EP2416874A1

EP2416874A1 - Ejector device for forming a pressurized mixture of liquid and gas, and use thereof

Info

Publication number: EP2416874A1
Application number: EP10723191A
Authority: EP
Inventors: Yves Lecoffre; Guillaume Maj; Jacques Marty
Original assignee: Total SE
Current assignee: TotalEnergies SE
Priority date: 2009-04-09
Filing date: 2010-04-02
Publication date: 2012-02-15
Anticipated expiration: 2030-04-02
Also published as: US20120034106A1; EP2416874B1; FR2944218B1; FR2944218A1; WO2010116076A1; AR076244A1

Abstract

Ejector device for forming a pressurized mixture of liquid and gas, comprising a suction chamber (2) and a diffuser (6). The suction chamber comprises an injection nozzle (5) for producing a jet of liquid flowing in a longitudinal direction (X), a gas inlet (3) for admitting into the suction chamber a gas to be driven by the liquid jet, and an outlet opening (4) for discharging the liquid jet and the driven gas from the suction chamber. The diffuser is connected to the outlet opening of the suction chamber and has, in the longitudinal direction, a transversal section that increases from said outlet opening, the diffuser being situated immediately after the outlet opening of the suction chamber, and in which the diffuser (6) comprises at least one first conical portion that has a first angle of between 0.1 and 7 degrees.

Description

EJECTOR DEVICE FOR FORMING PRESSURE MIXTURE OF LIQUID

AND GAS, AND ITS USE

The present invention relates to an ejector device for forming a pressurized mixture of liquid and gas.

WO-Ol / 34285 describes such an ejector device comprising a suction chamber, a tube

10 cylindrical and a conical shaped diffuser and flaring in a longitudinal direction. A nozzle injects a high velocity liquid into the suction chamber, which then sucks gas through an inlet. The cylindrical tube is located between the suction chamber and the diffuser, such

This causes the liquid and the gas to mix in this cylindrical tube before entering the diffuser.

Such an ejector device makes it possible to obtain compression ratios (see definition below) of the order of 4 to 8. Thus, a gas having at the inlet a pressure of 2

20 atm, can be compressed to a pressure of 16 atm.

It is very difficult to go beyond.

The present invention aims to improve an ejector device of this type, in particular to optimize its energy efficiency and increase the compression rate.

More particularly, the invention relates to an ejector device for forming a pressurized mixture of liquid and gas, comprising a suction chamber and a diffuser, wherein the suction chamber comprises: an injection nozzle for producing a jet of liquid flowing in a longitudinal direction;

a gas inlet for admitting into the suction chamber a gas to be entrained by the liquid jet; and an outlet opening for exiting the suction chamber, the liquid jet and the gas trained; wherein the diffuser is connected to the outlet opening of the suction chamber and has along the longitudinal direction an increasing cross section from said outlet opening, the expanding section diffuser being located immediately after the opening outlet of the suction chamber, and wherein the diffuser (6) comprises at least a first conical portion having a first angle of between 0.1 and 7 degrees.

Thanks to these arrangements, the mixture of liquid and gas can be made at different axial positions inside the diffuser, and the ejector device then allows operation over a wide range of compression ratio.

In various embodiments of the ejector device according to the invention, one or more of the following provisions may also be used: the first angle is preferably between 1.5 and 4 degrees;

- The diffuser further comprises a second conical portion continuously in the extension of the first portion in the longitudinal direction, said second portion having a second angle greater than the first angle;

the second angle is between 5 and 15 degrees, and preferably of the order of 7 degrees;

- The diffuser further comprises a second portion continuously in the extension of the first portion in the longitudinal direction, said second portion having a convex profile shape;

the second convex portion has a gradually increasing angle along the longitudinal direction from the first angle to an angle less than 15 degrees, and preferably of the order of 10 degrees; the diffuser is substantially coaxial with the injection nozzle and the outlet opening of the suction chamber;

the ejector device is such that: the outlet opening, also called a neck, has a neck surface S ₀ perpendicular to the longitudinal direction,

the injection nozzle has a nozzle surface S ₂ internally to the nozzle and perpendicular to the longitudinal direction, and

a geometric ratio R is the ratio between the nozzle surface S2 and at the neck surface S _c , said geometric ratio R being between 0.5 and 0.9; With this arrangement, the device makes it possible to maximize the compression ratio for a given injection speed; and in particular to achieve very high compression ratios of the mixture, for example greater than 30, with a single device stage, provided that the speed of the liquid jet is sufficiently high;

the ejector device is such that:

the injection nozzle comprises an end in the longitudinal direction,

the outlet opening has a circular section with a neck diameter Dc, and

the end is at a withdrawal distance x ₂ from the outlet opening, said withdrawal distance x ₂ being between one and five times the neck diameter Dc; the suction chamber comprises walls in the longitudinal direction extending radially in said suction chamber, so that the ga 2 flows into the suction chamber with a low turbulence flow, without rotation, the Axial velocity distribution is fairly homogeneous;

the injection nozzle comprises means for channeling the liquid adapted to obtain in the nozzle after said channeling means, a liquid flow little turbulent, without rotation and whose axial velocity distribution is substantially homogeneous;

the means for channeling the liquid in the nozzle are chosen from:

a device having walls extending in the longitudinal direction, and a device having walls extending in the longitudinal direction and said walls having a honeycomb shape, and

a device comprising a wall in a direction substantially perpendicular to the longitudinal direction and comprising holes for distributing the liquid flow substantially uniformly in the cross section of the nozzle.

The invention also relates to the use of an ejector device of the above type, in which: the suction pressure of the gas p _λ is measured at the gas inlet (3), the supply pressure of liquid p ₂ supplying the injection nozzle (5), the delivery pressure p ₃ of the mixture of gas and liquid downstream of the diffuser (6), and - at least one of said pressures is adjusted so that a parameter Ψ from compression defined by the following formula: ψ ₌ P3 ^~ P2-Pl _t P1 'is between 0.4 and 0.6. The invention also relates to the use of an ejector device of the above type, in which:

the suction pressure of the gas pi is measured at the gas inlet (3), the liquid supply pressure p ₂ supplying the injection nozzle (5), the delivery pressure p ₃ of the gas mixture and liquid downstream of the diffuser (6), and the absolute pressure of supply of liquid p _{2 is} adjusted to within twenty percent of an optimum pressure p ₂ , _O pt, such that: Thanks to these usage arrangements, the energy performance of the ejector device is optimized.

The invention may for example be used in a gas compressor comprising an ejector device fed with a gas on the one hand and a liquid on the other hand, and a separator device adapted to receive a mixture of liquid and gas from the ejector device and extracting a gaseous component of this mixture, wherein the ejector device comprises a suction chamber and a diffuser, wherein the suction chamber comprises: an injection nozzle for producing a jet of liquid flowing according to a longitudinal direction;

a gas inlet for admitting a entrained gas into the suction chamber; and

an outlet opening for exiting the suction chamber, the jet of liquid and the entrained gas; wherein the diffuser is connected to the outlet opening of the suction chamber and has along the longitudinal direction an increasing cross section from said outlet opening, the expanding section diffuser being located immediately after the opening outlet of the suction chamber, and wherein the gas separator device has two outlets, one for the gas and the other for the liquid.

In various embodiments of the gas compressor, one or more of the following arrangements may also be used: the diffuser comprises at least a first conical portion having a first angle of between 0, 1 and 7 degrees; the separator device is a gravity separator; the separating device is a cyclonic separator;

- The gas compressor further comprises a pump adapted to suck the pressurized liquid at the separator device, and to supply with said liquid the injection nozzle of the ejector device. Other features and benefits of

1 'invention will appear in the following description of one of its embodiments, given by way of non-limiting example, with reference to the accompanying drawings. In the drawings: FIG. 1 is a diagrammatic view in longitudinal section of an ejector device according to the invention,

FIG. 2 is a graph, based on experimental results, showing the entrainment rate τ _e (see definition below) as a function of the compression ratio τ _c (see definition below) for different values of the pressure. in the ejector device of FIG. 1, FIG. 3 is a graph showing the theoretical efficiency of the ejector device (see definition below) of FIG. 1, for a compression ratio of the order of 4, as a function of a geometric ratio R for different training rate values, FIG. 4 is a graph showing the efficiency of the ejector device of FIG. 1, as a function of a compression parameter Ψ for different values of the parameter The driving pressure χ (see definition below) is a schematic view of a gas compressor comprising the ejector device of FIG. The longitudinal direction mentioned in this description is understood to be the direction indicated by a mixed line X in FIG. 1, and corresponds to the direction of flow in the ejector device 1 between the upstream side situated to the left and the downstream side. located to the right in this figure.

FIG. 1 represents a schematic view in longitudinal section of an ejector device 1 according to the invention. This ejector device extends along the longitudinal axis X and comprises along this axis:

a suction chamber 2 adapted to suck a gas by injecting a jet of liquid at high speed into said suction chamber 2, and

- A diffuser 6 adapted to mix the liquid and the gas and compress, quite abruptly, this mixture by a phenomenon similar to a hydraulic jump, and then gradually compressing the mixture by converting the kinetic energy of the mixture into pressure energy. The suction chamber 2 comprises: a lateral inlet opening 3 through which the gas is fed,

an injection nozzle terminating in a cylindrical tube substantially coaxial with the longitudinal axis X and opening into said suction chamber, and through which a liquid is injected at a high speed into said suction chamber, and

- An outlet opening 4 opposite the nozzle 5 in the direction of flow, coaxial with the longitudinal axis X. The outlet opening 4 therefore forms at the outlet of the suction chamber 2 a shrinkage also called collar. The outlet opening 4 has a substantially circular section of diameter D _c . It has a neck surface Sc, S _c = π.D _c ^2/4, perpendicularly to the longitudinal axis X. A first upstream conduit 3a supplies gas the inlet opening 3 of the suction chamber 2, to one suction pressure p _x with volume flow Qi.

A second upstream pipe 5a feeds the injection nozzle 5 with liquid at a supply pressure p ₂ with a volume flow rate Q ₂ . The nozzle 5 has an end 5b in the suction chamber 2, of internal diameter D ₂ and having a nozzle surface S ₂ , perpendicularly to the longitudinal axis X. This end 5b is placed at a withdrawal distance X ₂ from the outlet opening 4 of the suction chamber 2. The internal diameter D ₂ of the end 5b is possibly less than one internal diameter of the nozzle 5, such that said nozzle has at its end 5b a contracted section.

The injection nozzle 5 optionally comprises liquid channeling means adapted to obtain in the nozzle after said channeling means, a liquid flow little turbulent, without rotation and whose axial velocity distribution is substantially homogeneous, that is, that is, whose axial velocity distribution in a cross-section of the nozzle is substantially constant. The jet of liquid produced by the nozzle 5 in the suction chamber 2 then remains substantially cylindrical to the outlet opening 4 of said chamber. Thus the liquid jet diverges little in this chamber and does not begin to mix with the gas before the diffuser 6. Usually the skilled person considers that having a jet of liquid diverges, helps to form a mixture of liquid and water. gas. However, the inventors have discovered that, on the contrary, this arrangement makes it possible to obtain a better mixture of liquid and gas in the diffuser 6 and a better compression ratio of this mixture.

Means for channeling the liquid in the nozzle

5 may for example be a device having walls extending in the longitudinal direction X, or a device having walls extending in the direction longitudinal X and said walls having a honeycomb shape, or a device comprising a wall in a direction substantially perpendicular to the longitudinal direction X and comprising holes for distributing the liquid flow substantially uniformly in the cross section of the nozzle, or a combination of these devices in the nozzle 5 and arranged one after the other along the longitudinal direction X.

The channeling means can then be placed in the nozzle at a short distance from its end 5b, for example at a distance of between 10 and 30 times the internal diameter D ₂ of the nozzle 5, and preferably equal to 20 times this diameter. .

The diffuser 6 is mounted in the extension of the outlet opening 4 of the suction chamber. This diffuser 6 has along the longitudinal direction X an increasing cross-section from said outlet opening 4. This diffuser 6 is for example of conical shape, flaring in the direction of the flow, and is also substantially coaxial to the longitudinal axis X. It therefore has an upstream diameter substantially equal to the diameter D _c of the outlet opening 4 of the suction chamber 2, and a downstream diameter D ₃ greater than the upstream diameter D _c . The diffuser 6 forms a cone having an angle CXa- The angle (Xd is defined as the total opening angle of the cone, and has a low value, at least in a first part of the diffuser 6.

A downstream pipe 6a outputs the mixture of liquid and gas at the discharge pressure p ₃ . Unlike the devices of the prior art, the ejector device 1 of the invention has a diffuser 6 located immediately at the outlet of the suction chamber 2, that is to say without interposition of a cylindrical tube for mixing liquid and gas, so that the mixture occurs directly in the diffuser 6.

The inventors have found that such an arrangement allowed the ejector device 1 to operate over a wide range of compression ratios τ _c -

The compression ratio x _c is defined as the ratio between the discharge pressure p ₃ and the suction pressure P ₁ of the gas: τ = 2l Pi

The entrainment rate τ _e is defined as the ratio between the volume flow rate Qi of the gas entrained at the inlet opening 3 and the volume flow rate Q ₂ of the liquid injected through the injection nozzle 5: τ _e = _ Qi

Q ₂

The driving pressure parameter% is defined as the ratio between the liquid supply pressure p ₂ supplying the injection nozzle 5 and the gas suction pressure pi:

These adimensional parameters, which can be determined by calculation or measurement on test devices, make it possible to establish design laws to ensure optimized operation of the device.

Tests have shown that the entrainment rate τ _e is related to the compression ratio τ _c . The curves of FIG. 2 show this dependence for several values of suction pressure P ₁ of the gas. The ejector device 1 operates as follows.

The liquid exits into the suction chamber 2 at the end 5b of the nozzle 5, at a pressure equal to the suction pressure pi of the gas and at a speed U ₂ . It forms a rectilinear and substantially cylindrical jet in the suction chamber 2. This high speed jet participates in driving the gas surrounding the jet towards the outlet opening 4 of said suction chamber 2. in the suction chamber two substantially separate phases: a liquid phase, the section of which is a disc, near the longitudinal axis X and a gaseous phase, whose section is a ring in contact with said disk, at a distance from this longitudinal axis and coaxial with the liquid phase. The suction chamber 2 optionally comprises from said distance from the longitudinal axis X radially and longitudinally extending walls, so that the liquid jet does not come into contact with said walls and that the gas contained in this suction chamber 2 is driven with a low turbulent flow, without rotation and whose axial velocity distribution is substantially homogeneous towards the outlet opening 4 of the suction chamber 2.

In the diffuser 6, the flow comprises along the X axis, a first, a second and a third zone. In the first zone of the flow, the two coaxial phases flow relatively independently. In the second flow zone, called the mixing zone, the flow changes its structure rather suddenly and becomes a mixture of the liquid and the gas, which is more and more homogeneous. This change in the structure of the flow is accompanied by a fairly sudden slowing down of the liquid phase and an increase in pressure. In the third flow zone, the two phases flow in the form of a finely mixed emulsion. In this third zone, the flow gradually slows under the effect of the section increase of the diffuser. The kinetic energy of the mixture is then converted into pressure energy. These first, second and third zones of the flow are not separated by clear and sharp transitions, the phenomena being continuous. On the other hand, these zones of the flow can move longitudinally in the diffuser 6, in particular by the effect of variations in the discharge pressure p ₃ downstream of the diffuser 6. Despite such variations, the operation of the ejector device is undisturbed, which shows that such a device is stable and tolerant of variations in operating parameters.

In a simplified manner, the amount of movement of the liquid jet at the inlet of the diffuser 6 is converted into pressure forces applied on both sides of the mixing zone. If one makes an analogy with the compressible flows, this conversion can be seen as a shock. If one makes an analogy with the free surface flows, this conversion can be seen as a hydraulic jump.

The diffuser 6 of conical shape, has a low angle (X _d , but not zero.A conical diffuser 6 with a higher angle OCa, for example greater than 10 degrees, does not cause a hydraulic shock as effective and does not allow achieve such high compression rates.

The inventors have therefore found that there is an optimum angle (Xd, _o pt for which the compression ratio is maximum, for a given U ₂ of injection speed. This optimum angle is in an angular range of values ( Xa is between 0.1 and 7 degrees, and preferably between 1.5 and 4. The value of the optimum angle 0Ca _{/ θpt} is difficult to determine by calculation a priori In a variant of the ejector device 1, the diffuser 6 comprises along the axis X a first conical portion with a first angle OCa / and then a second conical portion with a second angle.The second portion is continuously in the extension of the first portion.The second angle is greater than the first angle. The second angle may be between 5 and 15 degrees, and preferably of the order of 7. The first portion is intended to accommodate the mixing zone, which must operate under a slight angle of divergence in order to maximize the com rate The second portion provides the final pressure recovery by conversion of the kinetic energy of the mixture. This energy conversion can take place at a higher angle of divergence, for example of the order of 10 °, without generating a significant loss of load. Thus, a high compression ratio τ _c is obtained at the same time by the first portion with a small divergence angle and a total length of the shortened diffuser 6.

In another variant of the ejector device 1, the diffuser 6 has a flared shape with a first portion of conical shape with a small first angle, then in continuity a shape having a convex profile. The second convex portion has an incrementally increasing angle along the longitudinal direction X from the first angle to an angle, for example less than 15 degrees, and preferably of the order of 10 degrees. The overall length of the diffuser 6 can thus be further shortened without affecting the compression ratio.

In yet another variant of the ejector device 1, the diffuser 6 has a flared shape with a shape having a convex profile, said convex profile having a gradually increasing angle along the longitudinal direction X from a first angle OCa to an angle , for example less than 15 degrees, and preferably of the order of 10 degrees. The overall length of the diffuser 6 can thus be further shortened.

The first angle αa of the preceding variants preferably has a value in the range of 0.1 ° to 7 °, as indicated above.

In addition, the efficiency η of the ejector device 1 is the ratio between the compression power P _c in the ejector device 1 and the hydraulic power P _h provided.

If it is assumed that the compression is substantially isothermal, the following compression power P _c is obtained:

When a pump draws liquid at the separator located at the discharge of the ejector device 1, the hydraulic power supplied Ph is related to the supply pressure difference p ₂ of liquid in the injection nozzle 5 and the discharge pressure. p ₃ at the output of the diffuser 6, that is to say:

Ph = Q ₂ (P ₂ -Ps) where the following yield η: that one can write according to the adimensional parameters defined previously: ln (τ _c )

The efficiency η of an ejector device 1 can therefore be measured on experimental devices, or be calculated by a mathematical model of hydraulic flow.

The dimensionless geometric ratio R is also defined as being the ratio of the nozzle area S ₂ to the neck area S _c :

As shown by the theoretical curves of FIG. 3, with fixed drive ratio, the efficiency η is linked to this geometric ratio R of the ejector device 1. The efficiency η is maximum for a geometric ratio R between 0.5 and 0 , 9, or more precisely between 0.6 and 0.8. This trend has been confirmed by experimental results.

Experimental tests have also shown that the optimal retraction distance x ₂ for the targeted compression ratios is from one to five times the neck diameter D _c of the outlet opening 4 of the ejector device 1.

Another dimensioning criterion has been defined in introducing a new dimensionless parameter Ψ, called compression parameter and defined as follows: ψ ₌ P3 ^~ Pl

P2-P1

A first advantage of this compression parameter Ψ is that it can be calculated only with the pressure values, measurable on an experimental ejector device.

This compression parameter Ψ can be expressed as a function of the other dimensionless parameters by the following expression: ψ ₌ τ _c -l χ-i

For a given injection speed U ₂ , the efficiency η is related to the value of this compression parameter Ψ of the ejector device 1. The curves of FIG. 4 show this dependence for several values of the driving pressure parameter χ. yield η is then maximum for a compression parameter Ψ in the range of 0.4 to 0.6, or preferably equal to about 0.5. A second advantage of this compression parameter Ψ is that, inversely, it can make it possible to determine the liquid supply pressure p ₂ adapted to obtain the optimum efficiency η _ot of the ejector device 1. Indeed, the preceding interval for the compression parameter Ψ makes it possible to determine that the liquid supply pressure p ₂ must be in the following range:

1.66.P3 -0.66.p | <p ₂ <2.5.p ₃ - 1, 5.p _j with a central value of optimum liquid supply pressure p2, _O pt of:

P2, opt ^{= 2} -P3 - Pl

The ejector device 1 can then be used in a gas compressor 10 as shown in FIG. 5. This gas compressor 10 comprises: a gas inlet 11 at low pressure,

a high-pressure gas outlet 12,

- an internal hydraulic loop circuit. The hydraulic circuit comprises in series: an ejector device 1 supplied on the one hand with a low-pressure gas, coming from the gas inlet 11 and on the other hand with a high-pressure liquid; said ejector device 1 supplying a mixture of gas and liquid at intermediate pressure, - a separating device 13 supplied with a mixture of gas and liquid by the ejector device 1 and supplying on the one hand a gas component at the gas outlet 12 at intermediate pressure and a liquid, at the same intermediate pressure, at a return circuit 14, - a heat exchanger 15 in the return circuit 14 adapted to maintain the temperature of the hydraulic circuit at an adequate level,

a pump 16 fed by the liquid of the return circuit 14 and supplying a liquid of higher pressure to a supply circuit 17.

The supply circuit 17 then supplies the ejector device 1 of the gas compressor 10 with liquid.

The separator device 13 is either a gravity separator or a cyclonic separator. In addition, a bypass circuit 14a bypasses

The heat exchanger 15 of the return circuit 14 and comprises a valve 14b. This branch circuit 14a is adapted to adjust the temperature of the hydraulic circuit.

The heat exchanger 15 is also fed with a cold fluid, for example water, by a cooling circuit 15a and a pump 15b.

The gas compressor 10 operates as follows.

The ejector device 1 mixes the gas with a liquid injected at high speed, and compresses this mixture of gas and liquid at a high pressure. The mixture is separated in the separator device 13, which then supplies at the gas outlet 12 a high pressure gas, and the return circuit 14 also a high pressure liquid. The heat exchanger 15 makes it possible to extract heat from the liquid. The pump 16 increases the pressure of the liquid before supplying the supply circuit 17 and the ejector device 1. As already explained above, the ejector device 1 comprises an injection nozzle adapted to inject at high speed said liquid into its suction chamber. Thus, the injection nozzle of the ejector device 1 performs a relaxation of the liquid (transformation of the pressure energy of the liquid into kinetic energy). The diffuser of the ejection device 1 performs mixing and compression of the mixture. The pump 16 completes the compression of the liquid to reach the inlet supply pressure of the nozzle of the ejector device.

Claims

An ejector device for forming a pressurized mixture of liquid and gas, comprising a suction chamber (2) and a diffuser (6), wherein the suction chamber (2) comprises:

an injection nozzle (5) for producing a jet of liquid flowing in a longitudinal direction (X); a gas inlet (3) for admitting into the suction chamber (2) a gas to be entrained by the liquid jet; and

- an outlet opening (4) for exiting the suction chamber (2), the jet of liquid and the entrained gas; wherein the diffuser (6) is connected to the outlet opening (4) of the suction chamber (2) and has along the longitudinal direction (X) an increasing cross-section from said outlet opening ( 4), the expanding section diffuser (6) being located immediately after the outlet opening (4) of the suction chamber (2), and wherein the diffuser (6) comprises at least a first conical portion having a first angle between 0.1 and 7 degrees.

An ejector device according to claim 1, wherein the first angle is between 1.5 and 4 degrees.

3. Device according to claim 1, wherein the diffuser (6) further comprises a conical second portion continuously in the extension of the first portion in the longitudinal direction (X), said second portion having a second angle greater than the first angle.

4. Device according to claim 3, wherein the second angle is between 5 and 15 degrees, and preferably of the order of 7 degrees.

5. Device according to claim 1, wherein the diffuser (6) further comprises a second portion continuously in the extension of the first portion in the longitudinal direction (X), said second portion having a convex profile shape.

6. Device according to claim 5, wherein the second convex portion has a gradually increasing angle along the longitudinal direction (X) from the first angle to an angle less than 15 degrees, and preferably of the order of 10 degrees.

7. ejector device according to one of the preceding claims, wherein the diffuser (6) is substantially coaxial with the injection nozzle (5) and the outlet opening (4) of the suction chamber.

8. ejector device according to one of the preceding claims, wherein:

the outlet opening (4) has a neck surface S _c perpendicular to the longitudinal direction (X),

the injection nozzle (5) has a nozzle surface S ₂ internally to the nozzle and perpendicular to the longitudinal direction (X), and

a geometric ratio R is the ratio between the nozzle surface S ₂ and the neck surface S _c , said geometric ratio R being between 0.5 and 0.9.

9. ejector device according to one of the preceding claims, wherein:

the injection nozzle (5) comprises an end (5b) in the longitudinal direction (X), the outlet opening (4) has a circular section with a neck diameter D _c , and - The end (5b) is at a withdrawal distance X ₂ of the outlet opening (4), said withdrawal distance X ₂ is between one and five times the neck diameter D _c .

10. ejector device according to one of the preceding claims, wherein the suction chamber (2) has walls in the longitudinal direction (X) extending radially in said suction chamber (2), so that the gas flows into the suction chamber (2) with a low turbulent flow, without rotation and whose axial velocity distribution is substantially homogeneous.

11. ejector device according to one of the preceding claims, wherein the injection nozzle (5) comprises liquid channeling means adapted to obtain in the nozzle after said channeling means, a liquid flow little turbulent, without rotation and whose axial velocity distribution is substantially homogeneous.

12. Device according to claim 11, wherein the channeling means of the liquid in the nozzle (5) are chosen from:

a device having walls extending in the longitudinal direction (X), and

a device having walls extending in the longitudinal direction (X) and said walls having a honeycomb shape, and

- A device comprising a wall in a direction substantially perpendicular to the longitudinal direction (X) and including holes for distributing the liquid flow substantially uniformly in the cross section of the nozzle.

13. Use of an ejector device according to one of claims 1 to 12, wherein:

the suction pressure of the gas pi is measured at the gas inlet (3), the liquid supply pressure p ₂ supplying the injection nozzle (5), the delivery pressure p ₃ of the gas mixture and liquid downstream of the diffuser (6), and

at least one of said pressures is adjusted so that a compression parameter Ψ defined by the following formula: ψ ₌ P3-Pi _r P ₂ -Pi 'is between 0.4 and 0.6.

14. Use of an ejector device according to one of claims 1 to 12, wherein:

the liquid supply pressure p _{2 is} adjusted to plus or minus twenty percent of an optimum pressure P2, o _P t, such that:

P2, opt = 2.P3 ^~ Pl ^•