CN116601421A

CN116601421A - Method for aeration and gas testing in storage facilities for liquefied gases

Info

Publication number: CN116601421A
Application number: CN202180083286.2A
Authority: CN
Inventors: 斯坦尼斯拉斯·德雷塞格斯
Original assignee: Gaztransport et Technigaz SA
Current assignee: Gaztransport et Technigaz SA
Priority date: 2020-12-10
Filing date: 2021-12-09
Publication date: 2023-08-15
Also published as: FR3117572B1; WO2022122982A1; KR20230112138A; JP2023553928A; FR3117572A1

Abstract

A gas filling method comprising: introducing a liquid-phase liquefied gas stream (25) into a first storage tank (10A) to cool the first tank and vaporize the liquid-phase liquefied gas in the first tank , while introducing the liquefied gas stream (25) in the liquid phase into the first storage tank (10A), delivering the liquefied gas stream (26, 126) in the gas phase from the upper portion of the first tank to the second storage tank (10B) The upper portion of the gas phase of the liquefied gas stream (26, 126) is generated by the vaporization of the liquid phase of the liquefied gas and allows the inert gas stream (27) to be discharged from the lower portion of the second tank (10B), The liquefied gas (21) in gaseous phase replaces the inert gas (22) at least in the upper portion of the second storage tank (10B).

Description

Method for charging and gas testing in a liquefied gas storage facility

Technical Field

The present invention relates to the field of storage facilities for liquefied gases, and in particular to facilities on floating structures such as liquefied natural gas carriers and the like.

Liquefied gas storage facilities, in particular for storing liquefied natural gas (liquefied natural gas, LNG), may be for example onshore storage facilities, seabed storage facilities, or facilities carried on coastal or deepwater floating structures, in particular liquefied natural gas carriers, floating storage regasification units (floating storage and regasification unit, FSRU), floating production storage offloading (floating production, storage and unloading, FPSO) units, etc.

The liquefied gas may be a combustible gas, in particular Liquefied Natural Gas (LNG) or liquefied petroleum gas (liquefied petroleum gas, LPG) or the like.

Background

The commissioning of LNG storage tanks after manufacture or the re-commissioning of such tanks after overhaul involves a series of operations known as drying, inerting, aeration, cooling and loading.

In particular, these operations are performed during gas testing, which is testing performed prior to the lng carrier being put into service or re-put into service, to verify proper operation of the storage tanks and cargo handling system at low temperatures. In sigto information file (2019 version) ISBN 13: a more complete description of gas testing and best practice can be found in publication "Guide for planning Gas Trials for LNG Vessels (LNG container gas test plan guidelines)" in 978-1-85609-810-6 (9781856098106).

In particular, during offshore operations, gas testing is typically performed simultaneously in multiple storage tanks, specifically:

-inflating the storage tank with a gas phase gas stream generated by forced gasification in the lng gasification unit;

-subsequently cooling the storage tank using a liquid phase gas stream.

All of these offshore operations consume the lng previously loaded into the additional tanks and produce boil-off gas, i.e., liquefied gas in the gas phase, which cannot be stored on board the vessel. Conventional techniques for treating such boil-off gas include reliquefaction, consumption in propulsion engines, combustion in combustion units and/or venting to the atmosphere.

Disclosure of Invention

Some aspects of the invention are based on the following observations: gas testing, particularly inflation and cooling operations, can produce significant amounts of boil-off gas that should ideally be reduced to facilitate handling, save liquefied gas, and/or reduce gas emissions to the atmosphere.

One concept behind the present invention relates to the use of boil-off gas generated when cooling one tank to inflate the other tank, in particular during gas testing involving multiple tanks in a liquefied gas storage facility.

To this end, the invention proposes an aeration method for aerating a storage tank in a liquefied gas storage facility, preferably mounted on a floating structure, the method comprising:

bringing a liquefied gas storage facility into a ready state, the liquefied gas storage facility comprising a plurality of storage tanks and at least one manifold, the at least one manifold being connected in parallel to a top portion of each of the storage tanks, a first one of the storage tanks in the ready state being filled with a gas-phase liquefied gas, the temperature of the gas-phase liquefied gas in the first tank being higher than a liquid-gas equilibrium temperature of the liquefied gas, a second one of the storage tanks in the ready state being filled with an inert gas;

injecting a liquid phase liquefied gas stream into the first tank to cool the first tank and partially gasify or fully gasify the liquid phase liquefied gas within the first tank;

while injecting a liquid phase liquefied gas stream into the first tank, transporting a gas phase liquefied gas stream generated by gasification of the liquid phase liquefied gas from the top portion of the first tank to the top portion of the second tank through at least one manifold connected to the top portion of each of the storage tanks, the gas phase liquefied gas having a density lower than that of the inert gas;

the inert gas stream is released from the bottom portion of the second tank at the pressure of the gas phase liquefied gas stream such that the gas phase liquefied gas replaces the inert gas in at least the top portion of the second storage tank.

These features enable sequential or partial sequential inflation and cooling of multiple storage tanks, thereby producing less boil-off gas than conventional synchronization procedures.

According to advantageous embodiments, the method may have one or more of the following features:

the connection for transferring the gas phase liquefied gas stream from the first storage tank to the second storage tank may be performed in a variety of different ways.

According to one embodiment, the at least one manifold is a maintenance manifold connected in parallel to the top portion of each of the storage tanks via respective first isolation valves, the flow of gas phase liquefied gas being transferred from the top portion of the first storage tank to the maintenance manifold by the first isolation valve associated with the first tank, and/or the flow of gas phase liquefied gas being transferred from the maintenance manifold to the top portion of the second tank by the first isolation valve associated with the second tank.

Preferably, the maintenance manifold is not thermally insulated. In particular, the maintenance manifold may be a manifold connected to an inert gas production unit typically used for tank inerting.

According to one embodiment, the at least one manifold further comprises a vapor manifold, the vapor manifold being thermally insulated, the vapor manifold being connected in parallel to a top portion of each of the storage tanks via a respective second isolation valve, the vapor manifold being connected in series with a maintenance manifold, the vapor manifold delivering the vapor liquefied gas stream sequentially through the first isolation valve associated with the first tank, the maintenance manifold, the vapor manifold, and the second isolation valve associated with the second tank, or the vapor liquefied gas stream sequentially through the second isolation valve associated with the first tank, the vapor manifold, the maintenance manifold, and the first isolation valve associated with the second tank.

The flow of the gas phase liquefied gas from the first storage tank to the second storage tank may be accomplished in a variety of different ways.

According to one embodiment, the gas phase liquefied gas stream flows from the top portion of the first storage tank to the top portion of the second storage tank by natural convection. These features enable passive flow without additional energy consumption.

According to one embodiment, the liquefied gas storage facility further comprises a gas reheating device having an inlet connected to one of the maintenance manifold and the gasifier manifold and an outlet connected to the other of the maintenance manifold and the gasifier manifold, the gas phase liquefied gas stream being further conveyed through the gas reheating device to reheat the gas phase liquefied gas stream before reaching the top portion of the second tank. These features enable recovery of relatively cool boil-off gas, particularly obtained in the first tank when the cooling operation of the first tank is in an advanced state.

According to one embodiment, the liquefied gas storage facility further comprises a gas reheating device having an inlet connected to one of the maintenance manifold and the gasifier manifold and an outlet connected to the other of the maintenance manifold and the gasifier manifold,

and, during the first flow phase, a gas phase liquefied gas flow flows from the top portion of the first storage tank to the top portion of the second storage tank by natural convection, and

during the second flow phase, the vapor phase liquefied gas stream is also conveyed through a gas reheating device to reheat the vapor phase liquefied gas stream before the vapor phase liquefied gas stream reaches the top portion of the second tank.

According to one embodiment, the method further comprises the steps of:

monitoring the temperature of the gas phase liquefied gas leaving the first tank during the first flow phase; and

when the temperature of the gas phase liquefied gas meets a predetermined criterion, the gas phase liquefied gas flow is switched to the reheating device.

These features enable a natural flow to be established at the beginning of the cooling operation of the first tank until a predetermined criterion is met, such as a temperature threshold below which the gas phase liquefied gas becomes too dense to be subjected to the charging operation. The flow is then switched to the reheater to continue to charge the second storage tank.

The liquid phase liquefied gas flow may be produced in a number of different ways, for example, outside or inside a liquefied gas storage facility. According to some embodiments, the liquid phase liquefied gas stream is transported from an onshore terminal or a fueling vessel to which the liquefied gas storage facility is connected.

According to one embodiment, the liquefied gas storage facility comprises a third storage tank and an injection manifold connected in parallel to each of the storage tanks, the third storage tank in a ready state being partially or completely filled with liquid phase liquefied gas, and a liquid phase liquefied gas stream is pumped into the third tank and delivered by the injection manifold to the first tank.

According to one embodiment, the liquid phase liquefied gas stream is injected into the first storage tank by an injection device.

Inert gas may be removed in a variety of ways. According to one embodiment, the liquefied gas storage facility comprises a liquid manifold and a mast riser connected to the liquid manifold, the liquid manifold being connected in parallel to a bottom portion of each of the storage tanks, and the inert gas stream leaving the second tank being conveyed to the mast riser through the liquid manifold.

According to one embodiment, the present invention also provides a method for performing a gas test in a liquefied gas storage facility located on a floating structure, the gas test comprising:

the second storage tank is inflated using the method described above, and, when the second storage tank has been inflated,

a liquid phase liquefied gas stream is injected into the second storage tank to cool the second storage tank.

As above, the second storage tank may be cooled while the additional storage tank is being inflated. This enables a certain amount of boil-off gas generated during the cooling operation of the second storage tank to be used, thereby reducing the total amount of boil-off gas generated as compared to conventional synchronization procedures.

According to one embodiment, the present invention also provides a liquefied gas storage facility, preferably carried on a floating structure, comprising: a plurality of the storage tanks are arranged in the storage tank,

a maintenance manifold connected in parallel to a top portion of each of the storage tanks via a respective first isolation valve;

a vapor manifold connected in parallel to a top portion of each of the storage tanks via a respective second isolation valve, the vapor manifold being thermally insulated;

a liquid manifold connected in parallel to a bottom portion of each of the storage tanks, the liquid manifold being thermally insulated; and

a mast riser connected to the liquid manifold;

the first isolation valve is switchable to selectively communicate the maintenance manifold with a top portion of a first one of the storage tanks such that a flow of the vapor phase liquefied gas is transferred from the first storage tank to the maintenance manifold through the first isolation valve associated with the first storage tank.

According to advantageous embodiments, such a liquefied gas storage facility may have one or more of the following features.

According to one embodiment, each of the storage tanks comprises a filling line connected to the liquid manifold and a vapor line leading to a top portion of the storage tank, and the vapor line is connected in parallel to the maintenance manifold by a first isolation valve associated with the storage tank and the vapor line is connected in parallel to the vapor manifold by a second isolation valve associated with the storage tank.

According to one embodiment, the vapor manifold is connected in series with the maintenance manifold,

the second isolation valve is switchable to selectively communicate the vapor manifold with a top portion of a second one of the storage tanks such that the vapor liquefied gas stream is delivered from the first storage tank to the second storage tank sequentially through the first isolation valve associated with the first storage tank, the maintenance manifold, the vapor manifold, and the second isolation valve associated with the second storage tank.

According to one embodiment, the liquefied gas storage facility further comprises an injection manifold connected to each of the storage tanks in parallel, and an injection device arranged in a top portion of each of the tanks, and connected to the injection manifold.

According to one embodiment, the liquefied gas is liquefied natural gas.

According to one embodiment, the floating structure is a vessel for transporting liquefied gas. Such a ship for transporting liquefied gas may include a double hull and a storage tank disposed in the double hull. According to one embodiment, the storage tank is made using membrane technology and the double hull comprises an inner hull forming the load bearing wall of the storage tank.

According to one embodiment, the present invention also provides a test system for performing a gas test, the system comprising: the liquefied gas storage facility described above; a thermal insulation pipe arranged to connect the liquid manifold or the injection manifold to the onshore terminal; and a pump for driving the liquid phase liquefied gas from the onshore terminal through the thermal insulation pipe to flow to the liquid manifold or the injection manifold.

Drawings

The invention will be better understood and additional objects, details, features and advantages thereof will be more clearly set forth in the following detailed description of several specific embodiments of the invention, given by way of non-limiting example only, with reference to the accompanying drawings.

Fig. 1 is a diagram illustrating a portion of a liquefied gas storage and processing system in which a method according to the present invention may be implemented.

Fig. 2 is a view similar to fig. 1, fig. 2 showing the liquefied gas storage and processing system prior to the tank being inflated.

Fig. 3 is a view similar to fig. 1, fig. 3 showing the liquefied gas storage and processing system in a first stage of tank charging operation.

Fig. 4 is a graph showing a change in the state of the canister with time during the charging operation.

Fig. 5 is a view similar to fig. 1, fig. 5 showing the liquefied gas storage and processing system in a second stage of tank charging operation.

Fig. 6 is a view similar to fig. 1, fig. 6 showing the liquefied gas storage and processing system in a third stage of tank charging operation.

Fig. 7 is a timing diagram illustrating a test procedure implemented in a liquefied gas storage and processing system.

Fig. 8 is a schematic cross-sectional view of an lng carrier connected to a loading/unloading terminal.

Detailed Description

Fig. 1 is a schematic diagram of an LNG storage facility that may be carried on a floating structure, such as a LNG carrier.

Three reservoirs 10A, 10B and 10C are shown by way of example, however, this number may be greater or lesser. The tanks may be arranged continuously or otherwise along the length of the hull. The storage tank has a sealed and thermally insulated wall that can be manufactured using a variety of techniques, such as a double film technique.

A cargo handling system is shown in part connecting all of the tanks. Each of the storage tanks 10A to 10C specifically includes:

a filling line 9 connected to the liquid manifold 1;

a vapor line 6 which leads to the top part of the storage tank and which is connected in parallel to the maintenance manifold 4 via a first isolation valve 11 and to the vapor manifold 2 via a second isolation valve 12.

One or more spray bars 5 leading to the top part of the reservoir and connected to the spray manifold 3.

An injection pump 7 connected to the injection manifold 3 by a pumping line 8.

Other elements not shown may be present, such as one or more unloading pumps in each storage tank.

The above-mentioned manifold, which is for example the liquid manifold 1 connecting the filling lines 9 of all tanks and the injection manifold 3 connecting the injection bars 5 of all tanks, may be connected to other fluid circuits. For example, as shown by links 16 and 17, the liquid manifold 1 and the injection manifold 3 are connected to a transfer circuit for transporting fluid to or from an onshore terminal or another vessel.

In order to reduce the number of lines through the tank wall, a single gasifier line 6 is used for connecting the maintenance manifold 4 and the gasifier manifold 2 in parallel to the tank space. Alternatively, two separate gasifier lines may be provided.

The injection manifold 3, the liquid manifold 1 and the vapor manifold 2 are designed to convey cold fluid and therefore preferably the injection manifold 3, the liquid manifold 1 and the vapor manifold 2 are thermally insulated. In contrast, the service manifold 4 is little or no insulation, as the manifold 4 is typically used to deliver inert gas from an inert gas production unit (not shown) for tank and pipe inerting operations.

Fig. 1 also shows an angled connection 19 that connects one end of the service manifold 4 to the gasifier manifold 2 to form a particularly long flow path, which is used as explained below with reference to fig. 3. The angled connection 19 is optional.

The gas reheater 14 is connected to the maintenance manifold 4 via an isolation valve, for example at the outlet of the gas reheater 14, and to the gasifier manifold 2, for example at the inlet of the gas reheater 14. Similarly, the gasification unit 15 is connected to the injection manifold 3 via an isolation valve, e.g. at the inlet of the gasification unit 15, and to the gasifier manifold 2, e.g. at the outlet of the gasification unit 15.

Other components not shown may be connected to different manifolds. For example, the gasifier manifold 2 may be connected to a gas-phase gas powered device, as shown by connection 18, for example to a combustion unit or a propulsion engine.

The simultaneous operation of cooling the tank 10A and inflating the tank 10B is described below with reference to fig. 2 to 6. For this purpose, the installation is brought into a ready state by inerting the tank 10B and inflating the tank 10A. Any suitable method may be used to perform these operations.

Conventionally, the thick lines in the figures represent pipes or circuits suitable for transporting the fluids used in the system. Arrows in the figure represent liquid or gas flow in the pipe below the horizontal arrows or in the pipe to the left of the vertical arrows.

In the ready state shown in fig. 2, tank 10A is then filled with gas phase natural gas 21 at ambient temperature and tank 10B is filled with inert gas 22 at ambient temperature, such as nitrogen or carbon dioxide-rich gas resulting from the combustion of petroleum.

Fig. 2 shows a further storage tank partially filled with liquid phase liquefied gas in a ready state in dashed lines. The injection manifold 3 is also connected to the further reservoir.

Fig. 3 shows a first stage of simultaneously cooling tank 10A and inflating tank 10B.

LNG stream 25 is injected into tank 10A via injection manifold 3 and injected by injection bars 5 to cool tank 10A. The LNG vaporizes, releasing the latent energy of vaporization into tank 10A, which produces an excess of gas phase natural gas. This excess gas phase natural gas must be vented from tank 10A as it is produced to avoid increasing the pressure in tank 10A. To this end, a flow path is created to deliver a gaseous natural gas stream 26 from tank 10A to tank 10B to inflate tank 10B.

As shown in fig. 3, LNG stream 25 may be pumped to additional tanks and delivered to tank 10A through injection manifold 3.

Since the aeration of tank 10B must be performed using a lighter gas than inert gas 22, to force inert gas 22 to the bottom portion of tank 10B, it is advantageous to use a flow path for gas phase natural gas flow 26 that uses a non-insulated maintenance manifold 4 having a longer length, so some heat exchange with the ambient atmosphere can be achieved, helping to warm gas phase natural gas flow 26 before the flow reaches tank 10B. For this purpose, arrow 26 shows the flow path from tank 10A to maintenance manifold 4 via the gasifier line 6 and isolation valve 11, running the entire length of maintenance manifold 4 up to angled connection 19, and continuing into gasifier manifold 2 up to gasifier line 6 of tank 10B.

The flow path may be configured using isolation valve 11 and isolation valve 12 by:

closing all isolation valves 11 except the isolation valve of the tank 10A;

closing all isolation valves 12 except the isolation valve of tank 10B.

Other flow paths are also possible. For example, the flow paths described above may be reversed, starting from the gasifier manifold 2 to the maintenance manifold 4. The reverse path may be configured using isolation valve 11 and isolation valve 12 by:

closing all isolation valves 12 except the isolation valve of tank 10A;

closing all isolation valves 11 except the isolation valve of tank 10B.

The other shorter flow path is indicated by arrow 126. In this case, the flow path exits tank 10A via the vapor line 6 and isolation valve 11 of tank 10A toward the maintenance manifold 4 and reenters tank 10B via the vapor line 6 and isolation valve 11 of tank 10B.

During the aeration operation of tank 10B, gas phase natural gas stream 26 or 126 flushes inert gas 22 toward the bottom portion of tank 10B. To create a pressure differential that allows natural gas stream 26 or 126 to enter tank 10B, the pressure in tank 10B is maintained at a lower pressure than tank 10A by allowing inert gas stream 27 to exit via fill line 9, liquid manifold 1, and mast riser 13 connected to liquid manifold 1. This is preferably the front mast, furthest from the cabin of the vessel. The relative pressure in tank 10B during aeration may be, for example, about 60 millibar (6 kPa), while the relative pressure in tank 10A may be, for example, between 150 millibar (15 kPa) and 180 millibar (18 kPa).

Fig. 4 is a diagram showing the evolution of the thermodynamic state of the tank 10A during the cooling operation. The x-axis represents time in hours. The right y-axis represents the temperature of the gas phase in tank 10A in degrees celsius (°c), and curve 41 represents the evolution of the gas phase temperature from ambient temperature (30 ℃ in this example) to about-130 ℃. The left y-axis represents the mass flow rate of the boil-off gas in kg/h, and curve 42 represents the evolution of the mass flow rate of the boil-off gas exiting tank 10A from the initial zero flow rate at the start of operation. The cooling operation of the large-capacity tank may take about 15 hours.

The quantitative values given in fig. 4 are purely illustrative. These values clearly show the following trend: at the beginning of the cooling operation, the produced boil-off gas is relatively hot and therefore not very dense, and the yield of said gas is initially low but increases rapidly. After a certain period of time, for example about 2 hours in fig. 4, the boil-off gas reaches a temperature too cold, for example about-25 ℃ in fig. 4, so that the boil-off gas becomes too dense to directly charge the tank 10B.

In this case, it may be necessary to end the first phase described with reference to fig. 3 and begin the second phase operation using the gas reheater 14, as shown in fig. 5.

In fig. 5, LNG flow 25 and inert gas flow 27 continue as previously described, but gas phase natural gas flow 26 is routed along a further flow path through gas reheater 14 where the gas flow is heated to a suitable temperature, such as about 20 c, to continue to charge tank 10B. The heated natural gas stream is indicated by arrow 28. In the example shown in fig. 5, the flow path exits tank 10A via a vapor line 6 and isolation valve 12, through vapor manifold 2, gas reheater 14, maintenance manifold 4, isolation valve 11 of tank 10B, and vapor line 6 to tank 10B.

Switching the gas phase natural gas stream 26 to the gas reheater 14 to initiate the second stage may be manual or automatic. The criteria for ending the first phase and starting the second phase may be temperature or gas phase density. The criteria may be monitored by a human operator or automatically performed by a control system.

During the entire cooling operation of tank 10A, if the amount of boil-off gas produced is excessive relative to the rate of progression of the charging operation of tank 10B, then the excess gas phase natural gas may be directed to the gas powered apparatus, for example, via connection 18.

The two stages for inflating the reserve tank 10B described above make it possible to use the boil-off gas that is inevitably generated during the cooling operation of the reserve tank 10A. However, two stages are not essential. For example, if the inflation of tank 10B is completed before the vapor gas temperature in tank 10A drops too low, the second stage is not required.

Conversely, it may be decided that the inflation of the tank 10B is started only after the flow of the boil-off gas becomes more stable and colder when the boil-off gas yield is relatively low, instead of starting the inflation of the tank 10B when the cooling operation of the tank 10A is started. In this case, it may be decided to use the gas reheater 14 directly, in which case the first stage described above does not occur.

The cooling operation of tank 10A may thus be fully or partially coincident with the inflation operation of tank 10B. If the cooling operation of tank 10A is completed before the inflation operation of tank 10B is completed, the inflation operation of tank 10B may be completed using any conventional method, as shown in FIG. 6.

In fig. 6, the storage tank 10A has been partially filled with liquid phase LNG after cooling. To continue the aeration of tank 10B, LNG stream 30 is pumped in liquid phase 23 stored in the bottom portion of tank 10A using jet pump 7 and delivered to vaporization unit 15, for example, via jet manifold 3. The gasification unit 15 then produces a gasified natural gas stream 29, for example at a temperature of about 20 ℃, which natural gas stream 29 is sent to the storage tank 10B to complete the aeration operation.

The method described above for simultaneously performing the cooling operation of the storage tank 10A and the charging operation of the storage tank 10B may be used to improve the gas testing procedure in a LNG carrier or any other LNG storage facility. Such a procedure is described below with reference to fig. 7.

Fig. 7 is a timing diagram illustrating a series of operations that may be used to conduct gas testing in an lng carrier having four storage tanks of similar capacity arranged in sequence along the length of the ship. Tank a is a tank at the stern of the ship and tank D is a tank at the front of the ship. The x-axis represents time in hours.

The operations designated by reference numerals 101 to 118 are as follows:

101: aeration of tank A

102 cooling of tank A

103: inflation of tank B (partial)

104: partial filling of tank A

105: inflation (filling) of tank B

106: cooling of tank B

107: activation of free-flowing combustion unit (GCU)

108: activation of low load compressor (LDC)

109: inflation (filling) of tank C

111: final activation of combustion units

112: transfer of liquid phase from tank A to tank B (Pump test)

113: cooling of tank C

114: inflation (filling) of canister D

115: transferring liquid phase from tank B to tank C

116: cooling of tank D

117: transferring liquid phase from tank C to tank D

118: the liquid phase is transferred from tank D to tank a.

Steps 101 through 104 are performed in conjunction with an external source of LNG, i.e., an onshore terminal or a fueling vessel to which the LNG carrier is connected. Steps 105 to 118 may be performed offshore and thus do not incur the cost of leasing an onshore terminal.

Block 100 in fig. 7 indicates that the tank cooling operation may partially or completely coincide with the next tank charging operation, except, of course, the last tank cooling. The boil-off gas produced by cooling may then be used for inflation using the methods described above. As a result, the total amount of boil-off gas generated by gas testing using this procedure is significantly reduced compared to conventional synchronization procedures.

This reduced amount of boil-off gas is more manageable, whether by re-liquefaction, combustion, return to the terminal or venting to the atmosphere, and is therefore beneficial in all circumstances. Such benefits may be reduced operating costs and/or environmental benefits (reduced emissions).

The gas test may be performed in one or more tanks on board the vessel. In case of multiple vessels, the vessels need to be connected so that fluids can be exchanged during the gas testing procedure. Thus, while operations performed using a single ship cargo handling system have been described above, it will be appreciated that these operations may also be performed using two or more ships cargo handling systems coupled to one another. In this case, a manifold, such as a gasification manifold, may be understood as a combination of gasification manifolds of different interconnected vessels.

Referring to fig. 8, a cross-sectional view of a lng carrier ship 70 shows a sealed and insulated tank 71 having an overall prismatic shape mounted in a double hull 72 of the ship. The walls of the tank 71 have: a primary sealing barrier intended to be in contact with LNG contained in the tank; a secondary sealing barrier disposed between the first sealing barrier and the double hull 72 of the ship; and two thermal insulation barriers disposed between the first and second sealing barriers and between the second sealing barrier and the double hull 72, respectively.

In a known manner, loading/unloading pipelines 73 arranged on the upper deck of the ship can be connected to offshore or port terminals using suitable connectors to transfer LNG cargo to and from tanks 71.

Fig. 8 shows an exemplary offshore terminal comprising a loading/unloading point 75, a subsea pipeline 76 and an onshore facility 77. The loading/unloading point 75 is a static offshore facility comprising a movable arm 74 and a column 78 holding the movable arm 74. The movable arm 74 carries a bundle of insulated hoses 79 that can be connected to the load/unload conduit 73. The orientable and movable arm 74 may be adapted for use with all sizes of lng carriers. A connecting line (not shown) extends within column 78. The loading/unloading site 75 allows lng carrier 70 to be loaded and unloaded to and from an onshore facility 77, or from an onshore facility 77. The facility has a liquefied gas storage tank 80 and a connection line 81 connected to the loading/unloading site 75 via a subsea line 76. The subsea pipeline 76 enables liquefied gas to be transferred a significant distance, for example 5km, between the loading/unloading point 75 and the onshore facility 77, which enables the lng carrier 70 to be moved away from the shore during loading and unloading operations.

To generate the pressure required to transfer the liquefied gas, pumps carried on board the ship 70 and/or mounted at an onshore facility 77 and/or mounted at a loading/unloading point 75 are used.

While the invention has been described in connection with several specific embodiments, it is obvious that it is in no way limited thereto, and that the invention includes all technical equivalents of the means described and all combinations of them that fall within the scope of the invention.

Use of the verb "comprise" or "comprise" does not exclude the presence of other elements or steps than those mentioned in the claims, when included in the context of an homonym.

In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

Claims

CLAIMS 1. An inflation method for inflating a storage tank in a liquefied gas storage facility on a floating structure, the method comprising:

bringing a liquefied gas storage facility into readiness, the liquefied gas storage facility comprising a plurality of storage tanks (10A-10C) and at least one manifold (4, 2) connected in parallel to the a top portion of each of the storage tanks, a first storage tank (10A) of the storage tanks in the preparatory state is filled with a gaseous phase liquefied gas (21), and the gaseous phase in the first tank The temperature of the liquefied gas is higher than the liquid-gas equilibrium temperature of the liquefied gas, and the second storage tank (10B) of the storage tanks in the preparation state is filled with an inert gas (22);

Injecting a liquid-phase liquefied gas flow (25) into the first storage tank (10A) to cool the first tank and partially vaporize the liquid-phase liquefied gas in the first tank, or all vaporized;

Upon injection of said flow of liquefied gas in liquid phase (25) into said first storage tank (10A), said at least one manifold (4 , 2) delivering a gas-phase liquefied gas stream (26, 126) generated by vaporization of said liquid-phase liquefied gas from a top portion of said first tank to a top portion of said second storage tank (10B) , the density of the gas-phase liquefied gas (21) is lower than the density of the inert gas (22);

The inert gas flow (27) is released from the bottom portion of the second tank (10B) under the pressure of the gas-phase liquefied gas flow such that the gas-phase liquefied gas (21) is at least in the second storage tank (10B) The inert gas (22) is replaced in the top section.

2. The method according to claim 1, wherein said at least one manifold is a maintenance manifold (4) connected in parallel to said a top portion of each of the storage tanks, the gas phase liquefied gas stream (26, 126) is diverted from the first storage tank through a first isolation valve (11) associated with the first storage tank (10A) to the maintenance manifold (4), and/or divert the gas phase liquefied gas stream (26, 126) from the A maintenance manifold (4) transfers to the top portion of said second storage tank (10B).

3. The method according to claim 2, wherein said at least one manifold further comprises a vapor manifold (2), said vapor manifold is thermally insulated, said vapor manifold (2) via A corresponding second isolation valve (12) is connected in parallel to the top portion of each of the storage tanks, the vapor manifold (2) and the maintenance manifold (4) in series connection, the gas phase liquefied gas stream (26) is sequentially sent through the first isolation valve (11) associated with the first storage tank (10A), the maintenance manifold (4), the A gaseous product manifold (2) and said second isolation valve (12) associated with said second storage tank (10B), or said gas phase liquefied gas stream (26) sequentially passed through said first said second isolation valve (12), said vapor manifold (2), said maintenance manifold (4) associated with said second storage tank and said first isolation valve associated with said second storage tank (11).

4. The method according to one of the claims 1 to 3, wherein the gas phase liquefied gas flow (26, 126) flows by natural convection from the top part of the first storage tank (10A) to the The top part of the second storage tank (10B).

5. The method according to one of claims 1 to 3, wherein the liquefied gas storage facility further comprises a gas reheating device (14) having a gas reheating device connected to the maintenance manifold ( 4) and the inlet of one of the vapor manifold (2) and the outlet connected to the other of the maintenance manifold (4) and the vapor manifold (2), in the gas phase The gas phase liquefied gas stream (26, 28) is also passed through the gas reheating device to liquefy the gas phase before the liquefied gas stream (26, 28) reaches the top portion of the second storage tank (10B). The gas streams (26, 28) are reheated.

6. The method according to one of claims 1 to 3, wherein the liquefied gas storage facility further comprises a gas reheating device (14) having a gas reheating device connected to the maintenance manifold and an inlet of one of said vapor manifold (2) and an outlet connected to the other of said maintenance manifold (4) and said vapor manifold (2),

wherein during the first flow phase, the gas phase liquefied gas stream (26) flows by natural convection from the top portion of the first storage tank to the top portion of the second storage tank, and

During the second flow phase, the gas-phase liquefied gas stream (26, 28) is also conveyed through the gas reheating Means (14) for reheating said gas phase liquefied gas streams (26, 28).

7. The method according to claim 6, wherein said method further comprises the steps of:

monitoring the temperature of said gas-phase liquefied gas leaving said first storage tank (10A) during a first flow phase; and

The gas-phase liquefied gas flow (26) is switched to the reheating device (14) when the temperature of the gas-phase liquefied gas satisfies a predetermined criterion.

8. The method according to one of claims 1 to 7, wherein the liquid phase liquefied gas stream (25) is delivered from an onshore terminal (77) to which the liquefied gas storage facility is connected ( 77).

9. The method according to one of claims 1 to 7, wherein the stream of liquefied gas in liquid phase (25) is delivered from a bunkering ship to which the liquefied gas storage facility is connected .

10. The method according to one of claims 1 to 7, wherein the liquefied gas storage facility comprises a third storage tank and an injection manifold (3) connected in parallel to the Each of the storage tanks (10A-10C), the third storage tank in a standby state is partially filled or completely filled with the liquid-phase liquefied gas, and wherein the flow of the liquid-phase liquefied gas (25) Pumped into the third tank and delivered by the injection manifold (3) to the first tank.

11. The method according to one of claims 1 to 10, wherein the stream of liquefied gas in liquid phase is injected into the first storage tank by means of injection means (5).

12. The method according to one of claims 1 to 11, wherein the liquefied gas storage facility comprises a liquid manifold (1) and a mast riser (13) connected to the liquid manifold (1) , the liquid manifold is connected in parallel to the bottom portion of each of the storage tanks (10A-10C), and wherein, through the liquid manifold (1) will leave the second tank A flow of inert gas (27) from (10B) is delivered to said mast riser (13).

13. A method for gas testing in a liquefied gas storage facility on a floating structure, the gas testing comprising:

The second storage tank is charged (103, 105) using a method according to one of claims 1 to 12, and, when the second storage tank has been charged,

A stream of liquefied gas in liquid phase is injected (106) into the second storage tank to cool the second storage tank.

14. A liquefied gas storage facility carried on a floating structure, the liquefied gas storage facility comprising:

multiple storage tanks (10A-10C),

a maintenance manifold (4) connected in parallel to the top portion of each of the storage tanks via a respective first isolation valve (11);

a vapor manifold (2) connected in parallel to the top portion of each of the storage tanks via a respective second isolation valve (12), the vapor manifold is insulated;

a liquid manifold (1) connected in parallel to the bottom portion of each of the storage tanks, the liquid manifold being thermally insulated; and

a mast riser (13) connected to the liquid manifold;

Each of the storage tanks (10A-10C) includes a fill line (9) connected to the liquid manifold (1) and a vapor line (6), the vapor A line (6) leads to the top portion of the storage tank, and the vapor line (6) is connected in parallel to the a maintenance manifold (4), and said vapor line (6) is connected in parallel to said vapor manifold (2) through said second isolation valve (12) associated with said storage tank;

The first isolation valve (11) is switchable to selectively communicate the maintenance manifold (4) with the top portion of the first one of the storage tanks (10A) to allow gas phase liquefied gas flow (26) is transferred from said first storage tank (10A) to said maintenance manifold (4) through said first isolation valve (11) associated with said first storage tank (10A).

15. The liquefied gas storage facility according to claim 14, wherein the vapor manifold (2) is connected in series with the maintenance manifold (4), and the second isolation valve (12) can is switched to selectively connect the vapor manifold (2) with the top portion of a second of the storage tanks (10B) so that the gas phase liquefied gas stream (26) flows from the first A storage tank sequentially passes through said first isolation valve (11) associated with said first storage tank, said maintenance manifold (4), said vapor manifold (2) and with said second storage tank The second isolation valve (12) associated with the tank is delivered to the second storage tank.

16. The liquefied gas storage facility according to claim 14 or 15, further comprising an injection manifold (3) and an injection device (5), the injection manifolds (3) being connected in parallel to each of the storage tanks, the spraying device (5) is arranged in the top portion of each of the tanks, and the spraying device (5) is connected to the spraying manifold ( 3).

17. A liquefied gas storage facility according to any one of claims 14 to 16, wherein the floating structure is a vessel (70) for liquefied gas.

18. A test system for performing gas tests, said system comprising: a liquefied gas storage facility according to claim 17; arranged to connect said liquid manifold (1) or injection manifold (3) to insulated pipes (73, 79, 76, 81) of an onshore terminal (77); and a pump for driving liquid-phase liquefied gas from the onshore terminal through insulated pipes to the liquid manifold pipe (1) or the injection manifold (3).