JP7716288B2 - Power Recovery System - Google Patents

Description

This disclosure relates to a power recovery system for recovering the cold energy contained in liquefied gas as power via a working fluid for heating the liquefied gas.

Liquefied gases (e.g., liquefied natural gas) are liquefied for the purposes of transportation and storage, and when supplied to destinations such as city gas and thermal power plants, they are heated and vaporized using a heat transfer medium such as seawater. When vaporizing liquefied gas, there are power recovery systems (e.g., cold energy power generation cycles) that recover the cold energy used as power rather than discarding it into seawater.

ORC (Organic Rankine Cycle) is a known cryogenic power generation cycle using liquefied natural gas. In ORC, a low-temperature working fluid with a boiling point lower than that of water circulates in a closed loop. It is cooled and condensed with liquefied natural gas in a condenser, then pressurized by a pump. It is heated and evaporated in an evaporator using seawater or other heat sources, and the resulting steam is introduced into a cryogenic power generation turbine to generate power.

In an ORC, the temperature of the working fluid is reduced to its saturated vapor pressure in the condenser, but when the pressure is then increased by the pump, the working fluid can evaporate (gasify) locally in the pump, causing cavitation. If cavitation occurs in the pump, it could lead to damage to the pump. Furthermore, if gas is sucked into the pump, it could interfere with the pump's normal operation.

For this reason, Patent Document 1 discloses an ORC device in which a liquid reservoir tank is installed between the condenser and the pump, and a large water level head is provided between the liquid reservoir tank and the pump, in order to suppress gasification in the pump section. In this ORC device, the working fluid is introduced from the top (ceiling surface) of the liquid reservoir tank.

Patent No. 5608755

To further suppress gasification in the pump section using the technology disclosed in Patent Document 1, it is necessary to increase the capacity of the liquid reservoir tank and provide a large water level head between the liquid reservoir tank and the pump. However, because ORCs with a cold-energy power generation cycle use a working fluid with a boiling point lower than the ambient temperature (e.g., 25°C), increasing the capacity of the liquid reservoir tank increases the heat transfer area with the surrounding atmosphere, heating the working fluid stored in the liquid reservoir pump and making it more likely for bubbles to be generated (gasification) in the pump section. In addition, the large temperature difference between the heated pump and the working fluid further promotes gasification.

In light of the above-mentioned circumstances, an object of at least one embodiment of the present disclosure is to provide a power recovery system that suppresses the gasification of the working fluid in the pump section, thereby suppressing the occurrence of cavitation in the pump section and suppressing the intake of gas into the pump, allowing the pump to operate normally.

In order to achieve the above object, a power recovery system according to at least one embodiment of the present disclosure comprises:
A power recovery system for recovering cold energy contained in a liquefied gas as power via 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 the working fluid condensed by the condenser into liquid and gas and store the separated fluid;
a cold/heat pump 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 cold energy pump and a heating fluid introduced from outside the cold energy recovery system;
a cold turbine configured to be driven by the gaseous working fluid produced in the evaporator;
and a first pipeline for supplying the working fluid condensed by the condenser to the gas-liquid separation tank, the first pipeline being configured so that an outlet of the first pipeline is positioned below the liquid level in the gas-liquid separation tank.

The power recovery system disclosed herein can suppress the gasification of the working fluid in the pump section, thereby suppressing the occurrence of cavitation in the pump section and suppressing the intake of gas into the pump, thereby providing a power recovery system that can operate the pump normally.

1 is a schematic diagram illustrating an overall configuration of a power recovery system according to an embodiment of the present disclosure. 1 is a schematic diagram illustrating an overall configuration of a power recovery system according to an embodiment of the present disclosure. 1 is a schematic diagram illustrating an overall configuration of a power recovery system according to an embodiment of the present disclosure. 1 is a schematic diagram illustrating an overall configuration of a power recovery system according to an embodiment of the present disclosure. FIG. 1 is a schematic cross-sectional view of a gas-liquid separation tank according to an embodiment of the present disclosure. FIG. 1 is a schematic cross-sectional view of a gas-liquid separation tank according to an embodiment of the present disclosure. FIG. 1 is a schematic cross-sectional view of a gas-liquid separation tank according to an embodiment of the present disclosure. FIG. 1 is a schematic cross-sectional view of a gas-liquid separation tank according to an embodiment of the present disclosure. 1 is a schematic diagram illustrating an example of a power recovery system according to an embodiment of the present disclosure installed on a floating structure on water. FIG. 1 is a schematic diagram illustrating an example of a power recovery system according to an embodiment of the present disclosure installed at a land-based liquefied gas terminal. FIG.

Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure.
For example, expressions expressing relative or absolute arrangement such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""center,""concentric," or "coaxial" not only express such an arrangement exactly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained.
For example, expressions such as "identical,""equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained.
For example, expressions representing shapes such as a square shape or a cylindrical shape not only represent shapes such as a square shape or a cylindrical shape in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained.
On the other hand, the expressions "comprise,""include," or "have" one element are not exclusive expressions that exclude the presence of other elements.
Note that the same components will be denoted by the same reference numerals and the description thereof will be omitted.

(Example of application 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.

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 cold energy as electricity rather than discarding it in seawater.

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

(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.

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

The condenser 2 is configured to condense the working fluid through heat exchange between the working fluid and the liquefied gas. Inside the condenser 2, there is a heating-side pipe 21 into which the working fluid circulating through the circulation flow path 3 flows, and a heated-side pipe 22 into which liquefied gas introduced from outside the power recovery system 1 flows, so that heat exchange occurs between the working fluid and the liquefied gas. In the condenser 2, the working fluid is cooled and condensed through heat exchange, and the liquefied gas is heated.

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 energy pump 6, a third pipe 33 connecting the cold energy pump 6 and the evaporator 8, a fourth pipe 34 connecting the evaporator 8 and the cold energy turbine 10, and a fifth pipe 35 connecting the cold energy turbine 10 and the condenser 2. The working fluid circulates within the circulation flow path 3 while changing state between liquid and gas, and drives the power recovery system 1.
In the following description, "upstream side" means the upstream side in the flow direction of the working fluid flowing through the circulation flow path 3, and "downstream side" means the downstream side in the flow direction of the working fluid flowing through the circulation flow path 3.

The first pipe 31 is located downstream of the condenser 2 and upstream of the gas-liquid separation tank 4, connecting the condenser 2 and the gas-liquid separation tank 4. The upstream end of the first pipe 31 is connected to the downstream end of the heating side pipe 21 of the condenser 2. The downstream side of the first pipe 31 is connected to the gas-liquid separation tank 4. The liquid working fluid condensed by the condenser 2 flows through the first pipe 31 and is supplied to the gas-liquid separation tank 4.

The gas-liquid separation tank 4 is configured to separate the working fluid condensed in the condenser 2 into liquid and gas and store them. Inside the gas-liquid separation tank 4, a gas phase portion 42 composed of gaseous working fluid is formed above the liquid level 41, and a liquid phase portion 43 composed of liquid working fluid is formed below that.

The gas-liquid separation tank 4 is also installed so that its ceiling surface 44 is positioned vertically lower than the condenser 2. In other words, the upstream end of the first pipeline 31 is positioned vertically higher than the downstream end of the first pipeline 31, and the working fluid flows through the first pipeline 31 by gravity.

In the illustrated embodiment, the gas-liquid separation tank 4 has a cylindrical shape. However, the shape of the gas-liquid separation tank 4 is not particularly limited as long as it is able to separate and store the working fluid into liquid and gas. The shape of the gas-liquid separation tank 4 can be selected appropriately according to the embodiment, for example, a cylindrical shape, a spherical shape, or a rectangular parallelepiped shape. Note that if the gas-liquid separation tank 4 has a spherical shape, the ceiling surface 44 mentioned above corresponds to the highest part of the sphere, and the bottom surface 45 described below corresponds to the lowest part of the sphere.

The temperature of the gas phase 42 of the gas-liquid separation tank 4 is above the saturated steam temperature, and is either at the saturated steam temperature or slightly higher due to external influences. The temperature of the liquid phase 43 of the gas-liquid separation tank 4 is affected by the gas phase 42 at the liquid surface 41, which is above the saturated steam temperature, so there is a temperature gradient in the vertical direction, where the temperature decreases from the liquid surface 41 side of the liquid phase 43 toward the bottom surface 45 side.

The second pipeline 32 is located downstream of the gas-liquid separation tank 4 and upstream of the cold heat pump 6, connecting the gas-liquid separation tank 4 and the cold heat pump 6. The upstream end of the second pipeline 32 is located in the liquid phase section 43 of the gas-liquid separation tank 4 and is open so that 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 heat pump 6. The liquid working fluid stored in the liquid phase section 43 of the gas-liquid separation tank 4 flows through the second pipeline 32 and is supplied to the cold heat pump 6.

The cold heating pump 6 is configured to pressurize the liquid working fluid supplied from the gas-liquid separation tank 4. The liquid working fluid that flows in from the suction port is pressurized by a pressure-boosting section (for example, an impeller) of the cold heating pump 6 and flows out from the discharge port.
Furthermore, the cold heat pump 6 is installed vertically below the bottom surface 45 of the gas-liquid separation tank 4. In other words, the upstream end of the second conduit 32 is located vertically above the downstream end of the second conduit 32, and the working fluid flows through the second conduit 32 due to the head difference between the liquid level 41 and the suction port of the cold heat pump 6 and the suction force of the cold heat pump 6.

The cold/heat pump 6 may be of any type, as long as it is capable of pressurizing the working fluid. For example, a turbo pump (e.g., centrifugal pump, mixed flow pump, axial flow pump) or a positive displacement pump (e.g., reciprocating pump, rotary pump) may be used, and the type may be selected appropriately according to the embodiment.

The third pipe 33 is located downstream of the cold pump 6 and upstream of the evaporator 8, connecting the cold pump 6 and the evaporator 8. The upstream end of the third pipe 33 is connected to the discharge port of the cold pump. The downstream end of the third pipe 33 is connected to the upstream end of the heated pipe 81 of the evaporator 8. The liquid working fluid pressurized by the cold pump 6 flows through the third pipe 33 and is supplied to the evaporator 8.

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

The above-mentioned heating fluid may be any medium with a higher temperature than the working fluid pressurized by the cooling pump 6, such as steam, hot water, seawater, or engine coolant introduced from outside the power recovery system 1. In this embodiment, the cooling water for the engine 111 of the above-mentioned floating structure 101 is used as the heating fluid. Because the cooling water for the engine 111 is hotter than seawater, the heat exchange efficiency in the evaporator 8 can be improved compared to when seawater or the like is used as the heating fluid.

The fourth pipe 34 is located downstream of the evaporator 8 and upstream of the cold turbine 10, connecting the evaporator 8 and the cold 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 inlet of the cold turbine 10. The gaseous working fluid heated through heat exchange in the evaporator 8 flows through the fourth pipe 34 and is supplied to the cold turbine 10.

The cold energy turbine 10 is configured to be driven by the gaseous working fluid produced in the evaporator 8. The cold energy turbine 10 has, for example, an impeller consisting of a rotating shaft and at least one rotor blade attached to the rotating shaft, and is configured so that the working fluid flowing in from the inlet acts on the rotor blade, causing the rotating shaft to rotate.

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

The fifth pipe 35 is located downstream of the cold turbine 10 and upstream of the condenser 2, connecting the cold turbine 10 and the condenser 2. The upstream end of the fifth pipe 35 is connected to the outlet of the cold turbine 10. The downstream end of the fifth pipe 35 is connected to the upstream end of the heating side pipe 21 of the condenser 2. The gaseous working fluid that drives the cold turbine 10 flows through the fifth pipe 35 and is supplied to the condenser 2.

(Position of Outlet 311 of First Pipe 31)
5A to 5D are schematic cross-sectional views of a gas-liquid separation tank 4 according to one embodiment of the present disclosure.
In the power recovery system 1 according to one embodiment of the present disclosure, as shown in Figures 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.

Because the outlet 311 of the first conduit 31 is located below the liquid level 41 in the gas-liquid separation tank 4, the working fluid condensed by the condenser 2 is supplied directly to the liquid phase 43, not to the gas phase 42. Therefore, compared to when the outlet 311 of the first conduit 31 is located above the liquid level 41 in the gas-liquid separation tank 4, i.e., when the working fluid condensed by the condenser 2 is supplied to the liquid phase 43 via the gas phase 42, the working fluid is not heated in the gas phase 42, and can be supplied to the liquid phase 43 at a low temperature. Furthermore, when liquid working fluid is supplied from the gas-liquid separation tank 4 to the cold heat pump 6, it can be supplied at a low temperature, which prevents the working fluid from gasifying in the pump section of the cold heat pump 6. This prevents cavitation in the pump section of the cold heat pump 6 and prevents gas from being sucked into the cold heat pump 6, allowing the cold heat pump 6 to operate normally.

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

Generally, the liquid level 41 in the gas-liquid separation tank 4 is located above the intermediate position (50% position). Therefore, with this configuration, the working fluid condensed by the condenser 2 is supplied directly to the gas-liquid separation tank 4 from the outlet 311 of the first pipe 31 provided in the liquid phase portion 43 of the gas-liquid separation tank 4, rather than to the gas phase portion 42 of the gas-liquid separation tank 4.

In one embodiment, as described above, the tank 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. As shown in Figures 5A to 5D, if the bottom surface 45 is defined as the 0% position and 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%.

With this configuration, the outlet 311 of the first conduit 31 and the inlet 321 of the second conduit 32 are located in the range of 0% to 25% in the vertical direction of the gas-liquid separation tank 4 (i.e., on the bottom surface 45 side). Therefore, the working fluid that flows out of the outlet 311 of the first conduit 31 into the liquid phase portion 43 is not heated in the liquid phase portion 43 vertically above where the temperature of the working fluid is higher, but remains at a low temperature before flowing into the inlet 321 of the second conduit 32 and being supplied to the cold heat pump 6. This makes it possible to suppress gasification of the working fluid in the pump portion of the cold heat pump 6.

In one embodiment, as shown in FIG. 5A, the first pipe line 31 and the second pipe line 32 are inserted into the gas-liquid separation tank 4 from the bottom surface 45. The first pipe line 31 and the second pipe line 32 extend vertically upward from the bottom surface 45 through the liquid phase portion 43 below the liquid surface 41.

In one embodiment, as shown in FIG. 5B, the first pipe line 31 and the second pipe line 32 are inserted into the gas-liquid separation tank 4 from the side surface 46. The first pipe line 31 and the second pipe line 32 extend horizontally from the side surface 46 through the liquid phase portion 43 below the liquid surface 41.

In some embodiments, as shown in Figures 5C and 5D, the first conduit 31 includes an internal conduit 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 below the liquid level 41. The aforementioned outlet 311 is formed at the downstream end of the internal conduit 31B.

With this configuration, the first conduit 31 is inserted into the gas-liquid separation tank 4 from above the liquid level 41 in the gas-liquid separation tank 4. This reduces the distance over which the first conduit 31 is exposed to the atmosphere, which has a higher temperature than the working fluid condensed by the condenser 2, compared to when the first conduit 31 is inserted into the gas-liquid separation tank 4 from below the liquid level 41. This prevents the working fluid in the first conduit 31 from being heated by external heat input outside the gas-liquid separation tank 4.

In one embodiment, as shown in FIG. 5C, the first pipeline 31 includes an external pipeline 31A located outside the gas-liquid separation tank 4 and an internal pipeline 31B located 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 vertically downward from the ceiling surface 44 to a liquid phase portion 43 below the liquid level 41.

In one embodiment, as shown in FIG. 5D, the first pipeline 31 includes an external pipeline 31A located outside the gas-liquid separation tank 4 and an internal pipeline 31B located 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.

In one embodiment, as shown in FIGS. 5A to 5D, the outlet 311 of the first pipeline 31 is positioned higher than the inlet 321 of the second pipeline 32 in the vertical direction of the gas-liquid separation tank 4.
With this configuration, even if the working fluid flowing through the first pipeline 31 contains bubbles, the bubbles flowing out from the outlet 311 can be prevented from flowing into the inlet 321 of the second pipeline 32.

In some embodiments, the working fluid described above includes a fluid with a boiling point below 0°C.

With this configuration, the power recovery system 1 can be operated by using a fluid with a boiling point below 0°C as the working fluid. One example of such a working fluid is propane, but the system can also be applied to working fluids other than propane flowing through the circulation flow path 3.

(Recirculation line 5)
2, the power recovery system 1 further includes a recirculation line 5 that branches off between the cold energy pump 6 and the evaporator 8 and returns the working fluid pressurized by the cold energy pump 6 to the gas-liquid separation tank 4. As shown in FIGS. 5A and 5B, an outlet 51 of the recirculation line 5 is provided so as to be located below the liquid level 41 of the gas-liquid separation tank 4.

With this configuration, the outlet 51 of the recirculation line 5 is located below the liquid level 41 in the gas-liquid separation tank 4, so the working fluid condensed by the condenser 2 is supplied directly to the liquid phase 43, rather than to the gas phase 42. Therefore, the working fluid that flows out of the outlet 51 of the recirculation line 5 into the liquid phase 43 is not heated in the gas phase 42 vertically above, where the temperature of the working fluid increases, but remains at a low temperature and flows into the inlet 321 of the second line 32 and is supplied to the cold heat pump 6. This makes it possible to suppress gasification of the working fluid in the pump section of the cold heat pump 6.

In the embodiment shown in Figure 2, the upstream end of the recirculation line 5 is connected to a third line 33 that connects the refrigeration pump 6 and the evaporator 8. A valve 5V is provided downstream of the upstream end of the recirculation line 5, allowing the recirculation line 5 to be opened and closed. A valve 33V is provided downstream of the connection point with the upstream end of the recirculation line 5 on the third line 33, allowing the third line 33 to be opened and closed.

When the cold heat pump 6 is started, valve 33V is closed and valve 5V is opened. As a result, the liquid working fluid stored in the gas-liquid separation tank 4 flows through the second pipe 32, is sucked into the cold heat pump 6, where it is pressurized, and is discharged into the third pipe 33. It then flows through the recirculation pipe 5 and is returned to the gas-liquid separation tank 4. In this way, when the cold heat pump 6 is started, the liquid working fluid circulates between the gas-liquid separation tank 4 and the cold heat pump 6.

After the cold heating pump 6 is started, when it reaches a predetermined operating state (operating), valve 33V is opened and valve 5V is closed. As a result, the working fluid pressurized by the cold heating pump 6 circulates through the circulation flow path 3 without flowing through the recirculation pipe 5.

In one embodiment, as described above, the outlet 51 of the recirculation line 5 is positioned in the liquid phase portion 43 below the liquid level 41 of the gas-liquid separation tank 4. If the bottom surface 45 is defined as the 0% position and 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 line 5 should be located in the range of 0% to 25%.

With this configuration, the working fluid that flows out of the outlet 51 of the recirculation line 5 into the liquid phase section 43 is not heated in the liquid phase section 43 vertically above where the temperature of the working fluid increases, but remains at a low temperature before flowing into the inlet 321 of the second line 32 and being supplied to the cold heat pump 6. This makes it possible to suppress gasification of the working fluid in the pump section of the cold heat pump 6.

In one embodiment, as shown in Figures 5A and 5B, the outlet 51 of the recirculation pipeline 5 is located higher than the inlet 321 of the second pipeline 32 in the vertical direction of the gas-liquid separation tank 4.
With this configuration, even if the working fluid flowing through the recirculation line 5 contains bubbles, the bubbles flowing out from the outlet 51 can be prevented from flowing into the inlet 321 of the second line 32.

In one embodiment, as shown in FIG. 5A, the recirculation line 5 is inserted into the gas-liquid separation tank 4 from the bottom surface 45. The recirculation line 5 extends vertically upward from the bottom surface 45 through the liquid phase portion 43 below the liquid surface 41.

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

5A and 5B , the outlet 51 of the recirculation line 5 is located farther from the inlet 321 of the second line 31 than the outlet 311 of the first line 31. In other words, the outlet 311 of the first line 31 is located closer to the inlet 321 of the second line 31 than the outlet 51 of the recirculation line 5.
With this configuration, the working fluid can be quickly guided from the outlet 311 of the first pipe 31 to the inlet 321 of the second pipe 31 .

(First sub-pipe line 7)
3 and 4, the power recovery system 1 includes a first sub-pipe 7 for supplying the working fluid condensed by the condenser 2 to the gas-liquid separation tank 4. As shown in FIGS. 5A and 5B, an outlet 71 of the first sub-pipe 7 is configured to be located above the liquid level 41 of the gas-liquid separation tank 4.

With this configuration, the working fluid flowing in from the first secondary line 7 is directly supplied to the gas phase 42 above the liquid level 41 in the gas-liquid separation tank 4 because the outlet 71 of the first secondary line 7 is located above the liquid level 41 in the gas-liquid separation tank 4. This reduces the temperature of the gas phase 42 above the liquid level 41 in the gas-liquid separation tank 4, allowing a low saturated vapor pressure to be obtained. Reducing the pressure (saturated vapor pressure) in the gas phase 42 above the liquid level 41 in the gas-liquid separation tank 4 also reduces the pressure at the outlet of the chiller turbine 10, improving turbine efficiency.

In one embodiment, as shown in Figures 3 and 4, the upstream end of the first secondary conduit 7 is connected to the first conduit 31 that connects the condenser 2 and the gas-liquid separation tank 4. The downstream side of the first secondary conduit 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). As shown in Figures 5A and 5B, the outlet 71 of the first secondary conduit 7 is positioned in the gas phase portion 42 above the liquid level 41 of the gas-liquid separation tank 4.

In one embodiment, as shown in FIG. 5A, the first secondary conduit 7 is inserted into the gas-liquid separation tank 4 from the ceiling surface 44. The first secondary conduit 7 extends vertically downward from the ceiling surface 44 through the gas phase portion 42 above the liquid surface 41.

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

(Control device 9, first valve 31V, second valve 7V)
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-pipe 7, and a control device 9 capable of controlling the valve apertures of the first valve 31V and the second valve 7V. The control device 9 is configured to control the valve apertures of the first valve 31V and the second valve 7V so that a difference ΔT between a temperature T1 of a gas phase portion 42 above a liquid level 41 in the gas-liquid separation tank 4 and a liquid temperature T2 of the liquid working fluid flowing out of the gas-liquid separation tank 4 and before being drawn into the cold energy pump 6 is greater than a first threshold value and smaller than a second threshold value that is greater than the first threshold value.

With this configuration, the difference ΔT is controlled between the first and second thresholds. When the difference ΔT is smaller than the first threshold, the temperature difference between the liquid temperature T2 and the temperature T1 of the gas phase 42, which is the saturation temperature, becomes smaller, making it easier for the working fluid at the liquid temperature T2 to gasify when it flows into the cold energy pump 6 or even with slight heating in the pump section of the cold energy pump 6. On the other hand, when the difference ΔT is larger than the second threshold, the temperature T1 of the gas phase 42 is high, and the gas phase 42 has a high saturated vapor pressure, which may reduce the turbine efficiency of the cold energy turbine 10. Therefore, by using the difference ΔT as a control parameter and controlling the difference ΔT using first and second thresholds, it is possible to increase turbine efficiency without causing gasification of the working fluid.

The second valve 7V is provided in the first secondary line 7 and can control the flow rate of the working fluid flowing through the first secondary line 7. The first valve 31V is provided in the first line 31 downstream of the connection position with the upstream end of the first secondary line 7 and can control the flow rate of the working fluid flowing through the first line 31. The first valve 31V and the second valve 7V are connected to actuators (motors, etc.) so that their valve openings can be automatically adjusted.

If temperature T1 rises, the gas phase 42 will reach a high saturated vapor pressure, increasing the pressure at the outlet of the cold energy turbine 10 and potentially reducing turbine efficiency. Furthermore, if liquid temperature T2 rises, the temperature of the working fluid supplied to the cold energy pump 6 will rise, potentially making the working fluid more susceptible to gasification in the pump section of the cold energy pump 6.

In order to lower the temperature T1, it is advisable to adjust the second valve 7V in the opening direction and the first valve 31V in the closing direction so that more of the liquid working fluid condensed by the condenser 2 flows into the first secondary pipe 7. This increases the amount of working fluid supplied from the outlet 71 of the first secondary pipe 7 to the gas phase section 42 of the gas-liquid separation tank 4, thereby lowering the temperature T1.
However, by adjusting the second valve 7V in the opening direction and the first valve 31V in the closing direction, the amount of working fluid flowing through the first pipeline 31 decreases. As a result, 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, and the liquid temperature T2 of the liquid phase portion 43 of the gas-liquid separation tank 4 rises.

On the other hand, in order to lower the liquid temperature T2, it is advisable to adjust the second valve 7V in the closing direction and the first valve 31V in the opening direction so that more of the liquid working fluid condensed by the condenser 2 flows into the first pipe 31. This increases the amount of working fluid supplied to the liquid phase section 43 from the outlet 311 of the first pipe 31, thereby lowering the liquid temperature T2.
However, by adjusting the second valve 7V in the closing direction and the first valve 31V in the opening direction, the amount of working fluid flowing through the first secondary conduit 7 decreases. As a result, it becomes difficult for the working fluid to be supplied from the outlet 71 of the first secondary conduit 7 to the gas phase section 42 of the gas-liquid separation tank 4, and the temperature T1 of the gas phase section 42 of the gas-liquid separation tank 4 rises.

In other words, there is a trade-off between temperature T1 and liquid temperature T2; if you try to lower temperature T1, liquid temperature T2 will rise, and if you try to lower liquid temperature T2, temperature T1 will rise. Therefore, a first threshold and a second threshold are set for the difference ΔT between temperature T1 and liquid temperature T2.

When temperature T1 rises, the temperature difference between temperature T1 and liquid temperature T2 increases, and so does the difference ΔT. Then, to prevent the difference ΔT from exceeding the second threshold, the second valve 7V is adjusted to close and the first valve 31V is adjusted to open. This lowers temperature T1, reduces the difference ΔT, and maintains the difference ΔT below the second threshold.

Furthermore, when the liquid temperature T2 rises, the temperature difference between the temperature T1 and the liquid temperature T2 decreases, and the difference ΔT also decreases. Then, the second valve 7V is adjusted in the closing direction and the first valve 31V is adjusted in the opening direction so that the difference ΔT does not become smaller than the first threshold value. This lowers the liquid temperature T2, increases the difference ΔT, and maintains the difference ΔT greater than the first threshold value.

The control device 9 is an electronic control unit for controlling the valve opening of the first valve 31V and the second valve 7V, and may be configured as a microcomputer including a CPU (processor) (not shown), memory such as ROM and RAM, a storage device such as an external storage device, an I/O interface, a communication interface, etc. The CPU may then operate (e.g., perform data calculations) according to instructions from a program loaded into the main storage device of the memory, thereby achieving valve opening control of the first valve 31V and the second valve 7V, as described below.

In one embodiment, as shown in FIG. 4, the first sensor 131 measures temperature T1 and is installed in the gas phase section 42 of the gas-liquid separation tank 4 so as to be able to transmit the temperature to the control device 9. The second sensor 132 measures liquid temperature T2 and is installed near the cold/heat pump 6 in the second pipeline 32 so as to be able to transmit the temperature to the control device 9. The first sensor 131 and the second sensor 132 continuously transmit the measured temperature T1 and liquid temperature T2 as signals to the control device 9 via a wired or wireless communication line.

The control device 9 performs feedback control so that the difference ΔT between the temperature T1 and the liquid temperature T2 is greater than a first threshold value and less than a second threshold value. Specifically, the control device 9 calculates the valve openings of the first valve 31V and the second valve 7V so that the difference ΔT is greater than the first threshold value and less than the second threshold value, and outputs command signals to the first valve 31V and the second valve 7V. The first valve 31V and the second valve 7V adjust their valve openings based on the input command signals. This series of controls is repeated at predetermined intervals, thereby maintaining the difference ΔT at a value greater than the first threshold value and less than the second threshold value.

(Second recirculation pipe 15)
In one embodiment, as shown in FIG. 2 , the power recovery system 1 further includes a second recirculation line 15 that branches off from the recirculation line 5 and returns the working fluid pressurized by the refrigeration pump 6 to the condenser 2, a first recirculation valve 16V that can adjust the flow rate of the working fluid flowing through the second recirculation line 15, a second recirculation valve 17V that can adjust the flow rate of the working fluid flowing downstream of the branch point of the recirculation line 5 with the second recirculation line 15, and a control device 9 that can control the valve openings of the first recirculation valve 16V and the second recirculation valve 17V.

The control device 9 is configured to control the valve openings of the first reflux valve 16V and the second reflux valve 17V so that when the liquid temperature of the working fluid pressurized by the cold heating pump 6 falls below a predetermined temperature (third threshold), the working fluid pressurized by the cold heating pump 6 is returned to the gas-liquid separation tank 4, and when the liquid temperature of the working fluid pressurized by the cold heating pump 6 exceeds the predetermined temperature (third threshold), the working fluid pressurized by the cold heating pump 6 is returned to the condenser 2.

If the temperature of the working fluid rises above a predetermined temperature due to heat input from the cold pump 6, there is a risk that returning this heated working fluid to the gas-liquid separation tank 4 will raise the temperature of the working fluid stored in the gas-liquid separation tank 4. Therefore, with this configuration, if the temperature of the working fluid rises above a predetermined temperature (third threshold) due to heat input from the cold pump 6, the working fluid is returned to the condenser 2, where its temperature is reduced before being supplied to the gas-liquid separation tank 4, thereby preventing the temperature of the working fluid stored in the gas-liquid separation tank 4 from rising.

In the embodiment shown in FIG. 2 , the first recirculation valve 16V is provided in the second recirculation line 15 and can control the flow rate of the working fluid flowing through the second recirculation line 15. The second recirculation valve 17V is provided in the recirculation line 5 downstream of the branch point with the second recirculation line 15 and can control the flow rate of the working fluid flowing through the recirculation line 5 downstream of the branch point. The first recirculation valve 16V and the second recirculation valve 17V are connected to actuators (e.g., motors) so that their valve openings can be automatically adjusted. A third sensor 133 is provided in the recirculation line 5 upstream of the branch point with the second recirculation line 15, capable of measuring the temperature of the working fluid flowing through the recirculation line 5 (the temperature of the working fluid pressurized by the refrigeration pump 6). The third sensor 133 continuously transmits the measured working fluid temperature as a signal to the control device 9 via a wired or wireless communication line.

(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 off 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.

With this configuration, if the working fluid is not sufficiently liquefied in the condenser 2, the gas in the first pipeline 31 can be discharged to the outside by providing a gas vent pipe 11 in the first pipeline 31. This prevents gas from flowing into the liquid phase portion 43, which is located below the liquid level 41 in the gas-liquid separation tank 4, and prevents gas from being sucked into the cold heating pump 6.

In the embodiment shown in Figure 4, the gas vent pipe 11 branches off from the first pipeline 31 and extends vertically upward. The downstream end of the gas vent pipe 11 is located vertically above the liquid level 41 of the gas-liquid separation tank 4.

In the embodiment shown in FIG. 4, the downstream end of the gas vent pipe 11 is connected to the exhaust gas pipe 14. The exhaust gas pipe 14 connects the gas vent pipe 11 to the gas-liquid separation tank 4. As shown in FIGS. 5A and 5B, the downstream side of the exhaust gas pipe 14 is connected to the gas-liquid separation tank 4 from a position vertically above the liquid level 41 of the gas-liquid separation tank 4. The outlet 141 of the exhaust gas pipe 14 is positioned in the gas phase 42 above the liquid level 41 of the gas-liquid separation tank 4. With this configuration, the gaseous working fluid discharged outside the first pipe 31 can be circulated within the power recovery system 1 without being released outside the power recovery system 1. This reduces loss of working fluid circulating within the power recovery system 1.

In one embodiment, as shown in FIG. 5A, the exhaust gas pipe 14 is inserted into the gas-liquid separation tank 4 from the ceiling surface 44. The exhaust gas pipe 14 extends vertically downward from the ceiling surface 44 through the gas phase portion 42 above the liquid surface 41.

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

The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these embodiments.

The contents described in the above-mentioned embodiments can be understood, for example, as follows:

1) A power recovery system (1) according to one aspect includes:
A power recovery system (1) for recovering cold energy contained in a liquefied gas as power via 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 the working fluid condensed in the condenser (2) into liquid and gas and store the separated fluid;
a cold/heat pump (6) configured to pressurize 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 pressurized by the cold pump (6) and a heating fluid introduced from outside the power recovery system;
a cold turbine (10) configured to be driven by the gaseous working fluid produced in the evaporator (8);
and 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 so that an outlet (311) of the first pipeline (31) is located below the liquid level (41) of the gas-liquid separation tank (4).

In the power recovery system disclosed herein, the outlet of the first pipe is located below the liquid level in the gas-liquid separation tank, so the working fluid condensed by the condenser is supplied directly to the liquid phase, not to the gas phase. Therefore, compared to when the outlet of the first pipe is located above the liquid level in the gas-liquid separation tank, i.e., when the working fluid condensed by the condenser is supplied to the liquid phase via the gas phase, the working fluid is not heated in the gas phase, and can be supplied to the liquid phase at a low temperature. Furthermore, when liquid working fluid is supplied from the gas-liquid separation tank to the cold energy pump, it can be allowed to flow in at a low temperature, thereby suppressing gasification of the working fluid in the pump section of the cold energy pump. This suppresses cavitation in the pump section of the cold energy pump and prevents gas from being sucked into the cold energy pump, allowing the cold energy pump to operate normally.

2) A 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 cold heating pump (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%.

With this configuration, the outlet of the first pipe and the inlet of the second pipe are located within a range of 0% to 25% of the vertical height of the gas-liquid separation tank 4 (i.e., on the bottom side). Therefore, the working fluid that flows out of the liquid phase portion from the outlet of the first pipe is not heated by the liquid phase portion vertically above where the temperature of the working fluid is higher, but remains at a low temperature before flowing into the inlet of the second pipe and being supplied to the cold energy pump. This makes it possible to suppress gasification of the working fluid in the pump portion of the cold energy pump.

3) A further aspect of the power recovery system is the power recovery system (1) described in 1) or 2), in which the working fluid includes a fluid having a boiling point below 0°C.

With this configuration, the power recovery system can be operated by using a fluid with a boiling point below 0°C as the working fluid. One example of such a working fluid is propane, but the system can also be applied to working fluids other than propane flowing through the circulation flow path.

4) A power recovery system according to yet another aspect is the power recovery system (1) according to any one of 1) to 3), further comprising a recirculation pipe (5) branching off between the cold heat pump (6) and the evaporator (8) and returning the working fluid pressurized by the cold heat pump (6) to the gas-liquid separation tank (4);
The outlet (51) of the recirculation pipe (5) is located below the liquid level in the gas-liquid separation tank (4).

With this configuration, the outlet of the recirculation line is located below the liquid level in the gas-liquid separation tank, so the working fluid condensed by the condenser is supplied directly to the liquid phase, not the gas phase. Therefore, the working fluid that flows out of the outlet of the recirculation line into the liquid phase is not heated in the liquid phase vertically above, where the temperature of the working fluid is higher, but remains at a low temperature before flowing into the inlet of the second line and being supplied to the cold energy pump. This makes it possible to suppress gasification of the working fluid in the pump section of the cold energy pump.

5) A power recovery system according to yet another aspect is the power recovery system (1) according to 4),
a second recirculation pipe (15) branching from the recirculation pipe (5) and returning the working fluid pressurized by the cold 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 line (15);
a second reflux valve (17V) capable of adjusting the flow rate of the working fluid flowing downstream of a branch point of the recirculation pipe (5) with the second recirculation pipe (15);
a control device (9) capable of controlling the opening degree of each 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 heating pump (6) falls below a predetermined temperature, the working fluid pressurized by the cold heating pump (6) is returned to the gas-liquid separation tank (4), and
When the liquid temperature of the working fluid pressurized by the cold heating pump (6) exceeds the predetermined temperature, the valve openings of the first reflux valve (16V) and the second reflux valve (17V) are controlled so that the working fluid pressurized by the cold heating pump (6) is returned to the condenser (2).

If the temperature of the working fluid rises above a predetermined temperature due to heat input from the refrigeration pump, returning the heated working fluid to the gas-liquid separation tank may raise the temperature of the working fluid stored in the gas-liquid separation tank. Therefore, with this configuration, if the temperature of the working fluid rises above a predetermined temperature (third threshold) due to heat input from the refrigeration pump, the working fluid is returned to the condenser 2, where its temperature is reduced before being supplied to the gas-liquid separation tank, thereby preventing the temperature of the working fluid stored in the gas-liquid separation tank from rising.

6) A power recovery system according to yet another aspect is the power recovery system (1) described in any one of items 1) to 5), further comprising a first sub-pipe (7) for supplying the working fluid condensed by the condenser (2) to the gas-liquid separation tank (4), wherein an outlet (71) of the first sub-pipe (7) is configured to be positioned above the liquid level (41) in the gas-liquid separation tank (4).

With this configuration, the gas phase portion above the liquid level in the gas-liquid separation tank has the outlet of the first secondary pipe located above the liquid level in the gas-liquid separation tank, so the working fluid flowing in from the first secondary pipe is directly supplied to the gas phase portion. This reduces the temperature of the gas phase portion above the liquid level in the gas-liquid separation tank, making it possible to obtain a low saturated vapor pressure. Reducing the pressure (saturated vapor pressure) in the gas phase portion above the liquid level in the gas-liquid separation tank also reduces the pressure at the outlet of the chiller turbine, improving turbine efficiency.

7) A power recovery system according to yet another aspect is the power recovery system according to 6),
a first valve (31V) capable of adjusting the flow rate of the working fluid flowing through the first pipe (31);
a second valve (7V) capable of adjusting the flow rate of the working fluid flowing through the first sub-pipe (7);
a control device (9) capable of controlling the opening degree of each of the first valve (31V) and the second valve (7V),
The control device (9) is configured to control the valve openings of the first valve (31V) and the second valve (7V) so that a difference ΔT between a temperature T1 of the gas phase above the liquid level (41) in the gas-liquid separation tank (4) and a liquid temperature T2 of the working fluid in a liquid state before it flows out of the gas-liquid separation tank (4) and is sucked into the refrigeration pump (6) is greater than a first threshold value and smaller than a second threshold value that is greater than the first threshold value.

With this configuration, the difference ΔT is controlled between a first threshold and a second threshold. When the difference ΔT is smaller than the first threshold, the temperature difference between the liquid temperature T2 and the gas phase temperature T1, which is the saturation temperature, becomes smaller, making it easier for the working fluid at liquid temperature T2 to gasify when it flows into the cold energy pump or even with slight heating in the pump section of the cold energy pump. On the other hand, when the difference ΔT is larger than the second threshold, the gas phase temperature T1 is high, and the gas phase has a high saturated vapor pressure, which may reduce the turbine efficiency of the cold energy turbine 10. Therefore, by using the difference ΔT as a control parameter and controlling the difference ΔT using first and second thresholds, it is possible to increase turbine efficiency without causing gasification of the working fluid.

8) A power recovery system according to yet another aspect is the power recovery system (1) according to any one of 1) to 7),
The system further includes a gas vent pipe (11) branched off 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).

With this configuration, if the working fluid is not sufficiently liquefied in the condenser, a gas vent pipe is provided in the first pipeline, allowing the gas in the first pipeline to be discharged to the outside. This prevents gas from flowing into the liquid phase, which is located below the liquid level in the gas-liquid separation tank, and prevents gas from being sucked into the cooling pump section.

9) A power recovery system according to yet another aspect is the power recovery system (1) according to any one of 1) to 8),
The first pipe (31) includes an internal pipe (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 below the liquid level.

With this configuration, the first pipe is inserted into the gas-liquid separation tank from above the liquid level in the gas-liquid separation tank. This reduces the distance over which the first pipe is exposed to the atmosphere, which has a higher temperature than the working fluid condensed by the condenser, compared to when the first pipe is inserted into the gas-liquid separation tank from below the liquid level. This prevents the working fluid in the first pipe from being heated by external heat input outside the gas-liquid separation tank.

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

Claims (8)

A power recovery system for recovering cold energy contained in a liquefied gas as power via 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 the working fluid condensed by the condenser into liquid and gas and store the separated fluid;
a cold/heat pump 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 cold pump and a heating fluid introduced from outside the power recovery system;
a cold turbine configured to be driven by the gaseous working fluid produced in the evaporator;
a first pipe for supplying the working fluid condensed by the condenser to the gas-liquid separation tank, the first pipe having an outlet positioned below a liquid level in 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 heating 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 a range of 0% to 25%, and
The inlet of the second pipe is located lower than the outlet of the first pipe.
Power recovery system. A power recovery system for recovering cold energy contained in a liquefied gas as power via 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 the working fluid condensed by the condenser into liquid and gas and store the separated fluid;
a cold/heat pump 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 cold pump and a heating fluid introduced from outside the power recovery system;
a cold turbine configured to be driven by the gaseous working fluid produced in the evaporator;
a first pipe for supplying the working fluid condensed by the condenser to the gas-liquid separation tank, the first pipe having an outlet positioned below a liquid level in the gas-liquid separation tank;
a recirculation line branching off between the cold heating pump and the evaporator, for returning the working fluid pressurized by the cold heating pump to the gas-liquid separation tank ,
The outlet of the recirculation line is located below the liquid level in the gas-liquid separation tank.
Power recovery system. A power recovery system for recovering cold energy contained in a liquefied gas as power via 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 the working fluid condensed by the condenser into liquid and gas and store the separated fluid;
a cold/heat pump 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 cold pump and a heating fluid introduced from outside the power recovery system;
a cold turbine configured to be driven by the gaseous working fluid produced in the evaporator;
a first pipe for supplying the working fluid condensed by the condenser to the gas-liquid separation tank, the first pipe having an outlet positioned below a liquid level in the gas-liquid separation tank;
a first sub-pipe for supplying the working fluid condensed by the condenser to the gas-liquid separation tank, the first sub-pipe having an outlet located above the liquid level in the gas-liquid separation tank.
Power recovery system. The working fluid includes a fluid having a boiling point below 0°C.
4. A power recovery system according to any one of claims 1 to 3 . a second recirculation line branching from the recirculation line and returning the working fluid pressurized by the refrigeration pump to the condenser;
a first recirculation valve capable of adjusting the flow rate of the working fluid flowing through the second recirculation line;
a second recirculation valve capable of adjusting a flow rate of the working fluid flowing in the recirculation pipe downstream of a branch position between the recirculation pipe and the second recirculation pipe;
a control device capable of controlling the opening degree of each of the first reflux valve and the second reflux valve,
The control device
When the liquid temperature of the working fluid pressurized by the cold heating pump falls below a predetermined temperature, the working fluid pressurized by the cold heating pump is returned to the gas-liquid separation tank, and
3. The power recovery system according to claim 2, wherein the valve opening degree of each of the first return valve and the second return valve is controlled so that the working fluid pressurized by the cold heating pump is returned to the condenser when the liquid temperature of the working fluid pressurized by the cold heating pump exceeds the predetermined temperature. a first valve capable of adjusting the flow rate of the working fluid flowing through the first pipe;
a second valve capable of adjusting the flow rate of the working fluid flowing through the first sub-pipe;
a control device capable of controlling the opening degree of each of the first valve and the second valve,
4. The power recovery system according to claim 3, wherein the control device is configured to control the valve opening degrees of the first valve and the second valve so that a difference ΔT between a temperature T1 of the gas phase above the liquid level in the gas-liquid separation tank and a liquid temperature T2 of the working fluid in liquid form before it flows out of the gas-liquid separation tank and is sucked into the refrigeration pump is greater than a first threshold value and smaller than a second threshold value that is greater than the first threshold value. a gas vent pipe branching off from the first pipeline for discharging the gaseous working fluid that has not been condensed in the condenser to the outside of the first pipeline;
A power recovery system according to any one of claims 1 to 6 . the first pipe includes an internal pipe that is inserted into the gas-liquid separation tank from above the liquid level in the gas-liquid separation tank and extends below the liquid level.
A power recovery system according to any one of claims 1 to 7 .