Emission reduction of condensable particulate matter in ammonia-based desulfurized flue gas by heterogeneous vapor condensation

Abstract

With ultra-low emissions being implemented in China, the proportion of condensable particulate matter (CPM) increased gradually in total particulate matter (TPM). To reduce the CPM emission, a novel method based on heterogeneous vapor condensation via heat exchanger was proposed. The phase of gaseous CPM would be changed to solid or liquid phase by temperature drop of desulfurized flue gas and then the particle CPM might be enlarged by heterogeneous vapor condensation. With the effect of inertia force, thermophoretic force, and diffusiophoresis force, the enlarged CPM particles would be captured by liquid film, which was formed on the surface of fluoroplastic capillaries. The experimental results indicated that reduction rate for filterable particulate matter (FPM) and CPM would be 26.67% and 30.84% by heterogeneous vapor condensation under typical conditions, and the SO42− and NH4+ were main ions in water-soluble ions for FPM/CPM. The influences of temperature drop and original temperature of desulfurized flue gas were also investigated. The higher temperature drop of desulfurized flue gas was beneficial for reduction of CPM emission and the effect of original desulfurized flue gas temperature was limited for CPM emission reduction. The results also manifested that the optimum temperature drop is 4–6 °C for different desulfurized flue gas temperatures.