Power Recovery System

Abstract

To provide a power recovery system that suppresses generation of cavitation in a pump part by suppressing gasification of working fluid in the pump part and normally drives a pump by suppressing suction of gas to the pump.SOLUTION: A power recovery system 1 is for recovering cold energy of liquefied gas as power via working fluid for heating the liquefied gas. The power recovery system 1 includes: a condenser 2; a gas-liquid separation tank 4; a pump 6 for cold; an evaporator 8; a turbine 10 for cold; and a first pipeline 31 for supplying the working fluid condensed by the condenser 2 to the gas-liquid separation tank 4, the first pipeline 31 configured so that an outflow port of the first pipeline 31 is located below a liquid surface of the gas-liquid separation tank 4.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power recovery system for recovering the cold thermal energy of liquefied gas as power through a working fluid for heating the liquefied gas.

Background Art

[0002] Liquefied gas (e.g., liquefied natural gas) is liquefied for the purpose of transportation and storage, and when it is supplied to a supply destination such as city gas or thermal power generation, it is heated and vaporized by a heat medium such as seawater. There is a power recovery system (e.g., a cold thermal power generation cycle) that recovers the cold thermal energy as power instead of discarding it to seawater when vaporizing liquefied gas.

[0003] As a cold thermal power generation cycle for liquefied natural gas, ORC (Organic Rankine Cycle) is known. In ORC, a low-temperature working fluid with a boiling point lower than that of water circulating in a closed loop is cooled and condensed by liquefied natural gas in a condenser (condenser), then pressurized by a pump, heated and evaporated using seawater or the like as a heat source in an evaporator, and this vapor is introduced into a turbine for cold thermal power generation to obtain power. This is a cycle process.

[0004] In ORC, although the temperature of the working fluid is lowered to the saturated vapor pressure in the condenser, when the pressure is increased by the pump thereafter, the working fluid may locally evaporate (vaporize) in the pump section, and cavitation may occur. When cavitation occurs in the pump section, it may lead to damage to the pump. Also, if gas is sucked into the pump, it may interfere with the normal operation of the pump.

[0005] Therefore, in Patent Document 1, an ORC device is disclosed in which a liquid storage tank is installed between the condenser and the pump to suppress gasification in the pump section, and a large water level head is provided between the liquid storage tank and the pump. In the ORC device of this Patent Document 1, the working fluid is introduced from the top (ceiling surface) of the liquid storage tank.

Prior Art Documents

Patent Document

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the technology disclosed in Patent Document 1, when further suppressing gasification in the pump section, it is necessary to increase the capacity of the liquid storage tank and provide a large water level head between the liquid storage tank and the pump. However, in the ORC of the thermoelectric power generation cycle, since a working fluid having a boiling point lower than the atmospheric temperature (for example, 25°C) is used, when the capacity of the liquid storage tank increases, the heat transfer area with the surrounding atmosphere increases, and the working fluid stored in the liquid storage pump is heated, so that gas bubbles are easily generated (gasified) in the pump section. In addition, since the temperature difference between the heated pump and the working fluid is also large, gasification is more likely to be promoted.

[0008] In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a power recovery system that can suppress the generation of cavitation in the pump section by suppressing the gasification of the working fluid in the pump section, suppress the suction of gas into the pump, and drive the pump normally.

Means for Solving the Problems

[0009] To achieve the above object, a power recovery system according to at least one embodiment of the present disclosure is a power recovery system for recovering the cold thermal energy of the liquefied gas as power through a working fluid for heating the liquefied gas, a condenser configured to condense the working fluid by heat exchange between the working fluid and the liquefied gas, a gas-liquid separation tank configured to separate and store the working fluid condensed in the condenser into a liquid and a gas, A heat pump configured to boost the pressure of the liquid working fluid supplied from the gas-liquid separation tank An evaporator configured to evaporate the working fluid by heat exchange between the working fluid boosted by the heat pump and a heating fluid introduced from outside the heat recovery system A heat turbine configured to be driven by the gaseous working fluid generated in the evaporator A first pipeline for supplying the working fluid condensed by the condenser to the gas-liquid separation tank, the outlet of the first pipeline being configured to be located below the liquid level of the gas-liquid separation tank

Advantages of the Invention

[0010] According to the power recovery system of the present disclosure, by suppressing the gasification of the working fluid in the pump section, it is possible to suppress the occurrence of cavitation in the pump section, suppress the suction of gas into the pump, and provide a power recovery system that can drive the pump normally

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 5C

Figure 5D

Figure 6A

Figure 6B

Mode for Carrying Out the Invention

[0012] Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present disclosure thereto, but are merely illustrative examples. For example, expressions representing relative or absolute arrangements such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", or "coaxial" not only strictly represent such arrangements, but also represent a state of being relatively displaced with tolerances or at an angle or distance such that the same function can be obtained. For example, expressions representing a state where things such as "identical", "equal", and "homogeneous" are equal not only strictly represent an equal state, but also represent a state where there are tolerances or differences such that the same function can be obtained. For example, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent shapes such as a rectangular shape or a cylindrical shape in a geometrically strict sense, but also represent shapes including concave and convex portions, chamfered portions, etc. within a range where the same effect can be obtained. On the other hand, the expressions "comprising", "including", or "having" for one component are not exclusive expressions excluding the existence of other components. Note that the same reference numerals may be given to the same configurations and the description may be omitted.

[0013] (Application Examples of Power Recovery System) FIG. 6A is a schematic diagram showing an example in which a power recovery system 1 according to an embodiment of the present disclosure is installed on a floating structure 101. As shown in FIG. 6A, a power recovery system 1 according to an embodiment of the present disclosure is installed on a floating structure 101 above water. The floating structure 101 is a structure that can float on water. The floating structure 101 has a propulsion device configured to drive a propeller or other thruster, and includes ships that can move independently by driving the propulsion device, as well as floating bodies that do not have a propulsion device. The floating structure 101 stores liquefied gas in liquid form, which is heated by seawater or the like to vaporize and then flows into the engine 111 to generate propulsion power. When the liquefied gas is vaporized, the power recovery system 1 recovers the cold energy as electricity rather than discarding it in the seawater.

[0014] FIG. 6B is a schematic diagram illustrating an example in which the power recovery system 1 according to an embodiment of the present disclosure is installed in a land-based liquefied gas terminal 102. As shown in FIG. 6B , a power recovery system 1 according to an embodiment of the present disclosure is installed in an onshore LNG (liquefied gas) terminal 102. The onshore LNG (liquefied gas) terminal 102 receives and stores liquefied gas transported by an LNG carrier. When the liquefied gas is supplied to a liquefied gas supply destination 112, such as a city gas supply or a thermal power plant, the liquefied gas is heated using seawater or the like to return it to gas. When the liquefied gas is vaporized, the power recovery system 1 recovers the cold energy as electricity rather than discarding it in the seawater.

[0015] Here, the power recovery system 1 of the present disclosure is explained using liquefied natural gas (LNG) as an example of the above-mentioned liquefied gas, but the present disclosure is also applicable to liquefied gases other than liquefied natural gas (liquefied petroleum gas, liquefied hydrogen, etc.).

[0016] (Overall configuration of power recovery system 1) 1 to 4 are schematic diagrams illustrating the overall configuration of a power recovery system 1 according to an embodiment of the present disclosure.

[0017] The power recovery system 1 according to an embodiment of the present disclosure is a system for recovering the cold thermal energy of liquefied gas as power through a working fluid for heating the liquefied gas. As shown in FIGS. 1 to 4, the power recovery system 1 according to an embodiment of the present disclosure includes a condenser 2, a gas-liquid separation tank 4, a cold thermal pump 6, an evaporator 8, and a cold thermal turbine 10. The condenser 2, the gas-liquid separation tank 4, the cold thermal pump 6, the evaporator 8, and the cold thermal turbine 10 are respectively connected by a circulation flow path 3. The power recovery system 1 is configured to be driven by the working fluid circulating in the circulation flow path 3 while changing its state between liquid and gas.

[0018] The condenser 2 is configured to condense the working fluid by heat exchange between the working fluid and the liquefied gas. Inside the condenser 2, a heating-side pipe 21 into which the working fluid circulating in the circulation flow path 3 flows and a heated-side pipe 22 into which the liquefied gas introduced from outside the power recovery system 1 flows are provided, and they are configured to exchange heat between the working fluid and the liquefied gas. In the condenser 2, the working fluid is cooled and condensed by heat exchange, and the liquefied gas is heated.

[0019] The circulation flow path 3 includes a first pipe 31 connecting the condenser 2 and the gas-liquid separation tank 4, a second pipe 32 connecting the gas-liquid separation tank 4 and the cold thermal pump 6, a third pipe 33 connecting the cold thermal pump 6 and the evaporator 8, a fourth pipe 34 connecting the evaporator 8 and the cold thermal turbine 10, and a fifth pipe 35 connecting the cold thermal turbine 10 and the condenser 2. The working fluid circulates in the circulation flow path 3 while changing its state between liquid and gas, driving the power recovery system 1. In the following description, "upstream side" means the upstream side in the flow direction of the working fluid flowing in the circulation flow path 3, and "downstream side" means the downstream side in the flow direction of the working fluid flowing in the circulation flow path 3.

[0020] The first pipeline 31 is arranged on the downstream side of the condenser 2 and the upstream side of the gas-liquid separation tank 4, and connects the condenser 2 and the gas-liquid separation tank 4. The upstream end of the first pipeline 31 is connected to the downstream end of the heating-side pipeline 21 of the condenser 2. The downstream side of the first pipeline 31 is connected to the gas-liquid separation tank 4. The liquid working fluid condensed by the condenser 2 flows through the first pipeline 31 and is supplied to the gas-liquid separation tank 4.

[0021] The gas-liquid separation tank 4 is configured to separate and store the working fluid condensed by the condenser 2 into liquid and gas. Inside the gas-liquid separation tank 4, with the liquid level 41 as the boundary, a gas phase portion 42 composed of the gaseous working fluid is formed above it, and a liquid phase portion 43 composed of the liquid working fluid is formed below it.

[0022] Also, the gas-liquid separation tank 4 is installed such that the ceiling surface 44 of the gas-liquid separation tank 4 is located below the condenser 2 in the vertical direction. That is, the upstream end of the first pipeline 31 is located above the downstream end of the first pipeline 31 in the vertical direction, and the working fluid is configured to flow through the first pipeline 31 by natural downward flow.

[0023] In the illustrated embodiment, the gas-liquid separation tank 4 has a cylindrical shape. However, the gas-liquid separation tank 4 only needs to be able to separate and store the working fluid into liquid and gas, and its shape is not particularly limited. The gas-liquid separation tank 4 can be appropriately selected in shape according to the embodiment, such as a cylindrical shape, a spherical shape, a rectangular parallelepiped shape, etc. When the gas-liquid separation tank 4 has a spherical shape, the above-mentioned ceiling surface 44 corresponds to the highest part of the sphere, and the bottom surface 45 described later corresponds to the lowest part of the sphere.

[0024] The temperature of the gas phase portion 42 of the gas-liquid separation tank 4 is equal to or higher than the saturated vapor temperature, and is either the saturated vapor temperature or slightly higher than that due to the influence from the outside. The temperature of the liquid phase portion 43 of the gas-liquid separation tank 4 is affected by the gas phase portion 42 with a temperature equal to or higher than the saturated vapor temperature at the liquid level 41, and thus has a temperature gradient such that the temperature decreases from the liquid level 41 side to the bottom surface 45 side of the liquid phase portion 43 in the vertical direction.

[0025] The second pipeline 32 is arranged on the downstream side of the gas-liquid separation tank 4 and the upstream side of the cold and heat pump 6, and connects the gas-liquid separation tank 4 and the cold and heat pump 6. The upstream end of the second pipeline 32 is located in the liquid phase part 43 of the gas-liquid separation tank 4 and is open so that the liquid working fluid can flow into the second pipeline 32. The downstream end of the second pipeline 32 is connected to the suction port of the cold and heat pump 6. The liquid working fluid stored in the liquid phase part 43 of the gas-liquid separation tank 4 flows through the second pipeline 32 and is supplied to the cold and heat pump 6.

[0026] The cold and heat pump 6 is configured to boost the pressure of the liquid working fluid supplied from the gas-liquid separation tank 4. The liquid working fluid flowing in from the suction port is boosted by the pressure boosting part (for example, an impeller, etc.) of the cold and heat pump 6 and flows out from the discharge port. In addition, the cold and heat pump 6 is installed vertically below the bottom surface 45 of the gas-liquid separation tank 4. That is, the upstream end of the second pipeline 32 is located vertically above the downstream end of the second pipeline 32, and the working fluid is configured to flow in the second pipeline 32 by the head difference between the liquid level 41 and the suction port of the cold and heat pump 6 and the suction force of the cold and heat pump 6.

[0027] The cold and heat pump 6 only needs to be able to boost the pressure of the working fluid, and its type is not particularly limited. For example, a turbo pump (centrifugal pump, mixed flow pump, axial flow pump, etc.) or a positive displacement pump (reciprocating pump, rotary pump), etc., can be appropriately selected according to the embodiment.

[0028] The third pipeline 33 is arranged on the downstream side of the cold and heat pump 6 and the upstream side of the evaporator 8, and connects the cold and heat pump 6 and the evaporator 8. The upstream end of the third pipeline 33 is connected to the discharge port of the cold and heat pump. The downstream end of the third pipeline 33 is connected to the upstream end of the heated side pipeline 81 of the evaporator 8. The liquid working fluid boosted by the cold and heat pump 6 flows through the third pipeline 33 and is supplied to the evaporator 8.

[0029] The evaporator 8 is configured to evaporate the working fluid by heat exchange between the working fluid pressurized by the cold-heat pump 6 and the heating fluid introduced from outside the power recovery system 1. Inside the evaporator 8, a heated-side pipe 81 into which the working fluid pressurized by the cold-heat pump 6 flows and a heating-side pipe 82 into which the heating fluid introduced from outside the power recovery system 1 flows are provided, and the working fluid and the heating fluid are configured to perform heat exchange. In the evaporator 8, the working fluid is heated and evaporated by heat exchange, and the heating fluid is cooled.

[0030] Note that the above-described heating fluid may be a medium having a temperature higher than that of the working fluid pressurized by the cold-heat pump 6, such as steam, warm water, seawater, or engine cooling water introduced from outside the power recovery system 1. In the present embodiment, the cooling water of the engine 111 of the above-described floating structure 101 on water is used as the heating fluid. Since the cooling water of the engine 111 is at a higher temperature than seawater or the like, the heat exchange efficiency in the evaporator 8 can be increased as compared with the case where seawater or the like is used as the heating fluid.

[0031] The fourth pipe 34 is arranged on the downstream side of the evaporator 8 and the upstream side of the cold-heat turbine 10 and connects the evaporator 8 and the cold-heat turbine 10. The upstream end of the fourth pipe 34 is connected to the downstream end of the heated-side pipe 81 of the evaporator 8. The downstream end of the fourth pipe 34 is connected to the inflow portion of the cold-heat turbine 10. The gaseous working fluid heated by heat exchange in the evaporator 8 flows through the fourth pipe 34 and is supplied to the cold-heat turbine 10.

[0032] The cold-heat turbine 10 is configured to be driven by the gaseous working fluid generated in the evaporator 8. The cold-heat turbine 10 has, for example, an impeller including a rotating shaft and at least one moving blade provided on the rotating shaft, and is configured such that the working fluid flowing in from the inflow portion acts on the moving blade and the rotating shaft rotates.

[0033] In addition, a generator 12 is connected to the rotating shaft of the cold and heat turbine 10. The generator 12 is configured to generate electricity using the driving force of the cold and heat turbine 10 as a driving source. That is, by including the cold and heat turbine 10 and the generator 12, the power recovery system 1 can recover the cold and heat energy of the liquefied gas as power (electricity).

[0034] The fifth pipeline 35 is arranged on the downstream side of the cold and heat turbine 10 and the upstream side of the condenser 2, and connects the cold and heat turbine 10 and the condenser 2. The upstream end of the fifth pipeline 35 is connected to the outflow part of the cold and heat turbine 10. The downstream end of the fifth pipeline 35 is connected to the upstream end of the heating side pipeline 21 of the condenser 2. The gaseous working fluid that has driven the cold and heat turbine 10 flows through the fifth pipeline 35 and is supplied to the condenser 2.

[0035] (Position of the outlet 311 of the first pipeline 31) Figs. 5A to 5D are schematic cross-sectional views of the gas-liquid separation tank 4 according to an embodiment of the present disclosure. In the power recovery system 1 according to an embodiment of the present disclosure, as shown in Figs. 5A to 5D, the outlet 311 of the first pipeline 31 is configured to be located below the liquid level 41 of the gas-liquid separation tank 4.

[0036] Since the outlet 311 of the first pipeline 31 is located below the liquid level 41 of the gas-liquid separation tank 4, the working fluid condensed by the condenser 2 is directly supplied to the liquid phase part 43 instead of the gas phase part 42. Therefore, when the outlet 311 of the first pipeline 31 is located above the liquid level 41 of the gas-liquid separation tank 4, that is, compared with the case where the working fluid condensed by the condenser 2 is supplied to the liquid phase part 43 through the gas phase part 42, the working fluid is not heated in the gas phase part 42, so the working fluid can be supplied to the liquid phase part 43 while remaining in a low temperature state. And when supplying the liquid working fluid from the gas-liquid separation tank 4 to the cold heat pump 6, it can also flow in while remaining in a low temperature state, so the gasification of the working fluid in the pump part of the cold heat pump 6 can be suppressed. Thereby, the occurrence of cavitation in the pump part of the cold heat pump 6 is suppressed, and the suction of gas into the cold heat pump 6 is suppressed, so that the cold heat pump 6 can be driven normally.

[0037] In one embodiment, as shown in FIGS. 5A to 5D, the outlet 311 of the first pipeline 31 may be configured to be located below the vertical middle of the gas-liquid separation tank 4.

[0038] Generally, the liquid level 41 of the gas-liquid separation tank 4 is located above the middle position (50% position). For this reason, according to such a configuration, the working fluid condensed by the condenser 2 is directly supplied to the gas-liquid separation tank 4 from the outlet 311 of the first pipeline 31 provided in the liquid phase part 43 of the gas-liquid separation tank 4 instead of the gas phase part 42 of the gas-liquid separation tank 4.

[0039] In one embodiment, as described above, it further includes a second pipeline 32 configured to supply the liquid working fluid stored in the gas-liquid separation tank 4 to the cold heat pump 6. And as shown in FIGS. 5A to 5D, when the position of the bottom surface 45 is defined as the 0% position and the position of the ceiling surface 44 is defined as the 100% position in the vertical direction of the gas-liquid separation tank 4, the outlet 311 of the first pipeline 31 and the inlet 321 of the second pipeline 32 are located in the range of 0% to 25%.

[0040] According to such a configuration, the outlet 311 of the first pipeline 31 and the inlet 321 of the second pipeline 32 are located in the range of 0% to 25% (i.e., on the bottom surface 45 side) in the vertical direction of the gas-liquid separation tank 4. Therefore, the working fluid flowing out from the outlet 311 of the first pipeline 31 into the liquid phase portion 43 is maintained in a low temperature state without being heated in the liquid phase portion 43 above in the vertical direction where the temperature of the working fluid becomes higher, and flows into the inlet 321 of the second pipeline 32 and is supplied to the cold heat pump 6. Thereby, gasification of the working fluid in the pump portion of the cold heat pump 6 can be suppressed.

[0041] In one embodiment, as shown in FIG. 5A, the first pipeline 31 and the second pipeline 32 are inserted into the gas-liquid separation tank 4 from the bottom surface 45. The first pipeline 31 and the second pipeline 32 extend in the liquid phase portion 43 below the liquid surface 41 upward in the vertical direction from the bottom surface 45.

[0042] In one embodiment, as shown in FIG. 5B, the first pipeline 31 and the second pipeline 32 are inserted into the gas-liquid separation tank 4 from the side surface 46. The first pipeline 31 and the second pipeline 32 extend in the liquid phase portion 43 below the liquid surface 41 in the horizontal direction from the side surface 46.

[0043] In some embodiments, as shown in FIGS. 5C and 5D, the first pipeline 31 includes an internal pipeline 31B that is inserted into the gas-liquid separation tank 4 from above the liquid surface 41 of the gas-liquid separation tank 4 and extends downward from the liquid surface 41. And the above-mentioned outlet 311 is formed at the downstream end of the internal pipeline 31B.

[0044] According to such a configuration, since the first pipeline 31 is inserted into the gas-liquid separation tank 4 from above the liquid surface 41 of the gas-liquid separation tank 4, compared with the case where it is inserted into the gas-liquid separation tank 4 from below the liquid surface 41, the distance that the first pipeline 31 is exposed to the atmosphere with a higher temperature than the working fluid condensed by the condenser 2 is reduced. Therefore, outside the gas-liquid separation tank 4, heating of the working fluid in the first pipeline 31 by heat input from the outside can be suppressed.

[0045] In one embodiment, as shown in FIG. 5C, the first pipeline 31 includes an external pipeline 31A disposed outside the gas-liquid separation tank 4 and an internal pipeline 31B disposed inside the gas-liquid separation tank 4. The first pipeline 31 is inserted into the gas-liquid separation tank 4 from the ceiling surface 44. The internal pipeline 31B extends from the ceiling surface 44 vertically downward to the liquid phase portion 43 below the liquid level 41.

[0046] In one embodiment, as shown in FIG. 5D, the first pipeline 31 includes an external pipeline 31A disposed outside the gas-liquid separation tank 4 and an internal pipeline 31B disposed inside the gas-liquid separation tank 4. The first pipeline 31 is inserted into the gas-liquid separation tank 4 from the side surface 46 of the gas-liquid separation tank 4. The internal pipeline 31B has an internal horizontal pipeline 31B1 extending horizontally from the side surface 46 and an internal vertical pipeline 31B2 extending vertically downward from the downstream end of the internal horizontal pipeline 31B1 to the liquid phase portion 43 below the liquid level 41.

[0047] In one embodiment, as shown in FIGS. 5A to 5D, in the vertical direction of the gas-liquid separation tank 4, the outlet 311 of the first pipeline 31 is located above the inlet 321 of the second pipeline 32. According to such a configuration, even when the working fluid flowing through the first pipeline 31 contains air bubbles, it is possible to suppress the air bubbles flowing out from the outlet 311 from flowing into the inlet 321 of the second pipeline 32.

[0048] In some embodiments, the above-described working fluid includes a fluid having a boiling point of less than 0°C.

[0049] According to such a configuration, by using a fluid having a boiling point of less than 0°C as the working fluid, the power recovery system 1 can be operated. Examples of such a working fluid include propane, but it is also applicable when a working fluid other than propane is used as the working fluid flowing through the circulation passage 3.

[0050] (Recirculation pipeline 5) In one embodiment, as shown in FIG. 2, the power recovery system 1 further includes a recirculation pipeline 5 that branches from between the heat pump 6 for cooling and heating and the evaporator 8 and returns the working fluid pressurized by the heat pump 6 for cooling and heating to the gas-liquid separation tank 4. Then, as shown in FIGS. 5A and 5B, the outlet 51 of the recirculation pipeline 5 is provided so as to be located below the liquid level 41 of the gas-liquid separation tank 4.

[0051] According to such a configuration, since the outlet 51 of the recirculation pipeline 5 is located below the liquid level 41 of the gas-liquid separation tank 4, the working fluid condensed by the condenser 2 is directly supplied to the liquid phase part 43 instead of the gas phase part 42. Therefore, the working fluid flowing out from the outlet 51 of the recirculation pipeline 5 to the liquid phase part 43 is maintained in a low temperature state without being heated in the gas phase part 42 in the vertical upward direction where the temperature of the working fluid becomes high, and flows into the inlet 321 of the second pipeline 32 and is supplied to the heat pump 6 for cooling and heating. Thereby, gasification of the working fluid in the pump part of the heat pump 6 for cooling and heating can be suppressed.

[0052] In the embodiment shown in FIG. 2, the upstream end of the recirculation pipeline 5 is connected to a third pipeline 33 that connects the heat pump 6 for cooling and heating and the evaporator 8. A valve 5V is provided downstream of the upstream end of the recirculation pipeline 5 so that the recirculation pipeline 5 can be opened and closed. The third pipeline 33 is provided with a valve 33V downstream of the connection position with the upstream end of the recirculation pipeline 5 so that the third pipeline 33 can be opened and closed.

[0053] When the heat pump 6 for cooling and heating is started, the valve 33V is closed and the valve 5V is opened. Thereby, the liquid working fluid stored in the gas-liquid separation tank 4 flows through the second pipeline 32, is sucked into the heat pump 6 for cooling and heating and pressurized, and discharged to the third pipeline 33. Then, it flows through the recirculation pipeline 5 and is refluxed to the gas-liquid separation tank 4 again. In this way, when the heat pump 6 for cooling and heating is started, the liquid working fluid circulates between the gas-liquid separation tank 4 and the heat pump 6 for cooling and heating.

[0054] After the start of the hot and cold pump 6, when a predetermined operating state is reached (during operation), the valve 33V is opened and the valve 5V is closed. As a result, the working fluid pressurized by the hot and cold pump 6 circulates through the circulation passage 3 without flowing through the recirculation passage 5.

[0055] In one embodiment, as described above, the outlet 51 of the recirculation passage 5 is provided so as to be located in the liquid phase portion 43 below the liquid level 41 of the gas-liquid separation tank 4. When the position of the bottom surface 45 is defined as the 0% position and the position of the ceiling surface 44 is defined as the 100% position in the vertical direction of the gas-liquid separation tank 4, the outlet 51 of the recirculation passage 5 may be located in the range of 0% to 25%.

[0056] According to such a configuration, the working fluid flowing out from the outlet 51 of the recirculation passage 5 into the liquid phase portion 43 is maintained in a low temperature state without being heated in the liquid phase portion 43 above in the vertical direction where the temperature of the working fluid becomes high, flows into the inlet 321 of the second passage 32, and is supplied to the hot and cold pump 6. Thereby, gasification of the working fluid in the pump portion of the hot and cold pump 6 can be suppressed.

[0057] In one embodiment, as shown in FIGS. 5A and 5B, in the vertical direction of the gas-liquid separation tank 4, the outlet 51 of the recirculation passage 5 is located above the inlet 321 of the second passage 32. According to such a configuration, even when the working fluid flowing through the recirculation passage 5 contains bubbles, it is possible to suppress the bubbles flowing out from the outlet 51 from flowing into the inlet 321 of the second passage 32.

[0058] In one embodiment, as shown in FIG. 5A, the recirculation passage 5 is inserted into the gas-liquid separation tank 4 from the bottom surface 45. The recirculation passage 5 extends in the liquid phase portion 43 below the liquid level 41 upward in the vertical direction from the bottom surface 45.

[0059] In one embodiment, as shown in FIG. 5B, the recirculation pipeline 5 is inserted into the gas-liquid separation tank 4 from the side surface 46. The recirculation pipeline 5 extends horizontally from the side surface 46 through the liquid phase portion 43 below the liquid level 41.

[0060] In one embodiment, as shown in FIGS. 5A and 5B, the outlet 51 of the recirculation pipeline 5 is located farther from the inlet 321 of the second pipeline 31 than the outlet 311 of the first pipeline 31. That is, the outlet 311 of the first pipeline 31 is located closer to the inlet 321 of the second pipeline 31 than the outlet 51 of the recirculation pipeline 5. According to such a configuration, the working fluid can be quickly guided from the outlet 311 of the first pipeline 31 to the inlet 321 of the second pipeline 31.

[0061] (The first auxiliary pipeline 7) In one embodiment, as shown in FIGS. 3 and 4, the power recovery system 1 includes a first auxiliary pipeline 7 for supplying the working fluid condensed by the condenser 2 to the gas-liquid separation tank 4. And, as shown in FIGS. 5A and 5B, the outlet 71 of the first auxiliary pipeline 7 is configured to be located above the liquid level 41 of the gas-liquid separation tank 4.

[0062] According to such a configuration, in the gas phase portion 42 above the liquid level 41 of the gas-liquid separation tank 4, since the outlet 71 of the first auxiliary pipeline 7 is provided above the liquid level 41 of the gas-liquid separation tank 4, the working fluid flowing in from the first auxiliary pipeline 7 is directly supplied to the gas phase portion 42. For this reason, the temperature of the gas phase portion 42 above the liquid level 41 of the gas-liquid separation tank 4 decreases, and a low saturation vapor pressure can be obtained. When the pressure (saturation vapor pressure) of the gas phase portion 42 above the liquid level 41 of the gas-liquid separation tank 4 is decreased, the pressure at the outlet of the turbine 10 for cold heat also decreases, so the turbine efficiency can be improved.

[0063] In one embodiment, as shown in FIGS. 3 and 4, the upstream end of the first sub-pipeline 7 is connected to a first pipeline 31 that connects the condenser 2 and the gas-liquid separation tank 4. Also, the downstream side of the first sub-pipeline 7 is connected to the gas-liquid separation tank 4 from above the gas-liquid separation tank 4 in the vertical direction (above the liquid level 41). Then, as shown in FIGS. 5A and 5B, the outlet 71 of the first sub-pipeline 7 is provided so as to be located in the gas phase portion 42 above the liquid level 41 of the gas-liquid separation tank 4.

[0064] Also, in one embodiment, as shown in FIG. 5A, the first sub-pipeline 7 is inserted into the gas-liquid separation tank 4 from the ceiling surface 44. The first sub-pipeline 7 extends downward in the vertical direction from the ceiling surface 44 through the gas phase portion 42 above the liquid level 41.

[0065] In one embodiment, as shown in FIG. 5B, the first sub-pipeline 7 is inserted into the gas-liquid separation tank 4 from the side surface 46. The first sub-pipeline 7 extends horizontally from the side surface 46 through the gas phase portion 43 above the liquid level 41.

[0066] (Control device 9, first valve 31V, second valve 7V) In one embodiment, as shown in FIGS. 3 and 4, the power recovery system 1 includes a first valve 31V capable of adjusting the flow rate of the working fluid flowing through the first pipeline 31, a second valve 7V capable of adjusting the flow rate of the working fluid flowing through the first sub-pipeline 7, and a control device 9 capable of controlling the valve opening degrees of the first valve 31V and the second valve 7V respectively. The control device 9 is configured to control the valve opening degrees of the first valve 31V and the second valve 7V such that the difference ΔT between the temperature T1 of the gas phase portion 42 above the liquid level 41 of the gas-liquid separation tank 4 and the liquid temperature T2 of the liquid working fluid before flowing out of the gas-liquid separation tank 4 and being sucked into the cold heat pump 6 is greater than a first threshold value and less than a second threshold value greater than the first threshold value.

[0067] According to such a configuration, the difference ΔT is controlled between the first threshold value and the second threshold value. When the difference ΔT is smaller than the first threshold value, the temperature difference between the liquid temperature T2 and the temperature T1 of the gas phase part 42 which is the saturation temperature becomes small. Therefore, when the working fluid of the liquid temperature T2 flows into the cold heat pump 6 or is slightly heated in the pump part of the cold heat pump 6, it is likely to be gasified. On the other hand, when the difference ΔT is larger than the second threshold value, the temperature of the temperature T1 of the gas phase part 42 is high, the gas phase part 42 has a high saturation vapor pressure, and the turbine efficiency of the cold heat turbine 10 may decrease. Therefore, by using the difference ΔT as a control parameter and providing the first threshold value and the second threshold value to the difference ΔT for control, the turbine efficiency can be increased without causing gasification of the working fluid.

[0068] The second valve 7V is provided in the first sub-pipeline 7 and can control the flow rate of the working fluid flowing through the first sub-pipeline 7. Also, the first valve 31V is provided in the first pipeline 31 on the downstream side from the connection position with the upstream end of the first sub-pipeline 7 and can control the flow rate of the working fluid flowing through the first pipeline 31. Further, the first valve 31V and the second valve 7V are connected to an actuator (such as a motor) so that their valve openings can be automatically adjusted.

[0069] When the temperature T1 rises, the gas phase part 42 has a high saturation vapor pressure, the pressure at the outlet of the cold heat turbine 10 rises, and the turbine efficiency may decrease. Also, when the liquid temperature T2 rises, since the temperature of the working fluid supplied to the cold heat pump 6 rises, there is a possibility that the working fluid is likely to be gasified in the pump part of the cold heat pump 6.

[0070] In order to lower the temperature T1, it is advisable to adjust the second valve 7V in the valve opening direction and the first valve 31V in the valve closing direction so that more of the liquid working fluid condensed by the condenser 2 flows through the first sub-pipeline 7. Thereby, since the amount of the working fluid supplied from the outlet 71 of the first sub-pipeline 7 to the gas phase part 42 of the gas-liquid separation tank 4 increases, the temperature T1 can be lowered. However, by adjusting the second valve 7V in the valve opening direction and the first valve 31V in the valve closing direction, the amount of the working fluid flowing through the first pipeline 31 decreases. For this reason, it becomes difficult for the working fluid to be supplied from the outlet 311 of the first pipeline 31 to the liquid phase portion 43 of the gas-liquid separation tank 4, so the liquid temperature T2 of the liquid phase portion 43 of the gas-liquid separation tank 4 rises.

[0071] On the other hand, in order to lower the temperature of the liquid temperature T2, it is advisable to adjust the second valve 7V in the valve closing direction and the first valve 31V in the valve opening direction so that a large amount of the liquid working fluid condensed by the condenser 2 flows through the first pipeline 31. Thereby, since the amount of the working fluid supplied from the outlet 311 of the first pipeline 31 to the liquid phase portion 43 increases, the liquid temperature T2 can be lowered. However, by adjusting the second valve 7V in the valve closing direction and the first valve 31V in the valve opening direction, the amount of the working fluid flowing through the first sub-pipeline 7 decreases. For this reason, it becomes difficult for the working fluid to be supplied from the outlet 71 of the first sub-pipeline 7 to the gas phase portion 42 of the gas-liquid separation tank 4, so the temperature T1 of the gas phase portion 42 of the gas-liquid separation tank 4 rises.

[0072] That is, the temperature T1 and the liquid temperature T2 are in a trade-off relationship where when trying to lower the temperature T1, the liquid temperature T2 rises, and when trying to lower the liquid temperature T2, the temperature T1 rises. Therefore, a first threshold value and a second threshold value are provided for the difference ΔT between the temperature T1 and the liquid temperature T2.

[0073] When the temperature T1 rises, since the temperature difference between the temperature T1 and the liquid temperature T2 becomes large, the difference ΔT becomes large. Then, in order not to let the difference ΔT become larger than the second threshold value, the second valve 7V is adjusted in the valve closing direction and the first valve 31V is adjusted in the valve opening direction. Thereby, the temperature T1 can be lowered, the difference ΔT can be made smaller, and the difference ΔT can be maintained to be smaller than the second threshold value.

[0074] Also, when the liquid temperature T2 rises, the temperature difference between the temperature T1 and the liquid temperature T2 becomes smaller, so the difference ΔT becomes smaller. Then, so that the difference ΔT does not become smaller than the first threshold value, the second valve 7V is adjusted in the valve closing direction and the first valve 31V is adjusted in the valve opening direction. Thereby, the liquid temperature T2 can be lowered, the difference ΔT can be increased, and the difference ΔT can be maintained to be larger than the first threshold value.

[0075] The control device 9 is an electronic control unit for controlling the valve opening degrees of the first valve 31V and the second valve 7V, and may be configured as a microcomputer including a CPU (processor) not shown, a memory such as a ROM and a RAM, a storage device such as an external storage device, an I / O interface, a communication interface, and the like. Then, for example, the CPU operates (such as data calculation) according to the instructions of the program loaded in the main storage device of the memory, so that the valve opening degree control of the first valve 31V and the second valve 7V described later may be realized.

[0076] In one embodiment, as shown in FIG. 4, the first sensor 131 measures the temperature T1 and is installed in the gas phase portion 42 of the gas-liquid separation tank 4 so as to be able to transmit to the control device 9. The second sensor 132 measures the liquid temperature T2 and is installed near the heat pump 6 for cooling and heating in the second pipeline 32 so as to be able to transmit to the control device 9. The first sensor 131 and the second sensor 132 are configured to continuously transmit the measured temperature T1 and the liquid temperature T2 to the control device 9 as signals through a wired or wireless communication line.

[0077] The control device 9 performs feedback control so that the difference ΔT between the temperature T1 and the liquid temperature T2 described above becomes a value greater than the first threshold and less than the second threshold. Specifically, the control device 9 calculates the valve opening degrees of the first valve 31V and the second valve 7V such that the difference ΔT becomes a value greater than the first threshold and less than the second threshold, and outputs the command signal to the first valve 31V and the second valve 7V. The first valve 31V and the second valve 7V adjust the valve opening degree based on the input command signal. By repeating this series of controls at predetermined intervals, the difference ΔT is maintained to be a value greater than the first threshold and less than the second threshold.

[0078] (Second recirculation pipeline 15) In one embodiment, as shown in FIG. 2, the power recovery system 1 includes a second recirculation pipeline 15 that branches from the recirculation pipeline 5 and returns the working fluid pressurized by the heat pump 6 for cooling and heating to the condenser 2, a first reflux valve 16V that can adjust the flow rate of the working fluid flowing through the second recirculation pipeline 15, a second reflux valve 17V that can adjust the flow rate of the working fluid flowing downstream of the branch position of the second recirculation pipeline 15 in the recirculation pipeline 5, and a control device 9 that can control the valve opening degrees of the first reflux valve 16V and the second reflux valve 17V.

[0079] When the liquid temperature of the working fluid pressurized by the heat pump 6 for cooling and heating is lower than a predetermined temperature (third threshold), the control device 9 returns the working fluid pressurized by the heat pump 6 for cooling and heating to the gas-liquid separation tank 4, and when the liquid temperature of the working fluid pressurized by the heat pump 6 for cooling and heating is higher than a predetermined temperature (third threshold), the control device 9 is configured to control the valve opening degrees of the first reflux valve 16V and the second reflux valve 17V so as to return the working fluid pressurized by the heat pump 6 for cooling and heating to the condenser 2.

[0080] When the temperature of the working fluid rises above a predetermined temperature due to the heat input from the cold and heat pump 6, if the heated working fluid is refluxed to the gas-liquid separation tank 4, the temperature of the working fluid stored in the gas-liquid separation tank 4 may increase. Therefore, according to such a configuration, when the temperature of the working fluid rises above a predetermined temperature (third threshold value) due to the heat input from the cold and heat pump 6, the working fluid is refluxed to the condenser 2, cooled in the condenser, and then supplied to the gas-liquid separation tank 4, thereby suppressing the increase in the temperature of the working fluid stored in the gas-liquid separation tank 4.

[0081] In the embodiment shown in FIG. 2, the first reflux valve 16V is provided in the second recirculation pipeline 15 and can control the flow rate of the working fluid flowing through the second recirculation pipeline 15. The second reflux valve 17V is provided on the downstream side of the branch position of the recirculation pipeline 5 with respect to the second recirculation pipeline 15 and can control the flow rate of the working fluid flowing through the recirculation pipeline 5 on the downstream side of the branch position. The first reflux valve 16V and the second reflux valve 17V are connected to an actuator (such as a motor) so that their valve openings can be automatically adjusted. Further, a third sensor 133 capable of measuring the temperature of the working fluid flowing through the recirculation pipeline 5 (the liquid temperature of the working fluid pressurized by the cold and heat pump 6) is installed on the upstream side of the branch position of the recirculation pipeline 5 with respect to the second recirculation pipeline 15. The third sensor 133 continuously transmits the measured temperature of the working fluid to the control device 9 as a signal through a wired or wireless communication line.

[0082] (Gas vent pipe 11) In one embodiment, as shown in FIG. 4, the power recovery system 1 further includes a gas vent pipe 11 branched from the first pipeline 31 for discharging the gaseous working fluid that has not been condensed in the condenser 2 to the outside of the first pipeline 31.

[0083] According to such a configuration, when the working fluid is not sufficiently liquefied in the condenser 2, the vent pipe 11 is provided in the first pipeline 31, so that the gas in the first pipeline 31 can be discharged to the outside. Therefore, it is possible to suppress the inflow of gas into the liquid phase portion 43 located below the liquid level 41 of the gas-liquid separation tank 4 and the suction of gas into the heat and cold pump 6 section.

[0084] In the embodiment shown in FIG. 4, the vent pipe 11 branches from the first pipeline 31 and extends upward in the vertical direction. And the downstream end of the vent pipe 11 is located above the liquid level 41 of the gas-liquid separation tank 4 in the vertical direction.

[0085] Also, in the embodiment shown in FIG. 4, the downstream end of the vent pipe 11 is connected to the exhaust gas pipeline 14. The exhaust gas pipeline 14 connects the vent pipe 11 and the gas-liquid separation tank 4. The downstream side of the exhaust gas pipeline 14 is connected to the gas-liquid separation tank 4 from above the liquid level 41 of the gas-liquid separation tank 4 in the vertical direction as shown in FIGS. 5A and 5B. And the outlet 141 of the exhaust gas pipeline 14 is provided so as to be located in the gas phase portion 42 above the liquid level 41 of the gas-liquid separation tank 4. According to such a configuration, the gaseous working fluid discharged to the outside of the first pipeline 31 can be circulated within the power recovery system 1 without being released to the outside of the power recovery system 1. Therefore, it is possible to suppress the loss of the working fluid circulating in the power recovery system 1.

[0086] Also, in one embodiment, as shown in FIG. 5A, the exhaust gas pipeline 14 is inserted into the gas-liquid separation tank 4 from the ceiling surface 44. The exhaust gas pipeline 14 extends downward in the vertical direction from the ceiling surface 44 and extends in the gas phase portion 42 above the liquid level 41.

[0087] In one embodiment, as shown in FIG. 5B, the exhaust gas pipeline 14 is inserted into the gas-liquid separation tank 4 from the side surface 46. The exhaust gas pipeline 14 extends horizontally from the side surface 46 and extends in the gas phase portion 43 above the liquid level 41.

[0088] The present disclosure is not limited to the above-described embodiments, and includes forms obtained by modifying the above-described embodiments and forms obtained by appropriately combining these forms.

[0089] The content described in some of the above-described embodiments can be understood as follows, for example.

[0090] 1) The power recovery system (1) according to one aspect is a power recovery system (1) for recovering the cold thermal energy of the liquefied gas as power through a working fluid for heating the liquefied gas, a condenser (2) configured to condense the working fluid by heat exchange between the working fluid and the liquefied gas, a gas-liquid separation tank (4) configured to separate and store the working fluid condensed in the condenser (2) into a liquid and a gas, a cold thermal energy pump (6) configured to boost the pressure of the liquid working fluid supplied from the gas-liquid separation tank (4), an evaporator (8) configured to evaporate the working fluid by heat exchange between the working fluid boosted in pressure by the cold thermal energy pump (6) and a heating fluid introduced from outside the power recovery system, a cold thermal energy turbine (10) configured to be driven by the gaseous working fluid generated in the evaporator (8), a first pipeline (31) for supplying the working fluid condensed by the condenser (2) to the gas-liquid separation tank, the first pipeline (31) being configured such that an outlet (311) of the first pipeline (31) is located below a liquid level (41) of the gas-liquid separation tank (4).

[0091] According to the power recovery system of the present disclosure, since the outlet of the first pipeline is located below the liquid level of the gas-liquid separation tank, the working fluid condensed by the condenser is directly supplied to the liquid phase part instead of the gas phase part. Therefore, when the outlet of the first pipeline is located above the liquid level of the gas-liquid separation tank, that is, compared with the case where the working fluid condensed by the condenser is supplied to the liquid phase part through the gas phase part, the working fluid is not heated in the gas phase part, so the working fluid can be supplied to the liquid phase part while remaining in a low temperature state. And when supplying the liquid working fluid from the gas-liquid separation tank to the heat pump for cooling, it can also flow in while remaining in a low temperature state, so that the gasification of the working fluid in the pump part of the heat pump for cooling can be suppressed. Thereby, the occurrence of cavitation in the pump part of the heat pump for cooling is suppressed, and the suction of gas into the heat pump for cooling is suppressed, so that the heat pump for cooling can be driven normally.

[0092] 2) The power recovery system according to another aspect is the power recovery system (1) described in 1), further comprising a second pipeline (32) configured to supply the liquid working fluid stored in the gas-liquid separation tank (4) to the heat pump for cooling (6). In the vertical direction of the gas-liquid separation tank (4), when the position of the bottom surface is defined as the 0% position and the position of the ceiling surface is defined as the 100% position, The outlet (311) of the first pipeline (31) and the inlet (321) of the second pipeline (32) are configured to be located in the range of 0% to 25%.

[0093] According to such a configuration, the outlet of the first pipeline and the inlet of the second pipeline are located in the range of 0% to 25% (that is, the bottom surface side) in the vertical direction of the gas-liquid separation tank 4. For this reason, the working fluid flowing out from the outlet of the first pipeline into the liquid phase part is maintained in a low temperature state without being heated in the upper liquid phase part in the vertical direction where the temperature of the working fluid becomes high, and flows into the inlet of the second pipeline and is supplied to the heat pump for cooling. Thereby, the gasification of the working fluid in the pump part of the heat pump for cooling can be suppressed.

[0094] 3) Another aspect of the power recovery system is the power recovery system (1) described in 1) or 2), wherein the working fluid includes a fluid having a boiling point of less than 0°C.

[0095] According to such a configuration, by using a fluid having a boiling point of less than 0°C as the working fluid, the present power recovery system can be operated. Examples of such a working fluid include propane, but it is also applicable when a working fluid other than propane is used as the working fluid flowing through the circulation passage.

[0096] 4) Another aspect of the power recovery system is the power recovery system (1) according to any one of 1) to 3), further comprising a recirculation pipeline (5) that branches from between the cold heat pump (6) and the evaporator (8) and returns the working fluid pressurized by the cold heat pump (6) to the gas-liquid separation tank (4), The outlet (51) of the recirculation pipeline (5) is located below the liquid level of the gas-liquid separation tank (4).

[0097] According to such a configuration, since the outlet of the recirculation pipeline is located below the liquid level of the gas-liquid separation tank, the working fluid condensed by the condenser is directly supplied to the liquid phase part instead of the gas phase part. Therefore, the working fluid flowing out from the outlet of the recirculation pipeline to the liquid phase part is maintained in a low temperature state without being heated in the liquid phase part in the vertical upward direction where the temperature of the working fluid becomes high, and flows into the inlet of the second pipeline and is supplied to the cold heat pump. Thereby, gasification of the working fluid in the pump part of the cold heat pump can be suppressed.

[0098] 5) Another aspect of the power recovery system is the power recovery system (1) described in 4), a second recirculation pipeline (15) that branches from the recirculation pipeline (5) and returns the working fluid pressurized by the cold heat pump (6) to the condenser (2), a first reflux valve (16V) capable of adjusting the flow rate of the working fluid flowing through the second recirculation pipeline (15), A second reflux valve (17V) capable of adjusting the flow rate of the working fluid flowing downstream of the branch position from the second recirculation pipeline (15) in the recirculation pipeline (5); It further includes a control device (9) capable of controlling the valve opening degrees of the first reflux valve (16V) and the second reflux valve (17V). The control device (9) When the liquid temperature of the working fluid pressurized by the cold and heat pump (6) is lower than a predetermined temperature, the working fluid pressurized by the cold and heat pump (6) is refluxed to the gas-liquid separation tank (4), and When the liquid temperature of the working fluid pressurized by the cold and heat pump (6) exceeds the predetermined temperature, the valve opening degrees of the first reflux valve (16V) and the second reflux valve (17V) are controlled so that the working fluid pressurized by the cold and heat pump (6) is refluxed to the condenser (2).

[0099] When the temperature of the working fluid rises above a predetermined temperature due to the heat input from the cold and heat pump and the working fluid with the increased temperature is refluxed to the gas-liquid separation tank, there is a risk of increasing the temperature of the working fluid stored in the gas-liquid separation tank. Therefore, according to such a configuration, when the temperature of the working fluid rises above a predetermined temperature (the third threshold value) due to the heat input from the cold and heat pump, the working fluid is refluxed to the condenser 2, the temperature is lowered in the condenser, and then supplied to the gas-liquid separation tank, thereby suppressing the increase in the temperature of the working fluid stored in the gas-liquid separation tank.

[0100] 6) The power recovery system according to still another aspect is the power recovery system (1) according to any one of 1) to 5), and is a first sub-pipeline (7) for supplying the working fluid condensed by the condenser (2) to the gas-liquid separation tank (4), and the outlet (71) of the first sub-pipeline (7) is configured to be located above the liquid level (41) of the gas-liquid separation tank (4). It further includes a first sub-pipeline (7).

[0101] According to such a configuration, in the gas phase portion above the liquid level of the gas-liquid separation tank, since the outlet of the first sub-pipeline is provided above the liquid level of the gas-liquid separation tank, the working fluid flowing in from the first sub-pipeline is directly supplied to the gas phase portion. Therefore, the temperature of the gas phase portion above the liquid level of the gas-liquid separation tank decreases, and a low saturation vapor pressure can be obtained. When the pressure (saturation vapor pressure) of the gas phase portion above the liquid level of the gas-liquid separation tank is decreased, the pressure at the outlet of the turbine for cooling and heating also decreases, so the turbine efficiency can be improved.

[0102] 7) The power recovery system according to still another aspect is the power recovery system described in 6), wherein a first valve (31V) capable of adjusting the flow rate of the working fluid flowing through the first pipeline (31); a second valve (7V) capable of adjusting the flow rate of the working fluid flowing through the first sub-pipeline (7); and a control device (9) capable of controlling the valve opening degrees of the first valve (31V) and the second valve (7V) respectively. The control device (9) is configured to control the valve opening degrees of the first valve (31V) and the second valve (7V) such that the difference ΔT between the temperature T1 of the gas phase above the liquid level (41) of the gas-liquid separation tank (4) and the liquid temperature T2 of the liquid working fluid flowing out of the gas-liquid separation tank (4) and before being sucked into the cooling and heating pump (6) is greater than a first threshold value and smaller than a second threshold value greater than the first threshold value.

[0103] According to such a configuration, the difference ΔT is controlled between the first threshold value and the second threshold value. When the difference ΔT is smaller than the first threshold value, the temperature difference between the liquid temperature T2 and the temperature T1 of the gas phase part which is the saturation temperature becomes small. Therefore, the working fluid of the liquid temperature T2 is likely to be gasified even by a little heating when flowing into the cold heat pump or in the pump part of the cold heat pump. On the other hand, when the difference ΔT is larger than the second threshold value, the temperature of the temperature T1 of the gas phase part is high, the gas phase part has a high saturation vapor pressure, and the turbine efficiency of the cold heat turbine 10 may decrease. Therefore, by using the difference ΔT as a control parameter and providing the first threshold value and the second threshold value to control the difference ΔT, the turbine efficiency can be increased without causing gasification of the working fluid.

[0104] 8) The power recovery system according to still another aspect is the power recovery system (1) according to any one of 1) to 7), It further includes a gas vent pipe (11) branched from the first pipeline (31) for discharging the gaseous working fluid that has not been condensed in the condenser (2) to the outside of the first pipeline (31).

[0105] According to such a configuration, when the working fluid is not sufficiently liquefied in the condenser, the gas vent pipe is provided in the first pipeline, so that the gas in the first pipeline can be discharged to the outside. Therefore, it is possible to suppress the inflow of gas into the liquid phase part located below the liquid level of the gas-liquid separation tank and the suction of gas into the cold heat pump part.

[0106] 9) The power recovery system according to still another aspect is the power recovery system (1) according to any one of 1) to 8), The first pipeline (31) includes an internal pipeline (31B) that is inserted into the gas-liquid separation tank (4) from above the liquid level (41) of the gas-liquid separation tank (4) and extends downward from the liquid level.

[0107] According to such a configuration, since the first pipeline is inserted into the gas-liquid separation tank from above the liquid level of the gas-liquid separation tank, the distance that the first pipeline is exposed to the atmosphere, which is at a higher temperature than the working fluid condensed by the condenser, is reduced compared to the case where it is inserted into the gas-liquid separation tank from below the liquid level. Therefore, outside the gas-liquid separation tank, it is possible to suppress the working fluid in the first pipeline from being heated by heat input from the outside.

Explanation of symbols

[0108] 1 Power recovery system 2 Condenser 3 Circulation flow path 4 Gas-liquid separation tank 5 Recirculation pipeline 5V Valve 6 Chilled heat pump 7 First sub-pipeline 7V Second valve 8 Evaporator 9 Control device 10 Chilled heat turbine 11 Vent pipe 12 Generator 131 First sensor 132 Second sensor 133 Third sensor 14 Exhaust gas pipe 15 Second recirculation pipeline 16V First reflux valve 17V Second reflux valve 21 Heating side pipeline 22 Heated side pipeline 31 First pipeline 31V First valve 311 Outlet 31A External pipeline 31B Internal pipeline 31B1 Internal horizontal pipeline 31B2 Internal vertical pipeline 32 Second pipeline 321 Outlet 33 Third pipeline 33V Valve 34 Fourth pipeline 35 Fifth pipeline 41 Liquid level 42 Gas phase part 43 Liquid phase part 44 Ceiling surface 45 Bottom surface 46 Side surface 81 Heated side pipeline 82 Heating side pipeline 101 Floating structure on water 111 Engine 102 Onshore LNG (liquefied gas) base 112 Supply destination

Claims

1. A power recovery system for recovering the cold thermal energy of the liquefied gas as power through a working fluid for heating the liquefied gas, comprising: a condenser configured to condense the working fluid by heat exchange between the working fluid and the liquefied gas; a gas-liquid separation tank configured to separate and store the working fluid condensed in the condenser into a liquid and a gas; a cold thermal pump configured to boost the pressure of the liquid working fluid supplied from the gas-liquid separation tank; an evaporator configured to evaporate the working fluid by heat exchange between the working fluid boosted by the cold thermal pump and a heating fluid introduced from outside the power recovery system; a cold thermal turbine configured to be driven by the gaseous working fluid generated in the evaporator; a first pipeline for supplying the working fluid condensed by the condenser to the gas-liquid separation tank, the outlet of the first pipeline being configured to be located below the liquid level of the gas-liquid separation tank; a second pipeline configured to supply the liquid working fluid stored in the gas-liquid separation tank to the cold thermal pump. In the vertical direction of the gas-liquid separation tank, when the position of the bottom surface is defined as the 0% position and the position of the ceiling surface is defined as the 100% position, the outlet of the first pipeline and the inlet of the second pipeline are located in the range of 0% to 25%, and the inlet of the second pipeline is located below the outlet of the first pipeline. A power recovery system.

2. A power recovery system for recovering the cold thermal energy of the liquefied gas as power through a working fluid for heating the liquefied gas, comprising: a condenser configured to condense the working fluid by heat exchange between the working fluid and the liquefied gas; a gas-liquid separation tank configured to separate and store the working fluid condensed in the condenser into a liquid and a gas; a cold thermal pump configured to boost the pressure of the liquid working fluid supplied from the gas-liquid separation tank; an evaporator configured to evaporate the working fluid by heat exchange between the working fluid boosted by the cold thermal pump and a heating fluid introduced from outside the power recovery system; a cold thermal turbine configured to be driven by the gaseous working fluid generated in the evaporator; A first pipeline for supplying the working fluid condensed by the condenser to the gas-liquid separation tank, wherein the outlet of the first pipeline is configured to be located below the liquid level of the gas-liquid separation tank. A recirculation pipeline that branches from between the heat pump for heat and the evaporator and returns the working fluid pressurized by the heat pump for heat to the gas-liquid separation tank. The outlet of the recirculation pipeline is located below the liquid level of the gas-liquid separation tank. Power recovery system. According to claim 3, a power recovery system for recovering the cold energy of the liquefied gas as power through a working fluid for heating the liquefied gas. A condenser configured to condense the working fluid by heat exchange between the working fluid and the liquefied gas. A gas-liquid separation tank configured to separate and store the working fluid condensed in the condenser into liquid and gas. A heat pump for heat configured to pressurize the liquid working fluid supplied from the gas-liquid separation tank. An evaporator configured to evaporate the working fluid by heat exchange between the working fluid pressurized by the heat pump for heat and a heating fluid introduced from outside the power recovery system. A heat turbine configured to be driven by the gaseous working fluid generated in the evaporator. A first pipeline for supplying the working fluid condensed by the condenser to the gas-liquid separation tank, wherein the outlet of the first pipeline is configured to be located below the liquid level of the gas-liquid separation tank. A first sub-pipeline for supplying the working fluid condensed by the condenser to the gas-liquid separation tank, wherein the outlet of the first sub-pipeline is configured to be located above the liquid level of the gas-liquid separation tank. Power recovery system. According to claim 4 The working fluid includes a fluid having a boiling point of less than 0°C. The power recovery system according to any one of claims 1 to 3. According to claim 5 A second recirculation pipeline that branches from the recirculation pipeline and returns the working fluid pressurized by the heat pump for heat to the condenser. A first reflux valve capable of adjusting the flow rate of the working fluid flowing through the second recirculation pipeline. A second reflux valve capable of adjusting the flow rate of the working fluid flowing downstream of the branch position of the second recirculation pipeline in the recirculation pipeline. A control device capable of controlling the valve opening degrees of the first reflux valve and the second reflux valve, respectively, is further provided. The control device is configured to: When the liquid temperature of the working fluid pressurized by the cold and heat pump is lower than a predetermined temperature, reflux the working fluid pressurized by the cold and heat pump to the gas-liquid separation tank, and When the liquid temperature of the working fluid pressurized by the cold and heat pump exceeds the predetermined temperature, control the valve opening degrees of the first reflux valve and the second reflux valve respectively so as to reflux the working fluid pressurized by the cold and heat pump to the condenser. The power recovery system according to claim 2.

6. A first valve capable of adjusting the flow rate of the working fluid flowing through the first pipeline, A second valve capable of adjusting the flow rate of the working fluid flowing through the first sub-pipeline, A control device capable of controlling the valve opening degrees of the first valve and the second valve respectively, is further provided. The control device is configured to control the valve opening degrees of the first valve and the second valve respectively so that the difference ΔT between the temperature T1 of the gas phase above the liquid level of the gas-liquid separation tank and the liquid temperature T2 of the liquid working fluid flowing out of the gas-liquid separation tank and being sucked into the cold and heat pump before being condensed is greater than a first threshold value and smaller than a second threshold value greater than the first threshold value. The power recovery system according to claim 3.

7. A gas vent pipe branched from the first pipeline, and further provided with a gas vent pipe for discharging the gaseous working fluid that has not been condensed in the condenser to the outside of the first pipeline. The power recovery system according to any one of claims 1 to 6.

8. The first pipeline includes an internal pipeline that is inserted into the gas-liquid separation tank from above the liquid level of the gas-liquid separation tank and extends downward toward the liquid level. The power recovery system according to any one of claims 1 to 7.

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