EP4035985A1

EP4035985A1 - Cold recovery system, ship including cold recovery system, and cold recovery method

Info

Publication number: EP4035985A1
Application number: EP20893934.8A
Authority: EP
Inventors: Ryo TAKATA; Akira Kawanami; Eiji Saito
Original assignee: Mitsubishi Heavy Industries Marine Machinery and Equipment Co Ltd
Current assignee: Mitsubishi Heavy Industries Marine Machinery and Equipment Co Ltd
Priority date: 2019-11-26
Filing date: 2020-11-26
Publication date: 2022-08-03
Also published as: KR20220062651A; WO2021106984A1; CN114651148A; CN114651148B; JP7288842B2; JP2021085443A; EP4035985A4

Abstract

This cold recovery system is installed in a ship having a liquefied gas storage device that stores a liquid liquefied gas, the system comprising: a working fluid circulation line that causes a working fluid having a lower freezing point than water to circulate therethrough; a cold recovery device that includes a turbine driven by the working fluid; a first heat exchanger that exchanges heat between the liquefied gas and the working fluid; an intermediate heat medium circulation line that causes an intermediate heat medium having a lower freezing point than water to circulate therethrough; a second heat exchanger that is provided on the downstream side of the working fluid circulation line with respect to the first heat exchanger, and exchanges heat between the working fluid and the intermediate heat medium; and a third heat exchanger that exchanges heat between the intermediate heat medium and heated water introduced from the outside of the cold recovery system.

Description

TECHNICAL FIELD

The present disclosure relates to a cold energy recovery system installed in a ship which includes a liquefied gas storage device configured to store a liquid liquefied gas, a ship having the cold energy recovery system, and a cold energy recovery method by the cold energy recovery system.

BACKGROUND

A land LNG (liquefied natural gas) terminal receives and stores liquefied natural gas transported by an LNG carrier. Then, when liquefied natural gas is supplied to a supply destination such as city gas or a thermal power plant, liquefied natural gas is warmed with seawater or the like to be returned to a gas. When liquefied natural gas is vaporized, cryogenic power generation may be performed in which cold energy is recovered as electric power instead of being discarded in seawater (for example, Patent Document 1).
Providing the land LNG terminal corresponding to each supply destination of liquefied natural gas is difficult due to its cost to, for example, secure land. Thus, a ship, which is equipped with an LNG storage facility for storing liquefied natural gas or a regasification facility for regasifying liquefied natural gas, may be moored on sea, and the liquefied natural gas regasifyied by the ship may be sent to a supply destination on shore or a power gauge (floating power plant) on sea via a pipeline.
Since the ship is less expandable than an onshore facility, in order to install a cryogenic power generation facility, it is important to reduce the size of the cryogenic power generation system, especially a heat exchanger. As the small heat exchanger, a printed circuit heat exchanger (PCHE), a plate heat exchanger, or the like can be given as an example.

Citation List

Patent Literature

Patent Document 1: JP2017-180323A

SUMMARY

Technical Problem

If a temperature of another heat exchange object is lower than a solidifying point of one heat exchange object (for example, seawater), the one heat exchange object is solidified in heat exchange in the heat exchanger, and the solidified heat exchange object may adhere to a surface of the exchanger and block the heat exchanger. A small heat exchanger has a higher risk of blockage of the heat exchanger than a large heat exchanger (for example, a shell tube type heat exchanger), and thus has a problem in reliability.
In view of the above issues, an object of at least one embodiment of the present disclosure is to provide a cold energy recovery system capable of suppressing blockage of the heat exchanger due to solidification of a heat medium, and capable of improving reliability of the cold energy recovery system when the small heat exchanger is used.

Solution to Problem

A cold energy recovery system according to the present disclosure is a cold energy recovery system installed in a ship which includes a liquefied gas storage device configured to store a liquid liquefied gas, that includes a working fluid circulation line which is configured to circulate a working fluid having a lower solidifying point than water, a cold energy recovery device that includes a turbine which is configured to be driven by the working fluid flowing through the working fluid circulation line, a first heat exchanger which is configured to exchange heat between the liquefied gas and the working fluid flowing through the working fluid circulation line, an intermediate heat medium circulation line which is configured to circulate an intermediate heat medium having a lower solidifying point than water, a second heat exchanger disposed downstream of the first heat exchanger on the working fluid circulation line, the second heat exchanger being configured to exchange heat between the working fluid flowing through the working fluid circulation line and the intermediate heat medium flowing through the intermediate heat medium circulation line, and a third heat exchanger which is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line and heating water introduced from an outside of the cold energy recovery system.
A ship according to the present disclosure includes the cold energy recovery system.
A cold energy recovery method according to the present disclosure is a cold energy recovery method by a cold energy recovery system installed in a ship which includes a liquefied gas storage device configured to store a liquid liquefied gas, the cold energy recovery system including a working fluid circulation line which is configured to circulate a working fluid having a lower solidifying point than water, a cold energy recovery device that includes a turbine which is configured to be driven by the working fluid flowing through the working fluid circulation line, a first heat exchanger which is configured to exchange heat between the liquefied gas and the working fluid flowing through the working fluid circulation line, an intermediate heat medium circulation line which is configured to circulate an intermediate heat medium having a lower solidifying point than water, a second heat exchanger disposed downstream of the first heat exchanger on the working fluid circulation line, the second heat exchanger being configured to exchange heat between the working fluid flowing through the working fluid circulation line and the intermediate heat medium flowing through the intermediate heat medium circulation line, and a third heat exchanger which is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line and heating water introduced from an outside of the cold energy recovery system, the cold energy recovery method including a first heat exchange step of performing heat exchange between the liquefied gas and the working fluid by the first heat exchanger, a second heat exchange step of performing, by the second heat exchanger, heat exchange between the intermediate heat medium and the working fluid that has exchanged heat with the liquefied gas in the first heat exchange step, and a third heat exchange step of performing, by the third heat exchanger, heat exchange between the heating water and the intermediate heat medium that has exchanged heat with the working fluid in the second heat exchange step.

Advantageous Effects

According to at least one embodiment of the present disclosure, a cold energy recovery system is provided which is capable of suppressing blockage of a heat exchanger due to solidification of a heat medium, and is capable of improving reliability of a cold energy recovery system when a small heat exchanger is used.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram schematically showing the configuration of a ship having a cold energy recovery system according to an embodiment of the present disclosure.
FIG. 2 is a schematic configuration diagram schematically showing the overall configuration of the cold energy recovery system according to the first embodiment of the present disclosure.
FIG. 3 is a schematic configuration diagram schematically showing the overall configuration of the cold energy recovery system according to the second embodiment of the present disclosure.
FIG. 4 is a schematic configuration diagram schematically showing the overall configuration of the cold energy recovery system according to the third embodiment of the present disclosure.
FIG. 5 is a schematic configuration diagram schematically showing the overall configuration of the cold energy recovery system according a comparative example.
FIG. 6 is an explanatory view for describing an example of a heat exchanger in an embodiment of the present disclosure.
FIG. 7 is a flowchart of a cold energy recovery method according to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. It is intended, however, that unless particularly identified, dimensions, materials, shapes, relative positions and the like of components described or shown in the drawings as the embodiments shall be interpreted as illustrative only and not intended to limit the scope of the present disclosure.
For instance, an expression of relative or absolute arrangement such as "in a direction", "along a direction", "parallel", "orthogonal", "centered", "concentric" and "coaxial" shall not be construed as indicating only the arrangement in a strict literal sense, but also includes a state where the arrangement is relatively displaced by a tolerance, or by an angle or a distance whereby it is possible to achieve the same function.
For instance, an expression of an equal state such as "same", "equal", and "uniform" shall not be construed as indicating only the state in which the feature is strictly equal, but also includes a state in which there is a tolerance or a difference that can still achieve the same function.
Further, for instance, an expression of a shape such as a rectangular shape or a tubular shape shall not be construed as only the geometrically strict shape, but also includes a shape with unevenness or chamfered corners within the range in which the same effect can be achieved.
On the other hand, the expressions "comprising", "including" or "having" one constitutional element is not an exclusive expression that excludes the presence of other constitutional elements.
The same configurations are indicated by the same reference characters and may not be described again in detail.

(Ship having cold energy recovery system)

FIG. 1 is a schematic configuration diagram schematically showing the configuration of a ship having a cold energy recovery system according to an embodiment of the present disclosure.
As shown in FIG. 1, a cold energy recovery system 2 according to some embodiments is installed in a ship 1. As shown in FIG. 1, the ship 1 includes a hull 10, and the cold energy recovery system 2 mounted on the hull 10. In the illustrated embodiment, the ship 1 further includes a liquefied gas storage device (for example, a liquefied gas tank) 11 mounted on the hull 10. The liquefied gas storage device 11 is configured to store a liquid liquefied gas (for example, liquefied natural gas).
In the illustrated embodiment, the hull 10 internally forms an engine room 15. The engine room 15 is equipped with an engine (for example, a marine diesel engine) 16 for applying a propulsive force to the ship 1. In this case, by driving the engine 16, the ship 1 can be moved from a liquefied gas supply source to the vicinity of a liquefied gas supply destination.

(Cold energy recovery system)

FIG. 2 is a schematic configuration diagram schematically showing the overall configuration of the cold energy recovery system according to the first embodiment of the present disclosure. FIG. 3 is a schematic configuration diagram schematically showing the overall configuration of the cold energy recovery system according to the second embodiment of the present disclosure. FIG. 4 is a schematic configuration diagram schematically showing the overall configuration of the cold energy recovery system according to the third embodiment of the present disclosure.
As shown in FIGs. 2 to 4, the cold energy recovery system 2 according to some embodiments includes a liquefied gas supply line 3, a working fluid circulation line 4, a cold energy recovery device 41, an intermediate heat medium circulation line 6, a heating water supply line 7, a first heat exchanger 51, a second heat exchanger 52, and a third heat exchanger 53. Each of the liquefied gas supply line 3, the working fluid circulation line 4, the intermediate heat medium circulation line 6, and the heating water supply line 7 includes a flow passage through which a fluid flows.
The liquefied gas supply line 3 is configured to send a liquefied gas from the liquefied gas storage device 11. The working fluid circulation line 4 is configured to circulate a working fluid having a lower solidifying point than water. Hereinafter, liquefied natural gas (LNG) will be described as a specific example of the liquefied gas, and propane will be described as a specific example of the working fluid. However, the present disclosure is also applicable to a liquefied gas other than liquefied natural gas, and further is also applicable to a case where a heat medium other than propane is used as the working fluid.
In the illustrated embodiment, the cold energy recovery system 2 includes a liquefied gas pump 31 disposed on the liquefied gas supply line 3, and a working fluid circulation pump 44 disposed on the working fluid circulation line 4. The liquefied gas supply line 3 has one end side 301 connected to the liquefied gas storage device 11, and has another end side 302 which is connected to liquefied gas equipment 12 disposed outside the cold energy recovery system 2. As the liquefied gas equipment 12, a gas holder (see FIG. 1) disposed on shore, a gas pipe connected to the gas holder, or the like can be given as an example. By driving the liquefied gas pump 31, the liquefied gas stored in the liquefied gas storage device 11 is sent to the liquefied gas supply line 3, flows through the liquefied gas supply line 3 from upstream to downstream, and then is sent to the liquefied gas equipment 12. Further, by driving the working fluid circulation pump 44, the working fluid circulates through the working fluid circulation line 4.
The cold energy recovery device 41 includes a turbine 42 configured to be driven by the working fluid flowing through the working fluid circulation line 4. In the illustrated embodiment, the cold energy recovery device 41 further includes a generator 43 configured to generate electricity by driving the turbine 42. The turbine 42 includes a turbine rotor 421 disposed on the working fluid circulation line 4. The turbine rotor 421 is configured to be rotatable by the working fluid flowing through the working fluid circulation line 4. In some other embodiments, the cold energy recovery device 41 may not convert a rotational force of the turbine rotor 421 into electric power, but may recover the rotational force as power as it is by a power transmission device (for example, a coupling, a belt, a pulley, or the like).
The intermediate heat medium circulation line 6 is configured to circulate an intermediate heat medium having a lower solidifying point than water. The heating water supply line 7 is configured to send heating water introduced from the outside of the cold energy recovery system 2. The "heating water" can be water for heating a heat exchange object as a heat medium in the heat exchanger, and may be water at room temperature. The heating water is preferably water that is easily available in the ship 1 (for example, outboard water such as seawater, cooling water that has cooled an engine of the ship 1, or the like).
In the illustrated embodiment, the cold energy recovery system 2 includes an intermediate heat medium circulation pump 61 disposed on the intermediate heat medium circulation line 6, and a heating water pump 71 disposed on the heating water supply line 7. By driving the intermediate heat medium circulation pump 61, the intermediate heat medium circulates through the intermediate heat medium circulation line 6. The heating water supply line 7 has one end side 701 which is connected to a heating water supply source 13 disposed outside the cold energy recovery system 2, and another end side 702 which is connected to a heating water discharge destination 14 disposed outside the cold energy recovery system 2. By driving the heating water pump 71, the heating water is sent from the heating water supply source 13 to the heating water supply line 7, flows through the heating water supply line 7 from upstream to downstream, and then is sent to the heating water discharge destination 14.
As the heating water supply source 13, a water inlet 17 (see FIG. 1) provided in the hull 10 to introduce outboard water, a cooling water flow passage 18 (see FIG. 1) where the cooling water that has cooled the engine of the ship 1 (for example, the engine 16) flows, or the like can be given as an example. Further, as the heating water discharge destination 14, a water outlet 19 (see FIG. 1) provided in the hull 10 to discharge water outboard, or the like can be given as an example.
The intermediate heat medium may be the same type of heat medium as the working fluid, or may be a different type of heat medium. In the embodiment shown in FIG. 2, the intermediate heat medium is constituted by propane, and the heating water is constituted by the cooling water (engine jacket water) having cooled the engine. The cooling water draws heat from the engine and has a higher temperature than seawater at room temperature. In the embodiment shown in FIG. 3, the intermediate heat medium is constituted by propane, and the heating water is constituted by seawater acquired from the outside of the ship. In the embodiment shown in FIG. 4, the intermediate heat medium is constituted by antifreeze (more specifically, glycol water), and the heating water is constituted by seawater acquired from the outside of the ship. For reference, FIGs. 2 to 4 each show an example of a temperature and a pressure in each flow passage.
The first heat exchanger 51 is configured to exchange heat between the liquefied gas flowing through the liquefied gas supply line 3 and the working fluid flowing through the working fluid circulation line 4. In the illustrated embodiment, the first heat exchanger 51 forms a liquefied gas flow passage 511 which is disposed on the liquefied gas supply line 3 and through which the liquefied gas flows, and a working fluid flow passage 512 which is disposed on the working fluid circulation line 4 and in which the working fluid flows. The working fluid flow passage 512 is disposed at least partially adjacent to the liquefied gas flow passage 511, and heat exchange is performed between the working fluid flowing through the working fluid flow passage 512 and the liquefied gas flowing through the liquefied gas flow passage 511.
The second heat exchanger 52 is configured to exchange heat between the working fluid flowing through the working fluid circulation line 4 and the intermediate heat medium flowing through the intermediate heat medium circulation line 6. In the illustrated embodiment, the second heat exchanger 52 forms a working fluid flow passage 521 which is disposed on the working fluid circulation line 4 and through which the working fluid flows, and an intermediate heat medium flow passage 522 which is disposed on the intermediate heat medium circulation line 6 and in which the intermediate heat medium flows. The intermediate heat medium flow passage 522 is disposed at least partially adjacent to the working fluid flow passage 521, and heat exchange is performed between the intermediate heat medium flowing through the intermediate heat medium flow passage 522 and the working fluid flowing through the working fluid flow passage 521.
The third heat exchanger 53 is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line 6 and the heating water flowing through the heating water supply line 7. In the illustrated embodiment, the third heat exchanger 53 forms an intermediate heat medium flow passage 531 which is disposed on the intermediate heat medium circulation line 6 and through which the intermediate heat medium flows, and a heating water flow passage 532 which is disposed on the heating water supply line 7 and through which the heating water flows. The heating water flow passage 532 is disposed at least partially adjacent to the intermediate heat medium flow passage 531, and heat exchange is performed between the intermediate heat medium flowing through the heating water flow passage 532 and the working fluid flowing through the intermediate heat medium flow passage 531.
The first heat exchanger 51 (more specifically, the liquefied gas flow passage 511) is disposed downstream of the liquefied gas pump 31 on the liquefied gas supply line 3 and upstream of the liquefied gas equipment 12. The liquefied gas pump 31 is disposed downstream of the liquefied gas storage device 11 on the liquefied gas supply line 3. Further, the first heat exchanger 51 (more specifically, the working fluid flow passage 512) is disposed downstream of the turbine 42 on the working fluid circulation line 4 and upstream of the working fluid circulation pump 44.
The second heat exchanger 52 (more specifically, the working fluid flow passage 521) is disposed downstream of the working fluid circulation pump 44 on the working fluid circulation line 4 and upstream of the turbine 42. Further, the second heat exchanger 52 (more specifically, the intermediate heat medium flow passage 522) is disposed downstream of the third heat exchanger (more specifically, the intermediate heat medium flow passage 531) on the intermediate heat medium circulation line 6 and upstream of the intermediate heat medium circulation pump 61.
The third heat exchanger (more specifically, the heating water flow passage 532) is disposed downstream of the heating water pump 71 on the heating water supply line 7 and upstream of the heating water discharge destination 14. The heating water pump 71 is disposed downstream of the heating water supply source 13 on the heating water supply line 7.
The liquid liquefied gas boosted by the liquefied gas pump 31 is sent to the liquefied gas flow passage 511 of the first heat exchanger 51. The heat exchange in the first heat exchanger 51 heats the liquefied gas flowing through the liquefied gas flow passage 511 and cools the working fluid flowing through the working fluid flow passage 512. That is, the cold energy of the liquefied gas flowing through the liquefied gas flow passage 511 is recovered by the working fluid flowing through the working fluid flow passage 512. The heat exchange in the first heat exchanger 51 causes the working fluid flowing through the working fluid flow passage 512 to have the temperature lower than the solidifying point of water (heating water).
The intermediate heat medium boosted by the intermediate heat medium circulation pump 61 is sent to the intermediate heat medium flow passage 531 of the third heat exchanger 53. Further, the heating water boosted by the heating water pump 71 is sent to the heating water flow passage 532. The heat exchange in the third heat exchanger 53 heats the intermediate heat medium flowing through the intermediate heat medium flow passage 531.
The working fluid boosted by the working fluid the circulation pump 44 after being cooled by the first heat exchanger 51 is sent to the working fluid flow passage 521 of the second heat exchanger 52. Further, the intermediate heat medium heated by the third heat exchanger 53 is sent to the intermediate heat medium flow passage 522. The heat exchange in the second heat exchanger 52 heats the working fluid flowing through the working fluid flow passage 521 and cools the intermediate heat medium flow passage 522. Herein, since the intermediate heat medium has the lower solidifying point than water, it is possible to suppress solidification during the heat exchange with the low-temperature working fluid in the second heat exchanger. In the embodiments shown in FIGs. 2 to 4, the cold energy recovery system 2 decides a condition of each equipment in the cold energy recovery system 2 such that the intermediate heat medium flowing through the intermediate heat medium circulation line 6 has the temperature higher than the solidifying point of water.
The intermediate heat medium flowing through the intermediate heat medium flow passage 531 of the third heat exchanger 53 has a higher temperature than the working fluid flowing through the working fluid flow passage 521 of the second heat exchanger 52. In the illustrated embodiment, the intermediate heat medium flowing through the intermediate heat medium flow passage 531 has the temperature higher than the solidifying point of water (heating water). As described above, although the intermediate heat medium is cooled by the heat exchange with the working fluid in the second heat exchanger 52, the temperature higher than the solidifying point of water is maintained even after the cooling. Thus, it is possible to suppress solidification of the heating water during the heat exchange between the intermediate heat medium and the heating water in the third heat exchanger 53.
FIG. 5 is a schematic configuration diagram schematically showing the overall configuration of the cold energy recovery system according a comparative example. A cold energy recovery system 20 according to the comparative example includes the liquefied gas supply line 3, the working fluid circulation line 4, the cold energy recovery device 41, the heating water supply line 7, and the first heat exchanger 51. Then, the cold energy recovery system 20 further includes a heat exchanger 50 configured to exchange heat between the working fluid flowing through the working fluid circulation line 4 and the heating water flowing through the heating water supply line 7. In the comparative example shown in FIG. 5, the liquefied gas is constituted by liquefied natural gas, the working fluid is constituted by R1234ZE, and the heating water the heating water is constituted by seawater acquired from the outside of the ship. For reference, FIG. 5 shows an example of the temperature and the pressure in each flow passage.
The heat exchanger 50 forms a working fluid flow passage 501 disposed at a position corresponding to the above-described second heat exchanger 52 (working fluid flow passage 521) on the working fluid circulation line 4, and a heating water flow passage 502 disposed at a position corresponding to the above-described third heat exchanger 53 (heating water flow passage 532) on the heating water supply line 7. The heating water flow passage 502 is disposed at least partially adjacent to the working fluid flow passage 501, and heat exchange is performed between the heating water flowing through the heating water flow passage 502 and the working fluid flowing through the working fluid flow passage 501.
The working fluid flowing through the working fluid flow passage 501 has a temperature lower than the solidifying point of water (heating water) like the working fluid flowing through the working fluid flow passage 521. Thus, the heating water is solidified by the heat exchange between the working fluid and the heating water in the heat exchanger 50, the solidified heating water may freeze to the heating water flow passage 502 of the heat exchanger 50, and may block the heat exchanger 50.
As shown in FIGs. 2 to 4, the cold energy recovery system 2 according to some embodiments includes the above-described working fluid circulation line 4, the cold energy recovery device 41 including the turbine 42 described above, and the above-described intermediate heat medium circulation line 6, the above-described first heat exchanger 51, the above-described second heat exchanger 52, and the above-described third heat exchanger 53.
With the above configuration, the cold energy recovery system 2 at least includes the intermediate heat medium circulation line 6, the second heat exchanger 52, and the third heat exchanger 53. In such cold energy recovery system 2, the heating water and the working fluid circulating through the working fluid circulation line 4 indirectly exchange heat via the intermediate heat medium circulating through the intermediate heat medium circulation line 6, making it possible to suppress solidification of the heat medium (the intermediate heat medium, the heating water) during the heat exchange. Thus, it is possible to suppress that the solidified heat medium freezes to the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocks the heat exchanger.
More specifically, the working fluid circulating through the working fluid circulation line 4 has a temperature which is not greater than the solidifying point of water by the heat exchange with the liquefied gas in the first heat exchanger 51. In the second heat exchanger 52, heat exchange is performed between the working fluid which has passed through the first heat exchanger 51 and is decreased in temperature, and the intermediate heat medium circulating through the intermediate heat medium circulation line 6. Since the intermediate heat medium has a lower solidifying point than water, the intermediate heat medium is hardly solidified during heat exchange with the low-temperature working fluid in the second heat exchanger 52. Thus, it is possible to suppress that the solidified intermediate heat medium freezes to the second heat exchanger 52 and blocks the second heat exchanger 52.
Meanwhile, in the third heat exchanger 53, heat exchange is performed between the heating water and the intermediate heat medium which has passed through the second heat exchanger 52 and is decreased in temperature. Although the intermediate heat medium is cooled by the heat exchange with the working fluid in the second heat exchanger 52, the temperature higher than the solidifying point of water is maintained even after the cooling. Thus, it is possible to suppress solidification of the heating water during the heat exchange between the intermediate heat medium and the heating water in the third heat exchanger 53. Thus, it is possible to suppress that the solidified heating water freezes to the third heat exchanger 53 and blocks the third heat exchanger 53.
Thus, with the above configuration, since the cold energy recovery system 2 can suppress that the solidified heat medium (the intermediate heat medium, the heating water) freezes to the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocks the heat exchanger, it is possible to improve reliability of the cold energy recovery system 2 when the small heat exchanger is used.
In the embodiments shown in FIGs. 2 to 4, the above-described working fluid circulation line 4 includes a bypass flow passage 45 branches from downstream of the second heat exchanger 52, bypasses the turbine 42, and is connected to upstream of the first heat exchanger 51. A flow passage other than the bypass flow passage 45 of the working fluid circulation line 4 described above (a flow passage passing through the turbine 42 or the first heat exchanger 51) will be referred to as a main flow passage 40. The bypass flow passage 45 branches from the main flow passage 40 at a branch portion 451 and joins the main flow passage 40 at a merge portion 452. The above-described cold energy recovery system 2 further includes an on-off valve 46 disposed downstream of the branch portion 451 of the main flow passage 40 and upstream of the turbine 42, and an on-off valve 47 disposed on the bypass flow passage 45. When the cold energy recovery system 2 is started, the on-off valve 46 is closed and the on-off valve 47 is opened to allow the working fluid to bypass the turbine 42. After a predetermined period has elapsed, the on-off valve 46 is opened and the on-off valve 47 is closed to allow the working flow passage to pass through the turbine 42.
In the embodiments shown in FIGs. 2 to 4, the above-described cold energy recovery system 2 is configured to evaporate the intermediate heat medium flowing through the intermediate heat medium circulation line 6 in the third heat exchanger 53, and is configured to condense the intermediate heat medium flowing through the intermediate heat medium circulation line 6 in the second heat exchanger 52. In this case, it is possible to improve the overall efficiency of the cold energy recovery system 2 by utilizing latent heat or sensible heat.
In some embodiments, as shown in FIGs. 3 and 4, the above-described cold energy recovery system 2 further includes the above-described liquefied gas supply line 3, and an auxiliary heat exchanger 81 disposed downstream of the first heat exchanger 51 on the liquefied gas supply line 3. The auxiliary heat exchanger 81 is configured to exchange heat between the liquefied gas flowing downstream of the first heat exchanger 51 through the liquefied gas supply line 3 and a heating medium circulating in the cold energy recovery system 2.
In the illustrated embodiment, the heating medium has a lower solidifying point than water. The auxiliary heat exchanger 81 forms a liquefied gas flow passage 811 which is disposed downstream of the first heat exchanger on the liquefied gas supply line 3 and through which the liquefied gas flows, and a heating medium flow passage 812 through which the heating medium circulating in the cold energy recovery system 2 flows. The heating medium flow passage 812 is disposed at least partially adjacent to the liquefied gas flow passage 811, and heat exchange is performed between the heating medium flowing through the heating medium flow passage 812 and the liquefied gas flow passage 811 flowing through the liquefied gas flow passage 811.
The liquefied gas heated by the first heat exchanger 51 is sent to the liquefied gas flow passage 811 of the auxiliary heat exchanger 81. The heat exchange in the auxiliary heat exchanger 81 heats the liquefied gas flowing through the liquefied gas flow passage 811 and cools the heating medium flowing through the heating medium flow passage 812. Herein, since the heating medium has the lower solidifying point than water, it is possible to suppress solidification during the heat exchange with the liquefied gas in the auxiliary heat exchanger 81.
With the above configuration, the cold energy recovery system 2 includes the liquefied gas supply line 3, the first heat exchanger 51 disposed on the liquefied gas supply line 3, and the auxiliary heat exchanger 81 disposed downstream of the first heat exchanger 51 on the liquefied gas supply line 3. In such cold energy recovery system 2, the heat exchange in the first heat exchanger 51 and the auxiliary heat exchanger 81 raises the temperature of the liquefied gas and vaporizes the liquefied gas. In this case, it is not necessary to raise the temperature to a temperature, at which the liquid liquefied gas is completely vaporized, by the heat exchange in the first heat exchanger 51. Thus, compared to a case where the temperature of the liquefied gas is raised only by the first heat exchanger 51, it is possible to reduce the amount of the heat exchange in the first heat exchanger 51, and it is possible to reduce the temperature drop of the working fluid in the first heat exchanger 51. Thus, it is possible to effectively suppress solidification of the intermediate heat medium during the heat exchange between the working fluid and the intermediate heat medium in the second heat exchanger 52. Further, by reducing the amount of the heat exchange in the first heat exchanger 51, it is possible to reduce the size of the first heat exchanger 51.
In some embodiments, the above-described cold energy recovery system 2 is configured such that the above-described liquefied gas supply line 3 does not include a heat exchanger other than the first heat exchanger 51, as shown in FIG. 2. In this case, the liquefied gas is vaporized by the heat exchange in the first heat exchanger 51. With the above configuration, it is possible to simplify the structure of the cold energy recovery system 2.
In some embodiments, as shown in FIG. 3, the heating medium that exchanges heat with the liquefied gas in the auxiliary heat exchanger 81 described above is constituted by the intermediate heat medium heated by the third heat exchanger 53 and flowing through the intermediate heat medium circulation line 6. In this case, in the auxiliary heat exchanger 81, heat exchange is performed between the liquefied gas which has passed through the first heat exchanger 51 and is raised in temperature, and the intermediate heat medium heated by the third heat exchanger 53. Since the intermediate heat medium has the lower solidifying point than water, it is possible to suppress solidification during the heat exchange with the liquefied gas in the auxiliary heat exchanger 81. Thus, it is possible to suppress that the solidified intermediate heat medium freezes to the auxiliary heat exchanger 81 and blocks the auxiliary heat exchanger 81. Thus, it is possible to effectively heat the liquefied gas by the auxiliary heat exchanger 81.
If a heat medium circulating through a circulation line different from the intermediate heat medium circulation line 6 is used as the heating medium, a circulation pump for circulating the heat medium becomes necessary. With the above configuration, by using the intermediate heat medium circulating through the intermediate heat medium circulation line 6 as the heating medium, the above-described circulation pump becomes unnecessary, making it possible to suppress an equipment cost of the cold energy recovery system 2.
In some embodiments, as shown in FIG. 3, the above-described intermediate heat medium circulation line 6 includes a bypass flow passage 63 which branches from downstream of the third heat exchanger 53, bypasses the second heat exchanger 52, and is connected to upstream of the third heat exchanger 53. The above-described auxiliary heat exchanger 81 is configured to exchange heat between the liquefied gas flowing through the liquefied gas supply line 3 and the intermediate heat medium flowing through the bypass flow passage 63.
As shown in FIG. 3, a flow passage other than the bypass flow passage 63 of the intermediate heat medium circulation line 6 described above (a flow passage passing through the second heat exchanger 52 or the third heat exchanger 53) will be referred to as a main flow passage 62. In the illustrated embodiment, the cold energy recovery system 2 includes: an intermediate heat medium storage device (for example, a buffer tank) 64 which is disposed downstream of the second heat exchanger 52 on the main flow passage 62 and upstream of the intermediate heat medium circulation pump 61, and is configured to store the intermediate heat medium; and a flow regulating valve 65 which is disposed downstream of the auxiliary heat exchanger 81 on the bypass flow passage 63 and is configured to regulate the flow rate of the intermediate heat medium flowing through the bypass flow passage 63.
The bypass flow passage 63 has one end side 631 which is connected to downstream of the third heat exchanger 53 on the main flow passage 62 and upstream of the second heat exchanger 52, and another end side 632 connected to the intermediate heat medium storage device 64. The intermediate heat medium that has passed through the bypass flow passage 63 joins the intermediate heat medium that has passed through the second heat exchanger 52 on the main flow passage 62, in the intermediate heat medium storage device 64. The another end side 632 of the bypass flow passage 63 may be connected to downstream of the second heat exchanger 52 on the main flow passage 62 and upstream of the intermediate heat medium storage device 64.
The flow regulating valve 65 is disposed downstream of the auxiliary heat exchanger 81 (more specifically, the heating medium flow passage 812) on the bypass flow passage 63. By regulating the flow rate of the intermediate heat medium flowing through the bypass flow passage 63 with the flow regulating valve 65, the flow rate of the intermediate heat medium passing through the second heat exchanger 52 on the main flow passage 62 is also regulated.
Since the intermediate heat medium is a heat medium responsible for heating in the second heat exchanger 52 and the auxiliary heat exchanger 81, the intermediate heat medium is cooled by heat exchange in these heat exchangers. With the above configuration, the auxiliary heat exchanger 81 is configured to exchange heat between the liquefied gas and the intermediate heat medium which flows through the bypass flow passage 63 bypassing the second heat exchanger 52. That is, since the intermediate heat medium circulation line 6 does not form the flow passage passing through both the second heat exchanger 52 and the auxiliary heat exchanger 81, it is possible to prevent the temperature of the intermediate heat medium circulating through the intermediate heat medium circulation line 6 from becoming too low. Thus, it is possible to suppress solidification of the heating water during the heat exchange with the intermediate heat medium in the third heat exchanger 53.
In some embodiments, as shown in FIG. 4, the above-described cold energy recovery system 2 further includes a second intermediate heat medium circulation line 9 which is configured to circulate a second intermediate heat medium having a lower solidifying point than water. The heating medium which exchanges heat with the liquefied gas in the auxiliary heat exchanger 81 described above is constituted by the second intermediate heat medium flowing through the second intermediate heat medium circulation line 9. The heating medium flow passage 812 of the auxiliary heat exchanger 81 is disposed on the second intermediate heat medium circulation line 9.
In the illustrated embodiment, the cold energy recovery system 2 includes a second intermediate heat medium circulation pump 91 disposed downstream of the auxiliary heat exchanger 81 on the second intermediate heat medium circulation line 9. By driving the circulation pump 91, the second intermediate heat medium circulates through the second intermediate heat medium circulation line 9.
The second intermediate heat medium may be the same type of heat medium as the first intermediate heat medium which is the intermediate heat medium flowing through the intermediate heat medium circulation line 6, or may be a different type of heat medium. In the embodiment shown in FIG. 4, the second intermediate heat medium is constituted by R1234ZE.
With the above configuration, the heating medium which exchanges heat with the liquefied gas in the auxiliary heat exchanger 81 is constituted by the second intermediate heat medium flowing through the second intermediate heat medium circulation line 9. In this case, in the auxiliary heat exchanger 81, heat exchange is performed between the liquefied gas which has passed through the first heat exchanger 51 and is raised in temperature, and the second intermediate heat medium circulating through the second intermediate heat medium circulation line 9. Since the second intermediate heat medium has the lower solidifying point than water, it is possible to suppress solidification during the heat exchange with the liquefied gas in the auxiliary heat exchanger 81. Thus, it is possible to suppress that the solidified second intermediate heat medium freezes to the auxiliary heat exchanger 81 and blocks the auxiliary heat exchanger 81.
Further, with the above configuration, since the second intermediate heat medium circulation line 9 is different from the intermediate heat medium circulation line 6, it is possible to use, as the second intermediate heat medium, a heat medium different from the intermediate heat medium circulating through the intermediate heat medium circulation line 6. For example, as the second intermediate heat medium, it is possible to use a heat medium which is more suitable for conditions of the heat exchange in the auxiliary heat exchanger 81 than the intermediate heat medium circulating through the intermediate heat medium circulation line 6.
In some embodiments, as shown in FIG. 4, the above-described cold energy recovery system 2 further includes a second auxiliary heat exchanger 82 which is configured to exchange heat between the second intermediate heat medium flowing through the second intermediate heat medium circulation line 9 and the heating water introduced from the outside of the cold energy recovery system 2.
In the illustrated embodiment, the second auxiliary heat exchanger 82 forms a second intermediate heat medium flow passage 821 which is disposed downstream of the circulation pump 91 on the second intermediate heat medium circulation line 9 and through which the second intermediate heat medium flows, and a heating water flow passage 822 through which the heating water introduced from the outside of the cold energy recovery system 2 flows. The heating water flow passage 822 is disposed at least partially adjacent to the second intermediate heat medium flow passage 821, and heat exchange is performed between the heating water flowing through the heating water flow passage 822 and the second intermediate heat medium flowing through the second intermediate heat medium flow passage 821.
In the embodiment shown in FIG. 4, the above-described heating water supply line 7 includes a sub flow passage 72 which branches from downstream of the heating water pump 71 and upstream of the third heat exchanger 53, and is connected to a heating water discharge destination 14B. The heating water flow passage 822 of the second auxiliary heat exchanger 82 is disposed on the sub flow passage 72. As shown in FIG. 4, a flow passage other than the sub flow passage 72 of the heating water supply line 7 described above (a flow passage passing through the heating water pump 71 or the third heat exchanger 53) will be referred to as a main flow passage 70. The sub flow passage 72 has one end side 721 which is connected to downstream of the heating water pump 71 on the main flow passage 70 and upstream of the third heat exchanger 53, and another end side 722 connected to the heating water discharge destination 14B. In this case, since it is possible to send the heating water to each of the main flow passage 70 and the sub flow passage 72 by the heating water pump 71, a dedicated pump for flowing the heating water to the sub flow passage 72 becomes unnecessary. Thus, it is possible to suppress the equipment cost of the cold energy recovery system 2. The another end side 722 of the sub flow passage 72 may be connected to downstream of the third heat exchanger 53 on the main flow passage 70 or the heating water discharge destination 14.
The second intermediate heat medium, which is boosted by the circulation pump 91 after being cooled by the auxiliary heat exchanger 81, is sent to the second intermediate heat medium flow passage 821. Further, the heating water boosted by the heating water pump 71 is sent to the heating water flow passage 822. The second intermediate heat medium flowing through the second intermediate heat medium flow passage 821 has a higher temperature than the heating water flowing through the heating water flow passage 822. The heat exchange in the second auxiliary heat exchanger 82 heats the second intermediate heat medium flowing through the second intermediate heat medium flow passage 821. The second intermediate heat medium heated by the second auxiliary heat exchanger 82 is sent to the auxiliary heat exchanger 81.
In the illustrated embodiment, the second intermediate heat medium flowing through the second intermediate heat medium flow passage 821 has the temperature higher than the solidifying point of water (heating water). Although the second intermediate heat medium flowing through the second intermediate heat medium circulation line 9 is cooled by the heat exchange with the liquefied gas in the auxiliary heat exchanger 81, the temperature higher than the solidifying point of water is maintained even after the cooling. Thus, it is possible to suppress solidification of the heating water during the heat exchange between the second intermediate heat medium and the heating water in the second auxiliary heat exchanger 82.
In the cold energy recovery system 2, since the heat exchange in the first heat exchanger 51 and the auxiliary heat exchanger 81 raises the temperature of the liquefied gas, the amount of the heat exchange in the auxiliary heat exchanger 81 is small, and the amount of temperature drop of the second intermediate heat medium (heating medium) in the auxiliary heat exchanger 81 is small. With the above configuration, it is possible to suppress solidification of the heating water during the heat exchange between the heating water and the second intermediate heat medium in the second auxiliary heat exchanger 82.
In some embodiments, as shown in FIGs. 2 to 4, the above-described cold energy recovery device 41 includes the above-described turbine 42, and the above-described generator 43 configured to generate electricity by driving the turbine 42. In this case, since the cold energy recovery device 41 includes the turbine 42 and the generator 43, it is possible to generate electricity in the generator 43 by driving the turbine 42 with the working fluid which circulates through the working fluid circulation line 4 and recovers the cold energy from the liquefied gas. In this case, it is possible to effectively utilize the cold energy of the liquefied gas.
In some embodiments, as shown in FIGs. 2 to 4, the above-described cold energy recovery system 2 at least includes the liquefied gas supply line 3 configured to send the liquefied gas from the liquefied gas storage device 11, and the liquefied gas pump 31 disposed on the liquefied gas supply line 3. The liquefied gas pump 31 is configured to be driven by the electric power generated by the generator 43. In the illustrated embodiment, each of the circulation pump 44, the circulation pump 61, the heating water pump 71, and the second intermediate heat medium circulation pump 91 is also configured to be driven by the electric power generated by the generator 43. Not all of the liquefied gas pump 31, the circulation pump 44, the circulation pump 61, the heating water pump 71, and the second intermediate heat medium circulation pump 91, but one or not less than one of them may be configured to be driven by the electric power generated by the generator 43.
With the above configuration, it is possible to drive the liquefied gas pump 31 disposed on the liquefied gas supply line 3 by the electric power generated by the generator 43. In this case, an electric power system for supplying electric power from the onshore electric power equipment to the liquefied gas pump 31 becomes unnecessary, making it possible to reduce the size of the ship 1 provided with the liquefied gas pump 31. Alternatively, since it is possible to reduce the occupied space of the cold energy recovery system 2 in the ship 1, it is possible to increase the occupied space of the liquefied gas storage device 11 in the ship 1.
FIG. 6 is an explanatory view for describing an example of the heat exchanger in an embodiment of the present disclosure.
In some embodiments, as shown in FIG. 6, the third heat exchanger 53 is constituted by a microchannel heat exchanger 53A. The microchannel heat exchanger 53A includes a first microchannel 531A through which the intermediate heat medium flows, and a second microchannel 532A at least a part of which is disposed adjacent to the first microchannel 531A and through which the heating water flows.
In the illustrated embodiment, the microchannel heat exchanger 53Ais constituted by a PCHE (Printed Circuit Heat Exchanger) which is created by alternately stacking and joining to each other first metal plates 533 each in which a plurality of first microchannels 531A are formed and second metal plates 534 each in which a plurality of second microchannels 532A are formed. In some other embodiments, the microchannel heat exchanger 53A may be a plate heat exchanger or the like.
With the above configuration, since the third heat exchanger 53 is constituted by the microchannel heat exchanger 53A which allows for the heat exchange between the intermediate heat medium flowing through the first microchannels 531A and the heating water flowing through the second microchannels 532A, the third heat exchanger 53 is compact and can improve a heat-transfer coefficient. Since the cold energy recovery system2 using such heat exchanger can reduce the occupied space of the cold energy recovery system 2 in the ship 1, it is possible to increase the occupied space of the liquefied gas storage device 11 in the ship 1. The heat exchanger other than the third heat exchanger 53 may also be the microchannel heat exchanger.
As shown in FIG. 1, the ship 1 according to some embodiments includes the above-described cold energy recovery system 2. In this case, since it is possible to reduce the size of the cold energy recovery system 2 by using the small heat exchanger for the heat exchanger of the cold energy recovery system 2 (for example, the third heat exchanger 53 or the like), it is possible to reduce the size of the ship 1 having the cold energy recovery system 2. Alternatively, since it is possible to reduce the occupied space of the cold energy recovery system 2 in the ship 1, it is possible to increase the occupied space of the liquefied gas storage device 11 in the ship 1.
FIG. 7 is a flowchart of a cold energy recovery method according to an embodiment of the present disclosure.
A cold energy recovery method100 according to some embodiments is a cold energy recovery method by the above-described cold energy recovery system 2 which is installed in the ship 1 including the liquefied gas storage device 11 and as shown in FIG. 7, at least includes a first heat exchange step S101, a second heat exchange step S102, and a third heat exchange step S103.
The first heat exchange step S101 includes performing heat exchange between the liquefied gas and the working fluid by the first heat exchanger 51. The second heat exchange step S102 includes performing, by the second heat exchanger 52, heat exchange between the intermediate heat medium and the working fluid that has exchanged heat with the liquefied gas in the first heat exchange step S101. The third heat exchange step S103 includes performing, by the third heat exchanger 53, heat exchange between the heating water and the intermediate heat medium that has exchanged heat with the working fluid in the second heat exchange step S102.
The above method includes the first heat exchange step S101, the second heat exchange step S102, and the third heat exchange step S103. In such cold energy recovery method 100, the second heat exchange step S102 and the third heat exchange step S103 cause the heating water and the working fluid circulating through the working fluid circulation line 4 to indirectly exchange heat via the intermediate heat medium circulating through the intermediate heat medium circulation line 6, making it possible to suppress solidification of the heat medium (the intermediate heat medium, the heating water) during the heat exchange. Thus, it is possible to suppress that the solidified heat medium freezes to the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocks the heat exchanger.
More specifically, the first heat exchange step S101 includes performing heat exchange between the liquefied gas and the working fluid by the first heat exchanger 51. The working fluid that has passed through the first heat exchanger 51 has a low temperature which is not greater than the solidifying point of water. The second heat exchange step S102 includes performing, by the second heat exchanger 52, heat exchange between the working fluid, which is decreased in temperature by the heat exchange in the first heat exchange step S101, and the intermediate heat medium flowing through the intermediate heat medium circulation line 6. Since the intermediate heat medium has a lower solidifying point than water, the intermediate heat medium is hardly solidified during heat exchange with the low-temperature working fluid in the second heat exchange step S102. Thus, it is possible to suppress that the solidified intermediate heat medium freezes to the second heat exchanger 52 and blocks the second heat exchanger 52.
Meanwhile, the third heat exchange step S103 includes performing, by the third heat exchanger 53, heat exchange between the heating water and the intermediate heat medium which is decreased in temperature by the heat exchange in the second heat exchange step S102. Although the intermediate heat medium is cooled by the heat exchange with the working fluid in the second heat exchange step S102, the temperature higher than the solidifying point of water is maintained even after the cooling. Thus, it is possible to suppress solidification of the heating water during the heat exchange between the intermediate heat medium and the heating water in the third heat exchange step S103. Thus, it is possible to suppress that the solidified heating water freezes to the third heat exchanger 53 and blocks the third heat exchanger 53.
With the above method, since it is possible to suppress that the solidified heat medium (the intermediate heat medium, the heating water) freezes to the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocks the heat exchanger, it is possible to improve reliability of the cold energy recovery system 2 when the small heat exchanger is used.
As shown in FIG. 7, the cold energy recovery method 100 may further include a first auxiliary heat exchange step S201 or a second auxiliary heat exchange step S202. The first auxiliary heat exchange step S201 includes performing, by the auxiliary heat exchanger 81, heat exchange between the above-described heating water and the liquefied gas which is raised in temperature by the heat exchange in the first heat exchange step S101. The second auxiliary heat exchange step S202 includes performing, by the second auxiliary heat exchanger 82, heat exchange between the heating water and the second intermediate heat medium flowing through the second intermediate heat medium circulation line 9.
The present disclosure is not limited to the above-described embodiments, and also includes an embodiment obtained by modifying the above-described embodiments and an embodiment obtained by combining these embodiments as appropriate.
The contents described in some embodiments described above would be understood as follows, for instance.
1) A cold energy recovery system (2) according to at least one embodiment of the present disclosure is a cold energy recovery system (2) installed in a ship (1) which includes a liquefied gas storage device (11) configured to store a liquid liquefied gas, that includes a working fluid circulation line (4) which is configured to circulate a working fluid having a lower solidifying point than water, a cold energy recovery device (41) that includes a turbine (42) which is configured to be driven by the working fluid flowing through the working fluid circulation line (4), a first heat exchanger (51) which is configured to exchange heat between the liquefied gas and the working fluid flowing through the working fluid circulation line (4), an intermediate heat medium circulation line (6) which is configured to circulate an intermediate heat medium having a lower solidifying point than water, a second heat exchanger (52) disposed downstream of the first heat exchanger (51) on the working fluid circulation line (4), the second heat exchanger (52) being configured to exchange heat between the working fluid flowing through the working fluid circulation line (4) and the intermediate heat medium flowing through the intermediate heat medium circulation line (6), and a third heat exchanger (53) which is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line (6) and heating water introduced from an outside of the cold energy recovery system (2).
With the above configuration 1), the cold energy recovery system (2) includes the intermediate heat medium circulation line (6), the second heat exchanger (52), and the third heat exchanger (53). In such cold energy recovery system (2), the heating water and the working fluid circulating through the working fluid circulation line (4) indirectly exchange heat via the intermediate heat medium circulating through the intermediate heat medium circulation line (6), making it possible to suppress solidification of the heat medium (the intermediate heat medium, the heating water) during heat exchange. Thus, it is possible to suppress that the solidified heat medium freezes to the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocks the heat exchanger.
More specifically, the working fluid circulating through the working fluid circulation line (4) has a temperature which is not greater than the solidifying point of water by the heat exchange with the liquefied gas in the first heat exchanger (51). In the second heat exchanger (52), heat exchange is performed between the working fluid which has passed through the first heat exchanger (51) and is decreased in temperature, and the intermediate heat medium circulating through the intermediate heat medium circulation line (6). Since the intermediate heat medium has a lower solidifying point than water, the intermediate heat medium is hardly solidified during heat exchange with the low-temperature working fluid in the second heat exchanger (52). Thus, it is possible to suppress that the solidified intermediate heat medium freezes to the second heat exchanger (52) and blocks the second heat exchanger (52).
Meanwhile, in the third heat exchanger (53), heat exchange is performed between the heating water and the intermediate heat medium which has passed through the second heat exchanger (51) and is decreased in temperature. Although the intermediate heat medium is cooled by the heat exchange with the working fluid in the second heat exchanger (51), the temperature higher than the solidifying point of water is maintained even after the cooling. Thus, it is possible to suppress solidification of the heating water during the heat exchange between the intermediate heat medium and the heating water in the third heat exchanger (53). Thus, it is possible to suppress that the solidified heating water freezes to the third heat exchanger (53) and blocks the third heat exchanger (53).
With the above configuration, since the cold energy recovery system (2) can suppress that the solidified heat medium (the intermediate heat medium, the heating water) freezes to the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocks the heat exchanger, it is possible to improve reliability of the cold energy recovery system (2) when the small heat exchanger is used.
2) In some embodiments, the cold energy recovery system (2) according to the above 1) further includes a liquefied gas supply line (3) configured to send the liquefied gas from the liquefied gas storage device (11), and an auxiliary heat exchanger (81) disposed downstream of the first heat exchanger (51) on the liquefied gas supply line (3), the auxiliary heat exchanger (81) being configured to exchange heat between the liquefied gas flowing through the liquefied gas supply line (3) and a heating medium circulating in the cold energy recovery system (2).
With the above configuration 2), the cold energy recovery system (2) includes the liquefied gas supply line (3), the above-described first heat exchanger (51), and the auxiliary heat exchanger (81). In such cold energy recovery system (2), the heat exchange in the first heat exchanger (51) and the auxiliary heat exchanger (81) raises the temperature of the liquefied gas and vaporizes the liquefied gas. In this case, it is not necessary to raise the temperature to a temperature, at which the liquid liquefied gas is completely vaporized, by the heat exchange in the first heat exchanger (51). Thus, compared to a case where the temperature of the liquefied gas is raised only by the first heat exchanger (51), it is possible to reduce the amount of the heat exchange in the first heat exchanger (51), and it is possible to reduce the temperature drop of the working fluid in the first heat exchanger (51). Thus, it is possible to effectively suppress solidification of the intermediate heat medium during the heat exchange between the working fluid and the intermediate heat medium in the second heat exchanger (52). Further, by reducing the amount of the heat exchange in the first heat exchanger (51), it is possible to reduce the size of the first heat exchanger (51).
3) In some embodiments, in the cold energy recovery system (2) according to the above 2), the heating medium is constituted by the intermediate heat medium heated by the third heat exchanger (53) and flowing through the intermediate heat medium circulation line (6).
With the above configuration 3), in the auxiliary heat exchanger (81), heat exchange is performed between the liquefied gas which has passed through the first heat exchanger (51) and is raised in temperature, and the intermediate heat medium heated by the third heat exchanger (53). Since the intermediate heat medium has the lower solidifying point than water, it is possible to suppress solidification during the heat exchange with the liquefied gas in the auxiliary heat exchanger (81). Thus, it is possible to suppress that the solidified intermediate heat medium freezes to the auxiliary heat exchanger (81) and blocks the auxiliary heat exchanger (81). Thus, it is possible to effectively heat the liquefied gas by the auxiliary heat exchanger (81).
If a heat medium circulating through a circulation line different from the intermediate heat medium circulation line (6) is used as the heating medium, a circulation pump for circulating the heat medium becomes necessary. With the above configuration 3), by using the intermediate heat medium circulating through the intermediate heat medium circulation line (6) as the heating medium, the above-described circulation pump becomes unnecessary, making it possible to suppress an equipment cost of the cold energy recovery system (2).
4) In some embodiments, in the cold energy recovery system (2) according to the above 3), the intermediate heat medium circulation line (6) includes a bypass flow passage (63) which branches from downstream of the third heat exchanger (53), bypasses the second heat exchanger (52), and is connected to upstream of the third heat exchanger (53), and the auxiliary heat exchanger (81) is configured to exchange heat between the liquefied gas flowing through the liquefied gas supply line (3) and the intermediate heat medium flowing through the bypass flow passage (63).
Since the intermediate heat medium is a heat medium responsible for heating in the second heat exchanger (52) and the auxiliary heat exchanger (81), the intermediate heat medium is cooled by heat exchange in these heat exchangers. With the above configuration 4), the auxiliary heat exchanger (81) is configured to exchange heat between the liquefied gas and the intermediate heat medium which flows through the bypass flow passage (63) bypassing the second heat exchanger (52). That is, since the intermediate heat medium circulation line (6) does not form the flow passage passing through both the second heat exchanger (52) and the auxiliary heat exchanger (81), it is possible to prevent the temperature of the intermediate heat medium circulating through the intermediate heat medium circulation line (6) from becoming too low. Thus, it is possible to suppress solidification of the heating water during the heat exchange with the intermediate heat medium in the third heat exchanger (53).
5) In some embodiments, the cold energy recovery system (2) according to the above 2) further includes a second intermediate heat medium circulation line (9) which is configured to circulate a second intermediate heat medium having a lower solidifying point than water. The heating medium is constituted by the second intermediate heat medium flowing through the second intermediate heat medium circulation line (9).
With the above configuration 5), the heating medium which exchanges heat with the liquefied gas in the auxiliary heat exchanger (81) is constituted by the second intermediate heat medium flowing through the second intermediate heat medium circulation line (9). In this case, in the auxiliary heat exchanger (81), heat exchange is performed between the liquefied gas which has passed through the first heat exchanger (51) and is raised in temperature, and the second intermediate heat medium circulating through the second intermediate heat medium circulation line (9). Since the second intermediate heat medium has the lower solidifying point than water, it is possible to suppress solidification during the heat exchange with the liquefied gas in the auxiliary heat exchanger (81). Thus, it is possible to suppress that the solidified second intermediate heat medium freezes to the auxiliary heat exchanger (81) and blocks the auxiliary heat exchanger (81).
Further, with the above configuration 5), since the second intermediate heat medium circulation line (9) is different from the intermediate heat medium circulation line (6), it is possible to use, as the second intermediate heat medium, a heat medium different from the intermediate heat medium circulating through the intermediate heat medium circulation line (6). For example, as the second intermediate heat medium, it is possible to use a heat medium which is more suitable for conditions of the heat exchange in the auxiliary heat exchanger (81) than the intermediate heat medium circulating through the intermediate heat medium circulation line (6).
6) In some embodiments, the cold energy recovery system (2) according to the above 5) further includes a second auxiliary heat exchanger (82) which is configured to exchange heat between the second intermediate heat medium flowing through the second intermediate heat medium circulation line (9) and heating water introduced from an outside of the cold energy recovery system (2).
In the cold energy recovery system (2), since the heat exchange in the first heat exchanger (51) and the auxiliary heat exchanger (81) raises the temperature of the liquefied gas, the amount of the heat exchange in the auxiliary heat exchanger (81) is small, and the amount of temperature drop of the second intermediate heat medium (heating medium) in the auxiliary heat exchanger (81) is small. With the above configuration 6), it is possible to suppress solidification of the heating water during the heat exchange between the heating water and the second intermediate heat medium in the second auxiliary heat exchanger (82).
7) In some embodiments, in the cold energy recovery system (2) according to any one of the above 1) to 6), the cold energy recovery device (41) further includes a generator (43) configured to generate electricity by driving the turbine (42).
With the above configuration 7), since the cold energy recovery device (41) includes the turbine (42) and the generator (43), it is possible to generate electricity in the generator (43) by driving the turbine (42) with the working fluid which circulates through the working fluid circulation line 4 and recovers the cold energy from the liquefied gas. In this case, it is possible to effectively utilize the cold energy of the liquefied gas.
8) In some embodiments, the cold energy recovery system (2) according to the above 7) further includes a liquefied gas supply line (3) configured to send the liquefied gas from the liquefied gas storage device (11), and a liquefied gas pump (31) disposed on the liquefied gas supply line (3). The liquefied gas pump (31) is configured to be driven by electric power generated by the generator (43).
With the above configuration 8), it is possible to drive the liquefied gas pump (31) disposed on the liquefied gas supply line (3) by the electric power generated by the generator (43). In this case, an electric power system for supplying electric power from the onshore electric power equipment to the liquefied gas pump (31) becomes unnecessary, making it possible to reduce the size of the ship (1) provided with the liquefied gas pump (31). Alternatively, since it is possible to reduce the occupied space of the cold energy recovery system (2) in the ship (1), it is possible to increase the occupied space of the liquefied gas storage device (11) in the ship (1).
9) In some embodiments, in the cold energy recovery system (2) according to any one of the above 1) to 8), the third heat exchanger (53) is constituted by a microchannel heat exchanger (53A) that includes a first microchannel (531A) through which the intermediate heat medium flows, and a second microchannel (532A) through which the heating water flows, at least a part of the second microchannel (532A) being disposed adjacent to the first microchannel (531A).
With the above configuration 9), since the third heat exchanger (53) is constituted by the microchannel heat exchanger (53A) which allows for the heat exchange between the intermediate heat medium flowing through the first microchannel (531A) and the heating water flowing through the second microchannel (532A), the third heat exchanger (53) is compact and can improve a heat-transfer coefficient.
10) A ship (1) according to at least one embodiment of the present disclosure includes the cold energy recovery system (2) according to any one of the above 1) to 9).
With the above configuration 10), since it is possible to reduce the size of the cold energy recovery system (2) by using the small heat exchanger, it is possible to reduce the size of the ship (1) having the cold energy recovery system (2). Alternatively, since it is possible to reduce the occupied space of the cold energy recovery system (2) in the ship (1), it is possible to increase the occupied space of the liquefied gas storage device (11) in the ship (1).
11) A cold energy recovery method (100) according to at least one embodiment of the present disclosure is a cold energy recovery method (100) by a cold energy recovery system (2) installed in a ship (1) which includes a liquefied gas storage device (11) configured to store a liquid liquefied gas, the cold energy recovery system (2) including a working fluid circulation line (4) which is configured to circulate a working fluid having a lower solidifying point than water, a cold energy recovery device (41) that includes a turbine (42) which is configured to be driven by the working fluid flowing through the working fluid circulation line (4), a first heat exchanger (51) which is configured to exchange heat between the liquefied gas and the working fluid flowing through the working fluid circulation line (4), an intermediate heat medium circulation line (6) which is configured to circulate an intermediate heat medium having a lower solidifying point than water, a second heat exchanger (52) disposed downstream of the first heat exchanger (51) on the working fluid circulation line (4), the second heat exchanger (52) being configured to exchange heat between the working fluid flowing through the working fluid circulation line (4) and the intermediate heat medium flowing through the intermediate heat medium circulation line (6), and a third heat exchanger (53) which is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line (6) and heating water introduced from an outside of the cold energy recovery system (2), the cold energy recovery method (100) including a first heat exchange step (S101) of performing heat exchange between the liquefied gas and the working fluid by the first heat exchanger (51), a second heat exchange step (S102) of performing, by the second heat exchanger (52), heat exchange between the intermediate heat medium and the working fluid that has exchanged heat with the liquefied gas in the first heat exchange step (S101), and a third heat exchange step (S103) of performing, by the third heat exchanger (53), heat exchange between the heating water and the intermediate heat medium that has exchanged heat with the working fluid in the second heat exchange step (S102).
The above method 11) includes the first heat exchange step (S101), the second heat exchange step (S102), and the third heat exchange step (S103). In such cold energy recovery method (100), the second heat exchange step (S102) and the third heat exchange step (S103) cause the heating water and the working fluid circulating through the working fluid circulation line (4) to indirectly exchange heat via the intermediate heat medium circulating through the intermediate heat medium circulation line (6), making it possible to suppress solidification of the heat medium (the intermediate heat medium, the heating water) during heat exchange. Thus, it is possible to suppress that the solidified heat medium freezes to the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocks the heat exchanger.
More specifically, the first heat exchange step (S101) includes performing heat exchange between the liquefied gas and the working fluid by the first heat exchanger (51). The working fluid that has passed through the first heat exchanger (51) has a low temperature which is not greater than the solidifying point of water. The second heat exchange step (S102) includes performing, by the second heat exchanger (52), heat exchange between the working fluid, which is decreased in temperature by the heat exchange in the first heat exchange step (S101), and the intermediate heat medium flowing through the intermediate heat medium circulation line (6). Since the intermediate heat medium has a lower solidifying point than water, the intermediate heat medium is hardly solidified during heat exchange with the low-temperature working fluid in the second heat exchange step. Thus, it is possible to suppress that the solidified intermediate heat medium freezes to the second heat exchanger (52) and blocks the second heat exchanger (52).
Meanwhile, the third heat exchange step (S103) includes performing, by the third heat exchanger (53), heat exchange between the heating water and the intermediate heat medium which is decreased in temperature by the heat exchange in the second heat exchange step (SI02). Although the intermediate heat medium is cooled by the heat exchange with the working fluid in the second heat exchange step (S102), the temperature higher than the solidifying point of water is maintained even after the cooling. Thus, it is possible to suppress solidification of the heating water during the heat exchange between the intermediate heat medium and the heating water in the third heat exchange step. Thus, it is possible to suppress that the solidified heating water freezes to the third heat exchanger (53) and blocks the third heat exchanger (53).
With the above method, since it is possible to suppress that the solidified heat medium (the intermediate heat medium, the heating water) freezes to the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocks the heat exchanger, it is possible to improve reliability of the cold energy recovery system (2) when the small heat exchanger is used.

Reference Signs List

1: Ship
2: Cold energy recovery system
20: Cold energy recovery system according to comparative example
3: Liquefied gas supply line
301: One end side
302: Another end side
31: Liquefied gas pump
4: Working fluid circulation line
41: Cold energy recovery device
42: Turbine
421: Turbine rotor
43: Generator
44: (Working fluid) circulation pump
50: Heat exchanger (of comparative example)
501: Working fluid flow passage
502: Heating water flow passage
51: First heat exchanger
511: Liquefied gas flow passage
512: Working fluid flow passage
52: Second heat exchanger
521: Working fluid flow passage
522: Intermediate heat medium flow passage
53: Third heat exchanger
531: Intermediate heat medium flow passage
531A: First microchannel
532: Heating water flow passage
532A: Second microchannel
6: Intermediate heat medium circulation line
61: (Intermediate heat medium) circulation pump
62: Main flow passage
63: Bypass flow passage
631: One end side
632: Another end side
64: Intermediate heat medium storage device
65: Flow regulating valve
7: Heating water supply line
701: One end side
702: Another end side
71: Heating water pump
81: Auxiliary heat exchanger
811: Liquefied gas flow passage
812: Heating medium flow passage
82: Second auxiliary heat exchanger
821: Second intermediate heat medium flow passage
822: Heating water flow passage
9: Second intermediate heat medium circulation line
10: Hull
11: Liquefied gas storage device
12: Equipment
13: Heating water supply source
14: Heating water discharge destination
15: Engine room
16: Engine
17: Water inlet
18: Cooling water flow passage
19: Water outlet

Claims

A cold energy recovery system installed in a ship which includes a liquefied gas storage device configured to store a liquid liquefied gas, comprising:
a working fluid circulation line which is configured to circulate a working fluid having a lower solidifying point than water;

a cold energy recovery device that includes a turbine which is configured to be driven by the working fluid flowing through the working fluid circulation line;

a first heat exchanger which is configured to exchange heat between the liquefied gas and the working fluid flowing through the working fluid circulation line;

an intermediate heat medium circulation line which is configured to circulate an intermediate heat medium having a lower solidifying point than water;

a second heat exchanger disposed downstream of the first heat exchanger on the working fluid circulation line, the second heat exchanger being configured to exchange heat between the working fluid flowing through the working fluid circulation line and the intermediate heat medium flowing through the intermediate heat medium circulation line; and

a third heat exchanger which is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line and heating water introduced from an outside of the cold energy recovery system.
The cold energy recovery system according to claim 1, further comprising:
a liquefied gas supply line configured to send the liquefied gas from the liquefied gas storage device; and

an auxiliary heat exchanger disposed downstream of the first heat exchanger on the liquefied gas supply line, the auxiliary heat exchanger being configured to exchange heat between the liquefied gas flowing through the liquefied gas supply line and a heating medium circulating in the cold energy recovery system.
The cold energy recovery system according to claim 2,
wherein the heating medium is constituted by the intermediate heat medium heated by the third heat exchanger and flowing through the intermediate heat medium circulation line.
The cold energy recovery system according to claim 3,
wherein the intermediate heat medium circulation line includes a bypass flow passage which branches from downstream of the third heat exchanger, bypasses the second heat exchanger, and is connected to upstream of the third heat exchanger, and

wherein the auxiliary heat exchanger is configured to exchange heat between the liquefied gas flowing through the liquefied gas supply line and the intermediate heat medium flowing through the bypass flow passage.
The cold energy recovery system according to claim 2,
further comprising a second intermediate heat medium circulation line which is configured to circulate a second intermediate heat medium having a lower solidifying point than water,

wherein the heating medium is constituted by the second intermediate heat medium flowing through the second intermediate heat medium circulation line.
The cold energy recovery system according to claim 5, further comprising a second auxiliary heat exchanger which is configured to exchange heat between the second intermediate heat medium flowing through the second intermediate heat medium circulation line and heating water introduced from an outside of the cold energy recovery system.
The cold energy recovery system according to any one of claims 1 to 6,
wherein the cold energy recovery device further includes a generator configured to generate electricity by driving the turbine.
The cold energy recovery system according to claim 7, further comprising:
a liquefied gas supply line configured to send the liquefied gas from the liquefied gas storage device; and

a liquefied gas pump disposed on the liquefied gas supply line,

wherein the liquefied gas pump is configured to be driven by electric power generated by the generator.
The cold energy recovery system according to any one of claims 1 to 8,
wherein the third heat exchanger is constituted by a microchannel heat exchanger that includes:
a first microchannel through which the intermediate heat medium flows; and

a second microchannel through which the heating water flows, at least a part of the second microchannel being disposed adjacent to the first microchannel.
A ship comprising the cold energy recovery system according to any one of claims 1 to 9.
A cold energy recovery method by a cold energy recovery system installed in a ship which includes a liquefied gas storage device configured to store a liquid liquefied gas,
the cold energy recovery system including:
a working fluid circulation line which is configured to circulate a working fluid having a lower solidifying point than water;

a cold energy recovery device that includes a turbine which is configured to be driven by the working fluid flowing through the working fluid circulation line;

a first heat exchanger which is configured to exchange heat between the liquefied gas and the working fluid flowing through the working fluid circulation line;

an intermediate heat medium circulation line which is configured to circulate an intermediate heat medium having a lower solidifying point than water;

a second heat exchanger disposed downstream of the first heat exchanger on the working fluid circulation line, the second heat exchanger being configured to exchange heat between the working fluid flowing through the working fluid circulation line and the intermediate heat medium flowing through the intermediate heat medium circulation line; and

a third heat exchanger which is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line and heating water introduced from an outside of the cold energy recovery system,

the cold energy recovery method comprising:
a first heat exchange step of performing heat exchange between the liquefied gas and the working fluid by the first heat exchanger;

a second heat exchange step of performing, by the second heat exchanger, heat exchange between the intermediate heat medium and the working fluid that has exchanged heat with the liquefied gas in the first heat exchange step; and

a third heat exchange step of performing, by the third heat exchanger, heat exchange between the heating water and the intermediate heat medium that has exchanged heat with the working fluid in the second heat exchange step.