(71e) Multiscale Modelling and Simulation of Particle Formation through Mono-Disperse Droplet Spray Drying

Multiscale Modelling and Simulation of

Particle Formation Through Mono-disperse
Droplet Spray Drying

Xiao, J, Wu, WD and Chen, XD

*Presenting authorÕs e-mail: jie.xiao@suda.edu.cn

Suzhou Key laboratory of Green Chemical
Engineering, School of Chemical and Environmental Engineering, College of
Chemistry, Chemical Engineering and Materials Science, Soochow University,
Suzhou, China, 215123

Abstract

A mono-disperse droplet spray dryer (MDSD) can offer
uniform-sized droplets with well-controlled trajectory and drying history. It has
demonstrated great potential in obtaining in-depth understanding of structured
particle formation. Moreover, it has unique advantages in producing on-aim
tailored particle products. Our group has been developing experimental and
computational platforms for this promising technology.^1-4 In this
talk, we will report our recent achievements on the development of a multiscale
simulation platform for MDSD aiming at virtual manufacturing. Three new major contributions
respectively at different scales will be presented.

At the dryer scale (macro), a comprehensive CFD
modelling approach has been developed to characterize the multi-stage drying
process. A level-set based free surface tracking model was coupled with a
structural mechanics model of a piezo-ceramic nozzle, which allowed us to
simulate droplet formation through atomization. A unique discrete phase model (DPM)
was developed to track evaporating droplets flying through distinctively
different sized chambers, i.e., the small dispersion chamber followed by the
big drying chamber. For the first time, droplets in MDSD can be tracked from generation
to the end of drying. At the single droplet scale (meso), a liquid-gas two
phase flow model coupled with the moving mesh ALE method was developed to
simulate droplet drying. The ability of quantifying the local evaporation rate
and characterizing crust formation enabled us to track the shape evolution of a
shrinking droplet. At the dropletsÕ surface layer scale (micro), a
coarse-grained lattice Monte Carlo (LMC) approach was developed to simulate
evaporation induced self-assembly of solute molecules. Evolution of the
nanoscale surface morphology and chemistry under different drying conditions
could then be systematically investigated. Furthermore, how to couple models at different
scales aiming at multiscale structure based particle quality control will be
discussed.

References:

1. Xiao J^*, Li Y, George OA, Li ZH, Yang SJ, Woo MW, Wu WD, Chen XD^*. Numerical investigation of droplet pre-dispersion in a monodisperse droplet spray dryer. Particuology 2018; 38: 44-60.
2. George OA, Xiao J^*, Rodrigo CS, Mercade-Prieto R, Sempere J, Chen XD^*. Detailed numerical analysis of evaporation of a micrometer water droplet suspended on a glass filament. Chem. Eng. Sci. 2017; 165:33-47.
3. George OA, Chen XD^*, Xiao J^*, Woo M, Che L.  An effective rate approach to modelling single-stage spray drying.  AIChE J. 2015; 61(12): 4140-4151. 
4. Xiao J^*, Chen XD^*. Multiscale modeling for surface composition of spray-dried two-component powders.  AIChE J. 2014; 60: 2416-2427.