KR102533123B1 - Fluid management in sealed and insulated tanks - Google Patents

Abstract

The present invention relates to a method for fluid management of a sealed and insulated tank (1) for storing liquefied gas (8) at low temperatures. The wall of the tank having a multi-layer structure includes an outer load bearing wall (2), a first sealing membrane (9) in contact with the liquefied gas stored in the tank, and an intermediate space (3) disposed between the first sealing membrane and the outer load bearing wall. wherein the method sucks gaseous phase out of the wall of the tank in the intermediate space to lower the pressure in the intermediate space below the working pressure of the intermediate space, and detects a stabilization of the measured pressure in the intermediate space during the suction step; Including heating the walls of the tank.

Description

Fluid management in sealed and insulated tanks

The present invention is in the field of sealed and insulated tanks for the storage and/or transport of liquefied gas at low temperatures, and in particular in the field of membrane tanks.

The density of a gas can be reduced at a very high rate by liquefaction of the gas. Therefore, it is advantageous to store or transport gases in a liquefied state at low temperatures. For example, in the case of liquefied natural gas (LNG), the density decreases exponentially by 600 in the gaseous state at ambient temperature and pressure and in the liquid state at approximately -163 °C and atmospheric pressure.

It is known that sealed and insulated tanks have multi-layered walls. The multilayer structure comprises an outer bearing wall, a first sealing membrane in contact with the liquefied gas stored in the tank, a second sealing membrane disposed between the outer bearing wall and the first sealing membrane, and the second sealing membrane and the outer bearing wall. It includes a second space located between, a first space located between the second sealing membrane and the first sealing membrane, and a second insulating barrier made of a solid insulating material disposed within the second space.

In some tank structures, the first insulating barrier is also disposed in the first space. When the walls of the tank are in normal working condition, the storage of the tank is insulated from the outside by overlapping the first and second insulating barriers. After rupture or failure of the first membrane, if the liquefied gas stored in the tank flows into the first space, to prevent it from reaching an excessive cooling temperature at which load-bearing walls are likely to fail, especially in the case of a ship's hull. , a second insulating barrier is maintained to insulate the load-bearing structure from the cooled fluid.

Other tank structures have a first space that is very thin compared to the second space, so that the first insulating barrier is omitted or greatly reduced. For example, such tanks are disclosed in FR-A-2709725, FR-A-2781036 and EP-A-1898143.

An advantage of this choice is that the insulation of the load-bearing walls is substantially the same as in normal operation and when liquefied gas enters the first space. For this reason, the grade of the material of the load-bearing structure, in particular the steel of the ship's hull, can be optimized. Furthermore, since the thermal equilibrium changes little, there are no components likely to suffer a thermal shock if the sealing of the first membrane is lost. Therefore, it is possible to dimension the second sealing membrane for two very different operating points, which simplifies the optimization and design of such membranes to withstand fatigue stresses, for example stresses due to elongation of the ship's beams due to expansion. no need.

WO-A-2010139914 describes a method for testing the sealing of a membrane tank. The test is initially performed in a tank whose temperature is close to ambient temperature. This method is therefore not relevant for sealing and insulating tanks where the first sealing membrane is the low temperature of the liquefied gas load.

The idea underlying the invention is to prevent the occurrence of sudden overpressure in the first space of a membrane tank, especially in the case of a tank in which the first space is very thin.

Some aspects of the present invention start with observing the leakage of fluid or vapor through the first sealing membrane caused by the presence of a liquid phase in a very thin first space at a temperature of significant load. The liquid phase actually enters into liquid form and remains on the equilibrium curve, or enters into vapor form and condenses under the first sealing membrane or is based on materials present in the first space, or enters in any form and has high adsorption capacity or capillary can be absorbed by solid materials showing the phenomenon. To this end, plywood is a material commonly used for insulating barriers. For example, tests conducted in the laboratory indicate that the material can absorb LNG. Under the temperature and pressure conditions corresponding to the two-phase equilibrium curve of methane in the first space and the liquid leakage condition, the plywood can be filled with 18 to 20% of the LNG weight.

Upon heating the membrane tank, the heavy gas in the first space in condensed form or adsorbed by the wood will be vaporized. In systems with a reduced primary space where the head loss is very significant, there is a risk of overpressure forming in the region of the primary space away from the discharge point. The pressure can damage the first barrier enormously and thus cause serious damage to the tank. In some arrangements, the load on the anchorage connecting both barriers can damage the second barrier, which itself creates an outflow channel, threatening the integrity of the tanked vessel.

One object of the present invention is therefore to propose a heating process without the risk of an increase in pressure in the first space. The heating process may be applied in other situations, such as technical intervention of the user to the tank, for example regulatory inspection of the tank, maintenance or repair of components of the tank. It can also be applied to temporarily or permanently stop the driving of the tank.

To this end, according to one embodiment, the present invention provides a method for managing fluid in a sealed and insulated tank for storing liquefied gas at a low temperature,

The wall of the tank has a multi-layer structure and has an outer bearing wall, a first sealing membrane in contact with liquefied gas stored in the tank, and an intermediate space (3) disposed between the first sealing membrane and the outer bearing wall, wherein the method silver,

sucking the gaseous phase out of the wall of the tank in the intermediate space to lower the pressure in the intermediate space below the working pressure in the intermediate space;

detecting the stability of the pressure in the intermediate space during the suction phase;

and heating the walls of the tank.

Heating the walls of the tank may include emptying the tank of a liquefied gas load at a low temperature.

Thanks to this technical feature, when heating the walls of the tank, it is possible to forcibly vaporize the liquid phase that may accumulate in the intermediate space, in particular in the first space. Even in the solid phase, vaporization can be forced by shifting the pressure acting on the intermediate space below the parallel point at that temperature, which is the temperature of the load in contact with the first membrane.

The emptying and heating of this sealed and insulated tank can follow the sequence of the following steps when it is initially loaded with a load of liquefied gas at low temperatures:

- Offloading: The load is offloaded to the offloading tank using one or more main pumps located in the tank. At the end of offloading, a heel of liquefied gas remains which cannot be pumped by the main pump.

- Drying: Prior to technical shutdown of the tank, offloading can be completed using a drying pump discharged into a manifold with a smaller diameter than the main pump. At the end of this stage, the heel of the liquefied gas is reduced to a so-called unpumpable amount.

- Heating: Heating is an operation aimed at evaporating the non-pumpable load while bringing the temperature of the tank wall, including the insulation, closer to the ambient temperature.

Heating does not necessarily immediately follow off-loading. In fact, it is possible to maintain all or nearly all of the first membrane at the low temperature of the liquefied gas for a short or long time during and after the off-loading step. For this purpose, it is possible to inject liquefied gas onto the inner surface of the first sealing membrane. The spraying process is particularly applicable to liquefied gas transport vessels, ie bottom-loaded with almost empty tanks. In this case, the liquefied gas to be sprayed may come from the tank itself.

To reduce the stored vapor load on the tank and its associated conveying system, and to avoid the risk of ignition, heating can be done after the inert gas injection treatment: an operator can then access the inside of the tank to perform an internal inspection, or there Ventilation work is done in order to carry out periodic inspections.

According to a preferred embodiment, the method for managing the fluid may have one or more of the following features.

In the sequence indicated above, the fluid management method can be triggered in another step at the moment when the sealing membrane is at the lower temperature of the load. The method may be triggered in particular at the beginning, during or end of an offloading phase, or at the beginning, during or end of a drying phase as required.

According to one embodiment, the method is triggered while the sealed and insulated tank is still filled with a load of liquefied gas at low temperature.

According to one embodiment, the method is triggered while the sealing and insulating tank initially stores the heel of the liquefied gas at a low temperature, and the step of heating the walls of the tank with the heel of the liquefied gas at a low temperature. and emptying the tank.

According to an embodiment, the method may be used to seal the first seal at a low temperature of the liquefied gas during the duration of the pressure stabilization test and at least until the beginning of the heating step, for example by spraying the liquefied gas onto the inner surface of the first sealing membrane. Further comprising the step of maintaining the membrane.

According to one embodiment, the heel of liquefied gas at low temperature is triggered while the pump installed in the sealed and insulated tank at low temperature has an unpumpable quantity of liquefied gas. In order to maintain the first sealing membrane at said low temperature of the liquefied gas at least until the start of the heating phase, liquefied gas may be injected into it from a source other than the tank itself.

In one embodiment, suction of the gas phase is done by a vacuum pump regulated to reach a set pressure. Preferably, the difference between the preset set pressure and the working pressure of the intermediate space is greater than 10 kPa.

In one embodiment, stabilization of the pressure in the intermediate space is detected after the pressure has stopped changing for a settling time of at least 1 hour, preferably at least 2 hours. Qualitatively, the stability time should increase in direct proportion to the size of the free volume of the intermediate space.

Stabilization of the pressure can be verified using various quantitative criteria. One criterion that can be used to determine that a physical quantity has stabilized during a settling time (T) is to verify that the relative change in the quantity remains below a predetermined threshold (X). That is, when the pressure change at t0 is DP(t), the pressure P(t) is defined as:

The criterion for stability during the settling time (T) is:

,

,

During the methods described herein, the level of accuracy required will depend on considerations specific to the application set out and, in particular, the nature of the storage fixture and the associated safety requirements depending on the nature of the contents stored therein. X can be, for example, 5% or less, preferably 2% or less, even 1% or less. The above criterion also applies to other physical quantities such as temperature.

In one embodiment, the method further comprises selecting a heating procedure based on the stabilized pressure in the intermediate space during the suctioning step. Thanks to this feature, it is possible to select a heating process suitable for the conditions actually obtained in the intermediate space.

In one embodiment, the rapid heating process is selected when the stabilized pressure in the intermediate space during the suction phase is less than or equal to a predetermined threshold pressure lower than the working pressure. The rapid heating process may further include injecting hot gas into the tank from which the load of liquefied gas has been removed at low temperature. A hot gas is, for example, an exhaust gas from a heat engine, a gas heated through a heat exchanger, or other gas having a temperature higher than ambient temperature.

In one embodiment, a slow heating process is selected when the stabilized pressure in the intermediate space during the suction phase is higher than a preset threshold pressure value lower than the working pressure. The slow heating process may involve slowly emptying the tank and/or leaving the walls of the tank to naturally balance with the ambient temperature as the tank is emptied. The slow heating process may include injecting a cooling gas into the tank or injecting a stream of LNG or liquid nitrogen into the tank, particularly the top of the tank, while the tank is removing the load of liquefied gas at low temperatures. The cooling gas may be nitrogen or another inert gas below ambient temperature. Injecting a flow of liquefied gas can more effectively slow down the temperature rise naturally by consuming latent heat due to vaporization of the flow. If necessary, a liquid nitrogen tank connected to a spray boom may be used as follows.

In one embodiment, the method further comprises:

detecting the presence of a liquid phase in the intermediate space;

Maintaining suction of the gas phase into the intermediate space to substantially evaporate and/or adsorb any liquid phase prior to heating of the tank walls.

Detection of the liquid phase can be performed in a variety of ways. In one embodiment, the presence of the liquid phase is detected in response to stabilization of the pressure in the intermediate space at an intermediate level between the predetermined target pressure and the working pressure. Evaporation and/or adsorption of the entire liquid phase is detected in response to a subsequent drop in pressure in the intermediate space below the intermediate level.

In one embodiment, detection of the liquid phase includes:

Measuring the temperature of the intermediate space of the intermediate space for a period of time from the drop in absolute pressure in the intermediate space;

The liquid phase is detected in response to the stability of the temperature in the intermediate space near the liquid-vapor equilibrium point of the liquefied gas for the preset target pressure, and the entire liquid phase is detected in response to the stability of the temperature in the intermediate space near the temperature of the liquefied gas stored in the tank. detecting the evaporation and/or adsorption of

Thanks to this technical feature, the determining step constitutes whether the fluid in the intermediate space behaves like a two-phase equilibrium with the pressure taken into account, or whether the fluid is in thermal equilibrium with its environment independently of the applied pressure. do.

In one embodiment, lowering the pressure in the intermediate space includes:

lowering the pressure in the intermediate space to a first pressure threshold lower than the working pressure;

lowering the pressure to a first pressure threshold, then measuring a first pressure in the intermediate space;

lowering the pressure in the middle space to a second pressure threshold lower than the first pressure threshold;

measuring a second temperature of the intermediate space at successive instants after lowering the pressure to a second pressure threshold;

determining a difference between the second temperature and the first temperature;

If the difference between the second temperature and the first temperature is not lower than a predetermined threshold temperature value, delaying the heating of the tank and maintaining suction;

and selecting the heating step after the difference between the first temperature and the second temperature becomes lower than a preset threshold temperature value. A slow or fast process can be selected based on the stabilized pressure.

In one embodiment, if the difference between the second temperature and the first temperature is not less than a preset temperature threshold after a preset maximum intake time, a slow heating process is selected. Since such a situation implies a very high risk of ingress of the liquid phase present through the first membrane, heating of the tank must be accompanied by safety measures.

In an embodiment, the intermediate space includes a second sealing membrane disposed between the outer load bearing wall and the first sealing membrane, a second space located between the second sealing membrane and the outer load bearing wall, and a second sealing membrane and the first sealing membrane. A first space located therebetween, and a second solid insulating barrier disposed within the second space,

The thickness of the first space is much smaller than the thickness of the second space,

The pressure in the second space and the first space is lowered to keep the pressure difference between the second space and the first space below a safe threshold; and

Stability of the pressure in at least the first space is detected to select a heating process based on the stable pressure in the first space.

In one embodiment, the pressure in the second space is lowered below the pressure in the first space.

The present invention also provides a device for fluid management for a sealed and insulated tank for storing liquefied gas at low temperatures. The wall of the tank has a multi-layer structure, the multi-layer structure including an outer load bearing wall, a first sealing membrane in contact with the liquid gas stored in the tank, and an intermediate space located between the first sealing membrane and the outer load bearing wall;

Devices for fluid management include:

a pressure sensor for measuring the pressure in the intermediate space;

A vacuum pump connected to the intermediate space to suck gas from the intermediate space to the outside of the wall of the tank, and capable of lowering the pressure in the intermediate space below the working pressure of the intermediate space;

and a control module capable of detecting stabilization of the pressure in the intermediate space during the suction phase and selecting a heating process based on the stabilized pressure in the intermediate space during the suction phase.

The device can be applied to perform the methods described above. According to a preferred embodiment, the device may have one or more of the following features.

In one embodiment, the device further includes a temperature sensor for measuring the temperature in the Zhongshan space, and the control module drives the vacuum pump and the temperature sensor as follows.

lowering the pressure in the intermediate space to a first critical pressure value lower than the working pressure;

Measuring the first temperature of the intermediate space after lowering the pressure to a first critical pressure value;

lowering the pressure in the intermediate space to a second threshold pressure value lower than the first threshold pressure value;

measuring a second temperature in the intermediate space at successive instants after lowering the pressure to a second critical pressure value;

determining a difference between the second temperature and the first temperature;

If the difference between the second temperature and the first temperature is not lower than a preset threshold temperature value, delaying the heating of the tank and maintaining suction;

selecting the heating step after the difference between the first temperature and the second temperature becomes lower than a predetermined threshold temperature value.

In one embodiment, the middle space is a second sealing membrane disposed between the outer load bearing wall and the first sealing membrane, a second space located between the second sealing membrane and the outer load bearing wall, and between the second sealing membrane and the first sealing membrane. Including a first space located in, and a second solid heat insulating barrier disposed in the second space,

The thickness of the first space is much smaller than the thickness of the second space, and

A vacuum pump connected to at least the first space;

and a control module capable of detecting stability of pressure in at least the first space to select a heating process based on the stabilized pressure in the first space.

In one embodiment, the apparatus further comprises a fluid link connecting the second space and the first space, the fluid link being essentially closed, and a pressure difference between the first space and the second space greater than a predetermined opening threshold. and a valve that can be opened in response to

In one embodiment, the first vacuum pump is connected to the first space and the second vacuum pump is connected to the second space. In another embodiment, the vacuum pumps are connected in parallel to the first space by a first suction pipe and to the second space by a second suction pipe, each suction pipe having a head loss member.

Tanks with devices for fluid management are some form of land storage installations, for example for storing LNG, or offshore or deep-water offshore structures, in particular methane tankers, ethane tankers, floating storage and regasification units (FSRUs), floating It may be a crude oil production storage and offloading facility (FPSO).

According to one embodiment, a liquefied gas transport vessel includes a double hull and the aforementioned tank disposed in the double hull.

According to an embodiment, the present invention is also a method of loading or offloading the vessel, wherein the fluid is transferred from a floating structure or a land structure to a tank of the vessel or from a tank of the vessel to a floating structure or a land structure through an insulated pipeline. provides a way to become

According to one embodiment, the present invention also provides a delivery system for a fluid. The transportation system includes an insulation pipe arranged to connect the above-mentioned ship, a tank installed on the ship's hull to a floating storage facility or land storage facility, or a floating storage facility from a floating storage facility or land storage facility to a ship's tank or from a ship's tank to a floating storage facility. The facility or onshore storage facility has a pump to drive the fluid through an insulated pipeline.

One object of the present invention is therefore to propose a heating process without the risk of an increase in pressure in the first space. The heating process may be applied in other situations, such as technical intervention of the user to the tank, for example regulatory inspection of the tank, maintenance or repair of components of the tank. It can also be applied to temporarily or permanently stop the driving of the tank.

The present invention will be better understood, and other objects, features and advantages of the invention will be obtained from the following detailed description of several specific embodiments of the invention, which are described in an illustrative and non-limiting manner only, with reference to the accompanying drawings. it will become clear
- Figure 1 shows a cross-section of a sealing and insulating tank with a fluid management device according to an embodiment.
- Figure 2 is a diagram showing the steps of the management method applicable to the tank according to the first embodiment of Figure 1.
- Figure 3 is a diagram showing the steps of the management method applicable to the tank according to the second embodiment of Figure 1.
- Figure 4 is a diagram showing the complementary steps of the management of Figure 3;
- Figure 5 shows the pressure measured in the tank of Figure 1 in normal operating conditions.
- Figure 6 is a diagram showing the pressure measured in the tank of Figure 1 in the leaking state of the bearing wall.
- FIG. 7 is a diagram showing the pressure measured in the tank of FIG. 1 with the second membrane leaking.
- Figure 8 is a diagram showing the pressure measured in the tank of Figure 1 in the leaky state and the non-leak state of the first membrane.
- Figure 9 is a diagram showing the steps of a management method applicable to the tank of Figure 1 according to the third embodiment.
- Figure 10 is a diagram showing the complementary steps of the management of Figure 9;
- Figure 11 is a diagram showing the pressure measured in the tank of Figure 1 during the management method of Figure 9.
- Figure 12 is a diagram showing the temperature measured in the tank of Figure 1 during the management method of Figure 9.
- Figure 13 is a partial view of the fluid management device of Figure 1 according to a modified example.
- Figure 14 is a partial view of the fluid management device of Figure 1 according to another variant.
- Fig. 15 is a bottom view of a first insulating barrier member that can be applied in the tank of Fig. 1;
- FIG. 16 is a partial cross-sectional view of a tank wall to which the first insulating barrier member of FIG. 15 is applied.
- Figure 17 is a cut-away view of a methane tanker equipped with a tank and a terminal for loading/offloading the tank.

In the description and claims, the term "gas" refers to a gas having general properties and composed of a pure single substance or a mixture of a plurality of components. Thus, liquefied gas refers to a chemical or mixture of chemicals that is disposed in the liquid phase at low temperatures and exists in the vapor state at normal temperature and pressure.

Referring to Figure 1, a sealed and insulated tank 1 for storage and transport of liquefied gas is shown. The tank 1 may be installed on land or on a floating structure. In the case of a floating structure, the tank may be installed in the hull of a liquefied gas carrier such as a methane tanker. It can also be applied to any vessel that consumes gas-generated means such as power trains, generator sets, steam generators or other means of energy use. For example, it could be a cargo carrier, passenger ship, fishing boat, floating electricity generating unit or the like.

The tank 1 is a membrane tank having a multi-layered wall, and the wall of the multi-layered structure is a load-bearing wall 2, which is an inner wall of a double hull of a ship, from the outside to the inside of the tank 1, for example, a load-bearing wall 2 ) The second space 3 including the second insulating member 4 in contact, the second sealing membrane 5 in contact with the second insulating member 4, and the solid in contact with the second sealing membrane 5 a first space (6) which may have a member (7), and a first sealing membrane (9) in contact with the liquefied gas (8) stored in the tank.

The tank may in particular have the shape of a parallelepiped, prism or polyhedron.

The tank 1 shown in FIG. 1 has a first space 6 of small thickness and thus has a small volume. It is filled with a solid modular member 7 with a small thickness, which can perform a function of thermal insulation, load carrying function and/or mechanical protection against puncture of the second sealing membrane 5 . The solid modular member 7, like the second insulating member 4, may be made of different materials, for example plywood, polymer form, glass wool or rock wool, expanded perlite, aerosol, balsa (balsa) and other insulating materials.

In a variant, the first space 6 can also be an empty space between two sealing membranes, without solid material. An example of such a first space is described in publication EP-A-1898143.

Liquefied gas 8 is a cooling substance that can evaporate when heated to room temperature. In particular, the liquefied gas 8 may be liquefied natural gas (LNG), which is composed primarily of methane and one or more hydrocarbons, such as ethane, propane, n-butane, i-butane, n-pentane, i-pentane, It is a gaseous mixture containing small proportions of neopentane and nitrogen.

Liquefied gas 8 may also be ethane or liquefied petroleum gas (LPG), which is a mixture of hydrocarbons derived from refined oil that basically includes propane and butane. Liquefied gas 8 may also be nitrogen, helium, ethylene or liquefied hydrogen.

The liquefied gas 8 is stored in the inner space of the tank in a two-phase liquid-vapor equilibrium. Therefore, the gas is present in vapor state (10) at the top of the tank. The equilibrium temperature of liquefied natural gas corresponding to the two-phase liquid-vapor equilibrium is approximately -162°C when stored at atmospheric pressure.

During operation, the tank 1 is unavoidably subjected to high temperature fluctuations. In particular, since there is no load that is stored or transported in the tank 1 and used immediately, or intermediate repair or maintenance requires people and / or tools to enter the tank 1, the tank ( After 1) is operated to transport or store the liquefied gas 8, the tank must be completely emptied and the tank 1 heated to ambient temperature.

The tank 1 of FIG. 1 includes one or more pressure sensors 41 for measuring the pressure in the first space 6 and one or more pressure sensors 42 for measuring the pressure in the second space 3, At least one temperature sensor 45 for measuring the temperature of the first space 6 and at least one temperature sensor 46 for measuring the temperature of the second space 3 are provided. The purpose of the sensors will be explained in the detailed description of the methods below.

A detailed description of the procedures by which the tank 1 can be heated safely as a whole while avoiding the occurrence of unacceptable overpressure in the first space 6 follows. It is important to note that the pressure change produced by the flow of gas introduced into the proposed closed space is faster as the volume of the space is smaller. Therefore, the risk of overpressure suddenly generated in the first space due to vaporization of a certain amount in gaseous form in the liquid phase is higher in the small volume first space. Nevertheless, the process described below can be applied to any membrane tank regardless of the volume of the first space.

Referring to Fig. 2, a heating method according to the first embodiment will be described. For the sake of explanation, it is assumed that the tank 1 initially stores a stored LNG load at a tank pressure close to atmospheric pressure. At this time, the liquid-vapor equilibrium point is close to -162 ℃. The tank pressure here is expressed as the absolute pressure prevailing in the vapor phase at the top of the tank 1, and thus determines the equilibrium temperature of the two phases in the tank 1. Within the strength limits of the sealing membranes, this is approximately ±10 kPa difference at atmospheric pressure.

The actual storage of the first space 6 and the second space 3 is not specifically known at the start of the heating process, and the existence of a liquid state that can vaporize during the heating process is neither certain nor excluded. However, except for the presence of sealing defects in the first membrane 9 or the load-bearing wall 2, the first space 6 and the second space 3 are initially stored in gaseous state at a pressure close to the tank temperature. It is assumed that

In step 11, a heating process is started to empty the tank or finish emptying the tank and heat the walls of the tank. In step 12, the second space 3 is depressurized using the vacuum pump 22. A vacuum pump is installed to pump gas phase into the second space 3 and discharge the pumped gas through the vapor manifold of the vessel or tank 1 to the outside of the tank wall, for example to the atmosphere. In step 13, the first space 6 is depressurized using the vacuum pump 21 . A vacuum pump is installed to pump gas phase into the first space 6 and discharge the pumped gas through the vapor manifold of the vessel or tank 1 to the outside of the tank wall, for example to the atmosphere.

The vacuum pumps 21 and 22 are implemented to perform the regulation of the absolute pressure of the first space 6 and the second space 3, respectively. For this purpose, target pressures are set: a first target pressure P ₀ -dp1 for the first space 6 and a second target pressure P ₀ -dp2 for the second space 3, where P ₀ represents the pressure in the tank, and dp1 and dp2 represent positive values. The purpose of the reduced pressure (-dp1) is to shift the liquid-vapor equilibrium that can be established in the first space (6). For example, forced evaporation of the liquid phase may be induced if leakage of liquefied gas 8 occurs therein, or if other gases are condensed or absorbed therein. The reduced pressure (-dp1) must be high so that the vaporization exhibits sufficient kinetic energy. Preferably, dp1 is approximately 10 to 50 kPa, for example approximately 20 kPa. While the vacuum pump 21 regulates the pressure in the first space 6 to set and maintain the first target pressure P ₀ -dp1, the vacuum pump 22 controls the second set pressure P ₀ -dp2. ) Adjust the pressure of the second space (3) to set and maintain. The purpose of the reduced pressure (-dp2) is to maintain a relative pressure balance on both sides of the second membrane 5, in case the second membrane 5 cannot normally withstand a high pressure difference. The set pressure must satisfy the following relational expression.

|dp1-dp2| <DP,

DP represents a preset safety threshold that guarantees the integrity of the second membrane 5 . Preferably, DP is set between 0.5 kPa and 4 kPa, for example 2 kPa. Preferably, the set pressure also satisfies the following relational expression.

dp2>dp1

The pressure difference on both sides of the second membrane 5 tends to press the latter against the second insulating barrier and prevent it from tearing at the second insulating barrier.

The vacuum pumps 21 and 22 are cryogenic pumps and can withstand cryogenic temperatures lower than -150°C. Additionally, they are designed to comply with ATEX regulations and prevent the risk of explosion. The vacuum pump may be equipped in various ways, for example, Roots type (so-called rotary lobe), vane, liquid ring, screw, venturi type effector. Suppliers of vacuum pumps are, for example, MPR Industries or the Bosch Group.

Adjustment of the absolute pressure using the vacuum pumps 21, 22 in the first space 6 and the second space 3 can be initiated simultaneously or sequentially, for a time sufficient for the pressure to stabilize at the level of the target pressure. It can be maintained, and as shown in step 14, it can be stably maintained for a preset stability time.

According to one embodiment, if there are no other means to detect the presence or absence of a liquid phase, in particular in the first space 6, the settling time is relatively long in order to allow evaporation of all possible liquid phases with a sufficient safety margin. is chosen Thus, the settling time may be on the order of several hours, for example between 2 and 10 hours. Conversely, if detection of the liquid phase is also implemented, a shorter settling time can be chosen, which is explained below.

At the end of the settling time, step 15 comprises proceeding with the emptying and heating of the tank 1 . Depending on the initial state of the tank, emptying can here relate to all loads or only to the liquid heel at the bottom of the tank. Heating can be achieved by simply connecting the emptied tank to ambient air or by injecting hot gas, eg combustion gas from a heating device, to speed up the heating. Pressure regulation by the vacuum pumps 21 and 22 preferably continues during step 15. This preheating enables the flow of liquid into the first space 6 to continue to vaporize due to the sealing defect of the first membrane 9 .

Figure 5 shows an exemplary embodiment of the method, when the reduced pressure (dp1, dp2) is 20 kPa. 5 is a diagram showing absolute pressure expressed in kPa on the y-axis and time expressed in seconds on the x-axis. Curve 16 represents the pressure in the first space and curve 17 represents the pressure in the second space. In this embodiment, the pressures 16 and 17 effectively reach the desired target pressure, which means that there is no sealing defect. In practice, detection of the fact that the target pressure has been effectively reached involves detecting a downward crossing of the set pressure of the vacuum pump and a detection threshold representing a positive tolerance difference. The difference in these tolerances is small compared to dp1 and dp2, typically between 0.1 and 1 kPa. Depending on the function of the structural features of the tank, in particular as a function of the head loss between the inlet of the vacuum pump and the pressure sensor, on the other hand as a function of the settling time, it can be more specifically fixed.

The process described above may be implemented under the control of the electronic control device 50 such as, for example, a programmed computer. To this end, the control device 50 is connected by means of links 43 and 44 to the pressure sensors 41 and 42 in order to obtain pressure measurements over time. The control device 50 is connected with the vacuum pumps 21 and 22 by links 23 and 24 to drive the vacuum pumps 21 and 22 after the lapse of time. Step 11 can be triggered manually, for example by actuation of a control element of a non-represented human-machine interface, or automatically, for example by receipt of a command from a central computer system, which is not displayed.

In this embodiment, the first space 6 is initially assumed to be the tank pressure P ₀ of the tank 1 . In a variant, the first space 6 is initially depressurized so that the working pressure Ps of the first space 6 is the tank pressure P ₀ of the tank 1 when the tank is full with its load. lower than In this case, if the liquid phase incidentally exists in the first space 6, then it is in an equilibrium state at the pressure Ps. Thus, evaporation of the liquid phase can also occur by dropping the pressure below the working pressure Ps. Therefore, the above method can be used in this case by setting the set pressure (Ps-dp1) in the first space (6) and setting the set pressure (Ps-dp2) in the second space (3).

Also, the aforementioned method can be applied to a tank with a single sealed membrane. For example, it can be applied when the second membrane 5 is removed or replaced with a self-sealing cover capable of withstanding pressure differentials. In this case, step 12 can be omitted.

The process of FIG. 2 is a purge process based on reduced pressure, which does not identify anomalies such as sealing defects of the first membrane 9 or the second membrane 5 . Moreover, the existence of a significant margin of safety in settling time does not optimize the duration of the process. Therefore, a process capable of detecting sealing defects of the first membrane 9, the second membrane 5 or the load-bearing wall 2 may be preferred. A process capable of detecting the presence of liquefied gas or gas absorbed by the material in the first space 6 may also be preferred.

3 and 4 show a heating process according to a second embodiment that satisfies these conditions.

The first two steps 11 and 12 are unchanged compared to FIG. 2 . In step 25, the pressure trend in the second space 3 is monitored using a pressure sensor to determine if the pressure converges towards the expected target pressure P ₀ -dp2. If the above test is satisfied, ie true in the example of FIG. 5 , the method proceeds to step 13 which is unchanged compared to FIG. 2 . Otherwise, the process proceeds to FIG. 4 and is described below.

The test of step 25 is useful to prevent damage to the second membrane 5 in the event of a sealing defect in the bearing wall 2 . This case is explained with reference to FIG. 6 . FIG. 6 is a view similar to FIG. 5 and shows an illustrative embodiment of the method. At this time, the reduced pressure (dp1, dp2) is equal to 20 kPa and has a significant sealing defect of the load-bearing wall (2). Curve 117 is a reference curve showing the expected pressure trend in the second space 3 under normal operating conditions. Curve 117 converges rapidly towards the target pressure (P ₀ -dp2). Curve 17 represents the actually measured pressure in the second space 3 . In this case, due to the permanent leakage flow rate through the load-bearing wall 2, the target pressure is significantly stable. Due to said leakage, there is a risk of the second space 3 storing a significant amount of gas absorbed by the second insulating element 4 . The danger is that it evaporates suddenly during heating and damages the sealed membrane. For this reason, if the test of step 25 is not satisfied after a certain monitoring time, the process of FIG. 4 is performed.

Referring to FIG. 4 , step 31 includes modifying the first target pressure to be compatible with the actually measured pressure P ₀ -2 in the second space 3 . That is, the value of dp1 is |dp1-2| < It is modified to satisfy DP.

Step 32 is equivalent to step 13 described above, but with a new set pressure (P ₀ -dp1). Accordingly, curve 16 in FIG. 6 represents the pressure measured in the first space 6 during the course. If less pressure is applied, step 32 cannot ensure release of the liquid phase with the same degree of stability as step 13.

Step 33 consists in finally carrying out the emptying and heating of the tank 1, but with slow kinetic energy if there is a risk of sudden evaporation of the contents in the second space and/or the first space. Depending on the initial state of the tank, emptying can here involve either all loads or only the liquid heel at the bottom of the tank. The slow heating process includes, for example, injecting LNG into the tank 1 from a load during all or part of the emptying time or heating time.

Returning to FIG. 3 , when step 13 is performed, step 26 uses the pressure sensor 41 to determine whether the pressure converges toward the expected target pressure P ₀ -dp1, in the first space 6 monitoring the pressure trend of If the test is satisfied, for example true in the example of FIG. 5 , the method proceeds to step 15 unchanged compared to FIG. 2 . Otherwise, the method proceeds to step 27.

The test of step 26 is useful to determine if there is a leak in the first membrane 9 . This case is explained with reference to FIG. 8 . Figure 8 is a view similar to Figure 5 showing an exemplary embodiment of the present method. The reduced pressures dp1 and dp2 are equal to 20 kPa and there is a significant sealing defect of the first membrane 9 . Curve 116 is a reference curve representing the expected pressure trend in the first space 6 under normal operating conditions. Curve 116 converges rapidly towards the set pressure (P ₀ -dp1). Curve 16 represents the actually measured pressure in the first space 6 . In this case, because of the permanent leakage flow rate through the first membrane 9, it is considerably more stable than the target pressure. Due to said leakage, there is a risk that the first space 6 will contain a significant amount of liquid and/or gas absorbed by the first insulating member 7 . The danger is that it evaporates suddenly during heating and damages the sealed membrane. For this reason, if the test of step 26 is not satisfied after a certain monitoring time, step 27 is performed.

Step 27 includes analyzing the trend curve of the measured pressure in the first space 6 to detect whether an intermediate stabilization plateau has been crossed. Curve 16 in FIG. 8 illustrates this trend. The curve 16 forms a plateau at an intermediate value Pi between the initial pressure and the final stable pressure before the curve 16 finally stabilizes at a value close to 90 kPa beyond 27000 s at one moment. It is temporarily stable between 15,000s and 20,000s and approaches 97kPa. The existence of the ballast means that a regular flow of gas, either by evaporation of the accumulated liquid phase or by desorption of the adsorbed phase, takes place during the period under the effect of reduced pressure in the first space 6 . Therefore, the crossing of the ballast and the stabilization of the pressure at a low level means that the liquid or absorbed state has completely evaporated, and the current heating can be carried out slowly or quickly depending on whether there is current leakage. To this end the method returns to step 26 indicated by arrow 28 . In the example of curve 16 of FIG. 8 , shown as a broken line, the final stable pressure is clearly higher than the set pressure, meaning that there is a permanent leakage flow rate. The resting pressure arises from the balance between the pumping flow rate and the leakage flow rate. In this case, the slow heating process should continue, i.e. the pressure has stabilized, and the method returns to step 27.

In Fig. 8, the dashed curve 216 illustrates another embodiment, in which the amount of condensed or absorbed liquid phase is stored in the first space without a permanent leakage flow rate. After passing through the vaporization stabilizer, the pressure is finally stabilized at the target pressure level. The method is unchanged with respect to FIG. 2 and proceeds to step 15. The existence of condensed or absorbed gas in the first space without leakage flow rate in the membrane may have various causes. For example, the residual gas may be due to a faulty or misconfigured sweep gas generator. This means that instead of creating a flow of pure nitrogen, a significant amount of another gas such as carbon dioxide, nitrogen dioxide or other impurities is introduced into the first space. Another possible source of impurities is solid material introduced into the first space for thermal insulation and structural reinforcement purposes. For example, it may be in the form of a polymer filled with an expandable material that is released by diffusion during the operating period of the tank. At the end of an operating period of months or years, the phenomenon can create significant accumulations of gases that condense or are adsorbed into the interior of the first space.

Depending on the embodiment, there may be several successive stabilization plateaus before the final plateau in pressure. For example, there is a specific example of an adsorbent-adsorbent material pair. Conversely, if it drops right down to the final stable value without a plateau, it means that there is no significant amount of content in the liquid to be evaporated or in the absorbed state.

In all examples, it is the level of the final stabilization pressure that allows the choice of either a fast heating process or a slow process. However, a relatively long stabilization time must be observed to ensure that the final pressure is actually reached. Therefore, a faster and more reliable procedure for detecting the presence of a liquid phase may be to also monitor the trend in temperature as described below.

As described above, the case of defects in the second membrane 5 does not occur. In fact, the defect can only change the trend of the kinetic energy of the pressure in the first and second spaces under the operation of the vacuum pump, and by itself does not prevent a decrease in the pressure to the target pressure, especially to the lowest target pressure. This embodiment is shown in FIG. 7 . FIG. 7 is a view similar to FIG. 5 showing an illustrative embodiment of the method, wherein the reduced pressures dp1 and dp2 are equal to 20 kPa, and significant sealing defects of the second membrane 5 exist. Curve 117 is a reference curve representing the expected pressure trend in the second space 3 under normal operating conditions. Curve 117 converges rapidly towards the set pressure (P ₀ -dp2). Curve 17 represents the actually measured pressure in the second space 3 . Curve 16 represents the pressure actually measured in the first space 6 . Because of the connection between the two spaces, the vacuum pump 22 lowers the pressure in the second space 3 less quickly than expected. In a variant, step 25 is also modified in order to detect the presence of a defect in the second sealing membrane 5 . To this end, a comparison of the fluctuations over time between the measured pressure 17 and the reference curve 117 is performed. In the rest, the course remains unchanged.

The reference curves 116 and 117 are indicated when the operating condition of the tank 1 is checked directly, for example when the vessel is "bedded-in".

Referring to FIGS. 9 to 12 , a detailed description of the heating process according to the third embodiment using a temperature measuring device in which temperature measurement is used to detect the presence of a liquid state in the first space 6 follows. . The purpose of the temperature measuring device is to evaluate the local behavior of the fluid in the first space 6 . To obtain information about the properties of the fluid at a given point, the process involves reducing the pressure and following the temperature trend. Lowering the pressure is believed to cool the vapor phase by expansion. However, given the large exchange surface of the first membrane 6 together with the liquid load 8, the vapor cooled in the first space is immediately heated up to the temperature of the load 8 by contact with the first membrane 8. do. Thus, when the pressure is lowered, the temperature returns to the initial temperature within a few minutes, after which the fluid in the first space 6 goes into the vapor phase. However, if the temperature tends toward the equilibrium temperature of the liquid considered low, then the first space contains non-zero liquid at least close to the temperature measurement point. Therefore, a network of temperature and pressure sensors distributed on the wall of the tank 1 is needed in order to be able to make local measurements in different areas of the wall of the tank 1 .

9 shows a method of managing pressure and acquiring measured values. 11 is a diagram showing the absolute pressure expressed in kPa on the y-axis and the time expressed in seconds on the x-axis, and the curves 16 and 17 are respectively the first space 6 and the second space ( Indicates the pressure measured in 3). 12 is a diagram showing the temperature in degrees Celsius on the y-axis and the time in seconds on the x-axis, and the curves 37 and 40 show the first space ( Indicates the temperature measured in 6).

In step 51, the pressure of the second space is lowered by a small difference (Rs), for example, 1 kPa, in order to lower the pressure similarly to that of the first space without excessive load on the second membrane 5. At step 52, the pressure in the first space is lowered by a small difference Rp, where Rp≤Rs. In step 53, a predetermined time delay is performed so that the temperature of the vapor state in the first space 6 is stabilized. In step 54, a reference temperature measurement Tr is obtained in the first space 6 and generally reflects a slight cooling compared to the initial temperature, and a faster return to equilibrium both when the mass of the liquid phase is low. do.

In step 55, the pressure of the second space is lowered by a large difference (Qs), for example, 20 kPa, so that the pressure is similar to that of the first space without excessive load on the second membrane 5. At step 56, the pressure in the first space is lowered by a large difference Qp, where Qp≤Qs. In step 57, a predetermined time delay is performed so that the temperature of the vapor state in the first space 6 is stabilized. In step 58, a second temperature measurement value Tm is obtained in the first space 6.

10 shows how to process temperature measurements. In step 61, the two-phase equilibrium temperature of the liquefied gas at the set pressure (P ₀ -Rp) is expressed as Te. At step 62, |Te-Tr| A positive threshold proportional to is determined and denoted by ε. In step 63, the following inequality is tested:

|Tm-Tr|≤ε

If the above inequality is satisfied, it means that the temperature equilibrates considerably at the same level for small and large pressure differences. The method leads to detection of the dry vapor phase at step 65 at the level of the measurement point. This case corresponds to curve 39 in FIG. 12 . Heating can then be performed immediately without risk.

If the above inequality is not satisfied, it means that the temperature equilibrates at significantly different levels for small and large pressure differences. The method reaches step 64, where the two-phase equilibrium temperature of the liquefied gas at the set pressure (P ₀ -Qp) is denoted by Tf. At step 66 the following inequalities are tested:

|Tf-Tm|≤ε

If the above inequality is verified, it means that the temperature at the equilibrium point at low pressure is fairly equilibrated. The method leads to detection of a vaporizing liquid phase at step 68 at the level of the measuring point. This case corresponds to curve 40 in FIG. 12 .

If the above inequality is not satisfied, the stabilization factor τ is computed at step 67 according to the equation:

τ=(Tm-Tf)/(Tr-Tf)

Depressurization must be maintained in the first space prior to heating of the tank, a longer time if the stabilization rate is low. Referring to FIG. 12 , heating may be performed from the moment the curve 40 approaches the temperature Te sufficiently, for example, 20,000 seconds.

The above method can be performed simultaneously or sequentially in all measurement areas covered by the sensor network. The process of the third embodiment can easily create a map of the region containing the liquid portion. Through continuous measurement, it is possible to track the trend of the liquid content of the first space.

Therefore, the heating process according to the second and third embodiments can check the integrity of the storage system. These can be performed jointly to obtain macroscopic information on the condition of the tank and information about the trend of condensate or the purging process of the first space at different points in the first space. In addition, the above processes may be performed under the control of the electronic control device 50.

Advantageously, if the second membrane 5 is made of a thermally conductive material, for example a metal material, then the temperature sensors for measurement in the first space 6 are then fitted to the second membrane 5 to limit passing through. is placed under However, it is necessary to limit the contact resistance between the temperature sensor and the second membrane 5 .

Referring to another embodiment according to FIGS. 13 and 14 , a single vacuum pump is applied to depressurize the first space and the second space.

Accordingly, FIG. 13 shows a partial view of the wall of the tank with a connecting device 35 establishing a fluid connection between the second space 6 and the first space 3 . The connecting device 35 includes a regulating valve 36 . The regulating valve basically has a closed state and opens when the pressure in the second space 6 exceeds the pressure in the first space 3 by a value greater than a given threshold value. The opening threshold is preferably between 1 and 5 kPa, for example 3 kPa. In this case, if the pressure of only the first space 3 is adjusted using the vacuum pump 21, the vacuum pump 22 can be omitted, and the above-described method can be simplified. The pressure in the second space 6 is manually adjusted by means of the connection device 35 based on the trend in the first space 3 so that the integrity of the second membrane 5 is not compromised. The connecting device 35 can be permanently fixed to the wall of the tank.

Figure 14 shows a partial view of the wall of the tank with a T-shaped connection circuit 37 establishing a fluid connection between the vacuum pump 21 and each of the first space 3 and the second space 6 . Loss head measuring or regulating device 38 is installed in each branch of connection circuit 37 to generate a pressure difference between both sides of second membrane 5 without said difference exceeding a pre-set safety threshold, for example 3 kPa. are arranged in At least one sectional valve is provided to prevent any connection between the first space 3 and the second space 6 outside of the heating process. The head loss device 38 may be a shutoff valve.

In order to obtain accurate effectiveness of the depressurization of the first space, it is preferred that the head loss between the different areas of the first space 3 is not too high. In particular, if the first space 6 is filled with a solid modular member 7, it is advantageous that this solid modular member 7 inserted between the membranes engages a flow channel to facilitate the flow of gas. Thus, pressure regulation in the first space 3 becomes easy. Said flow channels are manufactured in such a way as not to impair the supporting function of the solid modular member 7 . Accordingly, FIGS. 15 and 16 are examples of a solid modular member in the form of a parallelepiped separating piece 47 comprising flow channels 48 , 49 made in the form of right-angled grooves arranged on the side of the second membrane 5 . shows an exemplary embodiment. 15 is a bottom view of the parallelepiped separation piece 47. 16 is a partial view of a cross section of a tank wall with the piece 47. In this embodiment, the membranes 5 and 9 are corrugated.

The above-described technique for heating a tank can be applied to various types of floating structures such as, for example, land-based LNG tanks or methane tankers or similar structures.

As mentioned above, thanks to the testing prior to heating, the heating of the tank can be performed more safely. If the preliminary test described above is satisfactory, heating can begin immediately after the test is finished. Various choices can be set at the moment this preliminary test begins. However, the first sealing membrane and the space below it should mainly maintain the temperature of the liquefied gas until the test is finished.

Referring to Fig. 17, there is a cutaway view of a methane tanker 70 showing a generally prismatic sealed and insulated tank 71 mounted on the vessel's double hull 72. The wall of the tank 71 includes a first sealing barrier contacting the LNG contained in the tank, a second sealing barrier disposed between the first sealing barrier 71 and the double hull 72 of the ship, and a second sealing barrier. and one or two insulating barriers possibly respectively disposed between the double hull 72 and between the first sealing barrier and the second sealing barrier.

As is well known, a loading/offloading pipeline 73 arranged on the deck of a ship is provided at a sea or port terminal with appropriate connectors to receive and transfer loads in the form of LNG from and to the tank 71. can be connected to

17 shows an example of a marine terminal comprising a loading and offloading station 75 , an underwater pipe 76 and an onshore installation 77 . The loading and unloading station 75 is a fixed offshore installation having a movable arm 74 and a riser 78 supporting the movable arm 74 . The movable arm 74 supports a bundle of insulated flexible pipes 79 which can be connected to a loading/offloading pipeline 73 . The adjustable movable arm 74 is applied to all methane tanker templates. A link duct, not shown, extends into the riser 78. Loading and offloading station 75 may load and offload methane tanker 70 to and from shore installation 77 . It then comprises a liquefied gas storage tank 80 and a link duct 81 connected to a loading or offloading station 75 by means of a submersible pipe 76. The submersible pipe 76 can deliver the liquefied gas over a long distance between the loading or offloading station 75 and the onshore installation 77, for example over 5 km. This can keep the methane tanker 70 a long distance from shore during loading and offloading operations.

To create the pressure required to deliver the liquefied gas, a pump aboard the vessel 70, and/or a pump aboard the shore installation, and/or a pump aboard the loading and offloading station 75 is implemented.

Although the present invention has been described in connection with a number of specific embodiments, the present invention is expressly not limited thereto, and all technical equivalents of the means described, as well as combinations thereof within the scope of the present invention provided in the latter, are provided. It is clear that it includes a combination of

The verb "comprises" or "comprises" and expressions in conjugation thereof do not exclude the existence of other elements or processes other than those specified in the claims. Unless otherwise specified, the expression of the indefinite article of "a" or "an" in a component or step does not exclude the presence of a plurality of such components or steps.

Reference numbers between parentheses in a claim shall not be construed as a limitation on that claim.

1: sealing and insulating tank
2: external load-bearing wall
3: middle space
5: second sealing membrane
6: 1st space
8: liquefied gas
9: first sealing membrane

Claims (27)

In the management method of the fluid in the sealing and insulating tank (1) for storing liquefied gas (8) at low temperature,
The wall of the tank includes an outer load-bearing wall (2) having a multi-layer structure, a first sealing membrane (9) in contact with the liquefied gas stored in the tank, and an intermediate space (3) disposed between the first sealing membrane and the outer load-bearing wall. and when the first sealing membrane (9) is at the lower temperature of the liquefied gas (8), the method comprises:
a suction step of sucking (13, 56) a gaseous phase out of the wall of the tank in the intermediate space to lower the pressure in the intermediate space below the working pressure of the intermediate space;
a measuring step of measuring the pressure in the intermediate space using a pressure sensor during the suction step;
a detection step (14, 57) of detecting a stabilized pressure measured in the intermediate space during the inhalation phase, wherein the stabilized pressure is detected after it has ceased to fluctuate for a period of more than one hour;
selecting (26) a heating process between a fast heating process and a slow heating process, based on the stabilized pressure in the intermediate space during the intake phase;
Method for managing fluid in a sealed and insulated tank (1), comprising a heating step (15, 33) of heating the walls of the tank through a selected heating procedure. According to claim 1,
The sealing and insulating tank is initially filled with a load of liquefied gas at low temperature, and heating the walls of the tank comprises emptying the tank of the load of liquefied gas at low temperature. ) How to manage the fluid within. According to claim 1,
The sealing and insulating tank initially contains a heel of liquefied gas at low temperature, and heating the walls of the tank comprises removing the heel of liquefied gas from the tank at low temperature. 1) How to manage fluid inside. According to claim 3,
maintaining the first sealing membrane (9) at the said low temperature of the liquefied gas (8) by spraying the liquefied gas on the inner surface of the first sealing membrane (9), at least until the start of the heating step; A method for managing the fluid in the tank (1). According to any one of claims 1 to 4,
A method for managing fluid in a sealed and insulated tank (1), wherein suction of gas phase is driven by a vacuum pump (21) regulated to reach a target pressure. According to claim 5,
A method for managing the fluid in the sealing and insulating tank (1), wherein the difference between the preset target pressure and the working pressure of the intermediate space is greater than 10 kPa. According to any one of claims 1 to 4,
A method for managing fluid in a sealed and insulated tank (1), wherein the stabilized pressure in the intermediate space is detected after the pressure has stopped fluctuating for a time exceeding 2 hours. According to any one of claims 1 to 4,
A method for managing fluid in a sealed and insulated tank (1), wherein a rapid heating process (15) is selected when the stabilized pressure in the intermediate space during the suction phase is lower than or equal to a preset threshold pressure value lower than the working pressure. According to claim 8,
The method of managing fluid in a sealed and insulated tank (1), wherein the rapid heating process (15) further comprises injecting hot gas into the tank from which the load of liquefied gas has been removed at low temperature. According to any one of claims 1 to 4,
A method for managing fluid in a sealing and insulating tank (1), wherein a slow heating process (33) is selected when the stabilized pressure in the intermediate space during the suction phase is higher than a preset threshold pressure value lower than the working pressure. According to claim 10,
The slow heating process (33) controls the fluid in the sealing and insulating tank (1), comprising the step of injecting a flow of liquefied gas at low temperature into the tank (1) while the load of liquefied gas at low temperature is removed from the tank. method. According to any one of claims 1 to 4,
detecting the presence of a liquid phase inside the intermediate space (27, 63);
Management of the fluid in the sealing and insulating tank (1), further comprising the step of maintaining (13, 56) suction of the gas phase into the intermediate space, in order to evaporate and/or desorb the entire liquid phase, before heating the walls of the tank. method. According to claim 12,
At an intermediate level (Pi) between the preset target pressure and the working pressure, the presence of the liquid phase is detected 27 corresponding to the stabilized pressure in the intermediate space, and below the intermediate level, responds to the subsequent pressure drop in the intermediate space. A method for managing fluid in a sealed and insulated tank (1), wherein evaporation and/or desorption of the entire liquid phase is detected. According to claim 12,
measuring (54, 58) the temperature of the intermediate space for a period of time from the drop (52, 56) of the absolute pressure in the intermediate space;
Step 68 of detecting a liquid phase in response to a stabilized temperature in the intermediate space in the vicinity of the liquid-vapor equilibrium point of the liquefied gas for a predetermined target pressure, and of the intermediate space in the vicinity of the temperature of the liquefied gas stored in the tank. Detecting (65) evaporation and/or desorption of the entire liquid phase in response to the stabilized temperature,
A method for managing fluid in a sealed and insulated tank (1), wherein the stabilized temperature has stopped fluctuating for a predetermined period of time. According to any one of claims 1 to 4,
The step of lowering the pressure in the intermediate space is:
lowering the pressure in the intermediate space to a first threshold pressure value lower than the working pressure (52);
After lowering the pressure to a first critical pressure value, measuring a first temperature (Tr) of the intermediate space (54);
lowering the pressure in the intermediate space to a second threshold pressure value lower than the first threshold pressure value (56);
After lowering the pressure to a second critical pressure value, measuring (58) a second temperature (Tm) of the intermediate space at successive instants;
determining (63) the difference between the second temperature and the first temperature;
If the difference between the second temperature and the first temperature is not lower than a preset threshold temperature value, delaying the heating of the tank and maintaining suction;
After the difference between the first temperature and the second temperature becomes lower than a preset critical temperature value, selecting a heating process. According to any one of claims 1 to 4,
middle space,
a second sealing membrane (5) disposed between the outer load-bearing wall (2) and the first sealing membrane (9), a second space (3) disposed between the second sealing membrane and the outer load-bearing wall, and a second sealing membrane; a first space (6) disposed between the first sealing membranes, and a second solid insulating barrier (4) disposed inside the second space;
The thickness of the first space is smaller than the thickness of the second space,
The pressure drops inside the second space and the first space, so that the pressure difference between the second space and the first space is maintained below a predetermined safety threshold of 0.5 kPa to 4 kPa;
The stabilized pressure measured in the intermediate space is detected in at least the first space in order to select a heating process among fast heating processes and slow heating processes based on the stabilized pressure in the first space. How to manage fluids. According to claim 16,
A method for managing fluid in a sealing and insulating tank (1), wherein the pressure in the second space is lower than the pressure in the first space. In the fluid management device for the sealing and insulating tank (1) for storing liquefied gas at low temperature,
The fluid management device is a device for carrying out the method of claim 1, wherein the wall of the tank is an outer load-bearing wall (2), a first sealing membrane (9) in contact with the liquefied gas stored in the tank, the first sealing membrane and the outer It has a multi-layer structure including an intermediate space (3) disposed between load-bearing walls,
The fluid management device:
a pressure sensor 41 for measuring the pressure in the intermediate space;
A vacuum pump (21) connected to the intermediate space to suck the gaseous phase out of the tank wall from the intermediate space, and capable of lowering the pressure in the intermediate space below the working pressure of the intermediate space;
A control module (50) capable of detecting a stabilized pressure in the intermediate space during the suction phase and selecting a heating process between a fast heating process and a slow heating process based on the stabilized pressure in the intermediate space during the suction phase, wherein the stabilization The fluid management device comprising a control module (50), wherein the detected pressure is detected after fluctuations in the pressure have ceased for a period of time greater than one hour. According to claim 18,
Further comprising a temperature sensor 45 for measuring the temperature in the intermediate space, the control module driving the vacuum pump and the temperature pump:
After lowering the pressure to a first critical pressure value, measuring (54) a first temperature in the intermediate space;
lowering the pressure in the intermediate space to a second threshold pressure value lower than the first threshold pressure value (56);
After lowering the pressure to a second critical pressure value, measuring (58) a second temperature of the intermediate space at successive instants;
determining (63) the difference between the second temperature and the first temperature;
If the difference between the second temperature and the first temperature is not lower than a preset threshold temperature value, delaying the heating of the tank and maintaining suction;
and selecting a heating step after a difference between the first temperature and the second temperature becomes lower than a preset threshold temperature value. According to claim 18 or 19,
The intermediate space includes a second sealing membrane disposed between the outer load-bearing wall and the first sealing membrane, a second space disposed between the second sealing membrane and the outer load-bearing wall, and a first disposed between the second sealing membrane and the first sealing membrane. 1 space, and a second solid heat insulating barrier 4 disposed inside the second space,
The thickness of the first space is smaller than the thickness of the second space,
The pump 21 is connected to at least the first space 3,
wherein the control module (50) is capable of detecting a stabilized pressure in at least the first space to select a heating process from a fast heating process and a slow heating process based on the stabilized pressure in the first space. According to claim 20,
It further includes a fluid link 35 connecting the second space and the first space, wherein the fluid link is basically closed and opens in response to a pressure difference greater than a preset opening threshold between the second space and the first space. A fluid management device comprising a valve (35), which can be According to claim 20,
A fluid management device comprising a first vacuum pump (21) connected in parallel with a first space and a second vacuum pump (22) connected with a second space. According to claim 20,
a vacuum pump (21) connected in parallel to a first space by a first suction pipe and to a second space by a second suction pipe, each suction pipe having a loss head member (38); management device. double hull,
A sealing and insulating tank 1 storing liquefied gas at low temperature and disposed in the double hull, and
A vessel (70) comprising a fluid management device according to claim 18 or 19 installed with a tank. A method for loading or offloading a vessel (70) according to claim 24, comprising:
The fluid is directed from the floating or land storage structure 77 to the tank 71 of the vessel 70 and from the tank 71 of the vessel 70 to the floating or land storage structure 77 through insulated pipelines 73, 79, 76, 81), a method for loading or offloading a vessel. 25. A fluid displacement system comprising the vessel (70) of claim 24, comprising:
Insulated pipelines (73, 79, 76, 81) arranged to connect a tank installed on the hull of a ship with a floating or onshore storage structure, and
A fluid transfer system comprising a pump for driving fluid through an insulated pipeline from a floating or onshore storage structure to a tank on a ship or from a tank on a ship to a floating or onshore storage structure. delete

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