Method for estimating composition of liquefied gas in storage tank

Abstract

This method for estimating the composition of a liquefied gas in a storage tank in which a liquefied gas containing a plurality of components is stored is used to estimate the composition of a liquefied gas in a storage tank. The method for estimating the composition of the liquefied gas in the storage tank comprises: a step of acquiring reference information for estimating the composition of the liquefied gas in the storage tank at a first time point; a step for setting first point-in-time composition information relating to the liquefied gas composition at the first point in time on the basis of the reference information acquired in the step for acquiring the reference information; a step for acquiring information relating to the amount of liquefied gas outflow in the tank between the first point in time and a second point in time different from the first point in time; and a step for estimating second time-point composition information relating to the liquefied gas composition at the second time point on the basis of the first time-point composition information set in the step for setting the first time-point composition information and the liquefied gas outflow amount acquired in the step for acquiring information relating to the liquefied gas outflow amount in the storage tank.

Description

Technical Field

[0001] The present invention relates to a method for estimating the composition of liquefied gas in a storage tank.

[0002] This application claims priority based on Japanese Patent Application No. 2022-193891 filed on December 5, 2022, and incorporates its content herein. Background Art

[0003] In storage tanks for storing liquefied gases such as liquefied natural gas and liquefied petroleum gas, due to heat input from the outside, the liquefied gas evaporates in the storage tank to generate evaporation gas. When the storage tank is mounted on a ship, the evaporation gas is sometimes used as fuel for the main engine or the like mounted on the ship.

[0004] For example, in Patent Document 1, a method for estimating the state of a storage tank is disclosed, which obtains information related to the state inside the storage tank at the starting point of a target section on a shipping route, and calculates the state inside the storage tank at the ending point of the section by assuming that the heat input to the storage tank in the section is used for the vaporization of the liquefied gas inside the storage tank. In this method for estimating the state of the storage tank, the heat inside the storage tank is estimated as the state inside the storage tank.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: WO 2018 / 189789 Summary of the Invention

[0008] Technical Problem to be Solved by the Invention

[0009] However, when there is no device for re-liquefying the evaporation gas of the storage tank, in order to suppress the rise in the pressure of the storage tank, it is sometimes necessary to discharge the gas inside the storage tank to the outside of the storage tank and consume it as fuel for the main engine or perform incineration treatment. However, when the liquefied gas is composed of multiple components, among these multiple components, the components with lower boiling points evaporate earlier than those with higher boiling points to become evaporation gas. Therefore, by discharging the gas inside the storage tank to the outside of the tank, the liquid composition inside the storage tank changes. That is, when the gas or liquid inside the storage tank is supplied to the outside of the storage tank, the composition of these gases or the composition of the liquid changes over time. For example, when the liquid inside the storage tank is used as fuel for a combustion device provided on a ship, since the composition of the fuel supplied from the storage tank changes, it may also affect the combustion state of the fuel in the combustion device.

[0010] However, using the method disclosed in Patent Document 1, the composition of the liquefied gas inside the storage tank cannot be grasped, so it is necessary to take a sample of the liquefied gas inside the storage tank and analyze its composition. Sampling and analyzing the composition of the liquefied gas requires effort and time.

[0011] The present invention is completed to solve the above problems, and its object is to provide a method for estimating the composition of liquefied gas in a storage tank that can easily grasp the composition of the liquefied gas stored in the storage tank.

[0012] Means for Solving Technical Problems

[0013] To solve the above problems, the method for estimating the composition of liquefied gas in a storage tank according to the present invention is the method for estimating the composition of the liquefied gas in a storage tank storing liquefied gas, and the liquefied gas contains multiple components. The method for estimating the composition of liquefied gas in the storage tank includes: a step of obtaining reference information; a step of setting the composition information at the first time point; a step of obtaining information related to the outflow amount of the liquefied gas in the storage tank; and a step of estimating the composition information at the second time point. In the step of obtaining reference information, reference information for estimating the composition of the liquefied gas in the storage tank is obtained at the first time point. In the step of setting the composition information at the first time point, the composition information at the first time point related to the composition of the liquefied gas at the first time point is set according to the reference information obtained in the step of obtaining reference information. In the step of obtaining information related to the outflow amount of the liquefied gas in the storage tank, information related to the outflow amount of the liquefied gas in the storage tank between the first time point and a second time point different from it is obtained. In the step of estimating the composition information at the second time point, the composition information at the second time point related to the composition of the liquefied gas at the second time point is estimated according to the composition information at the first time point set in the step of setting the composition information at the first time point and the outflow amount of the liquefied gas obtained in the step of obtaining information related to the outflow amount of the liquefied gas in the storage tank.

[0014] The method for estimating the composition of liquefied gas in a storage tank according to the present invention is the method for estimating the composition of the liquefied gas in a storage tank storing liquefied gas, and the liquefied gas contains multiple components. The method for estimating the composition of liquefied gas in the storage tank includes: a step of obtaining the composition information at the first reference time point; a step of obtaining the outflow amount information; and a step of estimating the composition information at the third time point. In the step of obtaining the composition information at the first reference time point, the composition information at the first reference time point related to the composition of the liquefied gas set at the past first reference time point is obtained. In the step of obtaining the outflow amount information, outflow amount information related to the outflow amount of the liquefied gas in the storage tank between the first reference time point and a third time point different from it is obtained. In the step of estimating the composition information at the third time point, the composition information at the third time point related to the composition of the liquefied gas at the third time point is estimated according to the composition information at the first reference time point obtained in the step of obtaining the composition information at the first reference time point and the outflow amount information obtained in the step of obtaining the outflow amount information related to the outflow amount of the liquefied gas in the storage tank between the third time point and the first reference time point.

[0015] The method for estimating the composition of liquefied gas in a storage tank according to the present invention is a method for estimating the composition of the liquefied gas in a storage tank storing liquefied gas, and the liquefied gas contains multiple components. The method for estimating the composition of liquefied gas in the storage tank includes: a step of obtaining composition information at a second reference time point; a step of obtaining inflow amount information and outflow amount information; a step of obtaining inflow liquefied gas composition information; and a step of estimating composition information at a fourth time point. In the step of obtaining composition information at the second reference time point, composition information at the second reference time point related to the composition of the liquefied gas set at a past second reference time point is obtained. In the step of obtaining inflow amount information and outflow amount information, inflow amount information related to the inflow amount of the liquefied gas in the storage tank between the second reference time point and a fourth time point different therefrom and outflow amount information related to the outflow amount are obtained. In the step of obtaining inflow liquefied gas composition information, inflow liquefied gas composition information related to the composition of the liquefied gas flowing into the storage tank is obtained. In the step of estimating composition information at the fourth time point, based on the composition information at the second reference time point obtained in the step of obtaining composition information at the second reference time point, the inflow amount information and the outflow amount information obtained in the step of obtaining inflow amount information related to the inflow amount of the liquefied gas in the storage tank between the fourth time point and the second reference time point and outflow amount information related to the outflow amount, and the inflow liquefied gas composition information obtained in the step of obtaining inflow liquefied gas composition information, composition information at the fourth time point related to the composition of the liquefied gas at the fourth time point is estimated.

[0016] Advantages of the Invention

[0017] According to the method for estimating the composition of liquefied gas in a storage tank of the present invention, the composition of the liquefied gas stored in the storage tank can be easily grasped. Description of the Drawings

[0018] Figure 1 It is a side view of a floating body having the method for estimating the composition of liquefied gas in a storage tank according to an embodiment of the present invention.

[0019] Figure 2 It is a diagram showing the hardware structure of a liquefied gas composition estimation device according to an embodiment of the present invention.

[0020] Figure 3 It is a functional block diagram of a liquefied gas composition estimation device according to an embodiment of the present invention.

[0021] Figure 4 It is a chart showing the usage situation of the method for estimating the composition of liquefied gas in a storage tank according to an embodiment of the present invention.

[0022] Figure 5 is a flowchart showing the steps of a first liquefied gas composition estimation method for estimating the composition of liquefied gas in a storage tank according to an embodiment of the present invention.

[0023] Figure 6 is a flowchart showing the steps of a second liquefied gas composition estimation method for estimating the composition of liquefied gas in a storage tank according to an embodiment of the present invention.

[0024] Figure 7 is a flowchart showing the steps of a third liquefied gas composition estimation method for estimating the composition of liquefied gas in a storage tank according to an embodiment of the present invention. Detailed Embodiment

[0025] Hereinafter, with reference to Figures 1 to 7 , the method for estimating the composition of liquefied gas in a storage tank according to an embodiment of the present invention will be described.

[0026] (Overall Structure of the Ship)

[0027] As Figure 1 shown, the method for estimating the composition of liquefied gas in a storage tank of this embodiment is executed in a ship equipped with a combustion device that burns or incinerates evaporation gas as fuel.

[0028] As Figure 1 shown, the ship 1 of this embodiment at least includes a hull 2, a superstructure 4, a combustion device 9, a storage tank 10, and a liquefied gas composition estimation device 60 for estimating the composition of liquefied gas in the storage tank 10. In addition, the ship 1 of this embodiment is described by taking a ship that can navigate by a main engine or the like as an example. The ship type of the ship 1 is not limited to a specific ship type. As the ship type of the ship 1, a liquefied gas carrier, a ferry, a RORO ship, a car carrier, a passenger ship, etc. can be exemplified.

[0029] The hull 2 has a pair of side plates 5A, 5B that form its outer shell and a bottom 6. The side plates 5A, 5B each include a pair of side shell plates that form the left and right side plates. The bottom 6 includes a bottom shell plate that connects these side plates 5A, 5B. Through these pair of side plates 5A, 5B and the bottom 6, the outer shell of the hull 2 is U-shaped in a cross section perpendicular to the ship's bow and stern direction FA.

[0030] The hull 2 also includes an upper deck 7 that is an all-through deck arranged on the topmost layer. The superstructure 4 is formed on this upper deck 7. A living area or the like is provided inside the superstructure 4. In the ship 1 of this embodiment, for example, a cargo loading area (cargo hold) 8 is formed on the bow 2a side in the ship's bow and stern direction FA that is closer to the ship's bow and stern direction FA than the superstructure 4.

[0031] The combustion device 9 is a device that generates thermal energy by burning fuel, and is provided inside the hull 2. As the combustion device 9, examples include internal combustion engines used in main engines for propelling the ship 1, internal combustion engines used in power generation equipment for supplying power to the ship's interior, boilers that generate steam as a working fluid, and the like.

[0032] The storage tank 10 is arranged in the hull 2. In the present embodiment, an example is shown where the storage tank 10 is in the shape of a cylinder extending in the horizontal direction, and a plurality of them are arranged side by side in the fore-and-aft direction FA within the cargo loading area 8. However, there are no restrictions on the shape, number, and arrangement of the plurality of storage tanks 10. For example, the storage tank 10 can also be arranged on the exposed deck. And, for example, the storage tank 10 can be spherical, square, or the like.

[0033] The storage tank 10 stores liquefied gas containing multiple components inside. As the liquefied gas containing multiple components, examples include LNG (Liquefied Natural Gas) and LPG (Liquefied Petroleum Gas), which are liquefied gases liquefied at low temperatures. In the present embodiment, LNG is taken as an example to illustrate the liquefied gas containing multiple components.

[0034] The liquefied gas in the storage tank 10 evaporates due to heat input from the outside, thus becoming evaporation gas. The liquefied gas liquid in the storage tank 10 and the evaporation gas generated in the storage tank 10 are supplied to the combustion device 9 as fuel in the combustion device 9, or are transported to an incineration device (not shown) for incineration treatment.

[0035] (Hardware structure diagram)

[0036] Figure 2 It is a diagram showing the hardware structure of the liquefied gas composition estimation device according to the embodiment of the present invention.

[0037] As Figure 2 shown, the liquefied gas composition estimation device 60 is a computer equipped with a CPU 61 (Central Processing Unit), a ROM 62 (Read Only Memory), a RAM 63 (Random Access Memory), a storage device 64, and a signal transceiver module 65. The signal transceiver module 65 receives detection signals from, for example, a pressure sensor that detects the pressure inside the storage tank 10, a temperature sensor that detects the temperature inside the storage tank 10, etc. (both not shown).

[0038] (Functional block diagram)

[0039] Figure 3is a functional block diagram of the liquefied gas composition estimation device according to an embodiment of the present invention. As Figure 3 shown, the CPU 61 of the liquefied gas composition estimation device 60 realizes the respective structures of the information acquisition unit 71, the in-tank change amount acquisition unit 72, the composition estimation unit 73, and the information storage unit 74 by executing a program pre-stored in a storage device such as the ROM 62 or the storage device 64.

[0040] The information acquisition unit 71 acquires in-tank composition information related to the liquefied gas composition in the storage tank 10 at each time point. The information acquisition unit 71 acquires detection data from, for example, a pressure sensor that detects the pressure in the storage tank 10 and a temperature sensor that detects the temperature in the storage tank 10, based on the detection signal received by the signal transceiver module 65.

[0041] The in-tank change amount acquisition unit 72 acquires the change amount of the liquefied gas in the storage tank 10 between multiple time points.

[0042] The composition estimation unit 73 estimates composition information related to the liquefied gas composition in the storage tank 10 based on the in-tank composition information at multiple time points acquired by the information acquisition unit 71 and the change amount of the liquefied gas in the storage tank 10 acquired by the in-tank change amount acquisition unit 72.

[0043] The information storage unit 74 stores various information required when performing the estimation process of the liquefied gas composition in the storage tank 10 in the liquefied gas composition estimation device 60. For example, as the specification information of the storage tank 10, the information storage unit 74 stores information such as the number, volume, heat insulation performance, and heat input from the outside of the storage tank 10. In addition, the information storage unit 74 stores various estimation results obtained by repeatedly performing the estimation process of the liquefied gas composition in the storage tank 10.

[0044] (Steps of the method for estimating the liquefied gas composition in the storage tank)

[0045] Figure 4 is a chart showing the differentiated usage of the method for estimating the liquefied gas composition in the storage tank according to an embodiment of the present invention.

[0046] The method S10 for estimating the liquefied gas composition in the storage tank according to the present embodiment includes a first liquefied gas composition estimation method S10A, a second liquefied gas composition estimation method S10B, and a third liquefied gas composition estimation method S10C.

[0047] The first liquefied gas composition estimation method S10A is executed in the state A1 where the liquefied gas composition in the storage tank 10 is unknown. And, in the state where no liquefied gas flows into the storage tank 10 from the outside (for example, during the voyage of the ship 1), the first liquefied gas composition estimation method S10A is executed. Here, as the state A1 where the liquefied gas composition in the storage tank 10 is unknown, for example, it can be exemplified from the state where no liquefied gas is stored in the storage tank 10 (for example, the state where all the liquefied gas is discharged, etc.) to the state after the liquefied gas is reinjected into the storage tank 10.

[0048] The second liquefied gas composition estimation method S10B is executed in the state A2 where the liquefied gas composition in the storage tank 10 has been estimated and is known. The second liquefied gas composition estimation method S10B estimates the liquefied gas composition in the storage tank 10, for example, by the first liquefied gas composition estimation method S10A, and then estimates the liquefied gas composition based on the estimation result. And, in the state where no liquefied gas flows into the storage tank 10 from the outside (for example, during the voyage of the ship 1), the second liquefied gas composition estimation method S10B is executed.

[0049] The third liquefied gas composition estimation method S10C is executed for the period during which liquefied gas is supplied from the outside to the storage tank 10 or at the time point after the supply when the liquefied gas composition in the storage tank 10 is known. For example, in the case of the ship 1 that uses liquefied gas as fuel, it is executed in the state A3 during the period of replenishing liquefied gas (so-called filling period).

[0050] Figure 5 It is a flowchart showing the steps of the first liquefied gas composition estimation method which is the liquefied gas composition estimation method in the storage tank according to the embodiment of the present invention.

[0051] As Figure 5 shown, the first liquefied gas composition estimation method S10A according to the present embodiment includes: a step S11 of obtaining reference information, a step S12 of setting the composition information at the first time point, a step S13 of obtaining the outflow amount information related to the outflow amount of the liquefied gas in the storage tank, a step S14 of estimating the composition information at the second time point, a step S15 of obtaining the state amount of the liquefied gas in the storage tank at the second time point, a step S16 of estimating the state amount of the liquefied gas in the storage tank based on the composition information at the second time point, and a step S17 of determining the error of the estimated value.

[0052] In the step S11 of obtaining reference information, reference information for estimating the liquefied gas composition in the storage tank 10 at the first time point T1 (refer to Figure 4 ) is obtained. Here, the first time point T1 is an arbitrary time point in the state A1 where the liquefied gas composition in the storage tank 10 is unknown. The first time point T1 is a time point after a certain time has passed from the start use time point T0 of the storage tank 10, and is the time point when the liquefied gas is stored in the storage tank 10.

[0053] As reference information for estimating the composition of liquefied gas in the storage tank 10, the state quantity of the storage tank 10 at the first time point T1 can be exemplified. The state quantity of the storage tank 10 is, for example, at least one of the pressure, temperature, density, etc. inside the storage tank 10. In the present embodiment, the pressure and temperature inside the storage tank 10 are used as the reference information obtained in step S11 for description. The pressure and temperature inside the storage tank 10 are obtained, for example, from a pressure sensor, a temperature sensor, etc. provided in the storage tank 10.

[0054] In step S12 of setting the composition information at the first time point, based on the reference information obtained in step S11 of obtaining the reference information, the composition information at the first time point related to the liquefied gas composition at the first time point T1 is set.

[0055] Specifically, in step S12, first, the liquid composition of the liquefied gas in the storage tank 10 at the first time point T1 is assumed. Regarding the liquid composition of the liquefied gas in the storage tank 10 at the first time point T1, for example, the amount of evaporated gas (ratio relative to the liquid liquefied gas) generated by the liquefied gas supplied to the storage tank 10 from after the start - of - use time point T0 to the first time point T1 can be used as a variable to assume the liquid composition of the liquefied gas in the storage tank 10, or a random number can be used to assume the liquid composition of a random number group. Here, the liquefied gas stored in the storage tank 10 can be supplied from a liquefied gas supply facility on land, a truck, a fueling ship, etc. On the supply side such as a liquefied gas supply facility on land, the liquid composition of the liquefied gas is grasped by pre - analyzing the liquefied gas supplied to the storage tank 10.

[0056] And, in this step S12, if it is determined in step S17 of determining the error of the estimated value described later that the error is not within the set range, the liquid composition of the liquefied gas in the storage tank 10 at the first time point T1 is assumed again as another numerical group. In addition, the liquid composition of the liquefied gas in the storage tank 10 at the first time point T1 can be assumed in multiple ways.

[0057] Next, in step S12, the assumed value of the state quantity of the liquefied gas in the assumed liquid composition of the liquefied gas is calculated. For example, as the state quantity of the liquefied gas in the assumed liquid composition of the liquefied gas, the liquid density of the liquefied gas can be calculated based on the assumed values of the pressure and temperature of the liquefied gas.

[0058] In addition, in step S12, based on the assumed value of the liquefied gas state quantity in the storage tank 10 at the first time point T1 calculated and the measured value of the liquefied gas state quantity in the storage tank 10 at the first time point T1 obtained in step S11, the first time point composition information is set. Here, as described above, in step S11 of the present embodiment, the detection data of the pressure and temperature of the liquefied gas are obtained as the liquefied gas state quantity in the storage tank 10 at the first time point T1. Therefore, in this step S12, based on the detection data of the pressure and temperature of the liquefied gas in the storage tank 10 at the first time point T1 obtained in step S11, the density of the liquefied gas in the storage tank 10 at the first time point T1 is calculated. Moreover, in this step S12, the assumed value of the density of the liquefied gas in the storage tank 10 at the first time point T1 calculated is compared with the density of the liquefied gas based on the measured value of the liquefied gas in the storage tank 10 at the first time point T1.

[0059] In addition, in step S12, by an appropriate optimization method, the liquid composition of the following liquefied gas is searched for and estimated: the error between the assumed value of the liquefied gas state quantity in the storage tank 10 at the first time point T1 calculated and the liquefied gas state quantity based on the measured value of the liquefied gas in the storage tank 10 at the first time point T1 is small enough or becomes 0. For example, if the error between the assumed value of the density of the liquefied gas in the storage tank 10 at the first time point T1 and the density of the liquefied gas based on the measured value of the liquefied gas in the storage tank 10 at the first time point T1 is within the pre-set allowable error range, then this assumed value can be set as the first time point composition information. And if there are multiple assumed values of the liquefied gas state quantity in the storage tank 10 at the first time point T1 within the allowable error range, among these multiple assumed values, the assumed value with the smallest error from the measured value of the liquefied gas state quantity in the storage tank 10 at the first time point T1 can be set as the first time point composition information.

[0060] In step S13 of obtaining the outflow information related to the outflow quantity of the liquefied gas in the storage tank, the outflow information related to the outflow quantity of the liquefied gas in the storage tank 10 between the first time point T1 and a second time point T2 different from it is obtained. Here, the second time point T2 different from the first time point T1 can be after the first time point T1 or before the first time point T1. In the present embodiment, the second time point T2 is set as, for example, the start use time point T0 before the first time point T1.

[0061] The outflow of the liquefied gas in the storage tank 10 between the second time point T2 and the first time point T1 occurs, for example, by supplying the liquid of the liquefied gas in the storage tank 10 as fuel to the combustion device 9. Also, the outflow of the liquefied gas in the storage tank 10 between the second time point T2 and the first time point T1 can occur, for example, by discharging the evaporation gas generated by evaporating the liquefied gas in the storage tank 10 to the outside of the storage tank 10.

[0062] The outflow volume of the liquefied gas in the storage tank 10 between the second time point T2 and the first time point T1 can be calculated, for example, based on the specification information related to the storage tank 10 pre-stored in the information storage unit 74, or measurement data can be used. As the specification information related to the storage tank 10, for example, the number of storage tanks 10, the volume of the storage tank 10, the heat insulation performance of the storage tank 10, the heat input from the outside to the storage tank 10, etc. can be exemplified. The heat input from the outside to the storage tank 10 can be obtained, for example, based on data such as the heat insulation performance of the storage tank 10 and the air temperature.

[0063] The outflow information related to the outflow volume of the liquefied gas in the storage tank 10 obtained in step S13 can be, for example, the outflow volume itself of the liquefied gas in the storage tank 10 between the second time point T2 different from the first time point T1 and the first time point T1, or other information related to the outflow volume of the liquefied gas (such as heat) can be obtained, and the outflow volume can be calculated based on this information.

[0064] Also, the outflow information related to the outflow volume of the liquefied gas in the storage tank 10 obtained in step S13 can be obtained, for example, from a data recorder mounted on the ship 1, etc., the consumption amount in the combustion device 9, etc. (consuming the liquefied gas flowing out of the storage tank 10).

[0065] In step S14 of estimating the composition information at the second time point, based on the composition information at the first time point set in step S12 and the outflow information related to the outflow volume of the liquefied gas obtained in step S13, the composition information at the second time point related to the liquefied gas composition at the second time point T2 is estimated. Specifically, in step S14, based on the composition information at the first time point T1 set in step S12 and the outflow volume of the liquefied gas in the storage tank 10 between the second time point T2 and the first time point T1 obtained in step S13, the change amount of the composition ratio of the various components constituting the liquefied gas between the second time point T2 and the first time point T1 is calculated. In step S14, based on the composition information at the first time point T1 set in step S12 and the calculated change amount of the composition ratio of the various components constituting the liquefied gas between the second time point T2 and the first time point T1, for example, the liquid composition of the liquefied gas in the storage tank 10 at the second time point T2 is estimated.

[0066] In step S15 of obtaining the state quantity of the liquefied gas in storage tank 10 at the second time point, the state quantity of the liquefied gas in storage tank 10 at the second time point T2 is obtained. Specifically, for example, as the state quantity of the liquefied gas in storage tank 10 at the second time point T2, the measured values of the pressure and temperature of the liquefied gas obtained from a pressure sensor, a temperature sensor, etc. provided in storage tank 10 are obtained.

[0067] In step S16 of estimating the state quantity of the liquefied gas in storage tank 10 based on the composition information at the second time point, the state quantity of the liquefied gas in storage tank 10 at the second time point T2 is estimated according to the composition information at the second time point estimated in step S14. Specifically, according to the composition information at the second time point estimated in step S14 and the measured value of the state quantity of the liquefied gas in storage tank 10 at the second time point T2 obtained in step S15, the estimated value of other state quantities of the liquefied gas at the second time point T2 is calculated. In this embodiment, for example, according to the liquid composition of the liquefied gas at the second time point T2 estimated in step S14, the pressure and temperature of the liquefied gas in storage tank 10 at the second time point T2, the density of the liquefied gas at the second time point T2 is calculated as the estimated value of the state quantity of the liquefied gas at the second time point T2.

[0068] In step S17, it is determined whether the error between the estimated value of the state quantity of the liquefied gas (such as density) at the second time point T2 calculated in step S16 and other state quantities of the liquefied gas in storage tank 10 at the second time point T2 (calculated based on the measured value of the state quantity of the liquefied gas in storage tank 10 at the second time point T2 obtained in step S15) is within a preset range. As for the determination result, if the error between the estimated value of the state quantity of the liquefied gas in storage tank 10 at the second time point T2 calculated and the measured value of the state quantity of the liquefied gas in storage tank 10 at the second time point T2 obtained in step S15 is within the set range (it is "yes" in step S17), then the liquefied gas composition in storage tank 10 at the first time point T1 based on the composition information at the first time point set in step S12 is adopted as the estimation result of the liquefied gas composition in storage tank 10 in the first liquefied gas composition estimation method S10A of this embodiment.

[0069] On the other hand, as for the above determination result, if the error between the estimated value of the state quantity of the liquefied gas in storage tank 10 at the second time point T2 calculated and the measured value of the state quantity of the liquefied gas in storage tank 10 at the second time point T2 obtained in step S15 is not within the set range (it is "no" in step S17), then return to step S12, further change the assumption of the liquid composition of the liquefied gas in storage tank 10 at the first time point T1, and repeatedly perform the processing after step S13.

[0070] Figure 6It is a flowchart showing the steps of the second liquefied gas composition estimation method for estimating the composition of the liquefied gas in the storage tank 10 according to an embodiment of the present invention.

[0071] As Figure 6 shown, the second liquefied gas composition estimation method S10B according to the present embodiment includes: a step S21 of obtaining outflow information related to the outflow amount of the liquefied gas in the storage tank 10 between the third time point T3 and the first reference time point Ts1, and a step S22 of estimating the composition information at the third time point.

[0072] The second liquefied gas composition estimation method S10B executes the first liquefied gas composition estimation method S10A, or measures the composition of the liquefied gas in the storage tank 10 by sampling, etc., and thus executes in a state A2 where the composition of the liquefied gas in the storage tank 10 is known (refer to Figure 4 ). As described above, in the first liquefied gas composition estimation method S10A, the composition of the liquefied gas in the storage tank 10 at the first time point T1 based on the composition information at the first time point set in step S12 is adopted as the estimation result of the composition of the liquefied gas in the storage tank 10.

[0073] In step S21 of obtaining the outflow information related to the outflow amount of the liquefied gas in the storage tank 10, the outflow amount of the liquefied gas in the storage tank 10 between the third time point T3 different from the first time point T1 and the second time point T2 and the first reference time point Ts1 is obtained. Here, the third time point T3 is a time point after the first reference time point Ts1. In the present embodiment, the first reference time point Ts1 is set as the first time point T1 that has most recently adopted the estimation result of the liquid composition of the liquefied gas.

[0074] The outflow of the liquefied gas in the storage tank 10 between the third time point T3 and the first reference time point Ts1 (the first time point T1) occurs, for example, by supplying the liquid of the liquefied gas in the storage tank 10 as fuel to the combustion device 9. And the outflow of the liquefied gas in the storage tank 10 between the third time point T3 and the first reference time point Ts1 may also occur, for example, by discharging the evaporation gas generated by evaporating the liquefied gas in the storage tank 10 to the outside of the storage tank 10.

[0075] The outflow amount of the liquefied gas in the storage tank 10 between the third time point T3 and the first reference time point Ts1 can be calculated, for example, based on the specification information related to the storage tank 10 pre-stored in the information storage unit 74, or measurement data can be used. As the specification information related to the storage tank 10, for example, the number of storage tanks 10, the volume of the storage tank 10, the heat insulation performance of the storage tank 10, the heat input from the outside to the storage tank 10, etc. can be exemplified. The heat input from the outside to the storage tank 10 can be obtained, for example, based on data such as the heat insulation performance of the storage tank 10 and the temperature outside the storage tank 10.

[0076] The outflow information related to the outflow volume of the liquefied gas in the storage tank 10 obtained in step S21 may be, for example, the outflow volume of the liquefied gas in the storage tank 10 between the third time point T3 and the first reference time point Ts1, or other information related to the outflow volume of the liquefied gas (for example, heat) may be obtained, and the outflow volume is calculated based on this information. Also, the outflow information related to the outflow volume of the liquefied gas in the storage tank 10 obtained in step S21 can be obtained, for example, from a data recorder mounted on the ship 1, etc. (the consumption of the liquefied gas in) the combustion device 9 that consumes the liquefied gas flowing out of the storage tank 10.

[0077] In the step S22 of estimating the composition information at the third time point, based on the first time point composition information (first reference time point composition information) of the first time point T1 as the first reference time point Ts1, and the outflow information related to the outflow volume of the liquefied gas between the third time point T3 and the first reference time point Ts1 obtained in step S21, the third time point composition information related to the liquefied gas composition at the third time point T3 is estimated. Specifically, in step S22, based on the first time point composition information of the first time point T1 as the first reference time point Ts1, and the outflow volume of the liquefied gas in the storage tank 10 between the third time point T3 and the first reference time point Ts1 obtained in step S21, the change amount of the composition ratio of the various components constituting the liquefied gas between the third time point T3 and the first reference time point Ts1 is calculated. In step S22, based on the first time point composition information of the first time point T1 as the first reference time point Ts1, and the calculated change amount of the composition ratio of the various components constituting the liquefied gas between the third time point T3 and the first reference time point Ts1, for example, the liquid composition of the liquefied gas in the storage tank 10 at the third time point T3 is estimated. Thus, the liquid composition of the liquefied gas in the storage tank 10 at the third time point T3 estimated in step S22 is adopted as the estimation result in the second liquefied gas composition estimation method S10B of the present embodiment.

[0078] Figure 7 It is a flowchart showing the steps of the third liquefied gas composition estimation method, which is the liquefied gas composition estimation method in the storage tank 10 according to the embodiment of the present invention.

[0079] As Figure 7 shown, the third liquefied gas composition estimation method S10C according to the present embodiment includes: a step S31 of obtaining the inflow information related to the inflow volume of the liquefied gas in the storage tank 10 between the fourth time point T4 and the second reference time point Ts2 and the outflow information related to the outflow volume of the liquefied gas in the storage tank 10, a step S32 of obtaining the inflow liquefied gas composition information, and a step S33 of estimating the fourth time point composition information.

[0080] In step S31 of obtaining the inflow information related to the inflow of liquefied gas in the storage tank 10 and the outflow information related to the outflow of liquefied gas in the storage tank 10, the inflow information related to the inflow of liquefied gas in the storage tank 10 and the outflow information related to the outflow of liquefied gas in the storage tank 10 between the fourth time point T4 and the second reference time point Ts2 are obtained. The fourth time point T4 is different from the first time point T1, the second time point T2, and the third time point T3. Here, the fourth time point T4 is a time point during the so-called refueling period when liquefied gas is supplied from the outside into the storage tank 10 after the second reference time point Ts2 or immediately after refueling. The fourth time point T4 is a time point after the first reference time point Ts1. In the present embodiment, the second reference time point Ts2 is set to the third time point T3 that has recently adopted the estimation result of the liquid composition of the liquefied gas. In addition, the second reference time point Ts2 is not limited to the third time point T3, and it may be set to other time points such as the first time point T1 and the second time point T2.

[0081] The inflow of liquefied gas in the storage tank 10 between the fourth time point T4 and the second reference time point Ts2 can be obtained, for example, based on the measurement data of the flow rate of the liquefied gas supplied to the storage tank 10. The outflow of liquefied gas in the storage tank 10 between the fourth time point T4 and the second reference time point Ts2 can be calculated, for example, based on the specification information related to the storage tank 10 pre-stored in the information storage unit 74, or measurement data can also be used.

[0082] In step S32 of obtaining the inflow liquefied gas composition information, the inflow liquefied gas composition information related to the liquefied gas composition flowing into the storage tank 10 between the fourth time point T4 and the second reference time point Ts2 (the third time point T3) is obtained. This inflow liquefied gas composition information can use, for example, the information on the liquid composition of the liquefied gas supplied to the storage tank 10 provided by the liquefied gas supply facility. In addition, the inflow liquefied gas composition information can be estimated by diverting past actual values, etc.

[0083] In step S33 of estimating the composition information at the fourth time point, based on the third time point composition information (second reference time point composition information) of the third time point T3 as the second reference time point Ts2, the inflow information related to the inflow of liquefied gas between the fourth time point T4 and the second reference time point Ts2 and the outflow information related to the outflow of liquefied gas in the storage tank 10 obtained in step S31, and the inflow liquefied gas composition information obtained in step S32, the fourth time point composition information related to the liquefied gas composition at the fourth time point T4 is estimated.

[0084] Specifically, in step S33 of estimating the composition information at the fourth time point, based on the composition information of the third time point T3 which is the second reference time point Ts2, the inflow amount of liquefied gas in the storage tank 10 between the fourth time point T4 and the second reference time point Ts2 (the third time point T3) obtained in step S31, the outflow amount of liquefied gas in the storage tank 10 between the fourth time point T4 and the second reference time point Ts2 (the third time point T3), and the inflow liquefied gas composition information obtained in step S32, the change amount of the composition ratios of various components constituting the liquefied gas between the fourth time point T4 and the third time point T3 is calculated. Moreover, in step S33 of estimating the composition information at the fourth time point, based on the composition information of the third time point T3 and the calculated change amount of the composition ratios of various components constituting the liquefied gas between the fourth time point T4 and the third time point T3, for example, the liquid composition of the liquefied gas in the storage tank 10 at the fourth time point T4 is estimated. Thus, the liquid composition of the liquefied gas in the storage tank 10 at the fourth time point T4 estimated in step S33 is adopted as the estimation result in the third liquefied gas composition estimation method S10C of the present embodiment.

[0085] (Function and effect)

[0086] In the liquefied gas composition estimation method S10 in the storage tank 10 of the above embodiment, based on the composition information of the liquefied gas obtained at the first time point T1 and the outflow amount of the liquefied gas in the storage tank 10 between the second time point T2 and the first time point T1, the composition information of the second time point related to the liquefied gas composition at the second time point T2 is estimated.

[0087] Therefore, without measuring the composition of the liquefied gas in the storage tank 10, it is possible to easily grasp the composition of the liquefied gas stored in the storage tank 10.

[0088] Moreover, in the above embodiment, it is possible to assume the liquid composition of the liquefied gas in the storage tank 10 at the first time point T1, and based on the assumed value of the liquefied gas state quantity calculated from the assumed liquid composition of the liquefied gas and the actual liquefied gas state quantity in the storage tank 10 at the first time point T1, the composition information of the first time point related to the liquid composition of the liquefied gas at the first time point T1 is set.

[0089] Further, in the above-described embodiment, the liquid composition of the liquefied gas in the storage tank 10 at the first time point T1 is assumed, and among the assumed values of the state quantities in the assumed liquid composition of the liquefied gas, the value within a preset range of the difference between the assumed value of the state quantity and the state quantity of the liquefied gas in the storage tank 10 at the first time point T1 is set as the first time point composition information. Thus, it is possible to select, from the assumed liquid composition of the liquefied gas, the liquid composition of the liquefied gas that is close to the composition of the liquefied gas in the storage tank 10 at the first time point T1, and therefore it is possible to improve the estimation accuracy of the assumed liquid composition of the liquefied gas.

[0090] Further, in the above-described embodiment, the state quantity of the liquefied gas at the second time point T2 is estimated, and the estimated value of the state quantity of the liquefied gas at the second time point T2 is compared with the actual state quantity of the liquefied gas in the storage tank 10 at the second time point T2, whereby it is possible to obtain an estimated value of the state quantity of the liquefied gas at the second time point T2 within a preset error setting range. Therefore, it is possible to obtain a reliable estimated composition based on the estimated value of this state quantity, that is, reliable second time point composition information and first time point composition information.

[0091] Further, in the above-described embodiment, between the third time point T3 and the first reference time point Ts1 (second time point T2), if there is an outflow of liquefied gas in the storage tank 10, outflow amount information related to the outflow amount of the liquefied gas in the storage tank 10 is obtained, whereby it is possible to estimate third time point composition information related to the liquefied gas composition at the third time point T3 based on the first time point composition information (first reference time point composition information) and the outflow amount information.

[0092] Further, in the above-described embodiment, between the fourth time point T4 and the second reference time point Ts2 (third time point T3), if there is an inflow of liquefied gas into the storage tank 10 and an outflow of liquefied gas in the storage tank 10, by obtaining inflow amount information related to the inflow amount of the liquefied gas in the storage tank 10 and outflow amount information related to the outflow amount of the liquefied gas in the storage tank 10, it is possible to estimate fourth time point composition information related to the liquefied gas composition at the fourth time point T4 based on the third time point composition information (second reference time point composition information), the inflow amount information, and the outflow amount information.

[0093] (Other Embodiments)

[0094] As described above, the embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the specific structure is not limited to this embodiment and also includes design changes and the like within the scope not departing from the gist of the present invention.

[0095] In the above-described embodiment, in step S11 and the like, the pressure and temperature inside the storage tank 10 are acquired as state quantities of the storage tank 10, and the density of the liquefied gas is calculated based on these pressure and temperature values. However, this is not limiting. For example, the composition of the liquefied gas can be estimated by calculating the temperature of the liquefied gas based on the pressure inside the storage tank 10 and the density of the liquefied gas. Also, information on more parameters can be acquired as state quantities of the liquefied gas inside the storage tank 10, and the composition of the liquefied gas can be estimated based on this information.

[0096] Also, in step S12 of the above-described embodiment, a hypothesis value for subsequent processing is selected from among a plurality of hypothesis values of the state quantity (density) of the liquefied gas inside the storage tank 10 at the first time point T1 by an appropriate optimization method, but the specific method can be any method.

[0097] Also, in the second liquefied gas composition estimation method S10B of the above-described embodiment, the second time point T2 is used as the first reference time point Ts1. However, as the first reference time point Ts1, as long as it is before the third time point T3, it is not limited to the second time point T2, and other time points can also be adopted.

[0098] Similarly, in the third liquefied gas composition estimation method S10B of the above-described embodiment, the third time point T3 is used as the second reference time point Ts2. However, as the second reference time point Ts2, as long as it is before the fourth time point T4, it is not limited to the third time point T3, and other time points can also be adopted.

[0099] In the above-described embodiment, the storage tank 10 provided on the ship 1 is taken as an example for explanation, but the storage tank 10 can also be a storage tank provided on land.

[0100] <Supplementary Note>

[0101] The method S10 for estimating the composition of the liquefied gas inside the storage tank 10 described in the embodiment is understood as follows, for example.

[0102] (1)The method S10 for estimating the composition of liquefied gas in the storage tank 10 according to the first mode is the method S10 for estimating the composition of liquefied gas in the storage tank 10. The storage tank 10 stores liquefied gas containing multiple components. The method S10 for estimating the composition of liquefied gas in the storage tank 10 includes: a step S11 of obtaining reference information for estimating the composition of the liquefied gas in the storage tank 10 at the first time point T1; a step S12 of setting first-time-point composition information related to the composition of the liquefied gas at the first time point T1 according to the reference information obtained in the step S11 of obtaining reference information; a step S13 of obtaining information related to the outflow amount of the liquefied gas in the storage tank 10 between the first time point T1 and a second time point T2 different from it; and a step S14 of estimating second-time-point composition information related to the composition of the liquefied gas at the second time point according to the first-time-point composition information set in the step S12 of setting first-time-point composition information and the outflow amount of the liquefied gas obtained in the step S13 of obtaining information related to the outflow amount of the liquefied gas in the storage tank 10.

[0103] As an example of the reference information, state quantities such as the pressure, temperature, and density of the liquefied gas and the liquefied gas composition can be cited.

[0104] The second time point T2 different from the first time point T1 can be a time point before the first time point T1 or a time point after the first time point T1.

[0105] Through the method S10 for estimating the composition of liquefied gas in the storage tank 10, according to the first-time-point composition information of the liquefied gas obtained at the first time point T1 and the outflow amount of the liquefied gas in the storage tank 10 between the second time point T2 and the first time point T1, the second-time-point composition information related to the composition of the liquefied gas at the second time point T2 is estimated. Therefore, without analyzing the composition of the liquefied gas in the storage tank 10, it is possible to easily grasp the composition of the liquefied gas stored in the storage tank 10.

[0106] (2)The method S10 for estimating the composition of liquefied gas in the storage tank 10 according to the second mode is the method S10 for estimating the composition of liquefied gas in the storage tank 10 in (1), wherein, in the step S11 of obtaining reference information, the state quantity of the liquefied gas in the storage tank 10 at the first time point T1 is obtained as the reference information. In the step S12 of setting first-time-point composition information, assuming the liquid composition of the liquefied gas in the storage tank 10 at the first time point T1, calculating an assumed value of the state quantity in the assumed liquid composition of the liquefied gas, and setting the first-time-point composition information according to the calculated assumed value of the state quantity and the state quantity of the liquefied gas in the storage tank 10 at the first time point T1.

[0107] As an example of the state quantity of liquefied gas, the pressure, temperature, density, etc. of the liquefied gas can be cited.

[0108] Thus, it is possible to assume the liquid composition of the liquefied gas in the storage tank 10 at the first time point T1, and based on the assumed value of the state quantity of the liquefied gas calculated from the assumed liquid composition of the liquefied gas and the actual state quantity of the liquefied gas in the storage tank 10 at the first time point T1, it is possible to set the first time point composition information related to the liquid composition of the liquefied gas at the first time point T1.

[0109] (3) The method S10 for estimating the composition of the liquefied gas in the storage tank 10 according to the third method is the method S10 for estimating the composition of the liquefied gas in the storage tank 10 in (2), wherein in the step S12 of setting the first time point composition information, the following processing is performed: assuming the liquid composition of the liquefied gas in the storage tank 10 at the first time point T1 to be multiple, and among the assumed values of each state quantity in the multiple assumed liquid compositions of the liquefied gas, determining the value within a preset range of the difference between the assumed value of the state quantity and the state quantity of the liquefied gas in the storage tank 10 at the first time point T1, and setting the liquid composition of the liquefied gas corresponding to the determined assumed value of the state quantity as the first time point composition information.

[0110] Thus, the liquid composition of the liquefied gas close to the composition of the liquefied gas in the storage tank 10 at the first time point T1 is selected from the multiple assumed liquid compositions of the liquefied gas, thereby improving the accuracy of the assumed liquid composition of the liquefied gas.

[0111] (4) The method S10 for estimating the composition of the liquefied gas in the storage tank 10 according to the fourth method is the method S10 for estimating the composition of the liquefied gas in the storage tank 10 in any one of (1) to (3), and it further includes: a step S15 of obtaining the state quantity of the liquefied gas in the storage tank at the second time point; a step S16 of estimating the state quantity of the liquefied gas in the storage tank 10 at the second time point T2 according to the second time point composition information estimated in the step S14 of estimating the second time point composition information; comparing the estimated value of the state quantity of the liquefied gas in the storage tank 10 at the second time point T2 estimated in the step S16 of estimating the state quantity of the liquefied gas in the storage tank 10 at the second time point T2 with the state quantity of the liquefied gas in the storage tank 10 at the second time point T2 obtained in the step S15 of obtaining the state quantity of the liquefied gas in the storage tank 10 at the second time point T2, and thereby determining the error of the estimated value of the state quantity of the liquefied gas in the storage tank 10 at the second time point T2 in the step S17.

[0112] Accordingly, it is possible to estimate the state quantity of the liquefied gas in the storage tank 10 at the second time point T2 based on the composition information at the second time point. Further, by comparing the estimated value of the state quantity of the liquefied gas at the second time point T2 estimated in step S16 with the state quantity of the liquefied gas in the storage tank 10 at the second time point T2 obtained in step S15, it is possible to obtain an estimated value of the state quantity of the liquefied gas at the second time point T2 within a preset error range. Therefore, it is possible to obtain a reliable estimated composition based on the estimated value of the state quantity, that is, the reliable composition information at the second time point estimated in step S14 and the composition information at the first time point set in step S12.

[0113] (5) The method S10 for estimating the composition of the liquefied gas in the storage tank 10 according to the fifth mode is the method S10 for estimating the composition of the liquefied gas in the storage tank 10 in any one of (1) to (4), and includes: a step S12 of obtaining first reference time point composition information related to the composition of the liquefied gas at a past first reference time point Ts1; a step S21 of obtaining outflow amount information related to the outflow amount of the liquefied gas in the storage tank 10 between the first reference time point Ts1 and a third time point T3 different therefrom; and a step S22 of estimating third time point composition information related to the composition of the liquefied gas at the third time point T3 based on the first reference time point composition information obtained in the step S12 of obtaining the first reference time point composition information and the outflow amount information obtained in the step S21 of obtaining the outflow amount information related to the outflow amount of the liquefied gas in the storage tank 10 between the third time point T3 and the first reference time point Ts1.

[0114] Accordingly, if the liquefied gas flows out in the storage tank 10 between the third time point T3 and the first reference time point Ts1, it is possible to obtain the outflow amount information related to the outflow amount of the liquefied gas in the storage tank 10. Therefore, it is possible to estimate the third time point composition information related to the composition of the liquefied gas at the third time point T3 based on the first reference time point composition information and the outflow amount information.

[0115] The method S10 for estimating the composition of liquefied gas in the storage tank 10 according to the sixth method is the method S10 for estimating the composition of liquefied gas in the storage tank 10 in (5), which includes: the step of obtaining the second reference time point composition information related to the composition of the liquefied gas set at the past second reference time point Ts2; the step S31 of obtaining the inflow amount information related to the inflow amount of the liquefied gas in the storage tank 10 between the second reference time point Ts2 and the fourth time point T4 different from it; the step S32 of obtaining the inflow liquefied gas composition information related to the composition of the liquefied gas flowing into the storage tank 10; and estimating the fourth time point composition information related to the composition of the liquefied gas at the fourth time point T4 according to the second reference time point composition information obtained in the step S22 of obtaining the second reference time point composition information, the inflow amount information obtained in the step S31 of obtaining the inflow amount information related to the inflow amount of the liquefied gas in the storage tank 10 between the fourth time point T4 and the second reference time point Ts2, and the inflow liquefied gas composition information obtained in the step S32 of obtaining the inflow liquefied gas composition information.

[0116] Thus, between the fourth time point T4 and the second reference time point Ts2, if the inflow of liquefied gas occurs in the storage tank 10, the inflow amount information related to the inflow amount of the liquefied gas in the storage tank 10 can be obtained. Therefore, the fourth time point composition information related to the composition of the liquefied gas at the fourth time point T4 can be estimated according to the second reference time point composition information and the inflow amount information.

[0117] The method S10 for estimating the composition of liquefied gas in the storage tank 10 according to the seventh method is the method S10 for estimating the composition of liquefied gas in the storage tank 10. The liquefied gas containing multiple components is stored in the storage tank 10. The method S10 for estimating the composition of liquefied gas in the storage tank 10 includes: the step S12 of obtaining the first reference time point composition information related to the composition of the liquefied gas set at the past first reference time point Ts1; the step S21 of obtaining the outflow amount information related to the outflow amount of the liquefied gas in the storage tank 10 between the first reference time point Ts1 and the third time point T3 different from it; and estimating the third time point composition information related to the composition of the liquefied gas at the third time point T3 according to the first reference time point composition information obtained in the step S12 of obtaining the first reference time point composition information and the outflow amount information obtained in the step S21 of obtaining the outflow amount information related to the outflow amount of the liquefied gas in the storage tank 10 between the third time point T3 and the first reference time point Ts1.

[0118] Thus, between the third time point T3 and the first reference time point Ts1, if a liquefied gas outflow occurs in the storage tank 10, outflow information related to the liquefied gas outflow volume in the storage tank 10 can be obtained. Therefore, based on the first reference time point composition information and the outflow information, the third time point composition information related to the liquefied gas composition at the third time point T3 can be estimated. Therefore, without analyzing the liquefied gas composition in the storage tank 10, it is possible to easily grasp the liquefied gas composition stored in the storage tank 10.

[0119] (8) The liquefied gas composition estimation method S10 in the storage tank 10 according to the eighth aspect is a liquefied gas composition estimation method S10 in the storage tank 10, in which the storage tank 10 stores liquefied gas containing multiple components. The liquefied gas composition estimation method S10 in the storage tank 10 includes: a step of obtaining second reference time point composition information related to the liquefied gas composition set at a past second reference time point Ts2; a step S31 of obtaining inflow volume information related to the liquefied gas inflow volume in the storage tank 10 and outflow volume information related to the liquefied gas outflow volume in the storage tank 10 between the second reference time point Ts2 and a fourth time point T4 different therefrom; a step S32 of obtaining inflow liquefied gas composition information related to the liquefied gas composition flowing into the storage tank 10; and estimating, based on the second reference time point composition information obtained in the step S22 of obtaining the second reference time point composition information, the inflow volume information and the outflow volume information obtained in the step S31 of obtaining the inflow volume information related to the liquefied gas inflow volume in the storage tank 10 and the outflow volume information related to the liquefied gas outflow volume in the storage tank 10 between the fourth time point T4 and the second reference time point Ts2, and the inflow liquefied gas composition information obtained in the step S32 of obtaining the inflow liquefied gas composition information, the fourth time point composition information related to the liquefied gas composition at the fourth time point T4 in step S33.

[0120] Thus, between the fourth time point T4 and the past second reference time point Ts2, if a liquefied gas inflow and outflow occur in the storage tank 10, inflow volume information related to the liquefied gas inflow volume in the storage tank 10 and outflow volume information related to the outflow can be obtained. Therefore, based on the second reference time point composition information, the inflow volume information, and the outflow volume information, the fourth time point composition information related to the liquefied gas composition at the fourth time point T4 can be estimated. Therefore, without analyzing the liquefied gas composition in the storage tank 10, it is possible to easily grasp the liquefied gas composition stored in the storage tank 10.

[0121] Industrial applicability

[0122] According to the liquefied gas composition estimation method in the storage tank of the present invention, it is possible to easily grasp the liquefied gas composition stored in the storage tank.

[0123] Symbol Explanation

[0124] 1 - Ship, 2 - Hull, 2a - Bow, 4 - Superstructure, 5A, 5B - Side, 6 - Bottom of the ship, 7 - Upper deck, 8 - Cargo loading area, 9 - Combustion device, 10 - Storage tank, 60 - Composition estimation device, 61 - CPU, 62 - ROM, 63 - RAM, 64 - Storage device, 65 - Signal transceiver module, 71 - Information acquisition unit, 72 - Variation amount acquisition unit inside the storage tank, 73 - Composition estimation unit, 74 - Information storage unit, A1 to A3 - States, FA - Bow - stern direction, S10 - Method for estimating the composition of liquefied gas inside the storage tank, S11 - Step of acquiring reference information, S12 - Step of setting the composition information at the first time point, S13 - Step of acquiring outflow amount information related to the outflow amount of liquefied gas inside the storage tank, S14 - Step of estimating the composition information at the second time point, S15 - Step of acquiring the state amount of liquefied gas inside the storage tank at the second time point, S16 - Step of estimating the state amount of liquefied gas inside the storage tank based on the composition information at the second time point, S17 - Step of determining the error of the estimated value, S21 - Step of acquiring outflow amount information related to the outflow amount of liquefied gas inside the storage tank between the third time point and the first reference time point, S22 - Step of estimating the composition information at the third time point, S31 - Step of acquiring inflow amount information related to the inflow amount of liquefied gas inside the storage tank between the fourth time point and the second reference time point, S32 - Step of acquiring the composition information of the inflowing liquefied gas, S33 - Step of estimating the composition information at the fourth time point, T0 - Start - of - use time point, T1 - First time point, T2 - Second time point, T3 - Third time point, T4 - Fourth time point, Ts1 - First reference time point, Ts2 - Second reference time point.

Claims

1. A method for estimating the composition of liquefied gas in a storage tank, where the storage tank stores the liquefied gas containing multiple components, and the method for estimating the composition of liquefied gas in the storage tank includes: The step of obtaining reference information for estimating the composition of the liquefied gas in the storage tank at a first time point; The step of setting first-time-point composition information related to the composition of the liquefied gas at the first time point according to the reference information obtained in the step of obtaining the reference information; The step of obtaining information related to the outflow amount of the liquefied gas in the storage tank between the first time point and a second time point different from it; And The step of estimating second-time-point composition information related to the composition of the liquefied gas at the second time point according to the first-time-point composition information set in the step of setting the first-time-point composition information and the outflow amount of the liquefied gas obtained in the step of obtaining information related to the outflow amount of the liquefied gas in the storage tank.

2. The method for estimating the composition of liquefied gas in a storage tank according to claim 1, wherein In the step of obtaining the reference information, the state quantity of the liquefied gas in the storage tank at the first time point is obtained as the reference information, In the step of setting the first-time-point composition information, assume the liquid composition of the liquefied gas in the storage tank at the first time point, calculate the assumed value of the state quantity in the assumed liquid composition of the liquefied gas, and set the first-time-point composition information according to the calculated assumed value of the state quantity and the state quantity of the liquefied gas in the storage tank at the first time point.

3. The method for estimating the composition of liquefied gas in a storage tank according to claim 2, wherein In the step of setting the first-time-point composition information, the following processing is performed: Assume that the liquid composition of the liquefied gas in the storage tank at the first time point is multiple, Among the assumed values of each state quantity in the liquid compositions of the liquefied gas assumed to be multiple, determine the value whose difference between the assumed value of the state quantity and the state quantity of the liquefied gas in the storage tank at the first time point is within a preset range, Set the liquid composition of the liquefied gas corresponding to the determined assumed value of the state quantity as the first-time-point composition information.

4. The method for estimating the composition of liquefied gas in a storage tank according to claim 1 or 2, which further includes: The step of obtaining the state quantity of the liquefied gas in the storage tank at the second time point; The step of estimating the state quantity of the liquefied gas in the storage tank at the second time point according to the second-time-point composition information estimated in the step of estimating the second-time-point composition information; And A step of comparing an estimated value of the state quantity of the liquefied gas in the storage tank at the second time point estimated in the step of estimating the state quantity of the liquefied gas in the storage tank at the estimated second time point with the state quantity of the liquefied gas in the storage tank at the second time point obtained in the step of obtaining the state quantity of the liquefied gas in the storage tank at the second time point, thereby determining the error of the estimated value of the state quantity of the liquefied gas in the storage tank at the second time point.

5. The method for estimating the composition of liquefied gas in a storage tank according to claim 1 or 2, comprising: A step of obtaining first reference time point composition information related to the composition of the liquefied gas at a past first reference time point; A step of obtaining outflow amount information related to the outflow amount of the liquefied gas in the storage tank between the first reference time point and a third time point different from it; And A step of estimating third reference time point composition information related to the composition of the liquefied gas at the third time point according to the first reference time point composition information obtained in the step of obtaining the first reference time point composition information and the outflow amount information obtained in the step of obtaining the outflow amount information related to the outflow amount of the liquefied gas in the storage tank between the third time point and the first reference time point.

6. The method for estimating the composition of liquefied gas in a storage tank according to claim 5, comprising: A step of obtaining second reference time point composition information related to the composition of the liquefied gas set at a past second reference time point; A step of obtaining inflow amount information related to the inflow amount of the liquefied gas in the storage tank between the second reference time point and a fourth time point different from it; A step of obtaining inflow liquefied gas composition information related to the composition of the liquefied gas flowing into the storage tank; And A step of estimating fourth reference time point composition information related to the composition of the liquefied gas at the fourth time point according to the second reference time point composition information obtained in the step of obtaining the second reference time point composition information, the inflow amount information obtained in the step of obtaining the inflow amount information related to the inflow amount of the liquefied gas in the storage tank between the fourth time point and the second reference time point, and the inflow liquefied gas composition information obtained in the step of obtaining the inflow liquefied gas composition information.

7. A method for estimating the composition of liquefied gas in a storage tank, wherein the storage tank stores the liquefied gas containing multiple components, and the method for estimating the composition of liquefied gas in the storage tank comprises: A step of obtaining first reference time point composition information related to the composition of the liquefied gas set at a past first reference time point; A step of obtaining outflow amount information related to the outflow amount of the liquefied gas in the storage tank between the first reference time point and a third time point different from it; And A step of estimating third-timepoint composition information related to the liquefied gas composition at the third timepoint, based on the first-reference-timepoint composition information obtained in the step of obtaining the first-reference-timepoint composition information and the outflow information obtained in the step of obtaining outflow information related to the amount of liquefied gas flowing out of the storage tank between the third timepoint and the first reference timepoint.

8. A method for estimating the liquefied gas composition in a storage tank, where the storage tank stores the liquefied gas containing multiple components, and the method for estimating the liquefied gas composition in the storage tank includes: A step of obtaining second-reference-timepoint composition information related to the liquefied gas composition set at a past second reference timepoint; A step of obtaining inflow information related to the amount of liquefied gas flowing into the storage tank and outflow information related to the amount of liquefied gas flowing out of the storage tank between the second reference timepoint and a fourth timepoint different from it; A step of obtaining inflow liquefied gas composition information related to the liquefied gas composition flowing into the storage tank; and A step of estimating fourth-timepoint composition information related to the liquefied gas composition at the fourth timepoint, based on the second-reference-timepoint composition information obtained in the step of obtaining the second-reference-timepoint composition information, the inflow information and the outflow information obtained in the step of obtaining inflow information related to the amount of liquefied gas flowing into the storage tank and outflow information related to the amount of liquefied gas flowing out of the storage tank between the fourth timepoint and the second reference timepoint, and the inflow liquefied gas composition information obtained in the step of obtaining the inflow liquefied gas composition information.

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