A modular liquefied natural gas regasification system and method

Abstract

The present invention discloses a modular liquefied natural gas regasification system and method. The system of the present invention comprises a liquefied natural gas system, an intermediate medium system and a seawater system; the liquefied natural gas system comprises a booster pump inlet buffer tank (1), an LNG booster pump (2), a BOG cooler (3), an LNG vaporizer (4) and an NG temperature compensator (5); the intermediate medium system comprises an intermediate medium storage tank (7), an intermediate medium circulation pump (8) and an intermediate medium evaporator / heater (6); and the seawater system comprises a seawater water supply main (9) and a seawater drainage main (10). The system of the present invention can adapt to various application conditions of floating devices and onshore terminals; all heat exchange units are completely cut, and high-efficiency compact heat exchangers are selected, with higher integration; the gasification and external transmission operation range is large, and the intermediate medium can be stably circulated to ensure the controllability of the medium; seawater is used as a heat source to enter each heat exchanger in parallel, which can increase the heat transfer temperature difference of the heat exchanger and reduce the heat exchange area of ​​the heat exchanger.

Description

Technical Field

[0001] The invention relates to a modular liquefied natural gas regasification system and method, belonging to the technical field of natural gas. Background Art

[0002] The modular LNG regasification system integrates the booster pump inlet buffer tank, LNG booster pump, LNG vaporizer and other equipment into a skid. It has the functions of BOG treatment, LNG pressurization, LNG gasification, etc. It has high integration and small footprint. It is widely used in offshore floating liquefied natural gas (LNG) storage and regasification units (FSRU). It can also be used on barges and used alone as a floating gasification unit (FRU).

[0003] Under the conventional construction mode of onshore LNG receiving station projects, construction is easily affected and restricted by many factors such as weather and resources. In recent years, factory prefabrication and modular construction have developed faster and faster, which can improve the overall efficiency of engineering construction and reduce the time used for project construction. It can not only reduce risks and ensure quality, but also reduce rework caused by unreasonable procedures. The modular liquefied natural gas regasification system can realize the factory prefabrication, modular construction and mechanized operation of the onshore LNG receiving station pressurized gasification and transmission system, which is the future development trend.

[0004] It is necessary to develop a modular natural gas regasification system that can be applied to floating units such as FSRU and FRU and onshore LNG receiving stations, which has the functions and characteristics of compact layout, adaptability to a wide range of seawater quality, and easy cold energy utilization to meet the needs of offshore and onshore applications. Summary of the invention

[0005] The purpose of the present invention is to provide a modular LNG regasification system and method, which uses seawater as a heat source and an intermediate medium gasification LNG process to meet the LNG regasification requirements; the system has BOG recondensation, LNG pressurization and LNG gasification functions, and can be applied to floating devices such as FSRU and FRU, and can also be applied to onshore LNG receiving stations to achieve stable and safe gas supply.

[0006] In the present invention, BOG (Boil Off Gas) is boil-off gas of liquefied natural gas, and NG (Natural Gas) is natural gas.

[0007] The present invention provides a modular liquefied natural gas regasification system, comprising:

[0008] A liquefied natural gas system, comprising a booster pump inlet buffer tank, an LNG booster pump, a BOG cooler, an LNG vaporizer and an NG compensator; a first outlet of the booster pump inlet buffer tank is connected to the inlet of the LNG booster pump, the outlet of the LNG booster pump is connected to the first inlet of the BOG cooler, the first outlet of the BOG cooler is connected to the first inlet of the LNG vaporizer, the first outlet of the LNG vaporizer is connected to the first inlet of the NG compensator, the first outlet of the NG compensator is a natural gas outlet, the second outlet of the BOG cooler is connected to the second inlet of the booster pump inlet buffer tank, the first inlet of the booster pump inlet buffer tank is an LNG inlet, and the second inlet of the BOG cooler is a BOG inlet;

[0009] An intermediate medium system, comprising an intermediate medium storage tank, an intermediate medium circulation pump and an intermediate medium evaporator / heater, wherein the outlet of the intermediate medium storage tank is connected to the inlet of the intermediate medium circulation pump, the outlet of the intermediate medium circulation pump is connected to the first inlet of the intermediate medium evaporator / heater, the first outlet of the intermediate medium evaporator / heater is connected to the second inlet of the LNG vaporizer, and the second outlet of the LNG vaporizer is connected to the inlet of the intermediate medium storage tank;

[0010] The seawater system includes a seawater water supply main pipe and a seawater drainage main pipe. The seawater water supply main pipe is respectively connected to the second inlet of the NG compensator and the second inlet of the intermediate medium evaporator / heater, and the second outlet of the NG compensator and the second outlet of the intermediate medium evaporator / heater are respectively connected to the seawater drainage main pipe.

[0011] In the modular LNG regasification system of the present invention, the seawater heat source enters in parallel, and each heat exchanger in the system that uses the seawater heat source can use a larger seawater temperature difference to reduce the total seawater consumption; at the same time, the seawater is distributed and enters the modular LNG regasification system, and the heat exchanger related to the seawater medium can be selected according to the different seawater qualities. The heat exchanger type with strong anti-impurity clogging ability such as the shell and tube heat exchanger can be selected, and the heat exchanger type with compact structure such as the plate heat exchanger can also be selected, and the heat exchanger selection is more flexible; the heat exchangers in the modular LNG regasification system are all independently arranged, which is convenient for the utilization of LNG cold energy. The modular LNG regasification system of the present invention is a modular equipment, and the capacity can be increased by combination, and it can adapt to various application conditions of floating devices and onshore terminals.

[0012] In the modular liquefied natural gas regasification system, preferably, the LNG booster pump uses two 50% capacity pumps (a 50% capacity pump is a single pump that meets 50% of the gasification capacity of the regasification module, and two pumps meet 100% of the gasification capacity) to operate in parallel to improve the gasification capacity operating range of the system;

[0013] Preferably, the intermediate medium evaporator / heater is one or two connected in parallel to reduce the size of the equipment and meet the layout requirements. The intermediate medium evaporator / heater refers to an intermediate medium evaporator or an intermediate medium heater.

[0014] In the modular liquefied natural gas regasification system, preferably, there is a certain height difference between the boosting pump inlet buffer tank (1) and the LNG boosting pump (2) to meet the NPSH requirement at the high-pressure pump inlet.

[0015] In the modular liquefied natural gas regasification system, the LNG gasifier (4) and the intermediate medium storage tank (7) can be combined.

[0016] The modular liquefied natural gas regasification system is suitable for application in an onshore LNG receiving station. Preferably, the BOG cooler (3) further comprises a bypass connecting the second inlet and the second outlet, for processing BOG using the booster pump inlet buffer tank (1) when the modular natural gas regasification system is not performing gasification and external transmission.

[0017] The modular liquefied natural gas regasification system is suitable for application in an onshore LNG receiving station. Preferably, a branch is added to the second outlet of the BOG cooler (3) for conveying the cooled BOG to a recondenser at an onshore receiving station, which does not affect the operation of the modular regasification system and increases the processing capacity of the recondenser at the onshore receiving station.

[0018] The modular liquefied natural gas regasification system is suitable for application in an onshore LNG receiving station. Preferably, the first outlet of the booster pump inlet buffer tank (1) has two destinations, the first destination is connected to the LNG booster pump inlet, and the second destination is used to transport low-pressure LNG to the onshore LNG receiving station.

[0019] The modular liquefied natural gas regasification system is suitable for application in an onshore LNG receiving station. Preferably, a branch is added to the outlet of the LNG boosting pump (2). The branch has bidirectional flow and is used to provide high-pressure LNG to the onshore receiving station or to introduce the high-pressure LNG of the onshore receiving station into the modular natural gas regasification system, thereby increasing operational flexibility and reliability.

[0020] In the modular liquefied natural gas regasification system, preferably, the intermediate medium is an aqueous solution of propane and ethylene glycol or a mixed refrigerant composed of any two or three of ethylene, propylene and propane; preferably, the intermediate medium is a low-boiling point organic substance with a boiling point below -5°C and a freezing point below -30°C, and the operating pressure can be adjusted to make the intermediate medium meet the boiling point and freezing point temperature conditions, and the intermediate medium is also used for cold energy power generation.

[0021] In the modular liquefied natural gas regasification system, the types of heat exchangers include but are not limited to printed circuit board heat exchangers, coiled tube heat exchangers, shell and tube heat exchangers or jacketed heat exchangers, and other available heat exchangers are also acceptable; preferably, the BOG cooler and the LNG gasifier are printed circuit board heat exchangers (PCHE) or shell and tube heat exchangers; according to the on-site seawater quality, the intermediate medium evaporator / heater is a plate heat exchanger or a shell and tube heat exchanger, and the NG compensator is a shell and tube heat exchanger.

[0022] The present invention provides a method for regasification using the modular liquefied natural gas regasification system, comprising the following steps:

[0023] LNG is mixed in the boosting pump inlet buffer tank (1) with BOG which is cooled in the BOG cooler (3) and returned to the boosting pump inlet buffer tank (1), and then transported to the LNG boosting pump (2). The LNG boosting pump (2) pumps out high-pressure LNG, and after heat exchange in the BOG cooler (3), the LNG enters the LNG vaporizer (4) and the NG warmer (5) in sequence. The LNG vaporizer (4) vaporizes the high-pressure LNG into NG, and then the NG is further heated by heat exchange in the NG warmer (5) to be output after reaching the temperature required for external transportation.

[0024] Seawater as a heat source comes from the seawater water supply main (9), and enters the intermediate medium evaporator / heater (6) and the NG compensator (5) in two ways respectively; the intermediate medium circulation pump (8) pumps the intermediate medium in the intermediate medium storage tank (7) to the intermediate medium evaporator / heater (6), and the intermediate medium is heated and evaporated by one way of seawater or enters the LNG vaporizer (4) after being heated to vaporize the liquefied natural gas therein, and the intermediate medium after heat exchange returns to the intermediate medium storage tank (7) to realize the circulation of the intermediate medium, and the seawater after heat exchange returns to the seawater drainage main (10); the other way of seawater enters the NG compensator (5), heats the low-temperature NG to a required temperature and then outputs it, and the seawater returns to the seawater drainage main (10).

[0025] In the method of the present invention, seawater is used as a heat source and enters each heat exchanger in parallel.

[0026] The method described above can optionally be used in an onshore LNG receiving station, where the low-pressure LNG can come from a low-pressure LNG main pipeline of the onshore receiving station or a low-pressure LNG outlet of a recondenser of the onshore receiving station.

[0027] In the method described, when the seawater temperature is high, the system uses seawater alone as a heat source; when the seawater temperature is low and cannot meet the vaporization requirements, the seawater is heated by other heat sources (such as water vapor) to meet the heat exchange requirements.

[0028] The present invention has the following beneficial effects: the modular regasification system of the present invention has a high degree of integration and the following technical advantages: ① it can adapt to various application conditions of floating devices and onshore terminals; ② all heat exchange units are completely divided, and high-efficiency and compact heat exchangers are selected, which have a higher degree of integration; ③ the gasification and external transmission operation range is large, and the stable circulation of the intermediate medium can be achieved to ensure the controllability of the medium; ④ LNG cold energy is used to treat BOG, thereby improving the energy utilization rate of the system; ⑤ seawater is used as a heat source to enter each heat exchanger in parallel, which can increase the heat transfer temperature difference of the heat exchanger and reduce the heat exchange area of ​​the heat exchanger compared with the traditional series connection method. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A schematic diagram for illustrating the structure of a modular regasification system and a process flow for gasifying liquefied natural gas according to the present invention;

[0030] The reference numerals in the figures are as follows:

[0031] 1-boosting pump inlet buffer tank; 2-LNG boosting pump; 3-BOG cooler; 4-LNG vaporizer; 5-NG compensating temperature device; 6-intermediate medium evaporator / heater; 7-intermediate medium storage tank; 8-intermediate medium circulation pump; 9-seawater supply main pipe; 10-seawater drainage main pipe. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work are within the scope of protection of the present invention.

[0033] In the description of the present invention, it should be understood that the use of terms such as "first", "second", and "third" to limit components is only for the convenience of distinguishing the above components. Unless otherwise stated, the above terms have no special meanings and therefore cannot be understood as limiting the scope of protection of the present invention.

[0034] The present invention will be further described below in conjunction with the accompanying drawings, but the present invention is not limited to the following embodiments.

[0035] Example 1

[0036] like Figure 1 As shown, this embodiment relates to a modular liquefied natural gas regasification system, comprising:

[0037] A liquefied natural gas system comprises a booster pump inlet buffer tank 1, an LNG booster pump 2, a BOG cooler 3, an LNG vaporizer 4 and an NG compensator 5; a first outlet of the booster pump inlet buffer tank 1 is connected to the inlet of the LNG booster pump 2, the outlet of the LNG booster pump 2 is connected to the first inlet of the BOG cooler 3, the first outlet of the BOG cooler 3 is connected to the first inlet of the LNG vaporizer 4, the first outlet of the LNG vaporizer 4 is connected to the first inlet of the NG compensator 5, and the first outlet of the NG compensator 5 is a natural gas outlet; a second outlet of the BOG cooler 3 is connected to the second inlet of the booster pump inlet buffer tank 1, the first inlet of the booster pump inlet buffer tank 1 is an LNG inlet; and a second inlet of the BOG cooler 3 is a BOG inlet;

[0038] The intermediate medium system includes an intermediate medium storage tank 7, an intermediate medium circulation pump 8 and an intermediate medium evaporator / heater 6, wherein the outlet of the intermediate medium storage tank 7 is connected to the inlet of the intermediate medium circulation pump 8, the outlet of the intermediate medium circulation pump 8 is connected to the first inlet of the intermediate medium evaporator / heater 6, the first outlet of the intermediate medium evaporator / heater 6 is connected to the second inlet of the LNG vaporizer 4, and the second outlet of the LNG vaporizer 4 is connected to the inlet of the intermediate medium storage tank 7;

[0039] The seawater system includes a seawater water supply main pipe 9 and a seawater drainage main pipe 10. The seawater water supply main pipe 9 is connected to the second inlet of the NG compensating temperature device 5 and the second inlet of the intermediate medium evaporator / heater 6 respectively. The second outlet of the NG compensating temperature device 5 and the second outlet of the intermediate medium evaporator / heater 6 are connected to the seawater drainage main pipe 10 respectively.

[0040] In this embodiment, preferably, the LNG boosting pump 2 can use two 50% capacity pumps to operate in parallel to improve the system gasification capacity operating range; the intermediate medium evaporator / heater 6 can use one or two to operate in parallel to reduce the equipment size and meet the modular layout requirements.

[0041] In this embodiment, preferably, there is a certain height difference between the boosting pump inlet buffer tank 1 and the LNG boosting pump 2 to meet the NPSH requirement at the high-pressure pump inlet.

[0042] In this embodiment, preferably, the intermediate medium includes propane, an aqueous solution of ethylene glycol or a mixed refrigerant of ethylene, propylene and propane, etc. Depending on the difference in heat exchange medium, the intermediate medium may undergo phase change during the system circulation process to utilize the latent heat of the intermediate medium, or may not undergo phase change and only utilize the sensible heat of the intermediate medium to achieve gasification of LNG in the system.

[0043] In this embodiment, preferably, when the intermediate medium is propane, the intermediate medium inlet state of the LNG gasifier 4 is gas phase, and the outlet state is liquid phase; the natural gas inlet of the NG warmer 5 is gas phase, not two-phase state; the evaporated gas outlet of the BOG cooler 3 is a gas phase state close to saturation.

[0044] In this embodiment, the types of heat exchangers include but are not limited to printed circuit board heat exchangers, coil heat exchangers, shell and tube heat exchangers or jacket heat exchangers, and other available heat exchangers are also acceptable; preferably, the BOG cooler and the LNG vaporizer use printed circuit board heat exchangers or shell and tube heat exchangers; according to the on-site seawater quality conditions, the intermediate medium evaporator / heater uses a plate heat exchanger or a shell and tube heat exchanger, and the NG compensator uses a shell and tube heat exchanger.

[0045] In this embodiment, optionally, in order to be suitable for application in onshore LNG receiving stations, a bypass is added between the second inlet and outlet of the modular regasification system BOG cooler 3. When the modular regasification system does not perform gasification and external transmission, the modular regasification system booster pump inlet buffer tank 1 can also be used for BOG treatment.

[0046] In this embodiment, optionally, in order to be suitable for application in an onshore LNG receiving station, a branch is added to the second outlet of the BOG cooler 3 of the modular regasification system, and the cooled BOG can be sent to the recondenser of the onshore receiving station, which does not affect the operation of the modular regasification system and increases the processing capacity of the recondenser of the onshore receiving station.

[0047] In this embodiment, optionally, in order to be suitable for application in an onshore LNG receiving station, a branch is added to the outlet of the modular regasification system LNG boosting pump 2, and the branch has bidirectional flow, so that the modular regasification system LNG boosting pump 2 can be used to provide high-pressure LNG for the onshore receiving station, and the high-pressure LNG of the onshore receiving station can also be introduced into the modular regasification system gasifier, thereby increasing operational flexibility and reliability.

[0048] In this embodiment, optionally, the LNG gasifier 4 and the intermediate medium storage tank 7 can be combined.

[0049] Example 2

[0050] like Figure 1 As shown, this embodiment relates to a modular liquefied natural gas regasification method, comprising the following steps:

[0051] LNG is mixed with BOG cooled in BOG cooler 3 and returned to booster pump inlet buffer tank 1 in booster pump inlet buffer tank 1 and then transported to LNG booster pump 2. LNG booster pump 2 pumps out high-pressure LNG and enters LNG vaporizer 4 and NG warmer 5 in sequence after heat exchange in BOG cooler 3. LNG vaporizer 4 vaporizes high-pressure LNG into NG, which is then further heated up by heat exchange in NG warmer 5 and output after reaching the temperature required for external transportation.

[0052] Seawater as a heat source comes from the seawater water supply main 9, and is divided into two routes to enter the intermediate medium evaporator / heater 6 and the NG warmer 5 respectively; the intermediate medium circulation pump 8 pumps the intermediate medium in the intermediate medium storage tank 7 to the intermediate medium evaporator / heater 6, and the intermediate medium is heated by the seawater on one route and evaporated / heated, and then enters the LNG vaporizer 4 and vaporizes the liquefied natural gas therein, and the intermediate medium after heat exchange is returned to the intermediate medium storage tank 7 to realize the circulation of the intermediate medium, and the seawater after heat exchange is returned to the seawater drainage main 10; the other route of seawater enters the NG warmer 5, heats the low-temperature NG to the required temperature and then outputs it, and the seawater returns to the seawater drainage main 10.

[0053] In this embodiment, optionally, when the seawater temperature is high, the system can use seawater alone as a heat source. When the seawater temperature is low and cannot meet the vaporization requirements, the seawater can be heated by other heat sources such as water vapor to meet the heat exchange requirements.

[0054] In this embodiment, optionally, to be suitable for application in an onshore LNG receiving station, the modular regasification system has two sources of low-pressure LNG, which can come from the low-pressure LNG main of the onshore receiving station or from the low-pressure LNG at the outlet of the recondenser of the onshore receiving station.

Claims

1. A method for regasification using a modular liquefied natural gas regasification system, characterized in that: The modular liquefied natural gas regasification system comprises: A liquefied natural gas system comprises a booster pump inlet buffer tank (1), an LNG booster pump (2), a BOG cooler (3), an LNG vaporizer (4) and an NG compensator (5); the first outlet of the booster pump inlet buffer tank (1) is connected to the inlet of the LNG booster pump (2), the outlet of the LNG booster pump (2) is connected to the first inlet of the BOG cooler (3), the first outlet of the BOG cooler (3) is connected to the first inlet of the LNG vaporizer (4), the first outlet of the LNG vaporizer (4) is connected to the first inlet of the NG compensator (5), the first outlet of the NG compensator (5) is a natural gas outlet, the second outlet of the BOG cooler (3) is connected to the second inlet of the booster pump inlet buffer tank (1), the first inlet of the booster pump inlet buffer tank (1) is an LNG inlet, and the second inlet of the BOG cooler (3) is a BOG inlet; An intermediate medium system comprises an intermediate medium storage tank (7), an intermediate medium circulation pump (8) and an intermediate medium evaporator / heater (6), wherein the outlet of the intermediate medium storage tank (7) is connected to the inlet of the intermediate medium circulation pump (8), the outlet of the intermediate medium circulation pump (8) is connected to the first inlet of the intermediate medium evaporator / heater (6), the first outlet of the intermediate medium evaporator / heater (6) is connected to the second inlet of the LNG vaporizer (4), and the second outlet of the LNG vaporizer (4) is connected to the inlet of the intermediate medium storage tank (7); The seawater system comprises a seawater supply main pipe (9) and a seawater drainage main pipe (10), wherein the seawater supply main pipe (9) is respectively connected to a second inlet of the NG compensating temperature device (5) and a second inlet of the intermediate medium evaporator / heater (6), and the second outlet of the NG compensating temperature device (5) and a second outlet of the intermediate medium evaporator / heater (6) are respectively connected to the seawater drainage main pipe (10); The LNG boosting pumps (2) are two 50% capacity pumps connected in parallel; The intermediate medium evaporator / heater is an intermediate medium evaporator or an intermediate medium heater, and the intermediate medium evaporator / heater is one; The BOG cooler (3) and the LNG vaporizer (4) are selected from printed circuit board type heat exchangers or shell and tube type heat exchangers; the intermediate medium evaporator / heater (6) is selected from plate type heat exchangers or shell and tube type heat exchangers; the NG compensating temperature device (5) is selected from shell and tube type heat exchangers; A branch line is added to the second outlet of the BOG cooler (3) for transporting the cooled BOG to a recondenser at an onshore receiving station; The first outlet of the booster pump inlet buffer tank (1) has two destinations, the first destination is connected to the LNG booster pump inlet, and the second destination is used to transport low-pressure LNG to an onshore LNG receiving station; The outlet of the LNG boosting pump (2) is provided with a branch line, the branch line has a bidirectional flow and is used to provide high-pressure LNG to an onshore receiving station or to introduce high-pressure LNG from an onshore receiving station into the modular liquefied natural gas regasification system; The method comprises the following steps: The LNG in the boosting pump inlet buffer tank (1) is mixed with the BOG cooled in the BOG cooler (3) and returned to the boosting pump inlet buffer tank (1), and then transported to the LNG boosting pump (2). The LNG boosting pump (2) pumps out high-pressure LNG, and after heat exchange in the BOG cooler (3), the LNG enters the LNG vaporizer (4) and the NG warmer (5) in sequence. The LNG vaporizer (4) vaporizes the high-pressure LNG into NG, and then the NG is further heated by heat exchange in the NG warmer (5) to be output after reaching the temperature required for external transportation. Seawater as a heat source comes from the seawater water supply main (9), and enters the intermediate medium evaporator / heater (6) and the NG compensating temperature device (5) in two ways respectively; the intermediate medium circulation pump (8) pumps the intermediate medium in the intermediate medium storage tank (7) to the intermediate medium evaporator / heater (6), and the intermediate medium is heated by one way of seawater to evaporate or enter the LNG vaporizer (4) to vaporize the liquefied natural gas therein, and the intermediate medium after heat exchange returns to the intermediate medium storage tank (7) to realize the circulation of the intermediate medium, and the seawater after heat exchange returns to the seawater drainage main (10); the other way of seawater enters the NG compensating temperature device (5), heats the low-temperature NG to a required temperature and then outputs it, and the seawater returns to the seawater drainage main (10); The intermediate medium is a low-boiling-point organic substance with a boiling point lower than -5°C and a freezing point lower than -30°C. The intermediate medium is also used for cold energy power generation.

2. The method according to claim 1, characterized in that: There is a certain height difference between the boosting pump inlet buffer tank (1) and the LNG boosting pump (2).

3. The method according to any one of claims 1 to 2, characterized in that: The LNG gasifier (4) and the intermediate medium storage tank (7) are combined.

4. The method according to any one of claims 1 to 2, characterized in that: The BOG cooler (3) further comprises a bypass connecting the second inlet and the second outlet, which is used for processing BOG using the booster pump inlet buffer tank (1) when the modular liquefied natural gas regasification system is not performing gasification and external transmission.

5. The method according to claim 1, characterized in that: The low-pressure LNG comes from the low-pressure LNG main pipeline of the onshore receiving station or the low-pressure LNG at the outlet of the recondenser of the onshore receiving station.

6. The method according to claim 1 or 5, characterized in that: When the seawater temperature is high, the system uses seawater as the only heat source; when the seawater temperature is low and cannot meet the gasification requirements, the seawater is heated by other heat sources to meet the heat exchange requirements.

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