DEVICE AND METHOD FOR CARRYING OUT A CONTINUOUS EMULSION OF TWO IMMISCIBLE LIQUIDS

Abstract

Some embodiments relate to a device for performing continuous emulsion of two immiscible fluids. The device includes: a first microsystem including at least two micro-channels for intake of each fluid, of different respective cross sections S1 and S2, which are offset and face each other along a central intake axis A; at least two micro-channels for output of the emulsion from the device once the emulsion is formed; and an area where the intake and output micro-channels intersect, the area being capable of generating an interface between the fluids and forming a pre-emulsion flowing in the output micro-channels until the emulsion is complete. The device also includes at least one singularity capable of destabilizing the interfaces between the fluids in the pre-emulsion.

Claims

1. A device for performing a continuous emulsion of two immiscible fluids, comprising: at least one first microsystem that includes: at least two micro-channels for the intake of each fluid into the device, the micro-channels, with respective sections S1 and S2 different from S1, facing each other along a central intake axis A and having an offset, linked to their difference in section, at least two micro-channels for the output from the device of the emulsion once formed, an intersection area wherein the intake and output micro-channels intersect, the intersection area being able to generate an interface between the fluids and as such forming a pre-emulsion intended to flow in the output micro-channels until the completion of the forming of the emulsion, and at least one singularity capable of destabilizing the interfaces between the fluids in the pre-emulsion.

2. The device according to claim 1, wherein the output micro-channels are arranged, in the microsystem symmetrically, with respect to the central intake axis (A).

3. The device as claimed in claim 1, wherein the singularity is a bend formed in each output micro-channel of the microsystem.

4. The device according to claim 3, further comprising two to six bends formed in each output micro-channel of the microsystem.

5. The device according to claim 1, wherein the singularity is an abrupt widening or narrowing formed in each output micro-channel of the microsystem.

6. The device according to claim 1, further comprising a second microsystem in series or in parallel comprising: at least two micro-channels for the intake into the device of each fluid, facing each other along a central intake axis, and at least two micro-channels for the output from the device of the emulsion formed.

7. The device according to claim 6, wherein the second microsystem is identical to the first microsystem.

8. The device as claimed in claim 1, wherein the intake and output micro-channels have a square or rectangular section S1, S2.

9. A method for performing a continuous emulsion of two immiscible liquids implementing the device according to claim 1, the method comprising: 1) supplying each fluid in the intake micro-channels of the microsystem, 2) enabling the frontal collision of the fluids at the intersection of the intake and output micro-channels, in such a way as to generate an interface between the two liquids forming a pre-emulsion, 3) enabling the intake of the pre-emulsion into the output channels, 4) enabling the output from the microsystem via the output channels of the finalised emulsion including a continuous phase and a dispersed phase, the flow rate of the fluid of the continuous phase is between 8.3.10.sup.7 m.sup.3/s to 20.10.sup.7 m.sup.3/s, and the fluid of the dispersed phase represents between 3 and 20% by volume of the continuous phase, and 5) splitting the pre-emulsion between the steps 3 and 4, in order to obtain an emulsion with an average diameter of the drops of the dispersed phase between 5 and 20 micrometres.

10. The method according to claim 9, wherein the fluid of the dispersed phase represents between 5 and 10% by volume of the continuous phase.

11. The method according to claim 9, wherein the flow rate of the fluid of the continuous phase is between 8.3.10.sup.7 m.sup.3/s and 12.10.sup.7 m.sup.3/s.

12. The method according to claim 9, wherein the fluids to be emulsified include: a hydrophilic fluid, preferably an aqueous phase, and a hydrophobic fluid, preferably a lipid or hydrocarbon fluid.

13. The method according to claim 12, wherein the hydrophilic fluid is a salt-free aqueous phase and the lipid or hydrocarbon fluid is free of surfactant.

14. A method of using the emulsion able to be obtained by the method according to claim 13, as a fuel for internal combustion engines, turbines, furnaces and boilers.

15. The device as claimed in claim 2, wherein the singularity is a bend formed in each output micro-channel of the microsystem.

16. The device according to claim 2, wherein the singularity is an abrupt widening or narrowing formed in each output micro-channel of the microsystem.

17. The device according to claim 2, further comprising a second microsystem in series or in parallel comprising: at least two micro-channels for the intake into the device of each fluid, facing each other along a central intake axis, and at least two micro-channels for the output from the device of the emulsion formed.

18. The device as claimed in claim 2, wherein the intake and output micro-channels have a square or rectangular section S1, S2.

19. The device as claimed in claim 3, wherein the intake and output micro-channels have a square or rectangular section S1, S2.

20. The device as claimed in claim 4, wherein the intake and output micro-channels have a square or rectangular section S1, S2.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0057] Other advantages and particularities of some embodiments shall result from the following description, provided as a non-limiting example and in reference to the following examples and to the corresponding accompanying figures:

[0058] FIG. 1 shows a perspective lateral view of a microsystem of the device according to related art;

[0059] FIG. 2 also shows a perspective lateral view of the intersection area of the microsystem shown in FIG. 1;

[0060] FIG. 3a shows a visualisation of a W/O pre-emulsion flowing into an output micro-channel of the microsystem shown in FIGS. 1 and 2 under the following flow conditions: [0061] flow rate of water in an intake micro-channel 23 Q.sub.e=9.7 mL/min, and [0062] flow rate of oil in the other intake micro-channel 24 Q.sub.h=74.0 mL/min;

[0063] FIG. 3b shows a view at a given frequency of the pre-emulsion W/O flowing in the same micro-channel as the one shown in FIG. 3, but under different flow conditions: [0064] flow rate of water in an intake micro-channel 23 Q.sub.e=10.0 mL/min, and [0065] flow rate of oil in the other intake micro-channel 24 Q.sub.h=59.5 mL/min;

[0066] FIG. 3c also shows a perspective lateral view of the intersection area shown in FIG. 1, showing the arrival of the water in an intake channel 23 and the arrival of the oil in the other intake channel 24;

[0067] FIG. 3d diagrammatically shows the frontal collision (or impinged stream) of the water and of the oil in the intersection area of the microsystem shown in FIG. 3c;

[0068] FIG. 4 is a block diagram of an emulsification bench including a first example of a device according to some embodiments, wherein each output micro-channel 25, 26 of the microsystem 2 includes a bend 31 (therefore two bends per microsystem); FIG. 4b is a photograph of a microsystem according to some embodiments

[0069] FIG. 5 is a block diagram of the intersection area 27 of the microsystem shown in FIG. 4b including 2 bends;

[0070] FIG. 6 is also a block diagram of the intersection area 27 of a microsystem of a second example of the device according to some embodiments, wherein each output micro-channel 25, 26 of the microsystem includes two bends (therefore four bends per microsystem);

[0071] FIG. 7 is also a block diagram of the intersection area 27 of a microsystem of a third example of the device according to some embodiments, wherein each output micro-channel 25, 26 of the microsystem includes three bends (therefore six bends per microsystem);

[0072] FIG. 8 is also a block diagram of the intersection area 27 of a microsystem of a fourth example of the device according to some embodiments, wherein each output micro-channel 25, 26 of the microsystem includes four bends (therefore eight bends per microsystem);

[0073] FIG. 9 is also a block diagram of the intersection area 27 of a microsystem of a fifth example of the device according to some embodiments, wherein each output micro-channel 25, 26 of the microsystem includes six bends (therefore twelve bends per microsystem)

[0074] FIG. 10 shows a photograph, on the first and second bends of an output micro-channel, of a W/O pre-emulsion flowing into an output micro-channel of the micro-system shown in FIG. 8 (microsystem with a total of eight bends) with the following flow conditions: [0075] flow rate of water in an intake micro-channel 23 Q.sub.e=14.9 mL/min, and [0076] flow rate of oil in the other intake micro-channel 24 Q.sub.h=62.5 mL/min;

[0077] FIG. 11 shows a photograph, on the second, third and fourth bends of an output micro-channel, of a W/O pre-emulsion flowing into an output micro-channel of the micro-system shown in FIG. 8 (microsystem with a total of eight bends) in the same flow conditions as for the FIG. 10;

[0078] FIG. 12 shows a photograph, on the first and second bends, of a W/O pre-emulsion flowing into an output micro-channel of the micro-system shown in FIG. 9 (microsystem with six bends per micro-channel and 12 bends in total) with the following flow conditions: [0079] flow rate of water in an intake micro-channel 23 Q.sub.e=15.0 mL/min, and [0080] flow rate of oil in the other intake micro-channel 24 Q.sub.h=62.35 mL/min;

[0081] FIG. 13 shows a photograph, on the fifth and sixth bends, of a W/O pre-emulsion flowing into an output micro-channel of the microsystem shown in FIG. 9 (microsystem with twelve bends in total) in the same flow conditions as for the FIG. 12;

[0082] FIG. 14 shows a photograph, on the fifth and sixth bends, of a W/O pre-emulsion flowing into an output micro-channel of the micro-system shown in FIG. 9 (microsystem with twelve bends) in the same flow conditions as for the FIG. 12;

[0083] FIG. 15 is a bar chart showing the influence of the flow rate of the dispersed phase and of the number of bends over the average diameter d.sub.10 of the droplets in the emulsion obtained.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0084] FIGS. 1 to 3d are commented in the description of related art.

[0085] FIG. 4 is a block diagram of an emulsification bench 1 including a first example of a device 1 according to some embodiments, wherein each output micro-channel 25, 26 of the microsystem 2 includes a bend 31 (therefore two bends per microsystem 2).

[0086] The microsystem 2 of the device according to some embodiments is differentiated from the one shown in FIGS. 1 to 3d by the presence of a bend 31 in each output micro-channel 25, 26.

[0087] This emulsification bench 1 was developed and used (cf. example hereinafter) to test in emulsification conditions corresponding to the targeted applications (properties of the fluids and flow rates called into play) the microsystems according to some embodiments such as shown in FIGS. 5 to 14.

[0088] This emulsification bench forms a device 1 according to some embodiments, wherein the microsystem 2 includes two plates made of transparent PMMA (for example of PMMA marketed under the registered trademark PLEXIGLAS) in order to facilitate the optical investigations. The micro-channels are etched using a micro-mill on one of these plates.

[0089] The microsystem 2 of the emulsification bench shown in FIG. 4 corresponds to the one shown in FIG. 5, including two bends (one on each output micro-channel 25, 26). But, the configurations of microsystems according to some embodiments such as shown in FIGS. 6 and 10 (4 bends in total), 7 (6 bends in total), 8, 10 and 11 (8 bends in total) and 9, and 12 to 14 (12 bends in total) were also tested. These configurations of microsystems 2 according to some embodiments represent significantly improved versions of the reference configuration shown in FIGS. 1 to 3d.

[0090] The emulsification bench 1 of FIG. 4 is moreover provided with two double-piston displacement pumps 40, 41 (for example those marketed by ARMEN under the commercial name APF-100). The maximum pressure and the maximum working flow rate of these pumps 40, 41 are respectively 25 bars and 100 ml/min (maximum flow rate in the case of use of water). In order to allow for a more accurate measurement of the flow rate, the bench 1 is provided with two scales 50, 51 (for example scales of the registered trademark Sartorius (model MSE2203) that allow for an acquisition of the mass weighed over time of which the precision is 10.sup.3 g. The measurement of the pressure is provided by two compact pressure transmitters 60, 61 (for example marketed under the registered trademark Gems, model 3100). The measurement range of the pressure sensor is 0-25 bars for a precision of 0.25% on full scale. These pressure sensors 60, 61 are connected to the water and oil circuit between the pump and the inlet of the micro-channel. The pressure sensors 60, 61 measure the static pressure for each one of the two mixed liquids. All of the connections between the pumps and the micro-channels are established using tubes made from Fluoropolymer (FEP) of which the dimensions are as follows: an inner diameter (ID) of 1.55 mm and an outer diameter (OD) of 3.125 mm.

[0091] The following example shows some embodiments without however limiting the scope thereof.

EXAMPLE

[0092] The emulsification bench described hereinabove and shown in FIG. 4 was used to test in different flow conditions close to the targeted applications (for the properties of the fluids and the flow rates called into play) the microsystems according to some embodiments such as shown in FIGS. 5 to 14, by comparing them to the microsystem without bends such as shown in FIGS. 1 to 3d.

Fluids Used

[0093] During these tests, using the emulsification bench shown in FIG. 4 and in accordance with the method according to some embodiments, an aqueous phase (dispersed phase) and a lipid phase (continuous phase) was continuously emulsified.

[0094] Water was used as aqueous phase in small quantities, not exceeding 20% by volume, compared to sunflower oil which represents the continuous phase therefore the major phase. Sunflower oil was chosen in order to operate according to the principle of a cold model. The viscosity of this oil, at ambient temperature, corresponds to the temperature of heavy fuel oil preheated in an engine. The characteristics of the various fluids used are gathered together in the table 1 hereinafter.

TABLE-US-00001 TABLE 1 Water Sunflower oil Properties of the fluids tested at 25 C. at 25 C. Surface tension in air 73.5 33.67 Inter-facial tension in water .sub.e/h [mN/m] 27.6 Dynamic viscosity [mPa .Math. s] 0.91 52.2 Density [g/l] 998 865

[0095] All of the emulsification tests were conducted at a temperature of 25 C. Due to the friction effects of the fluids, the emulsion at the outlet of the emulsification circuit experienced heating of about +5 C. in relation to the intake temperature.

[0096] For all of the tests carried out, the flow rate Q.sub.h of the oily phase in an intake micro-channel was set to about 60 ml/min, for three flow rates of water Q.sub.e tested (about 5 ml/min, 10 ml/min and 15 ml/min).

Emulsification Results

[0097] The properties of the pre-emulsion formed after the impact (frontal collision) are studied at the intersection between the stream of water and that of the sunflower oil in the intersection area 27 of the microsystem 2 (via high-frequency view of the flow in the output micro-channels), as well as via measurement of the diameter d.sub.10 of the droplets formed in the emulsion at the outlet of the micro-channels (bar chart shown in FIG. 15).

High-Frequency View of the Flows

[0098] Entailing flows of the two-phase type characterised by substantial flow speeds and implemented in complex geometries, it cannot be considered to carry out numerical simulations.

[0099] The views at high frequency are therefore indispensable for following the splitting of the fluids in the bend or bends present in the emulsion channel. The objective of these views makes it possible to show the favoured located of the splitting, and also the areas where the coalescence of the droplets can possibly be produced.

[0100] FIGS. 10 and 11 show the transformations that are produced on the filament in the microsystem with 4 bends per output micro-channel (eight bends in total), while FIGS. 12 to 14 concern the microsystem with 6 bends per micro-channel (12 bends in total: cf. also FIG. 9).

Bar Graph (FIG. 15)

[0101] FIG. 15 is a bar chart showing the influence of the flow rate of the dispersed phase and of the number of bends on the average diameter d.sub.10 of the droplets in the emulsion obtained, obtained by calculating the arithmetical average of the diameters of the droplets (d.sub.10) for the sample analysed (d.sub.10=.sub.id.sub.i/n.sub.i).

[0102] This bar chart makes it possible to judge the pertinence of adding one or several additional bends. The letters a, b and c represent the three ranges of flow rates of the dispersed phase. The data shows the interest in placing two bends in series and in provoking two impacts in the microsystem (configuration shown in FIG. 6) when a substantial flow rate of water is used (range c of the water flow rate of about 15 ml/min). The comparison of the average diameters d.sub.10 shows that the reference system without bend is not as suited for the water-in-oil dispersion (see the bar chart of FIG. 15).

[0103] The purpose of the presence of the bends is to generate, in addition to the viscous forces of which the role is preponderant on the splitting.sup.[15], with additional stresses used to fragment the filament of water initially formed (see FIGS. 3a and 3b) at the intersection at the time of the impact between the stream of water and the stream of oil. The various versions were designed so as to experimentally study the effect of an abrupt change in direction in a single or in several successive bends. The configuration including two bends and the one including six bends also include a second impact of the flows at the outlet of the device. This second impact involves the flows of emulsions formed initially at the first impact and refined by their passage through the bends.

LIST OF REFERENCES

[0104] [1] C.-X. Zhao, A. P. J. Middelberg. Two-phase microfluidic flows. Chemical Engineering Science 66.7 (2011): 1394-1411. [0105] [2] H. . Schubert, R. Engel. Product and formulation engineering of emulsions. Chemical Engineering 82: 1137-1143. [0106] [3] T. Nisisako, T. Hatsuzawa. A microfluidic cross-flowing emulsion generator for producing biphasic droplets and anisotropically shaped polymer particles. Microfluidics and Nanofluidics 9.2-3 (2009): 427-437. [0107] [4] N. Kiss, H. Pucher J. Wieser S. Scheler H. Jennewein D. Suzzi J. Khinast, G. Brenn. Formation of O/W emulsions by static mixers for pharmaceutical applications. Chemical Engineering Science 66: 5084-5094. [0108] [5] Belkadi, A. tude exprimentale du fractionnement liquide-liquide en micro-canaux pour la production en continu de biodiesels emulsionns. Ph.D. thesis, SPIGA, University of Nantes, France, 2015. [0109] [6] T. Nisisako, Toshiro Higuchi, Toru Torii. Droplet formation in a microchannel network. Lab on a chip 2.1 (2002b): 24-6. [0110] [7] T. Nisisako, T. Higuchi, T. Torii. Formation of droplets using branch channels in a microfluidic circuit. Proceedings of the 41st SICE Annual Conference. SICE 2002. vol. 2. 2002a, 957-959. [0111] [8] A. Tamir, S. Sobhi. A new Two-Impinging-Streams Emulsifier. AIChE Journal 31.12 (1985): 2089-2092. [0112] [9] Kiljanski, Tomasz. Preparation of emulsions using impinging streams. AIChE Journal 50: 1636-1639. [0113] [10] Ait-Mouheb, N. Caractrisations exprimentale and numrique de l'coulement and du transfert de matire dans des micromlangeurs. Ph.D. thesis, University of Nantes, France, 2010. [0114] [11] N. Ait Mouheb, C. Solliec J. Havlica P. Legentilhomme J. Comiti J. Tihon, A. Montillet. Flow characterization in T-shaped and crossshaped micromixers. Microfluidics and Nanofluidics 10.6 (2010): 1185-1197. [0115] [12] S. Nedjar, M. Tazerout, A. Montillet. Synthse en continu d'emulsions de type eau dans huile l'aide de micromlangeurs. la Socit Franaise de Gnie des Procds. Poster13e congrs de la socit Franaise de Gnie des Procds, 2011. [0116] [13] A. Montillet, M. Tazerout, S. Nedjar. Continuous production of water-in-oil emulsion using micromixers. Fuel 106: 410-416. [0117] [14] A. Belkadi, A. Montillet J. Bellettre P. Massoli, D. Tarlet. High-speed w/o emulsification within impinging and cross-flowing minichannels. Proceedings of the 3rd European Conference on Microfluidics. Heidelberg, Germany, 2012. [0118] [15] Galindo Alvarez, J.-M. Etude de l'inversion de phase catastrophique lors de l'emulsification de produits visqueux. Ph.D. thesis, Nancy, 2008.