Liquefied carbon dioxide storage tank system and control method of liquefied carbon dioxide storage tank system

Abstract

A liquefied carbon dioxide storage tank system is provided with: a storage tank for storing liquefied carbon dioxide; the circulating pipeline is used for pumping liquefied carbon dioxide in the storage tank out of the storage tank and returning the liquefied carbon dioxide to a gas phase part in the storage tank; a cooling device provided midway along the circulation line and capable of cooling the liquefied carbon dioxide; the pressure sensor is used for detecting the pressure in the storage tank; a temperature sensor that detects the temperature of the cooled liquefied carbon dioxide; and a control device for controlling the operation of the cooling device. The control device comprises: a first control unit that adjusts the cooling capacity of the liquefied carbon dioxide in the cooling device on the basis of the pressure in the tank detected by the pressure sensor; and a second control unit that reduces the cooling capacity of the liquefied carbon dioxide in the cooling device on the basis of the temperature of the liquefied carbon dioxide detected by the temperature sensor.

Description

Technical Field

[0001] The present invention relates to a liquefied carbon dioxide storage tank system and a control method for the liquefied carbon dioxide storage tank system.

[0002] This application claims priority based on patent application No. 2023-054611 filed in Japan on March 30, 2023, and incorporates the contents thereof herein. Background Art

[0003] In a tank storing liquefied gas, heat input from the outside causes the stored liquefied gas to vaporize, generating so-called boil-off gas. The generation of boil-off gas increases the pressure within the tank. Therefore, for example, Patent Document 1 discloses a structure in which liquefied gas drawn from a tank storing liquefied gas is subcooled and the cooled liquefied gas is injected into the tank.

[0004] Previous technical literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-163804 Summary of the Invention

[0007] Technical issues to be solved by the invention

[0008] When liquefied carbon dioxide is stored in a tank, it may freeze and form dry ice for the following reasons. Specifically, if the structure disclosed in Patent Document 1 is applied to a tank storing liquefied carbon dioxide, when the liquefied carbon dioxide is sprayed into the tank, the pressure of the liquefied carbon dioxide at the tip of the spray nozzle will be a pressure corresponding to the operating pressure of the tank.

[0009] The triple point pressure (triple point pressure) of liquefied carbon dioxide, where its gas, liquid, and solid phases coexist, is higher than that of liquefied natural gas (LNG) or liquefied petroleum gas (LPG). On the other hand, to reduce tank manufacturing costs, the design pressure of the tank must be kept as low as possible. Consequently, the difference between the tank operating pressure and the triple point pressure during liquefied carbon dioxide operation is smaller than for LNG or LPG. As a result, depending on the tank operating pressure and the temperature of the sprayed liquefied carbon dioxide, the pressure and temperature of the liquefied carbon dioxide at the tip of the spray nozzle can approach the triple point, potentially causing the liquefied carbon dioxide to freeze and form dry ice. The formation of dry ice can obstruct the flow of the liquefied carbon dioxide and affect tank operation.

[0010] The present invention has been made to solve the above-mentioned problems, and its object is to provide a liquefied carbon dioxide storage tank system and a control method for the liquefied carbon dioxide storage tank system that can suppress the generation of dry ice and the generation of boil-off gas, thereby preventing an excessive increase in the pressure within the tank.

[0011] Means for solving technical problems

[0012] In order to solve the above-mentioned problems, the liquefied carbon dioxide storage tank system involved in the present invention includes a storage tank, a circulation pipeline, a cooling device, a pressure sensor, a temperature sensor and a control device. The storage tank stores liquefied carbon dioxide. The circulation pipeline extracts the liquefied carbon dioxide in the storage tank to the outside of the storage tank and returns it to the gas phase part in the storage tank. The cooling device is arranged in the middle of the circulation pipeline and can cool the liquefied carbon dioxide. The pressure sensor detects the pressure in the storage tank. The temperature sensor detects the temperature of the liquefied carbon dioxide cooled by the cooling device. The control device controls the operation of the cooling device. The control device includes a first control unit and a second control unit. The first control unit adjusts the cooling capacity of the liquefied carbon dioxide in the cooling device according to the pressure in the storage tank detected by the pressure sensor. The second control unit reduces the cooling capacity of the liquefied carbon dioxide in the cooling device according to the temperature of the liquefied carbon dioxide detected by the temperature sensor.

[0013] A control method for a liquefied carbon dioxide storage tank system according to the present invention controls the liquefied carbon dioxide storage tank system. The liquefied carbon dioxide storage tank system includes a storage tank, a circulation line, a cooling device, a pressure sensor, and a temperature sensor. The storage tank stores liquefied carbon dioxide. The circulation line extracts the liquefied carbon dioxide from the storage tank and returns it to the gas phase within the tank. The cooling device is disposed midway in the circulation line. The cooling device is capable of cooling the liquefied carbon dioxide. The pressure sensor detects the pressure within the storage tank. The temperature sensor detects the temperature of the liquefied carbon dioxide cooled by the cooling device. The control method for the liquefied carbon dioxide storage tank system includes: adjusting the cooling capacity of the liquefied carbon dioxide in the cooling device; and reducing the cooling capacity of the liquefied carbon dioxide in the cooling device. In the step of adjusting the cooling capacity of the liquefied carbon dioxide in the cooling device, the cooling capacity of the liquefied carbon dioxide in the cooling device is adjusted based on the pressure within the storage tank detected by the pressure sensor. In the step of reducing the cooling capacity of the liquefied carbon dioxide in the cooling device, the cooling capacity of the liquefied carbon dioxide in the cooling device is reduced based on the temperature of the liquefied carbon dioxide detected by the temperature sensor.

[0014] Effects of the Invention

[0015] According to the liquefied carbon dioxide storage tank system and the control method of the liquefied carbon dioxide storage tank system of the present invention, the generation of dry ice and the generation of boil-off gas are suppressed, thereby suppressing an excessive increase in the pressure in the tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a cross-sectional view showing the structure of a liquefied carbon dioxide storage tank system according to an embodiment of the present invention.

[0017] Figure 2 It is a diagram showing the configuration of a cooling device included in a liquefied carbon dioxide storage tank system according to an embodiment of the present invention.

[0018] Figure 3 This is a block diagram showing the functional configuration of a control device according to an embodiment of the present invention.

[0019] Figure 4 This is a flowchart showing the flow of a control method for a liquefied carbon dioxide storage tank system according to an embodiment of the present invention.

[0020] Figure 5 This is a diagram showing a state in which liquefied carbon dioxide is not supercooled in the liquefied carbon dioxide storage tank system according to the embodiment of the present invention.

[0021] Figure 6 This is a diagram showing a state in which liquefied carbon dioxide is supercooled and returned to the gas phase portion in the tank in the liquefied carbon dioxide tank system according to the embodiment of the present invention. DETAILED DESCRIPTION

[0022] Below, reference Figures 1 to 6 , a liquefied carbon dioxide storage tank system and a control method of the liquefied carbon dioxide storage tank system according to an embodiment of the present invention will be described.

[0023] (Overall structure of liquefied carbon dioxide storage tank system)

[0024] like Figure 1 As shown, the liquefied carbon dioxide tank system 1 of this embodiment includes a container 5 , a tank 3 , and a cooling device 2 .

[0025] The container 5 is in the shape of a hollow rectangular parallelepiped. The container 5 illustrated in this embodiment is an ISO standard container, a so-called 20-foot container or a 40-foot container. The container 5 can be mounted on a cargo rack of a vehicle such as a trailer (not shown). The container 5 includes a frame 50 having a lower frame 51, a plurality of pillars 52, and an upper frame 54. When viewed from the vertical direction Dv, the lower frame 51 is formed into a rectangular frame shape with a first direction Da intersecting the vertical direction Dv as its long side and a second direction Dw intersecting the vertical direction Dv and the first direction Da as its short side. The plurality of pillars 52 are provided at at least four corners of the lower frame 51. In addition to being provided at the four corners of the lower frame 51, the pillars 52 can also be provided at other locations. Each pillar 52 rises from the lower frame 51 above the vertical direction Dv. The upper frame 54 is provided on the plurality of pillars 52. Similar to the lower frame 51 , the upper frame 54 is formed into a rectangular frame having its long sides in the first direction Da and its short sides in the second direction Dw when viewed from the vertical direction Dv. The upper frame 54 connects the upper ends of the plurality of pillars 52 .

[0026] In addition, although the container 5 includes a frame 50, its structure can be changed as appropriate. Furthermore, the container 5 is not limited to the structure including the frame 50, and may also be a hollow box shape.

[0027] The tank 3 is installed in the frame 50 of the container 5. The tank 3 includes a tank body 31, an outer shell 32, an insulating portion 33, an air supply and exhaust pipe 35, a pressure detection pipe 36, and a circulation pipe 40.

[0028] The tank body 31 is, for example, in a cylindrical shape extending in the first direction Da within the frame 50. The tank body 31 includes a cylindrical portion 31a and a mirror plate portion 31b. The cylindrical portion 31a extends with the first direction Da as the longitudinal direction Dx. In this embodiment, the cylindrical portion 31a is formed into a cylindrical shape, and the cross-sectional shape perpendicular to its longitudinal direction Dx is circular. The mirror plate portions 31b are respectively arranged at both ends of the cylindrical portion 31a in the longitudinal direction Dx. Each mirror plate portion 31b is spherical and closes the openings at both ends of the cylindrical portion 31a in the longitudinal direction Dx. The tank body 31 is capable of storing liquefied carbon dioxide L therein. The liquefied carbon dioxide L is stored in the lower portion of the tank body 31. The gas phase portion V in the upper portion of the tank body 31 stores distilled gas generated by gasifying the liquefied carbon dioxide L.

[0029] The outer shell 32 is provided within the frame 50 so as to cover the entire tank body 31 from the outside. The outer shell 32 includes a cylindrical shell portion 32a and a spherical shell portion 32b. The cylindrical shell portion 32a extends with the first direction Da as the longitudinal direction Dx. In this embodiment, the cylindrical shell portion 32a is formed into a cylindrical shape, and the cross-sectional shape perpendicular to its longitudinal direction Dx is circular. The cylindrical shell portion 32a is provided radially outwardly of the cylindrical shell portion 32a of the tank body 31 at a distance. The spherical shell portions 32b are respectively arranged at both ends of the cylindrical shell portion 32a in the longitudinal direction Dx. Each spherical shell portion 32b is provided radially outwardly of the mirror plate portion 31b at a distance. Each spherical shell portion 32b closes the openings at both ends of the cylindrical shell portion 32a in the longitudinal direction Dx. In addition, the tank body 31 and the outer shell 32 are not limited to cylindrical shapes, and may also be other shapes such as spherical and square. The outer shell 32 is supported on the lower frame 51 of the container 5, for example, via a plurality of legs 34. The mounting structure of the outer shell 32 on the outer frame 50 is not limited to the above. For example, the outer shell 32 is not limited to the legs 34 and may be supported on the pillars 52 or the upper frame 54 via appropriate brackets.

[0030] The insulating portion 33 is composed of, for example, an insulating material that fills the space between the outer circumference of the tank body 31 and the inner circumference of the outer shell 32. Such insulating portion 33 can be formed of, for example, expanded polystyrene, expanded polyurethane, or the like. Furthermore, the insulating portion 33 can be configured as a so-called vacuum insulation structure, which seals the space between the outer circumference of the tank body 31 and the inner circumference of the outer shell 32 to a negative pressure below a predetermined pressure. The insulating portion 33 suppresses heat input from outside the tank body 31.

[0031] The supply and exhaust pipe 35 is used to supply and exhaust liquefied carbon dioxide L within the tank body 31. One end 35a of the supply and exhaust pipe 35 is disposed at the bottom of the tank body 31 so as to communicate with the interior of the tank body 31. For example, the one end 35a of the supply and exhaust pipe 35 extends from the outside of the tank body 31 through the bottom of the tank body 31 and into the tank body 31. If the liquefied carbon dioxide L can be extracted from the bottom of the tank body 31, the layout of the supply and exhaust pipe 35 is a matter of design. For example, the supply and exhaust pipe 35 is not limited to the bottom of the tank body 31 and can also extend through other locations of the tank body 31. The other end 35b of the supply and exhaust pipe 35 is connected to a connecting member 120 supported by the frame 50 of the container 5 via an appropriate bracket. The connecting member 120 is exposed to the outside of the container 5. One end of a connection pipe (not shown) can be connected to the connecting member 120 from the outside of the container 5. The other end of the connecting pipe can be connected to an external tank (not shown) installed on a liquefied carbon dioxide transport ship, a liquefied carbon dioxide supply facility on land, or a tank truck capable of carrying liquefied carbon dioxide. In addition, an on-off valve 35V is provided midway in the water supply and drainage pipe 35.

[0032] The air supply and exhaust line 35 is used to load liquefied carbon dioxide L supplied from an external tank through a connecting pipe (not shown) into the tank body 31. The air supply and exhaust line 35 is also used to discharge liquefied carbon dioxide L in the tank body 31 to an external tank.

[0033] The pressure detection line 36 is used to detect the pressure within the tank body 31. One end 36a of the pressure detection line 36 is connected to the bottom of the tank body 31. The other end 36b of the pressure detection line 36 is connected to the top of the tank body 31. A pressure sensor 37 is connected to the upper portion of the pressure detection line 36 via a branch pipe 36s. Furthermore, a liquid level gauge 38 is provided midway along the pressure detection line 36.

[0034] An on-off valve 39V is provided at one end 36a of the pressure detection line 36, relative to the liquid level gauge 38. An on-off valve 39W is provided at the other end 36b of the pressure detection line 36, relative to the pressure sensor 37 and the liquid level gauge 38. The arrangement of the pressure sensor 37 and the liquid level gauge 38 shown here is merely an example, and the arrangement of the pressure sensor 37 and the liquid level gauge 38 is not limited to the above arrangement. For example, the pressure sensor 37 may be installed at the top of the tank body 31 via a directly connected pipe.

[0035] The pressure sensor 37 detects the pressure of the gas phase V within the tank body 31. When the on-off valves 39V and 39W are open, the pressure differential between the liquid phase and the gas phase within the tank body 31 acts on the liquid level gauge 38 via the pressure detection line 36. The liquid level gauge 38 detects the liquid level within the tank body 31 based on the pressure differential within the tank body 31. The on-off valves 39V and 39W are always open while the liquefied carbon dioxide L is stored in the tank body 31, except when the liquefied carbon dioxide L is being loaded or unloaded from the tank body 31 via the air supply and exhaust line 35.

[0036] The circulation line 40 is used to extract the liquefied carbon dioxide L from the tank body 31 and return it to the gas phase V within the tank body 31. One end 40a of the circulation line 40 is connected to the bottom of the tank body 31. The other end 40b of the circulation line 40 is connected to the top of the tank body 31. The other end 40b of the circulation line 40 passes through the top of the tank body 31 from the outside of the tank body 31 and is connected to the injection unit 45 within the tank body 31. The injection unit 45 is arranged in the upper part of the tank body 31. The injection unit 45 injects the liquefied carbon dioxide L returned to the tank body 31 through the circulation line 40 into the gas phase V in the upper part of the tank body 31. Note that the arrangement of the circulation line 40 is a design matter, and the location where the circulation line 40 passes through the tank body 31 is not limited to the top of the tank body 31 but may be located elsewhere.

[0037] The cooling device 2, described later, is provided midway through the circulation line 40. The circulation line 40 includes a first circulation line portion 40A and a second circulation line portion 40B. The first circulation line portion 40A is located on one side (the side connected to the bottom of the tank body 31) across from the cooling device 2. A portion of the first circulation line portion 40A is shared with the air supply and exhaust line 35. The second circulation line portion 40B is located on the other side (the side connected to the top of the tank body 31) across from the cooling device 2. An on-off valve 41V and a pump 42 are provided midway through the first circulation line portion 40A. An on-off valve 41W is provided midway through the second circulation line portion 40B.

[0038] Figure 2 It is a diagram showing the configuration of a cooling device included in a liquefied carbon dioxide storage tank system according to an embodiment of the present invention.

[0039] The cooling device 2 supercools (cools) the liquefied carbon dioxide L fed from the bottom of the tank body 31 through the circulation line 40. Figure 2 As shown, the cooling device 2 includes a compressor 21, a condenser 22, a fan 23, an expansion valve 24, a heat exchanger 25, and a control device 60. The compressor 21, condenser 22, expansion valve 24, and heat exchanger 25 are arranged in a refrigerant circuit 26. The compressor 21 compresses the refrigerant flowing through the refrigerant piping that constitutes the refrigerant circuit 26. The condenser 22 performs heat exchange between the air within the container 5 and the refrigerant flowing through the refrigerant piping. The fan 23 draws in air from the atmosphere outside the accumulator body 31 and blows it toward the condenser 22. The expansion valve 24 expands the refrigerant that has passed through the condenser 22. The heat exchanger 25 performs heat exchange between the refrigerant expanded by the condenser 22 and flowing through the refrigerant piping and the liquefied carbon dioxide L flowing through the circulation line 40. The heat exchanger 25 cools the liquefied carbon dioxide L through heat exchange with the refrigerant, subcooling it. Alternatively, other heat sources may be used in place of the fan 23.

[0040] A temperature sensor 28 is provided on the outlet side of the cooling device 2. The temperature sensor 28 is provided in the circulation line second portion 40B of the circulation line 40. The temperature sensor 28 detects the temperature of the liquefied carbon dioxide L supercooled by the cooling device 2.

[0041] The control device 60 mainly controls the operation of the cooling device 2. Figure 1As shown, one end of a power line 100 is connected to the control device 60. The other end of the power line 100 is connected to a power connection unit 101. The power connection unit 101 illustrated in this embodiment is supported by the support column 52. The power connection unit 101 can be connected to one end of a power supply wiring (not shown) from outside the liquefied carbon dioxide storage tank system 1. The other end of the power supply wiring (not shown) is connected to the external power source of the liquefied carbon dioxide storage tank system 1. Examples of the external power source for the liquefied carbon dioxide storage tank system 1 include a power supply device installed on a vehicle carrying the container 5 or a ship transporting the liquefied carbon dioxide L stored in the storage tank body 31. Examples of the power supply device include a generator including an AC generator, a battery, and the like. Furthermore, the external power source for the liquefied carbon dioxide storage tank system 1 includes a commercial power source supplied from a land-based liquefied carbon dioxide supply facility. The control device 60 is driven by the power supplied from such an external power source of the liquefied carbon dioxide storage tank system 1. The power connection unit 101 is not limited to a structure supported by the support column 52. For example, it may be supported on the outer surface of the housing of the cooling device 2 or the like.

[0042] Figure 3 This is a block diagram showing the functional configuration of a control device according to an embodiment of the present invention.

[0043] The control device 60 can be constructed using hardware such as a computer such as a microcomputer, a CPU (Central Processing Unit), and peripheral circuits or peripheral devices of the computer. Figure 3 As shown, the control device 60 includes a signal input unit 70 , a first control unit 71 , a second control unit 72 , and an output unit 75 , and is a functional structure composed of a combination of hardware and software such as a program executed by a computer.

[0044] The signal input unit 70 receives detection signals of the pressure in the tank body 31 detected by the pressure sensor 37 , the liquid level in the tank body 31 detected by the liquid level gauge 38 , and the temperature of the liquefied carbon dioxide L supercooled by the cooling device 2 detected by the temperature sensor 28 .

[0045] The first control unit 71 adjusts the supercooling capacity (cooling capacity) of the liquefied carbon dioxide L in the cooling device 2 based on the pressure in the tank body 31 detected by the pressure sensor 37 .

[0046] When the pressure in the tank body 31 detected by the pressure sensor 37 becomes equal to or greater than a predetermined first threshold value, the first control unit 71 increases the supercooling capacity of the liquefied carbon dioxide L in the cooling device 2. In the present embodiment, when the pressure in the tank body 31 detected by the pressure sensor 37 becomes equal to or greater than the predetermined first threshold value, the liquefied carbon dioxide L is supercooled starting from a state in which the liquefied carbon dioxide L is not being supercooled in the cooling device 2.

[0047] When subcooling the liquefied carbon dioxide L in the cooling device 2 begins, the first control unit 71 operates the compressor 21 and the fan 23. This causes the refrigerant to circulate within the refrigerant circuit. Furthermore, when subcooling the liquefied carbon dioxide L begins, the first control unit 71 opens the on-off valves 41V and 41W and operates the pump 42. This causes the liquefied carbon dioxide L at the bottom of the tank body 31 to be drawn from one end 40a of the circulation line 40 and fed into the cooling device 2. The liquefied carbon dioxide L fed into the cooling device 2 is subcooled by heat exchange with the refrigerant in the heat exchanger 25 and fed to the other end 40b of the circulation line 40. The liquefied carbon dioxide L fed to the other end 40b of the circulation line 40 is injected from the injection unit 45 into the gas phase V within the tank body 31. The injection of the cooled liquefied carbon dioxide L reliquefies the boil-off gas contained in the gas phase V. This reliquefaction of the boil-off gas reduces the pressure in the gas phase V within the tank body 31.

[0048] Furthermore, when the pressure within the tank body 31 detected by the pressure sensor 37 falls below a predetermined second threshold, the first control unit 71 reduces the subcooling capacity of the liquefied carbon dioxide L in the cooling device 2. Here, the second threshold is lower than the first threshold. In this embodiment, the first control unit 71 stops subcooling the liquefied carbon dioxide L when the pressure within the tank body 31 detected by the pressure sensor 37 falls below the predetermined second threshold. To stop subcooling the liquefied carbon dioxide L in the cooling device 2, the first control unit 71 stops the compressor 21 and the fan 23. Furthermore, the first control unit 71 stops the pump 42 and closes the on-off valves 41V and 41W.

[0049] While the cooling device 2 is subcooling the liquefied carbon dioxide L, the second control unit 72 reduces the subcooling capacity of the liquefied carbon dioxide L in the cooling device 2 based on the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28. The second control unit 72 reduces the subcooling capacity (cooling capacity) of the liquefied carbon dioxide L in the cooling device 2 based on the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28 and the pressure within the tank body 31 detected by the pressure sensor 37. In this embodiment, the second control unit 72 determines whether the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28 and the pressure within the tank body 31 detected by the pressure sensor 37 are close to the triple point based on a predetermined map (hereinafter referred to as the predetermined map) that compares the pressure of the gas phase portion V with the temperature of the liquefied carbon dioxide L at the outlet of the cooling device 2 and the state of carbon dioxide (including the triple point). If it is determined that the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28 and the pressure within the tank body 31 detected by the pressure sensor 37 are close to the triple point, the second control unit 72 stops subcooling the liquefied carbon dioxide L in the cooling device 2. Thus, the second control unit 72 suppresses the generation of dry ice from the liquefied carbon dioxide L that has returned from the injection unit 45 provided at the other end 40 b of the circulation line 40 to the gas phase V in the tank body 31 .

[0050] When stopping the subcooling of the liquefied carbon dioxide L in the cooling device 2, the second control unit 72 stops the compressor 21 and the fan 23. Furthermore, the first control unit 71 stops the pump 42 and closes the on-off valves 41V and 41W.

[0051] The output unit 75 outputs control signals to the compressor 21 , the fan 23 , the on-off valves 41V and 41W, and the pump 42 based on the control of the first control unit 71 and the second control unit 72 .

[0052] (Steps of a control method for a liquefied carbon dioxide storage tank system)

[0053] Figure 4 This is a flowchart showing the steps of a method for controlling a liquefied carbon dioxide storage tank system according to an embodiment of the present invention. Figure 5 This is a diagram showing a state in which liquefied carbon dioxide is not supercooled in the liquefied carbon dioxide storage tank system according to the embodiment of the present invention. Figure 6 This is a diagram showing a state in which liquefied carbon dioxide is supercooled and returned to the gas phase portion in the tank in the liquefied carbon dioxide tank system according to the embodiment of the present invention.

[0054] like Figure 4As shown, a control method S10 for a liquefied carbon dioxide storage tank system according to an embodiment of the present invention includes: S11, a step of obtaining the pressure within the tank body 31; S12, a step of determining whether the pressure within the tank body 31 is greater than a first threshold; S13, a step of starting supercooling the liquefied carbon dioxide L; S14, a step of obtaining the temperature of the liquefied carbon dioxide L; S15, a step of determining whether the temperature of the liquefied carbon dioxide L is close to the triple point; S16, a step of determining whether the pressure within the tank body 31 is less than a second threshold; and S17, a step of stopping supercooling the liquefied carbon dioxide L. The control method S10 for a liquefied carbon dioxide storage tank system is executed from the time the liquefied carbon dioxide L is loaded into the tank body 31 until the time the liquefied carbon dioxide L is discharged from the tank body 31.

[0055] Normally, such as Figure 5 As shown, after the liquefied carbon dioxide L is loaded into the tank body 31, the on-off valves 41V and 41W of the circulation line 40 are closed. In addition, the pump 42 and the compressor 21 are stopped.

[0056] In step S11 of acquiring the pressure in the tank body 31 , the detection result of the pressure of the gas phase portion V in the tank body 31 detected by the pressure sensor 37 is acquired through the signal input unit 70 of the control device 60 .

[0057] In step S12 of determining whether the pressure in the tank body 31 is equal to or greater than the first threshold, the first control unit 71 determines whether the pressure in the tank body 31 acquired in step S11 is equal to or greater than the preset first threshold.

[0058] As a result of this determination, if the pressure in the tank body 31 is lower than the first threshold value (No in step S12 ), the process returns to step S11 .

[0059] Then, when the pressure in the tank body 31 is equal to or higher than the first threshold value (step S12 , “Yes”), the process proceeds to step S13 .

[0060] In step S13 of starting to supercool the liquefied carbon dioxide L, the first control unit 71 starts to supercool the liquefied carbon dioxide L. Figure 6 As shown, the first control unit 71 operates the compressor 21 and the fan 23. This causes the refrigerant to circulate within the refrigerant circuit. Furthermore, the first control unit 71 opens the on-off valves 41V and 41W and operates the pump 42. This causes the liquefied carbon dioxide L at the bottom of the tank body 31 to be drawn from one end 40a of the circulation line 40 and fed into the cooling device 2. The liquefied carbon dioxide L fed into the cooling device 2 is subcooled by heat exchange with the refrigerant in the heat exchanger 25 and then fed to the other end 40b of the circulation line 40.

[0061] In step S14 of acquiring the temperature of the liquefied carbon dioxide L, the temperature of the liquefied carbon dioxide L supercooled by the cooling device 2 detected by the temperature sensor 28 is acquired.

[0062] In step S15 of determining whether the temperature of the liquefied carbon dioxide L is close to the triple point, the second control unit 72 determines whether the liquefied carbon dioxide L returned from the injection unit 45 to the gas phase portion V in the tank body 31 is close to the triple point based on the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28 and the pressure in the tank body 31 obtained in step S11, and with reference to a predetermined map.

[0063] As a result of this determination, if it is not determined that the supercooled liquefied carbon dioxide L is close to the triple point (“No” in step S15 ), the process proceeds to step S16 .

[0064] If it is determined that the supercooled liquefied carbon dioxide L is approaching the triple point ("YES" in step S15), the process proceeds to step S17. In this case, step S17 of stopping supercooling the liquefied carbon dioxide L is executed as a step of reducing the supercooling capacity of the liquefied carbon dioxide L in the cooling device 2 based on the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28.

[0065] In this case, the second control unit 72 stops subcooling the liquefied carbon dioxide L in the cooling device 2 based on the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28 and the pressure within the tank body 31 detected by the pressure sensor 37, according to a pre-set map. The second control unit 72 stops the compressor 21 and the fan 23. As a result, the second control unit 72 stops returning the subcooled liquefied carbon dioxide from the injection unit 45 provided at the other end 40b of the circulation line 40 to the gas phase V within the tank body 31.

[0066] In step S16 of determining whether the pressure in the tank body 31 is equal to or lower than the second threshold, the first control unit 71 determines whether the pressure in the tank body 31 detected by the pressure sensor 37 is equal to or lower than the preset second threshold.

[0067] As a result of this determination, if the pressure in the tank body 31 is equal to or higher than the second threshold value (“No” in step S16 ), the process returns to step S14 .

[0068] Then, when the pressure in the tank body 31 is equal to or lower than the second threshold value (YES in step S16 ), the process proceeds to step S17 .

[0069] When step S17 is executed after step S16, step S17, which stops subcooling the liquefied carbon dioxide L, is executed as step S16, which adjusts the subcooling capacity of the liquefied carbon dioxide L in the cooling device 2 based on the pressure within the tank body 31 detected by the pressure sensor 37. At this time, the first control unit 71 stops the compressor 21 and the fan 23. Furthermore, the first control unit 71 stops the pump 42 and closes the on-off valves 41V and 41W.

[0070] (Effect)

[0071] In the liquefied carbon dioxide storage tank system and control method for the liquefied carbon dioxide storage tank system of the above-described embodiment, the liquefied carbon dioxide L within the tank body 31 vaporizes due to external heat input, generating so-called boil-off gas (carbon dioxide gas). This generated boil-off gas is stored in the upper gas phase V within the tank body 31. To reliquefy the boil-off gas within the tank body 31, it is necessary to cool the boil-off gas. Therefore, in the above-described embodiment, the liquefied carbon dioxide L within the tank body 31 is drawn out of the tank body 31 via a circulation line 40 and then subcooled by a cooling device 2 provided midway along the circulation line 40. The subcooled liquefied carbon dioxide L then returns to the gas phase V within the tank body 31 via the circulation line 40. The subcooled liquefied carbon dioxide L cools the boil-off gas within the gas phase V within the tank body 31, causing it to reliquefy. This suppresses the generation of boil-off gas within the tank body 31.

[0072] The operation of the cooling device 2 of the above-described embodiment is controlled by the control device 60. The pressure in the tank body 31 is detected by the pressure sensor 37. If boil-off gas is generated in the tank body 31, the pressure in the tank body 31 rises. The first control unit 71 of the control device 60 adjusts the supercooling capacity of the liquefied carbon dioxide L in the cooling device 2 based on the pressure in the tank body 31 detected by the pressure sensor 37. For example, when boil-off gas is generated in the tank body 31 and the pressure in the tank body 31 rises, the supercooling capacity of the liquefied carbon dioxide L in the cooling device 2 can be increased by the first control unit 71. Thus, by returning the supercooled liquefied carbon dioxide L to the gas phase portion V in the tank body 31, the reliquefaction capacity of the boil-off gas is improved.

[0073] In the above embodiment, the temperature sensor 28 also detects the temperature of the liquefied carbon dioxide L supercooled by the cooling device 2. Furthermore, the second control unit 72 reduces the supercooling capacity of the liquefied carbon dioxide L in the cooling device 2 based on the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28. As a result, when the liquefied carbon dioxide L returns to the gas phase V within the tank body 31 through the circulation line 40, the supercooling of the liquefied carbon dioxide L by the cooling device 2 is suppressed until the temperature at which the liquefied carbon dioxide L solidifies and forms dry ice is reached.

[0074] As a result, the generation of dry ice is suppressed, and the generation of boil-off gas is suppressed, thereby suppressing an excessive increase in the pressure in the tank body 31 .

[0075] In the above embodiment, the supercooling capacity of the liquefied carbon dioxide L in the cooling device 2 is also reduced based on the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28 and the pressure within the tank body 31 detected by the pressure sensor 37. Therefore, the liquefied carbon dioxide L returning to the gas phase V within the tank body 31 through the circulation line 40 is prevented from approaching the triple point pressure. This effectively prevents the liquefied carbon dioxide L from solidifying and forming dry ice.

[0076] In the above embodiment, when the pressure within the tank body 31 detected by the pressure sensor 37 reaches or exceeds a predetermined first threshold value, the supercooling capacity of the liquefied carbon dioxide L in the cooling device 2 is also improved. Thus, when boil-off gas is generated within the tank body 31 and the pressure within the tank body 31 rises to or exceeds the first threshold value, the supercooling capacity of the liquefied carbon dioxide L in the cooling device 2 is improved. Therefore, by returning the supercooled liquefied carbon dioxide L to the gas phase portion V within the tank body 31, the reliquefaction capacity of the boil-off gas is improved.

[0077] Here, improving the supercooling capability of the liquefied carbon dioxide L in the cooling device 2 also includes starting the supercooling of the liquefied carbon dioxide L from a state where the supercooling of the liquefied carbon dioxide L by the cooling device 2 is stopped.

[0078] In the above embodiment, when the subcooled liquefied carbon dioxide L is supplied to the gas phase portion V within the tank body 31, the boil-off gas within the tank body 31 is reliquefied, causing the pressure within the tank body 31 to decrease. Furthermore, when the pressure within the tank body 31 detected by the pressure sensor 37 falls below a predetermined second threshold value, the subcooling capacity of the liquefied carbon dioxide L in the cooling device 2 is reduced. This allows the reliquefaction of the boil-off gas to be stopped.

[0079] In the liquefied carbon dioxide storage tank system 1 of the above-described embodiment, the tank body 31, the circulation line 40, the cooling device 2, the pressure sensor 37, the temperature sensor 28, and the control device 60 are housed in a movable container 5. Thus, in the tank body 31 housed in the movable container 5, the generation of boil-off gas can be suppressed, an excessive increase in pressure within the tank body 31 can be suppressed, and the generation of dry ice can be suppressed.

[0080] In the above embodiment, power is supplied to the cooling device 2 and the control device 60 from outside the liquefied carbon dioxide tank system 1. Consequently, in the liquefied carbon dioxide tank system 1 comprising the tank body 31 housed in the portable container 5, a generator, etc. for driving the cooling device 2 and the control device 60 can be omitted. This ensures ample space within the container 5 for installing the tank 3, and also suppresses the formation of dry ice and boil-off gas during transportation of the liquefied carbon dioxide tank system 1, thereby preventing excessive pressure increases within the tank body 31.

[0081] In the above embodiment, the liquefied carbon dioxide L circulating through the circulation line 40 can be injected into the upper portion of the tank body 31 by the injection unit 45. This allows the boil-off gas in the gas phase V in the tank body 31 to be efficiently reliquefied.

[0082] (Other Implementation Methods)

[0083] While the embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the specific configuration is not limited to the embodiments and includes design changes within the scope of the present invention.

[0084] In the above embodiment, in step S13 of starting supercooling of the liquefied carbon dioxide L, after supercooling of the liquefied carbon dioxide L in the cooling device 2 has started, supercooling of the liquefied carbon dioxide L in the cooling device 2 is stopped based on the pressure within the tank body 31 detected by the pressure sensor 37. However, this is not limiting, and the following may be employed: after supercooling of the liquefied carbon dioxide L in the cooling device 2 has started, the supercooling capacity of the liquefied carbon dioxide L in the cooling device 2 may be increased or decreased based on the pressure within the tank body 31 detected by the pressure sensor 37.

[0085] Furthermore, in the above embodiment, the boil-off gas in the tank body 31 is reliquefied by returning the liquefied carbon dioxide L supercooled by the cooling device 2 to the gas phase V within the tank body 31. However, this is not limiting. For example, if the temperature of the liquefied carbon dioxide L at the bottom of the tank body 31 is sufficiently low and is in a supercooled state or nearly supercooled, the liquefied carbon dioxide L at the bottom of the tank body 31 can be withdrawn from the bottom of the tank body 31 and returned to the gas phase V within the tank body 31. In this case, it is preferable to additionally provide a temperature sensor at the bottom of the tank body 31. The control device 60 detects the temperature of the liquefied carbon dioxide L at the bottom of the tank body 31 using the temperature sensor provided at the bottom of the tank body 31. Based on the detection result of the temperature sensor, the control device 60 withdraws the liquefied carbon dioxide L at the bottom of the tank body 31 and returns it to the gas phase V within the tank body 31.

[0086] Furthermore, in the above embodiment, the liquefied carbon dioxide L supercooled by the cooling device 2 is returned to the gas phase portion V within the tank body 31, but the present invention is not limited to this. If the boil-off gas within the tank body 31 can be reliquefied by returning the liquefied carbon dioxide L cooled by the cooling device 2 to the gas phase portion V within the tank body 31, the liquefied carbon dioxide L can be cooled in the cooling device 2 to prevent supercooling.

[0087] Furthermore, in the above embodiment, the injection unit 45 injects the liquefied carbon dioxide L that has returned to the tank body 31 through the circulation line 40 into the upper gas phase V within the tank body 31. However, this is not limiting. For example, the gas phase V and the liquefied carbon dioxide L that have returned to the tank body 31 through the circulation line 40 may be omitted from injection and may simply flow downward. This lowers the temperature of the surface layer of the liquefied carbon dioxide L, allowing the boil-off gas in the gas phase V to be reliquefied.

[0088] Furthermore, in the above embodiment, the container 5 can be mounted on a cargo bed (not shown) of a vehicle such as a trailer. However, it can also be hoisted by a crane or the like and mounted on a ship or the like. Furthermore, the liquefied carbon dioxide storage tank system 1 can be fixedly installed on a floating structure such as a ship. A configuration is also possible in which the liquefied carbon dioxide storage tank system 1 is not provided with the container 5 when the liquefied carbon dioxide storage tank system 1 is fixedly installed on a floating structure such as a ship.

[0089] <Note>

[0090] The liquefied carbon dioxide tank system 1 and the control method S10 of the liquefied carbon dioxide tank system 1 described in the embodiment can be understood as follows, for example.

[0091] (1) A liquefied carbon dioxide storage tank system 1 according to a first embodiment includes: a storage tank 31 for storing liquefied carbon dioxide L; a circulation line 40 for extracting the liquefied carbon dioxide L in the storage tank 31 to the outside of the storage tank 31 and returning it to the gas phase portion V in the storage tank 31; a cooling device 2 provided in the middle of the circulation line 40 and capable of cooling the liquefied carbon dioxide L; a pressure sensor 37 for detecting the pressure in the storage tank 31; a temperature sensor 28 for detecting the temperature of the liquefied carbon dioxide L cooled by the cooling device 2; and a control device 60 for controlling the operation of the cooling device 2, the control device 60 including: a first control unit 71 for adjusting the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 according to the pressure in the storage tank 31 detected by the pressure sensor 37; and a second control unit 72 for reducing the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 according to the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28.

[0092] In this liquefied carbon dioxide storage tank system 1, the liquefied carbon dioxide L in the tank 31 may sometimes vaporize due to external heat input, generating so-called boil-off gas (carbon dioxide gas). The generated boil-off gas is stored in the upper gas phase V of the tank 31. If the boil-off gas in the tank 31 needs to be reliquefied, it must be cooled. Therefore, the liquefied carbon dioxide L in the tank 31 is pumped out of the tank 31 through a circulation line 40 and cooled by a cooling device 2 located midway in the circulation line 40. When the liquefied carbon dioxide L cooled by the cooling device 2 is returned to the gas phase V in the tank 31 through the circulation line 40, the boil-off gas in the gas phase V in the tank 31 is cooled by the cooled liquefied carbon dioxide L and reliquefied. This suppresses the generation of boil-off gas in the tank 31.

[0093] The operation of the cooling device 2 is controlled by the control device 60. The pressure sensor 37 detects the pressure within the storage tank 31. If boil-off gas is generated within the storage tank 31, the pressure within the storage tank 31 increases. The first control unit 71 adjusts the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 based on the pressure within the storage tank 31 detected by the pressure sensor 37. For example, if boil-off gas is generated within the storage tank 31, the first control unit 71 can increase the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 when the pressure within the storage tank 31 increases. This improves the reliquefaction capacity of the boil-off gas by returning the cooled liquefied carbon dioxide L to the gas phase V within the storage tank 31.

[0094] Furthermore, the temperature sensor 28 detects the temperature of the liquefied carbon dioxide L cooled by the cooling device 2. The second control unit 72 reduces the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 based on the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28. This prevents the cooling of the liquefied carbon dioxide L by the cooling device 2 from reaching a temperature at which the liquefied carbon dioxide L solidifies and forms dry ice, as the liquefied carbon dioxide L returns to the gas phase portion V in the storage tank 31 through the circulation line 40.

[0095] As a result, the generation of dry ice is suppressed, and the generation of boil-off gas is suppressed, thereby suppressing an excessive increase in the pressure in the tank 31 .

[0096] (2) The liquefied carbon dioxide storage tank system 1 involved in the second embodiment is the liquefied carbon dioxide storage tank system 1 of (1), wherein the second control unit 72 reduces the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 based on the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28 and the pressure in the storage tank 31 detected by the pressure sensor 37.

[0097] Thus, the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 is reduced based on the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28 and the pressure in the storage tank 31 detected by the pressure sensor 37, thereby suppressing the liquefied carbon dioxide L returning to the gas phase portion V in the storage tank 31 through the circulation line 40 from approaching the triple point pressure. This effectively prevents the liquefied carbon dioxide L from solidifying and forming dry ice.

[0098] (3) The liquefied carbon dioxide storage tank system 1 according to the third embodiment is the liquefied carbon dioxide storage tank system 1 according to (1) or (2), wherein the first control unit 71 increases the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 when the pressure in the storage tank 31 detected by the pressure sensor 37 becomes equal to or higher than a predetermined first threshold value. Increasing the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 includes cooling the liquefied carbon dioxide L from a state in which the liquefied carbon dioxide L in the cooling device 2 is not cooled.

[0099] Thus, when the pressure in the storage tank 31 detected by the pressure sensor 37 reaches or exceeds a predetermined first threshold value, the cooling capacity for the liquefied carbon dioxide L in the cooling device 2 is increased. Thus, when boil-off gas is generated in the storage tank 31 and the pressure in the storage tank 31 rises and reaches or exceeds the first threshold value, the cooling capacity for the liquefied carbon dioxide L in the cooling device 2 is increased. Thus, by returning the cooled liquefied carbon dioxide L to the gas phase portion V in the storage tank 31, the reliquefaction capacity of the boil-off gas is improved.

[0100] (4) The liquefied carbon dioxide storage tank system 1 according to the fourth embodiment is the liquefied carbon dioxide storage tank system 1 according to (3), wherein the first control unit 71 reduces the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 when the pressure in the storage tank 31 detected by the pressure sensor 37 becomes lower than a predetermined second threshold value. Reducing the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 includes stopping the cooling of the liquefied carbon dioxide L in the cooling device 2 from a state in which the cooling of the liquefied carbon dioxide L is being performed.

[0101] By supplying the cooled liquefied carbon dioxide L to the gas phase V in the tank 31, the boil-off gas in the tank 31 is reliquefied, thereby reducing the pressure in the tank 31. When the pressure in the tank 31 detected by the pressure sensor 37 falls below a predetermined second threshold, the reliquefaction of the boil-off gas can be stopped by reducing the cooling capacity of the liquefied carbon dioxide L in the cooling device 2.

[0102] (5) The liquefied carbon dioxide storage tank system 1 according to the fifth embodiment is the liquefied carbon dioxide storage tank system 1 according to any one of (1) to (4), further comprising: a hollow box-shaped container 5 that accommodates the storage tank 31, the circulation line 40, the cooling device 2, the pressure sensor 37, the temperature sensor 28, and the control device 60, and is movable.

[0103] Thus, the liquefied carbon dioxide storage tank system 1 has a structure in which the storage tank 31, the circulation line 40, the cooling device 2, the pressure sensor 37, the temperature sensor 28, and the control device 60 are housed in a movable container 5. This suppresses the formation of dry ice and the generation of boil-off gas in the storage tank 31 housed in the movable container 5, thereby preventing an excessive increase in the pressure within the storage tank 31.

[0104] (6) The liquefied carbon dioxide tank system 1 according to the sixth aspect is the liquefied carbon dioxide tank system 1 according to (5), wherein the cooling device 2 and the control device 60 are driven by electric power supplied from the outside.

[0105] Thus, by supplying power from the outside to the cooling device 2 and the control device 60, the cooling device 2 and the control device 60 can be driven in the liquefied carbon dioxide tank system 1 including the tank 31 housed in the movable container 5. This suppresses the generation of dry ice and the generation of boil-off gas, even during transportation of the liquefied carbon dioxide tank system 1, thereby preventing an excessive increase in the pressure within the tank 31.

[0106] (7) The liquefied carbon dioxide storage tank system 1 according to the seventh embodiment is the liquefied carbon dioxide storage tank system 1 according to any one of (1) to (6), further comprising: an injection unit 45 for injecting the liquefied carbon dioxide L circulating through the circulation line 40 into the upper portion of the storage tank 31.

[0107] Thus, the liquefied carbon dioxide L circulating through the circulation line 40 can be injected into the upper portion of the tank 31 by the injection unit 45. Thus, the boil-off gas in the gas phase portion V in the tank 31 can be efficiently reliquefied.

[0108] (8) The control method S10 of the liquefied carbon dioxide storage tank system 1 according to the eighth embodiment comprises: a storage tank 31 for storing liquefied carbon dioxide L; a circulation line 40, which is provided midway in the gas phase portion V in the storage tank 31 and extracts the liquefied carbon dioxide L in the storage tank 31 to the outside of the storage tank 31 and returns the liquefied carbon dioxide L to the outside of the storage tank 31; a cooling device 2, which is provided midway in the circulation line 40 and is capable of cooling the liquefied carbon dioxide L; a pressure sensor 37, which detects the pressure in the storage tank 31; and a temperature sensor 28, which detects the temperature of the liquefied carbon dioxide L cooled by the cooling device 2. The control method S10 of the liquefied carbon dioxide storage tank system 1 includes the following steps: S13 and S16, which are steps of adjusting the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 according to the pressure in the storage tank 31 detected by the pressure sensor 37; and S17, which is a step of reducing the cooling capacity of the liquefied carbon dioxide L in the cooling device 2 according to the temperature of the liquefied carbon dioxide L detected by the temperature sensor 28.

[0109] This suppresses the generation of dry ice and the generation of boil-off gas, thereby suppressing an excessive increase in the pressure in the tank 31 .

[0110] Industrial applicability

[0111] According to the liquefied carbon dioxide storage tank system and the control method of the liquefied carbon dioxide storage tank system of the present invention, the generation of dry ice and the generation of boil-off gas are suppressed, thereby suppressing an excessive increase in the pressure in the tank.

[0112] Explanation of symbols

[0113] 1- liquefied carbon dioxide storage tank system, 2- cooling device, 3- storage tank, 5- container, 21- compressor, 22- condenser, 23- fan, 24- expansion valve, 25- heat exchanger, 26- refrigerant circuit, 28- temperature sensor, 31- storage tank body, 31a- cylindrical part, 31b- mirror plate part, 32- shell, 32a- cylindrical shell part, 32b- spherical shell part, 33- insulation part, 34- support leg, 35- supply and exhaust pipes, 3 5a-one end, 35b-the other end, 35V-on / off valve, 36-pressure detection pipeline, 36a-one end, 36b-the other end, 36s-branch pipe, 37-pressure sensor, 38-liquid level gauge, 39V, 39W-on / off valve, 40-circulation pipeline, 40A-the first part of the circulation pipeline, 40B-the second part of the circulation pipeline, 40a-one end, 40b-the other end, 41V, 41W-on / off valve, 42-pump, 45-injection part, 50-branch Frame, 51-lower frame, 52-support, 54-upper frame, 60-control device, 70-signal input part, 71-first control part, 72-second control part, 75-output part, 100-power supply line, 101-power supply connection part, 120-connecting component, L-liquefied carbon dioxide, V-gas phase part, Da-first direction, Dv-up and down direction, Dw-second direction, Dx-length direction, S10-control method of liquefied carbon dioxide storage tank system, S11-step of obtaining the pressure in the storage tank, S12-step of determining whether the pressure in the storage tank is above the first threshold value, S13-step of starting to supercool the liquefied carbon dioxide, S14-step of obtaining the temperature of the liquefied carbon dioxide, S15-step of determining whether the temperature of the liquefied carbon dioxide is close to the triple point, S16-step of determining whether the pressure in the storage tank is below the second threshold value, S17-step of stopping to supercool the liquefied carbon dioxide.

Claims

1. A liquefied carbon dioxide storage tank system comprising: Storage tanks, storing liquefied carbon dioxide; a circulation pipeline for extracting the liquefied carbon dioxide in the storage tank out of the storage tank and returning it to the gas phase in the storage tank; a cooling device, disposed midway along the circulation pipeline, capable of cooling the liquefied carbon dioxide; a pressure sensor, detecting the pressure in the storage tank; a temperature sensor for detecting the temperature of the liquefied carbon dioxide cooled by the cooling device; and a control device for controlling the operation of the cooling device, The control device comprises: a first control unit configured to adjust a cooling capacity of the liquefied carbon dioxide in the cooling device according to the pressure in the storage tank detected by the pressure sensor; and The second control unit reduces the cooling capacity of the liquefied carbon dioxide in the cooling device according to the temperature of the liquefied carbon dioxide detected by the temperature sensor.

2. The liquefied carbon dioxide storage tank system according to claim 1, wherein: The second control unit reduces the cooling capacity of the liquefied carbon dioxide in the cooling device based on the temperature of the liquefied carbon dioxide detected by the temperature sensor and the pressure in the storage tank detected by the pressure sensor.

3. The liquefied carbon dioxide storage tank system according to claim 1 or 2, wherein: The first control unit increases the cooling capacity of the liquefied carbon dioxide in the cooling device when the pressure in the storage tank detected by the pressure sensor becomes equal to or higher than a predetermined first threshold value.

4. The liquefied carbon dioxide storage tank system according to claim 3, wherein: The first control unit reduces the cooling capacity of the liquefied carbon dioxide in the cooling device when the pressure in the storage tank detected by the pressure sensor becomes equal to or lower than a preset second threshold value.

5. The liquefied carbon dioxide storage tank system according to claim 1 or 2, further comprising: The container accommodates the storage tank, the circulation pipeline, the cooling device, the pressure sensor, the temperature sensor and the control device, and is movable.

6. The liquefied carbon dioxide storage tank system according to claim 5, wherein: The cooling device and the control device are driven by externally supplied electric power.

7. The liquefied carbon dioxide storage tank system according to claim 1 or 2, further comprising: The injection unit injects the liquefied carbon dioxide circulating through the circulation line into the upper portion of the storage tank.

8. A method for controlling a liquefied carbon dioxide storage tank system, the liquefied carbon dioxide storage tank system comprising: Storage tanks, storing liquefied carbon dioxide; a circulation pipeline for extracting the liquefied carbon dioxide in the storage tank out of the storage tank and returning it to the gas phase in the storage tank; a cooling device, disposed midway along the circulation pipeline, capable of cooling the liquefied carbon dioxide; a pressure sensor for detecting the pressure in the storage tank; and a temperature sensor for detecting the temperature of the liquefied carbon dioxide cooled by the cooling device, The control method of the liquefied carbon dioxide storage tank system comprises the following steps: adjusting the cooling capacity of the liquefied carbon dioxide in the cooling device according to the pressure in the storage tank detected by the pressure sensor; and The cooling capacity of the liquefied carbon dioxide in the cooling device is reduced according to the temperature of the liquefied carbon dioxide detected by the temperature sensor.

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