A One-Dimensional Model for Coagulation, Sintering, and Surface Growth of Aerosol Agglomerates

Abstract

The size of the primary particles in aerosol agglomerates is determined in part by the interplay of surface growth, coagulation, and sintering. These processes are modelled by a one-dimensional (1-D) discrete-sectional model, DISGLOM2, which predicts the evolution of agglomerate and primary particle size distributions. DISGLOM2 is an extended version of DISGLOM (Rogak 1997), in which particles smaller than the "melting diameter" were assumed to sinter instantly while bigger particles did not sinter at all. Gradual sintering, "condensational obliteration" (whereby primary particles are lost during heavy surface growth), and diffusional wall deposition have been incorporated into DISGLOM2. Results from DISGLOM2 were comparable with those from 2-D sectional models, but DISGLOM2 was much faster. In addition, DISGLOM2 includes the effects of "condensation" of small spherical particles on large agglomerates, which were not modelled previously. The effect of condensation was shown to be significant at low temperature. DISGLOM2 was used to predict the primary particle diameter of titania particles generated by precursor reaction. By adding gradual sintering, the growth rate of agglomerate particles by coagulation was slightly decreased and the primary particle size considerably increased compared with the results given by DISGLOM. Although DISGLOM2 is an efficient model of the relevant physical processes, the predictions are sensitive to the kinetics of precursor reactions and particle sintering, which can be difficult to characterize in real experimental systems.

Large Eddy Simulation of Titanium Dioxide Nanoparticle Formation and Growth in Turbulent Jets

“…A good example is the inclusion of finite-rate sintering, which affects the formation of hard agglomerates. Sintering rates are highly dependent on the temperature field and in turbulent reacting flows, these require accurate capture/resolution (Wegner and Pratsinis 2003;Park and Rogak 2003;Heine and Pratsinis 2007;Garrick and Wang 2010). Grid-free approaches such as the probability-based, filtered density function maybe suitable in both accounting for the unresolved terms as well as removing oscillations (Colucci et al 1998;Garrick et al 1999;Givi 2006;Garmory and Mastorakos 2008).…”

Observations of a Correlation Between Primary Particle and Aggregate Size for Soot Particles

“…Particles formed in different combustion regions experience different formation and growth patterns, e.g., local equivalence ratio and residence time. The size of the primary particles and agglomerates forming in a combustion process depends on the interplay of complex formation and evolution mechanisms including nucleation, coagulation, surface growth, carbonization, oxidation, and sintering (Glassman 1988;Park and Rogak 2003;Park et al 2005;Kholghy et al 2013). Typically, surface growth and coagulation prior to carbonization lead to larger more spherical particles.…”

Population Balance-Monte Carlo Simulation for Gas-to-Particle Synthesis of Nanoparticles

“…In addition to measurement errors, the discrepancy between PB-MC simulation results and experimental measurements may be due to: (1) the MC does not consider condensation and diffusional wall deposition (Park and Rogak 2003); (2) the inhomogeneity of temperature and concentration profiles is not considered, and the modeled temperature and gas velocity profiles deviate from experimental measurements; (3) the used kernel models (especially τ s ) may not be accurate for the case (Buesser et al 2011); (4) surface growth will narrow the size distribution in the initial stage, which is not included in this MC (Tsantilis and Pratsinis 2004).…”

“…They modeled the growth of both agglomerates and primary particles by two-dimensional discretesectional method (DS), considering effect of temperature on the size distribution of TiO 2 nanoparticle product. Park and Rogak (2003) used a one-dimensional model for agglomeration, gradual sintering, condensational obliteration, and diffusional wall deposition in the same aerosol reactor. In their model particles smaller than the "melting diameter" were assumed to sinter instantly while bigger particles did not sinter at all.…”