Drying kinetics, coalescence and agglomeration of dairy...
Transcript of Drying kinetics, coalescence and agglomeration of dairy...
Drying kinetics, coalescence and agglomeration of dairy products particles- Validated modelling tools to support the design of spray-drying
processes
LOREDANA MALAFRONTE
SP Food and Bioscience/Chalmers University of Technology
New affiliation R&D Center, Valio Ltd
Spray-drying process
time and cost reduction
process design
operating conditions
quality enhancement of
final product
Energy-intensive operation
Design and scale-up
Final properties of powders
Limitations
Simulation tools
Spray-drying process
time and cost reduction
process design
operating conditions
quality enhancement of
final product
Energy-intensive operation
Design and scale-up
Final properties of powders
Limitations
Simulation tools
ATOMIZATION
FLOW OF THE
AIR AND FEED
PARTICLE-WALL
PARTICLE-PARTICLE
INTERACTION
Shrinkage
PARTICLE
FORMATION
Modelling approach
Heat Transport
Bi << 0.1
Lumped model
Mass Transport
Bi >> 0.1
Distributed model
Simplified approach
CFD model
Lumped drying-kinetics model(Gianfrancesco et al., 2010; Jin and Chen, 2009, 2010)
Less computational resources
Dairy products
Modelling approach
Heat Transport
Bi << 0.1
Lumped model
Mass Transport
Bi >> 0.1
Distributed model
Complex approach
CFD model
Distributed drying-kinetics model
Accurate description
Dairy products
Goal of the research project
To develop a validated distributed model to describe the drying-kinetics of single particles of dairy products
To use the model to understand the coalescence and agglomeration of particles during spray drying
I
II
Outline
Implementation of modelling tools in a real spray-
drying application
Experimental and modelling tools for drying-
kinetics of single particles
Experimental and modelling tools for coalescence,
agglomeration and non-agglomeration of single particles
Conclusions
Drying kinetics
Experimental procedure
Air
system
Balance
Drying chamber
Air
• Temperature• Humidity• Velocity
Sample
• Temperature• Moisture content• Shrinkage
Drying kinetics
Experimental procedure
Air
system
Balance
Drying chamber
Modelling tool
Shrinkage
Evaporation
Convective heating
Deff (T,w)
Effective water diffusion in dairyproducts
Deff (w,T) = f(T) g(w)
NMR
Parameter estimation
method
Modelling tool
Shrinkage
Evaporation
Convective heating
Deff (T,w)
Drying kinetics
Skim milk
Light miilk
Medium milk
Whole milk
Diluted coffee creamer
Coffee creamer
Heavy cream
Fa
t co
nte
nt
Effective water diffusion in dairyproducts
Fat
Proteins Fat
Regions of coalescence and agglomeration
CF
D m
od
el
Tamb,
RHamb
Liquid Feed Hot air
Powder particles
T(z)
Nu(z)
Sh(z)
RH(z)
d(0.1)
d(0.5)
d(0.9)
X0, T0
Coalescence and agglomeration
Drying-kinetics model
(L. Malafronte et al., 2015)
Coalescence and agglomeration
���~viscousforces
inertia · surfacetensionforces
��� < 1
Coalescence
��� > 1
Stickiness
Non - Stickiness
� − �� > ∆�∗
� − �� < ∆�∗
(Verdurmen et al 2004)
Coalescence region
�Oh2 < 1�Oh2 > 1
Surface Average
Coalescence• Physical properties (Oh2)• Kinetic energy• Impact parameters
Analysis of thickness and strength of particle shells
Impact Shell breakage
Leakageinternal material
Coalescence
Agglomeration regions
Case II Case III
Coalescence Non stickinessStickiness
Case I
∆�∗= 20 ÷ 40℃
Case I:
∆�∗> 20℃
Case II:
∆�∗> 30℃
Case III:
∆�∗> 40℃
Sticky point Conditions for coalescence
Oh2average vs Oh2
surface
Shell formation in a drying particle
Conditions for agglomeration
Accurate sticky conditions
Particle contact test
Air
system
Balance
Drying chamber
Suspension
system
Top view
Air
Experimental procedure Modelling tool
Shrinkage
Evaporation
Convective heating
Deff (T,w)
Particle contact test
Coalescence Stickiness Non-stickiness
∆Taverage > 140°C > 140°C > 140°C
∆Tsurface > 140°C > 30°C < 30°C
Glass transition temperature, ΔT=T-Tg
�
Oh2surface < 1
Coalescence
∆Tsurface > 140⁰C
Oh2surface > 1
Stickiness
∆Tsurface > 30⁰C
Ohnesorge number, Oh
Coalescence Non-coalescence
Oh2average < 1 < 1
Oh2surface < 1 > 1 �
Skim milk and Whole milk
Shell formation – skim milk
μlocal > μ*
Wet shell
ulocal > u*
Dry shell
Conclusions
We have developed an experimental set up, a methodology and a mathematical model able to:
• Determine the effect of feed composition on drying time
• Predict surface properties of particles
• Control agglomeration along the spray dryer and wall deposition
• Determine the wet and dry shell formation in a drying particle
Design and scale-up the process
Product stickiness and drying ability
Preliminary size of the chamber
Preliminary positioning of fines returns
Enhancement and control functional properties of
powders
Future Application
Acknowledgements
Supervisors
Pof. Lilia Ahrné, University of Copenhagen
Prof. Anders Rasmuson, Chalmers University of Technology
Dr. Fredrik Innings, TetraPak Processing Systems
Co-authors
Alfred Jongsma, TetraPak Processing Systems
Erich Schuster, SP Food and Bioscience
Erik Kaunisto, SP Food and Bioscience
Vincenzina Robertiello, Universitá degli Studi di Salerno
Thankyou!
Publications
• Malafronte, L., L. Ahrné, et al. (2015). "Prediction of regions of coalescence and agglomeration along a spray dryer—Application to skim milk powder." Chemical Engineering Research and Design 104: 703-712.
• Malafronte, L., L. Ahrné, et al. (2015). "Estimation of the effective diffusion coefficient of water in skim milk during single-drop drying." Journal of Food Engineering 147: 111-119.
• Malafronte, L., L. Ahrné, et al. (2016). "Coalescence and agglomeration of individual particles of skim milk during convective drying." Journal of Food Engineering 175: 15-23.
• Malafronte, L., L. Ahrné, et al. (2015). "Exploring drying kinetics and morphology of commercial dairy powders." Journal of Food Engineering 158: 58-65.