WO2019098075A1

WO2019098075A1 - Tank condensed-gas determination device and method

Info

Publication number: WO2019098075A1
Application number: PCT/JP2018/041023
Authority: WO
Inventors: 一夫大村; 淳立花; 一幸渋谷; 裕樹岩城; 武臣出田
Original assignee: 株式会社Ihi
Priority date: 2017-11-16
Filing date: 2018-11-05
Publication date: 2019-05-23
Also published as: JP2019090507A

Abstract

The present invention is provided with: a storage tank 4 that stores accumulated matter 3; an outer tank 2 inside which the storage tank 4 is accommodated; a pressure sensor 9 that measures the pressure of a space in a tank 1 that includes the storage tank 4 and the outer tank 2; and a determination unit 14 that determines the amount of condensed gas C condensed between the storage tank 4 and the outer tank 2, on the basis of at least a pressure value indicated by the pressure sensor 9 or a change in the pressure value. It is also possible to provide: a liquid sensor 10 that measures the amount of liquid in a lower section between the storage tank 4 and the outer tank 2; and a warning device 15 that issues a warning on the basis of a comparison between a calculated condensation amount L1 of the condensed gas C calculated at the determination unit 14 and a measured liquid amount L2 ascertained from a detection value from the liquid sensor 10.

Description

Apparatus and method for determining condensed gas in tank

The present disclosure relates to an apparatus and method for determining the amount of boil-off gas that condenses outside a storage tank in a tank that stores liquefied gas and the like.

Conventionally, a double tank type tank is used as a tank for storing liquefied gas and the like. In this type of tank, a storage tank formed of metal or the like is accommodated inside an outer tank formed of PC (prestressed concrete), metal or the like, and a heat insulating layer is provided in a space between the outer tank and the storage tank. Have.

The outer tank containing the reservoir is entirely supported on a foundation, and the space between the reservoir and the foundation is thermally insulated between the bottom surface of the reservoir and the top surface of the foundation. , Bottom insulation layer is provided. The bottom heat insulating layer is made of a heat insulating material which is not easily deformed, such as foam glass, foamed resin, and heat insulating concrete.

Further, a side heat insulating layer is provided in a space (annular space) between the side wall of the storage tank and the side wall of the outer tank. The side heat insulating layer is formed, for example, by filling the annular space with a heat insulating material such as pearlite.

As a prior art document related to this type of tank, there is, for example, the following Patent Document 1 etc.

JP, 2012-184017, A

In the case of storing a low temperature liquefied gas or the like as a reservoir in the double-tank type tank as described above, a part of the reservoir is evaporated by the heat input from the outside to generate a boil-off gas. Here, when the tank is, for example, a suspended deck type tank that suspends the deck above the storage tank, the storage tank is not sealed, so that the boil-off gas leaks out of the storage tank and stays in the annular space. There is. Boil-off gas in the annular space condenses depending on conditions such as the temperature on the surface of the reservoir and the pressure in the tank, and accumulates at the bottom of the annular space.

Such condensed gas itself is not a problem in particular, but it may cause a false alarm to be generated due to confusion with the leak from the storage tank. In the above-mentioned tank which stores liquefied gas etc., the leak from a storage tank is detected, for example by the thermometer installed in the lower part of the annular space. When damage or the like occurs in the storage tank and the liquefied gas which is the storage material leaks, the leaked liquefied gas first accumulates between the storage tank and the outer tank. As a result, the temperature sensor provided at the bottom of the annular space is rapidly cooled by the liquefied gas and the detected value of the temperature sensor is reduced, so that the occurrence of leakage can be grasped.

However, similar temperature changes can also be caused by the above-mentioned condensed gas in which the boil-off gas condenses in the annular space. If the temperature sensor detects the condensed gas accumulated at the bottom of the annular space, it is erroneously determined that a leak has occurred even if the reservoir is not leaked. However, conventionally, no method has been established to distinguish between the condensed gas condensed in the annular space and the liquefied gas leaking from the storage tank or to grasp the amount of the condensed gas.

In view of such circumstances, the present disclosure is intended to provide a condensed gas determination apparatus and method for a tank capable of grasping the amount of condensed gas generated outside the storage tank.

The present disclosure comprises at least a storage tank for storing a reservoir, an outer tank containing the storage tank inside, a pressure sensor for measuring pressure in a space including the storage tank and the outer tank, and This invention relates to a condensed gas determination apparatus for a tank including a determination unit that determines the amount of condensed gas condensed between the storage tank and the outer tank based on the pressure value indicated by the pressure sensor or the fluctuation of the pressure value. is there.

The condensed gas determination device for a tank described above includes a liquid sensor that measures the amount of liquid in the lower portion between the storage tank and the outer tank, and the calculated condensed amount of condensed gas calculated by the determination unit An alarm device may be provided which issues an alarm based on comparison with the amount of measured liquid grasped by the detection value of the liquid sensor.

In the condensed gas determination apparatus for a tank described above, the liquid sensor includes a cable disposed at an angle with respect to the horizontal direction at a lower portion between the storage tank and the outer tank, and a measurement terminal disposed along the cable. And may be provided.

In the condensed gas determination apparatus for a tank described above, when determining the amount of condensed gas condensed between the storage tank and the outer tank, the pressure value in the pressure sensor as a parameter or the fluctuation of the pressure value as a parameter Temperature of the reservoir, storage amount of the reservoir, physical properties of the reservoir, dimension of the tank, temperature of the component of the tank, dimension of the component of the tank, physical property of the component of the tank, temperature of the space in the tank, At least one of the outside air temperature, the ground temperature, the amount of solar radiation, and the wind speed may be used.

Further, the present disclosure relates to the pressure value in the space in the tank or the pressure value of the amount of condensed gas condensed between the storage tank storing the storage material and the outer tank housing the storage tank inside. The present invention relates to a method for determining condensed gas in a tank, which is determined based on fluctuation.

According to the apparatus and method for determining condensed gas of a tank of the present invention, it is possible to obtain an excellent effect that the amount of condensed gas generated outside the storage tank can be grasped.

It is a front sectional view showing an example of a form of a tank in the present disclosure. It is a perspective view showing arrangement of a temperature sensor in an example of this indication. It is an expanded view explaining arrangement of a temperature sensor in an example of this indication. It is a graph explaining an example of transition of pressure in a tank of this indication. It is a flowchart explaining the procedure until it issues the alarm of a leak detection in the example of this indication.

Hereinafter, embodiments of the present disclosure will be described with reference to the attached drawings.

1 and 2 show the form of a tank according to an embodiment of the present disclosure. The tank 1 is a suspended-deck double tank including the outer tank 2 forming an outer shell and the storage tank 4 for storing the reservoir 3. The outer tank 2 and the storage tank 4 each have a cylindrical shape having a circular flat cross section. The outer tank 2 is formed of metal, PC or the like, and the storage tank 4 is formed of metal or the like. Then, the outer tank 2 and the storage tank 4 are concentrically arranged in a plan view on the foundation 5 formed of concrete or the like so that the storage tank 4 is accommodated inside the outer tank 2. The upper portion of the storage tank 4 is covered by a deck 4 a suspended from the roof 2 a of the dome-shaped outer tank 2. The reservoir 3 is a low temperature liquid such as, for example, LNG, LPG, or liquefied ethylene.

A disk-shaped bottom heat insulating layer 6 is disposed between the bottom 4 c of the circular storage tank 4 and the foundation 5. The bottom heat insulating layer 6 is provided with a porous material such as foam glass, foamed resin, heat insulating concrete, etc. as a heat insulating material. In addition, although various structures, such as a support structure for supporting the storage tank 4 on the foundation 5 other than the said heat insulating material, may be provided as the bottom heat insulation layer 6, illustration is abbreviate | omitted here. There is.

A side heat insulating layer 7 is disposed between the side wall 4 b of the reservoir 4 and the side wall 2 b of the outer tub 2. The side heat insulating layer 7 is configured by filling an annular space A formed between the side of the storage tank 4 and the outer tank 2 with a granular heat insulating material such as perlite, for example.

Further, a blanket 8 is installed on the side wall 4 b of the storage tank 4 so as to cover the side wall 4 b from the outer side in the radial direction. The blanket 8 is formed of a material such as glass wool having flexibility in addition to the function of thermally insulating the storage tank 4 from the outside, and absorbs thermal deformation of the storage tank 4 in the annular space A. The heat insulating material 4 d is installed also on the upper surface side of the deck 4 a covering the upper part of the storage tank 4.
Furthermore, at the bottom of the annular space A, a protective material 2c is installed from the floor surface to the lower inside of the side wall 2b of the outer tank 2. The protective material 2c is a member for preventing damage to a material constituting the outer tank 2 due to a low temperature when a low temperature liquid such as condensed gas C described later is accumulated in the annular space A.

Thus, in the tank 1, the bottom heat insulating layer 6 installed below the storage tank 4, the heat insulating material 4 d installed on the deck 4 a above the storage tank 4, and the side installed on the side of the storage tank 4 A partial heat insulating layer 7 and a blanket 8 are provided. Thereby, the space between the lower foundation 5 and the outer space outside the outer tank 2 and the storage tank 4 are thermally insulated.

Pressure sensors 9 are provided in each of the spaces defined in the tank 1. Normally, as shown here, two pressure sensors 9 are provided to measure the pressure inside the storage tank 4 and the pressure between the storage tank 4 and the outer tank 2 respectively, but it is also necessary to Accordingly, pressure sensors 9 may be attached to various parts of the tank 1.

Further, a temperature sensor 10 is provided in the tank 1 to measure the temperatures of members and spaces at various places. For example, as shown in FIG. 2, the temperature sensor 10 has a configuration in which a plurality of measurement terminals 12 are disposed along a cable 11 provided with an optical fiber. In the case of the present embodiment, the temperature sensor 10 is installed such that the cable 11 extends to the annular space A from the termination box 13 installed at one place on the circumference of the upper end portion of the outer tank 2. The arrangement of the measurement terminals 12 illustrated in FIGS. 1 to 3 is schematic and does not necessarily accurately reflect the actual arrangement. For example, in each part of the cable 11, the arrangement of the measurement terminals 12 may be made denser or conversely sparse. The arrangement of the measurement terminals 12 can be appropriately adjusted in accordance with the portion where the temperature is to be measured.

The cable 11 is connected at both ends to the termination box 13 and forms an annulus with the termination box 13. Cable 11 extends vertically along the side wall 2b from the upper end of outer tub 2 along the side wall 2b to the bottom of outer tub 2 and is arranged to circle inside the side wall 2b along the circumferential direction. Ru. In the cable 11, the measurement terminals 12 are disposed at a portion disposed along the vertical direction and a portion disposed along the circumferential direction. The temperature in the annular space A is measured at the measurement terminal 12 provided on the portion of the cable 11 arranged in the vertical direction.

The measurement terminals 12 are provided at regular intervals in a portion of the cable 11 arranged along the circumferential direction, and the temperature of the lower portion of the annular space A is measured.

The detailed arrangement of the cable 11 in the annular space A is shown in FIG. FIG. 3 is a schematic view in which the side wall 2b of the cylindrical outer tank 2 is expanded in the circumferential direction, and the horizontal direction corresponds to the position in the circumferential direction of the side wall 2b, and the vertical direction corresponds to the position in the height direction of the side wall 2b. doing. The position in the circumferential direction is illustrated with the position where the termination box 13 is installed as 0 ° and the position opposite to the termination box 13 as 180 ° or -180 °.

The cable 11 extends downward from the two ends connected to the termination box 13 to the side wall 2b, and further extends circumferentially to the left and right at the lower portion of the side wall 2b. In FIG. 3, the cable 11 extending to the right side and the cable 11 extending to the left side are connected at a position of 180 ° (−180 °) opposite to the termination box 13 (see FIG. 2).

The cables 11 arranged along the circumferential direction are arranged with an appropriate inclination with respect to the horizontal direction. In the case of the present embodiment, the cable 11 extending to the right in FIG. 3 is at the lower end of the side wall 2b at the position of 0 °, and slopes upward from there to the position of 90 °. There is a downward slope from the 90 ° position to the 180 ° position. Further, in FIG. 3, the cable 11 extending to the left is at the lower end of the side wall 2b at the position of 0 °, and has an upward slope toward the position of −90 °. There is a downward slope from the -90 ° position to the -180 ° position. The inclination of the cable 11 at the lower portion of the side wall 2b is, for example, about 5% or more and 20% or less of the distance in the circumferential direction, preferably 10% (in FIG. 3, for convenience of description, the vertical direction of the side wall 2b And the gradient of the cable 11 is highlighted more than in fact). Thus, the cable 11 goes around the lower portion of the side wall 2b in the annular space A while gradually changing the position in the height direction.

The measurement terminal 12 arranged as described above along the cable 11 in the lower part of the annular space A is configured to monitor the liquid level of the liquid in the lower part of the annular space A. When the condensed gas C is accumulated at the bottom of the annular space A, or when the reservoir 3 leaks from the storage tank 4, the temperature drops significantly at the measurement terminal 12 which is sunk in the liquid at the bottom of the annular space A. Thus, the liquid level at the bottom of the annular space A can be grasped as the height at which the measurement terminal 12 whose temperature has dropped is disposed. That is, in the case of the present embodiment, the temperature sensor 10 also plays a role as a liquid sensor.

The inclined arrangement of the cables 11 as shown in FIGS. 2 and 3 is a configuration for securing resolution in the height direction when grasping the liquid level in the annular space A. In the case of the temperature sensor 10 having the measurement terminal 12 in the cable 11 as in the present embodiment, it is usual that the measurement terminal 12 is disposed along the cable 11 with a certain distance or more, due to technical limitations. . However, in such an arrangement, the resolution along the direction of the cable 11 is determined by the distance between the measurement terminals 12 when measuring the temperature distribution.

On the other hand, in the measurement of the liquid level in the annular space A, a resolution of about several cm or less is required in the vertical direction. This is because the speed at which the condensed gas C accumulates at the bottom of the annular space A is, for example, about several centimeters per hour. This is considerably smaller than the spacing between the measurement terminals 12 arranged on the cable 11 of the temperature sensor 10 as described above.

Therefore, if the cable 11 is not disposed vertically but is disposed with an appropriate gradient in the circumferential direction of the annular space A as in this embodiment, the distance between the measurement terminals 12 along the cable 11 is changed. Instead, the distribution of the measurement terminals 12 in the vertical direction can be made dense. For example, if the gradient of the cable 11 in which the measurement terminals 12 are arranged as described above is 10% with respect to the horizontal direction, the distance between the measurement terminals 12 in the vertical direction is less than one tenth of the distance along the cable 11 It becomes. Thus, in the cable 11, the temperature distribution in the height direction in the annular space A can be measured with high resolution.

Here, the arrangement of the cables 11 has been described by way of example in the case in which the cable 11 is sloped up and down twice along the circumferential direction of the outer tank 2, but it is not limited thereto. The cable 11 may be inclined as long as the required resolution can be obtained in the vertical direction with respect to temperature measurement, and various arrangements can be taken in addition to the arrangement shown here. For example, the side wall 2b may be disposed so as to spirally surround or may be disposed in a zigzag manner.

The detected value of the temperature measured at the measurement terminal 12 of the cable 11 is sent to the termination box 13 via the cable 11 and is input from the termination box 13 to the control device 14 as the temperature signal 10a. Moreover, the detection value of the pressure measured by the pressure sensor 9 provided in each place is input into the control apparatus 14 as a pressure signal 9a. The control device 14 operates the alarm device 15 as the case may be, based on the detected values received as the pressure signal 9 a and the temperature signal 10 a.

The control device 14 is a device that operates and manages the tank 1 and also has a function as a determination unit that determines the amount of the condensed gas C and the alert notification in the present embodiment. The control device 14 includes a storage unit 16 that stores various data such as detection values of the pressure sensor 9 and the temperature sensor 10 and calculation formulas, and a calculation unit 17 that performs calculation based on measurement data and the like. The state of each part is monitored by the pressure signal 9a and the temperature signal 10a as described above, and various operations such as reception and discharge of the reservoir 3 through piping (not shown) are controlled. The pressure signal 9a and the temperature signal 10a from the pressure sensor 9 and the temperature sensor 10 may be wired or wireless.

The alarm device 15 is a device that notifies an alarm when a specific situation such as an error or damage occurs in the tank 1. The content of the alarm may be, for example, a sound such as a buzzer, or may be in the form of an alarm light or a visual notification such as a specific screen display. It is also possible to combine these forms.

Furthermore, various instruments for measuring the temperature and other parameters of various places are installed in the tank 1 and its surroundings. Temperature sensors 18 are respectively installed in the side wall 4 b of the storage tank 4 and the external space of the outer tank 2. Further, in the storage tank 4, a temperature sensor 19 for measuring the temperature and the liquid level of the storage 3 is disposed. The temperature sensor 19 is a sensor in which measurement points are installed along a cable disposed longitudinally from the top of the storage tank 4 toward the inside, and the temperature at each measurement point is input to the control device 14 . The controller 14 can measure the temperature distribution of the reservoir 3 along the vertical direction according to the temperature information from the measurement point in the lower part of the temperature sensor 19. In addition, inside and outside the tank 1, various other instruments may be provided at various places.

In addition, the tank 1 has a receiving pipe for receiving the reservoir 3 in the reservoir 4, a discharge pipe for discharging the reservoir 3 from the storage tank 4, and a boil-off gas outlet pipe for discharging the boil-off gas B to the outside. Although various pipings are provided, illustration is abbreviate | omitted here.

Next, the operation of the above-described embodiment will be described.

In the tank 1 of the present embodiment, a low temperature liquid is stored in the storage tank 4 as the reservoir 3 as described above. In the tank 1 which is a suspended deck type tank, the storage tank 4 is not completely sealed, so when boil off gas B is generated from the storage material 3 by natural heat input, the boil off gas B leaks from the storage tank 4 and the outer tank Stay between 2 and The boil-off gas B retained here is condensed under conditions such as pressure and temperature, and is accumulated as condensed gas C at the bottom of the annular space A as shown in FIG.

One of the main factors causing condensation of the condensed gas C is the pressure in the tank 1 and the fluctuation of the pressure. The pressure in the tank 1 exhibits a fluctuation as shown in FIG. 4, for example, along the time axis of the day.

When the reservoir 3 is a fuel such as LNG or LPG, the reservoir 3 and the boil-off gas B fluctuate as shown in FIG. 4, for example. In the example shown here, the required amount of boil-off gas B is large during the day, and the required amount of night is reduced. Then, at night, the operation of accumulating the boil-off gas B generated from the reservoir 3 in the outer tank 2 is performed, and the pressure in the tank 1 gradually increases from night to morning. In the daytime, the reservoir 3 and the boil-off gas B are discharged and the pressure decreases. As described above, as shown in FIG. 4, the pressure in the tank 1 rises and falls in a cycle of approximately one day in accordance with the fluctuation of the consumption. The pressure fluctuation described here is merely an example, and the pressure fluctuation in the tank 1 exhibits various other patterns depending on the consumption amount and operation.

In such a fluctuating pressure situation, the condensed gas C is generated especially when the pressure rises. If the pressure in the tank 1 is rising very slowly, the fluid in the tank 1 exhibits a phase generally corresponding to the pressure and temperature as a whole. However, since the tank 1 is a huge apparatus generally having a size of several tens of meters, there may be a local occurrence of a part where the phase change can not catch up with the change in pressure or temperature as a whole. Specifically, when the pressure in the tank 1 rises at a certain rate of increase or more, the reservoir 3 in the reservoir 4 is in a state of supercooling that lowers the temperature as it is. Here, the reservoir 3 is in contact with the boil-off gas B in the annular space A via the side wall 4 b of the reservoir 4. When the cold heat of the supercooled reservoir 3 is transferred to the boil off gas B via the side wall 4b, the boil off gas B that has received the cold heat condenses and condenses on the bottom of the annular space A as condensed gas C.

Then, in the present embodiment, the amount of the condensed gas C accumulated at the bottom of the annular space A can be determined by the control device 14 as the determination unit.

Various conditions are associated with the amount of condensed gas C generated or the amount of accumulation at the bottom of the annular space A. Usually, the largest factor that influences the amount of condensed gas C is the above-mentioned pressure or fluctuation of pressure, but in addition, temperature, storage amount, physical properties (saturation vapor pressure curve, density, viscosity coefficient, specific heat of reservoir 3) , Thermal conductivity, latent heat of evaporation, dimensions of the tank 1, members constituting each part of the tank 1 (for example, the outer tank 2, the storage tank 4, the bottom heat insulating layer 6, the side heat insulating layer 7, etc. Hereinafter, "component members Temperature, dimensions and physical properties (thermal conductivity, density, specific heat, porosity, permeability coefficient), spaces in the tank 1 (annular space A, and other spaces defined inside the outer tank 2) Temperature, ambient temperature, solar radiation amount, wind speed, ground temperature (temperature of foundation 5 and temperature below ground of foundation 5), partial pressure of boil-off gas B in annular space A, etc. Related to quantity.

The condensed gas C increases as the boil-off gas B in the annular space A is cooled, that is, as the amount of transfer of cold heat from the inside to the outside of the storage tank 4 increases. The transfer amount of cold energy includes the storage amount and physical properties of the reservoir 3 (density, viscosity coefficient, specific heat, thermal conductivity), the dimensions and physical properties of the reservoir 4 (thermal conductivity, density, specific heat), the reservoir 3 and storage The temperature of the tank 4, the temperature in the annular space A, and the like are related.

On the other hand, the boil-off gas B and the condensed gas C in the annular space A are warmed by the heat input from the outside of the outer tank 2. This heat input works to reduce the condensed gas C. The heat input from the outside includes the dimensions and physical properties (thermal conductivity, density, specific heat, porosity, permeability coefficient) of the tank 1 to the outer tank 2, the temperature of the ambient temperature and the foundation 5, the amount of solar radiation, the wind velocity, the annular space A The temperature of the

Further, the amount of condensed gas C also varies depending on the amount of boil-off gas B filling the annular space A. In addition to the pressure in the tank 1, the physical properties of the reservoir 3 (saturated vapor pressure curve, latent heat of evaporation), the temperature of the reservoir 3, the temperature in the annular space A, and the partial pressure of the boil off gas B Is concerned.

Also, the parameters listed above are related to one another and, while affecting each other, some change over time.

Each of these parameters is input to the storage unit 16 of the control device 14 and stored. The controller 14 also includes a calculation tool T that determines the amount of condensed gas C based on the above-described parameters. The calculation unit 17 of the control device 14 can calculate the current amount of the condensed gas C in the annular space A as the liquid level by reading out and inputting each parameter from the storage unit 16 to the calculation tool T. There is.

The calculation tool T utilizes a calculation formula incorporating the various parameters described above. That is, the temperature, storage amount, physical properties (saturated vapor pressure curve, density, viscosity coefficient, specific heat, thermal conductivity, latent heat of evaporation) of the reservoir 3, dimensions of the tank 1, temperature, dimensions and physical properties of the components of the tank 1 Thermal conductivity, density, specific heat, porosity, permeability coefficient), pressure value in the tank 1 or fluctuation of the pressure value, temperature of space in the tank 1, outside temperature, underground temperature, and the like. The coefficient of viscosity, specific heat, thermal conductivity, evaporation latent heat, dimensions, thermal conductivity, density, specific heat, etc. of the constituent members of the reservoir 3 are constants. The saturated vapor pressure curve of the reservoir 3 is given as a function of temperature and the density is given as a function of temperature and pressure. The pressure in the tank 1 and its fluctuation, the temperature and storage amount of the reservoir 3, the temperature of the component members of the tank 1, the temperature of the space in the tank 1, the outside air temperature and the underground temperature, the amount of solar radiation and the wind speed are variables.

In establishing a specific calculation formula, first, the amount of condensed gas C is measured in an actual tank 1 under several kinds of conditions, and the value of each parameter at that time is recorded. Then, an appropriate coefficient or index may be determined for each parameter so that the amount of condensation of the condensed gas C can be calculated from the value of the parameter under each condition.

That is, assuming that each parameter used for calculation is X ₁ , X ₂ ,..., X _n and the liquid level of condensed gas C is L, the amount of condensation of condensed gas C is given by the following equation, for example Be
[Equation 1]
L = k ₁ X _{1 a} ¹ + k ₂ X _{2 a} ² +... + K _n X _n ^an + c

Here, k ₁ , k ₂ ,..., K _n are coefficients of respective parameters, a ₁ , a ₂ ,..., _An are exponents of respective parameters, and c is a constant. Then, X ₁ , X ₂ ,..., X _n and L under a plurality of measurement conditions are substituted into the above [Equation 1], and each coefficient k ₁ , k _{2 is set} so that [Equation 1] is satisfied under each condition. , K _n , the respective indexes a ₁ , a ₂ ,..., _An and the constant c may be determined.

At this time, X ₁ , X ₂ ,..., X _n may be selected appropriately from among the parameters listed above. However, as the amount of condensed gas C greatly affects the pressure value and the fluctuation of the pressure value as described above, the calculation formula should be designed to reflect at least one of the pressure value or the fluctuation of the pressure value. It is. In addition to the pressure value and its fluctuation, the amount of condensed gas C can be calculated more accurately by incorporating other parameters as appropriate. In addition, although the case where the amount of condensation of condensation gas C was computed as a liquid level was illustrated here, the amount of condensation may be computed as volume not only in a liquid level, for example.

In order not to complicate the formula, the parameter that has a small degree of contribution to the condensed gas C finally calculated may be rejected in the formula. Alternatively, estimated values or assumed values may be used for some of the parameters that are difficult to measure or calculate. For example, when the reservoir 3 is a fuel or the like, an inert gas such as nitrogen is filled between the reservoir 4 and the outer reservoir 2. In this case, the partial pressure of the boil-off gas B in the annular space A is It can not be calculated simply from the detection value of the pressure sensor 9 alone. Therefore, in calculating the amount of condensed gas C, it may be assumed that all the gas in the annular space A is replaced with the boil-off gas B. That is, with regard to the partial pressure of the boil-off gas B, if the maximum amount that can be assumed is calculated, it is sufficient for the determination related to the alerting of the alarm described later.

Other parameters can be obtained, for example, by the following method. The pressure value in the tank 1 and the fluctuation of the pressure value can be grasped by recording the detection value of the pressure sensor 9. The temperature of the space in the tank 1, the storage amount of the reservoir 3, and the temperature can be obtained by the detection values of the

temperature sensors

10 and 19.

The temperatures of the constituent members of the tank 1 can also be obtained by the

temperature sensors

18 and 19 installed at various places. For example, the temperature of the side wall 4b of the reservoir 4 can be measured directly by the temperature sensor 18 installed on the side wall 4b. In addition to this, for example, a correction value or the like based on physical properties of the reservoir 3 and the reservoir 4 can be added to the temperature of the reservoir 3 to calculate. Further, the temperature of the side wall 4b may be a variable of the temperature of the reservoir 3, and the temperature of the reservoir 3 may be adopted in the calculation formula so that the temperature of the side wall 4b is not used. Besides, for a space or a member where it is difficult to measure the temperature directly, for example, the temperature of the adjacent member may be used as an approximate value. Alternatively, for example, an appropriate initial value may be set, and the temperature of the target may be estimated based on the physical properties of surrounding members, fluctuations in pressure, and the like.

Among the physical properties of the reservoir 3, the viscosity coefficient, specific heat, thermal conductivity, and latent heat of evaporation are determined by the type of reservoir 3. The saturated vapor pressure and density of the reservoir 3 are determined by the temperature and pressure as described above in addition to the type of reservoir 3. The dimensions of the tank 1 and its constituent members can be obtained by measuring in advance. Further, the physical properties (thermal conductivity, density, specific heat, porosity, and permeability coefficient) of the tank 1 and the constituent members are determined by the type of the material. The outside temperature can be measured by the temperature sensor 18 provided outside the outer tank 2. The underground temperature may be measured by another temperature sensor (not shown), or may be estimated based on the outside air temperature. The solar radiation amount and the wind speed may be measured by separately providing a sensor (not shown) outside the tank 1.
The equation 1 described above is merely an example, and various other types of equation may be adopted as the calculation tool T. For example, the relationship between the parameters can be approximately calculated by numerical analysis using a macro operation of a computer or the like, and a calculation equation different from the equation 1 can be derived.

Alternatively, the calculation tool T may be a table in which the amount of condensed gas C corresponding to each of the parameters described above is input for each condition, and based on the detection values of the pressure sensor 9 and the

temperature sensors

10, 18 and 19, The amount of condensed gas C corresponding to the condition may be recalled. Also, the calculation formula and the table can be combined as appropriate.

The amount of liquid containing condensed gas C at the bottom of the annular space A can be measured by the detection value from the measurement terminal 12 provided on the cable 11 as described above. That is, the arrangement height of the measurement terminal 12 whose temperature has dropped can be grasped as the liquid level of the liquid at the bottom of the annular space A.

Thus, the determination unit 14 can grasp the amount of condensed gas C generated outside the storage tank 4 from the pressure value in the tank 1 and the fluctuation thereof. When the liquid is detected at the bottom of the annular space A through the detection value of the temperature sensor 10, the amount occupied by the condensed gas C is determined among them, and the liquid in the annular space A is the reservoir 3 leaked from the reservoir 4 And condensed gas C can be distinguished. Moreover, when these are mixed, the amount occupied by each can be grasped | ascertained.

Then, in the tank 1 of the present embodiment, the calculated amount of condensed gas C calculated using the calculation tool T based on the measurement by the pressure sensor 9 and the

temperature sensors

10, 18, 19 and the like (hereinafter, calculated condensation amount L1) An alarm is issued from the alarm device 15 based on the comparison with the amount of liquid calculated from the detection value of the measurement terminal 12 at the bottom of the annular space A (hereinafter referred to as the measured liquid amount L2). That is, the calculated condensed amount L1 and the measured liquid amount L2 are compared by the calculation unit 17 of the control device 14, and it is determined that the storage tank 4 has leaked when the measured liquid amount L2 exceeds the calculated condensed amount L1. The alarm device 15 issues an alarm.

The procedure up to the alarm issuance is shown as a flowchart in FIG. The detection values of the pressure sensor 9 and the temperature sensor 10 are inputted to the control device 14 every moment as the pressure signal 9a and the temperature signal 10a, and stored in the storage unit 16 (step S1). In addition,

temperature sensors

18, 19 and various sensors not shown in FIG. 1 are used to detect the temperature and level of the reservoir 3, the outside air temperature, the temperature of the side wall 4b of the reservoir 4, and other various detection values. Collected by the controller 14.

At step S2, based on the data collected at step S1, the calculated condensation amount L1 is calculated by the calculation tool T. Here, the pressure value in the tank 1 measured by the pressure sensor 9 or the fluctuation of the pressure value can be used as the main parameter. Also, other parameters may be used as appropriate.

In the case of using the fluctuation of the pressure value to calculate the calculated amount of condensation L1, for example, the derivative value of the pressure value which fluctuates from moment to moment can be used, but there is a problem that the influence of noise becomes large. Therefore, for example, a change in pressure value in a certain period of time up to the present time, that is, a difference between the current pressure value and a pressure value in a certain period of time Δt before may be used as the pressure fluctuation value. Alternatively, instead of the pressure value or its derivative value itself, the duration of the state in which the pressure value exceeds a predetermined threshold may be used as a parameter. In any case, the pressure value related to the amount of the condensed gas C and the value reflecting the fluctuation thereof can be appropriately used to calculate the calculated condensation amount L1.

Further, at step S3, based on the measurement data at the measurement terminal 12 of the cable 11, the current measurement liquid amount L2 is determined.

In the subsequent step S4, the calculated amount of condensation L1 and the amount of liquid to be measured L2 are compared and compared. Here, for example, the calculated condensation amount L1 obtained as the liquid level in step S2 is compared with the measured liquid amount L2 obtained as the liquid level in step S3. Although the case where the calculated condensation amount L1 is calculated as the liquid level is described here, for example, the calculated condensation amount L1 may be calculated as a volume. In this case, for example, the volume of the liquid in the annular space A is calculated by multiplying the measured liquid amount L2 obtained as the liquid level in step S3 by the cross sectional area, porosity, etc. of the annular space A, and obtained as volume in step S2. A process of comparing with the calculated condensation amount L1 is performed.

If the measured liquid amount L2 exceeds the calculated condensed amount L1 in step S4, it is determined that the storage tank 4 has leaked, and the process proceeds to step S5. In step S5, the alarm device 15 is operated to issue an alarm that a leak has occurred in the storage tank 4. In step S4, when the measurement liquid amount L2 is equal to or less than the calculated condensation amount L1, the process returns to step S1 and the subsequent steps are repeated.

In the above-described steps, the order may be appropriately interchanged, or division / integration may be performed as long as the calculated amount of condensation L1 and the amount of measurement liquid L2 can be appropriately compared. For example, the order of steps S2 and S3 does not matter. Step S3 may be performed before step S2, or step S2 and step S3 may be performed simultaneously in parallel. Also, for example, the process of collecting measurement data from each sensor in step S1 is divided, and the measurement for calculating the calculated amount of condensation L1 in step S2 and the measurement for the amount L2 of measured liquid in step S3 are different timing You may go there.

In the above-described process, the amount L2 of measured liquid can be directly grasped from the detection value at the measurement terminal 12 of the cable 11. On the other hand, the calculated condensation amount L1 is indirectly calculated from the pressure value and parameters such as its fluctuation, and the possibility that an error is included should be taken into consideration. If the calculated condensed amount L1 is calculated to be smaller than the actual amount of condensed gas C, the possibility of false alarm may increase, and conversely, if the calculated condensed amount L1 is calculated a lot Even if the storage tank 4 leaks, an alarm may not be issued.

As a measure for suppressing the possibility of false alarm, for example, when comparing the calculated condensation amount L1 and the measurement liquid amount L2, a predetermined reference value is set as the difference between the measurement liquid amount L2 and the calculation condensation amount L1. Then, when a value obtained by subtracting the calculated condensation amount L1 from the measurement liquid amount L2 exceeds the reference value, an alarm may be issued.

As another measure for suppressing the possibility of false alarm, for example, when calculating the calculated condensation amount L1 from each parameter, the value with which the calculation condensation amount L1 is maximized for a parameter having a large measurement error or a parameter for which estimation is difficult Can be used as a hypothetical value. The above-mentioned estimation on the partial pressure of the boil-off gas B (calculated assuming that all the gases in the annular space A are replaced with the boil-off gas B) is an example. If the calculated condensation amount L1 is calculated to be large, the threshold value of the alarm alert increases, and the possibility of false alarm decreases.

Also, conversely, as a measure to avoid the non-detection of the leakage, it is possible to assume a value such that the calculated condensation amount L1 decreases with respect to a parameter having a large measurement error or a parameter that is difficult to estimate. If the calculated condensed amount L1 is calculated to be smaller and the measured liquid amount L2 is larger than the calculated condensed amount L1, it is determined that the residual 3 has leaked. Therefore, while the possibility of false alarm is somewhat increased, the possibility of not detecting leak is reduced. Incidentally, even if the possibility of false alarm is increased as a result of adopting a measure to avoid the non-detection of the leak, it is not different itself to issue an alarm by comparing the calculated condensed amount L1 with the measured liquid amount L2. That is, if the amount of the condensed gas C can not be estimated and the generation of the condensed gas C can not be distinguished from the leakage of the reservoir 3 from the reservoir 4, the possibility of false alarm can be suppressed as well.

Other than this, the magnitude of the calculated condensation amount L1 related to the determination may be appropriately manipulated by adding an appropriate correction value to each parameter or the final calculated condensation amount L1. Such an operation corresponds to, for example, actual measurement data actually obtained through the operation of the tank 1, a request of a customer who operates the tank 1 (for example, which one of the reduction of false alarm and the prevention of leakage non-detection is emphasized) The calculation can be performed by adjusting the contents of the calculation formula and table used in the calculation tool T.

The operation of the calculated condensation amount L1 can also be performed by selecting the installation position of the pressure sensor 9. As described above, the pressure sensors 9 are installed at a plurality of locations in the tank 1, but the movement of pressure differs depending on the location. That is, there are a place where the pressure value tends to rise and fall, a place where the pressure value is difficult to reflect on the generation of the condensed gas C, and the like. When it is desired to obtain a value with high accuracy as the calculated condensation amount L1, detection of the pressure sensor 9 installed at a place where the fluctuation of the pressure value is large and the fluctuation of the pressure value there is easy to be interlocked with the amount of condensed gas C A value may be adopted as a parameter. However, in such a case, the influence of noise on the calculated amount of condensation L1 increases, and false alarms may easily occur. In that case, it is also effective to adopt the detection value of the pressure sensor 9 installed at a place where the pressure fluctuation is small to some extent. The selection of the installation place of the pressure sensor 9 may be performed empirically taking into consideration the measurement data and the like obtained through the operation of the tank 1 as well.

Alternatively, the calculated condensation amount L1 is calculated from the detection values of each of the pressure sensors 9 installed at a plurality of locations and compared with the measurement liquid amount L2 and the measurement liquid amount L2 exceeds any of the calculated condensation amounts L1 An alarm may be issued to In this method, by monitoring the possibility of leakage at a plurality of measurement points, it is possible to more reliably prevent the non-detection of the leakage.

As described above, in the condensed gas determination apparatus for a tank according to the present embodiment, the storage tank 4 storing the storage 3, the outer tank 2 storing the storage tank 4 inside, the storage tank 4 and the above Between the storage tank 4 and the outer tank 2 based on the pressure sensor 9 for measuring the pressure in the space in the tank 1 provided with the outer tank 2 and the pressure value indicated by the pressure sensor 9 or the fluctuation of the pressure value. And a determination unit (control device) 14 that determines the amount of condensed gas C to be condensed.

Further, in the method for determining condensed gas in a tank according to the present embodiment, the amount of condensed gas C condensed between the storage tank 4 for storing the reservoir 3 and the outer tank 2 for storing the storage tank 4 inside is It is determined based on the pressure value in the space in the tank 1 or the fluctuation of the pressure value. By doing this, the amount of condensed gas C accumulated between the storage tank 4 and the outer tank 2 can be determined.

Further, in the condensed gas determination apparatus for a tank according to the present embodiment, the determination unit is provided with a liquid sensor (temperature sensor) 10 that measures the amount of liquid in the lower part between the storage tank 4 and the outer tank 2 The alarm device 15 is provided to issue an alarm based on the comparison between the calculated condensation amount L1 of the condensed gas C calculated at 14 and the measurement liquid amount L2 grasped by the detection value of the liquid sensor 10. By doing this, it is possible to suppress the possibility that a false alarm of the occurrence of a leak in the storage tank 4 may be reported by the condensed gas C accumulated outside the storage tank 4.

Further, in the condensed gas determination apparatus for a tank according to the present embodiment, the liquid sensor 10 is a cable 11 disposed at a lower position between the storage tank 4 and the outer tank 2 with respect to the horizontal direction, and the cable And a measurement terminal 12 disposed along the line 11. By doing this, the temperature distribution in the height direction outside the storage tank 4 can be measured with high resolution, and the liquid level can be grasped.

In the apparatus for determining condensed gas in a tank according to the present embodiment, the pressure value in the pressure sensor 9 or the pressure value in the pressure sensor 9 is used as a parameter in determining the amount of the condensed gas C condensed between the storage tank 4 and the outer tank 2. Besides the fluctuation of the pressure value, the temperature of the reservoir 3, the storage amount of the reservoir 3, the physical properties of the reservoir 3, the dimensions of the tank 1, the temperatures of the components of the tank 1, the dimensions of the components of the tank 1, At least one of physical properties of components of the tank 1, temperature of space in the tank 1, ambient temperature, underground temperature, amount of solar radiation, and wind speed is used. By doing this, it is possible to more accurately determine the amount of condensed gas C accumulated between the storage tank 4 and the outer tank 2.

Therefore, according to the said Example, the quantity of the condensed gas which arose outside the storage tank can be grasped | ascertained.

In addition, the condensed gas determination apparatus and method of the tank demonstrated by this indication are not limited only to the above-mentioned Example, Of course in the range which does not deviate from a summary, a various change can be added.

Reference Signs List 1 tank 2 outer tank 2a roof 2b side wall 2c protective material 3 reservoir 4 reservoir 4a deck 4b side wall 4c bottom 4d heat insulating material 5 foundation 6 bottom heat insulating layer 7 side heat insulating layer 8 blanket 9 pressure sensor 9a pressure signal 10 temperature sensor 10a Temperature signal 11 Cable 12 Measurement terminal 13 Termination box 14 Control device (judgment part)
15 alarm device 16 storage unit 17 calculation unit 18 temperature sensor 19 temperature sensor A annular space B boil-off gas C condensed gas L1 calculated condensation amount L2 measurement liquid amount T calculation tool

Claims

A storage tank for storing a reservoir,
An outer tank containing the storage tank inside;
A pressure sensor that measures the pressure in a space in a tank including the storage tank and the outer tank;
A condensed gas determination apparatus for a tank, comprising: a determination unit that determines an amount of condensed gas condensed between the reservoir and the outer tank based on at least a pressure value indicated by the pressure sensor or fluctuation of the pressure value.
In addition to the pressure value in the pressure sensor or the fluctuation of the pressure value as a parameter in determining the amount of condensed gas condensed between the storage tank and the outer tank,
The temperature of the reservoir,
Amount of storage of the said reservoir,
Physical properties of said reservoir,
Tank dimensions,
The temperature of the components of the tank,
Dimensions of tank components,
Physical properties of tank components,
Temperature of the space in the tank,
Outside temperature,
Underground temperature,
Solar radiation,
The condensed gas determination device for a tank according to claim 1, wherein at least one of the wind speeds is used.
And a liquid sensor for measuring the amount of liquid in the lower part between the reservoir and the outer tank,
The alarm device according to claim 1, further comprising: an alarm device that issues an alarm based on comparison between the calculated condensation amount of condensed gas calculated by the determination unit and the measured liquid amount grasped by the detected value of the liquid sensor. Condensed gas determination device for tanks.
In addition to the pressure value in the pressure sensor or the fluctuation of the pressure value as a parameter in determining the amount of condensed gas condensed between the storage tank and the outer tank,
The temperature of the reservoir,
Amount of storage of the said reservoir,
Physical properties of said reservoir,
Tank dimensions,
The temperature of the components of the tank,
Dimensions of tank components,
Physical properties of tank components,
Temperature of the space in the tank,
Outside temperature,
Underground temperature,
Solar radiation,
The condensed gas determination device for a tank according to claim 2, wherein at least one of the wind speeds is used.
4. The liquid sensor according to claim 3, further comprising: a cable disposed at an angle with respect to the horizontal direction at a lower portion between the reservoir and the outer tank; and a measurement terminal disposed along the cable. Condensed gas determination device for the described tank.
In addition to the pressure value in the pressure sensor or the fluctuation of the pressure value as a parameter in determining the amount of condensed gas condensed between the storage tank and the outer tank,
The temperature of the reservoir,
Amount of storage of the said reservoir,
Physical properties of said reservoir,
Tank dimensions,
The temperature of the components of the tank,
Dimensions of tank components,
Physical properties of tank components,
Temperature of the space in the tank,
Outside temperature,
Underground temperature,
Solar radiation,
The condensed gas determination device for a tank according to claim 5, wherein at least one of the wind speeds is used.
The amount of condensed gas condensed between the storage tank storing the storage material and the outer tank containing the storage tank inside is determined based on the pressure value in the space in the tank or the fluctuation of the pressure value , Tank condensed gas judgment method.