Improvement in removal of fine particles and SO₃ acid mist from desulfurized flue gas with heterogeneous condensation

The supersaturated water vapor environment for condensational growth of fine particles (PM_2.5) and SO₃ acid mist was achieved by adding water vapor or humid air into the limestone-gypsum desulfurized flue gas. The influences of the addition amount of water vapor and humid air as well as the desulfurized flue gas temperature were analyzed based on the property analysis of PM_2.5 and SO₃ acid mist. The results show that except for coal-fired ash, the desulfurized flue gas also includes CaSO₄, CaSO₃ and unreacted CaCO₃ in PM_2.5. The removal efficiency of SO₃ acid mist is 35%-55% merely by wet flue gas desulfurization (WFGD) system because SO₃ acid mist is mostly submicron particles. PM_2.5 and SO₃ acid mist can be removed effectively by adding either water vapor or humid air, and the emission concentration decreases with increasing the amount of water vapor or humid air. Moreover, it is found that it is better to add water vapor to establish the supersaturated water vapor environment for lower temperature desulfurized flue gas (≤50-55 ℃), while it is more appropriate to add humid air for higher temperature desulfurized flue gas (≥55-60℃).