Breakup of immiscible liquids at the interface using high-power acoustic pulses

https://doi.org/10.1016/j.cep.2018.07.011Get rights and content

Highlights

  • Acoustic soliton can intensify mass transfer in the liquid substrate of an extractor.

  • The performed analysis of the breakup of immiscible liquids permits to find the optimum parameters of ultrasonic pulses.

  • The comparative efficiency of using various mechanisms of nonlinear acoustics in ultrasonic extraction is estimated.

Abstract

A method has been developed for the approximate analytical description of the properties of acoustic solitary waves that have a large difference between the values of spatial gradients of their parameters along different coordinates. In the presence of two- or three-dimensional nonuniformity of the initial perturbation, these waves maintain their spatial structure unchanged when propagating to large distances and make it possible to regulate pressure drop at the front and the rate of their movement. All of this ensures a wide range of the possibilities of producing special force action or organizing long-distance information exchange. In particular, the sequence of such compression or rarefaction pulses can break up immiscible liquids at their interface, which is of great importance for the intensification of mass transfer in extraction processes.

Graphical abstract

A method has been developed for using acoustic solitary waves that may intensify the mass transfer in the liquid substrate of an extractor as it is shown in the Figure below.

Membrane extractor based on the liquid pseudomembrane principle and ultrasonic intensification of extraction processes:

1 – original solution with the component being extracted.

2 – drops of heavy liquid also after breaking up; 3 – raffinate; 4 – stripped solution with the target substance; 5 – membrane phase; 6 – stripping agent; 7 generated acoustic solitons.

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Introduction

In recent years, the ability of nonlinear acoustic techniques to produce force action has been increasingly frequently used in various spheres of applied character, for example, in the development of ultrasonic miniextractors using liquid pseudomembranes [[1], [2], [3]], in the field of oil well stimulation [4,5], or for the reinforcement of the basic structure of materials [6]. There are studies [7,8] in which ultrasonic irradiation is used for the intensification of such fine mechanism of extraction as interphase mass transfer using the dynamic layer, which is controlled by self-organization and self-assembly processes. Even the simple creation of the cavitation region by different direct methods in the working zone of extraction leads to positive results [9]. Successful testing of power and resonance methods of the use of ultrasound in extraction processes suggests that the other nonlinear acoustic technique, such as the generation of solitary waves (solitons), can also have an effect on the intensification of mass transfer. The study of acoustic solitons [10,11] made it possible to determine some various aspects of the development of this nonlinearity in liquids and indicated new useful possibilities of its application. In particular, of special practical importance can be the use of acoustic solitary pulses in the treatment of molten metals [10]. The study of specific features of the generation and spatiotemporal structure of high-power acoustic pulses [11] is aimed at finding ways to produce special force action on the material being processed in a liquid medium. The specificity and conditions of the existence of such waves in plasma have also been well studied at present [[12], [13], [14]]. At the same time, a number of the important features of these waves, including the localization of force action in a limited volume, controllability by process parameters, and ability to propagate to long distances even in a dissipative medium, continue to attract well-founded scientific and applied interest in the study of these waves and their properties in liquids.

This study considers the specific features of the propagation of acoustic solitary waves in an ideal liquid in the case where there is a large difference between the values of the spatial gradients of their parameters along different coordinates, as applied to their interaction with the interface of immiscible liquids. When the multidimensionality of their spatial structure is ensured, which is the necessary condition of their existence, the movement of a soliton leads to the transport of the rarefaction or compression region in the given direction, thus producing the required force action. The performed calculations on the accurate determination of the character of the interaction between acoustic solitons and the surrounding medium are based on the separate description of the motion of a liquid in different directions that have a considerable difference in characteristic scales along the corresponding axes.

Section snippets

Original equations and approximate nonlinear solutions

The motion of an ideal liquid is described by the following well-known [15,16] system of the equations of fluid dynamics:ρ[tv+vv]= -p,tρ + div ρv=0,p=A0ρρ0γA1.Here, the functions v(r,t), ρ(r,t), and p(r,t) are the distributions of the liquid velocity, density, and pressure, respectively, along the spatial coordinates described by the radius vector r and their variation with time t under the conditions when the constants А0, А1, and γ, which appear in Tait equation of state (3), weakly

Results and discussion

The substantiation of the possibility of the existence and propagation of high-power acoustic pulses in the column of an extractor that was conducted in this study and examples of the application of this method of influence for the intensification of mass transfer offer new real prospects of using nonlinear acoustic techniques for the improvement of extraction technology. As it is discovered in the present work, one can irradiate solitary impulses in liquid media used for extractions under

Conclusions

It is well known that nonlinear acoustic techniques can quite successfully raise the efficiency of a large number of physical processes and chemical reactions. As applied to extraction technologies, these methods can be divided within the current state of research into three distinct groups, one of which, namely, the generation of nonlinear acoustic pulses, has been considered in detail in this study. For two other groups (the excitation of acoustic streaming and the use of parametric

Acknowledgement

The publication was carried out within the State Assignment on Fundamental Research to the Kurnakov Institute of General and Inorganic Chemistry.

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