Gas supply system for high and low pressure gas consumer appliance

Abstract

To provide a gas supply system in which the time required to bring large elements, such as a heat exchanger, up to temperature is reduced so as to speed up the time taken to get the gas supply system running.SOLUTION: A gas supply system (1) supplies gas to an appliance (4) consuming high-pressure gas of a floating structure including at least one tank (8). The supply system (1) includes at least one first supply circuit (2) for supplying the high-pressure consumer appliance (4), including a first heat exchanger (6), a second heat exchanger (7), and a pump (10). The gas supply system (1) also includes a pre-cooling system (17) for pre-cooling the first heat exchanger (6) to take gas in the liquid state from the tank (8). The pre-cooling system (17) includes a pre-cooling line (19) and a control valve (21) for controlling the circulation of gas within the pre-cooling line (19).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to the field of vessels for storing and / or transporting gas in liquid state, and more particularly to a gas supply system for supplying gas to consumers provided on board such vessels. [Background technology]

[0002] During a journey carried out by a vessel equipped with tanks of gas in liquid state, which are adapted to be consumed and / or delivered towards a destination, the vessel may be able to use at least a portion of said gas in liquid state to supply at least one of its engines via a gas supply system. This is the case for vessels equipped with ME-GI type propulsion engines. To supply this type of engine, the gas must be compressed to very high pressures by special compressors capable of compressing the gas to 300 bar, but such compressors are expensive, generate high maintenance costs and induce vibrations within the vessel.

[0003] Instead of installing these high-pressure compressors, the gas in liquid form is vaporized at 300 bar before it is sent to the propulsion engines. Since this solution does not eliminate the vaporized gas (or BOG, which stands for "boil-off gas") that naturally forms in the tanks that contain at least part of the cargo, low-pressure compressors can be installed to supply the boil-off gas at low pressure to the auxiliary engines, where it can be consumed. Summary of the Invention

[0004] However, the use of such a gas supply system requires corresponding provision for pre-cooling, during which some of its components are brought to a temperature below the threshold at which supply to the engine can commence. The size of the components that need to be brought to temperature can vary the time required for such pre-cooling; for example, provision of large components will delay the start of the gas supply system, even if smaller components are already at temperature.

[0005] The object of the present invention is to overcome this drawback by providing a gas supply system in which the time required to bring large components such as heat exchangers up to temperature is reduced so as to speed up the time it takes to put the gas supply system into operation.

[0006] The main object of the present invention is therefore a supply system for supplying gas to at least one appliance consuming high pressure gas and at least one appliance consuming low pressure gas of a floating structure, the floating structure comprising at least one tank configured to contain gas, the supply system comprising: at least one first gas supply circuit for supplying gas to the appliance consuming high pressure gas, the at least one first pump configured to pump gas taken from the tank in a liquid state, at least one first heat exchanger, a second heat exchanger, a second pump arranged between the first and second heat exchangers, and at least one high pressure evaporator configured to evaporate the gas circulating in the first gas supply circuit; and at least one second gas supply circuit for supplying gas to the appliance consuming low pressure gas, the at least one second gas supply circuit comprising at least one compressor configured to compress the gas taken from the tank in a vaporized state to the operating pressure of the appliance consuming low pressure gas. According to the present invention, the supply system comprises a pre-cooling system for pre-cooling a first heat exchanger configured to extract gas in a liquid state from a tank, the pre-cooling system comprising a pre-cooling line connected to the first supply circuit between the first heat exchanger and the second pump, and the pre-cooling system comprising at least one control valve for controlling the circulation of gas in the pre-cooling line.

[0007] The supply system according to the present invention is configured to be installed on a floating structure, for example, for the purpose of supplying gas to its consuming equipment. More specifically, the first gas supply circuit allows the fuel requirements of the high-pressure gas consuming equipment to be met. The high-pressure gas consuming equipment may be a propulsion means of the floating structure, for example, an engine ME-GI. The first supply circuit extends from the tank to the high-pressure gas consuming equipment. The first pump, installed at the bottom of the tank, pumps the gas in a liquid state so that it can circulate through the first supply circuit.

[0008] The high-pressure evaporator ensures that the gas is vaporized before it can be supplied to the equipment consuming the high-pressure gas. The high-pressure evaporator is the location of the heat exchange between the liquid gas circulating in the first supply circuit and a heat transfer fluid, such as glycol water, seawater, or steam. This must be at a temperature high enough to cause a change in the state of the gas, so that it becomes vaporized or supercritical in order to be supplied to the equipment consuming the high-pressure gas.

[0009] Before the liquid gas circulating in the first supply circuit is vaporized by the high-pressure evaporator, it passes through the first heat exchanger and then the second heat exchanger. To achieve this, the first and second heat exchangers are connected to each other by a portion of the first supply circuit so that the liquid gas can pass through the two heat exchangers in succession. Therefore, the temperature of the liquid gas tends to increase before passing through the high-pressure evaporator. In this way, the gas circulating in the first supply circuit can be in a two-phase state at the outlet of the second heat exchanger.

[0010] Generally speaking, gas stored in a tank can vaporize naturally or be forced to do so by a floating structure. Any gas in the tank that vaporizes must be vented to prevent excessive pressure from building up inside the tank. This function is performed by a second gas supply circuit for the equipment consuming the low-pressure gas. Such a second supply circuit extends from the tank to the equipment consuming the low-pressure gas. This may be an auxiliary motor, such as a generator. A compressor on the second supply circuit draws gas from the tank head so that it can be supplied to the equipment consuming the low-pressure gas and regulate the pressure inside the tank. At the compressor outlet, the vaporized gas can be supplied to the equipment consuming the low-pressure gas.

[0011] The first heat exchanger, the second heat exchanger, and the high-pressure evaporator are physically separate heat exchangers. For example, the first heat exchanger is a recondenser, and the second heat exchanger is a precooler. The second pump increases the pressure of the liquid gas circulating in the first supply circuit, so that the first supply circuit has a pressure suitable for supplying high-pressure gas-consuming equipment.

[0012] The supply system includes a system for pre-cooling the first heat exchanger, which is used to bring the first heat exchanger up to temperature during a preparation or pre-cooling step of the floating structure. During the preparation step, the temperature of the first heat exchanger is lowered, for example, to around -140°C. Such a preparation step is usually performed when the floating structure is docked, before supplying its consumers. For this purpose, the supply system is configured to extract gas in liquid form from the tank by circulating the gas through a portion of the first supply circuit, possibly extending between the first pump and the first heat exchanger. The supply system also includes a pre-cooling line connected to the first supply circuit upstream of the outlet of the first heat exchanger and the second pump, which is used to vent the gas that has passed through the first heat exchanger during pre-cooling. The passage of gas through this pre-cooling line is controlled by the presence of a control valve in the pre-cooling system. This control valve has an open and a closed configuration, and the open configuration of the control valve allows gas to enter the pre-cooling line. The presence of the pre-cooling circuit means that the first heat exchanger can be pre-cooled independently of the pre-cooling by the second pump.

[0013] The pre-cooling system allows the temperature of the first heat exchanger to be lowered before its operation in the supply system. To do this, the pre-cooling system increases the gas flow rate through the first heat exchanger to speed up the time required to bring the first heat exchanger up to temperature. The pre-cooling system allows the flow rate of gas circulating through the first heat exchanger to be doubled or tripled compared to the flow rate of gas normally used during operation of the first heat exchanger, for example, to supply equipment consuming high-pressure gas. In this way, the first heat exchanger can be brought up to temperature in a time similar to the time required to bring other smaller elements of the supply system, such as the second pump, up to temperature, thereby reducing the time required to prime the entire supply system.

[0014] According to an optional feature of the invention, the first supply circuit includes a first valve disposed between the first pump and the first heat exchanger and a second valve disposed between the first heat exchanger and the second pump, and the pre-cooling line is connected to the first supply circuit between the first heat exchanger and the second valve.

[0015] The first and second valves form a bypass circuit for bypassing the first heat exchanger. Such a bypass circuit, associated with a pre-cooling system, allows for purging the first path of the heat exchanger located between these two valves. When the first heat exchanger is bypassed in this way, it is possible to pre-cool the first heat exchanger while simultaneously supplying gas to the second pump. The use of the bypass circuit also makes it possible to perform maintenance work on the first heat exchanger.

[0016] According to an optional feature of the invention, the pre-cooling system is configured so that the pre-cooling line opens into a lower portion of the tank.

[0017] According to an optional feature of the invention, the pre-cooling system is configured so that the pre-cooling lines open into an upper portion of the tank.

[0018] In other words, the pre-cooling line extends between the first supply circuit and the tank. The tank comprises a lower part dedicated to storing the gas in the liquid state and an upper part dedicated to storing the gas evaporated from the liquid state, the lower part corresponding to the tank bottom and the upper part corresponding to the tank head. Depending on the embodiment, the pre-cooling line can open either at the bottom of the tank or in the tank head. In both of these cases, the pre-cooling line opens directly into the tank, i.e., it is not connected to any other duct in the supply system that opens into the tank.

[0019] According to an optional feature of the invention, the supply system includes a gas return line connected to the second supply circuit and configured to return gas to the tank, and the first heat exchanger and the second heat exchanger each include a first path constituting the first supply circuit and a second path constituting the return line.

[0020] In other words, the first and second heat exchangers are each configured to perform heat exchange between the gas circulating in the vapor return line and the liquid gas circulating in the first supply circuit. This return line is located between the compressor and the equipment consuming low-pressure gas and extends to the tank. When the equipment consuming low-pressure gas does not require fuel, the vapor gas circulates through the return line at the compressor outlet. The vapor gas circulating in the return line first passes through the second heat exchanger and then the first heat exchanger before returning to the tank. As a result of the heat exchange between the liquid gas circulating in the first supply circuit and the vapor gas circulating in the return line, the temperature of the vapor gas decreases as it passes through the heat exchangers until it condenses and returns to a substantially liquid state at the outlet of the first heat exchanger. The recondensed gas then circulates into the tank. The first heat exchanger is configured to condense the gas circulating in the return line. The first heat exchanger is the exchanger through which the liquid gas of the first supply circuit passes when the liquid gas is at its lowest temperature. It is the exchange of heat in the first heat exchanger that changes the state of the gas circulating in the return line from vapor to liquid. The second heat exchanger is configured to pre-cool the gas circulating through the return line before passing through the first heat exchanger.

[0021] According to an optional feature of the invention, a pre-cooling line is connected to the return line between the first heat exchanger and an outlet of the return line configured to open into the tank.

[0022] In other words, the pre-cooling line has a first end connected to the first supply circuit and a second end connected to the return line leaving the first heat exchanger, more precisely between the second pass of this first heat exchanger and the tank. This configuration makes it possible to avoid the need to manufacture and install a dedicated section of line to the tank.

[0023] According to an optional feature of the invention, the supply system includes a cooling system for cooling the second pump, the cooling system including a cooling line connected to the first supply circuit between an inlet port of the second pump and the second heat exchanger, and the cooling system including at least one control valve for controlling circulation of gas in the cooling line.

[0024] The cooling system for the second pump is the counterpart of the pre-cooling system for the first heat exchanger. Therefore, the system for cooling the second pump is used during the preparation stage of the supply system to lower the temperature of the second pump before its operation in the supply system. To do this, the cooling system extracts gas in a liquid state and increases the flow rate of this gas in a liquid state through the second pump, resulting in heating of the gas. The cooling line is either connected directly to the second pump or to the first supply circuit between the second pump and the second heat exchanger.

[0025] In some cases, the second pump may be cooled by the cooling system after, at the same time as, or even before the first heat exchanger is pre-cooled by the pre-cooling system.

[0026] According to an optional feature of the invention, the cooling system is configured such that the cooling lines open into the tank.

[0027] In other words, the cooling lines extend between the pump and the tank. Depending on the embodiment, the cooling lines can open into the bottom of the tank or into the tank head.

[0028] According to an optional feature of the invention, a cooling line opens into the return line between the first heat exchanger and an outlet of the return line configured to open into the tank.

[0029] The cooling line therefore runs between the inlet port of the second pump and the outlet of the second pass of the first heat exchanger. After pre-cooling the second pump, the gas in its liquid state circulates through the cooling line and then takes the return line to the tank. This configuration avoids the need to manufacture and install a dedicated section of line to the tank.

[0030] In embodiments where the return line opens into the bottom of the tank, the outlet of this return line may be equipped with an evacuation element, such as a foaming element, which allows at least a portion of the vaporized gas to liquefy as it returns to the tank, also increasing the temperature of the liquid gas within the tank.

[0031] According to an optional feature of the invention, the return line includes an expansion member disposed between the first heat exchanger and an outlet of the return line configured to open into the tank.

[0032] The expansion element reduces the pressure of the gas circulating in the return line as it condenses during its passage through the first heat exchanger. Thanks to the expansion element, the liquid gas is returned to the tank at a temperature close to the liquid-vapor equilibrium temperature of the gas. The expansion element also regulates the flow rate of the condensed gas circulating in the return line. If one or both of the pre-cooling and cooling lines open into the return line, they are connected between this expansion element and the outlet of the return line, i.e., downstream of the expansion element.

[0033] According to an optional feature of the invention, the supply system includes a bypass line for bypassing the first heat exchanger, the bypass line including a regulating member.

[0034] The bypass line and the adjustment member it carries serve to form a bypass system for bypassing the first pass of the first heat exchanger.

[0035] The present invention also relates to a floating structure for storing and / or transporting gas in liquid state, comprising at least one tank configured to contain gas in liquid state, at least one high-pressure gas consuming device, at least one low-pressure gas consuming device, and at least one gas supply system for supplying gas to the aforementioned consuming devices.

[0036] The present invention also covers a system for loading or unloading liquid gas, which combines at least one onshore and / or port facility with at least one floating structure for storing and / or transporting liquid gas as described above.

[0037] The present invention relates to a method for loading or unloading liquid gas from a floating structure for storing and / or transporting the gas as described above, wherein a pipeline for loading and / or unloading the gas in liquid state, arranged on the upper deck of the floating structure, can be connected by suitable connectors to a coastal or port terminal for transferring the gas in liquid state from or to the tank.

[0038] Finally, the invention relates to a method for supplying a floating structure as described above by a supply system as described above, comprising at least one pre-cooling step, including the sub-steps of withdrawing gas in liquid state from a tank, cooling a first heat exchanger and circulating the gas in a pre-cooling line, and the supply method comprises the step of supplying the gas in liquid state withdrawn from the tank to an appliance consuming high-pressure gas.

[0039] Therefore, a pre-cooling step is necessary for the implementation of a supply system, in particular for the purpose of supplying equipment of the supply system that consumes high-pressure gas, in order to bring the first heat exchanger up to temperature, thus allowing the high-pressure gas to be supplied to the equipment that consumes it, and also to subsequently condense the gas circulating in the return line.

[0040] According to an optional feature of the invention, during the pre-cooling step, a control valve of the pre-cooling system is opened.

[0041] Opening this control valve allows gas to flow through the pre-cooling line.

[0042] According to an optional feature of the invention, the supply method includes at least one cooling step before the supply step, and includes the substeps of removing gas in a liquid state from the tank, cooling the second pump, and circulating the gas in a cooling line.

[0043] During this cooling step, the gas in the liquid state circulates either in the first heat exchanger, more particularly in its first pass, or in the bypass line of the bypass circuit. For example, the cooling step is carried out simultaneously with the pre-cooling step.

[0044] Other characteristics, details and advantages of the invention will become more apparent on reading the following description on the one hand and the examples of embodiments given by way of indication and non-limitingly with reference to the attached drawings on the other hand. [Brief explanation of the drawings]

[0045] [Figure 1] 1 is a diagram illustrating a schematic view of a gas supply system according to the present invention in a first embodiment. [Figure 2] FIG. 2 is a diagram schematically illustrating the gas supply system shown in FIG. 1 according to a second embodiment. [Figure 3] FIG. 10 is a diagram schematically illustrating the gas supply system shown in FIG. 1 according to a third embodiment. [Figure 4]FIG. 10 is a diagram schematically illustrating the gas supply system shown in FIG. 1 according to a fourth embodiment. [Figure 5] FIG. 10 is a diagram schematically illustrating the gas supply system shown in FIG. 1 according to a fifth embodiment. [Figure 6] 1 shows a schematic representation of a tank of a floating structure according to the invention and a terminal for loading and / or unloading said tank; FIG. DETAILED DESCRIPTION OF THE INVENTION

[0046] The features, variations, and different embodiments of the invention can be associated with one another in various combinations, provided they are not incompatible or mutually exclusive. In particular, it is possible to envision variations of the invention that include only a selection of features described below in isolation from other features described, where this selection of features is sufficient to provide a technical advantage and / or distinguish the invention from the prior art.

[0047] In the figures, elements common to several figures carry the same reference numerals. As used in the following description, the terms "upstream" and "downstream" are used to denote the location of an element in a circuit of a gas in liquid or vapor state and refer to the direction of circulation of said gas in said circuit.

[0048] 1 to 5 show a schematic representation of a gas supply system 1 according to the invention, which is integrated into a floating structure. The supply system 1 allows gas, which may be in a liquid, vapor, two-phase or supercritical state, to be circulated 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, in order to supply fuel to the high-pressure gas consuming device 4 and / or the low-pressure gas consuming device 5.

[0049] The floating structure may for example be a ship capable of storing and / or transporting gas in liquid state, in which case the supply system 1 is able to use the gas in liquid state stored and / or transported by the floating structure to supply high pressure gas consuming equipment 4, which may for example be a propulsion engine, and low pressure gas consuming equipment 5, which may for example be a generator supplying electricity to the floating structure.

[0050] To ensure the circulation of the gas contained in the tank 8 to the high-pressure gas consuming equipment 4, the supply system 1 is provided with a first gas supply circuit 2. The first supply circuit 2 comprises a first pump 9 located in the tank 8. The first pump 9 is used to pump the gas in liquid state and in particular to circulate the gas in the first supply circuit 2. By drawing the gas into its liquid state, the first pump 9 also increases the pressure of the gas to between 6 and 17 bar.

[0051] The gas in liquid state passes through the first heat exchanger 6 in a circulation direction from the tank 8 towards the high-pressure gas consuming equipment 4, is pumped by the second pump 10 and passes through the second heat exchanger 7. The second pump 10 makes it possible to increase the pressure of the gas in liquid state to a value of 30 to 70 bar for use with liquefied petroleum gas, or to a value of 150 to 400 bar for use with liquefied natural gas, preferably consisting of ethane, ethylene or mainly methane.

[0052] After passing through the second heat exchanger 7, the gas is circulated to the high-pressure evaporator 11. The high-pressure evaporator 11 is used to change the state of the gas circulating in the first supply circuit 2 to a vaporized or supercritical state, making the gas suitable for supply to high-pressure gas consuming equipment 4. Evaporation of the gas in its liquid state can occur, for example, by heat exchange with a heat transfer fluid at a temperature high enough to evaporate the gas in its liquid state, in this case glycol water, seawater or steam.

[0053] Thanks to the combination of the second pump 10 and the high-pressure evaporator 11, the gas is at a pressure and condition suitable for supplying the high-pressure consumer 4. This arrangement makes it possible to avoid the need to install a costly, vibration-inducing high-pressure compressor in the first supply circuit 2.

[0054] Within the tank 8, a portion of the gas cargo may naturally transition to a vapor state and diffuse into the tank head 12, which corresponds to the upper part of the tank 8, as opposed to the tank bottom 16, which corresponds to the lower part of the tank 8. To prevent overpressure within the tank 8, the vapor state gas contained in the tank head 12 must be vented. The first supply circuit 2 is configured to supply high-pressure gas consuming equipment 4 using gas in a liquid state.

[0055] The supply system 1 includes a second gas supply circuit 3 that uses vaporized gas to supply the low-pressure gas consuming device 5. The second supply circuit 3 therefore extends between the tank head 12 and the low-pressure gas consuming device 5. The second supply circuit 3 includes a compressor 13 for aspirating the vaporized gas contained in the tank head 12. In addition to aspirating the vaporized gas, the compressor 13 also increases the pressure of the vaporized gas circulating in the second supply circuit 3 to a pressure of 6 to 20 bar absolute, so that the vaporized gas is at a pressure suitable for supplying the low-pressure gas consuming device 5. This allows the second supply circuit 3 to supply the low-pressure gas consuming device 5 while regulating the pressure in the tank 8 by aspirating the vaporized gas present in the tank head 12.

[0056] If there is too much vaporized gas in the tank head 12, the pressure in the tank 8 will become excessive. It is therefore necessary to vent the vaporized gas in order to reduce the pressure in the tank 8. The excess vaporized gas can then be removed, for example, by means of a burner 18. However, the supply system 1 according to the invention comprises a return line 14 extending from the second supply circuit 3 to the tank 8.

[0057] The return line 14 is connected to the second supply circuit 3 downstream of the compressor 13 in the direction of circulation of the vaporized gas circulating in the second supply circuit 3. Depending on the direction of circulation of the vaporized gas circulating in the return line 14, said gas first passes through the second heat exchanger 7 and then through the first heat exchanger 6. Thus, the heat exchange that takes place in the first heat exchanger 6 and the second heat exchanger 7 takes place between the liquid gas circulating in the first supply circuit 2 and the vaporized gas circulating in the return line 14.

[0058] The purpose of this heat exchange is to condense the gas in vapor form in the return line 14, thereby changing it into a liquid state, and to return it in this state to the tank 8, instead of the gas being rejected by the burner 18. More precisely, the gas circulating in the return line 14 is in vapor form when it enters the first heat exchanger 6 and leaves in liquid form as a result of the heat exchange that takes place in the first heat exchanger 6. From the above, it can be seen that the first heat exchanger 6 and the second heat exchanger 7 each comprise a first path constituting the first supply circuit 2 and a second path constituting the return line 14.

[0059] In order to adjust the pressure of the gas circulating in the return line 14 to the pressure prevailing in the tank 8, the return line 14 may be provided with an expansion element 15 arranged between the first heat exchanger 6 and the outlet of the return line 14 leading into the tank 8, which reduces the pressure of the gas to a pressure of 1 to 3 bar absolute. The gas is condensed in the first heat exchanger 6 and then expanded in the expansion element 15 before continuing its journey to the outlet of the return line 14, i.e. to the tank 8. The first heat exchanger 6 therefore functions as a condenser or recondenser.

[0060] The second heat exchanger 7 is located downstream of the first heat exchanger 6 in the direction of gas circulation in the first supply circuit 2 and upstream of the first heat exchanger 6 in the direction of gas circulation in the return line 14. The second heat exchanger 7 therefore pre-cools the gas in the vapor state circulating in the return line 14 before it is condensed in the first heat exchanger 6; in other words, the second heat exchanger 7 is a pre-cooler. In the first supply circuit 2, the gas in the liquid state at the inlet to the second heat exchanger 7 has previously passed through the first heat exchanger 6 and been pumped by the additional pump 10, thus increasing its temperature and its pressure. As a result of the heat exchange that takes place at the level of the second heat exchanger 7, the gas circulating in the first supply circuit 2 can therefore leave the second heat exchanger 7 in a two-phase state. The temperature of the gas circulating in the return line 14 is therefore reduced after passing through the second heat exchanger 7, thus providing the pre-cooling described above in relation to the second heat exchanger 7.

[0061] It should be noted that the first heat exchanger 6 must be pre-cooled in order to be able to optimally and without delay perform its function as a condenser for the gas circulating in the return line 14. This type of pre-cooling will be explained below in connection with the method for supplying the floating structure 20, but is a step prior to implementing the first heat exchanger 6 as a condenser in the return line 14.

[0062] For this purpose, according to the invention, the supply system 1 comprises a pre-cooling system 17 for cooling the first heat exchanger 6. The supply system 1 and its pre-cooling system 17 are shown in a first embodiment in Figure 1, a second embodiment in Figure 2, a third embodiment in Figure 3, a fourth embodiment in Figure 4 and a fifth embodiment in Figure 5.

[0063] The pre-cooling system 17 comprises, according to an embodiment, pre-cooling lines 19 connected differently within the supply system 1 and a control valve 21 for controlling the circulation of gas within the pre-cooling lines 19. This control valve 21 is carried by the pre-cooling lines 19 and controls the circulation of gas in the vaporized or liquid state therein.

[0064] The pre-cooling system 17 is configured to extract liquid gas from the tank 8 using the first pump 9 as needed and transport the gas to the first heat exchanger 6. The liquid gas is transported to the first heat exchanger 6 by a duct in the first supply circuit 2 that connects the tank 8 to the first heat exchanger 6. This duct is therefore involved in both supplying the high-pressure gas consuming equipment 4 and pre-cooling the first heat exchanger 6. It will be understood that the first heat exchanger 6 is pre-cooled as the liquid gas passes through it; therefore, the higher the flow rate of liquid gas passing through the first heat exchanger 6, the faster the temperature of this first heat exchanger 6 will decrease.

[0065] In addition to the pre-cooling system 17, the supply system 1 comprises a cooling system 24 for cooling the second pump 10, which makes it possible to circulate the gas in liquid state in the second pump 10 to bring it to a suitable temperature during the step before supplying the high-pressure gas to the equipment 4 consuming the gas. The cooling system 24 comprises a cooling line 28 and a control valve 29 carried by the cooling line 28. It will be understood that the control valve 29 controls the circulation of the gas in the cooling line 28.

[0066] The cooling system 24 is configured to take gas in liquid state from the tank 8 using the first pump 9 when necessary and to transport the gas to the second pump 10. The gas in liquid state is transported to the second pump 10 by a duct of the first supply circuit 2 which in particular connects the tank 8 to the first heat exchanger 6. This duct is therefore involved in supplying the high-pressure gas consuming equipment 4, pre-cooling the first heat exchanger 6 and cooling the second pump 10.

[0067] The cooling line 28 is connected to the first supply circuit 2 between the inlet port of the second pump 10 and the second heat exchanger 7. Thus, the cooling line 28 is either connected to the second pump 10 as shown in the figure, or is connected to the first supply circuit 2 between the outlet of this second pump 10 and the inlet of the second heat exchanger 7.

[0068] The control valve 29 is a proportional valve having a fully open configuration, a closed configuration, and at least one intermediate configuration that is partially open. When the control valve is in its closed configuration, the passage of liquid gas in the cooling line 28 is prevented. Conversely, when the second pump 10 is cold, the control valve 29 is in its fully open configuration.

[0069] In the first four embodiments, the cooling line 28 extends from the first supply circuit 1 to the tank 8. In the embodiment shown in FIGS. 1 to 4, the cooling line 28 extends to the upper part of the tank 8, i.e., opens into the tank head 12. However, alternative embodiments can be envisaged in which the cooling line 28 opens into the bottom 16 of the tank without departing from the scope of the invention. It should be noted that the control valve 29 regulating the passage of gas through the cooling line 28 has the function of expanding the gas to a liquid state. The gas in the liquid state circulating in the cooling line 28 therefore has a pressure of around 9 bar between the second pump 10 and the control valve 29, i.e., upstream of this control valve 29, and a pressure of less than 2 bar between the control valve 29 and the tank 8, i.e., downstream of the control valve 29, i.e., close to the pressure of the gas in the liquid state in the tank 8.

[0070] With respect to the pre-cooling system 17, in the five embodiments presented herein, the pre-cooling line 19 of the first heat exchanger 6 is connected to the first supply circuit 2 between the first heat exchanger 6 and the second pump 10. The control valve 21 has an open configuration in which gas can circulate through the pre-cooling line 19 and a closed configuration in which such circulation is prevented. It will be understood that in the open configuration, the gas is at least partially diverted towards the pre-cooling line 19, while in the closed configuration, the gas circulates to the second pump 10. The pre-cooling circuit 17 thus allows the flow rate of gas circulating through the first heat exchanger 6 to be increased without affecting the flow rate of gas sent to the second pump 10, with any excess gas flow being diverted into the pre-cooling line 19.

[0071] In the first and second embodiments shown in Figures 1 and 2 respectively, the pre-cooling line 19 extends between the first heat exchanger 6 and the second pump 10 on the one hand and to the tank 8 on the other hand. In other words, the pre-cooling line 19 extends from the first supply circuit 2 to the tank 8. In Figures 1 and 2, the pre-cooling line 19 extends to the upper part of the tank 8, i.e. opens into the tank head 12. As already mentioned for the cooling line 28, an alternative embodiment can be envisaged in which the pre-cooling line 19 opens into the bottom 16 of the tank.

[0072] It should be noted that in the second embodiment, the supply system 1 uses a bypass circuit 32 for bypassing the first heat exchanger 6. This bypass circuit 32 comprises a bypass line 33 arranged parallel to the first pass of the first heat exchanger 6 and an adjustment member 34 carried by said bypass line 33.

[0073] The bypass circuit 32 makes it possible to prevent gas from passing through the first heat exchanger 6, for example, for the purpose of purging the gas during maintenance work on the first heat exchanger 6. To do this, the bypass circuit 32 is used in conjunction with valves arranged in the first supply circuit 2 on both sides of the first heat exchanger 6, more specifically, a first valve 35 arranged upstream of the heat exchanger 6 and a second valve 36 arranged downstream of the heat exchanger 6. As shown in FIG. 2, the bypass line 33 is tapped into the first supply circuit 2 upstream of the first valve 35 and downstream of the second valve 36. In other words, the bypass line 33 runs parallel to the first supply circuit 2 between a first point between the tank 8 and the first heat exchanger 6, more specifically, between the tank 8 and the first valve 35, on the one hand, and a second point between the first heat exchanger 6 and the second pump 10, more specifically, between the second valve 36 and the second pump 10, on the other hand. It will be understood that the first and second valves 35, 36 are not incorporated into the bypass circuit 32 but form part of the portion of the first supply circuit 2 that the bypass circuit 32 allows to be avoided.

[0074] When open, the regulating member 34 allows liquid gas to pass through the bypass line 33. When open, the first valve 35 allows liquid gas to pass through the first pass of the first heat exchanger 6 and prevents such passage when closed. When open, the second valve 35 allows gas to circulate to the second pump 10 and thus to the high-pressure gas consuming equipment 4 and prevents such flow when closed. From the above, it follows that purging of the first heat exchanger 6 is performed when the regulating member 34 is open, the first valve 35 is closed, and the pre-cooling system 17 is operating, i.e., when the control valve 21 is in its open configuration.

[0075] It should be noted that the bypass circuit 32 may also be used if the first heat exchanger 6 has an excessively high temperature which could vaporize the gas circulating in the first heat exchanger 6 and damage the second pump 10, which would then be supplied with gas in a vaporized state rather than gas in a liquid state. The bypass circuit 32 in this regard makes it possible to bypass the first heat exchanger 6 and thus ensures that the second pump 10 is always supplied with gas in a liquid state so that it can operate optimally.

[0076] Furthermore, thanks to the second embodiment shown in FIG. 2, it is possible to pre-cool the first heat exchanger 6 while supplying the high-pressure gas to the consumer 4. In this case, the regulating element 34 is open, allowing the liquid gas to circulate through the bypass line 33 and then back through the first supply circuit 2 to the consumer 4. The second valve 36 is closed to prevent gas from flowing back towards the first heat exchanger 6. At the same time, the first valve 35 is opened, allowing a portion of the liquid gas coming from the tank 8 to pass through the first heat exchanger 6 before circulating in the pre-cooling line 19. To achieve this, the control valve 21 of this pre-cooling line 19 is in its open position. Mixing of the gas that has passed through the first heat exchanger 6 and the gas circulated in the bypass line 33 is prevented by the closed second valve 36. The second embodiment therefore makes it possible to manage the pre-cooling of the first heat exchanger 6 whilst supplying high pressure gas to the consuming equipment 4, thereby making it possible to bring the first heat exchanger 6 up to temperature whilst starting up the floating structure.

[0077] The third embodiment shown in Figure 3 differs from the first embodiment of Figure 1 in that the pre-cooling line 19 is not directly connected to the tank 8, in other words, it does not open into the tank 8. Instead, here the pre-cooling line 19 is connected to the cooling line 28. More specifically, the pre-cooling line 19 is connected to the cooling line 28 downstream of the control valve 29, i.e., between this control valve 29 and the tank 8. The pre-cooling line 19 then extends from the first supply circuit 2 to the cooling line 28.

[0078] In a fourth embodiment shown in Figure 4, the pre-cooling line 19 also does not open directly into the tank 8. Here, the pre-cooling line 19 is connected to the return line 14 by a convergence point 37. More specifically, the pre-cooling line 19 is connected to the return line 14 at the level of the convergence point 37 downstream of the expansion member 15, i.e. between this expansion member 15 and the outlet of the return line 14, which opens into the tank 8. If necessary, the outlet of the return line 14 can be equipped with an evacuation element, such as a foaming element, not shown here. In this fourth embodiment, as previously mentioned, the cooling line 28 opens into the tank 8.

[0079] The fifth embodiment, shown in Figure 5, is a variant of the fourth embodiment. In this fifth embodiment, like the fourth embodiment, the pre-cooling line 19 is connected to the return line 14 downstream of the expansion member 15 within the convergence point 37. However, the fifth embodiment differs from the fourth embodiment with regard to the connection of the cooling line 28. In this case, the cooling line 28 is also connected to the return line 14 at the level of the convergence point 37. From the above, it follows that the pre-cooling line 19 and the cooling line 28 are both connected to the return line 14 via the convergence point 37.

[0080] It should be noted that, unless incompatible, features presented in relation to one of the five embodiments may be applied mutatis mutandis to one or more other of these embodiments without departing from the scope of the invention, unless otherwise specified.

[0081] 6 is a cross-sectional view of a floating structure 20 showing a tank 8 containing gas in liquid and vapor states, the tank 8 being of generally prismatic shape attached to the double hull 22 of the floating structure 20. The wall of the tank 8 comprises a primary sealing membrane configured to be in contact with the gas in liquid state contained in the tank 8, a secondary sealing membrane arranged between the primary sealing membrane and the double hull 22 of the floating structure 20, and two insulating barriers arranged between the primary sealing membrane and the secondary sealing membrane and between the secondary sealing membrane and the double hull 22, respectively.

[0082] A pipeline 23 for loading and / or unloading gas in liquid state, arranged on the upper deck of the floating structure 20, can be connected by suitable connectors to a coastal or port terminal to transfer a cargo of gas in liquid state from or to the tanks 8.

[0083] 6 also shows an example of a coastal or port terminal comprising loading and / or unloading equipment 25, subsea ducts 26 and onshore and / or port equipment 27. The onshore and / or port equipment 27 may be located, for example, on a breakwater in a port or, in another example, on a concrete gravity platform. The onshore and / or port equipment 27 comprises a storage tank 30 for gas in liquid state and a connecting duct 31 connected to the loading and / or unloading equipment 25 by the subsea duct 26.

[0084] Pumps mounted on land and / or port facilities 27 and / or on the floating structure 20 are used to generate the pressure required to convert the gas into a liquid state.

[0085] A method for supplying a floating structure 20 using the supply system 1 will now be described. Such a supply method comprises two separate parts: a first part corresponding to the preparation of the supply system 1 and a second part being the actual supply of one and / or the other of the consumers 4, 5.

[0086] The supply method therefore comprises a step of pre-cooling the first heat exchanger 6 prior to the step of supplying one and / or the other of the gas consumers 4, 5. The supply method also comprises a step of cooling the second pump 10, also prior to the step of supplying the gas consumers 4, 5.

[0087] The pre-cooling step allows the first heat exchanger 6 to reach temperature. This pre-cooling step begins with a sub-step of removing gas in liquid state from the tank 8, during which the gas in liquid state is removed from the tank 8, for example using the first pump 9, and then circulated in the first supply circuit 2 to the first heat exchanger 6. The pre-cooling step then includes a sub-step for cooling the first heat exchanger 6, corresponding to the circulation of the gas in liquid state through the heat exchanger 6. The gas is then exhausted from the first heat exchanger 6, circulates in the pre-cooling line 19, and is then returned to the tank 8 in a circulation sub-step. For this purpose, the control valve 21 is in its open position. The gas is returned to the tank 8 either directly, as in the first and second embodiments, or by the cooling line 28, as described above for the third embodiment, or by the return line 14 in the fourth and fifth embodiments.

[0088] During the pre-cooling step according to the first, third, fourth and fifth embodiments, the bypass circuit 32 is not used, and therefore the regulating member 34 is closed, whereas the first valve 35 and the second valve 36 are both open.

[0089] The withdrawal, pre-cooling and circulation sub-steps are carried out continuously and simultaneously until a temperature of -140 °C is reached in the first heat exchanger 6. The time required to reach this temperature is, for example, 1 hour, which is improved by the increased flow rate through the first heat exchanger 6 provided by the pre-cooling system 17. It should be noted that at the start of the pre-cooling step, the first heat exchanger 6 has a particularly high temperature and actually vaporizes the liquid gas delivered to the first heat exchanger 6, so that it is the vaporized gas that circulates in the pre-cooling line 19. Conversely, at the end of the pre-cooling step, i.e., when the first heat exchanger 6 approaches its operating temperature of -140 °C, there is no vaporization in the first heat exchanger 6 and therefore the gas circulating through the pre-cooling line 19 is in a liquid state.

[0090] In parallel with the pre-cooling step, the supply method carries out a cooling step, by which the second pump 10 is brought to temperature. Similar to the pre-cooling step, this cooling step comprises a substep of extracting gas in liquid state from the tank 8, during which the gas in liquid state is extracted from the tank 8, for example using the first pump 9, and then circulating in the first supply circuit 2 to the second pump 10. The cooling step then comprises a substep of cooling the second pump 10, which corresponds to the gas in liquid state flowing through said second pump 10. The cooling step ends with a substep of circulating the gas cooled by the second pump 10 in the cooling line 28, such circulation being allowed because the control valve is in its fully open configuration.

[0091] As with the pre-cooling step, during the cooling step, the removal, cooling and circulation substeps are performed simultaneously and repeated until the desired temperature is reached for the second pump 10. The time required for the first heat exchanger 6 and second pump 10 to come up to temperature in this manner is, for example, one hour, and such time is improved here by the increased flow rate through the first heat exchanger 6 allowed by the pre-cooling system 17, thus equalizing the cooling times of the first heat exchanger 6 and second pump 10.

[0092] Once the first heat exchanger 6 is at its operating temperature, the pre-cooling step is completed by switching the control valve 21 from its open configuration to its closed configuration. Similarly, the step of cooling the second pump 10 is completed by moving the control valve 29 from its fully open configuration to its partially open configuration that matches the normal operating pressure of the equipment 4 consuming the high-pressure gas.

[0093] The supply step of the supply method can then be carried out, during which gas in liquid form is taken from the tank 8 and circulated in the first supply circuit 2, passing successively through the first heat exchanger 6, the second pump 10, the second heat exchanger 7 and the high-pressure evaporator 11, as previously described, for transport to and supply to the high-pressure gas consuming equipment 4.

[0094] In particular, in the particular case of the second embodiment, the pre-cooling step and the supply step are carried out simultaneously. During the supply method according to this second embodiment, during the withdrawal substep of the pre-cooling step, at least a portion of the gas in liquid state withdrawn from the tank 8 is diverted from the first heat exchanger 6 by circulating through the bypass line 33 in order to be conveyed to the equipment consuming the high-pressure gas. In this case, contrary to what has been described above, the regulating member 34 is open and the second valve 36 is closed.

[0095] The present invention therefore proposes a gas supply system in which the heating of the heat exchanger is carried out independently of the heating of other elements and the time required for this heating is reduced by increasing the flow rate of gas circulating in the heat exchanger.

[0096] However, the invention is not limited to the means and arrangements described and illustrated herein, but extends to any equivalent means and arrangements and to any technically operable combinations of such means.

Claims

1. A supply system (1) for supplying gas to 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 said gas, the supply system comprising: at least one first gas supply circuit (2) for supplying gas to the equipment (4) consuming the high-pressure gas, the at least one first gas supply circuit (2) comprising at least one first pump (9) configured to pump the gas taken from the tank (8) in a liquid state, at least one first heat exchanger (6), a second heat exchanger (7), a second pump (10) arranged between the first heat exchanger (6) and the second heat exchanger (7), and 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 supplying gas to the appliance (5) consuming the low-pressure gas, the at least one second gas supply circuit (3) comprising at least one compressor (13) configured to compress the gas taken in vapor form from the tank (8) to the operating pressure of the appliance (5) consuming the low-pressure gas; the supply system (1) comprises a pre-cooling system (17) for pre-cooling the first heat exchanger (6) configured to take in gas in a liquid state from the tank (8), the pre-cooling system (17) comprising a pre-cooling line (19) connected to the first supply circuit (2) between the first heat exchanger (6) and the second pump (10), and the pre-cooling system (17) comprises at least one control valve (21) for controlling the circulation of gas in the pre-cooling line (19).

2. 2. The supply system (1) according to claim 1, wherein the first supply circuit (2) comprises a first valve (35) arranged between the first pump (9) and the first heat exchanger (6) and a second valve (36) arranged between the first heat exchanger (6) and the second pump (10), and the pre-cooling line (19) is connected to the first supply circuit (2) between the first heat exchanger (6) and the second valve (36).

3. 3. The supply system (1) according to any one of claims 1 and 2, wherein the pre-cooling system (17) is configured such that the pre-cooling line (19) opens into a lower part of the tank (8).

4. 3. The supply system (1) according to any one of claims 1 and 2, wherein the pre-cooling system (17) is configured such that the pre-cooling line (19) opens into an upper part of the tank (8).

5. 5. The supply system (1) according to claim 1, further comprising a gas return line (14) connected to the second supply circuit (3) and configured to return the gas to the tank (8), wherein the first heat exchanger (6) and the second heat exchanger (7) each comprise a first path constituting the first supply circuit (2) and a second path constituting the return line (14).

6. 6. The supply system (1) according to claim 5, wherein the pre-cooling line (19) is connected to the return line (14) between the first heat exchanger (6) and an outlet of the return line (14) configured to open into the tank (8).

7. 7. The supply system (1) according to any one of claims 1 to 6, further comprising a cooling system (24) for cooling the second pump (10), the cooling system (24) comprising a cooling line (28) connected to the first supply circuit (2) between an inlet port of the second pump (10) and the second heat exchanger (7), the cooling system (24) comprising at least one control valve (29) for controlling the circulation of the gas in the cooling line (28).

8. 8. The supply system (1) according to claim 7, wherein the cooling system (24) is configured such that the cooling lines (28) open into the tank (8).

9. 8. The supply system (1) of claim 7 in combination with claim 5, wherein the cooling line (28) opens into the return line (14) between the first heat exchanger (6) and the outlet of the return line (14) configured to open into the tank (8).

10. The supply system (1) according to any one of claims 1 to 9 in combination with claim 5, wherein the return line (14) comprises an expansion member (15) arranged between the first heat exchanger (6) and an outlet of the return line (14) configured to open into the tank (8).

11. A supply system (1) according to any one of claims 1 to 10, comprising a bypass line (33) for bypassing the first heat exchanger (6), the bypass line (33) comprising an adjustment element (34).

12. A floating structure (20) for storing and / or transporting gas in a liquid state, comprising at least one tank (8) configured to contain gas in a liquid state, at least one appliance (4) consuming high-pressure gas, at least one appliance (5) consuming low-pressure gas, and at least one gas supply system (1) for supplying gas to these appliances (4, 5) as claimed in any one of claims 1 to 11.

13. A system for loading or unloading liquid gas, which combines at least one land and / or port facility (27) with at least one floating structure (20) for storing and / or transporting liquid gas as claimed in claim 12.

14. 13. A method for loading or unloading liquid gas from a floating structure (20) for storing and / or transporting gas as claimed in claim 12, wherein a pipeline (23) for loading and / or unloading gas in liquid state, arranged on the upper deck of the floating structure (20), can be connected by a suitable connector to a coastal or port terminal for transferring the gas in liquid state from or towards the tank (8).

15. 13. A method for supplying a floating structure (20) by a supply system (1) according to claim 12, comprising at least one pre-cooling step including the sub-steps of extracting gas in a liquid state from the tank (8), cooling the first heat exchanger (6) and circulating the gas in the pre-cooling line (19), said supplying method comprising the step of supplying the gas in a liquid state extracted from the tank (8) to an appliance (4) consuming the high-pressure gas.

16. 16. The method of claim 15, wherein during the pre-cooling step, the control valve (21) of the pre-cooling system (17) is opened.

17. 17. The method according to claim 15, further comprising at least one cooling step before the supplying step, the sub-steps being to remove gas in a liquid state from the tank (8), to cool the second pump (10) and to circulate the gas in the cooling line (28).

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