WO2019057541A1

WO2019057541A1 - Device and method for supplying gas with methane number optimised for at least one heat engine, in particular of a ship for transporting liquefied gas

Info

Publication number: WO2019057541A1
Application number: PCT/EP2018/074398
Authority: WO
Inventors: Diouf ABDOULAYE
Original assignee: Gaztransport Et Technigaz
Priority date: 2017-09-20
Filing date: 2018-09-11
Publication date: 2019-03-28
Also published as: RU2020112974A; RU2020112974A3; KR20200055749A; CN111448385A; CN111448385B; FR3071276A1; FR3071276B1

Abstract

The present invention concerns, in particular, a device (10) and a method for supplying gas with methane number optimised for at least one heat engine (12), in particular of a ship for transporting liquefied gas, characterised in that it comprises at least: - a pump (16) intended to be submerged at the bottom of a liquefied gas storage tank (14) and comprising an outlet (16a) for gas in liquid form, - a vaporiser (18) comprising a first circuit having an inlet (18aa) connected to the outlet of the pump and further comprising an outlet (18ab) for gas in liquid form and for gas in gaseous form, - a phase separator (20) comprising an inlet (20a) connected to said outlet of the vaporiser, and further comprising two outlets (20b, 20c) including a first outlet (20c) for gas in liquid form and a second outlet (20b) for gas in gaseous form, and - a heater (22) having a first circuit comprising an inlet (22a) connected to the outlet of the separator and an outlet (22b) for heated gas in gaseous form for the supply of said at least one engine.

Description

Device and method for supplying gas with an optimized methane index of at least one heat engine, in particular a liquefied gas transport vessel TECHNICAL FIELD

The invention relates to a device and method for supplying gas with an optimized methane index of at least one heat engine, in particular a liquefied gas transport vessel.

STATE OF THE ART

A liquefied gas transport vessel, such as liquefied natural gas

(LNG), is equipped with main and auxiliary engines, which are thermal engines fueled with fuel and in particular fuel gas. The fuel gas used for feeding these engines is obtained from the liquefied gas transported.

Liquefied gas comprises heavy gases and light gases, heavy gases having a higher molar mass than light gases and having a higher vaporization temperature than light ones. By way of example, methane is a light gas having a vaporization temperature of the order of -160 ° C. at atmospheric pressure, and n-butane is a heavy gas having a vaporization temperature of the order from 0 ° C to atmospheric pressure.

In known manner, it is preferable that the methane index of the fuel gas intended to supply the engines is as high as possible, in order to avoid the problems of "knocking" (or lapping) in the engines. For this, it is necessary that the fuel gas has a light gas concentration as high as possible.

In practice, the methane index of the fuel gas must be adapted to the engine speed and may therefore vary over time.

The present invention proposes an improvement to the existing technology which makes it possible to supply at least one engine with an optimal gas with an index of methane.

SUMMARY OF THE INVENTION The invention proposes an optimized methane index gas supply device for at least one heat engine, in particular a liquefied gas transport vessel, characterized in that it comprises at least:

a pump intended to be immersed at the bottom of a liquefied gas storage tank and having a gas outlet in liquid form,

a vaporizer comprising a first circuit comprising an inlet connected to the outlet of the pump and further comprising a gas outlet in liquid form and gas in gaseous form,

a phase separator comprising an inlet connected to said outlet of the vaporizer, and further comprising two outlets including a first gas outlet in liquid form (heavy compounds) and a second gas outlet in gaseous form.

According to a first aspect of the invention, the device further comprises: a heater comprising a first circuit comprising an inlet connected to the second outlet of the separator and a heated gas outlet in gaseous form for feeding said at least one a motor.

In order to increase the methane index of the gas intended to supply the engine (s), the invention thus proposes to carry out a phase separation of the liquefied gas and then to keep the gas in gaseous form which is rich in light gases and therefore has a high methane index. The phase separation is initiated in the vaporizer which heats the liquefied gas to a temperature sufficient to vaporize the light gases but not the heavy gases. The mixture is then injected into the separator in which the liquid and gaseous phases separate. The gaseous gas, containing the light gases, is reheated in the heater before feeding the engine (s). This heating is necessary because the temperature of the liquefied gas is very cold in the storage tank (about -160 ° C) and remains cold in the vaporizer and the separator (below 0 ° C). Spraying and separation therefore take place at cold temperatures which are determined to optimize phase separation and to ensure that light gases, and only light gases, vaporize. The heater then has the function of heating the gas in gaseous form to an ideal temperature for the operation of the engine or engines, for example greater than 0 ° C.

In the present application, "light gas" is understood to mean a gas having a molar mass of less than 28 g / mol (such as methane, nitrogen and ethane), and a "heavy gas", a gas having a molar mass greater than 28 g / mol (such as propane, butane, pentane and other hydrocarbons.

The device according to the invention may comprise one or more of the following features, taken separately from one another or in combination with each other:

said vaporizer is of the heat exchanger and / or expander type,

said separator is of the heat exchanger and / or expander type

said vaporizer comprises a second circuit for circulating a heating fluid, such as glycol or steam,

the output of the first circuit of the vaporizer is connected to a first input of a mixer which furthermore comprises a second input connected to the output of the pump and an output connected to the input of the separator,

the device comprises means for controlling the temperature of the liquefied gas in the vaporizer and / or in the separator in order to optimize the vaporization and / or phase separation,

said temperature control means are connected to a valve connected to an inlet of said second circuit of the vaporizer,

said temperature control means are connected to a valve connected to the second inlet of the mixer,

said temperature control means are connected to at least one temperature sensor fitted to said separator,

said means for controlling the temperature are connected to means for controlling the methane number of the gas at the outlet of said heater,

said methane index control means are configured to control said temperature control means and to receive data relating to the liquefied gas and operating parameters of said at least one engine, the device further comprises a gas storage tank in liquid form, a first inlet of which is connected to the first outlet of said separator,

said reservoir comprises at least one output configured to supply:

means for cooling a liquefied gas circulation line, and / or at least one burner,

said at least one outlet of said tank is connected to the burner by a valve and / or a heater,

the device comprises a compressor comprising an inlet intended to be connected to a gas outlet in gaseous form contained in said tank, and comprising a compressed gas outlet,

said compressed gas outlet is connected to the outlet of said heater, with a view to feeding said at least one motor,

said compressed gas outlet is connected to a second inlet of said tank.

said reservoir comprises a second inlet connected to pressurized nitrogen supply means.

The present invention also relates to a method for supplying gas with an optimized methane index of at least one heat engine, in particular a liquefied gas transport vessel, by means of a device as described above, characterized in that

- liquefied gas is taken by the pump at a temperature lower than -160 ° C,

the liquefied gas taken is heated in the vaporizer to reach a temperature between -130 and -10 ° C, and preferably between -100 and -40 ° C, so as to vaporize certain gases, called light gases, the other gases, said heavy gases, remaining in liquid form, separate the liquid and gaseous phases in the separator, and then heat the gas in gaseous form from the separator, at a temperature above 0 ° C, and for example of the order of 20 ° C .

Advantageously:

the liquefied gas is taken by the pump at a pressure of between 7 and 12 bar, and for example 8 bar, the pressure in the vaporizer is between 6 and 10 bar, and for example 7 bar,

the pressure in the separator is between 5 and 7 bar, and is for example 6.2 bar, and

- The pressure in the heater is between 5 and 7 bar, and is for example 6 bar.

The pressure in the tank may be between 1 and 10 bar, for example 2 bar.

According to a second aspect of the invention, the device further comprises: - derivation means comprising a gas outlet in gaseous form for supplying said at least one engine, and at least one input connected to said input of the separator and / or at a gaseous gas outlet of said tank.

In a liquefied gas storage tank, natural evaporation takes place. Gases that evaporate naturally are the lightest gases because they have the lowest evaporation temperatures. In other words, the gases resulting from the natural evaporation of the liquefied gas have a high methane index and are particularly suitable for their direct use, possibly through their heating, for the supply of the engine (s).

The derivation means may comprise at least one valve and / or a compressor.

This device may comprise an exchanger-type heater comprising a first circuit comprising an input connected to the output of the compressor and further comprising a heated gas outlet in gaseous form for the supply of said at least one engine. Alternatively, a heater can be integrated with the compressor.

This device may comprise all or part of the characteristics of the device according to the first aspect of the invention.

According to a third aspect of the invention, the device further comprises: a gas storage tank in liquid form, a first input of which is connected to the first output of said separator, said tank comprising at least one output configured to supply: means for cooling a liquefied gas circulation line, and / or

at least one burner.

This device may comprise all or part of the characteristics of the device according to the first and / or second aspects of the invention.

According to another aspect, the invention proposes a method for controlling the methane index of a feed gas of at least one heat engine, in particular of a liquefied gas transport vessel, characterized in that it includes the steps of:

- withdrawal of liquefied gas,

partial vaporization of the liquefied gas to produce gaseous gas comprising light gases of the liquefied gas, heavy gases of the liquefied gas remaining in liquid form,

characterized in that the methane number of the gaseous gas is controlled by controlling the temperature at which the vaporization takes place.

Vaporization is here a forced evaporation, as opposed to the natural vaporization that takes place in the liquid / gas interface of a liquefied gas storage tank.

The method according to the invention may comprise one or more of the following features or steps, taken separately from each other or in combination with each other:

the temperature is regulated by varying the feed rate of the heating fluid of a circuit of a vaporizer configured to ensure said vaporization,

the temperature is regulated by mixing the liquefied gas after partial vaporization with liquefied gas taken and not subjected to partial vaporization,

the temperature is regulated as a function of the temperature of the gaseous gas,

the temperature is regulated according to data relating to the liquefied gas and / or operating parameters of said at least one engine. BRIEF DESCRIPTION OF THE FIGURES

The invention will be better understood and other details, characteristics and advantages of the present invention will appear more clearly on reading the description which follows, given by way of non-limiting example and with reference to the accompanying drawings, in which:

FIG. 1 is a schematic view of an optimized methane index gas supply device, according to a first embodiment of the invention,

FIG. 2 is a schematic view of an optimized methane index gas supply device, according to a second embodiment of the invention,

FIG. 3 is a schematic view of an optimized methane index gas supply device, according to a third embodiment of the invention,

FIG. 4 is a schematic view of an optimized methane index gas supply device, according to a fourth embodiment of the invention, and

FIG. 5 is a block diagram illustrating steps of a method for controlling the methane number of a feed gas of at least one heat engine.

DETAILED DESCRIPTION

In the following description, the terms "upstream" and "downstream" refer to the flow of a fluid, such as a gas or a liquid, in a pipe or circuit.

FIG. 1 shows a first embodiment of an optimized methane index gas supply device 10 for at least one heat engine 12, in particular of a liquefied gas transport vessel. This engine 12 may be a main engine or an auxiliary engine of the ship.

The vessel comprises at least one tank 14 for storing liquefied gas such as liquefied natural gas (LNG). The tank 14 is at atmospheric pressure or pressurized. The LNG is stored in the tank in liquid form at a temperature of the order of -160 ° C. LNG is naturally evap- orated and some of the LNG vaporizes, so that the tank also contains some gaseous gas. The reference 1 6 designates a pump which is immersed in the LNG and is therefore intended to be supplied with LNG and not gas in gaseous form. The pump 1 6 is therefore preferably located at the bottom of the tank.

In addition to the pump 1 6, the device 10 comprises an evaporator or vaporizer 18, a separator 20 and a heater 22. They are here connected in series one after the other, downstream of the pump 16.

The pump 1 6 comprises an output 1 6a of LNG, that is to say gas in liquid form. The output 1 6a is connected to an input 18aa of a first fluid circuit of the vaporizer 18 which is here a two-circuit heat exchanger. The first vaporizer circuit 18 includes an output 18ab connected to an input 20a of the separator.

The second circuit of the vaporizer 18 comprises an inlet 18ba and an outlet 18bb and allows the circulation of a heating fluid such as steam or glycol. The circulation of a heating fluid in the second circuit makes it possible to raise the temperature of the LNG taken from the tank 14 to a predetermined temperature allowing partial evaporation of the LNG.

Part of the LNG containing light gases, such as nitrogen, methane and ethane, vaporizes, and the other part of the LNG containing heavy gases, such as n-butane, remains in liquid form . The output 18ab of the first circuit of the evaporator is therefore a gas outlet both in gaseous and liquid form.

This two-phase gas mixture supplies the separator 20 via its inlet 20a. A phase separation is sought in the separator 20 which comprises an outlet 20b of gas in gaseous form, and an outlet 20c of gas in liquid form containing the heavy gases. The separator may be of conventional technology, for example honeycomb or gravity.

The outlet 20b of the separator 20 is connected to an inlet 22a of the heater 22, whose function is to raise the temperature of the gas in gaseous form with a view to supplying gas with an optimized methane number of the engine 12 at a suitable temperature. and more precisely at a temperature in the temperature range accepted by the engine 12, ie: between 0 ° C and 60 ° C as indicated below. The device 10 of Figure 1 operates as follows. Liquefied gas is taken by the pump 1 6 at a temperature of less than or equal to -160 ° C, and a pressure for example of the order of 8 bar. The sampled gas is reheated in the vaporizer 18 to reach a temperature between -130 and -10 ° C, and preferably between -100 and -40 ° C, so as to vaporize the light gases, the heavy gases remaining in liquid form . The pressure in the vaporizer 18 is between 6 and 8 bar, and is for example 7 bar. The phase mixture is injected into the separator 20 for separation of these phases. The pressure in the separator is between 5 and 7 bar, and is for example 6.2 bar. The gaseous gas leaving the outlet 20b is heated to a temperature above 0 ° C, for example of the order of 20 ° C, by the heater 22. The pressure in the heater is between 5 and 7 bar , and is for example 6 bar. The engine 12 is thus supplied with fuel gas at a temperature of between 0 ° C. and 60 ° C., of 20 ° C. and a pressure of 6 bar, for example.

FIG. 2 shows another embodiment of the device 10 which furthermore comprises means 24 for checking the methane index of the gas intended to supply the engine 12.

The control means 24 may be in the form of a computer unit comprising in particular means for capturing, recording and saving data, calculation means, and control means.

The control means 24 are intended to receive information such as operating parameters 26 of the engine 12 and data

28 relating to LNG such as its composition, density, temperature, etc.

The parameters 26 characterize in particular the expected engine running speed 12. For an operating speed of the engine 12, there is a desired methane number for the fuel gas supplying the engine. Furthermore, charts exist or can be prepared upstream and recorded in the control means 24, so as to calculate the operating temperature of the vaporizer 18 as a function of the desired methane number and data 28 relating to LNG.

The data 28 can be obtained via a chromatograph which is an instrument capable of determining the composition of a gas or LNG and the concentration of its components. This instrument can be located in the device 10, between the LNG outlet of the tank 14 and the fuel gas inlet of the engines 12.

The means 24 are connected to means 30 for controlling the temperature which are connected to at least one temperature sensor 32 equipping for example the separator 20, and in particular a high stage of the separator so that the temperature of the gaseous gas is measured.

The control means 30 may be similar to a comparator which will receive a signal from the sensor 32 corresponding to a temperature measurement and which will compare it to a predetermined value calculated by the means 24, in order to transmit a signal to the attention of the means 24 for adjusting the operating temperature of the vaporizer 18 and / or the separator 20.

In the example shown, a valve 34 is located on the second circuit of the vaporizer 18, upstream of the inlet 18ba and its flow rate is regulated by the means 24, 30.

In addition, a mixer 36 is mounted between the outlet 18ba and the inlet 20a. This mixer 36 comprises two inputs, one of which is connected to the output 18ba and the other is connected to the output 1 6a of the pump 1 6, upstream of the vaporizer 18. Another valve 38 is located upstream of the inlet 36b mixer and regulates the flow of liquefied gas supplying the mixer. The mixer 36 has the function of mixing a certain amount of liquefied gas taken from the tank 14 a certain amount of two-phase gas leaving the vaporizer 18, to supply the separator 20 with a two-phase gas mixture at an optimized temperature. The flow rate of the valve 38 is regulated by the means 24, 30. The embodiment of FIG. 2 further shows bypass means 40 which are here configured to bypass the separator 20 and the heater 22.

The bypass means 40 comprise an inlet 40a connected to the outlet 18ab of the vaporizer 18 or the mixer 36, and an outlet 40b connected to the outlet 20b of the separator 20 or to the outlet 22b of the heater 22. The bypass means 40 comprise a valve 42 whose flow rate is regulated by the means 24, 30. FIG. 3 shows another embodiment of the device 10 which here comprises a reservoir 44 for storing gas in liquid form, a first inlet 44 a of which is connected to the first outlet 20c of the separator 20.

The reservoir 44 is therefore intended to receive and store the gas in liquid form, comprising the heavy gases, resulting from the partial vaporization and the phase separation of the LNG withdrawn.

The reservoir is for example configured to store the gas in liquid form at a pressure of the order of 2 to 3 bar. The temperature of the gas in the tank can be very low and one of the uses of this gas can be the cooling of LNG circulation lines. Another use of the gas contained in the tank 44 may be to be burned in burners 52 of the DF (dual fuel acronym) or GCU (gas combustion unit) or boiler type, for example for the steam generation used in the ship. This steam can be used to feed the second circuit of the vaporizer 18 or the heater 22. The steam can be used to heat an LNG storage tank of the ship, so that its temperature is not too cold which increases the viscosity of LNG .

The reservoir 44 comprises one or more outlets 44b such as an outlet for cooling a line 45 for circulating LNG, as mentioned in the foregoing. This outlet 44b is connected to a valve 46. The circulation of liquefied gas at a low temperature in a line makes it possible to cool this line, for example before a bunkering operation (filling of a tank of the vessel) in order to limit the thermal shock during of this operation. The reservoir 44 comprises an outlet 44c connected to a valve 48 or to a heater 50 for supplying the burner or burners 52. The outlet 44b can be connected by a loop to the outlet 44c, for example downstream of the valve 48, so that the gas in liquid form which participated in the cooling of the line 45 and which is thus heated by heat exchanger, can be used for feeding the burners. This loop is equipped with a valve 54.

The embodiment of FIG. 3 further comprises bypass means 56 which are here configured to bypass the vaporizer 18, the separator 20 and the heater 22.

The diversion means 56 comprise a compressor 58 having an inlet 58a connected to an outlet 14a of gas in gaseous form (obtained by natural evaporation of the LNG) from the tank 14. The outlet 58b of the compressor is connected directly or via a valve 60 at the outlet 22b of the heater, with a view to supplying natural evaporation gas to the engine 12, and / or to another inlet 44d of the tank 44, also directly or via a valve 62. Alternatively or in additional feature, means 64 for supplying gas, such as nitrogen, under pressure are connected to the inlet 44d of the tank.

Feeding the tank with gas under pressure, for example greater than 6 bar, from the compressor 58 or means 64 makes it possible to force and facilitate the flow of the gas in liquid form through the outlets 44b, 44c of the tank.

The valves 46, 48, 54, 60, 62 can be controlled by the means 24, 30.

The embodiment of FIG. 4 groups together all the characteristics described with reference to the embodiments of FIGS. 1 to 3. FIG. 5 is a block diagram illustrating steps of a method for controlling the methane index of a engine fuel gas 12. The vessel equipped with the engine 12 moves at a given speed, denoted V1. To reach this speed V1, the engine 12 or the main engines of the ship must be at a speed R1. To reach this regime R1, it is necessary that the fuel gas supplying the engine has a minimum methane index MNm. This index MNm is transmitted by the means 24 to the means 30 which will compare it to the current index MNa. This MNa index is calculated from LNG data 28 such as its composition.

If MNa is greater than or equal to MNm, the bypass means 40 or 56 can be used to supply the engine 12 directly with natural or forced evaporation gas which already has an optimum methane number for the engine speed.

In the opposite case, where MNa is less than MNm, the means 24, 30 receive the temperature T1 measured by the sensor 32 and calculate the optimum operating temperature of the vaporizer 18. They control this temperature, so that the quantity of gas of forced evaporation generated in the evaporator achieves the minimum objective in terms of methane index. In practice, iterations take place during which the temperature T1 is measured and monitored several times until the fuel gas has the right composition and therefore the methane index required for the considered regime. As discussed above, the relationship between gas temperature and gas composition is a thermodynamic relationship and several known models exist. The means 24, 30 control the valves 34, 38 accordingly.

The relationship between the gas composition and its methane number is generally defined by the engine manufacturer or can be obtained by EN 16726.

Claims

1. Apparatus (10) for supplying gas with an optimized methane number of at least one heat engine (12), in particular a liquefied gas transport vessel, characterized in that it comprises at least:

a pump (16) intended to be immersed at the bottom of a tank (14) for liquefied gas storage and comprising an outlet (1 6a) of gas in liquid form,

a vaporizer (18) comprising a first circuit comprising an inlet (18aa) connected to the outlet of the pump and further comprising an outlet (18ab) of gas in liquid form and of gas in gaseous form,

a phase separator (20) comprising an inlet (20a) connected to said outlet of the vaporizer, and further comprising two outlets (20b, 20c) of which a first liquid gas outlet (20c) and a second outlet (20b) ) gas in gaseous form, and

- A heater (22) having a first circuit comprising an inlet (22a) connected to the second outlet of the separator and an outlet (22b) of gas-heated gas for supplying said at least one engine.

2. Device (10) according to the preceding claim, wherein said vaporizer (18) comprises a second circulation circuit of a heating fluid, such as glycol or steam.

3. Device (10) according to one of the preceding claims, wherein the output (18ab) of the first vaporizer circuit (18) is connected to a first input of a mixer (36) which further comprises a second connected input at the outlet (1 6a) of the pump (1 6) and an outlet connected to the inlet (20a) of the separator (20).

4. Device (10) according to one of the preceding claims, wherein it comprises means (30) for controlling the temperature of the liquefied gas in the vaporizer (18) and / or in the separator (20) to optimize vaporization and / or phase separation.

5. Device (10) according to the preceding claim, in accordance with claim 2, wherein said means (30) for controlling the temperature are connected to a valve (34) connected to an inlet of said second circuit of the vaporizer (18) .

6. Device (10) according to the preceding claim, in accordance with claim 3, wherein said means (30) for controlling the temperature are connected to a valve (38) connected to the second inlet of the mixer (36).

7. Device according to one of claims 4 to 6, wherein said means (30) for controlling the temperature are connected to at least one temperature sensor (32) equipping said separator (20).

8. Device (10) according to one of claims 4 to 7, wherein said means (30) for controlling the temperature are connected to means (24) for controlling the methane index of the gas output of said heater (22).

9. Device (10) according to the preceding claim, wherein said means (24) for monitoring the methane index are configured to control said means (30) for controlling the temperature and for receiving data (28) relating to the liquefied gas and operating parameters (26) of said at least one engine (12).

10. Device (10) according to one of the preceding claims, wherein it further comprises a reservoir (44) for storing gas in liquid form, a first inlet (44a) is connected to the first outlet (20c) of said separator .

1 1. Device (10) according to the preceding claim, wherein said reservoir (44) comprises at least one outlet (44b, 44c) configured to supply:

means for cooling a line (45) for circulating liquefied gas, and / or

at least one burner (52).

12. Device (10) according to the preceding claim, wherein said at least one outlet (44b, 44c) of said tank (44) is connected to the burner (52) by a valve (46, 48, 54) and / or a heater (50).

13. Device (10) according to one of the preceding claims, wherein it comprises a compressor (58) having an inlet (58a) intended to be connected to an outlet (14a) of gaseous gas contained in said vessel (14). ), and having an outlet (58b) of compressed gas.

14. Device (10) according to the preceding claim, wherein said outlet (58b) of compressed gas is connected to the outlet (22b) of said heater (22), for the supply of said at least one motor (12).

15. Device (10) according to claim 13 or 14, according to one of claims 10 to 12, wherein said outlet (58b) of compressed gas is connected to a second inlet (44d) of said reservoir (44).

6. Device (10) according to one of claims 10 to 12, wherein said reservoir (44) comprises a second inlet (44d) connected to means (64) for supplying nitrogen under pressure.

17. Process for supplying gas with an optimized methane number of at least one heat engine, in particular a liquefied gas transport vessel, by means of a device (10) according to one of the preceding claims, characterized in that

- liquefied gas is taken by the pump (1 6) at a temperature lower than -160 ° C,

the liquefied gas taken off is heated in the vaporizer (18) to reach a temperature of between -130 ° C. and -10 ° C., and preferably between -100 ° C. and -40 ° C., so as to vaporize certain gases, referred to as light gases; the other gases, called heavy gases, remaining in liquid form,

- separating the liquid and gaseous phases in the separator (20), then

- Reheating the gaseous gas from the separator (20) at a temperature above 0 ° C, for example of the order of 20 ° C.

18. Process according to the preceding claim, in which:

the liquefied gas is taken by the pump (1 6) at a pressure of between 7 and 9 bars, and for example 8 bars, the pressure in the vaporizer (18) is between 6 and 12 bar, and for example 7 bar,

the pressure in the separator (20) is between 5 and 7 bar, and is for example 6.2 bar, and

- The pressure in the heater (22) is between 5 and 7 bar, and is for example 6 bar.

19. Method according to the preceding claim, wherein the device being as defined in one of claims 10 to 12, wherein the pressure in the reservoir (44) is between 1 and 10 bar, for example 2 bar.