GAS SUPPLY SYSTEM FOR HIGH PRESSURE AND LOW PRESSURE GAS CONSUMPTION DEVICES AND METHOD FOR CONTROLLING SUCH A SYSTEM - Patent application

Abstract

The invention relates to a supply system (1) for supplying gas to a high-pressure gas consumer (4) and a low-pressure gas consumer (5) of a floating structure comprising a tank (8). The supply system (1) comprises a first supply circuit (2), a second supply circuit (3), a return line (14) connected to the second supply circuit (3), a first heat exchanger (6) and a second heat exchanger (7). The supply system (1) comprises at least one branch (40) for cooling the gas withdrawn in gaseous state from the tank (8), the branch (40) connecting to the second supply circuit (3) upstream of the compressor (13). The supply system (1) comprises at least one heat exchanger (41) configured to perform a heat exchange between the gas in gaseous state flowing through the cooling branch (40) and the gas in liquid state flowing through the first supply circuit (2).

Description

[Technical field]

[0001] The present invention relates to the field of ships storing and / or transporting gas in liquid state, and more particularly to a gas supply system for gas consuming devices equipped on such ships, and to a method for controlling such a system. [Background technology]

[0002] During a voyage by a ship equipped with tanks for the consumption and / or delivery of gas in liquid state to a destination, said ship must be able to use at least a portion of said gas in liquid state to supply at least one of its motors via a gas supply system. This is the case for ships with ME-GI high pressure propulsion engines. To supply gas to such a motor, the gas needs to be compressed to very high pressures by dedicated compressors capable of compressing the gas up to 300 bar absolute, which are expensive, incur high maintenance costs and cause vibrations to the ship.

[0003] An alternative to installing such a high-pressure compressor is to boil off the gas in liquid state, in particular at a pressure of 300 bar absolute, in a high-pressure pump before sending it to the propulsion engine. Since such a solution does not allow the removal of the gaseous state (boil-off gas, BOG) that naturally occurs in the tanks that at least partially contain the cargo, low-pressure compression means can be installed that supply the gas to an auxiliary motor that can consume the gas as low-pressure steam. The surplus gaseous state can also be passed through the tanks by recondensation.

[0004] Although the efficiency of such a system is already high, there is room to further improve the overall performance of the system. Indeed, a drawback of this system is the fluctuations in temperature of the gaseous gas from the tank, which can exceed a threshold value, resulting in an increase in the consumption of the low pressure compression means, in particular the electricity consumption.

[0005] Another drawback is that a large amount of energy is required to vaporize the gas from its liquid state to reach a pressure of 300 bar absolute. Summary of the Invention

[0006] The present invention relates to a gas supply system for at least one high pressure gas consumer and at least one low pressure gas consumer for a floating structure, comprising at least one tank adapted to contain gas at least in a liquid state, at least one first gas supply circuit for said high pressure gas consumer, at least one high-pressure evaporator configured to vaporize the gas flowing through said first gas supply circuit; at least one second gas supply circuit for said low-pressure gas consumer, said second gas supply circuit comprising at least one compression device configured to compress the gas withdrawn in gaseous state from said tank to a pressure suitable for the needs of said low-pressure gas consumer; at least one gas return line connected to said second supply circuit downstream of said compressor and extending to said tank; at least one first and second heat exchanger, each configured to perform a heat exchange between the gas flowing in the return line and the gas in liquid state flowing in the first gas supply circuit; It is an object of the present invention to solve these problems by providing a gas supply system comprising:

[0007] The gas supply system is innovative in that it comprises at least one cooling branch for the gas withdrawn in gaseous state from the tank, the cooling branch being connected to the second supply circuit upstream of the compressor, and the gas supply system comprises at least one heat exchanger comprising at least one first line upstream of the high-pressure evaporator in the first gas supply circuit and a second line in the cooling branch.

[0008] The cooling branch branches off the gas in gaseous state from the tank from a portion of the second gas supply circuit. In this way, the gas is sent to a heat mass exchanger, which performs cooling of the gas flowing through the cooling branch by the gas in liquid state flowing through the first gas supply circuit. The heat exchange is more effective if it is carried out between the gas in liquid state and the gas in gaseous state. The cooling branch and its heat mass exchanger are therefore advantageous for supplying low-pressure gas consumers or for liquefying excess gas from the tank blanket. The densification of the gas in gaseous state after flowing through the heat mass exchanger reduces the power consumption of the compressor by up to 30% when the gas in gaseous state flows through the return line and condenses. If the gas in gaseous state flows through the second gas supply circuit and is provided to a low-pressure gas consumer, the reduction in the power consumption of the compressor can reach 45%.

[0009] The first gas supply circuit allows the fuel requirements of a high-pressure gas consumer to be met. This may be, for example, a propulsion means for a floating structure, for example an ME-GI motor. The first supply circuit runs from the tank to the high-pressure gas consumer. A pump is arranged at the bottom of the tank and pumps gas in liquid form so that it can flow through the first gas supply circuit.

[0010] Since the gas needs to be in a gaseous state to be supplied to the high-pressure gas consumer, a high-pressure evaporator vaporizes the gas before it is supplied to the high-pressure gas consumer. The high-pressure evaporator is where the heat exchange takes place between the liquid gas in the first gas supply circuit and a heat transfer fluid, e.g. water glycol, seawater, water vapor, etc. Whatever type of heat transfer fluid it is, it must have a sufficiently high temperature to cause a phase change in the gas so that the gas becomes in a gaseous or supercritical state and can be supplied to the high-pressure gas consumer.

[0011] The second gas supply circuit extends from the tank to a low-pressure gas consumer. This can be, for example, an auxiliary motor of an internal combustion engine of a generator, etc. The function of the compressor of 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 gas in gaseous state can be supplied to a low pressure gas consuming device and / or can flow through a return line if the low pressure gas consuming device does not or hardly requires a fuel supply. The return line is connected downstream of the compressor, so that the gaseous state gas sucked into the compressor can flow through the return line.

[0013] The gas in the return line flows first through the second heat exchanger, then through the first heat exchanger, and back to the tank. In this configuration, the heat of the gas in the return line is reduced by the heat exchange between the liquid gas passing through the first heat exchanger and the gas in the return line, until the gas is substantially condensed downstream of the first heat exchanger by passing through the two heat exchangers. The condensed gas in the liquid state then flows into the tank.

[0014] According to a feature of the invention, the heat exchanger comprises at least one first line upstream of the high pressure evaporator in the first gas supply circuit and a second line in the cooling branch, so that the gas in a liquid state flowing through the first gas supply circuit first flows through the heat exchanger and then through the first line of the high pressure evaporator.

[0015] According to another feature of the invention, the first line of the mass heat exchanger is arranged between the second heat exchanger and the high pressure evaporator, where it should be understood that the gas in liquid state flowing through the first gas supply circuit first flows through the first line of the first heat exchanger, then through the first line of the mass heat exchanger and then through the first line of the high pressure evaporator.

[0016] The successive heat exchanges achieved by the above variants utilize the thermal content of one and / or the other of the fluids involved in a sequence that increases the efficiency of the system.

[0017] According to another characteristic of the invention, the second line of the heat exchanger is arranged upstream of the compressor in the direction of gas flow through the second gas supply circuit, so that the gas in the gaseous state enters the compressor at a lower temperature, which allows the gas to have a higher density, thereby reducing the volumetric flow rate of the compressor.

[0018] According to another feature of the invention, the gas supply system comprises a branch point where the cooling branch and the second supply circuit branch off, and a junction point where the cooling branch and the second gas supply circuit join, the cooling branch extending between the branch point and the junction point, the branch point and the junction point defining a portion of the second gas supply circuit, so that the cooling branch is mounted in parallel to this portion.

[0019] Advantageously, the second gas supply circuit comprises at least one monitor unit for the flow of gas through the second gas supply circuit, the cooling branch being mounted in parallel to said monitor unit for the flow of gas through the second gas supply circuit, the monitor unit therefore being arranged in a portion of the second gas supply circuit.

[0020] In this state, the branching point is located upstream of a monitor unit for the flow of gas through the second gas supply circuit, and the confluence point is located downstream of the monitor unit in the direction of flow through the second gas supply circuit.

[0021] Advantageously, the cooling branch comprises at least one monitoring valve for the gas flow through it, so that the gas flow through the heat exchanger, in particular through its second line, is monitored.

[0022] For example, the monitoring unit and / or the monitor valve may be an on-off valve.

[0023] The gas supply system of the invention comprises at least one measuring means for the temperature of the gas withdrawn in gaseous state from the tank, the managing device commanding at least one of the monitor units for the gas flow through the second gas supply circuit and the monitor valve for the gas flow through the cooling branch, the measuring means directly or indirectly assessing or measuring the temperature of the gas withdrawn in gaseous state from the tank.

[0024] The management device can allow gas to flow through the cooling branch if the temperature measured by the measuring means is higher than a reference threshold value, and can prevent gas from flowing through the cooling branch if the temperature measured by the measuring means is lower than a reference threshold value.

[0025] Advantageously, the first gas supply circuit comprises a pump between the first and second heat exchangers, the pump being called a high-pressure pump, making it possible to increase the pressure of the gas in liquid state passing through the first gas supply circuit, so that it is suitable for supplying a high-pressure gas consumer.

[0026] According to a first embodiment, the high pressure evaporator and the heat mass exchanger form a single heat exchanger module. Alternatively, the second heat exchanger and the heat mass exchanger form a single heat exchanger module. In combination, at least the high pressure evaporator, the second heat exchanger and the heat mass exchanger form a single heat exchanger module. This single heat mass exchanger module is a single heat exchanger having at least three, four or five lines that are fluidly separate from one another.

[0027] According to a feature of the invention, the gas supply system comprises a heat treatment branch for the gaseous gas passing through the return line, the heat treatment branch being connected to the second supply circuit upstream of the compressor, and the gas supply system comprises a third heat exchanger configured to perform a heat exchange between the gaseous gas passing through the heat treatment branch and the gaseous gas passing through the return line. The heat treatment branch and the third heat exchanger allow the cold energy of the gaseous gas taken from the tank to be used and sent to the gaseous gas flowing through the return line, making it easier to liquefy this gas.

[0028] According to a feature of the invention, the first gas supply circuit comprises at least one pump for drawing gas in liquid state from the tank. Advantageously, the pump is a submersible pump at the bottom of the tank, drawing gas in liquid state and passing it through the first gas supply circuit. When drawing gas in liquid state by the pump, its pressure is increased to a value between 6 and 17 bar absolute.

[0029] The present invention also provides a control process for a gas supply system as described herein, comprising: - in a measuring step, measuring the temperature of the gas in gaseous state extracted from said tank; then, passing the gas in gaseous state through the cooling branch if the temperature of the gas measured in the measuring step is higher than a reference threshold, or - passing the gas in gaseous state through the second gas supply circuit if the temperature of the gaseous state measured in the measuring step is lower than the reference threshold value; Regarding the control process.

[0030] In other words, if the temperature of the gas withdrawn in gaseous state from the tank is higher than a reference threshold, the monitoring valve for the gas flow through the cooling branch allows the gas to flow through said cooling branch, and if the temperature of the gas withdrawn in gaseous state from the tank is lower than a reference threshold, the monitoring valve for the gas flow through the cooling branch prevents the gas from flowing through said cooling branch.

[0031] Depending on the selected reference threshold, the process allows gas to flow through the second gas supply circuit by opening a monitor unit for the flow of gas through the second gas supply circuit, and prevents gas from flowing through the return line, for example by closing a flow regulating unit.

[0032] The measuring step is performed by a measuring means for the gas in gaseous state removed from the tank. The management device performs a comparison of the measured temperature with a reference threshold value and performs a selection as a result.

[0033] The system reaches a good efficiency level when the reference threshold is -90°C, in particular ±10%, and the process comprises the step of condensing the gas in gaseous state passing through the return line.

[0034] According to an aspect of the invention, if the reference threshold is −150° C., the process comprises the step of supplying gas to the low pressure gas consumer via the second gas supply circuit.

[0035] Other characteristics and advantages of the invention will become apparent from the following description on the one hand and from a number of embodiments given by way of guide and in a non-limiting manner with reference to the attached drawings, in which: [Brief description of the drawings]

[0036] [Figure 1] 1 is a schematic diagram of a gas supply system according to the present invention; [Diagram 2] FIG. 2 is a schematic diagram of the gas supply system of FIG. 1 in a first operating state. [Diagram 3] FIG. 3 is a schematic diagram of the gas supply system of FIGS. 1 and 2 in a second operating state; [Figure 4] FIG. 2 is a schematic diagram of a gas supply system according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] In the following description, the relative positions of components in a gas circuit, in liquid or gaseous state, are defined using the terms upstream and downstream in the direction of flow of said gas through said circuit.

[0038] Identical items retain the same reference numbers in each drawing.

[0039] 1 shows a gas supply system 1 mounted on a floating structure, which allows gas in a liquid, gaseous, two-phase or supercritical state to flow from a storage and / or transport tank 8 to fuel high pressure gas consumers 4 and low pressure gas consumers 5.

[0040] The floating structure may for example be an LNG-carrying vessel capable of storing and / or transporting gas in liquid state, in particular natural gas. In this case, the gas supply system 1 may use the gas in liquid state stored and / or transported by the floating structure to supply a high-pressure gas consumer 4, which may for example be a propulsion engine, and a low-pressure gas consumer, which may for example be a generator for powering the floating structure.

[0041] To ensure the flow of gas from the tank 8 to the high-pressure gas consumer 4, the gas supply device 1 comprises a first gas supply circuit 2. The first gas supply circuit 2 comprises a submersible pump 9 arranged in the tank 8. The submersible pump 9 makes it possible to pump gas in liquid state and to pass this in particular through the first gas circuit 2. By sucking in the gas in liquid state, the submersible pump 9 increases its pressure to a value of 6-17 absolute pressure.

[0042] From the tank 8 to the high-pressure gas consumer 4, the gas in liquid state flows through a first heat exchanger 6 and is pressurized by a pump 10, also called high-pressure pump. The gas in liquid state then flows through a second heat exchanger 7 and then through a high-pressure evaporator 11 before reaching the high-pressure motor 4. The pump 10 is advantageously arranged between the first heat exchanger 6 and the second heat exchanger 7.

[0043] The high-pressure evaporator 11 allows the gas flow passing through the first gas supply circuit 2 to be in a gaseous state or in a supercritical state.

[0044] Such a state is suitable for supply to the high-pressure gas consuming device 4. Vaporization of the liquid gas can be performed, for example, by heat exchange between the liquid gas flowing into the high-pressure evaporator 11 and a heat transfer fluid, here water glycol, seawater or water vapor, which is at a temperature high enough to boil off the liquid gas.

[0045] The increase in gas pressure is brought about by the pump 10 when it pumps the gas in the liquid state. The pump 10 can increase the pressure of the gas in the liquid state to a value of 30-400 bar absolute, in particular when using ammonia or hydrogen, to a value of 30-70 bar absolute when using liquefied petroleum gas, and to a value of 150-400 bar absolute, preferably when using liquefied natural gas based on ethane, ethylene or methane.

[0046] The combination of the pump 10 and the high-pressure evaporator 11 brings the gas to a pressure and state suitable for supply to the high-pressure gas consuming device 4. This configuration eliminates the need to provide the first gas supply circuit 2 with a high-pressure compression device, which is cost-intensive and generates strong vibrations.

[0047] In the tank 8, some of the gas in the cargo may spontaneously become gaseous and spread to the tank blanket 12. To prevent excessive pressure in the tank 8, it is necessary to vent the gaseous state in the tank blanket 12.

[0048] The gas supply system 1 therefore comprises a second gas supply circuit 3, which uses gas in a gaseous state to supply the low-pressure gas consuming device 5. The second gas supply circuit 3 extends between the tank blanket 12 and the low-pressure gas consuming device 5. In order to suck the gaseous gas contained in the tank blanket 12, the second gas supply circuit 3 comprises a compression device 13, in particular a compressor. Besides sucking the gaseous gas, the compression device 13 is capable of compressing the gaseous gas passing through the second gas supply circuit 3 to an absolute pressure of 6 to 200 bar. This allows the gaseous gas to reach a pressure suitable for supply to the low-pressure gas consuming device 5. The second gas supply circuit 3 allows the supply to the low-pressure gas consuming device 5 and also allows the pressure in the tank 8 to be adjusted by sucking the gaseous gas from the tank blanket 12.

[0049] If there is an excess of gas in gaseous state in the tank blanket 12, the pressure in the tank 8 will be excessive. It is therefore necessary to reduce the pressure in the tank 8 by venting the gaseous state. For example, the excess gaseous state can then be removed by a burner 18 or, in a not shown embodiment, can be vented to the atmosphere. These solutions result in a loss of cargo. For this reason, the gas supply system 1 according to the invention comprises a gas return line 14 which runs from the second gas supply circuit 3 to the tank 8.

[0050] A gas return line 14 is connected to the second gas supply circuit 3 downstream of the compression device 13 in the flow direction of the gas in gaseous state through the second gas supply circuit 3. The return line 14 runs first through the second heat exchanger 7 and then through the first heat exchanger 6.

[0051] The first heat exchanger 6 comprises a first line 6a which is part of the first gas supply circuit 2. This first heat exchanger 6 comprises a second line 6b which is part of the return line 14. The direction of flow through the first line 6a is opposite to the direction of flow through the second line 6b of the first heat exchanger 6.

[0052] The second heat exchanger 7 is disposed in the first gas supply circuit 2 between the first heat exchanger 6 and the high-pressure evaporator 11 .

[0053] The second heat exchanger 7 comprises a first line 7a which is part of the first gas supply circuit 2. This second heat exchanger 7 comprises a second line 7b which is part of the return line 14. The direction of flow through the first line 7a is opposite to the direction of flow through the second line 7b of the second heat exchanger 7.

[0054] The gas in the liquid state in the first gas supply circuit 2 has its lowest temperature at the inlet of the first line 6 a of the first heat exchanger 6 .

[0055] In this way, the gas flowing through the return line 14 is condensed after flowing through the first heat exchanger 6. Therefore, the fluid in the return line 14 is in a gaseous state at the inlet of the second line 6b of the first heat exchanger 6, and after heat exchange in the first heat exchanger 6, it flows out in a liquid state.

[0056] The return line 14 further comprises a flow regulation unit 15 which monitors the flow rate of the fluid through the return line 14. This flow regulation unit 15 has a variable flow area. As the gas condenses it flows into the tank 8. Thus, the first heat exchanger 6 is used as a condenser, while the flow regulation unit 15 monitors the heat exchange in the first heat exchanger 6, the second heat exchanger 7 and the high pressure evaporator 11.

[0057] The gas supply system 1 also includes an auxiliary gas supply line 16 that extends from the first gas supply circuit 2 through a nipple between the submersible pump 9 and the first heat exchanger 6 to the second gas supply circuit 3 and connects to the compressor 13 between the low-pressure gas consuming device 5. The auxiliary gas supply line 16 allows gas to be supplied to the low-pressure gas consuming device 5 even when the flow rate of gaseous gas from the tank blanket 12 is insufficient.

[0058] If there is not enough gas in the gaseous state in the tank blanket 12, gas in the liquid state from the submersible pump 9 can flow through this auxiliary gas supply line 16 and be supplied to the low-pressure gas consumer 5. For this purpose, the auxiliary gas supply line 16 extends through the low-pressure evaporator 17 so that the gas in the liquid state flowing through the auxiliary gas supply line 16 becomes gaseous. For example, the operation of the low-pressure evaporator 17 can be the same as that of the high-pressure evaporator 11. That is, the gas is boiled off by heat exchange with a heat transfer fluid having a temperature high enough to boil off the gas in the liquid state. At the outlet of the low-pressure evaporator 17, the gas in the gaseous state flows through the auxiliary gas supply line 16 and reaches the second gas supply circuit 3 and is supplied to the low-pressure gas consumer 5.

[0059] From the above, the auxiliary gas supply line 16 is used only when there is not enough gas in the gaseous state within the tank blanket 12.

[0060] Therefore, the auxiliary gas supply line 16 is equipped with a valve 19. The valve 19 monitors the gas flow through the auxiliary gas supply line 16 when its use is not required.

[0061] According to the invention, the gas supply system 1 further comprises at least one cooling branch 40 for the gas in gaseous state withdrawn from the tank, through which the gas in gaseous state withdrawn from the tank 8 can flow and be cooled.

[0062] The cooling branch section 40 is fluidly connected to the second gas supply circuit 3 upstream of the compressor 13. Thus, the gas supply system includes a branch point 44 in the second gas supply circuit 3, which is the starting point of the cooling branch section 40. The gas supply system 1 further includes a junction point 45 where the second gas supply circuit 3 and the cooling branch section 40 join together. Both the branch point 44 and the junction point 45 are located in front of the compressor 13 in the second gas supply circuit 3.

[0063] The gas supply system 1 also comprises a heat exchanger 41 intended to cool the gas in gaseous state taken from the tank by heat exchange with the gas in liquid state flowing through the first supply circuit 2.

[0064] The heat exchanger 41 includes a first line 42 that exchanges heat with a second line 43 that is a part of the heat exchanger 41. The first line 42 of the heat exchanger 41 is a part of the first gas supply circuit 2, and liquid gas flows through it. On the other hand, the second line 43 of the heat exchanger 41 is a part of the cooling branch section 40, and gaseous gas from the tank 8 flows through it.

[0065] Originally, the first line 42 of the heat exchanger 41 is fluidly arranged between the first line 7 a of the second heat exchanger 7 and the first line 11 a of the high-pressure evaporator 11 .

[0066] Such an arrangement allows the gas in the gaseous state flowing through the cooling branch 40 to be cooled by heat exchange with the gas in the liquid state flowing through the first gas supply circuit 2, resulting in a reduction in the volumetric flow rate at the inlet of the compressor 13 and therefore in a reduction in its consumption, in particular in electricity consumption.

[0067] This arrangement also allows to reduce the flow rate of the heat transfer fluid boiling off the liquid gas from the tank 8 through the second line 11b of the high pressure evaporator 11. Since this is a heat source, the amount of heat provided by the heat transfer fluid according to the invention can be reduced, since part of the heat is provided by the gas in the gaseous state flowing through the cooling branch 40.

[0068] The flow of the gas in gaseous state through the second gas supply circuit 3 is designed to be controlled by a monitor unit 46. The latter is, for example, a valve. The flow of the gas in gaseous state through the cooling branch 40 is designed to be controlled by a monitor valve 47. This monitor unit 46 and / or monitor valve is, for example, a valve or an on-off valve.

[0069] The cooling branch 40 is mounted in parallel to this monitor unit 46. In other words, the branch point 44 is arranged upstream of the monitor unit 46 in the gas flow through the second gas supply circuit 3, and the junction 45 is arranged downstream of this same monitor unit 46.

[0070] The gas supply system also comprises a control device 49 and at least one measuring means 48 for the temperature of the gas in gaseous state taken from the tank 8. The measuring means 48 for the temperature is, for example, a temperature sensor arranged in the second gas supply circuit 3 between the tank 8 and the branch point 44. Alternatively, the measuring means 48 may be attached to the tank blanket 12.

[0071] The temperature measuring means 48 is electrically connected to the management device 49 since data from the measuring means 48 is used in the calculations carried out by the management device 49 .

[0072] The management device 49 is an electronic control module that receives data from the measuring means 48 and monitors the opening and closing of the monitor unit 46 and / or the monitor valve 47. The management device 49 performs the method and its various steps, except for the step of measuring the temperature of the gas in gaseous state withdrawn from the tank 8.

[0073] The process of the present invention is illustrated in FIGS.

[0074] If the temperature of the gas in gaseous state withdrawn from the tank 8 and measured by the measuring means 48 is higher than a temperature threshold, the management device 49 can allow the gas to flow through the cooling branch 40, where such temperature threshold is for example equal to -90°C, when most or all of the gas in gaseous state flows through the return line 14. Alternatively, the reference threshold is equal to or higher than -150°C, when most or all of the gas in gaseous state is sent to the low-pressure gas consumer 5 via the second gas supply circuit 3. In such a case, the flow regulating unit 15 reduces or possibly completely stops the flow of gas through the return line 14.

[0075] The management device 49 performs the opening of the monitor valve 47. The monitor valve 47 allows the gas in gaseous state taken out of the tank 8 to reach the heat exchanger 41, in particular the second line 43 thereof. In such a situation, the management device 49 prevents the gas in gaseous state from flowing through a portion of the second gas supply circuit 3 extending between the branch point 44 and the junction point 45. For this purpose, the management device 49 performs the closing of the monitor unit 46 attached to the portion 51.

[0076] 3, the management device 49 can also prevent the gas from flowing through the cooling branch 40 if the temperature measured by the measuring means 48 is lower than the above-mentioned reference threshold. For this purpose, the management device 49 performs the closing of the monitor valve 47. In such a case, the management device 49 performs the opening of the monitor unit 46, thereby allowing the gas in gaseous state to flow through the part 51 of the second gas supply circuit 3. This allows the gas in gaseous state taken from the tank 8 to reach the compressor 13 directly.

[0077] Naturally, the management device 49 can be assigned to other computational processes necessary for the functioning of the gas supply system 1 according to the invention, for example monitoring of the flow regulating unit 15, or of the valve 19 controlling the flow of gas through the auxiliary gas supply line 16, or of the compressor 13, or of the submersible pump 9 or the pump 10.

[0078] It should be noted that each heat exchange device described herein may be a two-line component. The present invention also covers examples where the heat exchangers are grouped together to form a single heat exchanger, for example a three-line or four-line heat exchanger. Thus, the high pressure evaporator and the mass heat exchanger 41, or the second heat exchanger 7 and the mass heat exchanger 41, or a combination of these three components, may form a single heat exchanger module 50.

[0079] FIG. 4 shows the gas supply system of FIGS. 1-3 with the addition of further components.

[0080] Therefore, the gas supply system 1 of Fig. 4 further comprises a heat treatment branch 33 for the gaseous gas flowing in the return line 14. This heat treatment branch 33 is intended to cool the gaseous gas flowing in the return line to facilitate its condensation. In this situation, the heat treatment branch 33 allows the cold energy of the gaseous gas taken from the tank 8 to be recovered and utilized by sending it to the return line 14.

[0081] The heat treatment branch 33 is connected to the second gas supply circuit 3 upstream of the compressor 13 via a branching zone 52 and a junction zone 53 specific to the heat treatment branch 33. Alternatively, both the heat treatment branch 33 and the cooling branch 40 may be connected to the branch point 44 and the junction point 45. In either connection mode, the heat treatment branch 33 and the cooling branch are mounted in parallel with each other and with the portion 51 of the second gas supply circuit 3.

[0082] 4 also shows a third heat exchanger 36 configured to perform a heat exchange between the gas in gaseous state passing through the heat treatment branch 33 and the gas in gaseous state passing through the return line 14. Such a third heat exchanger 36 comprises a first line 36a which is part of the return line 14 and is arranged between the second line 6b of the first heat exchanger 6 and the second line 7b of the second heat exchanger 7.

[0083] The heat treatment branch 33 further comprises a monitoring device 38 arranged to monitor the flow of gas in gaseous state through the heat treatment branch 33. This monitoring device 38 is designed to be controlled by a management device 49 and is in an open position when the temperature of the gas in gaseous state withdrawn from the tank 8 and measured by the measuring means 48 is lower than a temperature threshold value, for example equal to -110°C.

[0084] If the temperature of the gaseous gas measured by the measuring means is higher than the temperature threshold value, the control device 49 effects a shutoff of the monitor device 38 and allows the gaseous gas to flow through the second gas supply circuit 3 .

[0085] According to an advantageous aspect of Fig. 4, the present embodiment is suitable for managing the flow communication between the cooling branch 40 and the heat treatment branch 33. Thus, the process of the invention provides in particular for passing the gas in gaseous state only through the heat treatment branch 33, if the temperature of the gas in gaseous state measured by the measuring means 48 in the measuring step is lower than the temperature threshold value.

[0086] Complementarily, if the temperature of the gaseous gas measured by the measuring means 48 in the measurement step is lower than the temperature threshold, the gaseous gas is caused to flow only through the cooling branch 40. Finally, if the temperature of the gaseous gas measured by the measuring means 48 in the measurement step is between the temperature threshold and the reference threshold, the gaseous gas is caused to flow only through the second gas supply circuit 3.

[0087] 4, the single heat exchanger module 50 described above may be complemented with a third heat exchanger 36. Thus, such a single heat exchanger module 50 may comprise at least five lines that are fluidly separated from one another.

[0088] Naturally, the invention is not limited to the embodiments described above, and many modifications can be made to these within the framework of the invention.

[0089] As mentioned above, the present invention proposes a gas supply system which achieves the assigned goals and reduces the power consumption of the compressor and / or the high-pressure evaporator. Variations not described here are also possible within the framework of the present invention, provided they comprise a gas supply system according to the invention.

Claims

1. A gas supply system (1) for at least one high pressure gas consumer (4) and at least one low pressure gas consumer (5) for a floating structure, comprising at least one tank (8) adapted to contain gas at least in a liquid state, The gas supply system (1) comprises: at least one first gas supply circuit (2) for said high pressure gas consumer (4), at least one high-pressure evaporator (11) configured to boil off the gas flowing in said first gas supply circuit (2); at least one second gas supply circuit (3) for said low-pressure gas consumer (5), said second gas supply circuit (3) comprising at least one compression device (13) configured to compress the gas extracted in gaseous state from said tank (8) to a pressure suitable for the needs of said low-pressure gas consumer (5); at least one gas return line (14) connected to said second supply circuit (3) downstream of said compression device (13) and extending to said tank (8); at least one first heat exchanger (6) and a second heat exchanger (7), each configured to perform a heat exchange between the gas flowing in the return line (14) and the gas in liquid state flowing in the first gas supply circuit (2); Equipped with the gas supply system (1) comprises at least one cooling branch (40) for the gas withdrawn in gaseous state from the tank (8), the cooling branch (40) being connected to the second supply circuit (3) upstream of the compressor (13), the gas supply system (1) comprises at least one heat exchanger (41) configured to perform a heat exchange between gas in a gaseous state passing through the cooling branch (40) and gas in a liquid state passing through the first supply circuit (2), A gas supply system (1).

2. the heat exchanger (41) comprises at least one first line (42) upstream of the high-pressure evaporator (11) in the first gas supply circuit (2) and a second line (43) in the cooling branch (40); A gas supply system (1) according to claim 1.

3. the first line (42) of the heat exchanger (41) is disposed between the second heat exchanger (7) and the high-pressure evaporator (11); A gas supply system (1) according to claim 2.

4. the second line (43) of the heat exchanger (41) is arranged upstream of the compression device (13) in the direction of gas flow through the second gas supply circuit (3), A gas supply system (1) according to claim 3.

5. the gas supply system (1) comprises a branch point (44) at which the cooling branch section (40) and the second supply circuit (3) branch off, and a junction point (45) at which the cooling branch section (40) and the second gas supply circuit (3) join together, The cooling branch portion (40) extends between the branch point (44) and the junction point (45). A gas supply system (1) according to any one of the preceding claims.

6. the second gas supply circuit (3) comprises at least one monitor unit (46) for the flow of gas through the second gas supply circuit (3), the cooling branch (40) is mounted in parallel to the monitoring unit (46) of the flow of gas through the second gas supply circuit (3), A gas supply system (1) according to any one of the preceding claims.

7. the cooling branch (40) is provided with at least one monitor valve (47) for gas flow through the cooling branch (40); A gas supply system (1) according to claim 6.

8. The gas supply system (1) comprises at least one measuring means (48) for the temperature of the gas withdrawn in gaseous state from the tank (8) and a control device (49), said control device (49) commands at least said monitor unit (46) for the gas flow through said second gas supply circuit (3) and said monitor valve (47) for the gas flow through said cooling branch (40); A gas supply system (1) according to claim 7.

9. the first gas supply circuit (2) includes a pump (10) between the first heat exchanger (6) and the second heat exchanger (7); A gas supply system (1) according to any one of the preceding claims.

10. At least the high pressure evaporator (11) and the heat exchanger (41) constitute a single heat exchanger module (50). A gas supply system (1) according to any one of the preceding claims.

11. At least the high pressure evaporator (11), the second heat exchanger (7) and the heat exchanger (41) constitute a single heat exchanger module (50). A gas supply system (1) according to any one of the preceding claims.

12. The gas supply system (1) comprises a heat treatment branch (33) for gas in a gaseous state passing through the return line (14), the heat treatment branch (33) is connected to the second supply circuit (3) upstream of the compression device (13); the gas supply system (1) comprises a third heat exchanger (36) configured to perform a heat exchange between the gas in gaseous state passing through the heat treatment branch (33) and the gas in gaseous state passing through the return line (14); A gas supply system (1) according to any one of the preceding claims.

13. A control process for a gas supply system (1) according to any one of claims 1 to 12, comprising: - in a measuring step, measuring the temperature of the gas in gaseous state taken from said tank (8), and then - passing said gas in gaseous state through said cooling branch (40) if the temperature of said gaseous state measured in said measuring step is higher than a reference threshold value, or - passing said gas in gaseous state through said second gas supply circuit (3) if the temperature of said gaseous gas measured in said measuring step is lower than said reference threshold value; Control process.

14. The reference threshold is −90° C. The control process comprises the step of condensing the gas in gaseous state passing through the return line (14).

14. A control process according to claim 13.

15. The reference threshold is equal to or higher than −150° C. The process comprises the step of supplying gas to the low pressure gas consumer (5) via the second gas supply circuit (3), 15. A control process according to claim 14.

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