Complex fluids and applications in the process
industries: fluid homogenization and transport
Tuomas Koiranen / LUT, Finland
Introduction to complex fluids problematics
(Definitions, classification), rheologies
process conditions in applications and typical
process equipment
Complex fluids definitions:
1) Fluids showing non-linear viscous behaviour, as well as viscoelastic
materials, are Complex Fluids. (Complex fluids engineering laboratory, Universidad Huelva, Spain)
2) Typically multicomponent systems, complex fluids are highly
nonlinear with respect to composition changes, and often the fluid
states that provide the desired mechanical or chemical properties are
metastable and accessible only through precisely controlled processing
and formulation steps. (Carnegie Mellon, Center for Complex fluids Engineering)
- Summary of Definitions: Complex fluids have 2 or more fluid phases
which have physical interaction with each other, and they can have
typically a complex microstructure. Fluid phases refer to disperse
systems.
Classification of disperse systems
Continuous medium
(Björn Lindman, Surfactants and Cellulose polymers in aqueous solutions-course, Physical chemistry,
Lund University, Sweden, 2013)
GAS
LIQUID
SOLID
GAS
None
Foam
(whipped cream,
shaving cream,
flotation cell
foam)
Solid foam
(aerogel, polymer
foam, pumice)
Dispersed phase
LIQUID
Liquid aerosol
(fog, hair sprays)
Emulsion
(milk,
mayonnaise,
lotions,
ointments)
Gel
(agar, gelatin jelly)
SOLID
Solid aerosol
(air particles,
smoke)
Sol
(blood,
pigmented ink,
fiber suspensions)
Solid sol
(gemstone, jewel)
Liquid-gas: foams, gas-liquid dispersions
Gas-liquid: fog, liquid aerosols
Gas-solid: solid aerosols, powders
Solid-gas: solid foams
Liquid-liquid: liquid-liquid dispersions , emulsions
Solid-liquid: gels, pastes
Liquid-solid: solid-liquid suspensions, slurries, sols
Bulk rheologies (EKATO Mixing handbook, 2000)
- The macroscale fluid rheology
Bulk rheologies
- The macroscale fluid rheology
Sol-gel viscosity example as a function of shear rate at different temperatures. Gelling at 20 °C
curve.
Bulk rheologies
- The macroscale fluid rheology
Solution rheology example: Sol-gel transition
Illustration of the viscoelastic structure and gelation phenomenon
at elevated temperature. (Metzger 2011, Kalanti 2015)
Microrheology (Rep. Prog. Phys. 68 (2005) 685, J. Non-Newtonian Fluid Mech. 112 (2003) 237).
1) Microrheology is concerned with how materials store and dissipate
mechanical energy as a function of length scale.
2) It is closely connected to the field of microfluidics (ink jet printing,
microreactors, valves etc.)
3) Classification (Waigh 2005)
1) Large amplitude oscillatory shear (LAOS) behavior studies of
complex fluids in forming microstructures.
Type I. Strain thinning: most polymer solutions or melts
Type II. Strain thickening: ion dipoles or hydrogen bonding (PVA+Na2B4O7, alcohol+clay with water bridge)
Type III. Weak strain overshoot: surfactant solutions, biopolymers (dough), liquid emulsions
Type IV. Strong strain overshoot: HASE polymers (acid/acrylate with ethoxylated hydrophobe)
Microstructures (Quemada, 1997)
Required shear rates in different applications
Typical shear rates of different processes (Fried, 1995; Paul et al. 2004;Kessler, 1998)
Process
Shear rate, 1/s
Application
Particle sedimentation in suspension
Extrusion, pipe flow
Mixing in stirred tank
Spray drying
High speed coating
1E-6 - 1E-3
1 - 1E+3
10-1000
1E+3 - 1E+5
1E+4 - 1E+6
paints, medicines
food, polymers
food, chemicals
food, chemicals
paper
Mixing power for Production of O/W dispersions (Paul et. al, 2004)
Emulsions (John Texter, Practical Survey course on small particle formation, Strider Res. Co. 2009)
- Emulsions are unstable but microemulsions are stable.
- Critical micelle forming concentration
+ charged
Small to long
chain
- charged
long to small
chain
Mesophases (John Texter, Practical Survey course on small particle formation, Strider Res. Co. 2009)
Microstructure formation
(Lindman, 2013)
PARTICLE STABILIZATION
- Hard wall and electrostatic repulsion, and Van der Waals attraction
forces define the electrostatic stabilized colloids
-In steric stabilization polymer chains form steric
hindrance for particles to form aggregates
Mixers for complex fluids
Static mixers
- Large variety of fluids mixing
(Laminar/Turbulent, S/L/G)
- Short residence times (τc)
- Large shear rate region and dispersed
phase/continuous phase –ratios (Rµ)
based on different geometries
- Simple sizing procedures (pump)
P = ∆𝑝𝑄
Mixers for complex fluids
Mixing tanks
- Large residence time regions
- Large distributions of shear rates
- Liquids, emulsions, gels, pastes
Some special cases
- Ultrasonication can be used
for emulsification, difficult
slurry formations
(e.g. nanomaterial wetting).
- Electrocapillarity: Internal
phase breaks into emulsion
droplet in continuous phase
when electric potential difference
is applied between phases (Watanabe et al., 1978)
- Initial dispersion is pressed through
porous membrane to form emulsion
(Omi et al., 1994).
Summary of homogenization methods
Type of complex fluids
Paints
Adhesives
Paint pastes
Greases
Ceramics (heavy
consistency)
Fibrous mixes
Resins (heavy
consistency)
Rubbers&Elastomers
(stiff gels)
Mineral slurries
Emulsions (food,
cosmetics, pharma)
Foams (gas-liquid)
Mixers used
rotor-stators, stirred tanks (shearing action)
kneaders, rotor-stators
roll mills, ball mills, tube mills, rotor-stators
stirred tanks (dual action), kneaders (sigma
blade, dispersion blade)
pan mixers, pug mills, planetary mills
kneaders, sigma/dispersion blade), intensive
mixers (Banbury type)
kneaders, roll mills, intensive mixers (Banbury,
rotor-stator)
intensive mixers, roll mills, kneaders
stirred tanks (dual action), in-line mixers (rotorstators)
paddle stirred tanks, static mixers, in-line mixers
(rotor-stators), pressure homogenizer
Gas-liguid Injectors, stirred tanks
- Complex fluids can also be present in changing process conditions:
Chemical reactions, crystallizations, melting processes etc.
-
Complex fluids transport
Centrifugal pumps are the most common pumps for fluid transport
The problems arise typically for
1) shear thickening fluids=> viscosity increases=> flow rate decreases
2) high solid contents => material abrasion
3) preserving fluid microstructure => shear rate changes occur
Special pumps can be used in complex fluids transport: peristaltic
pumps, positive displacement pumps like eccentric screw pumps
(e.g. Flowrox Ltd)
Literature :Equipment
EKATO Handbook of Mixing Technology, EKATO Rühr- und Mischtechnik GmbH, 2000
Matijevic, E., Good, R.J. (eds.), Surface and colloid science Vol 13, Ch. 1: Electrochemistry of oil-water interfaces, Springer, USA, 1984
McDonough,R.J., Mixing for the Process Industries, Van Nostrand Rheinhold, New York, USA, 1992
Paul, L.E., Atiemo-Obeng, V., Kresta, S., (eds.), Handbook of industrial mixing, Wiley, 2004
Pehrman, N., Slurry flows in progressive cavity and peristaltic hose pumps, LUT 2014
Thakur, R.K. et al., Static mixers in the process industries - a review, Trans IChemE 81 A, (2003) 787-826
Grace, H.P., Chem Eng Commun 14 (1982), 225–277
Zlokarnik, M., Judat, H., Ullmann's Encyclopedia of Industrial Chemistry, Vol. B2., Ch. 25: Stirring , VCH Verlagsgesellschaft GmbH, Germany, 1988
Literature: Processes
Florence, A.T., Attwood, D. (eds.), Physicochemical principles of pharmacy, Pharmaceuitical press, UK, 2011
Dickinson, E., Leser, M. (eds.), Food colloids – self-assembly and material science, RSC publishing, UK, 2007
Fried, J.R., Polymer science and technology, Prentice Hall, USA, 1995
Kessler, H.G., Food and bio process engineering – dairy technology, Verlag A. Kessler, Germany, 1998
Mixing in polymer processing, Rauwendaal, C. (ed.), Marcel Dekker, USA, 1991
Omi, S., Katami, K., Yamamoto, A., Iso, M., Synthesis of polymeric microspheres employing SPG emulsification technique, J. Appl. Polym. Sci. 51 (1994) 1-11
Watanabe, A. et al., J. Colloid Interface Sci 64 (1978) 278
Literature: Complex fluids, disperse systems, rheology and microrheology
Chen, D.T. et al., Rheological microscopy: local mechanical properties from microrheology, Phys. Rev. Lett. 90 (2003) 108301-1 - 108301-4
Lindman, B., Surfactants and cellulose polymers in aqueous solutions (course material), Physical Chemistry Dept., Lund University, Sweden, 2013.
Luckham, P.F., Rossi, S., The colloidal and rheological properties of bentonite suspensions, Advances in Colloid and Interface Science 82 (1999) 43-92
Texter, J., Practical survey course on small particle formation (course material), Strider Research Company, USA, 2009
Quemada, D., Rheological modelling of complex fluids. I. The concept of efective volume fraction revisited, Eur. Phys. J. AP 1 (1998) 119-127
Quemada, D., Berli, C, Energy of interaction in colloids and its implications in rheological modeling, Advances in Colloid and Interface Science 98 (2002) 51-85
Gelbart, W.M., Ben-Shaul, A., The “New” Science of “Complex Fluids”, J. Phys. Chem. 100 (1996) 13169-13189
Waigh, T.A., Microrheology of complex fluids, Rep. Prog. Phys. 68 (2005) 685–742
Sim, H.G., Ahn, K.H., Lee, S.J., J. Non-Newtonian Fluid Mech. 112 (2003) 237–250
Mezger T. The Rheology Handbook. 3rd Edition, Vincentz Network, 2011.
Kalanti A. 2014. Basics of rheology (course material in Finnish), Anton Paar. Imatra, Finland, 2015.
Some research questions
1) Is the response of one probe particle a true measure of the bulk
rheology? An interconnection of microstructures to bulk rheology is
welcome.
2) The equipment selection and sizing are based on dynamic viscosity
data. Elastic and viscous moduli data are available for a vast amount of
different complex fluid systems. Focus also for dynamic rheology
measurements.
3) Complex fluid structures formation. Systematic, uniform and technoscientific approach for product design ? e.g. formation energies,
characteristic residence times, critical surface areas, etc.
THANK YOU / KIITOS