System for managing a gas contained in a tank

Abstract

System for managing a gas contained in a tank The present invention relates to a management system (1) comprising: at least one supply circuit (6) comprising a compression device (7) comprising a first compression stage (11), a second compression stage (12) and a third compression stage (13), at least one heat treatment circuit (8), at least one first heat exchanger (14), at least one cooling circuit (17), at least one second heat exchanger (16), characterized in that the heat treatment circuit (8) comprises a first portion (51) configured to circulate compressed gas through the first compression stage (11) and a second portion (52) configured to circulate compressed gas through the second compression stage (12), the second portion (52) being provided with an expansion member (15). (figure 1)

Description

Title of the invention: System for managing a gas contained in a tank

[0001] The present invention relates to the field of floating structures for storing and / or transporting gas in the liquid state and more particularly concerns a system for managing a gas stored and / or transported within such structures.

[0002] 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 can use the gas having evaporated within the tank, then compress it in order to supply the motor(s) of the floating structure.

[0003] It is also known, in the event of excess gas evaporating within the tank, to reliquefy the gas not used to power the motor(s) of the floating structure by circulating it through one or more heat exchangers, then returning it to the tank.

[0004] During a journey from a starting point to a destination point made by the floating structure, it may happen that the latter does not have the same needs in terms of supplying consumers with gas in the vapor state, for example depending on the duration of the journey, or depending on a quantity of gas in the vapor state likely to form within the tank. These data also influence the capacity for reliquefaction of the gas in the vapor state by the management system.

[0005] It is therefore known to reliquefy this gas to prevent it from becoming a loss. It is in particular known to reliquefy a portion of compressed gas which has not been consumed on the floating structure.

[0006] A first drawback of these known technologies lies in the fact that they are not optimized from the point of view of overall system consumption. For example, oversized means in a majority of use cases are implemented, which causes overconsumption. In such a case, the cooling of the gas cargo in the liquid state is excessive and thus leads to overconsumption of energy.

[0007] The present invention allows optimal gas management by proposing a system for managing a gas contained in at least one tank of a floating structure which comprises at least one gas-consuming device, the management system comprising: - at least one gas supply circuit for the gas-consuming appliance, the supply circuit comprising at least one compression device comprising at least a first compression stage, a second compression stage and a third compression stage and configured to compress gas taken in the vapor state from the tank, the compression device delivering the gas in the vapor state at three different pressure levels, - at least one circuit for thermal treatment of the gas in the vapor state compressed by at least one of the compression stages of the compression device, - at least one first heat exchanger configured to carry out a heat exchange between the gas in the vapor state circulating in the supply circuit between the tank and the compression device and the gas in the vapor state circulating in the heat treatment circuit, - at least one cooling circuit comprising at least one pump configured to draw the gas in the liquid state from the tank, - at least one second heat exchanger configured to carry out a heat exchange between the gas in vapor state circulating in the heat treatment circuit downstream of the first heat exchanger and the gas circulating in the cooling circuit,

[0008] characterized in that the heat treatment circuit comprises at least a first portion configured to circulate compressed gas through the first compression stage of the compression device and a second portion configured to circulate compressed gas through the second compression stage of the compression device, the second compression stage being arranged downstream of the first compression stage, the first portion and the second portion extending at least partially between the compression device and the second heat exchanger, the second portion being provided with an expansion member.

[0009] Thanks to the management system according to the invention, the gas in the vapor state, in particular the gas in the vapor state intended to be reliquefied, can be compressed to different pressure levels, each of these pressure levels being adapted to different situations in which the floating structure is located. From these different pressure levels, the gas in the vapor state is treated differently while circulating in the heat treatment circuit, in particular at the level of the heat exchanges occurring within the heat exchangers and the potential expansion of the gas in the vapor state. The invention thus makes it possible to exploit available cold resources without over-consuming to reliquefy the gas in the vapor state.

[0010] The feed circuit makes it possible to collect the gas in the vapor state which accumulates at the level of a tank ceiling. This gas in the vapor state comes from the evaporation of a part of the cargo of gas in the liquid state contained in the tank. The gas in the vapor state can therefore be consumed or reliquefied, but must generally be evacuated in order to regulate the pressure in the tank.

[0011] The compression device therefore ensures the suction of the gas in the vapor state out of the tank and compresses it. The compression device may for example be a plurality of compressors arranged in series with respect to one another, or a single compressor with multiple compression stages.

[0012] The first portion is thus associated with the first pressure level, that is to say when the compressed gas leaves the compression device between the first compression stage and the second compression stage.

[0013] The second portion is associated with the second pressure level, i.e. when the compressed gas exits the compression device between the second compression stage and the third compression stage.

[0014] The gas compressed by the third compression stage is thus compressed by the entire compression device. The gas in the vapor state can then reach a pressure of between 250 and 400 bars. The gas in the vapor state compressed by the second compression stage reaches a pressure lower than the pressure delivered by the third compression stage, for example between 120 and 150 bars, and the gas in the vapor state compressed by the first compression stage reaches a pressure lower than the pressure delivered by the second compression stage, for example between 7 and 20 bars.

[0015] The pressure of the gas in the vapor state is particularly important for supplying the gas-consuming device because the latter can only consume the gas in the vapor state if it is at a compatible pressure.

[0016] If the gas in the vapor state is not compatible with the gas consuming device or if the gas consuming device does not require to be supplied, the gas in the vapor state then circulates in the heat treatment circuit. If the gas consuming device only needs a fraction of the gas in the vapor state for its own consumption, the remainder of the gas in the vapor state then also circulates in the heat treatment circuit. One of the functions of this heat treatment circuit is to participate in the reliquefaction of the compressed gas in the vapor state.

[0017] The first heat exchanger makes it possible to pre-cool the gas in the compressed vapor state on the one hand and to reheat the gas in the vapor state at the outlet of the tank on the other hand. The pre-cooling of the compressed gas facilitates its subsequent thermal treatment, in particular its reliquefaction. The first heat exchanger thus makes it possible to improve the overall efficiency of the management system because the low temperature of the gas in the vapor state at the outlet of the tank indirectly contributes to the reliquefaction of gas in the compressed vapor state via the heat exchange taking place in the first heat exchanger.

[0018] The cooling circuit can have several functions such as participation in the reliquefaction of the gas in the vapor state circulating in the cooling circuit. heat treatment, or even tank pressure management. To do this, the liquid gas from the tank is taken by the pump and circulates within the cooling circuit, this pump being able for example to be submerged at the bottom of the tank.

[0019] By circulating in the cooling circuit, the gas in the liquid state can pass through the second heat exchanger, which is also crossed by the gas in the vapor state circulating in the heat treatment circuit. This heat exchange thus makes it possible to reliquefy the gas in the vapor state without leading to the evaporation of the gas in the liquid state circulating in the cooling circuit. Once the gas in the vapor state has been reliquefied, the latter can return to the tank, just like the gas in the liquid state used for reliquefaction by circulating within the cooling circuit.

[0020] The advantage of the thermal treatment system according to the invention is the presence of two portions within which the gas in the vapor state circulates at different pressures. Thus, depending for example on the duration of the journey made by the floating structure and / or depending on the quantity of gas in the vapor state generated in the tank headspace, it may be more judicious to compress the gas in the vapor state to the first compression level or to the second compression level, the management system allowing such a choice in order to carry out a reliquefaction of the gas in the vapor state with the least energy consumption.

[0021] Due to the pressure of the gas in the vapor state circulating therein, the second portion is capable of ensuring the expansion of the gas using the expansion member. Pressurization by the second compression stage followed by subsequent expansion promotes the reliquefaction of the unconsumed gas, for example when the duration of the journey is long and / or the quantity of gas in the vapor state generated in the tank headspace is high. If the journey is short, for example less than two days, and / or the quantity of gas in the vapor state generated in the tank headspace is low, then it is preferable to raise the pressure of the gas in the vapor state only via the first compression stage and to circulate it within the first portion.

[0022] According to a characteristic of the invention, the second heat exchanger is connected to the tank by a return branch comprising a termination opening into the tank and an orifice arranged on a portion of the return branch present in the tank. Preferably, the orifice is arranged at the end of the return branch present in the tank. This thus allows the liquefied gas leaving the second heat exchanger to return to the tank.

[0023] According to a characteristic of the invention, the orifice is a calibrated orifice. Thanks to this calibrated orifice, it is possible to complete the expansion of the liquefied gas in the return branch at the level of the tank and thus reduce or even eliminate the vaporization of a fraction of the liquefied gas during its expansion.

[0024] According to a characteristic of the invention, the first portion of the heat treatment circuit is devoid of an expansion member. The gas in the vapor state which circulates in the first portion is expanded by the pressure losses of this first portion, but the system does not comprise an active member which generates an expansion within the first portion.

[0025] According to a characteristic of the invention, the first portion comprises a first valve and the second portion comprises a second valve, the first valve and the second valve being configured to control the circulation of the gas within said portions. Depending on the portion within which it is desirable to circulate the compressed gas, such a choice being relative to the desired pressure in the circuit for thermal treatment of the gas in the vapor state, the first valve and the second valve are capable of being opened or closed.

[0026] According to a characteristic of the invention, the heat treatment circuit comprises a point of divergence from which the first portion and the second portion begin, the point of divergence being arranged between the first heat exchanger and the second heat exchanger. This is a first embodiment of the heat treatment circuit. Regardless of the pressure at which the gas in the vapor state is raised, it passes through at least the first heat exchanger while circulating within a single portion of the heat treatment circuit. It is only downstream of the first heat exchanger that the gas in the vapor state circulates in the first portion or in the second portion.

[0027] According to another characteristic of the invention, the first portion and the second portion start respectively at the first compression stage and at the second compression stage of the compression device. This is therefore a second embodiment of the heat treatment circuit. Each portion is directly attached to the compression device, at the level of the compression stage specific to it.

[0028] According to a characteristic of the invention, the first portion and the second portion meet at a point of convergence. Whatever the embodiment of the heat treatment circuit, the two portions extend in parallel with each other up to the point of convergence. Several locations can be chosen within the heat treatment circuit for said point of convergence.

[0029] According to a characteristic of the invention, the point of convergence is arranged between the first heat exchanger and the second heat exchanger. In other words, in this configuration, it is a single portion of the heat treatment circuit which passes through the second heat exchanger. According to one aspect, if the heat treatment circuit is provided with a point of divergence, then the point of convergence is arranged between the point of divergence and the second heat exchanger.

[0030] According to another characteristic of the invention, the convergence point is arranged downstream of the second heat exchanger. In this embodiment of the heat treatment circuit, the first portion and the second portion therefore pass through the second heat exchanger before joining downstream thereof.

[0031] According to a characteristic of the invention, the heat treatment circuit comprises at least a first branch connected to the first compression stage of the compression device and a second branch connected to the second compression stage of the compression device, the first branch and the second branch joining at a junction point of the heat treatment circuit arranged between the compression device and the divergence point. Such a configuration is specific to the first embodiment, where the first portion and the second portion are not directly connected to the compression device. When the first portion and the second portion are not directly connected to the compression device, it is the first branch and the second branch which implement this function.The junction point is located on the heat treatment circuit, downstream of the compression device and upstream of the point of divergence. In other words, the heat treatment circuit starts from the first branch and the second branch which join at the junction point. Then, the heat treatment circuit separates at the point of divergence and forms the first portion and the second portion which extend to the point of convergence.

[0032] According to a characteristic of the invention, the first branch comprises a first valve and the second branch comprises a second valve, the first valve and the second valve being configured to control the circulation of gas within said branches. Just like the first valve and the second valve arranged respectively on the first portion and the second portion, the first valve and the second valve are arranged on the first branch and the second branch and ensure the management of the circulation of gas within them.

[0033] According to a characteristic of the invention, the first portion and the second portion of the heat treatment circuit each comprise a pass of the first heat exchanger and / or the second heat exchanger. Depending on the positioning of the convergence point, and possibly that of the divergence point and the junction point, the first portion and the second portion may both pass through the first heat exchanger and / or the second heat exchanger. The latter may therefore be two-pass or three-pass heat exchangers, with one pass per portion and one pass forming part of the supply circuit for the first heat exchanger, and one pass forming part of the cooling circuit for the second heat exchanger.

[0034] According to a characteristic of the invention, the management system comprises a third heat exchanger configured to carry out a heat exchange between the gas in the liquid state circulating in the cooling circuit and a refrigerant circulating in a cooling loop. This third heat exchanger makes it possible to subcool the gas in the liquid state, for example in order to improve the reliquefaction of the gas in the vapor state circulating through the second heat exchanger by circulating the subcooled gas in the liquid state within this same second heat exchanger. Such a configuration can be used for example in the case of a large quantity of gas in the vapor state to be reliquefied. The subcooled gas in the liquid state can also return to the tank in order to lower the overall temperature thereof and thus reduce the pressure of the tank.The refrigerant circulating in the cooling loop used to subcool the gas to the liquid state can for example be nitrogen.

[0035] According to a characteristic of the invention, the management system comprises an additional branch connecting the first compression stage of the compression device to the tank, the management system further comprising a heat exchanger configured to carry out a heat exchange between the gas in the vapor state circulating in the additional branch and a refrigerant fluid circulating in a reliquefaction loop. This is an alternative configuration that can be implemented for example in the absence of the third heat exchanger mentioned above to treat a large quantity of gas in the vapor state intended to be reliquefied.

[0036] The presence of the additional branch and the heat exchanger may also be useful, for example, in the case where there is too little gas in the vapor state circulating from the tank to the compression device to carry out effective pre-cooling. The heat exchanger may also be used when the gas in the liquid state contained in the tank is at too high a temperature to correctly reliquefy the gas in the vapor state circulating in the heat treatment circuit and said gas in the liquid state cannot otherwise be sub-cooled.

[0037] In this configuration, at least a portion of the gas in the compressed vapor state and intended to be reliquefied can circulate in the additional branch and be reliquefied separately thanks to the heat exchange carried out within the heat exchanger. Just like the cooling loop mentioned above, the reliquefaction loop can be traversed by a refrigerant fluid, for example nitrogen.

[0038] The additional branch extends to the tank so that the gas, once reliquefied within the heat exchanger, can circulate in the liquid state to the tank.

[0039] According to a characteristic of the invention, the power supply circuit comprises at least one compression element arranged at least partially in parallel with the compression device. The compression element has in particular a redundancy function in in the event of a failure of the compression device. The compression element can also assist the compression device in the event of a high power requirement for the gas-consuming appliance or appliances.

[0040] According to a characteristic of the invention, the compression element is connected to the first compression stage of the compression device. This is an outlet of the compression element which is connected to the first compression stage of the compression device. Advantageously, the compression element compresses the gas to the same pressure level as the first compression stage, for example in order to be able to supply a low-pressure gas-consuming device or to circulate compressed gas within the first portion.

[0041] According to a characteristic of the invention, the heat treatment circuit joins the cooling circuit downstream of the second heat exchanger. At this stage, the gas circulating in the heat treatment circuit is reliquefied. The cooling circuit extends to the tank in order to guarantee a return of the reliquefied gas and the gas in the liquid state circulating in the cooling circuit to the tank.

[0042] According to a characteristic of the invention, the heat treatment circuit comprises a separation device, one inlet of which is arranged downstream of the second heat exchanger. Before joining the cooling circuit, the heat treatment circuit may in fact comprise such a separator making it possible to separate the gaseous phase from the liquid phase of the gas circulating in the heat treatment circuit, and this after said gas has passed through the second heat exchanger. The separation device may be used in the event of partial reliquefaction of the gas circulating in the heat treatment circuit in order to retain the fraction of gas which has not reliquefied.

[0043] According to a characteristic of the invention, the separation device comprises a steam outlet, the heat treatment circuit comprising a first path connecting the steam outlet of the separation device to the supply circuit at a point located between the tank and the first heat exchanger. The first path makes it possible to recirculate the gas in the vapor state which has not reliquefied to the supply circuit in order to be consumed by the gas-consuming device or to cause a new attempt at reliquefaction.

[0044] According to a characteristic of the invention, the separation device comprises a liquid outlet, the heat treatment circuit comprising a second path connecting the liquid outlet of the separation device to the cooling circuit. The reliquefied gas therefore leaves the separation device in the liquid state and circulates in the second path in order to return to the tank via the cooling circuit.

[0045] The invention also covers a floating structure comprising at least one tank, at least one gas-consuming device and a management system as described previously.

[0046] 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 appended schematic drawings on the other hand, in which:

[0047] [Fig-1] is a representation of a first embodiment of a management system according to the invention,

[0048] [Fig.2] is a representation of a second embodiment of the management system according to the invention,

[0049] [Fig.3] illustrates a first variant of the first embodiment of the management system,

[0050] [Fig.4] illustrates a first variant of the second embodiment of the management system,

[0051] [Fig.5] illustrates a second variant of the first embodiment of the management system,

[0052] [Fig.6] illustrates a second variant of the first embodiment of the management system,

[0053] [Fig.7] illustrates a third variant of the first embodiment of the management system.

[0054] [Fig.l] illustrates a first embodiment of a management system 1 according to the invention. The management system 1 can be integrated within a floating structure, for example a vessel for storing and / or transporting a gas in the liquid state contained in at least one tank 2 which equips the floating structure. The gas in the liquid state can naturally partially evaporate within a ceiling 3 of the tank 2.

[0055] In order to manage the pressure of the tank 2 which increases due to the presence of gas in the vapor state within the headspace 3, the management system 1 can process this gas so that the latter supplies fuel to at least one gas-consuming device. In [Fig.l], the management system 1 is configured to be able to supply a high-pressure gas-consuming device 4 and a low-pressure gas-consuming device 5. The high-pressure gas-consuming device 4 can for example be an engine ensuring the propulsion of the floating structure. The low-pressure gas-consuming device 5 can be a generator supplying the floating structure with electricity.

[0056] In order to ensure a supply of gas to the gas-consuming devices 4, 5, the management system 1 comprises a supply circuit 6 extending between the tank 2 and the gas-consuming devices 4, 5. The supply circuit 6 comprises a compression device 7 for sucking in the gas in vapor state contained in the ceiling 3 and the tank 2 and compressing it to a pressure compatible with the needs of the high-pressure gas-consuming device 4, for example above 250 bars, or of the low-pressure gas-consuming device 5, in particular between 7 and 20 bars.

[0057] In [Fig. 1], the compression device 7 is illustrated by a series of compressors, but the compression device 7 can also be a single multi-stage compressor. Thus, the compression device 7 has several compression stages in order to compress the gas in the vapor state to a higher or lower pressure, such a compression device 7 comprising at least three outlets, at least two of which are arranged between two compression stages. The more compression stages the gas in the vapor state passes through, the more its pressure is increased.

[0058] The compression device 7 shown in [Fig.l] thus comprises at least a first compression stage 11, a second compression stage 12 and a third compression stage 13. The compression device 7 also comprises a first outlet 56 arranged between the first compression stage 11 and the second compression stage 12, a second outlet 57 arranged between the second compression stage 12 and the third compression stage 13 and a third outlet 58 after the third compression stage 13.

[0059] These three outlets 56, 57, 58 each provide an outlet for the gas in the vapor state from the compression device 7. The gas in the vapor state passes through the entire compression device 7 and exits through the third outlet 58 to reach the pressure compatible with supplying the high-pressure gas-consuming device 4. At the outlet of the third compression stage 13 of the compression device 7, the gas in the vapor state can reach a pressure of between 250 and 400 bars.

[0060] The gas in the vapor state compressed by the first compression stage 11 has a pressure of between 7 and 20 bars while the gas in the vapor state compressed by the second compression stage 12 has a pressure of between 120 and 150 bars. The first compression stage 11 also makes it possible to raise the pressure of the gas in the vapor state to a value compatible with supplying the low-pressure gas-consuming device 5.

[0061] The management system 1 also comprises a heat treatment circuit 8. The heat treatment circuit 8 is connected to the supply circuit 6, more particularly at the compression device 7. According to the first embodiment of the management system 1, the heat treatment circuit 8 comprises a first branch 9 and a second branch 10, respectively connected to the first output 56 of the compression device 7 arranged downstream of the first compression stage 11 and upstream of the second compression stage 12, and to the second outlet 57 of the compression device 7 arranged downstream of the second compression stage 11 and upstream of the third compression stage 13. The first branch 9 and the second branch 10 make it possible to circulate the gas in the vapor state within the heat treatment circuit 8 at two different pressure levels.

[0062] The first branch 9 and the second branch 10 join at a junction point 53. Preferably, the gas in the vapor state only circulates within one of the two branches 9, 10. In order to control the circulation within said branches 9, 10, the first branch 9 comprises a first valve 43 and the second branch 10 comprises a second valve 44.

[0063] One of the objectives of the heat treatment circuit 8 is to participate in the reliquefaction of the gas in the vapor state not used for supplying the gas consuming devices 4, 5. To do this, the management system 1 comprises a first heat exchanger 14 configured to carry out a heat exchange between the gas in the compressed vapor state circulating in the heat treatment circuit 8 and the gas in the vapor state circulating in the supply circuit 6 upstream of the compression device 7.

[0064] The first heat exchanger 14 thus makes it possible to pre-cool the gas in the vapor state circulating in the heat treatment circuit 8 by using the gas in the vapor state at the outlet of the tank 2. The latter is then heated by capturing the calories from the gas in the vapor state circulating in the heat treatment circuit 8.

[0065] The gas in the vapor state circulating in the heat treatment circuit 8 is pre-cooled within the first heat exchanger 14, regardless of the branch 9 or 10 used. Thus, the junction point 53 is advantageously arranged upstream of the first heat exchanger 14 so that all of the gas in the vapor state circulating in the heat treatment circuit 8 passes through the first heat exchanger 14 to be pre-cooled. According to such a configuration, the first heat exchanger 14 comprises two passes, one of which circulates the gas in the vapor state circulating in the supply circuit 6 upstream of the compression device 7 and the other where the compressed gas in the vapor state circulating in the heat treatment circuit 8 circulates after the first branch 9 and the second branch 10 have joined at the junction point 53.

[0066] The pre-cooled gas in the vapor state continues its circulation at the outlet of the first heat exchanger 14. The particularity of the management system 1 according to the invention is that the heat treatment circuit 8 comprises a first portion 51 and a second portion 52, each being adapted to the circulation of the gas in the vapor state previously compressed by the first compression stage 11 or by the second compression stage 12.

[0067] In [Fig. 1], it can be seen that the second portion 52 comprises an expansion member 15, while the first portion 51 does not. It can thus be understood that the first portion 51 is specific to the circulation of gas in the vapor state compressed only by the first compression stage 11, while the second portion 52 is specific to the circulation of gas in the vapor state compressed by the second compression stage 12. Pressurizing the second compression stage 12 in fact requires a subsequent expansion, which is ensured by the expansion member 15.

[0068] It may be advantageous in terms of reliquefaction optimization to perform compression and then expansion of the gas in the vapor state. Such a choice depends on a plurality of parameters, for example the quantity of gas in the vapor state generated in the ceiling 3 of tank 2, or the duration of the journey to be made by the floating structure transporting the gas in the liquid state. The management system 1 according to the invention makes it possible to optimize the reliquefaction of the gas in the vapor state by saving a maximum of energy and by maintaining the temperature of the gas cargo in the state below a determined threshold. This optimization is obtained by favoring the use of the first branch 9 combined with the use of the first portion 51, compared to the use of the second branch 10 combined with the use of the second portion 52.

[0069] The heat treatment circuit 8 illustrated in FIGS. 1, 3 and 5 comprises a divergence point 54 and a convergence point 55, respectively where the first portion 51 and the second portion 52 begin and end. The latter also respectively comprise a first valve 41 and a second valve 42 which control the circulation of gas within the respective portions.

[0070] After having circulated within the first portion 51 or the second portion 52, the gas in the vapor state then passes through a second heat exchanger 16 in order to be at least partially reliquefied. The convergence point 55 is arranged upstream of the second heat exchanger 16. Thus, just as for the first heat exchanger 14, the second heat exchanger 16 comprises two passes.

[0071] In order to carry out an efficient reliquefaction, the management system 1 comprises a cooling circuit 17 within which circulates gas in the liquid state taken from the tank 2. The cooling circuit 17 comprises a pump 18, advantageously immersed at the bottom of the tank 2 and which circulates gas in the liquid state within the cooling circuit 17. Among the different functions of the cooling circuit 17, one of them is to participate in the reliquefaction of the gas in the vapor state circulating in the heat treatment circuit 8. The gas in the liquid state circulating in the cooling circuit 17 can thus pass through the second heat exchanger 16 within which the heat exchange takes place with the gas to the vapor state circulating in the heat treatment circuit 8. The gas in the vapor state is then reliquefied.

[0072] In order to optimize the reliquefaction of the gas in the vapor state circulating in the second heat exchanger 16, the management system 1 comprises a third heat exchanger 19, which the gas in the liquid state circulating in the cooling circuit 17 can pass through or bypass.

[0073] The third heat exchanger 19 makes it possible to subcool the gas in the liquid state in order to compensate for the calories captured by the gas in the liquid state during the heat exchange occurring within the second heat exchanger 16. In order to subcool the gas in the liquid state, the system 1 according to the invention may comprise a cooling loop 20 which passes through the third heat exchanger 19, such a cooling loop 20 being traversed by a refrigerant fluid ensuring the subcooling of the gas in the liquid state. This is advantageous in that the frigories contained in the gas in the liquid state contained in the tank are used to carry out the reliquefaction. The refrigerant fluid circulating in the cooling loop 20 may for example be nitrogen.

[0074] The choice of sub-cooling the gas in the liquid state via the third heat exchanger 19 or not is also dependent on the quantity of gas in the vapor state generated in the tank 2 and / or the duration of the journey of the floating structure, just as for the choice of the pressure level applied to the gas in the vapor state intended to be reliquefied. Such a choice makes it possible to determine whether or not it is necessary to use the third heat exchanger 19 and the cooling loop 20 to ensure the reliquefaction of the gas in the vapor state circulating in the heat treatment circuit 8. This avoids using this cooling loop 20 superfluously when it is not essential for the reliquefaction of the gas in the vapor state, which limits energy consumption.

[0075] At the outlet of the second heat exchanger 16, the reliquefied gas joins the cooling circuit 17, also at the outlet of the second heat exchanger 16. The cooling circuit 17 extends to the tank 2 so that the return of the gas to the liquid state can take place within the latter. The cooling circuit 17 therefore comprises at least one termination 29 which may be an orifice 30 arranged at the bottom of the tank 2.

[0076] It is also possible to lower the temperature of the gas in the liquid state contained in the tank 2 thanks to the third heat exchanger 19 mentioned above. The gas in the liquid state is thus taken from the tank 2, then sub-cooled by passing through the third heat exchanger 19, and returns sub-cooled to the tank 2 via another termination 29 arranged in the ceiling 3 of the tank 2, which can be a spraying member 31. The latter makes it possible to spray gas in the liquid state subcooled in the headspace 3 of tank 2 in order to condense the gas in the vapor state present in the headspace 3 and thus lower the pressure of tank 2.

[0077] When the generation of gas in the vapor state in the headspace 3 of the tank 2 is not sufficient to satisfy the consumption of the high-pressure gas-consuming device 4, the management system 1 can be configured to supply the gas to the latter. Thus, the management system 1 can comprise an additional supply circuit 33. The additional supply circuit 33 comprises an additional pump 35, a high-pressure pump 36 and a high-pressure evaporator 37. The additional pump 35 makes it possible to take the gas in the liquid state from the tank 2, then the high-pressure pump 36 pumps the gas in the liquid state up to a pressure compatible with the pressure required by the high-pressure gas-consuming device 4. The high-pressure evaporator 37 makes it possible to evaporate the gas in the liquid state put under high pressure so that the gas passes into the vapor state and can be consumed by the high-pressure gas-consuming device 4.

[0078] As illustrated in the figures, the additional pump 35 and the pump 18 of the cooling circuit 17 are separate and distinct pumps. According to an alternative, the system is devoid of an additional pump dedicated to the additional supply circuit 33. In such a case, the additional supply circuit 33 is connected to the cooling circuit 17, between an outlet of the pump 18 and an inlet of the second heat exchanger 16 and it is the pump 18 which, in addition to its initial function, takes gas in the liquid state from the tank 2 to supply it to the high-pressure pump 36.

[0079] [Fig.2] represents a second embodiment of the management system 1 according to the invention. The second embodiment differs from the first embodiment in that the first portion 51 and the second portion 52 extend over the entirety or substantially the entirety of the heat treatment circuit 8. Unlike the first embodiment, the second embodiment of the management system 1 illustrated in [Fig.2] therefore does not include the first branch, the second branch, the junction point and the divergence point.

[0080] It is therefore the first portion 51 and the second portion 52 which are directly connected to the compression device 7, respectively to the first outlet 56, at the level of the first compression stage 11, and to the second outlet 57, between the second compression stage 12 and the third compression stage 13. The first valve 41 and the second valve 42 are always present in order to control the circulation of the gas in the vapor state within the first portion 51 and the second portion 52.

[0081] In Figures 1 to 4, it can be seen that the heat treatment circuit 8 comprises a flow regulating member 40 arranged downstream of the point of convergence 55 between the first portion 51 and the second portion 52. This flow regulating member 40 adapts the pressure and the flow rate within the heat treatment circuit 8 so as to bring this pressure closer to the pressure which prevails within the tank 2.

[0082] This flow regulating member 40 is arranged downstream of the branch of the heat treatment circuit 8 which passes through the second heat exchanger 16, and upstream of a mixing point 39 between the heat treatment circuit 8 and the cooling circuit 17.

[0083] The first portion 51 and the second portion 52 thus extend in parallel to each other, including within the first heat exchanger 14 and the second heat exchanger 16. The heat exchangers 14, 16 are thus composed of three passes, at the rate of one pass per portion of the heat treatment circuit 8, a pass where the gas in the vapor state circulates circulating in the supply circuit 6 upstream of the compression device 7 for the first heat exchanger 14, and a pass where the gas in the liquid state circulates circulating in the cooling circuit 17 for the second heat exchanger 16.

[0084] As illustrated in [Fig.2], the point of convergence 55 between the first portion 51 and the second portion 52 is arranged downstream of the second heat exchanger 16. The heat treatment circuit 8 subsequently joins the cooling circuit 17.

[0085] Generally speaking, the positioning of the convergence point 55, but also that of the junction point 53 and the divergence point 54 illustrated in [Fig.l], may differ in a non-exhaustive manner from what is illustrated in Figures 1 and 2. Depending on the positioning of these points, the first heat exchanger 14 and the second heat exchanger 16 may comprise two or three passes.

[0086] The expansion member 15 is always positioned at the level of the second portion 52 and ensures the expansion of the compressed gas by the second compression stage 12. Just as has been described previously, the level of compression of the gas by the compression device 7 as well as the use of the third heat exchanger 19 and the cooling loop 20 are dependent for example on the duration of the journey of the floating structure and the quantity of gas in the vapor state generated in the ceiling 3 of tank 2.

[0087] All of the other structural and functional characteristics of the second embodiment of the management system 1 being identical to those of the first embodiment, reference will be made to the description of [Fig.l] concerning the description of the characteristics common to the two embodiments.

[0088] Figures 3 to 6 represent a variant of the first embodiment or a variant of the second embodiment of the management system 1 according to the invention. Only the structural and functional differences compared to what has been mentioned previously will be described regarding these variants. Reference will therefore be made to the description in [Fig.l] and / or [Fig.2] for all characteristics not detailed below regarding these variants.

[0089] Figures 3 and 4 thus respectively represent a first variant of the first embodiment and a first variant of the second embodiment. This first variant differs from what has been described previously in particular by the absence of the third heat exchanger making it possible to sub-cool the gas in the liquid state circulating in the cooling circuit 17.

[0090] Instead, according to such a variant of the management system 1 according to the invention, the latter comprises an additional branch 48 connected to the first outlet 56 of the compression device 7, in parallel with the first branch 9 or the first portion 51 depending on the embodiment, and which extends to the tank 2. This additional branch 48 conducts the gas in the vapor state through a heat exchanger 49, which is configured to carry out a heat exchange between the gas in the vapor state and a refrigerant circulating in a reliquefaction loop 50. At the outlet of the heat exchanger 49, the reliquefied gas circulates in the additional branch 48 until it returns to the tank 2.

[0091] The additional branch 48 and the heat exchanger 49 can thus be used when it is not possible to sub-cool the gas in the liquid state within the cooling circuit 17, which can lead to poor reliquefaction of the gas in the vapor state passing through the second heat exchanger 16, for example in a case where it is desired to limit the heating of the cargo or in the case of gas in the vapor state in too large a quantity. Just as has been described previously, the operation of the management system 1 can also depend on the duration of the journey of the floating structure.

[0092] In such a situation, it may be judicious to distribute the gas in the compressed vapor state between the heat treatment circuit 8 and the additional branch 48 so that all of said gas in the vapor state is reliquefied, while reducing the use of the reliquefaction loop 50 as much as possible.

[0093] Another difference from what has been described is the presence of a compression element 32, arranged at least partially in parallel with the compression device 7, in particular at least with the first compression stage 11. This compression element 32 ensures at least partial redundancy with the compression device 7. This compression element 32 is optional.

[0094] In Figures 3 and 4, the compression element 32 is configured to compress the gas in the vapor state to a pressure identical or similar to that delivered by the first compression stage 11 of the compression device 7. An inlet of the compression element 32 is connected to the supply circuit 6 at a point located between the outlet of the first heat exchanger 14 and an inlet of the compression device 7. The compression element 32 is also capable of supplying the low-pressure gas-consuming device 5 with gas in the vapor state, the supply circuit 6 then comprising a line connecting an outlet of the compression element 32 with an inlet of the low-pressure gas-consuming device 5.

[0095] The gas in the vapor state compressed by the compression element 32 can also circulate in the first branch 9 or directly in the first portion 51 depending on the embodiment of the management system 1. Finally, the gas in the vapor state compressed by the compression element 32 can also reach the compression device 7 and be further compressed by the latter by means of the second compression stage 12, to circulate in the second branch 10 or the second portion 52, or be further compressed by the third compression stage 13 to supply the high-pressure gas-consuming device 4.

[0096] The compression element 32 is shown in Figures 3 and 4, but can also be integrated into the embodiments illustrated in Figures 1 and 2, as well as the variants described below.

[0097] Figures 5 and 6 respectively represent a second variant of the first embodiment and a second variant of the second embodiment. This second variant differs from what is illustrated in Figures 1 and 2 in that the heat treatment circuit 8 comprises at least one separation device 21 arranged downstream of the second heat exchanger 16. Such a separation device 21 has the advantage of preventing a fraction of gas in the vapor state from circulating to the tank 2.

[0098] At the outlet of the second heat exchanger 16, the predominantly reliquefied or totally reliquefied gas can circulate to the separation device 21. The latter comprises an inlet 22 through which this gas enters a volume of the separation device 21. The latter makes it possible to separate a liquid fraction from a vapor fraction of the gas if the latter is not completely reliquefied. The separation device 21 comprises a vapor outlet 23 allowing the vapor fraction to exit the separation device 21 and a liquid outlet 24 allowing the liquid fraction to exit the separation device 21.

[0099] The vapor fraction, if present in the separation device 21, can exit via the vapor outlet 23 and circulate within a first path 25. The first path 25 is connected to the supply circuit 6 and allows the recirculation of the gas in the non-reliquefied vapor state within said supply circuit 6 so that said gas is consumed or reliquefied.

[0100] The liquid fraction present in the separation device 21 can exit through the liquid outlet 24 and circulate within a second channel 26 which connects the device separation 21 to the cooling circuit 17. After joining the latter, the reliquefied gas then circulates to the tank 2 via the orifice 30.

[0101] In Figures 5 and 6, the separation device 21 and the two paths 25, 26 are illustrated within a management system equipped with the third heat exchanger 19. It is nevertheless entirely possible to combine the first variant and the second variant of the management system 1 illustrated in Figures 3 to 6, and thus to implement a management system 1 with the separation device 21, the two paths 25, 26, as well as the additional branch 48 and the heat exchanger 49, regardless of the embodiment of said management system 1.

[0102] [Fig.7] represents a management system similar to [Fig.l] and comprising in plus a calibrated orifice 60. The management system 1 comprises the second heat exchanger 16 connected to the tank 2 by a return branch comprising a termination 29 opening into the tank and an orifice 30 arranged on a portion of the return branch present in the tank. Preferably, the orifice 30 is arranged at the end of the return branch present in the tank.

[0103] In the embodiment of [Fig.7], the orifice 30 is a calibrated orifice 60. For example, for a flow rate of cryogenic liquid returned to the tank 2 of 60 m3 / h and with a calibrated orifice 60 with a diameter of 11 millimeters, the pressure reduction will be 2 bars. For a flow rate of 30 m3 / h and with a calibrated orifice 60 with a diameter of 8.5 millimeters, the pressure reduction will be 2.2 bars. For a flow rate of 20 m3 / h and with a calibrated orifice 60 with a diameter of 7.5 millimeters, the pressure reduction will be 2.1 bars,

[0104] The calibrated orifice 60 is illustrated only in [Fig.7] but it is nevertheless entirely possible to combine the presence of the calibrated orifice 60 with the variants of the first mode and the second mode as well as its first variant of the management system 1 illustrated in Figures 1 to 5.

[0105] 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.

[0106] The invention, as just described, achieves the aim it set itself, and proposes a system for managing a gas contained in a floating structure capable of optimizing the consumption necessary to liquefy the gas not consumed by the consuming device of the floating structure, as a function of conditions linked to the duration of a journey of the floating structure and / or to a quantity of gas in the vapor state present in the tank ceiling. 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 management system in accordance with the invention.

Claims

1. Claims Management system (1) for a gas contained in at least one tank (2) of a floating structure which comprises at least one gas-consuming device (4, 5), the management system (1) comprising: - at least one gas supply circuit (6) for the gas-consuming device (4, 5), the supply circuit (6) comprising at least one compression device (7) comprising at least a first compression stage (11), a second compression stage (12) and a third compression stage (13) and configured to compress gas taken in the vapor state from the tank (2), the compression device (7) delivering the gas in the vapor state at three different pressure levels, - at least one thermal treatment circuit (8) for the gas in the vapor state compressed by at least one of the compression stages (11, 12) of the compression device (7), - at least one first heat exchanger (14) configured to carry out a heat exchange between the gas in the vapor state circulating in the supply circuit (6) between the tank (2) and the compression device (7) and the gas in the vapor state circulating in the heat treatment circuit (8), - at least one cooling circuit (17) comprising at least one pump (18) configured to take the gas in the liquid state from the tank (2), - at least one second heat exchanger (16) configured to carry out a heat exchange between the gas in vapor state circulating in the heat treatment circuit (8) downstream of the first heat exchanger (14) and the gas circulating in the cooling circuit (17), characterized in that the heat treatment circuit (8) comprises at least a first portion (51) configured to circulate compressed gas through the first compression stage (11) of the compression device (7) and a second portion (52) configured to circulate compressed gas through the second compression stage (12) of the compression device (7), the second compression stage (12) being arranged downstream of the first stage compression device (11), the first portion (51) and the second portion (52) extending at least partially between the compression device (7) and the second heat exchanger (16), the second portion (52) being provided with an expansion member (15) and a divergence point (54) from which the first portion (51) and the second portion (52) start, the divergence point (54) being arranged between the first heat exchanger (14) and the second heat exchanger (16).

2. A management system (1) according to claim 1, wherein the first portion (51) comprises a first valve (41) and the second portion (52) comprises a second valve (42), the first valve (41) and the second valve (42) being configured to control the circulation of gas within said portions.

3. Management system (1) according to any one of claims 1 to 2, wherein the first portion (51) and the second portion (52) start respectively at the first compression stage (11) and at the second compression stage (12) of the compression device (7).

4. Management system (1) according to any one of claims 1 to 3, wherein the first portion (51) and the second portion (52) meet at a convergence point (55).

5. Management system (1) according to claim 4, wherein the convergence point (55) is arranged between the first heat exchanger (14) and the second heat exchanger (16).

6. Management system (1) according to claim 4, wherein the convergence point (55) is arranged downstream of the second heat exchanger (16).

7. Management system (1) according to any one of claims 1 to 6, wherein the first portion (51) and the second portion (52) of the heat treatment circuit (8) each comprise a pass of the first heat exchanger (14) and / or of the second heat exchanger (16).

8. Management system (1) according to any one of claims 1 to 7, in which the heat treatment circuit (8) comprises a separation device (21) of which an inlet (22) is arranged downstream of the second heat exchanger (16).

9. Management system (1) according to any one of claims 1 to 8, wherein the second heat exchanger (16) is connected to the 21 tank (2) by a return branch comprising a termination (29) opening into the tank and an orifice (30) arranged on a portion of the return branch present in the tank.

10. Management system (1) according to claim 9, wherein the orifice (30) is a calibrated orifice (60).

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