JP7774459B2 - Cold energy circulation system and cold energy circulation method - Google Patents

Description

The present invention relates to a cold energy circulation system and a cold energy circulation method.

Conventionally, on-site hydrogen production equipment installed inside various factories and on-site hydrogen stations that supply hydrogen to fuel cell vehicles often use hydrogen production equipment that produces hydrogen using steam reforming methods using raw materials such as natural gas, methane gas, or liquefied petroleum gas (LP gas).

Generally, hydrogen production devices produce not only hydrogen gas as the target product but also carbon dioxide gas (CO ₂ ) as a by-product. Currently, in on-site hydrogen production devices such as those described above, the by-product carbon dioxide gas is almost always released into the atmosphere, regardless of the installation structure of the hydrogen production device, except in cases where a carbon dioxide gas treatment facility is also installed, such as in large-scale plants. This release of carbon dioxide gas into the atmosphere is a major problem from the perspective of the risk of accelerating global warming.

In recent years, in order to achieve carbon neutrality in the future, it has become important to gradually reduce the amount of fossil fuels used by promoting a shift from fossil fuels such as gasoline to hydrogen fuels. However, at present, it is necessary to continue using fossil fuels for the time being while promoting the capture, storage, and reuse of carbon dioxide gas generated during the production of hydrogen gas.

From the perspective of preventing global warming as mentioned above, technologies such as carbon dioxide capture and storage (CCS) and carbon dioxide capture, utilization, and storage (CCUS) have been developed and demonstrated (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2008-273802

On the other hand, capturing carbon dioxide using methods such as CCS and CCUS as described in Patent Document 1 requires extremely large-scale facilities, enormous installation costs, and a large installation space. For this reason, at present, on-site hydrogen production equipment and hydrogen stations are not expected to capture and store carbon dioxide (carbon dioxide gas) as described in Patent Document 1, due to considerations such as business profitability and the availability of installation space.

Generally, carbon dioxide capture is achieved using carbon dioxide liquefaction equipment with conventionally known configurations. However, as mentioned above, such equipment has the problems of requiring enormous equipment costs, a large installation space, and large amounts of electricity consumption (liquefaction energy).

The present invention was made in consideration of the above-mentioned problems, and aims to provide a cold energy circulation system and cold energy circulation method that can liquefy carbon dioxide gas efficiently, with low cost and simple configuration, and with low power consumption, without releasing carbon dioxide gas into the atmosphere, even in the case of on-site hydrogen production equipment or hydrogen stations where the installation location of ancillary equipment is limited.

The inventors conducted extensive research to solve the above-mentioned problems. As a result, they discovered that by first recovering cold energy from liquefied carbon dioxide stored in a liquefied carbon dioxide storage facility that recycles carbon, such as a methanation plant, before the liquefied carbon dioxide is used for recycling, storing it in a mobile cold energy recovery device, and transporting it to an on-site location where a hydrogen production device is installed, it is possible to utilize the cold energy through circulation. They further discovered that by liquefying carbon dioxide (carbon dioxide gas) emitted from a hydrogen production device configured, such as a steam reforming device, on-site using the cold energy stored in a mobile cold energy recovery device and transporting it to a liquefied carbon dioxide storage facility, it is possible to recycle the liquefied carbon dioxide while effectively utilizing the cold energy, and thus completed the present invention.

That is, the invention of claim 1 is a cold energy circulation system comprising a liquefied carbon dioxide storage facility, a carbon dioxide recovery facility, and a mobile cold energy recovery device, wherein the mobile cold energy recovery device recovers cold energy from liquefied carbon dioxide stored in the liquefied carbon dioxide storage facility, and further wherein the mobile cold energy recovery device uses the cold energy recovered from the liquefied carbon dioxide storage facility to liquefy carbon dioxide emitted from the carbon dioxide recovery facility to produce liquefied carbon dioxide, and supplies the liquefied carbon dioxide to the liquefied carbon dioxide storage facility.

The invention of claim 2 is a cold energy circulation system as described in claim 1, characterized in that the mobile cold energy recovery device has a brine tank that recovers the cold energy from the liquefied carbon dioxide stored in the liquefied carbon dioxide storage facility using brine.

The invention of claim 3 is a cold energy circulation system according to claim 1 or 2, wherein the mobile cold energy recovery device has a room temperature brine tank and a low temperature brine tank as the brine tanks, and also has a heat exchange means, and the room temperature brine tank, the heat exchange means, and the low temperature brine tank are connected in this order by the same line, thereby recovering the cold energy from the liquefied carbon dioxide stored in the liquefied carbon dioxide storage facility, or adding the cold energy recovered from the liquefied carbon dioxide storage facility to carbon dioxide emitted from the carbon dioxide recovery facility.

The invention of claim 4 is a cold energy circulation system according to any one of claims 1 to 3, characterized in that the carbon dioxide capture facility includes a hydrogen production device.

The invention of claim 5 is a cold energy circulation method that uses the cold energy circulation system described in any one of claims 1 to 4 to recover cold energy from the liquefied carbon dioxide stored in the liquefied carbon dioxide storage facility using the mobile cold energy recovery device, and further uses the cold energy recovered from the liquefied carbon dioxide storage facility by the mobile cold energy recovery device to liquefy carbon dioxide emitted from the carbon dioxide recovery facility to produce the liquefied carbon dioxide, and supplies the liquefied carbon dioxide to the liquefied carbon dioxide storage facility.

According to the cold energy circulation system of the present invention, by adopting the above-mentioned configuration, carbon dioxide gas recovered from a carbon dioxide recovery facility including a hydrogen production device, etc. can be converted into liquefied carbon dioxide on-site using cold energy recovered at a liquefied carbon dioxide storage facility, and this liquefied carbon dioxide can then be transported to the liquefied carbon dioxide storage facility.
This makes it possible to liquefy carbon dioxide gas efficiently and with less power consumption by using circulated cold energy without releasing the carbon dioxide gas into the atmosphere, thereby obtaining liquefied carbon dioxide.
Therefore, even in the case of on-site hydrogen production equipment or hydrogen stations where the installation location of ancillary equipment is limited, it is possible to build an environmentally friendly cold energy circulation system with a low-cost and simple configuration.

Furthermore, the cold energy circulation method according to the present invention uses the cold energy circulation system according to the present invention described above, so even in the case of on-site hydrogen production equipment or hydrogen stations, which, like the above, have installation location limitations, it can be operated in an environmentally friendly manner with a low-cost, simple configuration.

1 is a diagram for schematically explaining a cold energy circulation system and a cold energy circulation method according to an embodiment of the present invention, and is a schematic diagram showing the configuration of a mobile cold energy recovery device that constitutes the cold energy circulation system. This is a diagram that schematically explains the cold energy circulation system and cold energy circulation method that are embodiments of the present invention, and is a schematic diagram that shows the connection form when the mobile cold energy recovery device shown in Figure 1 is connected to a liquefied carbon dioxide storage facility that constitutes the cold energy circulation system, and the flow of fluid within the mobile cold energy recovery device. FIG. 1 is a diagram for schematically explaining a cold energy circulation system and a cold energy circulation method according to an embodiment of the present invention, and is a schematic diagram showing the connection configuration when the mobile cold energy recovery device shown in FIG. 1 is connected to a carbon dioxide recovery facility that constitutes a cold energy circulation system, as well as the flow of fluid within the mobile cold energy recovery device. FIG. 1 is a diagram for schematically explaining the cold energy circulation system and cold energy circulation method according to an embodiment of the present invention, and is a schematic diagram showing the connection configuration and fluid flow when the mobile cold energy recovery device shown in FIG. 1 is mounted on a truck, moved, and connected to a liquefied carbon dioxide storage facility. FIG. 2 is a diagram for schematically explaining the cold energy circulation system and cold energy circulation method according to an embodiment of the present invention, and is a schematic diagram showing the connection configuration and fluid flow when the mobile cold energy recovery device shown in FIG. 1 is mounted on a truck, moved, and connected to a carbon dioxide recovery facility.

The following describes a cold energy circulation system and cold energy circulation method, which are one embodiment of the present invention, with appropriate reference to Figures 1 to 5. Note that the drawings used in the following description may show enlarged portions of key features for ease of understanding, and the dimensional proportions of each component may not be the same as in reality. Furthermore, the materials exemplified in the following description are merely examples, and the present invention is not limited to them. Appropriate modifications can be made within the scope of the present invention.

In the following explanation, the cold energy circulation system and cold energy circulation method of this embodiment (hereinafter sometimes abbreviated as the "circulation system" or "circulation method") will be specifically explained using an example of its overall configuration and operating method.

<Overall configuration of the cold energy circulation system>
FIG. 1 is a schematic diagram showing the configuration of a mobile cold energy recovery device 10 that constitutes the circulation system of this embodiment.
2 is a schematic diagram showing the connection configuration when the mobile cold energy recovery device 10 shown in FIG. 1 is connected to a liquefied carbon dioxide storage facility (see liquefied carbon dioxide storage facility 20 shown in FIG. 4) that constitutes a cold energy circulation system, as well as the flow of fluid within the mobile cold energy recovery device 10, and FIG. 3 is a schematic diagram showing the connection configuration when the mobile cold energy recovery device 10 shown in FIG. 1 is connected to a carbon dioxide recovery facility (see carbon dioxide recovery facility 30 shown in FIG. 5) that constitutes a cold energy circulation system, as well as the flow of fluid within the mobile cold energy recovery device 10.
4 is a schematic diagram showing the connection configuration and fluid flow when the mobile cold energy recovery device 10 shown in FIG. 1 is loaded onto a truck 40 for movement and connected to a liquefied carbon dioxide storage facility 20, and FIG. 5 is a schematic diagram showing the connection configuration and fluid flow when the mobile cold energy recovery device 10 shown in FIG. 1 is loaded onto a truck 40 for movement and connected to a carbon dioxide recovery facility 30.

In addition, in the above-mentioned Figures 1 to 5, the equipment included in the area surrounded by a rectangular dashed line is optional equipment in the circulation system of the present invention, and is equipment that can be installed appropriately as needed, and even if it is not installed, the effects of the present invention can be fully obtained.
In addition, in FIGS. 1 to 5, the arrows attached to the lines connecting the various pieces of equipment indicate the flow direction of each fluid in each connection and operation mode.

The circulation system of this embodiment is generally configured to include the mobile cold energy recovery device 10, the liquefied carbon dioxide storage facility 20, and the carbon dioxide recovery facility 30 as described above.
The circulation system of this embodiment is applicable to, for example, on-site hydrogen production devices installed inside various factories, etc., and on-site hydrogen stations that supply hydrogen to fuel cell vehicles.

[Mobile cold energy recovery device]
As shown in Fig. 1 (also see Figs. 2 to 5 as appropriate), the mobile cold energy recovery device 10 provided in the circulation system of this embodiment liquefies carbon dioxide (carbon dioxide) _GCO2 discharged from a carbon dioxide capture facility 30, the details of which will be described later, to form liquefied carbon dioxide _LCO2 , and recovers cold energy from the liquefied carbon dioxide _LCO2 stored in a liquefied carbon dioxide storage facility 20. Furthermore, the mobile cold energy recovery device 10 liquefies carbon dioxide GCO2 discharged from the carbon dioxide capture facility 30, the details of which will be described later, to form liquefied carbon dioxide _LCO2 , and supplies the liquefied liquefied carbon dioxide _LCO2 to the liquefied carbon dioxide storage facility ₂₀ , using the cold energy recovered from the liquefied carbon dioxide storage facility 20, the details of which will be described later.

As shown in FIG. 1, the mobile cold energy recovery device 10 includes a _CO2 separation storage tank 1, a heat recovery heat exchanger 2, a first nitrogen cylinder 3, a liquefaction heat exchanger (heat exchange means) 4, a room temperature brine tank (brine tank) 5, a second nitrogen cylinder 6, and a low temperature brine tank (brine tank) 7.

The mobile cold energy recovery system 10 shown in Figure 1 is further equipped with optional equipment consisting of a hydrogen heat exchanger 8, a refrigerator heat exchanger 9, and a refrigerator unit 110.

The mobile cold energy recovery device 10 also has connection ports for connection to each inlet and outlet of the liquefied carbon dioxide storage facility 20. Specifically, the mobile cold energy recovery device 10 has a liquefied carbon dioxide evaporator inlet connection port 11 connected to a liquefied carbon dioxide evaporator inlet 26 of the liquefied carbon dioxide storage facility 20, which will be described in detail later, a liquefied carbon dioxide storage tank connection port 12 connected to a liquefied carbon dioxide storage tank inlet 27, and a liquefied carbon dioxide evaporator outlet connection port 13 connected to a liquefied carbon dioxide evaporator outlet 28 (see also Figures 2 to 5 as appropriate). The mobile cold energy recovery device 10 also has a recovered _CO2 connection port 14 connected to a recovered _CO2 outlet 38 of the carbon dioxide capture facility 30. The mobile cold energy recovery device 10 also has hydrogen connection ports 15 and 16 connected to hydrogen connection ports 29a and 29b of the liquefied carbon dioxide storage facility 20 and hydrogen connection ports 39a and 39b of the carbon dioxide capture facility 30.

The _CO2 separation storage tank 1 stores liquefied carbon dioxide ( _LCO2) obtained by liquefying carbon dioxide gas recovered from a carbon dioxide recovery facility 30 (described later), and also separates the small amount of carbon dioxide gas ( _GCO2 ) that is vaporized from the liquefied carbon dioxide (LCO2 ₎ due to heat intrusion from the outside air, etc., into gas and liquid.
The _CO2 separation storage tank 1 is connected to the liquefied carbon dioxide storage tank connection port 12 via the liquefied carbon dioxide storage tank line F2, and as shown in Figure 2, when the mobile cold energy recovery device 10 is placed near the liquefied carbon dioxide storage facility 20, liquefied carbon dioxide _LCO2 is supplied to the liquefied carbon dioxide storage tank inlet 27 connected to the liquefied carbon dioxide storage tank connection port 12.

A valve V2 is provided on the path of the liquefied carbon dioxide storage tank line F2, and a _CO2 line F3 is connected to the liquefied carbon dioxide evaporator line F1 (described later) via a valve V3. As a result, the _CO2 separation and storage tank 1 is configured so that liquefied carbon dioxide (LC02 ₎ is introduced into the _CO2 separation and storage tank 1 via the _CO2 line F3, as shown in FIG.

A carbon dioxide gas discharge line F12 for discharging a portion of the gas-liquid separated carbon dioxide gas _GCO2 to the outside is connected to the top of the _CO2 separation storage tank 1. A valve V12 for controlling the amount of carbon dioxide gas _GCO2 discharged from the _CO2 separation storage tank 1 is provided on the carbon dioxide gas discharge line F12, and a heat recovery line F10 connected to a heat recovery heat exchanger 2 (described later) is connected to the _CO2 separation storage tank 1 side of this valve V12.

Furthermore, the _CO2 separation storage tank 1 in the illustrated example is provided with a liquid level sensor LD1 for detecting the liquid level of the liquefied carbon dioxide _LCO2 inside, a pressure sensor PD1 for detecting the pressure P1 inside the tank, and a temperature sensor TD6 for detecting the temperature T6 inside the tank.

The material of the _CO2 separation and storage tank 1 is not particularly limited, but for example, a vacuum double-structured heat-insulating tank made of stainless steel or the like can be appropriately adopted. The size of the _CO2 separation and storage tank 1 can also be appropriately set taking into consideration the amount of liquefied carbon dioxide (LCCO2 ₎ that can be stored.

The heat recovery heat exchanger 2 is located near the carbon dioxide recovery facility 30 and exchanges heat between low-temperature carbon dioxide _GCO2 flowing through the heat recovery line F10 and room-temperature carbon dioxide _GCO2 recovered via the _CO2 recovery line F5 from the recovery _CO2 connection port 14 connected to the recovery _CO2 outlet 38 of the carbon dioxide recovery facility 30 (see Figures 1, 3, and 5).

Further, the heat recovery heat exchanger 2 is located near the liquefied carbon dioxide storage facility 20 and exchanges heat between the low-temperature carbon dioxide gas _GCO2 flowing through the heat recovery line F10 and the liquefied carbon dioxide LCO2 introduced through the liquefied carbon dioxide evaporator line F1 from the liquefied carbon dioxide evaporator inlet connection port 11 connected to the liquefied carbon dioxide evaporator inlet 26 of the liquefied carbon dioxide storage facility 20 and having exchanged heat with brine LB in the liquefaction heat exchanger ₄ described later (see FIGS. 1, 2, and 4).

The heat recovery heat exchanger 2 is connected to a discharge line F11 for discharging nitrogen gas _GN2 supplied from a first nitrogen cylinder 3 described below, and a valve V11 for controlling the discharge of nitrogen gas _GN2 is provided on the path of this discharge line F11.
In addition, a valve V10 is provided downstream of the heat recovery heat exchanger 2 in the route of the heat recovery line F10, and by controlling the discharge of nitrogen gas _GN2 using this valve V10, nitrogen gas _GN2 can be discharged from the downstream side as appropriate.

The carbon dioxide gas discharge line F12 is connected to the liquefied coal evaporator line F1 between the heat recovery heat exchanger 2 and the liquefaction heat exchanger 4. A temperature sensor TD3 for detecting a temperature T3 of the carbon dioxide gas GCO2 is provided in the liquefied coal evaporator line F1 between the heat recovery heat exchanger 2 and the junction of the carbon dioxide gas discharge line F12, and a temperature sensor _TD2 for detecting a temperature T2 of the carbon dioxide gas _GCO2 is also provided between the junction of the carbon dioxide gas discharge line F12 and the liquefaction heat exchanger 4.

In addition, the heat recovery heat exchanger 2 is connected via a discharge line F11 to the above-mentioned _CO2 recovery line F5 and a shared line for the liquefied coal evaporator line F4, which is connected to the liquefied coal evaporator outlet connection port 13.
A control valve CV5 is provided on the _CO2 recovery line F5 at a position on the heat recovery heat exchanger 2 side, and a pressure sensor PD4 is provided on the recovered _CO2 connection port 14 side to detect the pressure P4 of the recovered carbon dioxide _GCO2 .
In addition, a control valve CV4 is provided in the path of the liquid coal evaporator line F4.

The heat recovery heat exchanger 2 is not particularly limited, and any heat exchanger commonly used in this field can be used without any restrictions.

The first nitrogen cylinder 3 stores nitrogen gas _GN2 inside, and in the illustrated example, is configured to be able to supply nitrogen gas _GN2 toward the inside of the _CO2 separation storage tank 1 by being connected to the carbon dioxide gas discharge line F12 via the nitrogen supply line F17 and the nitrogen gas introduction line F9.
In addition, the first nitrogen cylinder 3 is connected to the liquid carbon dioxide evaporator line F1 via a nitrogen supply line F17 and a nitrogen gas introduction line F8, so that inert nitrogen gas _GN2 can be introduced into the liquefied carbon dioxide _LCO2 flowing through the liquid carbon dioxide evaporator line F1.
Further, a pressure reducing valve RV17 for controlling the supply pressure of the nitrogen gas _GN2 from the first nitrogen cylinder 3 is provided on the route of the nitrogen supply line F17.
Further, a valve V9 for controlling the amount of nitrogen gas _GN2 supplied to the inside of the _CO2 separation storage tank 1 is provided on the route of the nitrogen gas introduction line F9.
Further, the nitrogen gas introduction line F8 is provided with a valve V8 for controlling the supply amount of nitrogen gas _GN2 introduced into the liquid coal evaporator line F1.

As the first nitrogen cylinder 3, one or more nitrogen cylinders that are generally available for industrial use (for example, filling pressure: 14.7 MPa, nitrogen gas volume: 7 m ³ ) can be used.

The nitrogen gas _GN2 stored in the first nitrogen cylinder 3 is, for example, _N2 : approximately 99.99% (purity).

The liquefaction heat exchanger 4 performs heat exchange between carbon dioxide GCO2, which is recovered via a _CO2 recovery line F5 from a _CO2 recovery connection port 14 connected to a _CO2 recovery outlet 38 near the carbon dioxide recovery facility 30 and has been heat exchanged with low-temperature carbon dioxide GCO2 in the heat recovery heat exchanger ₂ , and low-temperature brine (heat medium) _LB , which is introduced via a liquefied carbon evaporator line F1 and supplied from a low-temperature brine tank 7 described below via a brine supply line F7 (see FIGS. 1, 3, and 5).

Further, the liquefaction heat exchanger 4 is located near the liquefied carbon dioxide storage facility 20 and performs heat exchange between liquefied carbon dioxide _LCO2 introduced via a liquefied carbon dioxide evaporator line F1 from a liquefied carbon dioxide evaporator inlet connection port 11 connected to a liquefied carbon dioxide evaporator inlet 26 of the liquefied carbon dioxide storage facility 20, and room temperature brine LB supplied via a brine supply line F6 from a room temperature brine tank 5 described later (see FIGS. 1, 2, and 4).

A valve V7 is provided in the brine supply line F7 connected to the liquefaction heat exchanger 4 to control the flow rate of the low-temperature brine LB. Furthermore, a temperature sensor TD5 is provided on the liquefaction heat exchanger 4 side of the valve V7 in the brine supply line F7 to detect the temperature T5 of the low-temperature brine LB supplied from the low-temperature brine tank 7.

Further, the brine supply line F6, which communicates with the brine supply line F7 via the liquefaction heat exchanger 4, is provided with a control valve CV6 for controlling the flow rate of the room temperature brine LB.
A temperature sensor TD4 for detecting the temperature T4 of the room temperature brine LB supplied from the room temperature brine tank 5 is provided on the liquefaction heat exchanger 4 side of the control valve V6 in the path of the brine supply line F6.

In addition, a brine heat exchange line F19 connected to a hydrogen heat exchanger 8, an optional equipment described in detail below, is connected between the control valve V6 and the temperature sensor TD4 in the brine supply line F6. The brine heat exchange line F19 is provided with the hydrogen heat exchanger 8 and the refrigerator heat exchanger 9, both of which are optional equipment, and its other end is connected back to the brine supply line F6, between the room temperature brine tank 5 and the control valve CV6. In addition, a control valve CV19 that controls the flow rate of brine LB is provided between the refrigerator heat exchanger 9 and the room temperature brine tank 5 in the brine heat exchange line F19.

The liquefaction heat exchanger 4 is not particularly limited, and any heat exchanger commonly used in this field can be used without any restrictions.

The room-temperature brine tank 5 stores the room-temperature brine LB that has been heat exchanged in the liquefaction heat exchanger 4. The room-temperature brine tank 5 uses, for example, a calcium chloride aqueous solution, a sodium chloride aqueous solution, or a fluorine-based inert liquid as the brine LB, and stores the cold energy imparted by the heat exchange.

The room-temperature brine tank 5 is located near the carbon dioxide capture facility 30 and is connected to the liquefaction heat exchanger 4 via brine supply lines F7 and F6. The liquefaction heat exchanger 4 exchanges heat with the recovered carbon dioxide gas _GCO2 , thereby converting the temperature of the brine LB from low to room temperature (see Figures 1, 3, and 5).

The room-temperature brine tank 5 introduces room-temperature brine LB via a brine supply line F6 into the liquefaction heat exchanger 4 provided in communication with the room-temperature brine tank 5 near the liquefied carbon dioxide storage facility 20. As a result, in the liquefaction heat exchanger 4, heat exchange occurs between the room-temperature brine LB and the liquefied carbon dioxide _LCO2 before it is introduced into the liquefied carbon dioxide evaporator 22 of the liquefied carbon dioxide storage facility 20, and the brine LB cooled by this heat exchange is introduced into the low-temperature brine tank 7 via a brine supply line F7 (see FIGS. 1, 2, and 4).

Furthermore, the illustrated room temperature brine tank 5 is equipped with a liquid level sensor LD2 for detecting the liquid level of the brine LB inside, a pressure sensor PD2 for detecting the pressure P2 inside the tank, and a temperature sensor TD7 for detecting the temperature T7 inside the tank.

The material of the room-temperature brine tank 5 is not particularly limited, and a storage tank made of, for example, stainless steel or other materials can be used as appropriate. The size of the room-temperature brine tank 5 can also be set appropriately, taking into account the capacity of the brine LB.

In the circulation system of this embodiment, a room temperature brine tank 5 is provided as a brine tank, and further, a low temperature brine tank 7 described later is provided, so that the brine LB can recover and store cold energy from the liquefied carbon dioxide _LCO2 stored in the liquefied carbon dioxide storage facility 20.

The second nitrogen cylinder 6, like the first nitrogen cylinder 3, stores nitrogen gas _GN2 inside, and in the illustrated example, is configured to be able to supply nitrogen gas _GN2 to the inside of a low-temperature brine tank 7 described below via a nitrogen supply line F18 and a nitrogen gas introduction line F15.
The second nitrogen cylinder 6 is configured to be able to supply nitrogen gas _GN2 into the room-temperature brine tank 5 via a nitrogen supply line F18 and a nitrogen gas introduction line F14.

Further, a pressure reducing valve RV18 for controlling the supply pressure of the nitrogen gas _GN2 from the second nitrogen cylinder 6 is provided on the route of the nitrogen supply line F18.
Further, a valve V15 for controlling the amount of nitrogen gas _GN2 supplied into the low-temperature brine tank 7 is provided on the nitrogen gas introduction line F15.
Further, a valve V14 for controlling the amount of nitrogen gas _GN2 supplied into the room temperature brine tank 5 is provided on the nitrogen gas introduction line F14.

Furthermore, a nitrogen gas discharge line F16 is connected between the valve V15 in the nitrogen gas introduction line F15 and the low-temperature brine tank 7, and is configured so that the discharge of nitrogen gas _GN2 can be controlled by the valve V16 provided in this line.
Similarly, a nitrogen gas discharge line F13 is connected between the valve V14 in the nitrogen gas introduction line F14 and the room temperature brine tank 5, and is configured so that the discharge of nitrogen gas _GN2 can be controlled by the valve V13 provided in this line.

As the second nitrogen cylinder 6, similar to the first nitrogen cylinder 3, one or more nitrogen cylinders that are commonly distributed for industrial use (for example, filling pressure: 14.7 MPa, nitrogen gas volume: 7 m ³ ) can be used.

The nitrogen gas _GN2 stored in the second nitrogen cylinder 6 is also, like the first nitrogen cylinder 3, _N2 : approximately 99.99% (purity), for example.

The low-temperature brine tank 7 introduces low-temperature brine LB via a brine supply line F7 into the liquefaction heat exchanger 4 provided in communication with the low-temperature brine tank 7 near the carbon dioxide capture facility 30. In the liquefaction heat exchanger 4, the brine LB is heat-exchanged from low temperature to room temperature by heat exchange with the carbon dioxide gas _GCO2 recovered from the carbon dioxide capture facility 30, and is introduced into the room-temperature brine tank 5 via a brine supply line F6 (see FIGS. 1, 3, and 5).

Further, low-temperature brine LB that has been heat-exchanged with liquefied carbon dioxide LCO2 before being introduced into the liquefied carbon dioxide evaporator 25 of the carbon dioxide recovery facility 30 in the liquefaction heat exchanger 4 provided in communication with the liquefied carbon dioxide storage facility 20 via brine supply lines _F6 and F7 is introduced into the low-temperature brine tank 7 (see FIGS. 1, 2, and 4).

Furthermore, the low-temperature brine tank 7 in the illustrated example is provided with a liquid level sensor LD3 for detecting the liquid level of the brine LB inside, a pressure sensor PD3 for detecting the pressure P3 inside the tank, and a temperature sensor TD8 for detecting the temperature T8 inside the tank.

The material of the low-temperature brine tank 7 is not particularly limited; for example, a vacuum double-walled insulated tank made of stainless steel or the like can be used as appropriate. The size of the low-temperature brine tank 75 can also be set appropriately, taking into account the capacity of the brine LB.

The mobile cold energy recovery device 10 provided in the circulation system of the example described in this embodiment is configured to include a room temperature brine tank 5, a liquefaction heat exchanger 4, and a low temperature brine tank 7, which are connected in this order by the same line. This allows cold energy to be effectively recovered and stored from the liquefied carbon dioxide _LCO2 stored in the liquefied carbon dioxide storage facility 20 by the brine LB. Therefore, the mobile cold energy recovery device 10 can recover cold energy from the liquefied carbon dioxide _LCO2 stored in the liquefied carbon dioxide storage facility 20, and can also liquefy carbon dioxide _GCO2 emitted from the carbon dioxide capture facility 30 by applying the cold energy recovered from the liquefied carbon dioxide storage facility 20 to liquefy it, thereby obtaining liquefied carbon dioxide _LCO2 .

As described above, the hydrogen heat exchanger 8 , together with the refrigerator heat exchanger 9 and the refrigerator unit 110 , constitutes optional equipment in the mobile cold energy recovery system 10 .
The hydrogen heat exchanger 8 is located near the liquefied carbon dioxide storage facility 20 and exchanges heat between the liquefied hydrogen _LH2 introduced from the hydrogen connection port 29a of the liquefied carbon dioxide storage facility 20 via the hydrogen line F20 connected to the hydrogen connection port 15 and the room temperature brine LB introduced via the above-mentioned brine heat exchange line F19 (see Figures 1, 2, and 4).

Further, the hydrogen heat exchanger 8 is located near the carbon dioxide capture facility 30 and exchanges heat between liquefied hydrogen _LH2 introduced from the hydrogen connection port 39b of the carbon dioxide capture facility 30 via a hydrogen line F21 connected to the hydrogen connection port 16 and room temperature brine LB introduced via a brine heat exchange line F19 (see Figures 1, 3 and 5).

As described above, when the mobile cold energy recovery device 10 is connected to the liquefied carbon dioxide storage facility 20 as shown in Figures 1, 2 and 4, the flow direction of the brine LB in the brine heat exchange line F19 is opposite to that when the mobile cold energy recovery device 10 is connected to the carbon dioxide recovery facility 30 as shown in Figures 1, 3 and 5. Furthermore, when the mobile cold energy recovery device 10 is connected to the liquefied carbon dioxide storage facility 20, the flow direction of the hydrogen gas GH2 introduced into the hydrogen heat exchanger 8 is opposite to that when the mobile cold energy recovery device ₁₀ is connected to the carbon dioxide recovery facility 30.

The hydrogen heat exchanger 8 is not particularly limited, and any heat exchanger commonly used in this field can be used without any restrictions.

The refrigerator heat exchanger 9 is located between the hydrogen heat exchanger 8 and the brine supply line F6 in the path of the brine heat exchange line F19 described above, and is also located in the path of the refrigerator line FR1 through which the refrigerant GR supplied from the refrigerator unit 110 described below flows. This allows the refrigerator heat exchanger 9 to rapidly cool the brine LB flowing through the brine heat exchange line F19. The brine heat exchange line F19 is configured as a loop-shaped refrigeration circuit that passes through the refrigerator heat exchanger 9 and the refrigerator unit 110.

With the above configuration, the brine LB can be rapidly cooled even in carbon dioxide capture equipment 30 that does not have a backup liquefied hydrogen storage tank 37, details of which will be described later.

The refrigerator heat exchanger 9 is not particularly limited, and any heat exchanger commonly used in this field can be used without any restrictions.

The refrigerator unit 110, although not shown in detail, is composed of, for example, a conventionally known compressor and condenser, and supplies refrigerant GR to the refrigerator heat exchanger 9 via the refrigerator line FR1, as described above.

The optional equipment consisting of the hydrogen heat exchanger 8, refrigerator heat exchanger 9, and refrigerator unit 110 described above may or may not be installed in the mobile cold energy recovery system 10 as needed.

The mobile cold energy recovery device 10 having the above configuration can be mounted on a truck 40 and configured for transport, as shown in the example in Figures 4 and 5, and can be moved to the vicinity of a liquefied carbon dioxide storage facility 20 or a carbon dioxide recovery facility 30 as needed, connected to them, and operated.

The connection structure between the inlets and outlets of the mobile cold energy recovery device 10 and the inlets and outlets of the liquefied carbon dioxide storage facility 20 and carbon dioxide recovery facility 30 is not particularly limited, and although detailed illustrations are omitted, a configuration using couplers to connect the inlets and outlets using flexible hoses can be used, for example.

In this embodiment, by providing the mobile cold energy recovery device 10 configured as described above, cold energy is recovered from liquefied carbon dioxide (LCO2 ₎ stored in a liquefied carbon dioxide storage facility 20 that performs carbon recycling in a methanation plant or the like before the liquefied carbon dioxide (LCO2 ₎ is used for recycling, stored in the mobile cold energy recovery device 10, and transported to an on-site carbon dioxide capture facility 30 where a hydrogen production device is installed, thereby enabling utilization through circulation of cold energy. Furthermore, carbon dioxide gas ( _GCO2 ) discharged from a hydrogen production device configured as a steam reforming type or the like is liquefied on-site using the cold energy stored in the mobile cold energy recovery device 10 to form liquefied carbon dioxide (LCO2 ₎ , and transported to the liquefied carbon dioxide storage facility 20, making it possible to recycle the liquefied carbon dioxide (LCO2 ₎ while effectively utilizing cold energy.

[Liquefied carbon dioxide storage facility]
As described above, the liquefied carbon dioxide storage facility 20 is a facility that accommodates and stores liquefied carbon dioxide (LCO2 ₎ liquefied by the mobile cold energy recovery device 10 that is moved and placed nearby in the circulation system of this embodiment. The liquefied carbon dioxide storage facility 20 is a facility that includes methanation equipment for supplying methane ( _CH4 ) required in various factories, etc.
The liquefied carbon dioxide storage facility 20 is a facility that not only stores the liquefied carbon dioxide LCO ₂ but also recovers the cold energy contained in the stored liquefied carbon dioxide LCO ₂ by the mobile cold energy recovery device 10 .

Specifically, as shown in Figure 4, the liquefied carbon dioxide storage facility 20 comprises a liquefied carbon dioxide storage tank 21, a liquefied carbon dioxide evaporator 22, and methanation equipment 23.

The liquefied carbon dioxide storage facility 20 shown in Figure 4 is further equipped with optional equipment consisting of a liquid water evaporator 24 and a liquefied hydrogen storage tank 25.

The liquefied carbon dioxide storage facility 20 also has connection ports for connecting to the various inlets and outlets of the mobile cold energy recovery device 10. Specifically, the liquefied carbon dioxide storage facility 20 has a liquefied carbon dioxide evaporator inlet 26 to which the liquefied carbon dioxide evaporator inlet connection port 11 of the mobile cold energy recovery device 10 is connected, a liquefied carbon dioxide storage tank inlet 27 to which the liquefied carbon dioxide storage tank connection port 12 is connected, and a liquefied carbon dioxide evaporator outlet 28 to which the liquefied carbon dioxide evaporator outlet connection port 13 is connected. The liquefied carbon dioxide storage facility 20 also has hydrogen connection ports 29a and 29b to which the hydrogen connection ports 15 and 16 of the mobile cold energy recovery device 10 are connected (see also the mobile cold energy recovery device 10 shown in Figures 1 and 2).

The liquefied carbon dioxide storage tank 21 accommodates and stores liquefied carbon dioxide LCO ₂ that is obtained by liquefying carbon dioxide gas GC0 ₂ in the mobile cold energy recovery device 10 .
The liquefied carbon dioxide storage tank 21 is connected to the liquefied carbon dioxide storage tank inlet 27 via a liquefied carbon dioxide storage tank line F22, and as shown in Figure 4, when the mobile cold energy recovery device 10 is placed near the liquefied carbon dioxide storage facility 20, liquefied carbon dioxide _LCO2 is supplied from the liquefied carbon dioxide storage tank connection port 12 of the mobile cold energy recovery device 10.
In addition, a control valve CV22 for controlling the flow rate of the liquefied carbon dioxide _LCO2 is provided in the path of the liquefied carbon dioxide storage tank line F222.

The inlet side of a liquefied carbon dioxide storage tank 21 is connected to a liquefied carbon dioxide evaporator 22, and a liquefied carbon dioxide evaporator inlet 26 is connected to the inlet side of the liquefied carbon dioxide evaporator 22 via a liquefied carbon dioxide evaporator inlet line F26. A valve V26 for controlling the flow rate of the liquefied carbon dioxide _LCO2 is provided on the path of the liquefied carbon dioxide evaporator inlet line F26.

The material of the liquefied carbon dioxide storage tank 21 is not particularly limited, and similarly to the above, for example, a vacuum double-structured heat-insulating tank made of stainless steel or the like can be appropriately adopted. The size of the liquefied carbon dioxide storage tank 21 can also be appropriately set taking into consideration the amount of liquefied carbon dioxide (LCO2 ₎ that can be stored.

The liquefied carbon dioxide evaporator 22 vaporizes the liquefied carbon dioxide _LCO2 stored in the liquefied carbon dioxide storage tank 21, and introduces the vaporized carbon dioxide _GCO2 into the methanation equipment 23 connected to the outlet side via the liquefied carbon dioxide evaporator inlet line F26.
Furthermore, a liquefied coal evaporator outlet 28 to which carbon dioxide GCO2 is supplied from the liquefied coal evaporator outlet connection port 13 of the mobile cold recovery device 10 is connected via a liquefied coal evaporator outlet line F23 to the outlet side of the liquefied coal evaporator ₂₂ in the liquefied coal evaporator inlet line F26. Furthermore, a control valve V23 for controlling the flow rate of carbon dioxide _GCO2 is provided on the path of the liquefied coal evaporator inlet line F26.

As described above, the methanation facility 23 is a facility for supplying methane required in, for example, various factories, and carbon dioxide gas _GCO2 for producing methane is supplied from the liquid coal evaporator 22.
The methanation facility 23 is also connected to the outlet side of a liquid water evaporator 24, which constitutes optional equipment described below, and hydrogen gas _GH2 for producing methane is supplied from the liquid water evaporator 24.

As described above, the methanation facility 23 receives the supply of carbon dioxide gas GCO ₂ and hydrogen gas GH ₂ and reacts them to synthesize methane (CH ₄ ).
In addition, the methanation facility 23 is connected to a methane supply line FM1 for supplying synthesized methane to locations where methane is used, such as various factories.

As described above, the liquid water evaporator 24 and the liquefied hydrogen storage tank 25 constitute optional equipment in the liquefied carbon dioxide storage facility 20.
The liquid water evaporator 24 vaporizes liquefied hydrogen _LH2 supplied to the inlet side from a liquefied hydrogen storage tank 25, the details of which will be described later, and supplies hydrogen gas _GH2 , which is the raw material for methane, to the methanation facility 23, as described above.
A hydrogen connection port 29b is connected to the outlet side of the liquid water evaporator 24 via a hydrogen receiving line F24, and this hydrogen connection port 29b is connected to the hydrogen connection port 16, which is an optional facility in the mobile cold recovery device 10. A control valve CV24 is provided in the hydrogen receiving line F24 to control the flow rate of hydrogen gas _GH2 flowing therethrough.

Furthermore, a hydrogen connection port 29a is connected to the inlet side of the liquid water evaporator 24 via a hydrogen delivery line F25, and this hydrogen connection port 29a is connected to the hydrogen connection port 15, which is an optional facility in the mobile cold recovery device 10. In addition, a valve V25 is provided on the route of the hydrogen delivery line F25 to control the flow rate of the liquefied hydrogen _LH2 flowing inside.

As described above, the liquefied hydrogen storage tank 25 stores liquefied hydrogen _LH2 , which is the raw material for methane synthesized in the methanation facility 23, and is connected to the inlet side of the liquid water evaporator 24.

The material of the liquefied hydrogen storage tank 25 is not particularly limited, and similarly to the above, for example, a vacuum double-structured heat-insulated storage tank made of stainless steel or the like can be appropriately adopted. The size of the liquefied hydrogen storage tank 25 can also be appropriately set taking into consideration the amount of liquefied hydrogen _LH2 that can be stored.

[Carbon dioxide capture facility]
As described above, the carbon dioxide capture facility 30 is a facility in which carbon dioxide _GCO2 is captured by the mobile cold energy recovery device 10 in the circulation system of this embodiment. The carbon dioxide capture facility 30 is, for example, a facility including a hydrogen production device that emits carbon dioxide _GCO2 as a by-product. In this embodiment, the carbon dioxide capture facility 30 will be described using a facility including a hydrogen production device 31 as an example.

The carbon dioxide capture facility 30 includes a hydrogen production device 31 , a purifier 32 , a compressor 33 , a captured CO ₂ holder 34 , and a hydrogen gas holder 35 .

The carbon dioxide capture facility 30 shown in Figure 5 is further equipped with optional equipment consisting of a liquid water evaporator 36 and a backup liquefied hydrogen storage tank 37.

The carbon dioxide recovery facility 30 also has connection ports for connecting to the respective entrances and exits of the mobile cold energy recovery device 10. Specifically, the carbon dioxide recovery facility 30 has a recovered _CO2 outlet 38 to which the recovered _CO2 connection port 14 of the mobile cold energy recovery device 10 is connected, and hydrogen connection ports 39a, 39b to which the hydrogen connection ports 15, 16 are connected (see also the mobile cold energy recovery device 10 shown in Figures 1 and 3).

As described above, the hydrogen production device 31 is a facility for producing hydrogen gas _GH2 used in various factories, etc., and as shown in FIG. 5, methane ( _CH4 ) and pure water ( _H2O ) are supplied from the outside as raw materials for hydrogen gas _GH2 .
The hydrogen gas _GH2 produced by the hydrogen production device 31 is introduced into a hydrogen gas holder 35, the details of which will be described later, via a hydrogen supply line F27. A control valve CV27 for controlling the flow rate of the hydrogen gas GH2 is provided in the hydrogen supply line _F27 .

In addition, the hydrogen production device 31 is connected to a _CO2 recovery line F29 for discharging carbon dioxide gas _GCO2 , which is generated as an exhaust gas during the production of hydrogen gas _GH2 , toward a purifier 32, which will be described later.

The hydrogen production device 31 provided in the carbon dioxide capture facility 30 of this embodiment is a steam reforming facility used as an on-site hydrogen production device, for example, in various factories, etc.

The purifier 32 purifies, through a predetermined process, carbon dioxide gas GCO ₂ that is generated as an exhaust gas when hydrogen gas GH ₂ is produced in the hydrogen production device 31 .
The carbon dioxide gas _HCO2 purified by the purifier 32 is introduced into a compressor 33 (described later) through a _CO2 recovery line F29.

The purifier 32 is not particularly limited, but may be one that can purify carbon dioxide gas _GCO2 by a method such as adsorption or membrane separation.
The refiner 32 may be installed as needed, or may not be installed.

The compressor 33 converts the purified carbon dioxide gas _GCO2 introduced through the _CO2 recovery line F29 into a compressed gas, and for example, a general compressor is used.
The carbon dioxide gas _GCO2 compressed by the compressor 33 is introduced into a _CO2 recovery holder 34 (described later) via a _CO2 recovery line F29.

The recovered _CO2 holder 34 is a container that temporarily stores the carbon dioxide gas _GCO2 compressed by the compressor 33, and also functions as a buffer before it is supplied to the mobile cold energy recovery device 10 from the recovered _CO2 outlet 38 mentioned above.
In addition, a valve V29 for controlling the flow rate of carbon dioxide gas _GCO2 is provided between the recovered _CO2 holder 34 and the recovered _CO2 outlet 38 in the path of the _CO2 recovery line F29.

As the recovered CO ₂ holder 34, any conventionally known holder used for storing gas in this field can be used without any restrictions.

The hydrogen gas holder 35 is a container that temporarily stores the hydrogen gas _GH2 produced by the hydrogen production device 31, and also functions as a buffer before the hydrogen gas _GH2 is supplied to the place where it is used.
A hydrogen use line F28 for supplying hydrogen gas _GH2 to the place of use is connected to the hydrogen gas holder 35. In addition, a valve V28 for controlling the flow rate of the hydrogen gas _GH2 is provided on the hydrogen use line F28.

As described above, the liquid water evaporator 36 and the backup liquefied hydrogen storage tank 37 constitute optional equipment in the carbon dioxide capture facility 30.
The liquid water evaporator 36 vaporizes backup liquefied hydrogen LH2, which is supplied to the inlet side from a backup liquefied hydrogen storage tank 37 (details of which will be described later) via a liquefied hydrogen evaporation line _F32 , to produce hydrogen gas _GH2 , which is introduced from the outlet side into the above-mentioned hydrogen supply line F27 via a hydrogen addition line F30.

The liquefied hydrogen evaporation line F32 is provided with a valve V32 for controlling the flow rate of backup liquefied hydrogen _LH2 . One end of a hydrogen delivery line F34 is connected to the liquefied hydrogen evaporation line F32 between the valve V32 and the liquid water evaporator 36, and the other end of the hydrogen delivery line F34 is connected to the hydrogen connection port 39b. The hydrogen delivery line F34 is also provided with a valve V34 for controlling the flow rate of hydrogen gas _GH2 .

The hydrogen addition line F30 is provided with a valve V30 that controls the flow rate of hydrogen gas _GH2 vaporized in the liquid-water evaporator 36. One end of a hydrogen receiving line F31 is connected to the hydrogen addition line F30 between the liquid-water evaporator 36 and the valve V30, and the other end is connected to a hydrogen connection port 39a. The hydrogen receiving line F31 is provided with a control valve CV31 that controls the flow rate of hydrogen gas _GH2 .

The backup liquefied hydrogen storage tank 37 stores backup liquefied hydrogen _LH2 for producing hydrogen gas _GH2 to be supplied to the place where hydrogen gas _GH2 is used, and is connected to the inlet side of the liquid water evaporator 36 via a liquefied hydrogen evaporation line F32.

The material of the backup liquefied hydrogen storage tank 37 is not particularly limited, and similarly to the above, for example, a vacuum double-walled heat-insulating storage tank made of stainless steel or the like can be appropriately adopted. The size of the backup liquefied hydrogen storage tank 37 can also be appropriately set taking into consideration the capacity of liquefied hydrogen _LH2 to be stored.

<Cold energy circulation method>
Next, a cold energy circulation method of this embodiment using the above-described cold energy circulation system will be described.
The cold energy circulation method of this embodiment (hereinafter sometimes simply referred to as the circulation method) is a method in which, using the circulation system of this embodiment as shown in FIGS. 1 to 5 , cold energy is recovered from liquefied carbon dioxide (LCO2 ₎ stored in a liquefied carbon dioxide storage facility 20 by a mobile cold energy recovery device 10, and further, the cold energy recovered from the liquefied carbon dioxide storage facility 20 by the mobile cold energy recovery device 10 is used to liquefy carbon dioxide gas (GCO2 ₎ emitted from a carbon dioxide recovery facility 30 to form liquefied carbon dioxide (LCO2 ₎ , and the liquefied carbon dioxide (LCO2 ₎ is supplied to the liquefied carbon dioxide storage facility 20.

The circulation method of this embodiment will be described below by taking an example in which specific operating conditions are set.
The circulation method of this embodiment can be carried out by operating the circulation system in the following procedures and under the following conditions.

[Operation at carbon dioxide capture facility]
First, the mobile cold energy recovery device 10 is moved and placed near the carbon dioxide recovery facility 30, and connected to the carbon dioxide recovery facility 30 in the connection configuration shown in Figure 5 (see also Figures 1 and 3), and then carbon dioxide gas _GCO2 is recovered from the carbon dioxide recovery facility 30 in the procedures and conditions shown in (1) to (11) below.

(Carbon dioxide recovery preparation operation)
(1) First, the pressure in the first nitrogen cylinder 3 is adjusted in advance to a set pressure (for example, 0.60 MPa) by operating the pressure reducing valve RV17.
(2) Next, it is confirmed that the pressure P1 in the _CO2 separation storage tank 1 detected by the pressure sensor PD1 is a predetermined pressure (for example, 0.58 MPa; _CO2 sublimation pressure = 0.52 MPa or more). At this time, if the pressure P1 is below the set pressure, the valves V3 and V12 are opened to allow the liquefied carbon dioxide _LCO2 to flow back toward the liquefaction heat exchanger 4 and evaporate, thereby increasing the pressure P1 to the set pressure. On the other hand, if the pressure P1 is above the set pressure, the valve V10 is opened to decrease the pressure.

(Brine tank preparation operation)
(3) Next, the pressure in the second nitrogen cylinder 6 is adjusted to a set pressure (for example, 0.3 MPa) by operating the pressure reducing valve RV18.
(4) Next, the valve V15 provided on the nitrogen gas introduction line F15 is opened. Thereafter, the valve V15 is controlled to open and close so that the pressure P3 of the low-temperature brine tank 7 detected by the pressure sensor PD3 becomes a set pressure (e.g., 0.28 MPa).
(5) Next, the valve V14 is opened and closed after 5 seconds. After that, the valve V13 is controlled to open and close so that the pressure P2 of the room-temperature brine tank 5 detected by the pressure sensor PD2 becomes the set pressure (for example, 0.05 MPa).

(Liquefaction and storage of carbon dioxide (CO ₂ ))
(6) Next, the valve V7 provided on the brine supply line F7 is opened.
(7) Next, the valve V3 provided on the _CO2 line F3 is opened.
(8) Next, the control valve CV5 provided on the _CO2 recovery line F5 is gradually opened at a set speed (e.g., 0.5%/sec) to a set opening (e.g., 40%) and fixed at the set opening. At the same time, the control valve CV6 provided on the brine supply line F6 is opened at a set speed (e.g., 3%/sec) to a set opening (e.g., 30%), and then the flow rate is controlled so that the temperature T1 detected by the temperature sensor TD1 provided on the liquid coal evaporator line F1 becomes the set temperature (e.g., -40°C).
(9) During the liquefaction and storage of carbon dioxide gas, the valve V10 is controlled to open and close so that the pressure P1 in the _CO2 separation storage tank 1 is always at a set pressure (for example, 0.58 MPa; _CO2 sublimation pressure = 0.52 MPa or higher).
(10) Next, when the liquid level L1 detected by the liquid level sensor LD1 provided in the _CO2 separation storage tank 1 is at the set value H, the valve V3 is closed, and the liquefaction of carbon dioxide gas is terminated normally. However, if the pressure P4 detected by the pressure sensor PD4 provided in the liquefied carbon evaporator line F4 is equal to or lower than the set pressure (for example, 0.65 MPa), or if the liquid level L3 detected by the liquid level sensor LD3 provided in the low-temperature brine tank 7 is at the set value L, the valve V3 is closed, and the liquefaction of carbon dioxide gas is terminated prematurely.

(Maintenance operation)
(11) In each of the above steps, if water freezes onto the heat recovery heat exchanger 2 or the liquefaction heat exchanger 4, the valves V8 and V11 are opened to thaw the frozen material and perform a nitrogen purge.

[Operation at a liquefied carbon dioxide storage facility]
First, the mobile cold energy recovery device 10 is moved and placed near the liquefied carbon dioxide storage facility 20, which is the carbon recycling location, and connected to the liquefied carbon dioxide storage facility 20 in the connection configuration shown in FIG. 4 (see also FIGS. 1 and 2). After that, liquefied carbon dioxide LCO2 is stored in the liquefied carbon dioxide storage facility 20 and cold energy is recovered from the liquefied carbon dioxide _LCO2 according to the procedures and conditions shown in ( ₁ ) to (10) below.

(Carbon dioxide preparation operation)
(1) First, it is confirmed that the pressure P1 detected by the pressure sensor PD1 provided in the _CO2 separation storage tank 1 is a set pressure (for example, 0.58 MPa; _CO2 sublimation pressure = 0.52 MPa or more). At this time, if the pressure P1 is below the set pressure, the valves V3 and V12 are opened to allow the liquefied carbon dioxide _LCO2 to flow back toward the liquefaction heat exchanger 4 and evaporate, thereby increasing the pressure P1 to the set pressure. On the other hand, if the pressure P1 is above the set pressure, the valve V10 is opened to decrease the pressure.

(Brine tank preparation operation)
(2) The valve V14 is opened. After that, the valve V13 is controlled to open and close so that the pressure P2 detected by the pressure sensor PD2 provided in the room-temperature brine tank 5 becomes a set pressure (for example, 0.28 MPa).
(3) Next, the valve V15 provided on the nitrogen gas inlet line F15 is opened and closed after 5 seconds. After that, the valve V16 provided on the nitrogen gas outlet line F16 is controlled to open and close so that the pressure P3 detected by the pressure sensor PD3 provided on the low-temperature brine tank 7 becomes the set pressure (e.g., 0.05 MPa).

(Brine tank cooling operation)
(4) Open the valve V7 provided on the brine supply line F7.
(5) Next, the valve V1 provided on the liquid coal evaporator line F1 is opened.
(6) Next, the control valve CV4 provided in the liquefied coal evaporator line F4 is gradually opened at a set speed (e.g., 0.5%/second) to a set opening (e.g., 40%) and fixed at the set opening. At the same time, the control valve CV6 provided in the brine supply line F6 is opened at a set speed (e.g., 3%/second) to a set opening (e.g., 30%), and then the flow rate is controlled so that the temperature T2 detected by the temperature sensor TD2 provided in the liquefied coal evaporator line F1 becomes the set temperature (e.g., 10°C).
(7) When the liquid level L2 detected by the liquid level sensor LD2 provided in the room temperature brine tank 5 reaches the set value L, or when the liquid level L3 detected by the liquid level sensor LD3 provided in the low temperature brine tank 7 reaches the set value H, the valve V1 closes and the cooling of the brine LB ends.

(Carbon dioxide recovery operation)
(8) The valve V2 installed on the liquefied carbon dioxide storage tank line F2 is opened to start the recovery of carbon dioxide gas _GCO2 .
(9) During the recovery operation of carbon dioxide gas _GCO2 , it is always confirmed that the pressure P1 detected by the pressure sensor PD1 provided in the _CO2 separation storage tank 1 is equal to or higher than the set pressure (for example, 0.70 MPa).
(10) When the liquid level L1 detected by the liquid level sensor LD1 provided in the _CO2 separation storage tank 1 reaches the set value L, the valve V2 closes and the recovery of carbon dioxide gas is completed.

<Action and effect>
According to the cold energy circulation system of the present embodiment, by adopting a configuration including the mobile cold energy recovery device 10 as described above, carbon dioxide gas _GCO2 recovered from a carbon dioxide recovery facility 30 including a hydrogen production device 31 and the like can be converted on-site into liquefied carbon dioxide _LCO2 using cold energy recovered in a liquefied carbon dioxide storage facility 20, and further, this liquefied carbon dioxide _LCO2 can be transported to the liquefied carbon dioxide storage facility 20.
This makes it possible to liquefy carbon dioxide _GCO2 efficiently and with less power consumption by using circulated cold energy without releasing carbon dioxide _GCO2 into the atmosphere, thereby obtaining liquefied carbon dioxide _LCO2 .
Therefore, even in the case of on-site hydrogen production equipment or hydrogen stations where the installation location of ancillary equipment is limited, it is possible to build an environmentally friendly cold energy circulation system with a low-cost and simple configuration.

Furthermore, the cold energy circulation method of this embodiment uses the cold energy circulation system of this embodiment described above, so even in the case of on-site hydrogen production equipment or hydrogen stations that, like the above, have installation location limitations, it can be operated in an environmentally friendly manner with a low-cost, simple configuration.

Furthermore, according to this embodiment, when the mobile cold energy recovery device 10 is provided with the room temperature brine tank 5 and the low temperature brine tank 7 and adopts a configuration in which cold energy is stored and transported using the brine LB, the cold energy can be stored with high thermal efficiency near the carbon dioxide recovery facility 30, which is the carbon recycling location. This makes it possible to use this cold energy to more efficiently liquefy carbon dioxide _GCO2 and obtain liquefied carbon dioxide _LCO2 .

Furthermore, according to this embodiment, by adopting a configuration in which carbon dioxide _GCO2 is liquefied and stored and recovered as liquefied carbon dioxide _LCO2 , the storage amount can be increased compared to a configuration in which carbon dioxide _GCO2 is stored and recovered in a gaseous state, and transportation costs can be reduced compared to transporting the same amount of carbon dioxide _GCO2 .

Generally, storing carbon dioxide (GCO2 ₎ in a gaseous state requires a compressor, which makes the equipment complex and large, requires laborious maintenance, and increases installation and operating costs. In contrast, the circulation system of this embodiment has a simple configuration with few sliding parts, allowing it to be installed in a small space and is easy to maintain, thereby reducing installation and operating costs. Furthermore, when adopting a configuration in which cold energy is stored and transported using the above-described brine LB, a general-purpose brine LB that can be used at temperatures from -45°C to room temperature can be used, thereby achieving maintenance-free operation and further reducing operating costs.

Furthermore, by liquefying carbon dioxide (GCO2 ₎ to form liquefied carbon dioxide ( _LCO2) , minor impurities mixed in the carbon dioxide (GCO2 ₎ can be removed, which can suppress the progression of equipment deterioration and further reduce operating costs.

Furthermore, by adopting the above-described equipment configuration for recovering cold energy, the power required for operation is only the power for instrumentation, and no large electrical equipment is required, making it possible to liquefy carbon dioxide _GCO2 to produce liquefied carbon dioxide _LCO2 efficiently and with low power consumption.

Furthermore, by adopting a configuration in which the internal flow direction of the liquefaction heat exchanger 4, which exchanges heat between carbon dioxide gas _GCO2 and brine LB, can be changed when the mobile cold energy recovery device 10 is connected to the carbon dioxide recovery facility 30 and when the mobile cold energy recovery device 10 is connected to the liquefied carbon dioxide storage facility 20, further space saving and cost reduction are possible.

Furthermore, since the mobile cold energy recovery device 10 is a facility that moves between the liquefied carbon dioxide storage facility 20 and the carbon dioxide recovery facility 30, by loading it onto a large truck 40 such as the example shown in Figures 4 and 5 in a fixed or detachable manner, it becomes easier to move and maintenance is also improved.
Furthermore, when a large-scale cold energy circulation system is constructed, it is also possible to adopt a transportation method in which the mobile cold energy recovery device 10 is loaded onto a trailer (not shown).

Furthermore, in this embodiment, the mobile cold energy recovery device 10 is provided with the hydrogen heat exchanger 8 as optional equipment, so that when a backup liquefied hydrogen storage tank 37 for the hydrogen production device 31 is installed as optional equipment in the carbon dioxide capture facility 30, the hydrogen cold energy corresponding to the pressure increase caused by heat intrusion into the backup liquefied hydrogen storage tank 37 can be efficiently recovered. Furthermore, it becomes possible to recover part of the cold energy of the liquefied hydrogen _LH2 in the carbon dioxide capture facility 30.

Furthermore, in this embodiment, the mobile cold energy recovery device 10 is equipped with a refrigerator unit 110 and a refrigerator heat exchanger 9 as optional equipment, making it possible to connect it to equipment other than the liquefied carbon dioxide storage facility 20 to recover cold energy. However, in this case, separate power equipment is required and additional power consumption will occur.

<Other aspects of the present invention>
Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments described above, and various modifications and changes are possible within the scope of the gist of the present invention as set forth in the claims.

The cold energy circulation system of the present invention is capable of liquefying carbon dioxide gas to obtain liquefied carbon dioxide efficiently, at low cost, and with a simple configuration, without releasing carbon dioxide gas into the atmosphere, even in the case of on-site hydrogen production equipment or hydrogen stations where installation locations for ancillary equipment are limited. Therefore, the cold energy circulation system of the present invention is extremely useful in cases where a hydrogen production equipment that produces hydrogen using the steam reforming method is installed, such as on-site hydrogen production equipment installed inside various factories, or on-site hydrogen stations that supply hydrogen to fuel cell vehicles.

10...Mobile cold energy recovery device (cold energy circulation system)
1... _CO2 separation storage tank 2...Heat recovery heat exchanger 3...First nitrogen cylinder 4...Liquefaction heat exchanger 5...Normal temperature brine tank (brine tank)
6... Second nitrogen cylinder 7... Low temperature brine tank (brine tank)
8...Hydrogen heat exchanger 9...Refrigeration unit heat exchanger 110...Refrigeration unit unit 11...Liquefied coal evaporator inlet connection port 12...Liquefied carbon dioxide storage tank connection port 13...Liquefied coal evaporator outlet connection port 14...Recovered _CO2 connection port 15, 16...Hydrogen connection ports V1, V2, V3, V7, V8, V9, V10, V11, V12, V13, V14, V15, V16...Valves CV4, CV5, CV6, CV19, CV20, CV21...Control valves RV17, RV18...Pressure reducing valves PD1, PD2, PD3, PD4...Pressure sensors TD1, TD2, TD3, TD4, TD5, TD6, TD7, TD8...Temperature sensors LD1, LD2, LD3...Liquid level sensors F1...Liquefied coal evaporator line F2...Liquefied carbon dioxide storage tank line F3... _CO2 line F4...Liquefied carbon dioxide evaporator line F5... _CO2 recovery line F6...Brine supply line F7...Brine supply line F8...Nitrogen gas introduction line F9...Nitrogen gas introduction line F10...Heat recovery line F11...Discharge line F12...Carbon dioxide gas exhaust line F13...Nitrogen gas exhaust line F14...Nitrogen gas introduction line F15...Nitrogen gas introduction line F16...Nitrogen gas exhaust line F17...Nitrogen supply line F18...Nitrogen supply line F19...Brine heat exchange line F20...Hydrogen line F21...Hydrogen line FR1...Refrigeration machine line 20...Liquefied carbon dioxide storage facility 21...Liquefied carbon dioxide storage tank 22...Liquefied carbon dioxide evaporator 23...Methanation equipment 24...Liquid water evaporator 25...Liquefied hydrogen storage tank 26...Liquefied carbon dioxide evaporator inlet 27...Liquefied carbon dioxide storage tank inlet 28...Liquid coal evaporator outlet 29a, 29b...Hydrogen connection ports V25, V26...Valves CV22, CV23, CV24...Control valves F22...Liquefied carbon dioxide storage tank line F23...Liquefied coal evaporator outlet line F24...Hydrogen receiving line F25...Hydrogen delivery line F26...Liquefied coal evaporator inlet line FM1...Methane supply line 30...Carbon dioxide recovery facility (cold energy circulation system)
31...Hydrogen production device 32...Purifier 33...Compressor 34...Recovered _CO2 holder 35...Hydrogen gas holder 36...Liquid water evaporator 37...Backup liquefied hydrogen storage tank 38...Recovered _CO2 outlet 39a, 39b...Hydrogen connection port V28, V29, V30, V32, V33, V34...Valves CV27, CV31...Control valve F27...Hydrogen supply line F28...Hydrogen use line F29... _CO2 recovery line F30...Hydrogen addition line F31...Hydrogen receiving line F32...Liquefied hydrogen evaporation line F33...Hydrogen delivery line F34...Hydrogen delivery line 40...Truck _GCO2 ...Carbon dioxide
LCO ₂ ... liquefied carbon dioxide GN ₂ ... nitrogen gas LB ... brine LH ₂ ... liquefied hydrogen GH ₂ ... hydrogen gas GR ... refrigerant

Claims (3)

The system comprises a liquefied carbon dioxide storage facility, a carbon dioxide recovery facility, and a mobile cold and heat recovery device;
The mobile cold energy recovery device recovers cold energy from the liquefied carbon dioxide stored in the liquefied carbon dioxide storage facility,
Furthermore, the mobile cold energy recovery device liquefies carbon dioxide emitted from the carbon dioxide recovery facility using the cold energy recovered from the liquefied carbon dioxide storage facility to produce liquefied carbon dioxide, and supplies the liquefied carbon dioxide to the liquefied carbon dioxide storage facility ,
The mobile cold energy recovery device has a brine tank that recovers the cold energy from the liquefied carbon dioxide stored in the liquefied carbon dioxide storage facility by brine,
The mobile cold energy recovery device has a room temperature brine tank and a low temperature brine tank as the brine tank, and also has a heat exchange means,
A cold energy circulation system characterized in that the room temperature brine tank, the heat exchange means, and the low temperature brine tank are connected in this order by the same line, thereby recovering the cold energy from the liquefied carbon dioxide stored in the liquefied carbon dioxide storage facility, or adding the cold energy recovered from the liquefied carbon dioxide storage facility to carbon dioxide emitted from the carbon dioxide recovery facility. 2. The cold energy circulation system according to claim 1 , wherein the carbon dioxide recovery facility includes a hydrogen production device. Using the cold energy circulation system according to claim 1 or 2 , cold energy is recovered from the liquefied carbon dioxide stored in the liquefied carbon dioxide storage facility by the mobile cold energy recovery device,
Furthermore, the cold energy circulation method is characterized in that the mobile cold energy recovery device uses the cold energy recovered from the liquefied carbon dioxide storage facility to liquefy carbon dioxide emitted from the carbon dioxide recovery facility to produce the liquefied carbon dioxide, and the liquefied carbon dioxide is supplied to the liquefied carbon dioxide storage facility.