Patent Description:
Priority is claimed on <CIT>, and <CIT>.

In a floating structure such as a ship including a tank for storing a liquefied gas, the liquefied gas stored inside the tank is vaporized due to heat input from an outside, and so-called a boil-off gas is generated. When the boil-off gas is generated, a pressure inside the tank rises. Therefore, for example, PTL <NUM> discloses a configuration as follows. In order to reliquefy a fuel boil-off gas generated from a liquefied gas fuel stored in a fuel tank, the fuel boil-off gas is cooled by cold heat of the boil-off gas of the liquefied gas generated in a cargo tank. Document PTL <NUM> discloses the preamble of independent claim <NUM>.

Incidentally, when liquefied carbon dioxide is stored in a tank, the liquefied carbon dioxide is liquefied to recover carbon dioxide released into an atmosphere in the first place. Therefore, it is desirable that energy required for reliquefying carbon dioxide gas generated by vaporizing the liquefied carbon dioxide inside the tank is suppressed as much as possible. From a viewpoint of suppressing the energy required for reliquefication, it is conceivable to release the carbon dioxide gas into the atmosphere. However, as a matter of course, it is not preferable to release the recovered carbon dioxide into the atmosphere.

The present invention is made to solve the above-described problem, and an object of the present invention is to provide a floating structure which can efficiently cool and reliquefy liquefied carbon dioxide vaporized inside a tank while effectively utilizing energy.

According to the present invention, in order to solve the above-described problem, there is provided a floating structure according to claim <NUM>.

According to the floating structure of the present invention, the liquefied carbon dioxide vaporized inside the tank can be efficiently cooled and reliquefied while energy is effectively utilized.

Hereinafter, a floating structure according to an embodiment of the present disclosure will be described with reference to <FIG>.

As illustrated in <FIG>, in this embodiment, a ship 1A serving as a floating structure includes at least a hull <NUM> serving as a floating main structure, a combustor <NUM>, a first tank <NUM>, a second tank <NUM>, and a reliquefying/fuel supply system 30A (refer to <FIG>).

The hull <NUM> has a pair of broadsides 3A and 3B, a ship bottom (not illustrated), and an upper deck <NUM> which form an outer shell of the hull <NUM>. The broadsides 3A and 3B have a pair of broadside outer plates respectively forming right and left broadsides. The ship bottom (not illustrated) has a ship bottom outer plate connecting the broadsides 3A and 3B. The pair of broadsides 3A and 3B and the ship bottom (not illustrated) cause the outer shell of the hull <NUM> to have a U-shape in a cross section orthogonal to a bow-stern direction Da. The upper deck <NUM> described as an example in this embodiment is a whole deck exposed outward. In the hull <NUM>, a superstructure <NUM> having an accommodation space is formed on the upper deck <NUM> on a stern 2b side. A position of the superstructure <NUM> is merely an example, and may be disposed on a bow 2a side of the hull <NUM>, for example.

A cargo tank storage compartment (hold) <NUM> for storing the first tank <NUM> is formed inside the hull <NUM>.

The combustor <NUM> is disposed inside the hull <NUM>. The combustor <NUM> shows a required function by combusting a liquefied combustible gas F stored in the second tank <NUM>. For example, as the combustor <NUM>, a main engine, a generator, and a boiler may be adopted. The main engine is an engine (internal combustion engine) that uses the liquefied combustible gas F as a fuel, and shows a propulsive force for propelling the hull <NUM>. The generator includes an engine (internal combustion engine) that uses the liquefied combustible gas F as the fuel, and generates electric power used inside the hull <NUM> by using a driving force of the engine. The boiler combusts the liquefied combustible gas F to generate steam used inside the hull <NUM>.

The first tank <NUM> is disposed in the hull <NUM>. The first tank <NUM> is disposed inside the cargo tank storage compartment <NUM>. In this embodiment, two first tanks <NUM> are disposed at an interval in the bow-stern direction Da. In the present embodiment, for example, the first tank <NUM> has a cylindrical shape extending in a horizontal direction. The first tank <NUM> is not limited to the cylindrical shape, and the first tank <NUM> may have a spherical shape or a square shape.

The first tank <NUM> can store carbon dioxide C having a gas phase and a liquid phase. The carbon dioxide C stored in the first tank <NUM> is a cargo (freight) of the ship 1A.

As illustrated in <FIG>, the carbon dioxide C stored inside the first tank <NUM> is separated into the liquid phase and the gas phase inside the first tank <NUM>. The liquid phase, that is, the carbon dioxide C in a liquid state (hereinafter, referred to as a carbon dioxide liquid C1) is stored in a lower portion inside the first tank <NUM>. The gas phase, that is, the carbon dioxide C in a gas state (hereinafter, referred to as a carbon dioxide gas C2) is stored in an upper portion inside the first tank <NUM>. The carbon dioxide gas C2 is a boil-off gas generated in such a manner that the carbon dioxide liquid C1 inside the first tank <NUM> is naturally vaporized by heat input from an outside.

The first tank <NUM> includes a loading pipe <NUM> and an unloading pipe <NUM>.

The loading pipe <NUM> loads the carbon dioxide C (carbon dioxide liquid C1) supplied from an onshore facility into the first tank <NUM>. The loading pipe <NUM> penetrates a top portion of the first tank <NUM> from the outside of the first tank <NUM>, and extends to the inside of the first tank <NUM>. A tip portion of the loading pipe <NUM> is open inside the first tank <NUM>. <FIG> illustrates a case where the tip portion of the loading pipe <NUM> is located in the lower portion of the first tank <NUM>. However, a disposition of the tip portion of the loading pipe <NUM> is not limited thereto (the same applies to a loading pipe of a second embodiment to be described later).

The unloading pipe <NUM> feeds the carbon dioxide C (carbon dioxide liquid C1) inside the first tank <NUM> outboard. The unloading pipe <NUM> penetrates the top portion of the first tank <NUM> from the outside of the first tank <NUM>, and extends to the inside of the first tank <NUM>. An unloading pump <NUM> is provided in a tip portion of the unloading pipe <NUM>. The unloading pump <NUM> suctions the carbon dioxide C (carbon dioxide liquid C1) inside the first tank <NUM>. The unloading pipe <NUM> guides the carbon dioxide C (carbon dioxide liquid C1) delivered from the unloading pump <NUM> to the outside of the first tank <NUM> (outboard).

The second tank <NUM> is disposed in the hull <NUM>. The liquefied combustible gas F is stored in the second tank <NUM>. The liquefied combustible gas F is a fuel in the ship 1A, and is combusted in the combustor <NUM>. That is, the second tank <NUM> is a so-called fuel tank for storing the fuel.

A temperature of the liquefied combustible gas F stored in the second tank <NUM> in a liquid state is lower than a temperature of the liquid phase of the carbon dioxide C stored in the first tank <NUM>. Examples of the liquefied combustible gas F include a liquefied natural gas (LNG), methane, ethane, and hydrogen. In the present embodiment, a case where the liquefied natural gas is used as the liquefied combustible gas F will be described as an example.

The reliquefying/fuel supply system 30A reliquefies the carbon dioxide gas C2 stored inside the first tank <NUM>. Furthermore, the reliquefying/fuel supply system 30A vaporizes the liquefied combustible gas F in a liquid state inside the second tank <NUM>, and supplies the vaporized liquefied combustible gas F to the combustor <NUM>. The reliquefying/fuel supply system 30A includes at least a first heat exchanger 31A and a second heat exchanger <NUM>.

The first heat exchanger 31A exchanges heat between the carbon dioxide gas C2 and the liquefied combustible gas F. Each of a feed line 33A, a return line 34A, a first fuel line <NUM>, and a second fuel line <NUM> is connected to the first heat exchanger 31A.

The feed line 33A guides the carbon dioxide gas C2 to the first heat exchanger 31A from the first tank <NUM>. In the present embodiment, one end of the feed line 33A is connected to the top portion of the first tank <NUM>. The feed line 33A guides the carbon dioxide gas C2 to the first heat exchanger 31A from the upper portion inside the first tank <NUM>. A compressor <NUM> that compresses the carbon dioxide gas C2 is disposed in the feed line 33A.

The return line 34A guides the carbon dioxide liquid C1 liquefied by the first heat exchanger 31A to the first tank <NUM> from the first heat exchanger 31A.

The first fuel line <NUM> feeds the liquefied combustible gas F to the first heat exchanger 31A from the second tank <NUM> by using the fuel pump <NUM>. The second fuel line <NUM> guides the liquefied combustible gas F to the second heat exchanger <NUM> from the first heat exchanger 31A.

The second heat exchanger <NUM> vaporizes the liquefied combustible gas F by exchanging heat of the liquefied combustible gas F passing through the first heat exchanger 31A with a heat medium H. In the second heat exchanger <NUM> in this embodiment, the liquefied natural gas is vaporized to be a natural gas. Examples of the heat medium H used in the second heat exchanger <NUM> include steam used inside the hull <NUM> and an exhaust gas from the combustor <NUM>. A third fuel line <NUM> is connected to the second heat exchanger <NUM>. The third fuel line <NUM> guides a gas obtained by vaporizing the liquefied combustible gas F to the combustor <NUM> from the second heat exchanger <NUM>.

In the reliquefying/fuel supply system 30A configured in this way, the carbon dioxide gas C2 is fetched from the upper portion inside the first tank <NUM> by operating the compressor <NUM>. The fetched carbon dioxide gas C2 is compressed by the compressor <NUM>, and thereafter, is fed to the first heat exchanger 31A through the feed line 33A. On the other hand, the liquefied combustible gas F inside the second tank <NUM> is fed to the first heat exchanger 31A through the first fuel line <NUM> by the fuel pump <NUM>. Then, in the first heat exchanger 31A, the heat is exchanged between the carbon dioxide gas C2 and the liquefied combustible gas F.

The temperature of the liquefied combustible gas F in a liquid state is lower than the temperature of the carbon dioxide C. Therefore, the compressed carbon dioxide gas C2 is cooled and reliquefied by the heat exchange in the first heat exchanger 31A. The cooled and reliquefied carbon dioxide liquid C1 is returned to the first tank <NUM> through the return line 34A.

In addition, the liquefied combustible gas F is heated by exchanging the heat with the carbon dioxide gas C2 having a higher temperature than the liquefied combustible gas F in the first heat exchanger 31A, and the temperature of the liquefied combustible gas F rises. The liquefied combustible gas F whose temperature is raised is fed to the second heat exchanger <NUM> through the second fuel line <NUM>. The liquefied combustible gas F is further heated and vaporized by exchanging the heat with the heat medium H in the second heat exchanger <NUM>. The vaporized liquefied combustible gas F is supplied to the combustor <NUM> through the third fuel line <NUM>.

In the ship 1A of the above-described embodiment, the carbon dioxide gas C2 supplied to the first heat exchanger 31A from the first tank <NUM> through the feed line 33A is cooled and reliquefied by exchanging the heat with the liquefied combustible gas F in the first heat exchanger 31A. The reliquefied carbon dioxide liquid C1 is returned to the first tank <NUM> through the return line 34A. The temperature of the reliquefied carbon dioxide liquid C1 is lower than the temperature of the carbon dioxide C stored inside the first tank <NUM>. Therefore, the cooled carbon dioxide liquid C1 is returned to the first tank <NUM> so that the temperature of the carbon dioxide C inside the first tank <NUM> is lowered. In this manner, a temperature rise inside the first tank <NUM> can be suppressed, and new vaporization of the carbon dioxide liquid C1 inside the first tank <NUM> can be suppressed.

On the other hand, the temperature of the liquefied combustible gas F stored in the second tank <NUM> is raised by exchanging the heat with the carbon dioxide gas C2 in the first heat exchanger 31A, and thereafter, the liquefied combustible gas F is fed to the second heat exchanger <NUM>. Therefore, in the second heat exchanger <NUM>, the liquefied combustible gas F in a state of being heated in advance by the first heat exchanger 31A is vaporized by exchanging the heat with the heat medium H. Therefore, heat energy required for vaporizing the liquefied combustible gas F in the second heat exchanger <NUM> may be reduced, compared to a case where the first heat exchanger 31A is not provided.

In this way, the carbon dioxide gas C2 generated inside the first tank <NUM> can be efficiently reliquefied the energy is effectively utilized.

In addition, the carbon dioxide gas C2 has a higher temperature than the carbon dioxide liquid C1 cooled by latent heat of vaporization when the boil-off gas is generated. Therefore, in the first heat exchanger 31A, the temperature of the liquefied combustible gas F can be raised to a higher temperature, compared to a case of the heat exchange with the carbon dioxide liquid C1. In this regard, the heat energy required for vaporizing the liquefied combustible gas F in the second heat exchanger <NUM> is further reduced.

Next, a second embodiment of the floating structure according to the present invention will be described. The second embodiment described below is different from the first embodiment in only a configuration of a first heat exchanger 31B. Therefore, description will be made by assigning the same reference numerals to elements which are the same as those of the first embodiment, and repeated description will be omitted.

As illustrated in <FIG>, a reliquefying/fuel supply system 30B of a ship 1B serving as a floating structure in the present embodiment includes the first heat exchanger 31B and the second heat exchanger <NUM>.

The first heat exchanger 31B exchanges the heat between the carbon dioxide C (carbon dioxide liquid C1) and the liquefied combustible gas F. A feed line 33B, a return line 34B, the first fuel line <NUM>, and the second fuel line <NUM> are connected to the first heat exchanger 31B.

The feed line 33B guides the carbon dioxide C to the first heat exchanger 31B from the first tank <NUM>. More specifically, the feed line 33B guides the carbon dioxide liquid C1 to the first heat exchanger 31B from the lower portion in the first tank <NUM>. The feed line 33B guides the carbon dioxide liquid C1 delivered from the unloading pump <NUM> to the first heat exchanger 31B. The feed line 33B is branched from the unloading pipe <NUM>. On-off valves 39A and 39B are disposed in a portion where the feed line 33B and the unloading pipe <NUM> are branched. The on-off valve 39A opens and closes a flow path inside the unloading pipe <NUM>. The on-off valve 39B opens and closes a flow path inside the feed line 33B. For example, when the carbon dioxide liquid C1 inside the first tank <NUM> is fed to the first heat exchanger 31B by the unloading pump <NUM>, the on-off valve 39A is in a closed state, and the on-off valve 39B is in an open state. A case has been described where the carbon dioxide liquid C1 is delivered to the feed line 33B by the unloading pump <NUM>. However, a small capacity pump may be installed separately from the unloading pump <NUM>, and the carbon dioxide liquid C1 may be delivered to the feed line 33B by using the small capacity pump.

The return line 34B guides the carbon dioxide liquid C1 to the first tank <NUM> from the first heat exchanger 31B. In the present embodiment, the return line 34B is connected to the top portion of the first tank <NUM>. An injection unit <NUM> is disposed in the top portion of the first tank <NUM>. The injection unit <NUM> injects the carbon dioxide liquid C1 returned to the first tank <NUM> from the first heat exchanger 31B through the return line 34B to the gas phase of the upper portion inside the first tank <NUM>. Examples of this injection form include a shower-like form and a mist-like form. The injected carbon dioxide liquid C1 falls downward while coming into wide contact with the carbon dioxide gas C2 stored inside the first tank <NUM>.

In the reliquefying/fuel supply system 30B configured in this way, the carbon dioxide liquid C1 is delivered from the lower portion inside the first tank <NUM> by operating the unloading pump <NUM>. The delivered carbon dioxide liquid C1 is fed to the first heat exchanger 31B through the feed line 33B. In the first heat exchanger 31B, the heat is exchanged between the carbon dioxide liquid C1 and the liquefied combustible gas F. Due to the heat exchange in the first heat exchanger 31B, the carbon dioxide liquid C1 is further cooled than the carbon dioxide liquid C1 inside the first tank <NUM>, and is brought into a supercooled state. The carbon dioxide liquid C1 in the supercooled state is returned to the first tank <NUM> through the return line 34B.

The carbon dioxide liquid C1 in the supercooled state is injected into the carbon dioxide gas C2 inside the first tank <NUM> by the injection unit <NUM>. In this manner, the carbon dioxide gas C2 stored in the upper portion inside the first tank <NUM> is cooled by the injected carbon dioxide liquid C1. In this manner, at least a portion of the carbon dioxide gas C2 is reliquefied.

On the other hand, the liquefied combustible gas F is heated by exchanging the heat with the carbon dioxide liquid C1 having a temperature higher than that of the liquefied combustible gas F in the first heat exchanger 31B, and the temperature of the liquefied combustible gas F rises. The liquefied combustible gas F whose temperature is raised is fed to the second heat exchanger <NUM> through the second fuel line <NUM>. The liquefied combustible gas F is further heated and vaporized by exchanging the heat with the heat medium H in the second heat exchanger <NUM>. The vaporized liquefied combustible gas F is supplied to the combustor <NUM> through the third fuel line <NUM>.

In the ship 1B of the above-described second embodiment, the carbon dioxide liquid C1 supplied from the first tank <NUM> through the feed line 33B is cooled by exchanging the heat with the liquefied combustible gas F in the first heat exchanger 31B. The cooled carbon dioxide liquid C1 is returned to the first tank <NUM> through the return line 34B. Since the cooled carbon dioxide liquid C1 is supplied into the first tank <NUM>, the temperature of the carbon dioxide C inside the first tank <NUM> is lowered. In this manner, the temperature rise inside the first tank <NUM> can be suppressed, and new vaporization of the carbon dioxide liquid C1 can also be suppressed.

Furthermore, the temperature of the liquefied combustible gas F stored in the second tank <NUM> is raised by exchanging the heat with the carbon dioxide C having a higher temperature than the liquefied combustible gas F in the first heat exchanger 31B, and thereafter, the liquefied combustible gas F is fed to the second heat exchanger <NUM>. Therefore, in the second heat exchanger <NUM>, the liquefied combustible gas F in a state of being heated in advance by the first heat exchanger 31B is vaporized by exchanging the heat with the heat medium H. Therefore, the heat energy required for vaporizing the liquefied combustible gas F in the second heat exchanger <NUM> may be reduced, compared to a case where the first heat exchanger 31B is not provided.

In addition, in the first heat exchanger 31B of the second embodiment, the heat is exchanged between the carbon dioxide liquid C1 fetched from the inside of the first tank <NUM> and the liquefied combustible gas F. In this manner, the carbon dioxide liquid C1 in the supercooled state is fed into the first tank <NUM>. Therefore, the carbon dioxide gas C2 inside the first tank <NUM> can be cooled and reliquefied.

In addition, in the ship 1B of the second embodiment, the carbon dioxide liquid C1 is supplied to the first heat exchanger 31B from the first tank <NUM> by the unloading pump <NUM>. The unloading pump <NUM> is provided to deliver the carbon dioxide liquid C1 inside the first tank <NUM> to the outside of the floating main structure <NUM> through the unloading pipe <NUM>. In this way, the unloading pump <NUM> can also be used to reliquefy the carbon dioxide gas C2. Therefore, an increase in the number of components can be suppressed, and a cost increase can be suppressed.

In addition, in the ship 1B of the second embodiment, the carbon dioxide liquid C1 brought into the supercooled state by the heat exchange in the first heat exchanger 31B is injected into the upper portion inside the first tank <NUM> by the injection unit <NUM>. Therefore, the carbon dioxide liquid C1 in the supercooled state can be brought into wider contact with the carbon dioxide gas C2 inside the first tank <NUM>. Therefore, a larger amount of the carbon dioxide gas C2 can be reliquefied.

Next, a third embodiment of the floating structure according to the present invention will be described. The third embodiment described below is different from the first embodiment in that a target for exchanging the heat with the liquefied combustible gas F is a refrigerant. Therefore, <FIG> will be used as a reference, and description will be made by assigning the same reference numerals to elements which are the same as those of the first embodiment. Furthermore, detailed description of the elements which are the same as those of the first embodiment will be omitted.

As illustrated in <FIG>, a reliquefying/fuel supply system 30C of a ship 1C serving as a floating structure in the present embodiment includes at least a first heat exchanger 31C, a second heat exchanger <NUM>, a circulation line 33C, and a circulation pump <NUM>.

The first heat exchanger 31C exchanges the heat between a refrigerant R and the liquefied combustible gas F. The first fuel line <NUM>, the second fuel line <NUM>, and the circulation line 33C are connected to the first heat exchanger 31C.

The circulation line 33C forms a flow path that circulates the refrigerant R between the inside of the first tank <NUM> and the first heat exchanger 31C. One end of the circulation line 33C is connected to a refrigerant outlet 31Co of the first heat exchanger 31C, and the other end of the circulation line 33C is connected to a refrigerant inlet 31Ci of the first heat exchanger 31C. Then, an intermediate portion of the circulation line 33C passes through the inside of the first tank <NUM>. The circulation line 33C in the third embodiment passes through the gas phase inside the first tank <NUM>. In the third embodiment, a portion of the circulation line 33C which passes through at least the first tank <NUM> (hereinafter, referred to as a portion passing through the inside of the first tank <NUM>) can be formed of a material having high thermal conductivity such as metal, a material having a large heat transfer area such as a fin tube, and a combination thereof. In addition, a portion of the circulation line 33C which is disposed outside the first tank <NUM> (particularly, a portion between the refrigerant outlet 31Co and the first tank <NUM>) may be formed of a material having high heat insulating performance, or may be covered with a heat insulating material. As the above-described refrigerant R, a refrigerant having a boiling point of approximately -<NUM> can be used. A case has been described where the portion passing through the inside of the first tank <NUM> passes through only the gas phase. However, the portion passing through the inside of the first tank <NUM> is not limited to a case of passing through only the gas phase. For example, some of the portion passing through the inside of the first tank <NUM> may be in contact with the liquid phase. In addition, without being limited to a configuration in which the portion passing through the inside of the first tank <NUM> is always in contact with the gas phase, for example, the portion passing through the inside of the first tank <NUM> may be submerged in the liquid phase when a liquid level inside the first tank <NUM> rises.

The circulation pump <NUM> is installed in an intermediate portion of the circulation line 33C. The circulation pump <NUM> of the present embodiment is disposed between an outlet 31Co of the first heat exchanger 31C and the first tank <NUM> in the circulation line 33C. The circulation pump <NUM> delivers the refrigerant R inside the circulation line 33C from one end to the other end of the circulation line 33C.

In the reliquefying/fuel supply system 30C configured in this way, the circulation pump <NUM> is operated so that the refrigerant R discharged from the outlet 31Co of the first heat exchanger 31C flows toward the first tank <NUM> through a flow path inside the circulation line 33C. Then, the refrigerant R flows through the flow path of the circulation line 33C disposed inside the first tank <NUM>. In this case, the refrigerant R exchanges the heat with the carbon dioxide C (at least one of the carbon dioxide gas C2 and the carbon dioxide liquid C1) inside the first tank <NUM>, and the temperature of the refrigerant R rises.

Thereafter, the refrigerant R flows through the flow path of the circulation line 33C disposed outside the first tank <NUM>, and thereafter, reaches the refrigerant inlet 31Ci of the first heat exchanger 31C. Then, the refrigerant R exchanges the heat with the liquefied combustible gas F in the first heat exchanger 31C to lower the temperature, and is discharged again from the refrigerant outlet 31Co. In this way, the refrigerant R is circulated inside the circulation line 33C. As a timing at which the circulation pump <NUM> is operated in the third embodiment, the circulation pump <NUM> may be operated only when a pressure inside the first tank <NUM> rises above a threshold value. Alternatively, the circulation pump <NUM> may be always operated when the combustor <NUM> is operated.

The liquefied combustible gas F which is heated by exchanging the heat with the refrigerant R having a temperature higher than that of the liquefied combustible gas F in the first heat exchanger 31B and whose temperature is raised is fed to the second heat exchanger <NUM> through the second fuel line <NUM> as in the first embodiment. The liquefied combustible gas F is further heated and vaporized by exchanging the heat with the heat medium H in the second heat exchanger <NUM>. The vaporized liquefied combustible gas F is supplied to the combustor <NUM> through the third fuel line <NUM>.

In addition, the temperature of the carbon dioxide C inside the first tank <NUM> exchanging the heat with the refrigerant R is lowered. In this case, the temperature of the carbon dioxide gas C2 is lowered by directly exchanging the heat with the refrigerant R or by coming into contact with the carbon dioxide liquid C1 whose heat is exchanged with the refrigerant R. In this manner, a volume of the carbon dioxide gas C2 is reduced in the gas state, or the carbon dioxide gas C2 is liquefied. In this manner, a pressure increase inside the first tank <NUM> is suppressed.

The ship 1C of the above-described third embodiment includes the hull <NUM>, the first tank <NUM> disposed in the hull <NUM> and storing the carbon dioxide C having the gas phase and the liquid phase, the second tank <NUM> disposed in the hull <NUM> and capable of storing the liquefied combustible gas F whose temperature in the liquid state is lower than the temperature of the liquid phase of the carbon dioxide C, the first heat exchanger 31C that exchanges the heat between the liquefied combustible gas F and the refrigerant R, the circulation line 33C that circulates the refrigerant R between the inside of the first tank <NUM> and the first heat exchanger 31C, the circulation pump <NUM> provided in the intermediate portion of the circulation line 33C and circulate the refrigerant R, the second heat exchanger <NUM> that vaporizes the liquefied combustible gas F passing through the first heat exchanger 31C by exchanging the heat with the heat medium H, and the combustor <NUM> that combusts the liquefied combustible gas F vaporized by the second heat exchanger <NUM>.

According to the third embodiment, in addition to the operational effect of the first embodiment, the heat can be exchanged between the carbon dioxide C inside the first tank <NUM> and the liquefied combustible gas F via the refrigerant R. Therefore, the carbon dioxide gas C2 or the carbon dioxide liquid C1 does not need to flow into a pipe outside the first tank <NUM>. Therefore, the heat input to the carbon dioxide C can be suppressed, and the pressure inside the first tank <NUM> can be efficiently reduced.

In addition, in the ship 1C of the above-described third embodiment, the circulation line 33C passes through at least the liquid phase of the first tank <NUM>.

According to this configuration, the temperature of the carbon dioxide gas C2 inside the first tank <NUM> whose heat is exchanged with the refrigerant R can be lowered. In this manner, a volume of the carbon dioxide gas C2 can be reduced in the gas state, or the carbon dioxide gas C2 can be liquefied. Therefore, a pressure increase inside the first tank <NUM> can be efficiently suppressed.

In the above-described embodiment, a configuration including two first tanks <NUM> has been adopted. However, the present disclosure is not limited thereto. The configuration may include one, three, or more first tanks <NUM>. In addition, in the above-described embodiment, a case where the plurality of first tanks <NUM> are aligned in the bow-stern direction Da has been described as an example. However, the first tanks <NUM> may be aligned in a ship width direction (in other words, a right-left broadside direction).

In addition, in the above-described embodiment, the ships 1A and 1B have been described as examples of the floating structure. However, the present disclosure is not limited thereto. The floating structure may be an offshore floating structure facility which does not include a propulsion mechanism.

In addition, in the above-described third embodiment, a case has been described where the heat is exchanged between the refrigerant R and the carbon dioxide C by utilizing the heat conduction of the pipe of the circulation line 33C. However, another heat exchanger that exchanges the heat between the refrigerant R and the carbon dioxide C may be provided in the intermediate portion of the circulation line 33C inside the first tank <NUM>.

In addition, in the circulation line 33C in the above-described third embodiment, the flow path of the refrigerant R may meander in the portion disposed inside the first tank <NUM>.

In addition, in the above-described third embodiment, a case has been described where the refrigerant R is circulated in the liquid state. However, according to the invention, as illustrated in <FIG>, instead of the above-described circulation pump <NUM>, an expansion valve <NUM> and a compressor <NUM> is provided to construct a refrigerating cycle in the intermediate portion of the circulation line 33C. In this case, the expansion valve <NUM> may be provided between the refrigerant outlet 31Co of the first heat exchanger 31C and the first tank <NUM>, and the compressor <NUM> may be provided between the first tank <NUM> and the refrigerant inlet 31Ci of the first heat exchanger 31C. When a refrigerating cycle is constructed in this way, capacity to cool the carbon dioxide gas C2 can be improved. Therefore, for example, even when the pressure inside the first tank <NUM> is changed in a short time, the refrigerating cycle can quickly dealt with the pressure change.

Claim 1:
A floating structure (1C) comprising:
a floating main structure (<NUM>);
a first tank (<NUM>) disposed in the floating main structure (<NUM>) and storing carbon dioxide having a gas phase and a liquid phase;
a second tank (<NUM>) disposed in the floating main structure (<NUM>) and capable of storing a liquefied combustible gas whose temperature in a liquid state is lower than a temperature of the liquid phase of the carbon dioxide;
a first heat exchanger (31C) that exchanges heat between the liquefied combustible gas and a refrigerant;
a second heat exchanger (<NUM>) that vaporizes the liquefied combustible gas by exchanging heat of the liquefied combustible gas which has passed through the first heat exchanger (31C), with a heat medium; and
a combustor (<NUM>) that combusts the liquefied combustible gas vaporized by the second heat exchanger (<NUM>), characterized in that
the floating structure further comprises a circulation line (33C) that circulates the refrigerant between an inside of the first tank (<NUM>) and the first heat exchanger (31C), wherein the circulation line (33C) passes through at least a gas phase of the first tank (<NUM>), and
an expansion valve (<NUM>) and a compressor (<NUM>) to construct a refrigerating cycle in the circulation line (33C).