Modeling Small Cluster Deposition on the Primary Particles of Aerosol Agglomerates

Dense particles, such as the primary particles in aerosol agglomerates, are formed by coagulation with rapid coalescence, or by condensation-like growth. This latter mechanism is explored in a new model. It uses the discrete-sectional model to describe the evolution of the particle mass distribution. In addition, new equations are used to describe the formation of primary particles. Primary particles are "born" when a new particle is formed above a critical size D melt • Particles smaller than Dmelt are assumed to be liquid-like, sintering rapidly in the available time. Changes in the final primary particle size D p can be attributed to growth from small particle deposition. This growth increases as the monomer source rate decreases. For conditions representative of Ti02 formation from chloride in a tube reactor, Dp/ Dmelt ranges from 1.5 to 3. When D melt decreases, as would be expected if temperature decreases, DplDmelt increases. The result is that Dp is much less sensitive to temperature than would be expected from simple sintering models.