JP2015124860A - Storage system of cryogenic liquefied gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the strain, deformation, and roll-over phenomenon of a storage tank by eliminating the temperature difference generated when loading cryogenic liquefied gas.SOLUTION: A storage system 10A comprises: a LNG carrier tank 12 for storing LNG; a supply system 41 for supplying the LNG to the LNG carrier tank 12; an optical fiber cable 24 extending along a height direction of a wall surface of the LNG carrier tank 12; a laser pulse transmitter 28 for transmitting the laser pulse to the optical fiber cable 24; a measuring instrument 30 into which rear side scattered light scattered from the optical fiber cable 24 is inputted so as to obtain a temperature distribution of the LNG stored in the LNG carrier tank 12 from the rear side scattered light; and a management device 23A for managing the storage state of the LNG in the LNG carrier tank 12 on the basis of the temperature distribution of the LNG obtained by the measuring instrument 30.

Description

  The present invention relates to a storage system that performs temperature measurement using an optical fiber and manages low-temperature liquefied gas stored in a storage container.

In a transport ship for transporting a low-temperature liquefied gas such as liquefied natural gas (hereinafter referred to as “LNG”) or a land storage facility for storing the low-temperature liquefied gas, a large storage container having a spherical shape or a cylindrical shape is used. Yes.
In FIG. 10, the LNG carrier 100 includes an LNG inboard tank 102. Each LNG inboard tank 102 includes a LNG loading piping system 108 indicated by a solid line sent from the LNG tank 104 of the land base by the LNG pump 106, and a gas indicated by a broken line for sending the natural gas vaporized in each LNG inboard tank 102 to the land base. And a delivery piping system 110.

The gas delivery piping system 110 supplies the natural gas in each LNG inboard tank 102 to the engine unit 112 and guides it to the flare stack 114 on the land base for combustion.
In the LNG carrier, LNG is vaporized and a large amount of natural gas is generated when the LNG is loaded into the LNG inboard tank. For this reason, surplus gas that cannot be consumed by the transport ship is returned to the land base and incinerated at the land base. Moreover, a reliquefaction device is required for the treatment of surplus gas, which increases costs.

  In order to solve the above problem, the applicant first increases the internal pressure of the storage tank at the time of LNG loading, raises the boiling point of the loading LNG to a supercooled state, and sets the loaded LNG to a supercooled state. In addition to cooling the storage tank, a supply system is provided for dropping the loaded LNG into the tank from the vicinity of the top of the tank, and the stored LNG is cooled by promoting stirring and heat exchange between the falling LNG and the stored LNG. And the surplus gas suppression means which suppresses generation | occurrence | production of surplus gas is proposed (patent document 1).

  In a large-sized low-temperature liquefied gas storage tank, the liquefied gas in the lower region is pressurized, so that the boiling point of the liquefied gas in the lower region increases. Therefore, a temperature gradient is generated in the height direction. When the temperature gradient of the low-temperature liquefied gas increases in the height direction, the storage tank may be distorted or deformed due to the temperature difference.

  Further, due to the temperature gradient in the vertical direction generated by the low-temperature liquefied gas, the liquid density of the low-temperature liquefied gas in the lower layer area is reduced as compared with the upper layer area, and large convection is generated in the vertical direction. Due to this convection, the heat previously accumulated in the lower layer region generates a large amount of boil-off gas (BOG). This suddenly increases the internal pressure inside the storage tank, and in some cases, the storage tank may be broken or damaged (rollover phenomenon).

  On the other hand, in Patent Document 2, an optical fiber is provided on the outer wall of a storage tank for storing a low-temperature liquefied gas, and the temperature of the outer wall of the storage tank is measured. Means for detecting are disclosed.

International Publication 2012-114851 JP 09-323784 A

As described above, in the low-temperature liquefied gas storage tank, it is necessary to control the temperature of the low-temperature liquefied gas and suppress the generation of surplus gas.
Further, when the temperature gradient in the height direction of the low-temperature liquefied gas stored in the storage tank is increased, the storage tank may be deformed due to a temperature difference or the above-described rollover phenomenon may occur.

In addition, when the low temperature liquefied gas is loaded, the temperature difference between the stored liquefied gas and the loaded liquefied gas causes an imbalance in the temperature distribution of the storage tank, which causes a large internal stress on the tank partition wall, and the storage tank There is a risk of distortion or deformation.
However, the conventional temperature measuring means using a temperature sensor such as a thermocouple requires a huge number of temperature sensors when it is necessary to precisely measure the temperature distribution of the entire storage tank. Therefore, it is difficult to accurately measure the temperature distribution of a large structure such as a storage tank. Therefore, it is not possible to appropriately manage the temperature of the low-temperature liquefied gas stored in the storage tank.

  The means disclosed in Patent Document 2 is a storage tank leakage detection means by temperature measurement using an optical fiber, and does not accurately measure the temperature distribution of the low-temperature liquefied gas, and does not solve the above-mentioned problem. .

  At least one embodiment of the present invention is capable of managing the low-temperature liquefied gas stored in the storage container by using an optical fiber for measuring the temperature of the low-temperature liquefied gas stored in the storage container in view of the problems of the prior art. The purpose is to.

  To achieve the above object, a storage system according to an embodiment of the present invention includes a storage container for storing a low-temperature liquefied gas, a supply system for supplying the low-temperature liquefied gas to the storage container, An optical fiber cable arranged along the wall surface so as to extend in the height direction of the outer surface or the inner surface of the wall surface, and pulse light transmission configured to transmit pulse light to the optical fiber cable A measuring device configured to obtain a temperature distribution of a low-temperature liquefied gas stored in a storage container from the backscattered light, and a measuring device configured to obtain the temperature distribution of the low-temperature liquefied gas stored in the storage container from the backscattered light. And a management device configured to manage the storage state of the low-temperature liquefied gas in the storage container based on the temperature distribution of the low-temperature liquefied gas.

Temperature measuring means using an optical fiber uses a known principle called the Raman effect. That is, when pulsed light is incident on an optical fiber, various scattered light is generated in the optical fiber. Among the scattered light, Raman scattered light includes Stokes light and anti-Stokes light. From the intensity ratio of backscattered light of anti-Stokes light with strong temperature dependence and backscattered light of Stokes light with low temperature dependence. Temperature can be calculated.
In addition, since the light propagation speed in the optical fiber is constant, if the round-trip time from when the pulsed light enters the optical fiber until the generated backward Raman scattered light returns to the incident end is measured, the scattered light It is possible to identify the point where the occurrence occurred.

  In the said embodiment of this invention, the exact temperature distribution of the height direction of a storage container is measurable by sticking an optical fiber cable in the height direction area | region of the outer surface or inner surface of a storage container wall surface. As long as the temperature of the low-temperature liquefied gas can be accurately detected, the optical fiber cable can be provided on the inner surface, outer surface, or partition wall of the storage container partition wall. Based on the precise temperature distribution thus obtained, the state of the low-temperature liquefied gas stored in the storage container can be managed by the management means.

  As one embodiment of the present invention, a supply system for supplying a low-temperature liquefied gas to a storage container has one or a plurality of spray nozzles provided near the top of the storage container and having a variable spray direction, and the management device includes: A control device is provided for controlling the direction of the spray nozzle and the amount of low-temperature liquefied gas supplied from the spray nozzle based on the temperature distribution obtained by the measuring instrument.

In this embodiment, when injecting low-temperature liquefied gas into an empty storage container, the control device controls the direction of the spray nozzle of the input system and the amount of liquefied gas injected from the spray nozzle, thereby increasing the height of the storage container. The temperature distribution in the vertical direction can be made uniform. Thereby, distortion and deformation of the storage container can be prevented.
For example, the optical fiber can be arranged in the storage container in a spiral manner in the height direction of the storage container, or the temperature distribution in the height direction can be measured by arranging the optical fiber in accordance with this.

As one embodiment of the present invention, the management device comprises a gas vent pipe configured to discharge natural gas vaporized in a storage container, and a gas distribution based on a temperature distribution of a low-temperature liquefied gas obtained by a measuring instrument. And a control device for controlling the opening and closing of the extraction tube.
The inside of the storage container is naturally pressurized due to the vaporized natural gas. Therefore, the opening and closing of the gas vent pipe can be controlled to adjust the pressure in the storage container to a target pressurized state. As a result, the inside of the storage container can be brought into a desired pressure state and brought into a desired supercooled state, so that generation of excess gas can be suppressed.

As another embodiment of the present invention, the management device includes a stirring pump for forming a circulating flow in the height direction in the low-temperature liquefied gas stored in the storage container, and the operation of the stirring pump. And a control device for controlling the temperature distribution in the height direction of the low-temperature liquefied gas stored in the storage container.
In this embodiment, by operating the agitation pump, it is possible to achieve temperature uniformity in the height direction of the stored low-temperature liquefied gas, thereby preventing distortion and deformation of the storage container and storing the stored liquefied gas. The above-mentioned rollover phenomenon caused by the difference in liquid density in the vertical direction can be prevented in advance.

As yet another embodiment of the present invention, the management device includes a calibration unit that calibrates the temperature obtained from the backscattered light based on a plurality of calibration curves prepared in advance corresponding to a plurality of temperature ranges. Furthermore, it can have.
Thereby, the temperature distribution of the stored low-temperature liquefied gas can be grasped more accurately over the entire region where the optical fiber is disposed.

Yet another embodiment of the present invention is an embodiment when the storage container is mounted on a ship and stores low-temperature liquefied gas used as fuel for a ship engine.
This embodiment is provided with a fuel supply path for supplying low-temperature liquefied gas in a storage container to a marine diesel engine, a fuel supply pump provided in the fuel supply path, and a fuel supply path downstream of the fuel supply pump. And a second storage container that stores gaseous natural gas at a pressure higher than a saturation pressure, and the management device includes a fuel supply pump. A pressure sensor for detecting the pressure of the low-temperature liquefied gas supplied to the fuel, and when the detected value of the pressure sensor does not reach the saturation pressure of the low-temperature liquefied gas, the gaseous natural gas stored in the second storage container is fueled And a control device that supplies the supply pump and holds the detected value of the pressure sensor at or above the saturation pressure.

  When the fuel supply pump is operated and the low-temperature liquefied gas stored in the storage container is supplied to the marine diesel engine through the fuel supply path, the above-described configuration always supplies the low-temperature liquefied gas in the fuel supply path upstream of the fuel supply pump. Since it can be maintained above the saturation pressure, cavitation can be prevented.

  As yet another embodiment of the present invention, an optical fiber cable includes a protective tube made of stainless steel, a core and a clad portion made of quartz glass, and covering the core and the clad portion. And a covering material made of an ultraviolet curable resin or a polyimide resin.

In this embodiment, when the protective tube is made of stainless steel that does not cause low temperature brittle fracture, sufficient durability can be obtained in a low temperature environment. Further, by configuring the core and the clad portion with quartz glass, the reflection performance of the pulsed light can be improved and the scattering of the pulsed light can be suppressed.
Further, by using a coating material made of an ultraviolet curable resin or a polyimide resin as the coating material, it is possible to improve durability in a low temperature environment and pulse light scattering suppression capability.

  According to one embodiment of the present invention, the temperature measurement means using an optical fiber can accurately measure the temperature distribution in the height direction of the low-temperature liquefied gas stored in the storage container, and the storage based on the measured temperature distribution. The state of the low-temperature liquefied gas stored in the container can be appropriately managed.

It is a typical sectional view of the LNG storage system concerning a 1st embodiment of the present invention. It is a cross-sectional view of the optical fiber cable which comprises the LNG storage system shown in FIG. It is sectional drawing of the LNG supply system of the LNG storage system shown in FIG. It is a diagram which shows the calibration method of the calibration part of the LNG storage system shown in FIG. It is a diagram which shows the difference of the temperature distribution measured value of a platinum resistance thermometer and the temperature distribution measuring unit shown in FIG. It is a typical sectional view of the LNG storage system concerning a 2nd embodiment of the present invention. It is a systematic diagram of the LNG storage system which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the control system of the LNG storage system shown in FIG. It is a saturation pressure diagram of LNG. It is explanatory drawing which shows the loading operation which loads LNG into an LNG carrier from a land base.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

(Embodiment 1)
1st Embodiment of this invention is described based on FIGS. FIG. 1 shows an LNG inboard tank 12 mounted on an LNG carrier 11. The inner shell 14 constituting the wall of the LNG inboard tank 102 is composed of a primary barrier 16, a heat insulation barrier 18 made of a heat insulating material, and a tank cover 20 from the position side. The inner shell 14 is fixed on the skirt 22.

  The storage system 10 </ b> A according to the present embodiment has an optical fiber cable 24 attached to the wall surface of the primary barrier 16. The optical fiber cable 24 is spirally arranged around the vertical axis along the outer surface or inner surface wall surface of the LNG inboard tank 12. The optical fiber cable 24 is arranged over the entire height direction of the LNG inboard tank 12. The start and end of the optical fiber cable 24 are connected to a temperature distribution measurement unit 26 provided in an inboard monitoring room (not shown) outside the LNG inboard tank 12.

  The temperature distribution measuring unit 26 is connected to the start end of the optical fiber cable 24, is connected to the laser pulse transmitter 28 that transmits a laser pulse to the optical fiber cable 24, and the end of the optical fiber cable 24, and is scattered from the optical fiber cable 24. A measuring instrument 30 for detecting the Raman backscattered light R, a calibration unit 32 for calibrating the temperature distribution detected by the measuring instrument 30, and a signal detected by the measuring instrument 30 and calibrated by the calibration unit 32 to process the light And an arithmetic processing unit 33 for obtaining a temperature distribution measured by the fiber cable 24, that is, a temperature distribution of stored LNG.

  Next, a calibration method by the calibration unit 32 will be described with reference to FIGS. FIG. 4 is a graph showing the relationship between the temperature ratio between the backscattered light of anti-Stokes light and the backscattered light of Stokes light, and line A is a theoretical value, and line B is conventionally used. It is a calibration curve. As shown in FIG. 4, the difference between the theoretical curve A and the conventional calibration curve B is large in the cryogenic region.

In FIG. 4, the vertical axis represents the LNG temperature, and the horizontal axis represents the intensity ratio (Ia / Is) of the backscattered light between the anti-Stokes light intensity Ia and the Stokes light intensity Is calculated by the following equation.
Ia / Is = [(Wo + Wk) ⁴ / (Wo−Wk) ⁴ ] · exp (−hcWk / kT)
However, Wo; incident wave number (m-1)
Wk: Shift wave number (m-1)
h: Planck's constant (J · s)
k; Boltzmann constant (J ・ K-1)
c: Speed of light in optical fiber (m · s-1)
T: Absolute temperature (K)
Ia: Anti-Stokes light intensity (W · sr-1)
Is: Stokes light intensity (W · sr-1)

The calibration method of this embodiment is, for example, −250 ° C. or lower, −250 ° C. to −200 ° C., −200 ° C. to −160 ° C., −160 ° C. to −70 ° C., −70 ° C. for each temperature range. The temperature is divided into temperature ranges from 50 ° C. to 50 ° C., and a calibration curve is created for each temperature range, and the temperature obtained from the intensity ratio (Ia / Is) is calibrated based on the calibration curve.
The calibration curve is created by measuring the temperature of nitrogen gas or liquid nitrogen using the optical fiber cable 24 and a platinum resistance thermometer, and obtaining the temperature difference between them.
In FIG. 5, the horizontal axis represents the measured value by the temperature distribution measuring unit 26, and the vertical axis represents the measured value of the platinum resistance thermometer and the measured value obtained from the intensity ratio (Ia / Is) by the temperature distribution measuring unit 26. Showing the difference.

  In FIG. 5, points C, D, E, and F are the results of actual measurement. It is a value measured with a platinum resistance thermometer. In the calibration method of the present embodiment, an approximate curve connecting the points is drawn, and a measurement value obtained from the intensity ratio (Ia / Is) by the temperature distribution measurement unit 26 is calibrated based on the approximate curve.

  Next, the internal configuration of the optical fiber cable 24 will be described with reference to FIG. The core 34 through which the laser pulse propagates and the cladding portion 36 that confines the laser pulse in the core 34 are made of silica glass. The resin film 38 covering the core 34 and the clad portion 36 is made of an ultraviolet curable resin or a polyimide resin. The protective tube 40 that protects the core 34, the clad portion 36, and the resin coating 38 from the outside is made of stainless steel.

As shown in FIG. 1, an LNG supply system 41 is provided at the top of the LNG inboard tank 12. The LNG supply system 41 includes an LNG supply pipe 42 provided at the top of the LNG inboard tank 12 and a header 44 provided at the top of the LNG inboard tank 12 and connected to the LNG supply pipe 42. .
As shown in FIG. 3, the header 44 is provided with a plurality of spray nozzles 46. Furthermore, the drive device 48 which makes direction of each spray nozzle 46 variable is provided. The LNG supply pipe 42 is provided with a flow rate adjustment valve 50.

The arithmetic processing unit 33 displays the temperature distribution across the wall surface of the LNG inboard tank 12. This data is input to the control device 52. The control device 52 controls the drive device 48 of each spray nozzle 46 to adjust the direction of each spray nozzle 46 so that the temperature distribution across the LNG inboard tank is uniform, and the opening degree of the flow rate adjustment valve 50 is adjusted. It controls and adjusts the flow volume of the loading LNG injected from each spray nozzle 46.
The management device 23 </ b> A is configured by the drive device 48, the flow rate adjusting valve 50, the control device 52, a gas vent pipe 54, which will be described later, and an on-off valve 56.

Further, as shown in FIG. 1, a gas vent pipe 54 and an opening / closing valve 56 provided in the gas vent pipe 54 are provided in the upper part of the LNG inboard tank 12.
As shown in FIG. 3, the opening / closing operation of the opening / closing valve 56 is controlled by the control device 52. Conventionally, when loading LNG into the LNG inboard tank 12, the pressure of the LNG inboard tank 12 is set to an operating pressure of 0.25 barG or less at maximum. When the pressure in the LNG inboard tank 12 is set to a pressure higher than the operating pressure, the boiling point of the loaded LNG rises in the LNG inboard tank 12 and enters a supercooled state. Therefore, inside the LNG inboard tank 12, the sensible heat of the loaded LNG can be used as a cold heat source for recondensing the natural gas (residual gas and generated gas) in the LNG inboard tank 12.

That is, the loaded LNG charged into the LNG inboard tank 12 is pressurized to a pressure exceeding 0.25 barG and is in a supercooled state at the temperature T1, and therefore is in a state lower than the temperature T2 of the natural gas (T1 <T2 )It has become. After a certain amount of LNG has been loaded into the LNG inboard tank 12, the supercooled state of the LNG, which has a relatively low temperature, is obtained from natural gas in the LNG inboard tank 12, as indicated by the white arrow H in the figure. Since it absorbs heat and cools, it can be used as a cold heat source that condenses natural gas and changes its state to liquid LNG.
At this time, pressurization of the internal pressure of the LNG inboard tank 12 can be easily achieved by utilizing the self-evaporation of the loaded LNG. The internal pressure of the LNG inboard tank 12 can be controlled by opening and closing the gas vent pipe 54.

  According to the present embodiment, the temperature distribution measuring unit 26 can measure a precise temperature distribution in the height direction of the LNG inboard tank 12. When injecting LNG into the empty LNG inboard tank 12, the controller 52 controls the direction of the spray nozzle 46 and the flow rate of the loaded LNG based on the temperature distribution obtained by the temperature distribution measurement unit 26. The temperature distribution in the height direction of the stored LNG can be made uniform. Thereby, distortion and deformation of the LNG inboard tank 12 can be prevented.

Moreover, since the agitation of both can be accelerated | stimulated by dropping LNG from the top part vicinity of the LNG inboard tank 12 to the liquid level of storage LNG, temperature equalization of the height direction of stored liquefied gas can be accelerated | stimulated.
Further, the temperature distribution measuring unit 26 includes the calibration unit 32, so that the temperature distribution of the LNG stored in the LNG inboard tank 12 can be grasped more accurately.

  In addition, since the core 34 and the clad portion 36 of the optical fiber cable 24 are made of quartz glass, scattering of laser pulses propagating through the core 34 can be suppressed. Further, since the resin film 38 covering the core 34 and the clad portion 36 is made of an ultraviolet curable resin or a polyimide resin, the durability in a low temperature environment can be improved, and the scattering of pulsed light can be suppressed to detect the temperature. Performance can be improved. Furthermore, since the protective tube 40 is made of stainless steel, sufficient durability can be maintained without causing low temperature brittle fracture in a low temperature environment.

Furthermore, by providing the gas vent pipe 54, the internal pressure of the LNG inboard tank 12 is increased to a desired pressure, and the LNG loaded into the LNG inboard tank 12 is brought into a supercooled state, whereby the storage LNG of the LNG inboard tank 12 is stored. The temperature can be reduced and the generation of excess gas can be suppressed.
Moreover, in this embodiment, temperature can be calculated | required with the liquid level of the stored LNG. Therefore, it is possible to appropriately increase the pressure in the LNG inboard tank 12 according to the saturated vapor pressure corresponding to the liquid surface temperature, and to effectively suppress the evaporation of LNG.

  In the present embodiment, as the management device 23A, the LNG supply system 41 having the spray nozzle 46 and the internal pressure adjustment mechanism of the LNG inboard tank 12 by the gas vent pipe 54 are used in combination, but only one of these is used. It is good also as a management apparatus which has.

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 6, the storage system 10 </ b> B according to the present embodiment arranges the optical fiber cable 24 in the horizontal direction on the partition wall of the LNG inboard tank 12, bends in opposite directions at both ends in the horizontal direction, and forms a meandering shape. It is arranged. In addition, a stirring pump 58 is provided at the bottom of the LNG inboard tank 12 to form a circulating flow c in the height direction below the liquid level of the stored LNG. The operation of the agitation pump 58 is controlled by the control device 52. The management device 23B of this embodiment is obtained by adding a stirring mechanism by a stirring pump 58 to the management device 23A of the first embodiment. Other configurations are the same as those of the first embodiment.

According to the present embodiment, in addition to the effects obtained in the first embodiment, the stirring pump 58 is provided to form the circulating flow c in the height direction below the liquid level of the storage LNG. Stirring is promoted. For this reason, the temperature gradient in the height direction of the stored LNG can be made more uniform, so that distortion and deformation of the LNG inboard tank 12 can be effectively prevented.
Also, as shown in the figure, for the above-described rollover phenomenon caused by the difference in the liquid density in the vertical direction of the stored LNG, the stirring pump 58 is operated during the loading of the LNG, and the difference in liquid density in the vertical direction. The rollover phenomenon can be prevented from occurring by performing the LNG loading while eliminating the above. Furthermore, even after LNG storage, the occurrence of a rollover phenomenon can be suppressed by operating the stirring pump 58.

  In this embodiment, the LNG supply system 41 having the spray nozzle 46, the internal pressure adjusting mechanism of the LNG inboard tank 12 by the gas vent pipe 54, and the agitation mechanism by the agitation pump 58 provided in the LNG inboard tank 12 are provided. The management device 23B is configured as described above, but only one of these or any two of them may be used as a management device.

(Embodiment 3)
Next, a third embodiment of the present invention will be described with reference to FIGS. In the storage system 10C according to the present embodiment, a storage container is mounted on a ship and stores low-temperature liquefied gas used as fuel for a marine diesel engine.
In FIG. 7, the storage system 10 </ b> C includes a fuel LNG tank 60 and a gas tank 62 mounted on the LNG carrier 11. LNG is supplied to the fuel LNG tank 60 from an LNG inboard tank 12 mounted on the LNG carrier 11 via an LNG supply system 64. A gas phase is formed above the liquid level L of the fuel LNG tank 60, and a liquid phase is formed below.

  The fuel supply path 66 is connected to the bottom of the fuel LNG tank 60. The LNG stored in the fuel LNG tank 60 is supplied as fuel to a marine gas diesel engine 72 (hereinafter referred to as “marine engine 72”) that drives the propulsion device 74 via a fuel supply path 66. The fuel supply path 66 is provided with a fuel supply pump 68 and a heater 70, and LNG sent to the heater 70 by the fuel supply pump 68 is gasified by the heater 70 and supplied to the marine engine 72. Is done.

  The optical fiber cable 24 is spirally arranged around the vertical axis over the entire height direction on the outer or inner surface of the fuel LNG tank 60, and then the fuel supply path upstream of the fuel supply pump 68. The outer surface or inner surface of 66 is also arranged in a spiral shape. The start and end of the optical fiber cable 24 are connected to a temperature distribution measurement unit 26 provided in an inboard monitoring room (not shown) outside the LNG inboard tank 12. The configuration of the temperature distribution measurement unit 26 is the same as the temperature distribution measurement unit 26 used in the first embodiment or the second embodiment.

  The gas tank 62 stores gaseous natural gas. The top of the gas tank 62 and the fuel supply path 66 between the heater 70 and the marine engine 72 are connected by a natural gas flow path 76. The top of the gas tank 62 and the top of the fuel LNG tank 60 are connected by a natural gas passage 77. On-off valves 78, 79, and 80 are provided in the fuel supply passage 66 and the natural gas passages 76, 77 at the outlet of the fuel LNG tank 60, respectively. Further, pressure sensors 82 and 84 for detecting the pressure in the gas phase region of the fuel LNG tank 60 and the gas tank 62 are provided. Further, a pressure sensor 86 for detecting the pressure of the fuel supply path 66 at the inlet of the fuel supply pump 68 is provided.

As shown in FIG. 8, the control device 88 includes temperature distribution information of the fuel LNG tank 60 and the fuel supply path 66 detected by the optical fiber cable 24 from the arithmetic processing device 33 and detection of the pressure sensors 82, 84 and 86. A value is entered. Based on these input information, the control device 88 controls the driving device of the fuel supply pump 68 and the opening / closing operations of the on-off valves 78, 79 and 80.
FIG. 9 is a saturation pressure diagram at each temperature of LNG. The gas phase region in the gas tank 62 is always controlled to be equal to or higher than the saturation pressure at each temperature of LNG.
The temperature distribution measuring unit 26, the gas tank 62, the natural gas flow path 76, the on-off valves 79 and 80, the pressure sensors 82, 84 and 86, and the control device 88 constitute a management device 23C.

  In such a configuration, when the on-off valve 78 is opened and the LNG stored in the fuel LNG tank 60 is supplied to the marine engine 72 via the fuel supply path 66, the control device 88 is the temperature distribution measuring unit 26. From the measured temperature distribution information of LNG and the detected values of the pressure sensors 82 and 86, it is determined whether or not the LNG in the fuel LNG tank 60 and the LNG in the fuel supply path 66 have reached saturation pressure. When the detected values of the pressure sensors 82 and 86 have not reached the saturation pressure, the control device 88 opens the on-off valve 80 and passes the natural gas stored in the gas tank 62 through the natural gas passage 77 for fuel. Supply to the LNG tank 60.

When the pressure of the natural gas stored in the gas tank 62 decreases, the on-off valve 79 is opened and the natural gas is replenished from the fuel supply path 66. The fuel supply path 66 downstream of the heater 70 has a pressure of 30 MPa, for example, and the gas tank 62 is held at a pressure of 10 MPa, for example, so that the natural gas can be replenished to the gas tank 62 simply by opening the on-off valve 79.
As a result, the LNG in the fuel LNG tank 60 and the fuel supply path 66 can always be equal to or higher than the saturation pressure, so that cavitation in the fuel supply path 66 and the fuel supply pump 68 can be prevented.

  In the present embodiment, since the optical fiber cable 24 is arranged over the entire height direction of the LNG inboard tank 12, the temperature distribution in the entire height direction of the fuel LNG tank 60 can be measured. Therefore, the boundary between the gas phase region and the liquid phase region in the fuel LNG tank 60, that is, the height of the liquid level L of the LNG is obtained from this temperature distribution value and the LNG saturation pressure diagram shown in FIG. be able to. The LNG supply amount of the LNG supply system 64 can be adjusted from the obtained liquid level L of the fuel LNG tank 60.

The present invention is applicable not only to LNG but also to liquefied petroleum gas (LPG), and other low-temperature liquefied gases having a boiling point of 0 ° C. or lower, such as methane, ethane, propane, butane, oxygen, hydrogen, and argon. it can.
The present invention can be applied not only to an inboard tank but also to a tank provided at an offshore base or an onshore base.

10A, 10B, 10C Storage system 11,100 LNG carrier 12, 102 LNG inboard tank 14 Inner shell 16 Primary barrier 18 Thermal barrier 20 Tank cover 22 Skirt 23A, 23B, 23C Management device 24 Optical fiber cable 26 Temperature distribution measurement unit 28 Laser pulse transmitter 30 Measuring instrument 32 Calibration unit 33 Arithmetic processing unit 34 Core 36 Clad unit 38 Resin coating 40 Protective tube 41, 64 LNG supply system 42 LNG supply tube 44 Header 46 Spray nozzle 48 Drive device 50 Flow rate adjusting valve 52, 88 Control device 54 Gas vent pipe 56, 78, 79, 80 On-off valve 58 Stirring pump 60 LNG tank for fuel 62 Gas tank 66 Fuel supply path 68 Fuel supply pump 70 Heater 72 Marine gas diesel engine 74 Propeller 76, 7 Natural gas channel 82, 84, 86 pressure sensor 104 LNG tank 106 LNG pump 108 LNG loading piping 110 gas delivery piping system 112 engine unit 114 flare stack L liquid level R the Raman backscattered light c circulation

Claims (7)

A storage container for storing cryogenic liquefied gas;
A supply system for supplying low-temperature liquefied gas to the storage container;
An optical fiber cable disposed along the wall surface of the storage container so as to extend in the height direction of the outer surface or the inner surface of the wall surface;
A pulsed light transmitter configured to transmit pulsed light to the optical fiber cable; and
A backscattered light scattered from the optical fiber cable is input, and a measuring instrument configured to obtain a temperature distribution of a low-temperature liquefied gas stored in the storage container from the backscattered light;
A management device configured to manage the storage state of the low-temperature liquefied gas in the storage container based on the temperature distribution of the low-temperature liquefied gas obtained by the measuring instrument. Storage system. The supply system is
One or more spray nozzles provided near the top of the storage container and having a variable spray direction,
The management device
2. The control device according to claim 1, further comprising: a control device that controls a direction of the spray nozzle and an amount of the low-temperature liquefied gas supplied from the spray nozzle based on a temperature distribution of the low-temperature liquefied gas obtained by the measuring instrument. Low temperature liquefied gas storage system. The management device
A vent pipe configured to discharge the natural gas vaporized in the storage container;
The low-temperature liquefied gas storage system according to claim 1, further comprising: a control device that controls opening and closing of the degassing pipe based on a temperature distribution of the low-temperature liquefied gas obtained by the measuring instrument. The management device
A stirring pump for forming a circulating flow in a height direction in the low-temperature liquefied gas stored in the storage container in the storage container;
The control apparatus which controls the temperature distribution of the height direction of the low-temperature liquefied gas stored in the said storage container by controlling operation | movement of the said stirring pump, In any one of Claim 1 thru | or 3 characterized by the above-mentioned. The cryogenic liquefied gas storage system described. The management device
5. The apparatus according to claim 1, further comprising a calibration unit that calibrates the temperature obtained from the backscattered light based on a plurality of calibration curves prepared in advance corresponding to a plurality of temperature ranges. The storage system for the low-temperature liquefied gas according to Item. A fuel supply passage for supplying the low-temperature liquefied gas in the storage container to the marine engine;
A fuel supply pump provided in the fuel supply path;
A heater provided in the fuel supply path on the downstream side of the fuel supply pump, for heating and gasifying the low-temperature liquefied gas;
A second storage container for storing gaseous natural gas at a pressure higher than the saturation pressure;
The management device
A pressure sensor for detecting the pressure of the low-temperature liquefied gas supplied to the fuel supply pump;
When the detection value of the pressure sensor does not reach the saturation pressure of the low-temperature liquefied gas, gaseous natural gas stored in the second storage container is supplied to the storage container, and the detection value of the pressure sensor is set to the saturation pressure. 2. The low-temperature liquefied gas storage system according to claim 1, further comprising a control device that holds the above. The optical fiber cable is
A protective tube made of stainless steel;
A core and a clad portion made of quartz glass, incorporated in the protective tube;
The storage of the low-temperature liquefied gas according to any one of claims 1 to 6, further comprising a covering material made of an ultraviolet curable resin or a polyimide resin so as to cover the core and the clad portion. system.

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