WO2001036569A1

WO2001036569A1 - Method for continuously preparing a stable water-fuel emulsion and device therefor

Info

Publication number: WO2001036569A1
Application number: PCT/FR2000/003162
Authority: WO
Inventors: Philippe Schulz; Philippe Tanguy; Benjamin Brocart; César Magnin
Original assignee: Elf Antar France
Priority date: 1999-11-15
Filing date: 2000-11-13
Publication date: 2001-05-25
Also published as: EP1240278A1; FR2801057A1; PL356207A1; CZ20021694A3; MY129893A; NZ518850A; AU1712201A; ZA200203512B; HUP0204165A2; AU781512B2; FR2801057B1; MXPA02004745A

Abstract

The invention concerns a method for continuously preparing a water-in-oil emulsified fuel to mix additives, water and a hydrocarbon phase and optionally in recycling the resulting mixture. The method comprises two steps: the first consists in providing at least a phase A consisting of the additives required for stabilising the emulsion and the water in the hydrocarbon phase for a homogeneous spatial distribution of water droplets less than 200 νm in size; and the second phase consists in reducing the size of the droplets by dispersion using an emulsifying device having a peripheral moving speed of at least 10 m/s, preferably higher than 25 m/s and enabling a retention time in the emulsifying device between 1 second and 80 seconds, preferably between 2 and 30 seconds.

Description

PROCESS FOR THE CONTINUOUS PREPARATION OF A STABLE WATER-FUEL EMULSION AND ITS IMPLEMENTING DEVICE

The present invention relates to a continuous process for the preparation of an emulsified fuel, that is to say an emulsified mixture of water and at least one organic compound with a view to distributing it like other liquid fuels of the fuel type. or domestic fuel oils. In these fuels the organic phase is a petroleum cut, a vegetable or animal oil, or any other fuel used in motor vehicles and domestic boilers, and more generally for the supply of internal combustion engines and others, and for l of power generation devices. This invention also relates to the device or unit for industrial implementation of this continuous process.

Many researchers have looked into the processes for preparing emulsified fuels, but quickly encountered their difficult implementation mainly linked to the lack of stability of the emulsions obtained. The storage stability of these emulsions was the subject of a definition by the Directorate General of Hydrocarbons of the French Ministry of Industry. According to this administration, a water emulsion in gas oil, therefore in a hydrocarbon, is considered to be stable on storage when, maintained at room temperature, ie from 10 to 20 ° C, for at least four months, no rupture of the emulsion in two or more phases.

To remedy the lack of stability of emulsions, the patents DE 19 704 874, DD 216 863, US 5 445 656 and WO 95/33023 have proposed methods and devices for fuel emulsions capable of being carried on board vehicles terrestrial, in particular of diesel motor vehicles. The emulsions described are emulsions of often aqueous external phase, this emulsion being capable of being subsequently reversed by subsequent dilution in a combustible organic phase, as in patent DE 19 704 874. The emulsion described in application WO 95/33023 contains less than 20% water which constitutes the external phase of the emulsion.

In application WO 92/1 1927, it is a question of preparing a concentrated emulsion containing from 40 to 80% by volume of water, this process consisting in separately preparing an oil / demulsifying additive mixture and a water / alcohol mixture, introduce these two mixtures at two separate locations in a circulation loop comprising a pump fulfilling the two setting functions emulsion and circulation of the mixture in the loop. The emulsion thus obtained is recovered at another end on the loop.

In patent application WO 95/27021, an emulsified fuel is claimed, which comprises 20 to 80% by volume of water, this constituting the external phase of the emulsion, 2 to 20% by volume of an alcohol , the complement consisting of hydrocarbons and at least one nonionic emulsifying additive. The hydrocarbons introduced into this emulsion are gasolines, kerosene, gas oils, synthetic fuel oils or derivatives of vegetable or animal oils. The claimed process is a bulk emulsion preparation process, stable for at least three months, which consists in mixing a water / alcohol solution with a liquid composed of hydrocarbons and a demulsifying additive.

In none of these patent applications is described a method for the industrial preparation of stable emulsified fuels in which the external phase consists of an organic phase. However, for obvious reasons of compatibility of the fuel with the equipment present on a vehicle, from the tank to the system of introduction into the engine, it is preferred to use a fuel whose external phase is identical to that of the fuel for which this equipment has been dimensioned. In the case of fuel whose external phase is aqueous, the risks of corrosion of the metal surfaces and / or of premature wear of elastomeric materials are increased.

This is why the Applicant has developed a first batch manufacturing process for water-in-oil emulsions as described in French patent application FR 98/15625 of December 8, 1998. Such emulsions proposed by the Applicant in the WO 97/34969, have the advantage, compared to oil-in-water emulsions, of improving the combustion by the brutal vaporization of the water droplets dispersed in the oil whose effect is to disperse the hydrocarbons in the chamber combustion. (SAE 89 0449 and SAE 92 0464 from M. Tsukhara et al., SAE 92 0198 from N. Sawa et al.).

The present invention relates to the preparation of such water-in-oil emulsions, therefore with organic external phase, stable for a period greater than 4 months, but this time continuously for the preparation of either emulsions usable directly as fuels. or fuels easily distributed by a pump, either as fuel precursors or fuel making it possible to limit industrial manufacturing costs and storage volumes and / or distribution costs to depots.

The term “fuel or fuel precursor” means a fuel or a concentrated fuel which it suffices to dilute with a hydrocarbon phase to obtain the fuel or the fuel. The subject of the present invention is therefore a process for the continuous preparation of a water / oil emulsion, preferably water-in-oil, making it possible to mix the additives, water and a hydrocarbon phase by stirring and optionally to recirculate the mixture obtained in a circulation loop, characterized in that in a first step, it is distributed in a hydrocarbon phase at least one phase A consisting of the additives necessary for stabilizing the emulsion, water and optionally any additive useful for producing the emulsion, these compounds being introduced alone or as a mixture, the distribution of the drops of each phase A in the hydrocarbon phase corresponding to a homogeneous spatial distribution of the water droplets of size less than 200 μm, and in a second step, when all the A phases are distributed in the hydrocarbon phase, the size of the drops is reduced by dispersion by means of an emulsifying device with a peripheral speed in motion of at least 10 m / s, preferably greater than 25 m / s, and allowing a residence time in the enclosure containing the setting device in emulsion, varying from 1 second to 80 seconds, preferably from 2 to 30 seconds.

In the context of the present invention, it has been found that the dispersion of water into droplets in the hydrocarbons is favored by the combined effect of the emulsion stabilizing additives and of the two-stage emulsification method, the first consisting of a consecutive distribution of one or more phases A in the hydrocarbon phase, the second consisting in putting in stable emulsion the water / additives / hydrocarbon phase mixture, the distribution and emulsifying devices being chosen in an appropriate manner.

In addition, for the continuous process according to the invention, the emulsion stabilization additives are introduced into the hydrocarbon phase and / or the aqueous phase.

Thus, in the first step of the invention, at least one first phase A is constituted in whole or in part by the additives necessary for the stabilization of the emulsion. Thus, it is possible to imagine as many phases A as there are emulsifying additives or even a single phase A for the mixture of additives or the mixture of additives and water, the intermediate cases not being excluded. It is also possible to introduce at this stage the specific additives required in any fuel, such as in particular in diesel fuels, these additives possibly being cold-resistance additives, combustion additives, antioxidants, detergents, etc.

In phase A consisting of water, specific additives can be introduced to maintain the physical and chemical characteristics of this water, such as, for example, antibacterial additives, anti-fungal additives, antifreeze and / or any additive necessary for use of said emulsion. For the distribution of each phase A in the hydrocarbon phase, the distribution device is chosen from the group consisting of orifice tapping systems, frits, impact jet mixers, mixing heads, static mixers, sonicators and mechanically agitated turbines.

For the formation of the emulsion, the emulsification device is chosen from the group consisting of multistage or non-storied rotor-stators, smooth or fluted frustoconical emulsifiers, very shear static mixers and in-line turbine systems .

In a preferred embodiment, the method according to the invention can comprise a third additional step consisting in recycling all or part of the emulsion formed in the hydro- carbon upstream of the distribution devices of phase (s) A, the recirculation rate varying from one to three times the rate of the emulsion recovered.

A particular implementation of the method consists in diluting the emulsified mixture in a second hydrocarbon phase injected by means of a dilution device chosen from the group consisting of orifice stitching systems, frits, impact jet mixers, mixing heads, static mixers and mechanically agitated turbines. This dilution device can be placed on the production line or at the place of storage or even before the emulsified fuel distributor. In this case, it is possible to transport the fuel or fuel precursor to the place of distribution, which is a considerable saving on the cost of transporting these fuels or emulsified fuels, the volume to be transported being less.

The present invention also relates to the emulsion obtained by the continuous process of the invention containing from 5 to 20% by weight of water in the hydrocarbon phase.

This emulsion can be a concentrated emulsion also called a water-in-oil emulsion precursor containing more than 20% by weight of water in a first hydrocarbon phase which is subsequently diluted in a second hydrocarbon phase, these two phases being likewise nature or different.

The invention also relates to the emulsion precursor obtained according to the process of the invention which will comprise from 20 to 90% by weight of water in a hydrocarbon phase, and preferably from 40 to 70% by weight of water.

Another subject of the present invention is a device for implementing the method according to the invention which comprises: i) an inlet pipe for the hydrocarbon phase onto which at least one inlet pipe arrives provided with a distribution device at least one phase A, preferably two pipes for at least two phases A, a first pipe for the emulsion stabilization additives and a second pipe for water, ii) an emulsification device arranged on said pipe downstream of the arrival pipes of phases A, of peripheral speed in motion of at least 10 m / s, preferably greater than 25 ms, and authorizing a residence time of the emulsion varying from 1 second to 80 seconds, preferably from 2 to 30 seconds, iii) a storage capacity on the outlet pipe of the emulsifying device, and iv) optionally a pipe for bypassing part of the emulsified mixture returning said part in the supply line for the hydrocarbon phase upstream of the distribution devices. In another embodiment, the device may further comprise a dilution device disposed on the outlet pipe of the emulsifying device, this device comprising a distributor and a storage capacity for the diluted emulsion. It is thus possible to provide intermediate emulsification and storage devices. Another subject of the invention is the application of the continuous process according to the invention to the preparation of combustible emulsions, in particular water / petrol, water / diesel and water / fuel emulsions, or their emulsion precursor of hydrocarbon external phase. Figures 1 to 4 are given to illustrate the invention. Figure 1 relates to the device for implementing the method according to the invention for directly obtaining the emulsion comprising at most 20% water or an emulsion precursor comprising from 40 to 70% by weight of water.

FIG. 2 corresponds to the device for diluting the emulsion precursor, this device being able to be placed on the production line of the emulsion precursor or on a site for distribution and / or storage of the latter before use.

FIG. 3 is a diagram representing the volume of the water drops as a function of the diameter of the drops at high tangential speed.

FIG. 4 is a diagram representing the volume of the water drops as a function of the diameter of the drops at low tangential speed. Returning to FIG. 1, it can be seen that the hydrocarbon phase, fuel or combustible, arrives via line 1 in the emulsifying device. A first pipe 2 brings one or more additives arriving via the channels 2i and / or the water into the mixture through a first distribution device 3, this device possibly being one of the devices described above.

Optionally a second pipe 4 brings the water and the soluble additives coming from the channels 4i via a distribution device 5, into the pipe in which the hydrocarbon phase and the additives previously introduced circulate. Line 1 then opens into the emulsifying device 6, the outlet line 10 bringing the emulsified phase into a storage capacity 7 comprising an evacuation 8. Via line 9, all or part of the emulsified phase can be recirculated upstream of the emulsification device 6, either before the introduction of the A phases or just before the device itself.

In FIG. 2, the fuel or fuel precursor is brought from storage or by truck in a pipe 20 into which a hydrocarbon phase is introduced via the pipe 21 and the distribution device 22, the product obtained being sent to the capacity of storage or the distribution pump 23 comprising an outlet 24. The distribution device is similar to those already used in the previous figure.

The examples given below aim to illustrate the implementation of the invention and its essential characteristics without, however, limiting the scope thereof.

EXAMPLE I The present example consists in describing the efficiency of the process implemented in the present invention, in particular the influence of the choice of distributors and of the emulsifying device on the stability of the emulsions. The tests were carried out on a pilot of semi-industrial size as described in FIG. 1. However, upstream of the pipe 1, is placed a tank for storing the diesel fuel to be emulsified and, upstream of the pipe 2 , a capacity for storing the composition of additives necessary for stabilizing the emulsion. The distribution devices 3 and 5 are mixing valves. The water / water-soluble additives mixture is brought from a tank arranged upstream of the pipe 4.

Two types of emulsification device 6 have been tested: they are multi-stage rotor-stators which laminate the drops of water in a field of tangential speed, the speed of rotation of the motor determining the peripheral or tangential rolling speed of these drops. These are the DIPAX 3-6 / 6A from the company IKA WORKS (device Dl) usable for small volumes, and the homogenizing foam concentrate from the company VMI-RAYNERI (device D2) for semi-industrial volumes.

Water and diesel emulsions containing 13 and 26% by weight of water with D2 and 52% by weight of water with D1 were prepared in the presence of the combination of additives as described in patent application WO 97 / 34969.

During these tests, the diesel used is a diesel that meets the specifications of standard EN590. Table I collates the results obtained with these two devices.

TABLE I

In this table, the stability of the emulsion is quantified by the time measured between the date of manufacture of the emulsion and the date of rupture of the emulsion, that is to say the date on which it occurs. of free water at the bottom of the emulsion storage container. It can be seen that the manufacturing efficiency varies according to the size and the geometry of the rotors-stators used. With the Dl device, the peripheral speed must be greater than 25 m / s for a residence time of at least one second. In the case where this speed is less than 25 ms and / or the residence time is less than 1 second, the emulsion separates into two phases beyond one or two months.

With the device D2, of geometry different from Dl, for a peripheral speed greater than 25 m / s, the residence time must exceed 14 seconds for an emulsion containing 13% by weight of water. If the peripheral speed is less than 25 m / s and / or the residence time is less than 14 seconds, the emulsion is unstable and separates quickly.

The more the water content increases with the same D2 device, the more the peripheral speed and the residence time must increase.

EXAMPLE II

The present example aims to demonstrate the importance of the tangential peripheral speed of the device for obtaining a monodispersed distribution of the drops promoting the stability of the emulsion over time.

The operation is carried out on a pilot of semi-industrial size as described in Example I. A single device D2 is used with an emulsion having a water content of 13% by weight. The tangential speed of this device is varied and the particle size distribution of the drops is measured as a function of this tangential speed. The results are given in Table II below.

TABLE II

The results of tests 1 and 2 are shown in Figures 3 and 4, respectively.

Claims

1. Process for the continuous preparation of an emulsified water-in-oil fuel making it possible to mix the additives, the water and a hydrocarbon phase by stirring and optionally to recirculate the mixture obtained in a circulation loop characterized in that in a first step, at least one phase A is distributed by means of a distribution device in the hydrocarbon phase consisting of the additives necessary for the stabilization of the emulsion, water and possibly any additive useful for the implementation of the emulsion, these compounds being introduced alone or as a mixture, the distribution of the drops of each phase A in the hydrocarbon phase corresponding to a homogeneous spatial distribution of the water droplets of size less than 200 μm, and in a second step, all phases A being distributed in the hydrocarbon phase, the size of the drops is reduced by dispersion by means of a setting device peripheral speed emulsion in motion of at least 10 m / s, preferably greater than 25 m / s, and allowing a residence time in the enclosure containing the emulsifying device, varying from 1 second to 80 seconds, preferably 2 to 30 seconds.

2. Method according to claim 1, characterized in that at least a first phase A consists wholly or partly of the additives necessary for the stabilization of the emulsion.

3. Method according to claims 1 and 2, characterized in that at least a second phase A consists of water, optionally comprising the anti-bacterial additives and / or any additive necessary for the use of said emulsion.

4. Method according to claims 1 to 3, characterized in that the distribution device is chosen from the group consisting of orifice stitching systems, frits, impact jet mixers, mixing heads, static mixers and mechanically agitated turbines.

5. Method according to claims 1 to 4, characterized in that the emulsifying device is chosen from the group consisting of multistage or non-storied rotor-stators, smooth or fluted frustoconical emulsifiers, very shear static mixers and online turbine systems.

6. Method according to one of claims from 1 to 5, characterized in that in a third step, the emulsion formed is recycled in whole or in part in the supply line of the phase hydrocarbon upstream of the A phase distribution devices, the recirculation rate varying from one to three times the rate of the emulsion recovered.

7. Method according to one of claims 1 to 6, characterized in that the emulsified mixture is diluted in a second hydrocarbon phase by means of a dilution device chosen from the group consisting of orifice stitching systems, frits , impact jet mixers, mixing heads, static mixers and mechanically agitated turbines.

8. Emulsion obtained according to the method according to claims 1 to 7, characterized in that it contains from 5 to 20% by weight of water in the hydrocarbon phase.

9. Emulsion according to claim 8, obtained by dilution in a second hydrocarbon phase of an emulsion precursor obtained by the process according to one of claims 1 to 5, containing more than 20% by weight of water in a first hydrocarbon phase, the two hydrocarbon phases being of the same nature.

10. An emulsion precursor of an emulsion according to claim 9, characterized in that it contains from 20 to 90% by weight of water, preferably between 40 and 70% by weight of water in the hydrocarbon phase.

1 1. Device for implementing the method according to one of claims 1 to 7, characterized in that it comprises: i) an inlet pipe (1) of the hydrocarbon phase on which arrives at least one pipe d inlet fitted with a distribution device (3, 5) of at least one phase A, preferably two lines for at least two phases A, a first line (2) for the emulsion stabilization additives and a second pipe (4) for water, ii) an emulsifying device (6) disposed on said pipe downstream of the arrival pipes of phases A, of peripheral speed in movement of at least 10 ms, preferably greater than 25 m / s, and allowing an emulsion residence time varying from 1 second to 80 seconds, preferably from 2 to 30 seconds, iii) a storage capacity (7) on the outlet pipe (10) of the device (6), and iv) optionally a bypass line (9) of part of the emulsified mixture r bringing said part into the inlet pipe (1) of the hydrocarbon phase upstream of the distribution devices (3, 5).

12. Device according to claim 1 1, characterized in that it comprises on the outlet pipe of the device (6) or of the capacity (7) or (20) an identical distribution device (22) devices (3) and (5) and a storage capacity (23), the hydrocarbon dilution phase being supplied via the line (21).

13. Device according to claims 1 1 and 12, characterized in that the dilution device is chosen from the group consisting of orifice stitching systems, frits, impact jet mixers, mixing heads, static mixers and mechanically agitated turbines.

14. Device according to claims 1 1 to 13, characterized in that the emulsifying device is chosen from multi-stage or non-multistage rotor-stators, smooth or fluted frusto-conical emulsifiers, very shear static mixers and turbines in line.

15. Application of the method according to one of claims 1 to 7 to the preparation of water-gasoline, water-diesel and water-oil emulsions or their hydrocarbon external phase emulsion precursor.