Dispersion and Phase Separation of Water‐Oil‐Amphiphile Systems in Stirred Tanks

Abstract

Drop size distributions and phase separation behavior of water-oil-nonionic amphiphile systems are investigated using an in situ endoscope measurement technique and an external camera in stirred tanks in batch mode. The fitting procedure and the simulation results of a phase separation model are analyzed under the condition that either the swarm sedimentation speed or the mean drop size during sedimentation is known. The steady-state drop size distributions are self-similar over the whole range of process parameters, but not in the decaying turbulence field after agitation stop. The coalescence rate in the first seconds after agitation stop clearly affects the separation behavior, so that a prediction of the separation time based on the initial conditions in steady state is not trivial.

Influence of Different Silica Nanoparticles on Drop Size Distributions in Agitated Liquid‐Liquid Systems

“…A change of coalescence behavior, induced for example by ions or a change of pH, can reduce this value . In w/o systems with amphiphilic molecules a value of σ n / d 32 ≈ 0.35 was found while varying agitation speed, temperature and tank geometry . In case of the nanoparticle‐stabilized dispersions presented here, the values deviate around an arithmetic mean of σ n / d 32 ≈ 0.32.…”

“…Using viscosity values at shear rates of 10 s −1 and 1000 s −1 only changes the Sauter mean diameter value in the first digit after the decimal point. For emulsions with high particle mass fractions in the continuous phase, the complex rheology should be taken into account since the swarm sedimentation model is very sensitive towards the continuous phase viscosity , . However, this case was not investigated in this work.…”

Automation of a Procedure for the Experimental Investigation of Liquid‐Liquid Phase Separation

“…, the decrease of phase separation time by increasing the operating temperature shows an asymptotic behavior. By an increase of operating temperature from 22.0 ± 0.0 to 43.3 ± 1.6 °C, the phase separation time decreases approximately by factor 2, from 84.5 ± 1.2 to 47.3 ± 0.2 s. An increase of operating temperature from 22.0 ± 0.0 to 99.2 ± 0.4 °C results in a decrease of phase separation time by factor 3.5, from 84.5 ± 1.2 to 24.5 ± 0.0 s. The change in phase separation behavior by increasing the operating temperature can be explained by the temperature dependence of physicochemical substance properties, e.g., density, viscosity, and interfacial tension . In future work, the effect of temperature on phase separation behavior of liquid‐liquid dispersions should be investigated systematically to establish a causal connection between operating temperature and phase separation behavior.…”

Analysis of immiscible liquid-liquid mixing in stirred tanks by Electrical Resistance Tomography

“…The investigated diesel fuel-water mixture has similar physical properties of other liquid-liquid systems used for the analysis of bioreactors for biodesulfuration of crude oil (Tsouris et al, 1996), for the analysis of drops coalescence and breakage in stirred tanks (Daglas & Stamatoudis, 2000, De Bona et al, 2016, for the analysis of macromixing phenomena (Zhao et al, 2011), for the analysis of homogeneously catalysed hydroformylation of olefins (Hohl et al, 2019), for the isobutene alkylation (Duan et al, 2019).…”