AU781512B2

AU781512B2 - Method for continuously preparing a stable water-fuel emulsion and device therefor

Info

Publication number: AU781512B2
Application number: AU17122/01A
Authority: AU
Inventors: Benjamin Brocart; Cesar Magnin; Philippe Schulz; Philippe Tanguy
Original assignee: Elf Antar France
Current assignee: Elf Antar France
Priority date: 1999-11-15
Filing date: 2000-11-13
Publication date: 2005-05-26
Anticipated expiration: 2020-11-13
Also published as: FR2801057B1; PL356207A1; NZ518850A; CZ20021694A3; MY129893A; AU1712201A; FR2801057A1; HUP0204165A2; ZA200203512B; MXPA02004745A; WO2001036569A1; EP1240278A1

Description

PROCESS FOR CONTINUOUS PREPARATION OF A STABLE WATER-FUEL EMULSION AND APPARATUS FOR CARRYING IT OUT The present invention relates to a continuous process for preparing an emulsified fuel, in other words an emulsified mixture of water and at least one organic compound with a view to distributing it like other internal combustion engine fuels or domestic heating oils. In such fuels, the organic phase is a petroleum cut, a vegetable or animal oil, or any other fuel employed in motorized vehicles and domestic boilers, and more generally for supplying internal and other combustion engines, and for supplying energy generation apparatus. This invention also relates to the apparatus or unit for carrying out this process continuously on an industrial scale.

Numerous researchers have investigated processes for preparing emulsified fuels, but have rapidly been confronted with the difficulties of implementing them, principally arising through a lack of stability of the emulsions obtained. Storage stability of such emulsions is covered by a definition from the French Industry Ministry Department responsible for hydrocarbons.

According to this Government Department, a water in gas oil, i.e. a hydrocarbon, emulsion is considered as stable in storage when, kept at ambient temperature, in other words 10 to 20 0 C, for at least four months, no splitting of the emulsion into two or more phases is observed.

To overcome a lack of stability of emulsions, German patents DE 19,704,874 and DD 216863, United States Patent 5,445,656 and International application WO 95/33023 have disclosed processes and devices for emulsifying fuels intended to be carried on board terrestrial vehicles, notably diesel engine vehicles. The emulsions described are emulsions of an external, frequently aqueous, phase, this emulsion being able to be subsequently reversed by R:\Brevets\I 7900\1 7928GB.doc emulsifying and circulating the mixture within the loop. The emulsion thus obtained is recovered at another end, on the loop.

In International Application WO 95/27021, an emulsified fuel is claimed comprising 20 to 80% by volume of water, the latter constituting the external phase of the emulsion, 2-20% by volume of alcohol, the remainder being constituted by hydrocarbons and at least one non-ionic emulsifying additive. The hydrocarbons introduced into this emulsion are gasolines, kerosene, gas oils, synthetic fuels or derivatives of vegetable or animal oils. The claimed process is a process for preparing a bulk emulsion that is stable over at least three months, and consisting in mixing a water/alcohol solution with a liquid composed of hydrocarbons and a deemulsifying additive.

None of these patent applications discloses a method for industrial preparation of a stable emulsified fuel in which the external phase is constituted by an organic phase. Now, for obvious reasons of compatibility of the fuel with an automobile fuel system running from the tank to the system for introducing it into the engine, it is preferable to use a fuel the external phase of which is identical to that of the fuel for which the fuel system has been dimensioned. In the case of a fuel the external phase of which is aqueous, there are increased risks of corroding metal surfaces and/or premature wear of elastomer materials.

This is the reason why the applicant developed a first discontinuous production process for water in oil emulsions as disclosed in French patent application serial number 98/15625 of 8th December, 1998. Such emulsions proposed by the applicant in International application WO 97/34969 have the advantage, when compared to oil in water emulsions, of improving combustion by sudden vaporization of water droplets dispersed in the oil the effect of which is to disperse the hydrocarbons in the combustion chamber (SAE 89 0449 and SAE 92 0464 in the name of Mr Tsukhara et al, SAE 92 0198 in the name of N. Sawa et al).

The present invention sets out to prepare such water-in-oil emulsions, i.e.

having an organic external phase, which are stable over a period greater than four months, but this time by a continuous process with a view to preparing either emulsions able to be used directly as internal combustion engine fuels or combustible fuels, which are readily distributed by a pump, or precursors thereof allowing R:\Brevets\l 7900\17928 English translation of IPER annexes.doc industrial production costs and the storage volumes and/or distribution costs to depots to be limited.

Precursors of such fuels should here be taken to mean a concentrated internal combustion engine or combustible fuel which it is sufficient to dilute with a hydrocarbon phase in order to obtain the corresponding fuel.

The present invention consequently provides a process for continuous preparation of a water in-oil emulsified monodispersed fuel allowing additives, water and a hydrocarbon phase to be mixed by agitation and optionally allowing recirculation of the mixture obtained in a circulation loop, wherein in a first step, using a distribution device, at least one phase A constituted by additives necessary for stabilising an emulsion, water and optionally any additive useful for implementing the emulsion are distributed in the hydrocarbon phase, these components being introduced alone or in a mixture, the droplet contribution of each phase A in the hydrocarbon phase corresponding to a homogeneous spatial distribution of water 15 droplets of size less than 200 pm and, in a second step, all phases A having been distributed in the hydrocarbon phase, droplet size is decreased by dispersion using an emulsifying device chosen from *the group constituted by multi-stage or non-multistage rotors/stators, smooth or grooved :..!tapered emulsifiers, the emulsifying device having a dynamic peripheral velocity of at 20 least 10 m/s and allowing a dwell time in an enclosure containing the emulsifying device S.varying from 1 second to 80 seconds.

S.

1 In the framework of this invention, it has been noted that the dispersion of water in droplet formed in hydrocarbons is favoured by the combined effect of emulsionstabilising additives and the dual-step emulsifying method, the first step consisting in consecutively distributing one or several phases A in the hydrocarbon phase and the second step consisting in putting the water/additive/hydrocarbon phase mixture into stable emulsion form, the devices for distribution and putting into emulsion form being suitably chosen.

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

(R:LIBZZ]595843speci.doc:GYM Thus, in the first step of the invention, at least a first phase A is completely or partially constituted by the additives needed to stabilise the emulsion. Thus, we can imagine there will be as many phases A as there are emulsifying additives or, alternatively, one single phase A for the mixture of additives or the mixture of additives and water, intermediate cases not being excluded. At this stage, the specific additives required in every fuel notably in the case of diesel oils, can be added, typically for withstanding low temperatures, combustion additives, anti-oxidizing agents, detergents, etc...

In phase A, constituted by water, the specific additives for maintaining physical and chemical characteristics of this water such as for example anti-bacterial additives, fungicides, anti-freeze and/or any additive needed for the use of the said emulsion, can be added.

For distributing each phase A in the hydrocarbon phase, the distribution device is chosen from the group comprising orifice injection systems, sintered materials, impacting jet mixers, mixing heads, static mixers, sonic mixers and mechanically agitated turbines.

For forming the emulsion, the emulsifying device is chosen from the group constituted by multi-stage or non-multistage rotors/stators, smooth or grooved tapered emulsifiers and in-line turbine systems.

In a preferred embodiment, the process can comprise a third additional step in which the emulsion formed is recycled totally or in part into the inlet conduit of the hydrocarbon phase, upstream of the distribution devices for phase A, recirculation throughput varying from one to three times the recovered emulsion throughput.

In a particular embodiment, the emulsified mixture is diluted in a second hydrocarbon phase injected by means of a dilution device selected from the group comprising orifice injection systems, sintered materials, impacting jet mixers, mixing heads, static mixers, sonic mixers and mechanically agitated turbines. This dilution device can be arranged on the production line or at the place of storage or, yet again, prior to the emulsified fuel distributor. In this case, it is possible to transport the fuel precursor to, the place of distribution which represents non-negligible transport cost economies for these emulsified fuels, there being less volume to transport.

R:\Brevets\17900\17928 English translation of IPER annexes.doc The present invention also provides an emulsion obtained by the continuous process of the invention, containing from 5 to 20% by weight 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 water in a first hydrocarbon phase which is subsequently diluted in a second hydrocarbon phase, these two phases being able to be of the same or different natures.

The invention also provides an emulsion precursor obtained by the process of the invention, comprising from 20-90 by weight water, preferably between 40 and 70% by weight water.

The invention also provides an apparatus for carrying out the process according to the invention comprising: an inlet conduit for a hydrocarbon phase at which there arrives at least one inlet conduit provided with a distribution device for a least one phase A, preferably i 15 two conduits for at least two phases A, a first conduit for emulsion stabilising additives and a second conduit for water, ii) an emulsifying device chosen from the group constituted by multi-stage or e* :oo: non-multistage rotors/stators, smooth or grooved tapered emulsifiers, this device being arranged on said conduit downstream of said inlet conduits for phases A, 20 having a dynamic peripheral velocity of at least 10 m/s, preferably greater than m/s, and allowing a dwell time for the emulsion varying from one second to seconds, preferably from 2-30 seconds, iii) storage means on an outlet conduit from the emulsifying device, iv) and, optionally, a conduit for tapping a portion of emulsified mixture and for bringing said portion into the inlet conduit for the hydrocarbon phase upstream of said distribution devices.

Alternately, the device can further comprise, on the outlet conduit from the emulsifying device or storage means a distribution device comprising a distributor and storage means for diluted emulsion. Intermediate emulsifying and storage means can consequently be provided.

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7 The invention also covers the application of the continuous process according to the invention to the preparation of combustible emulsions, namely water-petroleum, watergas oil and water/fuel emulsions or their emulsion precursor for an external hydrocarbon phase.

FIGS. 1-4 illustrate the invention.

FIG. 1 shows apparatus for carrying out the process of the invention, allowing the emulsion comprising at the most 20% water or an emulsion precursor comprising from to 70% by weight water to be obtained directly.

FIG. 2 shows apparatus for diluting the emulsion precursor, this apparatus being S 10 able to be arranged on the emulsion precursor production line or at a distribution and/or S. storage site for the latter, before use.

FIG. 3 is a diagram representing the volume of the droplets versus the diameter o. of the particles, with a high peripheral velocity.

FIG. 4 is a diagram representing the volume of the droplets versus the diameter of the particles, with a low peripheral velocity.

S oThe hydrocarbon phase, i.e. internal combustion engine or combustible fuel, arrives on the line 1 in the emulsifying device. A first conduit 2 introduces one or several o additives arriving on the lines 2i and/or water into the mixture, via a first distribution device 3, this device being able to be one of the devices mentioned above. Optionally, a 20 second conduit 4 introduces water and soluble additives originating from lines 4i via a distribution device 5, into the conduit in which the hydrocarbon phase and the previously oo"o introduced additives are circulating. Conduit 1 then discharges into emulsifying device 6, outlet conduit 10 leading the emulsified phase into a storage vessel 7 that includes a discharge outlet 8. By means of conduit 9, all or part of [R:\LIBZZ]595843speci.doc:GYM the emulsified phase can be recirculated upstream of emulsifying device 6, either prior to introducing phases A, or just ahead of the apparatus itself.

In FIG. 2, the fuel precursor is supplied from a storage vessel, or by tanker, into a conduit 20 in which a hydrocarbon phase is introduced through conduit 21 and distribution device 22, the product obtained being delivered to a storage vessel or distribution pump 23, comprising a discharge outlet 24. The distribution device is similar to the one already used in FIG. 1.

The examples given below illustrate the implementation of the invention and its essential characteristics without however limiting the scope 1 thereof.

S• EXAMPLE I This example consists in describing the effectiveness of the process implemented in the present invention, in particular the influence of the choice of distributor and emulsifying device on emulsion stability.

0066 The tests were carried out on a pilot plant of semiindustrial scale such as described in FIG. 1. However, .ahead of conduit 1, a storage tank for gas oil to be :emulsified was provided and, ahead of conduit 2, storage means were provided for the additive composition needed S. for stabilising the emulsion. Distribution devices 3 and are mixing valves. The water/water-soluble additive mixture was introduced from a tank arranged upstream of conduit 4.

Two types of emulsifying device 6 were tested: these are multi-stage rotors/stators which shear the water droplets in a tangential velocity field, motor rotation speed determining the peripheral or tangential shearing speed of the droplets. The device was an Ika Works Dipax 3-6/6A (device Dl) able to be used for small volumes, and the VMI-Rayneri emulsifier/homogeniser (device D2) for semi-industrial scale volumes.

3 :\I~revecs\ l 7900\1 7928GB3doc Water/gas oil emulsions having 13% and 26% by weight water were prepared using device D2, and water/gas oil emulsions having 52% by weight water using device D1 in the presence of the combination of additives as disclosed in International Application WO 97/34969.

For these tests, the gas oil used was a gas oil meeting the specifications of the EN590 standard. The results obtained with the two devices are given in Table 1.

Table 1 Device D %H 2 0/G O peripheral throughput dwell time stability tangential in D over time velocity (months) (m/s) Dl 52 29.3 0.07 1.58 >4 52 29.3 1.23 0.59 1 52 19.3 0.07 1.58 2 D2 13 35.3 2.5 17.3 >4 13 35.3 3 14 >4 13 33 4 10.8 13 19.3 4 10.8 1 26 35.3 1.5 28.8 >4 26 35.3 4 10.8 26 19.3 1.5 28.8 1 In this table, emulsion stability is quantified by the time measured between the date the emulsion was produced on and the date the emulsion broke, in other words the date on which free water at the bottom of the storage recipient for the emulsion appeared.

It is noticed that the effectiveness of production varied depending on the size and geometry of the rotor/stator employed. With device Dl, peripheral velocity needs to be greater than 25 m/s for a dwell time R:\3revets\1 7900\1 7928GB doc of at least one second. Where this velocity is less than m/s and/or dwell time is less than 1 second, the emulsion splits into two phases after the first or second month.

With the device D2, of different geometry to Dl, for a peripheral velocity greater than 25 m/s, dwell time should exceed 14 seconds for an emulsion containing 13% by weight water. If peripheral velocity is less than m/s and/or dwell time is less than 14 seconds, the emulsion is unstable and rapidly separates.

For a given device D2, the greater the water content, the more peripheral velocity and dwell time need to increase.

EXAMPLE II This example aims at demonstrating the importance of the peripheral tangential velocity of the device for the obtention of a monodispersed distribution of the droplets .which favours the stability over time.

20 An semi-industrial pilot plant was used as in Example I. A single device D2 was used with emulsions having 13% by weight water. The tangential velocity of the device was varied and the size distribution of the droplets was measured as a function of the tangential 25 velocity. The results are given below in Table 2.

30 Table 2 Trial peripheral throughput dwell time size tangential in D distribution velocity (m 3 /h) (m/s) 35.3 2.5 17.3 monodispersed 2 23.6 4 10.8 polydispersed R:\Brcvcts\i 7900\1 7928GBdoc The results for Trials 1 and 2 are represented on FIG. 3 and 4, respectively.

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Claims

1. A process for continuous preparation of a water in-oil emulsified monodispersed fuel allowing additives, water and a hydrocarbon phase to be mixed by agitation and optionally allowing recirculation of the mixture obtained in a circulation loop, wherein in a first step, using a distribution device, at least one phase A comprising additives necessary for stabilising an emulsion, water and optionally any additive useful for implementing the emulsion are distributed in the hydrocarbon phase, these components being introduced alone or in a mixture, the droplet contribution of each phase A in the hydrocarbon phase corresponding to a homogeneous spatial distribution of water droplets of size less than 200 tm and, in a second step, all phases A having been distributed in the hydrocarbon phase, droplet size is decreased by dispersion using an emulsifying device chosen from the group constituted by multi-stage or non-multistage rotors/stators, smooth or grooved S 15 tapered emulsifiers, the emulsifying device having a dynamic peripheral velocity of at least 10 m/s and allowing a dwell time in an enclosure containing the emulsifying device varying from 1 second to 80 seconds. S2. The process according to claim 1, wherein the dynamic peripheral velocity is greater than 25 m/s. 20 3. The process according to claim 1 or 2, wherein the dwell time is from o 2-30 seconds.

4. The process according to any one of claims 1 to 3, wherein at least a first phase A is constituted totally or in part by additives necessary for stabilising the Semulsion.

5. The process according to any one of the preceding claims, wherein at least one second phase A comprises water, optionally comprising anti-bacterial additive and/or any additive needed for the use of said emulsion.

6. The process according to any one of claims 1-5, wherein the distribution device is selected from the group consisting of orifice injection systems, sintered materials, impacting jet mixers, mixing heads, static mixers, sonic mixers and mechanically agitated turbines.

7. The process according to any one of claims 1-6, wherein, in a third step, the emulsion formed is recycled totally or in part into the inlet conduit of the hydrocarbon [R:\IBZZ]595843speci.doc:GYM phase, upstream of the distribution devices for phase A, recirculation throughput varying from one to three times the recovered emulsion throughput.

8. The process according to any one of claims I to 7, wherein the emulsified mixture is diluted in a second hydrocarbon phase by means of a dilution device selected from the group consisting of orifice injection systems, sintered materials, impacting jet mixers, mixing heads, static mixers, sonic mixers and mechanically agitated turbines.

9. A process for continuous preparation of a water in-oil emulsified monodispersed fuel substantially as hereinbefore described with reference to the accompanying drawings.

10. A monodispersed emulsion obtained by the process according to any one of claims 1-9, wherein the emulsion comprises from 5 to 20% by weight water in the hydrocarbon phase.

11. The emulsion according to claim 10, obtained by dilution in a second hydrocarbon phase of an emulsion precursor obtained by the process according to any one s15 of claims 1-9 comprising more than 20% by weight water in a first hydrocarbon phase, the two hydrocarbon phases being of the same nature.

12. An emulsion precursor for an emulsion according to claim 11, wherein the .emulsion precursor comprises from 20-90% by weight water in the hydrocarbon phase.

13. The emulsion precursor of claim 12, wherein the emulsion precursor 20 comprises from 40 to 70% by weight water in the hydrocarbon phase.

14. The process according to any one of claims 1-9 carried out in an apparatus comprising: *:Soo an inlet conduit for a hydrocarbon phase at which there arrives at least one -inlet conduit provided with a distribution device for at least one phase A, a first conduit 25 for emulsion stabilizing additives and a second conduit for water, (ii) an emulsifying device chosen from the group constituted by multi-stage or non-multistage rotors/stators, smooth or grooved tapered emulsifiers, this device being arranged on said conduit downstream of said inlet conduits for phases A having a dynamic peripheral velocity of at least 10 m/s and allowing a dwell time for the emulsion varying from one second to 80 seconds, (iii) storage means on an outlet conduit from the emulsifying device, (iv) and, optionally, a conduit for tapping a portion of the emulsified mixture and for bringing said portion into the inlet conduit for the hydrocarbon phase upstream of said distribution devices. [R:\LIBZZ]595843speci.doc:GYM I 14 The process of claim 14, wherein there are provided two conduits for at least two phases A.

16. The process according to claim 14 or 15, wherein the dynamic peripheral velocity is greater than 25 m/s.

17. The process according to claim 14, 15 or 16, wherein the dwell time is from 2-30 seconds.

18. The process according to claim 17, wherein the apparatus comprises, on the outlet conduit from emulsifying device or storage means or a distribution device identical to the distribution devices and storage means, the diluting hydrocarbon phase being introduced via a conduit.

19. The process according to claim 17 or 18, wherein the distribution device is selected from the group consisting of orifice injection systems, sintered materials, impacting jet mixers, mixing heads, static mixers, sonic mixers and mechanically agitated turbines. .i 15 20. Use of the process according to any one of claims 1 to 9 in the preparation of combustible water-petroleum, water-gas oil and water fuel monodispersed emulsions or their monodispersed emulsion precursor for an external hydrocarbon phase.

21. A monodispersed emulsion obtained by the process according to any one of claims 14 to 19. Dated 8 November, 2004 Elf Antar France 00*** 0 Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON [R:\LIBZZ]595843speci.doc:GYM