Comparison of impinging jet mixers by using barium sulfate precipitation and stabilisation of precipitated nanosuspensions Ricco Kügler, Josefine Morgenstern, Martin Kucher, Matthias Kind Dipl.-Ing. Ricco Kügler 0721-608 43078 [email protected] same initial particle sizes about x = 40 nm 50,3 (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 temperatures aggregation despite electrostatical stabilisation full 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-mixer T-mixer d 2 l u ñ æ Äp 2 fluid tube × × × × = Outlook particle sizes resulting from barium sulfate precipitation in Y-mixer 1 after t = 2 s (equilibrium achieved for used supersaturation) addition of the additives in Y-mixer 2 Motivation particle size analysis by laserlight scattering (Zetasizer Nano ZS) å å - - = transition tube exp mix Äp Äp Äp Äp 2 u ñ 0,4 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 the Y-Mixer = 0.64 bar at to achieve the initial supersaturation and initial free lattice ion ration: () () () fl fi + - + s 4 2 aq 4 2 aq aSO B SO a B () 2 2 l mol 11 SP 10 82 . 9 C 25 K - × = ° free SO free Ba 2 4 2 c ~ c ~ R - + = SP free SO free Ba SP free SO free Ba a K c ~ c ~ K a a S 2 4 2 2 4 2 - + - + × g = × = – Initial supersaturation: Initial free lattice ion ratio: with Mixing: Stabilisation: reaction mixing ô ô < Example: S = 1000, R = 5, T = 25 °C a c = 0.297 mol/l, c = 0.088 mol/l [1] (calculation with Bromley model ) BaCl 2 add ~ Na SO 4 2 add ~ exp Äp [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 the mixers are taken into account useful, when the jet tubes have the same geometries Reynolds-number in the mixing zone of the shown Roughton-mixer is unknown no dimensions of the mixing zone are taken into account best way, but determi- nation of the pressure drop in the mixing zone is difficult mix Äp fluid mix mix mean ñ V Äp V å × × = & . x = f(R) ? 50,3 faster aggregation with Tween and Span very good stabilisation with Melpers 0045 ® 20 ® 20 ® Y-mixer and T-mixer show at a total volume stream of 300 ml/min no more influence of the mixing Y-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 quality with a Roughton mixer in a comparable design (same jet tube and 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 additive Na2SO4 BaCl2 deionised water Y-mixer 1 Y-mixer 2 gear pump 3 gear pump 2 gear pump 1 ô FIC FIC FI waste direct sample from free jet sample from stirred tank Na2SO4 BaCl2 deionised water mixer gear pump 1 gear pump 2 FIC FIC waste direct sample from free jet PDI 0.14 0.08 0.41 bar 0.01 KIT - University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association