Gas supply system for high- and low-pressure gas-consuming devices and method for controlling such a system

Abstract

The present invention relates to a supply system (1) for supplying a high-pressure gas-consuming device (4) and a low-pressure gas-consuming device (5), the supply system (1) comprising: a first supply circuit (2), a second supply circuit (3), a return line (14), a first heat exchanger (6) and a second heat exchanger (7), the supply system (1) comprising a heat treatment branch (33) connected to the second supply circuit (3), the supply system (1) comprising a third heat exchanger (36) configured to operate a heat exchange between the gas flowing through the heat treatment branch (33) and the gas flowing through the return line (14).

Description

[0001] DESCRIPTION

[0002] Title of the invention: Gas supply system for high and low pressure gas consuming appliances and method for controlling such a system

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

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

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

[0006] The efficiency achieved by such a system is already high, but there is still room for improvement in the overall efficiency of this system. One such improvement is the use of gas in vapor form to improve the condensation of excess gas in vapor form recirculating back to the tank.

[0007] The present invention aims to implement such an improvement by proposing a gas supply system for at least one high-pressure gas-consuming device and at least one low-pressure gas-consuming device of a floating structure comprising at least one tank configured to contain the gas at least in the liquid state, the supply system comprising: at least one first gas supply circuit for the high-pressure gas-consuming device, at least one high-pressure evaporator configured to evaporate the gas circulating in the first supply circuit, at least one second gas supply circuit for the low-pressure gas-consuming device, comprising at least one compression device configured to compress gas taken in the vapor state from the tank to a pressure compatible with the needs of the low-pressure gas-consuming device,at least one gas return line connected to the second supply circuit downstream of the compression device and extending to the tank, at least one first heat exchanger and one second heat exchanger, each configured to carry out a heat exchange between the gas circulating in the return line in the vapor state and the gas in the liquid state circulating in the first supply circuit, characterized in that the supply system comprises a branch for heat treatment of the gas in the vapor state circulating in the return line, the heat treatment branch being connected to the second supply circuit upstream of the compression device,the supply system comprising a third heat exchanger configured to carry out a heat exchange between the gas in the vapor state circulating in the heat treatment branch and the gas in the vapor state circulating in the return line. The supply system can thus use the gas in the vapor state present in the tank, more particularly in a headspace of the tank, in order to participate in the condensation of the gas in the vapor state circulating in the return line. The heat exchange carried out within the third heat exchanger constitutes an additional heat exchange involving the gas in the vapor state circulating in the return line in order to improve the condensation thereof. The heat exchange carried out within the third heat exchanger is implemented provided that the gas in the vapor state taken from the tank is at a suitable temperature,that is to say preferably lower than the temperature of the gas in the vapor state circulating in the return line, at the inlet of the third heat exchanger. If this condition is respected, the gas in the vapor state then circulates within the heat treatment branch in order to pass through the third heat exchanger.,

[0008] The first gas supply circuit is used to meet the fuel requirements of the high-pressure gas-consuming device. This may, for example, be the means of propulsion of the floating structure, for example, a ME-GI engine. The first supply circuit extends from the tank to the high-pressure gas-consuming device. The liquid gas can be drawn from the tank using a submersible pump installed at the bottom of the tank. The submersible pump thus ensures the pumping of the liquid gas so that it can circulate in the first supply circuit.

[0009] Since the gas must be in the vapor state to be able to supply the high-pressure gas-consuming device, the high-pressure evaporator ensures the evaporation of the gas before its supply to the high-pressure gas-consuming device. The high-pressure evaporator is the site of an exchange of calories between the gas in the liquid state circulating in the first supply circuit and a heat transfer fluid, for example glycolated water, sea water or water vapor. This heat transfer fluid, whatever its form, must be at a sufficiently high temperature to create a change of state of the gas so that the latter passes into the vapor or supercritical state and supplies the high-pressure gas-consuming device. Generally speaking, the gas contained in the tank can pass naturally, or forced by the floating structure, into the vapor state. The gas within the tank passing into the vapor state must be evacuated so as not to create excess pressure within the tank.

[0010] Such a function is provided by the second gas supply circuit of the low-pressure gas-consuming device. Such a second supply circuit extends from the tank to the low-pressure gas-consuming device. The latter may, for example, be an auxiliary engine such as an internal combustion engine of an electric generator. The compression device arranged on the second supply circuit is responsible for sucking the gas present in the tank headspace in order to be able to both supply the low-pressure gas-consuming device and also to regulate the pressure within the tank.

[0011] At the outlet of the compression device, the gas in vapor state can supply the low-pressure gas-consuming device, and / or circulate through the return line if the low-pressure gas-consuming device requires little or no fuel supply. Since the return line is connected downstream of the compression device, the gas in vapor state drawn in by the compression device can therefore circulate through it.

[0012] The gas in the vapor state circulating in the return line first passes through the second heat exchanger, then the third heat exchanger, then the first heat exchanger, before returning to the tank. A heat exchange takes place within the three heat exchangers mentioned above, in order to gradually cool the gas in the vapor state circulating in the return line. By passing through the first heat exchanger and the second heat exchanger, it is the gas in the liquid state circulating in the first supply circuit which allows the gas in the vapor state circulating in the return line to be cooled. By passing through the third heat exchanger, it is the gas in the vapor state circulating in the heat treatment branch which allows the gas in the vapor state circulating in the return line to be cooled.

[0013] The temperature of the gas in the vapor state then decreases as it passes through the three heat exchangers, until the gas condenses and returns to the liquid state substantially downstream of the first heat exchanger. The gas thus condensed, that is to say in the liquid state, then circulates to the tank.

[0014] The heat treatment branch being connected to the second supply circuit, the supply system can be configured so that the gas in the vapor state at the tank outlet can circulate directly within the heat treatment branch and pass through the third heat exchanger before being compressed by the compression device and continuing its circulation to the low-pressure gas-consuming device or within the return line.

[0015] According to a characteristic of the invention, the third heat exchanger comprises a first pass installed on the return line between the first heat exchanger and the second heat exchanger, and a second pass installed on the heat treatment branch. In other words, when the gas in the vapor state circulates within the return line, it circulates in particular within the first pass of the third heat exchanger, as well as within a pass of the first heat exchanger and a pass of the second heat exchanger.

[0016] More precisely, the gas in the vapor state is pre-cooled by initially circulating within the pass of the second heat exchanger. The gas in the vapor state is then cooled by circulating within the first pass of the third heat exchanger, and is finally condensed by passing through the pass of the first heat exchanger. It is thus understood that the heat exchanges are carried out in a precise order in order to optimize the condensation of the gas in the vapor state circulating in the return line.

[0017] According to a feature of the invention, the second feed circuit comprises a divergence zone where the heat treatment branch and the second feed circuit separate and a convergence zone where the heat treatment branch and the second feed circuit join, the heat treatment branch extending between the divergence zone and the convergence zone. The gas in the vapor state circulates out of the tank until it reaches the divergence zone and then circulates either directly in the second feed circuit or in the heat treatment branch before joining the second feed circuit via the convergence zone. The latter is arranged at the level of the second feed circuit upstream of the compression device, through which the gas in the vapor state must necessarily pass.

[0018] According to a characteristic of the invention, the supply system comprises a member for controlling the circulation of gas within the second supply circuit, the heat treatment branch being in parallel with the control member. The control member may for example be a valve that can be opened or closed in order to respectively authorize or prohibit the circulation of gas in the vapor state within the second supply circuit. When the control member is closed, the gas in the vapor state then bypasses the control member by circulating within the heat treatment branch. For example, the control member may be an on / off valve.

[0019] According to a feature of the invention, the heat treatment branch comprises a control device configured to control the circulation of gas in the vapor state within the heat treatment branch. Just as for the control member, the control device can be opened or closed to authorize or prohibit the circulation of gas in the vapor state within the heat treatment branch. The control device can also be a valve.

[0020] According to a characteristic of the invention, the supply system comprises a means for determining the temperature of the gas taken in the vapor state from the tank and a management device which controls the control member and the control device. As mentioned previously, the circulation of the gas in the vapor state through the heat treatment branch is in particular dependent on the temperature of said gas. The temperature of the gas in the vapor state contained in the tank must therefore be determined by the determination means, the latter being able for example to be a temperature sensor. Depending on the temperature of the gas, the management device controls the control member and the control device in order to circulate the gas in the vapor state in the second supply circuit or in the heat treatment branch.The circulation of gas in the vapor state is managed by the management device which closes the control organ and opens the control device or vice versa.

[0021] According to a feature of the invention, the third heat exchanger is configured to carry out a heat exchange between the gas in the vapor state circulating in the return line, the gas in the vapor state circulating in the heat treatment branch and the gas in the liquid state circulating in the first supply circuit. This is a variant of the structure of the third heat exchanger which makes it possible to further optimize the cooling of the gas in the vapor state circulating in the return line. The heat exchange carried out within the third heat exchanger is therefore carried out here between three passes where the gas circulates in the vapor state or in the liquid state, the objective always being to cool the gas in the vapor state circulating in the return line.

[0022] According to a characteristic of the invention, the third heat exchanger comprises a first pass installed on the return line between the first heat exchanger and the second heat exchanger, a second pass installed on the heat treatment branch and a third pass installed on the first supply circuit between the first heat exchanger and the second heat exchanger. The heat exchange therefore takes place between the different passes of the third heat exchanger in order to cool the gas in the vapor state circulating in the first pass. The structure of the third heat exchanger may be such that the heat exchanges take place between several groups of passes grouped together two by two or between the three passes simultaneously.

[0023] According to a feature of the invention, at least the second heat exchanger, the third heat exchanger and the high-pressure evaporator form a unitary heat exchange module. In other words, two or three elements from among the second heat exchanger, the third heat exchanger and / or the high-pressure evaporator are combined into a single heat exchanger. The number of passes within the unitary heat exchange module depends on the number of elements combined within the latter. Such a configuration may be advantageous, for example, in order to reduce the mechanical size of the supply system.According to a characteristic of the invention, the supply system comprises at least one branch for cooling the gas taken in the vapor state from the tank connected to the second supply circuit upstream of the compression device, the supply system comprising at least one heat exchanger configured to carry out a heat exchange between the gas in the vapor state which circulates in the cooling branch and the gas in the liquid state which circulates in the first supply circuit. This is a second embodiment of the supply system according to the invention, the supply system described previously and comprising the heat treatment branch and not the cooling branch corresponding to a first embodiment.

[0024] The cooling branch has the function of cooling the gas in the vapor state intended to circulate within the second supply circuit when said gas is at a high temperature. The cooling of the gas in the vapor state contained in the tank is carried out thanks to the heat exchanger operating the heat exchange between said gas in the vapor state and the gas in the liquid state circulating in the first supply circuit.

[0025] The cooling branch thus has two advantages. On the one hand, the gas in the vapor state passing through the heat exchanger is cooled, which limits the energy required for its compression by the compression device subsequently within the second supply circuit. On the other hand, the gas in the liquid state circulating in the first supply circuit is heated, which facilitates its subsequent evaporation within the high-pressure evaporator by reducing the flow rate of heat transfer fluid required to completely evaporate the gas in the liquid state, which also limits the energy required for the operation of the supply system.It has been estimated that up to 30% of the electrical energy consumption of the compression device can be saved when the gas in the vapor state circulates in the return line for condensing, and up to 45% when the gas in the vapor state circulates in the second supply circuit for supply to the low-pressure gas-consuming apparatus. It is thus understood that the supply system according to the invention can comprise both the heat treatment branch and the cooling branch in order to improve the versatility of said supply system.

[0026] According to a feature of the invention, the cooling branch comprises a control valve configured to control the circulation of gas in the vapor state within the cooling branch. Just like the control member for the second supply circuit and the control device for the heat treatment branch, the control valve can be opened or closed to respectively authorize or prohibit the circulation of gas in the vapor state within the cooling branch.

[0027] According to a feature of the invention, at least the second heat exchanger, the heat exchanger and the high-pressure evaporator form a unitary heat exchange module. Bringing these three exchangers together is particularly advantageous insofar as these three exchangers are configured to operate a high-pressure heat exchange and are therefore compatible for being brought together.

[0028] According to a characteristic of the invention, at least the second heat exchanger, the third heat exchanger, the heat exchanger and the high-pressure evaporator form a unitary heat exchange module. As previously described, two, three or four elements among the second heat exchanger, the third heat exchanger, the heat exchanger and the high-pressure evaporator can be combined and form a single exchanger, for example in order to limit the mechanical size and / or the production costs of said elements.

[0029] According to a feature of the invention, the first supply circuit comprises a pump interposed between the first heat exchanger and the second heat exchanger. The pump is interposed between the first heat exchanger and the second heat exchanger. It is the pump which makes it possible to increase the pressure of the gas in the liquid state circulating in the first supply circuit, so that the latter has a pressure compatible with the supply of the high-pressure gas-consuming appliance. The optimal arrangement consists of placing the pump between the two heat exchangers. It is therefore essential to ensure that the gas circulating in the first supply circuit and passing through the first heat exchanger remains in the liquid state at the outlet thereof.

[0030] The invention also covers a method for controlling a gas supply system as described above, during which: in a determination step, the temperature of the gas in the vapor state taken from the tank is determined, then the gas in the vapor state is circulated within the second supply circuit if the temperature of the gas in the vapor state determined in the determination step is higher than a temperature threshold, or the gas in the vapor state is circulated within the heat treatment branch if the temperature of the gas in the vapor state determined in the determination step is lower than the temperature threshold.

[0031] It is understood from the various stages of the control method according to the invention that the circulation of the gas in the vapor state contained in the tank is dependent on its temperature. It is therefore initially the determination of the temperature of the gas in the vapor state which will condition the rest of the control method. The temperature can be determined by the determination means mentioned above.

[0032] Once the temperature of the gas in the vapor state has been determined, it is compared to the temperature threshold. The temperature threshold corresponds to a value according to which the gas in the vapor state contained in the tank can or cannot be used to participate in the condensation of the gas in the vapor state circulating in the return line.

[0033] If the vapor gas temperature is below the temperature threshold, this means that the vapor gas in the tank is at a temperature low enough to cool the vapor gas circulating in the return line. The vapor gas is then circulated within the heat treatment branch to pass through the third heat exchanger and thus cool the vapor gas circulating in the return line. If the vapor gas temperature is above the temperature threshold, this means that the vapor gas in the tank is at a temperature too high to participate in cooling the vapor gas circulating in the return line.In this situation, sending the vapor gas contained in the tank to the heat treatment branch is useless, or even counterproductive for the vapor gas condensation operation circulating in the return line. The vapor gas contained in the tank is then sent to the second supply circuit in order to supply the low-pressure gas consumer device or to be condensed while circulating in the return line.

[0034] The sending of the gas contained in the tank to the second supply circuit or to the heat treatment branch is ensured for example by the management device which opens and / or closes the control organ and / or the control device according to the temperature determined by the determination means.

[0035] According to a characteristic of the process, the temperature threshold is -110°C. The gas in the vapor state is therefore circulated within the heat treatment branch if its temperature is lower than -110°C or within the second supply circuit if its temperature is higher than -110°C.

[0036] According to a characteristic of the method: the gas in the vapor state is circulated within the heat treatment branch if the temperature of the gas in the vapor state determined in the determination step is lower than the temperature threshold, or the gas in the vapor state is circulated within the cooling branch if the temperature of the gas in the vapor state determined in the determination step is higher than a reference threshold, said reference threshold being higher than the temperature threshold, or the gas in the vapor state is circulated within the second supply circuit if the temperature of the gas in the vapor state determined in the determination step is between the temperature threshold and the reference threshold. This is the control method relating to the second embodiment of the supply system according to the invention, that is to say comprising the heat treatment branch and the cooling branch.As with the first embodiment, the circulation of the gas in the vapor state contained in the tank is dependent on its temperature. The temperature of the gas in the vapor state contained in the tank is determined and compared to the temperature threshold and to the reference threshold which corresponds to a temperature value higher than that of the temperature threshold and beyond which the gas in the liquid state contained in the tank is at a temperature high enough to cause excess energy consumption of the compression device during the compression of the gas in the vapor state contained in the tank.

[0037] If the vapor gas temperature is below the temperature threshold, this means that the vapor gas in the tank is at a temperature low enough to cool the vapor gas circulating in the return line. The vapor gas is then circulated within the heat treatment branch to pass through the third heat exchanger and thus cool the vapor gas circulating in the return line.

[0038] If the temperature of the gas in the vapor state is higher than the reference threshold, this means that the gas in the vapor state contained in the tank is at a temperature such that it causes overconsumption of the compression device during the compression operation. The gas in the vapor state is then circulated within the cooling branch in order to pass through the heat exchanger to be cooled by the gas in the liquid state circulating in the first supply circuit and thus be at a correct temperature to be compressed by the compression device without the latter consuming too much energy.

[0039] If the temperature of the vapor gas contained in the tank is higher than the temperature threshold and lower than the reference threshold, this means that the vapor gas contained in the tank is at a temperature too high to participate in the cooling of the vapor gas circulating in the return line but also at a temperature low enough to be compressed by the compression device without over-consumption of energy. The vapor gas contained in the tank is then sent to the second supply circuit.

[0040] As with the first embodiment, it is the management device which manages the circulation of the gas in the liquid state contained in the tank by opening or closing the control member, the control device and the control valve, and this depending on the determined temperature of the gas in the vapor state contained in the tank.

[0041] According to a characteristic of the method, the reference threshold is -90°C, the control method comprising a step of condensation of the gas in the vapor state circulating in the return line. In other words, the gas in the vapor state is circulated within the heat treatment branch if its temperature is lower than -110°C, within the cooling branch if its temperature is higher than -90°C, or within the second supply circuit if its temperature is between -90°C and -110°C. The reference threshold of -90°C is used when the compressed gas in the vapor state subsequently circulates at least partially in the return line.

[0042] When the gas in the vapor state is intended to supply the low-pressure consumer device, the reference threshold may be greater than or equal to -150°C.

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

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

[0045] [fig 2] is a schematic representation of a first example of operation of the first embodiment of the power supply system,

[0046] [fig 3] is a schematic representation of a second example of operation of the first embodiment of the power supply system,

[0047] [fig 4] is a schematic representation of a variant of the first embodiment of the power supply system, [fig 5] is a schematic representation of a second embodiment of the power supply system according to the invention,

[0048] [fig 6] is a schematic representation of a first example of operation of the second embodiment of the power supply system,

[0049] [fig 7] is a schematic representation of a second example of operation of the second embodiment of the power supply system,

[0050] [fig 8] is a schematic representation of a third example of operation of the second embodiment of the power supply system.

[0051] Figure 1 represents a first embodiment of a gas supply system 1 on board a floating structure. The supply system 1 makes it possible to circulate gas which may be in the liquid state, in the vapor state, in the two-phase state or in the supercritical state, and this from a storage and / or transport tank 8, and to a high-pressure gas-consuming device 4 and to a low-pressure gas-consuming device 5, in order to supply the latter with fuel.

[0052] Said floating structure may for example be a vessel of the LNG carrier type capable of storing and / or transporting gas in the liquid state, in particular natural gas. The supply system 1 is in this case capable of using the gas in the liquid state that the floating structure stores and / or transports to supply the high-pressure gas-consuming device 4, which may for example be a propulsion engine, and the low-pressure gas-consuming device 5, which may for example be an electric generator supplying the floating structure with electricity.

[0053] In order to ensure the circulation of the gas contained in the tank 8 to the high-pressure gas-consuming device 4, the supply system 1 is provided with a first gas supply circuit 2. The first supply circuit 2 comprises a submersible pump 9 arranged within the tank 8. The submersible pump 9 makes it possible to pump the gas in the liquid state and to circulate it in particular within the first supply circuit 2. By sucking in the gas in the liquid state, the submersible pump 9 raises the pressure thereof to a value between 6 and 17 bars absolute. The gas in the liquid state, in a direction of circulation going from the tank 8 to the high-pressure gas-consuming device 4, passes through a first heat exchanger 6 and is pressurized by a pump 10, otherwise called a high-pressure pump. Subsequently, the gas in the liquid state passes through a second heat exchanger 7, then a high-pressure evaporator 11 before reaching the high-pressure engine 4.The pump 10 is advantageously arranged between the first heat exchanger 6 and the second heat exchanger 7.

[0054] The high-pressure evaporator 11 makes it possible to modify the state of the gas circulating in the first supply circuit 2 in order to change it to the vapor or supercritical state. Such a state is a state compatible with supplying the high-pressure gas-consuming device 4. The evaporation of the gas to the liquid state can, for example, be done by heat exchange between the gas in the liquid state which enters the high-pressure evaporator 11 and a heat transfer fluid at a temperature high enough to evaporate the gas to the liquid state, here glycolated water, sea water or water vapor.

[0055] The increase in gas pressure is ensured by the pump 10 when it pumps the gas in the liquid state. The pump 10 makes it possible to raise the pressure of the gas in the liquid state to a value between 30 and 400 bars absolute, in particular for use with ammonia or hydrogen, between 30 and 70 bars absolute for use with liquefied petroleum gas, and preferably between 150 and 400 bars absolute for use with ethane, ethylene or even with liquefied natural gas consisting mainly of methane.

[0056] Thanks to the combination of the pump 10 and the high-pressure evaporator 11, the gas is at a pressure and in a state compatible for supplying the high-pressure consumer device 4. Such a configuration makes it possible to avoid the installation of high-pressure compression devices on the first supply circuit 2 which present cost constraints and generate strong vibrations.

[0057] Within the tank 8, a portion of the gas cargo can naturally pass into the vapor state and be contained in a tank canopy 12. In order to avoid overpressure within the tank 8, the gas in the vapor state contained in the tank canopy 12 must be evacuated. The supply system 1 therefore comprises a second gas supply circuit 3, which uses the gas in the vapor state to supply the low-pressure gas-consuming device 5. The second supply circuit 3 extends between the tank canopy 12 and the low-pressure gas-consuming device 5. In order to suck in the gas in the vapor state contained in the tank canopy 12, the second supply circuit 3 comprises a compression device 13, in particular a compressor.In addition to sucking in the gas in the vapor state, the compression device 13 also makes it possible to compress the gas in the vapor state circulating in the second supply circuit 3 to a pressure of between 6 and 20 bars absolute, so that the gas in the vapor state is at a pressure compatible with supplying the low-pressure gas-consuming device 5. The second supply circuit 3 thus makes it possible to supply the low-pressure gas-consuming device 5, while regulating the pressure within the tank 8 by sucking in the gas in the vapor state present in the tank crown 12.

[0058] The feed system 1 further comprises a heat treatment branch 33 which extends between a divergence zone 52 arranged on the second feed circuit downstream of the tank 8, and a convergence zone 53 arranged on the second feed circuit 3 downstream of the divergence zone 52 and upstream of the compression device 13. The heat treatment branch 33 is thus arranged in parallel with a portion 51 of the second feed circuit 3, said portion 51 extending between the divergence zone 52 and the convergence zone 53. The feed system 1 further comprises a third heat exchanger 36, one of the passes of which is part of the heat treatment branch 33.

[0059] The presence of gas in the vapor state in excessive quantity within the tank head 12 causes an overpressure within the tank 8. It is therefore necessary to evacuate the gas in the vapor state in order to lower the pressure within the tank 8. The excess gas in the vapor state can then for example be eliminated by a burner 18 or, in a manner not illustrated, discharged into the atmosphere. These solutions cause a loss of cargo. This is why the supply system 1 according to the invention comprises a return line 14 which extends from the second supply circuit 3 to the tank 8. The return line 14 is connected to the second supply circuit 3 downstream of the compression device 13 relative to a direction of circulation of the gas in the vapor state circulating in the second supply circuit 3.The return line 14 first passes through the second heat exchanger 7, then continues its path by passing through the third heat exchanger 36, and finally through the first heat exchanger 6.

[0060] The first heat exchanger 6 comprises a first pass 6a which is part of the first supply circuit 2. This first heat exchanger 6 comprises a second pass 6b which is part of the return line 14. The direction of circulation within the first pass 6a is opposite to the direction of circulation within the second pass 6b of the first heat exchanger 6.

[0061] The second heat exchanger 7 is installed between the first heat exchanger 6 and the high pressure evaporator 11, on the first supply circuit 2.

[0062] The second heat exchanger 7 comprises a first pass 7a which is part of the first supply circuit 2. This second heat exchanger 7 comprises a second pass 7b which is part of the return line 14. The direction of circulation within the first pass 7a is opposite to the direction of circulation within the second pass 7b of the second heat exchanger 7.

[0063] The third heat exchanger 36 is installed on the return line 14, between the first heat exchanger 6 and the second heat exchanger 7. This third heat exchanger 36 comprises a first pass 36a which is part of the return line 14 and a second pass 36b which is part of the heat treatment branch 33. The first pass 36a of the third heat exchanger 36 is arranged on the return line 14 between the second pass 7b of the second heat exchanger 7 and the second pass 6b of the first heat exchanger 6.

[0064] The heat treatment branch 33 therefore has the function of participating in the cooling of the gas in the vapor state which circulates in the return line 14, so as to facilitate its condensation. In this situation, the heat treatment branch 33 makes it possible to collect the cold of the gas in the vapor state taken from the tank 8 and to recover it by transferring it to the return line 14. Such an operation is only appropriate if the gas in the vapor state contained in the tank 8 is at a sufficiently low temperature, or more generally at a temperature lower than the temperature of the gas in the vapor state circulating in the return line 14 at the inlet of the first pass 36a of the third heat exchanger 36.

[0065] In order to correctly ensure the management of the second supply circuit 3 and the heat treatment branch 33 as a function of the temperature of the gas in the vapor state contained in the tank 8, the circulation of the latter is placed under the control of a control member 46. The latter is for example a valve. The circulation of gas in the vapor state within the heat treatment branch 33 is placed under the control of a control device 38. This control member 46 and / or this control device 38 is for example a valve or an on / off valve.

[0066] The heat treatment branch 33 is installed in parallel with the control member 46. In other words, the divergence zone 52 is positioned upstream of the control member 46 for controlling the circulation of the gas within the second supply circuit 3, while the convergence zone 53 is positioned downstream of this same control member 46.

[0067] The supply system 1 also comprises a management device 49 and at least one means 48 for determining the temperature of the gas in the vapor state taken from the tank 8. The means 48 for determining the temperature is for example a temperature sensor positioned on the second supply circuit 3, between the tank 8 and the divergence zone 52. Alternatively, the determination means 48 can be installed in the tank ceiling 12. This means 48 for determining the temperature is electrically connected to the management device 49 since the information recorded by the determination means 48 is used in a calculation implemented by the management device 49.

[0068] This management device 49 is an electronic control module which receives the information from the determination means 48 and which controls the opening or closing of the control member 46 and / or the control device 38. The management device 49 implements the method and its various steps, with the exception of the step of determining the temperature of the gas in the value state taken from the tank 8.

[0069] The method which is the subject of the invention is illustrated by Figure 2 and by Figure 3, representing two examples of circulation of the gas in the vapor state contained in the tank 8 as a function of its temperature. In Figures 2 and 3, the solid lines correspond to lines where gas circulates while the dotted lines correspond to lines where there is no circulation of gas.

[0070] The management device 49 is capable of authorizing the circulation of gas within the heat treatment branch 33 when the temperature of the gas in the vapor state taken from the tank 8 and determined by the determination means 48 is lower than a temperature threshold, such a temperature threshold being for example equal to - 110°C. To do this, the management device 49 commands an opening of the control device 38, thus authorizing the gas in the vapor state taken from the tank 8 to reach the third heat exchanger 36, in particular its second pass 36b. In such a situation, the management device 49 prohibits the passage of gas in the vapor state within a portion 51 of the second supply circuit 3 located between the divergence zone 52 and the convergence zone 53. To do this, the management device 49 commands a closing of the control member 46 installed on this portion 51.

[0071] As shown in Figure 3, the management device 49 is also capable of prohibiting the circulation of gas within the heat treatment branch 33 when the temperature determined by the determination means 48 is higher than the temperature threshold mentioned above. In this case, it is counterproductive to circulate gas at this temperature within the heat treatment branch 33 because this risks heating the gas in the vapor state circulating in the return line instead of cooling it. In this configuration, the management device 49 controls a closing of the control device 38, and authorizes the circulation of gas in the vapor state through the portion 51 of the second supply circuit 3, by controlling the opening of the control member 46, thus authorizing the gas in the vapor state taken from the tank 8 to directly reach the compression device 13.Of course, the management device 49 can be assigned to other calculation operations necessary for the operation of the supply system 1 according to the invention, such as for example the control of the flow regulating member 15 or the control of the valve 19 controlling the circulation of gas within the auxiliary supply line 16, or even the control of the compression device 13 or the control of the submerged pump 9 or the pump 10.

[0072] The gas in the vapor state circulating in the return line 14 can therefore potentially be cooled by the gas in the vapor state contained in the tank if the temperature of the latter allows it. Subsequently, it is at the inlet of the first pass 6a of the first heat exchanger 6 that the gas in the liquid state of the first supply circuit 2 has the lowest temperature. As a result, it is after passing through the first heat exchanger 6 that the gas circulating in the return line 14 is condensed. The fluid circulating in the return line 14 is therefore in the vapor state at the inlet of the second pass 6b of the first heat exchanger 6 and leaves in the liquid state following the exchange of calories taking place within the first heat exchanger 6.

[0073] The return line 14 further comprises a flow regulating member 15 which controls the flow rate of the fluid circulating in the return line 14. This flow regulating member 15 has a passage section which can be modified. Once the gas is condensed, it circulates to the tank 8. The first heat exchanger 6 therefore acts as a condenser while the flow regulating member 15 controls the heat exchange taking place in the first heat exchanger 6, in the second heat exchanger 7 and in the high-pressure evaporator 11.

[0074] The supply system 1 also comprises an auxiliary supply line 16, extending from the first supply circuit 2, via a tapping arranged between the submersible pump 9 and the first heat exchanger 6, to the second supply circuit 3, connecting to the latter between the compression device 13 and the low-pressure gas-consuming device 5. The auxiliary supply line 16 makes it possible to supply the low-pressure gas-consuming device 5 in the event of an insufficient flow rate of gas in the vapor state formed within the tank head 12. When the gas in the vapor state is not present in sufficient quantity in the tank head 12, the gas in the liquid state pumped by the submersible pump 9 can then circulate within this auxiliary supply line 16 in order to supply the low-pressure gas-consuming device 5.To do this, the auxiliary supply line 16 passes through a low-pressure evaporator 17 so that the gas in the liquid state circulating in the auxiliary supply line 16 changes to the vapor state. The operation of the low-pressure evaporator 17 may, for example, be identical to that of the high-pressure evaporator 11, i.e. the gas is evaporated by heat exchange with a heat transfer fluid at a temperature high enough to evaporate the gas in the liquid state. At the outlet of the low-pressure evaporator 17, the gas in the vapor state circulates within the auxiliary supply line 16, then joins the second supply circuit 3 in order to supply the low-pressure gas-consuming device 5.

[0075] It is understood from the above that the auxiliary supply line 16 is only used in the absence of gas in the vapor state in sufficient quantity within the tank head 12. Thus, the auxiliary supply line 16 comprises a valve 19 controlling the circulation of gas within the auxiliary supply line 16 when the use thereof is not necessary.

[0076] It is noted that each exchanger described in the present document may be a two-pass component. The invention also covers the case where certain exchangers are assembled to form only one exchanger, for example with three or four passes. Thus, a combination of two or three of the components among the second heat exchanger 7, the third heat exchanger 36 and the high-pressure evaporator 11 may form a unitary heat exchange module 50. The assembly into a unitary heat exchange module 50 makes it possible, for example, to reduce a spatial footprint that may be caused by a plurality of exchangers independent of each other.

[0077] Figure 4 represents a variant of the first embodiment of the supply system 1 according to the invention. Compared to what has been described in the previous figures, the variant is distinguished by the structure of the third heat exchanger 36. The latter still comprises the first pass 36a forming part of the return line 14 and the second pass 36b forming part of the heat treatment branch 33, but also comprises a third pass 36c forming part of the first supply circuit 2. It is thus understood that the third heat exchanger 36 according to the variant illustrated in Figure 4 is configured to carry out a heat exchange between the gas in the vapor state circulating in the return line 14, the gas in the vapor state taken from the tank 8 and circulating in the heat treatment branch 33, and the gas in the liquid state circulating in the first supply circuit 2.Such a variant makes it possible to optimize the cooling of the gas in the vapor state circulating in the return line 14 and passing through the first pass 36a of the third heat exchanger 36, and this by using the cold of the gas in the liquid state circulating in the first supply circuit 2 and passing through the third pass 36c of the third heat exchanger 36. The latter is therefore a three-pass exchanger, which can be combined with the second heat exchanger 7 and / or the high-pressure evaporator 11 to form the unitary heat exchange module 50.

[0078] All of the structural and functional elements with the exception of the third heat exchanger 36 being identical to what was described previously, reference will be made to the description of FIG. 1 concerning the elements common to the first embodiment and its variant.

[0079] Figure 5 is a second embodiment of the power supply system 1 according to the invention. This second embodiment corresponds to the first embodiment, to which additional components are added.

[0080] The second embodiment of the supply system 1 thus further comprises a cooling branch 40 for the gas taken in the vapor state from the tank. Such a branch makes it possible to circulate the gas taken in the vapor state from the tank 8 in order to cool it.

[0081] The cooling branch 40 is connected to the second supply circuit 3 upstream of the compression device 13, via a divergence point 44 and a convergence point 45 specific to the cooling branch 40. Alternatively, the cooling branch 40 and the heat treatment branch 33 can both be connected to the divergence zone 52 and to the convergence zone 53. Whatever the connection method, the heat treatment branch 33 and the cooling branch 40 are in parallel with each other, and with respect to the portion 51 of the second supply circuit 3.

[0082] The feed system 1 illustrated in Figure 5 also comprises a heat exchanger 41 responsible for cooling the gas taken in the vapor state from the tank by exchanging calories with the gas in the liquid state which circulates in the first feed circuit 2.

[0083] This heat exchanger 41 comprises a first pass 42 which exchanges calories with a second pass 43 constituting this heat exchanger 41. The first pass 42 of the heat exchanger 41 is part of the first supply circuit 2 and is traversed by the gas in the liquid state, while the second pass 43 of the heat exchanger 41 is part of the cooling branch 40 and is traversed by the gas in the vapor state taken from the tank 8.

[0084] Ingeniously, the first pass 42 of the heat exchanger 41 is fluidically arranged between the first pass 7a of the second heat exchanger 7 and a first pass 11a of the high-pressure evaporator 11.

[0085] Such a location makes it possible to cool the gas in the vapor state which circulates in the cooling branch 40 by heat exchange with the gas in the liquid state which circulates in the first supply circuit 2, which ultimately makes it possible to reduce the volume flow rate at the inlet of the compression device 13 and thus reduce its consumption, in particular electrical consumption.

[0086] This location also makes it possible to reduce the flow rate of heat transfer fluid which travels through a second pass 11b of the high-pressure evaporator 11 in order to evaporate the gas in the liquid state which comes from the tank 8. Since it is a hot source, the invention makes it possible to reduce the quantity of calories supplied by the heat transfer fluid since a portion of the calories is supplied by the gas in the vapor state which circulates in the cooling branch 40. The cooling branch 40 further comprises a control valve 47 configured to control the circulation of gas in the vapor state within the cooling branch 40.This control valve 47 is placed under the control of the management device 49 and is in the open position when the temperature of the gas in the vapor state taken from the tank 8 detected by the determination means 48 is higher than a reference threshold, for example equal to -90°C when the gas in the vapor state flows mainly or exclusively through the return line 14. In this configuration, the reference threshold is higher than the temperature threshold.

[0087] Alternatively, the reference threshold is greater than or equal to -150°C when the gas in the vapor state is mainly or exclusively sent to the low-pressure gas-consuming device 5, via the second supply circuit 3. In such a case, the flow regulating member 15 reduces the flow of gas circulating in the return line 14, or interrupts it completely if necessary.

[0088] When the temperature of the gas in the vapor state determined by the determination means 48 is lower than the reference threshold, the management device 49 controls the closing of the control valve 47.

[0089] In the case of the second embodiment, the unitary heat exchange module 50 mentioned above can be completed with the heat exchanger 41. Such a unitary heat exchange module 50 can then comprise at least five passes fluidically separated from each other. Advantageously, the unitary heat exchange module 50 can group together the second heat exchanger 7, the heat exchanger 41 and the high-pressure evaporator 11, these three exchangers being high-pressure exchangers.

[0090] Figures 6 to 8 illustrate examples of circulation of the gas in the vapor state contained in the tank 8 within the second supply circuit 3, the heat treatment branch 33 or the cooling branch 40, and this as a function of the determined temperature of the gas in the vapor state contained in the tank 8. The circulation of the gas in the vapor state contained in the tank 8 is governed by the management device 49 which opens or closes the control member 46, the control device 38 or the control valve 47 as a function of the temperature of the gas in the vapor state contained in the tank 8 measured by the temperature determination means 48 and the comparison with this temperature with respect to the temperature threshold and the reference threshold mentioned previously. As for Figures 2 and 3, the solid lines correspond to lines where gas circulates while the dotted lines correspond to lines where there is no gas circulation.

[0091] Figure 6 thus corresponds to the circulation of the gas in the vapor state contained in the tank 8 when the determined temperature of the gas in the vapor state contained in the tank 8 is lower than the temperature threshold, meaning that the gas in the vapor state contained in the tank 8 is at a temperature low enough to participate in the cooling of the gas in the vapor state circulating in the return line 14.

[0092] In response to the temperature thus determined by the determining means 48, the management device 49 closes the control member 46 and the control valve 47 and opens the control device 38 so that the gas in the vapor state contained in the tank 8 circulates within the heat treatment branch 33 and passes through the second pass 36b of the third heat exchanger 36 in order to cool the gas in the vapor state circulating in the return line 14 and passing through the first pass 36a of the third heat exchanger 36.

[0093] Figure 7 corresponds to the circulation of the gas in the vapor state contained in the tank 8 when the determined temperature of the gas in the vapor state contained in the tank 8 is higher than the reference threshold, meaning that the gas in the vapor state contained in the tank 8 is at a temperature too high for the compression device 13 to be able to compress it without causing excess energy consumption. In order to avoid said excess energy consumption, the gas in the vapor state contained in the tank 8 must be cooled before being compressed.To do this, the management device 49 closes the control member 46 and the control device 38 and opens the control valve 47 so that the gas in the vapor state contained in the tank 8 circulates within the cooling branch 40 and passes through the second pass 43 of the heat exchanger 41 in order to be cooled by the gas in the liquid state circulating in the second supply circuit 2 and passing through the first pass 42 of the heat exchanger 41. The gas in the vapor state cooled within the heat exchanger 41 can subsequently circulate to the compression device 13 and be compressed without overconsumption of energy.

[0094] Figure 8 corresponds to the circulation of the gas in the vapor state contained in the tank 8 when the determined temperature of the gas in the vapor state contained in the tank 8 is between the temperature threshold and the reference threshold, that is to say higher than the temperature threshold and lower than the reference threshold.

[0095] In this configuration, the gas in the vapor state contained in the tank 8 is therefore at a temperature low enough to be compressed by the compression device 13 without excess energy consumption, but is nevertheless at a temperature too high to participate in the cooling of the gas in the vapor state circulating in the return line 14. It may be counterproductive to circulate the gas in the vapor state contained in the tank 8 within the heat treatment branch 33.

[0096] In this configuration, the management device 49 closes the control device 38 and the control valve 47 and opens the control member 46 so that the gas in the vapor state contained in the tank 8 circulates directly within the second supply circuit 3 passing through the portion 51 in order to be directly compressed by the compression device 13 to subsequently be consumed by the low-pressure gas-consuming device 5 or be recondensed by circulating within the return line 14.

[0097] 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.

[0098] The invention, as just described, achieves the aim it set itself, and makes it possible to propose a gas supply system exploiting the cold of the gas in the vapor state contained in a tank in order to carry out condensation of said gas in the vapor state. Variants not described here could be implemented without departing from the context of the invention, provided that, in accordance with the invention, they comprise a supply system in accordance with the invention.

Claims

Tl DEMANDS 1- Gas supply system (1) for at least one high-pressure gas-consuming appliance (4) and at least one low-pressure gas-consuming appliance (5) of a floating structure comprising at least one tank (8) configured to contain the gas at least in a liquid state, the supply system (1) comprising: at least one first gas supply circuit (2) for the high-pressure gas-consuming appliance (4), at least one high-pressure evaporator (11) configured to evaporate the gas circulating in the first supply circuit (2), at least one second gas supply circuit (3) for the low-pressure gas-consuming appliance (5), comprising at least one compression device (13) configured to compress gas taken in vapor form from the tank (8) to a pressure compatible with the requirements of the low-pressure gas-consuming appliance (5),at least one gas return line (14) connected to the second supply circuit (3) downstream of the compression device (13) and extending to the tank (8), at least one first heat exchanger (6) and one second heat exchanger (7), each configured to perform heat exchange between the gas flowing in the return line (14) in the vapor state and the gas in the liquid state flowing in the first supply circuit (2), characterized in that the supply system (1) includes a heat treatment branch (33) for the gas in the vapor state flowing in the return line (14), the heat treatment branch (33) being connected to the second supply circuit (3) upstream of the compression device (13),the feed system (1) comprising a third heat exchanger (36) configured to operate a heat exchange between the gas in the vapor state circulating in the heat treatment branch (33) and the gas in the vapor state circulating in the return line (14). 2- Feeding system (1) according to claim 1, wherein the third heat exchanger (36) comprises a first pass (36a) installed on the line of return (14) between the first heat exchanger (6) and the second heat exchanger (7), and a second pass (36b) installed on the heat treatment branch (33). 3- Power supply system (1) according to any one of the preceding claims, wherein the second power supply circuit (3) comprises a divergence zone (52) where the heat treatment branch (33) and the second power supply circuit (3) separate and a convergence zone (53) where the heat treatment branch (33) and the second power supply circuit (3) rejoin, the heat treatment branch (33) extending between the divergence zone (52) and the convergence zone (53). 4- Supply system (1) according to any one of the preceding claims, comprising a control element (46) for the gas circulation within the second supply circuit (3), the heat treatment branch (33) being in parallel with the control element (46). 5- Feeding system (1) according to the preceding claim, wherein the heat treatment branch (33) includes a control device (38) configured to control the flow of gas in the vapor state within the heat treatment branch (33). 6- Supply system (1) according to the preceding claim, comprising a means for determining (48) the temperature of the gas taken in vapor state in the tank (8) and a management device (49) which controls the control member (46) and the control device (38). 7- Feeding system (1) according to any one of the preceding claims, wherein the third heat exchanger (36) is configured to operate a heat exchange between the gas in the vapor state flowing in the return line (14), the gas in the vapor state flowing in the heat treatment branch (33) and the gas in the liquid state flowing in the first feed circuit (2). 8- Feeding system (1) according to the preceding claim, wherein the third heat exchanger (36) comprises a first pass (36a) installed on the return line (14) between the first heat exchanger (6) and the second exchanger of heat (7), a second pass (36b) installed on the heat treatment branch (33) and a third pass (36c) installed on the first supply circuit (2) between the first heat exchanger (6) and the second heat exchanger (7). 9- Power supply system (1) according to any one of the preceding claims, wherein at least the second heat exchanger (7), the third heat exchanger (36) and the high-pressure evaporator (11) form a unit heat exchange module (50). 10- Supply system (1) according to any one of the preceding claims, comprising at least one cooling branch (40) of the gas taken in vapor form from the tank (8) connected to the second supply circuit (3) upstream of the compression device (13), the supply system (1) comprising at least one heat exchanger (41) configured to operate a heat exchange between the gas in vapor form which flows in the cooling branch (40) and the gas in liquid form which flows in the first supply circuit (2). 11- Supply system (1) according to the preceding claim, in which the cooling branch (40) includes a control valve (47) configured to control the circulation of gas in the vapor state within the cooling branch (40). 12- Power supply system (1) according to claim 10 or 11, wherein at least the second heat exchanger (7), the heat exchanger (41) and the high-pressure evaporator (11) form a unit heat exchange module. 13- Power supply system (1) according to the preceding claim, wherein at least the second heat exchanger (7), the third heat exchanger (36), the heat exchanger (41) and the high-pressure evaporator (11) form a unit heat exchange module (50). 14- Supply system (1) according to any one of the preceding claims, wherein the first supply circuit (2) comprises a pump (10) interposed between the first heat exchanger (6) and the second heat exchanger (7). 15- Method of controlling a gas supply system (1) according to any one of the preceding claims, wherein: at a determination step, the temperature of the gas in the vapor state taken from the tank (8) is determined, then the gas in the vapor state is circulated within the second supply circuit (3) if the temperature of the gas in the vapor state determined at the determination step is above a temperature threshold, or the gas in the vapor state is circulated within the heat treatment branch (33) if the temperature of the gas in the vapor state determined at the determination step is below the temperature threshold. 16- Control method according to the preceding claim, during which the temperature threshold is -110°C. 17- A control method according to claim 15 or 16, in combination with any one of claims 10 to 13, wherein: the gas is circulated in the vapor state within the heat treatment branch (33) if the temperature of the gas in the vapor state determined in the determination step is below the temperature threshold, or the gas is circulated in the vapor state within the cooling branch (40) if the temperature of the gas in the vapor state determined in the determination step is above a reference threshold, said reference threshold being above the temperature threshold, or the gas is circulated in the vapor state within the second supply circuit (3) if the temperature of the gas in the vapor state determined in the determination step is between the temperature threshold and the reference threshold. 18- Control method according to the preceding claim, wherein the reference threshold is -90°C, the control method comprising a step of condensation of the gas in the vapor state circulating in the return line (14).

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