Abstract
SO(3) in coal-fired flue gas causes equipment corrosion and sulfuric acid mist emissions. As the flue gas temperature decreases, SO(3) converts to gaseous H(2)SO(4) and condenses with H(2)O via binary heterogeneous condensation. Here, based on thermodynamic equilibrium theory, a model for H(2)SO(4)-H(2)O binary heterogeneous condensation is developed and verified by comparing the calculated planar acid dew point (T (ADP,plane)) with the previously reported experimental data. The equilibrium parameters of condensation on both planar and particle surfaces are investigated. On planar surface, T (ADP,plane) increases with the gas concentration, while the equilibrium sulfuric acid mass fraction (ω (PE,plane)) increases with H(2)SO(4) concentration and decreases with H(2)O concentration. For H(2)SO(4) concentrations of 0.5-50 ppm and H(2)O concentrations of 0.5%-15%, T (ADP,plane) ranges from 356.37 to 426.67 K and the equilibrium sulfuric acid mass fraction (ω (PE,plane)) ranges from 71.922% to 91.058%. The equilibrium parameters on micrometer particle surfaces are similar to those on planar surfaces, while on submicrometer particle surfaces, the acid dew point (T (ADP,particle)) decreases and the equilibrium liquid film sulfuric acid mass fraction (ω (PE,particle)) increases with decreasing particle diameter (d (p)) due to the Kelvin effect. We found that T (ADP,particle)/T (ADP,plane) and ω(PE,particle)/ω(PE,plane) are barely unaffected by p (v,i) and can be considered as a function of d (p). Based on the numerical results, formulas with good prediction accuracy for T (ADP,particle) and ω (PE,particle) are proposed. The results provide predictive models for acid dew points on particle surfaces, which are crucial for guiding strategies to mitigate corrosion and reduce sulfuric acid mist emissions in coal-fired power plants.