System for supplying gas to a floating structure

Abstract

The present invention relates to a system (1) for supplying gas to an apparatus consuming high-pressure gas (4) and to an apparatus consuming low-pressure gas (5) of a floating structure, comprising: - a first supply circuit (2), - a high-pressure evaporator (11), - a second supply circuit (3), and - a gas return line (14); the supply system (1) comprising a first heat exchanger (6) and a second heat exchanger (7), the first supply circuit (2) comprising a second pumping device (10) inserted between the first heat exchanger (6) and the second heat exchanger (7), characterised in that the supply system (1) comprises a recirculation branch (15), the first supply circuit (2) comprising a first bypass branch (16) and a second bypass branch (17).

Description

[0001] DESCRIPTION

[0002] Title of the invention: Gas supply system for a floating structure

[0003] The present invention relates to the field of floating structures for transporting and / or storing gas in the liquid state and more particularly concerns a gas supply system for consumer devices included within such floating structures, as well as a method for managing such a system.

[0004] During a journey made by a floating structure comprising a tank of gas in the liquid state intended to be consumed and / or to be delivered to a destination point, said floating structure may be able to use at least part of said gas in the liquid state in order to supply at least one of its engines, via a gas supply system. This is the case for ships equipped with a high-pressure propulsion engine of the ME-GI type. In order to supply this type of engine, the gas must be compressed to very high pressure by special compressors capable of compressing the gas up to 300 bars absolute, but such compressors are expensive, generate significant maintenance costs and induce vibrations within the ship.

[0005] An alternative to installing these high-pressure compressors is to vaporize the gas into a liquid state at 300 bars absolute, in particular using a high-pressure pumping device, before it is sent to the propulsion engine. Since such a solution does not allow the removal of the gas in vapor state (or BOG, which in English stands for "Boil-Off Gas") naturally forming within a tank containing at least part of the cargo, a low-pressure compression device is then installed to supply an auxiliary engine, capable of consuming the gas in vapor form at low pressure.

[0006] It is also known to recirculate, downstream of the compression device, the excess gas in vapor form and to reliquefy it by means of one or more heat exchanges, operated by one or more heat exchangers, between the gas in the liquid state intended to supply the high-pressure propulsion engine and the gas in the vapor state intended to be reliquefied. A disadvantage may arise within this supply system if the compression device used is an oil compressor, which is the case in the majority of arrangements of such a system. Although oil compressors are provided with filtration means preventing oil from leaving the compressor to circulate within the supply system, there is always a small quantity of oil which manages to leave the compressor and which subsequently circulates in the branches of the supply system circuit.

[0007] If the oil subsequently circulates within the heat exchanger(s) mentioned above, the oil is then cooled and can solidify within the heat exchanger. Over time, the solidified oil accumulates within at least one heat exchanger, clogging it, thus seriously impairing the heat treatment capabilities of said heat exchanger. It is possible to change the compressor to an oil-free compressor, but changing a compressor is restrictive and expensive.

[0008] The present invention addresses this problem and as such proposes a system for supplying gas to at least one high-pressure gas-consuming device and to at least one low-pressure gas-consuming device of a floating structure comprising at least one tank configured to contain the gas, the supply system comprising: at least one first supply circuit configured to supply gas to the high-pressure gas-consuming device, comprising at least one first pumping device configured to pump the gas taken in the liquid state from the tank, at least one high-pressure evaporator configured to evaporate the gas circulating in the first supply circuit, at least one second supply circuit configured to supply gas to the low-pressure gas-consuming device,comprising at least one compression device configured to compress gas taken in the vapor state from the tank to a pressure compatible with the needs of the low-pressure gas-consuming device, at least one gas return line connected to the second supply circuit downstream of the compression device and extending to the tank, the supply system comprising at least one first heat exchanger and at least one second heat exchanger each configured to carry out a heat exchange between the gas in the vapor state circulating in the return line and the gas in the liquid state circulating in the first supply circuit, the first supply circuit comprising a second pumping device interposed between the first heat exchanger and the second heat exchanger,characterized in that the supply system comprises a recirculation branch connected at the inlet to a divergence point arranged on the return line between the first heat exchanger and the tank, the recirculation branch comprising an outlet connected to the second supply circuit between the tank and the compression device, the first supply circuit comprising a first bypass branch arranged in parallel with a first portion of the first through supply circuit of the first heat exchanger and a second bypass branch arranged in parallel with a second portion of the first through supply circuit of the second heat exchanger.,

[0009] The supply system, in addition to being capable of supplying gas-consuming appliances while reliquefying excess gas in the vapor state, is also capable of implementing a configuration ensuring the elimination of oil that has accumulated within one or more heat exchangers.

[0010] To do this, the recirculation branch makes it possible to form a loop of gas in the vapor state between the second supply circuit and the return line so that the gas in the vapor state circulates in a loop within the heat exchangers. Such a loop can be semi-closed or fully closed depending on an embodiment of the supply system according to the invention. In the case of a semi-closed loop, in addition to ensuring a loop circulation of the gas in the vapor state in the heat exchangers, the gas in the vapor state contained in the tank is always sucked by the compression device to circulate in the second supply circuit, and the low-pressure gas-consuming device is always supplied. Such a configuration corresponds to a first embodiment of the supply system according to the invention.The circulation of the gas in the vapor state within the heat exchangers causes a rise in temperature within them and a melting of the oil that has accumulated within them, which can then be evacuated by being carried along by the flow of gas in the vapor state. The oil then circulates to the compression device where it is filtered and therefore stored.

[0011] In order to ensure a temperature rise in the heat exchangers, only gas in the vapor state must circulate therein, the gas in the liquid state circulating in the first supply circuit being at a temperature too low to guarantee such a temperature rise. The supply of the high-pressure gas-consuming device must however be ensured, including during the melting operation of the oil contained in the heat exchangers. The bypass branches thus ensure the gas supply to the high-pressure consuming device without the gas in the liquid state disturbing the temperature rise of the heat exchangers. The treatment of the gas in the liquid state is thus initially only ensured by the second pumping device, and the high-pressure evaporator alone evaporates the gas in the liquid state so that the gas is compatible with the needs of the high-pressure gas-consuming device.

[0012] As mentioned above, the first gas supply circuit is used to meet the fuel requirements of the high-pressure gas-consuming device. The latter may, for example, be the means of propulsion of the floating structure, for example an ME-GI engine. The first supply circuit extends from the tank to the high-pressure gas-consuming device. The first pumping device is installed at the bottom of the tank and pumps the gas in the liquid state so that it can circulate in the first supply circuit. The second pumping device is used to increase the pressure of the gas in the liquid state circulating in the first supply circuit, so that it has a pressure compatible with supplying the high-pressure gas-consuming device.The positioning of the second pumping device between the two heat exchangers is particularly advantageous because it ensures both efficient thermal treatment of the gas in the vapor state circulating in the return line by the gas in the liquid state circulating in the first supply circuit, while avoiding premature evaporation of said gas in the liquid state which could damage the second pumping device. When the gas in the liquid state bypasses the heat exchangers, it continues to be pumped by the second pumping device.

[0013] Since the gas must be in the vapor state to be able to supply the high-pressure gas-consuming device, the high-pressure evaporator ensures the evaporation of the gas before its supply to the high-pressure gas-consuming device. The high-pressure evaporator is the site of an exchange of calories between the gas in the liquid state circulating in the first supply circuit and a heat transfer fluid, for example glycolated water, sea water or water vapor. The latter must be at a sufficiently high temperature to create a change of state of the gas so that it passes into the vapor or supercritical state in order to supply the high-pressure gas-consuming device, whether the gas in the liquid state has previously passed through the heat exchangers or not.

[0014] In a configuration for reliquefying excess gas in the vapor state, before the gas in the liquid state circulating in the first supply circuit is vaporized by means of the high-pressure evaporator, the gas in the liquid state passes through the first heat exchanger, then the second heat exchanger. For this, the first heat exchanger and the second heat exchanger are connected to each other by a section of the first supply circuit so that the gas in the liquid state can pass through the two heat exchangers successively, said section advantageously comprising the second pumping device. The temperature of said gas in the liquid state thus tends to increase before it passes through the high-pressure evaporator. Thus, the gas circulating in the first supply circuit can be in a two-phase state at the outlet of the second heat exchanger.

[0015] Generally speaking, the gas contained in the tank can pass naturally, or forced by the floating structure, into the vapor state. The gas within the tank passing into the vapor state must be evacuated so as not to create excess pressure within the tank.

[0016] Such a function is provided by the second gas supply circuit of the low-pressure gas-consuming device. Such a second supply circuit extends from the tank to the low-pressure gas-consuming device. The latter may, for example, be an auxiliary engine such as an electric generator. The compression device arranged on the second supply circuit is responsible for sucking the gas present in the tank headspace in order to be able to both supply the low-pressure gas-consuming device and regulate the pressure within the tank. Such a compression device may be an oil compressor.

[0017] At the outlet of the compression device, the gas in the vapor state can supply the low-pressure gas-consuming device, or circulate through the return line if the low-pressure gas-consuming device does not require fuel or if the quantity of gas in the vapor state is greater than the supply requirement of the low-pressure gas-consuming device. The return line being connected downstream of the compression device, the gas in the vapor state sucked in by said compression device can therefore circulate therein, as can a tiny quantity of oil having escaped from the compression device if the latter is oil-operated.

[0018] The gas in the vapor state circulating in the return line first passes through the second heat exchanger, then the first heat exchanger, before joining the first supply circuit. Thanks to the exchange of calories taking place between the gas in the liquid state circulating in the first supply circuit and the gas in the vapor state circulating in the return line, the temperature of the gas in the vapor state decreases while passing through the heat exchangers, until said gas reliquefies and returns to the liquid state substantially at the outlet of the first heat exchanger and can circulate to the tank thereafter. The traces of oil accompanying the gas in the vapor state also pass through the heat exchangers and cool and solidify within one or other of said heat exchangers.Although the amount of oil escaping from the compression device is tiny, the buildup of solidified oil over time eventually impairs the proper functioning of the fuel system.

[0019] As mentioned above, the recirculation branch allows a loop to be formed so that the gas can circulate from the return line to the second supply circuit. This allows the vapor gas to be circulated a plurality of times within the heat exchangers, while the circulation of liquid gas is interrupted in these same heat exchangers. Since the vapor gas is at a higher temperature, this causes a rise in temperature within the heat exchangers, melting the accumulated oil aggregates and removing them. Once the oil has been completely removed from the heat exchangers, the configuration of the supply system can again be modified in order to be able to implement the reliquefaction of the excess vapor gas again.

[0020] According to a feature of the invention, the supply system comprises a recirculation valve arranged on the recirculation branch and a return valve arranged on the return line between the point of divergence and the tank. The valves are capable of switching between an open position and a closed position in order to respectively authorize or prohibit the circulation of gas in the branch or in the circuit in question. The return valve controls the return of the gas to the tank after its reliquefaction. The recirculation valve controls the circulation of the gas in the vapor state so that the latter circulates in a loop through the heat exchangers to increase their temperature. Thus, when one of the valves among the recirculation valve and the return valve is open, the other valve is necessarily closed.

[0021] In the case of a loop circulation within the heat exchangers according to a semi-closed loop, that is to say according to the first embodiment, the recirculation valve also ensures an expansion of the gas in the vapor state which has previously been compressed by the compression device. This expansion makes it possible to balance the pressure between the gas in the vapor state coming from the return line and the gas in the vapor state leaving directly from the tank.

[0022] According to a feature of the invention, the supply system comprises a bypass valve arranged on the first bypass branch and a control valve arranged on the first portion of the first supply circuit. The control valve and the bypass valve allow the gas in the liquid state circulating in the first supply circuit to pass through the first exchanger or to bypass the latter so that it rises in temperature in order to melt the oil accumulated therein. Just as for the valves previously described, the control valve and the bypass valve are capable of switching between an open position and a closed position in order to respectively authorize or prohibit the circulation of gas in the branch or in the circuit in question.

[0023] According to a feature of the invention, the control valve is arranged on the first portion upstream of the first heat exchanger, the supply system comprising a regulating valve arranged on the first portion downstream of the first heat exchanger. Thus, advantageously, the first heat exchanger can be completely isolated from the circulation of gas in the liquid state within the first supply circuit. This makes it possible to prevent traces of gas in the liquid state from circulating within the first heat exchanger and disturbing the temperature increase thereof and / or evaporating therein and generating an undesired pressure increase. Thus, advantageously, the control valve and the regulating valve are opened simultaneously or closed simultaneously.

[0024] According to a characteristic of the invention, the power supply system comprises a bypass member arranged on the second bypass branch and a control member arranged on the second portion of the first power supply circuit.

[0025] According to another characteristic of the invention, the control member is arranged on the second portion upstream of the second heat exchanger, the supply system comprising a regulating member arranged on the second portion downstream of the second heat exchanger. The bypass member, the control member and the regulating member are the counterpart of the eponymous valves described previously, but applied to the second heat exchanger in place of the first heat exchanger. The operation of the bypass member, the control member and the regulating member is therefore respectively identical to the operation of the bypass valve, the control valve and the regulating valve.

[0026] According to a feature of the invention, the supply system comprises a first measuring member and a second measuring member configured to respectively measure a pressure of the gas circulating in the return line at the inlet and outlet of the first heat exchanger and / or at the inlet and outlet of the second heat exchanger. The measuring members make it possible to detect whether it is time to operate the supply system in order to eliminate potential oil aggregates that have accumulated in one and / or the other of the heat exchangers.

[0027] Such a need can be detected by measuring a pressure drop of the gas in the vapor state at the outlet of at least one of the heat exchangers compared to before entering this same heat exchanger. The pressure drop is manifested by a pressure differential of the gas between its inlet and its outlet of at least one of the heat exchangers. If the pressure differential is high, for example from 40 mbar for the first heat exchanger or from 200 mbar for the second heat exchanger, this means that oil aggregates are present in significant quantities and that they are detrimental to the proper functioning of the supply system. Such a pressure differential can be measured at one of the heat exchangers or at both heat exchangers simultaneously.

[0028] It may also be advantageous to calculate a change in the pressure differential over time in order to determine from what point it is appropriate to implement the evacuation of the accumulated oil within at least one of the heat exchangers. For example, a variation in the pressure differential of more than 150%, preferably more than 100% relative to the pressure differential when the heat exchangers do not have oil aggregates, is considered to be the point at which the evacuation of the accumulated oil is necessary.

[0029] According to a characteristic of the invention, the supply system comprises a first measuring device and a second measuring device configured to respectively measure a temperature of the gas circulating in the first supply circuit at the inlet of the first heat exchanger and of the gas circulating in the return line at the outlet of the first heat exchanger and / or of the gas circulating in the first supply circuit at the inlet of the second heat exchanger and of the gas circulating in the return line at the outlet of the second heat exchanger.

[0030] Alternatively or additionally to the pressure measurement of the measuring devices, detection of a need to eliminate oil aggregates present within one and / or the other can be done using a temperature differential between a temperature of the gas in the liquid state circulating in the first supply circuit at the inlet of one of the heat exchangers and a temperature of the gas circulating in the return line at the outlet of this same heat exchanger. The temperature differential is therefore calculated from measurements carried out relating to a single heat exchanger. Too high a differential between these two temperatures means that the heat exchange carried out in the heat exchanger in question is not sufficiently efficient due to the presence of too large a quantity of oil aggregates in the heat exchanger in question.The temperature differential from which it is considered necessary to evacuate the oil can be of the order of 10°C, preferably 5°C.

[0031] It may also be advantageous to calculate a change in the temperature differential over time in order to determine from what point it is appropriate to implement the evacuation of the oil accumulated within at least one of the heat exchangers.

[0032] The measurement of the pressure differential described above and the temperature differential can be implemented simultaneously in order to perform a double check of the need to eliminate oil aggregates within one and / or the other heat exchanger. During such an operation, the pressure differential can be monitored over time in order to check whether the removal of oil aggregates is taking place correctly and at what point such an operation can be stopped.

[0033] According to a characteristic of the invention, the supply system comprises an auxiliary supply branch connected at the input to the second supply circuit between the tank and the outlet of the recirculation branch, the auxiliary supply branch comprising an outlet connected to the second supply circuit between the connection to the return line and the low-pressure gas-consuming device, the auxiliary supply branch comprising a compression member. Such a configuration constitutes a second embodiment according to the invention.

[0034] In this second embodiment, the gas in the vapor state circulates within the heat exchangers in a completely closed loop. It is understood that the evacuation of the gas in the vapor state from the tank and the supply of the low-pressure gas-consuming device is done thanks to the auxiliary supply branch, while the heat exchangers increase in temperature over time thanks to a defined and constant quantity of gas in the vapor state which circulates in a loop between the second supply circuit and the return line.

[0035] According to a characteristic of the invention, the second supply circuit comprises a first auxiliary valve arranged between the inlet of the auxiliary supply branch and the outlet of the recirculation branch and a second auxiliary valve arranged between the connection to the return line and the outlet of the auxiliary supply branch. Still according to the second embodiment of the supply system according to the invention, the first auxiliary valve and the second auxiliary valve allow the total isolation of the gas loop in the vapor state guaranteeing the increase in the temperature of the heat exchangers. Thus, the tank and the low-pressure gas-consuming device are only in communication with each other via the auxiliary supply branch. The auxiliary valves are therefore in the closed position when it is necessary to evacuate the oil accumulated in at least one of the heat exchangers.According to a characteristic of the invention, the first pumping device is configured to raise a pressure of the gas in the liquid state to a value of between 6 and 17 bars and the second pumping device is configured to raise the pressure of the gas in the liquid state to a value of between 30 and 400 bars. The increase in the pressure of the gas by the second pumping device depends on the type of gas transported and / or stored. Thus, the pressure of the gas in the liquid state is raised to a value of between 30 and 400 bars absolute, in particular for use with ammonia or hydrogen, between 30 and 70 bars absolute for use with liquefied petroleum gas, and preferably between 150 and 400 bars absolute for use with ethane, ethylene or even with liquefied natural gas consisting mainly of methane.

[0036] According to a characteristic of the invention, the compression device is configured to raise a gas pressure to a value between 6 and 20 bars absolute.

[0037] The invention also covers a floating structure for storing and / or transporting gas in the liquid state, comprising at least one tank of gas in the liquid state, at least one high-pressure gas-consuming device, at least one low-pressure gas-consuming device and at least one gas supply system for these devices as described above.

[0038] The invention also covers a gas management method implemented by a supply system as described above, used within a floating structure comprising at least one tank configured to contain the gas, during which: the gas is circulated in the liquid state in the first supply circuit within the first heat exchanger and the second heat exchanger and the gas is circulated in the vapor state within the return line to the tank according to a first configuration, the gas is circulated in the liquid state in the first supply circuit within the first bypass branch and the second bypass branch and the gas is circulated in the vapor state within the recirculation branch according to a second configuration.It follows from the above that the first configuration corresponds to the configuration where the excess gas in the vapor state is reliquefied before returning to the tank using the gas in the liquid state circulating in the first feed circuit and the heat exchangers, while the second configuration corresponds to the configuration where the gas in the vapor state circulates in a loop in the heat exchangers in order to create a temperature increase ensuring the elimination of the oil aggregates that have accumulated within said heat exchangers. The feed system can switch from the first configuration to the second configuration if necessary, and then back to the first configuration once the oil has been completely evacuated from the heat exchanger(s).The first configuration corresponds to the major operating configuration of the power system while the second configuration is implemented exceptionally and temporarily.

[0039] Such a gas management method is thus particularly suitable for a floating structure for storing and / or transporting gas in the liquid state as described above.

[0040] According to a feature of the method, the return valve, the control valve, the regulating valve, the control member and the regulating member are open while the recirculation valve, the bypass valve and the bypass member are closed when the first configuration is active, the return valve, the control valve, the regulating valve, the control member and the regulating member being closed while the recirculation valve, the bypass valve and the bypass member being open when the second configuration is active.

[0041] According to a characteristic of the method, a selection between the first configuration and the second configuration is dependent on a pressure difference between the pressure measured by the first measuring member and the pressure measured by the second measuring member of the gas circulating in the return line at the inlet and outlet of the first heat exchanger and / or at the inlet and outlet of the second heat exchanger.According to another characteristic of the method, a selection between the first configuration and the second configuration is dependent on a temperature difference between the temperature measured by the first measuring device and the temperature measured by the second measuring device respectively of the gas circulating in the first supply circuit at the inlet of the first heat exchanger and of the gas circulating in the return line at the outlet of the first heat exchanger and / or of the gas circulating in the first supply circuit at the inlet of the second heat exchanger and of the gas circulating in the return line at the outlet of the second heat exchanger.

[0042] A calculation of one or both of these differentials at one or both heat exchangers can result in a change in the configuration of the feed system. The valves and components then change position to change the configuration.

[0043] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0044] [fig 1] is a schematic representation of a first embodiment of a power supply system according to the invention,

[0045] [fig 2] illustrates a first configuration of the first embodiment of the power supply system according to the invention,

[0046] [fig 3] illustrates a second configuration of the first embodiment of the power supply system according to the invention,

[0047] [fig 4] is a schematic representation of a second embodiment of the power supply system according to the invention.

[0048] The terms "upstream" and "downstream" used in the following description are used to express positions of elements within gas circuits in the liquid state or in the vapor state and refer to the direction of circulation of said gas within said circuit. Figure 1 represents a first embodiment of a gas supply system 1 arranged on a floating structure. The supply system 1 makes it possible to circulate gas which may be in the liquid state, in the vapor state, in the two-phase state or in the supercritical state, and this from a storage and / or transport tank 8, and to a high-pressure gas-consuming device 4 and / or a low-pressure gas-consuming device 5, in order to supply the latter with fuel.

[0049] Said floating structure may for example be a ship capable of storing and / or transporting gas in the liquid state. The supply system 1 is in this case capable of using the gas in the liquid state that the floating structure stores and / or transports to supply the high-pressure gas-consuming device 4, which may for example be a propulsion engine, and the low-pressure gas-consuming device 5, which may for example be an electric generator supplying the floating structure with electricity.

[0050] In order to ensure the circulation of the gas contained in the tank 8 to the high-pressure gas-consuming device 4, the supply system 1 is provided with a first gas supply circuit 2. The first supply circuit 2 comprises a first pumping device 9 arranged within the tank 8. The first pumping device 9 makes it possible to pump the gas in the liquid state and to circulate it in particular within the first supply circuit 2. By sucking in the gas in the liquid state, the first pumping device 9 also makes it possible to raise the pressure thereof to a value between 6 and 17 bars.

[0051] The gas in the liquid state, in a direction of circulation going from the tank 8 to the high-pressure gas-consuming device 4, passes through a first heat exchanger 6, is pumped by a second pumping device 10 and passes through a second heat exchanger 7. The details concerning the two heat exchangers 6, 7 will be described later.

[0052] After passing through the second heat exchanger 7, the gas circulates to a high-pressure evaporator 11. The high-pressure evaporator 11 makes it possible to modify the state of the gas circulating in the first supply circuit 2 in order to change it to the vapor or supercritical state. Such a state makes the gas compatible with supplying the high-pressure gas-consuming device 4. The evaporation of the gas to the liquid state can, for example, be done by heat exchange with a heat transfer fluid at a temperature high enough to evaporate the gas to the liquid state, here glycolated water, sea water or water vapor.

[0053] The increase in gas pressure is ensured by the second pumping device 10 when it pumps the gas in the liquid state. The second pumping device 10 makes it possible to raise the pressure of the gas in the liquid state to a value between 30 and 70 bars for use with liquefied petroleum gas, and preferably between 150 and 400 bars for use with ethane, ethylene or even with liquefied natural gas consisting mainly of methane.

[0054] Thanks to the combination of the second pumping device 10 and the high-pressure evaporator 11, the gas is at a pressure and in a state compatible for supplying the high-pressure consumer device 4. Such a configuration makes it possible to avoid the installation of high-pressure compressors on the first supply circuit 2 which present cost constraints and generate strong vibrations.

[0055] Within the tank 8, a portion of the gas cargo can naturally pass into the vapor state and diffuse into a tank headspace 12. In order to avoid overpressure within the tank 8, the gas in the vapor state contained in the tank headspace 12 must be evacuated. However, the first supply circuit 2 is configured to use the gas in the liquid state to supply the high-pressure gas-consuming device 4.

[0056] The supply system 1 therefore comprises a second gas supply circuit 3, which uses the gas in the vapor state to supply the low-pressure gas-consuming device 5. The second supply circuit 3 therefore extends between the tank canopy 12 and the low-pressure gas-consuming device 5. In order to suck up the gas in the vapor state contained in the tank canopy 12, the second supply circuit 3 comprises a compression device 13. In addition to sucking up the gas in the vapor state, the compression device 13 also makes it possible to raise a pressure of the gas in the vapor state circulating in the second supply circuit 3 to a pressure of between 6 and 20 bars absolute, so that the gas in the vapor state is at a pressure compatible with supplying the low-pressure gas-consuming device 5.The second supply circuit 3 thus makes it possible to supply the low-pressure gas-consuming device 5, while regulating the pressure within the tank 8 by sucking in the gas in the vapor state present in the tank ceiling 12.

[0057] The presence of the gas in the vapor state in excessive quantity within the tank head 12 causes an overpressure within the tank 8. It is therefore necessary to evacuate the gas in the vapor state in order to lower the pressure within the tank 8. The excess gas in the vapor state can then for example be eliminated by a burner 18. However, the supply system 1 according to the invention comprises a return line 14 connected to the second supply circuit 3 downstream of the compression device 13 with respect to a direction of circulation of the gas in the vapor state circulating in the second supply circuit 3. Depending on the direction of circulation of the gas in the vapor state circulating in the return line 14, said gas passes through the second heat exchanger 7 initially, then passes through the first heat exchanger 6.The exchange of calories taking place within the first heat exchanger 6 and the second heat exchanger 7 is therefore between the gas in the liquid state circulating in the first supply circuit 2 and the gas in the vapor state circulating in the return line 14. The objective of this exchange of calories is to reliquefy the gas in the vapor state of the return line 14, so that it passes into the liquid state, then to return it to the tank 8 once this has been done.

[0058] The compression device 13 may be an oil compressor. The oil allows the compression device 13 to cool while lubricating the moving parts of the compressor to limit the wear of said moving parts and contributing to the dissipation of noise, which makes the oil compressor a preferred means for compressing the gas in the vapor state. This type of compression device 13 comprises a plurality of filters preventing the escape of oil from the compression device 13. However, such filtration is not perfect, and traces of oil may escape from the compression device 13, carried along by the flow of gas in the vapor state. The traces of oil may then circulate in the return line 14 to the second heat exchanger 7.The heat exchanges carried out within the first heat exchanger 6 and the second heat exchanger 7 cause the gas in the vapor state circulating in the return line 14 to cool. The traces of oil also circulating in the return line 14 are therefore also cooled. However, the oil has threshold temperatures for changing state that are significantly higher than those of the gas contained in the tank 8 and circulating in the supply system 1. The very high cooling capacities of the heat exchangers 6, 7 therefore cause the traces of oil to solidify and to aggregate within said heat exchangers 6, 7. Since the second heat exchanger 7 is the first through which the oil circulating in the return line 14 passes, it is within the latter that the probability of solidification and aggregation of the oil is the highest.However, such a phenomenon can also occur at the first heat exchanger 6.

[0059] Although the amount of oil exiting the compression device 13 is tiny, the accumulation of oil escaping from the compression device 13 and solidifying within one or other of the heat exchangers 6, 7 over time eventually becomes problematic, resulting in obstructions within the heat exchangers 6, 7, cooling defects and significant pressure drops of the gas in the vapor state circulating in the return line 14 and intended to be reliquefied. The possibility of replacing the compression device 13 with an oil-free compressor is conceivable but is restrictive and time-consuming.

[0060] To circumvent such a problem without having to replace the compression device 13, the supply system 1 is equipped with a recirculation branch 15 starting at a divergence point 19 arranged on the return line 14 downstream of the second heat exchanger 7 and extending to the second supply circuit 3 upstream of the compression device 13. The recirculation branch 15 makes it possible to form a loop between the second supply circuit 3 and the return line 14. Thanks to the recirculation branch 15, it is possible to circulate the gas in the vapor state in a loop through the heat exchangers 6, 7. The objective is to gradually increase the temperature within the heat exchangers 6, 7 so that the oil aggregates that have accumulated there merge and return to the liquid state and are then evacuated from the heat exchangers 6, 7 by being carried along by the gas flow. the vapor state.The merged oil then circulates in the return line 14, then in the recirculation branch 15 to join the second supply circuit 3. The oil then enters the compression device 13 and is filtered there.

[0061] According to the first embodiment, the gas in the vapor state circulates within the heat exchangers 6, 7 according to a semi-closed loop, that is to say that, while circulating within the return line 14 and the heat exchangers 6, 7, the gas in the vapor state is always evacuated from the tank top 12 and the low-pressure gas-consuming device 5 is always supplied with gas in a common manner.

[0062] To ensure a temperature increase within the heat exchangers 6, 7 and thus evacuate the oil that has accumulated there, the circulation of gas in the liquid state in the first supply circuit 2 must be stopped within the heat exchangers 6, 7. This must not, however, cause an interruption in the supply to the high-pressure gas-consuming device 4. The supply system 1 thus comprises a first bypass branch 16 and a second bypass branch 17, each extending in parallel with the first heat exchanger 6 and the second heat exchanger 7 respectively and thus making it possible to divert the circulation of gas in the liquid state so that it does not pass through the heat exchangers 6, 7 but still continues to supply the high-pressure gas-consuming device 4.As there is no longer any circulation of gas in the liquid state, which comes from the tank 8 and therefore has a very low temperature, within the heat exchangers 6, 7, these can rise in temperature via the gas in the vapor state which circulates there in a loop.

[0063] Each bypass branch 16, 17 is connected on either side of one of the heat exchangers 6, 7. Thus, the gas in the liquid state circulating in the first supply circuit 2, although bypassing the heat exchangers 6, 7, is always raised in pressure by the second pumping device 10 to have a pressure compatible with the needs of the high-pressure gas-consuming device 4. The gas in the liquid state circulating in the first supply circuit 2 is also evaporated by the high-pressure evaporator 11. The configuration of the latter must however be modified, in particular at the level of the energy supply thereof, because as the gas in the liquid state has not previously been heated by passing through the heat exchangers 6, 7, its evaporation therefore requires more energy.

[0064] Thus, the supply system 1 according to the invention is capable of implementing a management method allowing the supply system 1 to operate according to a first configuration, operated in a majority manner, during which the gas-consuming devices 4, 5 are supplied and the excess gas in the vapor state is reliquefied before being returned to the tank, and according to a second configuration, operated occasionally, the aim of which is to eliminate the oil aggregates which have accumulated within the heat exchangers 6, 7.

[0065] In order to control the circulation of gas within the supply system 1 according to the configuration to be applied, the supply system 1 comprises a recirculation valve 20 arranged on the recirculation branch 15 and a return valve 21 arranged on the return line 14 between the divergence point 19 and the tank 8. The recirculation valve 20 authorizes or prohibits the circulation of gas towards the second supply circuit 3 while the return valve 21 authorizes or prohibits the circulation of gas towards the tank 8. It is thus understood that, depending on the configuration implemented of the supply system 1, one of these valves is open while the other is closed.

[0066] Advantageously, the recirculation valve 20 also allows the expansion of the gas circulating in the recirculation branch 15. This expansion allows, downstream of the recirculation branch 15, a mixture of the gas coming from the return line 14, and therefore previously compressed by the compression device 13, and the gas leaving directly from the tank 8 at an equivalent pressure level. The supply system 1 also comprises a bypass valve 22, as well as a control valve 23 and a regulating valve 24. The bypass valve 22 is arranged on the first bypass branch 16, while the control valve 23 and the regulating valve 24 are arranged on a first portion 25 of the first supply circuit 2, which corresponds to the portion arranged in parallel with the first bypass branch 16 and which therefore passes through the first heat exchanger 6.

[0067] It is thus understood that access to the first bypass branch 16 is controlled by the bypass valve 22. Access to the first portion 25 is controlled by the control valve 23 and by the regulating valve 24. Advantageously, the control valve 23 and the regulating valve 24 are arranged on the first portion 25 on either side of the first heat exchanger 6, the control valve 23 being upstream of the first heat exchanger 6 while the regulating valve 24 being downstream of the first heat exchanger 6. The presence of two valves makes it possible to completely isolate the first heat exchanger 6 from the rest of the first supply circuit 2.Although the control valve 23 alone is sufficient to prevent the circulation of gas in the liquid state in the first heat exchanger 6, it is advantageous to also implement the regulating valve 24 in order to avoid creating a pressure differential which could cause evaporation of the gas in the liquid state.

[0068] The supply system 1 also comprises a bypass member 26 arranged on the second bypass branch 17, as well as a control member 27 and a regulating member 28 arranged on a second portion 29 of the first supply circuit 2 which is arranged in parallel with the second bypass branch 17. The control member 27 and the regulating member 28 are arranged on either side of the second heat exchanger 7, the control member 27 being upstream of the second heat exchanger 7 while the regulating member 28 being downstream of the second heat exchanger 7. The bypass member 26, the control member 27 and the regulating member 28 are respectively the counterparts of the bypass valve 22, the control valve 23 and the regulating valve 24, but interacting at the level of the second heat exchanger 7. The operation of the members raised in relation to the raised valves is therefore the same.

[0069] In order to detect whether it is necessary to implement the second configuration of the supply system 1 to remove the oil present within the heat exchangers 6, 7, the supply system 1 comprises a first measuring member 31, a second measuring member 32, a first measuring device 33 and a second measuring device 34.

[0070] The first measuring member 31 is configured to measure the pressure of the gas in the vapor state circulating in the return line 14 at the inlet of the first heat exchanger 6 and / or at the inlet of the second heat exchanger 7, while the second measuring member 32 is configured to measure the pressure of the gas in the vapor state circulating in the return line 14 at the outlet of the first heat exchanger 6 and / or at the outlet of the second heat exchanger 7. From these pressure measurements, a pressure differential can be deduced.There is always a pressure differential between the gas at the inlet and outlet of a heat exchanger 6, 7, but, if the pressure differential at the inlet and outlet of one of the heat exchangers 6, 7 is significant, for example from 40 mbar for the first heat exchanger or from 200 mbar for the second heat exchanger, this means that the gas undergoes a significant pressure drop when passing through said heat exchanger 6, 7 and this is potentially due to an accumulation of oil aggregates within it. The second configuration of the supply system 1 can therefore be implemented following a pressure measurement by the measuring members 31, 32. The second configuration can also be implemented after a measurement of a change in the pressure differential calculated over time at at least one of the heat exchangers 6, 7.For example, a variation in the pressure differential of more than 150%, preferably more than 100% relative to the pressure differential when the heat exchangers do not have oil aggregates, is considered to be the instant when the evacuation of the accumulated oil is necessary. The first measuring device 33 and the second measuring device 34 are configured to measure a temperature of the gas. More particularly, the first measuring device 33 is configured to measure the temperature of the gas in the liquid state circulating in the first supply circuit 2 at the inlet of the first heat exchanger 6 and / or at the inlet of the second heat exchanger 7. The second measuring device 34 is configured to measure the temperature of the gas circulating in the return line 14 at the outlet of the first heat exchanger 6 and / or at the outlet of the second heat exchanger 7.

[0071] A temperature differential between the temperature measured by the first measuring device 33 and the temperature measured by the second measuring device 34 is then calculated on the same heat exchanger. In other words, the temperature differential is calculated between the temperature of the gas in the liquid state circulating in the first supply circuit 2 at the inlet of the first heat exchanger 6, respectively of the second heat exchanger 7, and the temperature of the gas circulating in the return line 14 at the outlet of the first heat exchanger 6, respectively of the second heat exchanger 7.If there is a significant temperature differential between the gas circulating in the first supply circuit 2 at the inlet of one of the heat exchangers 6, 7 and the gas circulating in the return line 14 at the outlet of this same heat exchanger 6, 7, this means that the heat treatment efficiency of said heat exchanger 6, 7 is abnormally reduced and this may be due to the presence of oil aggregates within the heat exchanger 6, 7 in question. The temperature differential from which it is considered necessary to implement the second configuration may be of the order of 10°C, preferably 5°C. The second configuration may also be implemented after measuring a change in the temperature differential calculated over time at at least one of the heat exchangers 6, 7.

[0072] The supply system 1 can therefore be implemented according to the second configuration as a function of the pressure differential or the temperature differential deduced from the various measurements previously described. The two differentials can be calculated in order to limit potential false measurements. It should also be noted, as illustrated in FIGS. 1 to 3, that the second measuring member 32 and the second measuring device 34 can be combined into a single entity.

[0073] Figure 2 represents the circulation of gas within the supply system 1 when the latter is implemented according to the first configuration. For Figures 2 and 3, the solid lines symbolize a circulation of gas while the dotted lines symbolize an absence of circulation of gas.

[0074] As mentioned previously, the first configuration consists of supplying the gas-consuming devices 4, 5 while reliquefying the excess gas to the vapor state before returning it to the tank 8. In this first configuration, the return valve 21, the control valve 23, the regulating valve 24, the control member 27 and the regulating member 28 are open, while the recirculation valve 20, the bypass valve 22 and the bypass member 26 are closed.

[0075] According to this first configuration, the gas in the liquid state contained in the tank 8 is pumped by the first pumping device 9 and circulates within the first supply circuit 2. The gas in the liquid state passes through the first heat exchanger 6, is pumped and raised to a pressure compatible with the high-pressure gas-consuming device 4 by the second pumping device 10, passes through the second heat exchanger 7 and is evaporated by the high-pressure evaporator 11 before supplying the high-pressure consuming device 4.

[0076] During the passage through the heat exchangers 6, 7, the gas in the liquid state undergoes a rise in temperature due to the heat exchange carried out with the gas in the vapor state circulating in the return line 14, which facilitates its subsequent evaporation.

[0077] The gas in the vapor state present in the tank head 12 is sucked into the second supply circuit 3, is compressed by the compression device 13 and supplies the low-pressure gas-consuming device 5. The excess gas in the vapor state, that is to say a surplus of gas in the vapor state compared to the supply requirement of the low-pressure gas-consuming device 5, circulates in the return line 14 and passes through the second heat exchanger 7 and then the first heat exchanger 6. The gas in the vapor state is precooled within the second heat exchanger 7 and is finally reliquefied within the first heat exchanger 6. Subsequently, the reliquefied gas returns to the tank 8.

[0078] As stated previously, after compression by the compression device 13, traces of oil exit the compression device 13, entrained by the gas in the vapor state. If these traces of oil circulate within the return line 14, their passage within one or other of the heat exchangers 6, 7 cools them and can solidify them within said heat exchangers 6, 7.

[0079] Figure 3 represents the circulation of the gas within the supply system 1 when the latter is implemented according to the second configuration. As previously stated, this second configuration is implemented following an accumulation of oil aggregates within one or other of the heat exchangers 6, 7 and these aggregates must be eliminated to maintain the proper functioning of the supply system 1. Such an accumulation can be detected by the first measuring member 31 and the second measuring member 32 and / or by the first measuring device 33 and the second measuring device 34.

[0080] In this second configuration, the return valve 21, the control valve 23, the regulating valve 24, the control member 27 and the regulating member 28 are closed, while the recirculation valve 20, the bypass valve 22 and the bypass member 26 are open.

[0081] The objective being to increase the temperature within the heat exchangers 6, 7, there is no question of circulating the gas in the liquid state within them.

[0082] However, the supply of the high-pressure gas-consuming device 4 must be continued.

[0083] Thus, the gas in the liquid state contained in the tank 8 is pumped by the first pumping device 9 and circulates within the first supply circuit 2. The gas in the liquid state bypasses the first heat exchanger 6 by circulating in the first bypass branch 16, is pumped and raised to a pressure compatible with the high-pressure gas-consuming device 4 by the second pumping device 10, also bypasses the second heat exchanger 7 by circulating in the second bypass branch 17 and is evaporated by the high-pressure evaporator 11 before supplying the high-pressure consuming device 4. Even if the gas in the liquid state is not cooled due to its bypassing the heat exchangers 6, 7, the high-pressure evaporator 11 is capable of evaporating said gas in the liquid state.

[0084] The gas in the vapor state is sucked from the tank head 12 by the compression device 13 and circulates in the second supply circuit 3. When implemented according to the second configuration, the low-pressure gas-consuming device 5 must also be supplied. As mentioned previously, the first embodiment of the supply system 1 implements the second configuration according to a semi-closed loop. A portion of the gas in the vapor state can therefore supply the low-pressure gas-consuming device 5 if necessary, that is to say that the gas leaving the compression device 13 is distributed simultaneously to the low-pressure gas-consuming device 5 and in the return line 14.

[0085] The gas in the vapor state also circulates in the return line 14 and passes through the second heat exchanger 7 and then the first heat exchanger 6. Since the gas in the liquid state does not circulate in the heat exchangers 6, 7, the gas in the vapor state is not reliquefied on the one hand and causes an increase in the temperature within the heat exchangers 6, 7 on the other hand. At the outlet of the first heat exchanger 6, the gas in the vapor state does not return to the tank 8 and circulates in the recirculation branch 15 to be compressed again by the compression device 13 and recirculate in the return line 14 to pass through the heat exchangers 6, 7 again. The circulation of the gas in the vapor state in a loop through the heat exchangers 6, 7 increases the temperature within them. The oil aggregates then coalesce and the oil is eventually discharged from the heat exchangers 6, 7 entrained by the gas in the vapor state.The oil then also reaches the compression device 13 via the recirculation branch 15 and is then retained by the filtration means of said compression device 13. Tl.

[0086] The second operating mode is implemented until the oil is completely removed from the heat exchangers 6, 7. A measurement of the pressure differential by the first measuring member 31 and by the second measuring member 32 at each heat exchanger 6, 7 makes it possible to determine whether the oil has been evacuated. This being done, the supply system 1 can again operate according to the first configuration. During the implementation of the second configuration, the low-pressure gas-consuming device 5 can still be supplied with the gas in the vapor state circulating in the second supply circuit 3. Access to the tank 8 to suck in the gas in the vapor state present in the tank crown 12 is also open during the implementation of the second configuration.

[0087] Figure 4 is a representation of a second embodiment of the supply system 1 according to the invention. The second embodiment differs from the first embodiment in that, when the second configuration is implemented, the gas in the vapor state circulates within the heat exchangers 6, 7 in a completely closed loop.

[0088] Since the supply of the low-pressure gas-consuming device 5 must however be maintained, the second embodiment of the supply system 1 comprises an auxiliary supply branch 35 which ensures a fluid connection between the tank 8 and the low-pressure gas-consuming device 5, in order to be able to supply the latter despite the closed loop implemented via the second supply circuit 3, the return line 14 and the recirculation branch 15.

[0089] The auxiliary supply branch 35 comprises a compression member 36 capable of sucking the gas in the vapor state present in the tank head 12 and raising it to a pressure compatible with the needs of the low-pressure gas-consuming device 5. Thus, when the gas in the vapor state circulates in the closed loop after having been put into circulation by the compression device 13, it is the compression member 36 which sucks the gas in the vapor state contained in the tank head 12 in order to supply the low-pressure gas-consuming device 5. Furthermore, as illustrated in FIG. 4, the supply system 1 comprises a first auxiliary valve 37 arranged on the second supply circuit 3 between the inlet of the auxiliary supply branch 35 and the outlet of the recirculation branch.The supply system 1 also comprises a second auxiliary valve 38 arranged on the second supply circuit 3 between the connection of the return line 14 and the outlet of the auxiliary supply branch 35.

[0090] The first auxiliary valve 37 and the second auxiliary valve 38 completely isolate the closed loop, comprising a part of the second supply circuit, the return line 14 and the recirculation branch 15, from the supply of the low-pressure gas-consuming device 5 which is provided in particular by the auxiliary supply branch 35. Such a configuration makes it possible to avoid any unwanted thermal phenomenon between the gas flow coming from the return line 14 and comprising fused oil and the gas leaving directly from the tank head 12 which has a much lower temperature, for example frosting of the oil in contact with the gas in the vapor state at low temperature coming from the tank head 12.

[0091] The remaining structural and functional characteristics of the second embodiment being identical to those of the first embodiment, reference will be made to the descriptions of figures 1 to 3 for the elements common to both embodiments.

[0092] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention.

[0093] The invention, as just described, achieves the aim it set itself, and makes it possible to propose a gas supply system for two gas-consuming appliances, allowing reliquefaction of the excess gas in the vapor state but also implementation of evacuation of the oil accumulated in the heat exchangers of said supply system. 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 system in accordance with the invention.

Claims

CLAIMS 1- Gas supply system (1) for at least one high-pressure gas-consuming device (4) and at least one low-pressure gas-consuming device (5) of a floating structure comprising at least one tank (8) configured to contain the gas, the supply system (1) comprising: at least one first supply circuit (2) configured to supply gas to the high-pressure gas-consuming device (4), comprising at least one first pumping device (9) configured to pump the gas taken in the liquid state from the tank (8), at least one high-pressure evaporator (11) configured to evaporate the gas circulating in the first supply circuit (2), at least one second supply circuit (3) configured to supply gas to the low-pressure gas-consuming device (5),comprising at least one compression device (13) configured to compress gas taken in the vapor state from the tank (8) to a pressure compatible with the needs of the low-pressure gas-consuming device (5), at least one gas return line (14) connected to the second supply circuit (3) downstream of the compression device (13) and extending to the tank (8), the supply system (1) comprising at least one first heat exchanger (6) and at least one second heat exchanger (7) each configured to carry out a heat exchange between the gas in the vapor state circulating in the return line (14) and the gas in the liquid state circulating in the first supply circuit (2), the first supply circuit (2) comprising a second pumping device (10) interposed between the first heat exchanger (6) and the second heat exchanger (7),characterized in that the supply system (1) comprises a recirculation branch (15) connected at the inlet to a divergence point (19) arranged on the return line (14) between the first heat exchanger (6) and the tank (8), the branch of, recirculation (15) comprising an outlet connected to the second supply circuit (3) between the tank (8) and the compression device (13), the first supply circuit (2) comprising a first bypass branch (16) arranged in parallel with a first portion (25) of the first supply circuit (2) passing through the first heat exchanger (6) and a second bypass branch (17) arranged in parallel with a second portion (29) of the first supply circuit (2) passing through the second heat exchanger (7). 2- Feed system (2) according to claim 1, comprising a recirculation valve (20) arranged on the recirculation branch (15) and a return valve (21) arranged on the return line (14) between the divergence point (16) and the tank (8). 3- Supply system (1) according to claim 1 or 2, comprising a bypass valve (22) arranged on the first bypass branch (16) and a control valve (23) arranged on the first portion (25) of the first supply circuit (2). 4- Supply system (1) according to claim 3, wherein the control valve (23) is arranged on the first portion (25) upstream of the first heat exchanger (6), the supply system (1) comprising a regulating valve (24) arranged on the first portion (25) downstream of the first heat exchanger (6). 5- Power supply system (1) according to any one of claims 1 to 4, comprising a bypass member (26) arranged on the second bypass branch (17) and a control member (27) arranged on the second portion (29) of the first power supply circuit (2). 6- Supply system (1) according to claim 5, wherein the control member (27) is arranged on the second portion (29) upstream of the second heat exchanger (7), the supply system (1) comprising a regulating member (28) arranged on the second portion (29) downstream of the second heat exchanger (7). 7- Power supply system (1) according to any one of claims 1 to 6, comprising a first measuring member (31) and a second measuring member (32) configured to respectively measure a pressure of the gas circulating in the return line (14) at the inlet and outlet of the first heat exchanger (6) and / or at the inlet and outlet of the second heat exchanger (7). 8- Supply system (1) according to any one of claims 1 to 7, comprising a first measuring device (33) and a second measuring device (34) configured to respectively measure a temperature of the gas circulating in the first supply circuit (2) at the inlet of the first heat exchanger (6) and of the gas circulating in the return line (14) at the outlet of the first heat exchanger (6) and / or of the gas circulating in the first supply circuit (2) at the inlet of the second heat exchanger (7) and of the gas circulating in the return line (14) at the outlet of the second heat exchanger (7). 9- Supply system (1) according to any one of claims 1 to 8, comprising an auxiliary supply branch (35) connected at the input to the second supply circuit (3) between the tank (8) and the output of the recirculation branch (15), the auxiliary supply branch (35) comprising an output connected to the second supply circuit (3) between the connection to the return line (14) and the low-pressure gas-consuming device (5), the auxiliary supply branch (35) comprising a compression member (36). 10- A supply system (1) according to claim 9, wherein the second supply circuit (3) comprises a first auxiliary valve (37) arranged between the inlet of the auxiliary supply branch (35) and the outlet of the recirculation branch (15) and a second auxiliary valve (38) arranged between the connection to the return line (14) and the outlet of the auxiliary supply branch (35). 11- Supply system (1) according to any one of claims 1 to 10, wherein the first pumping device (9) is configured to raise a pressure of the gas in the liquid state to a value between 6 and 17 bars and the second pumping device (10) is configured to raise the pressure of the gas in the liquid state to a value between 30 and 400 bars. 12- Supply system (1) according to any one of claims 1 to 11, wherein the compression device (13) is configured to raise a pressure of the gas to a value between 6 and 20 bars absolute. 13- Floating structure for storing and / or transporting gas in the liquid state, comprising at least one tank (8) of gas in the liquid state, at least one high-pressure gas-consuming device (4), at least one low-pressure gas-consuming device (5) and at least one gas supply system (1) for these devices according to any one of claims 1 to 12. 14- A gas management method implemented by a supply system (1) according to any one of claims 1 to 12, used within a floating structure comprising at least one tank (8) configured to contain the gas, during which: the gas is circulated in the liquid state in the first supply circuit (2) within the first heat exchanger (6) and the second heat exchanger (7) and the gas is circulated in the vapor state within the return line (14) to the tank (8) according to a first configuration, the gas is circulated in the liquid state in the first supply circuit (2) within the first bypass branch (16) and the second bypass branch (17) and the gas is circulated in the vapor state within the recirculation branch (15) according to a second configuration. 15- Management method according to claim 14, implemented by a supply system (1) according to claims 2, 4 and 6, during which the return valve (21), the control valve (23), the regulating valve (24), the control member (27) and the regulating member (28) are open while the recirculation valve (20), the bypass valve (22) and the bypass member (26) are closed when the first configuration is active, the return valve (21), the control valve (23), the regulating valve (24), the control member (27) and the regulating member (28) being closed while the recirculation valve (20), the bypass valve (22) and the bypass member (26) being open when the second configuration is active. 16- Management method according to claim 14 or 15, implemented by a supply system (1) according to claim 7, during which a selection between the first configuration and the second configuration is dependent on a pressure difference between the pressure measured by the first measuring member (31) and the pressure measured by the second measuring member (32) of the gas circulating in the return line (14) at the inlet and outlet of the first heat exchanger (6) and / or at the inlet and outlet of the second heat exchanger (7). 17- Management method according to any one of claims 14 to 16, implemented by a supply system (1) according to claim 8, during which a selection between the first configuration and the second configuration is dependent on a temperature difference between the temperature measured by the first measuring device (33) and the temperature measured by the second measuring device (34) respectively of the gas circulating in the first supply circuit (2) at the inlet of the first heat exchanger (6) and of the gas circulating in the return line (14) at the outlet of the first heat exchanger (6) and / or of the gas circulating in the first supply circuit (2) at the inlet of the second heat exchanger (7) and of the gas circulating in the return line (14) at the outlet of the second heat exchanger (7).

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