Gas supply system for high and low pressure gas consuming appliances

Abstract

Gas supply system for high and low pressure gas consuming appliances The present invention relates to a gas supply system (1) for a high pressure gas consuming appliance (4) and a low pressure gas consuming appliance (5) of a floating structure comprising a tank (8) containing the gas, the supply system (1) comprising a first supply circuit (2) comprising a first pump (9), a second supply circuit (3), a gas return line (14), a first heat exchanger (6) and a second heat exchanger (7) configured to carry out a heat exchange between the gas of the first supply circuit (2) and the gas circulating in the return line (14), characterized in that the return line (14) is connected to the first supply circuit (2), the return line (14) comprising a second pump (42). (figure 1)

Description

Title of the invention: Gas supply system for high and low pressure gas consuming appliances

[0001] 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.

[0002] During a journey made by a ship comprising a tank of gas in the liquid state intended to be consumed and / or to be delivered to a destination point, said ship 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 engines, via a gas supply system. This is the case for ships equipped with a ME-GI type propulsion engine. In order to supply this type of engine, the gas must be compressed to very high pressure by special compressors capable of compressing the gas up to 400 bars, but such compressors are expensive, generate significant maintenance costs and induce vibrations within the ship.

[0003] An alternative to installing these high-pressure compressors is to vaporize the gas into liquid form at 400 bars 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 means "boil-off gas") forming naturally within a tank containing at least part of the cargo, low-pressure compressors can be installed to power an auxiliary engine, capable of consuming the gas in vapor form at low pressure. Furthermore, in the event of excess gas in vapor form, it can be reliquefied by heat exchange and then expanded before being returned to the tank.

[0004] However, before returning to the tank, a fraction of approximately 15% of the reliquefied gas vaporizes again during expansion. The gas therefore returns to the tank partially in the vapor state, which harms the productivity of the feed system.

[0005] The present invention makes it possible to solve this problem and proposes a system for supplying gas to at least one high-pressure gas-consuming device and to at least one low-pressure gas-consuming device of a floating structure comprising at least one tank configured to contain the gas, the supply system comprising: - at least one first gas supply circuit for the high-pressure gas-consuming device, comprising at least one first pump configured to pump the gas taken in the liquid state from the tank, - at least one high pressure evaporator configured to evaporate the gas circulating in the first gas supply circuit, - at least one second gas supply circuit of the low-pressure gas-consuming device, comprising at least one compressor 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 at the input to the second supply circuit downstream of the compressor, - at least one first heat exchanger and at least 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,

[0006] characterized in that the return line is connected at the output to the first supply circuit at a convergence point arranged between the first pump and the first heat exchanger, the return line comprising a second pump arranged between the first heat exchanger and the convergence point.

[0007] The supply system according to the invention thus makes it possible to avoid returning gas in the vapor state to the tank following its prior expansion. The reliquefied gas circulating in the return line is however used to supply the high-pressure gas-consuming device by joining the first supply circuit. As a result, even if the reliquefied gas is not returned to the tank, it is used for useful purposes.

[0008] The first gas supply circuit makes it possible to meet the fuel requirements of the high-pressure gas-consuming device. The latter may, for example, be the means of propulsion of the floating structure, for example an ME-GI engine. The first supply circuit extends from the tank to the high-pressure gas-consuming device. The first pump is installed at the bottom of the tank and ensures the pumping of the gas in the liquid state so that it can circulate in the first supply circuit.

[0009] Since the gas must be in the vapor state in order to be able to supply the high-pressure gas-consuming device, the high-pressure evaporator ensures the evaporation of the gas before it is supplied to the high-pressure gas-consuming device. The high-pressure evaporator is the site of an exchange of calories between the gas in the liquid state circulating in the first supply circuit and a heat transfer fluid, for example glycolated water, sea water or water vapor. The latter must be at a sufficiently high temperature to create a change of state of the gas so that the latter passes into the vapor or supercritical state in order to supply the high-pressure gas-consuming device.

[0010] Before the gas in the liquid state circulating in the first supply circuit is vaporized by means of the high-pressure evaporator, the gas in the liquid state passes through the first heat exchanger, then the second heat exchanger. For this, the first heat exchanger and the second heat exchanger are connected to each other by a portion of the first supply circuit so that the gas in the liquid state can pass through the two heat exchangers successively. The temperature of said gas in the liquid state thus tends to increase before it passes through the high-pressure evaporator. Thus, the gas circulating in the first supply circuit can be in a two-phase state at the outlet of the second heat exchanger.

[0011] 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.

[0012] 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 motor such as an electric generator. The compressor arranged on the second supply circuit is responsible for sucking the gas present in the top of the tank in order to be able to both supply the low-pressure gas-consuming device and also to regulate the pressure within the tank.

[0013] At the compressor outlet, the gas in the vapor state can supply the low-pressure gas-consuming device, or circulate through the return line if the low-pressure gas-consuming device does not require a fuel supply. The return line being connected downstream of the compressor, the gas in the vapor state sucked in by the compressor can therefore circulate therein.

[0014] The gas in the vapor state circulating in the return line initially passes through the second heat exchanger, then the first heat exchanger, before joining the first supply circuit. Thanks to the exchange of calories taking place between the gas in the liquid state circulating in the first supply circuit and the gas in the vapor state circulating in the return line, the temperature of the gas in the vapor state decreases while passing through the heat exchangers, until said gas condenses and returns to the liquid state substantially at the outlet of the first heat exchanger.

[0015] At the outlet of the first heat exchanger, the reliquefied gas circulating in the return line is pumped by the second pump. The latter makes it possible to raise the pressure of the reliquefied gas so that it is balanced with the pressure of the gas in the liquid state circulating in the first supply circuit after having been pumped by the first pump.

[0016] The presence of the second pump also makes it possible to limit the increase in the pressure of the gas in the vapor state by the compressor. It would indeed be possible for the compressor to raise the pressure of the gas in the vapor state to a higher pressure to anticipate the pressure balancing between the reliquefied gas circulating in the return line and the gas in the liquid state pumped by the first pump, but such a configuration requires a significant energy supply to the compressor and possibly a pressure regulation system so that the pressure remains compatible with the low-pressure gas-consuming device. The second pump therefore guarantees this function in order to limit an excessive energy supply to the compressor.

[0017] According to one example, the first heat exchanger and the second heat exchanger are upstream of the high-pressure evaporator along the first supply circuit. This ensures that the gas is in the liquid state in the part of the first supply circuit which is located within the first heat exchanger and within the second heat exchanger.

[0018] According to a characteristic of the invention, the return line comprises a divergence point arranged between the first heat exchanger and the second pump, the supply system comprising a return branch configured to extend between the divergence point and the tank. Alternatively, it is possible to retain the return function to the tank after reliquefaction within the supply system according to the invention. The divergence point is arranged on the return line downstream of the first heat exchanger so that only reliquefied gas circulates in the return branch. The reliquefied gas can then continue its circulation in the return line and be pumped by the second pump before joining the first supply circuit, or else circulate in the return branch to return to the tank.It is also possible to implement a configuration such that a portion of the reliquefied gas flows to the first supply circuit while another portion of the reliquefied gas returns to the tank via the return branch.

[0019] According to a characteristic of the invention, the return branch comprises an expansion member. The expansion member makes it possible to lower the pressure of the reliquefied gas circulating in the return branch once it has condensed during its passage through the first heat exchanger. Thanks to the expansion member, the gas in the liquid state is returned to the tank at a temperature close to the liquid-vapor equilibrium temperature of the LNG.

[0020] The expansion member also makes it possible to regulate the flow rate of reliquefied gas circulating in the return branch. Thus, it is possible to limit this flow rate of reliquefied gas in order to minimize the fraction of gas which vaporizes during expansion by the expansion member. expansion. In addition, the expansion member can be completely closed to prevent the circulation of reliquefied gas within the return branch. In this configuration, all of the reliquefied gas circulates in the return line to the first supply circuit.

[0021] According to a characteristic of the invention, the first supply circuit comprises an additional pump interposed between the first heat exchanger and the second heat exchanger. The additional pump 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 supplying the high-pressure gas-consuming device.

[0022] The positioning of the additional pump between the two heat exchangers is particularly advantageous. Indeed, placing the additional pump upstream of the first heat exchanger results in an increase in the pressure and temperature of the gas in the liquid state as soon as it passes through the first heat exchanger, which is detrimental to the condensation of the gas in the vapor state circulating in the return line and also passing through the first heat exchanger. Furthermore, since the gas circulating in the first supply circuit may be in a two-phase state at the outlet of the second heat exchanger, placing the additional pump downstream of the second heat exchanger may be detrimental to the proper functioning of the latter given that the additional pump only allows the pumping of a fluid in the liquid state. The optimal arrangement therefore consists of placing the additional pump between the two heat exchangers.

[0023] According to a characteristic of the invention, the additional pump is configured to raise the pressure of the gas in the liquid state to a value of between 30 and 400 bars. More particularly, the additional pump makes it possible to raise the pressure of the gas in the liquid state to a value of between 30 and 400 bars, in particular for use with ammonia and / or hydrogen, between 30 and 70 bars for use with liquefied petroleum gas, and preferably between 150 and 400 bars for use with ethane, ethylene or even with liquefied natural gas consisting mainly of methane.

[0024] According to a characteristic of the invention, the first heat exchanger is configured to condense the gas circulating within the return line. The first heat exchanger is the exchanger crossed by the gas in the liquid state of the first supply circuit when said gas in the liquid state is at its lowest temperature. It is therefore the exchange of calories taking place within the first heat exchanger which will change the state of the gas circulating in the return line to make it pass from the vapor state to the liquid state.

[0025] According to a characteristic of the invention, the second heat exchanger is configured to pre-cool the gas circulating within the return line. At the outlet of the first heat exchanger, the gas in the liquid state circulating in the first supply circuit is less cold than at the inlet of the first heat exchanger, a heat exchange having served to condense the gas in the vapor state of the return line. Subsequently, the gas in the liquid state is compressed by the additional pump and then passes through the second heat exchanger. A heat exchange also takes place within the second heat exchanger, allowing the pre-cooling of the gas in the vapor state within the return line. Even if the flow rate of gas in the liquid state circulating in the first supply circuit is insufficient to operate a total condensation of the gas in the vapor state circulating in the return line, a cooling is nevertheless carried out within the second heat exchanger.

[0026] According to a characteristic of the invention, the compressor is configured to raise a gas pressure to a value of 8 bars absolute + / - 1 bar. This pressure value ensures compatibility of the gas in the vapor state present in the tank head and sucked into the second supply circuit with the low-pressure gas-consuming device. Thanks to the presence of the second pump, it is not necessary to compress the gas circulating in the return line to a pressure equal to that of the gas in the liquid state circulating in the first supply circuit. This limits the energy consumption of the compressor.

[0027] According to a characteristic of the invention, the second pump is configured to raise a pressure of the gas in the liquid state circulating in the return line to a value equivalent to the pressure of the gas in the liquid state generated by the first pump. As previously described, the gas in the vapor state circulating in the second supply circuit is compressed to a pressure of 8 bars absolute + / - 1 bar. The gas in the vapor or reliquefied state circulating in the return line is therefore at a pressure of approximately 8 bars absolute. The gas in the liquid state circulating in the first supply circuit after having been pumped by the first pump is raised to a pressure greater than 8 bars. The second pump must therefore further raise the pressure of the reliquefied gas until it reaches a pressure equivalent or substantially equivalent to the pressure of the gas circulating in the first supply circuit between the first pump and the first heat exchanger.Such pressure balancing is carried out so that the reliquefied gas can join the first supply circuit without circulation difficulties linked to a potential pressure differential between the reliquefied gas and the gas in the liquid state circulating in the first supply circuit.

[0028] According to a characteristic of the invention, the first pump is configured to raise a pressure of the gas in the liquid state to a value between 9 and 17 bars absolute.

[0029] According to a characteristic of the invention, the second heat exchanger and the high-pressure evaporator can form a single heat exchanger. The first heat exchanger is then separate and arranged upstream of a single heat exchanger which brings together the second heat exchanger and the high-pressure evaporator. Such an alternative can be advantageous, for example, in order to reduce the size of the supply system.

[0030] The invention also covers a floating structure for storing and / or transporting gas in the liquid state, comprising at least one tank of gas in the liquid state, at least one high-pressure gas-consuming device, at least one low-pressure gas-consuming device and at least one system for supplying gas to these devices.

[0031] The invention also covers a system for loading or unloading a liquid gas which combines at least one onshore and / or port installation and at least one floating structure for storing and / or transporting liquid gas.

[0032] The invention finally covers a method for loading or unloading a liquid gas from a floating gas storage and / or transport structure in which pipelines for loading and / or unloading gas in the liquid state arranged on an upper deck of the floating structure can be connected, by means of appropriate connectors, to a maritime or port terminal in order to transfer the gas in the liquid state from or to the tank.

[0033] 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:

[0034] [Fig. 1] represents a first embodiment of a gas supply system for at least one high-pressure gas-consuming device and at least one low-pressure gas-consuming device according to the invention,

[0035] [Fig.2] represents a second embodiment of the power supply system,

[0036] [Fig.3] represents a third embodiment of the power supply system,

[0037] [Fig.4] is a schematic cutaway representation of a tank of a floating structure and of a terminal for loading and / or unloading this tank.

[0038] The terms "upstream" and "downstream" used in the following description are used to express positions of elements within gas circuits in the liquid state or in the vapor state and refer to the direction of circulation of said gas within said circuit.

[0039] Figures 1 to 3 show different embodiments of a gas supply system 1 arranged on a floating structure. The supply system 1 makes it possible to circulate gas which may be in the liquid state, the vapor state, the two-phase state or the supercritical state, from a storage and / or transport tank 8, and to a high-pressure gas-consuming device 4 and / or a low-pressure gas-consuming device 5, in order to supply the latter with fuel.

[0040] Said floating structure may for example be a ship capable of storing and / or transporting gas in the liquid state. The supply system 1 is in this case capable of using the gas in the liquid state that the floating structure stores and / or transports to supply the high-pressure gas-consuming device 4, which may for example be a propulsion engine, and the low-pressure gas-consuming device 5, which may for example be an electric generator supplying the floating structure with electricity.

[0041] In order to ensure the circulation of the gas contained in the tank 8 to the high-pressure gas-consuming device 4, the supply system 1 is provided with a first gas supply circuit 2. The first supply circuit 2 comprises a first pump 9 arranged within the tank 8. The first 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 first pump 9 also makes it possible to raise the pressure thereof to a value between 9 and 17 bars.

[0042] The gas in the liquid state, in a direction of circulation going from the tank 8 to the high-pressure gas-consuming device 4, passes through a first heat exchanger 6, is pumped by an additional pump 10 and passes through a second heat exchanger 7. The details concerning the two heat exchangers 6, 7 will be described later.

[0043] After passing through the second heat exchanger 7, the gas circulates to a high-pressure evaporator 11. The high-pressure evaporator 11 makes it possible to modify the state of the gas circulating in the first supply circuit 2 in order to change it to the vapor or supercritical state. Such a state makes the gas compatible for supplying the high-pressure gas-consuming device 4. The evaporation of the gas to the liquid state can, for example, be done by heat exchange with a heat transfer fluid at a temperature high enough to evaporate the gas to the liquid state, here glycolated water, sea water or water vapor.

[0044] According to a first embodiment illustrated in [Fig. 1], the first heat exchanger 6, the second heat exchanger 7 and the high-pressure evaporator 11 are heat exchangers separate from each other. Such a configuration makes it possible to design and manufacture each of the heat exchangers in a technology adapted to the pressure of the fluids flowing through them. In this case, the first heat exchanger 6 can be produced using a less expensive technology than that used to manufacture the second heat exchanger 7, because the pressure within the first exchanger is significantly lower than that present within the second heat exchanger 7. The same applies to the high-pressure evaporator 11.

[0045] The increase in gas pressure is ensured by the additional pump 10 when it pumps the gas in the liquid state. The additional pump 10 makes it possible to raise the pressure of the gas in the liquid state to a value between 30 and 70 bars for use with liquefied petroleum gas, and preferably between 150 and 400 bars for use with ethane, ethylene or even with liquefied natural gas consisting mainly of methane.

[0046] Thanks to the combination of the additional 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 compressors on the first supply circuit 2 which present cost constraints and generate strong vibrations.

[0047] Within the tank 8, a portion of the gas cargo can naturally pass into the vapor state and diffuse into a tank headspace 12. In order to avoid overpressure within the tank 8, the gas in the vapor state contained in the tank headspace 12 must be evacuated. However, the first supply circuit 2 is configured to use the gas in the liquid state to supply the high-pressure gas-consuming device 4.

[0048] The supply system 1 therefore comprises a second gas supply circuit 3, which uses the gas in the vapor state to supply the low-pressure gas-consuming device 5. The second supply circuit 3 therefore extends between the tank canopy 12 and the low-pressure gas-consuming device 5. In order to suck in the gas in the vapor state contained in the tank canopy 12, the second supply circuit 3 comprises a compressor 13. In addition to sucking in the gas in the vapor state, the compressor 13 also makes it possible to raise a pressure of the gas in the vapor state circulating in the second supply circuit 3 to a pressure of 8 bars absolute + / - 1 bar, so that the gas in the vapor state is at a pressure compatible with supplying the low-pressure gas-consuming device 5.The second supply circuit 3 thus makes it possible to supply the low-pressure gas-consuming device 5, while regulating the pressure within the tank 8 by sucking in the gas in the vapor state present in the tank ceiling 12.

[0049] The presence of the gas in the vapor state in excessive quantity within the tank ceiling 12 causes an overpressure within the tank 8. It is therefore necessary to evacuate the gas in the vapor state in order to lower the pressure within the tank 8. The excess gas in the vapor state can then for example be eliminated by a burner 18. However, the supply system 1 according to the invention comprises a return line 14 connected to the second supply circuit 3 downstream of the compressor 13 with respect to a direction of circulation of the gas in the vapor state circulating in the second supply circuit 3. According to the direction of circulation of the gas in the vapor state circulating in the return line 14, said gas passes through the second heat exchanger 7 first, then passes through the first heat exchanger 6. The exchange of calories taking place within the first heat exchanger 6 and the second heat exchanger 7 is therefore between the gas in the liquid state circulating in the first supply circuit 2 and the gas in the vapor state circulating in the return line 14. The objective of this exchange of calories is to condense the gas in the vapor state of the return line 14, so that it passes into the liquid state.

[0050] Once the gas circulating in the return line 14 has been recondensed, it is possible to return it to the tank 8. However, such a return requires the recondensed gas to be expanded, which may lead to partial vaporization thereof before returning to the tank 8. Thus, a fraction of up to 15% of the recondensed gas is vaporized, which is detrimental to the productivity of the supply system 1.

[0051] To avoid this, the return line 14 extends to a convergence point 41 arranged at the level of the first supply circuit 2, between the first pump 9 and the first heat exchanger 6. In other words, the gas circulating in the return line 14 joins the first supply circuit 2 instead of returning to the tank 8. The recirculation in the first supply circuit 2 makes it possible to subsequently supply the high-pressure gas-consuming device 4 as described previously.

[0052] The return line 14 further comprises a second pump 42 arranged between the first heat exchanger 6 and the convergence point 4L. The second pump 42 makes it possible to increase the pressure of the gas circulating in the return line 14 in order to achieve pressure balancing with the pressure of the gas in the liquid state circulating in the first supply circuit 2 after having been pressurized by the first pump 9. This pressure balancing makes it possible to fluidify the circulation of the reliquefied gas from the return line 14 to the first supply circuit 2.

[0053] The second pump 42 also makes it possible to avoid the compressor 13 pressurizing the gas in the vapor state circulating in the second supply circuit 3 to a pressure greater than approximately 8 bars. This limits the energy required to supply the compressor 13.

[0054] It is at the inlet of the first heat exchanger 6 that the gas in the liquid state of the first supply circuit 2 has the lowest temperature. Therefore, it is after passing through the first heat exchanger 6 that the gas circulating in the return line 14 is condensed. The gas in the return line 14 is therefore in the vapor state at the inlet 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, and this before being pumped by the second pump 42 and joining the first supply circuit 2. The first heat exchanger 6 therefore acts as a condenser.

[0055] The ratio of the quantity of gas in the condensed vapor state to the quantity of gas in the liquid state circulating within the first supply circuit 2 is approximately 16% + / - 5%. In other words, for approximately six tons per hour of gas in the liquid state circulating in the first supply circuit 2, approximately one ton per hour of gas in the vapor state circulating in the return line is condensed.

[0056] The second heat exchanger 7 is located downstream of the first heat exchanger 6 in the direction of circulation of the gas in the first supply circuit 2, and upstream of the first heat exchanger 6 in the direction of circulation of the gas in the return line 14. The second heat exchanger 7 therefore ensures pre-cooling of the gas in the vapor state circulating in the return line 14 before it is condensed within the first heat exchanger 6. At the level of the first supply circuit 2, the gas in the liquid state at the inlet of the second heat exchanger 7 has previously passed through the first heat exchanger 6 and has been pumped by the additional pump 10, which has therefore increased its temperature and its pressure.It is thus possible that following the exchange of calories occurring at the level of the second heat exchanger 7, the gas circulating within the first supply circuit 2 leaves the second heat exchanger 7 in a two-phase state. The temperature of the gas circulating in the return line 14 is therefore lowered after passing through the second heat exchanger 7, implementing the pre-cooling indicated above.

[0057] The additional pump 10 is advantageously arranged between the two heat exchangers 6, 7. The presence of the additional pump 10 between the first heat exchanger 6 and the second heat exchanger 7 ensures that only gas in the liquid state circulates through the additional pump 10, and not gas in a two-phase state which risks damaging the latter.

[0058] Furthermore, the presence of the additional pump 10 downstream of the first heat exchanger 6 ensures the increase in pressure of the gas in the liquid state, and this without disturbing the exchange of calories occurring within the first heat exchanger 6. The condensation of the gas in the vapor state circulating in the return line 14 is thus carried out in an optimal manner.

[0059] The supply system 1 also comprises an auxiliary supply line 16, extending from the first supply circuit 2, via a tapping between the first pump 9 and the first heat exchanger 6, to the second supply circuit 3, connecting to the latter between the compressor 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 crown 12.

[0060] When the gas in the vapor state is not present in sufficient quantity in the sky of tank 12, the gas in the liquid state pumped by the first 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 can for example be identical to that of the high-pressure evaporator 11, that is to say that 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.

[0061] 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 ensuring the control of the circulation of gas within the auxiliary supply line 16 when the use of the latter is not necessary.

[0062] [Fig. 2] represents a second embodiment of the supply system 1 according to the invention. This second embodiment is distinguished from the first embodiment by the fact that the supply system comprises a return branch 44 extending between a divergence point 43 arranged on the return line 14 and the tank 8. The divergence point 43 is more precisely arranged between the first heat exchanger 6 and the second pump 42.

[0063] The return branch 44 offers the alternative to the reliquefied gas by returning the latter to the tank 8 rather than circulating it within the first supply circuit 2. In order to align the pressure of the gas circulating in the return line 14 with the pressure prevailing in the tank 8, the return line 14 may comprise an expansion member 15 which lowers the pressure of the gas to a pressure of between 1 and 3 bars absolute. Once the gas is condensed, it continues its course to the tank 8.

[0064] In order to limit the vaporization of the reliquefied gas circulating in the return branch 44 during the expansion thereof by the expansion member 15, the reliquefied gas can circulate in a limited manner within the return branch 44. The expansion member 15, in addition to operating an expansion on the gas circulating in the return branch 44, also makes it possible to regulate the flow rate thereof. It is thus possible to distribute the reliquefied gas into a first fraction continuing its circulation in the return line 14 and joining the first supply circuit 2 after having been pumped by the second pump 42, and into a second fraction circulating within the return branch 44 and returning to the tank 8 after having been expanded by the expansion member 15.

[0065] The expansion member 15 can also be completely closed so that all of the reliquefied gas circulating in the return line 14 reaches the first supply circuit 2.

[0066] The undescribed characteristics of the second embodiment being identical to those of the first embodiment, reference will therefore be made to the description of [Fig.l] for the description of the elements common to said embodiments.

[0067] [Fig.3] shows a third embodiment of the power supply system 1 in all respects identical to that described in [Fig.2], with the exception of the following elements.

[0068] According to the third embodiment of the supply system 1, the second heat exchanger 7 and the high-pressure evaporator 11 form a single heat exchanger 21. The illustration of the third embodiment makes it possible to design and manufacture the single heat exchanger 21 bringing together the second heat exchanger 7 and the high-pressure evaporator 11, these two components being subjected to the same high pressure which dictates the technology used for the manufacture of this common heat exchanger. Such a solution can also be justified by a lack of space not allowing the second heat exchanger 7 and the high-pressure evaporator 11 to be installed separately from each other.

[0069] The undescribed characteristics of the third embodiment being identical to those of the first and second embodiments, reference will therefore be made to the description of Figures 1 and 2 for the description of the elements common to said embodiments. It should be noted that the third embodiment includes the return branch 44, but it is entirely possible to implement a supply system 1 without the return branch 44, as illustrated in [Fig. 1], but whose second heat exchanger 7 and the high-pressure evaporator 11 form the single heat exchanger 21 as illustrated in [Fig. 3].

[0070] [Fig. 4] is a cutaway view of a floating structure 20 which shows the tank 8 which contains the gas in the liquid state and in the vapor state, this tank 8 being of generally prismatic shape mounted in a double shell 22 of the floating structure 20. The wall of the tank 8 comprises a primary sealing membrane intended to be in contact with the gas in the liquid state contained in the tank 8, a secondary sealing membrane arranged between the primary sealing membrane and the double shell 22 of the floating structure 20, and two thermally insulating barriers arranged respectively between the primary sealing membrane and the secondary sealing membrane and between the secondary sealing membrane and the double shell 22.

[0071] Pipelines 23 for loading and / or unloading gas in the liquid state arranged on the upper deck of the floating structure 20 can be connected, by means of appropriate connectors, to a maritime or port terminal to transfer the cargo of gas in liquid state from or to tank 8.

[0072] [Fig. 4] also represents an example of a maritime or port terminal comprising loading and / or unloading equipment 25, an underwater pipeline 26 and an onshore and / or port installation 27. The onshore and / or port installation 27 may for example be arranged on the quay of a port, or according to another example be arranged on a concrete gravity platform. The onshore and / or port installation 27 comprises liquid gas storage tanks 30 and connecting pipelines 31 connected by the underwater pipeline 26 to the loading and / or unloading equipment 25.

[0073] To generate the pressure necessary for transferring the gas to the liquid state, pumps equipping the onshore and / or port installation 27 and / or pumps equipping the floating structure 20 are used.

[0074] 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.

[0075] The invention, as just described, achieves the aim it set itself, and makes it possible to propose a gas supply system for high-pressure or low-pressure gas-consuming appliances, the high-pressure of which is achieved using pumps and an evaporator, and comprising a means for condensing a gas in the vapor state in order to return it to a circuit supplying one or other of the gas-consuming appliances. Variants not described here could be implemented without departing from the context of the invention, provided that, in accordance with the invention, they comprise a supply system in accordance with the invention.

Claims

Claims

1. Gas supply system (1) for at least one high-pressure gas-consuming device (4) and at least one low-pressure gas-consuming device (5) of a floating structure (20) comprising at least one tank (8) configured to contain the gas, the supply system (1) comprising: - at least one first gas supply circuit (2) for the high-pressure gas-consuming device (4), comprising at least one first pump (9) configured to pump the gas taken in the liquid state from the tank (8), - at least one high-pressure evaporator (11) configured to evaporate the gas circulating in the first gas supply circuit (2), - at least one second gas supply circuit (3) for the low-pressure gas-consuming device (5),comprising at least one compressor (13) configured to compress gas taken in the vapor state from the tank (8) to a pressure compatible with the needs of the low-pressure gas-consuming device (5), - at least one gas return line (14) connected at the inlet to the second supply circuit (3) downstream of the compressor (13), - at least one first heat exchanger (6) and at least one second heat exchanger (7) each configured to carry out a heat exchange between the gas circulating in the return line (14) in the vapor state and the gas in the liquid state circulating in the first supply circuit (2), characterized in that the return line (14) is connected at the outlet to the first supply circuit (2) at a convergence point (41) arranged between the first pump (9) and the first heat exchanger (6),the return line (14) comprising a second pump (42) arranged between the first heat exchanger (6) and the convergence point (41).,

2. A feed system (1) according to claim 1, wherein the return line (14) comprises a divergence point (43) disposed between the first heat exchanger (6) and the second pump (42), the feed system (1) comprising a return branch (44) configured to extend between the divergence point (43) and the tank (8).

3. Feeding system (1) according to the preceding claim, in which the return branch (44) comprises a relaxation member (15).

4. A power supply system (1) according to any preceding claim, wherein the first power supply circuit (2) comprises an additional pump (10) interposed between the first heat exchanger (6) and the second heat exchanger (7).

5. Supply system (1) according to the preceding claim, in which the additional pump (10) is configured to raise the pressure of the gas in the liquid state to a value between 30 and 400 bars.

6. A supply system (1) according to any preceding claim, wherein the first heat exchanger (6) is configured to condense the gas flowing within the return line (14).

7. A supply system (1) according to any preceding claim, wherein the second heat exchanger (7) is configured to pre-cool the gas flowing within the return line (14).

8. A power supply system (1) according to any preceding claim, wherein the compressor (13) is configured to raise a pressure of the gas to a value of 8 bar absolute + / - 1 bar.

9. A supply system (1) according to any preceding claim, wherein the second pump (42) is configured to raise a pressure of the liquid gas flowing in the return line (14) to a value equivalent to the pressure of the liquid gas generated by the first pump (9).

10. A supply system (1) according to any preceding claim, wherein the first pump (9) is configured to raise a pressure of the gas in the liquid state to a value of between 9 and 17 bars absolute.

11. A power system according to any preceding claim, wherein the second heat exchanger (7) and the high pressure evaporator (11) form a single heat exchanger (21).

12. Floating structure (20) for storing and / or transporting gas in the liquid state, comprising at least one tank (8) of gas in the liquid state, at at least one high-pressure gas-consuming device (4), at least one low-pressure gas-consuming device (5) and at least one gas supply system (1) for these devices according to any one of the preceding claims.

13. System for loading or unloading a liquid gas which combines at least one onshore and / or port installation (27) and at least one floating structure (20) for storing and / or transporting liquid gas according to the preceding claim.

14. A method of loading or unloading a liquid gas from a floating structure (20) for storing and / or transporting gas according to claim 12, wherein pipelines (23) for loading and / or unloading gas in the liquid state arranged on an upper deck of the floating structure (20) can be connected, by means of suitable connectors, to a maritime or port terminal in order to transfer the gas in the liquid state from or to the tank (8).

Images