System and method for gasifying LNG (Liquefied Natural Gas) by using combined intermediate medium

Abstract

The invention belongs to the technical field of LNG (Liquefied Natural Gas), and discloses a system and a method for gasifying LNG by using a combined intermediate medium. The system comprises an evaporator and a preheater, and the shell side of the evaporator and the shell side of the preheater are communicated and connected from bottom to top. An intermediate medium closed circulation system is constructed, cold energy generated after LNG gasification is fully recycled, namely, the cold energy is conveyed to the power generation device and the air conditioner refrigeration device, full utilization of energy is achieved to the maximum extent, and environmental pollution is effectively avoided.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of LNG, and more particularly relates to a combined intermediate medium gasification LNG system and method. BACKGROUND

[0002] Natural gas is widely used in various aspects of daily life as a clean energy. In recent years, with the substantial growth of natural gas consumption demand, the transportation and storage technology of natural gas has also developed rapidly. In order to facilitate the transportation and storage of natural gas, the commonly used method is to first liquefy natural gas into LNG, and then heat it before use to make it gasify into natural gas.

[0003] In the process of LNG gasification, an intermediate medium gasifier is usually used to heat the intermediate medium with warm seawater as the heat medium, and the intermediate medium after absorbing heat heats the LNG to make it gasify. The commonly used intermediate medium gasifier at present mostly adopts a combined mode of multiple horizontal heat exchangers in series or parallel. The problems of this technical solution are: (1) in order to obtain a higher heat exchange effect, it is usually necessary to increase the length of the heat exchange tube or increase the number of heat exchange tubes, which will lead to a series of problems such as complex equipment structure, high manufacturing difficulty, large occupied space, high investment cost, etc.; (2) a large amount of cold energy is released in the process of LNG gasification from low-temperature liquid to normal-temperature gas, and this part of cold energy is mostly not effectively utilized, thus causing a great waste of energy; (3) the low-temperature seawater obtained after the warm seawater is cooled is mostly directly discharged into the sea, which not only seriously affects the marine ecological environment, but also causes a waste of resources. SUMMARY

[0004] The present application aims at the deficiencies of the prior art and provides a combined intermediate medium gasification LNG system and method. The present application constructs an intermediate medium closed circulation system, fully recovers the cold energy generated after LNG gasification, i.e. the cold energy is delivered to a power generation device and an air conditioning refrigeration device, thus maximizing the full utilization of energy and effectively avoiding environmental pollution.

[0005] In order to achieve the above-mentioned purpose, the present application provides a combined intermediate medium gasification LNG system in one aspect, which comprises an evaporator and a preheater;

[0006] The shell side of the evaporator and the shell side of the preheater are connected from bottom to top;

[0007] The evaporator comprises an evaporation heat exchange tube, which is arranged close to the bottom of the shell in the shell side of the evaporator and is completely immersed in the liquid intermediate medium in the shell side of the evaporator; the tube side inlet of the evaporator is connected with a heat source supply device; and the tube side outlet of the evaporator is connected with an air conditioning refrigeration system.

[0008] The tube side of the preheater comprises first heat exchange tubes and second heat exchange tubes, which are arranged in a double flow winding form in the shell of the preheater; the tube side inlets of the first heat exchange tubes and the second heat exchange tubes are connected with the liquid state intermediate medium outlet of the power generation device and the liquid state intermediate medium outlet of the LNG gasifier respectively; the tube side outlets of the first heat exchange tubes and the second heat exchange tubes are connected with the shell side of the evaporator through connecting pipes.

[0009] The shell side outlet of the preheater is connected with the gaseous state intermediate medium inlet of the power generation device and the LNG gasifier respectively.

[0010] In the present application, the evaporator is a kettle-type fixed tube sheet heat exchanger, according to the present application, preferably, the shell of the evaporator is connected by a left conical shell, an intermediate cylinder and a right conical shell; the evaporator comprises a left tube box and a right tube box.

[0011] The left tube box is connected with the other end of the left conical shell through a first flange and is arranged outside the shell of the evaporator; the right tube box is connected with the other end of the right conical shell through a second flange and is arranged outside the shell of the evaporator.

[0012] The left tube plate is clamped between the two flange plates of the first flange; the right tube plate is clamped between the two flange plates of the second flange; the inlet end of the evaporative heat exchange tube is fixed on the left tube plate; the outlet end of the evaporative heat exchange tube is fixed on the right tube plate.

[0013] The left tube box is connected with the inlet end of the evaporative heat exchange tube and is provided with the tube side inlet of the evaporator; the right tube box is connected with the outlet end of the evaporative heat exchange tube and is provided with the tube side outlet of the evaporator.

[0014] According to the present application, preferably, the bottom of the shell of the evaporator is provided with a plurality of equally spaced evaporative support plates for supporting the evaporative heat exchange tube close to the bottom of the shell in the shell side of the evaporator.

[0015] According to the present application, preferably, the left conical shell and the right conical shell are eccentric conical shells, and the inclination angles of the left conical shell and the right conical shell are independently in the range of 20°-60°, so that the shell of the evaporator has sufficient evaporation space.

[0016] In the present application, the bottom of the shell of the evaporator is further provided with two supports for supporting the combined intermediate medium gasification LNG system.

[0017] According to the present application, preferably, the inlet end of the evaporative heat exchange tube is welded on the left tube plate; the outlet end of the evaporative heat exchange tube is welded on the right tube plate.

[0018] According to the application, preferably, the tube-pass inlet of the evaporator is arranged at the upper part of the left tube box; and the tube-pass outlet of the evaporator is arranged at the lower part of the right tube box.

[0019] According to the application, preferably, the evaporative heat exchange tube is a high-flux heat exchange tube, and the material of the evaporative heat exchange tube is copper alloy with seawater corrosion resistance. The high-flux heat exchange tube can improve the heat flux per unit heat exchange area, so that the evaporator is smaller in size and more compact in structure.

[0020] In the application, the tube bundle of the evaporator is detachable, and after the tube bundle is extracted, the first flange and the second flange can be used as an inspection hole, so that the shell of the evaporator does not need to be separately provided with an inspection hole.

[0021] In the application, the preheater is a double-flow winding tube heat exchanger. According to the application, preferably, the shell of the preheater is composed of an upper head and a lower cylinder connected by a flange; and the shell of the evaporator and the lower cylinder of the preheater are connected through.

[0022] The lower cylinder is provided with a core cylinder and a support beam, the two ends of the support beam are horizontally fixed to the side wall of the lower cylinder, and the support beam is used for supporting the core cylinder in the lower cylinder; and the first heat exchange tube and the second heat exchange tube are wound in double flows on the core cylinder.

[0023] The tube-pass inlet and the tube-pass outlet of the first heat exchange tube are located on one side wall of the lower cylinder; and the tube-pass inlet and the tube-pass outlet of the second heat exchange tube are located on the other side wall of the lower cylinder.

[0024] The tube-pass inlet of the first heat exchange tube and the second heat exchange tube is arranged at the upper part of the lower cylinder; and the tube-pass outlet of the first heat exchange tube and the second heat exchange tube is arranged at the lower part of the lower cylinder.

[0025] The upper head is vertically provided with a longitudinal partition plate, the number of the shell-pass outlets of the preheater is two, and the two shell-pass outlets of the preheater are located on the two sides of the longitudinal partition plate.

[0026] According to the application, preferably, the material of the first heat exchange tube and the second heat exchange tube is stainless steel with low-temperature resistance.

[0027] In the application, the upper head of the preheater is detachable, and after the upper head is detached, the shell of the preheater can be accessed from the upper part for maintenance, so that the shell does not need to be separately provided with an inspection hole.

[0028] According to the application, preferably, the power generation device is a driving turbine power generation device.

[0029] Another aspect of the present application provides a method for combined intermediate medium gasification of LNG, which adopts the system and comprises the following steps:

[0030] The liquid intermediate medium enters the bottom of the shell in the shell side of the evaporator, exchanges heat with the heat source in the evaporating heat exchange tube, so that the liquid intermediate medium is heated and gasified to obtain gaseous intermediate medium, and flows to the top of the shell in the shell side of the preheater; the heat source in the evaporating heat exchange tube is cooled and sent to the air conditioning refrigeration system;

[0031] Part of the gaseous intermediate medium reaching the top of the shell in the shell side of the preheater is respectively delivered to the power generation device and the LNG gasifier through the shell side outlet of the preheater, respectively generates power for the power generation device and recovers the cold energy of LNG in the LNG gasifier to obtain supercooled liquid phase intermediate medium; the supercooled liquid phase intermediate medium obtained by the power generation device flows into the first heat exchange tube through the liquid intermediate medium outlet of the power generation device; the supercooled liquid phase intermediate medium obtained by the LNG gasifier flows into the second heat exchange tube through the liquid intermediate medium outlet of the LNG gasifier;

[0032] The remaining part of the gaseous intermediate medium reaching the top of the shell in the shell side of the preheater exchanges heat with the supercooled liquid phase intermediate medium flowing into the first heat exchange tube and the second heat exchange tube, the gaseous intermediate medium of the remaining part is condensed into liquid intermediate medium after being cooled and falls back to the bottom of the shell in the shell side of the evaporator, and the supercooled liquid phase intermediate medium in the first heat exchange tube and the second heat exchange tube is heated and flows back to the bottom of the shell in the shell side of the evaporator through the connecting pipe as the liquid intermediate medium for circulation.

[0033] According to the present application, preferably, the temperature of the supercooled liquid phase intermediate medium obtained by the power generation device is-45℃ to-55℃.

[0034] According to the present application, preferably, the temperature of the supercooled liquid phase intermediate medium obtained by the LNG gasifier is-55℃ to-65℃.

[0035] According to the present application, preferably, the liquid intermediate medium is at least one of R125, propane, isobutane and ammonia.

[0036] According to the present application, preferably, the heat source in the evaporating heat exchange tube is at least one of seawater, industrial water and air.

[0037] The technical scheme of the present application has the following beneficial effects:

[0038] (1) Compared with the prior art, the LNG gasification can be realized, and the cold energy released during the LNG gasification can be fully recycled and used for a power generation device, so that the energy is fully utilized and converted;

[0039] (2) The warm sea water in nature is used as a heat source, so that the system is environment-friendly and economical, the low-temperature sea water generated after the warm sea water is cooled can be used for an air conditioning refrigeration system, the resource utilization efficiency is improved, and the ecological environment is protected;

[0040] (3) The evaporator and the preheater shell of the present application are mutually penetrated, so that sufficient evaporation and condensation space is provided for the intermediate medium, and the circulating flow resistance of the intermediate medium is greatly reduced;

[0041] (4) The evaporator of the present application adopts a high-flux type heat exchange pipe, so that the heat flux of the unit area heat exchange pipe can be effectively improved, thereby being beneficial to reducing the equipment volume and reducing the manufacturing cost;

[0042] (5) The liquid intermediate medium is heated for the first time in the first heat exchange pipe and the second heat exchange pipe, and then is heated again in the evaporator shell, so that the intermediate medium is completely gasified, and the utilization efficiency of the intermediate medium is greatly improved;

[0043] (6) The first heat exchange pipe and the second heat exchange pipe of the present application are both winding pipes, so that the self-temperature difference stress can be eliminated, the stress state is good, and the unit volume has a large heat transfer area and high heat transfer efficiency;

[0044] (7) Compared with the prior art, the system structure of the present application is compact, the land occupation area is small, the equipment investment is low, and the operation is stable.

[0045] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0046] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the several views, and in which exemplary embodiments of the present application are shown.

[0047] Figure 1 A schematic view of a combined intermediate medium gasification LNG system according to an embodiment of the present application is shown.

[0048] The reference signs are explained as follows:

[0049] E1, evaporator; 1, left tube box; 2, tube side inlet of evaporator; 3, left tube plate; 4, first flange; 5, shell of evaporator; 6, evaporating heat exchange tube; 7, evaporating support plate; 8, support; 9, second flange; 10, right tube plate; 11, tube side outlet of evaporator; 12, right tube box;

[0050] E2, preheater; 13, shell side outlet of preheater; 14, upper head; 15, tube side inlet of first heat exchange tube; 16, first heat exchange tube; 17, shell of preheater; 18, support beam; 19, tube side outlet of first heat exchange tube; 20, longitudinal partition plate; 21, core barrel; 22, tube side inlet of second heat exchange tube; 23, second heat exchange tube; 24, tube side outlet of second heat exchange tube; 25, connecting tube.

[0051] A, seawater; B, seawater sent into air conditioning refrigeration system; C, gaseous intermediate working medium delivered to power generation device; D, gaseous intermediate working medium delivered to LNG gasifier; E, supercooled liquid phase intermediate working medium obtained by power generation device; F, supercooled liquid phase intermediate working medium obtained by LNG gasifier. DETAILED DESCRIPTION

[0052] The preferred embodiments of the present application will be described in more detail below. Although the preferred embodiments of the present application are described below, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present application can be more thoroughly and completely conveyed to those skilled in the art, and the scope of the present application can be fully conveyed to those skilled in the art.

[0053] Example 1

[0054] The present embodiment provides a combined intermediate medium gasification LNG system, as shown in Figure 1 The system comprises an evaporator E1 and a preheater E2;

[0055] The shell side of the evaporator and the shell side of the preheater are connected from bottom to top;

[0056] The evaporator E1 comprises evaporating heat exchange tubes 6, which are arranged close to the bottom of the shell in the shell side of the evaporator and are completely immersed in the liquid intermediate working medium in the shell side of the evaporator; the evaporating heat exchange tubes 6 are high-flux heat exchange tubes, and the material of the evaporating heat exchange tubes is a copper alloy with seawater corrosion resistance;

[0057] The shell 5 of the evaporator is connected by a left conical shell, an intermediate cylinder and a right conical shell, both the left conical shell and the right conical shell are eccentric conical shells, and the inclination angles of the left conical shell and the right conical shell are independently in the range of 20°-60°; the evaporator comprises a left tube box 1 and a right tube box 12;

[0058] The left tube box 1 is connected with the other end of the left conic shell through the first flange 4 and is arranged outside the shell 5 of the evaporator; the right tube box is connected with the other end of the right conic shell through the second flange 9 and is arranged outside the shell 5 of the evaporator;

[0059] The left tube box 1 is connected with the other end of the left conic shell through the first flange 4 and is arranged outside the shell 5 of the evaporator; the right tube box is connected with the other end of the right conic shell through the second flange 9 and is arranged outside the shell 5 of the evaporator;

[0060] The left tube box 1 is connected with the other end of the left conic shell through the first flange 4 and is arranged outside the shell 5 of the evaporator; the right tube box is connected with the other end of the right conic shell through the second flange 9 and is arranged outside the shell 5 of the evaporator;

[0061] The bottom of the shell 5 of the evaporator is provided with a plurality of equidistant evaporation support plates 7, which are used to support the evaporation heat exchange pipes 6 to be closely arranged on the bottom of the shell in the shell side of the evaporator;

[0062] The tube side of the preheater E2 includes first heat exchange pipes 16 and second heat exchange pipes 23, the tube side inlets of the first heat exchange pipes and the second heat exchange pipes are connected with the liquid intermediate medium outlet of the power generation device and the liquid intermediate medium outlet of the LNG gasifier respectively; the tube side outlets of the first heat exchange pipes and the second heat exchange pipes are connected with the shell side of the evaporator through the connecting pipes 25; the materials of the first heat exchange pipes 16 and the second heat exchange pipes 23 are stainless steel with low-temperature resistance;

[0063] The shell 17 of the preheater is composed of the upper head 14 and the lower cylinder through the flange connection; the shell 5 of the evaporator and the lower cylinder of the preheater are connected through;

[0064] The lower cylinder is provided with the core cylinder 21 and the support beam 18, the two ends of the support beam 18 are horizontally fixed on the side wall of the lower cylinder, and the support beam 18 is used to support the core cylinder 21 in the lower cylinder; the first heat exchange pipes 16 and the second heat exchange pipes 23 are wound on the core cylinder 21 in double strands;

[0065] The tube side inlet and the tube side outlet of the first heat exchange pipes are located on one side wall of the lower cylinder; the tube side inlet and the tube side outlet of the second heat exchange pipes are located on the other side wall of the lower cylinder;

[0066] The tube side inlet of the first and second heat exchange tubes is arranged at the upper part of the lower cylinder, and the tube side outlet of the first and second heat exchange tubes is arranged at the lower part of the lower cylinder.

[0067] The longitudinal partition plate 20 is arranged vertically in the upper head 14, and the number of the shell side outlets 13 of the preheaters is two. The shell side outlets of the two preheaters are respectively arranged at the two sides of the longitudinal partition plate 20, and are respectively connected with the gaseous intermediate medium inlet of the power generation device and the LNG gasifier.

[0068] The power generation device is a turbine driving power generation device.

[0069] Embodiment 2

[0070] The embodiment provides a combined intermediate medium gasification LNG method, which adopts the system in embodiment 1 and comprises the following steps.

[0071] The liquid intermediate medium (propane) enters the bottom of the shell in the shell side of the evaporator E1, exchanges heat with the heat source (sea water A) in the evaporation heat exchange tube 6, so that the liquid intermediate medium is heated and gasified to obtain the gaseous intermediate medium, and flows to the top of the shell in the shell side of the preheater; the heat source in the evaporation heat exchange tube 6 is cooled and then sent to the air conditioning refrigeration system;

[0072] Part of the gaseous intermediate medium reaching the top of the shell in the shell side of the preheater E2 is respectively transported to the power generation device and the LNG gasifier through the shell side outlets 13 of the preheater, respectively drives the power generation device to generate power and recovers the LNG cold energy in the LNG gasifier to obtain the supercooled liquid phase intermediate medium; the supercooled liquid phase intermediate medium E (temperature: -50 DEG C) obtained by the power generation device flows into the first heat exchange tube 16 through the liquid intermediate medium outlet of the power generation device; the supercooled liquid phase intermediate medium F (temperature: -60 DEG C) obtained by the LNG gasifier flows into the second heat exchange tube 23 through the liquid intermediate medium outlet of the LNG gasifier;

[0073] The remaining part of the gaseous intermediate medium reaching the top of the shell in the shell side of the preheater exchanges heat with the supercooled liquid phase intermediate medium flowing into the first heat exchange tube 16 and the second heat exchange tube 23, the remaining part of the gaseous intermediate medium is cooled and condensed into the liquid intermediate medium and then falls back to the bottom of the shell in the shell side of the evaporator, and the supercooled liquid phase intermediate medium in the first heat exchange tube 16 and the second heat exchange tube 23 is heated and then flows back to the bottom of the shell in the shell side of the evaporator through the connecting pipe 25, and is used as the liquid intermediate medium.

[0074] Having described various embodiments of the application, it is to be understood that the above description is meant to be illustrative only, and that many modifications and variations of the embodiments are possible without departing from the scope and spirit of the described embodiments. Many modifications and variations of the described embodiments are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the described embodiments can be practiced otherwise than as specifically described.

Claims

1. A combined intermediate medium gasification LNG system, characterized by, The system comprises an evaporator and a preheater; The shell side of the evaporator and the shell side of the preheater are connected through from bottom to top; The evaporator comprises evaporation heat exchange pipes which are arranged close to the bottom of the shell in the shell side of the evaporator and are completely immersed in the liquid intermediate medium in the shell side of the evaporator; the tube side inlet of the evaporator is connected with a heat source supply device; the tube side outlet of the evaporator is connected with an air conditioning refrigeration system; The tube side of the preheater comprises first heat exchange pipes and second heat exchange pipes which are arranged in the shell of the preheater in the form of double-flow winding; the tube side inlets of the first heat exchange pipes and the second heat exchange pipes are respectively connected with the liquid intermediate medium outlet of a power generation device and the liquid intermediate medium outlet of an LNG gasifier; the tube side outlets of the first heat exchange pipes and the second heat exchange pipes are both connected with the shell side of the evaporator through a connecting pipe; The shell side outlet of the preheater is respectively connected with the gaseous intermediate medium inlet of the power generation device and the LNG gasifier.

2. The combined intermediate media vaporized LNG system of claim 1, wherein, The shell of the evaporator is composed of a left conical shell, an intermediate cylinder and a right conical shell; the evaporator comprises a left tube box and a right tube box; The left tube box is connected with the other end of the left conical shell through a first flange and is arranged outside the shell of the evaporator; the right tube box is connected with the other end of the right conical shell through a second flange and is arranged outside the shell of the evaporator; The left tube plate is clamped between the two flange plates of the first flange; the right tube plate is clamped between the two flange plates of the second flange; the inlet end of the evaporation heat exchange pipe is fixed on the left tube plate; the outlet end of the evaporation heat exchange pipe is fixed on the right tube plate; The left tube box is connected with the inlet end of the evaporation heat exchange pipe and is provided with the tube side inlet of the evaporator; the right tube box is connected with the outlet end of the evaporation heat exchange pipe and is provided with the tube side outlet of the evaporator.

3. The combined intermediate medium gasification LNG system according to claim 2, wherein The bottom of the shell of the evaporator is provided with a plurality of equidistant evaporation support plates for supporting the evaporation heat exchange pipes arranged close to the bottom of the shell in the shell side of the evaporator; The left conical shell and the right conical shell are both eccentric conical shells, and the inclination angles of the left conical shell and the right conical shell are respectively independently in the range of 20°-60°; The inlet end of the evaporation heat exchange pipe is welded on the left tube plate; the outlet end of the evaporation heat exchange pipe is welded on the right tube plate; The tube side inlet of the evaporator is arranged at the upper part of the left tube box; the tube side outlet of the evaporator is arranged at the lower part of the right tube box.

4. The combined intermediate media vaporized LNG system of any of claims 1-3, wherein, The evaporation heat exchange pipe is a high-flux type heat exchange pipe, and the material of the evaporation heat exchange pipe is a copper alloy with seawater corrosion resistance.

5. The combined intermediate media vaporized LNG system of claim 1, wherein, The shell of the preheater is composed of an upper head and a lower cylinder through flange connection; the shell of the evaporator and the lower cylinder of the preheater are connected through; The lower cylinder is internally provided with a core cylinder and a support beam, two ends of the support beam are horizontally fixed to the side wall of the lower cylinder, and the support beam is used for supporting the core cylinder in the lower cylinder; the first heat exchange pipe and the second heat exchange pipe are double-strand flow winding on the core cylinder; The pipe passage inlet and the pipe passage outlet of the first heat exchange pipe are located on one side wall of the lower cylinder at the same time; the pipe passage inlet and the pipe passage outlet of the second heat exchange pipe are located on the other side wall of the lower cylinder at the same time; The pipe passage inlet of the first heat exchange pipe and the pipe passage inlet of the second heat exchange pipe are arranged at the upper part of the lower cylinder; the pipe passage outlet of the first heat exchange pipe and the pipe passage outlet of the second heat exchange pipe are arranged at the lower part of the lower cylinder; The upper head is vertically provided with a longitudinal partition plate, the number of the shell passage outlets of the preheaters is two, and the shell passage outlets of the two preheaters are located on the two sides of the longitudinal partition plate respectively.

6. The combined intermediate media vaporized LNG system of claim 5, wherein, The material of the first heat exchange pipe and the second heat exchange pipe is stainless steel with low-temperature resistance.

7. The combined intermediate media vaporized LNG system of claim 1, wherein, The power generation device is a driving turbine power generation device.

8. A method of combined intermediate media vaporization of LNG, characterized by, The method adopts the system in any one of claims 1-7, and comprises the following steps: The liquid intermediate working medium enters the bottom of the shell in the shell passage of the evaporator, exchanges heat with the heat source in the evaporation heat exchange pipe, is heated and gasified to obtain gaseous intermediate working medium, and flows to the top of the shell in the shell passage of the preheater; the heat source in the evaporation heat exchange pipe is cooled and then sent to the air conditioning refrigeration system; Part of the gaseous intermediate working medium reaching the top of the shell in the shell passage of the preheater is respectively delivered to the power generation device and the LNG gasifier through the shell passage outlets of the preheater, is used for power generation of the power generation device and recovery of LNG cold energy in the LNG gasifier respectively, and overcooled liquid phase intermediate working medium is obtained; the overcooled liquid phase intermediate working medium obtained by the power generation device flows into the first heat exchange pipe through the liquid intermediate working medium outlet of the power generation device; the overcooled liquid phase intermediate working medium obtained by the LNG gasifier flows into the second heat exchange pipe through the liquid intermediate working medium outlet of the LNG gasifier; The remaining part of the gaseous intermediate working medium reaching the top of the shell in the shell passage of the preheater exchanges heat with the overcooled liquid phase intermediate working medium flowing into the first heat exchange pipe and the second heat exchange pipe, the gaseous intermediate working medium of the remaining part is condensed into liquid intermediate working medium after being cooled, and then falls back to the bottom of the shell in the shell passage of the evaporator, and the overcooled liquid phase intermediate working medium in the first heat exchange pipe and the second heat exchange pipe is heated and then flows back to the bottom of the shell in the shell passage of the evaporator through the connecting pipe, and is used as the liquid intermediate working medium.

9. The method according to claim 8, wherein, The temperature of the overcooled liquid phase intermediate working medium obtained by the power generation device is -45℃ to -55℃; The temperature of the overcooled liquid phase intermediate working medium obtained by the LNG gasifier is -55℃ to -65℃.

10. The method according to claim 8, wherein, The liquid intermediate working medium is at least one of R125, propane, isobutane and ammonia. The heat source in the evaporation heat exchange pipe is at least one of seawater, industrial water and air.

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