Synergistic removal of particles, SO2, and NO2 in desulfurized flue gas during condensation.

Abstract

The synergistic removal of multi-pollutants, including particles, SO2, and NO2, is a key concern in the process of flue gas purification, during which the supersaturated environment is an essential premise for the nucleation and deep reduction of particles. The condensation of desulfurized flue gas using heat exchangers can not only recover condensed water and latent heat but also create supersaturated environment to promote the flue gas purification. In this study, an experimental system for desulfurized flue gas condensation is established. The effect and associated mechanism of condensation process on the removal of multi-pollutions are clarified. The results show that particles with an aerodynamic diameter larger than 2.5 μm accounts for 50% in mass proportion. The flue gas temperature drop has positive influence to the increase of the ideal supersaturation degree, which is beneficial for the removal of particles (especially when the aerodynamic diameter is less than 1 μm), SO2, and NO2. The ideal supersaturation degree slightly reduces with the rise of inlet flue gas temperature, which can promote the removal efficiency of small particles, while weaken that of large particles, SO2, and NO2. Caused by the increase of flue gas flow rate, the nucleation process weakens, reducing the removal efficiency of all pollutants (particles, 45.2-28.3%; SO2, 27.5-14.5%; NO2, 21.5-15%). On the whole, the increase of the ideal supersaturation degree contributes to the synergistic removal of pollutants especially particles with smaller radius in the flue gas. The reduction of particles with aerodynamic diameter less than 1 μm is conductive to the synergistic removal of SO2 and NO2.