Method for predicting the state of liquefied gas in a tank, system for predicting the state of liquefied gas in a tank

Abstract

To predict the state of liquefied gas in a tank.SOLUTION: Provided is a method for predicting the state of liquefied gas in a tank, including: acquiring a state quantity of liquefied gas in a tank at a first time point; acquiring information about the tank necessary for predicting the state of the liquefied gas in the tank; acquiring information about the amount of the liquefied gas in the tank consumed by a combustion device that uses the liquefied gas as fuel, between the first time point and a second time point; acquiring information about a consumption plan of boil-off gas, which is generated by evaporation of the liquefied gas in the tank, between the first time point and the second time point; and predicting a predicted state quantity of the liquefied gas in the tank at the second time point, on the basis of the acquired state quantity of the liquefied gas, the information about the tank, the information about the consumed amount of the liquefied gas, and the information about the consumption plan of the boil-off gas.SELECTED DRAWING: Figure 5

Description

Technical Field

[0006] , ,

[0001] The present disclosure relates to a method for predicting the state of liquefied gas in a tank and a system for predicting the state of liquefied gas in a tank.

Background Art

[0002] In a tank for 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 and boil-off gas is generated. When boil-off gas is generated in the tank, the pressure in the tank rises. Therefore, the pressure in the tank is adjusted so that the pressure in the tank does not rise excessively.

[0003] For example, Patent Document 1 discloses a configuration that acquires data on the environment inside and outside a tank for storing liquefied gas, predicts an event that causes the tank pressure to fluctuate, and formulates an operation plan for a compressor that sucks gas in the tank based on the prediction result.

[0004] Also, when the tank is mounted on a ship, the pressure in the tank is adjusted by consuming the boil-off gas in the tank as fuel for, for example, a main engine mounted on the ship.

Prior Art Documents

Patent Documents

[0007] This disclosure was made to solve the above-mentioned problems and aims to provide a method for predicting the state of liquefied gas in a tank, and a system for predicting the state of liquefied gas in a tank, which can predict the state of liquefied gas in the tank. [Means for solving the problem]

[0008] To solve the above problems, the method for predicting the state of liquefied gas in a tank according to this disclosure is: LNG The tank in which the above LNG The state is predicted. The method for predicting the state of the liquefied gas in the tank is: LNG The steps include obtaining state variables and obtaining information about the tank, LNG The steps include obtaining information on the amount of consumption of, obtaining information on the boil-off gas consumption plan, and the second time point in time the amount of in the tank LNG The process includes the steps of predicting the predicted state variables and outputting the information to the outside. LNG In the step of acquiring the state quantity, the state quantity in the tank at the first time point LNG The state quantities are obtained. In the step of obtaining information about the tank, the state quantities inside the tank are obtained. of The aforementioned LNG To obtain information about the tank necessary for predicting its state, the LNG In the step of obtaining information on the amount of consumption, the following is obtained: between the first time point and the second time point which is after the first time point, LNG The combustion device that uses the above as fuel in the tankLNG Information regarding the consumption of the boil-off gas is obtained. In the step of obtaining information regarding the boil-off gas consumption plan, the following information is obtained regarding the consumption of the boil-off gas in the tank between the first time point and the second time point. LNG Information is obtained regarding the consumption plan of the boil-off gas generated by the evaporation of the second time point in the tank. LNG In the step of predicting the predicted state quantities, LNG The state variables obtained in the step of obtaining the state variables LNG State quantities, information about the tank obtained in the step of obtaining information about the tank, LNG The information obtained in the step of obtaining information on the consumption of LNG Based on the information regarding the consumption amount of and the information regarding the boil-off gas consumption plan obtained in the step of obtaining information regarding the boil-off gas consumption plan, the amount of in the tank at the second time point LNG The predicted state quantities are predicted. In the step of outputting the information to the outside, the predicted state quantities in the tank at the second time point are predicted. LNG The predicted state variables and information regarding the consumption plan for the boil-off gas are output to the outside.

[0009] The liquefied gas state prediction system in the tank relating to this disclosure is LNG The tank in which the above LNG The state of the liquefied gas in the tank is predicted. The state prediction system for the liquefied gas in the tank includes a liquefied gas state quantity acquisition unit, a tank information acquisition unit, a liquefied gas consumption information acquisition unit, a boil-off gas consumption plan acquisition unit, a liquefied gas state quantity prediction unit, and an information output unit. The liquefied gas state quantity acquisition unit predicts the state of the liquefied gas in the tank at a first point in time. LNG The state quantity of the tank is acquired. The tank information acquisition unit acquires the state quantity of the tank. LNG The unit acquires information about the tank necessary to predict its state. The liquefied gas consumption information acquisition unit acquires information about the tank between the first time point and a second time point that is later than the first time point. LNG The combustion device that uses the above as fuel in the tank LNGObtain information regarding the consumption amount. The boil-off gas consumption plan acquisition unit obtains information regarding the consumption plan of the boil-off gas generated by the evaporation of the LNG within the tank between the first time point and the second time point. The liquefied gas state quantity prediction unit predicts the predicted state quantity of the LNG within the tank at the second time point based on the state quantity of the LNG obtained by the liquefied gas state quantity acquisition unit, the information regarding the tank obtained by the tank information acquisition unit, the information regarding the consumption amount of the LNG obtained by the liquefied gas consumption amount information acquisition unit, and the information regarding the consumption plan of the boil-off gas obtained by the boil-off gas consumption plan acquisition unit. The information output unit outputs the predicted state quantity of the LNG within the tank at the second time point and the information regarding the consumption plan of the boil-off gas to the outside.

Advantages of the Invention

[0010] According to the method for predicting the state of liquefied gas in the tank and the system for predicting the state of liquefied gas in the tank of the present disclosure, the state of the liquefied gas in the tank can be predicted.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0012] Hereinafter, a method for predicting the state of liquefied gas in a tank and a system for predicting the state of liquefied gas in a tank according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 6. (Overall Structure of the Ship) As shown in FIG. 1, the method for predicting the state of liquefied gas in a tank and the system for predicting the state of liquefied gas in a tank of this embodiment are applied to a ship equipped with a combustion device that burns boil-off gas as fuel or incinerates it. As shown in FIG. 1, a ship 1 according to an embodiment of the present disclosure includes at least a hull 2, a superstructure 4, a combustion device 9, a tank 10, and a liquefied gas state prediction system 60 (see FIGS. 2 and 3) for predicting the state of liquefied gas in the tank 10. Note that the ship 1 of this embodiment will be 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. Examples of the ship type of the ship 1 include a liquefied gas carrier, a ferry, a RORO ship, a car carrier, a passenger ship, and the like.

[0013] The hull 2 has a pair of side plates 5A and 5B forming its outer shell and a bottom 6. The side plates 5A and 5B include a pair of side outer plates forming the left and right side plates respectively. The bottom 6 includes a bottom outer plate connecting these side plates 5A and 5B. With these pair of side plates 5A and 5B and the bottom 6, the outer shell of the hull 2 forms a U shape in a cross section perpendicular to the ship's bow and stern direction FA.

[0014] The hull 2 further includes an upper deck 7 which is an all-through deck arranged at the uppermost layer. The superstructure 4 is formed on this upper deck 7. Living quarters and the like are provided in the superstructure 4. In the ship of this embodiment, for example, a cargo loading compartment (hold) 8 is formed on the bow 2a side in the ship's bow and stern direction FA rather than the superstructure 4.

[0015] The combustion device 9 is a device that generates thermal energy by burning fuel and is installed inside the hull 2 ​​described above. Examples of combustion devices 9 include an internal combustion engine used as the main engine for propelling the ship 1, an internal combustion engine used in a power generation facility that supplies electricity to the ship, and a boiler that generates steam as a working fluid.

[0016] The tanks 10 are located on the hull 2. In this embodiment, the tanks 10 are shown as being cylindrical in shape and extending horizontally, with multiple tanks arranged in a row in the bow-stern direction FA within the cargo loading compartment 8. However, the shape, number, and arrangement of the tanks 10 are not limited in any way. For example, the tanks 10 can be located on the exposed deck. Also, for example, the tanks 10 may be spherical, rectangular, or the like.

[0017] Tank 10 stores liquefied gas containing multiple components inside. Examples of liquefied gas containing multiple components include LNG (Liquefied Natural Gas) and LPG (Liquefied Petroleum Gas), which are liquefied gases liquefied at low temperatures. In this embodiment, LNG will be used as an example of a liquefied gas containing multiple components.

[0018] The liquefied gas in tank 10 evaporates due to heat input from the outside, becoming boil-off gas. The liquid from the liquefied gas in tank 10, and the boil-off gas generated in tank 10, are either supplied to the combustion device 9 as fuel, or sent to an incinerator (not shown) for incineration.

[0019] (Hardware configuration diagram) Figure 2 shows the hardware configuration of a liquefied gas state prediction system according to an embodiment of this disclosure. As shown in Figure 2, the liquefied gas state prediction system 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 sensors (not shown) that detect state quantities such as pressure and temperature inside the tank 10.

[0020] (Functional block diagram) Figure 3 is a functional block diagram of a liquefied gas state prediction system according to an embodiment of this disclosure. Figure 4 is a chart showing the different uses of the liquefied gas state prediction method in a tank according to an embodiment of this disclosure. As shown in Figure 3, the CPU 61 of the liquefied gas state prediction system 60 executes programs pre-stored in memory devices such as ROM 62 and storage 64 to realize the following configurations: liquefied gas state quantity acquisition unit 71, tank information acquisition unit 72, liquefied gas consumption information acquisition unit 73, boil-off gas consumption plan acquisition unit 74, liquefied gas state quantity prediction unit 75, learning unit 76, information storage unit 77, information output unit 78, and inflow liquefied gas state quantity acquisition unit 79. As shown in Figures 3 and 4, the liquefied gas state prediction system 60 predicts the state of the liquefied gas in the tank 10 at the second time point T2 and the third time point T3, which are after the first time point T1. Here, the heat input to the tank 10 is allocated to the evaporation of the liquefied gas and the temperature rise of the liquefied gas in its liquid state. For example, even in a pressurized state where there is no boil-off gas outflow from the tank 10, if the temperature of the liquefied gas in its liquid state rises, the saturated vapor pressure increases. And as the saturated vapor pressure rises in this way, a portion of the liquefied gas in its liquid state evaporates. In other words, the evaporation of the liquefied gas and the temperature rise of the liquefied gas in its liquid state are interrelated. Therefore, the state of the liquefied gas in the tank 10 in this embodiment is not limited to the amount of evaporation of the liquefied gas in its liquid state, but also includes the temperature, pressure, and other conditions of the liquefied gas in its liquid state.

[0021] The liquefied gas state quantity acquisition unit 71 acquires the state quantities of the liquefied gas in the tank 10 at various points in time, such as the first time point T1, the second time point T2, and the third time point T3. Examples of the state quantities of the liquefied gas in the tank 10 include the pressure, temperature, density, methane number, and the amount of liquefied gas contained in the tank 10 (in other words, the liquid level height and mass of the liquefied gas). The liquefied gas state quantity acquisition unit 71 acquires at least one of the following: the pressure, temperature, density, methane number, and the amount of liquefied gas contained in the tank 10. Based on the detection signal received by the signal transmission / reception module 65, the liquefied gas state quantity acquisition unit 71 acquires data of actual values ​​detected by sensors that detect state quantities such as pressure and temperature in the tank 10. In addition, the liquefied gas state quantity acquisition unit 71 may acquire predicted values ​​predicted from the actual values ​​of other state quantities, rather than being limited to actual values ​​from sensors, etc., as the state quantities of the liquefied gas in the tank 10.

[0022] The tank information acquisition unit 72 acquires information about the tank 10 necessary for predicting the state of the liquefied gas inside the tank 10. The tank information acquisition unit 72 acquires information such as the quantity, volume, heat retention performance, and heat input from the outside of the tank 10 from the information storage unit 77, which will be described later. The information storage unit 77, which will be described later, has information such as the quantity, volume, heat retention performance, and heat input from the outside of the tank 10 stored in advance. The tank information acquisition unit 72 may also acquire weather information such as the outside temperature from external meteorological data, etc., for at least the period during which the state of the liquefied gas inside the tank 10 is predicted. In the following description, the period during which the state of the liquefied gas inside the tank 10 is predicted will be simply referred to as the prediction period.

[0023] The liquefied gas consumption information acquisition unit 73 acquires information regarding the amount of liquefied gas consumed by the combustion device 9 in the tank 10 during the forecast period. The information regarding the amount of liquefied gas consumed by the combustion device 9 in the tank 10, acquired by the liquefied gas consumption information acquisition unit 73, includes, for example, the ship's operation plan for the forecast period, the planned value of the amount of liquefied gas consumed by the combustion device 9 based on the operation plan, and so on.

[0024] The boil-off gas consumption plan acquisition unit 74 acquires information regarding the boil-off gas consumption plan generated by the evaporation of liquefied gas in the tank 10 during the forecasting period. The information regarding the boil-off gas consumption plan includes a pre-set boil-off gas consumption plan. The information regarding the boil-off gas consumption plan may also include the amount of boil-off gas consumed based on the boil-off gas consumption plan. Here, the boil-off gas consumption plan is, for example, one that can maintain the composition of the liquefied gas in the tank 10 at a composition that can be used as fuel.

[0025] The liquefied gas state quantity prediction unit 75 predicts the predicted state quantities of the liquefied gas in the tank 10 from the present time onward. Based on the state quantities of the liquefied gas acquired by the liquefied gas state quantity acquisition unit 71, information about the tank 10 acquired by the tank information acquisition unit 72, information about the consumption of liquefied gas acquired by the liquefied gas consumption information acquisition unit 73, and information about the boil-off gas consumption plan acquired by the boil-off gas consumption plan acquisition unit 74, the liquefied gas state quantity prediction unit 75 predicts the predicted state quantities of the liquefied gas in the tank 10.

[0026] The learning unit 76 performs learning based on the predicted state quantities of the liquefied gas in the tank 10, as predicted by the liquefied gas state quantity prediction unit 75, and the actual state quantities of the liquefied gas measured at the time the liquefied gas state quantity prediction unit 75 predicted the state quantities (second time point T2, third time point T3). If the prediction process using the liquefied gas state prediction method S10 in the tank has been performed multiple times in the past, the learning unit 76 accumulates data such as the predicted state quantities of the liquefied gas and the actual state quantities of the liquefied gas from the past, and generates learning data by analyzing the accumulated data.

[0027] The information storage unit 77 stores various types of information necessary for the liquefied gas state prediction system 60 to perform prediction processing of the state of the liquefied gas in the tank 10. For example, the information storage unit 77 stores information such as the number, volume, heat retention performance, and external heat input of the tank 10 as specification information for the tank 10. For example, the information storage unit 77 stores information such as the upper limit of the pressure inside the tank 10 and the lower limit of the methane number, which indicates the proportion of methane contained in the liquefied gas inside the tank 10, as management conditions for the tank 10. The information storage unit 77 also stores various estimation results obtained by repeatedly performing prediction processing of the state of the liquefied gas inside the tank 10, and learning data generated by learning in the learning unit 76.

[0028] The information output unit 78 outputs to the outside the predicted state quantities of the liquefied gas in the tank 10, which were predicted by the liquefied gas state quantity prediction unit 75, and information regarding the boil-off gas consumption plan, which was acquired by the boil-off gas consumption plan acquisition unit 74.

[0029] The inflow liquefied gas state quantity acquisition unit 79 acquires information on the state quantity of the liquefied gas flowing into the tank 10. Specifically, the inflow liquefied gas state quantity acquisition unit 79 acquires information on the state quantity of the liquefied gas flowing into the tank 10 between the second time point T2 and the third time point T3. Here, the state quantity of the liquefied gas flowing into the tank 10 is the amount of liquefied gas flowing into the tank 10 and the composition of the liquefied gas flowing into the tank 10, and can be obtained, for example, from the onshore supply facility that supplies the liquefied gas flowing into the tank 10. Note that the information on the state quantity of the liquefied gas flowing into the tank 10 acquired by the inflow liquefied gas state quantity acquisition unit 79 may be a predicted value. This predicted value may be a predicted value predicted within the ship 1 or a predicted value obtained from the supply source.

[0030] (Procedure for predicting the state of liquefied gas in a tank) Figure 5 is a flowchart showing the procedure for a first liquefied gas state prediction method as a method for predicting the state of liquefied gas in a tank according to an embodiment of this disclosure. Figure 6 is a flowchart showing the procedure for a second liquefied gas state prediction method as a method for predicting the state of liquefied gas in a tank according to an embodiment of this disclosure. As shown in Figures 5 and 6, the method S10 for predicting the state of liquefied gas in a tank according to this embodiment includes a first method S10A for predicting the state of liquefied gas and a second method S10B for predicting the state of liquefied gas. The first liquefied gas state prediction method S10A is performed in state A1, when no liquefied gas is flowing into the tank 10 from the outside, for example, while the ship 1 is at sea. The second liquefied gas state prediction method S10B is performed in state A2, when liquefied gas is supplied into the tank 10 from the outside, such as during bunkering.

[0031] The first liquefied gas state prediction method S10A predicts the state of the liquefied gas in the tank 10 at a second time point T2, which is after the first time point T1, with the first time point T1 being either the present time, a past time point prior to the present time, or a future time point. The first liquefied gas state prediction method S10A may be repeated multiple times at appropriate intervals.

[0032] As shown in Figure 5, the first liquefied gas state prediction method S10A according to this embodiment includes the steps of: acquiring the state quantity of the liquefied gas in step S11; acquiring information about the tank 10 in step S12; acquiring information about the consumption amount of liquefied gas in the tank 10 in step S13; acquiring information about the management conditions for the state quantity in the tank in step S14; acquiring information about the boil-off gas consumption plan in step S15; predicting the predicted state quantity of the liquefied gas in the tank 10 in step S16; determining whether the management conditions are satisfied or not in step S17; outputting the information to the outside in step S18; performing learning in step S19; and updating the information about the boil-off gas consumption plan in step S20. Note that the order in which steps S11 to S15 are performed is not limited to the order shown in Figure 5. For example, the order of steps S11 to S15 may be changed as appropriate, or they may be performed in parallel and simultaneously.

[0033] In step S11, which involves acquiring the state quantity of the liquefied gas, the liquefied gas state quantity acquisition unit 71 acquires the state quantity of the liquefied gas in the tank 10 at a first time point T1. In this embodiment, the first time point T1 is, for example, a point in time that has elapsed for a certain period of time from the start of use of the tank 10 T0.

[0034] In step S11, which involves acquiring the state quantities of the liquefied gas, the state quantity of the tank 10 acquired by the liquefied gas state quantity acquisition unit 71 is, for example, at least one of the following: pressure, temperature, density, composition of the liquefied gas, methane number, etc. The state quantity of the tank 10 acquired in step S11 may be an actual measured value detected by a sensor or the like, or it may be a predicted value based on past performance, etc.

[0035] In step S12, which involves acquiring information about the tank 10, the tank information acquisition unit 72 acquires information about the tank 10 necessary for predicting the state of the liquefied gas inside the tank 10. The tank information acquisition unit 72 acquires information about the tank 10 necessary for predicting the state of the liquefied gas inside the tank 10 between the first time point T1 and the second time point T2. As information about the tank 10, the tank information acquisition unit 72 acquires information such as the number of tanks 10, volume, heat retention performance, and heat input from the outside, which are pre-stored in the information storage unit 77. The tank information acquisition unit 72 may also acquire weather information such as the outside temperature from the first time point T1 to the second time point T2 from external meteorological data, etc.

[0036] In step S13, which involves acquiring information on the consumption of liquefied gas in tank 10, the liquefied gas consumption information acquisition unit 73 acquires information on the consumption of liquefied gas in tank 10 by the combustion device 9 during the period from the first time point T1 to the second time point T2, which is the period for which the prediction is made. The information on the consumption of liquefied gas in tank 10 acquired by the liquefied gas consumption information acquisition unit 73 includes, for example, the operating plan of the ship 1 for the period for which the prediction is made, the planned value of the liquefied gas consumption in the combustion device 9 based on the operating plan, and so on.

[0037] To give a more specific example, information regarding the consumption of liquefied gas in tank 10 may be obtained based on the ship's operation plan, including the distance traveled by ship 1 from the first time point T1 to the second time point T2, which is the period for which the forecast is made, the ship's speed, and the rotational speed of the combustion device 9 when ship 1 is sailing at that speed. Furthermore, as information regarding the consumption of liquefied gas in tank 10, it is also possible to obtain information on the actual measured consumption of liquefied gas when ship 1 has previously sailed along the same route as ship 1 in ship 1's operational plan. Furthermore, if the flight plan is undecided, information such as a hypothetical flight plan estimated from past flight performance or a flight plan assuming the current operating conditions are maintained may be used as information regarding the consumption of liquefied gas in tank 10. Furthermore, if there are other vessels that have the same or similar type of tank 10 as vessel 1, information regarding the consumption of liquefied gas in the tank 10 may be obtained, specifically, information on the measured consumption of liquefied gas when those vessels previously navigated the same route as vessel 1.

[0038] In step S14, which involves acquiring information on the management conditions for the state quantities in the tank, the liquefied gas state quantity prediction unit 75 acquires information on the management conditions for the state quantities in the tank 10 that is stored in the information storage unit 77. Examples of the management conditions for the tank 10 acquired in step S14 include the upper limit of the pressure in the tank 10 and the lower limit of the methane number, which indicates the proportion of methane contained in the liquefied gas in the tank 10. The management conditions for the tank 10 acquired in step S14 are those that can be compared with the predicted state quantities of the liquefied gas in the tank 10 at the second time point T2, which were predicted in step S16, which involves predicting the predicted state quantities of the liquefied gas in the tank 10.

[0039] In step S15, which involves acquiring information on the boil-off gas consumption plan, the boil-off gas consumption plan acquisition unit 74 acquires information on the boil-off gas consumption plan generated by the evaporation of liquefied gas in the tank 10 between the first time point T1 and the second time point T2. The information on the boil-off gas consumption plan is pre-set. For example, if the prediction process using the liquefied gas state prediction method S10 in the tank has been performed in the past, information on the boil-off gas consumption plan set in the past may be acquired.

[0040] In step S16, which predicts the predicted state quantities of the liquefied gas in tank 10, the liquefied gas state quantity prediction unit 75 predicts the predicted state quantities of the liquefied gas in tank 10 at the second time point T2. The liquefied gas state quantity prediction unit 75 predicts the predicted state quantities of the liquefied gas in tank 10 based on the state quantities of the liquefied gas obtained in step S11, information about tank 10 obtained in step S12, information about the consumption of liquefied gas obtained in step S13, and information about the boil-off gas consumption plan obtained in step S15. The liquefied gas state quantity prediction unit 75 predicts the predicted state quantities of the liquefied gas in tank 10 at the second time point T2 based on the state quantities of the liquefied gas, information about tank 10, information about the consumption of liquefied gas in tank 10, and information about the boil-off gas consumption plan obtained at the first time point T1. In step S16, which predicts the predicted state quantities of the liquefied gas in tank 10, the liquefied gas state quantity prediction unit 75 predicts that the predicted state quantities of the liquefied gas in tank 10 include, for example, at least a portion of the amount (retaining amount), temperature, composition, and methane number of the liquefied gas in liquid state in tank 10, and the amount, temperature, and composition of the boil-off gas in tank 10. Furthermore, if the prediction process using the liquefied gas state prediction method S10 in the tank has been performed in the past, and learning has been performed by the learning unit 76 in step S19, which will be described later, the predicted state quantity of the liquefied gas in the tank 10 is corrected based on the learning data, which is the result of that learning.

[0041] In step S17, which determines whether the management conditions are satisfied, it is determined whether the predicted state quantities of the liquefied gas in tank 10 at the second time point T2, as predicted in step S16 for predicting the predicted state quantities of the liquefied gas in tank 10, satisfy the management conditions for the state quantities obtained in step S14 for obtaining information on the management conditions for the state quantities in the tank. If, as a result of this determination, the predicted state quantities of the liquefied gas in tank 10 at the second time point T2, as predicted in step S16 for predicting the predicted state quantities of the liquefied gas in tank 10, satisfy the management conditions (Yes in step S17), the process proceeds to step S18, which outputs the information to the outside.

[0042] In step S18, which outputs information to the outside, the predicted state quantities of the liquefied gas in the tank 10 at the second time point T2, which were determined to be satisfied in step S17, which determines whether the management conditions are met, and the information regarding the boil-off gas consumption plan obtained in step S15, which acquires information regarding the boil-off gas consumption plan, or the information regarding the boil-off gas consumption plan updated in step S20, which updates the information regarding the boil-off gas consumption plan, are output to the outside. The predicted state quantities of the liquefied gas in the tank 10 at the second time point T2 and the information regarding the boil-off gas consumption plan in step S18, which outputs information to the outside, can be output to the outside, for example, by displaying on a monitor screen, transmitting data to an external terminal, or printing on paper.

[0043] Subsequently, the liquefied gas state prediction system 60 measures the actual state quantities of the liquefied gas in the tank 10 when it reaches the second time point T2 predicted in step S16, which predicts the state quantities of the liquefied gas in the tank 10. In the learning step S19, learning is performed based on the predicted state quantities of the liquefied gas in the tank 10 at the second time point T2, which were predicted in step S16, and the actual state quantities (measured values) of the liquefied gas in the tank 10 at the second time point T2.

[0044] On the other hand, if, as a result of the determination in step S17, which determines whether or not the management conditions are met, the predicted state quantities of the liquefied gas in tank 10 at the second time point T2, as predicted in step S16, do not meet the management conditions (No in step S17), the process proceeds to step S20, which updates the information regarding the boil-off gas consumption plan.

[0045] In step S20, which updates the information regarding the boil-off gas consumption plan, the liquefied gas state quantity prediction unit 75 updates the information regarding the boil-off gas consumption plan. Specifically, if the pressure value inside the tank 10 is predicted as the predicted state quantity of the liquefied gas inside the tank 10 at the second time point T2, and the predicted pressure value exceeds, for example, the upper limit of the pressure inside the tank 10 included in the control conditions, then the information regarding the boil-off gas consumption plan is updated to be different from the information regarding the boil-off gas consumption plan obtained in step S15, which is used to obtain the information regarding the boil-off gas consumption plan. Then, the process returns to step S16, which predicts the predicted state quantity of the liquefied gas inside the tank 10. In this case, in step S16, which predicts the predicted state quantity of the liquefied gas inside the tank 10, the predicted state quantity of the liquefied gas inside the tank 10 at the second time point T2 is predicted based on the updated information regarding the boil-off gas consumption plan. Then, step S17 is performed to determine again whether or not the control conditions are satisfied based on this predicted state quantity of the liquefied gas inside the tank 10 at the second time point T2.

[0046] As shown in Figure 6, the second liquefied gas state prediction method S10B predicts the state of the liquefied gas in tank 10 at a third time point T3, which is after the time Ts when the inflow of liquefied gas into tank 10 begins, during bunkering, in state A2 (see Figure 4) when liquefied gas is flowing into tank 10 from the outside. The second liquefied gas state prediction method S10B predicts the state of the liquefied gas in tank 10 at a third time point T3, using as a reference a time (for example, a second time point T2) when the state quantity of liquefied gas in tank 10 has already been predicted, prior to the time Ts when the inflow of liquefied gas into tank 10 begins.

[0047] The second liquefied gas state prediction method S10B according to this embodiment includes the steps of: S21 acquiring the state quantity of the liquefied gas; S22 acquiring the state quantity of the liquefied gas flowing into the tank 10; S23 predicting the state quantity of the liquefied gas in the tank 10; and S24 outputting the prediction result to the outside.

[0048] In step S21, which involves acquiring the state quantities of the liquefied gas, the predicted state quantities of the liquefied gas in the tank 10 at the second time point T2, as predicted by the liquefied gas state quantity acquisition unit 71 in step S16, are acquired. The predicted state quantities of the tank 10 acquired by the liquefied gas state quantity acquisition unit 71 in step S21 are, for example, at least one of the following: pressure, temperature, density, composition of the liquefied gas, methane number, amount of liquefied gas in the tank 10.

[0049] In step S22, which involves acquiring the state quantity of liquefied gas flowing into the tank 10, the inflow liquefied gas state quantity acquisition unit 79 acquires information on the state quantity of liquefied gas flowing into the tank 10 between the second time point T2 and the third time point T3.

[0050] In step S23, which predicts the state quantity of liquefied gas in tank 10, the state quantity of liquefied gas in tank 10 at the third time point T3 is predicted based on the predicted state quantity of tank 10 at the second time point T2, obtained in step S21, which acquires the state quantity of liquefied gas, and the state quantity of liquefied gas flowing into tank 10, obtained in step S22, which acquires the state quantity of liquefied gas flowing into tank 10. At the third time point T3, the liquefied gas in tank 10 at the second time point T2 and the liquefied gas that has flowed into tank 10 between the second time point T2 and the third time point T3 are in a mixed state.

[0051] In step S24, which outputs the prediction results externally, the predicted result of the state amount of liquefied gas in tank 10 at the third time point T3, which was predicted in step S23, is output externally. The output of the prediction results externally in step S24 can be done, for example, by displaying it on a monitor screen, transmitting the data to an external terminal, or printing it on paper.

[0052] (Effects and Benefits) In the above embodiment, the method S10 for predicting the state of liquefied gas in tank 10 and the system 60 for predicting the state of liquefied gas in tank 10 can predict the predicted state of liquefied gas in tank 10 at a second time point T2 based on the state quantity of liquefied gas at a first time point T1, information about tank 10, information about the amount of liquefied gas consumed between the first time point T1 and the second time point T2, and information about the boil-off gas consumption plan. Furthermore, based on the state quantity of liquefied gas at the first time point T1 and information about tank 10, the amount of boil-off gas generated by the evaporation of liquefied gas in tank 10 can be predicted. In addition, based on the amount of liquefied gas consumed in the combustion device 9 that uses liquefied gas as fuel and the boil-off gas consumption plan generated in tank 10, the amount of liquefied gas and boil-off gas in tank 10 at a second time point T2 can be predicted. As a result, the state of the liquefied gas inside tank 10 can be predicted.

[0053] In the above embodiment, by updating the information regarding the boil-off gas consumption plan based on the predicted state quantity of the liquefied gas in the tank 10, the accuracy of the information regarding the boil-off gas consumption plan can be improved according to the state quantity of the liquefied gas in the tank 10.

[0054] In the above embodiment, if the predicted state quantity of the liquefied gas in the tank 10 at the second time point T2 satisfies the state quantity management conditions, information regarding the predicted state quantity of the liquefied gas in the tank 10 at the second time point T2 and the boil-off gas consumption plan is output externally. Therefore, the liquefied gas in the tank 10 can be managed to an appropriate state while consuming boil-off gas based on the boil-off gas consumption plan. This prevents the pressure in the tank 10 from rising excessively due to the generation of boil-off gas, and minimizes the amount of generated boil-off gas that needs to be processed by incineration, allowing it to be effectively utilized as fuel for the combustion device 9.

[0055] Furthermore, when liquefied gas consists of multiple components such as LNG, the component with the lower boiling point evaporates before the component with the higher boiling point, becoming a boil-off gas. When the liquefied gas is LNG, methane, which has a lower boiling point than the other components in LNG, evaporates first. As a result, the boil-off gas contains a large amount of methane gas. Consequently, the methane content in the liquefied gas remaining in liquid form in tank 10 decreases. By setting the management conditions in tank 10 to suppress an excessive decrease in the methane content of the liquefied gas in liquid form present in tank 10, an excessive decrease in the methane content of the liquefied gas in liquid form can be prevented. As a result, when liquefied gas in liquid form in tank 10 is supplied to combustion device 9 as fuel, the influence of the liquefied gas on the combustion state can be effectively suppressed.

[0056] In the above embodiment, learning is performed based on the predicted state quantities of the liquefied gas in the tank 10 at the second time point T2 and the actual state quantities of the liquefied gas in the tank 10 at the second time point T2, and the predicted state quantities of the liquefied gas are corrected based on the learning results. This makes it possible to predict the predicted state quantities of the liquefied gas in tank 10 at the second time point T2 with higher accuracy.

[0057] In the above embodiment, liquefied gas flows into the tank 10 between the second time point T2 and the third time point T3. In this case, at the third time point T3, the liquefied gas in the tank 10 at the second time point T2 and the liquefied gas that flows into the tank 10 between the second time point T2 and the third time point T3 are mixed in the tank 10. In the above embodiment, since the state quantity of the liquefied gas flowing into the tank 10 between the second time point T2 and the third time point T3 is acquired, the state quantity of the liquefied gas in the tank 10 after the liquefied gas flows into the tank 10 from the outside can be predicted based on the predicted state quantity of the tank 10 at the second time point T2 and the acquired state quantity of the liquefied gas flowing into the tank 10. This makes it possible to predict the state of the liquefied gas inside the tank 10, even if liquefied gas flows into the tank 10 between the second time point T2 and the third time point T3.

[0058] (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 S20, which updates the information regarding the boil-off gas consumption plan, the information regarding the boil-off gas consumption plan is updated if the predicted state quantities of the liquefied gas in tank 10, predicted in step S16, which predicts the predicted state quantities of the liquefied gas in tank 10, do not satisfy the control conditions. However, the embodiment is not limited to this. For example, in the initial stages after the start of use of tank 10, the information regarding the boil-off gas consumption plan may not be updated.

[0059] Furthermore, the prediction of the state quantities of the liquefied gas in tank 10 may be performed using, for example, an estimated value of the composition obtained by estimating the composition of the liquefied gas in tank 10. To estimate the composition of the liquefied gas in tank 10, the process may include, for example, the 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 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; acquiring information on the amount of liquefied gas flowing out of the tank between the first time point and a second time point different from the first time point; and 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 on the amount of liquefied gas flowing out of the tank.

[0060] Furthermore, although the above embodiment described an example where the liquefied gas state prediction system 60 is installed on a ship 1, the installation location of the liquefied gas state prediction system 60 is not limited to a ship 1. For example, the liquefied gas state prediction system 60 may be installed on land. In this case, the measurement data measured on the ship 1 can be transmitted wirelessly to the liquefied gas state prediction system 60 installed on land to perform state prediction.

[0061] <Note> The method S10 for predicting the state of liquefied gas in tank 10 and the system 60 for predicting the state of liquefied gas in tank 10, as described in the embodiment, can be understood, for example, as follows.

[0062] (1) The first embodiment of the method S10 for predicting the state of liquefied gas in a tank 10 is a method S10 for predicting the state of liquefied gas in a tank 10 that stores liquefied gas, comprising: a step S11 for acquiring the state amount of the liquefied gas in the tank 10 at a first time point T1; a step S12 for acquiring information about the tank 10 necessary for predicting the state of the liquefied gas in the tank 10; a step S13 for acquiring information about the amount of liquefied gas consumed in the tank 10 by a combustion device 9 that uses the liquefied gas as fuel between the first time point T1 and a second time point T2 that is later than the first time point T1; and the boil-off gas generated by the evaporation of the liquefied gas in the tank 10 between the first time point T1 and the second time point T2. The process includes: step S15 to obtain information regarding the consumption plan of the liquefied gas; step S16 to predict the predicted state quantity of the liquefied gas in the tank 10 at the second time point T2 based on the state quantity of the liquefied gas obtained in step S11 to obtain the state quantity of the liquefied gas, information regarding the tank 10 obtained in step S12 to obtain information regarding the tank 10, information regarding the consumption amount of the liquefied gas obtained in step S13 to obtain information regarding the consumption plan of the liquefied gas, and information regarding the consumption plan of the boil-off gas obtained in step S15 to obtain information regarding the consumption plan of the boil-off gas; and step S18 to output to the outside the predicted state quantity of the liquefied gas in the tank 10 at the second time point T2 and information regarding the consumption plan of the boil-off gas. Examples of state variables and predicted state variables for liquefied gas include the pressure, temperature, density, composition, methane number, and amount of liquefied gas contained in tank 10. Examples of information regarding tank 10 include the number of tanks 10, their volume, insulation performance, and the amount of heat input from the outside.

[0063] The method S10 for predicting the state of liquefied gas in tank 10 can predict the predicted state of liquefied gas in tank 10 at a second time point T2, based on the state quantity of liquefied gas at a first time point T1, information about tank 10, information about the amount of liquefied gas consumed between the first time point T1 and the second time point T2, and information about the boil-off gas consumption plan. Based on the state quantity of liquefied gas at the first time point T1 and information about tank 10, the amount of boil-off gas generated by the evaporation of liquefied gas in tank 10 can be predicted. Furthermore, based on the amount of liquefied gas consumed in a combustion device that uses liquefied gas as fuel and the consumption plan for the boil-off gas generated in tank 10, the amount of liquefied gas and boil-off gas in tank 10 at a second time point T2 can be predicted. As a result, the state of liquefied gas in tank 10 can be predicted.

[0064] (2) The method S10 for predicting the state of liquefied gas in a tank 10 according to the second embodiment is the method S10 for predicting the state of liquefied gas in a tank 10 according to (1), further comprising a step S20 for updating information regarding the boil-off gas consumption plan based on the predicted state amount of the liquefied gas in the tank 10 predicted in step S16 for predicting the predicted state amount of the liquefied gas in the tank 10, and in step S18 for outputting to the outside the predicted state amount of the liquefied gas in the tank 10 at the second time point T2 and information regarding the boil-off gas consumption plan, the information regarding the boil-off gas consumption plan updated in step S20 for updating information regarding the boil-off gas consumption plan is output to the outside. This allows the accuracy of the information regarding the boil-off gas consumption plan to be improved according to the state quantities of the liquefied gas in tank 10, by updating the information regarding the boil-off gas consumption plan based on the predicted state quantities of the liquefied gas in tank 10.

[0065] (3) The third embodiment of the method S10 for predicting the state of liquefied gas in a tank 10 is the method S10 for predicting the state of liquefied gas in a tank 10 according to (1) or (2), comprising: a step S14 for acquiring information on the management conditions for the state quantity in the tank 10; a step S17 for determining whether the predicted state quantity of the liquefied gas in the tank 10 at the second time point T2, predicted in step S16 for predicting the predicted state quantity of the liquefied gas, satisfies the management conditions for the state quantity acquired in step S14 for acquiring information on the management conditions for the state quantity; and, if the predicted state quantity of the liquefied gas in the tank 10 at the second time point T2 satisfies the management conditions for the state quantity, a step S18 for outputting to the outside the predicted state quantity of the liquefied gas in the tank 10 at the second time point T2 and information on the boil-off gas consumption plan. As a result, if the predicted state quantities of the liquefied gas in tank 10 at the second time point T2 satisfy the state quantity management conditions, information regarding the predicted state quantities of the liquefied gas in tank 10 at the second time point T2 and the boil-off gas consumption plan is output externally. Therefore, it is possible to manage the liquefied gas in tank 10 to an appropriate state while consuming boil-off gas based on the boil-off gas consumption plan.

[0066] (4) The fourth embodiment of the method S10 for predicting the state of liquefied gas in a tank 10 is a method S10 for predicting the state of liquefied gas in a tank 10, which is any one of (1) to (3), and further comprises a step S19 for learning based on the predicted state amount of the liquefied gas in the tank 10 at the second time point T2 predicted in step S16 for predicting the predicted state amount of the liquefied gas, and the actual state amount of the liquefied gas in the tank 10 at the second time point T2, wherein in step S16 for predicting the predicted state amount of the liquefied gas in the tank 10 at the second time point T2, the predicted state amount of the liquefied gas is corrected based on the learning result in step S19 for learning. In this configuration, learning is performed based on the predicted state quantities of the liquefied gas in tank 10 at the second time point T2 and the actual state quantities of the liquefied gas in tank 10 at the second time point T2. Based on the learning results, the predicted state quantities of the liquefied gas are corrected. This makes it possible to predict the predicted state quantities of the liquefied gas in tank 10 at the second time point T2 with higher accuracy.

[0067] (5) A fifth embodiment of the method S10 for predicting the state of liquefied gas in a tank 10 is a method S10 for predicting the state of liquefied gas in a tank 10 according to any one of (1) to (4), further comprising: a step S22 for acquiring the state amount of the liquefied gas flowing into the tank 10 between the second time point T2 and a third time point T3 that is after the second time point T2; and a step S23 for predicting the state amount of the liquefied gas in the tank 10 in a state in which the liquefied gas in the tank 10 at the second time point T2 and the liquefied gas flowing into the tank 10 between the second time point T2 and the third time point T3 are mixed, based on the predicted state amount in the tank 10 at the second time point T2 predicted in step S16 for predicting the predicted state amount of the liquefied gas, and the state amount of the liquefied gas flowing into the tank 10 acquired in step S22 for acquiring the state amount of the liquefied gas flowing into the tank 10. With this configuration, if liquefied gas flows into the tank 10 between the second time point T2 and the third time point T3, at the third time point T3, the liquefied gas in the tank 10 at the second time point T2 and the liquefied gas that flows into the tank 10 between the second time point T2 and the third time point T3 will be mixed within the tank 10. By acquiring the state quantity of the liquefied gas flowing into the tank 10 between the second time point T2 and the third time point T3, the state quantity of the liquefied gas in the tank 10 can be predicted based on the predicted state quantity of the tank 10 at the second time point T2 and the state quantity of the liquefied gas flowing into the tank 10. As a result, even if liquefied gas flows into the tank 10 between the second time point T2 and the third time point T3, the state of the liquefied gas in the tank 10 can be predicted.

[0068] (6) The liquefied gas state prediction system 60 in the tank 10 according to the sixth embodiment is a liquefied gas state prediction system 60 in the tank 10 that stores the liquefied gas, comprising: a liquefied gas state quantity acquisition unit 71 that acquires the state quantity of the liquefied gas in the tank 10 at a first time point T1; a tank information acquisition unit 72 that acquires information about the tank 10 necessary for predicting the state of the liquefied gas in the tank 10; a liquefied gas consumption information acquisition unit 73 that acquires information about the amount of liquefied gas consumed in the tank 10 by a combustion device 9 that uses the liquefied gas as fuel between the first time point T1 and a second time point T2 that is later than the first time point T1; and information about the amount of liquefied gas consumed in the tank 10 by a combustion device 9 that uses the liquefied gas as fuel between the first time point T1 and the second time point T2. The system includes a boil-off gas consumption plan acquisition unit 74 that acquires information regarding the consumption plan of boil-off gas generated by the evaporation of the liquefied gas, a liquefied gas state quantity prediction unit 75 that predicts the predicted state quantity of the liquefied gas in the tank 10 at the second time point T2 based on the state quantity of the liquefied gas acquired by the liquefied gas state quantity acquisition unit 71, information regarding the tank 10 acquired by the tank information acquisition unit 72, information regarding the consumption amount of the liquefied gas acquired by the liquefied gas consumption amount information acquisition unit 73, and information regarding the boil-off gas consumption plan acquired by the boil-off gas consumption plan acquisition unit 74, and an information output unit 78 that outputs to the outside the predicted state quantity of the liquefied gas in the tank 10 at the second time point T2 and information regarding the boil-off gas consumption plan. This makes it possible to predict the state of the liquefied gas inside tank 10. [Explanation of symbols]

[0069] 1...Ship 2...Hull 2a...Bow 4...Superstructure 5A,5B...Side 6...Bottom 7...Upper deck 8...Cargo loading compartment 9...Combustion device 10...Tank 60...State prediction system 61...CPU 62...ROM 63...RAM 64...Storage 65...Signal transmission / reception module 71...Liquefied gas state quantity acquisition unit 72...Tank information acquisition unit 73...Liquefied gas consumption information acquisition unit 74...Boil-off gas consumption plan acquisition unit 75...Liquefied gas state quantity prediction unit 76...Learning unit 77...Information storage unit 78...Information output unit A1,A2...State FA...Bow / stern direction S10...Method for predicting the state of liquefied gas in a tank S10A...First method for predicting the state of liquefied gas S10B...Second method for predicting the state of liquefied gas S11...Step to acquire the state quantity of liquefied gas S12...Step to acquire information about the tank S13...Step to obtain information on the consumption of liquefied gas in the tank S14...Step to obtain information on the management conditions for the state quantities in the tank S15...Step to obtain information on the boil-off gas consumption plan S16...Step to predict the predicted state quantities of liquefied gas in the tank S17...Step to determine whether the management conditions are met S18...Step to output the information externally S19...Step to perform learning S20...Step to update the information on the boil-off gas consumption plan S21...Step to obtain the state quantities of liquefied gas S22...Step to obtain the state quantities of liquefied gas flowing into the tank S23...Step to predict the state quantities of liquefied gas in the tank S24...Step to output the prediction results externally T0...Start of use T1...First time point T2...Second time point T3...Third time point

Claims

1. A method for predicting the state of liquefied natural gas (LNG) in a tank storing LNG, the method being used to predict the state of LNG in the tank. A step of obtaining the state quantity of the LNG, which is the composition of the LNG in liquid state in the tank at a first point in time, The steps include: obtaining information about the tank necessary for predicting the state of the LNG in the tank; A step of obtaining information regarding the amount of LNG consumed in the tank by a combustion device using LNG as fuel, between the first time point and a second time point that is after the first time point; The steps include obtaining information regarding a consumption plan for boil-off gas generated by the evaporation of LNG in the tank between the first and second time points, which allows the composition of the liquid LNG in the tank to be maintained at a composition usable as fuel for the combustion device, A step of predicting the predicted state amount of the LNG, which is the predicted composition of the LNG in liquid state in the tank at the second time point, based on the state amount of the LNG obtained in the step of obtaining the state amount of the LNG, the information about the tank obtained in the step of obtaining the information about the tank, the information about the consumption of the LNG obtained in the step of obtaining the information about the consumption plan of the boil-off gas, and the information about the boil-off gas consumption plan obtained in the step of obtaining the information about the consumption plan of the boil-off gas. The step includes outputting to the outside information regarding the predicted state quantity of the LNG in the tank at the second time point, and the consumption plan for the boil-off gas. A method for predicting the state of liquefied gas inside a tank.

2. The step further includes updating information regarding the boil-off gas consumption plan based on the predicted state amounts of the LNG in the tank predicted in the step of predicting the predicted state amounts of the LNG in the tank, In the step of outputting to the outside the predicted state quantity of the LNG in the tank at the second time point and information regarding the boil-off gas consumption plan, the information regarding the boil-off gas consumption plan updated in the step of updating the information regarding the boil-off gas consumption plan is output to the outside. A method for predicting the state of liquefied gas in a tank according to claim 1.

3. The steps include: obtaining information regarding the management conditions of the state quantities in the tank; A step to determine whether the predicted state quantity of the LNG in the tank at the second time point, predicted in the step of predicting the predicted state quantity of the LNG, satisfies the state quantity management conditions obtained in the step of obtaining information on the state quantity management conditions, If the predicted state quantity of the LNG in the tank at the second time point satisfies the state quantity management conditions, the step of outputting to the outside the predicted state quantity of the LNG in the tank at the second time point and information regarding the boil-off gas consumption plan is performed. A method for predicting the state of liquefied gas in a tank according to claim 1 or 2.

4. The procedure further comprises a step of learning based on the predicted state quantities of the LNG in the tank at the second time point, which were predicted in the step of predicting the predicted state quantities of the LNG, and the actual state quantities of the LNG in the tank at the second time point. In the step of predicting the predicted state quantities of the LNG in the tank at the second time point, the predicted state quantities of the LNG are corrected based on the learning results in the learning step. A method for predicting the state of liquefied gas in a tank according to claim 1 or 2.

5. A step of obtaining the state amount of the LNG flowing into the tank between the second time point and a third time point that is after the second time point, The step further includes predicting the state amount of LNG in the tank in a state where the LNG in the tank at the second time point and the LNG that flows into the tank between the second and third time points are mixed, based on the predicted state amount of LNG in the tank at the second time point predicted in the step of predicting the predicted state amount of LNG and the state amount of LNG flowing into the tank obtained in the step of obtaining the state amount of LNG flowing into the tank. A method for predicting the state of liquefied gas in a tank according to claim 1 or 2.

6. A system for predicting the state of liquefied natural gas (LNG) in a tank that stores LNG, A liquefied gas state quantity acquisition unit acquires the state quantity of the LNG, which is the composition of the LNG in liquid state in the tank at a first point in time, A tank information acquisition unit that acquires information about the tank necessary for predicting the state of the LNG in the tank, A liquefied gas consumption information acquisition unit acquires information regarding the amount of LNG consumed in the tank by a combustion device using LNG as fuel, between the first time point and a second time point that is after the first time point. A boil-off gas consumption plan acquisition unit acquires information regarding a boil-off gas consumption plan that is capable of maintaining the composition of the liquid LNG in the tank at a composition that can be used as fuel for the combustion device, between the first time point and the second time point, the boil-off gas consumption plan being acquired at a time point that can maintain the composition of the liquid LNG in the tank at a composition that can be used as fuel for the combustion device. A liquefied gas state quantity prediction unit predicts the predicted state quantity of the LNG, which is the predicted composition of the LNG in liquid state in the tank at the second time point, based on the state quantity of the LNG acquired by the liquefied gas state quantity acquisition unit, information about the tank acquired by the tank information acquisition unit, information about the consumption of the LNG acquired by the liquefied gas consumption information acquisition unit, and information about the consumption plan of the boil-off gas acquired by the boil-off gas consumption plan acquisition unit. Includes an information output unit that outputs to the outside information regarding the predicted state quantity of the LNG in the tank at the second time point and the consumption plan for the boil-off gas. A system for predicting the state of liquefied gas inside a tank.

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