Gas supply system for devices consuming high-pressure gas and low-pressure gas
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-03-13
- Publication Date
- 2026-03-26
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
[Technical field]
[0001] The present invention relates to the field of ships storing and / or transporting liquid gas, and more particularly to gas supply systems for consumers equipped on such ships. [Background technology]
[0002] During the voyage of a ship equipped with tanks of liquid gas for consumption and / or delivery to a destination, it is desirable for the ship to be able to use at least a portion of said liquid gas to supply at least one prime mover via a gas supply system. This is the case for ships equipped with ME-GI propulsion engines. To supply such a prime mover, the gas needs to be compressed to very high pressures by special compressors, which can compress the gas up to 400 bar, but such compressors are expensive, generate significant maintenance costs and induce vibrations in the ship.
[0003] One alternative to the installation of such a high pressure compressor is to vaporize the liquid gas at 400 bar before it is sent to the propulsion engines. Since such a solution does not allow the extraction of the gas phase (boil-off gas, BOG) that naturally forms at least partly in the tanks containing the cargo, a low pressure compressor can be installed to supply the gas as low pressure vapor to an auxiliary motor that can consume it. Furthermore, in case of an excess of gas in the gas phase, the gas can be re-liquefied by heat exchange and then expanded before being returned to the tanks.
[0004] However, before being returned to the tank, approximately 15% of the reliquefied gas vaporizes again upon expansion, so the gas returns to the tank partially in the vapor phase, which reduces the productivity of the gas supply system. Summary of the Invention [Means for solving the problem]
[0005] The present invention solves this problem and provides a gas supply system for at least one high pressure gas consuming device and at least one low pressure gas consuming device for a floating structure, comprising at least one tank adapted to contain gas, - at least one first gas supply circuit for a high-pressure gas consumer, comprising at least one first pump configured to pump gas taken in liquid form from the tank; at least one high-pressure evaporator configured to evaporate gas flowing through the first gas supply circuit; - at least one second gas supply circuit for a low-pressure gas consumer, comprising at least one compressor configured to compress the gas taken in vapour form from the tank to a pressure suitable for the needs of the low-pressure gas consumer; - at least one gas return line connected downstream of the compressor to an inlet of the second supply circuit; at least one first heat exchanger and at least one second heat exchanger, each configured to perform a heat exchange between a gas in a gas phase flowing through the return line and a gas in a liquid phase flowing through the first supply circuit; A gas supply system comprising: The gas supply system is characterized in that the return line is connected at its outlet to the first gas supply circuit at a junction between the first pump and the first heat exchanger, the return line comprising a second pump between the first heat exchanger and the junction.
[0006] The gas supply system according to the invention thus prevents the gas in the gas phase from returning to the tank as a result of the previous expansion, but the reliquefied gas flowing through the return line is used to supply the high-pressure gas consumer by entering the first supply circuit, thus using the reliquefied gas for a useful purpose even if it is not returned to the tank.
[0007] The first gas supply circuit allows to meet the fuel requirements of a high-pressure gas consumer, which may be, for example, a propulsion means for a floating structure, for example, an ME-GI engine. The first supply circuit extends from the tank to the high-pressure gas consumer. A first pump is arranged at the bottom of the tank and pumps liquid gas, which causes the liquid gas to flow through the first gas supply circuit.
[0008] Since the gas must be in a gas phase to be supplied to the high pressure gas consumer, the high pressure evaporator provides for the vaporization of the gas before it is supplied to the high pressure gas consumer. The high pressure evaporator is the point of heat exchange between the liquid gas in the first gas supply circuit and a heat transfer fluid, such as water glycol, seawater or steam. The temperature of the steam must be high enough to cause a phase change of the gas, which causes the gas to change to a steam or supercritical state and be supplied to the high pressure gas consumer.
[0009] Before the liquid gas flowing through the first gas supply circuit is vaporized by the high-pressure evaporator, the liquid gas flows through the first heat exchanger and then through the second heat exchanger. To achieve this, the first and second heat exchangers are connected to each other via a portion of the first gas supply circuit, so that the liquid gas can flow through the two heat exchangers in succession. Thus, the temperature of the liquid gas tends to increase before it flows through the high-pressure evaporator. Thus, the gas flowing through the first gas supply circuit can be two-phase at the outlet of the second heat exchanger.
[0010] Typically, gas in a tank can turn to steam either naturally or when forced by the floating structure. Gas in a tank that turns to steam must be released to prevent excessive pressure in the tank.
[0011] This is achieved by a second gas supply circuit of the low-pressure gas consumer. Such a second gas supply circuit extends from the tank to the low-pressure gas consumer. The low-pressure gas consumer can be, for example, an auxiliary engine, such as a generator. The function of the compressor in the second gas supply circuit is to suck gas from the blanket of the tank and supply it to the low-pressure gas consumer while at the same time regulating the pressure in the tank.
[0012] At the outlet of the compressor, the vapor gas can be supplied to a low-pressure gas consumer or circulated through a return line if the low-pressure gas consumer does not require any fuel supply. The return line is connected downstream of the compressor so that the vapor gas sucked in by the compressor can be circulated through the return line.
[0013] The vapor gas in the return line first flows through the second heat exchanger, then through the first heat exchanger, and then into the first gas supply circuit. Due to the heat exchange between the liquid gas through the first heat exchanger and the vapor gas through the return line, the temperature of the vapor phase gas decreases through the heat exchangers until the gas condenses and returns to liquid at the outlet of the first heat exchanger.
[0014] At the outlet of the first heat exchanger, the liquefied gas flowing through the return line is pumped by a second pump which increases the pressure of the liquefied gas and thus makes it possible to equalize the pressure of the liquid gas flowing through the first gas supply circuit after being pumped by the first pump.
[0015] The second pump also makes it possible to limit the increase in pressure of the vaporous gas by the compressor. Indeed, the compressor increases the pressure of the vaporous gas to a higher value, assuming a pressure equilibrium between the reliquefied gas through the return line and the liquefied gas pumped by the first pump, but such an arrangement requires a significant energy input to the compressor and may also require a pressure regulation system to keep the pressure suitable for the low-pressure gas consumer. The second pump therefore performs this function, thereby preventing any excessive energy supply to the compressor.
[0016] In one example, the first and second heat exchangers are located along the first gas supply circuit upstream of the high pressure evaporator, ensuring that the gas in the first and second heat exchangers is in liquid form in that portion of the first gas supply circuit.
[0017] In one aspect of the invention, the return line has a branch point between the first heat exchanger and the second pump, in which case the supply system includes a return branch configured to extend between the branch point and the tank. Alternatively, it is also possible to maintain the function of returning the gas to the tank after reliquefaction in the gas supply system according to the invention. This branch point is arranged in the return line downstream of the first heat exchanger, so that only the reliquefied gas flows through the return branch. In this case, the reliquefied gas can continue to flow through the return line and be pumped by the second pump into the first gas supply circuit, or it can flow through the return branch and return to the tank. It is also possible to realize an arrangement in which a part of the reliquefied gas flows to the first gas supply circuit, while another part of the reliquefied gas returns to the tank through the return branch.
[0018] In one aspect of the invention, the return branch comprises a pressure reducer which makes it possible to reduce the pressure of the reliquefied gas flowing through the return branch and condensed through the first heat exchanger, such that the liquid gas returns to the tank at a temperature close to the liquid gas equilibrium temperature for the LNG.
[0019] The pressure reducer furthermore allows to adjust the flow rate of the reliquefied gas through the return branch. It is thus possible to reduce this flow rate of the reliquefied gas and set the portion of the gas that reverts to vapor when expanded through the pressure reducer to a minimum. The pressure reducer furthermore can be completely closed to prevent the reliquefied gas from flowing through the return branch. In this configuration, all the reliquefied gas flows through the return line to the first gas supply circuit.
[0020] In one aspect of the invention, the first gas supply circuit comprises an additional pump between the first and second heat exchangers, which makes it possible to increase the pressure of the liquid gas passing through the first gas supply circuit, so that this pressure is suitable for supplying a high-pressure gas consumer.
[0021] The location of the additional pump between the two heat exchangers is particularly advantageous. Rather, locating the additional pump upstream of the first heat exchanger would increase the pressure and temperature of the liquid gas when it flows through the first heat exchanger, which would prevent the condensation of the vapor gas flowing through the return line and the first heat exchanger. Moreover, since the gas flowing through the first gas supply circuit can be two-phase at the outlet of the second heat exchanger, locating the additional pump downstream of the second heat exchanger would hinder the function of the pump, since the additional pump can only pump liquid fluids. Therefore, the ideal location of the additional pump is between the two heat exchangers.
[0022] In one aspect of the invention, the additional pump is configured to increase the pressure of the liquid gas to a value between 30 and 400 bar. In particular, the additional pump makes it possible to increase the pressure of the liquid gas to a value between 30 and 400 bar, in particular for use with ammonia or hydrogen, to a value between 30 and 70 bar for use with liquefied petroleum gas, and preferably to a value between 150 and 400 bar for use with ethane, ethylene or for use with liquefied natural gas produced mainly from methane.
[0023] In one aspect of the invention, the first heat exchanger is configured to condense the gas flowing in the return line, through which the liquid gas of the first gas supply circuit flows when this liquid gas is in its cryogenic state, and the heat exchange in the first heat exchanger thus changes the state of the gas flow in the return line, changing this gas flow from vapor to liquid.
[0024] In one aspect of the invention, the second heat exchanger is configured to pre-cool the gas flowing through the return line. At the output of the first heat exchanger, the liquid gas flowing through the first gas supply circuit is not as cold as at the input of the first heat exchanger, in which case the heat exchange is used to condense the gas in the gas phase flowing through the return line. The liquid gas is subsequently compressed by an additional pump and then flows through the second heat exchanger. Heat exchange also takes place in the second heat exchanger, which makes it possible to pre-cool the vaporous gas in the return line. Cooling is still produced in the second heat exchanger, even if the flow of liquid gas through the first heat exchanger is not sufficient for complete condensation of the vaporous gas through the return line.
[0025] In one aspect of the invention, the compressor is configured to increase the pressure of the gas to a value of 8+ / -1 bar abs. This pressure value ensures the suitability of the vapour gas present in the blanket of the tank and to be sucked into the second gas supply circuit with the low pressure gas consumer. Due to the presence of the second pump, it is not necessary to compress the gas flowing through the return line to a pressure equal to the pressure of the liquid gas flowing through the first gas supply circuit. This limits the power consumption of the compressor.
[0026] In one aspect of the invention, the second pump is configured to increase the pressure of the liquid gas passing through the return line to a value equal to the pressure of the liquid gas generated by the first pump. As described above, the vapour gas passing through the gas supply circuit is compressed to a pressure of 8+ / -1 bar abs. Thus, the vapour gas or reliquefied gas passing through the return line is subjected to a pressure of about 8 bar abs. The liquid gas passing through the first gas supply circuit after being pumped by the first pump is raised to a pressure of more than 8 bar. Thus, the second pump needs to increase the pressure of the reliquefied gas until it reaches a value equal or substantially equal to the pressure of the gas passing through the first gas supply circuit between the first pump and the first heat exchanger. Such pressure balance allows the reliquefied gas to flow into the first gas supply circuit without impediments resulting from pressure differences that may arise between the reliquefied gas and the liquid gas flowing through the first gas supply circuit.
[0027] In one aspect of the invention, the first pump is configured to increase the pressure of the liquid gas to a value between 9 and 17 bar abs.
[0028] In one aspect of the invention, the second heat exchanger and the high pressure evaporator may form a single heat exchanger, with the first heat exchanger being arranged separately upstream of the single heat exchanger that combines the second heat exchanger and the high pressure evaporator. Such an alternative may be advantageous, for example, to reduce the size of the gas supply system.
[0029] The present invention also relates to a floating structure for storing and / or transporting liquefied gas, comprising at least one tank of liquefied gas, at least one high-pressure gas consuming device, at least one low-pressure gas consuming device and at least one gas supply system for these devices.
[0030] The present invention also relates to a system for loading or unloading liquefied gas, connecting at least one onshore and / or port facility with at least one floating structure for storing and / or transporting liquefied gas.
[0031] Finally, the present invention also relates to a method for loading or unloading liquefied gas to or from a floating structure for storing and / or transporting the liquefied gas, in which a liquefied gas loading and / or unloading pipe arranged on the upper deck of the floating structure can be connected by suitable connectors to a marine or port terminal, thereby allowing the liquefied gas to be transferred from or to the tank.
[0032] Other characteristics and advantages of the invention will become apparent on the one hand on the basis of the following description and on the other hand on the basis of some embodiments given by way of guide and non-limitingly with reference to the attached schematic drawings, in which: [Brief description of the drawings]
[0033] [Figure 1] FIG. 1 shows 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. [Diagram 2] FIG. 2 illustrates a second embodiment of a gas supply system. [Diagram 3] FIG. 3 illustrates a third embodiment of a gas supply system. [Figure 4] FIG. 2 is a schematic cutaway view showing a tank of a floating structure and a loading and / or unloading terminal for said tank. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0034] The terms upstream and downstream are used in the following description to define the relative positions of components in a liquid or vapor gas circuit with respect to the direction of flow of said gas through said circuit.
[0035] 1 to 3 show various embodiments of a gas supply system 1 mounted on a floating structure. The gas supply system 1 enables gas to be circulated in liquid, vapor, two-phase or supercritical state from a storage and / or transport tank 8 to a high-pressure gas consuming device 4 and / or a low-pressure gas consuming device 5, thereby supplying fuel to the high-pressure gas consuming device 4 and / or the low-pressure gas consuming device 5.
[0036] The floating structure may be, for example, a ship capable of storing and / or transporting liquefied gas. In this case, the gas supply system 1 may use the liquefied gas stored and / or transported by the floating structure to supply high-pressure gas consuming devices 4, which may be, for example, propulsion engines, and low-pressure gas consuming devices 5, which may be, for example, generators for powering the floating structure.
[0037] To ensure the circulation of gas from the tank 8 to the high-pressure gas consumer 4, the gas supply device 1 has a first gas supply circuit 2. The first gas supply circuit 2 comprises a first pump 9 arranged in the tank 8. The first pump 9 makes it possible to pump the liquid gas and in particular to circulate it through the first gas supply circuit 2. By sucking in the liquid gas, the first pump 9 also makes it possible to increase the pressure of the liquid gas to a value of 9 to 17 bar abs.
[0038] According to the direction of circulation from the tank 8 towards the high pressure gas consumer 4, the liquid gas flows through a first heat exchanger 6 and is pumped by an additional pump 10 through a second heat exchanger 7. In the following, the two heat exchangers 6, 7 are described in more detail.
[0039] After flowing through the second heat exchanger 7, the gas flows to the high-pressure evaporator 11. The high-pressure evaporator 11 changes the state of the gas flowing through the first gas supply circuit 2, thereby making it possible to change the gas into a vapor state or into a supercritical state. Such a state makes the gas suitable for supplying to a high-pressure gas consumer 4. The evaporation of the liquefied gas may be carried out, for example, by heat exchange with a heat transfer fluid, in this case water glycol, seawater or water steam, at a temperature high enough for the liquefied gas to evaporate.
[0040] In the first embodiment as shown in FIG. 1, the first heat exchanger 6, the second heat exchanger 7 and the high-pressure evaporator 11 are heat exchangers isolated from each other. Such an arrangement allows each heat exchanger to be designed and manufactured using a technology suitable for the pressure of the fluid passing through them. In this case, the first heat exchanger 6 can be manufactured using a cheaper technology than the manufacturing technology of the second heat exchanger 7, since the pressure in the first heat exchanger is substantially lower than in the second heat exchanger 7. The same applies to the high-pressure evaporator 11.
[0041] When the additional pump 10 pumps the liquid gas, an increase in the pressure of the gas is brought about by the additional pump 10. The additional pump 10 makes it possible to increase the pressure of the liquid gas to a value of 30-70 bar for use with liquefied petroleum gas, preferably to a value of 150-400 bar for use with ethane, ethylene or with liquefied natural gas produced mainly from methane.
[0042] Due to the combination of the additional pump 10 and the high-pressure evaporator 11, the gas is at a pressure and in a state suitable for supply to the high-pressure gas consumer 4. Such an arrangement makes it possible to avoid the installation in the first gas supply circuit 2 of a high-pressure compressor, which has cost restrictions and generates strong vibrations.
[0043] In the tank 8, some of the cargo gas may naturally turn into vapor and diffuse into the tank blanket 12. To prevent overpressure in the tank 8, it is necessary to vent the vapor gas in the tank blanket 12. Nevertheless, the first gas supply circuit 2 is configured to supply the high-pressure gas consumer 4 with liquid gas.
[0044] In this case, the gas supply system 1 comprises a second gas supply circuit 3, which supplies the low-pressure gas consumer 5 with vaporous gas. The second gas supply circuit 3 thus extends between the tank blanket 12 and the low-pressure gas consumer 5. To draw in the vaporous gas contained in the tank blanket 12, the second gas supply circuit 3 comprises a compressor 13. In addition to drawing in the vaporous gas, the compressor 13 also makes it possible to increase the pressure of the vaporous gas passing through the second gas supply circuit 3 to 8+ / -1 bar abs, so that the vaporous gas reaches a pressure suitable for supplying to the low-pressure gas consumer 5. The second gas supply circuit 3 thus allows for the supply to the low-pressure gas consumer 5, while also allowing for the regulation of the pressure in the tank 8 by drawing in the vaporous gas from the tank blanket 12.
[0045] Excess vapor gas in the tank blanket 12 leads to excess pressure in the tank 8. It is therefore necessary to vent the vapor gas and reduce the pressure in the tank 8. In this case, the excess vapor gas can be removed by means of a burner 18. However, the gas supply system 1 according to the invention has a return line 14 connected to the second gas supply circuit 3 downstream of the compressor 13 with respect to the direction of flow of the vapor gas through the second gas supply circuit 3. According to the direction of circulation of the vapor gas through the return line 14, said gas first flows through the second heat exchanger 7 and then through the first heat exchanger 6. Thus, in the first heat exchanger 6 and in the second heat exchanger 7, heat exchange takes place between the liquid gas flow through the first gas supply circuit 2 and the vapor gas flow through the return line 14. The purpose of this heat exchange is to condense the vapor gas in the return line 14 and turn it into liquid.
[0046] Once the gas stream has been recondensed through the return line 14, it is possible to send the gas stream back to the tank 8. However, such a return requires expansion of the recondensed gas, which may lead to the gas being partially vaporized before being returned to the tank 8. Thus, a portion of the recondensed gas, up to 15%, is vaporized, which reduces the productivity of the gas supply system 1.
[0047] To prevent this, the return line 14 extends to a junction 41 arranged in the first gas supply circuit 2 between the first pump 9 and the first heat exchanger 6. In other words, the gas flowing through the return line 14 flows into the first gas supply circuit 2 instead of returning to the tank 8. Recirculation through the first gas supply circuit 2 allows the supply to the high-pressure gas consumer 4, as described above.
[0048] Furthermore, the return line 14 is provided with a second pump 42 between the first heat exchanger 6 and the junction 41. This second pump 42 increases the pressure of the gas passing through the return line 14, thereby making it possible to balance the pressure of the liquefied gas which has been pressurized by the first pump 9 and which flows through the first gas supply circuit 2. The pressure balance makes it possible to mobilize the flow of the reliquefied gas through the return line 14 to the first gas supply circuit 2.
[0049] Furthermore, the second pump 42 makes it possible to prevent the compressor 13 from pressurizing the vapour gas passing through the second gas supply circuit 3 to a pressure of more than about 8 bar. This limits the energy required to supply the compressor 13.
[0050] The liquid gas in the first gas supply circuit 2 is in a low temperature state at the inlet of the first heat exchanger 6. Thus, the gas flowing through the return pipe 14 is condensed when it flows through the first heat exchanger 6. Therefore, the gas in the return pipe 14 is in a vapor state at the inlet of the first heat exchanger 6, and after heat exchange in the first heat exchanger 6, it flows out in a liquid state and is pumped by the second pump 42 to flow into the first gas supply circuit 2. In other words, the first heat exchanger 6 is used as a condenser.
[0051] The ratio of the amount of condensed vapour gas to the amount of liquid gas passing through the first gas supply circuit 2 is about 16% + / - 5%. In other words, about 6 tonnes of liquid gas per hour flows through the first gas supply circuit 2 and about 1 tonne of vapour gas per hour passing through the return line is condensed.
[0052] The second heat exchanger 7 is arranged downstream of the first heat exchanger 6 according to the direction of circulation of the gas through the first gas supply circuit 2 and upstream of the first heat exchanger 6 according to the direction of circulation of the gas through the return line 14. The second heat exchanger 7 thus pre-cools the vaporous gas flowing through the return line 14 before it is condensed in the first heat exchanger 6. In the first gas supply circuit 2, the liquid gas has previously flowed through the first heat exchanger 6 and is pumped by the additional pump 10 to the inlet of the second heat exchanger 7, so that its temperature and pressure are increased. As a result of the heat exchange in the second heat exchanger 7, the gas flowing through the first gas supply circuit 2 can leave the second heat exchanger 7 in a two-phase state. The temperature of the gas flowing through the return line 14 is thus lowered after flowing through the second heat exchanger 7, whereby the above-mentioned pre-cooling is performed.
[0053] The additional pump 10 is advantageously arranged between the two heat exchangers 6, 7. The additional pump 10 ensures that between the first heat exchanger 6 and the second heat exchanger 7, only liquid gas flows through the additional pump 10, and not two-phase gas, which could damage the additional pump 10.
[0054] Furthermore, the additional pump 10 downstream of the first heat exchanger 6 provides an increase in the pressure of the liquid gas without impeding the heat exchange in the first heat exchanger 6. Thus, condensation of the vapor gas flowing through the return line 14 is optimally provided.
[0055] The gas supply system 1 also comprises an auxiliary gas supply line 16 which extends from the first gas supply circuit 2 via a nipple between the first pump 9 and the first heat exchanger 6 to the second gas supply circuit 3 and is connected to the second gas supply circuit 3 between the compressor 13 and the low-pressure gas consumer 5. The auxiliary gas supply line 16 allows the supply of vaporous gas to the low-pressure gas consumer 5 in the event that the flow rate of the vaporous gas from the tank blanket 12 is insufficient.
[0056] If there is not enough vapor gas in the tank blanket 12, liquid gas from the first pump 9 can flow through the auxiliary gas supply line 16 and be supplied to the low-pressure gas consumer 5. To do this, the auxiliary gas supply line 16 extends through a low-pressure evaporator 17, which converts the liquid gas flowing through the auxiliary gas supply line 16 into vapor. For example, the operation of the low-pressure evaporator 17 can be the same as that of the high-pressure evaporator 11, i.e. the gas is vaporized by heat exchange with a heat transfer fluid at a temperature high enough to vaporize the liquid gas. At the outlet of the low-pressure evaporator 17, the vapor gas flows through the auxiliary gas supply line 16 and then into the second gas supply circuit 3 and is supplied to the low-pressure gas consumer 5.
[0057] The above means that the auxiliary gas supply line 16 is only used when there is not enough vaporous gas present in the tank blanket 12. Therefore, the auxiliary gas supply line 16 is equipped with a valve 19 that allows monitoring of the gas flowing through the auxiliary gas supply line 16 when its use is not required.
[0058] 2 shows a second embodiment of the gas supply system 1 according to the invention. This second embodiment differs from the first embodiment in that the gas supply system comprises a return branch 44 which runs between a branch point 43 in the return line 14 and the tank 8. The branch point 43 is more particularly arranged between the first heat exchanger 6 and the second pump 42.
[0059] The return branch 44 allows the reliquefied gas to alternatively be returned to the tank 8 instead of being circulated through the first gas supply circuit 2. In order to equalize the pressure of the gas passing through the return branch 44 with the pressure in the tank 8, the return branch 44 may be equipped with a pressure reducer 15 which reduces the pressure of the gas to a value of 1-3 bar abs. Once the gas has been condensed it continues to flow towards the tank 8.
[0060] In order to limit the evaporation of the reliquefied gas through the return branch 44 during its expansion by the pressure reducer 15, the reliquefied gas can flow through the return branch 44 in a limited manner. In addition to the expansion of the gas flowing through the return branch 44, the pressure reducer 15 allows the adjustment of the flow rate of this gas. It is thus possible to split the reliquefied gas into a first portion which continues through the return line 14 and enters the first gas supply circuit 2 after being pumped by the second pump 42, and a second portion which flows through the return branch 44 and enters the tank 8 after expansion by the pressure reducer 15.
[0061] Furthermore, the pressure reducer 15 can be closed, which causes all reliquefied gas through the return line 14 to flow into the first gas supply circuit 2 .
[0062] Features of the second embodiment that are not described are the same as those of the first embodiment, so reference should be made to the description of FIG. 1 for a description of components common to the two embodiments.
[0063] FIG. 3 shows a third embodiment of the gas supply system 1, which corresponds in every respect to what is described in FIG. 2, except for the following points.
[0064] In a third embodiment of the gas supply system 1, the second heat exchanger 7 and the high-pressure evaporator 11 form one heat exchanger 21. The diagram of the third embodiment makes it possible to design and manufacture one heat exchanger 21 combining the second heat exchanger 7 and the high-pressure evaporator 11, these two components being exposed to the same high pressure, which determines the technology used to manufacture this joint heat exchanger. Such a solution may also be required by a lack of space that makes it impossible to install the second heat exchanger 7 and the high-pressure evaporator 11 separately from each other.
[0065] The undescribed features of the third embodiment are the same as those of the first and second embodiments, so reference is made to the description of figures 1 and 2 for a description of the components common to said embodiments. It should be noted that although the third embodiment comprises a return branch 44, the gas supply system 1 can be realised without the return branch 44 as shown in figure 1, but with the second heat exchanger 7 and the high-pressure evaporator 11 constituting one heat exchanger 21 as shown in figure 3.
[0066] 4 is a cutaway view of a floating structure 20 showing a tank 8 containing liquid and vapor gas, in this case having a substantially prismatic shape and mounted within a double hull 22 of the floating structure 20. The wall of the tank 8 comprises a primary water-resistant membrane designed to be in contact with the liquid gas in the tank 8, a secondary water-resistant membrane arranged between the primary water-resistant membrane and the double hull 22 of the floating structure 20, and two insulating barriers arranged respectively between the primary water-resistant membrane and the secondary water-resistant membrane and between the secondary water-resistant membrane and the double hull 22.
[0067] A liquefied gas loading and / or unloading pipe 23 located on the upper deck of the floating structure 20 is connected by suitable connectors to a marine or port terminal to enable the transfer of liquefied gas cargo from or to the tanks 8.
[0068] Also shown in Figure 4 is an example of a marine or port terminal including loading and / or unloading equipment 25, subsea pipes 26, and onshore and / or port facilities 27. For example, the onshore and / or port facilities 27 may be located on a wharf at a port, or in another example, on a gravity-based concrete structure. The onshore and / or port facilities 27 include tanks 30 for storing liquid gas and connecting pipes 31 connected to the loading and / or unloading equipment 25 by the subsea pipes 26.
[0069] Pumps installed on land and / or on the port facility 27 and / or on the floating structure 20 are used to generate the pressure required to transport the liquid gas.
[0070] Of course, the invention is not limited to the examples given above, and many modifications can be made to these examples within the framework of the invention.
[0071] The invention, as explained, achieves the assigned objectives and makes it possible to propose a gas supply system for high-pressure or low-pressure gas consumers, which includes means for pressurization by means of a pump and an evaporator and for condensing the vaporous gas in a given circuit and supplying it to one or more gas consumers. Variations not described in this specification can also be readily realized within the scope of the invention, provided that they include a gas supply system according to the invention.
Claims
1. A gas supply system (1) for a floating structure (20) comprising at least one high-pressure gas consumption device (4) and at least one low-pressure gas consumption device (5), wherein the floating structure (20) comprises at least one tank (8) configured to contain gas, - At least one first gas supply circuit (2) for the high-pressure gas consumption device (4), comprising at least one first pump (9) configured to pressurize the gas extracted in liquid form from the tank (8), - At least one high-pressure evaporator (11) configured to vaporize the gas flowing through the first gas supply circuit (2), - At least one second gas supply circuit (3) for the low-pressure gas consumption device (5), comprising at least one compressor (13) configured to compress the gas extracted from the tank (8) in vapor form to a pressure suitable for the needs of the low-pressure gas consumption device (5), - At least one gas return pipe (14) connected to the inlet of 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 perform heat exchange between vaporized gas flowing through the return pipe (14) and liquid gas flowing through the first gas supply circuit (2), and In a gas supply system (1) including, The gas supply system (1) is characterized in that the return pipe (14) is connected at the outlet to the first gas supply circuit (2) at a confluence point (41) between the first pump (9) and the first heat exchanger (6), and the return pipe (14) is equipped with a second pump (42) between the first heat exchanger (6) and the confluence point (41).
2. The gas supply system (1) according to claim 1, wherein the return pipeline (14) has a branch point (43) between the first heat exchanger (6) and the second pump (42), and the supply system (1) includes a return branch section (44) configured to extend between the branch point (43) and the tank (8).
3. The gas supply system (1) according to claim 2, wherein the return branch section (44) is equipped with a pressure reducer (15).
4. The gas supply system (1) according to any one of claims 1 to 3, wherein the first gas supply circuit (2) includes an additional pump (10) between the first heat exchanger (6) and the second heat exchanger (7).
5. The gas supply system (1) according to claim 4, wherein the additional pump (10) is configured to increase the pressure of the liquid gas to a value of 30 to 400 bar.
6. The gas supply system (1) according to any one of claims 1 to 3, wherein the first heat exchanger (6) is configured to condense the gas flowing through the return pipe (14).
7. The gas supply system (1) according to any one of claims 1 to 3, wherein the second heat exchanger (7) is configured to pre-cool the gas flowing through the return pipe (14).
8. The gas supply system (1) according to any one of claims 1 to 3, wherein the compressor (13) is configured to increase the gas pressure to a value of 8+ / -1 bar abs.
9. The gas supply system (1) according to any one of claims 1 to 3, wherein the second pump (42) is configured to increase the pressure of the liquid gas passing through the return pipe (14) to a value equal to the pressure of the liquid gas generated by the first pump (9).
10. The gas supply system (1) according to any one of claims 1 to 3, wherein the first pump (9) is configured to increase the pressure of the liquid gas to a value of 9 to 17 bar abs.
11. The gas supply system (1) according to any one of claims 1 to 3, wherein the second heat exchanger (7) and the high-pressure evaporator (11) constitute a single heat exchanger (21).
12. A floating structure (20) for storing and / or transporting liquid gas, comprising at least one liquid gas tank (8), at least one high-pressure gas consumption device (4), at least one low-pressure gas consumption device (5), and at least one gas supply system (1) for these devices according to any one of claims 1 to 3.
13. A system for loading or unloading liquid gas, connecting at least one onshore facility and / or port facility (27) to at least one floating structure (20) for storing and / or transporting liquid gas according to claim 12.
14. A method for loading liquid gas onto or from a floating structure (20) for storing and / or transporting liquid gas, according to claim 12, wherein a liquid gas loading and / or unloading pipe (23) located on the upper deck of the floating structure (20) is connected to an ocean or port terminal by appropriate connectors, thereby enabling the transfer of the liquid gas from or to the tank (8).