JP2023057807A - Cooling system of carbon dioxide gas and/or liquefied carbon dioxide, cooling method, liquefied carbon dioxide gas storage tank having the cooling system and marine vessel having the liquefied carbon dioxide storage tank - Google Patents

Abstract

To provide a cooling system of a carbon dioxide gas and/or a liquefied carbon dioxide which can store a carbon dioxide without discharging the carbon dioxide to an atmosphere.SOLUTION: A cooling system 1 comprises: a cooling device 10 having a primary refrigerant tank 11 for accommodating a primary refrigerant R1 which is sent from a liquefied carbon dioxide storage tank 5, and lower than a carbon dioxide gas in temperature, a heat exchange passage part 12 in which the carbon dioxide gas cooled by the primary refrigerant R1 moves, and a secondary refrigerant passage part 13 in which a secondary refrigerant R2 for cooling the primary refrigerant R1 moves; a secondary refrigerant tank 21 for storing the secondary refrigerant R2 which is lower than the primary refrigerant R1 in temperature; a secondary refrigerant introduction part 22 for introducing the secondary refrigerant R2 to the secondary refrigerant passage part 13 from the secondary refrigerant tank 21: and a secondary refrigerant discharge part 23 connected to the secondary refrigerant passage part 13, and introducing the second refrigerant R2.SELECTED DRAWING: Figure 1A

Description

The present invention relates to a cooling system for carbon dioxide gas and/or liquefied carbon dioxide, a cooling method, a liquefied carbon dioxide storage tank equipped with the cooling system, and a ship (tanker) equipped with the liquefied carbon dioxide storage tank.

In recent years, in order to deal with the problem of climate change, carbon dioxide, a typical greenhouse gas, is recovered, transported to depleted oil and gas fields, etc. and stored, thereby reducing the concentration of carbon dioxide in the atmosphere. There is an attempt. For this reason, the use of liquefied carbon dioxide transport ships is being considered for large-scale transportation.

US Pat. No. 6,200,008 discloses cooling and recovering carbon dioxide gas released from a carbon dioxide storage tank using a refrigerant.
US Pat. No. 5,300,000 discloses recovering carbon dioxide gas released from a liquefied carbon dioxide storage tank, liquefying it in a cooling unit, and returning it to the liquefied carbon dioxide storage tank.
US Pat. No. 5,300,000 discloses compressing natural gas in a liquefied natural gas carrier with a compressor, cooling and liquefying it back to the liquefied natural gas tanks.

U.S. Pat. No. 4,350,018 JP 2004-100862 A Patent No. 6843099

From the viewpoint of climate change countermeasures, it is desirable to prevent carbon dioxide from being released into the atmosphere from the storage tank. However, since the heat input from the environment into the storage tank cannot be completely eliminated, it is desired to cool the carbon dioxide in the storage tank to offset the heat input. Furthermore, it is desired to suppress the emission of new carbon dioxide generated by the cooling. Therefore, it is preferable to use renewable energy as the energy required for the cooling. However, access to such energy sources is not always easy. For example, when transporting carbon dioxide by ship, it is difficult to connect to the renewable energy grid. Therefore, for example, when cooling or compressing carbon dioxide to liquefy it as in the methods of Patent Documents 2 and 3, it is necessary to permanently install a storage battery or carbon-neutral fuel charged by a renewable energy power source on the ship. comes out. On the other hand, both are very expensive.

Also, referring to the method of Patent Document 1, it will be possible to cool carbon dioxide by loading a large amount of refrigerant on a ship. However, loading a large amount of refrigerant is expensive, and at the same time, the refrigerant itself, which is suitable for cooling carbon dioxide, has a greenhouse effect and may deplete the ozone layer, so it cannot be a means of solving the climate change problem. .

An object of the present invention is to provide a cooling system for carbon dioxide gas and/or liquefied carbon dioxide, a cooling method, and a liquefied dioxide provided with the cooling system, which can store carbon dioxide without releasing carbon dioxide into the atmosphere. To provide a carbon storage tank and a ship equipped with the liquefied carbon dioxide storage tank.
In addition, by reducing the pressure in the storage tank, liquefied carbon dioxide (also called "liquefied carbon dioxide gas") is suppressed from solidifying (also called "dry ice" or "solid carbonic acid"), while holding and storing liquefied carbon dioxide. Provide a possible storage method.

(cooling system)
A cooling system (1) of carbon dioxide gas and/or liquefied carbon dioxide comprising:
a primary refrigerant tank (11) containing a primary refrigerant (R1) having a lower temperature than the temperature of carbon dioxide gas and/or liquefied carbon dioxide delivered (directly or indirectly) from a liquefied carbon dioxide storage tank (5); A heat exchange passage (12) in which the carbon dioxide gas and/or liquefied carbon dioxide cooled by the primary refrigerant (R1) moves, and a secondary refrigerant (R2) for cooling the primary refrigerant (R1) moves. a cooling device (10) having a secondary refrigerant passage portion (13) that
a secondary refrigerant tank (21) storing a secondary refrigerant (R2) for cooling the primary refrigerant (R1);
a secondary refrigerant introduction portion (22) for introducing the secondary refrigerant (R2) from the secondary refrigerant tank (21) into the secondary refrigerant passage portion (13);
a secondary refrigerant discharge portion (23) connected to the secondary refrigerant passage portion (13) for leading out the secondary refrigerant (R2);
Prepare.
The primary refrigerant tank (11) contains the primary refrigerant (R1), and the secondary refrigerant passage (13) and the heat exchange passage (12) pass through the primary refrigerant tank (11), or The carbon dioxide gas and/or liquefied carbon dioxide moving in the heat exchange passage (12) may be cooled by the primary refrigerant (R1) by contact.
The cooling system (1) comprises:
a primary refrigerant passage (11d) through which the primary refrigerant (R1) sent from the primary refrigerant tank (11a) moves;
a first heat exchanger (11b) through which the primary refrigerant passage portion (11d) passes and the secondary refrigerant passage portion (13) passes to cool the primary refrigerant (R1) with the secondary refrigerant (R2); ,
Passage of the primary refrigerant passage (11d) that has passed through the first heat exchanger (11b) and passage of the heat exchange passage (12) causes the primary refrigerant (R1) to produce carbon dioxide gas and/or liquefied dioxide. and a second heat exchanger (11c) for cooling the carbon.
The heat exchange passage portion (12) may be introduced into heat exchange means with the primary refrigerant, for example, the primary refrigerant tank (11) or the second heat exchanger (11c). good.

The temperature of the primary refrigerant (R1) is preferably higher than the solidification point (temperature at which carbon dioxide solidifies). By cooling with the primary refrigerant (R1), the carbon dioxide is in the range between the triple point (pressure 0.54 MPaA, temperature -56.6°C) and the critical point (pressure 7.68 MPaA, temperature +31.1°C) and maintains a liquid state. preferably.
The primary refrigerant (R1) may be, for example, one or a mixture of two or more of hydrocarbon compounds such as propane, ethane, ethylene, fluorocarbons, ammonia, and water.

The secondary refrigerant (R2) preferably has a boiling point lower than (or lower than) the triple point temperature of carbon dioxide (−56.6° C.) under atmospheric pressure. The liquefied gas used as the secondary refrigerant (R2) preferably has a boiling point lower than the boiling point of carbon dioxide. As a result, the latent heat of vaporization is used to cool the primary refrigerant (R1), the primary refrigerant can cool carbon dioxide, and the available cold heat per unit weight can be increased, thereby reducing the load capacity of the refrigerant. be able to. Furthermore, when the secondary refrigerant (R2) is used directly for cooling carbon dioxide, there is a risk of overcooling and solidification of carbon dioxide, but the composition and temperature of the primary refrigerant (R1) can be changed. Variables can be adjusted. This avoids the risk of solidification of carbon dioxide.
The secondary refrigerant (R2) is preferably a substance liquefied by renewable energy. This makes it possible to eliminate greenhouse gas emissions associated with carbon dioxide cooling.
The secondary refrigerant (R2) is preferably lower in temperature than the primary refrigerant (R1) when cooling the primary refrigerant (R1).
The secondary refrigerant (R2) may be, for example, one or a mixture of two or more of nitrogen, air, oxygen, argon, and the like. These gases, even if released into the atmosphere after releasing the cold, do not contribute to the greenhouse effect as they are the gases extracted from the atmosphere.
Said secondary refrigerant (R2) may be, for example, hydrogen, methane, natural gas. These gases are loaded on ships as liquefied gas fuels, and after being vaporized, are consumed by engines, fuel cells, or the like to obtain power and electric power for driving ships. If the cold released during this vaporization is used to cool the carbon dioxide in the cooling device (that is, to cool the primary refrigerant), the liquefied gas fuel tank of the fuel can also be used as a secondary refrigerant tank, and the overall can be operated at low cost.

The cooling system (1) comprises:
An introduction part (31) for introducing carbon dioxide gas and/or liquefied carbon dioxide, which is connected to the inlet side of the heat exchange passage part (12) and sent (directly or indirectly) from the liquefied carbon dioxide storage tank (5). and,
a return section (32) connected to the outlet side of the heat exchange passage section (12), from which cooled carbon dioxide gas and/or liquefied carbon dioxide is led out, and returned to the liquefied carbon dioxide storage tank (5);
may be provided.
The introduction part (31) and/or the return part (32) are provided with, for example, valves such as gate valves, automatic on-off valves, flow control valves (regardless of whether they are manual or automatic), temperature sensors, flow sensors, pressure sensors, etc. may have been
The introduction part (31) may be provided with a liquid feed pump for sending liquefied carbon dioxide to the cooling device (10). The introduction part (31) may be connected to a liquid feed pump (35) arranged below the liquid level of the liquefied carbon dioxide storage tank (5). The liquid feed pump (35) may also serve as a discharge pump for discharging the liquefied carbon dioxide installed in the liquefied carbon dioxide storage tank (5).
On the route from the liquefied carbon dioxide storage tank (5) to the primary refrigerant tank (11) or the second heat exchanger (11c) or to the introduction part (31), from the liquefied carbon dioxide storage tank (5) A compressing means or pressurizing means (compressor or pressurizer) for compressing or pressurizing the carbon dioxide gas to be discharged may be provided. Liquefaction can be promoted by increasing the pressure of the carbon dioxide gas.
The return part (32) may have its tip outlet extending above or below the liquid surface of the liquefied carbon dioxide storage tank (5).
The return section (32) may, for example, be provided with a spray nozzle. The spray nozzle may be configured to spray liquefied carbon dioxide cooled to gas phase and/or liquid phase and/or cooled carbon dioxide gas.
The return part (32) may be provided with, for example, a suction pump, a liquid feed pump, a vacuum pump, or the like for sucking gas and/or liquid.

The primary refrigerant passage (11d) may be provided with, for example, valves such as gate valves, automatic on-off valves, and flow control valves (regardless of whether they are manual or automatic), temperature sensors, flow sensors, pressure sensors, and the like.
The primary refrigerant passage portion (11d) and/or the primary refrigerant tank (11a) passes the primary refrigerant (R1) from the primary refrigerant tank (11a) through the first heat exchanger (11b) and the second heat exchanger (11c). A circulation pump (11e) (for example, a liquid feed pump) may be provided for circulating through to the primary refrigerant tank (11a).

The primary refrigerant tank (11) may be in a negative pressure state lower than the atmospheric pressure. To draw air into the primary refrigerant tank (11) and pressurize it without using a pressurizing device such as an expensive compressor when there is a risk that carbon dioxide will be supercooled by creating a negative pressure state. can raise the temperature of the primary refrigerant (R1). As a result, heat exchange between carbon dioxide and the primary refrigerant (R1) is suppressed, and supercooling and solidification of carbon dioxide can be avoided.
Said liquefied carbon dioxide storage tank (5) may for example have an internal pressure of less than 7 MPa, less than 5 MPa, less than 4 MPa, less than 2 MPa.

The cooling system (1) comprises:
A pressure measuring unit (53) that measures the internal pressure (pressure in the gas phase space) of the liquefied carbon dioxide storage tank (5);
When the internal pressure measured by the pressure measuring unit (53) exceeds the tank internal pressure set value (the set value includes a wide numerical range), the carbon dioxide gas and / or liquefied carbon dioxide is heat exchanged Means (the primary refrigerant tank (11) or the second heat exchanger (11c)) through the introduction part (31) (for example, by opening the valve, driving the liquid transfer pump (35), etc.) and an introduction control unit (55) that controls to

The cooling system (1) comprises:
a temperature measuring unit that measures the internal temperature (e.g., gas phase temperature, liquid phase temperature) of the liquefied carbon dioxide storage tank (5);
The introduction control unit (55) adjusts the internal temperature measured by the temperature measurement unit to a tank internal temperature set value (the set value of the gas phase temperature and/or the liquid phase temperature includes a wide range of numerical values). When it exceeds, carbon dioxide gas and / or liquefied carbon dioxide is controlled to be sent to the heat exchange means (the primary refrigerant tank (11) or the second heat exchanger (11c)) through the introduction part (31) may
The temperature measuring unit may have a plurality of temperature measuring means, and may be arranged in the liquefied carbon dioxide storage tank (5) at predetermined intervals in the height direction.
The introduction control unit (55) may control the internal temperature (liquid phase, gas phase) and/or internal pressure (liquid phase, gas phase) of the liquefied carbon dioxide storage tank (5). .
When the measured internal temperature (liquid phase temperature) exceeds the tank internal temperature set value (third threshold value), the introduction control unit (55) transfers liquefied carbon dioxide to the heat exchange means (primary refrigerant tank (11 ) or the second heat exchanger (11c)).
When the measured internal temperature (gas phase temperature) exceeds the tank internal temperature set value (fourth threshold (greater than third threshold)), the introduction control unit (55) converts the carbon dioxide gas into the heat exchange It may be controlled to send to means (primary refrigerant tank (11) or second heat exchanger (11c)).
The introduction control section (55) is installed in the introduction section (31) and/or the return section (32). A flow rate sensor, a pressure sensor, a liquid feed pump (35), etc. may be controlled.
The tank internal pressure set value (gas phase) may be, for example, 10% or more, 20% or more than the internal pressure set in the specifications of the liquefied carbon dioxide storage tank (5).
The set temperature in the tank (liquid phase, gas phase) is, for example, 10% or more, 20% or more than the temperature set according to the specifications of the liquefied carbon dioxide storage tank (5) and the state of liquefied carbon dioxide. can be a value.

The cooling system (1) comprises:
at least one temperature measurement part (18) for measuring the temperature of the primary refrigerant (R1) in the primary refrigerant tank (11, 11a) or the primary refrigerant passage (11d);
The temperature of the primary refrigerant measured by the temperature measuring unit (18) (any one of the average value of two or more temperatures measured at multiple locations, each temperature measured at multiple locations, the maximum value, and the minimum value ) does not fall below the solidification point (solidification temperature) of carbon dioxide at an arbitrary pressure (preferably a preset threshold value or a tank internal pressure setting value or less) (higher than the solidification point and a secondary refrigerant flow rate control section (231) for controlling the flow rate of the secondary refrigerant (R2).
The secondary refrigerant flow control unit (231) controls, for example, a liquid feed pump provided in the secondary refrigerant tank (21), the secondary refrigerant introduction unit (22) and/or the secondary refrigerant discharge unit (23). may be used to control the flow rate of the secondary refrigerant (R2), and the secondary refrigerant passage (13), the secondary refrigerant introduction (22) and/or the secondary refrigerant discharge (23) on the path such as The flow rate of the secondary refrigerant (R2) may be controlled by controlling a mass flow meter and its interlocking valve, a mass flow controller, a flow control valve, etc. provided at any location.
Said secondary refrigerant discharge part (23) may comprise an outlet at its distal end for discharging the secondary refrigerant to the atmosphere.

The secondary refrigerant flow rate control section (231) determines the state of carbon dioxide from the differential pressure between the introduction section (31) and the return section (32), The flow rate of the secondary refrigerant (R2) may be controlled.
Said differential pressure may be calculated from measurements of pressure measuring means (e.g., pressure gauges) provided in each of the introduction section (31) and the return section (32), and the pressure of the liquefied carbon dioxide storage tank (5) The pressure of the gas phase may be regarded as the pressure of the inlet (31).

The secondary refrigerant flow rate control unit (231) controls the physical quantity (e.g., temperature, heat quantity, pressure) of carbon dioxide gas and/or liquefied carbon dioxide flowing through the introduction unit (31) and/or the return unit (32). , The state of carbon dioxide (for example, solid, liquid, gas, gas-liquid mixed state, liquid-solid mixed state, etc.) is determined, and the flow rate of the secondary refrigerant (R2) is controlled according to the determination result. good.
The physical quantities (e.g., temperature, heat quantity, pressure) are measured by measuring means (e.g., temperature sensor, calorie measuring means, pressure sensor, etc.) provided in each of the introduction part (31) and the return part (32). may be obtained from measurements of
In addition, a flow control unit different from the secondary refrigerant flow control unit (231) that controls based on the primary refrigerant temperature, differential pressure, and physical quantity performs the same control as the secondary refrigerant flow control unit (231). You may

The heat exchange passage (12) has a first heat exchange passage (612) for transferring carbon dioxide gas and/or a second heat exchange passage (712) for transferring liquefied carbon dioxide,
A first introduction part (631) that is connected to the inlet side of the first heat exchange passage part (612) and that introduces carbon dioxide gas sent (directly or indirectly) from the liquefied carbon dioxide storage tank (5); Connected to the outlet side of the first heat exchange passage section (612), the cooled carbon dioxide gas (including liquefied state) is led out and returned to the liquefied carbon dioxide storage tank (5) First return section (632 ) and/or
A second introduction part (731) for introducing liquefied carbon dioxide, which is connected to the inlet side of the second heat exchange passage part (712) and sent (directly or indirectly) from the liquefied carbon dioxide storage tank (5); A second return part (732) connected to the outlet side of the second heat exchange passage part (712), from which the cooled liquefied carbon dioxide is led out, and returned to the liquefied carbon dioxide storage tank (5);
may be provided.
The introduction control unit (55) is installed in the first introduction unit (631) and/or the first return unit (632), for example, valves such as gate valves, automatic on-off valves, flow control valves, temperature sensors , a flow rate sensor, a pressure sensor, a liquid feed pump (35), and the like.
The introduction control section (55) is installed in the second introduction section (731) and/or the first return section (732), for example, a valve such as a gate valve, an automatic on-off valve, a flow control valve, a temperature sensor , a flow rate sensor, a pressure sensor, a liquid feed pump (35), and the like.
The secondary refrigerant flow control section (231) controls the differential pressure between the first introduction section (631) and the first return section (632), and/or the second introduction section (731) and the second return section ( 732) may be used to control the flow rate of the secondary refrigerant (R2).
The secondary refrigerant flow rate control unit (231) controls the physical quantity of carbon dioxide gas and/or liquefied carbon dioxide (e.g., temperature, heat quantity, pressure ), the flow rate of the secondary refrigerant (R2) may be controlled.
The secondary refrigerant flow rate control unit (231) controls the physical quantity of carbon dioxide gas and/or liquefied carbon dioxide (e.g., temperature, heat quantity, pressure ), the flow rate of the secondary refrigerant (R2) may be controlled.

The heat exchange passages (e.g., first and second heat exchange passages) are inlets (e.g., , warm end 121) and an outlet (eg, cold end 122) through which the cooled carbon dioxide gas and/or liquefied carbon dioxide, cooled by the primary refrigerant, is discharged.
The introduction section (first and second introduction sections) may be connected to the inlet section (eg, first and second warm ends). A return section (eg, first, second return section) may be connected to an outlet section (eg, first, second cold end).
At the inlet (e.g. first, second warm end) and/or outlet (e.g., first, second cold end) of the heat exchange passage (first, second heat exchange passage), for example a partition A valve, an automatic on-off valve, a valve such as a flow control valve, a temperature sensor, a flow sensor, a pressure sensor, etc. may be provided.

The secondary refrigerant passage portion (13) includes a secondary refrigerant inlet portion (for example, a cold end 131) into which the secondary refrigerant (R2) is introduced, and a secondary refrigerant passage portion (for example, a cold end 131) through which the primary refrigerant (R1) is supplied with cold heat. and a coolant outlet (eg, warm end 132).
A secondary refrigerant inlet (22) may be connected to the secondary refrigerant inlet (eg cold end 131). A secondary refrigerant outlet (23) may be connected to a secondary refrigerant outlet (eg, warm end 132).
The secondary refrigerant passage (13) has a valve such as a gate valve, an automatic on-off valve, a flow control valve, a temperature sensor, a flow sensor, and a pressure sensor at the secondary refrigerant inlet and/or the secondary refrigerant outlet. may be provided.
The secondary refrigerant introduction part (22) and/or the secondary refrigerant discharge part (23) are provided with, for example, valves such as a gate valve, an automatic on-off valve, a flow control valve, a temperature sensor, a flow sensor, and a pressure sensor. good too.

Carbon dioxide exists as a liquid in the range between the triple point (pressure 0.54 MPaA, temperature -56.6 ° C) and the critical point (pressure 7.68 MPaA, temperature +31.1 ° C), and liquefied carbon dioxide ("liquefied carbon dioxide gas ”).
The cooled carbon dioxide gas and/or liquefied carbon dioxide is at a temperature lower than the temperature of the carbon dioxide gas and/or liquefied carbon dioxide introduced at least at the inlet (e.g., warm end 121), preferably The returned carbon dioxide is in a liquefied state, more preferably at a temperature lower than the temperature of the liquefied carbon dioxide introduced at the inlet (eg warm end 121). However, when it is in a state of flowing as a fluid together with other liquids, it may be partially solidified.

The cooling system (1) comprises:
A heating device (140) for heating the secondary refrigerant (R2) (after heat exchange with the primary refrigerant) that has passed through the primary refrigerant tank (11) or the first heat exchanger (11b) and/or a compressor It may further comprise a compression device (150) for compressing.
The heated secondary refrigerant can be supplied at an appropriate temperature for uses other than refrigerant. The compressed secondary refrigerant can be supplied at a pressure suitable for introduction into a combustion furnace or engine when used for fuel. The overall cost effectiveness of the cooling system and destination system can be improved.

Each control unit may be realized by the cooperative action of hardware and programs such as one or more processors and memory (for example, a storage medium that stores a processing program, etc.), dedicated circuits, firmware, computers, etc. It may be composed of one type or a combination of two or more types.
"Send directly or indirectly" means that there is one pipe when sending by pipe, that the pipe is equipped with joints, flanges, valves, various measuring devices, pumps, pressure devices, etc., and that the main pipe and bypass piping, and a buffer tank in the middle of the piping.

(Cooling method)
A method for cooling carbon dioxide gas and/or liquefied carbon dioxide includes:
A step (A) of cooling the primary refrigerant (R1) with a secondary refrigerant (R2) having a lower temperature than the primary refrigerant (R1);
When the internal pressure of the liquefied carbon dioxide storage tank (5) (pressure in the gas phase space) exceeds a preset threshold (for example, it may be a tank internal pressure set value), carbon dioxide gas and / or A heat exchange means (e.g. primary refrigerant tank (11) or a second heat exchanger) for exchanging heat with the primary refrigerant from the liquefied carbon dioxide storage tank (5) in order to cool the liquefied carbon dioxide with the primary refrigerant (R1) (11c)) an introduction step (B);
Step (C) of cooling carbon dioxide gas and/or liquefied carbon dioxide sent from a liquefied carbon dioxide storage tank (5) with a primary refrigerant (R1) having a temperature lower than that temperature;
including.
The step (A) may be performed before the start of the step (B), at the same timing as the start (including substantially the same timing), or after the start, as long as the object is achieved.
The cooling method is
The flow rate of the secondary refrigerant (R2) is adjusted so that the temperature of the primary refrigerant (R1) does not fall below the solidification point of carbon dioxide at any pressure (same as or higher than the solidification point). and a step of controlling (A-1).
The cooling method is
Carbon dioxide gas and/or liquefied carbon dioxide is sent from the liquefied carbon dioxide storage tank (5) to the heat exchange means (for example, introduction section (31)) and from the heat exchange means to the liquefied carbon dioxide storage tank ( 5) The state of carbon dioxide is determined from the differential pressure between the return path returning to 5) (for example, the return section (32)), and the flow rate of the secondary refrigerant (R2) is controlled according to the determination result. A step (A-2) may be included.
The cooling method is
An introduction path (e.g., introduction section (31)) through which carbon dioxide gas and/or liquefied carbon dioxide is sent from a liquefied carbon dioxide storage tank (5) to the heat exchange means and/or from the heat exchange means to liquefied carbon dioxide storage From the physical quantity (e.g., temperature, heat quantity, pressure) of carbon dioxide gas and/or liquefied carbon dioxide flowing through the return route (e.g., return section (32)) returning to the tank (5), determine the state of carbon dioxide, A step (A-3) of controlling the flow rate of the secondary refrigerant (R2) according to the determination result may be included.

(liquefied carbon dioxide storage tank)
The liquefied carbon dioxide storage tank (5) may be equipped with the cooling system (1) described above.
The cooling system (1) may comprise a liquefied carbon dioxide storage tank (5).
A safety valve may be provided in the liquefied carbon dioxide storage tank (5).

(ship)
The ship may be equipped with said cooling system (1) and a liquefied carbon dioxide storage tank (5).
The vessel may be provided with supply means to which the heated secondary refrigerant (R2) is supplied.
The ship may be equipped with a combustion furnace or engine in which said compressed secondary refrigerant (R2) is used for fuel applications.

1 is a diagram showing a configuration example of a cooling system according to Embodiment 1; FIG. 4 is a diagram showing another configuration example of the cooling system of Embodiment 1. FIG. 4 is a diagram showing another configuration example of the cooling system of Embodiment 1. FIG. FIG. 10 is a diagram showing a configuration example of a cooling system according to Embodiment 2; FIG. 11 is a diagram showing a configuration example of a cooling system according to Embodiment 3; FIG. 11 is a diagram showing a configuration example of a cooling system according to Embodiment 4; FIG. 12 is a diagram showing a configuration example of a cooling system according to Embodiment 5;

Several embodiments of the present invention are described below. The embodiments described below describe examples of the present invention. The present invention is by no means limited to the following embodiments, and includes various modifications implemented within the scope of the present invention. Note that not all of the configurations described below are essential configurations of the present invention.

(Embodiment 1)
A cooling system 1 of Embodiment 1 will be described with reference to FIG. 1A.
The cooling system 1 includes a cooling device 10 , a secondary refrigerant tank 21 , a first introduction section 631 and a first return section 632 .
The first introduction part 631 is a means for introducing carbon dioxide gas sent from the liquefied carbon dioxide storage tank 5 into the first heat exchange passage part 612 of the cooling device 10, for example, piping, automatic pressure adjustment valve (preset A valve whose opening and closing is automatically adjusted when the pressure set value is exceeded).
The first return part 632 is connected to the outlet side of the first heat exchange passage part 612, and the cooled carbon dioxide gas and/or liquefied carbon dioxide that has passed through the first heat exchange passage part 612 is led out, It is a means for returning to the liquefied carbon dioxide storage tank 5, and for example, a pipe and a spray nozzle may be provided at the tip of the pipe.

The cooling device 10 includes a primary refrigerant tank 11 , a first heat exchange passage portion 612 and a secondary refrigerant passage portion 13 .
The primary refrigerant tank 11 contains the primary refrigerant R1 sent from the liquefied carbon dioxide storage tank 5 and having a temperature lower than that of the carbon dioxide gas. The first heat exchange passage portion 612 passes through the interior of the primary refrigerant tank 11, and carbon dioxide gas moves through the interior thereof. In the process of moving, the carbon dioxide gas is cooled by the cold heat of the primary refrigerant R1. The first heat exchange passage portion 612 has an inlet portion (warm end 121) into which carbon dioxide gas sent from the liquefied carbon dioxide storage tank 5 is introduced, and a cooled carbon dioxide gas cooled by the primary refrigerant R1 is led out. and an outlet (cold end 122). The first introduction part 631 is connected with the inlet part (warm end 121), and the first return part 632 is connected with the outlet part (cold end 122).

The secondary refrigerant passage portion 13 passes through the primary refrigerant tank 11, and the secondary refrigerant R2 moves therein. During the movement, the cold heat of the secondary refrigerant R2 cools the primary refrigerant R1. The secondary refrigerant passage portion 13 has a secondary refrigerant inlet portion (cold end 131) into which the secondary refrigerant R2 is introduced, and a secondary refrigerant outlet portion (warm end 132) that is introduced after applying cold heat to the primary refrigerant R1. and have The secondary refrigerant introduction portion 22 is connected to the secondary refrigerant inlet portion (cold end 131), and the secondary refrigerant discharge portion 23 is connected to the secondary refrigerant outlet portion (warm end 132).

The secondary refrigerant tank 21 stores secondary refrigerant R2 having a temperature lower than that of the primary refrigerant R1. The secondary refrigerant tank 21 has therein a liquid feed pump 211 for sending out the secondary refrigerant R2, and the liquid feed pump 211 is connected to the secondary refrigerant introduction portion 22 . The secondary refrigerant introduction portion 22 is connected to the secondary refrigerant inlet portion (cold end 131 ) of the secondary refrigerant passage portion 13 to send the secondary refrigerant R2 from the secondary refrigerant tank 21 .
The secondary refrigerant discharge portion 23 is connected to the secondary refrigerant outlet portion (warm end 132 ) to lead out the secondary refrigerant R2 that has passed through the secondary refrigerant passage portion 13 . If the secondary refrigerant R2 led out by the secondary refrigerant discharge part 23 is the same as any atmospheric component, for example, in the case of nitrogen, oxygen, argon, or air, it may be discharged to the atmosphere as it is.

(Action)
A threshold value at which the pressure of the gas phase is preset due to the influence of carbon dioxide gas accumulated in the gas phase of the liquefied carbon dioxide storage tank 5 (the threshold value may be, for example, the tank internal pressure set value, or another value. ), the automatic pressure regulating valve opens, carbon dioxide gas enters the first introduction part 631, is cooled in the first heat exchange passage part 612, and passes through the first return part 632 Return to liquefied carbon dioxide storage tank 5 . The carbon dioxide gas is cooled by the first refrigerant R1 of the cooling device 10 and returned to the liquefied carbon dioxide storage tank 5 as liquefied carbon dioxide, cooled gaseous carbon dioxide, or gas-liquid mixed carbon dioxide. This eliminates the need to release carbon dioxide gas to the atmosphere. Further, the carbon dioxide gas in the gas phase space can be cooled by spraying the cooled liquefied carbon dioxide with a spray nozzle onto the carbon dioxide gas in the gas phase space.
Also, the primary refrigerant R1 is cooled by the secondary refrigerant R2 that is continuously or discontinuously supplied. In order to send the secondary refrigerant R2, the driving of the liquid feed pump 211 is started when the pressure of the carbon dioxide gas accumulated in the gas phase of the liquefied carbon dioxide storage tank 5 exceeds a preset threshold value (automatic pressure regulating valve is opened).

In Embodiment 1, a heat exchange effect due to natural convection of the primary refrigerant R1 in the primary refrigerant tank 11 is employed. In the primary refrigerant tank 11, the primary refrigerant R1 is evaporated by carbon dioxide gas and recondensed by the secondary refrigerant R2. This is heat exchange using latent heat (evaporation), and the amount of heat per flow rate is large, and the size of the heat exchanger itself can be kept compact.

(Another configuration example 1)
Another configuration example of FIG. 1B will be described. In another configuration example of FIG. 1B, a liquid feed pump 35 inside the liquefied carbon dioxide storage tank 5 pumps the liquefied carbon dioxide in the tank to the cooling device 10 . Since the same reference numerals are the same as those of Embodiment 1 of FIG. 1A, the description is omitted or simplified.
The second introduction part 731 is connected to the liquid feed pump 35, and liquefied carbon dioxide is introduced into the second introduction part 731, and through the second heat exchange passage part 712 and the second return part 732, the liquefied carbon dioxide storage tank. Go back to 5. The liquefied carbon dioxide is cooled by the first refrigerant R1 of the cooling device 10 and returned to the liquefied carbon dioxide storage tank 5 in the state of cooled liquefied carbon dioxide. Thereby, the liquefied carbon dioxide in the tank can be cooled (that is, subcooled), and for example, the generation of carbon dioxide gas from the liquid phase to the gas phase in the tank can be suppressed. Furthermore, the liquefied carbon dioxide in the tank can be kept cold so as to suppress the pressure rise in the tank.
The cooling system 1 includes a temperature measurement unit that measures the internal temperature of the liquefied carbon dioxide storage tank 5 (eg, gas phase temperature, liquid phase temperature), and the internal temperature measured by the temperature measurement unit is used as the tank internal temperature setting. value (the set value of the temperature of the gas phase and/or the temperature of the liquid phase includes a wide numerical range), the liquid feed pump 35 is driven and the liquefied carbon dioxide is transferred to the primary refrigerant tank 11. A control section may be provided to control the delivery through the introduction section 731 .

The cooling device 10 has the configuration of FIG. 1A (first introduction portion 631, first heat exchange passage portion 612, first return portion 632) and the configuration of FIG. Both of the second return unit 732) may be provided.

(Another configuration example 2)
Another configuration example of FIG. 1C will be described. In another configuration example of FIG. 1C, a liquid feed pump 35 inside the liquefied carbon dioxide storage tank 5 pumps the liquefied carbon dioxide in the tank to the cooling device 10 . Since the same reference numerals are the same as those of another configuration example 1 in FIG. 1B, the description is omitted or simplified.
The primary refrigerant tank 11a accommodates the primary refrigerant R1. The primary refrigerant tank 11a, the first heat exchanger 11b, and the second heat exchanger 11c are connected by a primary refrigerant passage portion 11d. The primary refrigerant R1 in the primary refrigerant tank 11a is circulated through the primary refrigerant passage portion 11d by the circulation pump 11e arranged in the primary refrigerant passage portion 11d.
In the first heat exchanger 11b, the primary refrigerant R1 is cooled by the secondary refrigerant R2 as the primary refrigerant passage portion 11d and the secondary refrigerant passage portion 13 pass through. In the second heat exchanger 11c, the liquefied carbon dioxide is cooled (that is, subcooled) by the primary refrigerant R1 as the primary refrigerant passage portion 11d and the heat exchange passage portion 12 pass through.
The primary refrigerant R1 is cooled by the secondary refrigerant R2 in the first heat exchanger 11b and immediately thereafter supplied to the cold end side of the second heat exchanger 11c. That is, the liquefied carbon dioxide with the lowest temperature is returned to the liquefied carbon dioxide storage tank 5 . The primary refrigerant R1 drawn out from the second heat exchanger 11c is returned to the primary refrigerant tank 11a and then circulated again to the first heat exchanger 11b by the circulation pump 11e.

In configuration example 2, a heat exchange action by forced convection is employed outside the primary refrigerant tank 11a. In the case of the subcooler using the second heat exchanger 11c, heat exchange using sensible heat is performed, so the amount of heat per unit flow rate is small. Therefore, heat exchange by forced convection is preferable to natural convection for processing a large flow rate. Since natural convection has a small heat transfer coefficient, it is necessary to increase the heat transfer area of the heat exchanger, but forced convection can reduce the heat transfer area and the heat exchanger.

(Embodiment 2)
A cooling system 1 of Embodiment 2 will be described with reference to FIG. Since the same reference numerals are the same as those of Embodiment 1 of FIG. 1A, the description is omitted or simplified.
The cooling system 1 includes an introduction-side pressure measurement section 53 and an introduction control section 55 .
The introduction-side pressure measurement unit 53 measures the internal pressure of the liquefied carbon dioxide storage tank 5 (pressure in the gas phase space=inlet side of the first introduction unit 631). When the internal pressure measured by the pressure measuring unit 53 exceeds the tank internal pressure set value, the introduction control unit 55 opens the introduction flow control valve 531 to introduce gaseous carbon dioxide gas into the primary refrigerant tank 11. control to send. Since the pressure of the gas phase is high, the set value of the tank internal pressure is set so that when the valve is opened, the gas is introduced without using the drive of the suction pump.
The introduction control unit 55 may control to send carbon dioxide gas to the primary refrigerant tank 11 when the internal pressure measured by the pressure measurement unit 53 exceeds the tank internal pressure set value (first threshold value). . In addition, in the configuration of FIG. 1B, the introduction control unit 55 controls to send liquefied carbon dioxide to the primary refrigerant tank 11 when the measured internal pressure exceeds the tank internal pressure set value (second threshold value). may

The cooling system 1 includes a temperature measurement section 18 , a secondary refrigerant flow control section 231 and a secondary refrigerant flow control valve 2311 .
The temperature measurement unit 18 measures the temperature of the primary refrigerant R1 inside the primary refrigerant tank 11 . One or a plurality of temperature measurement units 18 may be arranged.
The secondary refrigerant flow control unit 231 is arranged in the secondary refrigerant discharge unit 23 so that the temperature of the primary refrigerant R1 measured by the temperature measurement unit 18 does not fall below the solidification point of carbon dioxide at an arbitrary pressure. The secondary refrigerant flow control valve 2311 is controlled to adjust the flow rate of the secondary refrigerant (R2).
The secondary refrigerant flow control unit 231 reduces the flow rate or stops the supply (or intermittently supplies) when the measured temperature of the primary refrigerant becomes lower than the solidification point, and the measured temperature of the primary refrigerant becomes the same as the solidification point. Alternatively, when the temperature is higher than the solidification point, the flow rate may be controlled so as to maintain a predetermined temperature range from the solidification point (for example, a temperature 5 to 20% higher than the solidification point).
Further, the secondary refrigerant flow rate control unit 231 may control the liquid feed pump 211 provided in the secondary refrigerant tank 21 to control the flow rate of the secondary refrigerant R2.
The secondary refrigerant flow control valve 2311 controls the flow rate of the secondary refrigerant R2 after heat exchange with the primary refrigerant R1. . Also, the secondary refrigerant flow rate control valve 2311 is arranged in the secondary refrigerant discharge portion 23 , but may be arranged in the secondary refrigerant introduction portion 22 .

For example, the temperature control criteria for the primary refrigerant R1 and the secondary refrigerant R2 are as follows.
(1) The boiling point of the secondary refrigerant R2 is lower than the triple point of carbon dioxide (-56.6°C or lower). The temperature and supply of the secondary refrigerant R2 are controlled so as to satisfy the following (2).
(2) The primary refrigerant R1 has a higher solidification point than the carbon dioxide to be cooled.
For example, a temperature higher by 1° C. than the solidification point of carbon dioxide at the operating pressure of the liquefied carbon dioxide storage tank 5 may be set as the control temperature of the primary refrigerant R1.

(Embodiment 3)
A cooling system 1 according to Embodiment 3 will be described with reference to FIG. Since the same reference numerals are the same as those of the first and second embodiments of FIGS. 1A and 2, the description is omitted or simplified.
The cooling system 1 includes an introduction-side pressure measurement section 53 , an introduction flow control valve 531 , a return-side pressure measurement section 532 , a secondary refrigerant flow control section 231 , and a secondary refrigerant flow control valve 2311 .
The introduction-side pressure measurement unit 53 measures the internal pressure of the liquefied carbon dioxide storage tank 5 (pressure in the gas phase space=inlet side of the first introduction unit 631).
The return-side pressure measurement unit 532 measures the pressure in the first return unit 632 (state of carbon dioxide gas, liquid, gas-liquid mixture, solid-liquid mixture, gas-solid mixture, gas-liquid-solid mixture, etc.).
The secondary refrigerant flow control section 231 calculates the difference (differential pressure) between the pressure measured by the introduction side pressure measurement section 53 and the pressure measured by the return side pressure measurement section 532 .
The secondary refrigerant flow control unit 231 determines the state of carbon dioxide from the calculated differential pressure, controls the secondary refrigerant flow control valve 2311 according to the determination result, and controls the flow rate of the secondary refrigerant R2. to adjust. For example, the flow rate of the secondary refrigerant R2 is controlled and the temperature of the primary refrigerant R1 is adjusted so that the carbon dioxide to be cooled does not fall below the solidification point during cooling or when it is returned to the storage tank 5.
When the differential pressure exceeds the first differential pressure threshold, the secondary refrigerant flow rate control unit 231 determines that the liquid and solid are mixed or solidified, and reduces the flow rate of the secondary refrigerant R2 or stops the supply. Or you may control so that it may supply intermittently.
When the differential pressure is less than the second differential pressure threshold value (<the first differential pressure threshold value and = substantially zero), the secondary refrigerant flow rate control unit 231 determines that the outlet remains in a gaseous state and is not cooled and liquefied. Then, the supply of the secondary refrigerant R2 may be started or controlled to increase the flow rate.
Further, the secondary refrigerant flow rate control unit 231 may control the liquid feed pump 211 provided in the secondary refrigerant tank 21 to control the flow rate of the secondary refrigerant R2. Also, the secondary refrigerant flow rate control valve 2311 is arranged in the secondary refrigerant discharge portion 23 , but may be arranged in the secondary refrigerant introduction portion 22 .

(Embodiment 4)
A cooling system 1 according to Embodiment 4 will be described with reference to FIG. Since the same reference numerals are the same as those of the second embodiment in FIG. 2, the description is omitted or simplified.
The cooling system 1 includes a heating device 140 that heats the secondary refrigerant R2 after passing through the primary refrigerant tank 11 and exchanging heat with the primary refrigerant R1. The warming device 140 may be arranged in the secondary refrigerant discharge section 23 . Secondary refrigerant R2 may be, for example, hydrogen, methane, or natural gas.

(Embodiment 5)
A cooling system 1 according to Embodiment 5 will be described with reference to FIG. Since the same reference numerals are the same as those of Embodiment 3 in FIG. 3, the description is omitted or simplified.
The cooling system 1 includes a compression device 150 that heats the secondary refrigerant R2 after passing through the primary refrigerant tank 11 and exchanging heat with the primary refrigerant R1. The compression device 150 may be arranged in the secondary refrigerant discharge section 23 . Secondary refrigerant R2 may be, for example, hydrogen, methane, or natural gas.

(another embodiment)
(1) Embodiments 2 and 3 are not limited to separate configurations, and may include both functional elements. The cooling system 1 includes an introduction-side pressure measurement unit 53, an introduction flow control valve 531, a return-side pressure measurement unit 532, a temperature measurement unit 18, a secondary refrigerant flow control unit 231, and a secondary refrigerant flow control valve 2311. and The secondary refrigerant flow control unit 231 may control the secondary refrigerant flow control valve 2311 based on either one or both of the temperature of the primary refrigerant and the differential pressure.
(2) In Embodiments 2 and 3, the carbon dioxide gas in the liquefied carbon dioxide storage tank 5 is cooled. The pump 35 may be configured to send liquefied carbon dioxide in the tank to the cooling device 10, and furthermore, the configuration of FIG. (the second introduction part 731, the second heat exchange passage part 712, the second return part 732).
(3) As another configuration example of the third embodiment, the secondary refrigerant flow rate control unit 231 controls the physical quantity (for example, the temperature , heat quantity, pressure), determine the state of carbon dioxide (for example, solid, liquid, gas, gas-liquid mixed state, liquid-solid mixed state, etc.), and depending on the judgment result, the secondary refrigerant flow control valve 2311 may be controlled to adjust the flow rate of the secondary refrigerant R2. Physical quantities (e.g., temperature, calorific value, pressure) are measured values of each measuring means (e.g., temperature sensor, calorimetric means, pressure sensor, etc.) provided in each of the first introduction section and/or the first return section. obtained from For example, when the secondary refrigerant flow control unit 231 determines that the liquid and solid are mixed or solidified in the return unit, the flow rate of the secondary refrigerant R2 is reduced or the supply is stopped (or intermittent supply). good too. For example, when it is determined that the return unit is in a gaseous state (not cooled and liquefied), the secondary refrigerant flow control unit 231 starts supplying the secondary refrigerant R2 or controls the flow rate to increase. may
(4) Embodiments 4 and 5 are not limited to separate configurations and may include functional elements of both (ie, the warming device and the compression device). It may be similarly employed in the other configuration examples described above.
(6) Also in Embodiments 2, 3, 4, and 5, the configuration of another configuration example 2 (FIG. 1C) of Embodiment 1 (primary refrigerant tank, first heat exchanger, second heat exchanger, primary refrigerant passage part, circulation pump).

<Simulation Example 1>
In the configuration of Embodiment 1 (FIG. 1A), the conditions of the primary refrigerant and secondary refrigerant required to liquefy 1 ton of carbon dioxide gas are as follows. The temperature of the primary refrigerant is adjusted by controlling the flow rate of the secondary refrigerant so that the liquefied carbon dioxide that is cooled by the cooling device and returned to the liquefied carbon dioxide storage tank has a temperature of about -40°C.
Primary Refrigerant: Propane Propane temperature is controlled at -41°C. Propane is evaporated by heat exchange with carbon dioxide gas and condensed by the secondary refrigerant.
Secondary refrigerant: Any one of the following refrigerants a to c can be used. Both are pressure 1 MPaA (absolute pressure in saturated state))
a: liquefied nitrogen: about 1.12 tons b: liquefied methane: about 0.55 tons c: liquefied hydrogen: about 0.10 tons

<Simulation Example 2>
In another configuration example 2 (FIG. 1C) of Embodiment 1, cold heat equivalent to the latent heat is derived from the liquefied carbon dioxide storage tank so as to suppress the evaporation of liquefied carbon dioxide at an absolute pressure of 1 MPaA in the saturated state. Cools (in other words, subcools) the liquefied carbon dioxide.
To prevent the liquefied carbon dioxide cooled by the cooling system from solidifying in the heat exchange passage, the return, and the liquefied carbon dioxide storage tank.
The temperature of the primary refrigerant is adjusted by controlling the flow rate of the secondary refrigerant so that the temperature of 11.8 tons of liquefied carbon dioxide falls within the temperature range of about -40°C to -54°C.
Primary refrigerant:
The propane temperature range is controlled from -56°C to -42°C.
Secondary refrigerant: Any one of the following refrigerants a to c can be used. Both pressure 1 MPaA (absolute pressure in saturated state)
a: liquefied nitrogen: about 1.23 tons b: liquefied methane: about 0.60 tons c: liquefied hydrogen: about 0.11 tons

<Simulation Example 3>
In the temperature control of the cooling system of Embodiment 2 (FIG. 2), propane is used as the primary refrigerant and liquefied methane as the secondary refrigerant.
The heat exchange between the primary refrigerant and the secondary refrigerant is performed by condensing the primary refrigerant (propane) from gas to liquid at -41°C and heating the secondary refrigerant (liquefied methane) from -124°C to -51°C. will be implemented.
In this case, the logarithmic average temperature difference between the fluids (between the fluids of the primary refrigerant and the secondary refrigerant) is 34.5°C. When the temperature of the primary refrigerant is near the solidification point of carbon dioxide (eg, -56.6°C), the logarithmic mean temperature difference between the fluids is 40.4°C. This temperature difference rises by about 17% from the steady state. This means that the increased amount of cold heat is being supplied to the cooling system in excess. At this time, in order to prevent solidification of carbon dioxide by the cooling system, control is performed so as to reduce the secondary refrigerant flow rate corresponding to excessive cooling.

1 cooling system 5 liquefied carbon dioxide storage tank 10 cooling device 11, 11a primary refrigerant tank 11b first heat exchanger 11c second heat exchanger 11d primary refrigerant passage portion 11e circulation pump 12 heat exchange passage portion 13 secondary refrigerant passage portion 21 Secondary refrigerant tank 22 Secondary refrigerant introduction part 23 Secondary refrigerant discharge part R1 Primary refrigerant R2 Secondary refrigerant

Claims (9)

A primary refrigerant tank containing a primary refrigerant having a temperature lower than the temperature of the carbon dioxide gas and/or liquefied carbon dioxide delivered from the liquefied carbon dioxide storage tank, and the carbon dioxide gas and/or liquefied dioxide cooled by the primary refrigerant. A cooling device having a heat exchange passage portion in which carbon moves and a secondary refrigerant passage portion in which a secondary refrigerant for cooling the primary refrigerant moves;
a secondary refrigerant tank for storing a secondary refrigerant for cooling the primary refrigerant;
a secondary refrigerant introduction portion that introduces the secondary refrigerant from the secondary refrigerant tank into the secondary refrigerant passage;
a secondary refrigerant discharge portion connected to the secondary refrigerant passage portion for leading out the secondary refrigerant;
comprising
Carbon dioxide gas and/or liquefied carbon dioxide cooling system. an introduction part connected to the inlet side of the heat exchange passage part for introducing carbon dioxide gas and/or liquefied carbon dioxide sent from a liquefied carbon dioxide storage tank;
a return section connected to the outlet side of the heat exchange passage section, from which cooled carbon dioxide gas and/or liquefied carbon dioxide is led out, and returned to the liquefied carbon dioxide storage tank;
A cooling system according to claim 1 . at least one temperature measuring unit for measuring the temperature of the primary refrigerant;
a secondary refrigerant flow control unit that controls the flow rate of the secondary refrigerant so that the temperature of the primary refrigerant measured by the temperature measurement unit does not fall below the solidification point of carbon dioxide at an arbitrary pressure. ,
3. A cooling system according to claim 1 or 2. Judging the state of carbon dioxide from the differential pressure between the introduction portion and the return portion, and controlling the flow rate of the secondary refrigerant according to the judgment result, and/or
determining the state of carbon dioxide from the physical quantity of carbon dioxide gas and/or liquefied carbon dioxide flowing through the introduction portion and/or the return portion, and controlling the flow rate of the secondary refrigerant according to the determination result; Equipped with a secondary refrigerant flow control unit,
3. The cooling system of claim 2. A heating device for warming the secondary refrigerant and/or a compression device for compressing the secondary refrigerant,
5. A cooling system according to any one of claims 1-4. A step (A) of cooling the primary refrigerant with a secondary refrigerant having a lower temperature than the primary refrigerant;
exchanging heat from the liquefied carbon dioxide storage tank with the primary refrigerant to cool the carbon dioxide gas and/or liquefied carbon dioxide with the primary refrigerant when the internal pressure of the liquefied carbon dioxide storage tank exceeds a preset threshold; An introduction step (B) of sending to a heat exchange means for
Step (C) of cooling carbon dioxide gas and/or liquefied carbon dioxide from the liquefied carbon dioxide storage tank with a primary refrigerant having a temperature lower than that temperature;
including,
A method for cooling carbon dioxide gas and/or liquefied carbon dioxide. Step (A-1) of controlling the flow rate of the secondary refrigerant so that the temperature of the primary refrigerant does not fall below the solidification point of carbon dioxide at an arbitrary pressure;
From the differential pressure between the inlet path through which carbon dioxide gas and/or liquefied carbon dioxide is sent from the liquefied carbon dioxide storage tank to the heat exchange means and the return path from the heat exchange means back to the liquefied carbon dioxide storage tank, the carbon dioxide A step (A-2) of determining the state of carbon and controlling the flow rate of the secondary refrigerant according to the determination result; and/or
Carbon dioxide gas and/or liquefied carbon dioxide flowing through an introduction route through which the carbon dioxide gas and/or liquefied carbon dioxide is sent from the liquefied carbon dioxide storage tank to the heat exchange means and/or a return route through which the heat exchange means returns to the liquefied carbon dioxide storage tank. Alternatively, a step (A-3) of determining the state of carbon dioxide from the physical quantity of liquefied carbon dioxide and controlling the flow rate of the secondary refrigerant according to the determination result;
including,
The cooling method according to claim 6. A liquefied carbon dioxide storage tank comprising a cooling system according to any one of claims 1-5. A ship comprising a cooling system according to any one of claims 1 to 5 or a liquefied carbon dioxide storage tank according to claim 8.

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