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

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 SOx release characteristic. Properly addressing these fundamental issues and technological challenges is beneficial for reducing SOx 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.