Study on the characteristics of sulfate ion in condensable particulate matter from ultra-low emission coal-fired power plants

Abstract

The sulfate ion (SO42−) in condensable particulate matters (CPM) discharged by ultra-low emission coal-fired power plants has caused a series of environmental problems. In this work, condensation temperature, H2O, NOx and NH3 were investigated to elucidate the characteristics of SO42− under fast condensation. The results demonstrated that SO3 was a crucial component for the formation of SO42− in CPM, and the SO42− concentration increased with the increase of proportion of deposited H2SO4. The SO42− produced by heterogeneous reaction of SO2 could be enhanced in low temperature, and SO2 and SO3 could jointly promote the formation of SO42−. Furthermore, H2O vapor could also strengthen the formation of SO42−, which was caused by the Stefan flow. NH3 acted as the core, and the formation of SO42− was promoted. NOx could provide an acidic environment, which would interfere with the state of SO42− and even suppress the aqueous-phase oxidation of SO2. Finally, the formation of fine particles would aggravate the capture difficulty of CPM, which might help to explain the decrease of SO42− concentration in real flue gas. The results could provide basic guidance for improving the control of SO42− in CPM emitted from coal-fired power plants.