Liquefied gas storage device

Abstract

A liquefied gas storage device, in particular for a liquefied gas carrier or for a land-based installation, comprising: - at least one liquefied gas storage reservoir (12) having a reservoir bottom (14) and a reservoir top plate (16) together defining a reservoir height (H), - means (20) for withdrawing gas in liquid and / or gaseous form from the at least one reservoir, and - means (10) for injecting gas in liquid form into the reservoir, characterized in that the gas injection means comprise at least one injector-mixer (10) located in an upper region of the reservoir extending between 60 and 100% of the reservoir height, measured from the reservoir bottom, and intended to be immersed in the liquefied gas contained in the reservoir.

Description

[0001] This application is a divisional application of the invention patent application with application number 201980048776.1, application date May 28, 2019, and invention title "Liquefied Gas Storage Device". Technical Field

[0002] The present invention relates in particular to a liquefied gas storage device, especially for liquefied gas transport vehicles or for land-based facilities. Background Technology

[0003] To facilitate the long-distance transport of gases, such as natural gas, the gas is typically liquefied (becoming liquefied natural gas - LNG) by cooling it to cryogenic temperatures, such as cooling it to 160°C at atmospheric pressure. The liquefied gas is then loaded into vehicles, such as LNG carriers and bunkering vessels.

[0004] To limit the evaporation of liquefied gases contained in ship storage tanks, the known practice is to store them under pressure in the tanks so as to shift along the vaporization curve of the liquefied gas under consideration, thereby increasing its vaporization temperature. The liquefied gas can thus be stored at a higher temperature, which results in limited evaporation.

[0005] However, natural evaporation of gases is unavoidable; this phenomenon is called NBOG, an abbreviation for Natural Boil-Off Gas (as opposed to Forced Boil-Off Gas, or FBOG). Naturally evaporating gases in a ship's storage tanks are typically used to power the ship's energy generation systems, designed to meet the energy demands of ship operation, particularly propulsion and / or the generation of electricity for onboard equipment.

[0006] In current technology, improvements to storage tanks have led to increasingly lower natural evaporation rates (BOR) of liquefied gases, while increasing the mechanical efficiency of ships. As a result, there is a significant difference between the amount of gas naturally generated by evaporation and the amount required by the ship's facilities. This excess gas is particularly significant when the ship's consumption is low—that is, when the ship is idling, in a standby state, or under malfunction (e.g., affecting processing equipment or consumption is not zero).

[0007] Excess naturally evaporated gas (NBOG) is then recondensed and reinjected into the storage tank. This is done using a reliquefaction or recondensation device, which converts the NBOG into liquefied gas and then reinjects it into the storage tank.

[0008] NBOG generation can also be reduced by lowering the temperature of the gas top plate above the liquid-gas interface contained in the reservoir. To do this, the liquefied gas can be extracted, cooled (or supercooled, since it is already cold), and then reinjected into the reservoir via a liquefied gas spray bar in the top gas.

[0009] This allows for pressure control within the storage tank via the BOG recondensed in the gas top plate (first objective). It also allows for temperature control of the liquefied gas to facilitate the delivery of "cold" LNG (second objective). In practice, in the case of LNG carriers or bunkering vessels, the maximum temperature of the LNG to be delivered can be determined by the receiving terminal or the vessel.

[0010] The primary objective is to facilitate LNG transfer operations between multiple storage units within the same facility and / or between multiple storage units across multiple facilities, in order to condense excess gas generated during the LNG transfer operation so that the transfer can be completed within a given timeframe. The primary objective may also address the need for loaded or nearly empty storage units (if the objective is pressure control).

[0011] The second objective is to respond to the bunkering vessel's requirement to receive relatively cold LNG in order to maintain a safety margin relative to the safety valves. Therefore, after the fuel loading operation, the charterer will want to keep its cargo as cold as possible, or even cooled, to comply with the contract with the LNG-powered vessel. Consequently, it will use its own subcooling equipment to cool the LNG and prevent pressure drops.

[0012] One of the objectives of this invention is to optimize storage in liquefied gas reservoirs according to desired needs, particularly for controlling pressure or liquid temperature. Summary of the Invention

[0013] According to a first aspect, the present invention provides a liquefied gas storage device, particularly for liquefied gas transport vehicles or for land-based facilities, the liquefied gas storage device comprising:

[0014] - At least one liquefied gas storage container having a storage container bottom and a storage container top plate that together define the height of the container.

[0015] - Devices for extracting liquid and / or gaseous forms of gas from the reservoir, and

[0016] - A device for injecting liquid gas into the reservoir, preferably connected to a gas extraction device.

[0017] The gas injection device is characterized in that it includes at least one syringe-mixer located in a lower region of the reservoir extending between 0 and 25% of the reservoir height, preferably between 0 and 15%, more preferably between 0 and 10%, the reservoir height being measured from the bottom of the reservoir, and the syringe-mixer being intended to be immersed in the liquefied gas contained in the reservoir.

[0018] Preferably, the at least one syringe-mixer is configured to inject a liquid gas stream in a direction inclined upward relative to the horizontal plane at an angle α. The angle α can be from 5° to 45°, preferably from 5° to 30°, and more preferably from 5° to 20°. In variations, the angle α can be from 5° to 85°, preferably from 15° to 75°, and more preferably from 30° to 60°.

[0019] According to a second aspect, the present invention provides a liquefied gas storage device, particularly for liquefied gas transport vehicles or for land-based facilities, the liquefied gas storage device comprising:

[0020] - At least one liquefied gas storage container having a storage container bottom and a storage container top plate that together define the height of the container.

[0021] Devices for extracting liquid and / or gaseous gases from at least one of the reservoirs, and

[0022] - A device for injecting liquid gas into the reservoir, preferably connected to a gas extraction device.

[0023] The gas injection device is characterized by comprising at least one syringe-mixer located in the upper region of the reservoir extending between 60% and 100% of the reservoir height, or even between 75% and 100%, preferably between 60% and 98%, more preferably between 65% and 95%, or even more preferably between 65% and 80%, or 80% and 95%, the reservoir height being measured from the bottom of the reservoir, and the syringe-mixer being intended to be immersed in the liquefied gas contained in the reservoir.

[0024] Preferably, at least one syringe-mixer is configured to inject a liquid gas stream in a direction inclined downwards at an angle β relative to the horizontal plane. The angle β can be from 5° to 45°, preferably from 5° to 30°, and more preferably from 5° to 20°. In variations, the angle β can be from 5° to 85°, preferably from 15° to 75°, and more preferably from 30° to 60°.

[0025] Advantageously, the at least one syringe-mixer is fixed to the wall of the reservoir. Preferably, the reservoir includes a vertical longitudinal sidewall connected to the top plate of the reservoir via an inclined wall, and the at least one syringe-mixer is fixed to a region for connecting the vertical longitudinal wall to the inclined wall. The at least one syringe-mixer may be fixed to a thickened metal plate and / or at least one wooden block in the connection region. This plate may form part of the membrane of the reservoir, and therefore, like the membrane, the plate is in contact with the liquefied gas contained in the reservoir (when the liquefied gas is present in the reservoir, or at least in the absence of leakage). The wooden block may be located between the membrane and the hull of the vessel.

[0026] In each of the above aspects, the key principle sought is the ability to reinject liquefied gas into the liquid contained in the reservoir, rather than into the top gas, which may or may not be pre-subcooled. In practice, reinjecting most of the cooling power into the top gas would result in a significant pressure drop and cooling of the top gas, forcing the heat flow back into the upper portion of the reservoir. Much of the liquefied gas reinjected into the top gas would unnecessarily vaporize, limiting the cooling power supplied to the liquid. This is particularly true because the latter would only be distributed to the free surface of the liquid, leading to slower diffusion kinetics. Instead, the invention proposes injecting cooling power directly into the liquid below the free surface to reduce the impact on the temperature and pressure of the top gas. Furthermore, injecting liquefied gas below the free surface allows for mixing and agitation effects to be achieved by adjusting the liquid kinetics, orientation, and height at the injector-mixer outlet. The invention also relates to cases where the liquefied gas does not need to be subcooled before injection into the reservoir. The primary function of the injected liquefied gas would then be to mix the liquefied gas contained in the reservoir. This is particularly useful for limiting the evaporation of liquefied gases, especially when supercooled liquefied gases are poured into the bottom of the reservoir, which are then obtained through the reliquefaction of the evaporated gas. The nitrogen content forced to evaporate from the reservoir is much higher than that of naturally evaporating liquid (because nitrogen is more volatile than methane). The evaporated gas is liquefied by the reliquefaction device and returned to the bottom of the reservoir. Therefore, the condensate is much heavier than the surrounding liquefied gas (because it is nitrogen-rich, but also colder). The nitrogen-enriched liquid accumulates at the bottom of the reservoir. As it naturally heats up, nitrogen bubbles vaporize and rise to the surface, thus enriching the top gas with nitrogen. However, nitrogen is difficult to condense, which reduces the capacity of the liquefier and makes it difficult to control the pressure in the reservoir. This phenomenon is exacerbated when the reservoir is nearly empty because the nitrogen bubbles do not have time to re-dissolve during their rise to the surface. This is why such devices are never considered for injection via a spray bar at the top of the reservoir due to the risk of nitrogen enrichment. When using a nearly empty reservoir, this phenomenon leads to aging of the bottom layer, which limits the bottom layer's ability to cool the reservoir before the next load.

[0027] The invention also relates to the case where the liquefied gas is superheated before being injected into the reservoir. The primary function of the injected liquefied gas will be to mix with the liquefied gas contained in the reservoir. This is particularly useful for limiting the evaporation of the superheated liquefied gas, especially when it is poured into the bottom of the reservoir. The superheated liquefied gas is hotter and therefore lighter than the surrounding (cooler) liquefied gas, and it will evaporate without a mixing device, even if injected at the bottom of the reservoir. In fact, being lighter, it will rise in the cooler and therefore heavier surrounding liquid until it evaporates when its hydrostatic pressure becomes below its bubble point pressure. This is especially true when the liquid level in the reservoir is low, because the hydrostatic pressure at the bottom of the reservoir is lower compared to higher liquid levels. Using a mixing device via the Venturi effect, suction, entrainment, etc., is particularly suitable for injecting the superheated liquefied gas, as it allows for at least a 4-fold dilution. The superheated liquefied gas is obtained by recondensing (i.e., mixing) the pressurized evaporated gas with the liquefied gas from the reservoir. Superheated liquefied gas is typically vaporized and injected into the land-based gas network. If the land-based gas network requires the vaporization unit to stop sending gas to the network, the superheated liquefied gas can be returned to the storage tank via a mixing device, while limiting the natural evaporation of the gas stored in the tank. Without a mixing device, the evaporation generated by injecting the superheated liquefied gas into the storage tank produces additional evaporation, which is added to the natural evaporation and must be recondensed before being reinjected into the storage tank. This results in accelerated heating of the liquefied gas contained in the storage tank, and therefore a faster pressure rise compared to using a mixing device.

[0028] Here, the injection of liquefied gas is carried out by a syringe-mixer, which is configured to inject a stream of liquefied gas and mix it with a liquid (which is injected into the liquid through the Venturi effect, suction, entrainment, etc.).

[0029] The device according to the invention may also have one or more of the following features, which may be considered independently or in combination with each other:

[0030] - The at least one syringe-mixer is positioned as close as possible to the longitudinal sidewall of the reservoir; in this application, the terms "closest to" or "closest to" should be understood as meaning a distance of less than one meter, and preferably less than or equal to 0.5 meters, or even less.

[0031] The injection device includes at least one horizontal row of syringes (one or more) and mixers (one or more) configured to inject liquid-gas streams in parallel or different directions.

[0032] The injection device includes at least two horizontal rows of syringe-mixers arranged on and / or along the two longitudinal sidewalls of the reservoir.

[0033] The gas injection device is connected via a reliquefaction device to a device for extracting gas from the reservoir or another reservoir.

[0034] The reliquefaction device is configured to condense the evaporated gas drawn from the reservoir or another reservoir, and then pressurize it by heat exchange with the liquefied gas drawn from the reservoir or another reservoir.

[0035] - The gas injection device is connected via a subcooling device to a device for extracting liquid gas from the reservoir or another reservoir.

[0036] - The extraction device is configured to extract liquid gas from the lower region.

[0037] - The extraction device includes at least one pump and piping, located in the reservoir or another reservoir and intended to be at least partially immersed in the liquefied gas.

[0038] The pump is configured to have a variable flow rate or rotor speed.

[0039] - The reservoir is of the "full fill" type and is configured to be filled to any liquid level.

[0040] - The reservoir is of the "restricted fill" type and is configured to fill only to 10% or less, or 70% or more.

[0041] The extraction device and the injection device are located in the reservoir and are connected to each other via pipes that are entirely located within the reservoir.

[0042] - The conduit extends at least partially, substantially parallel to and close to the bottom wall of the reservoir, and preferably extends to at least one side wall of the reservoir.

[0043] -When the extraction device is located in the center and bottom of the reservoir, the conduit can extend in the opposite direction along the bottom wall of the reservoir to the side wall of the reservoir.

[0044] - Pipes can be configured to match the specific shape of the bottom of the reservoir, especially the shape of any connection bevels between the bottom and sidewalls of the reservoir.

[0045] The extraction device and the injection device are positioned perpendicular to the liquid dome of the reservoir, and are preferably equipped with a pump tower accessible through the liquid dome.

[0046] The at least one syringe-mixer is connected to and supported by the liquid column in the pump tower.

[0047] The syringe-mixer includes a main conduit for allowing a main jet of liquid to pass through, and a secondary conduit for forcing a secondary jet of liquid to pass through via the Venturi effect.

[0048] - The injection device or even the extraction device is positioned relative to each other and configured such that they generate back pressure and suction effects in the reservoir, which produce a predetermined stirring cycle of liquefied gas in the reservoir.

[0049] The present invention also relates to a liquefied gas transport vehicle comprising at least one device as described above, wherein there is no supercooling and reliquefaction device between the extraction device and the injection device, and the reservoir is of the "full fill" type and configured to be filled to any liquid level.

[0050] The present invention also relates to a liquefied gas transport vehicle comprising at least one device as described above, the device including a supercooling and / or reliquefaction device between the extraction device and the injection device, the reservoir being of a "fully filled" or "restricted filled" type.

[0051] The present invention also relates to a liquefied gas transport vehicle comprising at least one device as described above, wherein there is no supercooling and reliquefaction device between the extraction device and the injection device, and the reservoir is of the "restricted filling" type and configured to be filled only to 10% and less or 70% and more.

[0052] The present invention also relates to a liquefied gas transport vehicle comprising at least one device as described above, the device including a supercooling and / or reliquefaction device between the extraction device and the injection device, the reservoir being of the "restricted filling" type and configured to be filled only to 10% and less or 70% and more.

[0053] When injection is carried into the lower portion of the reservoir, the injection device is oriented upwards to create back pressure and suction effects in both a nearly empty (“ballast”) and a nearly full (“full”) reservoir, and to generate a stirring cycle. In the case of a nearly empty reservoir (liquid at the bottom), this configuration allows the liquid to be stirred along most of the reservoir's length (at a sufficiently small angle, i.e., close to the horizontal), but without dispersing the liquid in the air gap, as this would cool the gas and thus increase heat transfer.

[0054] An angle that is too large (i.e., close to the vertical) will cause the injected liquid to accumulate near the syringe and extraction device, and will cause the injected liquid to be resampled toward the supercooled device, which poses a risk of the supercooled liquid freezing (in the case of a combination with a supercooled device located between the extraction and injection devices).

[0055] With the reservoir nearly full, this configuration allows for stirring of the liquid across most of the reservoir's height (at a sufficiently large angle, i.e., close to the vertical), resulting in a uniform liquid temperature throughout the entire height. An angle that is too small (i.e., close to horizontal) will cause an accumulation of injected liquid near the extraction device at the bottom of the reservoir, and will cause the injected liquid to be resampled towards the supercooled device, posing a risk of supercooled liquid freezing (in the case of a supercooled device located between the extraction and injection devices). There is also a risk of sudden pressure drops in the reservoir, even with the supercooled liquid accumulating uniformly at the bottom; if the pressure drops below atmospheric pressure, the safety valve may open.

[0056] The present invention also relates to a method for injecting a gas in liquid form into a storage vessel of a ship as described above.

[0057] According to the first embodiment, injection is performed when the “limited-fill” reservoir is filled to 10% or less (in the lower region).

[0058] According to a variant embodiment, injection is performed when the "fully filled" reservoir has any fill level, the injection angle (in the lower region) is independent of the fill level, and the injection rate is controlled according to the fill level. Preferably, the larger the volume of liquid in the reservoir, the greater the injection rate.

[0059] The present invention also relates to a method for injecting gas in liquid form into a reservoir of a ship as described above, wherein the injection is carried out in the upper region when the "restricted fill" reservoir is filled to 70% or higher.

[0060] The present invention also relates to a method for injecting a gas in liquid form into a storage tank of a ship as described above, wherein the injection into the storage tank is configured to prevent the heated liquefied gas from rising along the longitudinal sidewall of the storage tank.

[0061] The present invention also relates to a method for injecting a gas in liquid form into a storage vessel of a ship as described above, wherein the injected liquefied gas has a temperature lower than that of the liquefied gas contained in the storage vessel.

[0062] Advantageously, the injection device, or even the extraction device, is controlled to generate back pressure and suction effects in the reservoir, which produce a predetermined stirring cycle of the liquefied gas within the reservoir. Advantageously, the stirring cycle is designed such that the liquefied gas circulates substantially parallel to and close to the liquid-gas interface in the reservoir. This limits the risk of forming a hot liquid layer at the interface, and thus limits the risk of liquefied gas evaporation.

[0063] In this application,

[0064] - "Storage container" means any storage container with an internal liquefied gas storage capacity greater than 100 m3, preferably greater than 1000 m3, or even 10,000 m3, or even 20,000 m3; and / or any storage container configured to store liquefied gas at a temperature of -163°C or lower.

[0065] - "Fully filled" type storage tanks refer to storage tanks configured to store any volume of liquefied gas, for example, they can occupy 50% of their total internal volume; this type of storage tank is commonly found on ships of the FSRU (Floating Storage and Regasification Unit), ST (Shoreside Storage Unit), GBS (Gravity Foundation Structure), LBV (LNG Bunkering Vessel), and LFS (LNG Fueling Vessel) types.

[0066] - A "restricted-fill" type of storage tank refers to a tank configured to store liquefied gas at 10% or less and more than 70% of its volume; therefore, especially for safety reasons, it cannot store moderate amounts of liquefied gas, such as 50% of its total internal volume. This is because LNG carriers are susceptible to transport conditions during voyages that can cause fluctuations in the liquefied gas content of the storage tank. LNGC-type vessels (LNG carriers) are typically equipped with this type of storage tank.

[0067] - "Ships" refers to any unit used for the maritime transport of liquefied gases, such as LNG carriers, bunkering vessels, etc.

[0068] - A "reliquefaction device" or "recondensation device" refers to a device configured to cause the condensation of a gas and thus convert that gas into a liquefied gas, typically BOG or NBOG; they may include, for example, devices for compressing the gas under temperature and pressure conditions that allow for gas condensation.

[0069] - A "supercooling" device refers to a device configured to further cool a liquefied gas that is normally at -163°C or lower, such supercooling as to lower the temperature of the liquefied gas by, for example, about 10°C; a supercooling device includes, for example, devices for evaporating or vaporizing the liquefied gas to generate cooling energy, and devices for exchanging heat with the liquefied gas so that the liquefied gas is supercooled by the energy.

[0070] The concepts of “up” and “down” or “upper” and “lower” are assessed relative to the ship’s usual position when landing and floating on the water, i.e., its usual position during operation, and more generally relative to the center of the earth (the top is farther from the center of the earth than the bottom). Attached Figure Description

[0071] The invention will be better understood by reading the following description, given by way of non-limiting example and with reference to the accompanying drawings, and other details, features and advantages of the invention will be more clearly presented, in which:

[0072] Figure 1 This is a schematic longitudinal cross-sectional view of a first embodiment of a liquefied gas storage device according to the present invention.

[0073] Figure 2 yes Figure 1 A schematic cross-sectional view,

[0074] Figure 3 yes Figure 1 A magnified view,

[0075] Figure 4 This is a schematic longitudinal cross-sectional view of a second embodiment of a liquefied gas storage device according to the present invention.

[0076] Figure 5 yes Figure 4 A schematic cross-sectional view,

[0077] Figure 6 yes Figure 4 A magnified view,

[0078] Figure 7 These are schematic perspective and cross-sectional views of a liquefied gas storage device.

[0079] Figure 8 This is a schematic perspective view of the connection area of ​​the storage container's walls, such as... Figure 7 storage device,

[0080] Figure 9 and 10 It is a very schematic partial view of a storage device with different geometry.

[0081] Figure 11 and 12 This is a very schematic cross-sectional view of a variant embodiment of the device according to the invention. Figure 9 A cross-sectional view of the device at its midpoint is shown. Figure 10 Cross-sectional views of each longitudinal end of the device are shown.

[0082] Figure 13 This is a very schematic top view of a variant embodiment of the device according to the invention.

[0083] Figures 14 to 26 This is a very schematic cross-sectional view of a variant embodiment of the device according to the invention.

[0084] Figure 27 and 28 These are schematic cross-sectional views and schematic perspective views of an exemplary embodiment of the syringe-mixer, respectively.

[0085] Figure 29 This is a block diagram illustrating several embodiments of the ship and method according to the present invention.

[0086] Figure 30 and 31 It is similar to Figure 4 The views show the same reservoir in two states: one in a "ballasted state" and thus filled with liquid heel, and the other in a "full-loaded state" and almost completely filled. Detailed Implementation

[0087] As mentioned earlier, the temperature and pressure in a liquefied gas (LNG) storage tank can be specifically controlled to control the generation of NBOG in the storage tank.

[0088] Liquefied gas storage devices, particularly liquefied gas storage devices for liquefied gas transport vehicles, typically include:

[0089] - At least one liquefied gas storage device

[0090] - Devices for extracting liquid and / or gaseous gases from a storage container, and

[0091] - A device for injecting liquid gas into a reservoir, which is connected to a gas extraction device.

[0092] As part of the first objective mentioned above, the overhead gas is cooled using a subcooled LNG spray bar. LNG is extracted by the extraction device, subcooled by the subcooling device, and then injected by the bar (injection device) at the top of the reservoir. By maximizing the exchange surface between the droplets and the gas to induce condensation, the spraying allows for direct influence on the temperature and pressure of the overhead gas.

[0093] In practice, there are usually two spray bars that are identical: they are usually used simultaneously for initial cooling, while a single bar allows for normal cooling before loading (under ballast conditions).

[0094] If this device is used in a full storage tank, the supercooled LNG is mainly sprayed at the liquid-gas interface, which is not very suitable if the purpose is to affect the temperature of the liquid over the entire height of the storage tank and therefore the entire liquid volume.

[0095] If one or two rods are used under ballast conditions (with a reservoir containing liquid at the bottom), the temperature of the gas above (including the top plate) will be very cold (close to the equilibrium point = dew point temperature), and the heat flow from the outside through the insulation layer will therefore increase.

[0096] Without the use of a rod-sprayed subcooled gas system, the upper gas layer exhibits significant temperature stratification (hotter gas concentrates at the top, and colder gas concentrates at the bottom), which reduces evaporation and thus reduces the cooling power required to control the pressure and temperature within the storage tank. If a subcooling device is used under ballast conditions while the upper gas is already warmed, the spraying of the subcooled liquid, in addition to increasing heat flux, will also cause an increase in storage tank pressure because the dispersed LNG evaporates as it cools the insulation of the heated storage tank.

[0097] In the case of the second objective, namely, controlling or even cooling the stored LNG, it is ideal to re-inject the subcooled LNG into the storage tank. However, the subcooled LNG would return directly to the storage tank without mixing with the LNG already present in the tank. Furthermore, LNG subcooled by approximately 10°C would be heavier than the LNG in the storage tank and would be difficult to mix with. If the subcooled LNG is re-injected at the bottom of the storage tank, it will concentrate at the bottom and can be directly extracted again via the aforementioned extraction device, which would adversely affect the efficiency of subcooling. In practice, this would mean extracting already subcooled LNG, which would be overcooled because the output temperature of the subcooling device is limited to avoid LNG freezing (primarily heavy compounds). Therefore, it is necessary to reduce the instantaneous power of the subcooling device. However, in order to avoid limiting this power (and avoid the recirculation of subcooled LNG) and reduce the power consumption of the equipment (avoiding the cooling of the gas above), the present invention proposes injecting the subcooled LNG below the liquid-gas interface via at least one syringe-mixer.

[0098] Figures 1 to 3 One aspect of the invention is illustrated, wherein the gas injection device includes at least one syringe-mixer 10 located in the upper region of a reservoir 12, extending between 60% and 100% of the height of the reservoir as measured from its bottom 14. The height of the reservoir 12 is measured between the bottom 14 and the top plate 16 of the reservoir. Reference numeral 18 indicates a liquid-gas interface or free surface of liquefied gas in the reservoir, where the liquid formed from the liquefied gas is heavier and therefore below the gas above, which is formed by the natural evaporation of the liquefied gas.

[0099] In addition to the reservoir 12 and the syringe-mixer 10, the liquefied gas storage device also includes a device for extracting the gas, which is in liquid form. The extraction device includes a pump 20, which is immersed in the liquefied gas and preferably located at the bottom of the reservoir. The liquefied gas can be extracted and injected into the same reservoir or into another reservoir.

[0100] Pump 20 is connected to syringe-mixer 10 directly or via subcooling device 22. The subcooling device may be configured to reduce the temperature of the liquefied gas pumped by the pump by approximately 10°.

[0101] The reservoir 12 can be of the "fully filled" or "restricted filled" type. In both cases, when filled with liquefied gas (excluding the liquefied gas residue at the bottom of the reservoir), it is filled to at least 70% of its volume. In practice, it is filled to 95% or greater of its volume, preferably 98.5%.

[0102] The syringe-mixer 10 is positioned and designed to inject liquefied gas extracted (and possibly supercooled) below the interface 18, thereby mixing the liquefied gas stream with the liquefied gas contained in the reservoir 12.

[0103] Advantageously, the syringe-mixer 10 is configured to inject a stream of liquefied gas in a direction inclined downward at an angle β relative to the horizontal plane. Figure 3 The angle β is, for example, 5° to 85°, preferably 15° to 75°, and more preferably 30° to 60°.

[0104] This allows for the liquefied gas to be mixed within the storage tank over virtually the entire height and the maximum possible distance, such as... Figure 1 The arrow in the diagram is shown schematically.

[0105] In the case of injecting supercooled or superheated liquefied gas, that is, injecting from the aforementioned supercooling device or recondenser, the syringe-mixer (one or more) can be advantageously fixed to the pump tower.

[0106] The reservoir 12 has a generally parallelepiped and elongated shape, but it can also have beveled angles, such as... Figure 1 and 2 As shown. The reservoir 12 includes a rear longitudinal end 12a and a front longitudinal end 12b, where the terms "rear" and "front" refer to the rear and front portions of the vehicle and its direction of travel. The reservoir also includes longitudinal sidewalls 12c.

[0107] In the example shown, the pump 20 and the syringe-mixer 10 are located at the rear end 12a of the reservoir 12.

[0108] The syringe-mixer 10 is configured to inject a forward flow of liquefied gas to promote good mixing of the liquefied gas in the reservoir. In the case of supercooled liquefied gas, it will be colder and therefore heavier than the liquefied gas at the point of injection, justifying positioning it slightly below the surface and oriented slightly downward at a small angle β in the upper portion of the reservoir to mix the front of the reservoir as much as possible. This allows for limiting the recirculation of the supercooled liquefied gas to the pump 20 and limiting the spraying of the reservoir wall opposite the syringe-mixer 10. Furthermore, since the density of the supercooled liquefied gas is slightly greater than that of the liquefied gas in the reservoir and therefore flows downward slowly, injection at the top of the reservoir further facilitates mixing by diffusion due to gravity. Therefore, when the reservoir is loaded, an injection just below the nominal liquid level, but sufficiently below the free surface, is sought to avoid drawing gas from the top gas, especially by means of the Venturi effect.

[0109] Pump 20 and syringe-mixer 10 can be positioned as a "liquid dome" substantially perpendicular to the reservoir, schematically indicated by the capital letter LD. In this configuration, pump 20 and syringe-mixer 10 can be connected to vertical pipes of a "pump tower." These pipes, in turn, support syringe 10.

[0110] Alternatively, the syringe-mixer 10 can be fixed to one side of the reservoir 12. Figure 7 A more precise example of the general shape of a reservoir 12 for storing liquefied gas is shown. The reservoir includes longitudinal sidewalls 12c, which are vertical and connected to the top plate 16 and the bottom 14 of the reservoir via inclined walls 12d and 12e, respectively. The dimensions of walls 12c, 12d, and 12e are variable, such as... Figure 9 and 10 As shown schematically. In these figures, reference numeral H indicates the height of the aforementioned reservoir, measured between the reservoir bottom 14 and the reservoir top plate 16. H is, for example, greater than or equal to 15m, and can be, for example, 27m.

[0111] The reservoir 12 is typically membrane-type, meaning its walls 12c, 12d, and 12e, as well as its bottom 14, are formed by a series of layers extending from the inside of the reservoir outwards, including, for example, a metal plate membrane, a heat insulation layer, another metal plate membrane, a heat insulation layer, and then the hull. In the connection areas of walls 12c, 12d, and 12e, for example, by… Figure 7 In the area indicated by the arrow, the reservoir is reinforced by a structure comprising a wooden block 30 and a metal reinforcement 32 made of a metal plate, which is thicker than the metal plate used for the membrane.

[0112] The reinforcement 32 may form part of the membrane of the reservoir, which is in contact with the liquefied gas contained in the reservoir. The reservoir may include a single membrane, with the reinforcement 32 forming part of that membrane, or the reservoir may include two membranes, a primary membrane and a secondary membrane, with an insulating layer placed between them, and the reinforcement 32 forming part of the primary layer and thus intended to be in contact with the liquefied gas.

[0113] Wooden block 30 can be located between the (primary) membrane of the reservoir and the hull of the ship.

[0114] The syringe-mixer 10 of the device can be fixed to the reservoir 12 in a connection area, such as the connection area between the side wall 12c and the inclined wall 12d. Figure 9 and 10 As shown schematically.

[0115] As mentioned above Figure 1 and 3 As mentioned, the syringe-mixer 10 is positioned such that it can produce an optimal volume of liquefied gas mixture in the reservoir. The power of the syringe-mixer—that is, the flow rate of the liquid it can deliver—depends particularly on the power of the pump 20. Advantageously, this pump is one already assembled into the reservoir, especially the aforementioned pump tower, and therefore has a limited power, for example less than or equal to 100 m³ / h, or for example less than or equal to 60 m³ / h.

[0116] Pumps can be of the type with variable speed and therefore variable flow rate. This in particular allows the power of the pump, and therefore the flow rate of the liquid injected by the syringe-mixer, to be matched with the volume of liquefied gas in the reservoir and therefore the fill level of the reservoir.

[0117] To remedy this and allow for mixing of the total volume of liquefied gas in the reservoir, the reservoir can be equipped with multiple syringe-mixers 10.

[0118] exist Figures 9 to 20 In all the concepts shown, that is, where the reservoir-mixer rod is located at the top of the reservoir, below the liquid surface, the syringe-mixer is advantageously positioned close to the vertical wall of the reservoir, because one of the purposes is to prevent the LNG heated by the vertical wall from rising. In reality, the LNG in the reservoir is heated near the vertical wall. When it becomes hotter than the surrounding LNG, it becomes lighter and therefore rises along the vertical wall. Figure 13As shown, this figure is a top view of the reservoir, where the annular space in contact with the vertical wall is where heated LNG rises. Without a mixing device, although the deeper LNG is colder than the surface LNG, the heated LNG reaches the surface and forms a hotter liquid layer there, which preferably evaporates. This evaporation increases the pressure in the reservoir. Therefore, positioning the syringe(s)-mixer(s) rod in the liquid in the upper portion prevents the heated liquid from rising and prevents the formation of a hot liquid layer on the surface.

[0119] Figure 13 An exemplary reservoir 12 is shown, equipped with a plurality of syringe-mixers 10, arranged in two horizontal rows on two longitudinal sides of the reservoir. Viewed from above, the reservoir is indicated by reference numeral LD ​​for a liquid dome and reference numeral GD for a gas dome. Line T1 represents the connection region between the inclined wall 12d and the top plate 16 of the reservoir, while line T2 represents the connection region between the inclined wall 12d and the side wall 12c. The syringe-mixers 10 are uniformly distributed along the reservoir in this region.

[0120] The reservoir or syringe-mixer 10 may have similar or different orientations. Figure 13 In one embodiment, the two syringe-mixer 10 located at the longitudinal end of the reservoir in each row are oriented toward the bottom of the reservoir at an angle βmin, for example, between 0° and 45°. Figure 12 The angle is preferably 0° to 30°, more preferably 5° to 15°. This angle allows for as much mixing of the liquefied gas as possible near the vertical transverse wall, as it is close to the vertical surface where the liquefied gas is heated and rises toward the surface to form a hot liquid layer (the formation of which should be avoided). Other syringe-mixers located between the syringe-mixers at the longitudinal ends of the reservoir in each row are oriented at an angle βmax toward the bottom of the reservoir, which is greater than βmin and, for example, 45° to 90°, preferably 70° to 90°, more preferably 80° to 85°. Figure 11 ).

[0121] As in Figure 11 and 12 As can be seen, it is best to control the angle β to minimize the amount of liquefied gas in the reservoir and maximize the amount of liquefied gas in contact with the vertical wall. If the angle is too small, and the syringe-mixer injects the liquefied gas directly toward the center of the reservoir, the risk is that a large amount of central liquefied gas from the reservoir will be mixed (schematically indicated by reference numeral V). However, mixing a large amount of liquefied gas requires high pumping power, which has the undesirable effect of reheating the liquefied gas and thus increasing the pressure in the reservoir more quickly.

[0122] exist Figure 11In this case, the liquid surface layer is drawn up and discharged at a depth to mix with the cargo. The downward tilt of the syringe-mixer 10 allows this liquid surface layer to be drawn up and mixed in small quantities. The syringe-mixers located at the front and rear of the reservoir are oriented towards the center of the reservoir to prevent the LNG heated by the vertical front and rear walls from rising.

[0123] Figure 14 This illustrates a configuration where the injector-mixer is oriented towards the top of the reservoir, and mixing of a small amount of liquefied gas contained within the reservoir is not permitted. Because the injector-mixer is close to the surface, the liquid layer is effectively disrupted, which advantageously reduces the power required to renew the liquid surface layer; however, the low pumping power still carries the risk of heating the LNG remaining in the upper portion of the reservoir. The injector-mixer's position is advantageously feasible due to the reinforcing angle (the aforementioned connection area) between the vertical wall and the inclined upper wall. The injector-mixer is oriented towards the top of the reservoir at an angle βmax, which is greater than βmin and, for example, 0° to 60°, preferably 0° to 30°, more preferably 15° to 30°. Figure 14 ).

[0124] Figure 15 and Figure 16 Other cases are shown where the first transverse row syringe-mixer and the second transverse row syringe-mixer positioned opposite the first row syringe-mixer do not have the same orientation. Figure 15 In this case, because the injector-mixer is close to the surface, the liquid layer is effectively disrupted, which advantageously reduces the power required to renew the liquid surface layer. However, the low pumping power still carries the risk of heating the LNG remaining in the upper part of the reservoir. The upward-oriented first injector-mixer rod delivers the liquefied gas toward a laterally opposite, horizontally oriented second injector-mixer rod, which in turn delivers it toward the first injector-mixer rod. The first injector-mixer is oriented toward the top of the reservoir at an angle βmax greater than βmin and, for example, 0° to 60°, preferably 15° to 60°, more preferably 30° to 45°. Figure 15 The second syringe-mixer is oriented with an angle βmax toward the bottom of the reservoir, which is greater than βmin and is, for example, 0° to 30°, and preferably 0° to 15°. Figure 15 The mixing volume appears to be low. Working two rods together helps reduce the mixing power. Figure 16 In the case of, with Figure 15Compared to the previous case, its particularity lies in the orientation of the second injector-mixer rod, which is advantageously oriented downwards at an angle β to discharge at a depth and mix the liquid surface layer with LNG from the cooler bottom. β includes the range βmax, which is greater than βmin and is, for example, 90° to 30°, preferably 90° to 60°, more preferably 85° to 75°. Figure 16 The mixing volume appears to be low. The two rods working in tandem help reduce mixing power and therefore contribute to low pump-related heat generation.

[0125] However, syringe-mixers 10 with different orientations can be associated with each other so that the entire volume of liquefied gas stored in the reservoir is effectively mixed and thus affected by the liquefied gas injected into the reservoir.

[0126] Figures 17 to 20 Several feasible scenarios for supplying syringe-mixers are shown. Figure 17 This illustrates a scenario where rows on both sides are supplied in parallel. Figure 18 This illustrates a scenario where the rows on both sides are supplied independently. Figure 19 The diagram illustrates a configuration where the reservoir includes one or more rows of supply pipes 34 passing through the reservoir wall. Figure 20 The diagram illustrates a configuration where the reservoir includes one or more rows of supply pipes 34 that do not penetrate the reservoir walls. The pipes 34 are then housed within the reservoir along with the pump and injector-mixer to create a fully autonomous system. This is particularly interesting because, in the case of LNG-propelled vessels, the specification could require the isolation of the reservoir should the vessel or parts thereof be damaged, and if the reservoir is isolated, the mixing system would cease operation.

[0127] Figures 4 to 6 Another aspect of the invention is shown, wherein the gas injection device includes at least one syringe-mixer 10 located in the lower region of the reservoir 12, extending between 0% and 25% of the height of the reservoir as measured from the bottom 14 of the reservoir.

[0128] In addition to the reservoir 12 and the syringe-mixer 10, the liquefied gas storage device also includes a device for extracting the gas, which is in liquid form here. The extraction device includes a pump 20, which is immersed in the liquefied gas and preferably located at the bottom of the reservoir.

[0129] Liquefied gases can be extracted and injected into the same storage tank, or injected into another storage tank.

[0130] Pump 20 is connected to syringe-mixer 10 directly or via subcooling device 22. The subcooling device is, for example, of the type described above. The subcooling device can be configured to reduce the temperature of the liquefied gas pumped by the pump by approximately 10°C.

[0131] The reservoir 12 can be of the "fully filled" or "restricted filled" type. In both cases, it can be filled with a liquefied gas sump at the bottom of the reservoir, representing up to 10% of the total internal volume of the reservoir. In the case of a fully filled reservoir, the reservoir can contain any volume of liquefied gas.

[0132] The syringe-mixer 10 is positioned and designed to inject liquefied gas extracted (and possibly supercooled) below the interface 18, thereby mixing the liquefied gas stream with the liquefied gas contained in the reservoir 12.

[0133] The injection and mixing of liquefied gas in the reservoir bottom allows for limiting evaporation from the bottom and keeping it at a low temperature for cooling before loading, without requiring cooling of the environment within the reservoir. Maintaining a cold liquid bottom helps reduce excess gas at the start of loading.

[0134] Injecting and mixing liquefied gas in a larger volume storage tank allows for limiting the risk of temperature stratification within the tank. Preferably, ensuring hybrid dynamics and orientation of the liquid flow ensures adequate mixing along the height of the storage tank. In practice, the top gas naturally tends to stratify temperature when there is less evaporation. That is, because it is lighter, hot gas accumulates at the top plate, which significantly reduces heat flow from the outside. Therefore, cooling the environment within the storage tank (via return through the spray bar) increases heat flow, and thus requires a higher capacity of subcooling to compensate for this heat flow, which represents energy loss and therefore loss of liquefied gas. If the top gas temperature has stratified, even if the LNG is subcooled, cooling the storage environment via return through the spray bar can lead to an increase in storage pressure because the dispersed LNG evaporates while cooling the heated insulation of the storage tank. Once the insulation has cooled, the injection of subcooled LNG allows for control or even reduction of the storage pressure. Therefore, even if the top gas has already been heated, injecting and mixing liquefied gas into the bottom of the reservoir allows for immediate control / reduction of the reservoir pressure.

[0135] Advantageously, the syringe-mixer 10 is configured to inject a stream of liquefied gas in a direction inclined upward at an angle α relative to the horizontal plane. Figure 6 The angle α is, for example, 5° to 85°, preferably 15° to 75°, and more preferably 30° to 60°.

[0136] As shown in the storage device Figure 4 , 6 As shown in 21 to 24, 30 and 31, the injection device is located at the bottom of the reservoir, preferably with a control angle α, so that the mixing device can be used in ballast conditions. Figure 4 , 2324 and 30) and full load conditions ( Figure 21 , 22 and 30).

[0137] - Under ballast conditions (with the reservoir almost empty), this configuration allows for the agitation of the liquid over most of the reservoir's length (achieving a large distance with a sufficiently small angle, i.e., close to the horizontal). An angle that is too large (i.e., close to the vertical) would cause the liquid to disperse in the air gap, which would cool the gas and thus increase heat transfer. When using the supercooling device 22, an angle that is too large would also create an accumulation of injected liquid near the injector and extraction device, causing the injected liquid to be drawn back towards the supercooling device; there is a risk that the supercooled liquid may freeze.

[0138] - Under full load conditions (the reservoir is almost full), a sufficiently large angle (i.e., close to the vertical) allows the liquid to be agitated over most of the reservoir's height, resulting in a uniform liquid temperature across the entire height of the liquid, thus preventing the formation of a hot liquid layer on the surface. An angle that is too small (i.e., close to the horizontal) will not reach the liquid surface where a hot liquid layer might form. When using a supercooling device, an angle that is too small can cause the injected liquid to accumulate at the bottom of the reservoir and near the extraction device, causing the injected liquid to be drawn back towards the supercooling device; there is a risk that the supercooled liquid may freeze. Even with a uniform accumulation of supercooled liquid at the bottom of the reservoir, there is also a risk of a sudden pressure drop in the reservoir; if the pressure drops below atmospheric pressure, the safety valve may open.

[0139] Still in Figure 4 , 6 In cases 21 to 24, 30, and 31, the injected flow can be advantageously controlled according to the height of the liquid in the reservoir. In a nearly empty reservoir, the flow rate can be reduced to limit the power consumed by the extraction device and to prevent the liquid from being dispersed in the air gap (which would cool the gas and thus increase heat transfer). The flow rate can be increased to agitate the liquid over most of the reservoir's height so that it reaches the surface and thus avoids the formation of a hot liquid layer on the surface. This flow rate control can be performed in various ways, for example, by a speed reducer of the extraction device or by a set of control valves.

[0140] This allows for the liquefied gas to be mixed within the storage tank over virtually the entire height and the maximum possible distance, such as... Figure 4 The arrow in the diagram is shown schematically.

[0141] The storage container 12 has a generally parallelepiped and elongated shape, and may also have an oblique angle, such as Figure 4 and 5 As shown. The reservoir 12 includes a rear longitudinal end 12a and a front longitudinal end 12b.

[0142] In the example shown, pump 20 and syringe-mixer 10 are located at the rear end 12a of reservoir 12. They can be positioned substantially perpendicular to the liquid dome of the reservoir. In this case, pump 20 and syringe-mixer 10 can be connected to vertical pipes of a "pump tower". These pipes then support syringe 10.

[0143] As mentioned above, the syringe-mixer 10 is positioned such that it can produce an optimal volume of liquefied gas mixture in the reservoir. The power of the syringe-mixer—that is, the flow rate of the liquid it can deliver—depends particularly on the power of the pump 20. Advantageously, this pump is one already assembled into the reservoir, especially a pump tower, and therefore has a limited power, for example less than or equal to 100 m³ / s. 3 / h, for example, less than or equal to 60m 3 / h.

[0144] Pumps can be of the type with variable speed and therefore variable flow rate. This in particular allows the power of the pump, and therefore the flow rate of the liquid injected by the syringe-mixer, to be matched with the volume of liquefied gas in the reservoir and therefore the fill level of the reservoir.

[0145] To remedy this and allow for mixing of the total volume of liquefied gas in the reservoir, the reservoir can be equipped with multiple syringe-mixers 10, such as... Figure 13 As shown and as previously stated.

[0146] like Figures 21 to 24 As shown, this illustrates a fully filled or wire-filled reservoir, ideally with angle α controlled to maximize the mixing of liquefied gas within the reservoir. If angle α is too small, and the syringe-mixer injects the liquefied gas directly towards the bottom wall, there is a risk that not all the liquefied gas in the reservoir will be mixed. A downward-facing syringe-mixer can be combined with an upward-facing syringe-mixer in the same reservoir. Figure 11-13 and 24).

[0147] Injectors-mixers with different orientations can be associated with each other so that the full volume of liquefied gas stored in the reservoir is effectively mixed and thus affected by the liquefied gas injected into the reservoir.

[0148] Therefore, the orientation and number of syringe-mixers 10 are chosen to promote good mixing of the liquefied gas in the reservoir, limit the recirculation of subcooled liquefied gas to the pump, and slightly upward to limit the accumulation of heavier subcooled gas (if the reservoir is full, the liquid will stratify at different temperatures). Injection as close as possible to the bottom of the reservoir allows the injected liquefied gas to remain in the liquid at a lower fill level to limit cooling of the top gas as much as possible (in the worst case, injection would cause deformation of the free surface of the liquefied gas at the interface), and to prevent gas from being drawn in, for example, through the Venturi effect.

[0149] Figures 21 to 24 The device shows that the liquid extraction device (pump 20) can be connected to the syringe-mixer 10 via a conduit 34, and the components (including the conduit 34) are located within the reservoir, which avoids wall penetration that could lead to sealing problems.

[0150] The conduit extends at least partially, substantially parallel to and close to the bottom wall of the reservoir, and preferably extends to at least one side wall of the reservoir. In the case shown in the figures where the pump is located at the center and bottom of the reservoir, the conduit may extend in the opposite direction along the bottom wall of the reservoir to the side wall. The conduit may be configured to match the specific shape of the bottom of the reservoir, particularly the shape of the bevel between the bottom and the side wall of the reservoir.

[0151] exist Figure 25 In a variant embodiment, the syringe (one or more)-mixer (one or more) rod in the upper portion of the reservoir is combined with another rod in the lower portion so that they can work together. The one in the upper portion discharges surface liquid to prevent the formation of a hot liquid layer on the surface of the syringe positioned at the bottom of the reservoir. The liquid drawn in is in contact with the vertical wall so as to return it to the first row of syringes. This forced circulation of liquid around the vertical wall and surface makes it possible to prevent the formation of a liquid layer (because the liquid layer consists of LNG heated by the vertical wall).

[0152] exist Figure 26 In a variant embodiment, the syringe (one or more)-mixer (one or more) rod in the upper portion of the reservoir is combined with another rod in the lower portion so that they can work together. The one in the upper portion discharges surface liquid towards the bottom to prevent the formation of a hot liquid layer on the surface of the syringe positioned at the bottom of the reservoir. This forced circulation of liquid around the vertical wall and surface prevents the formation of a liquid layer (since the liquid layer consists of LNG heated by the vertical wall). In fact, the angle of the injector allows for efficient renewal of the liquid in contact with the vertical wall.

[0153] As previously described, the two aspects of the invention can be combined to allow the same reservoir to be equipped with multiple syringe-mixers, some oriented upwards and others downwards. Furthermore, the syringe-mixers can be oriented further to the right or further to the left, that is, more towards the forward or more towards the aft side of the vessel when the syringe-mixers are located on the longitudinal side of the vessel. Therefore, multiple positioning and orientation configurations of the syringe-mixers in the reservoir are feasible.

[0154] Figure 1 , 11 -12 and 14 to 26 illustrate another advantage of the invention.

[0155] The syringe-mixer 10 and the feasible pump 20 are positioned relative to each other and configured to generate both a suction effect and a back pressure effect in the reservoir. These suction and back pressure effects result in a predetermined stirring cycle of the liquefied gas in the reservoir, indicated by arrows forming a closed loop.

[0156] The syringe-mixer 10 itself can generate a back pressure effect by injecting liquefied gas, and a suction effect due to the vacuum created in the injection area. It should also be understood that the pump 20 can generate a suction effect.

[0157] Advantageously, the stirring cycle is designed such that the liquefied gas circulates substantially parallel to and close to the liquid-gas interface in the reservoir. This limits the risk of a hot liquid layer forming at the interface, and thus the risk of liquefied gas evaporation.

[0158] The stirring cycle is completed by the natural convection of the liquefied gas due to temperature changes within the reservoir. This is, for example, the case of a very cold liquefied gas, which is heavier than a warmer liquefied gas and tends to rise towards the liquid-gas interface in the reservoir. The liquefied gas can rise, for example, along the sidewalls of the reservoir, particularly when a brazing cycle occurs in the center of the reservoir.

[0159] exist Figure 11 and 12 The injection of liquefied gas into the reservoir directly causes the liquefied gas to be discharged downward along these walls, and indirectly (through induction) causes the liquefied gas to be drawn from the center of the reservoir toward the center of the reservoir and, in particular, toward the syringe-mixer.

[0160] The observed effects and Figure 14 Conversely, injection upwards and into the side wall of the reservoir directly causes the liquefied gas to be discharged upwards, and indirectly causes the liquefied gas to be drawn from the center of the reservoir toward the center of the reservoir, and especially toward the syringe-mixer.

[0161] exist Figure 15 and16 In this case, the syringe-mixer located on one side of the reservoir (on the left in the diagram) is oriented upwards and delivers liquefied gas to the syringe-mixer located on the opposite side, which is oriented downwards and delivers liquefied gas to other syringe-mixers. The discharge of liquefied gas at the outlet of the syringe-mixer creates a depression at the syringe-mixer, which attracts liquefied gas discharged from other syringe-mixers, thus forming a closed loop and therefore a concept of a stirring cycle.

[0162] As in Figures 21 to 26 As can be seen, the stirring cycle caused by the syringe-mixer located on one side of the reservoir can be symmetrical or different from the stirring cycle caused by the syringe-mixer located on the other side of the reservoir. In these figures where pump 20 is submerged, pump 20 itself generates a suction effect in the reservoir, which actively participates in generating the stirring cycle. The pump can be located in the center of the reservoir and generate a suction effect, which, combined with the back pressure effect of the syringe-mixer located on the side of the reservoir, can induce a single stirring cycle in the reservoir. Figure 22 and 24 26) or cause separate stirring on both sides of the reservoir ( Figure 21 and 23 ).

[0163] Figure 27 and 28 A specific example of a syringe-mixer 10 is shown. This syringe-mixer 10 includes a main conduit 40 through which a main jet 42 of liquid passes, and a secondary conduit 44 coaxial with the main conduit 40, which forces a secondary jet 46 of liquid through the outlet of the main conduit 40 via the Venturi effect. The jets 42 and 46 are mixed in the secondary conduit 44, and these jets can be mixed with a liquefied gas 48 at the outlet of the secondary conduit 44, into which they are injected.

[0164] An example of the relationship between the velocities of different jets is:

[0165] o Main jet 42 = 1 part, for example 25m 3 / h,

[0166] o Sub-jet 46 = 3 parts, for example 75m 3 / h,

[0167] o Mixed jet stream 42 and 46 = 4 parts, for example 100m 3 / h,

[0168] liquefied gas drives a flow rate of 48 = 12 to 80 parts.

[0169] This example demonstrates the efficiency of a syringe-mixer with the Venturi effect, allowing for a four-fold dilution of the flow rate of supercooled liquids (without considering induced flow). It has further allowed for the mixing of supercooled liquefied gases and limited the risk of buildup (stratification) in the lower portion of the reservoir, as well as a greater driving effect on fluids with lower density and viscosity compared to water.

[0170] As mentioned earlier, using a variable flow pump or a more powerful pump will allow for an increase in the flow velocity of the main jet and the unloading velocity, thereby increasing the jet's range. However, excessively increasing the flow rate can be counterproductive, as a more powerful pump will generate more heat, which will increase evaporation in the reservoir (e.g., the purpose of a subcooler is cooling). The pressure drop per bar between the main jet and the secondary jet can, for example, increase the jet's range by approximately five meters.

[0171] Figure 29 Several examples of applications of different aspects of the invention are shown and summarized.

[0172] The right side of Figure A illustrates the case where there is no cooling and / or recondensation device between the extraction device (pump) and the injection device (syringe-mixer):

[0173] A-1 - When the storage container is a confined-fill type (LNGC type):

[0174] This concept is particularly relevant to the storage of LNG vehicles because intermediate fillers are unauthorized (10% to 70% unauthorized). Moreover, the formation of a thermoplastic layer with low filler (bottom) is not feasible, thus the bottom mixing system is less efficient.

[0175] Therefore, the present invention includes one or more syringe-mixer rods located in a liquid and as close as possible to the liquid-gas interface.

[0176] The syringe-mixer is positioned at the top of the reservoir, close to the interface, in the liquid because its purpose is to renew the hot liquid layer at the interface. Therefore, given the high reservoir height (up to 27m on LNG vehicles), this positioning is most effective for reaching the water surface.

[0177] Considering the hot liquid layer at the surface and the heat flow from the vertical wall, the distribution and orientation of the syringe-mixer can make it possible to avoid mixing the liquid core and thus reduce the mixing power (because they do not participate in the formation of the hot liquid layer), as described above.

[0178] Given this positioning of the injector-mixer (close to the surface), the pump can be of the variable flow type in order to reduce power and thus reduce the heat input generated by mixing (and thus increase the pressure rise time).

[0179] A-2 - When the memory is a fully filled type (LFS, FSRU, GBS, RT, LBV type):

[0180] The device includes a syringe-mixer located at its bottom and oriented upwards. The pump is ideally controlled such that the flow rate and supply pressure of the syringe-mixer adapt as the surface approaches the mixer (i.e., the LNG level in the reservoir drops). This allows for limiting the cooling of the top gas and preventing gas spraying due to excessive jetting. Furthermore, if the pump is variablely controlled, this control will increase the pressure rise time and reduce pump heat generation.

[0181] Especially for passenger ships, the device can be "self-contained," with no piping protruding outside the reservoir. In practice, in the event of damage (e.g., SOLAS SRTP = Safe Return Port constraint and IGF code), the reservoir must be automatically isolated (therefore, all valves at the intersection will automatically close). The pressure rise time should preferably be long enough to allow the ship and its passengers to return to port without degassing the reservoir (SRTP constraint), or should be greater than 15 days (IGF code constraint).

[0182] The left side of Figure B illustrates the case where there are cooling and / or recondensation devices between the extraction device (pump) and the injection device (syringe-mixer):

[0183] In each of the following concepts, the key principle sought is the ability to re-inject cold power (transported by subcooled LNG) into the liquid rather than into the top gas.

[0184] In practice, re-injecting most of the cold power into the top gas will first cause a significant pressure drop due to the cooling of the top gas, then the cooling of the storage tank's insulation blocks will cause the dispersed LNG to evaporate, which will significantly increase the pressure during cooling. Finally, the cooling of the top gas will force heat flow into the upper part of the storage tank, and thus most of the LNG re-injected into the top gas will be unnecessarily vaporized, which will limit the cold power supplied to the liquid. This is especially true because it will only be distributed to the free surface of the liquid, which will lead to slower diffusion kinetics.

[0185] In contrast, this invention proposes injecting cold power directly into the liquid below the free surface to reduce the impact on the temperature and pressure of the top gas. Furthermore, injection below the free surface will produce mixing and agitation effects by adjusting the liquid dynamics, orientation, and height at the return line outlet.

[0186] In these cases, it is not necessarily necessary to dispense the syringe-mixer into the reservoir in a uniform manner, since the purpose is simply to dilute the injected liquid with the existing liquid (without reaching the liquid-gas interface).

[0187] B-1 - When the storage container is full:

[0188] The storage tank is loaded (both after loading and before unloading). Injection and mixing at the top of the storage tank promotes good mixing of the subcooled LNG with the stored LNG. In fact, the injected LNG is colder and heavier than the surrounding LNG, justifying positioning the upper section of the storage tank slightly below the surface and oriented slightly downwards at a small angle α to mix the front of the storage tank as much as possible. As a variant or additional feature, LNG injection can be carried out using a spray bar, thus allowing it to occur in the top gas.

[0189] B-2 - When the reservoir is empty or partially filled:

[0190] When the reservoir is empty (during the ballast stroke prior to loading) or at a medium level, injection and mixing allow for the cutting off of evaporation from the residue and keep it at a low temperature for cooling before loading, without requiring cooling of the environment within the reservoir.

[0191] When the storage tank is partially loaded (after loading and before unloading), cold LNG is at risk of temperature stratification. It is necessary to ensure the hybrid dynamics and orientation of the liquid flow to guarantee adequate mixing along the height of the storage tank.

[0192] When there is less evaporation, the top gas naturally tends to stratify at different temperatures. That is, because it is lighter, the hot gas accumulates at the top of the storage tank, which greatly reduces the heat flow from the outside. Therefore, cooling the environment in the storage tank (via spray bars) increases the heat flow, and thus requires the use of a higher-capacity subcooling device to compensate for this flow, resulting in energy loss and therefore LNG loss. Simply dumping LNG at the bottom of the storage tank without mixing carries the risk of drawing in subcooled LNG, which would require stopping the subcooling device. Cooling the cold liquid at the bottom helps reduce excess gas at the start of loading.

[0193] When the reservoir is nearly empty and the supercooling device 22 is engaged, for the reasons described above, it is preferable to inject the liquid at the bottom of the reservoir directly into the reservoir. However, this injection system at the bottom of the reservoir can also be used when the reservoir is full (or nearly full), provided that the syringe angle α is appropriately selected. The reservoir is shown... Figure 4 , 6 As shown in 21 to 24, 30 and 31, the injection devices are located at the bottom of the reservoir, preferably with a controlled angle, so that these injection devices, and therefore the mixing devices, can be used in ballast conditions. Figure 4 , 23 24 and 30) and full load conditions ( Figure 21 ,22 and 31).

[0194] - Under ballast conditions (with the reservoir almost empty), this configuration allows for the agitation of the liquid over most of the reservoir's length (achieving a large distance with a sufficiently small angle, i.e., close to the horizontal). An angle that is too large (i.e., close to the vertical) would cause the liquid to disperse in the air gap, which would cool the gas and thus increase heat transfer. When using the supercooling device 22, an angle that is too large would also create an accumulation of injected liquid near the injector and extraction device, causing the injected liquid to be drawn back towards the supercooling device; there is a risk that the supercooled liquid may freeze.

[0195] - Under full load conditions (the reservoir is almost full), a sufficiently large angle (i.e., close to the vertical) allows the liquid to be agitated over most of the reservoir's height, resulting in a uniform liquid temperature across the entire height of the liquid, thus preventing the formation of a hot liquid layer on the surface. An angle that is too small (i.e., close to the horizontal) will not reach the liquid surface where a hot liquid layer might form. When using a supercooling device, an angle that is too small can cause the injected liquid to accumulate at the bottom of the reservoir and near the extraction device, causing the injected liquid to be drawn back towards the supercooling device; there is a risk that the supercooled liquid may freeze. Even with a uniform accumulation of supercooled liquid at the bottom of the reservoir, there is also a risk of a sudden pressure drop in the reservoir; if the pressure drops below atmospheric pressure, the safety valve may open.

Claims

1. A liquefied gas storage device for use in liquefied gas transport vehicles or for use in land-based facilities, the liquefied gas storage device comprising: - At least one liquefied gas storage container (12) having a container bottom (14) and a container top plate (16) that together define the container height (H), and - A gas injection device for injecting liquid gas into the reservoir. - An extraction device for extracting liquid gas from the reservoir. The gas injection device is characterized by comprising at least one syringe-mixer (10) located in the upper region of the reservoir extending between 60% and 100% of the reservoir height, the reservoir height being measured from the bottom of the reservoir, and the syringe-mixer being immersed in a liquefied gas contained in the reservoir, the at least one syringe-mixer (10) being configured at an angle relative to the horizontal plane ( Inject liquid gas streams in a downward-sloping direction; The gas injection device or the extraction device is positioned relative to each other and configured such that they generate back pressure and suction effects in the reservoir, which produce a predetermined stirring cycle of liquefied gas in the reservoir.

2. The liquefied gas storage device according to claim 1, wherein, The angle ( The angle is 5° to 45°.

3. The liquefied gas storage device according to claim 1, wherein, The angle ( The angle is 5° to 30°.

4. The liquefied gas storage device according to claim 1, wherein, The angle ( The angle is 5° to 20°.

5. The liquefied gas storage device according to claim 1, wherein, The at least one syringe-mixer (10) is fixed to the wall of the reservoir (12).

6. The liquefied gas storage device according to any one of claims 1 to 5, wherein, The at least one syringe-mixer (10) is positioned as close as possible to the vertical longitudinal sidewall (12c) of the reservoir.

7. The liquefied gas storage device according to claim 6, wherein, The reservoir includes a vertical longitudinal sidewall (12c) connected to the top plate (16) of the reservoir via an inclined wall (12d), and the at least one syringe-mixer (10) is fixed to a connection area for connecting the vertical longitudinal sidewall to the inclined wall.

8. The liquefied gas storage device according to claim 7, wherein, The at least one syringe-mixer (10) can be fixed to the thickened metal plate (32) and / or at least one wooden block (30) of the connection area.

9. The liquefied gas storage device according to any one of claims 1 to 5, wherein, The gas injection device includes at least one horizontal row of syringe-mixers (10) configured to inject liquid gas streams in parallel or different directions.

10. The liquefied gas storage device according to any one of claims 1 to 5, wherein, The gas injection device includes at least two horizontal rows of syringe-mixers (10) arranged on and / or along the two longitudinal sidewalls (12c) of the reservoir.

11. The liquefied gas storage device according to any one of claims 1 to 5, wherein, The gas injection device is connected via a reliquefaction device to a device for extracting gas from the reservoir or another reservoir.

12. The liquefied gas storage device according to claim 11, wherein, The reliquefaction device is configured to condense the evaporated gas drawn from the reservoir or another reservoir, and then pressurize it by exchanging heat with the liquefied gas drawn from the reservoir or another reservoir.

13. The liquefied gas storage device according to any one of claims 1 to 5, wherein, The gas injection device is connected via a subcooling device (22) to a device for extracting liquid gas from the reservoir or another reservoir.

14. The liquefied gas storage device according to any one of claims 1 to 5, wherein, The extraction device is configured to extract liquid gas from the lower region.

15. The liquefied gas storage device according to any one of claims 1 to 5, wherein, The extraction device includes at least one pump (20) located in the reservoir (12) or another reservoir and immersed in the liquefied gas.

16. The liquefied gas storage device according to claim 15, wherein, The pump (20) is configured to have a variable flow rate.

17. The liquefied gas storage device according to any one of claims 1 to 5, wherein, The reservoir (12) is of the "limited fill" type and is configured to fill to less than or equal to 10% or greater than or equal to 70%.

18. The liquefied gas storage device according to claim 17, wherein, The extraction device and the gas injection device are located within the reservoir (12) and are connected to each other via a pipe (34) located entirely within the reservoir.

19. The liquefied gas storage device according to claim 18, wherein, The extraction device and the gas injection device are positioned perpendicular to the liquid dome (LD) of the reservoir (12).

20. The liquefied gas storage device according to claim 19, wherein, The extraction device and the gas injection device are equipped with a pump tower accessible through the liquid dome.

21. The liquefied gas storage device according to claim 20, wherein, The at least one syringe-mixer (10) is connected to and supported by the liquid column of the pump tower.

22. The liquefied gas storage device according to any one of claims 1 to 5, wherein, The syringe-mixer (10) includes a main conduit (40) through which the main jet (42) of liquid is passed, and a secondary conduit (44) through which a secondary jet (46) of liquid is forced to pass by means of the Venturi effect.

23. A liquefied gas transport vehicle comprising at least one liquefied gas storage device as claimed in any one of claims 1 to 22, wherein the liquefied gas storage device has no supercooling and reliquefaction device between the extraction device and the gas injection device, the storage device being of the "restricted filling" type and configured to be filled to less than or equal to 10% or greater than or equal to 70%.

24. A liquefied gas transport vehicle comprising at least one liquefied gas storage device as claimed in any one of claims 1 to 22, the liquefied gas storage device including a supercooling and / or reliquefaction device between the extraction device and the gas injection device, the storage device being of the "restricted filling" type and configured to be filled to less than or equal to 10% or greater than or equal to 70%.

25. A method for injecting a gas in liquid form into a reservoir of a liquefied gas carrier as described in claim 23 or 24, wherein, Injection into the upper region is performed when the "limited fill" reservoir is filled to more than 70%.

26. The method according to claim 25, wherein, The injection into the reservoir is configured to prevent the heated liquefied gas from rising along the longitudinal sidewalls of the reservoir.

27. The method according to claim 25 or 26, wherein, The injected liquefied gas has a lower temperature than the liquefied gas contained in the reservoir.

28. The method according to claim 25 or 26, wherein, The gas injection device or the extraction device is controlled to generate back pressure and suction effects in the reservoir, which produce a predetermined stirring cycle of liquefied gas in the reservoir.

29. The method according to claim 28, wherein, The predetermined stirring cycle is designed such that the liquefied gas circulates substantially parallel to and close to the liquid-gas interface (18) in the reservoir.

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