Mixer-Settler Based on Phase Inversion:  Design of the Mixing Zone

Abstract

The aim of this work is to improve the separation efficiency in the case of liquid−liquid dispersions using a new type of mixer-settler design called MSPI (mixer-settler based on phase inversion) and a so-called solvent assisted method. The phase inversion is used to decrease the distance between the drops of the disperse phase and the interface in spherical decanters called carrier drops, while a solvent injection in the mixer allows for optimal drop diameters and, therefore, for better and easier separation. In this study, a new design method for the mixing zone in a mixer-settler is proposed. It is based on the capacity of the settler to provide high separation efficiency while throughput increases. This separation is of essential importance when residual water of good quality has to be released. A number of correlations are identified that allow reasonable prediction of the D 3,2 of carriers formed using a perforated plate, as well as the drop size distribution and the Sauter mean diameter (d̄ min) of the primary dispersion. They allow predicting the influence of the organic/aqueous phase ratio as well as the contact angle on these parameters. The method is applied to design operating conditions in MSPI devices used in two particular cases, a heavy metal extraction and a crude oil emulsion separation. The results show that it is possible to obtain very good extraction efficiency coupled with good separation efficiency. They make the MSPI a viable alternative in the treatment of residual water contaminated with crude oil as well as in hydrometallurgy. At the same time the study shows that the MSPI is a simple piece of equipment to work with and very easy to maintain. While the results obtained are for some specific cases, the design methodology presented here can allow the rapid evaluation of other separation processes in the MSPI unit.

Understanding the interfacial behavior in isopycnic Lennard-Jones mixtures by computer simulations

“…In this context, the characterization and analysis of the evolution of the concentration profiles across the interfaces of binary systems that exhibit density inversion are very important due to the possible formation of special and unique interfacial structures directly related, which may represent a barrier to the mass transport between both bulk phases. [25][26][27] In spite of the impact that density gradients have on phase equilibrium, interfacial behavior and transport properties of heterogeneous mixtures have received limited attention so far, under thermo-physical conditions (i.e. temperature, pressure, composition) where density inversion phenomena becomes relevant in various technological applications.…”

Short-cut calculations for integrated product recovery options in fermentative production of bio-bulk chemicals

“…The required amount of interfacial area needed depends on the speed of agitation in the mixer-settler. Paulo et al [61] found an average Sauter mean droplet diameter over a wide range of Reynolds numbers. Therefore, we apply an average drop diameter (d vs ) of 3.4 mm in our calculations.…”

Effects of Geometry and Internals of a Continuous Gravity Settler on Liquid–Liquid Separation

“…As interfacial coalescence proceeds, clear organic phase is formed continuously. Further, several studies − were carried out to separate liquid–liquid dispersion using phase inversion (with less settling area and high throughput). For example, Hadjiev and Paulo , successfully improved separation efficiency by using a smaller settling area and allowing high throughput.…”

“…Further, several studies − were carried out to separate liquid–liquid dispersion using phase inversion (with less settling area and high throughput). For example, Hadjiev and Paulo , successfully improved separation efficiency by using a smaller settling area and allowing high throughput. They varied the phase ratio in a vertical settler to achieve an increase in the coalescence rate between dispersed drops in a small settling area.…”