A liquefied natural gas cold energy power generation device

Abstract

In order to overcome the problem in the prior art that the liquefied natural gas cold energy power generation device is affected by the temperature of the reheating medium in winter, resulting in low power generation or even failure to operate normally, the present invention discloses a liquefied natural gas cold energy power generation device, including a Rankine cycle power generation unit loaded with a working medium; an LNG liquid phase pipe, which introduces LNG in a liquid phase state into the Rankine cycle power generation unit for heat exchange; a reheating unit loaded with a reheating medium, and an auxiliary heating unit, which gradually extends from the outside of the reheating unit to the vicinity of the bottom of the reheating unit to heat the reheating medium. The present invention provides a liquefied natural gas cold energy power generation device, which uses an auxiliary heating unit to heat the reheating medium to compensate for the reheating effect of the working medium when the temperature of the reheating medium is lower than 5°C~10°C in winter. It has high integration, is not affected by external environmental factors, and efficiently recovers cold energy in the LNG gasification process, which can ensure the continuous and stable operation of LNG cold energy power generation throughout the year.

Description

Technical Field

[0001] The present invention belongs to the technical field of liquefied natural gas cold energy utilization, and in particular relates to a liquefied natural gas cold energy power generation device. Background Art

[0002] Liquefied Natural Gas (LNG) is a highly efficient and clean energy source. my country currently has more than 20 large-scale LNG receiving stations in operation along the coast, and more than 40 large-scale LNG receiving stations under construction or planned. At large-scale LNG receiving stations along the coast, in order to meet the transportation requirements of the natural gas pipeline network, LNG needs to be pressurized by a high-pressure pump and gasified into room-temperature gas before being sent into the natural gas pipeline network. During the LNG gasification process, LNG releases a large amount of cold energy. Recycling the cold energy released during the LNG gasification process is a policy requirement to improve energy utilization efficiency, comply with the national policy of energy conservation and emission reduction, and develop a "low-carbon economy".

[0003] The performance of LNG cold energy power generation is closely related to external environmental factors, especially in large coastal LNG receiving stations, which generally use low-temperature Rankine cycle power generation. In this power generation process, the low-temperature natural gas and circulating working fluid generally use seawater as a heat source for reheating to meet the natural gas transmission temperature requirements, and at the same time, the circulating working fluid is gasified so that it can enter the power generation expander for expansion. In winter, due to the low seawater temperature, the low-temperature natural gas reheating requirements cannot be met. At the same time, the low temperature of the circulating working fluid entering the expansion generator will cause the expander to generate low power. Therefore, when the seawater temperature in winter is lower than 5℃~10℃, the cold energy power generation device of the large LNG receiving station has the problem of low power generation or even failure to operate normally, which has a great impact on the operation of the cold energy power generation device. Summary of the invention

[0004] In order to overcome the problem in the prior art that the liquefied natural gas cold energy power generation device is affected by the temperature of the reheating medium in winter, resulting in low power generation or even failure to operate normally, the present invention provides a liquefied natural gas cold energy power generation device, which uses an auxiliary heat unit to heat the reheating medium to compensate for the reheating effect of the working medium when the temperature of the reheating medium is lower than 5°C~10°C in winter. The device has high integration, is not affected by external environmental factors, and efficiently recovers cold energy in the LNG gasification process, which can ensure continuous and stable operation of LNG cold energy power generation throughout the year.

[0005] The technical solution adopted by the present invention is:

[0006] A liquefied natural gas cold energy power generation device, comprising

[0007] The Rankine cycle power generation unit is loaded with a working fluid; the working fluid in the liquid phase is pressurized to become a high-pressure liquid phase, and after the high-pressure liquid phase is reheated to the gas phase, the volume expands to do work externally and thereby generate electricity;

[0008] An LNG liquid phase pipe, for introducing LNG in a liquid phase into the Rankine cycle power generation unit and exchanging heat with a working medium in a low-pressure gas phase in the Rankine cycle power generation unit;

[0009] A reheating unit, loaded with a reheating medium, reheats the working fluid in a low-temperature liquid phase state to a working fluid in a superheated high-temperature gas phase state; and

[0010] The auxiliary heating unit gradually extends from the outside of the reheating unit to the vicinity of the bottom of the reheating unit to heat the reheating medium.

[0011] In one embodiment disclosed in the present application, the Rankine cycle power generation unit comprises

[0012] Expansion generator set;

[0013] A first heat exchanger having independent first heat exchange channels and second heat exchange channels;

[0014] Working fluid booster pump;

[0015] A second heat exchanger, immersed in the reheating medium of the reheating unit;

[0016] A first pipeline, two ends of which are respectively connected to the outlet end of the expansion generator set and the inlet end of the second heat exchange channel of the first heat exchanger;

[0017] A second pipeline, two ends of which are respectively connected to the outlet end of the second heat exchange channel of the first heat exchanger and the inlet end of the working fluid booster pump;

[0018] a third pipeline, both ends of which are connected to the outlet of the working fluid booster pump and the inlet of the second heat exchanger respectively; and

[0019] a fourth pipeline, two ends of which are respectively connected to the outlet end of the second heat exchanger and the inlet end of the expansion generator set;

[0020] Wherein, the LNG liquid phase pipe is connected to the first heat exchange channel of the first heat exchanger.

[0021] In one embodiment disclosed in the present application, the reheating unit comprises

[0022] A water tank, a closed structure, containing a reheating medium;

[0023] An exhaust port is connected to the top of the pool.

[0024] In one embodiment disclosed in the present application, the auxiliary heat unit comprises

[0025] A burner having a combustion chamber; the combustion chamber gradually extends from the outside of the recuperation unit to near the bottom of the recuperation unit;

[0026] Fan;

[0027] a fuel gas pipe connected to the burner; and

[0028] The two ends of the air duct are respectively connected to the burner and the fan.

[0029] In one embodiment disclosed in the present application, the device further includes an LNG gas supply unit.

[0030] In one embodiment disclosed in the present application, the LNG gas supply unit comprises

[0031] A third heat exchanger, immersed in the reheating medium of the reheating unit;

[0032] a fifth pipeline, both ends of which are respectively connected to the outlet end of the first heat exchange channel of the first heat exchanger and the inlet end of the third heat exchanger; and

[0033] a sixth pipeline, both ends of which are respectively connected to the outlet end of the third heat exchanger and the gas supply network;

[0034] Wherein, the LNG liquid phase pipe is connected to the inlet end of the first heat exchange channel of the first heat exchanger.

[0035] In one embodiment disclosed in the present application, the second heat exchanger and the third heat exchanger adopt an integrated coupled heat exchanger; the coupled heat exchanger has a first channel, a second channel and a third channel; the working medium flows in the first channel; the natural gas flows in the second channel; the first channel and the second channel are located in the third channel, and the reheating medium flows therein.

[0036] In one embodiment disclosed in the present application, the LNG gas supply unit further includes a bypass valve, and two ends of the bypass valve are respectively connected to the LNG liquid phase and the fifth pipeline.

[0037] The beneficial effects of the present invention are:

[0038] In order to solve the problem that large LNG receiving stations are affected by the reheating heat source in winter, resulting in low power generation of cold energy power generation devices or even unable to operate normally, the present invention provides a liquefied natural gas cold energy power generation device. The device includes a Rankine cycle power generation unit, an LNG liquid phase pipe, a reheating unit and an auxiliary heat unit. Among them, the Rankine cycle power generation unit is loaded with propane and other working fluids, and circulates internally. When the working fluid expands from a high-pressure gas phase state to a low-pressure gas phase state, the volume expands, and work is done externally, thereby generating electricity. The LNG liquid phase pipe introduces LNG in a liquid phase state into the Rankine cycle power generation unit, and exchanges heat with the working fluid in a low-pressure gas phase state in the Rankine cycle power generation unit. The low temperature of the LNG in a liquid phase state flowing in the LNG liquid phase pipe is utilized to cool the working fluid in a low-pressure gas phase state into a working fluid in a low-temperature liquid phase state. The reheating unit is filled with a reheating medium such as water, and the flow passage of the working fluid in the low-temperature liquid phase is immersed in the reheating medium, thereby reheating the pressurized high-pressure low-temperature liquid phase working fluid to the superheated high-temperature gas phase working fluid. The auxiliary heating unit gradually extends from the outside of the reheating unit to the bottom of the reheating unit to heat the reheating medium to compensate for the reheating effect of the working fluid when the temperature of the reheating medium is lower than 5°C~10°C in winter. The liquefied natural gas cold energy power generation device of the present invention has a high degree of integration and is not affected by external environmental factors, which can ensure the continuous and stable operation of LNG cold energy power generation throughout the year. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 This is a schematic diagram of the connection structure of the liquefied natural gas cold energy power generation device in Example 1.

[0041] Figure 2 This is a schematic diagram of the connection structure of the liquefied natural gas cold energy power generation device in Example 2.

[0042] Figure 3 This is a schematic diagram of the connection structure of the liquefied natural gas cold energy power generation device in Example 3. DETAILED DESCRIPTION

[0043] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0044] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0045] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention.

[0046] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0047] Example 1

[0048] In the process of LNG cold energy power generation, the circulating working fluid generally uses seawater as a heat source for reheating, so that the circulating working fluid is vaporized so that it can enter the power generation expander for expansion. In winter, due to the low seawater temperature, the reheating requirements cannot be met. At the same time, the low temperature of the circulating working fluid entering the expansion generator will cause the expander to generate low power. Therefore, when the seawater temperature in winter is lower than 5℃~10℃, the cold energy power generation device of the large LNG receiving station has the problem of low power generation or even failure to operate normally, which has a great impact on the operation of the cold energy power generation device.

[0049] In order to solve the problem that the power generation of cold energy power generation devices of large LNG receiving stations is low or even cannot operate normally due to the influence of the reheating heat source in winter, the present invention provides a liquefied natural gas cold energy power generation device, the structure of which is as shown in the attached figure. Figure 1As shown. The device includes a Rankine cycle power generation unit 1, an LNG liquid phase pipe 2, a reheating unit 3 and an auxiliary heat unit 4. Among them, the Rankine cycle power generation unit 1 is loaded with a working fluid such as propane, and circulates internally. When the working fluid expands from a high-pressure gas phase state to a low-pressure gas phase state, the volume expands, and work is performed externally, thereby generating electricity. The LNG liquid phase pipe 2 introduces LNG in a liquid phase state into the Rankine cycle power generation unit 1, and exchanges heat with the working fluid in a low-pressure gas phase state in the Rankine cycle power generation unit 1. The low temperature of the LNG in a liquid phase state flowing in the LNG liquid phase pipe 2 is utilized to cool the working fluid in a gas phase state into a working fluid in a low-temperature liquid phase state. The reheating unit 3 is filled with a reheating medium such as water, and the flow path of the working fluid in a low-temperature liquid phase state is immersed in the reheating medium, thereby reheating the pressurized high-pressure and low-temperature liquid phase state working fluid to a superheated high-temperature gas phase state working fluid. The auxiliary heating unit 4 gradually extends from the outside of the reheating unit to the bottom of the reheating unit to heat the reheating medium. The liquefied natural gas cold energy power generation device in this embodiment has high integration and is not affected by external environmental factors, which can ensure the continuous and stable operation of LNG cold energy power generation throughout the year.

[0050] Specifically, the Rankine cycle power generation unit 1 includes an expansion power generation unit 11 , a first heat exchanger 12 , a working fluid booster pump 13 , and a second heat exchanger 14 .

[0051] The first heat exchanger 12 is a stainless steel U-shaped heat exchanger having an independent first heat exchange channel 121 and a second heat exchange channel 122. The LNG liquid phase pipe 2 is connected to the inlet end of the first heat exchange channel 121. The expansion generator set 11 is composed of a centripetal turbine expander and a generator, etc., and its outlet end is connected to the inlet end of the second heat exchange channel 122 through a first pipeline 15. The working fluid booster pump 13 adopts a barrel bag submersible pump, and its inlet end is connected to the outlet end of the second heat exchange channel 122 through a second pipeline 16. The outlet end of the working fluid booster pump 13 is connected to the inlet end of the second heat exchanger 14 through a third pipeline 17. The outlet end of the second heat exchanger 14 and the inlet end of the expansion generator set 11 are connected through a fourth pipeline 18. The second heat exchanger 14 is immersed in the reheating medium.

[0052] When the working medium in the gas phase and the LNG in the liquid phase flow in the first heat exchange channel 121 and the second heat exchange channel 122 respectively, heat exchange is performed, and the working medium in the gas phase is cooled and becomes a working medium in the low-temperature liquid phase. When the working medium in the high-pressure and low-temperature liquid phase flows through the second heat exchanger 14, it is converted into a working medium in the superheated high-temperature and high-pressure gas phase. When the working medium in the superheated high-temperature and high-pressure gas phase passes through the expansion generator set 11, the volume expands, so that the expansion generator set 11 performs work externally and generates electricity.

[0053] The reheating unit 3 includes a water pool 31 and an exhaust port 32 .

[0054] The water pool 31 is a closed structure and contains a reheating medium such as seawater. The liquid level of the reheating medium needs to be higher than the second heat exchanger 14. The exhaust port 32 is connected to the top of the water pool 31. The liquid level of the reheating medium in the water pool 31 is set according to requirements and replenished in time to maintain the liquid level.

[0055] The auxiliary heating unit 4 includes a fan 41 , a burner 42 and a fuel gas pipe 43 .

[0056] The fan 31 is connected to the burner 42 via an air duct 44. The fuel gas pipe 43 is also connected to the burner 42. The combustion chamber 421 of the burner 42 gradually sinks into the water pool 31 and extends to the bottom of the second heat exchanger 14. After the fuel gas is burned, the high-temperature flue gas generated overflows from the combustion chamber 421, contacts and mixes with the reheating medium, and heats the reheating medium.

[0057] In this embodiment, the principle of the liquefied natural gas cold energy power generation device is:

[0058] The high-pressure LNG enters the first heat exchanger 12 to transfer the cold energy to the working fluid in the gas phase, cooling it to a working fluid in the low-temperature liquid phase. The working fluid in the low-temperature liquid phase is pressurized by the working fluid booster pump 13, and the pressurized high-pressure and low-temperature liquid phase working fluid enters the second heat exchanger 14. In the reheating unit 3, the second heat exchanger 14 performs heat exchange, and the working fluid in the high-pressure and low-temperature liquid phase is heated and vaporized to a high-pressure gas phase, and then enters the expansion generator set 11. The working fluid volume expands, and during the expansion process, the expander drives the generator to do external work, thereby converting the cold energy of LNG into electrical energy. The expanded low-pressure gas phase working fluid enters the first heat exchanger 12 again, completing a cycle.

[0059] The heat required for heating and gasifying the working medium in the high-pressure and low-temperature liquid phase state to the high-pressure superheated gas phase state is provided by the reheating medium in the reheating unit 3 .

[0060] The high-pressure LNG of a large LNG receiving station has a pressure of 9.5MPa and a temperature of -145℃. The seawater temperature in winter is 5℃, and propane is used as the circulating medium. Under this condition, the power generation capacity per ton of LNG is about 19 KW. After adopting the device of the present invention, the cold energy of LNG can be efficiently utilized to maintain a stable power generation state all year round.

[0061] Example 2

[0062] In the process of LNG cold energy power generation, the low-temperature natural gas and circulating working fluid generally use seawater as a heat source for reheating to meet the natural gas transmission temperature requirements, and at the same time, the circulating working fluid is gasified so that it can enter the power generation expander for expansion. In winter, due to the low seawater temperature, the low-temperature natural gas reheating requirements cannot be met. At the same time, the low temperature of the circulating working fluid entering the expansion generator will cause the expander to generate low power. Therefore, when the seawater temperature is lower than 5℃~10℃ in winter, the cold energy power generation device of the large LNG receiving station has the problem of low power generation or even failure to operate normally, which has a great impact on the operation of the cold energy power generation device.

[0063] In order to solve the problem that the power generation of cold energy power generation devices of large LNG receiving stations is low or even cannot operate normally due to the influence of the reheating heat source in winter, and the problem that the temperature requirements for natural gas transmission are not met, the present invention provides a liquefied natural gas cold energy power generation device, the structure of which is as shown in the attached figure. Figure 2 As shown. The device includes a Rankine cycle power generation unit 1, an LNG liquid phase pipe 2, a reheating unit 3, an auxiliary heat unit 4 and an LNG gas supply unit 5. Among them, the Rankine cycle power generation unit 1 is loaded with a working medium such as propane, and circulates internally. When the working medium expands from a high-pressure gas phase state to a low-pressure gas phase state, the volume expands, and work is performed externally, thereby realizing power generation. The LNG liquid phase pipe 2 introduces LNG in a liquid phase state into the Rankine cycle power generation unit 1, and exchanges heat with the working medium in a gas phase state in the Rankine cycle power generation unit 1. The low temperature of the LNG in the liquid phase state flowing in the LNG liquid phase pipe 2 is used to cool the working medium in the gas phase state into a working medium in a low-temperature liquid phase state. The reheating unit 3 is filled with a reheating medium such as water, and the flow passage of the pressurized high-pressure low-temperature liquid phase working medium is immersed in the reheating medium, and the flow passage of the low-temperature natural gas in the gas phase state is immersed in the reheating medium, thereby gasifying the working medium in the high-pressure low-temperature liquid phase state into a working medium in a high-pressure superheated gas phase state. The auxiliary heating unit 4 gradually extends from the outside of the reheating unit to the bottom of the reheating unit to heat the reheating medium. The LNG gas supply unit 5 reheats the low-temperature natural gas to the required temperature of the external transmission pipeline network and then enters the gas supply pipeline network.

[0064] The liquefied natural gas cold energy power generation device in this embodiment has a high degree of integration and is not affected by external environmental factors, which can ensure the continuous and stable operation of LNG cold energy power generation throughout the year. At the same time, the liquefied natural gas cold energy power generation device in this embodiment has power generation and gasification functions, that is, it fully utilizes LNG cold energy and realizes LNG gas supply at the same time, and has a wider range of functions.

[0065] Specifically, the Rankine cycle power generation unit 1 includes an expansion power generation unit 11 , a first heat exchanger 12 , a working fluid booster pump 13 , and a second heat exchanger 14 .

[0066] The first heat exchanger 12 is a stainless steel U-shaped heat exchanger having an independent first heat exchange channel 121 and a second heat exchange channel 122. The LNG liquid phase pipe 2 is connected to the inlet end of the first heat exchange channel 121. The outlet end of the first heat exchange channel 121 is connected to the LNG gas supply unit. The expansion generator set 11 is composed of a centripetal turbine expander and a generator, etc., and its outlet end is connected to the inlet end of the second heat exchange channel 122 through a first pipeline 15. The working fluid booster pump 13 adopts a barrel bag submersible pump, and its inlet end is connected to the outlet end of the second heat exchange channel 122 through a second pipeline 16. The outlet end of the working fluid booster pump 13 is connected to the inlet end of the second heat exchanger 14 through a third pipeline 17. The outlet end of the second heat exchanger 14 and the inlet end of the expansion generator set 11 are connected through a fourth pipeline 18. The second heat exchanger 14 is immersed in the reheating medium.

[0067] When the working medium in the gas phase and the LNG in the liquid phase flow in the first heat exchange channel 121 and the second heat exchange channel 122 respectively, heat exchange is performed, and the working medium in the gas phase is cooled and becomes a working medium in the low-temperature liquid phase. When the working medium in the high-pressure and low-temperature liquid phase flows through the second heat exchanger 14, it is converted into a working medium in the high-pressure superheated gas phase. When the high-pressure gas phase working medium passes through the expansion generator set 11, the volume expands, so that the expansion generator set 11 performs work externally to generate electricity.

[0068] The reheating unit 3 includes a water pool 31 and an exhaust port 32 .

[0069] The water pool 31 is a closed structure and contains a reheating medium such as seawater. The liquid level of the reheating medium needs to immerse the second heat exchanger 14. The exhaust port 32 is connected to the top of the water pool 31. The liquid level of the reheating medium in the water pool 31 is set according to requirements and replenished in time to maintain the liquid level.

[0070] The auxiliary heating unit 4 includes a fan 41 , a burner 42 and a fuel gas pipe 43 .

[0071] The fan 31 is connected to the burner 42 via an air duct 44. The fuel gas pipe 43 is also connected to the burner 42. The combustion chamber 421 of the burner 42 gradually sinks into the water pool 31 and extends to the bottom of the second heat exchanger 14. After the fuel gas is burned, the high-temperature flue gas generated overflows from the combustion chamber 421, contacts and mixes with the reheating medium, and heats the reheating medium.

[0072] The LNG gas supply unit 5 includes a third heat exchanger 51 .

[0073] The third heat exchanger 51 is immersed in the reheating medium, located above the second heat exchanger 14, and also located above the gas outlet of the combustion chamber 421. The inlet end of the third heat exchanger 51 is connected to the outlet end of the first heat exchange channel 121 through the fifth pipeline 52. The inlet end of the third heat exchanger 51 is connected to the gas supply network through the sixth pipeline 53.

[0074] Natural gas in a low-temperature state enters the gas supply network after being reheated to the required temperature of the external transmission pipeline network.

[0075] In this embodiment, the second air exchanger 14 and the third heat exchanger 51 adopt an integrated coupled heat exchanger such as a stainless steel serpentine heat exchange tube heat exchanger, which has a first channel, a second channel and a third channel. The working medium flows in the first channel, and the low-temperature natural gas flows in the second channel. The first channel and the second channel are located in the third channel, and the reheating medium flows therein.

[0076] In this embodiment, the principle of the liquefied natural gas cold energy power generation device is:

[0077] The high-pressure LNG enters the first heat exchanger 12 to transfer the cold energy to the working medium in the gas phase, cooling it to a working medium in the low-temperature liquid phase. The working medium in the low-temperature liquid phase is pressurized by the working medium booster pump 13, and the pressurized working medium in the low-temperature liquid phase enters the second heat exchanger 14. In the reheating unit 3, the second heat exchanger 14 performs heat exchange, and the working medium in the high-pressure and low-temperature liquid phase is vaporized into a high-pressure superheated gas phase, and then enters the expansion generator set 11. The volume of the working medium expands, and during the expansion process, the expander drives the generator to work externally, thereby converting the cold energy of LNG into electrical energy. The expanded working medium in the gas phase enters the first heat exchanger 12 again, completing a cycle.

[0078] The LNG is heat exchanged in the first heat exchanger 12 and then enters the third heat exchanger 51 to be restored to the temperature required by the external transmission pipeline network before entering the gas supply pipeline network.

[0079] The heat required for gasifying and heating the working medium in the low-temperature liquid phase state to the superheated gas phase state and the heat for reheating the LNG are provided by the reheating medium in the reheating unit 3 .

[0080] The high-temperature flue gas generated by the combustion of fuel gas and air in the burner is brought into the water pool 31 to heat the reheating medium.

[0081] The high-pressure LNG of a large LNG receiving station has a pressure of 9.5MPa and a temperature of -145℃. The seawater temperature in winter is 5℃, and propane is used as the circulating working fluid. Under this condition, the power generation per ton of LNG is about 19 KW, and the liquefied natural gas can be reheated to room temperature. After adopting the device of the present invention, the cold energy of LNG can be efficiently utilized to maintain a stable power generation state all year round.

[0082] Example 3

[0083] In the process of LNG cold energy power generation, the low-temperature natural gas and circulating working fluid generally use seawater as a heat source for reheating to meet the natural gas transmission temperature requirements, and at the same time, the circulating working fluid is gasified so that it can enter the power generation expander for expansion. In winter, due to the low seawater temperature, the low-temperature natural gas reheating requirements cannot be met. At the same time, the low temperature of the circulating working fluid entering the expansion generator will cause the expander to generate low power. Therefore, when the seawater temperature is lower than 5℃~10℃ in winter, the cold energy power generation device of the large LNG receiving station has the problem of low power generation or even failure to operate normally, which has a great impact on the operation of the cold energy power generation device.

[0084] In order to solve the problem that the power generation of cold energy power generation devices of large LNG receiving stations is low or even cannot operate normally due to the influence of the reheating heat source in winter, and the problem that the temperature requirements for natural gas transmission are not met, the present invention provides a liquefied natural gas cold energy power generation device, the structure of which is as shown in the attached figure. Figure 3 As shown. The device includes a Rankine cycle power generation unit 1, an LNG liquid phase pipe 2, a reheating unit 3, an auxiliary heat unit 4 and an LNG gas supply unit 5. Among them, the Rankine cycle power generation unit 1 is loaded with a working medium such as propane, and circulates internally. When the working medium expands from a high-pressure gas phase state to a low-pressure gas phase state, the volume expands, and work is performed externally, thereby realizing power generation. The LNG liquid phase pipe 2 introduces LNG in a liquid phase state into the Rankine cycle power generation unit 1, and exchanges heat with the working medium in a gas phase state in the Rankine cycle power generation unit 1. The low temperature of the LNG in a liquid phase state flowing in the LNG liquid phase pipe 2 is used to cool the working medium in a gas phase state into a working medium in a low-temperature liquid phase state. The reheating unit 3 is filled with a reheating medium such as water, and the flow passage of the working medium in a low-temperature liquid phase state is immersed in the reheating medium and the flow passage of the natural gas in a low-temperature gas phase is immersed in the reheating medium, thereby gasifying the working medium in a low-temperature liquid phase state to a working medium in a superheated gas phase state. The auxiliary heating unit 4 gradually extends from the outside of the reheating unit to the bottom of the reheating unit to heat the reheating medium to compensate for the reheating effect of the working medium when the reheating medium temperature is lower than 5℃~10℃ in winter. The LNG gas supply unit 5 enters the gas supply network after reheating to the required temperature of the external transmission pipeline network.

[0085] The liquefied natural gas cold energy power generation device in this embodiment has high integration and is not affected by external environmental factors, which can ensure the continuous and stable operation of LNG cold energy power generation throughout the year. At the same time, the liquefied natural gas cold energy power generation device in this embodiment can switch between power generation mode and gas supply mode.

[0086] Specifically, the Rankine cycle power generation unit 1 includes an expansion power generation unit 11 , a first heat exchanger 12 , a working fluid booster pump 13 , and a second heat exchanger 14 .

[0087] The first heat exchanger 12 is a stainless steel U-shaped heat exchanger having an independent first heat exchange channel 121 and a second heat exchange channel 122. The LNG liquid phase pipe 2 is connected to the inlet end of the first heat exchange channel 121. The outlet end of the first heat exchange channel 121 is connected to the LNG gas supply unit. The expansion generator set 11 is composed of a centripetal turbine expander and a generator, etc., and its outlet end is connected to the inlet end of the second heat exchange channel 122 through a first pipeline 15. The working fluid booster pump 13 adopts a barrel bag submersible pump, and its inlet end is connected to the outlet end of the second heat exchange channel 122 through a second pipeline 16. The outlet end of the working fluid booster pump 13 is connected to the inlet end of the second heat exchanger 14 through a third pipeline 17. The outlet end of the second heat exchanger 14 and the inlet end of the expansion generator set 11 are connected through a fourth pipeline 18. The second heat exchanger 14 is immersed in the reheating medium.

[0088] When the working medium in the gas phase and the LNG in the liquid phase flow in the first heat exchange channel 121 and the second heat exchange channel 122 respectively, heat exchange is performed, and the working medium in the gas phase is cooled and becomes a working medium in the low-temperature liquid phase. When the working medium in the high-pressure and low-temperature liquid phase flows through the second heat exchanger 14, it is converted into a working medium in the high-pressure superheated gas phase. When the working medium in the high-pressure superheated gas phase passes through the expansion generator set 11, the high-pressure superheated gas phase is converted into a working medium in the low-pressure gas phase, and the volume expands, so that the expansion generator set 11 performs work externally and generates electricity. After heat exchange, the temperature of the LNG in the liquid phase rises, and it enters the gas supply network after further reheating.

[0089] The reheating unit 3 includes a water pool 31 and an exhaust port 32 .

[0090] The water pool 31 is a closed structure and contains a reheating medium such as seawater. The liquid level of the reheating medium must be above the second heat exchanger 14. The exhaust port 32 is connected to the top of the water pool 31. The liquid level of the reheating medium in the water pool 31 is set according to requirements and replenished in time to maintain the liquid level.

[0091] The auxiliary heating unit 4 includes a fan 41 , a burner 42 and a fuel gas pipe 43 .

[0092] The fan 31 is connected to the burner 42 via an air duct 44. The fuel gas pipe 43 is also connected to the burner 42. The combustion chamber 421 of the burner 42 gradually sinks into the water pool 31 and extends to the bottom of the second heat exchanger 14. After the fuel gas is burned, the high-temperature flue gas generated overflows from the combustion chamber 421 and contacts and mixes with the reheating medium to heat the reheating medium.

[0093] The LNG gas supply unit 5 includes a third heat exchanger 51 and a bypass valve 54 .

[0094] The third heat exchanger 51 is immersed in the reheating medium, located above the second heat exchanger 14, and at the same time located above the gas outlet position of the combustion chamber 421. The inlet end of the third heat exchanger 51 is connected to the outlet end of the first heat exchange channel 121 through the fifth pipeline 52. The inlet end of the third heat exchanger 51 is connected to the gas supply network through the sixth pipeline 53. Natural gas in the low-temperature gas phase state enters the gas supply network after being reheated to the required temperature of the external transmission pipeline network. The bypass valve 54 is arranged outside the first heat exchanger 12, and its two ends are respectively connected to the LNG liquid phase pipe 2 and the fifth pipeline 52. Close the Rankine cycle power generation unit 1, open the bypass valve 54, and only perform gas supply operations.

[0095] In this embodiment, the second air exchanger 14 and the third heat exchanger 51 adopt an integrated coupled heat exchanger such as a stainless steel serpentine heat exchange tube heat exchanger, which has a first channel, a second channel and a third channel. The working medium flows in the first channel, and the low-temperature natural gas flows in the second channel. The first channel and the second channel are located in the third channel, and the reheating medium flows therein.

[0096] In this embodiment, the principle of the liquefied natural gas cold energy power generation device is:

[0097] The high-pressure LNG enters the first heat exchanger 12 to transfer the cold energy to the working fluid in the gas phase, cooling it to a working fluid in the low-temperature liquid phase. The working fluid in the low-temperature liquid phase is pressurized by the working fluid booster pump 13, and the pressurized working fluid in the low-temperature liquid phase enters the second heat exchanger 14. In the reheating unit 3, the second heat exchanger 14 performs heat exchange, and the working fluid in the high-pressure and low-temperature liquid phase is vaporized and heated to a superheated high-pressure gas phase, and then enters the expansion generator set 11. The volume of the working fluid expands, and during the expansion process, the expander drives the generator to do external work, thereby converting the cold energy of LNG into electrical energy. The expanded working fluid in the gas phase enters the first heat exchanger 12 again, completing a cycle.

[0098] The LNG is heat exchanged in the first heat exchanger 12 and then enters the third heat exchanger 51 to be restored to the required temperature of the external transmission pipeline network before entering the gas supply pipeline network.

[0099] The heat required for gasification of the working medium in the high-pressure and low-temperature liquid phase state to a superheated state and the heat for reheating the low-temperature natural gas are provided by the reheating medium in the reheating unit 3 .

[0100] Winter reheating is provided by the high temperature flue gas produced by the combustion of combustion gas and air in the burner.

[0101] When power generation is not required, the Rankine cycle power generation unit 1 can be closed, the bypass valve 54 can be opened, and only the gas supply operation can be performed.

[0102] The high-pressure LNG of a large LNG receiving station has a pressure of 9.5MPa and a temperature of -145℃. The seawater temperature in winter is 5℃, and propane is used as the circulating working fluid. Under this condition, the power generation capacity per ton of LNG is about 19 KW, and the natural gas can be reheated to room temperature. At the same time, if no power is generated, this embodiment can be converted to a pure gasification mode. After adopting the device of the present invention, the cold energy of LNG can be efficiently utilized to maintain a stable power generation state all year round.

Claims

1. A liquefied natural gas cold energy power generation device, suitable for large coastal LNG receiving stations, characterized by: include The Rankine cycle power generation unit is loaded with a working fluid; the working fluid in the liquid phase is pressurized to become a high-pressure liquid phase, and after the high-pressure liquid phase is reheated to the gas phase, the volume expands to do work externally and thereby generate electricity; An LNG liquid phase pipe, for introducing LNG in a liquid phase into the Rankine cycle power generation unit and exchanging heat with a working medium in a low-pressure gas phase in the Rankine cycle power generation unit; A reheating unit, loaded with a reheating medium, reheats the working medium in a low-temperature liquid phase state to a working medium in a superheated high-temperature gas phase state; the reheating medium is seawater; as well as An auxiliary heating unit gradually extends from the outside of the reheating unit to the vicinity of the bottom of the reheating unit to heat the reheating medium; Wherein, the Rankine cycle power generation unit comprises: Expansion generator set; A first heat exchanger having independent first heat exchange channels and second heat exchange channels; Working fluid booster pump; A second heat exchanger, immersed in the reheating medium of the reheating unit; Wherein, the LNG liquid phase pipe is in communication with the first heat exchange channel; The reheating unit comprises: A water tank, a closed structure, is filled with a reheating medium; the liquid level of the reheating medium needs to be higher than the second heat exchanger; An exhaust port connected to the top of the pool; The auxiliary heat unit comprises: A burner having a combustion chamber; the combustion chamber gradually extends from the outside of the recuperation unit to the vicinity of the bottom of the recuperation unit and extends to the bottom of the second heat exchanger, heats the recuperation medium, and exchanges heat with the second heat exchanger to compensate for the recuperation effect on the working medium when the temperature of the recuperation medium is lower than 5°C to 10°C in winter; Fan; a fuel gas pipe connected to the burner; and The two ends of the air duct are respectively connected to the burner and the fan.

2. The liquefied natural gas cold energy power generation device according to claim 1, characterized in that: The Rankine cycle power generation unit further comprises: A first pipeline, two ends of which are respectively connected to the outlet end of the expansion generator set and the inlet end of the second heat exchange channel of the first heat exchanger; A second pipeline, two ends of which are respectively connected to the outlet end of the second heat exchange channel of the first heat exchanger and the inlet end of the working fluid booster pump; a third pipeline, both ends of which are connected to the outlet of the working fluid booster pump and the inlet of the second heat exchanger respectively; and The fourth pipeline has two ends connected to the outlet of the second heat exchanger and the inlet of the expansion generator set respectively.

3. The liquefied natural gas cold energy power generation device according to claim 1, characterized in that: The device also includes a LNG gas supply unit.

4. The liquefied natural gas cold energy power generation device according to claim 3, characterized in that: The LNG gas supply unit includes A third heat exchanger, immersed in the reheating medium of the reheating unit; a fifth pipeline, both ends of which are respectively connected to the outlet end of the first heat exchange channel and the inlet end of the third heat exchanger; and a sixth pipeline, both ends of which are respectively connected to the outlet end of the third heat exchanger and the gas supply network; Wherein, the LNG liquid phase pipe is connected to the inlet end of the first heat exchange channel.

5. The liquefied natural gas cold energy power generation device according to claim 4, characterized in that: The second heat exchanger and the third heat exchanger adopt an integrated coupled heat exchanger; the coupled heat exchanger has a first channel, a second channel and a third channel; the working medium flows in the first channel; the natural gas flows in the second channel; the first channel and the second channel are located in the third channel, and the reheating medium flows therein.

6. The liquefied natural gas cold energy power generation device according to claim 4, characterized in that: The LNG gas supply unit also includes a bypass valve, and two ends of the bypass valve are respectively connected to the LNG liquid phase and the fifth pipeline.

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