Comparison of impinging jet mixers by using barium sulfateprecipitation and stabilisation of precipitated nanosuspensionsRicco Kügler, Josefine Morgenstern, Martin Kucher, Matthias Kind

Dipl.-Ing. Ricco Kügler0721-608 43078kuegler@kit.edu

same initial particle sizes about x = 40 nm50,3

(initial precipitation conditions at S = 1000, R = 5 and T = 25 °C)a

aggregation at different temperatures:

Stabilisation

Aggregation after precipitation

Detergents:

Roughton-mixer

faster aggregation kinetics at higher temperaturesaggregation despite electrostatical stabilisationfull suppression by sterical stabilisation?

Institute of Thermal Process Engineering (TVT)

Kaiserstrasse 12

76131 Karlsruhe (Germany)

www.tvt.uni-karlsruhe.de

Mixing

Experimental setup

Experimental setup

162

Tween® 20, Span® 20,Melpers® 0045

Results and discussion

Y-mixerT-mixer

d2

luñæ Äp

2

fluid

tube×

×××=

Outlook

particle sizes resulting from

barium sulfate precipitation in Y-mixer 1

after t = 2 s (equilibrium achieved for usedsupersaturation) addition of the additivesin Y-mixer 2

Motivation

particle size analysis by laserlightscattering (Zetasizer Nano ZS)

åå--=transitiontubeexpmix

ÄpÄpÄpÄp

2

uñ0,4 Äp

2

fluid

transition

××=

First results

Supersaturation

What is the right coefficient to compare the mixing quality of different impinging jet mixers?

Reaction:

Measured pressure drop at V = 200 ml/min:total

by theY-Mixer = 0.64 bar at

to achieve the initial supersaturation and initialfree lattice ion ration:

() () ()̄®+-+

s4

2

aq4

2

aqaSOBSOaB

() 2

2

l

mol11

SP1082.9C25K -×=°

free

SO

free

Ba

24

2

c~c~

R-

+

=

SP

free

SO

free

Ba

SP

free

SO

free

Ba

aK

c~c~

K

aaS

24

224

2 -+-+ ×g=

×= ±

Initialsupersaturation:

Initial freelattice ion ratio:

with

Mixing: Stabilisation:

reactionmixingôô <

Example: S = 1000, R = 5, T = 25 °Ca

c = 0.297 mol/l, c = 0.088 mol/l[1](calculation with Bromley model )

BaCl2

add~Na SO42

add~

expÄp

[2] C. Kim, Y.C. Hsieh. Wetting and absorbency of nonionic surfactant solutions on cotton fabrics. Colloid Surf. A, 385:187-188, 2001

no dimensions of themixers are taken intoaccount

useful, when the jet tubeshave the same geometriesReynolds-number in themixing zone of the shownRoughton-mixer is unknown

no dimensions of themixing zone are taken into account

best way, but determi-nation of the pressuredrop in the mixing zone is difficult

mixÄp

fluidmix

mixmean

ñV

ÄpVå

×

×=&

.

x = f(R) ?50,3

faster aggregation with Tween and Spanvery good stabilisation with Melpers 0045

® 20 ® 20

®

Y-mixer and T-mixer show at a total volume streamof 300 ml/min no more influence of the mixingY-mixer increase slower than the particle sizes from the T-mixer at total volume streams under 300 ml/min

Roughton-mixer remain a function of the mixing (higher total volume streams/pressure drop limited by gear pumps)

Testing of some surfacant concentrations

Pressure drop in the mixer

comparison of the mixing qualitywith a Roughton mixer in acomparable design (same jet tubeand tube of the mixing zone)

[1] L.A. Bromley. Thermodynamic properties of strong electrolytes in aqueous solutions. AIChE Journal, 19(2):313-320, 1973.

optimisation of the steric stabilisation with

Melpers® 0045(adding time, concentration)stabilisation by increasing the viscosity (thickening agents)

Mixer

additiveNa2SO4 BaCl2 deionised water

Y-mixer 1

Y-mixer 2gear pump 3

gear pump 2gear pump 1

ô

FIC

FIC

FI

waste

direct samplefrom free jet

sample from stirred tank

Na2SO4 BaCl2 deionised water

mixer

gear pump 1 gear pump 2

FIC FIC

waste

direct samplefrom free jet

PDI

0.14 0.08

0.41 bar

0.01

KIT - University of the State of Baden-Wuerttemberg andNational Research Center of the Helmholtz Association