Calculated Droplet Size Distributions and Opacities of Condensed Sulfuric Acid Aerosols

The properties of condensed polydisperse sulfuric acid aerosols in industrial flue gas were calculated. The condensed aqueous acid volume concentration, composition, droplet size distributions and condensed plume opacity were calculated for typical flue gas compositions, condensation nucleus size distributions and flue gas dilution ratios. The assumed initial flue gas at 170°C contained 0.035 g/acm fly ash particles, 1-20% water vapor, and 1-50 ppmv sulfuric acid vapor. The assumed gas cooling mechanism was by adiabatlc dilution with cool ambient air. Polydisperse droplet growth was calculated by assuming equal surface area increase for each particle. The calculations show that sulfuric acid condensation should have minimal effect on particles larger than 1 μm, but will form a high concentration of particles in the narrow size range of 0.05-0.5 μm diameter. Depending on the initial sulfuric acid and water vapor concentrations in the hot flue gas, the calculated maximum plume opacity following gas dilution ranged from 5% to 25%, compared to 4% for the dry condensation nucleus aerosol.