Method for estimating the composition of liquefied gas in a tank

Abstract

To easily grasp a composition of liquefied gas stored in a tank.SOLUTION: A composition estimation method for liquefied gas in a tank is used for estimating a composition of liquefied gas in the tank that stores liquefied gas containing a plurality of components. The composition estimation method for liquefied gas in the tank includes steps of: acquiring reference information for estimating the composition of the liquefied gas in the tank at a first time point; setting first time point composition information on the composition of the liquefied gas at the first time point on the basis of the reference information acquired in the step of acquiring the reference information; acquiring information on outflow amount of the liquefied gas in the tank between a second time point different from the first time point and the first time point; and estimating second time point composition information on the composition of the liquefied gas at the second time point on the basis of 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 acquired in the step of acquiring the information on the outflow amount of the liquefied gas in the tank.SELECTED DRAWING: Figure 4

Description

Technical Field

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

Background Art

[0002] In a tank storing liquefied gas such as liquefied natural gas or liquefied petroleum gas, due to heat input from the outside, the liquefied gas evaporates in the tank, generating boil-off gas. When the tank is mounted on a ship, the boil-off gas may be used as fuel for, for example, the main engine mounted on the ship. For example, Patent Document 1 discloses a tank state estimation method for obtaining information related to the state in the tank at the start point of a target section on a route and calculating the state in the tank at the end point of the section on the assumption that the heat input to the tank in the section is used for vaporization of the liquefied gas in the tank. In this tank state estimation method, the amount of heat in the tank is estimated as the state in the tank.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Incidentally, if a tank does not have a device to reliquefy the boil-off gas, it may be necessary to discharge the gas from the tank to the outside and consume it as fuel for the main engine or incinerate it in order to suppress the rise in tank pressure. However, if the liquefied gas consists of multiple components, the component with the lower boiling point will evaporate before the component with the higher boiling point and become the boil-off gas. Therefore, discharging the gas from the tank to the outside will change the composition of the liquid inside the tank. In other words, when supplying gas or liquid from a tank to the outside of the tank, the composition of these gases and liquids will change over time. For example, if the liquid inside a tank is used as fuel for a combustion device installed on a ship, a change in the composition of the fuel supplied from the tank may affect the combustion state of the fuel in the combustion device. However, the method disclosed in Patent Document 1 does not allow for the determination of the composition of the liquefied gas in the tank; therefore, it is necessary to sample the liquefied gas in the tank and analyze its composition. Sampling and analyzing the composition of the liquefied gas is time-consuming and laborious.

[0005] This disclosure was made to solve the above-mentioned problems and aims to provide a method for estimating the composition of liquefied gas stored in a tank, which allows for easy determination of the composition of the liquefied gas stored in the tank. [Means for solving the problem]

[0006] To solve the above problems, the method for estimating the composition of liquefied gas in a tank according to this disclosure is a method for estimating the composition of liquefied gas in a tank that stores liquefied gas containing multiple components. The method for estimating the composition of liquefied gas in a tank includes the steps of: acquiring reference information; setting first time point composition information; acquiring information on the amount of liquefied gas flowing out of the tank; and estimating second time point composition information. The step of acquiring reference information involves acquiring reference information for estimating the composition of the liquefied gas in the tank at a first time point. The step of setting first time point composition information involves setting first time point composition information regarding the composition of the liquefied gas at the first time point based on the reference information acquired in the step of acquiring reference information. The step of acquiring information on the amount of liquefied gas flowing out of the tank involves acquiring information on the amount of liquefied gas flowing out of the tank between a second time point different from the first time point and the first time point. In the step of estimating the second time point composition information, the second time point composition information regarding the composition of the liquefied gas at the second time point is estimated based on the first time point composition information set in the step of setting the first time point composition information, and the amount of liquefied gas discharged in the step of acquiring information on the amount of liquefied gas discharged from the tank. In the step of acquiring the reference information, the state quantities of the liquefied gas in the tank at the first time point are acquired as the reference information. In the step of setting the composition information at the first time point, the liquid composition of the liquefied gas in the tank at the first time point is assumed, and an assumed value for the state quantities in the assumed liquid composition of the liquefied gas is calculated. If the difference between the calculated assumed value for the state quantities and the state quantities of the liquefied gas in the tank at the first time point is within a preset range, the assumed value for the state quantities is set as the composition information at the first time point.

[0007] The method for estimating the composition of liquefied gas in a tank according to this disclosure is a method for estimating the composition of liquefied gas in a tank that stores liquefied gas containing multiple components. The method for estimating the composition of liquefied gas in a tank is: The steps include: obtaining reference information, setting the composition information at the first point in time, obtaining information on the amount of liquefied gas flowing out of the tank, and estimating the composition information at the second point in time. Steps to obtain composition information at the first reference point, and the amount of leakage Outflow amount related to The steps include acquiring information and estimating the composition information at a third point in time. The steps include: estimating the composition information at a third time point; obtaining the composition information at a second reference time point; obtaining the inflow amount information; obtaining the inflow liquefied gas composition information; and estimating the composition information at a fourth time point.This includes the following. The step of acquiring the reference information involves acquiring reference information for estimating the composition of the liquefied gas in the tank at a first time point. The step of setting the first time point composition information involves setting first time point composition information regarding the composition of the liquefied gas at the first time point based on the reference information acquired in the step of acquiring the reference information. The step of acquiring information regarding the amount of liquefied gas flowing out of the tank involves acquiring information regarding the amount of liquefied gas flowing out of the tank between a second time point different from the first time point and the first time point. The step of estimating the second time point composition information involves estimating second time point composition information regarding the composition of the liquefied gas at the second time point based on the first time point composition information set in the step of setting the first time point composition information and the amount of liquefied gas flowing out acquired in the step of acquiring information regarding the amount of liquefied gas flowing out of the tank. The step of acquiring first reference point composition information involves acquiring first reference point composition information relating to the composition of the liquefied gas at a past first reference point. The step of acquiring outflow amount information involves acquiring outflow amount information relating to the amount of liquefied gas outflow from the tank between a third reference point different from the first reference point and the first reference point. The step of estimating third time point composition information estimates third time point composition information relating to the composition of the liquefied gas at the third time point based on the first reference point composition information acquired in the step of acquiring first reference point composition information and the outflow amount information acquired in the step of acquiring outflow amount information relating to the amount of liquefied gas outflow from the tank between the third time point and the first reference point. The step of acquiring second reference point composition information involves acquiring second reference point composition information relating to the composition of the liquefied gas set at a past second reference point. The step of acquiring inflow amount information involves acquiring inflow amount information relating to the amount of liquefied gas flowing into the tank between a fourth reference point different from the second reference point and the second reference point. The step of acquiring inflow liquefied gas composition information involves acquiring inflow liquefied gas composition information relating to the composition of the liquefied gas that has flowed into the tank. The step of estimating the fourth time point composition information involves estimating the fourth time point composition information relating to the composition of the liquefied gas at the fourth time point, based on the second reference time point composition information acquired in the step of acquiring the second reference time point composition information, the inflow amount information acquired in the step of acquiring inflow amount information relating to the amount of liquefied gas flowing into the tank between the fourth time point and the second reference time point, and the inflow liquefied gas composition information acquired in the step of acquiring the inflow liquefied gas composition information. [Effects of the Invention]

[0009] According to the method for estimating the composition of liquefied gas in a tank as disclosed herein, the composition of the liquefied gas stored in the tank can be easily determined. [Brief explanation of the drawing]

[0010] [Figure 1] This is a side view of a floating body equipped with a method for estimating the composition of liquefied gas in a tank according to an embodiment of the present disclosure. [Figure 2] This figure shows the hardware configuration of the liquefied gas composition estimation apparatus according to the embodiment of this disclosure. [Figure 3] This is a functional block diagram of a liquefied gas composition estimation apparatus according to an embodiment of the present disclosure. [Figure 4] This chart illustrates the different applications of the method for estimating the composition of liquefied gas in a tank according to the embodiments of this disclosure. [Figure 5] This flowchart shows the procedure for a first method of estimating the composition of liquefied gas in a tank according to an embodiment of the present disclosure. [Figure 6]This flowchart shows the procedure for a second method for estimating the composition of liquefied gas in a tank according to the embodiment of this disclosure. [Figure 7] This flowchart shows the procedure for a third method for estimating the composition of liquefied gas in a tank according to the embodiment of this disclosure. [Modes for carrying out the invention]

[0011] Hereinafter, a method for estimating the composition of liquefied gas in a tank according to the embodiment of this disclosure will be described with reference to Figures 1 to 7. (Overall configuration of the ship) As shown in Figure 1, the method for estimating the composition of liquefied gas in a tank according to this embodiment is carried out on a vessel equipped with a combustion device that burns or incinerates boil-off gas as fuel. As shown in Figure 1, the vessel 1 of this embodiment comprises at least a hull 2, a superstructure 4, a combustion device 9, a tank 10, and a liquefied gas composition estimation device 60 for estimating the composition of the liquefied gas in the tank 10. The vessel 1 of this embodiment is described as an example of a vessel capable of navigation using a main engine, etc. The type of vessel 1 is not limited to a specific type. Examples of vessel types for vessel 1 include liquefied gas carriers, ferries, RORO ships, car carriers, passenger ships, etc.

[0012] The hull 2 ​​has a pair of side plates 5A and 5B that form its outer shell, and a bottom 6. The side plates 5A and 5B are each provided with a pair of side plates that form the port and starboard sides, respectively. The bottom 6 is provided with bottom plates that connect these side plates 5A and 5B. Together with these pair of side plates 5A and 5B and the bottom 6, the outer shell of the hull 2 ​​has a U-shape in a cross section perpendicular to the bow-stern direction FA.

[0013] The hull 2 ​​further includes an upper deck 7, which is a full-length deck located at the uppermost level. The superstructure 4 is formed on this upper deck 7. Accommodation areas and the like are provided within the superstructure 4. In the vessel 1 of this embodiment, for example, a cargo hold 8 is formed on the bow 2a side in the forward-stern direction FA from the superstructure 4.

[0014] The combustion device 9 is a device that generates thermal energy by burning fuel, and is provided inside the hull 2 described above. Examples of the combustion device 9 include an internal combustion engine used as a main engine for propelling the ship 1, an internal combustion engine used for power generation equipment that supplies electricity to the ship, a boiler that generates steam as a working fluid, and the like.

[0015] The tank 10 is arranged in the hull 2. In the present embodiment, an example is shown in which the tank 10 has a cylindrical shape extending in the horizontal direction and a plurality of tanks 10 are arranged side by side in the fore-and-aft direction FA in the cargo loading section 8. However, the shape, number, and arrangement of the plurality of tanks 10 are not limited in any way. For example, the tank 10 can also be arranged on the exposed deck. Also, for example, the tank 10 may be spherical, square, or the like.

[0016] The tank 10 stores liquefied gas containing a plurality of components inside it. Examples of the liquefied gas containing a plurality of components include LNG (Liquefied Natural Gas), LPG (Liquefied Petroleum Gas), etc., which are liquefied gases liquefied in a low-temperature state. In the present embodiment, LNG is taken as an example to explain the liquefied gas containing a plurality of components.

[0017] The liquefied gas in the tank 10 evaporates due to heat input from the outside and becomes boil-off gas. The liquid of the liquefied gas in the tank 10 and the boil-off gas generated in the tank 10 are supplied to the combustion device 9 as fuel in the combustion device 9, or sent to an incinerator (not shown) for incineration disposal.

[0018] (Hardware Configuration Diagram) FIG. 2 is a diagram showing the hardware configuration of a liquefied gas composition estimation device according to an embodiment of the present disclosure. As shown in Figure 2, the liquefied gas composition estimation device 60 is a computer equipped with a CPU 61 (Central Processing Unit), ROM 62 (Read Only Memory), RAM 63 (Random Access Memory), storage 64, and a signal transmission / reception module 65. The signal transmission / reception module 65 receives detection signals from, for example, a pressure sensor that detects the pressure inside the tank 10, a temperature sensor that detects the temperature inside the tank 10, etc. (none of which are shown).

[0019] (Functional block diagram) Figure 3 is a functional block diagram of a liquefied gas composition estimation apparatus according to an embodiment of this disclosure. As shown in Figure 3, the CPU 61 of the liquefied gas composition estimation device 60 executes a program pre-stored in a storage device such as a ROM 62 or storage device 64 to realize the configurations of the information acquisition unit 71, the tank change amount acquisition unit 72, the composition estimation unit 73, and the information storage unit 74.

[0020] The information acquisition unit 71 acquires tank composition information regarding the composition of the liquefied gas in the tank 10 at each point in time. Based on the detection signals received by the signal transmission / reception module 65, the information acquisition unit 71 acquires detection data from, for example, a pressure sensor that detects the pressure inside the tank 10 and a temperature sensor that detects the temperature inside the tank 10.

[0021] The tank change amount acquisition unit 72 acquires the amount of change in the liquefied gas inside the tank 10 over a period of multiple time points. The composition estimation unit 73 estimates composition information regarding the composition of the liquefied gas in the tank 10 based on the tank composition information at multiple time points acquired by the information acquisition unit 71, and the amount of change in the liquefied gas in the tank 10 acquired by the tank change amount acquisition unit 72.

[0022] The information storage unit 74 stores various types of information necessary for the liquefied gas composition estimation device 60 to perform the estimation process of the composition of the liquefied gas in the tank 10. For example, the information storage unit 74 stores information such as the quantity, volume, heat retention performance, and external heat input of the tank 10 as specification information for the tank 10. The information storage unit 74 also stores various estimation results obtained by repeatedly performing the estimation process of the composition of the liquefied gas in the tank 10.

[0023] (Procedure for estimating the composition of liquefied gas in a tank) Figure 4 is a chart illustrating the different applications of the method for estimating the composition of liquefied gas in a tank according to the embodiments of this disclosure. The method S10 for estimating the composition of liquefied gas in a tank according to this embodiment includes a first method S10A for estimating the composition of liquefied gas, a second method S10B for estimating the composition of liquefied gas, and a third method S10C for estimating the composition of liquefied gas.

[0024] The first liquefied gas composition estimation method S10A is performed in state A1 where the composition of the liquefied gas in tank 10 is unknown. Furthermore, the first liquefied gas composition estimation method S10A is performed in a state where no liquefied gas is flowing into tank 10 from the outside, for example, while ship 1 is at sea. Here, state A1, where the composition of the liquefied gas in tank 10 is unknown, can be exemplified by a state where no liquefied gas is stored in tank 10 (for example, a state where all the liquefied gas has been discharged) and then a state after new liquefied gas has been injected into tank 10.

[0025] The second liquefied gas composition estimation method S10B is performed in state A2, when the composition of the liquefied gas in tank 10 has been estimated and is known. The second liquefied gas composition estimation method S10B is performed, for example, after the composition of the liquefied gas stored in tank 10 has been estimated by the first liquefied gas composition estimation method S10A, and the composition of the liquefied gas is estimated based on that estimation result. The second liquefied gas composition estimation method S10B is also performed when there is no inflow of liquefied gas into tank 10 from the outside, for example, while ship 1 is at sea.

[0026] The third method for estimating the composition of liquefied gas, S10C, is performed assuming the composition of the liquefied gas in tank 10 is known, and during or immediately after the supply of liquefied gas to tank 10 from an external source. For example, in the case of a ship 1 that uses liquefied gas as fuel, it is performed during refueling, in the so-called bunkering state A3.

[0027] Figure 5 is a flowchart showing the procedure for a first liquefied gas composition estimation method as a method for estimating the composition of liquefied gas in a tank according to the present disclosure. As shown in Figure 5, the first liquefied gas composition estimation method S10A according to this embodiment includes the steps of: acquiring reference information in step S11; setting first time point composition information in step S12; acquiring outflow amount information regarding the outflow amount of liquefied gas in the tank in step S13; estimating second time point composition information in step S14; acquiring the state quantity of the liquefied gas in the tank at the second time point in step S15; estimating the state quantity of the liquefied gas in the tank from the second time point composition information in step S16; and determining the error of the estimated value in step S17.

[0028] In step S11, which involves acquiring reference information, reference information is obtained to estimate the composition of the liquefied gas in tank 10 at the first time point T1 (see Figure 4). Here, the first time point T1 is any point in time during state A1, when the composition of the liquefied gas in tank 10 is unknown. The first time point T1 is a point in time when a certain amount of time has elapsed since the start of use of tank 10 T0, and when liquefied gas is stored in tank 10.

[0029] As reference information for estimating the composition of the liquefied gas in tank 10, the state quantities of tank 10 at the first time point T1 can be exemplified. The state quantities of tank 10 are, for example, at least one of the following: pressure, temperature, density, etc. In this embodiment, the reference information acquired in step S11 will be described using the pressure and temperature inside tank 10. The pressure and temperature inside tank 10 are acquired, for example, from a pressure sensor, a temperature sensor, etc., installed in tank 10.

[0030] In step S12, which sets the first time point composition information, the first time point composition information regarding the composition of the liquefied gas at the first time point T1 is set based on the reference information obtained in step S11, which obtains the reference information.

[0031] Specifically, in step S12, first, the liquid composition of the liquefied gas in tank 10 at the first time point T1 is assumed. The liquid composition of the liquefied gas in tank 10 at the first time point T1 may be assumed by using, for example, the amount of boil-off gas generated in tank 10 between the time of initial use T0 and the first time point T1 (as a percentage of the liquid liquefied gas), or by assuming a liquid composition of a set of random numbers. Here, the liquefied gas stored in tank 10 can be supplied from onshore liquefied gas supply facilities, tanker trucks, bunker ships, etc. On the supply side, such as onshore liquefied gas supply facilities, the liquid composition of the liquefied gas is known in advance by analyzing the liquefied gas to be supplied to tank 10. Furthermore, in step S12, if the error is determined to be outside the set range by step S17, which will be described later, the liquid composition of the liquefied gas in tank 10 at the first time point T1 is assumed to be a different set of values. Note that multiple assumptions may be made for the liquid composition of the liquefied gas in tank 10 at the first time point T1.

[0032] Next, in step S12, the assumed values ​​of the state variables of the liquefied gas in the assumed liquid composition are calculated. For example, the liquid density of the liquefied gas can be calculated from the assumed values ​​of the pressure and temperature of the liquefied gas as state variables of the liquefied gas in the assumed liquid composition.

[0033] In step S12, the composition information for the first time point is set based on the assumed value of the state quantity of the liquefied gas in the tank 10 at the first time point T1, which has been calculated, and the measured value of the state quantity of the liquefied gas in the tank 10 at the first time point T1, which was obtained in step S11. As described above, in step S11 of this embodiment, detection data of the pressure and temperature of the liquefied gas in the tank 10 at the first time point T1 is obtained. Therefore, in step S12, the density of the liquefied gas in the tank 10 at the first time point T1 is calculated based on the detection data of the pressure and temperature of the liquefied gas in the tank 10 at the first time point T1, which was obtained in step S11. Then, in step S12, the assumed value of the density of the liquefied gas in the tank 10 at the first time point T1, which has been calculated, is compared with the density of the liquefied gas based on the measured value of the liquefied gas in the tank 10 at the first time point T1.

[0034] In step S12, the liquid composition of the liquefied gas is further estimated by searching for an appropriate optimization method such that the error between the assumed value of the state quantity of the liquefied gas in the tank 10 at the first time point T1 and the state quantity of the liquefied gas based on the measured value of the liquefied gas in the tank 10 at the first time point T1 is sufficiently small or zero. For example, if the error between the assumed value of the density of the liquefied gas in the 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 tank 10 at the first time point T1 is within a preset tolerance range, that assumed value may be set as the first time point composition information. Also, if there are multiple assumed values ​​for the state quantity of the liquefied gas in the tank 10 at the first time point T1 that are within the tolerance range, the assumed value with the smallest error between these multiple assumed values ​​and the measured value of the state quantity of the liquefied gas in the tank 10 at the first time point T1 may be set as the first time point composition information.

[0035] In step S13, which involves acquiring discharge information regarding the amount of liquefied gas discharged from the tank, discharge information regarding the amount of liquefied gas discharged from the tank 10 between the first time point T1 and a second time point T2 that is different from the first time point T1. Here, the second time point T2, which is different from the first time point T1, may be after the first time point T1 or before the first time point T1. In this embodiment, the second time point T2 is, for example, the start time T0 which is before the first time point T1.

[0036] The outflow of liquefied gas from tank 10 between the second time point T2 and the first time point T1 occurs, for example, by supplying the liquid liquefied gas from tank 10 to the combustion device 9 as fuel. Alternatively, the outflow of liquefied gas from tank 10 between the second time point T2 and the first time point T1 can also occur, for example, by discharging boil-off gas, which is generated by the evaporation of liquefied gas from tank 10, to the outside of tank 10.

[0037] The amount of liquefied gas flowing out of the tank 10 between the second time point T2 and the first time point T1 may be calculated, for example, based on specification information about the tank 10 stored in advance in the information storage unit 74, or it may be calculated using measurement data. Examples of specification information about the tank 10 include the number of tanks 10, the volume of the tanks 10, the heat retention performance of the tanks 10, and the amount of heat input to the tanks 10 from the outside. The amount of heat input to the tanks 10 from the outside can be obtained, for example, based on the heat retention performance of the tanks 10 and data such as ambient temperature.

[0038] The outflow information regarding the amount of liquefied gas outflow from the tank obtained in step S13 may be, for example, the amount of liquefied gas outflow from the tank 10 itself between the first time point T1 and a second time point T2 which is different from the first time point T1, or other information correlated with the amount of liquefied gas outflow (e.g., heat quantity) may be obtained and the outflow amount calculated from this information. Furthermore, the outflow information regarding the amount of liquefied gas flowing out of the tank, acquired in step S13, may be obtained, for example, from a data logger or the like installed on the ship 1, regarding the amount consumed by the combustion device 9 that consumes the liquefied gas flowing out of the tank 10.

[0039] In step S14, which estimates the composition information at the second time point, the composition information at the second time point T2 is estimated based on the composition information at the first time point set in step S12 and the outflow amount information regarding the outflow amount of liquefied gas obtained in step S13. Specifically, in step S14, the change in the composition ratio of multiple components constituting the liquefied gas between the second time point T2 and the first time point T1 is calculated based on the composition information at the first time point T1 set in step S12 and the outflow amount of liquefied gas in the tank 10 between the second time point T2 and the first time point T1 obtained in step S13. In step S14, the liquid composition of the liquefied gas in the tank 10 at the second time point T2 is estimated based on the composition information at the first time point T1 set in step S12 and the calculated change in the composition ratio of multiple components constituting the liquefied gas between the second time point T2 and the first time point T1.

[0040] In step S15, which involves acquiring the state quantities of the liquefied gas in the tank at the second time point, the state quantities of the liquefied gas in the tank 10 at the second time point T2 are acquired. Specifically, for example, the measured values ​​of the pressure and temperature of the liquefied gas obtained from pressure sensors, temperature sensors, etc., installed in the tank 10 are acquired as the state quantities of the liquefied gas in the tank 10 at the second time point T2.

[0041] In step S16, which estimates the state quantities of the liquefied gas in the tank from the composition information at the second time point, the state quantities of the liquefied gas in the tank 10 at the second time point T2 are estimated from the composition information at the second time point estimated in step S14. Specifically, estimated values ​​of other state quantities of the liquefied gas at the second time point T2 are calculated based on the composition information at the second time point estimated in step S14 and the measured values ​​of the state quantities of the liquefied gas in the tank 10 at the second time point T2 obtained in step S15. In this embodiment, for example, the density of the liquefied gas at the second time point T2 is calculated as an estimated value of the state quantities of the liquefied gas at the second time point T2 based on the liquid composition of the liquefied gas at the second time point T2 estimated in step S14, and the pressure and temperature of the liquefied gas in the tank 10 at the second time point T2.

[0042] In step S17, it is determined whether the error between the estimated value of the liquefied gas state quantity (e.g., density) at the second time point T2 calculated in step S16 and the other state quantities of the liquefied gas in tank 10 at the second time point T2, calculated from the measured value of the liquefied gas state quantity in tank 10 at the second time point T2 obtained in step S15, is within a preset range. If, as a result of this determination, the error between the estimated value of the liquefied gas state quantity in tank 10 at the second time point T2 calculated and the measured value of the liquefied gas state quantity in tank 10 at the second time point T2 obtained in step S15 is within the set range (Yes in step S17), then the composition of the liquefied gas in tank 10 at the first time point T1, based on the first time point composition information set in step S12, is adopted as the estimated result of the composition of the liquefied gas in tank 10 in the first liquefied gas composition estimation method S10A in this embodiment. On the other hand, if, as a result of the above determination, the error between the estimated state quantity of the liquefied gas in tank 10 at the second time point T2 calculated and the measured state quantity of the liquefied gas in tank 10 at the second time point T2 obtained in step S15 is not within the set range (No in step S17), the process returns to step S12, and the assumption of the liquid composition of the liquefied gas in tank 10 at the first time point T1 is further changed, and the process from step S13 onwards is repeated.

[0043] Figure 6 is a flowchart showing the procedure for a second liquefied gas composition estimation method as a method for estimating the composition of liquefied gas in a tank according to the present disclosure. As shown in Figure 6, the second liquefied gas composition estimation method S10B according to this embodiment includes a step S21 of acquiring outflow amount information regarding the outflow amount of liquefied gas in the tank 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.

[0044] The second liquefied gas composition estimation method S10B is performed in state A2 (see Figure 4) where the composition of the liquefied gas in tank 10 is known by performing the first liquefied gas composition estimation method S10A or by measuring the composition of the liquefied gas in tank 10 by sampling. In the first liquefied gas composition estimation method S10A, as described above, the composition of the liquefied gas in tank 10 at the first time point T1, based on the first time point composition information set in step S12, is adopted as the estimated result of the composition of the liquefied gas in tank 10.

[0045] In step S21, which acquires information on the amount of liquefied gas flowing out of the tank, the amount of liquefied gas flowing out of the tank 10 between a third time point T3 (which is different from the first time point T1 and the second time point T2) and the first reference time point Ts1 is acquired. Here, the third time point T3 is a time point after the first reference time point Ts1. In this embodiment, the first reference time point Ts1 is set to the first time point T1, which is the most recent time point in which the estimated liquid composition of the liquefied gas was adopted.

[0046] The outflow of liquefied gas from tank 10 between the third time point T3 and the first reference time point Ts1 (first time point T1) occurs, for example, by supplying the liquid liquefied gas from tank 10 to the combustion device 9 as fuel. Alternatively, the outflow of liquefied gas from tank 10 between the third time point T3 and the first reference time point Ts1 can also occur, for example, by discharging boil-off gas, generated by the evaporation of liquefied gas from tank 10, to the outside of tank 10.

[0047] The amount of liquefied gas flowing out of the tank 10 between the third time point T3 and the first reference time point Ts1 may be calculated, for example, based on specification information about the tank 10 stored in advance in the information storage unit 74, or it may be calculated using measurement data. Examples of specification information about the tank 10 include the number of tanks 10, the volume of the tanks 10, the heat retention performance of the tanks 10, and the amount of heat input to the tanks 10 from the outside. The amount of heat input to the tanks 10 from the outside can be obtained, for example, based on data such as the heat retention performance of the tanks 10 and the ambient temperature outside the tanks 10.

[0048] The discharge amount information regarding the amount of liquefied gas discharged from the tank, acquired in step S21, may be, for example, the amount of liquefied gas discharged from the tank 10 between the third time point T3 and the first reference time point Ts1, or other information correlated with the amount of liquefied gas discharged (e.g., heat quantity) may be acquired and the discharge amount calculated from this information. Alternatively, the discharge amount information regarding the amount of liquefied gas discharged from the tank 10, acquired in step S21, may be, for example, the amount of liquefied gas consumed by the combustion device 9 that consumes the liquefied gas discharged from the tank 10, acquired from a data logger or the like installed on the ship 1.

[0049] In step S22, which estimates the composition information at the third time point, the composition information at the third time point T3 is estimated based on the composition information at the first time point T1, which is the first reference time point Ts1 (first reference time point composition information), and the outflow information regarding the outflow amount of liquefied gas between the third time point T3 and the first reference time point Ts1, which was obtained in step S21. Specifically, in step S22, the change in the composition ratio of multiple components constituting the liquefied gas between the third time point T3 and the first reference time point Ts1 is calculated based on the composition information at the first time point T1, which is the first reference time point Ts1, and the outflow amount of liquefied gas in the tank 10 between the third time point T3 and the first reference time point Ts1, which was obtained in step S21. In step S22, the liquid composition of the liquefied gas in the tank 10 at the third time point T3 is estimated, for example, based on the first time point composition information at the first time point T1, which is the first reference time point Ts1, and the amount of change in the composition ratio of multiple components constituting the liquefied gas between the calculated third time point T3 and the first reference time point Ts1. In this way, the liquid composition of the liquefied gas in the 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 in this embodiment.

[0050] Figure 7 is a flowchart showing the procedure for a third method of estimating the composition of liquefied gas in a tank according to an embodiment of this disclosure. As shown in Figure 7, the third liquefied gas composition estimation method S10C according to this embodiment includes the steps of: S31 acquiring inflow information and outflow information between the fourth time point T4 and the second reference time point Ts2; S32 acquiring inflow liquefied gas composition information; and S33 estimating the composition information at the fourth time point.

[0051] In step S31, which acquires inflow information regarding the amount of liquefied gas flowing into the tank 10 and outflow information regarding the amount of liquefied gas flowing out of the tank, inflow information regarding the amount of liquefied gas flowing into the tank 10 and outflow information regarding the amount of liquefied gas flowing out of the tank 10 are acquired between a fourth time point T4, which is different from the first time point T1, the second time point T2, and the third time point T3, and the second reference time point Ts2. Here, the fourth time point T4 is a time after the second reference time point Ts2, during so-called bunkering, when liquefied gas is being supplied into the tank 10 from the outside, or immediately after bunkering. The fourth time point T4 is a time after the first reference time point Ts1. In this embodiment, the second reference time point Ts2 is set to the third time point T3, which is the most recent time when the estimated liquid composition of the liquefied gas is adopted. Note that the second reference time point Ts2 is not limited to the third time point T3, but may be any other time point such as the first time point T1 or the second time point T2. The amount of liquefied gas flowing into the tank 10 between the fourth time point T4 and the second reference time point Ts2 can be obtained, for example, based on measurement data of the flow rate of liquefied gas supplied to the tank 10. The amount of liquefied gas flowing out of the tank 10 between the fourth time point T4 and the second reference time point Ts2 may be calculated, for example, based on specification information about the tank 10 stored in the information storage unit 74, or using measurement data.

[0052] In step S32, which involves acquiring inflow liquefied gas composition information, inflow liquefied gas composition information is acquired regarding the composition of the liquefied gas that flowed into the tank 10 between the fourth time point T4 and the second reference time point Ts2 (third time point T3). This inflow liquefied gas composition information can be, for example, information on the liquid composition of the liquefied gas supplied to the tank 10, provided by the liquefied gas supply facility. In addition, the inflow liquefied gas composition information may be estimated by reusing past performance values.

[0053] In step S33, which estimates the composition information at the fourth time point, the composition information at the fourth time point T4 is estimated based on the composition information at the third time point T3, which is the second reference time point Ts2 (composition information at the second reference time point), the inflow amount information regarding the amount of liquefied gas flowing in between the fourth time point T4 and the second reference time point Ts2, and the outflow amount information regarding the amount of liquefied gas flowing out of the tank 10, which were obtained in step S31, and the inflow liquefied gas composition information obtained in step S32.

[0054] Specifically, in step S33, which estimates the composition information for the fourth time point, the amount of change in multiple components constituting the liquefied gas between the fourth time point T4 and the third time point T3 is calculated based on the composition information for the third time point T3, which is the second reference time point Ts2, the amount of liquefied gas flowing into the tank 10 between the fourth time point T4 and the second reference time point Ts2 (third time point T3) obtained in step S31, the amount of liquefied gas flowing out of the tank 10 between the fourth time point T4 and the second reference time point Ts2 (third time point T3), and the composition information of the incoming liquefied gas obtained in step S32. Then, in step S33, which estimates the composition information for the fourth time point, the liquid composition of the liquefied gas in the tank 10 at the fourth time point T4 is estimated based on the composition information for the third time point T3 and the calculated amount of change in multiple components constituting the liquefied gas between the fourth time point T4 and the third time point T3. In this way, the liquid composition of the liquefied gas in the 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 in this embodiment.

[0055] (Effects and Benefits) In the method S10 for estimating the composition of liquefied gas in the tank according to the above embodiment, the second time point composition information regarding the composition of liquefied gas at the second time point T2 is estimated based on the first time point composition information of the liquefied gas acquired at the first time point T1 and the amount of liquefied gas that flowed out of the tank 10 between the second time point T2 and the first time point T1. Therefore, the composition of the liquefied gas stored in the tank 10 can be easily determined without measuring the composition of the liquefied gas in the tank 10.

[0056] Furthermore, in the above embodiment, the liquid composition of the liquefied gas in the tank 10 at the first time point T1 is assumed, and the first time point composition information regarding the liquid composition of the liquefied gas at the first time point T1 can be set 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 tank 10 at the first time point T1.

[0057] Furthermore, in the above embodiment, the liquid composition of the liquefied gas in the 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, those in which the difference between the assumed value of the state quantity and the state quantity of the liquefied gas in the tank 10 at the first time point T1 falls within a predetermined range are set as the first time point composition information. This makes it possible to select from the assumed liquid compositions of the liquefied gas that are close to the composition of the liquefied gas in the tank 10 at the first time point T1, thereby improving the accuracy of estimating the assumed liquid composition of the liquefied gas.

[0058] Furthermore, in the above 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 tank 10 at the second time point T2. This allows obtaining an estimated value of the state quantity of the liquefied gas at the second time point T2 that falls within a preset error range. Therefore, based on this estimated value of the state quantity, a reliable estimated composition, i.e., reliable second time point composition information and first time point composition information, can be obtained.

[0059] Furthermore, in the above embodiment, if liquefied gas leaks out of the tank 10 between the third time point T3 and the first reference time point Ts1 (second time point T2), by acquiring leak amount information regarding the amount of liquefied gas leaked out of the tank 10, the third time point composition information regarding the composition of the liquefied gas at the third time point T3 can be estimated based on the first time point composition information (first reference time point composition information) and the leak amount information.

[0060] Furthermore, in the above embodiment, if liquefied gas flows into the tank 10 and flows out of the tank 10 between the fourth time point T4 and the second reference time point Ts2 (third time point T3), by acquiring inflow information regarding the amount of liquefied gas flowing into the tank 10 and outflow information regarding the amount of liquefied gas flowing out of the tank 10, the fourth time point composition information regarding the composition of the liquefied gas at the fourth time point T4 can be estimated based on the third time point composition information (second reference time point composition information), the inflow information, and the outflow information.

[0061] (Other embodiments) Although embodiments of this disclosure have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and may include design changes and the like that do not depart from the gist of this disclosure. In the above embodiment, in step S11, etc., the pressure and temperature inside the tank 10 are obtained as state variables of the tank 10, and the density of the liquefied gas is calculated from these pressure and temperature values. However, the embodiment is not limited to this. For example, the composition of the liquefied gas may be estimated by calculating the temperature of the liquefied gas from the pressure inside the tank 10 and the density of the liquefied gas. Alternatively, information on even more parameters may be obtained as state variables of the liquefied gas inside the tank 10, and the composition of the liquefied gas may be estimated from this information.

[0062] Furthermore, in step S12 of the above embodiment, a hypothetical value to be used for subsequent processing is selected from among several hypothetical values ​​of the state quantity (density) of the liquefied gas in the tank 10 at the first time point T1 using an appropriate optimization method, but the specific method may be any.

[0063] Furthermore, in the second liquefied gas composition estimation method S10B of the above embodiment, the second time point T2 is used as the first reference time point Ts1. However, as the first reference time point Ts1, any time point other than the second time point T2 may be used, as long as it is before the third time point T3. Similarly, in the third liquefied gas composition estimation method S10B of the above embodiment, the third time point T3 is used as the second reference time point Ts2. However, as the second reference time point Ts2, any time point other than the third time point T3 may be used, as long as it is before the fourth time point T4.

[0064] In the above embodiment, a tank 10 provided on a ship 1 was described as an example, but the tank 10 may be a tank installed on land.

[0065] <Note> The method S10 for estimating the composition of liquefied gas in a tank described in the embodiment can be understood, for example, as follows.

[0066] (1) A method S10 for estimating the composition of liquefied gas in a tank according to the first embodiment is a method S10 for estimating the composition of liquefied gas in a tank 10 that stores liquefied gas containing multiple components, and includes: a step S11 for acquiring reference information for estimating the composition of the liquefied gas in the tank 10 at a first time point T1; a step S12 for setting first time point composition information relating to the composition of the liquefied gas at the first time point T1 based on the reference information acquired in step S11 for acquiring the reference information; a step S13 for acquiring information on the amount of liquefied gas flowing out of the tank between a second time point T2 different from the first time point T1 and the first time point T1; and a step S14 for estimating second time point composition information relating to the composition of the liquefied gas at a second time point based on the first time point composition information set in step S12 for setting the first time point composition information and the amount of liquefied gas flowing out acquired in step S13 for acquiring information on the amount of liquefied gas flowing out of the tank. Examples of standard information include state variables such as pressure, temperature, and density of the liquefied gas, and the composition of the liquefied gas. The second time point T2, which is different from the first time point T1, may be a time point before the first time point T1, or it may be a time point after the first time point T1.

[0067] This method S10 for estimating the composition of liquefied gas in the tank estimates the composition of the liquefied gas at the second time point T2 based on the first time point T1 composition information of the liquefied gas obtained at the first time point T1 and the amount of liquefied gas that flowed out of the tank 10 between the second time point T2 and the first time point T1. Therefore, the composition of the liquefied gas stored in the tank 10 can be easily determined without analyzing the composition of the liquefied gas in the tank 10.

[0068] (2) A method S10 for estimating the composition of liquefied gas in a tank according to a second embodiment is the method S10 for estimating the composition of liquefied gas in a tank according to (1), wherein in step S11 of acquiring the reference information, the state quantities of the liquefied gas in the tank 10 at the first time point T1 are acquired as the reference information, and in step S12 of setting the composition information at the first time point, the liquid composition of the liquefied gas in the tank 10 at the first time point T1 is assumed, and an assumed value of the state quantity in the assumed liquid composition of the liquefied gas is calculated, and the composition information at the first time point is set based on the calculated assumed value of the state quantity and the state quantities of the liquefied gas in the tank 10 at the first time point T1. Examples of state variables for liquefied gases include their pressure, temperature, and density.

[0069] This allows us to assume the liquid composition of the liquefied gas in the tank 10 at the first time point T1, and then set the first time point composition information regarding the liquid composition of the liquefied gas at the first time point T1 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 tank 10 at the first time point T1.

[0070] (3) A third embodiment of the method S10 for estimating the composition of liquefied gas in a tank is the method S10 for estimating the composition of liquefied gas in a tank according to (2), wherein in step S12 for setting the first time point composition information, a plurality of liquid compositions of the liquefied gas in the tank 10 at the first time point T1 are assumed, and among the assumed values ​​of the state quantities for each of the plurality of assumed liquid compositions of the liquefied gas, the one in which the difference between the assumed value of the state quantity and the state quantity of the liquefied gas in the tank 10 at the first time point T1 is within a predetermined range is identified, and the liquid composition of the liquefied gas corresponding to the identified assumed value of the state quantity is set as the first time point composition information.

[0071] This allows for the selection of a liquid composition from among several assumed liquefied gases that is closest to the composition of the liquefied gas in tank 10 at the first time point T1, thereby improving the accuracy of the assumed liquid composition of the liquefied gas.

[0072] (4) A fourth embodiment of the method S10 for estimating the composition of liquefied gas in a tank is a method S10 for estimating the composition of liquefied gas in any one of the tanks from (1) to (3), further comprising: a step S15 for acquiring the state quantity of the liquefied gas in the tank at the second time point; a step S16 for estimating the state quantity of the liquefied gas in the tank 10 at the second time point T2 based on the second time point composition information estimated in step S14 for estimating the composition information at the second time point; and a step S17 for determining the error of the estimated value of the state quantity of the liquefied gas in the tank 10 at the second time point T2 by comparing the estimated value of the state quantity of the liquefied gas in the tank 10 at the second time point T2, which was estimated in step S16 for estimating the state quantity of the liquefied gas in the tank 10 at the second time point T2, with the state quantity of the liquefied gas in the tank 10 at the second time point T2, which was acquired in step S15 for acquiring the state quantity of the liquefied gas in the tank 10 at the second time point T2.

[0073] This allows us to estimate the state quantities of the liquefied gas in the tank 10 at the second time point T2 based on the composition information at the second time point. Furthermore, by comparing the estimated state quantities of the liquefied gas at the second time point T2, estimated in step S16, with the state quantities of the liquefied gas in the tank 10 at the second time point T2, obtained in step S15, we can obtain an estimated value of the state quantities of the liquefied gas at the second time point T2 that falls within the preset error range. Based on this estimated state quantity, we can obtain a plausible estimated composition, i.e., the plausible second time point composition information estimated in step S14 and the first time point composition information set in step S12.

[0074] (5) A fifth embodiment of the method S10 for estimating the composition of liquefied gas in a tank is a method S10 for estimating the composition of liquefied gas in any one of the tanks from (1) to (4), comprising: a step S12 for acquiring first reference time point composition information relating to the composition of the liquefied gas at a past first reference time point Ts1; a step S21 for acquiring outflow amount information relating to the outflow amount of liquefied gas in the tank 10 between a third time point T3 different from the first reference time point Ts1 and the first reference time point Ts1; and a step S22 for estimating third time point composition information relating to the composition of the liquefied gas at the third time point T3 based on the first reference time point composition information acquired in step S12 for acquiring the first reference time point composition information and the outflow amount information acquired in step S21 for acquiring outflow amount information relating to the outflow amount of liquefied gas in the tank 10 between the third time point T3 and the first reference time point Ts1.

[0075] As a result, if liquefied gas leaks out of the tank 10 between the third time point T3 and the first reference time point Ts1, leak amount information regarding the amount of liquefied gas leaked out of the tank 10 can be obtained. Therefore, based on the composition information at the first reference time point and the leak amount information, the composition information at the third time point T3 regarding the composition of the liquefied gas can be estimated.

[0076] (6) The sixth embodiment of the method S10 for estimating the composition of liquefied gas in a tank is the method S10 for estimating the composition of liquefied gas in a tank according to (5), comprising the steps of: acquiring second reference time point composition information relating to the composition of the liquefied gas set at a past second reference time point Ts2; acquiring inflow amount information relating to the amount of liquefied gas flowing into the tank 10 between a fourth time point T4 different from the second reference time point Ts2 and the second reference time point Ts2; and acquiring inflow liquefied gas composition information relating to the composition of the liquefied gas that has flowed into the tank 10. The process includes a step S32 to obtain information, and a step S33 to estimate a fourth time point composition information relating to the composition of the liquefied gas at the fourth time point T4, based on the second reference time point composition information obtained in step S22 to obtain the second reference time point composition information, the inflow amount information obtained in step S31 to obtain inflow amount information relating to the amount of liquefied gas flowing into the tank 10 between the fourth time point T4 and the second reference time point Ts2, and the inflow liquefied gas composition information obtained in step S32 to obtain the inflow liquefied gas composition information.

[0077] As a result, if liquefied gas flows into the tank 10 between the fourth time point T4 and the second reference time point Ts2, inflow information regarding the amount of liquefied gas flowing into the tank 10 can be obtained. Therefore, based on the composition information at the second reference time point and the inflow information, the composition information at the fourth time point T4 regarding the composition of the liquefied gas can be estimated.

[0078] (7) A method S10 for estimating the composition of liquefied gas in a tank according to the seventh embodiment is a method S10 for estimating the composition of liquefied gas in a tank 10 storing liquefied gas containing multiple components, and includes: a step S12 for acquiring first reference time point composition information relating to the composition of the liquefied gas set at a past first reference time point Ts1; a step S21 for acquiring outflow amount information relating to the outflow amount of liquefied gas in the tank 10 between a third time point T3 different from the first reference time point Ts1 and the first reference time point Ts1; and a step S22 for estimating third time point composition information relating to the composition of the liquefied gas at the third time point T3 based on the first reference time point composition information acquired in step S12 for acquiring the first reference time point composition information and the outflow amount information acquired in step S21 for acquiring outflow amount information relating to the outflow amount of liquefied gas in the tank 10 between the third time point T3 and the first reference time point Ts1.

[0079] This allows us to obtain leakage information regarding the amount of liquefied gas leaked from tank 10 if leakage occurs between the third time point T3 and the first reference time point Ts1. Based on the composition information at the first reference time point and the leakage information, we can estimate the composition information at the third time point T3 regarding the composition of the liquefied gas. Therefore, we can easily determine the composition of the liquefied gas stored in tank 10 without analyzing the composition of the liquefied gas in tank 10.

[0080] (8) The eighth embodiment of the method S10 for estimating the composition of liquefied gas in a tank is a method S10 for estimating the composition of liquefied gas in a tank 10 that stores liquefied gas containing multiple components, comprising the steps of: acquiring second reference time point composition information regarding the composition of the liquefied gas set at a past second reference time point Ts2; acquiring inflow amount information regarding the amount of liquefied gas flowing into the tank 10 and outflow amount information regarding the amount of liquefied gas flowing out of the tank between a fourth time point T4 different from the second reference time point Ts2 and the second reference time point Ts2; and acquiring inflow liquefied gas composition information regarding the composition of the liquefied gas that has flowed into the tank 10. The process includes a step S32 for acquiring information, and a step S33 for estimating a fourth time point composition information regarding the composition of the liquefied gas at the fourth time point T4, based on the second reference time point composition information acquired in step S22 for acquiring the second reference time point composition information, the inflow amount information and the outflow amount information acquired in step S31 for acquiring the inflow amount information regarding the amount of liquefied gas flowing into the tank 10 and the outflow amount information regarding the amount of liquefied gas flowing out of the tank between the fourth time point T4 and the second reference time point Ts2, and the inflow liquefied gas composition information acquired in step S32 for acquiring the inflow liquefied gas composition information.

[0081] As a result, if there is an inflow or outflow of liquefied gas into the tank 10 between the fourth time point T4 and the past second reference time point Ts2, inflow information regarding the amount of liquefied gas in the tank 10 and outflow information regarding the amount of liquefied gas outflow can be obtained. Therefore, based on the composition information at the second reference time point, the inflow information, and the outflow information, the composition information at the fourth time point T4 regarding the composition of the liquefied gas can be estimated. Consequently, the composition of the liquefied gas stored in the tank 10 can be easily determined without analyzing the composition of the liquefied gas in the tank 10. [Explanation of symbols]

[0082] 1...Ship 2...Hull 2a...Bow 4...Superstructure 5A,5B...Side 6...Bottom 7...Upper Deck 8...Cargo Loading Compartment 9...Combustion Equipment 10...Tank 60...Composition Estimation Device 61...CPU 62...ROM 63...RAM 64...Storage 65...Signal Transceiver Module 71...Information Acquisition Unit 72...Tank Change Amount Acquisition Unit 73...Composition Estimation Unit 74...Information Storage Unit A1~A3...State FA...Bow and Stern Direction S10...Method for Estimating the Composition of Liquefied Gas in a Tank S11...Step to Acquire Reference Information S12...Step to Set First Time Point Composition Information S13...Step to Acquire Outflow Information Regarding the Outflow Amount of Liquefied Gas in a Tank S14...Step to Estimate Second Time Point Composition Information S15...Step to Acquire the State Amount of Liquefied Gas in a Tank at the Second Time Point S16...Step to Estimate the State Amount of Liquefied Gas in a Tank from the Second Time Point Composition Information S17...Step to Determine the Error of the Estimated Value S21...Step to obtain outflow information regarding the outflow amount of liquefied gas in the tank between the third time point and the first reference time. S22...Step to estimate the composition information at the third time point. S31...Step to obtain inflow information regarding the inflow amount of liquefied gas in the tank between the fourth time point and the second reference time. S32...Step to obtain the composition information of the inflowing liquefied gas. S33...Step to estimate the composition information at the fourth time point. T0...Time of commencement of use. T1...First time point. T2...Second time point. T3...Third time point. T4...Fourth time point. Ts1...First reference time. Ts2...Second reference time.

Claims

1. A method for estimating the composition of liquefied gas in a tank storing liquefied gas containing multiple components, A step of obtaining reference information for estimating the composition of the liquefied gas in the tank at a first point in time, A step of setting first time point composition information relating to the composition of the liquefied gas at the first time point, based on the reference information obtained in the step of obtaining the reference information, A step of obtaining information regarding the amount of liquefied gas flowing out of the tank between a second time point different from the first time point and the first time point, The process includes: estimating second time point composition information regarding the composition of the liquefied gas at a second time point based on the first time point composition information set in the step of setting first time point composition information, and the amount of liquefied gas discharged in the step of acquiring information regarding the amount of liquefied gas discharged from the tank; In the step of obtaining the aforementioned reference information, As the reference information, the state quantity of the liquefied gas in the tank at the first time point is obtained. In the step of setting the composition information at the first time point, Assuming the liquid composition of the liquefied gas in the tank at the first time point, an assumed value for the state quantity in the assumed liquid composition of the liquefied gas is calculated, and if the difference between the calculated assumed value for the state quantity and the state quantity of the liquefied gas in the tank at the first time point is within a predetermined range, the assumed value for the state quantity is set as the composition information at the first time point. A method for estimating the composition of liquefied gas in a tank.

2. In the step of setting the composition information at the first time point, Assuming multiple liquid compositions of the liquefied gas in the tank at the first time point, Among the multiple assumed values ​​of state quantities for each of the liquid composition of the liquefied gas, identify the one in which the difference between the assumed value of the state quantity and the state quantity of the liquefied gas in the tank at the first time point falls within a predetermined range. The liquid composition of the liquefied gas corresponding to the assumed values ​​of the identified state quantities is set as the first time point composition information. A method for estimating the composition of liquefied gas in a tank according to claim 1.

3. The steps include obtaining the state quantity of the liquefied gas in the tank at the second time point, A step of estimating the state amount of the liquefied gas in the tank at the second time point based on the second time point composition information estimated in the step of estimating the second time point composition information, The step further includes determining the error in the estimated value of the state quantity of the liquefied gas in the tank at the second time point by comparing the estimated value of the state quantity of the liquefied gas in the tank at the second time point, which was estimated in the step of estimating the state quantity of the liquefied gas in the tank at the second time point, with the state quantity of the liquefied gas in the tank at the second time point, which was obtained in the step of acquiring the state quantity of the liquefied gas in the tank at the second time point. A method for estimating the composition of liquefied gas in a tank according to claim 1 or 2.

4. A step of obtaining first reference point composition information regarding the composition of the liquefied gas at a past first reference point, A step of acquiring discharge amount information regarding the amount of liquefied gas discharged from the tank between a third time point different from the first reference time point and the first reference time point, The process includes a step of estimating third-timepoint composition information relating to the composition of the liquefied gas at the third time point, based on the first-timepoint composition information obtained in the step of obtaining the first-timepoint composition information, and the outflow amount information obtained in the step of obtaining outflow amount information relating to the outflow amount of liquefied gas in the tank between the third time point and the first-timepoint. A method for estimating the composition of liquefied gas in a tank according to claim 1 or 2.

5. A method for estimating the composition of a liquefied gas in a tank that stores a liquefied gas containing multiple components, A step of obtaining reference information for estimating the composition of the liquefied gas in the tank at a first point in time, A step of setting first time point composition information relating to the composition of the liquefied gas at the first time point, based on the reference information obtained in the step of obtaining the reference information, A step of obtaining information regarding the amount of liquefied gas flowing out of the tank between a second time point different from the first time point and the first time point, A step of estimating second time point composition information regarding the composition of the liquefied gas at the second time point, based on the first time point composition information set in the step of setting first time point composition information, and the amount of liquefied gas discharged in the step of acquiring information regarding the amount of liquefied gas discharged from the tank, A step of obtaining first reference point composition information regarding the composition of the liquefied gas at a past first reference point, A step of acquiring discharge amount information regarding the amount of liquefied gas discharged from the tank between a third time point different from the first reference time point and the first reference time point, A step of estimating third-time point composition information relating to the composition of the liquefied gas at the third time point, based on the first-time point composition information obtained in the step of obtaining the first-time point composition information, and the discharge amount information obtained in the step of obtaining discharge amount information relating to the amount of liquefied gas discharged from the tank between the third time point and the first-time point; A step of obtaining second reference point composition information regarding the composition of the liquefied gas set at a past second reference point, A step of acquiring inflow information regarding the amount of liquefied gas flowing into the tank between a fourth time point different from the second reference time point and the second reference time point, The steps include: acquiring inflow liquefied gas composition information relating to the composition of the liquefied gas that flows into the tank; The process includes a step of estimating a fourth time point composition information relating to the composition of the liquefied gas at the fourth time point, based on 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 inflow amount information relating to the amount of liquefied gas flowing into the 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. A method for estimating the composition of liquefied gas in a tank.

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