(410c) Multiscale Modeling for Surface Composition of Spray-Dried Powders

Multiscale
Modeling for Surface Composition of Spray-dried Powders

Jie
Xiao, Winston Duo Wu and Xiao Dong Chen

School
of Chemical and Environmental Engineering

College
of Chemistry, Chemical Engineering and Materials Science

Soochow
University, Suzhou, China

Abstract

Spray
drying is the most effective process for large-scale manufacturing of various
powder products.  One of the most important properties of powders is the
ability to get wet, which is critically influenced by the powders' surface structure
and chemical composition. Furthermore, surface composition also influences the
efficiency of production as it affects the stickiness of the powder. 

In
this work, an innovative multiscale modeling approach is introduced to analyze
the surface composition of spray-dried powders produced under various conditions. 
A molecular-level geometrical packing interpretation is seamlessly coupled with
a continuum diffusion analytical model. The predictions are compared with the
measurements using X-ray photoelectron spectroscopy (XPS).  Sample
calculations for the lactose-protein two-component system demonstrate that the
integrated multiscale framework actually works quite well in terms of bridging
quantitatively the composition result in the thick continuum-scale surface
layer and that in the thin layer detected by the XPS instrument (see Figure 1).
 Moreover, we explore the possibility of integrating the macroscopic diffusion
model with a microscopic lattice Monte Carlo model that can characterize
evaporation induced self-assembly of solute molecules on the droplet/particle
surface.  In this way, detailed 3D surface morphology and chemistry (rather
than a single value of surface composition) can be revealed.  This work provides
a good basis for a fruitful area of study towards structure-focused powder
quality control that will have a positive impact in industries.

Keywords: Spray drying; surface
composition; multiscale modeling; self-assembly; multi-component diffusion;
molecular packing