Patent ID: 12202589

FIG.1shows a supply and cooling device1, which can be arranged within a floating structure capable of transporting and/or storing gas in liquid form, for example within a tank2. This gas is for example natural gas. The gas in liquid form is stored in the tank2at very low temperature. For various reasons, for example naturally during transport, the gas in liquid form can partially evaporate at a headspace200of the tank2. The gas evaporation phenomenon contributes to an increase in the internal pressure of the tank2. Such an increase in the internal pressure must be regulated, for example by evacuating from the tank2the gas in the vapor state having formed in the headspace200of the tank. It is also possible to recondense the gas having evaporated so that the latter returns to liquid form, which leads to a reduction in the internal pressure of the tank2.

The supply and cooling system1comprises a supply circuit3. This supply circuit3is configured to suck in the evaporated gas that has formed in the headspace200of the tank2. The gas can subsequently be used as fuel for a first gas-consuming device5and/or a second gas-consuming device6. By way of example, the first gas-consuming device5can be an engine allowing the propulsion of the floating structure and the second gas-consuming device6can be an auxiliary motor responsible for the electrical supply of the floating structure.

In order to adapt the pressure of the gas circulating in the supply circuit3to raise it to a pressure compatible with the gas-consuming devices, the supply circuit3comprises a compression device10ensuring the compression of the gas. The latter can then supply the gas-consuming devices. If the latter do not require a supply of energy via the gas, this gas can be eliminated, for example via a burner7.

The supply and cooling system also comprises a cooling circuit4. The cooling circuit4is configured, directly or indirectly, to participate in the pressure management of the tank2. The cooling circuit4is configured to circulate a refrigerant, which can for example be the gas sucked into the supply circuit3, or else a third-party refrigerant.

The cooling circuit4is connected to the supply circuit3, more particularly upstream and downstream of the compression device10. The latter can thus participate in the circulation and compression of the refrigerant.

It is understood from the above that the compression device10can participate in the activity of the supply circuit3or in the activity of the cooling circuit4. The determination of such an activity can for example depend on the position of a first valve41arranged on the supply circuit3upstream of the compression device10and the connection to the cooling circuit4, of a second valve42arranged on the supply circuit3downstream of the compression device10and the connection to the cooling circuit4, of a third valve43arranged on the cooling circuit4downstream of the compression device10and the connection to the supply circuit3, and of a fourth valve44arranged on the cooling circuit4upstream of the compression device10and the connection to the supply circuit3.

Thus, when the first valve41and the second valve42are in the open position, and the third valve43and the fourth valve44are in the closed position, the compression device10is integrated into the supply circuit3for the purpose of compressing the gas to supply gas-consuming devices.

When the first valve41and the second valve42are in the closed position, and the third valve43and the fourth valve44are in the open position, the compression device10is integrated into the cooling circuit4for the purpose of compressing the refrigerant to participate in the management of the pressure of the tank2.

The cooling circuit4comprises a turbocompressor13, an internal heat exchanger18and a heat exchanger17. The turbocompressor13comprises a compression member14and a turbine15mechanically connected to each other by a shaft16. The compression member14is arranged upstream of a first pass of the internal heat exchanger18while the turbine15is arranged downstream of this same first pass of the heat exchanger18. The turbine15is set in rotation, and thus drives the shaft16, which itself drives the compression member14. The refrigerant is therefore initially compressed by the compression member14and then passes through the first pass of the internal heat exchanger18and is subsequently expanded by the turbine15. The expansion allows a decrease in the temperature of the refrigerant which circulates through the heat exchanger17, then through a second pass of the internal heat exchanger18. There is therefore an exchange of heat between the refrigerant circulating within the first pass of the internal heat exchanger18and the refrigerant circulating within the second pass of the internal heat exchanger18in order to regulate the temperature of the refrigerant circulating in the cooling circuit4.

The supply and cooling system1also comprises a circuit8for gas in the liquid state, within which circulates gas in liquid form coming from the tank2. The circuit8for gas in the liquid state allows the condensation of the gas having evaporated in the headspace200of the tank2and thus participates in the management of the pressure of the tank.

The gas in the liquid state of the tank2is sucked into the circuit8for gas in the liquid state by means of a pump19. The gas in the liquid state then circulates until it passes through the heat exchanger17. It is thus understood that the heat exchange effected within the heat exchanger17is carried out between the refrigerant circulating in the cooling circuit4and the gas in the liquid state circulating in the circuit8for gas in the liquid state. The gas in the liquid state thus exits cooled from the heat exchanger17.

After having been cooled, the gas in the liquid state can return to the lower part of the tank2via an outlet orifice21. Such an operation contributes to lowering the average temperature of the tank2, which leads to a drop in the saturation pressure of the tank2and thus a drop in pressure in the tank2.

The gas in the cooled liquid state can also be sprayed in the form of a spray in the headspace200of the tank2. To do this, the circuit for gas in the liquid state comprises a spraying member20for spraying of the gas in the liquid state. The spraying of the gas in the liquid state makes it possible to condense the gas having evaporated in the headspace200of the tank2. The condensation of the gas thus reduces the quantity of evaporated gas, which therefore leads to a drop in the internal pressure of the tank2. In order to authorize or not the circulation of the gas in the liquid state, the circuit8for gas in the liquid state comprises an additional valve51.

FIG.2schematically illustrates a structure internal to the compression device10. The compression of fluid within the compression device can be done in various ways, depending on the need to be met by the supply and cooling system. The fluid is compressed within the compression device10by a plurality of compression stages. InFIG.2, the compression device10comprises a first compression stage30and a second compression stage31. Each compression stage is followed by a cooler35. The compression device10can comprise more than two compression stages.

The compression stages can be connected together in series or in parallel. Such a connection is made via a control module9. The control module9comprises a main line32which extends from one end to the other of the compression device10. The first compression stage30and the second compression stage31are both arranged on the main line32.

The control module9also comprises a first peripheral line33, connected to the main line32via a first connection arranged upstream of the first compression stage30and via a second connection arranged downstream of the cooler35of the first compression stage30. The first peripheral line33is therefore configured to cause gas to circulate therein which bypasses the first compression stage30. The first peripheral line comprises a first valve36.

The control module9also comprises a second peripheral line34, connected to the main line32via a first connection arranged downstream of the cooler35of the first compression stage30and via a second connection arranged downstream of the cooler35of the second compression stage31. The second peripheral line34is therefore configured to cause gas to circulate therein which bypasses the first compression stage30.

The second connection of the first peripheral line33is arranged downstream of the first connection of the second peripheral line34. Thus, the gas circulating in the first peripheral line33cannot circulate within the second peripheral line34thereafter. The first connection of the second peripheral line34comprises a second valve37which can for example be a three-way valve.

FIG.3shows a first arrangement of compression stages of the compression device10. InFIG.3, as well as inFIG.4, the solid lines representing the lines of the control module9correspond to lines where a fluid circulates therein, while the dotted lines correspond to lines where the fluid does not circulate. Within this first arrangement, the compression stages are connected in series with respect to one another. The series connection of the compression stages is implemented by the control module9when the gas circulating through the compression device10is intended to supply the gas-consuming devices shown inFIG.1. When the gas is intended to supply said gas-consuming devices, the gas pressure must be favored over the flow rate. The gas must therefore be compressed by all of the compression stages, and a connection of said compression stages in series is more suitable.

When the compression stages are connected in series, the first valve36is closed. The gas therefore circulates only within the main line32and is compressed by the first compression stage30, then passes through the cooler35of the first compression stage30. The gas then reaches the second valve37which maintains the circulation of the gas within the main line32so that the gas is compressed by the second compression stage31, then passes through the cooler35of the second compression stage31before leaving the compression device10.

FIG.4shows a second arrangement of compression stages of the compression device10. InFIG.4, the compression stages are arranged in parallel with respect to one another. The arrangement in parallel is indicated when the compression device10compresses the refrigerant intended to circulate within the cooling circuit, in order to favor the flow rate of refrigerant over its pressure. For this second arrangement of compression stages, the control module9opens the first valve36arranged on the first peripheral line33.

According to this arrangement, the refrigerant circulates within the main line32and separates into two fractions. A first fraction continues its circulation in the main line32and is compressed by the first compression stage30and then passes through the cooler35of the first compression stage30. A second fraction circulates within the first peripheral line33and bypasses the first compression stage30. The second fraction then reaches the main line32and is compressed by the second compression stage31and is cooled by the cooler35of the second compression stage31.

The first refrigerant fraction reaches the second valve37, which directs the refrigerant toward the second peripheral line34and thus bypasses the second compression stage31.

Thus, the two refrigerant fractions have each been compressed by a compression stage. Connecting the compression stages in parallel ensures a higher fluid flow rate than a series connection.

FIG.5shows a second embodiment of the supply and cooling system1. This second embodiment differs from the first embodiment in that it comprises a first compression device11and a second compression device12. The first compression device11is installed in the supply circuit3while the second compression device12is installed within the cooling circuit4. The function of the two compression devices is, however, not defined by their location, as will be described in detail later.

The presence of two compression devices also makes it possible to set up redundancy within the supply and cooling system1. Thus, for example, if one of the compression devices breaks down, the other compression device can still perform its function and keep the supply and cooling system1operational.

The supply circuit3and the cooling circuit4both comprise a plurality of valves allowing access to each of the circuits to each of the compression devices so that the latter can both meet the gas supply needs of the gas-consuming devices or, if necessary, the refrigerant supply needs of the cooling circuit. Thus, in addition to the four valves already found in the first embodiment, the second embodiment of the supply and cooling system1comprises a fifth valve45, a sixth valve46, a seventh valve47, an eighth valve48, a ninth valve49and a tenth valve50.

The fifth valve45and the sixth valve46allow the connection of the first compression device11to the cooling circuit4or else the connection of the second compression device12to the supply circuit3depending on the configuration of the supply and cooling system1.

The seventh valve47and the eighth valve48are installed on either side of the first compression device11and make it possible to isolate the latter when they are in the closed position. Closing these valves is useful in the event of failure of the first compression device11. The ninth valve49and the tenth valve50make it possible for their part to isolate the second compression device12from the rest of the supply and cooling system1.

The supply and cooling system1also comprises a return line60connected to the supply circuit3, upstream of the second gas-consuming device6and the burner7. The return line60makes it possible to recirculate the excess gas circulating within the supply line3and not necessary for the consumption of the gas-consuming devices. Thus, instead of being eliminated by the burner7, the gas circulates in the return line in order to return to the tank2.

In order to recondense the gas circulating in the return line60, the supply and cooling system1comprises a first heat exchanger61and a second heat exchanger62. The first heat exchanger61operates a heat exchange between the gas circulating in the return line60and the gas in the cooled liquid state circulating in the circuit8for gas in the liquid state, within which a branch can be arranged to cross the first heat exchanger61and thus recondense the gas circulating in the return line60.

The second heat exchanger62is arranged upstream of the first heat exchanger61and operates a heat exchange between the gas circulating in the return line and the gas from the supply circuit3at the outlet of the tank2. With the gas leaving the tank2being necessarily at a lower temperature, this makes it possible to cool the gas circulating in the return line60. Said gas is thus pre-cooled initially by crossing the second heat exchanger62, then is recondensed by crossing the first heat exchanger61. At the outlet of the latter, the recondensed gas reaches the circuit8for gas in the liquid state and then the tank2via the outlet orifice21or by being projected via the spraying member20.

FIGS.6,7and8represent the second embodiment of the supply and cooling system1according to three different operating modes. For each of these operating modes, the two devices meet the supply needs of the gas-consuming devices and/or the supply needs of the cooling circuit4. The solid lines represent pipes where a fluid circulates therein while the dotted lines represent pipes where no fluid circulates.

FIG.6therefore shows a first operating mode of the supply and cooling system1. In this first operating mode, the first compression device11is connected to the supply circuit3in order to supply the gas-consuming devices and the second compression device12is connected to the cooling circuit4in order to supply the latter. The compression stages of the first compression device11are therefore arranged in series as shown inFIG.3, while the compression stages of the second compression device12are arranged in parallel as shown inFIG.4. The fifth valve45and the sixth valve46are closed in order to isolate the supply circuit3and the first compression device11from the cooling circuit4and from the second compression device12.

FIG.7shows a second operating mode of the supply and cooling system1. In this second operating mode, the first compression device11and the second compression device12are connected to the supply circuit3in order to supply the gas-consuming devices. The compression stages of the first compression device11and of the second compression device12are therefore both arranged in series as shown inFIG.3. The fifth valve45and the sixth valve46are open in order to connect the second compression device12to the supply circuit3, and the third valve43and the fourth valve44are closed in order to isolate the cooling circuit4from the rest of the supply and cooling system1.

Although the gas in the liquid state circulating in the circuit8for gas in the liquid state is not cooled due to the inactivity of the cooling circuit4, the gas in the liquid state can, however, circulate therein in order to condense the gas possibly circulating in the return line60.

FIG.8shows a third operating mode of the supply and cooling system1. In this second operating mode, the first compression device11and the second compression device12are connected to the cooling circuit4in order to supply the latter. The compression stages of the first compression device11and of the second compression device12are therefore both arranged in parallel as shown inFIG.4. The fifth valve45and the sixth valve46are open in order to connect the first compression device11to the cooling circuit4, and the first valve41and the second valve42are closed in order to isolate the supply circuit3from the rest of the supply and cooling system1.

Because the supply circuit3is inactive, the gas evaporating in the tank2is not sucked in and there is therefore no excess gas circulating in the return line60either. A means for managing the internal pressure of the tank2is therefore the use of the circuit8for gas in the liquid state in order to cool the gas in the liquid state thanks to the cooling circuit4, then to return the gas in the cooled liquid state to the tank2via the spraying member20or the outlet orifice21.

FIG.9shows a third embodiment of the supply and cooling system1. This third embodiment does not comprise either the circuit for gas in the liquid state described previously or the return line of the second embodiment.

The difference of this third embodiment lies in the positioning of the heat exchanger17which here is directly placed at least partially within the tank2. The heat exchanger17therefore participates directly in the management of the pressure of the tank, and not indirectly by cooling the circuit for gas in the liquid state as for the previous embodiments.

The heat exchanger17therefore comprises only a single pass through which the refrigerant passes. The pass may consist of a spiral pipe so that the refrigerant path within the heat exchanger17is longer. The heat exchanger17therefore cools the headspace200of the tank2. The gas having evaporated in the headspace200of the tank2is therefore condensed in the vicinity of the heat exchanger17, and falls back into the tank2. The heat exchanger17therefore acts here as a gravity condenser.

The operation of the two compression devices, of the supply circuit3and of the cooling circuit4is for their part identical to what has been described inFIG.5.

Of course, the invention is not limited to the examples which have just been described and many modifications can be made to these examples without departing from the scope of the invention.

The invention as has just been described clearly achieves its set objective and makes it possible to propose a supply and cooling system for a floating structure comprising at least one compression device capable of meeting various needs depending on the connection of its compression stages. Variants not described here could be implemented without departing from the context of the invention, provided that, in accordance with the invention, they comprise a supply and cooling system in accordance with the invention.