ES3060712T3 - Cold recovery system, ship including cold recovery system, and cold recovery method - Google Patents

Abstract

This cold recovery system is installed on a vessel equipped with a liquefied gas storage device that stores liquid liquefied gas. The system comprises: a working fluid circulation line through which a working fluid with a freezing point lower than that of water is circulated; a cold recovery device including a turbine driven by the working fluid; a first heat exchanger that exchanges heat between the liquefied gas and the working fluid; an intermediate thermal medium circulation line through which an intermediate thermal medium with a freezing point lower than that of water is circulated; a second heat exchanger located downstream of the working fluid circulation line with respect to the first heat exchanger, and which exchanges heat between the working fluid and the intermediate thermal medium; and a third heat exchanger that exchanges heat between the intermediate thermal medium and hot water introduced from outside the cold recovery system.

Description

[0001] DESCRIPTION

[0002] Cold recovery system, vessel including a cold recovery system, and cold recovery method

[0003] Technical field

[0004] This disclosure relates to a cold energy recovery system installed on a vessel that includes a liquefied gas storage device configured to store a liquid liquefied gas, and to a method of cold energy recovery by means of the cold energy recovery system.

[0005] Background

[0006] An onshore LNG (liquefied natural gas) terminal receives and stores liquefied natural gas transported by an LNG carrier. Then, when the liquefied natural gas is delivered to a supply destination such as a town gas station or a thermal power plant, the liquefied natural gas is heated with seawater or similar liquid to vaporize it back into a gas. When the liquefied natural gas is vaporized, cryogenic power generation can be carried out in which the cold energy is recovered as electrical power instead of being discharged into seawater (e.g., patent document 1).

[0007] Providing a suitable onshore LNG terminal for each liquefied natural gas (LNG) supply destination is difficult due to its cost, for example, the cost of acquiring land. Therefore, a vessel equipped with an LNG storage facility for storing LNG or a regasification facility for regasifying LNG can be anchored at sea, and the regasified LNG can be piped from the vessel to an onshore supply destination or a power meter (floating power station) at sea.

[0008] Since a vessel is less expandable than a land-based facility, in order to install a cryogenic power generation system, it is important to reduce the size of the cryogenic power generation system, especially the heat exchanger. A printed circuit heat exchanger (PCHE), a plate heat exchanger, or similar small heat exchanger can be provided as an example.

[0009] WO 2010/007535 A1 relates to the conversion of liquefied natural gas and describes a method and apparatus for converting liquefied natural gas (LNG) into a superheated fluid by vaporizing and superheating the LNG. An LNG installation comprises a thermally insulated storage tank having a submerged LNG pump. The installation is located on board a marine vessel. The apparatus includes a first main heat exchanger in series with a second main heat exchanger. The first main heat exchanger is heated by a first condensing heat exchange fluid (propane) flowing in a first heat exchange circuit that includes a first supplementary heat exchanger for re-vaporizing the first heat exchange fluid, and the second main heat exchanger by a second condensing heat exchange fluid flowing in a second heat exchange circuit that includes a second heat exchanger for vaporizing the second heat exchange fluid. The first auxiliary heat exchanger may be divided and comprise two parallel heat exchange units. The first heat exchange circuit has an intermediate turboexpander between the steam outlet of the auxiliary heat exchanger and the steam inlet of the main heat exchanger.

[0010] Document GB 2 062 111 A relates to recovering energy from liquefied natural gas. Water is used to heat and vaporize liquefied natural gas (LNG) by means of an intermediate heat exchange medium such as propane, which is circulated around a closed circuit in which it undergoes liquefaction and vaporization alternately by means of heat exchange with the LNG and water in heat exchangers. The vaporized intermediate heat exchange medium from the heat exchanger expands through a turbine to drive an electricity generator.

[0011] EP 0009 387 A1 relates to a process for generating energy during the regasification of liquefied gases. The liquefied gas is heated in a cryogenic heat exchanger by indirect heat exchange with a working fluid circulating in a closed cycle and is then further heated by passing it through indirect heat exchange with air before being fed into a gas turbine. The working fluid passes through a recuperator where it is heated by indirect heat exchange with working fluid expanded from an expansion turbine. KR 101792460 B1 relates to a method of vaporizing LNG from a vaporizer for an LNG carrier, which vaporizes LNG stored in a storage tank of an LNG carrier and supplies the LNG to an engine. The LNG transporter uses a heat pump system, in which a heat medium to vaporize LNG into a vapor state in the vaporizer undergoes heat exchange and is heated by the heat pump system using seawater or air as the heat source.

[0012] Document JP 2017/190829 A relates to a system integrating a gas supply installation and a cooling installation. The gas supply installation supplies gas obtained by vaporizing low-temperature liquefied gas, and the cooling installation includes a cooling portion, a gas cold recovery portion for recovering vaporized cold from the low-temperature liquefied gas, and a cooling cold supply portion for supplying the recovered cold to the cooling portion. The gas cold recovery portion includes a first heat exchanger for exchanging heat between the low-temperature liquefied gas and a first brine to vaporize the low-temperature liquefied gas and recover the vaporized cold in the first brine, a gas cold transport line for circulating the first brine, and a second heat exchanger arranged in the gas cold transport line for transferring the cold from the first brine to the cooling cold supply portion.

[0013] WO 2018/100486 A1 relates to a prime mover heat pump for cryogenic applications and refrigerants. A liquefied gas regasification line comprises a vaporization section for said gas, a prime mover, a first heat exchanger operating in the circuit of a first intermediate fluid, and a heat pump. The heat pump comprises an evaporator and a condenser. The heat pump operates with a refrigerant which, in the evaporator, absorbs heat from a second intermediate fluid and, in the condenser, transfers heat to a third intermediate fluid. The third intermediate fluid drives an additional heat exchanger, thereby transferring heat to the liquefied gas. The prime mover supplies mechanical or electrical power to the heat pump and thermal power to the first heat exchanger.

[0014] List of references

[0015] Patent Bibliography

[0016] Patent document 1: document JP 2017- 180323 A.

[0017] Summary

[0018] Technical Problem

[0019] If the temperature of another heat exchange medium is lower than the freezing point of a heat exchange medium (e.g., seawater), that heat exchange medium will solidify within the heat exchanger, and the solidified heat exchange medium may adhere to a surface of the exchanger and block it. A small heat exchanger has a higher risk of blockage than a large heat exchanger (e.g., a shell-and-tube type heat exchanger), and therefore presents a reliability issue.

[0020] In view of the above problems, one objective of at least one embodiment of the present disclosure is to provide a cold energy recovery system capable of suppressing heat exchanger blockage due to solidification of a heat medium, and capable of improving the reliability of the cold energy recovery system when using the small heat exchanger.

[0021] Solution to the problem

[0022] A cold energy recovery system according to the present invention is a cold energy recovery system installed on a vessel that includes a liquefied gas storage device configured to store a liquid liquefied gas, as defined in claim 1. The cold energy recovery system includes a working fluid circulation line configured to circulate a working fluid having a freezing point lower than water, a cold energy recovery device including a turbine configured to be driven by the working fluid flowing through the working fluid circulation line, a first heat exchanger 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 configured to circulate an intermediate heat medium having a freezing point lower than water, and a second heat exchanger disposed downstream of the first heat exchanger in the working fluid circulation line, the second heat exchanger being configured to exchange heat between the working fluid and the intermediate heat medium having a freezing point lower than water. work 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 that is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line and heating water introduced from outside the cold energy recovery system.

[0023] The cold energy recovery system further comprises a liquefied gas supply line configured to deliver liquefied gas from the liquefied gas storage device, and an auxiliary heat exchanger disposed downstream of the first heat exchanger in 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, 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.

[0024] A cold energy recovery method according to the present invention is a cold energy recovery method by means of a cold energy recovery system installed on a vessel that includes a liquefied gas storage device configured to store a liquid liquefied gas, as defined in claim 8. The cold energy recovery system includes a working fluid circulation line configured to circulate a working fluid having a freezing point lower than water, a cold energy recovery device including a turbine configured to be driven by the working fluid flowing through the working fluid circulation line, a first heat exchanger 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 configured to circulate an intermediate heat medium having a freezing point lower than water, and a second heat exchanger disposed downstream of the first heat exchanger in 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 that is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line and heating water introduced from outside the cold energy recovery system. The cold energy recovery system further comprises a liquefied gas supply line configured to deliver liquefied gas from the liquefied gas storage device, and an auxiliary heat exchanger disposed downstream of the first heat exchanger in 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, 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 method includes a first heat exchange stage of performing heat exchange between the liquefied gas and the working fluid by means of the first heat exchanger, a second heat exchange stage of performing, by means of 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 stage, and a third heat exchange stage of performing, by means of 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 stage.

[0025] Advantageous effects

[0026] According to at least one embodiment of the present disclosure, a cold energy recovery system is provided that is capable of suppressing the blockage of a heat exchanger due to solidification of a heat medium, and is capable of improving the reliability of a cold energy recovery system when using a small heat exchanger.

[0027] Brief description of drawings

[0028] Figure 1 is a schematic configuration diagram showing schematically the configuration of a vessel having a cold energy recovery system according to an illustrative example or embodiment of the present invention.

[0029] Figure 2 is a schematic configuration diagram showing schematically the overall configuration of the illustrative example of the cold energy recovery system lacking the claimed feature of an auxiliary heat exchanger arranged downstream of the first heat exchanger in the liquefied gas supply line.

[0030] Figure 3 is a schematic configuration diagram showing schematically the overall configuration of the cold energy recovery system according to the first embodiment of the present invention.

[0031] Figure 4 is a schematic configuration diagram showing schematically the overall configuration of the cold energy recovery system according to the second embodiment of the present invention.

[0032] Figure 5 is a schematic configuration diagram that schematically shows the overall configuration of the cold energy recovery system according to a comparative example.

[0033] Figure 6 is an explanatory view to describe an example of a heat exchanger in an embodiment of the present invention.

[0034] Figure 7 is a flow diagram of a cold energy recovery method according to an embodiment of the present invention.

[0035] Detailed description

[0036] The following will describe embodiments of this disclosure with reference to the accompanying drawings. However, unless specifically identified, the dimensions, materials, shapes, relative positions, and the like of components described or shown in the drawings as embodiments are intended to be illustrative only and are not intended to limit the scope of this disclosure. For example, an expression of relative or absolute arrangement such as “in one direction,” “along one direction,” “parallel,” “orthogonal,” “centered,” “concentric,” and “coaxial” should not be construed as indicating the arrangement only in a strict literal sense, but also as including a state in which the arrangement is relatively offset by a tolerance, or by an angle or distance, by which the same function can be achieved.

[0037] For example, an expression of an equal state such as “same”, “equal”, and “uniform” will not be interpreted as indicating only the state in which the feature is strictly equal, but also includes a state in which there is a tolerance or difference that can still achieve the same function.

[0038] Furthermore, for example, an expression of a shape such as a rectangular shape or a tubular shape will not be interpreted solely as the geometrically strict shape, but will also include a shape with irregularity or chamfered corners within the range in which the same effect can be achieved.

[0039] On the other hand, the expressions “comprising”, “including” or “having” a constituent element are not an exclusive expression that excludes the presence of other constituent elements.

[0040] The same configurations are indicated by the same reference characters and may not be described again in detail.

[0041] (Vessel that has a cold energy recovery system)

[0042] Figure 1 is a schematic configuration diagram showing schematically the configuration of a vessel having a cold energy recovery system according to an illustrated example or embodiment of the present invention.

[0043] As shown in Figure 1, a cold energy recovery system 2 according to some embodiments is installed on a vessel 1. As shown in Figure 1, the vessel 1 includes a hull 10, and the cold energy recovery system 2 mounted on the hull 10. In Figure 1, the vessel 1 further includes a liquefied gas storage device 11 (e.g., a liquefied gas tank) mounted on the hull 10. The liquefied gas storage device 11 is configured to store a liquid liquefied gas (e.g., liquefied natural gas).

[0044] In Figure 1, the hull 10 internally forms an engine room 15. The engine room 15 is equipped with an engine 16 (for example, a marine diesel engine) to apply a propulsive force to the vessel 1. In this case, by operating the engine 16, the vessel 1 can move from a liquefied gas supply source to the vicinity of a liquefied gas supply destination.

[0045] (Cold energy recovery system)

[0046] Figure 2 is a schematic configuration diagram showing the overall configuration of the cold energy recovery system according to the illustrative example, which does not include the auxiliary heat exchanger arranged downstream of the first heat exchanger in the liquefied gas supply line as in the claimed invention. Figure 3 is a schematic configuration diagram showing the overall configuration of the cold energy recovery system according to the first embodiment of the present invention. Figure 4 is a schematic configuration diagram showing the overall configuration of the cold energy recovery system according to the second embodiment of the present invention.

[0047] As shown in Figures 2 to 4, the cold energy recovery system 2 according to the illustrative example and 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 conduit through which a fluid flows.

[0048] Liquefied gas supply line 3 is configured to deliver liquefied gas from liquefied gas storage device 11. Working fluid circulation line 4 is configured to circulate a working fluid that has a freezing point lower than water. Hereafter, 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, this disclosure is also applicable to a liquefied gas other than liquefied natural gas, and is also applicable to a case where a heat medium other than propane is used as the working fluid.

[0050] In Figures 2 to 4, the cold energy recovery system 2 includes a liquefied gas pump 31 arranged on the liquefied gas supply line 3, and a working fluid circulation pump 44 arranged 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 another end side 302 connected to liquefied gas equipment 12 arranged outside the cold energy recovery system 2. As an example, the liquefied gas equipment 12 may be a gas tank (see Figure 1) arranged on land, a gas pipeline connected to the gas tank, or similar equipment. When the liquefied gas pump 31 is activated, 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 is then sent to the liquefied gas equipment 12. Additionally, when the working fluid circulation pump 44 is activated, the working fluid circulates through the working fluid circulation line 4.

[0052] 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 Figures 2 to 4, 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 in the working fluid circulation line 4. The turbine rotor 421 is configured to be rotated by the working fluid flowing through the working fluid circulation line 4. In some other embodiments, the cold energy recovery device 41 cannot convert a rotational force of the turbine rotor 421 into electrical power, but can recover the rotational force as power as such by means of a power transmission device (e.g., a coupling, belt, pulley, or the like).

[0054] Intermediate heat medium circulation line 6 is configured to circulate an intermediate heat medium having a freezing point lower than water. Heating water supply line 7 is configured to supply heating water introduced from outside the cold energy recovery system 2. The “heating water” may be water for heating a heat exchange object as a heat medium in the heat exchanger, and may be ambient temperature water. The heating water is preferably water that is readily available on vessel 1 (e.g., water from outside the vessel such as seawater, cooling water that has cooled an engine on vessel 1, or similar).

[0056] In Figures 2 to 4, the cold energy recovery system 2 includes an intermediate heat medium circulation pump 61 arranged in the intermediate heat medium circulation line 6, and a heating water pump 71 arranged in the heating water supply line 7. When the intermediate heat medium circulation pump 61 is operated, the intermediate heat medium circulates through the intermediate heat medium circulation line 6. The heating water supply line 7 has one end side 701 that is connected to a heating water supply source 13 arranged outside the cold energy recovery system 2, and another end side 702 that is connected to a heating water discharge destination 14 arranged outside the cold energy recovery system 2. When the heating water pump 71 is activated, 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 is then sent to the heating water discharge destination 14.

[0058] As a heating water supply source 13, an example may be provided of a water inlet 17 (see Figure 1) provided in the hull 10 for introducing water from outside the vessel, a cooling water flow conduit 18 (see Figure 1) through which flows the cooling water that has cooled the vessel's engine 1 (e.g., engine 16), or similar. In addition, as a heating water discharge destination 14, an example may be provided of a water outlet 19 (see Figure 1) provided in the hull 10 for discharging water outside the vessel, or similar.

[0060] The intermediate heating medium may be the same type of heating medium as the working fluid, or it may be a different type of heating medium. In the illustrative example shown in Figure 2, the intermediate heating medium is propane, and the heating water is the cooling water (engine jacket water) that has cooled the engine. The cooling water extracts heat from the engine and has a higher temperature than seawater at ambient temperature. In the embodiment shown in Figure 3, the intermediate heating medium is propane, and the heating water is seawater taken from outside the vessel. In the embodiment shown in Figure 4, the intermediate heating medium is antifreeze (more specifically, glycol water), and the heating water is seawater taken from outside the vessel. For reference, Figures 2 to 4 each show an example of a temperature and pressure in each flow conduit.

[0061] 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 Figures 2 to 4, the first heat exchanger 51 forms a liquefied gas flow conduit 511 arranged in the liquefied gas supply line 3, through which the liquefied gas flows, and a working fluid flow conduit 512 arranged in the working fluid circulation line 4, through which the working fluid flows. The working fluid flow conduit 512 is arranged at least partially adjacent to the liquefied gas flow conduit 511, and heat exchange is effected between the working fluid flowing through the working fluid flow conduit 512 and the liquefied gas flowing through the liquefied gas flow conduit 511.

[0062] 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 Figures 2 to 4, the second heat exchanger 52 forms a working fluid flow conduit 521 arranged in the working fluid circulation line 4, through which the working fluid flows, and an intermediate heat medium flow conduit 522 arranged in the intermediate heat medium circulation line 6, through which the intermediate heat medium flows. The intermediate heat medium flow conduit 522 is arranged at least partially adjacent to the working fluid flow conduit 521, and heat exchange is effected between the intermediate heat medium flowing through the intermediate heat medium flow conduit 522 and the working fluid flowing through the working fluid flow conduit 521.

[0063] 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 Figures 2 to 4, the third heat exchanger 53 forms an intermediate heat medium flow conduit 531 arranged in the intermediate heat medium circulation line 6, through which the intermediate heat medium flows, and a heating water flow conduit 532 arranged in the heating water supply line 7, through which the heating water flows. The heating water flow conduit 532 is arranged at least partially adjacent to the intermediate heat medium flow conduit 531, and heat exchange is effected between the intermediate heat medium flowing through the heating water flow conduit 532 and the working fluid flowing through the intermediate heat medium flow conduit 531.

[0064] The first heat exchanger 51 (more specifically, the liquefied gas flow conduit 511) is located 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 located downstream of the liquefied gas storage device 11 on the liquefied gas supply line 3. In addition, the first heat exchanger 51 (more specifically, the working fluid flow conduit 512) is located downstream of the turbine 42 on the working fluid circulation line 4 and upstream of the working fluid circulation pump 44.

[0065] The second heat exchanger 52 (more specifically, the working fluid flow duct 521) is arranged downstream of the working fluid circulation pump 44 in the working fluid circulation line 4 and upstream of the turbine 42. In addition, the second heat exchanger 52 (more specifically, the intermediate heat medium flow duct 522) is arranged downstream of the third heat exchanger (more specifically, the intermediate heat medium flow duct 531) in the intermediate heat medium circulation line 6 and upstream of the intermediate heat medium circulation pump 61.

[0066] The third heat exchanger (more specifically, the heating water flow conduit 532) is located 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 located downstream of the heating water supply source 13 on the heating water supply line 7.

[0067] The liquefied gas pumped by the liquefied gas pump 31 is sent to the liquefied gas flow line 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 line 511 and cools the working fluid flowing through the working fluid flow line 512. In other words, the cooling energy of the liquefied gas flowing through the liquefied gas flow line 511 is recovered by the working fluid flowing through the working fluid flow line 512. The heat exchange in the first heat exchanger 51 brings the working fluid flowing through the working fluid flow line 512 to a temperature below the freezing point of water (heating water).

[0068] The intermediate heat medium, driven by the intermediate heat medium circulation pump 61, is sent to the intermediate heat medium flow duct 531 of the third heat exchanger 53. Additionally, the heating water, driven by the heating water pump 71, is sent to the heating water flow duct 532. The heat exchange in the third heat exchanger 53 heats the intermediate heat medium flowing through the intermediate heat medium flow duct 531.

[0069] The working fluid, driven by the circulation pump 44, is cooled by the first heat exchanger 51 and sent to the working fluid flow line 521 of the second heat exchanger 52. Additionally, the intermediate heat medium, heated by the third heat exchanger 53, is sent to the intermediate heat medium flow line 522. The heat exchange in the second heat exchanger 52 heats the working fluid flowing through the working fluid flow line 521 and cools the intermediate heat medium flow line 522. In this document, since the intermediate heat medium has a lower freezing point than water, it is possible to suppress freezing during heat exchange with the low-temperature working fluid in the second heat exchanger. In the illustrative example and embodiments shown in Figures 2 to 4, the cold energy recovery system 2 decides a condition for each piece of equipment in the cold energy recovery system 2 such that the intermediate heat medium flowing through the intermediate heat medium circulation line 6 has a temperature above the freezing point of water.

[0070] The intermediate heat medium flowing through the intermediate heat medium flow conduit 531 of the third heat exchanger 53 has a higher temperature than the working fluid flowing through the working fluid flow conduit 521 of the second heat exchanger 52. In Figures 2 to 4, the intermediate heat medium flowing through the intermediate heat medium flow conduit 531 has a temperature above the freezing point of water (heating water). As described above, although the intermediate heat medium is cooled by heat exchange with the working fluid in the second heat exchanger 52, the temperature above the freezing point of water is maintained even after cooling. Therefore, it is possible to suppress the freezing of the heating water during the heat exchange between the intermediate heat medium and the heating water in the third heat exchanger 53.

[0071] Figure 5 is a schematic configuration diagram showing the overall configuration of the cold energy recovery system according to 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. 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 Figure 5, the liquefied gas is liquefied natural gas, the working fluid is R1234ZE, and the heating water is seawater drawn from outside the vessel. For reference, Figure 5 shows an example of the temperature and pressure in each flow duct.

[0072] The heat exchanger 50 forms a working fluid flow conduit 501 arranged in a position corresponding to the second heat exchanger 52 described above (working fluid flow conduit 521) in the working fluid circulation line 4, and a heating water flow conduit 502 arranged in a position corresponding to the third heat exchanger 53 described above (heating water flow conduit 532) in the heating water supply line 7. The heating water flow conduit 502 is arranged at least partially adjacent to the working fluid flow conduit 501, and heat exchange is effected between the heating water flowing through the heating water flow conduit 502 and the working fluid flowing through the working fluid flow conduit 501. The working fluid flowing through the working fluid flow line 501 has a temperature lower than the freezing point of water (heating water) than the working fluid flowing through the working fluid flow line 521. Therefore, the heating water solidifies through heat exchange between the working fluid and the heating water in the heat exchanger 50. This solidified heating water can freeze in the heating water flow line 502 of the heat exchanger 50 and may block the heat exchanger 50.

[0073] As shown in Figures 2 to 4, the cold energy recovery system 2 includes the previously described working fluid circulation line 4, the cold energy recovery device 41 which includes the previously described turbine 42, and the previously described intermediate heat medium circulation line 6, the previously described first heat exchanger 51, the previously described second heat exchanger 52, and the previously described third heat exchanger 53.

[0074] With the above configuration, the cold energy recovery system 2 includes at least the intermediate heat medium circulation line 6, the second heat exchanger 52, and the third heat exchanger 53. In such a cold energy recovery system 2, the heating water and the working fluid circulating through the working fluid circulation line 4 exchange heat indirectly through the intermediate heat medium circulating through the intermediate heat medium circulation line 6, making it possible to suppress the solidification of the heat medium (the intermediate heat medium, the heating water) during heat exchange. Therefore, it is possible to prevent the solidified heat medium from freezing in the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocking it. More specifically, the working fluid circulating through working fluid circulation line 4 has a temperature no higher than the freezing point of water, achieved through heat exchange with the liquefied gas in the first heat exchanger 51. In the second heat exchanger 52, heat exchange occurs between the working fluid, which has passed through the first heat exchanger 51 and has been cooled, and the intermediate heat medium circulating through intermediate heat medium circulation line 6. Since the intermediate heat medium has a lower freezing point than water, it barely solidifies during heat exchange with the low-temperature working fluid in the second heat exchanger 52. Therefore, it is possible to prevent the intermediate heat medium from solidifying in the second heat exchanger 52 and blocking it.

[0075] Meanwhile, in the third heat exchanger 53, heat exchange takes place between the heating water and the intermediate heat medium that has passed through the second heat exchanger 52 and whose temperature has been reduced. Although the intermediate heat medium is cooled by heat exchange with the working fluid in the second heat exchanger 52, the temperature remains above the freezing point of water even after cooling. Therefore, it is possible to prevent the heating water from freezing during the heat exchange between the intermediate heat medium and the heating water in the third heat exchanger 53. This prevents the solidified heating water from freezing in the third heat exchanger 53 and blocking it.

[0076] Therefore, with the above configuration, since the cold energy recovery system 2 can suppress the solidified heat medium (the intermediate heat medium, the heating water) from freezing in the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocking the heat exchanger, it is possible to improve the reliability of the cold energy recovery system 2 when using the small heat exchanger.

[0077] In the illustrative example and embodiments shown in Figures 2 to 4, the working fluid circulation line 4 described above includes a bypass flow conduit 45 that branches off downstream of the second heat exchanger 52, bypasses the turbine 42, and is connected upstream of the first heat exchanger 51. A flow conduit other than the bypass flow conduit 45 of the working fluid circulation line 4 described above (a flow conduit that passes through the turbine 42 or the first heat exchanger 51) shall be referred to as the main flow conduit 40. The bypass flow conduit 45 branches off from the main flow conduit 40 at a bifurcation portion 451 and joins the main flow conduit 40 at a confluence portion 452. The previously described cold energy recovery system 2 further includes an on/off valve 46 located downstream of the branch portion 451 of the main flow conduit 40 and upstream of the turbine 42, and an on/off valve 47 located in the bypass flow conduit 45. When the cold energy recovery system 2 is started, the on/off valve 46 closes and the on/off valve 47 opens to allow the working fluid to bypass the turbine 42. After a predetermined period, the on/off valve 46 opens and the on/off valve 47 closes to allow the working flow conduit to pass through the turbine 42.

[0078] In the illustrative example and embodiments shown in Figures 2 to 4, the previously 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 using latent heat or sensible heat.

[0079] In some embodiments of the claimed invention, as shown in Figures 3 and 4, the previously described cold energy recovery system 2 further includes the previously described liquefied gas supply line 3 and an auxiliary heat exchanger 81 arranged downstream of the first heat exchanger 51 in 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.

[0080] In the illustrated embodiment, the heating medium has a freezing point lower than that of water. The auxiliary heat exchanger 81 forms a liquefied gas flow conduit 811, which is arranged downstream of the first heat exchanger in the liquefied gas supply line 3 and through which the liquefied gas flows, and a heating medium flow conduit 812 through which the heating medium circulating in the cold energy recovery system 2 flows. The heating medium flow conduit 812 is arranged at least partially adjacent to the liquefied gas flow conduit 811, and heat exchange is effected between the heating medium flowing through the heating medium flow conduit 812 and the liquefied gas flow conduit 811.

[0081] The liquefied gas heated by the first heat exchanger 51 is sent to the liquefied gas flow line 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 line 811 and cools the heating medium flowing through the heating medium flow line 812. In this document, since the heating medium has a freezing point lower than that of water, it is possible to suppress freezing during the heat exchange with the liquefied gas in the auxiliary heat exchanger 81.

[0082] With the above configuration, the cold energy recovery system 2 includes the liquefied gas supply line 3, the first heat exchanger 51 arranged on the liquefied gas supply line 3, and the auxiliary heat exchanger 81 arranged downstream of the first heat exchanger 51 on the liquefied gas supply line 3. In such a 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 it. In this case, it is not necessary to raise the temperature to a point at which the liquid liquefied gas is completely vaporized by the heat exchange in the first heat exchanger 51. Therefore, compared to a case where the liquefied gas temperature is increased solely by the first heat exchanger 51, it is possible to reduce the amount of heat exchange in the first heat exchanger 51, and thus reduce the temperature drop of the working fluid in the first heat exchanger 51. Consequently, it is possible to effectively suppress the 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. Furthermore, by reducing the amount of heat exchange in the first heat exchanger 51, it is possible to reduce the size of the first heat exchanger 51.

[0083] In the illustrative example, the previously described cold energy recovery system 2 is configured such that the previously described liquefied gas supply line 3 does not include a heat exchanger other than the first heat exchanger 51, as shown in Figure 2. In this case, the liquefied gas is vaporized by 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.

[0084] In some embodiments, as shown in Figure 3, the heating medium that exchanges heat with the liquefied gas in the auxiliary heat exchanger 81 described above consists of the intermediate heat medium heated by the third heat exchanger 53 and flowing through the intermediate heat medium circulation line 6. In this case, heat exchange occurs in the auxiliary heat exchanger 81 between the liquefied gas that has passed through the first heat exchanger 51 and increased in temperature, and the intermediate heat medium heated by the third heat exchanger 53. Since the intermediate heat medium has a lower freezing point than water, it is possible to suppress solidification during the heat exchange with the liquefied gas in the auxiliary heat exchanger 81. Therefore, it is possible to prevent the solidified intermediate heat medium from freezing in the auxiliary heat exchanger 81 and blocking it. Therefore, it is possible to efficiently heat the liquefied gas using the auxiliary heat exchanger 81.

[0085] If a heat medium circulating through a circulation line other than the intermediate heat medium circulation line 6 is used as the heating medium, a circulation pump becomes necessary to circulate the heat medium. With the above configuration, using the intermediate heat medium circulating through the intermediate heat medium circulation line 6 as the heating medium, the circulation pump described above becomes unnecessary, making it possible to eliminate an equipment cost from the cold energy recovery system 2.

[0086] In some embodiments, as shown in Figure 3, the intermediate heat medium circulation line 6 described above includes a bypass flow conduit 63 that branches off downstream of the third heat exchanger 53, bypasses the second heat exchanger 52, and is connected upstream of the third heat exchanger 53. The auxiliary heat exchanger 81 described above 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 conduit 63.

[0087] As shown in Figure 3, a flow conduit other than the bypass flow conduit 63 of the intermediate heat medium circulation line 6 described above (a flow conduit passing through the second heat exchanger 52 or the third heat exchanger 53) shall be referred to as the main flow conduit 62. In the illustrated embodiment, the cold energy recovery system 2 includes: an intermediate heat medium storage device 64 (e.g., an intermediate tank) that is arranged downstream of the second heat exchanger 52 in the main flow conduit 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 that is arranged downstream of the auxiliary heat exchanger 81 in the bypass flow conduit 63 and is configured to regulate the flow rate of the intermediate heat medium flowing through the bypass flow conduit 63.

[0088] The bypass flow conduit 63 has one end side 631 that is connected downstream of the third heat exchanger 53 to the main flow conduit 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 conduit 63 joins the intermediate heat medium that has passed through the second heat exchanger 52 in the main flow conduit 62, in the intermediate heat medium storage device 64. The other end side 632 of the bypass flow conduit 63 can be connected downstream of the second heat exchanger 52 to the main flow conduit 62 and upstream of the intermediate heat medium storage device 64.

[0089] The flow regulating valve 65 is arranged downstream of the auxiliary heat exchanger 81 (more specifically, the heating medium flow line 812) in the bypass flow line 63. By regulating the flow rate of the intermediate heating medium flowing through the bypass flow line 63 with the flow regulating valve 65, the flow rate of the intermediate heating medium passing through the second heat exchanger 52 in the main flow line 62 is also regulated.

[0090] Since the intermediate heat medium is responsible for heating in the second heat exchanger 52 and the auxiliary heat exchanger 81, it 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 flowing through the bypass flow conduit 63, which bypasses the second heat exchanger 52. That is, since the intermediate heat medium circulation line 6 does not form the flow conduit 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. Therefore, it is possible to suppress the solidification of the heating water during heat exchange with the intermediate heat medium in the third heat exchanger 53.

[0091] In some embodiments, as shown in Figure 4, the previously described cold energy recovery system 2 further includes a second intermediate heat medium circulation line 9 configured to circulate a second intermediate heat medium having a freezing point lower than water. The heating medium that exchanges heat with the liquefied gas in the previously described auxiliary heat exchanger 81 is the second intermediate heat medium flowing through the second intermediate heat medium circulation line 9. The heating medium flow line 812 of the auxiliary heat exchanger 81 is arranged in 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 arranged downstream of the auxiliary heat exchanger 81 in the second intermediate heat medium circulation line 9. When the circulation pump 91 is activated, the second intermediate heat medium circulates through the second intermediate heat medium circulation line 9.

[0092] 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 it may be a different type of heat medium. In the embodiment shown in Figure 4, the second intermediate heat medium is R1234ZE.

[0093] With the above configuration, the heating medium that exchanges heat with the liquefied gas in the auxiliary heat exchanger 81 consists of the second intermediate heat medium flowing through the second intermediate heat medium circulation line 9. In this case, heat exchange occurs in the auxiliary heat exchanger 81 between the liquefied gas that has passed through the first heat exchanger 51 and whose temperature has been increased, and the second intermediate heat medium circulating through the second intermediate heat medium circulation line 9. Since the second intermediate heat medium has a lower freezing point than water, it is possible to suppress solidification during the heat exchange with the liquefied gas in the auxiliary heat exchanger 81. Therefore, it is possible to prevent the second intermediate heat medium from solidifying in the auxiliary heat exchanger 81 and blocking it. Furthermore, 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 a different intermediate heat medium as the second intermediate heat medium than the one circulating through intermediate heat medium circulation line 6. For example, a heat medium that is more suitable for the heat exchange conditions in the auxiliary heat exchanger 81 than the intermediate heat medium circulating through intermediate heat medium circulation line 6 can be used as the second intermediate heat medium.

[0094] In some embodiments, as shown in Figure 4, the above-described cold energy recovery system 2 further includes a second auxiliary heat exchanger 82 that 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 outside the cold energy recovery system 2.

[0096] In the illustrated embodiment, the second auxiliary heat exchanger 82 forms a second intermediate heat medium flow conduit 821, which is arranged downstream of the circulation pump 91 in the second intermediate heat medium circulation line 9 and through which the second intermediate heat medium flows, and a heating water flow conduit 822 through which the heating water introduced from outside the cold energy recovery system 2 flows. The heating water flow conduit 822 is arranged at least partially adjacent to the second intermediate heat medium flow conduit 821, and heat exchange is effected between the heating water flowing through the heating water flow conduit 822 and the second intermediate heat medium flowing through the second intermediate heat medium flow conduit 821.

[0098] In the embodiment shown in Figure 4, the heating water supply line 7 described above includes a secondary flow conduit 72 that branches off 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 conduit 822 from the second auxiliary heat exchanger 82 is arranged in the secondary flow conduit 72. As shown in Figure 4, a flow conduit other than the secondary flow conduit 72 of the heating water supply line 7 described above (a flow conduit passing through the heating water pump 71 or the third heat exchanger 53) shall be referred to as the main flow conduit 70. The secondary flow pipe 72 has one end side 721 connected downstream of the heating water pump 71 to the main flow pipe 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 heating water can be supplied to both the main flow pipe 70 and the secondary flow pipe 72 by the heating water pump 71, a dedicated pump for supplying heating water to the secondary flow pipe 72 becomes unnecessary. Therefore, the equipment cost of the cold energy recovery system 2 can be eliminated. The other end side 722 of the secondary flow pipe 72 can be connected downstream of the third heat exchanger 53 to either the main flow pipe 70 or the heating water discharge destination 14B.

[0100] The second intermediate heat medium, which is pumped by the circulation pump 91 after being cooled by the auxiliary heat exchanger 81, is sent to the second intermediate heat medium flow duct 821. Additionally, the heating water pumped by the heating water pump 71 is sent to the heating water flow duct 822. The second intermediate heat medium flowing through the second intermediate heat medium flow duct 821 is at a higher temperature than the heating water flowing through the heating water flow duct 822. Heat exchange in the second auxiliary heat exchanger 82 heats the second intermediate heat medium flowing through the second intermediate heat medium flow duct 821. The second intermediate heat medium, heated by the second auxiliary heat exchanger 82, is sent to the auxiliary heat exchanger 81.

[0102] In the illustrated embodiment, the second intermediate heat medium flowing through the second intermediate heat medium flow conduit 821 has a temperature above the freezing point of water (heating water). Although the second intermediate heat medium flowing through the second intermediate heat medium circulation line 9 is cooled by heat exchange with the liquefied gas in the auxiliary heat exchanger 81, the temperature above the freezing point of water is maintained even after cooling. Therefore, it is possible to suppress the freezing 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.

[0104] In the cold energy recovery system 2, since the heat exchange in the first heat exchanger 51 and the auxiliary heat exchanger 81 increases the temperature of the liquefied gas, the amount of heat exchange in the auxiliary heat exchanger 81 is small, and the amount of temperature decrease 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 the 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.

[0106] In the illustrative example and some embodiments, as shown in Figures 2 to 4, the previously described cold energy recovery device 41 includes the previously described turbine 42 and the previously 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 circulating through the working fluid circulation line 4 and recovering cold energy from the liquefied gas. In this case, it is possible to efficiently utilize the cold energy of the liquefied gas.

[0107] In the illustrative example and some embodiments, as shown in Figures 2 to 4, the above-described cold energy recovery system 2 includes at least the liquefied gas supply line 3 configured to send liquefied gas from the liquefied gas storage device 11, and the liquefied gas pump 31 arranged on the liquefied gas supply line 3. The liquefied gas pump 31 is configured to be driven by the electrical power generated by the generator 43. In Figures 2 to 4, 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 electrical 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 no less than one of them, may be configured to be driven by the electrical power generated by the generator 43.

[0108] With the above configuration, it is possible to operate the liquefied gas pump 31 located on the liquefied gas supply line 3 using the electrical power generated by generator 43. In this case, an electrical power system to supply electrical power from the shore-based electrical power equipment to the liquefied gas pump 31 becomes unnecessary, making it possible to reduce the size of vessel 1 equipped with the liquefied gas pump 31. Alternatively, since it is possible to reduce the footprint of the cold energy recovery system 2 on vessel 1, it is possible to increase the footprint of the liquefied gas storage device 11 on vessel 1.

[0109] Figure 6 is an explanatory view to describe an example of the heat exchanger in an embodiment of the present disclosure.

[0110] In some embodiments, as shown in Figure 6, the third heat exchanger 53 is comprised of a microchannel heat exchanger 53A. The microchannel heat exchanger 53A includes a first microchannel 531A through which the intermediate heating medium flows, and a second microchannel 532A, at least a portion of which is arranged adjacent to the first microchannel 531A and through which the heating water flows.

[0111] In the illustrated embodiment, the microchannel heat exchanger 53A is constituted by a PCHE (printed circuit heat exchanger) created by alternately stacking and joining together first metal plates 533, each of which has a plurality of first microchannels 531A formed, and second metal plates 534, each of which has a plurality of second microchannels 532A formed. In some other embodiments, the microchannel heat exchanger 53A may be a plate heat exchanger or the like.

[0112] With the above configuration, since the third heat exchanger 53 is comprised of the microchannel heat exchanger 53A, which enables heat exchange between the intermediate heating 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 the heat transfer coefficient. Since the cold energy recovery system 2 using such a heat exchanger can reduce the space occupied by the cold energy recovery system 2 on vessel 1, it is possible to increase the space occupied by the liquefied gas storage device 11 on vessel 1. The heat exchanger other than the third heat exchanger 53 can also be the microchannel heat exchanger.

[0113] As shown in Figure 1, vessel 1 includes the previously 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 smaller heat exchanger for the cold energy recovery system 2 heat exchanger (e.g., the third heat exchanger 53 or similar), it is possible to reduce the size of vessel 1 that has the cold energy recovery system 2. Alternatively, since it is possible to reduce the footprint of the cold energy recovery system 2 on vessel 1, it is possible to increase the footprint of the liquefied gas storage device 11 on vessel 1.

[0114] Figure 7 is a flow diagram of a cold energy recovery method according to an embodiment of the present disclosure.

[0115] A cold energy recovery method 100 according to some embodiments is a cold energy recovery method using the cold energy recovery system 2 described above that is installed on vessel 1 that includes the liquefied gas storage device 11 and, as shown in Figure 7, includes at least a first heat exchange stage S101, a second heat exchange stage S102, and a third heat exchange stage S103.

[0116] The first heat exchange stage S101 includes heat exchange between the liquefied gas and the working fluid using the first heat exchanger 51. The second heat exchange stage S102 includes heat exchange between the intermediate heat medium and the working fluid, which exchanged heat with the liquefied gas in the first heat exchange stage S101, using the second heat exchanger 52. The third heat exchange stage S103 includes heat exchange between the heating water and the intermediate heat medium, which exchanged heat with the working fluid in the second heat exchange stage S102, using the third heat exchanger 53.

[0117] The above method includes the first heat exchange stage S101, the second heat exchange stage S102, and the third heat exchange stage S103. In such a cold energy recovery method 100, the second heat exchange stage S102 and the third heat exchange stage S103 cause the heating water and the working fluid circulating through the working fluid circulation line 4 to exchange heat indirectly through the intermediate heat medium circulating through the intermediate heat medium circulation line 6, making it possible to suppress the solidification of the heat medium (the intermediate heat medium, the heating water) during the heat exchange. Therefore, it is possible to prevent the solidified heat medium from freezing in the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocking the heat exchanger.

[0118] More specifically, the first heat exchange stage S101 includes heat exchange between the liquefied gas and the working fluid using the first heat exchanger 51. The working fluid that has passed through the first heat exchanger 51 has a low temperature, not exceeding the freezing point of water. The second heat exchange stage S102 includes heat exchange, using the second heat exchanger 52, between the working fluid, whose temperature has been reduced by the heat exchange in the first heat exchange stage S101, and the intermediate heat medium flowing through the intermediate heat medium circulation line 6. Since the intermediate heat medium has a freezing point lower than water, it barely solidifies during heat exchange with the low-temperature working fluid in the second heat exchange stage S102. Therefore, it is possible to prevent the solidified intermediate heat medium from freezing in the second heat exchanger 52 and blocking the second heat exchanger 52.

[0119] Meanwhile, the third heat exchange stage S103 involves heat exchange between the heating water and the intermediate heat medium, the temperature of which has been reduced by the heat exchange in the second heat exchange stage S102, via the third heat exchanger 53. Although the intermediate heat medium is cooled by heat exchange with the working fluid in the second heat exchange stage S102, the temperature remains above the freezing point of water even after cooling. Therefore, it is possible to prevent the heating water from freezing during the heat exchange between the intermediate heat medium and the heating water in the third heat exchange stage S103. This prevents the solidified heating water from freezing in the third heat exchanger 53 and blocking it.

[0120] With the above method, since it is possible to prevent the solidified heat medium (the intermediate heat medium, the heating water) from freezing in the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocking the heat exchanger, it is possible to improve the reliability of the cold energy recovery system 2 when using the small heat exchanger.

[0121] As shown in Figure 7, the cold energy recovery method 100 may further include a first auxiliary heat exchange stage S201 or a second auxiliary heat exchange stage S202. The first auxiliary heat exchange stage S201 includes heat exchange between the previously described heating water and the liquefied gas, the temperature of which is increased by heat exchange in the first heat exchange stage S101, using the auxiliary heat exchanger 81. The second auxiliary heat exchange stage S202 includes heat exchange between the heating water and the second intermediate heat medium flowing through the second intermediate heat medium circulation line 9, using the second auxiliary heat exchanger 82.

[0122] The present invention is not limited to the embodiments described above, and also includes an embodiment obtained by modifying the embodiments described above and an embodiment obtained by combining these embodiments as appropriate, within the scope of the appended claims.

[0123] The content described in some of the realizations described above shall be understood as follows, for example.

[0124] A cold energy recovery system (2) is a cold energy recovery system (2) installed on a vessel (1) that includes a liquefied gas storage device (11) configured to store a liquid liquefied gas, including a working fluid circulation line (4) configured to circulate a working fluid having a freezing point lower than water, a cold energy recovery device (41) that includes a turbine (42) configured to be driven by the working fluid flowing through the working fluid circulation line (4), a first heat exchanger (51) 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) configured to circulate an intermediate heat medium having a freezing point lower than water, and a second heat exchanger (52) disposed downstream of the first heat exchanger (51). heat in 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) being configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line (6) and heating water introduced from outside the cold energy recovery system (2).

[0125] With the above configuration, 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 a cold energy recovery system (2), the heating water and the working fluid circulating through the working fluid circulation line (4) exchange heat indirectly through the intermediate heat medium circulating through the intermediate heat medium circulation line (6), making it possible to suppress the solidification of the heat medium (the intermediate heat medium, the heating water) during heat exchange. Therefore, it is possible to prevent the solidified heat medium from freezing in the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocking it. More specifically, the working fluid circulating through the working fluid circulation line (4) has a temperature no higher than the freezing point of water, achieved through heat exchange with the liquefied gas in the first heat exchanger (51). In the second heat exchanger (52), heat exchange occurs between the working fluid, which has passed through the first heat exchanger (51) and its reduced temperature, and the intermediate heat medium circulating through the intermediate heat medium circulation line (6). Since the intermediate heat medium has a lower freezing point than water, it barely solidifies during heat exchange with the low-temperature working fluid in the second heat exchanger (52). Therefore, it is possible to prevent the solidified intermediate heat medium from freezing in the second heat exchanger (52) and blocking it.

[0126] Meanwhile, in the third heat exchanger (53), heat exchange takes place between the heating water and the intermediate heat medium that has passed through the second heat exchanger (51) and whose temperature has been reduced. Although the intermediate heat medium is cooled by heat exchange with the working fluid in the second heat exchanger (51), the temperature remains above the freezing point of water even after cooling. Therefore, it is possible to prevent the heating water from freezing during the heat exchange between the intermediate heat medium and the heating water in the third heat exchanger (53). This prevents the solidified heating water from freezing in the third heat exchanger (53) and blocking it.

[0127] With the above configuration, since the cold energy recovery system (2) can suppress the solidified heat medium (the intermediate heat medium, the heating water) from freezing in the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocking the heat exchanger, it is possible to improve the reliability of the cold energy recovery system (2) when using the small heat exchanger.

[0128] The cold energy recovery system (2) further includes a liquefied gas supply line (3) configured to send liquefied gas from the liquefied gas storage device (11), and an auxiliary heat exchanger (81) disposed downstream of the first heat exchanger (51) in 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).

[0129] With the above configuration, the cold energy recovery system (2) includes the liquefied gas supply line (3), the first heat exchanger (51) described above, and the auxiliary heat exchanger (81). In such a 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 it. In this case, it is not necessary to raise the temperature to a point where the liquid liquefied gas is completely vaporized by the heat exchange in the first heat exchanger (51). Therefore, compared to a case where the liquefied gas temperature is raised solely by the first heat exchanger (51), it is possible to reduce the amount of heat exchange in the first heat exchanger (51) and the temperature drop of the working fluid in the first heat exchanger (51). Therefore, it is possible to effectively suppress the solidification of the intermediate heat medium during heat exchange between the working fluid and the intermediate heat medium in the second heat exchanger (52). Furthermore, by reducing the amount of heat exchange in the first heat exchanger (51), it is possible to reduce the size of the first heat exchanger (51).

[0130] The heating medium consists of the intermediate heat medium heated by the third heat exchanger (53) and flowing through the intermediate heat medium circulation line (6).

[0131] With the above configuration, heat exchange takes place in the auxiliary heat exchanger (81) between the liquefied gas that has passed through the first heat exchanger (51) and whose temperature has been increased, and the intermediate heat medium heated by the third heat exchanger (53). Since the intermediate heat medium has a lower freezing point than water, it is possible to suppress solidification during heat exchange with the liquefied gas in the auxiliary heat exchanger (81). Therefore, it is possible to prevent the solidified intermediate heat medium from freezing in the auxiliary heat exchanger (81) and blocking it. Thus, it is possible to efficiently heat the liquefied gas using the auxiliary heat exchanger (81).

[0132] If a heat medium circulating through a circulation line other than the intermediate heat medium circulation line (6) is used as the heating medium, a circulation pump becomes necessary to circulate the heat medium. With the above configuration, using the intermediate heat medium circulating through the intermediate heat medium circulation line (6) as the heating medium, the circulation pump described above becomes unnecessary, making it possible to eliminate an equipment cost from the cold energy recovery system (2).

[0133] In the cold energy recovery system (2), the intermediate heat medium circulation line (6) may include a bypass flow duct (63) that branches off downstream of the third heat exchanger (53), bypasses the second heat exchanger (52), and is connected 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 duct (63).

[0134] Since the intermediate heat medium is responsible for heating in the second heat exchanger (52) and the auxiliary heat exchanger (81), it 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 flowing through the bypass flow conduit (63), bypassing the second heat exchanger (52). That is, since the intermediate heat medium circulation line (6) does not form the flow conduit 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. Therefore, it is possible to suppress the solidification of the heating water during heat exchange with the intermediate heat medium in the third heat exchanger (53).

[0135] The cold energy recovery system (2) may further include a second intermediate heat medium circulation line (9) configured to circulate a second intermediate heat medium having a lower freezing point than water. In this case, the heating medium is the second intermediate heat medium flowing through the second intermediate heat medium circulation line (9). With the above configuration, the heating medium exchanging heat with the liquefied gas in the auxiliary heat exchanger (81) is the second intermediate heat medium flowing through the second intermediate heat medium circulation line (9). In this case, heat exchange occurs in the auxiliary heat exchanger (81) between the liquefied gas that has passed through the first heat exchanger (51) and whose temperature has been increased, and the second intermediate heat medium circulating through the second intermediate heat medium circulation line (9). Since the second intermediate heat medium has a lower freezing point than water, it is possible to suppress solidification during heat exchange with the liquefied gas in the auxiliary heat exchanger (81). Therefore, it is possible to prevent the solidified second intermediate heat medium from freezing in the auxiliary heat exchanger (81) and blocking it.

[0136] Furthermore, 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 a 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 a second intermediate heat medium, it is possible to use a heat medium that is more suitable for the heat exchange conditions in the auxiliary heat exchanger (81) than the intermediate heat medium circulating through the intermediate heat medium circulation line (6).

[0137] The cold energy recovery system (2) may further include a second auxiliary heat exchanger (82) that 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 outside the cold energy recovery system (2).

[0138] In the cold energy recovery system (2), since the heat exchange in the first heat exchanger (51) and the auxiliary heat exchanger (81) increases the temperature of the liquefied gas, the amount of heat exchange in the auxiliary heat exchanger (81) is small, and the amount of temperature decrease 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 the 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).

[0139] The cold energy recovery device (41) may further include a generator (43) configured to generate electricity by driving the turbine (42).

[0140] With the above configuration, 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 circulating through the working fluid circulation line 4 and recovering cold energy from the liquefied gas. In this case, it is possible to efficiently utilize the cold energy of the liquefied gas.

[0141] The cold energy recovery system (2) may further include a liquefied gas supply line (3) configured to deliver liquefied gas from the liquefied gas storage device (11), and a liquefied gas pump (31) disposed in the liquefied gas supply line (3). The liquefied gas pump (31) is configured to be driven by electrical power generated by the generator (43).

[0142] With the above configuration, it is possible to operate the liquefied gas pump (31) located on the liquefied gas supply line (3) using electrical power generated by the generator (43). In this case, an electrical power system to supply power from the shore-based electrical power equipment to the liquefied gas pump (31) becomes unnecessary, making it possible to reduce the size of the vessel (1) equipped with the liquefied gas pump (31). Alternatively, since it is possible to reduce the footprint of the cold energy recovery system (2) on the vessel (1), it is possible to increase the footprint of the liquefied gas storage device (11) on the vessel (1).

[0143] In the cold energy recovery system (2), the third heat exchanger (53) may consist of a microchannel heat exchanger (53A) comprising a first microchannel (531A) through which the intermediate heating medium flows, and a second microchannel (532A) through which the heating water flows, at least a portion of the second microchannel (532A) being disposed adjacent to the first microchannel (531A).

[0144] With the above configuration, since the third heat exchanger (53) is made up of the microchannel heat exchanger (53A) which allows 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.

[0145] In the case where a vessel (1) includes the above-described cold energy recovery system (2), since it is possible to reduce the size of the cold energy recovery system (2) using the small heat exchanger, it is possible to reduce the size of the vessel (1) that has the cold energy recovery system (2).

[0146] Alternatively, since it is possible to reduce the space occupied by the cold energy recovery system (2) on the vessel (1), it is possible to increase the space occupied by the liquefied gas storage device (11) on the vessel (1).

[0147] A cold energy recovery method (100) is a cold energy recovery method (100) by means of a cold energy recovery system (2) installed on a vessel (1) that 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) configured to circulate a working fluid having a freezing point lower than water, a cold energy recovery device (41) including a turbine (42) configured to be driven by the working fluid flowing through the working fluid circulation line (4), a first heat exchanger (51) configured to exchange heat between the liquefied gas and the working fluid flowing through the working fluid circulation line (4), and an intermediate heat medium circulation line (6) configured to circulate an intermediate heat medium having a freezing point lower than water. a second heat exchanger (52) disposed downstream of the first heat exchanger (51) in 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) being configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line (6) and heating water introduced from outside the cold energy recovery system (2), including the cold energy recovery method (100) a first heat exchange stage (S101) of effecting heat exchange between the liquefied gas and the working fluid by means of the first heat exchanger (51), a second heat exchange stage (S102) of effecting, by means of the second heat exchanger (52), heat exchange between the medium of intermediate heat and the working fluid that has exchanged heat with the liquefied gas in the first heat exchange stage (S101), and a third heat exchange stage (S103) to perform, by means of 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 stage (S102).

[0148] The above method includes the first heat exchange stage (S101), the second heat exchange stage (S102), and the third heat exchange stage (S103). In such a cold energy recovery method (100), the second heat exchange stage (S102) and the third heat exchange stage (S103) cause the heating water and the working fluid circulating through the working fluid circulation line (4) to exchange heat indirectly through the intermediate heat medium circulating through the intermediate heat medium circulation line (6), thus preventing the solidification of the heat medium (the intermediate heat medium, the heating water) during the heat exchange. Therefore, it is possible to prevent the solidified heat medium from freezing in the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocking it.

[0149] More specifically, the first heat exchange stage (S101) includes performing heat exchange between the liquefied gas and the working fluid using the first heat exchanger (51). The working fluid that has passed through the first heat exchanger (51) has a low temperature that is no higher than the freezing point of water. The second heat exchange stage (S102) includes performing, using the second heat exchanger (52), heat exchange between the working fluid, whose temperature has been reduced by the heat exchange in the first heat exchange stage (S101), and the intermediate heat medium flowing through the intermediate heat medium circulation line (6). Since the intermediate heat medium has a freezing point lower than water, it barely solidifies during heat exchange with the low-temperature working fluid in the second heat exchange stage. Therefore, it is possible to prevent the solidified intermediate heat medium from freezing in the second heat exchanger (52) and blocking the second heat exchanger (52).

[0150] Meanwhile, the third heat exchange stage (S103) involves heat exchange between the heating water and the intermediate heat medium, whose temperature has been reduced by the heat exchange in the second heat exchange stage (S102), via the third heat exchanger (53). Although the intermediate heat medium is cooled by heat exchange with the working fluid in the second heat exchange stage (S102), the temperature remains above the freezing point of water even after cooling. Therefore, it is possible to prevent the heating water from freezing during the heat exchange between the intermediate heat medium and the heating water in the third heat exchange stage. This prevents the solidified heating water from freezing in the third heat exchanger (53) and blocking it.

[0151] With the above method, since it is possible to prevent the solidified heat medium (the intermediate heat medium, the heating water) from freezing in the heat exchanger (the second heat exchanger 52, the third heat exchanger 53) and blocking the heat exchanger, it is possible to improve the reliability of the cold energy recovery system (2) when using the small heat exchanger.

[0152] List of reference signs

[0153] 1 Vessel

[0154] 2 Cold energy recovery system

[0155] 20 Cold energy recovery system according to the comparative example

[0156] 3 Liquefied gas supply line

[0157] 301 One end side

[0158] 302 Other end side

[0159] 31 Liquefied gas pump

[0160] 4 Working fluid circulation line

[0161] 41 Cold energy recovery device

[0162] 42 Turbine

[0163] 421 Turbine rotor

[0164] 43 Generator

[0165] 44 Circulation pump (for working fluid)

[0166] 50 Heat exchanger (comparative example)

[0167] 501 Working fluid flow conduit

[0168] 502 Heating water flow conduit

[0169] 51 First heat exchanger

[0170] 511 Liquefied gas flow conduit

[0171] 512 Working fluid flow conduit

[0172] 52 Second heat exchanger

[0173] 521 Working fluid flow conduit

[0174] 522 Intermediate heat medium flow duct

[0175] 53 Third heat exchanger

[0176] 531 Intermediate heat medium flow duct

[0177] 531A First microchannel

[0178] 532 Heating water flow conduit

[0179] 532A Second microchannel

[0180] 6 Intermediate heat medium circulation line

[0181] 61 Circulation pump (intermediate heat medium)

[0182] 62 Main flow conduit

[0183] 63 Bypass flow conduit

[0184] 631 One end side

[0185] 632 Other end side

[0186] 64 Intermediate heat medium storage device

[0187] 65 Flow regulating valve

[0188] 7 Heating water supply line

[0189] 701 One end side

[0190] 702 Other end side

[0191] 71 Heating water pump

[0192] 81 Auxiliary heat exchanger

[0193] 811 Liquefied gas flow conduit

[0194] 812 Heating medium flow duct

[0195] 82 Second auxiliary heat exchanger

[0196] 821 Second Intermediate Heat Medium Flow Conduit 822 Heating Water Flow Conduit

[0197] 9 Second line of intermediate heat medium circulation

[0198] 10 Helmet

[0199] 11 Liquefied gas storage device

[0200] 12 Team

[0201] 13 Heating water supply source

[0202] 14 Heating water discharge destination

[0203] 15 Engine room

[0204] 16 Motor

[0205] 17 Water inlet

[0206] 18 Cooling water flow conduit

[0207] 19 Water outlet

Claims (8)

1. CLAIMS 1. Cold energy recovery system (2) installed on a vessel (1) including a liquefied gas storage device (11) configured to store a liquid liquefied gas, comprising: a working fluid circulation line (4) configured to circulate a working fluid having a freezing point lower than water; a cold energy recovery device (41) including a turbine (42) configured to be driven by the working fluid flowing through the working fluid circulation line (4); a first heat exchanger (51) 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) that is configured to circulate an intermediate heat medium having a freezing point lower than water; a second heat exchanger (52) disposed downstream of the first heat exchanger (51) in 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); a third heat exchanger (53) that is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line (6) and heating water introduced from outside the cold energy recovery system (2); a liquefied gas supply line (3) configured to send liquefied gas from the liquefied gas storage device (11); and an auxiliary heat exchanger (81) disposed downstream of the first heat exchanger (51) in 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), wherein 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). 2. Cold energy recovery system (2) according to claim 1, wherein the intermediate heat medium circulation line (6) includes a bypass flow duct (63) that branches off downstream of the third heat exchanger (53), bypasses the second heat exchanger (52), and is connected upstream of the third heat exchanger (53), and wherein 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 duct (63). 3. Cold energy recovery system (2) according to claim 1, further comprising a second intermediate heat medium circulation line (9) configured to circulate a second intermediate heat medium having a lower freezing point than water, wherein the heating medium is constituted by the second intermediate heat medium flowing through the second intermediate heat medium circulation line (9). 4. Cold energy recovery system (2) according to claim 3, further comprising a second auxiliary heat exchanger (82) 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 outside the cold energy recovery system (2). 5. Cold energy recovery system (2) according to any one of claims 1 to 4, wherein the cold energy recovery device (41) further includes a generator (43) configured to generate electricity by driving the turbine (42). 6. Cold energy recovery system (2) according to claim 5, further comprising: a liquefied gas supply line (3) configured to send liquefied gas from the liquefied gas storage device (11); and a liquefied gas pump (31) arranged in the liquefied gas supply line (3), in which the liquefied gas pump (31) is configured to be driven by electrical power generated by the generator (43). 7. Cold energy recovery system (2) according to any one of claims 1 to 6, wherein the third heat exchanger (53) consists of a microchannel heat exchanger (53A) comprising: a first microchannel (531A) through which the intermediate heating medium flows; and a second microchannel (532A) through which the heating water flows, at least a part of the second microchannel (532A) being arranged adjacent to the first microchannel (531A). 8. Method (100) of cold energy recovery by means of a cold energy recovery system (2) installed on a vessel (1) that includes a liquefied gas storage device (11) configured to store a liquid liquefied gas, including the cold energy recovery system (2): a working fluid circulation line (4) that is configured to circulate a working fluid that has a freezing point lower than water; a cold energy recovery device (41) including a turbine (42) configured to be driven by the working fluid flowing through the working fluid circulation line (4); a first heat exchanger (51) 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) that is configured to circulate an intermediate heat medium having a freezing point lower than water; a second heat exchanger (52) disposed downstream of the first heat exchanger (51) in 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); a third heat exchanger (53) that is configured to exchange heat between the intermediate heat medium flowing through the intermediate heat medium circulation line (6) and heating water introduced from outside the cold energy recovery system (2); a liquefied gas supply line (3) configured to send liquefied gas from the liquefied gas storage device (11); and an auxiliary heat exchanger (81) disposed downstream of the first heat exchanger (51) in 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), wherein 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), and in which the cold energy recovery method comprises: a first heat exchange stage (S101) of performing heat exchange between the liquefied gas and the working fluid by means of the first heat exchanger (51); a second heat exchange stage (S102) of carrying out, by means of 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 stage (S 101); and a third heat exchange stage (S103) to perform, by means of 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 stage (S102).