Agglomerate TiO2 aerosol dynamics at high concentrations

Primary and agglomerate particle dynamics are investigated for aerosol synthesis of titania at high solids concentrations that are typically used for its industrial scale manufacture. Particle formation and growth are simulated accounting for chemical reaction, coagulation and sintering. Process conditions are chosen so that the resulting primary and hard-agglomerate sizes are comparable with commercial product specifications. Neglecting aerosol polydispersity, the evolution of the diameter of primary particles, hard- and soft-agglomerates along with the agglomerate effective volume fraction are investigated. During synthesis of nanostructured titania (e.g. for catalysts and cosmetics) the effective soft-agglomerate volume fraction can exceed 30% within 100 s residence time indicating that a transition takes place from dilute to concentrated aerosol dynamics. At these conditions, classic Smoluchowski theory may no longer describe agglomerate coagulation and particles may affect fluid flow and heat transfer in industrial aerosol reactors. Furthermore, this could lead to restructuring and fragmentation of the product powder.