveals that the formation of SO₃ is proportional to SO₂ concentration and the 0.5th power of O₂ concentration.