Condensation of sulfuric acid vapors. Dynamics of binary aerosol condensation

摘要

The scope of the thesis is to investigate the formation of aerosols during condensation of sulfuric acid vapors. The dynamics of the aerosol particles are described quantitatively by a population balance, including the rate equations for diffusional growth and aerosol formation by homogeneous nucleation. A general model for a laminar flow aerosol condenser (LFAC) is presented. The LFAC is a tube with an externally cooled wall. Due to the decreasing temperature condensable components in the gas can condense on the wall, on existing seed particles or form droplets by spontaneous homogeneous nucleation. The density of the gas changes due to temperature variation in both radial and axial direction. This affects the profile of the linear gas velocity, which is distorted so as to deviate from the parabolic, radial relationship. Momentum, mass and energy balances for the condenser are derived for the general case and simplified with the assumption that the radial profile of the mass velocity remains parabolic. A laboratory scale laminar flow aerosol condenser has been constructed, making it possible to perform experiments with well defined conditions. The acid content in the gas is controlled by saturating the gas over a liquid acid at fixed composition and temperature. The number concentration of seed particles in the gas can be controlled within a wide range. The gas is cooled below the dew point by decreasing the temperature of the condenser tube wall. The experimental findings are well described by the simulations. Comparison between simulations and experiments show that the sticking coefficient for sulfuric acid is about 1.0. (EG) (71 refs.)