FR3119013A1 - Gas supply system for appliances using high and low pressure gas - Google Patents

Abstract

The present invention relates to a system for supplying (1) a high-pressure gas-consuming appliance (4) and a gas-consuming appliance at high pressure. low pressure (5) of a floating structure, the supply system (1) comprising a first supply circuit (2) of the device consuming high pressure gas (4) and a second supply circuit ( 3) of the low pressure gas consuming device (5), a return line (14), a first heat exchanger (6) and a second heat exchanger (7) effecting a heat exchange between the gas of the first supply circuit (2) and the gas flowing in the return line (14), characterized in that the first supply circuit (2) comprises a main path (40) and a bypass path (41) d a portion (50) of the main track (40). (figure 1)

Description

Gas supply system for appliances using high and low pressure gas

The present invention relates to the field of vessels for storing and/or transporting gas in the liquid state and more particularly relates to a gas supply system for consumer appliances included within such vessels.

During a journey made by a ship comprising a tank of gas in the liquid state intended to be consumed and/or to be delivered to a point of destination, said ship may be able to use at least part of said gas to the liquid state in order to supply at least one of its motors, via a gas supply system. This is the case for ships equipped with an ME-GI type propulsion engine. In order to supply this type of engine, the gas must be compressed at very high pressure by special compressors capable of compressing the gas up to 300 bars, but such compressors are expensive, generate substantial maintenance costs and induce vibrations. within the ship.

An alternative to installing these high-pressure compressors is to vaporize the gas in liquid form at 300 bars before it is sent to the propulsion engine. This operation can be done by a high pressure evaporator. Since such a solution does not make it possible to eliminate the gas in vapor form (or BOG, which in English means "boil-off gas") which forms naturally within a tank containing at least partially the cargo, low-pressure compressors can be installed to power an auxiliary engine capable of consuming the gas in vapor form at low pressure. On the other hand, in such a configuration, if the gas in vapor form is present in too large a quantity, or more generally in a quantity greater than a consumption requirement of the auxiliary engine, the gas in vapor form not consumed by the auxiliary engine is then accumulated. in the form of pressure in the vessel within a certain limit, then eliminated by combustion or as a last resort by jettisoning in the atmosphere. Disposal in this way wastes fuel and has damaging consequences for the environment.

With the constant aim of improving the performance of such a power supply system, one objective is in particular to avoid the waste of fuel, while saving energy used for certain components of said power supply system.

The present invention makes it possible to meet such an objective by proposing a gas supply system for at least one high-pressure gas-consuming device and at least one low-pressure gas-consuming device of a floating structure comprising at least one tank configured to contain the gas, the supply system comprising:

• at least one first gas supply circuit of the high-pressure gas-consuming device, comprising at least one pump configured to pump the gas sampled in the liquid state from the tank,
• at least one high pressure evaporator configured to evaporate the gas flowing in the first gas supply circuit,
• at least one second gas supply circuit of the low-pressure gas consuming device, comprising at least one compressor configured to compress gas taken in the vapor state from the tank up to a pressure compatible with the needs of the low pressure gas consuming device,
• at least one gas return line connected to the second supply circuit downstream of the compressor and extending to the tank,
• at least a first heat exchanger and a second heat exchanger each configured to perform a heat exchange between the gas flowing in the return line and the gas flowing in the first supply circuit,

characterized in that the first supply circuit comprises a main path and a bypass path arranged in parallel with at least a portion of the main path, the second heat exchanger being configured to effect a heat exchange between the circulating gas in the return line and the gas flowing in the bypass path.

The presence of the bypass path thus makes it possible to circulate the gas through the second heat exchanger only when necessary, for example in the event of excess gas in the vapor state present in the vessel. The gas can also circulate within the main channel in its entirety, including the portion of the main channel arranged in parallel with the bypass channel, and is directly treated by the high pressure evaporator after having passed through the first heat exchanger . The gas taken from within the tank and intended to supply the high-pressure gas-consuming device thus has several circulation modes, which ensures that the circulation of superfluous gas is avoided and can also limit the quantity of energy linked to the use of the high pressure evaporator and/or the second heat exchanger.

In addition, thanks to such a supply system, the gas in the vapor state present in the tank and not used for the consumption of the low-pressure gas-consuming device can be recondensed and is thus returned to the tank at the liquid state, instead of being eliminated. The loss of gas in the vapor state present in excess in the tank is then at least reduced.

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

As the gas must be in the vapor state to be able to supply the high-pressure gas-consuming device, the high-pressure evaporator guarantees the evaporation of the gas before it is supplied to the high-pressure gas-consuming device. The high pressure evaporator is the site of a heat exchange between the gas circulating in the first supply circuit and a heat transfer fluid, for example glycol water, sea water or steam. water. The latter must be at a temperature high enough to create a change of state of the gas so that the latter changes to the vapor or supercritical state and supplies the high-pressure gas-consuming device.

The gas circulating in the first supply circuit passes through the first heat exchanger, then possibly the second heat exchanger depending on the chosen configuration. The gas can then be vaporized through the high pressure evaporator. The temperature of said gas thus tends to increase more or less before it passes through the high-pressure evaporator if the configuration of the first supply circuit allows it. Thus, the gas circulating in the first supply circuit can be in a two-phase, vapour, liquid or supercritical state at the outlet of the second heat exchanger if the bypass route is taken by the gas.

In general, the gas contained in the tank can pass naturally, or forced by the floating structure, into the vapor state. The gas within the tank passing to the vapor state must be evacuated so as not to create an overpressure within the tank.

Such a function is performed by the second gas supply circuit of the device consuming low-pressure gas. The second supply circuit extends from the tank to the low pressure gas consuming device. The latter can for example be an auxiliary motor such as an electric generator. The compressor arranged on the second supply circuit is responsible for sucking in the gas present in the top of the tank in order to be able to supply the low-pressure gas consumer device, but also to regulate the pressure within tank.

At the outlet of the compressor, the gas in the vapor state can supply the device consuming gas at low pressure, or circulate through the return line if the device consuming gas at low pressure does not require a supply of fuel . Since the return line is connected downstream of the compressor, the gas in the vapor state sucked in by the compressor can therefore circulate through it.

The gas in the vapor state circulating in the return line first passes through the second heat exchanger, then the first heat exchanger, before returning to the vessel. Depending on the circulation of the gas in the first supply circuit, the heat exchange can take place within the two heat exchangers or only within the first heat exchanger.

Thanks to the heat exchange taking place between the gas circulating in the first supply circuit and the gas circulating in the return line, the temperature of the gas in the vapor state decreases as it passes through the heat exchangers, up to so that said gas condenses and returns to the liquid state substantially at the outlet of the first heat exchanger. The recondensed gas then circulates to the tank.

According to a characteristic of the invention, the main path comprises an additional pump interposed between the first heat exchanger and the high pressure evaporator. It is the additional pump which makes it possible to increase the pressure of the gas circulating in the first supply circuit, so that it has a pressure compatible with the supply of the device consuming high-pressure gas.

The positioning of the additional pump is particularly advantageous. Indeed, setting up the additional pump upstream of the first heat exchanger leads to a rise in the pressure and temperature of the gas in the liquid state as soon as it passes through the first heat exchanger, which is detrimental to the condensation of the gas. in the vapor state circulating in the return line and also passing through the first heat exchanger. The optimum arrangement therefore consists of placing the additional pump downstream of the first heat exchanger.

According to one characteristic of the invention, the branch path begins at a point of divergence arranged on the main path between the additional pump and the high pressure evaporator. It is from the point of divergence that the first supply circuit is divided between the portion of the main track and the bypass track. Depending on the configuration of the first supply circuit, the gas which circulates therein, after having passed through the first heat exchanger, can circulate in the portion of the main path to subsequently be directly treated by the high pressure evaporator and /or within the bypass path to cross the second heat exchanger.

The point of divergence is downstream of the additional pump so that the second heat exchanger is also downstream of the additional pump. Indeed, the gas circulating in the bypass path can be in a vapor, liquid, diphasic or supercritical state at the outlet of the second heat exchanger, placing the additional pump downstream of the second heat exchanger can affect the proper functioning of the latter. given that the additional pump only allows the pumping of a fluid in the liquid state.

According to a characteristic of the invention, the first supply circuit comprises a distribution device configured to control a distribution of the flow of gas towards the portion of the main track and/or towards the branch track. The distribution device can be controlled remotely, so that the circulation of the gas within the first supply circuit is optimal for the consumption of the gas by the consuming device and for the condensation of the gas circulating in the return line .

According to a feature of the invention, the bypass path ends at a convergence point arranged on the main path between the divergence point and the high pressure evaporator. Such a configuration corresponds to a first embodiment of the power supply system according to the invention. In this first embodiment, the point of convergence of the portion of the main channel and the bypass channel is arranged downstream of the point of divergence and upstream of the high pressure evaporator. In other words, the gas circulating in the bypass path passes through the second heat exchanger, then rejoins the main path before being treated by the high pressure evaporator. All of the gas circulating in the first supply circuit is therefore treated by the high pressure evaporator according to the first embodiment. The latter therefore allows the gas to pass through the second heat exchanger and/or to bypass the latter.

According to one characteristic of the invention, the distribution device comprises a first valve configured to manage the circulation of gas within the bypass channel and a second valve arranged on the portion of the main channel. The valves can be controlled remotely in order to switch to the open or closed position and thus determine the circulation of the gas circulating within the first supply circuit.

The first valve can be arranged on the branch path upstream or downstream of the second heat exchanger. The second valve is for its part arranged on the portion of the main track arranged in parallel with the bypass track.

The first valve makes it possible to control the flow of gas in the bypass channel, while the second valve makes it possible to control the flow of gas in the portion of the main channel arranged in parallel with the bypass channel. If the first valve is closed and the second valve open, then the gas flows within the main path in its entirety. If the first valve is open and the second valve closed, then the gas flows entirely through the bypass channel then joins the main channel upstream of the high pressure evaporator. The two valves can also be opened so that the gas separates into two fractions, one directly joining the high pressure evaporator via the portion of the main path, the other circulating within the bypass path crossing the second heat exchanger.

According to a characteristic of the invention, the bypass channel and the first valve are configured so that the gas which circulates between the point of divergence and the second heat exchanger is maintained in the liquid state. In other words, the first valve has the sole function of authorizing or not the circulation of gas within the bypass channel without causing any change of state, for example by releasing the gas flowing in the bypass channel. Thus the gas circulating in the bypass channel is maintained in the liquid state until it passes through the second heat exchanger. At the outlet of the latter, and depending on a flow rate of gas circulating in the return line and its influence on the heat exchange, the gas circulating in the bypass path can leave the second heat exchanger in a liquid state. , steam, two-phase or supercritical.

According to a feature of the invention, the bypass path ends at a convergence point arranged on the main path downstream of the high pressure evaporator. Such a configuration corresponds to a second embodiment of the power supply system according to the invention. In this embodiment, the bypass route bypasses the high pressure evaporator. The latter is therefore located within the portion of the main track arranged in parallel with the bypass track.

According to the second embodiment, the gas circulating in the first supply circuit is therefore either treated by the high pressure evaporator if the gas circulates within the portion of the main channel, or is treated by the second heat exchanger whether the gas is flowing within the bypass path. At the outlet of the high-pressure evaporator or the second heat exchanger, the gas has compatible characteristics for its consumption by the high-pressure gas-consuming device, for example by being in a vapor or supercritical state. The second embodiment therefore makes it possible to distribute the load of the change of state of the gas circulating within the first supply circuit, and this while cooling the gas circulating in the return line thanks to the heat exchange operated at the within the second heat exchanger.

According to one characteristic of the invention, the distribution device comprises a distribution valve. The distribution valve makes it possible to control the flow of gas circulating in the portion of the main channel and/or in the bypass channel. By way of example, the valve may have a degree of opening, a distribution of the gas flowing between the portion of the main channel and/or the bypass channel being dependent on the degree of opening of the distribution valve.

According to a characteristic of the invention, the distribution valve is arranged on the portion of the main track. In this configuration, the greater the degree of opening of the distribution valve, the greater the proportion of gas circulating within the portion of the main channel. Conversely, the lower the degree of opening of the distribution valve, the greater the proportion of gas circulating within the bypass channel. If the distribution valve is completely open, the gas flows exclusively in the portion of the main channel. If the distribution valve is closed, the gas flows exclusively in the bypass path. The distribution valve can be positioned either between the point of divergence and the high pressure evaporator, or between the high pressure evaporator and the point of convergence.

According to another feature of the invention, the distribution valve is arranged on the branch line. In this configuration, the higher the degree of opening of the distribution valve, the greater the proportion of gas circulating within the bypass channel. Conversely, the lower the degree of opening of the distribution valve, the greater the proportion of gas circulating within the portion of the main channel. If the distribution valve is completely open, the gas flows exclusively in the bypass path. If the distribution valve is closed, the gas flows exclusively in the portion of the main track. The distribution valve can be positioned either between the point of divergence and the second heat exchanger, or between the second heat exchanger and the point of convergence.

According to one characteristic of the invention, the return line comprises an expansion member disposed between the first heat exchanger and the vessel and configured to regulate a gas flow rate circulating in the return line, said expansion member and the valve distribution being configured so that the gas which circulates within the branch path passes from the liquid state to the vapor or supercritical state.

As mentioned, the gas circulating in the first supply circuit is treated by the high pressure evaporator or by the second heat exchanger. In other words, unlike the first embodiment, the gas flowing in the bypass path must be, at the outlet of the second heat exchanger, in a state compatible to be consumed by the high-pressure gas-consuming device, for example in a vapor or supercritical state. It is therefore important that the gas circulating in the bypass channel is entirely in the vapor or supercritical state at the outlet of the second heat exchanger.

The flow rate of gas circulating in the bypass path can be proportional to the flow rate of gas circulating in the return line so that, during the heat exchange, all of the gas circulating in the bypass path is in a vapor state. or supercritical at the outlet of the second heat exchanger. The expansion device arranged on the return line therefore makes it possible to control the flow of gas circulating in the return line, while the distribution valve makes it possible to control the flow of gas circulating in the bypass channel. Thus, thanks to the control by the expansion device and by means of the distribution valve, the gas circulating in the bypass channel leaves the second heat exchanger in a state compatible with its consumption by the gas-consuming device at high pressure, without having been treated by the high pressure evaporator.

According to a characteristic of the invention, the first heat exchanger is configured to condense the gas circulating within the return line. The first heat exchanger is the exchanger through which the gas in the liquid state of the first supply circuit passes when said gas in the liquid state is at its lowest temperature. It is therefore the heat exchange taking place within the first heat exchanger that will change the state of the gas circulating in the return line to change it from the vapor state to the liquid state.

According to a characteristic of the invention, the second heat exchanger is configured to pre-cool the gas circulating within the return line. At the outlet of the first heat exchanger, the gas circulating in the first supply circuit is less cold than at the inlet of the first heat exchanger, a heat exchange having served to condense the gas circulating in the return line. Subsequently, the gas in liquid state is compressed by the additional pump and then reaches the point of divergence. Depending on the configuration of the first or second embodiment, the gas may subsequently pass through the second heat exchanger. If this is the case, there is also a heat exchange within the second heat exchanger, allowing the pre-cooling of the gas in the vapor state within the return line.

According to one characteristic of the invention, the supply system comprises an auxiliary supply line connected to the first supply circuit, upstream of the first heat exchanger, and extending as far as the second supply circuit, in downstream of the compressor, the supply system comprising a low pressure evaporator configured to evaporate the gas circulating in the auxiliary supply line. Such an auxiliary supply line is used when the low-pressure gas-consuming device needs to be supplied with gas in the vapor state, but the latter is not in sufficient quantity within the top of the tank. The auxiliary supply line thus makes it possible to divert part of the gas in the liquid state circulating in the first supply circuit. This part is then evaporated by the low pressure evaporator, according to an operation similar to that of the high pressure evaporator, that is to say by heat exchange with a heat transfer fluid such as glycol water, sea water or water vapour, for example. The low pressure evaporator thus induces an exchange of calories between the gas in the liquid state circulating in the auxiliary supply line and this heat transfer fluid.

Once in the vapor state, the gas continues to circulate within the auxiliary supply line and joins the second supply circuit in order to supply the low-pressure gas-consuming device.

If gas in the vapor state is present in sufficient quantity in the top of the tank, then the auxiliary supply line is not used and can for example be closed by a valve.

The invention also covers a floating structure for storing and/or transporting gas in the liquid state, comprising at least one tank containing gas in the liquid state, at least one device consuming high-pressure gas, at least a low-pressure gas-consuming appliance and at least one gas supply system for these appliances.

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

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

Other characteristics and advantages of the invention will become apparent through the description which follows on the one hand, and several embodiments given by way of indication and not limiting with reference to the appended diagrammatic drawings on the other hand, on which :

represents a first embodiment of a supply system according to the invention,

represents a second embodiment of the power supply system,

is a cutaway schematic representation of a tank of a floating structure and a terminal for loading and/or unloading this tank.

Figures 1 and 2 show a gas supply system 1 arranged on a floating structure. The supply system 1 makes it possible to circulate gas which may be in the liquid state, in the vapor state, in the two-phase state or in the supercritical state, from a storage tank 8 and/or transport, and to a high-pressure gas-consuming device 4 and/or a low-pressure gas-consuming device 5, in order to supply the latter with fuel.

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

In order to ensure the circulation of the gas contained in the tank 8 to the high-pressure gas-consuming device 4, the supply system 1 is provided with a first gas supply circuit 2. The first supply circuit 2 comprises a pump 9 disposed within the tank 8. The pump 9 makes it possible to pump the gas in the liquid state and to cause it to circulate in particular within the first supply circuit 2. By sucking and by compressing the gas in the liquid state, the pump 9 makes it possible to raise the pressure of the latter to a value comprised between 6 and 17 bars.

The first supply circuit 2 comprises a main channel 40 and a bypass channel 41. The main channel 40 extends from the pump 9 to the high pressure gas consuming device 4. The bypass channel 41 is as for it arranged in parallel with a portion 50 of the main channel 40. The gas circulating in the first supply circuit 2 can therefore circulate via the portion 50 of the main channel 40 or via the bypass channel 41.

The gas circulating in the first supply circuit 2, in a direction of circulation going from the tank 8 to the high-pressure gas-consuming device 4, circulates within the main channel 40, passes through a first heat exchanger 6 , is pumped by an additional pump 10 and reaches a point of divergence 42 in order to circulate within the portion 50 of the main channel 40 or within the bypass channel 41. The control of the circulation of the gas within the portion 50 of the main channel 40 and/or of the bypass channel 41 is managed by a distribution device 60 which ensures the distribution of the gas according to factors and/or needs which will be detailed subsequently. If the gas flows within the bypass path 41, the gas passes through a second heat exchanger 7. The details concerning the two heat exchangers 6, 7 will be described later. The branch path 41 comprises a first part 41a extending between the point of divergence 42 and the second heat exchanger 7, and a second part 41b extending between the second heat exchanger 7 and the point of convergence 43.

The portion 50 of the main channel 40 and the branch channel 41 both extend from the point of divergence 42 to a point of convergence 43. From the latter, the gas circulates again within the main channel 40 until to a high pressure evaporator 11. The high pressure evaporator 11 makes it possible to modify the state of the gas circulating in the first supply circuit 2 in order to make it pass to the vapor state. Such a state allows the gas to be compatible for supplying the high-pressure gas-consuming device 4, for example by being in a vapor or supercritical state. The evaporation of the gas in the liquid state can for example be done by heat exchange with a heat transfer fluid at a temperature high enough to evaporate the gas in the liquid state, here glycol water, sea water or water vapour.

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

Thanks to the combination of the additional pump 10 and the high pressure evaporator 11, the gas is at a pressure and in a state compatible for the supply of the high pressure consuming device 4. Such a configuration makes it possible to avoid the installation of high pressure compressors on the first supply circuit 2 which present cost constraints and generate strong vibrations.

In order to determine a configuration of the circulation of the gas within the first supply circuit 2, the distribution device 60 comprises a first valve 44 arranged at the level of the bypass path 41 and a second valve 45 arranged at the level of the portion 50 of the main channel 40. Thus, depending on the opening or closing of these two valves 44, 45, the gas flows from the point of divergence 42 to the point of convergence 43 passing through the portion 50 or through the channel bypass 41 as needed. These valves can be controlled remotely according to a desired circulation mode.

On the , the first valve 44 is arranged at the level of the first part 41a of the bypass channel 41. Alternatively, the first valve 44 can also be arranged on the second part 41b of the bypass channel 41.

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

The supply system 1 therefore comprises a second gas supply circuit 3, which uses the gas in the vapor state to supply the low-pressure gas-consuming device 5. The second supply circuit 3 extends therefore between the top of the tank 12 and the low-pressure gas consuming device 5. In order to suck the gas in the vapor state contained in the top of the tank 12, the second supply circuit 3 comprises a compressor 13. In addition to sucking in the gas in the vapor state, the compressor 13 also makes it possible to compress the gas in the vapor state circulating in the second supply circuit 3 to a pressure of between 6 and 20 bar absolute, and this in order to that the gas in the vapor state is at a pressure compatible with supplying the low-pressure gas-consuming device 5. The second supply circuit 3 thus makes it possible to supply the low-pressure gas-consuming device 5, and this while regulating the pressure within the tank 8 by sucking the gas in the vapor state present in the top of the tank 12.

The presence of gas in the vapor state in excessive quantity within the top of the tank 12 causes an overpressure within the tank 8. It is therefore necessary to evacuate the gas in the vapor state in order to lower the pressure within the tank 8. The gas in the excess vapor state can then for example be eliminated by a burner 18. However, the supply system 1 according to the invention comprises a return line 14 which extends from the second supply circuit 3 to tank 8.

The return line 14 is connected to the second supply circuit 3 downstream of the compressor 13 with respect to a direction of circulation of the gas in the vapor state circulating in the second supply circuit 3. According to the direction of circulation of the gas in the vapor state circulating in the return line 14, said gas first passes through the second heat exchanger 7, then passes through the first heat exchanger 6. The heat exchange taking place within the first exchanger of heat 6 and of the second heat exchanger 7 is therefore between the gas circulating in the first supply circuit 2 and the gas circulating in the return line 14. More particularly, the heat exchange taking place within the second heat exchanger 7 takes place between the gas flowing in the branch path 41 and the gas flowing in the return line 14. The purpose of this heat exchange via the second heat exchanger 7 then the first heat exchanger 6 is of co Denser the gas in the vapor state of the return line 14, so that it changes to the liquid state and returns to the tank 8 in this state, instead of being eliminated by the burner 18.

It is at the inlet of the first heat exchanger 6 that the gas in the liquid state of the first supply circuit 2 has the lowest temperature. Therefore, it is therefore after having passed through the first heat exchanger 6 that the gas circulating in the return line 14 is condensed. The gas in the return line 14 is therefore in the vapor state at the inlet of the first heat exchanger 6 and exits in the liquid state following the heat exchange taking place within the first heat exchanger 6.

In order to align the pressure of the gas circulating in the return line 14 with the pressure which prevails in the tank 8, the return line 14 can comprise an expansion device 15 which lowers the pressure of the gas to a pressure comprised between 1 and 3 bar absolute. The expansion member 15 is also able to regulate a flow of gas circulating within the return line 14. Once the gas is condensed, it continues its course to the tank 8. The first heat exchanger Heat 6 therefore acts as a condenser.

The second heat exchanger 7 is located downstream of the first heat exchanger 6 according to the direction of circulation of the gas in the first supply circuit 2, and upstream of the first heat exchanger 6 according to the direction of circulation of the gas in the return line 14. Provided that the gas circulating within the first supply circuit 2 passes through the bypass path 41, the second heat exchanger 7 therefore provides pre-cooling of the gas in the vapor state circulating in the return line 14 before the latter is condensed within the first heat exchanger 6. At the branch line 41, the gas at the inlet of the second heat exchanger 7 has previously passed through the first heat exchanger 6 and was pumped by the additional pump 10, which therefore increased its temperature and pressure. It is thus possible that following the heat exchange occurring at the level of the second heat exchanger 7, the gas circulating within the first supply circuit 2 leaves the second heat exchanger 7 in a liquid, vapor, diphasic state. or supercritical. The temperature of the gas circulating in the return line 14 is therefore lowered after passing through the second heat exchanger 7, implementing the pre-cooling indicated above.

If at least the first valve 44 is closed, the gas does not flow in the bypass channel 41, and the gas flowing in the return line 14 crosses the second heat exchanger 7 without being pre-cooled there. The circulation of the gas via the portion 50 of the main channel 40 can also be preferred when there is no gas to be recondensed circulating in the return line 14. On the other hand, the heat exchange operated within the second heat exchanger 7 makes it possible to increase the temperature of the gas circulating in the bypass path 41 and thus makes it possible to limit the energy necessary to be supplied to the heat transfer fluid circulating in the high pressure evaporator 11 to evaporate the gas having passed through the second heat exchanger 7 beforehand.

The additional pump 10 is advantageously arranged downstream of the first heat exchanger 6 and upstream of the second heat exchanger 7 if the gas circulates via the bypass channel 41. Thanks to the expansion device 15, the regulation of the gas flow circulating within the return line 14 ensures that the gas circulating in the first supply circuit 2 and passing through the first heat exchanger 6 is maintained in the liquid state at the outlet of the latter. The additional pump 10 then sucks in the gas maintained in the liquid state without risking being damaged by the presence of at least a fraction of gas in the vapor state.

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

The supply system 1 also comprises an auxiliary supply line 16, extending from the first supply circuit 2, via a connection between the pump 9 and the first heat exchanger 6, to the second supply circuit 3, connecting to it between the compressor 13 and the low-pressure gas-consuming device 5. The auxiliary supply line 16 makes it possible to supply the low-pressure gas-consuming device 5 in the event of flow insufficient gas in the vapor state formed within the top of the vessel 12.

When the gas in the vapor state is not present in sufficient quantity in the head of the vessel 12, the gas in the liquid state pumped by the pump 9 can then circulate within this auxiliary supply line 16 in order to supplying the low-pressure gas-consuming device 5. To do this, the auxiliary supply line 16 passes through a low-pressure evaporator 17 so that the gas in the liquid state circulating in the auxiliary supply line 16 passes to the vapor state. The operation of the low pressure evaporator 17 can for example be identical to that of the high pressure evaporator 11, that is to say that the gas is evaporated by heat exchange with a heat transfer fluid at a sufficiently high temperature to evaporate gas in liquid state. At the outlet of the low-pressure evaporator 17, the gas in the vapor state circulates within the auxiliary supply line 16, then joins the second supply circuit 3 in order to supply the appliance consuming gas at low pressure 5.

It is understood from the foregoing that the auxiliary supply line 16 is used only in the absence of gas in the vapor state in sufficient quantity within the head of the vessel 12. Thus, the line of auxiliary supply 16 comprises a valve 19 controlling the flow of gas within the auxiliary supply line 16 when the use of the latter is not necessary.

There represents a second embodiment of the supply system 1 according to the invention. The second embodiment differs from the first embodiment by the configuration of the main channel 40 and of the bypass channel 41. Reference will therefore be made to the description of the for the notions common to the two embodiments.

According to the second embodiment of the supply system 1, the point of convergence 43 is here arranged downstream of the high pressure evaporator 11. In other words, the branch path, still comprising the second heat exchanger 7, is configured to bypass the high pressure evaporator 11. The latter is therefore arranged within the portion 50 of the main channel 40. Thus, if the gas flows within the branch channel 41, it then joins the point convergence 43 then circulates to the high pressure gas consuming device 4 without being treated by the high pressure evaporator 11. If the first supply circuit 2 is configured so that the gas circulates entirely within the channel main 40, the latter, after having passed through the first heat exchanger 6 and the additional pump 10, is directly treated by the high pressure evaporator 11 by circulating within the portion 50.

According to the second embodiment, the distribution device 60 comprises a distribution valve 47 arranged on the first part 41a of the bypass channel 41. Alternatively, the distribution valve 47 can be arranged on the second part 41b of the branch line 41, or on the portion 50 of the main line 40, between the point of divergence 42 and the high pressure evaporator 11 or between the high pressure evaporator 11 and the point of convergence 43.

The distribution of the gas flowing in the portion 50 of the main channel 40 and/or in the bypass channel 41 is done according to a degree of opening of the distribution valve 47.

On the , the distribution valve 47 is arranged on the bypass channel 41. Thus, the more the distribution valve 47 is open, the higher the proportion of gas flowing in the bypass channel 41. By controlling the degree of opening of the distribution valve 47, it is therefore possible to manage the distribution of the gas in the portion 50 of the main channel 40 and/or in the bypass channel 41.

Because the gas flowing in the bypass channel 41 is not treated by the high pressure evaporator 11, it is essential that the characteristics of the gas, after passing through the second heat exchanger 7, conform to its use as fuel for the high-pressure gas-consuming device 4, for example by corresponding to a vapor or supercritical state. The distribution valve 47 is thus controlled in order to allow the circulation in the bypass channel 41 of a quantity of gas such that the heat exchange occurring in the second heat exchanger 7 is sufficient for the totality of said quantity of gas changes to the vapor or supercritical state in order to be compatible with the high pressure gas consuming device 4. The expansion device 15 of the return line 14 can also influence such a condition by controlling the flow rate of gas circulating in the return line 14.

Just as for the first embodiment, the gas circulating in the return line 14 is pre-cooled within the second heat exchanger 7, provided that at least a fraction of gas circulating within the first supply circuit 2 passes through bypass 41.

Advantageously, the second embodiment allows the distribution of the evaporation of the gas circulating in the first supply circuit 2 between the portion 50 via the high-pressure evaporator 11 and the bypass channel 41 via the second heat exchanger of heat 7. Such evaporation carried out in parallel makes it possible to limit the activity of the high pressure evaporator 11 and therefore to partly save the energy necessary for its operation when all of the gas circulating in the first circuit of feed 2 is treated by the high pressure evaporator 11.

When there is no gas to be recondensed circulating in the return line 14, and the heat exchange is not taking place within the second heat exchanger 7, the distribution valve 47 is closed, and this in order to circulate the gas entirely within the portion 50 so that the latter is treated by the high pressure evaporator 11.

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

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

There also represents an example of a maritime or port terminal comprising loading and/or unloading equipment 25, an underwater pipeline 26 and an onshore and/or port installation 27. The onshore and/or port installation 27 can by example be arranged on the quay of a port, or according to another example be arranged on a concrete gravity platform. The onshore and/or port installation 27 comprises liquid state gas storage tanks 30 and connection pipes 31 connected by the subsea pipe 26 to the loading and/or unloading equipment 25.

To generate the pressure necessary for the transfer of the gas in the liquid state, pumps fitted to the onshore and/or port installation 27 and/or pumps fitted to the floating structure 20 are used.

Of course, the invention is not limited to the examples which have just been described and many adjustments can be made to these examples without departing from the scope of the invention.

The invention, as it has just been described, achieves the object it had set itself, and makes it possible to propose a gas supply system for appliances consuming gas at high or low pressure whose the high pressure is made using pumps and an evaporator, comprising a means of condensing a gas in the vapor state before its return to the tank as well as a supply of high pressure gas making it possible to optimize the energy used for the high pressure of said gas. Variants not described here could be implemented without departing from the context of the invention, provided that, in accordance with the invention, they comprise a power supply system in accordance with the invention.

Claims (17)

System for supplying (1) gas to at least one high-pressure gas-consuming device (4) and at least one low-pressure gas-consuming device (5) of a floating structure (20) comprising at at least one tank (8) configured to contain the gas, the supply system (1) comprising:

• at least one first gas supply circuit (2) of the high-pressure gas consuming device (4), comprising at least one pump (9) configured to pump the gas sampled in the liquid state from the tank ( 8),
• at least one high pressure evaporator (11) configured to evaporate the gas flowing in the first gas supply circuit (2),
• at least one second gas supply circuit (3) of the low-pressure gas consuming device (5), comprising at least one compressor (13) configured to compress gas taken off in the vapor state from the tank ( 8) up to a pressure compatible with the needs of the low-pressure gas consuming device (5),
• at least one gas return line (14) connected to the second supply circuit (3) downstream of the compressor (13) and extending as far as the tank (8),
• at least a first heat exchanger (6) and a second heat exchanger (7) each configured to operate a heat exchange between the gas circulating in the return line (14) and the gas circulating in the first supply circuit (2),

characterized in that the first power supply circuit (2) comprises a main channel (40) and a bypass channel (41) arranged in parallel with at least a portion (50) of the main channel (40), the second heat exchanger (7) being configured to operate a heat exchange between the gas flowing in the return line (14) and the gas flowing in the bypass path (41). Supply system (1) according to claim 1, in which the main path (40) comprises an additional pump (10) interposed between the first heat exchanger (6) and the high pressure evaporator (11). Supply system (1) according to the preceding claim, in which the branch line (41) begins at a point of divergence (42) disposed on the main line (40) between the additional pump (10) and the high evaporator pressure (11). A supply system (1) according to any preceding claim, wherein the first supply circuit (2) comprises a distribution device (60) configured to control a distribution of the flow of gas to the portion (50 ) of the main track (40) and/or to the bypass track (41). A supply system (1) according to claim 3, wherein the bypass path (41) terminates at a convergence point (43) disposed on the main path between the divergence point (42) and the high pressure evaporator (11). Supply system (1) according to the preceding claim, combined with claim 4, in which the distribution device (60) comprises a first valve (44) configured to manage the circulation of gas within the bypass path (41 ) and a second valve (45) disposed on the portion (50) of the main channel (40). A feed system (1) according to claim 3, wherein the bypass path (41) terminates at a convergence point (43) disposed on the main path (40) downstream of the high pressure evaporator (11) . Supply system (1) according to the preceding claim, combined with claim 4, in which the distribution device (60) comprises a distribution valve (47). Supply system (1) according to the preceding claim, in which the distribution valve (47) is arranged on the portion (50) of the main line (40). A supply system (1) according to claim 8, wherein the diverter valve (47) is arranged on the bypass path (41). Supply system (1) according to any one of Claims 8 to 10, in which the return line (14) comprises an expansion member (15) arranged between the first heat exchanger (6) and the vessel (8 ) and configured to regulate a flow of gas circulating in the return line (14), said expansion member (15) and the distribution valve (47) being configured so that the gas which circulates within the bypass channel ( 41) changes from the liquid state to the vapor or supercritical state. A supply system (1) according to any preceding claim, wherein the first heat exchanger (6) is configured to condense gas flowing within the return line (14). Supply system (1) according to any one of the preceding claims, in which the second heat exchanger (7) is configured to pre-cool the gas circulating within the return line (14). Supply system (1) according to any one of the preceding claims, comprising an auxiliary supply line (16) connected to the first supply circuit (2), upstream of the first heat exchanger (6), and s extending to the second supply circuit (3), downstream of the compressor (13), the supply system (1) comprising a low pressure evaporator (17) configured to evaporate the gas circulating in the supply line auxiliary (16). Floating structure (20) for storing and/or transporting gas in the liquid state, comprising at least one tank (8) containing gas in the liquid state, at least one device consuming high-pressure gas (4) , at least one low-pressure gas-consuming appliance (5) and at least one gas supply system (1) for these appliances according to any one of the preceding claims. System for loading or unloading a liquid gas which combines at least one onshore and/or port installation (27) and at least one floating structure (20) for storing and/or transporting liquid gas according to the preceding claim. A method of loading or unloading a liquid gas from a floating structure (20) for storing and/or transporting gas according to claim 15, in which pipes (23) for loading and/or unloading gas at the liquid state arranged on an upper deck of the floating structure (20) can be connected, by means of appropriate connectors, to a maritime or port terminal in order to transfer the gas in the liquid state from or to the tank (8 ).