System for managing a gas in liquid state transported and / or stored by a floating structure

Abstract

System for managing a gas in the liquid state transported and / or stored by a floating structure The present invention relates to a system (1) for managing a gas in the liquid state transported and / or stored by a floating structure comprising at least one tank (2), the management system (1) comprising: a supply circuit (4), a heat treatment line (6), a heat exchanger (7), a cooling line (8), characterized in that the management system (1) comprises a mixing device (9) configured to mix the gas in the vapor state circulating in the heat treatment line (6) and the gas in the liquid state circulating in the cooling line (8), the management system (1) comprising a return line (14) comprising at least one outlet orifice (15) configured to be positioned at the bottom of the tank (2). (figure 1)

Description

Title of the invention: System for managing a gas in liquid state transported and / or stored by a floating structure

[0001] The present invention relates to the field of floating structures for storing and / or transporting gas in the liquid state comprising at least one tank allowing the transport and / or storage of said gas and more particularly concerns a gas management system arranged within such floating structures.

[0002] During a journey made by a floating structure comprising at least one 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 a portion of said gas in the liquid state in order to supply at least one of its gas-consuming devices, and this via a supply circuit of the gas management system mentioned above.

[0003] Generally speaking, it is known to favor the consumption of the gas that has evaporated within the tank in order to supply the gas-consuming device. Such evaporation can occur following an overall increase in the temperature of the tank over time and the gas in the vapor state generated must be evacuated in order to avoid overpressure of the tank. The gas supply to the gas-consuming device is carried out using the management system mentioned above.

[0004] In the event of an excessive quantity of gas in the vapor state compared to the supply requirement of the gas-consuming device, it is also known to return the excess gas in the vapor state to the tank. This return to the tank is generally preceded by an operation of reliquefying the gas in the vapor state in order to return it to the liquid state and thus avoid a rise in pressure in the tank. Such reliquefaction can be implemented using means for cooling the gas in the vapor state so that the latter liquefies.

[0005] It is known to arrange a separator within the management system downstream of the aforementioned cooling means. The separator makes it possible to separate a liquid fraction from a vapor fraction of the gas intended to be returned to the tank. The separator provides safety in the event of partial reliquefaction of the gas in the vapor state and thus avoids returning gas in the vapor state to the tank, for example by returning the vapor fraction to the feed circuit. The presence of the separator is, however, a source of constraints. On the one hand, it is an expensive element because it is equipped with a plurality of instruments and valves, on the other hand it is in the form of a bulky tank and therefore affects the spatial size of the management system. It is possible to do without such a separator by implementing sub-re cooling ensuring complete reliquefaction of the gas in the vapor state intended to be returned to the tank, but this also entails an additional cost and does not resolve the spatial footprint constraint mentioned previously.

[0006] The present invention makes it possible to do without a separator and / or any sub-cooling means and therefore proposes a system for managing a gas in the liquid state transported and / or stored by a floating structure comprising at least one tank configured to contain the gas and 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 configured to compress gas taken in the vapor state from the tank to a pressure compatible with the needs of the gas-consuming appliance, - at least one heat treatment line for the gas in the vapor state compressed by the compression device, the heat treatment line being connected to the supply circuit downstream of the compression device, - at least one 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 line, - at least one cooling line comprising at least one pumping device configured to take the gas in the liquid state from the tank,

[0007] characterized in that the management system comprises a mixing device configured to mix the gas in the vapor state circulating in the heat treatment line and the gas in the liquid state circulating in the cooling line, the management system further comprising a return line connected to an outlet of the mixing device and configured to extend to the tank, the return line comprising at least one outlet orifice configured to be positioned at the bottom of the tank.

[0008] The combination of the mixing device and the return line and its outlet orifice arranged at the bottom of the tank makes it possible to design a compact and inexpensive gas management system because it makes it possible to do without a separator and / or sub-cooling means. The management system according to the invention thus guarantees a limitation of costs and spatial footprint.

[0009] The supply circuit allows the gas in the vapor state forming in the tank to be taken and used as fuel for the gas-consuming device. Although the tank has properties ensuring thermal insulation, the gas in the vapor state forms naturally over time and must be treated in one way or another in order to limit the increase in pressure in the tank. The circuit supply therefore allows it to be used as fuel for the gas-consuming device. The compression device, in addition to ensuring the suction of the gas in vapor state out of the tank, allows the latter to be raised to a pressure compatible with the gas-consuming device.

[0010] The gas-consuming device may, for example, be a motor providing propulsion for the floating structure or an electric generator supplying the floating structure with electricity. It is also possible for the management system to be capable of supplying a plurality of gas-consuming devices, in which case the supply circuit is adapted accordingly in order to be able to supply each of them with gas in the vapor state.

[0011] The heat treatment line is connected to the supply circuit downstream of the compression device and allows the circulation of the gas in the vapor state present in excess of the supply requirement of the gas consuming device. Instead of wasting this excess gas in the vapor state, it circulates in the heat treatment line in order to be able to return to the tank. The heat exchanger allows it to be pre-cooled upon its return, thanks to a heat exchange with the gas in the vapor state leaving the tank and circulating in the supply circuit. The excess gas in the vapor state is therefore preserved by returning to the tank instead of being burned or released into the atmosphere.

[0012] The cooling line ensures the circulation of the gas in the liquid state allowing the reliquefaction of the gas in the vapor state circulating in the heat treatment line. The pumping device ensuring the collection of the gas in the liquid state is advantageously arranged at the bottom of the tank in order to pump the gas in the liquid state at the lowest possible temperature.

[0013] Subsequently, the precooled vapor gas circulating in the heat treatment line and the liquid gas circulating in the cooling line join together within the mixing device. Since the liquid gas is at a very low temperature, this makes it possible to cool the vapor gas flow coming from the heat treatment line until it is reliquefied by direct mixing. It should be noted that the mixing device has an advantageous compactness compared to other devices capable of reliquefying the vapor gas coming from the heat treatment line, for example a heat exchanger.

[0014] At the outlet of the mixing device, the gas mixture is in the liquid state. It then circulates within the return line to the tank. It enters the tank via the outlet orifice located at the bottom of the tank. Thanks to the thermal inertia of the gas cargo in the liquid state, the return of the gas mixture to the bottom of the tank has little effect on the state of said cargo. This makes it possible to avoid having to sub-cool the gas mixture at the outlet of the mixing device and before returning it to the tank. The management system according to the invention therefore does without a sub-cooling device which may be expensive and / or bulky and / or energy-intensive.

[0015] According to an optional feature, the outlet orifice has a section between 5% and 30% of a section of the return line. The outlet orifice is therefore a calibrated orifice, the role of which is in particular to maintain at all times the gas leaving the mixer at at least the pressure which prevails at the bottom of the tank. The sections mentioned above are measured in a section plane perpendicular to a main direction of elongation of the outlet orifice or of the return line.

[0016] For example, if the nominal diameter of the return line is 80mm, the diameter of the calibrated orifice is then between 4mm and 24mm.

[0017] In addition, returning the gas mixture precisely to the bottom of the tank makes it possible to avoid a partial evaporation phenomenon, also called flash, when returning to the tank.

[0018] According to a characteristic of the invention, the mixing device comprises a first inlet at which the heat treatment line is connected and a second inlet at which the cooling line is connected. The first inlet and the second inlet guarantee access to an internal volume of the mixing device common to both inlets. Thus, when the flow of gas in the vapor state coming from the heat treatment line enters the mixing device via the first inlet while the flow of gas in the liquid state coming from the cooling line enters the mixing device via the second inlet, the two flows mix together directly in order to reliquefy the flow of gas in the vapor state. The outlet of the mixing device mentioned above allows the evacuation of the mixture of gas flows and its circulation within the return line.

[0019] It is thus understood that the heat treatment line extends from the feed circuit to the first inlet of the mixing device, while the cooling line extends from the tank to the second inlet of the mixing device.

[0020] According to a characteristic of the invention, the heat treatment line comprises a regulating element arranged between the heat exchanger and the first inlet of the mixing device. The regulating element performs two functions: on the one hand, it regulates the flow rate of the gas in the vapor state which circulates in the heat treatment line, on the other hand, it allows the compression device to work at the pressure of the consumer independently of the pressure which prevails in the mixing device.

[0021] The regulating element may also implement an expansion of the gas in the vapor state circulating in the heat treatment line. Such an expansion is carried out before mixing with the flow of gas in the liquid state coming from the cooling line in order to promote the reliquefaction of the flow of gas in the vapor state coming from the line heat treatment within the mixing device.

[0022] According to a characteristic of the invention, the management system comprises a measuring member configured to measure a temperature of the gas in the vapor state circulating in the heat treatment line between the regulating element and the first inlet of the mixing device. Measuring the temperature of the flow of gas in the vapor state circulating in the heat treatment line downstream of the regulating element makes it possible to obtain its temperature at its inlet into the mixing device.

[0023] Knowing this temperature is essential in order to ensure optimal reliquefaction of the gas flow in the vapor state within the mixing device. Indeed, depending on the temperature recorded, it is possible to deduce the flow rate of the gas flow in the liquid state necessary to mix with the gas flow in the vapor state for optimal reliquefaction of the latter. Thus, the flow rate of the gas flow in the liquid state circulating in the cooling line can be adjusted according to the temperature recorded by the measuring device, in order to guarantee total reliquefaction of the gas flow in the vapor state without consuming too much energy by sending a gas flow in the liquid state at a flow rate that is superfluous compared to the flow rate necessary to guarantee said reliquefaction.

[0024] According to a characteristic of the invention, the cooling line comprises a regulating component. The latter is a component which regulates or controls the flow rate of the gas in the liquid state circulating in the cooling line, which is advantageous with respect to what has been described previously concerning the reading of the temperature of the flow of gas in the vapor state circulating in the heat treatment line. Incidentally, this regulating component can ensure an expansion of the gas in the liquid state coming from the tank and circulating in the cooling line. The lowering of the pressure has the consequence of lowering the temperature.

[0025] The regulating element and the regulating component are controlled to avoid a large pressure difference between the flow of gas in the vapor state and the flow of gas in the liquid state, so as to achieve good mixing of these flows in the mixing device. Such a pressure differential is of the order of 6 bars + / -25%. For example, the pressure of the gas in the vapor state present in the heat treatment line downstream of the regulating element is for example equal to 13 bars. The pressure of the gas in the liquid state circulating in the cooling line downstream of the regulating component is for example equal to 7 bars. The pressure within the mixing device is then less than 7 bars, for example of the order of 4 bars.

[0026] According to a characteristic of the invention, the compression device can be configured to raise the pressure of the gas in the vapor state to a pressure of between 6 and 18 bars.

[0027] According to another characteristic of the invention, the compression device can be configured to raise the pressure of the gas in the vapor state to a pressure between 150 and 400 bars.

[0028] The pressure range implemented by the compression device is dependent on the compatibility with the gas consuming device or at least one of the consuming devices if several of them can be supplied by the management system, particularly when it is the engine ensuring the propulsion of the floating structure.

[0029] In the case where the gas in the vapor state must be raised to a pressure of between 150 and 400 bars, the compression device may for example be in the form of several compressors aligned in series and each raising the pressure of the gas in the vapor state progressively until reaching a pressure of between 150 and 400 bars. In this configuration, if the management system is capable of supplying several consumer devices which do not have the same requirements in terms of pressure of the gas in the vapor state supplied, the management system may comprise an auxiliary supply line connected to the supply circuit between two compressors of the compression device and making it possible to supply a gas consumer device having a lower pressure compatibility.

[0030] According to a characteristic of the invention, when the management system is configured to interact with at least two tanks, the supply circuit is divided into at least two branches, each of the branches being configured to circulate the gas in the vapor state contained in one of the tanks within the supply circuit, each of the branches comprising a flow regulating member. Generally speaking, a floating structure, for example an LNG carrier or any other vessel specialized in the transport and / or storage of gas in the liquid state, is equipped with a plurality of tanks in order to optimize a total possible capacity of gas in the liquid state. The management system according to the invention can therefore advantageously be capable of treating the gas in the liquid state or in the vapor state with respect to a plurality of tanks.

[0031] In such a configuration, since the gas in the vapor state can form within each of the tanks, it must be evacuated under all circumstances so that the saturation pressure of each of the tanks can be regulated. Thus, the supply circuit is divided into several branches and each of them extends to one of the tanks. Thus, a fluid connection is set up between each of the tanks and the gas-consuming device so that the gas in the vapor state from all of the tanks can supply the consuming device, but also so that the saturation pressure of each of the tanks can be regulated.

[0032] Advantageously, the branches join between the tanks and the heat exchanger, so that all of the gas in the vapor state taken from the tanks subsequently undergoes the same thermal treatment, but also to limit the multiplication of pipelines or any other elements of the management system.

[0033] In order to regulate the circulation of gas in the vapor state in the supply circuit from one tank to another, each flow regulating member of each of the branches is capable of opening more or less in order to define a passage section of the branch in question and therefore a flow rate of gas in the vapor state circulating in it. This makes it possible to favor the evacuation of gas in the vapor state out of one or more tanks compared to one or more other tanks, for example if one of the tanks has a higher saturation pressure than the other tanks.

[0034] According to a characteristic of the invention, when the management system is configured to interact with at least two tanks, the return line is divided into at least two paths, each of the paths being configured to circulate the gas in the liquid state to one of the tanks, each of the paths comprising a flow regulation device.

[0035] Like the branches of the supply circuit, the return line can be divided into paths to circulate the gas in the liquid state leaving the mixing device to one of the tanks or to several tanks simultaneously. Each flow control device arranged on the paths is able to open more or less in order to define a passage section of the path in question and therefore a flow rate of gas in the liquid state circulating in the path in question. This makes it possible to distribute in each of the tanks the gas mixture coming from the mixing device according to any condition.

[0036] By way of example, it is possible to favor a return of the gas to the liquid state in the tank having the lowest overall temperature in order to avoid an excessive rise in temperature in the tanks having a higher overall temperature. According to another example, it is possible to favor a return of the gas to the liquid state in the least filled tank.

[0037] The invention also covers a floating structure comprising at least one tank, at least one gas-consuming device and at least one management system as described previously.

[0038] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several exemplary embodiments given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0039] [Fig-1] represents a gas management system according to the invention adapted to a structure floating comprising a tank intended to store said gas in the liquid state,

[0040] [Fig.2] represents the gas management system according to the invention adapted to a structure floating comprising a plurality of tanks intended to store said gas in the liquid state.

[0041] [Fig. 1] is a schematic representation of a gas management system 1 according to the invention. Such a management system 1 can for example be integrated into a structure floating structure for transporting and / or storing gas in the liquid state, said gas being able for example to be natural gas, also called LNG. Generally speaking, such a floating structure comprises at least one tank 2 ensuring the transport and / or storage of gas in the liquid state, but according to the configuration illustrated in [Fig.l], said floating structure comprises a single tank 2. Such a floating structure also comprises at least one gas-consuming device 3, which may be for example a motor ensuring the propulsion of the floating structure or an electric generator ensuring the supply of electricity to the floating structure.

[0042] The tank 2 is configured to ensure sealing and thermal insulation with respect to the gas in the liquid state that it contains. However, over time, the gas in the liquid state present in the tank 2 partially evaporates, leading to an increase in the saturation pressure of the tank 2. The management system 1 therefore makes it possible to prevent a potential overpressure within the tank 2 by evacuating the gas in the vapor state therefrom.

[0043] To do this, the management system 1 comprises a supply circuit 4 extending between the tank 2 and the gas-consuming device 3. The supply circuit 4 comprises a compression device 5 configured to suck in the gas in the vapor state present in the tank 2. In addition, the compression device 5 is also configured to raise the pressure of the gas in the vapor state so that the latter has a pressure compatible with the needs of the gas-consuming device 3. The supply circuit 4 thus makes it possible, on the one hand, to regulate the saturation pressure of the tank 2 and, on the other hand, to supply fuel to the gas-consuming device 3, the latter of course having to be compatible with the nature of the gas contained in the tank 2.

[0044] In [Fig.l], a single gas-consuming device 3 is shown, but, in a manner not illustrated, the management system 1 can be configured to supply a plurality of gas-consuming devices 3, for example a first gas-consuming device which is a motor ensuring the propulsion of the floating structure and a second gas-consuming device which is an electric generator ensuring the supply of electricity to the floating structure.

[0045] Depending on the pressure requirements of the gas-consuming device(s) 3, the compression device 5 may be capable of raising the pressure according to different pressure ranges, for example between 6 and 18 bars, or between 150 and 400 bars.

[0046] In the event that the compression device 5 is configured to raise the pressure of the gas in the vapor state to a pressure of between 150 and 400 bars, the compression device 5 may be in the form of a plurality of compressors aligned in series and progressively increasing the pressure of the gas in the vapor state up to this pressure range.

[0047] The management system 1 also comprises a heat treatment line 6 connected to the supply circuit 4 downstream of the compression device 5 and extending to the tank 2. It is a flow of gas in the vapor state which circulates in the heat treatment line 6, said flow corresponding to an excess of gas in the vapor state compared to the supply requirements of the gas consuming device 3. The heat treatment line 6 thus participates in a return of the excess gas in the vapor state to the tank 2. The objective of the management system 1 according to the invention is to carry out a reliquefaction of the excess gas in the vapor state before returning it to the tank 2.

[0048] In this respect, the management system 1 comprises a heat exchanger 7 configured to carry out a heat exchange between the gas in the vapor state circulating in the supply circuit 4 and the gas in the vapor state circulating in the heat treatment line 6 in order to precool the latter. Implementing such precooling subsequently makes it possible to facilitate the reliquefaction of the gas in the vapor state intended to return to the tank 2.

[0049] The reliquefaction of the gas in the vapor state intended to return to the tank 2 is carried out in particular using a cooling line 8 and a mixing device 9. The cooling line 8 comprises a pumping device 10 making it possible to take the gas in the liquid state from the tank 2. The flow of gas in the liquid state circulating in the cooling line 8 allows the reliquefaction of the gas in the vapor state circulating in the heat treatment line 6.

[0050] It is within the mixing device 9 that the gas in the vapor state coming from the heat treatment line 6 is reliquefied. To do this, the mixing device 9 comprises a first inlet 11 to which the heat treatment line 6 is connected, and a second inlet 12 to which the cooling line 8 is connected. The first inlet 11 and the second inlet 12 guarantee access to an internal volume of the mixing device 9 common to the two inlets 11, 12.

[0051] The flow of gas in the vapor state coming from the heat treatment line 6 thus enters the mixing device 9 via the first inlet 11 while the flow of gas in the liquid state enters the mixing device 9 via the second inlet 12. The two flows mix with each other, and this allows the flow of gas in the liquid state, due to its low temperature, to reliquefy the gas in the vapor state. In order to promote the mixing of the gas flows, and therefore the reliquefaction, the internal volume of the mixing device 9 comprises a plurality of obstacles, which take for example a helical shape, in order to lengthen a circulation time of the gas mixture and also to disturb a trajectory of the gas flows to mix them more with each other. During this mixing, the flow of gas in the liquid state reliquefies the flow of gas in the vapor state. A flow of mixed gas is therefore formed in the liquid state within the mixing device 9.

[0052] The mixing device 9 also comprises an outlet 13 through which the mixture of gas in the liquid state exits, which comprises the flow of gas in the liquid state coming from the cooling line 8 and the flow of reliquefied gas coming from the heat treatment line 6. The management system 1 further comprises a return line 14 connected to the outlet 13 of the mixing device 9 and extending to the tank 2. It is within the return line 14 that the gas mixture circulates in order to return to the tank 2.

[0053] The return line 14 comprises an outlet orifice 15 opening at the bottom of the tank 2. Such an orifice is for example arranged at the end of the return line 4, the latter being in the liquid part contained in the tank 2.

[0054] The outlet orifice 15 is for example a calibrated orifice, in the sense that it has a smaller section than a section of the return line 14 measured just before the outlet orifice 15. The section of the outlet orifice 15 is between 5% and 30% of the section of the return line 14. This has the effect of maintaining a pressure within the return line 14 higher than that at the bottom of the tank 2.

[0055] For example, for a flow rate of gas in the liquid state returned to the tank 2 of 60 m3 / h and with a calibrated orifice with a diameter of 11 millimeters, the reduction in pressure will be 2 bars. For a flow rate of 30 m3 / h and with a calibrated orifice with a diameter of 8.5 millimeters, the reduction in pressure will be 2.2 bars. For a flow rate of 20 m3 / h and with a calibrated orifice with a diameter of 7.5 millimeters, the reduction in pressure will be 2.1 bars.

[0056] The previously described configuration of the management system 1 is particularly advantageous. The mixing device 9 is in fact more compact than a potential other element ensuring the reliquefaction of the gas in the vapor state, for example a heat exchanger. In addition, the mixing device is configured to guarantee the total reliquefaction of the gas flow in the vapor state coming from the heat treatment line 6. The management system 1 according to the invention thus does without a separator arranged at the outlet of the mixing device 9. Such a separator makes it possible to separate a liquid fraction from a vapor fraction of a gas flow in the two-phase state, but has constraints of cost and spatial size. The presence of the mixing device 9 thus avoids the installation of a separator and its gas return line, thus ensuring compactness and cost savings for installing the management system 1 according to the invention.

[0057] The outlet orifice 15 also has an advantage due to its positioning at the bottom of the tank 2. In fact, the pressure is higher at the bottom of the tank 2 due to the static pressure of the column of gas in the liquid state stored in the tank 2. For liquefied natural gas at a temperature of -154°C for example, the gas remains in the liquid state. liquid at a pressure of 2.2 bars at the bottom of tank 2. The management system 1 thus also makes it possible to do without a sub-cooling device, which is also expensive, bulky and energy-intensive.

[0058] In order to facilitate reliquefaction, the heat treatment line 6 comprises a regulating element 16. For its part, the cooling line 8 comprises a regulating component 17. The regulating element 16 is positioned between the heat exchanger 7 and the first inlet 11 of the mixing device 9.

[0059] The regulating component 17 is positioned between the pumping device 10 and the second inlet 12 of the mixing device 9.

[0060] The regulating element 16 and the regulating component 17 make it possible to regulate, that is to say to control, the flow rate respectively of gas in the vapor state and of gas in the liquid state which circulates in the heat treatment line 6 and in the cooling line 8. This flow rate regulation affects the liquid-gas mixture which takes place within the mixing device 9 and also promotes the reliquefaction of the flow of gas in the vapor state within the mixing device 9.

[0061] The management system 1 further comprises a measuring member 18 configured to measure the temperature of the flow of gas in the vapor state circulating in the heat treatment line 6 between the regulating element 16 and the first inlet 11. The measuring member 18 thus makes it possible to know the temperature of the gas in the vapor state at its entry into the mixing device 9. The measuring member 18 can also act as a flow meter in order to also know the quantity of gas in the vapor state entering the mixing device 9. Knowing these parameters, it is thus possible to deduce the quantity of gas in the liquid state to carry out a total reliquefaction of the gas in the vapor state during mixing within the mixing device 9.

[0062] As a result, a flow rate of gas in the liquid state circulating in the cooling line 8 can be adjusted so that said flow rate is sufficient to ensure total reliquefaction of the gas in the vapor state but while being limited as much as possible to avoid consuming too much energy by sending gas in the liquid state in superfluous quantity. In this respect, the regulation component 17 controls the flow rate of the gas in the liquid state circulating in the cooling line 8 as a function of the data of the flow of gas in the vapor state recorded by the measuring member 18.

[0063] [Fig. 2] represents the gas management system 1 according to the invention, but this time adapted to a floating structure comprising a plurality of tanks intended to store said gas in the liquid state. In [Fig. 2], two tanks 2a, 2b are represented but the management system 1 can be adapted to interact with more tanks.

[0064] When the floating structure comprises two tanks 2a, 2b, at least a portion of the circuits and lines of the management system 1 interacting directly with said tanks 2a, 2b are split in order to ensure gas management with respect to all of the latter. This is particularly the case for the supply circuit 4, for the cooling line 8 and for the return line 14.

[0065] Thus, the supply circuit 4 is divided into a first branch 19a making it possible to participate in the suction of the gas in the vapor state contained in a first tank 2a, and into a second branch 19b making it possible to participate in the suction of the gas in the vapor state contained in a second tank 2b. As a result, the compression device 5 is capable of sucking the gas in the vapor state present in one and / or the other of the tanks 2.

[0066] Preferably, the branches 19 join between the tanks 2 and the heat exchanger 7 so that the entire gas in the vapor state subsequently undergoes the same heat treatment. This also avoids multiplying the installation of elements that can be used in common.

[0067] Each branch 19 comprises a flow regulating member 20 capable of more or less opening a passage section in order to regulate the flow of gas in the vapor state circulating within the branch 19 considered. As such, the first branch 19a comprises a first regulating member 20a and the second branch 19b comprises a second regulating member 20b. The regulating members 20 make it possible in particular to prioritize the evacuation of the gas in the vapor state from one tank 2 compared to the other. This may prove important when one of the tanks 2 has a high saturation pressure due to a greater quantity of gas in the vapor state within it. Said tank 2 must therefore be emptied of gas in the vapor state as a priority.

[0068] The gas in the liquid state circulating in the cooling line 8 can also be taken from one and / or the other tank 2. The management system thus comprises a first pumping device 10a and a second pumping device 10b, each of the pumping devices 10 being immersed within one of the tanks 2. The gas in the liquid state circulating in the cooling line 8 and allowing the reliquefaction of the gas in the vapor state circulating in the heat treatment line 6 within the mixing device 9 can therefore come from one and / or the other of the tanks 2.

[0069] Finally, the return line 14 is divided into two paths 21, each of the paths 21 extending to the bottom of one of the tanks 2. Of course, each path 21 comprises an outlet orifice 15 opening at the bottom of the tank 2 in question, such an orifice being for example a calibrated orifice like that described above in relation to [Fig.l]. The return line 14 therefore comprises a first path 21a provided with a first outlet orifice 15a opening at the bottom of the first tank 2a and a second path 21b provided with a second outlet orifice 15b opening at the bottom of the second tank 2b.

[0070] Each channel 21 further comprises a flow regulation device 22 capable of more or less open a passage section in order to regulate the flow of gas in the liquid state circulating within the channel 21 considered. As such, the first channel 21a comprises a first regulation device 22a and the second channel 21b comprises a second regulation device 22b.

[0071] The regulating devices 22 make it possible in particular to favor the return of the gas mixture in the liquid state within one tank 2 compared to the other. The gas mixture, which is at a higher temperature than the gas in the liquid state contained in the tanks 2 following the reliquefaction operation, can for example return in a preferential manner to the tank 2 having the lowest temperature. According to another example, the gas mixture can return as a priority to the least filled tank 2.

[0072] It is understood from the above that the management system 1 according to the invention can be adapted so as to guarantee the management of a plurality of tanks 2 while remaining as compact as possible. The structural and functional elements not described of the management system 1 of [Fig.2] being identical to those shown in [Fig.l], reference will be made to the description of [Fig.l] concerning the elements common to both representations.

[0073] 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.

[0074] The invention, as just described, achieves the goal it set itself, and makes it possible to propose a management system combining reliquefaction efficiency and compactness. 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

Claims

1. Management system (1) for a gas in the liquid state transported and / or stored by a floating structure comprising at least one tank (2, 2a, 2b) configured to contain the gas and at least one gas-consuming device (3), the management system (1) comprising: - at least one gas supply circuit (4) for the gas-consuming appliance, the supply circuit (4) comprising at least one compression device (5) configured to compress gas taken in the vapor state from the tank (2, 2a, 2b) to a pressure compatible with the needs of the gas-consuming appliance (3), - at least one heat treatment line (6) for the gas in the vapor state compressed by the compression device (5), the heat treatment line (6) being connected to the supply circuit (4) downstream of the compression device (5), - at least one heat exchanger (7) configured to carry out a heat exchange between the gas in the vapor state circulating in the supply circuit (4) between the tank (2, 2a, 2b) and the compression device (5) and the gas in the vapor state circulating in the heat treatment line (6), - at least one cooling line (8) comprising at least one pumping device (10, 10a, 10b) configured to take the gas in the liquid state from the tank (2, 2a, 2b), characterized in that the management system (1) comprises a mixing device (9) configured to mix the gas in the vapor state circulating in the heat treatment line (6) and the gas in the liquid state circulating in the cooling line (8), the management system (1) further comprising a return line (14) connected to an outlet (13) of the mixing device (9) and configured to extend to the tank (2, 2a, 2b), the return line (14) comprising at least one outlet orifice (15, 15a, 15b) configured to be positioned at the bottom of the tank (2, 2a, 2b).

2. Management system (1) according to claim 1, wherein the mixing device (9) comprises a first inlet (11) at which the heat treatment line (6) is connected and a second inlet (12) to which the cooling line (8) is connected.

3. Management system (1) according to the preceding claim, wherein the heat treatment line (6) comprises a regulating element (16) arranged between the heat exchanger (7) and the first inlet (11) of the mixing device (9).

4. Management system (1) according to the preceding claim, comprising a measuring member (18) configured to measure a temperature of the gas in the vapor state circulating in the heat treatment line (6) between the regulating element (16) and the first inlet (11) of the mixing device (9).

5. Management system (1) according to any one of the preceding claims, wherein the cooling line (8) comprises a regulation component (17).

6. Management system (1) according to any one of claims 1 to 7, wherein the outlet orifice (15, 15a, 15b) has a section between 5% and 30% of a section of the return line (14).

7. Management system (1) according to any one of the preceding claims, wherein the compression device (5) is configured to raise the pressure of the gas in the vapor state to a pressure of between 6 and 18 bars.

8. Management system (1) according to any one of claims 1 to 6, wherein the compression device (5) is configured to raise the pressure of the gas in the vapor state to a pressure of between 150 and 400 bars.

9. Management system (1) according to any one of the preceding claims, configured to interact with at least two tanks (2, 2a, 2b), in which the supply circuit (4) is divided into at least two branches (19, 19a, 19b), each of the branches (19, 19a, 19b) being configured to circulate the gas in the vapor state contained in one of the tanks (2, 2a, 2b) within the supply circuit (4), each of the branches (19, 19a, 19b) comprising a flow regulating member (20, 20a, 20b).

10. Management system (1) according to any one of the preceding claims, configured to interact with at least two tanks (2, 2a, 2b), in which the return line (14) divides into at least two paths (21, 21a, 21b), each of the paths (21, 21a, 21b) being configured to circulate the gas in the liquid state to one of the tanks (2, 2a, 2b), each of the channels (21, 21a, 21b) comprising a flow control device (22, 22a, 22b).

11. Floating structure comprising at least one tank (2, 2a, 2b), at least one gas-consuming device (3) and at least one management system (1) according to any one of the preceding claims.

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