Method for supplying gas to a gas-consuming appliance on a floating structure

Abstract

Method for supplying gas to a gas-consuming appliance in a floating structure. The present invention relates to a method for supplying gas to a gas-consuming appliance (3, 3a, 3b) in a floating structure comprising at least one tank (2), wherein: according to a first supply method, the gas-consuming appliance (3, 3a, 3b) is supplied with gas via a first supply circuit (4) and / or the gas-consuming appliance (3, 3a, 3b) is supplied with gas via a second supply circuit (5); according to a second supply method, the gas-consuming appliance (3, 3a, 3b) is supplied with gas via the first supply circuit (4) in which gas in liquid form is circulated by means of a pressure differential without the aid of the pumping device (8), and gas in vapor form is returned to the tank (2). (Figure 1)

Description

Title of the invention: Method for supplying gas to a gas-consuming appliance in a floating structure

[0001] The present invention relates to the field of floating structures for the transport and / or storage of gas in liquid state and relates more particularly to a gas supply system for at least one consuming device included within such floating structures, as well as a method for controlling such a system.

[0002] During a journey undertaken by a floating structure comprising a tank of gas in liquid form intended for consumption, said floating structure may be capable of using at least a portion of said gas in liquid form to supply at least one gas-consuming appliance, via a gas supply system.

[0003] Thus, it is known to draw the gas in vapor form that has formed naturally in the tank, compress it, and then circulate it to the gas-consuming appliance to supply it. It is also known that, in the event of an insufficient quantity of gas in vapor form within the tank, the gas in liquid form can be pumped directly into the tank and circulated first through an evaporation device to evaporate the gas into liquid form, since the gas-consuming appliance can only be supplied with gas in vapor form, and then supplied as fuel to the gas-consuming appliance.

[0004] To pump gas in its liquid state, it is known to arrange a pumping device submerged at the bottom of the tank. When the liquid gas contained in the tank is intended solely for consumption, the tank's capacity is smaller compared to that of a floating vessel such as an LNG carrier, which is designed to deliver the gas in its liquid state. Thus, the volume of liquid gas within the tank can decrease significantly. This can eventually lead to the pumping device becoming exposed, which may then lose its prime or, more generally, be unable to pump the gas in its liquid state. Such an event can also occur even if the pumping device is theoretically submerged, for example, in the event of significant rolling that could temporarily expose the pumping device.

[0005] The present invention falls within this context and, as such, proposes a method for supplying gas to at least one gas-consuming appliance of a floating structure comprising at least one tank, implemented by a gas supply system for the gas-consuming appliance of the floating structure, during which: - According to a first supply method, the gas-consuming appliance is supplied with gas via a first supply circuit in which gas in liquid state is circulated using a pumping device and / or supplies the gas-consuming appliance with gas via a second supply circuit in which gas is circulated in vapor form using a compression device, - according to a second supply method, the gas-consuming appliance is supplied with gas via the first supply circuit, within which gas in liquid state is circulated using a pressure differential without the aid of the pumping device, and gas in vapor state is returned to the tank,

[0006] the choice of the supply method being dependent on information relating to the quantity of gas in liquid state contained in the tank.

[0007] Thanks to the feeding method according to the invention, it is possible to alternate between two feeding methods to supply gas to the gas-consuming device. The latter can thus be supplied at any time without risking malfunction or loss of prime in the pumping device used to draw the gas in its liquid state, due to a lack of liquid gas in the tank or excessive rolling. The feeding method according to the invention also makes it possible to use a larger quantity of liquid gas as fuel for a tank of the same capacity.

[0008] The supply method is suitable for a floating structure capable of storing gas in liquid form, particularly for consumption by the gas-consuming appliance. It is even more suitable for a floating structure in which the sole purpose of storing the gas in liquid form is consumption by such a gas-consuming appliance, the tank intended to be emptied as the vessel sails on, having a capacity that is smaller than the tanks of a floating structure specifically designed to transport a cargo of gas in liquid form.

[0009] The gas-consuming device may, for example, be a motor providing propulsion for the floating structure, or an electric generator supplying electricity to the floating structure. Furthermore, the power supply method may be configured to power several gas-consuming devices simultaneously or alternately. The term "electric generator" refers to various types of means, such as a fuel cell or a gas boiler, consuming gas at low pressure between 1 and 4 bar relative.

[0010] According to the first supply method, the first supply circuit and the second supply circuit supply the gas-consuming appliance with gas, that is, either by pumping the gas in a liquid state before supplying it to the gas-consuming appliance via the first supply circuit, or by drawing in and compressing the gas in a vapor state contained in a tank head via the second supply circuit. The gas in the Vapor may form in the tank headspace due to partial evaporation of the gas in its liquid state. Depending on the presence or absence of significant vapor gas, either supply circuit can be used independently. Both supply circuits can also be used simultaneously.

[0011] The second supply method allows for the continued extraction of the gas in its liquid state from the tank, without the aid of the pumping device. A pressure differential is created to lower the pressure, particularly within the first supply circuit, relative to the tank. Furthermore, gas in its vapor state is introduced into the tank to increase its pressure and further increase the pressure differential. Thanks to this pressure differential, the gas in its liquid state can thus circulate without a pump. However, the amount of gas in its vapor state introduced into the tank is moderate to avoid overpressure that could damage the tank walls.

[0012] As mentioned previously, the choice of the supply method to be applied during the implementation of the supply process depends on the remaining quantity of liquid gas in the tank. Indeed, potential malfunctions of the pumping device occur when it emerges from the liquid gas contained in the tank, which therefore implies a limited quantity of remaining liquid gas. During a journey undertaken by the floating structure, and assuming no refueling occurs during said journey, the quantity of gas in the tank gradually decreases as the gas is consumed by the gas-consuming equipment. This remaining quantity must therefore be constantly monitored in order to determine when to implement the second supply method.

[0013] According to a feature of the process, the information relating to the quantity of gas in liquid state contained in the tank is determined by a measurement of the level of gas in liquid state in the tank relative to the pumping device.

[0014] To determine the gas level, the supply system may include a level sensor positioned in the tank. This level sensor measures the level of the liquid gas within the tank, which is compared to a threshold value determined according to the position of the pumping device. Alternatively, the level may be measured, for example, using radar or a float. A low level of the liquid gas remaining in the tank, for example, less than 2 m³ + / - 0.5 m³, means that a switch from the first supply mode to the second supply mode must be made to prevent the pumping device from losing its prime. Large variations in the liquid gas level over time may also be an indicator for switching to the second supply mode. Indeed, these variations may be due to significant rolling, increasing the risk of the pumping device losing its prime.

[0015] According to another feature of the process, the information relating to the quantity of liquid gas contained in the tank is determined by measuring the internal pressure differential of the tank. The remaining quantity of gas can also be determined by pressure measurement, more specifically by measuring a pressure differential. For this purpose, a first pressure sensor is configured to measure the pressure at the bottom of the tank, that is, the pressure of all the gas contained in the tank, namely the liquid gas and the vapor gas present in the tank head. A second pressure sensor is configured to measure only the pressure of the vapor gas present in the tank head. The pressure differential between these two pressure measurements makes it possible to deduce the height of the liquid gas in the tank and therefore the quantity of liquid gas remaining in the tank.

[0016] Either of these parameters can be used to determine the remaining quantity of gas in liquid state contained in the tank.

[0017] The pressure within the tank is also an indicator of the remaining quantity of gas in its liquid state within the tank. Thus, a pressure that is too low means a small quantity of gas remaining in its liquid state within the tank.

[0018] According to one feature of the process, it is implemented by the gas supply system of the gas-consuming appliance of the floating structure, in which the first supply circuit includes at least the pumping device configured to pump the gas taken in liquid form from the tank and at least one evaporation device configured to evaporate the gas in liquid form circulating in the first supply circuit, the second supply circuit including at least the compression device configured to compress gas taken in vapor form from the tank to a pressure compatible with the needs of the gas-consuming appliance, the supply system further including at least one siphon line and at least one connecting line,the siphon line being connected to the first supply circuit between the pumping device and the evaporator and comprising one end configured to be immersed in the tank, the compressor being capable of drawing the gas in liquid form from the tank via the siphon line and the connecting line, the supply system further comprising a return line connected to the second supply circuit between the compressor and the gas-consuming appliance and configured to extend to the tank, the return line being capable of returning the gas in vapor form compressed by the compressor to the tank, during which: , - according to the first supply method, the gas in liquid state is drawn by the pumping device, evaporated by the evaporation device and supplied to the gas-consuming appliance, and / or the gas in vapor form is drawn by the compression device and supplied to the gas-consuming appliance, - according to the second supply method, the gas in liquid state is taken and drawn in by the compression device, circulates within the siphon line, is evaporated by the evaporation device, is compressed by the compression device while circulating via the junction line, a first fraction being supplied to the gas-consuming device, a second fraction circulating in the return line and returning to the tank in order to increase the pressure of the tank and to facilitate the circulation of the gas in liquid state within the siphon line.

[0019] According to the first supply method, after being pumped by the pumping device, the gas in its liquid state circulates in the first supply circuit and is evaporated by the evaporator before being supplied to the gas-consuming appliance as fuel. The evaporator can be a heat exchanger configured to perform a heat exchange between the gas in its liquid state circulating in the first supply circuit and a third fluid. The third fluid can, for example, be glycol water or seawater. During the heat exchange taking place in the evaporator, the third fluid heats the gas in its liquid state, which rises in temperature until it evaporates.

[0020] The connecting line extends from a first junction point to a second junction point in order to fluidly connect the first supply circuit, downstream of the evaporation device with respect to the direction of gas flow, to the second supply circuit upstream of the compression device with respect to the direction of gas flow. In other words, the connecting line extends from a first junction point located on the first supply circuit between the evaporation device and the gas-consuming appliance to a second junction point located on the second supply circuit between the tank and the compression device. Thus, the evaporated gas circulating in the first supply circuit can flow to the second supply circuit to be compressed by the compression device when the feeding process is implemented according to the second feeding method.

[0021] The siphon line allows the tank to be connected to the first supply circuit in parallel with the pumping device. The end of the siphon line is immersed in the tank, advantageously at the bottom of the tank, for example a maximum of 2m from the bottom of the tank, and extends until it is connected to the first supply circuit, upstream of the evaporation device with respect to the direction of gas flow.

[0022] When the gas is able to flow in the siphon line and in the junction line, the compression device is active and it is the compression device which makes it possible to generate a pressure differential in the circulation loop formed by the siphon line, the junction line and where applicable the return line.

[0023] The return line ensures the return of at least some of the gas in a compressed vapor state to the tank head. As mentioned previously, this increases the internal pressure of the tank and thus facilitates the flow of the gas in a liquid state in the siphon line. It is therefore understood that this return line is used when it is necessary to supply the gas-consuming appliance with the assistance of the siphon line and the connecting line, during the implementation of the second supply mode.

[0024] According to a feature of the process, when implemented by a supply system in which the first supply circuit comprises a first control element disposed between the pumping device and the connection to the siphon line and a second control element disposed between the evaporator and the gas-consuming appliance, wherein the first and second control elements permit gas flow when the first supply mode is implemented and prohibit gas flow when the second supply mode is implemented. The first and second control elements manage gas flow within the first supply circuit.The first control unit manages a fluid connection between the pumping device and the connection to the siphon line, while the second control unit manages a fluid connection between the first junction point and the gas-consuming appliance.

[0025] According to a feature of the process, when implemented by a feed system in which the second feed circuit includes a control element disposed between the tank and the second junction point, the control element permits gas flow when the first feed mode is implemented and prohibits gas flow when the second feed mode is implemented. The control element manages gas flow within the second feed circuit. The control element manages a fluid connection between the tank and the second junction point.

[0026] According to a feature of the process, when implemented by a supply system in which the siphon line and the connecting line respectively comprise a first control device and a second control device, wherein the first control device and the second control device prohibit gas flow when the first supply mode is implemented and permit gas flow when the second The power supply mode is implemented. In other words, the first control device and the second control device manage the fluid flow within the siphon line and the junction line respectively.

[0027] According to a feature of the process, when implemented by a feed system in which the return line includes a control module, the control module prohibits gas flow when the first feed mode is implemented and allows gas flow when the second feed mode is implemented. The control module manages the gas return within the tank.

[0028] According to a feature of the process, the control module is driven by the pressure in the tank. Thus, the pressure measurement, in addition to determining the remaining quantity of gas in the liquid state, is also important for determining whether a pressure increase via the return line is necessary to ensure the proper operation of the second feed mode. It has been determined that a pressure greater than or equal to 0.4 bar relative, for example 0.5 or 0.7 bar relative, is sufficient to implement the second feed mode without needing to increase the tank pressure by returning gas in the vapor state via the return line.

[0029] Of course, the maximum pressure within the tank must be controlled to prevent damage to the tank walls due to overpressure. Depending on the type of tank, the maximum pressure can be between 0.7 and 3 bar relative, for example 0.7, 1.6, or 2 bar relative.

[0030] Depending on the measured pressure, the control module is controlled to return or not return gas in vapor state to the tank via the return line.

[0031] According to one feature of the process, a transition from the first feeding mode to the second feeding mode comprises: - a first step during which the second control device is opened to allow at least partial circulation of the gas evaporated by the evaporation device within the junction line, - a second step during which the control element is closed and then the control module is opened to generate a return of gas in vapor form into the tank while preventing any evacuation of said gas in vapor form in order to increase the pressure within the tank - a third step in which the first control device is closed, the second control device is closed and the pumping device is stopped, then the first control device is opened to allow the flow of gas in liquid state within the siphon line.

[0032] The three stages forming the transition from the first feeding mode to the second feeding mode preferably take place one after the other.

[0033] The first step consists of opening the second control device to allow fluid flow in the junction line and create a fluid connection between the first and second supply circuits. This results in some of the evaporated gas exiting the evaporator flowing into the junction line. The evaporated gas then enters the second supply circuit and is compressed by the compressor. The first step also lowers the pressure in the junction line to initiate the pressure differential associated with the second supply mode.

[0034] The second step closes the control element, thus preventing any release of vaporized gas from the tank, while the control module is open to allow vaporized gas to be returned to the tank via the return line. In other words, the second step allows the tank pressure to increase in order to continue establishing the pressure differential initiated in the first step. This has the effect, in particular, of starting to push liquid gas through the siphon line.

[0035] Finally, the third step consists of closing the control devices to stop the pumping device on the one hand, and to cut off the fluid connection between the first supply circuit on the other, and opening the first control device on the other hand to open the siphon line. Since the pressure differential has been established during the first two steps, the liquid gas contained in the tank is then able to circulate in the siphon line without the aid of a pumping device, immediately upon opening the first control device, thus avoiding any delay in supplying gas to the evaporator. At the end of this third step, the configuration of the supply system is such that the second supply mode is implemented.

[0036] The invention also covers a gas supply system for at least one gas-consuming appliance of a floating structure comprising at least one tank, implementing a supply method as described above, comprising - at least one first supply circuit configured to supply gas to the gas-consuming appliance, the first supply circuit comprising at least one pumping device configured to, in a first supply mode, draw the gas in liquid form from the tank and at least one evaporation device configured to evaporate the gas in liquid form circulating in the first supply circuit, - at least one second supply circuit configured to supply gas to the gas-consuming appliance, the second supply circuit including at least one compression device configured to, in the first supply mode, draw gas in vapor state from the tank and compress it to a pressure compatible with the needs of the gas-consuming appliance,

[0037] characterized in that the supply system comprises at least one junction line and at least one siphon line, the junction line extending between a first junction point disposed on the first supply circuit between the evaporator and the gas-consuming device and a second junction point disposed on the second supply circuit between the tank and the compression device, the siphon line being connected to the first supply circuit between the pumping device and the evaporator and comprising an end configured to be immersed in the tank, the compression device being capable of, in a second supply mode, drawing the gas in liquid form from the tank via the siphon line and the junction line.

[0038] Other features and advantages of the invention will become apparent from the following description on the one hand, and from several illustrative and non-limiting examples given in the accompanying schematic drawings on the other hand, in which:

[0039] [Fig-1] represents a gas supply system according to the invention,

[0040] [Fig.2] illustrates the power supply system of [Fig.1] operating according to a first power supply method,

[0041] [Fig.3] illustrates a first step in a transition from the first power supply mode illustrated in [Fig.2] to a second power supply mode,

[0042] [Fig.4] illustrates a second stage of a transition from the first power supply mode illustrated in [Fig.2] to the second power supply mode,

[0043] [Fig.5] illustrates a third stage of a transition from the first power supply mode illustrated in [Fig.2] to the second power supply mode.

[0044] Figure 1 schematically represents a gas supply system 1 according to the invention. The supply system 1 is, for example, integrated within a floating structure comprising a tank 2 ensuring the storage of said gas in liquid form and at least one gas-consuming device 3 that can be supplied with the gas contained in the tank 2. In Figure 1 and the following figures, a first gas-consuming device 3a and a second gas-consuming device 3b are shown. The floating structure may, however, contain more gas-consuming devices 3, or contain only one gas-consuming device 3. By way of example, the gas-consuming devices 3 may be an engine providing propulsion for the floating structure, a generator supplying the floating structure with electricity such as a fuel cell, a gas boiler, or a burner.

[0045] The supply system 1 comprises a first supply circuit 4 and a second supply circuit 5, each of which is suitable for supplying the gas-consuming devices 3. More specifically, the first supply circuit 4 is suitable for pumping gas in liquid form 6 contained in the tank 2 while the second supply circuit 5 is suitable for drawing gas in vapor form stagnant in the head 7 of the tank 2.

[0046] The first supply circuit 4 includes a pumping device 8 arranged at the bottom of the tank 2, which circulates the gas in its liquid state within the first supply circuit 4. The first supply circuit 4 also includes an evaporation device 9 through which the gas in its liquid state circulating in the first supply circuit 4 flows to be evaporated. The first supply circuit 4 then extends to the gas-consuming appliances 3.

[0047] The evaporation device 9, as illustrated in Figures 1 to 5, can, for example, be a heat exchanger configured to perform a heat exchange between the gas circulating in the first supply circuit 4 and a third fluid, which could be glycol water. The third fluid thus increases the temperature of the gas in its liquid state until it evaporates. Not shown, the evaporated gas exiting the evaporation device 9 can circulate within a heating device, which could also be a heat exchanger, in order to further increase the temperature of the evaporated gas so that it reaches a temperature compatible with the supply requirements of the gas-consuming appliances 3.

[0048] The second supply circuit 5 includes at least one compression device 10 for drawing in the gas in the vapor state stagnant in the head 7 of the tank 2 and raising it to a pressure compatible with the needs of the gas-consuming devices 3.

[0049] In the example illustrated in Figures 1 to 5, the supply system 1 comprises a first compression device 10a and a second compression device 10b arranged in parallel with each other. The first compression device 10a is located on the second supply circuit 5, while the second compression device 10b is located on an auxiliary line 11 connected to the second supply circuit 5. The presence of two compression devices 10 ensures redundancy, making it possible to compensate for any malfunction, such as a failure, of one of the compressors 10.

[0050] As the liquid gas 6 contained in the tank 2 is pumped by the pumping device 8, the level of liquid gas 6 within the tank 2 decreases, and it can reach a critical level, particularly if the journey undertaken by the floating structure is long and without the possibility of refueling. This can create a malfunction at the level of the pumping device 8 in the event of the latter emerging outside of the gas in liquid state 6 in the event of too low a quantity remaining or in the event of too much rolling.

[0051] To enable efficient supply of gas-consuming appliances, even in this critical level situation, the supply system 1 according to the invention comprises a junction line 12 extending between a first junction point 13 located on the first supply circuit 4 between the evaporation device 9 and the gas-consuming appliances 3 and a second junction point 14 located on the second supply circuit 5 located between the tank 2 and the compression devices 10, as well as a siphon line 15 connected to the first supply circuit 4 between the pumping device 8 and the evaporation device 9 and comprising an end 16 immersed in the tank 2. The end 16 of the siphon line is advantageously located at the bottom of the tank, for example at most 2m from the bottom of the tank 2.In this way, liquid gas can enter the siphon line 15 via this end 16 even when the pumping device, and in particular the liquid inlet orifice, is no longer immersed.

[0052] The junction line 12 fluidly connects the first supply circuit 4 to the second supply circuit 5, more particularly the evaporation device 9 to the compression devices 10.

[0053] Thus, in the event of a risk of the pumping device 8 activating, it can be stopped to prevent any malfunction. At least one of the compression devices 10 then allows the remaining liquid gas 6 in the tank 2 to be drawn off via the siphon line 15 and the connecting line 12, without the need to activate the pumping device. Indeed, the compression device 10 compresses the fluid, thus generating a pressure differential with a gas pressure upstream of the compression device 10 which is higher than a lower pressure upstream of the compression device 10, and therefore at the level of the evaporation device 9, which tends to facilitate the arrival of the liquid gas towards this evaporation device 9 via the siphon line 15. This then results in a circulation of the gas in the liquid state within the siphon line 15 without requiring the arrangement of a pumping device.The pumping device 8 can then be stopped to avoid any risk of malfunction due to a low level of gas in liquid state 6, but the supply system 1 still ensures a supply to the gas-consuming devices 3, via the compression device 10 and the end of the second supply circuit 5.

[0054] The supply system 1 also includes a return line 17 connected to the second supply circuit 5 between the compression device 10 and the gas-consuming appliances 3. The return line 17 allows gas to be returned in vapor state compressed by the compression device 10 within tank 2. This return of gas in vapor state into tank 2 has the effect of increasing the pressure within tank 2 and thus promoting the circulation of gas in liquid state within the siphon line 15. A portion of gas in liquid state is then pushed out of tank 2, since the siphon line 15 is at this moment the only one open to evacuate liquid gas.

[0055] It should be noted that the auxiliary line 11 is connected to the second supply circuit 5 between the second junction point 14 and a convergence point 18 located on the second supply circuit 5 between the first compression device 10a and the connection to the return line 17, so that all the functions of the supply system 1 are ensured regardless of which compression device 10 is used. Furthermore, the two compression devices 10a and 10b, although initially used to provide redundancy, can be used simultaneously to improve the pressure differential and further facilitate the flow of the gas in its liquid state in the siphon line 15.

[0056] The gas circulation in the first supply circuit 4 is placed under the control of a first control element 19 and a second control element 20. The first control element 19 is disposed on the first supply circuit 4 between the pumping device 8 and the connection with the siphon line 15, while the second control element 20 is disposed on the first supply circuit 4 between the first junction point 13 and the gas-consuming appliances 3. The first control element 19 and the second control element 20 can be valves capable of alternating between an open position and a closed position, respectively in order to allow or prohibit the circulation of fluid.

[0057] The second supply circuit 5 includes a control element 21 disposed between the tank 2 and the second junction point 14. The control element 21 allows or prohibits a fluid connection from the top 7 of the tank 2 and to the compression devices 10.

[0058] The siphon line 15 and the junction line 12 respectively include a first control device 22 and a second control device 23 allowing to authorise or prohibit a circulation of fluid within the siphon line 15 or the junction line 12.

[0059] Finally, the return line 17 includes a control module 24 allowing the circulation of fluid within the return line 17 to be authorized or prohibited.

[0060] The feeding system 1 also includes measuring means 25 configured to be arranged within the tank 2 or in contact with the tank 2 via a fluidly connected line to the tank, or at least to perform measurements within the tank 2. The measuring means 25 are specifically configured to determine a quantity of gas in liquid state 6 remaining in tank 2. Such monitoring of the remaining quantity of gas in liquid state is particularly interesting insofar as it is because of a small remaining quantity that a malfunction in the pumping device 8 can occur.

[0061] In order to measure the remaining quantity of liquid gas 6 contained in the tank 2, the measuring means 25 can measure a level of liquid gas 6 contained in the tank 2. To measure the gas level, one of the measuring means 25 can, for example, be a level measuring sensor, a radar, or a float. A low level of the liquid gas remaining in the tank 2, for example, less than 2 m³ + / - 0.5 m³, means that there is a risk of malfunction of the pumping device 8.

[0062] The remaining quantity of gas in the liquid state in tank 2 can also be determined by pressure measurement, more particularly by measuring a pressure differential. For example, the measuring means 25 may include a first pressure sensor configured to measure the pressure at the bottom of the tank, and a second pressure sensor configured to measure only the pressure of the gas in the vapor state present in the headspace 7 of tank 2. The pressure differential between these two pressure measurements makes it possible to deduce the height of the gas in the liquid state in tank 2 and therefore the remaining quantity of gas in the liquid state in tank 2.

[0063] The pressure measurement by the measuring means 25 also makes it possible to determine whether a pressure increase via the return line 17 is necessary to ensure the proper functioning of the supply system 1. A pressure greater than or equal to 0.4 bar relative, for example 0.5 or 0.7 bar relative, within the tank 2 is sufficient to ensure the circulation of the gas in the liquid state. However, the pressure must not exceed a maximum pressure threshold to avoid damage to the walls of the tank 2. Depending on the type of tank, the maximum pressure can be between 0.7 and 3 bar relative, for example 0.7, 1.6, or 2 bar relative.

[0064] The measurement means 25 are thus configured to be able to transmit these measurements to a central unit, not shown, which will modify the configuration of the power supply system as a consequence of the measurements in relation to predetermined threshold values.

[0065] Figures 2 to 5 represent the supply system 1 according to the invention as just described, according to different supply methods for gas-consuming appliances. In Figures 2 to 5, the portions through which the gas flows are shown in solid lines and the portions without gas flow are shown in dashed lines.

[0066] In order to manage the gas supply, the supply system 1 allows for the implementation of a gas supply process, which consists of determining and implementing a specific supply method based on the quantity of liquid gas present in the tank, in order to optimize the supply to the devices gas consumers 3. In [Fig.2], a first mode of supplying the supply system 1 is represented.

[0067] According to the first supply method, the gas flows in liquid form in the first supply circuit 4 and in vapor form in the second supply circuit 5. In [Fig. 2], gas flows in both supply circuits 4 and 5, but depending on the amount of gas in vapor form present in the headspace 7 of the tank 2, it is possible that only one of the supply circuits 4 and 5 allows gas circulation. If there is sufficient gas in vapor form in the headspace 7 of the tank 2 to meet the supply requirements of the gas-consuming devices 3, then the second supply circuit 5 can be used alone. Conversely, if there is no gas in vapor form present in the headspace 7 of the tank 2, then the first supply circuit 4 can be used alone. In [Fig. 2], both supply circuits 4 and 5 are used simultaneously.

[0068] According to this first supply method, the liquid gas 6 contained in the tank 2 is pumped by the pumping device 8 to circulate in the first supply circuit 4. The liquid gas is then evaporated within the evaporation device 9, as the gas-consuming devices 3 can only be supplied with gas in the vapor state. The evaporated gas then circulates within the first supply circuit 4 until it supplies the gas-consuming devices 3. In this supply method, the first control element 19 and the second control element 20 are configured to allow, respectively, the passage of liquid gas upstream of the evaporation device 9 and evaporated gas downstream of the evaporation device 9.

[0069] The vapor gas present in the headspace 7 of the tank 2 is drawn in and compressed within the second supply circuit 5 by the compression device 10. In [Fig. 2], it is the first compression device 10a that compresses the vapor gas. The second compression device 10b can be used, for example, in the event of a failure of the first compression device 10a, the vapor gas then circulating within the auxiliary line 11. After being compressed, the vapor gas then supplies the gas-consuming devices 3. The compression of the vapor gas is carried out so that the vapor gas pressure at the outlet of the compression device 10. In this supply mode, the control element 21 is configured to allow the passage of vapor gas upstream of the compression device 10.

[0070] This first supply mode is used when the measuring means 25 detect a sufficient quantity of gas in liquid state 6 to avoid any risk of malfunctioning the pumping device 8. In this mode of implementation, the first control device 22, the second control device 23 and the control module 24 are in the closed position.

[0071] When the measuring means 25 detect a lower quantity of gas in the liquid state to the point where there is an imminent risk of malfunction of the pumping device 8, a switch from the first supply mode to a second supply mode is then implemented to prevent this malfunction. Such detection may, for example, correspond to a level of gas in the liquid state below a level threshold, or to a differential pressure value measured above a pressure threshold.

[0072] The central unit can then consider this detection as revealing an imminent malfunction of the pumping device 8, and can then issue a command to change the power supply mode.

[0073] Fig. 3 illustrates a first step in the transition from the first power supply mode to the second power supply mode.

[0074] During this first transition step, the second control device 23 is opened to allow the evaporated gas from the outlet of the evaporation device 9 to flow through the connecting line 12. Part of the evaporated gas then flows from the first supply circuit 4 to the second supply circuit 5 via the connecting line 12, drawn in by the compression device 10, while the remainder of the evaporated gas flowing through the first supply circuit 4 continues to supply the gas-consuming devices 3. This first step ensures a fluid connection between the first supply circuit 4 and the second supply circuit 5 via the connecting line 12. This first step also initiates the pressure differential by lowering the pressure upstream of the compression device 10.

[0075] Figure 4 illustrates a second stage in the transition from the first power supply mode to the second power supply mode. This second stage occurs after the first stage illustrated in Figure 3. Therefore, the starting point of this second stage will be considered to be the configuration illustrated in Figure 3.

[0076] During the second stage, the control element 21 located on the second supply circuit 5 is closed. Thus, the gas compressed by the compression device 10 comes only from the first supply circuit 4, downstream of the evaporation device 9. In other words, the gas in the vapor state present in the headspace 7 of the tank 2 is no longer discharged.

[0077] In the example illustrated in [Fig. 4], the control module 24 is open so that some of the compressed gas flows within the return line 17 downstream of the compression device 10. Compressed gas in the vapor state is thus partially returned to the tank 2 via the return line 17. Since the gas in the vapor state is As more gas is evacuated from tank 2, and as the return line 17 ensures the return of gas in vapor form to tank 2, the internal pressure of the latter begins to increase. This increase in the internal pressure of tank 2 will facilitate the subsequent circulation of gas in liquid form. Depending on the pressure measured in tank 2, it is possible to limit the opening of the control module 24 if the pressure within tank 2 is sufficiently high.

[0078] Figure 5 illustrates a third and final transition stage to the second supply mode. Therefore, Figure 5 also illustrates the gas flow when the second supply mode is implemented. This second supply mode, as previously mentioned, eliminates the need for the pumping device 8 to supply the gas-consuming appliances 3.

[0079] After the second step illustrated in [Fig.4], the third step consists of closing the first control member 19 and the second control member 20, while opening the first control device 22 to allow the flow of gas in the liquid state within the siphon line 15.

[0080] Closing the first control device 19 is accompanied by the shutdown of the pumping device 8 before any potential malfunction occurs. The siphon line 15 is then opened to allow the circulation of gas in a liquid state within it. Indeed, the compression device 10 generates the pressure differential between the evaporation device 9 and downstream of the compression device 10 within the first supply circuit 4. The pressure differential is reinforced by the pressure increase within the tank 2 due to the return of gas in a vapor state via the return line 17 into the tank 2.

[0081] The generated pressure differential allows the gas to circulate in the liquid state within the siphon line 15 and in the first supply circuit 4 without the need to implement the pumping device 8. The gas in the liquid state 6 contained in the tank 2 rushes into the siphon line 15 via the end 16 and joins the first supply circuit 4.

[0082] The gas in liquid state is then evaporated by the evaporation device 9 and circulates entirely within the junction line 12. The closure of the second control member 20 makes it possible to improve the suction capacity of the junction line 12 by pressure differential implemented in part by the compression device 10.

[0083] The evaporated gas thus joins the second supply circuit 5 via the junction line 12, is compressed by the compression device 10 and is finally supplied to the gas-consuming devices 3. It is possible to implement the two compression devices 10 simultaneously, in order to generate a pressure differential more easily and thus promote the circulation of gas in the liquid state within the siphon line 15.

[0084] Of course, the invention is not limited to the examples just described and many modifications can be made to these examples without departing from the scope of the invention.

[0085] The invention, as described above, achieves its intended purpose and provides a supply method for continuously supplying a gas-consuming appliance even if the bottom-of-tank pumping device is unusable or at risk of malfunction. Variations not described here could be implemented without departing from the scope of the invention, provided that, in accordance with the invention, they include a supply method consistent with the invention.

Claims

Demands

1. A method for supplying gas to at least one gas-consuming appliance (3, 3a, 3b) of a floating structure comprising at least one tank (2), implemented by a gas supply system (1) for the gas-consuming appliance (3, 3a, 3b) of the floating structure, wherein: - according to a first supply method, the gas-consuming appliance (3, 3a, 3b) is supplied with gas via a first supply circuit (4) through which gas is circulated in liquid form using a pumping device (8) and / or the gas-consuming appliance (3, 3a, 3b) is supplied with gas via a second supply circuit (5) through which gas is circulated in vapor form using a compression device (10), - according to a second supply method, the gas-consuming appliance (3, 3a,3b) with the gas via the first supply circuit (4) in which gas in liquid state is circulated using a pressure differential without the aid of the pumping device (8), and gas in vapor state is returned to the tank (2), the choice of the supply method being dependent on information relating to the quantity of gas in liquid state contained in the tank (2).

2. A feeding method according to claim 1, wherein the information relating to the quantity of gas in the liquid state contained in the tank (2) is determined by a measurement of the level of gas in the liquid state in the tank (2) relative to the pumping device (8).

3. A feeding method according to claim 1, wherein the information relating to the quantity of gas in the liquid state contained in the tank (2) is determined by a measurement of an internal pressure differential of the tank (2).

4. A supply method according to any one of claims 1 to 3, implemented by the gas supply system (1) of the gas-consuming appliance (3, 3a, 3b) of the floating structure in which the first supply circuit (4) comprises at least the pumping device (8) configured to pump the gas drawn from the liquid state in the tank (2) and at least one evaporation device (9) configured to evaporate the gas in the liquid state circulating in the first supply circuit (4), the second supply circuit (5) comprising at least the compression device (10) configured to compress gas taken in the vapor state from the tank (2) to a pressure compatible with the requirements of the gas-consuming appliance (3, 3a, 3b), the supply system (1) further comprising at least one siphon line (15) and at least one connecting line (12), the siphon line (15) being connected to the first supply circuit (4) between the pumping device (8) and the evaporation device (9) and comprising one end (16) configured to be immersed in the tank (2), the compression device (10) being capable of taking the gas in the liquid state from the tank (2) via the siphon line (15) and the junction line (12),the supply system (1) further comprising a return line (17) connected to the second supply circuit (5) between the compression device (10) and the gas-consuming appliance (3, 3a, 3b) and configured to extend to the tank (2), the return line (17) being capable of returning the gas in the vapor state compressed by the compression device (10) into the tank (2), during which:, - according to the first supply method, the gas in liquid state is taken by the pumping device (8), evaporated by the evaporation device (9) and supplied to the gas consuming device (3, 3a, 3b), and / or the gas in vapor state is taken by the compression device (10) and supplied to the gas consuming device (3, 3a, 3b), - according to the second supply method, the gas in liquid state is taken and drawn in by the compression device (10), circulates within the siphon line (15), is evaporated by the evaporation device (9), is compressed by the compression device (10) by circulating via the junction line (12), a first fraction being supplied to the gas-consuming device (3, 3a, 3b), a second fraction circulating in the return line (17) and returning to the tank (2) in order to increase the pressure of the tank (2) and to facilitate the flow of gas in liquid form within the siphon line (15).

5. A feeding method according to claim 4, implemented by a feeding system (1) in which the first feeding circuit (4) comprises a first control element (19) disposed between the pumping device (8) and the connection with the siphon line (15) and a second control element (20) disposed between the evaporation device (9) and the gas-consuming device (3, 3a, 3b), in which the first control element (19) and the second control element (20) permit the flow of gas when the first feeding mode is implemented and prohibit the flow of gas when the second feeding mode is implemented.

6. A feeding method according to claim 4 or 5, implemented by a feeding system (1) in which the second feeding circuit (5) includes a control element (21) disposed between the tank (2) and the second junction point (14), in which the control element (21) permits gas flow when the first feeding mode is implemented and prohibits gas flow when the second feeding mode is implemented.

7. A feeding method according to any one of claims 4 to 6, implemented by a feeding system (1) in which the siphon line (15) and the junction line (12) respectively comprise a first control device (22) and a second control device (23), in which the first control device (22) and the second control device (23) prohibit the flow of gas when the first feeding mode is implemented and permit the flow of gas when the second feeding mode is implemented.

8. A feeding method according to any one of claims 4 to 7, implemented by a feeding system (1) in which the return line (17) includes a control module (24), in which the control module (24) prohibits gas flow when the first feeding mode is implemented and permits gas flow when the second feeding mode is implemented.

9. Feeding method according to claim 8, wherein the control module (24) is controlled according to the pressure in the tank (2).

10. A feeding method according to claims 5 to 9, wherein a transition from the first feeding mode to the second feeding mode comprises: - a first step in which the second control device (23) is opened to circulate at least partially the gas evaporated by the evaporation device (9) within the junction line (12), - a second step in which the control element (21) is closed and then the control module (24) is opened to generate a return of gas in the vapor state into the tank (2) while preventing any discharge of said gas in the vapor state in order to increase the pressure within the tank (2) - a third step in which the first control element (19) is closed, the second control element (20) is closed and the pumping device (8) is stopped,Then the first control device (22) is opened to allow the flow of gas in liquid state within the siphon line (15).

11. A gas supply system (1) for at least one gas-consuming appliance (3, 3a, 3b) of a floating structure comprising at least one tank (2), implementing a supply method according to any one of claims 1 to 10, comprising: - at least one first supply circuit (4) configured to supply gas to the gas-consuming appliance (3, 3a, 3b), the first supply circuit (4) comprising at least one pumping device (8) configured to, in a first supply mode, draw gas in liquid form from the tank (2) and at least one evaporating device (9) configured to evaporate the gas in liquid form circulating in the first supply circuit (4), - at least one second supply circuit (5) configured to supply gas to the gas-consuming appliance (3, 3a, 3b), the second supply circuit (5) comprising at least one compression device (10) configured for, In the first supply mode, gas is drawn in vapor form from the tank (2) and compressed to a pressure compatible with the needs of the gas-consuming appliance (3, 3a, 3b), characterized in that the supply system (1) comprises at least one connecting line (12) and at least one siphoning line (15), the connecting line (12) extending between a first junction point (13) disposed on the first supply circuit (4) between the evaporator (9) and the gas-consuming appliance (3, 3a, 3b) and a second junction point (14) disposed on the second supply circuit (5) between the tank (2) and the compression device (10), the siphoning line (15) being connected to the first supply circuit (4) between the pumping device (8) and the evaporator (9) and comprising an end (16) configured to be immersed in the tank (2), the compression device (10) being capable of, in a second supply mode, drawing the gas in liquid form from the tank (2) via the siphoning line (15) and the junction line (12).

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