EP2817087B1

EP2817087B1 - Installation and process for preparing a water/diesel fuel emulsion

Info

Publication number: EP2817087B1
Application number: EP13713958.0A
Authority: EP
Inventors: Enrico Carlo FUMAGALLI
Original assignee: Advanced Financial Services SA
Current assignee: Advanced Financial Services SA
Priority date: 2012-02-24
Filing date: 2013-02-22
Publication date: 2016-01-20
Anticipated expiration: 2033-02-22
Also published as: AR090133A1; EP2817087A1; HRP20160377T1; WO2013124726A1; ITRM20120070A1; SI2817087T1

Description

Field of the invention

The present invention relates to the field of water/diesel fuel emulsions and particularly to an installation and a process for preparing a water/diesel fuel emulsion.

Prior art

An emulsion is a stable dispersion of a fluid in form of extremely small droplets or bubbles (dispersed phase) in another immiscible fluid (dispersing phase or carrier).
Its stability depends on the density of the two phases, on temperature, on the presence of surfactants (emulsifying agents), and on the presence of electrolytes. Emulsions belong to a wider class of two-phase systems called colloids.
A colloid is a substance in a finely dispersed state, intermediate between that of a homogeneous solution and that of a heterogeneous dispersion. This "micro-heterogeneous" state thus consists of two phases: a substance with microscopic dimensions (diameter of 10^-9 m to 1 µm) dispersed in a continuous phase being in a physical state which determines the macroscopic physical properties of the whole system.
Water/diesel fuel emulsions are fuels usable in Diesel cycle internal combustion engines and in heating burners and have the purpose of reducing the presence of harmful pollutants in exhaust gases and/or in stacks.
From the chemical point of view, water/diesel fuel emulsions are dispersions of extremely small water micro-drops in the diesel fuel, stabilized by addition of specific surfactant substances capable of stabilizing an emulsion (Pickering stabilizer).
Water/diesel fuel emulsions represent a modern technology for feeding diesel engines, either installed on-board of vehicles or in fixed installations.
They are suitable for direct use in engines in place of traditional diesel fuel, may be formulated with diesel fuels having very low Sulphur content and are compatible with modern devices for emission reduction.
However, the emulsions available on the market up to now do not exhibit high stability, high performance in terms of regularity, increased energy efficiency and improved specific consumption.
Document EP0958853 A1 discloses an installation for preparing a water/diesel fuel emulsion.
It is thus an object of the present industrial invention to provide a technology which allows creating a water/diesel fuel emulsion which overcomes the drawbacks of the prior art.

Summary of the invention

Therefore, in a first aspect thereof, the invention relates to an installation for preparing a water/diesel fuel emulsion comprising:

at least one water feeding unit;
at least one activator feeding unit; ;
at least one diesel fuel feeding unit;
at least one pre-mixing tank;
characterized by comprising a mixing device downstream of said pre-mixing tank comprising:
at least one tubular duct defining an extension direction (X-X);
at least one first helical channel arranged inside the tubular duct for generating a turbulent flow of the mixture of water, activator and diesel fuel inside said tubular element;
at least one first baffle (31), arranged perpendicularly to said extension direction X-X and downstream of said first helical channel (10); said first baffle (31) comprising a plurality of holes (33) arranged with an axis of extension parallel to the axis X-X;
at least one inlet element (28) comprising a tapered portion (27) at an end thereof and a plurality of holes (26) arranged with an axis of extension substantially parallel to the axis X-X and adapted to let the inlet fluid into the first helical channel (10).

The turbulent flow according to a helical path which is generated inside the tubular duct allows obtaining a stable emulsion.
The present invention, in the above-mentioned aspect, may have at least one of the preferred features hereinafter described.
Preferably, the pre-mixing tank comprises a water nebulizing device. Conveniently, the emulsion discharge unit arranged downstream of said pre-mixing tank comprises:

at least one pump;
at least one filter;
at least one pressure valve.

Advantageously, the water feeding unit comprises at least one first water tank, in fluid communication with the pre-mixing tank, at least one water pre-heating device, at least one temperature sensor, at least one pressure control valve and at least one pressure sensor.
Conveniently, the installation comprises a volumetric sliding vane pump, comprising:

at least one rotor; and
at least one eccentric chamber in which said rotor rotates.

Advantageously, the sliding vane pump is arranged downstream of said pre-mixing tank and upstream of said mixing device.
Preferably, the first baffle has disk-like shape and extends radially about the axis X-X.
Preferably, the mixing device further comprises at least one second helical channel arranged downstream of the first helical channel.
Advantageously, the mixing device comprises at least one second baffle arranged perpendicularly to said extension direction X-X and downstream of said second helical channel, the second baffle comprising a plurality of holes. Conveniently, the mixing device comprises an outlet element comprising:

at least one first blind wall arranged transversally to the extension direction X-X;
at least one second blind wall arranged transversally to the extension direction X-X; and
a plurality of outlet channels positioned downstream of the first wall and arranged radially to the extension direction X-X.

Advantageously, the mixing device comprises:

at least one first retaining ring for removably positioning the first baffle downstream of the first helical channel;
at least one second retaining ring for positioning the second baffle downstream of the second helical channel.

The nebulizing device comprises a central body, at least one rotor arranged inside the central body, at least one feeding duct for feeding water to the central body and at least two elements which project radially from the central body and are angularly staggered. The radially projecting elements comprise a plurality of nebulizing nozzles spaced apart from one another and extending from the free end of said radially projecting elements.
According to another aspect thereof, the present invention relates to a process for preparing a water/diesel fuel emulsion by means of an installation as described above.
The process comprises the steps of:

drawing a predetermined amount of diesel fuel Qg and sending it to the pre-mixing tank;
drawing a predetermined amount of an activator Qa and sending it to the pre-mixing tank;
drawing a predetermined amount of water Qw and sending it to the pre-mixing tank;
pre-mixing the aforesaid mixture of water, diesel fuel and activator;
sending the pre-mixed mixture to a mixing device for subjecting the mixture to a turbulent flow according to at least one first helical path,
said mixing device comprising at least one first baffle, arranged perpendicularly to said extension direction X-X and downstream of said first helical channel; said first baffle comprising a plurality of holes arranged with an axis of extension parallel to the axis X-X,
forcing the pre-mixed mixture to collide, upstream of said first helical path, with a surface perpendicular to the extension axis X-X of said mixing device and to flow through a plurality of holes, arranged parallel to the axis X-X, said holes being provided at the inlet of said mixing device for determining a speed and kinetic energy loss in said pre-mixed mixture upstream of said helical path.

Advantageously, the step of drawing a predetermined amount of water Qw and sending it to the pre-mixing tank comprises a step of nebulizing the water to be introduced into said pre-mixing tank.
Preferably, the step of sending the pre-mixed mixture to a mixing device for subjecting the mixture to a turbulent flow according to at least one first helical path is carried out inside a tubular duct into which the pre-mixed fluid enters at a pressure p1 and from which the pre-mixed fluid comes out at a pressure p2, with p1>p2.
Preferably the pre-mixed mixture is subjected to a turbulent flow according to a second helical path downstream of the first helical path.
Advantageously, the process for preparing a water/diesel fuel emulsion comprises a step of making the fluid to lose kinetic energy and speed between said first helical path and the second helical path.
Conveniently, the process comprises a further step of making the fluid to lose kinetic energy and speed between the second helical path and the outlet element.
Preferably, the process comprises a step in which the fluid is forced to come out from the tubular element in a radial direction with respect to the extension direction X-X.
Preferably, the process comprises a step in which the fluid is made to flow through said mixing device at least a number of times between 4 and 12.

Brief description of the drawings

Further features and advantages of the invention will become more apparent from the detailed description of some preferred, although not exclusive, embodiments of an installation for preparing a water/diesel fuel emulsion according to the present invention.
Such description will be presented hereinafter with reference to the accompanying drawings, provided only for indicating, and thus non-limiting, purposes, wherein:

figure 1 is a schematic perspective view of a first embodiment of the installation for preparing a water/diesel fuel emulsion according to the present invention;
figure 2 is a schematic view of the installation for preparing a water/diesel fuel emulsion according to the present invention shown in figure 1;
figure 3 is a schematic enlarged view of the mixing device of the installation for preparing a water/diesel fuel emulsion according to the present invention;
figure 4 is a schematic exploded view of the mixing device of figure 3;
figure 5 is a schematic enlarged sectional view of a portion of the mixing device of the installation for preparing a water/diesel fuel emulsion of figure 3; and
figures 6a, 6b are schematic views of an embodiment of the nebulizing device of the installation for preparing a water/diesel fuel emulsion according to the present invention.

Detailed description of embodiments of the invention

Referring to figures 1-2, an installation for preparing a water/diesel fuel emulsion, according to the present invention, is identified by reference numeral 100.
The installation 100, in the embodiment shown in figures 1 and 2, has at least one water feeding unit 1, at least one activator feeding unit 2, at least one diesel fuel feeding unit 3, at least one pre-mixing tank 4 and at least one mixing device 5 downstream of said pre-mixing tank 4.
Preferably, in the embodiment shown in figures 1 and 2, two mixing devices 5, in parallel with each other, are present downstream of the pre-mixing tank 4. The water feeding unit 1, the activator feeding unit 2 and the diesel fuel feeding unit 3 are arranged downstream of the pre-mixing tank 4 and in fluid communication with the same.
The water feeding unit 1 comprises a first water tank 51, preferably made of stainless steel, a water preheating unit, suitable for heating water in the tank 51 to a temperature between 4°C and 40°C, preferably between 5°C and 35°C, at least one volumetric load pump provided with at least one by-pass valve and a liter counter device, preferably of the digital type for ensuring high measurement accuracy and repeatability.
The valves and pumps of the water feeding unit 1 are controlled by a control unit 30 which controls the operating parameters of the entire installation and takes care of the proper operation thereof.
The diesel fuel feeding unit 3 comprises at least one delivery pump for delivering diesel fuel to the pre-mixing tank 4, at least one filter suitable for eliminating possible impurities which might enter into the pre-mixing tank 4 and pressure control valves.
Preferably, the delivery pump for delivering diesel fuel to the pre-mixing tank 4 is a volumetric electric pump with mechanical seal, e.g. of the Viton type, with a flow rate of 500 liters/min, a head of 25 meters, 1450 rpm, coupling by means of spider and elastic joint, provided with an explosion-proof electric motor.
In the outlet duct of the diesel fuel feeding unit 3 a gauge for controlling temperature may be present.
The diesel fuel feeding unit 3 further comprises at least one diesel fuel tank, not shown in the figure, from which the diesel fuel to be sent to the pre-mixing tank 4 is drawn.
Also the unit 3 for feeding diesel fuel to the pre-mixing tank 4 is controlled by the control unit 30.
The activator feeding unit 2 comprises at least one delivery pump for delivering an activator to the pre-mixing tank 4, at least one activator tank 52, preferably made of stainless steel, and an activator preheating device.
In the outlet duct of the activator feeding unit 2 to the pre-mixing tank a ball valve may be present, preferably made of stainless steel, with wafer actuation and driven by an electric actuator controlled by the control unit.
The activator preheating device may be of many kinds, generally known to a person skilled in the art and thus hereinafter not further described in detail. The activator preheating device allows the activator in the tank 52 to be heated to a temperature between 15°C and 40°C, preferably between 20°C and 35°C.
As previously mentioned, the water feeding unit 1, the activator feeding unit 2 and the diesel feeding unit fuel 3 are arranged downstream of the pre-mixing tank 4 and in fluid communication with the same.
The pre-mixing tank 4, also preferably made of steel, has at least one delivery valve for delivering the pre-mixed mixture of water, activator and diesel fuel to the mixing device 5, and at least one nebulizing device 7, better shown in figures 6a, 6b.
Preferably, three delivery valves for delivering the pre-mixed mixture of water, activator and diesel fuel to the mixing device 5 are present. These valves are arranged in the lower part of the pre-mixing tank 4, preferably are of the ball type, are made of stainless steel, have a wafer actuation, and comprise actuators controlled by the control unit 30.
In the embodiment shown in figures 6a, 6b, the nebulizing device 7 comprises a central body 13, at least one rotor 17 arranged inside the central body, a feeding duct 14 for feeding water to the central body 13 and four elements 15 which project radially from the central body 13.
The nebulizing device 7 is arranged in the upper part of the pre-mixing tank 4 and allows feeding the mixture of diesel fuel and additive contained in the pre-mixing device 4 substantially uniformly and in form of a micro-rain.
To this end, the radially projecting elements 15 are configured as four angularly staggered ducts departing from the central body 13.
The radially projecting elements 15 comprise a plurality of nebulizing nozzles, arranged spaced apart from one another and extending from the free end of said radially projecting elements 15.
In the embodiment shown in figures 1 and 2, a manifold 29 is present downstream of the pre-mixing tank 4.
Two mixing devices 5 in parallel with each other and in fluid communication with the pre-mixing tank 4 are present downstream of the manifold 29.
The manifold 29 acts as a decoupling chamber and allows avoiding that one of the two mixing devices 5 takes fluid away from the other during intake.
Each mixing device 5 is configured as a tubular duct 9 extending along an extension direction X-X, as better shown in figures 3 and 4.
The tubular duct 9 comprises at least one inlet, at least one outlet and at least one first helical channel 10 arranged inside the tubular duct 9 for generating a turbulent flow of the mixture of water, activator and diesel fuel inside said tubular element 9, along a helical path.
In detail, in the embodiment shown in figures 4 and 5 two helical channels, i.e. a first 10 and a second 11 helical channel, are present, arranged in series to each another and suitably separated by a first baffle 31 provided with holes.
The first 10 and the second 11 helical channels are formed in the inner walls of the tubular duct 9.
Given a length L of the tubular duct, the first helical channel 10 extends in the extension direction X-X by a dimension I₁ ≥ 0,05 L. Preferably, I₁ ≤ 0,75 L, even more preferably 0,1 ≤ I₁ ≤ 0,5.
The first 10 and the second 11 helical channels have opposite winding directions. In other words, in the embodiment shown in figure 3, the first helical channel 10 has a right-handed winding direction, whereas the second helical channel has a left-handed winding direction.
The second helical-channel 11, like the first one, extends in the extension direction X-X by a dimension I2 ≥ 0,05 L. Preferably, I2 ≤ 0,75 L, even more preferably 0,1 ≤ I2 ≤ 0,5.
Preferably, the first channel 10 and the second channel 11 have a cross section for the passage of fluid s ≥ 7 mm, even more preferably s ≥ 9 mm. Advantageously, the first channel 10 and the second channel 11 have a cross section for the passage of fluid s ≤ 15 mm, preferably s ≤ 12 mm.
The first helical channel 10 has a distance d1 between two consecutive turns, measured between two corresponding points of the two consecutive turns in a direction parallel to the extension direction X-X, which is substantially constant. Preferably, d1 ≤ 0,01L, in any case d1 ≥ 0,03L.
Similarly, the second helical channel has a distance d2 between two consecutive turns, measured between two corresponding points of the two consecutive turns in a direction parallel to the extension direction X-X, which is substantially constant.
Preferably, d2 ≤ 0,01L, in any case d2 ≥ 0,03L.
As previously mentioned, for making the fluid flow within the duct as turbulent and irregular as possible, between the first 10 and the second 11 helical channels a first baffle 31 provided with holes is provided.
The first baffle 31 is arranged transversally to the extension direction X-X downstream of the first helical channel 10 and has a plurality of holes 33 arranged with an axis of extension substantially parallel to the axis X-X.
The first baffle 31 radially extends about axis X-X so as to form a barrier to the passage downstream of the first helical channel 10.
The fluid coming out from the first helical channel 10 is forced to flow through the holes 33, having axes parallel to the axis X-X.
The holes 33 of the first baffle 31 are through holes and overall have a passage cross section s3 in the range 2 mm ≤ s3 ≤ 5 mm.
Each hole 33 of the first baffle 31 has a passage cross section s4 preferably in the range 0,05 mm ≤ s4 ≤ 0,2 mm.
The first baffle 31 may be interchangeable with another first baffle having a different number of holes and a different size of the holes.
To this end, the first baffle 31 is mounted on a retaining ring 59, preferably made of steel, removable from to the tubular duct 9.
In the embodiment shown in figures 3, 4, downstream of the second helical channel 11 a second baffle 32 provided with holes is present.
The second baffle 32 is arranged transversally to the extension direction X-X and has a plurality of holes 34, also arranged with their extension axes substantially parallel to the axis X-X.
The second baffle 32 radially extends about axis X-X so as to form a barrier to the passage downstream of the second helical channel 11.
The fluid coming out from the second helical channel 11 is forced to flow through the holes 34 having axes parallel to the axis X-X, before coming out form the outlet element 35, as better described hereinafter.
Between the second baffle 32 and the outlet element an outlet chamber is thus formed, defined by a portion of the tubular duct 9 and, at the axially outer ends, by the second baffle 32 and by the outlet element 35.
Referring to the embodiment shown in the figures, the outlet chamber does not have helical channels.
The holes 34 of the second baffle 32 overall have a passage cross section s5 in the range 2 mm ≤ s5 ≤ 5 mm.
Each hole 34 of the second baffle 32 has a passage cross section substantially in the same range of the passage cross section s4 of the holes 33 of the first baffle.
Upstream of the first helical channel 10 an inlet element 28 is arranged comprising a tapered portion 27 at an end thereof and a plurality of holes 26 arranged with an axis of extension substantially parallel to the axis X-X and adapted to let the inlet fluid into the first helical channel 10.
The tapered portion 27 is arranged at the end of the inlet element 28 closest to the first helical channel 10.
The tapered portion 27 thus has a conical surface with a plurality of through holes 26 formed in it.
Downstream of the second baffle 32 provided with holes an outlet element 35 is arranged, better shown in figure 5, comprising at least one first blind wall 36 arranged transversally to the extension direction X-X; and at least one second blind wall 37 staggered relative to the extension direction X-X with respect to the first blind wall 36.
In the embodiment shown in figure 5, the first blind wall 36 has a substantially disk-like shape, while the second blind wall 37 has substantially the shape of a circular crown.
The first blind wall 36 is arranged concentrically relative to the second blind wall 37.
A cylindrical lateral wall 39 connects the first blind wall 36 with the second blind wall 37. The outlet element 35 has a plurality of outlet channels 38 arranged radially to the extension direction X-X.
Still referring to the embodiment shown in figure 5, the outlet channels 38 are arranged on the cylindrical lateral wall 39 in rows parallel to the extension direction X-X and angularly staggered on the same cylindrical lateral wall 39. As it comes out from the holes 34 of the second baffle 32, the fluid is forced to collide, in order to dissipate kinetic energy, against the first blind wall 36 and/or the second blind wall 37 and to exit through the outlet channels 38.
Each mixing device 5 is connected downstream with an appropriate faucet for tapping the emulsion and with a duct 40 adapted to form a closed loop with the pre-mixing tank 4 for circulating the fluid through the mixing devices many times, in order to obtain a stable emulsion.
The installation 100 described above allows a stable water/diesel fuel emulsion to be prepared.
To this end, a predetermined amount of diesel fuel Qg is drawn from said diesel fuel feeding unit 3. This amount of diesel fuel Qg is sent to the pre-mixing tank 4. Preferably, Qg is comprised between 70 and 95 vol% of the emulsion to be prepared.
Immediately afterwards a predetermined amount of activator Qa is drawn from said activator feeding unit 2 and sent to the pre-mixing tank 4. Preferably, Qa is comprised between 0,5 and 3 vol% of the emulsion to be prepared. Even more preferably, it is comprised between 1 and 2 %, extremes included. Preferably, the predetermined amount of activator Qa is sent to said pre-mixing tank 4 only after the feeding of the predetermined amount of diesel fuel Qg to the same tank 4 has ended.
At this point, a predetermined amount of water Qw is drawn and sent to the pre-mixing tank 4.
Preferably, Qw is comprised between 5 and 30 vol% of the emulsion to be prepared. Even more preferably, it is comprised between 7 and 20 %, extremes included.
Preferably, the predetermined amount of water Qw is sent to said pre-mixing tank 4 only after the feeding of the predetermined amount of activator Qa has ended.
Preferably, the water is demineralized water.
In order to distribute the predetermined amount of water Qw inside the pre-mixing tank 4, it is nebulized in form of a very thin rain and distributed from above as uniformly as possible.
The pre-mixed mixture of nebulized water, diesel fuel and activator is then sent to a mixing device 5, after having flown through collector 29.
In the mixing device 5 the pre-mixed mixture of nebulized water, diesel fuel and activator is made to move along a spiral path for obtaining a turbulent flow.
In detail, at the inlet of the tubular duct 9 the fluid is forced by means of a tapered portion 27 to flow through a series of holes 26 suitable for reducing the speed thereof and for determining a kinetic energy loss; subsequently the fluid is made to move along a first helical path, which determines a turbulent flow according a helical path, besides increasing the speed and thus the kinetic energy of the fluid.
As it comes out from the first helical channel 10 and thus from its helical path, the fluid is in front of the first baffle 31 provided with holes and collides against the latter loosing kinetic energy. The fluid is thus forced to flow through the holes 33 of the first baffle 31 provided with holes. In other words, the fluid coming out from the first helical path undergoes a kinetic energy and speed loss caused by the interaction with the first baffle 31 and the holes 33 thereof, arranged parallel to the axis X-X.
As it comes out from the holes 33 of the first baffle 31, the pre-mixed fluid of nebulized water, diesel fuel and activator is made to flow through a second helical channel 1 1 for obtaining a turbulent flow along a helical path, for increasing again the kinetic energy and speed of the fluid itself.
As it comes out from the second helical channel 11, the fluid is in front of a second baffle 32 provided with holes and collides against the latter loosing kinetic energy. The fluid is forced to flow through the holes 34 of the second baffle 31.
As it comes out from the holes 34 of the second baffle 32, the fluid is in front of two blind walls, respectively 36 and 37, arranged substantially perpendicularly to the extension direction X-X of the tubular duct 9.
The fluid collides with the first 36 and/or the second 37 blind wall, further loosing kinetic energy, and is forced to come out from the tubular duct 9. The fluid is forced to come out in a radial direction with respect to the extension direction X- X. In detail, the fluid is forced by the blind walls 36, 37 to come out through the radial channels 38.
In flowing through the tubular duct 9, which represents the mixing device 5, the mixture of pre-mixed water, diesel fuel and activator enters at a pressure p1 and comes out at a pressure p2, with p1 >p2.
Preferably, p1 is comprised in the range between 2 and 20 bar, extremes included. Preferably, p2 is the room pressure.
In order to obtain an emulsion which is stable in time, the fluid is subjected to the mixing cycle many times. To this end, as it comes out from the tubular duct 9, the fluid is sent again, by means of the duct 40, to the pre-mixing tank 4, from which it will be drawn so as to flow again through one of the mixing devices 5, after having flown again through the manifold 29.
Preferably, the fluid is made to flow through a mixing device at least a number of times between 4 and 12, preferably between 6 and 10, for example 9 times.

Claims

Installation (100) for preparing a water/diesel fuel emulsion comprising:
- at least one water feeding unit (1);

- at least one activator feeding unit (2);

- at least one diesel fuel feeding unit (3);

- at least one pre-mixing tank (4);
characterized by comprising a mixing device (5) downstream of said pre-mixing tank (4) comprising:

- at least one tubular duct (9) defining an extension direction (X-X);

- at least one first helical channel (10) arranged inside the tubular duct (9) for generating a turbulent flow of the mixture of water, activator and diesel fuel inside said tubular element (9);

- at least one first baffle (31), arranged perpendicularly to said extension direction X-X and downstream of said first helical channel (10); said first baffle (31) comprising a plurality of holes (33) arranged with an axis of extension parallel to the axis X-X;

- at least one inlet element (28) comprising a tapered portion (27) at an end thereof and a plurality of holes (26) arranged with an axis of extension substantially parallel to the axis X-X and adapted to let the inlet fluid into the first helical channel (10).
Installation (100) for preparing a water/diesel fuel emulsion according to claim 1, characterized in that said pre-mixing tank (4) comprises a water nebulizing device (7).
Installation (100) for preparing a water/diesel fuel emulsion according to claim 1, characterized by comprising an emulsion discharge unit arranged downstream of said pre-mixing tank (4) comprising:
- at least one pump;

- at least one filter;

- at least one pressure valve.
Installation (100) for preparing a water/diesel fuel emulsion according to any one of claims 1 to 3, characterized in that said water feeding unit (1) comprises at least one first water tank (51) in fluid communication with the premising tank (4), at least one water pre-heating device, at least one temperature sensor, at least one pressure control valve and at least one pressure sensor.
Installation (100) for preparing a water/diesel fuel emulsion according to any one of the previous claims 1 to 4, characterized by comprising a volumetric sliding vane pump, comprising:
- at least one rotor; and

- at least one eccentric chamber in which said rotor rotates.
Installation (100) for preparing a water/diesel fuel emulsion according to claim 5, characterized in that said sliding vane pump is arranged downstream of said pre-mixing tank (4) and upstream of said mixing device.
Installation (100) for preparing a water/diesel fuel emulsion according to claim 1 , characterized in that said first baffle (31) has disk-like shape and extends
radially about the axis X-X.
Installation (100) for preparing a water/diesel fuel emulsion according to claim 1, characterized in that said mixing device further comprises:
- at least one second helical channel (11) arranged downstream of said first helical channel (10).
Installation (100) for preparing a water/diesel fuel emulsion according to claim 8, characterized in that said mixing device (5) comprises at least one second baffle (32) arranged perpendicularly to said extension direction X-X and downstream of said second helical channel (11), said second baffle (32) comprising a plurality of holes (34).
Installation (100) for preparing a water/diesel fuel emulsion according to claim 1, characterized in that said mixing device (5) comprises an outlet element (35) comprising:
- at least one first blind wall (36) arranged transversally to the extension direction X-X;

- at least one second blind wall (37) arranged transversally to the extension direction X-X; and

- a plurality of outlet channels (38) positioned downstream of said first wall (36) and arranged radially to the extension direction X-X.
Installation (100) for preparing a water/diesel fuel emulsion according to claim 1, characterized in that said mixing device (5) comprises:
- at least one first retaining ring (59) for removably positioning said first baffle (31) downstream of said first helical channel (10);

- at least one second retaining ring (59) for positioning said second baffle (32) downstream of said second helical channel (11).
Installation (100) for preparing a water/diesel fuel emulsion according to claim 5, characterized in that said nebulizing device (7) comprises a central body (13), at least one rotor arranged inside said central body, at least one feeding duct (14) for feeding water to the central body and at least two elements (15) which project radially from the central body (13) and are angularly staggered; said radially projecting elements (15) comprise a plurality of nebulizing nozzles (17) arranged spaced apart from one another and extending from the free end of said radially projecting elements (15).
Process (100) for preparing a water/diesel fuel emulsion by means of an installation according to any one of the previous claims 1 to 12, comprising a step of:
- drawing a predetermined amount of diesel fuel Qg and sending it to the pre-mixing tank (4);

- drawing a predetermined amount of an activator Qa and sending it to the pre-mixing tank (4);

- drawing a predetermined amount of water Qw and sending it to the pre-mixing tank (4);

- pre-mixing the aforesaid mixture of water, diesel fuel and activator;

- sending the pre-mixed mixture to a mixing device (5) for subjecting the mixture to a turbulent flow according to at least one first helical path, said mixing device (5) comprising at least one first baffle (31), arranged perpendicularly to said extension direction X-X and downstream of said first helical channel (10); said first baffle (31) comprising a plurality of holes (33) arranged with an axis of extension parallel to the axis X-X

- forcing the pre-mixed mixture to collide, upstream of said first helical path, with a surface perpendicular to the extension axis X-X of said mixing device (5)
and to flow through a plurality of holes (26), arranged parallel to the axis X-X, said holes being provided at the inlet of said mixing device (5) for determining a speed
and kinetic energy loss in said pre-mixed mixture upstream of said helical path.
Process (100) for preparing a water/diesel fuel emulsion according to claim 13, characterized in that the step of drawing a predetermined amount of water Qw and sending it to the pre-mixing tank (4) comprises a step of nebulizing the water to be introduced into said pre-mixing tank (4).
Process (100) for preparing a water/diesel fuel emulsion according to claim 13, characterized in that the step of sending the pre-mixed mixture to a mixing device (5) for subjecting the mixture to a turbulent flow according to at least one first helical path is carried out inside a tubular duct (9) into which the pre-mixed fluid enters at a pressure p1 and from which the pre-mixed fluid comes out at a pressure p2, with p1 >p2.
Process (100) for preparing a water/diesel fuel emulsion according to claim 13, characterized by subjecting the pre-mixed mixture to a turbulent flow according to a second helical path downstream of said first helical path.
Process (100) for preparing a water/diesel fuel emulsion according to claim 13, characterized by comprising a step of making the fluid to lose kinetic energy and speed between said first helical path and said second helical path.
Process (100) for preparing a water/diesel fuel emulsion according to claim 13, characterized by comprising a further step of making the fluid to lose kinetic energy and speed between said second helical path and said outlet element (35).
Process (100) for preparing a water/diesel fuel emulsion according to claim 13, characterized by comprising a step in which the fluid is forced to come out in a radial direction with respect to the extension direction X-X.
Process (100) for preparing a water/diesel fuel emulsion according to claim 13, characterized by making the fluid to flow through said mixing device at least a number of times between 4 and 12.