WO2018203011A1

WO2018203011A1 - Storage facility for a liquefied gas

Info

Publication number: WO2018203011A1
Application number: PCT/FR2018/051113
Authority: WO
Inventors: Fabrice Lombard; Arnaud Bouvier; Bruno Deletre
Original assignee: Gaztransport Et Technigaz
Priority date: 2017-05-05
Filing date: 2018-05-03
Publication date: 2018-11-08
Also published as: KR20200004236A; CN109219720B; RU2770338C2; RU2019132481A3; FR3066007B1; RU2019132481A; FR3066007A1; KR102579882B1; CN109219720A

Abstract

The invention relates to a storage facility for a liquefied gas, comprising: a tank having an interior space delimited by sealed and thermally insulating walls, a pump (10) arranged in the interior space (6) of the tank near a bottom wall (8) of the tank and intended to be immersed at least partially in a cargo of liquefied gas for pumping the cargo of liquefied gas, and a temperature sensor (20) arranged to measure a temperature of the pump or a temperature of a fluid contained in the interior space of the tank at a height located between the lowest point of the pump and the highest point of the pump. The use method has the step of determining the temperature of the pump (10) by means of a measurement signal produced by the temperature sensor (20).

Description

STORAGE FACILITY FOR LIQUEFIED GAS

Technical area

The invention relates to the field of storage of liquefied gases, in particular to the construction and operation of a storage facility for a liquefied gas comprising a tank having an interior space delimited by sealed and thermally insulating walls and a pump. disposed in the interior space of the tank near a bottom wall of the tank and intended to be at least partially immersed in a cargo of liquefied gas for pumping the cargo of liquefied gas.

In one embodiment, the liquefied gas is a high methane content mixture stored at a temperature of about -162 ° C at atmospheric pressure. Other liquefied gases can also be envisaged, in particular ethane, propane, butane or ethylene. Liquefied gases may also be stored under pressure, for example at a relative pressure of between 2 and 20 bar, and in particular at a relative pressure close to 2 bar. The tank may be made according to various techniques, in particular in the form of an integrated membrane tank or a self-supporting tank.

Technological background

A pump intended to be immersed in a cargo of liquefied gas, for example Liquefied Natural Gas which is a mixture with a high methane content, must meet high mechanical requirements, since it must be designed to operate at very low temperature and that it must withstand very large temperature variations during its operation, in particular according to the state of filling of the tank. In particular, an unloading pump disposed in the tank of a LNG carrier is generally made in the form of a rotary machine such as a centrifugal pump, see for example EP-A-1314927.

Thus, unless precautions are taken with regard to the evolution of its temperature, and in particular to ensure the progressivity of this evolution, such a pump runs the risk of being exposed to high thermal shocks during its operation. which is likely to affect its life. summary

An idea underlying the invention is to monitor the temperature of the pump with a temperature sensor that can give reliable information on the actual temperature of the pump. Another idea underlying the invention is to control the operation of the tank, including tank filling operations or starting the pump with reliable information on the actual temperature of the pump .

For this, the invention provides a storage facility for a liquefied gas, comprising:

a tank having an interior space defined by sealed and thermally insulating walls,

a pump disposed in the interior space of the tank near a bottom wall of the tank and intended to be at least partially immersed in a cargo of liquefied gas for pumping the cargo of liquefied gas,

a discharge line connecting an outlet of the pump to a liquid collecting circuit located outside the tank, and

a temperature sensor arranged to measure a temperature of the pump or a temperature of a fluid contained in the interior space of the tank at a height between a lowest point of the pump and an uppermost point of the pump .

Thanks to these characteristics, a relevant temperature measurement to determine the actual state of the pump can be obtained, since it is possible to measure either the temperature of a pump component or the temperature of a fluid environment in the pump. which the pump is immersed, in particular the temperature of a gaseous atmosphere in which the pump is immersed.

According to advantageous embodiments, such an installation may have one or more of the following characteristics.

Several arrangements of the temperature sensor may be suitable for obtaining reliable temperature information. A first possibility is to have the temperature sensor, that is to say at least the sensitive part of this sensor, in direct contact with a component of the pump, in particular on or in a component of the pump. According to embodiments, the temperature sensor is disposed on a member selected from the group comprising an envelope outside the pump, a portion of the discharge line adjacent to the outlet of the pump, and a fastening flange connecting the discharge line and the outlet of the pump.

According to embodiments, the temperature sensor is disposed in the pump, preferably in a stator of the pump when the pump is in the form of a centrifugal pump or other rotating machine. Such a temperature sensor may in particular be arranged to measure the temperature in an internal channel of the pump for discharging the fluid in operation.

According to one embodiment, the temperature sensor comprises means for measuring the intensity I and the voltage U of a motor coil of the discharge pump. For example, these measuring means may be a voltmeter, a tensiometer, a multimeter or any other measuring device to know the intensity and / or voltage of a coil.

According to one embodiment, the temperature T is related to the measurements of the intensity I and the voltage U using the following equation:

T = 293.15 + B _mat (- ^ 1) with R ₂₀ ° c the resistance of the coil at 20 ° C, B _mat a coefficient depending on the material used for the coil.

According to one embodiment, the installation comprises a calculation unit configured to calculate the temperature of the pump using measurements of the intensity I and the voltage U of the discharge pump coil.

According to one embodiment, a support mast extends in the interior space of the tank between a top wall of the tank and the bottom wall of the tank and supports the unloading line, and the temperature sensor is disposed on the support mast for measuring the temperature of a fluid contained in the interior space of the vessel. According to one embodiment, the temperature sensor is disposed on a surface of the support mast facing the unloading pump.

Several technologies are available to realize the temperature sensor, in particular according to the temperature ranges to be reached in use. In embodiments suitable for LNG, the temperature sensor is a thermocouple or a platinum resistance thermometer.

In one embodiment, the storage facility further includes an information system operably connected to the temperature sensor for acquiring a temperature measurement signal from the temperature sensor, the information system further comprising a human interface. -machine configured to communicate the temperature measurement provided by the temperature sensor to a personnel in charge of the operation of the tank.

The invention also provides a method of operating such a storage facility for liquefied gas, wherein the temperature of the pump is determined by a measurement signal produced by the temperature sensor and it is determined whether an authorization criterion is satisfied by the temperature of the pump.

In one embodiment, a filling operation of the tank with liquefied gas is prohibited in response to the determination that the temperature of the pump does not meet the authorization criterion. In one embodiment, a start operation of the pump is prohibited in response to the determination that the temperature of the pump does not meet the authorization criterion. Such an authorization criterion is, for example, that the temperature of the pump has fallen below a tripping threshold and / or has remained below a tripping threshold for a certain duration.

In one embodiment, triggering or authorizing the triggering of a filling operation of the tank with liquefied gas in response to the determination that the temperature of the pump has fallen below the trigger threshold. A filling operation of the tank may also be subject to other conditions, cumulative with the temperature condition of the pump, for example conditions related to the connection to the terminal or others.

In one embodiment, the pump is started or allowed to start in response to the determination that the temperature of the pump has fallen below the trip threshold. A start operation of the pump may also be subject to other cumulative conditions with the temperature condition of the pump.

The trip threshold can be chosen according to the properties of the cargo. In an embodiment suitable for pressure LNG atmospheric, the trigger point is less than or equal to -130 ° C. Other values of the starting threshold can also be used, for example -100 ° C or -50 ° C.

The storage facility may be in the form of a floating structure comprising a hull, in particular a vessel for transporting liquefied gas, and in which the vessel is disposed in the hull of the floating structure. In the case of a floating structure, the tank may be intended for the transport of liquefied gas or to receive liquefied gas used as fuel for the propulsion of the floating structure. Alternatively, the storage facility may be in the form of a land installation or placed on the seabed or a land vehicle. In the case of a land vehicle, the tank may be for the transport of liquefied gas or for receiving liquefied gas as fuel for the propulsion of the land vehicle.

According to one embodiment, the pump is an unloading pump having a nominal flow rate greater than 100 m ³ / h, for example between 1000 and 3000 m ³ / h, for example for a tank having a capacity of between 6000 m ³ and 60000 m ³ , and the discharge line is an unloading line.

The invention also provides a method of unloading a floating structure, in which a fluid is conveyed through isolated pipes to a floating or land storage facility from the tank of the floating structure using the pump.

The invention also provides a transfer system for a fluid, the system comprising a floating structure, insulated pipes arranged to connect the vessel installed in the hull to a floating or land storage facility and in which the pump is adapted to driving a fluid through the isolated pipes to the floating or ground storage facility from the tank.

Brief description of the figures

The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly in the course of the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes. with reference to the accompanying drawings. - Figure 1 is a schematic sectional view of an installation according to one embodiment of the invention in the form of a vessel vessel LNG.

FIG. 2 is an enlarged schematic view of zone II of FIG.

- Figure 3 is a schematic cutaway representation of a LNG tanker and a loading / unloading terminal of this vessel.

Detailed description of embodiments

In the description below, a pump housed in a tank for storing and / or transporting liquefied gas, in the vicinity of a bottom wall of the tank and intended to be at least partially immersed in the cargo of gas, is described. liquefied. The bottom wall designates a wall, preferably generally flat, located in the bottom of the tank relative to the earth's gravity field. The proximity between the pump and the bottom wall depends on the size of the pump and the volume of the tank. The objective of this proximity is to allow the pump to take the bulk of the cargo stored in the tank, with the exception of a possible liquid heel representing less than 10% of the volume of the tank.

The general geometry of the tank can also be of different types. Polyhedral geometries are the most common. A cylindrical, spherical or other geometry is also possible. Furthermore, such a tank can be installed in different structures such as a double hull ship, a land installation or other.

Referring to Figure 1, a sealed and insulating tank for the transport and storage of LNG comprises tank walls mounted in a carrier structure 1 of polyhedral geometry. In the case of a membrane technology, each vessel wall has a multilayer structure superimposed in a thickness direction, with a secondary thermal insulation barrier 2, a secondary waterproof membrane 3 carried by the insulation barrier secondary thermal 2, a primary thermal insulation barrier 4 carried by the secondary waterproof membrane 3 and a primary waterproof membrane 5 carried by the primary thermal insulation barrier 4. This primary waterproof membrane 5 is intended to be in contact with the product contained in the tank and delimits the interior space 6 of the tank. Other tank technologies are also usable, for example self-supporting tank.

In the case of a LNG ship, several pumps are usually arranged at the bottom of a support mast 7 which supports different pipes for handling the cargo and which extends over the entire height of the tank from the wall bottom 8 to the ceiling wall 9, which it passes through an area called liquid dome.

FIG. 1 shows, as an illustration, an unloading pump 10 which is attached to the support mast 7 near the bottom wall 8, for example at a distance of approximately 1 m above the wall of 8. The unloading pump 10 is a centrifugal pump adapted to suck a flow of liquid through an inlet 14 located at the bottom of the unloading pump 10 and to discharge this flow in an unloading line 11, which is connected to an outlet located at the top of the unloading pump 10 at a fastening flange 12. The unloading line 11 rises all along the support mast, to a not shown liquid collector circuit. The discharge pump 10 has a high nominal flow rate to ensure rapid handling of a large cargo, for example 500m ³ / h.

To measure the temperature of the unloading pump 10, a temperature sensor 20 is disposed in, on or in the immediate vicinity of the unloading pump 10. The temperature sensor 20 is operatively connected to an information system 21, for example by a wired or wireless link 22, to allow the exploitation of temperature measurements by the staff responsible for the operation of the vessel and / or by controllers controlling the operation of the vessel.

FIG. 2 illustrates several possible positions of the temperature sensor 20, namely a sensor 201 located inside the pump, a sensor 202 located on the outer surface of the pump casing, a sensor 203 located on the mounting flange. 12 and a sensor 204 located on the support mast 7 at the same height as the pump, namely at a level located between the highest point (here the clamp 12) and the lowest point (here the input 14) of the pump 10.

Because it is immersed in the same fluid surrounding the housing of the pump 10 and close thereto, the sensor 204 located on the support mast 7 can provide a temperature measurement relatively reliably reflecting the actual state of the pump 10. In particular, in the case where the surrounding fluid is a vapor phase having a stratified temperature field, the position of the sensor 204 substantially to the same height that the pump 10 ensures a reliable measurement.

As indicated in FIG. 23, the information system 21 may also have connections with other sensors according to the known technique, in particular temperature sensors measuring the temperature, for example in the walls of the tank, at different heights as shown schematically. at number 24.

In the case of a ship, the information system 21 belongs to the tank management system on board the ship. The information system 21 includes unrepresented human-machine interfaces, for example screens, dials, printers or other, located in an operating room of the tank or in a ship's supervision room to inform an operator supervising the tank. about the status of the tank 1. The information system 21 formats the temperature data and transmits them to the man-machine interface.

The same temperature sensor arrangement can be used with other pumps in the vessel, for example a dewatering pump or a circulation pump for spraying liquid in the vessel.

Thanks to the reliable temperature measurement provided by the sensor 20, it is possible to make decisions on the control of the tank by ensuring each time that the temperature of the pump 10 is compatible with the operation envisaged. For example, the decision relates to the triggering of the filling of the tank from a substantially empty state and assumes to verify beforehand that the pump has undergone pre-cooling sufficient to prevent damaging thermal shock. With the temperature sensor 20, the operator can know that the pump 10 has actually reached the expected temperature threshold, for example -130 ° C, before triggering this filling. This trigger could also be realized by a programmed automaton.

In contrast, in the absence of the temperature sensor 20, the temperature of the pump 10 should be estimated from other available measurements, for example wall temperature measurements. However, the hypothesis which the pump 10 must be at the same temperature as the walls of the surrounding tank may be faulted in some cases.

The tank described above can be used in various types of installations such as land installations or in a floating structure such as a LNG tank or other.

Referring to Figure 3, a cutaway view of a LNG tank 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary sealed barrier intended to be in contact with the LNG contained in the tank, a secondary sealed barrier arranged between the primary waterproof barrier and the double hull of the vessel, and two thermally insulating barriers arranged respectively between the primary watertight barrier and secondary watertight barrier, and between secondary watertight barrier and double hull 72.

In a manner known per se, loading / unloading lines arranged on the upper deck of the ship can be connected, by means of appropriate connectors, to a marine or port terminal to transfer a cargo of LNG from or to the tank 71.

FIG. 3 shows an example of a marine terminal comprising a loading and / or unloading station 75, an underwater pipe 76 and an on-shore installation 77. The loading and / or unloading station 75 is a fixed, off-site installation. shore comprising a movable arm 74 and a tower 78 which supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 which can be connected to the loading / unloading pipes 73. The movable arm 74 is adaptable to all the gauges of LNG carriers. A link pipe (not shown) extends inside the tower 78. The loading and / or unloading station 75 enables the loading and unloading of the LNG tank 70 from or to the shore facility 77. comprises liquefied gas storage tanks 80 and connecting pipes 81 connected by the underwater pipe 76 to the loading and / or unloading station 75. The underwater pipe 76 allows the transfer of the liquefied gas between the station of loading and / or unloading 75 and the land installation 77 over a large distance, for example 5 km, which makes it possible to keep the LNG tanker 70 at a great distance from the coast during the loading and unloading operations. In order to generate the pressure necessary for the transfer of the liquefied gas, pumps on board the vessel 70 are used, in particular the aforementioned unloading pump 10 and / or pumps fitted to the shore installation 77 and / or pumps equipping the station. loading and / or unloading 75.

In another embodiment, the temperature sensor is a winding of the pump motor and the temperature is obtained by measuring the evolution of the resistivity of the motor winding of the pump. The windings are of a size of the same order of magnitude as the pump itself, which makes it possible, by measuring the resistivity of the winding, to obtain by calculation a measurement of the temperature of the pump in order to obtain an overall assessment of the setting in cold of the pump. The principle in this embodiment is to avoid housing sensors in the pumps or their vicinity and thus avoid pulling the cables of these sensors inside the tank. For this, only instruments and cabling already present for the use of the pump are used. The instruments already present on the pump make it possible to measure the voltage U and the intensity I of the winding of the motor of the pump. It is then possible by a simple U / l ratio to obtain the resistance R _{b 0} bine over the time of the winding of the motor pump. It is then possible after obtaining the resistant Rbobine to calculate the temperature T of the coil as a function of time using the following formula:

^ coil = # 20 ° C * 0- + ^ mat * (- 293,15)) with R ₂₀ <> c the resistance of the coil at 20 ° C, C _mat a coefficient depending on the material used for the coil.

Thus, it is therefore possible to connect the average value of the winding temperature with the electrical resistance thereof and thus obtain the average value of the temperature of the discharge pump 6. The choice of a resistance threshold value which is considered sufficient cold setting can be determined.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention. The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim.

In the claims, any reference sign in parentheses can not be interpreted as a limitation of the claim.

Claims

1. Storage installation for a liquefied gas, comprising:

a pump (10) disposed in the interior space (6) of the tank near a bottom wall (8) of the tank and intended to be at least partially immersed in a cargo of liquefied gas for pumping the cargo of a liquefied gas, a discharge line (11) connecting an outlet of the pump to a liquid collecting circuit located outside the tank, and

a temperature sensor (20, 201-204) arranged to measure a temperature of the pump or a temperature of a fluid contained in the interior space of the tank at a height between a lowermost point of the pump and a highest point of the pump.

2. Storage installation according to claim 1, wherein the temperature sensor (202, 203) is disposed on a member selected from the group comprising an outer casing of the pump (10) and a fixing flange (12) forming the connection between the discharge line (11) and the outlet of the pump.

3. Storage installation according to claim 1, wherein the temperature sensor (20, 201) is arranged in the pump (10), preferably in a stator of the pump in the form of a rotating machine.

4. Storage installation according to one of claims 1 to 3, carried out in the form of a floating structure (70) comprising a shell (72), in particular a liquefied gas transport vessel, and in which the vessel is arranged. in the hull (72) of the floating structure (70).

5. Storage installation according to one of claims 1 to 4, wherein the pump (10) is an unloading pump having a nominal flow rate greater than 100m ³ / h, the discharge line being an unloading line.

6. Storage installation according to one of claims 1 to 5, further comprising a support mast (7) extending in the interior of the vessel between a top wall (9) of the tank and the wall the bottom (8) of the tank and supporting the unloading line (11), wherein the temperature sensor (204) is disposed on the support mast (7) for measuring the temperature of a fluid contained in the interior space of the vessel.

7. Storage installation according to one of claims 1 to 6, wherein the temperature sensor (20) is a thermocouple or platinum resistance thermometer.

8. Storage installation according to one of claims 1 to 6, wherein the temperature sensor (20) comprises means for measuring the intensity I and the voltage U of a motor coil of the unloading pump. .

9. Storage installation according to one of claims 1 to 8, further comprising an information system (21) operatively connected to the temperature sensor (20) for acquiring a temperature measurement signal from the temperature sensor, the information system further comprising a man-machine interface configured to communicate the temperature measurement provided by the temperature sensor to a personnel in charge of the operation of the tank.

10. Storage facility according to one of claims 1 to 9, wherein the liquefied gas is a mixture of high methane content stored at atmospheric pressure at a temperature of about -162 ° C.

11. A method of operating a storage facility for a liquefied gas according to one of claims 1 to 10, wherein a temperature state of the pump (10) is determined by means of a measurement signal. produced by the temperature sensor (20) and determines whether an approval criterion is satisfied by the temperature of the pump.

12. The method of claim 11, wherein a filling operation of the tank with liquefied gas is prohibited in response to the determination that the temperature of the pump (10) does not meet the authorization criterion.

13. The method of claim 11, wherein it is prohibited to start the pump in response to the determination that the temperature of the pump (10) does not meet the authorization criterion.

14. Method according to one of claims 11 to 13, wherein the authorization criterion comprises the fact that the temperature state of the pump has passed below a trigger threshold.

The method of unloading a floating structure (70) according to claim 4, wherein a fluid is conveyed through isolated conduits (73, 79, 76, 81) to a floating or land storage facility (77) from the tank (71) of the floating structure (70) using the pump (10).

16. Transfer system for a fluid, the system comprising a floating structure (70) according to claim 4, insulated pipes (73, 79, 76, 81) arranged to connect the tank (71) installed in the shell ( 72) to a floating or land storage facility (77) and wherein the pump (10) is adapted to drive fluid through the insulated pipelines to the floating or land storage facility from the vessel (71).