Experimental and theoretical characterization on the sublimation kinetics of fine aerosol particles

English Summary Sublimation (Evaporation) is widely used in different industrial applications. The important applications are the sublimation (evaporation) of small particles (solid and liquid), e. g., spray drying and fuel droplet evaporation. Since a few decades, sublimation technology has been used widely together with aerosol technology. This combination is aiming to get various products with desired compositions and morphologies. It can be used in the fields of nanoparticles generation, particle coating through physical vapor deposition (PVD) and particle structuring. This doctoral thesis deals with the experimental and theoretical investigations of sublimation (evaporation) kinetics of fine aerosol particles (droplets). The experimental study was conducted in a test plant including on-line control of the most important paramters, such as heating temperature, gas flow and pressure. On-line and in-line particle measurements (Optical sensor, APS) were employed. Relevant parameters in sublimation (evaporation) such as heating temperature, particle concentration and aerosol residence time were investigated. Polydispersed particles (droplets) were introduced into the test plant as precursor aerosols. Two kinds of materials were used as test materials, including inorganic particles of NH4Cl and organic particles of DEHS. NH4Cl particles with smooth surface and porous structure were put into the experiments, respectively. The influence of the particle morphology on the sublimation process was studied. Basing on the experiments, different theoretical models were developed. The simulation results under different parameters were compared with experimental results. The change of concentration of particles was specially discussed. The discussion was focused on the relationship of the total particle concentration and the change of single particles with diverse initial diameters. The study of the sublimation kinetics of particles with different morphologies and different specific surface areas was carried out. The factor of increased surface area on the sublimation process was taken into the simulation and the results were compared with experimental results. A sublimation (evaporation) kinetics was investigated in this thesis. Basing on the property of a material, such as molecular weight, molecular size and vapor pressure, the sublimation (evaporation) kinetics was described. The optimum sublimation (evaporation) conditions with respect to the material properties were advanced. A Phase Transition Effect during the sublimation (evaporation) was found, which describes the increase of the large particles on the cost of small particles. A similar effect is observed in crystal suspension (called Ostwald ripening) but with another physical background. In order to meet the need of in-line particle measurement, a hot gas sensor (O. P. C.) was developed in this study, for measuring the particle size and the size distribution of an aerosol. With the newly developed measuring cell, the operating conditions of the aerosol could be increased up to 500°C.