Experimental and numerical investigation on sulfur transformation in pressurized oxy-fuel combustion of pulverized coal

Highlights: • A lab-scale pressurized oxy-fuel combustion reactor was designed and established. • SO₂ emission variations with pressure, temperature and oxygen content were studied. • Great agreement between experimental and numerical results is observed. • Reaction paths on S transformation in pressurized oxy-fuel combustion are revealed. -- Abstract: Pressurized oxy-fuel combustion, as a novel and promising technology for CO₂ capture from power plants, has attracted worldwide attentions. The high partial pressure of CO₂ induces significant changes to the SO_x release characteristic. Properly addressing these fundamental issues and technological challenges is beneficial for reducing SO_x emissions and complementing pressurized oxy-fuel combustion technology. In this study, experimental and numerical investigations are carried out to explore the sulfur transformation mechanism under different operation parameters in the pressurized oxy-fuel combustion of pulverized coal. The experimental results reveal an obvious decline of 50% in SO₂ emissions as the operating pressure increased from 0.1 MPa to 1.6 MPa, which is ascribed to the enhanced oxidation from SO₂ to SO₃ and the reduction of SO₂ to elemental sulfur. As the operation temperature increased from 700 °C to 1100 °C, the SO₂ concentration first decreased and then increased, and the minimum SO₂ emission was observed at 900 °C. Additionally, when the oxygen concentration increased from 10% to 60%, the SO₂ emissions were significantly reduced by 74%. The simulation results show great agreement with experimental data and indicate that SO₂ emissions were synergistically affected by seven elementary reactions in which HSO, SO, SH and other intermediate species were involved. The key reaction paths from fuel-S to different S products were revealed, where SO and HSO act as the major precursors to form SO₂, and SH is an important intermediate product that participates in the sulfur transformation of both H₂S and COS.