FR3148284A1 - Installation for storing and treating a gas resulting from the evaporation of a cryogenic liquid - Google Patents

Abstract

Title of the invention: Installation for storing and treating a gas resulting from the evaporation of a cryogenic liquid The present invention relates to an installation for storing and treating a gas resulting from the evaporation of a cryogenic liquid (G), comprising at least one tank (4), at least one consumer (26) which consumes a fuel prepared at least from the gas (G), a high-capacity compression device (16) and a low-capacity compression device (24) which supplies the fuel to the consumer (26), the storage and treatment installation comprising a main circuit (14) connecting a roof of the tank (4) to the high-capacity compression device (16) and an accessory circuit (28) fluidically in parallel with the main circuit (14), the accessory circuit (28) being configured to directly supply the gas (G) to the low-capacity compression device (24). Abstract figure: Figure 1

Description

Installation for storing and treating a gas resulting from the evaporation of a cryogenic liquid

The present invention relates to the field of transport and/or storage of a cryogenic liquid, and more particularly the transport and/or storage of a gas prepared from this cryogenic liquid.

Gaseous hydrocarbons at room temperature and atmospheric pressure are liquefied at cryogenic temperatures, that is, temperatures below
- 60 °C, in order to facilitate their transport and/or storage. The hydrocarbons thus liquefied, also called cryogenic liquids, are then placed in tanks of a structure, in particular a floating structure.

However, such tanks are never perfectly thermally insulated, so that natural evaporation of the cryogenic liquid is inevitable. The phenomenon of natural evaporation is called boil-off in English and the gas resulting from this natural evaporation is called boil-off gas in English, its acronym being BOG. The tanks of the floating structure thus contain both the cryogenic liquid and the gas resulting from the natural evaporation of this cryogenic liquid.

Part of the gas resulting from the natural evaporation of the cryogenic liquid can be used as fuel to power at least one consumer, such as an engine, intended to provide for the energy or operating needs of the floating structure. Thus, it is possible to produce electricity for electrical equipment of this structure.

The gas circulates to the consumer through a pipe which generally has a significant diameter, such a diameter being adapted to facilitate and accelerate operations of loading the cryogenic liquid onto the floating structure.

However, the large diameter of the piping causes the gas resulting from the evaporation of the cryogenic liquid to heat up when it is conveyed to the consumer. The gas resulting from the evaporation of the cryogenic liquid then sometimes reaches temperatures that prevent the consumer from being supplied, in particular because these temperatures are incompatible with the operation of a compression device located upstream of the consumer and intended to be crossed by the gas resulting from the evaporation of the cryogenic liquid.

In order to lower the temperature of the gas resulting from the evaporation of the cryogenic liquid within the piping, it is customary to spray cryogenic liquid from the tanks of the floating structure. However, such a solution leads to an increase in the quantity of fluid to be treated, and also complicates the equipment required to supply the consumer, in particular due to the need to use pumps to collect the cryogenic liquid from the tanks.

The present invention aims to overcome this drawback by proposing an installation in which the gas resulting from the evaporation of the cryogenic liquid is supplied to the consumer, thereby limiting its heating during its circulation within the piping of the floating structure.

The main subject of the present invention is thus an installation for storing and treating a gas resulting from the evaporation of a cryogenic liquid, comprising at least one tank configured to contain both the cryogenic liquid and the gas resulting from the evaporation of the cryogenic liquid, at least one consumer who consumes a fuel prepared at least from the gas resulting from the evaporation of the cryogenic liquid, a high-capacity compression device intended to be connected to a cryogenic liquid storage terminal and a low-capacity compression device which supplies the fuel to the consumer, the storage and treatment installation comprising a main circuit connecting a roof of the tank to the high-capacity compression device and an accessory circuit at least partly arranged fluidically in parallel with the main circuit, the accessory circuit being configured to directly supply the gas resulting from the evaporation of the cryogenic liquid to the low-capacity compression device.

The storage and treatment facility according to the invention is for example integrated within a floating structure. It is configured for the circulation of a cryogenic liquid on the one hand, and for the circulation of a gas resulting from the evaporation of this cryogenic liquid on the other hand, both the cryogenic liquid and the gas being stored within one or more tanks of the storage and treatment facility. The cryogenic liquid is more particularly stored in a bottom of the tank, the gas resulting from the evaporation of the cryogenic liquid being on the contrary stored in a sky of the tank.

A consumer of the storage and treatment facility is configured to be supplied from the tank; this consumer is for example supplied with a fuel in liquid form and/or a fuel in gaseous form, i.e. by the cryogenic liquid and/or by the gas resulting from its evaporation. The storage and treatment facility comprises at least two circuits within which the gas resulting from the evaporation of the cryogenic liquid circulates: a main circuit which allows it to be conducted to a high-capacity, low-pressure discharge compression device connected to a storage terminal, and an accessory circuit which conducts the gas resulting from the evaporation of the cryogenic liquid to a low-capacity, high-pressure discharge device connected to the consumer. The two circuits are therefore both dedicated to the supply of gas resulting from the evaporation of the cryogenic liquid from a compression device, the compression devices of each of the circuits being distinguished by the flow rates and pressures at which they operate. The low-capacity compression device thus operates at higher pressures than the high-capacity compression device. The low-capacity compression device operates, for example, for pressures between 5 and 7 bar abs and flow rates of 2,000 to 6,000 m3/h, while the high-capacity compression device operates for pressures between 1.5 and 2.5 bar abs and flow rates of 12,000 to 30,000 m3/h.

The storage terminal is for example located on a land coast, while the consumer is on board the floating structure at sea and participates in its power supply. This storage terminal allows the storage of cryogenic liquid and gas resulting from the evaporation of the cryogenic liquid.

The main circuit and the accessory circuit are at least partly arranged in parallel with each other, i.e. they are at least partly independent. Here, “independent” means that conduits making up the main circuit are distinct from conduits making up the accessory circuit. Preferably, the main circuit and the accessory circuit are predominantly independent, i.e. the majority of conduits making up the main circuit do not participate in the accessory circuit.

The main circuit is connected to the tank sky, that is to say to the portion of the tank in which the gas resulting from the evaporation of the cryogenic liquid is stored.

The accessory circuit is configured to directly supply the gas resulting from the evaporation of the cryogenic liquid to the low-capacity compression device; it is understood that this gas resulting from the evaporation of the cryogenic liquid is conveyed to the low-capacity compression device by circulating exclusively in pipes. The accessory circuit is notably devoid of a heat exchanger. The gas resulting from the evaporation of the cryogenic liquid thus benefits from a dedicated circuit to be conveyed to the consumer, which makes it possible to limit its heating during its circulation.

According to an optional feature of the invention, the main circuit and the accessory circuit are thermally independent.

Thus, there is no exchange of calories between the main circuit and the accessory circuit.

According to an optional feature of the invention, the accessory circuit is connected to the main circuit at the tank ceiling outlet.

The accessory circuit is for example connected to the main circuit outside the tank, near the tank roof.

According to an optional feature of the invention, the storage and treatment installation comprises at least one valve arranged at a separation between the main circuit and the accessory circuit.

The valve, which is either a three-way valve or a combination of two two-way valves, is used to connect the accessory circuit to the main circuit. Upstream of this valve, the gas resulting from the evaporation of the cryogenic liquid circulates in a pipe common to the main circuit and the accessory circuit, this pipe opening into the tank top.

According to an optional feature of the invention, the accessory circuit is directly connected to a gas dome of the tank.

The gas dome corresponds to an outgrowth of the tank, arranged towards its exterior and upwards, in which the gas resulting from the evaporation of the cryogenic liquid is present. When the accessory circuit is directly connected to the gas dome, the connections of each of the circuits to the tank are independent; it is understood that the main circuit and the accessory circuit do not share a pipe extending from the tank.

According to an optional feature of the invention, a nominal diameter of the conduits forming the main circuit is between 300 and 600 mm.

The dimension of the main circuit conduits is thus adapted to loading and unloading operations between the storage and treatment facility and the storage terminal.

According to an optional feature of the invention, a nominal diameter of the pipes forming the accessory circuit is between 100 and 250 mm.

The size of the accessory circuit pipes allows rapid routing of the gas resulting from the evaporation of the cryogenic liquid to the low-capacity compression device and therefore to the consumer, which limits its heating. The gas resulting from the evaporation of the cryogenic liquid is thus supplied to the low-capacity compression device at suitable pressures and temperatures, which limits the need for devices to cool its temperature.

In some embodiments, a diameter of the conduits and/or pipes is scalable, this diameter being larger near the compression device than near the tank.

According to an optional feature of the invention, the accessory circuit is thermally insulated.

Such thermal insulation can be achieved by placing foam around the pipes forming the accessory circuit. Alternatively, it can be achieved by vacuum insulation, by placing the pipes of the accessory circuit in larger pipes and creating a vacuum between the two.

According to an optional feature of the invention, the main circuit comprises a point of divergence between a first branch dedicated to the gas supply of the high-capacity compression device and a second branch connected to the accessory circuit via at least one valve.

This point of divergence constitutes a division within the main circuit. When it circulates in the main circuit, the gas resulting from the evaporation of the cryogenic liquid is therefore routed either to the high-capacity compression device via the first branch, or to the accessory circuit via the second branch.

According to an optional feature of the invention, the valve is arranged between the divergence point and the low capacity compression device.

It is understood that when the gas resulting from the evaporation of the cryogenic liquid takes the second branch of the main circuit, it is intended to supply the low capacity compression device.

According to an optional feature of the invention, the storage and treatment installation comprises a branch configured to cool the second branch using cryogenic liquid taken from the tank.

This branch constitutes a cooling device for the second branch upstream of the valve; it thus makes it possible to cool the gas resulting from the evaporation of the liquid having circulated within the second branch of the main circuit. The branch opens, for example, between the valve and the low-capacity compression device.

According to an optional feature of the invention, the storage and treatment installation comprises an auxiliary circuit dedicated to filling the tank with cryogenic liquid, this auxiliary circuit being configured to connect the storage terminal to a bottom zone of the tank.

The tank bottom area corresponds to a lower portion of the tank, which is intended to receive and store the cryogenic liquid. This tank bottom area corresponds, for example, to a space located between a bottom wall of the tank and a plane substantially parallel to the bottom wall extending one meter above it.

The invention further relates to a floating structure intended for the transport and/or storage of cryogenic liquid and gas resulting from the evaporation of the cryogenic liquid, comprising a storage and treatment installation as mentioned above.

Other characteristics, details and advantages of the invention will emerge more clearly from reading the description which follows on the one hand, and from examples of embodiment given for informational and non-limiting purposes with reference to the appended drawings on the other hand, in which:

illustrates, schematically, a storage and treatment installation according to the invention;

represents, according to a cutaway view, a floating structure comprising the storage and treatment facility for the .

The features, variants and different embodiments of the invention may be combined with each other, in various combinations, to the extent that they are not incompatible or mutually exclusive. In particular, variants of the invention may be imagined comprising only a selection of features described below in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage and/or to differentiate the invention from the prior art.

In the figures, elements common to several figures retain the same reference.

There thus illustrates, schematically, a storage and treatment installation 1 according to the invention, such a storage and treatment installation 1 being here integrated within a floating structure 2, such a floating structure 2 being represented in the . The storage and treatment facility 1 is configured for the circulation of cryogenic liquid LC on the one hand and gas resulting from the evaporation of the cryogenic liquid G on the other hand. The cryogenic liquid LC is stored in at least one tank 4 of the storage and treatment facility 1. Since the thermal insulation of the tank 4 is not perfect, part of the cryogenic liquid LC evaporates naturally and forms the gas resulting from the evaporation of the cryogenic liquid G. The tank 4 therefore comprises both the cryogenic liquid LC and the gas resulting from the evaporation of the cryogenic liquid G, a separation between these two fluids being shown in the by a dotted horizontal line.

The storage and treatment facility 1 has at least one tank 4 intended for storing the cryogenic liquid LC and the gas resulting from the evaporation of the cryogenic liquid G, the cryogenic liquid LC being, for example, methane. The storage and treatment facility 1 comprises, in the embodiment illustrated here, four tanks 4. It is understood that the description which follows in relation to one of these four tanks 4 is applicable to each of the other tanks 4.

The tank 4 is delimited by a bottom wall 6, which corresponds to its lowest wall. From this bottom wall 6 extends a tank bottom zone, which corresponds for example to a zone between this bottom wall 6 and a plane parallel to it and arranged at a distance of one meter from it. At least the tank bottom zone is intended for storing the cryogenic liquid LC. Conversely, the gas resulting from the evaporation of the cryogenic liquid G is stored in a ceiling of the tank 4, which corresponds to its highest portion. The ceiling of the tank 4 is here equipped with a gas dome 8, which is a portion of the tank 4 through which the gas resulting from the evaporation of the cryogenic liquid G is taken.

The storage and processing facility 1 is connected to a storage terminal 10 located on a coast. A cooperation between the floating structure 2 and this storage terminal 10 will be described in more detail later in connection with the . The storage terminal 10 can store both cryogenic liquid LC and gas resulting from the evaporation of the cryogenic liquid G. More particularly, the gas resulting from the evaporation of the cryogenic liquid G can be discharged from the tank 4 of the storage and treatment facility 1 to the storage terminal 10, and the cryogenic liquid LC can be loaded from the storage terminal 10 to the tank 4. Such loading of cryogenic liquid LC from the storage terminal 10 to the tank 4 is carried out via an auxiliary circuit 12, this auxiliary circuit 12 more precisely connecting the storage terminal 10 to the tank bottom zone. It is understood that the auxiliary circuit 12 is dedicated to filling the tank 4 with cryogenic liquid LC.

The discharge of the gas resulting from the evaporation of the cryogenic liquid G from the tank 4, for example with a view to filling it with cryogenic liquid LC, is carried out using a main circuit 14. This main circuit 14 makes it possible to connect the top of the tank 4 to the storage terminal 10.

The main circuit 14 opens into the tank 4; more particularly, it is connected to the gas dome 8 of this tank 4. The main circuit 14 comprises at least one conduit which extends from the gas dome 8 to a high-capacity compression device 16, such a high-capacity compression device 16 thus being interposed between the tank 4 and the storage terminal 10. The conduit participating in forming the main circuit 14 and within which the gas resulting from the evaporation of the cryogenic liquid G circulates has a diameter of between 300 and 600 millimeters. A heat exchanger can be arranged on the conduit of the main circuit 14 between the tank 4 and the high-capacity compression device 16, so as to ensure that a pressure and a temperature of the gas resulting from the evaporation of the cryogenic liquid G are adequate to supply this high-capacity compression device 16.

In some embodiments and as seen in the , the main circuit 14 comprises a point of divergence 18, which consists of a separation between a first branch 20 of the main circuit 14 and a second branch 22 of this main circuit 14. The first branch 20 corresponds to the portion of the main circuit 14 intended to supply the high-capacity compression device 16, as described above. Conversely, the second branch 22 is intended to supply a low-capacity compression device 24 of the storage and treatment installation 1, this low-capacity compression device 24 being arranged between the tank 4 and a consumer 26 of the storage and treatment installation 1.

The consumer 26 is for example an engine, and more precisely an electric generator of the DFDE (dual fuel diesel electric) type, that is to say a consumer aiming to ensure the electrical supply of the floating structure 2. The consumer 26 is configured to be able to use as fuel both cryogenic liquid LC and gas resulting from the evaporation of the cryogenic liquid G, alternately; it is understood that depending on its operating mode, the consumer 26 can be supplied either by cryogenic liquid LC or by gas resulting from the evaporation of the cryogenic liquid G.

When the consumer 26 uses gas resulting from the evaporation of the cryogenic liquid G as fuel, this gas resulting from the evaporation of the cryogenic liquid G can be conveyed to it via an accessory circuit 28 of the storage and treatment installation 1. According to the embodiments, the consumer 26 is thus supplied with gas resulting from the evaporation of the cryogenic liquid G either solely by the accessory circuit 28, or both by this accessory circuit 28 and by the second branch 22 of the main circuit 14 when this main circuit 14 has a point of divergence 18, or solely by this second branch 22.

The accessory circuit 28 is constituted by at least one pipe. This pipe has dimensions smaller than the pipe of the main circuit 14, so as to allow faster routing of the gas resulting from the evaporation of the cryogenic liquid G to the low-capacity compression device 24 and to the consumer 26 than if this gas resulting from the evaporation of the cryogenic liquid G took the main circuit 14. Faster routing of the gas resulting from the evaporation of the cryogenic liquid G makes it possible to limit pressure losses and its cooling, and therefore to supply it to the low-capacity compression device 24 at a temperature and pressure which are both adapted to the operation of this low-capacity compression device 24. For this purpose, the pipe of the accessory circuit 28 has for example a diameter of between 100 and 250 millimeters.

The accessory circuit 28 is further thermally insulated. Such thermal insulation of the accessory circuit 28 consists, for example, of a foam tube arranged around its pipe. Alternatively, the thermal insulation results from vacuum insulation, the pipe of the accessory circuit 28 being arranged for this purpose in a pipe of larger diameter in which a vacuum is applied. In this case, the pipe of the accessory circuit 28 and the pipe of larger diameter are arranged concentrically, the pipe of larger diameter surrounding the pipe of the accessory circuit 28 within which the gas resulting from the evaporation of the cryogenic liquid G circulates.

As illustrated in the alternative embodiment shown in , the accessory circuit 28 is connected to the main circuit 14 at the outlet of the ceiling of the tank 4. More particularly, the main circuit 14 is connected to the gas dome 8, the accessory circuit 28 being connected to the main circuit 14 in the vicinity of this gas dome 8. It is thus understood that the gas resulting from the evaporation of the cryogenic liquid G intended to be conveyed to the low-capacity compression device 24 and to the consumer 24 circulates in a conduit of the main circuit 14 before taking the accessory circuit 28. The gas resulting from the evaporation of the cryogenic liquid G, whether it is intended for the low-capacity compression device 24 or the high-capacity compression device 16, circulates at least partially within the main circuit 14. In other words, the gas resulting from the evaporation of the cryogenic liquid G takes the same pipe 30 connected to the gas dome 8 independently of its compression device 16, 24 of destination. The connection between the main circuit 14 and the accessory circuit 28 is made by means of a valve, here a three-way valve 32, which is arranged at a separation between these two circuits 14, 28. The three-way valve 32 is thus arranged on the common pipe 30. Alternatively, the three-way valve 32 could be replaced by two two-way valves.

However, without departing from the scope of the invention and although this is not shown in the figures, it is possible to envisage alternative embodiments in which the accessory circuit 28 is directly connected to the gas dome 8, i.e. this accessory circuit 28 is independent of the main circuit 16 in the vicinity of the outlet of the tank ceiling 4. In these alternative embodiments, the gas resulting from the evaporation of the cryogenic liquid G does not use a common pipe 30 for the main circuit 14 and the accessory circuit 16.

It follows from the above that the main circuit 14 and the accessory circuit 28 are, at least in part, arranged in parallel with each other. It is understood that the conduits of the main circuit 14 are distinct from the conduits of the accessory circuit 28 on at least a portion of the storage and treatment installation 1 between the tank 4 and one of the compression devices 16, 24. The main circuit 14 and the accessory circuit 28 are in parallel either from the gas dome 8 of the tank 4, for the variant embodiments where each of the two circuits 14, 28 is connected directly to this gas dome 8, or from the three-way valve 32 when the circuits 14, 28 have the common pipe 30 as is the case on the . Similarly, the main circuit 14 and the accessory circuit 28 are in parallel either for the remainder of the storage and treatment installation 1, or up to the point of divergence 18 when the main circuit 14 has the first branch 20 and the second branch 22.

For the embodiments in which the main circuit 14 is divided between the first branch 20 and the second branch 22, a valve, for example a three-way valve 34, is arranged between the second branch 22 and the accessory circuit 28. It is understood that this three-way valve 34 constitutes a junction point between the second branch 22 and the accessory circuit 28, which allows the main circuit 14 to supply gas resulting from the evaporation of the cryogenic liquid G to the consumer 26. The three-way valve 34 is for this purpose arranged between the divergence point 18 and the low-capacity compression device 24. Alternatively, the valve could comprise two two-way valves.

As mentioned above, the main circuit 14 is formed of at least one conduit having a larger diameter than a conduit participating in forming the accessory circuit 28. In order to ensure that the gas resulting from the evaporation of the cryogenic liquid G conveyed by the main circuit 14 is supplied to the low-capacity compression device 24 at a suitable temperature and pressure, the storage and treatment installation 1 comprises a branch 36 which cools the second branch 22 using the cryogenic liquid LC upstream of the three-way valve 34. This branch 36 extends more precisely between a first end connected to the second branch 22 in the vicinity of the three-way valve 34, and a second end opening into the tank 4. The end opening into the tank 4 is for example arranged in the vicinity of the bottom wall 6, within the tank bottom zone. This second end is here equipped with a pump 38, this pump 38 making it possible to suck up the cryogenic liquid LC to convey it to the second branch 22. The purpose of the branch 36 is to cool, using this cryogenic liquid LC, the gas resulting from the evaporation of the cryogenic liquid G having circulated within the main circuit 14 and its second branch 22. To do this, a heat exchanger is positioned between the second branch 22 and the branch 36, each of these branches 22, 36 constituting a pass of the heat exchanger.

Although not illustrated in the figures, the main circuit 14 may, as mentioned above, comprise a heat exchanger separate from the heat exchanger. This heat exchanger is then intended to adapt the temperature of the gas resulting from the evaporation of the cryogenic liquid G circulating within the main circuit 14 to supply it to the high-capacity compression device 16 at a temperature and pressure required for proper operation of this high-capacity compression device 16. Such a heat exchanger is thus arranged between the tank 4 and the high-capacity compression device 16, where appropriate between the three-way valve 32 and the high-capacity compression device 16.

Conversely, the accessory circuit 24 does not have a heat exchanger. It is thus connected directly to the low-capacity compression device 24, either from the gas dome 8 or from the three-way valve 32. Thus, the gas resulting from the evaporation of the cryogenic liquid G circulating within the accessory circuit 24 is not intended to gain calories other than those which would possibly result from its circulation within the pipe of the accessory circuit 28, such a gain in calories being further limited by the aforementioned thermal insulation of the accessory circuit 28. It is understood here that no heat exchange device is arranged on the accessory circuit 28. In particular, the main circuit 14 and the accessory circuit 28 are thermally independent. There is no exchange of calories between these two circuits 14, 28; for example, the main circuit 14 and the accessory circuit 28 do not constitute the passes of a heat exchanger which would be arranged between these two circuits 14, 18.

The implementation of the high-capacity compression device 16 and the implementation of the low-capacity compression device 24 depend on the operation carried out by the storage and treatment installation 1. The high-capacity compression device 16 and the low-capacity compression device 24 are for example both arranged in the same area of the floating structure 2, for example a compression room of this floating structure 2.

When a loading and/or unloading operation carried out within the storage and treatment facility 1 consists of unloading gas resulting from the evaporation of the cryogenic liquid G to the storage terminal 10, the high-capacity compression device 16 is in operation. In other words, the gas resulting from the evaporation of the cryogenic liquid G contained in the tank 4 is conveyed to the storage terminal 10 via the main circuit 14 and therefore via the high-capacity compression device 16.

During the discharge of the gas resulting from the evaporation of the cryogenic liquid G to the storage terminal 10, the low-capacity compression device 24 can also be implemented, for example to supply the consumer 26 in order to maintain the electrical functions of the floating structure 2. The low-capacity compression device 24 and the consumer 26 are for this purpose supplied indifferently either by the main circuit 14, or by the accessory circuit 28, or by these two circuits 14, 28 for the embodiments where the main circuit 14 comprises the second branch 22 which joins the accessory circuit 28.

Such an operation of unloading the gas resulting from the evaporation of the cryogenic liquid G may be simultaneous or prior to an operation of loading cryogenic liquid LC from the storage terminal 10 to the tank 4 of the storage and treatment installation 1, this loading operation then involving the annex circuit 12.

Outside of loading and/or unloading operations, i.e. in particular when the floating structure 2 is making a sea voyage, the high-capacity compression device 16 is stopped since it is no longer in fluid communication with the storage terminal 10. During such a sea voyage, only the low-capacity compression device 24 is implemented. This low-capacity compression device 24 is preferably supplied by the accessory circuit 28, but in certain embodiments both the main circuit 14 and the accessory circuit 28 supply the consumer 26 via the low-capacity compression device 24.

There represents the floating structure 2 comprising the tank 4, which is watertight and thermally insulated. It is generally prismatic in shape and is mounted in a double hull 40 of the floating structure 2, which may be a ship or a floating platform. A wall of the tank 4 comprises a primary watertight barrier intended to be in contact with the cryogenic liquid LC contained in the tank 4, a secondary watertight barrier arranged between the primary watertight barrier and the double hull 40 of the ship, and two thermally insulating barriers arranged respectively between the primary watertight barrier and the secondary watertight barrier and between the secondary watertight barrier and the double hull 40. In a simplified version, the floating structure 2 comprises a single hull.

Loading/unloading pipes 42 arranged on an upper deck of the floating structure 2 can be connected, by means of appropriate connectors, to the storage terminal 10 to transfer a cargo of cryogenic liquid LC and/or gas resulting from the evaporation of the cryogenic liquid G from or to the tank 4. It is understood that in the case of loading cryogenic liquid LC from the storage terminal 10 to the tank 4 of the floating structure 2, these loading/unloading pipes 42 correspond to the annex circuit 12, while in the case of unloading gas resulting from the evaporation of the cryogenic liquid G from the floating structure 2 to the storage terminal 10, the loading/unloading pipes 42 correspond to the main circuit 14.

There also illustrates the storage terminal 10 comprising a loading and/or unloading station 44, an underwater pipeline 46 and a land-based installation 48. The loading and/or unloading station 44 is a fixed offshore installation comprising a mobile arm 50 and a tower 52 which supports the mobile arm 50. The mobile arm 50 carries a bundle of insulated flexible pipes 54 which can be connected to the loading/unloading pipes 42. The mobile arm 50 is orientable and adapts to all sizes of floating structure 2. A connecting pipeline not shown extends inside the tower 52. The loading and/or unloading station 44 allows the loading and/or unloading of the floating structure 2 from or to the storage terminal 10, which comprises storage tanks 56 for the cryogenic liquid LC and/or the gas resulting from the evaporation of the cryogenic liquid G as well as connecting pipes 58 connected by the underwater pipe 46 to the loading and/or unloading station 44. The underwater pipe 46 allows the transfer of the cryogenic liquid LC and/or the gas resulting from the evaporation of the cryogenic liquid G between the loading and/or unloading station 44 and the floating structure 2 over a great distance, for example five kilometers, which makes it possible to keep the floating structure 2 at a great distance from the coast during the loading and/or unloading operations.

To generate the pressure necessary for the transfer of the cryogenic liquid LC and/or the gas resulting from the evaporation of the cryogenic liquid G, pumps on board the floating structure 2 and/or pumps equipping the land-based installation 48 and/or pumps equipping the loading and unloading station 44 are used.

The examples have been described for a floating structure 2; however, they are also applicable to a land structure.

The present invention thus proposes a storage and treatment installation in which gas resulting from the evaporation of a cryogenic liquid is conveyed to a consumer of the storage and treatment installation by a dedicated circuit, thus limiting the pressure losses of this gas resulting from the evaporation of the cryogenic liquid.

The present invention cannot, however, be limited to the means and configurations described and illustrated here and it also extends to any equivalent means and configuration as well as to any technically effective combination of such means.

Claims (13)

Installation for storing and treating a gas resulting from the evaporation of a cryogenic liquid (G), comprising at least one tank (4) configured to contain both the cryogenic liquid (LC) and the gas resulting from the evaporation of the cryogenic liquid (G), at least one consumer (26) which consumes a fuel prepared at least from the gas resulting from the evaporation of the cryogenic liquid (G), a high-capacity compression device (16) intended to be connected to a storage terminal (10) for the cryogenic liquid (LC) and a low-capacity compression device (24) which supplies the fuel to the consumer (26), the storage and treatment installation comprising a main circuit (14) connecting a roof of the tank (4) to the high-capacity compression device (16) and an accessory circuit (28) at least partly arranged fluidically in parallel with the main circuit (14), the accessory circuit (28) being configured to directly supply the gas resulting from the evaporation of the cryogenic liquid (G) to the low capacity compression device (24). Storage and treatment installation according to the preceding claim, in which the main circuit (14) and the accessory circuit (28) are thermally independent. Storage and treatment installation according to any one of the preceding claims, in which the accessory circuit (28) is connected to the main circuit (14) at the outlet of the tank (4). Storage and treatment installation according to the preceding claim, comprising at least one valve (32) arranged at a separation between the main circuit (14) and the accessory circuit (28). Storage and treatment installation according to any one of claims 1 and 2, in which the accessory circuit (28) is directly connected to a gas dome (8) of the tank (4). Storage and treatment installation according to any one of the preceding claims, in which a nominal diameter of the conduits forming the main circuit (14) is between 300 and 600 mm. Storage and treatment installation according to any one of the preceding claims, in which a nominal diameter of the pipes forming the accessory circuit (28) is between 100 and 250 mm. Storage and treatment installation according to any one of the preceding claims, in which the accessory circuit (28) is thermally insulated. Storage and treatment installation according to any one of the preceding claims, in which the main circuit (14) comprises a point of divergence (18) between a first branch (20) dedicated to the supply of gas resulting from the evaporation of the cryogenic liquid (G) from the high-capacity compression device (16) and a second branch (22) connected to the accessory circuit (28) via at least one valve (34). Storage and treatment installation according to the preceding claim, in which the valve (34) is arranged between the divergence point (18) and the low capacity compression device (24). Storage and treatment installation according to any one of the preceding claims in combination with claim 9, comprising a branch (36) configured to cool the second branch (22) from cryogenic liquid (LC) taken from the tank (4). Storage and treatment installation according to any one of the preceding claims, comprising an auxiliary circuit (12) dedicated to filling the tank (4) with cryogenic liquid (LC), this auxiliary circuit (12) being configured to connect the storage terminal (10) to a bottom zone of the tank (4). Floating structure (2) intended for the transport and/or storage of cryogenic liquid (LC) and gas resulting from the evaporation of the cryogenic liquid (G), comprising a storage and treatment installation (1) according to any one of the preceding claims.