Dehydration and desulfurization treatment system and method for liquefied natural gas

Abstract

The invention relates to the technical field of natural gas purification, in particular to a dehydration and desulfurization treatment system and method.The dehydration and desulfurization treatment system for liquefied natural gas comprises a desulfurization device, a dehydration device and an automatic salt discharging device, the automatic salt discharging device comprises a cyclone I and a cyclone II which alternately work in a time sequence, the dehydration device comprises a molecular sieve regeneration device, and the molecular sieve regeneration device comprises a regeneration gas heat exchanger, a primary heater and a secondary heater which are connected in series step by step; the dehydration and desulfurization treatment method for liquefied natural gas is applied to the treatment system, secondary salt generated in the desulfurization tower can be discharged on the premise that stable operation of the desulfurization tower is guaranteed, manual shutdown for salt discharge is not needed, regeneration gas is heated stage by stage, stepped temperature rise of a molecular sieve is achieved, the service life of the molecular sieve is prolonged, and energy consumption is reduced. And the maintenance cost of the treatment system is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas purification, and in particular to a dehydration and desulfurization treatment system and method for liquefied natural gas. Background Art

[0002] During the liquefaction process of natural gas, the water in the natural gas may freeze in the form of ice or frost in the working part of the liquefaction unit, causing blockage of pipelines, nozzles and separation equipment; and the sulfides in the natural gas will corrode the pipelines and equipment inside the liquefaction unit after entering the liquefaction unit, seriously affecting the liquefaction process of natural gas. Compared with the natural gas dehydration and desulfurization treatment system that does not require liquefaction, the natural gas liquefaction unit is in a low temperature and high pressure state, and is more sensitive to the residual water and residual sulfur content in the natural gas. Therefore, a more stringent and higher standard natural gas dehydration and desulfurization treatment system is required.

[0003] In order to obtain deeply purified natural gas, some liquefied natural gas dehydration and desulfurization systems choose to adopt a combined process of wet desulfurization and molecular sieve dehydration. Wet desulfurization can efficiently remove hydrogen sulfide and sulfur components, and molecular sieve can deeply dehydrate and remove residual sulfur components. This combined process can meet the strict requirements of natural gas liquefaction for high purity, low sulfur content and ultra-low dew point.

[0004] During the wet flue gas desulfurization process, secondary salts such as sulfate and thiosulfate generated by side reactions in the desulfurization tower are easily accumulated in the desulfurization tower, resulting in decreased desulfurization efficiency, equipment blockage and increased pressure difference, which will further aggravate the instability of the treatment system. For this reason, the existing treatment system will select a dedicated time period to close all devices and valves, and shut down the desulfurization tower for salt removal. The shutdown interrupts the continuity of the production process, consumes additional time, manpower and material costs, and reduces the economic benefits of the treatment system; after the molecular sieve is dehydrated, it is necessary to regenerate the molecular sieve through a regeneration process. The industrial molecular sieve regeneration mostly adopts the method of introducing heated regeneration gas to heat the molecular sieve, but the sharp increase in temperature can easily cause thermal stress damage to the molecular sieve, accelerate the deterioration process of the molecular sieve, and reduce the service life of the molecular sieve. The molecular sieve needs to be replaced frequently to ensure the good operation of the system, which increases the equipment maintenance cost and time cost.

[0005] Therefore, a natural gas dehydration and desulfurization processing system and method are needed to enable the dehydration and desulfurization process of liquefied natural gas to be carried out continuously, effectively and stably for a long time, thereby reducing the waste of time, manpower and material costs. Summary of the invention

[0006] The object of the present invention is to provide a dehydration and desulfurization treatment system and method for liquefied natural gas to solve the technical problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions: A dehydration and desulfurization treatment system for liquefied natural gas includes a desulfurization device, a dehydration device and an automatic salt removal device. The desulfurization device is connected to the dehydration device, and the automatic salt removal device is connected to the desulfurization device. The automatic salt removal device includes a cyclone 1 and a cyclone 2 that work in a time-sequential alternating manner. The dehydration device includes a molecular sieve regeneration device, and the molecular sieve regeneration device includes a regeneration gas heat exchanger, a primary heater and a secondary heater. The regeneration gas heat exchanger, the primary heater and the secondary heater are connected in series step by step.

[0008] Furthermore, the desulfurization device includes a desulfurization tower, which includes a tower body and a filter membrane. The filter membrane is arranged at the bottom of the tower body, and the filter membrane separates the bottom of the tower body into a high-salt amine liquid area and a low-salt amine liquid area. Cyclone 1 and cyclone 2 are respectively arranged on both sides outside the tower body, and the inlets of cyclone 1 and cyclone 2 are both connected to the high-salt amine liquid area above the filter membrane, and the overflow ports on the top of cyclone 1 and cyclone 2 are both connected to the low-salt amine liquid area below the filter membrane. The desulfurization tower is provided with an amine liquid inlet on the side of the low-salt amine liquid area.

[0009] Furthermore, the automatic salt discharge device also includes a reactor 1, a reactor 2 and a liquid inlet flowmeter, the inlets of the reactor 1 and the reactor 2 are respectively connected to the outlets at the bottom of the cyclone 1 and the cyclone 2, the connecting pipe between the cyclone 1 and the reactor 1 is provided with a liquid outlet flowmeter 1, the connecting pipe between the cyclone 2 and the reactor 2 is provided with a liquid outlet flowmeter 2, the outlets of the reactor 1 and the reactor 2 are respectively connected to a liquid inlet pump 1 and a liquid inlet pump 2, the outlets of the liquid inlet pump 1 and the liquid inlet pump 2 are both connected to the amine liquid inlet, and the liquid inlet flowmeter is arranged at On the connecting pipe of the amine liquid inlet.

[0010] Furthermore, the automatic salt discharge device also includes an amine liquid replenishing tank and a replenishment return valve, the amine liquid replenishing tank is respectively connected to a replenishment pump and a return liquid pump, the replenishment return valve includes a replenishment port, a return liquid port, a liquid inlet 1 and a liquid inlet 2, the replenishment port is connected to the outlet of the replenishment pump, the return liquid port is connected to the inlet of the return liquid pump, the liquid inlet 1 is connected to the liquid inlet pump 1, and the liquid inlet 2 is connected to the liquid inlet pump 2.

[0011] Furthermore, the desulfurization tower also includes a lean liquid distributor, a swirl plate, a scraper and an agitator. The agitator is arranged in the high-salt amine liquid area, and the agitator is rotatably connected to the bottom of the tower body. The lean liquid distributor is installed in the tower body, and the lean liquid distributor is arranged in multiple layers from bottom to top. The swirl plate is installed under each layer of the lean liquid distributor. The scraper is symmetrically installed on the upper and lower sides of the swirl plate, and multiple scrapers are evenly arranged on each side along the circumference of the tower body. The scraper is rotatably connected to the middle part of the swirl plate through a connecting rod, and the scraper abuts against the inner wall of the tower body.

[0012] Furthermore, the molecular sieve regeneration device also includes a primary reversing valve and a secondary reversing valve, the primary reversing valve includes a primary air inlet, a first air outlet and a second air outlet, the primary air inlet is connected to the outlet end of the heating side of the regeneration gas heat exchanger, the second air outlet is connected to the inlet of the primary heater, the secondary reversing valve includes a secondary air inlet, a third air outlet and a fourth air outlet, the secondary air inlet is connected to the outlet of the primary heater, and the fourth air outlet is connected to the inlet of the secondary heater.

[0013] Furthermore, the dehydration device also includes a dehydration tower 1 and a dehydration tower 2, the bottom inlets of the dehydration tower 1 and the dehydration tower 2 are respectively connected to the first air outlet, the third air outlet and the outlet of the secondary heater, the top outlets of the dehydration tower 1 and the dehydration tower 2 are connected to the cooling side inlet end of the regeneration gas heat exchanger, the heating side inlet end of the regeneration gas heat exchanger is connected to a compressor, the cooling side outlet end of the regeneration gas heat exchanger is connected to a cooler, the outlet end of the cooler is connected to a water separator, and the outlet of the water separator is connected to the inlet end of the compressor.

[0014] Furthermore, the desulfurization device also includes an amine liquid regeneration device, which includes a flash device, a lean-rich liquid heat exchanger and a regeneration tower. The bottom outlet of the desulfurization tower is connected to the inlet of the flash device, the bottom outlet of the flash device is connected to the inlet end of the lean-rich liquid heat exchanger, the outlet end of the lean-rich liquid heat exchanger is connected to the upper inlet of the regeneration tower, the bottom outlet of the regeneration tower is connected to the lean-rich liquid heat exchanger, the outlet end of the lean-rich liquid heat exchanger is connected to a regeneration pump, and the outlet end of the regeneration pump is connected to the upper part of the desulfurization tower.

[0015] Furthermore, the top inlets of the dehydration tower 1 and the dehydration tower 2 are connected to the top outlet of the desulfurization tower, the bottom outlets of the dehydration tower 1 and the dehydration tower 2 are connected to the gas storage tank, and the outlet of the gas storage tank is connected to the liquefaction device.

[0016] The present invention also provides a dehydration and desulfurization method for liquefied natural gas, which is applied to the dehydration and desulfurization system for liquefied natural gas, and comprises the following steps: S1: The raw gas enters the desulfurization tower and contacts with the lean amine liquid sprayed from top to bottom in the tower in countercurrent to remove the sulfur components to obtain desulfurized gas. The lean amine liquid that adsorbs the sulfur components is converted into rich amine liquid. S2 and S5 are executed alternately during the desulfurization process; S2: Close cyclone 2, start cyclone 1, high-salt amine solution flows out from the bottom of cyclone 1 and enters reactor 1 for desalination reaction, start liquid inlet pump 2, amine solution in buffer tank 2 returns to the bottom of desulfurization tower, liquid outlet flowmeter 1 and liquid inlet flowmeter monitor cyclone 1 outlet flow and amine solution inlet flow respectively, if cyclone 1 outlet flow is greater than amine solution inlet flow, execute S3; if the outlet flow of cyclone 1 is less than or equal to the amine solution inlet flow, execute S4; S3: The return liquid valve is adjusted to connect the liquid replenishment pump with the liquid inlet pump, the liquid replenishment pump is started, the return liquid pump is closed, and the amine liquid replenishment tank replenishes amine liquid to the amine liquid inlet; S4: The return liquid valve is adjusted to connect the return liquid pump with the inlet liquid pump, the liquid replenishment pump is closed, the return liquid pump is started, and the excess amine liquid in front of the amine liquid inlet is returned to the amine liquid replenishment tank; S5: Close the cyclone 1, start the cyclone 2, and the high-salt amine solution flows out from the bottom of the cyclone 2 into the reactor 2 for desalination reaction. Start the liquid inlet pump 1, and the amine solution in the buffer tank 1 returns to the bottom of the desulfurization tower. The liquid outlet flowmeter 2 and the liquid inlet flowmeter monitor the outlet flow of the cyclone 2 and the inlet flow of the amine solution inlet, respectively. If the outlet flow of the cyclone 2 is greater than the inlet flow of the amine solution inlet, execute S6; if the outlet flow of the cyclone 2 is less than or equal to the inlet flow of the amine solution inlet, execute S7; S6: The liquid replenishment valve is adjusted to connect the liquid replenishment pump and the liquid inlet pump 2, the liquid replenishment pump is started, the liquid return pump is closed, and the amine liquid replenishment tank replenishes amine liquid to the amine liquid inlet; S7: The liquid return valve is adjusted to connect the liquid return pump and the liquid inlet pump, the liquid replenishment pump is closed, the liquid return pump is started, and the excess amine liquid in front of the amine liquid inlet is returned to the amine liquid replenishment tank; S8: The rich amine liquid flows from the bottom of the desulfurization tower into the amine liquid regeneration device for regeneration and then returns to the desulfurization tower. The desulfurized gas enters the dehydration device for dehydration. The dehydration tower 1 and the dehydration tower 2 in the dehydration device perform dehydration and regeneration processes alternately. S9: After being pressurized by the compressor, the cold regeneration gas enters the regeneration gas heat exchanger for heat exchange and temperature increase. The primary reversing valve and the secondary reversing valve are adjusted to gradually increase the temperature of the molecular sieve. The temperature increase process goes through a low temperature stage, a medium temperature stage and a high temperature stage respectively. S10: the regeneration gas after heat exchange with the molecular sieve enters the regeneration gas heat exchanger for heat exchange and cooling, and then enters the water separator after further cooling in the cooler to obtain cold regeneration gas, and the cold regeneration gas returns to the inlet end of the compressor again; S11: The desulfurized gas is dehydrated to obtain dry natural gas, which enters the gas storage tank and then enters the liquefaction device for natural gas liquefaction to finally obtain liquefied natural gas.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention provides a dehydration and desulfurization treatment system for liquefied natural gas. By alternately executing cyclone 1 and cyclone 2 of the automatic salt discharge device, the desulfurization tower can continuously perform salt slurry discharge, desalination reaction and amine liquid inlet processes. Under the premise of ensuring the stable operation of the desulfurization tower, the secondary salt generated in the desulfurization tower is discharged in real time. There is no need to manually stop the machine for salt discharge, which saves time and labor costs and expands the economic benefits of the treatment system.

[0018] 2. The present invention provides a dehydration and desulfurization treatment system for liquefied natural gas. A scraper and a stirrer are arranged in the desulfurization tower. The rotation of the scraper and the stirring of the stirrer ensure that the secondary salt will not be deposited on the tower body.

[0019] 3. The present invention provides a dehydration and desulfurization treatment system for liquefied natural gas. By adjusting the number of heaters involved in heating the regenerated gas, the molecular sieve is heated in a step-by-step manner in three different heating stages, thereby reducing thermal stress damage during the regeneration process of the molecular sieve, extending the life of the molecular sieve, and reducing the equipment maintenance cost and time cost of the treatment system.

[0020] 4. The present invention provides a method for dehydrating and desulfurizing liquefied natural gas, and the beneficial effects are the same as those of a dehydrating and desulfurizing system for liquefied natural gas, which will not be described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of a dehydration and desulfurization treatment system for liquefied natural gas according to an embodiment of the present invention; Figure 2 This is a schematic diagram of an automatic salt discharge device according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the internal structure of a desulfurization tower according to an embodiment of the present invention; Figure 4 This is a schematic diagram of a molecular sieve regeneration device according to an embodiment of the present invention.

[0022] In the figure: 1. desulfurization tower; 11. tower body; 111. lean liquid distributor; 112. cyclone plate; 113. scraper; 114. agitator; 115. pressure sensor; 116. filter membrane; 117. amine liquid inlet; 12. flash evaporation device; 13. lean and rich liquid heat exchanger; 14. amine absorber; 2. regeneration tower; 21. reboiler; 22. acid gas treatment device; 23. sulfur storage tank; 24. regeneration pump; 3. dehydration tower 1; 31. dehydration tower 2; 4. amine liquid replenishing tank; 41. cyclone 1; 411. cyclone 2; 412. valve 1; 413. valve 2; 42. liquid outlet flow Meter 1; 421, liquid outlet flow meter 2; 43, reactor 1; 431, reactor 2; 44, buffer tank 1; 441, buffer tank 2; 45, liquid inlet pump 1; 451, liquid inlet pump 2; 46, liquid replenishment valve; 47, liquid replenishment pump; 471, liquid return pump; 48, liquid inlet flow meter; 49, regulating valve 1; 491, regulating valve 2; 5, compressor; 51, regeneration gas heat exchanger; 52, primary heater; 53, secondary heater; 54, primary reversing valve; 55, secondary reversing valve; 56, cooler; 57, water distributor; 6, sulfur recovery device; 7, gas storage tank; 8, liquefaction device. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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 technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the following description of the invention, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicating directions or positional relationships, are based on directions or positional relationships shown in the drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific direction or be constructed and operated in a specific direction. The term "connection" only indicates the connection between devices and has no special meaning.

[0025] In addition, the technical fields and installation methods involved in the embodiments of the present invention described below can be combined with each other as long as there is no conflict between them.

[0026] For specific embodiments, please refer to Figure 1-Figure 4 A dehydration and desulfurization treatment system for liquefied natural gas includes a desulfurization device, a dehydration device and an automatic salt removal device. The desulfurization device is connected to the dehydration device, and the automatic salt removal device is connected to the desulfurization device. The raw gas first passes through the desulfurization device for desulfurization treatment, and then enters the dehydration device for dehydration and deep desulfurization.

[0027] Furthermore, the desulfurization device adopts a wet desulfurization process. In this example, an organic solvent methyldiethanolamine (MDEA) is selected as a desulfurizing agent. The desulfurization device includes a desulfurization tower 1 and an amine liquid regeneration device. The amine liquid regeneration device includes a flash device 12, a lean-rich liquid heat exchanger 13, a regeneration tower 2 and an acid gas treatment device 22. The bottom outlet of the desulfurization tower 1 is connected to the inlet of the flash device 12, and the top outlet of the desulfurization tower 1 is connected to an amine absorber 14. The outlet of the amine absorber 14 is connected to a dehydration device; the lean-rich liquid heat exchanger 13 includes a rich liquid heating channel and a lean liquid cooling channel. The bottom outlet of the flash device 12 is connected to the inlet end of the rich liquid heating channel, and the upper outlet of the flash device 12 is connected to a fuel gas storage tank 7; the inside of the regeneration tower 2 is sequentially connected from top to bottom. It is a gas-liquid separation zone, an absorption zone and a sedimentation zone. The outlet end of the rich liquid heating channel is connected to the upper inlet of the absorption zone of the regeneration tower 2, the bottom outlet of the regeneration tower 2 is connected to the inlet end of the lean liquid cooling channel, the outlet end of the lean liquid cooling channel is connected to a regeneration pump 24, and the outlet end of the regeneration pump 24 is connected to the upper part of the desulfurization tower 1; a reboiler 21 is arranged outside the regeneration tower 2, the inlet of the reboiler 21 is connected to the bottom sedimentation zone of the regeneration tower 2, the outlet of the reboiler 21 is connected to the absorption zone of the regeneration tower 2, the bottom outlet of the acid gas treatment device 22 is connected to the absorption zone of the regeneration tower 2, the upper inlet of the acid gas treatment device 22 is connected to the top of the regeneration tower 2, the other outlet of the acid gas treatment device 22 is connected to a sulfur storage tank 23, and the outlet of the sulfur storage tank 23 is connected to a sulfur recovery device 6.

[0028] The raw gas enters the desulfurization tower 1 from the bottom and contacts with the lean amine liquid flowing from top to bottom in countercurrent. The sulfur-containing components in the raw gas are adsorbed by the lean amine liquid to obtain desulfurized gas, which then flows out from the top of the desulfurization tower 1. The desulfurized gas enters the amine absorber 14 to remove the small amount of amine liquid carried, and then enters the dehydration device. The lean amine liquid becomes rich amine liquid after absorbing the sulfur-containing components in the raw gas. The rich amine liquid flows out from the bottom of the desulfurization tower 1 and enters the flash device 12. The rich amine liquid flashes out the dissolved hydrocarbon gas in the flash device 12, and the hydrocarbon gas enters the fuel gas storage tank 7 for storage. The rich amine liquid after the hydrocarbon gas is removed enters the rich liquid heating channel of the lean-rich liquid heat exchanger 13 for heating. The heated rich amine liquid enters the upper part of the absorption zone of the regeneration tower 2, and the rich amine liquid flowing from top to bottom is heated by the rich amine liquid flowing from bottom to top. The flowing steam contacts in countercurrent to desorb the sulfur-containing components therein. The steam is generated by the reboiler 21 to heat the regeneration solution flowing out from the settling zone. The regenerated rich amine liquid becomes lean amine liquid and flows out from the bottom of the settling zone of the regeneration tower 2 and enters the lean liquid cooling channel of the lean-rich liquid heat exchanger 13 for cooling. The lean amine liquid after cooling is driven by the regeneration pump 24 and returns to the upper part of the desulfurization tower 1. The acid steam that absorbs the sulfur-containing components flows out from the top of the regeneration tower 2, and is treated by the acid gas treatment device 22 to separate free acid water and regeneration solution. The regeneration solution flows out from the bottom of the acid gas treatment device 22 and returns to the absorption zone of the regeneration tower 2. The free acid water flows into the sulfur storage tank 23. The sulfur components in the sulfur storage tank 23 enter the sulfur recovery device 6 for recovery treatment.

[0029] Furthermore, the desulfurization tower 1 includes a tower body 11, a lean liquid distributor 111, a swirl plate 112, a scraper 113, an agitator 114 and a filter membrane 116. The lean liquid distributor 111 is installed in the tower body 11. The lean liquid distributor 111 is provided with multiple layers from top to bottom. Each layer of the lean liquid distributor 111 is connected to the outlet of the regeneration pump 24 through a pipeline. A plurality of nozzles are installed on the lean liquid distributor 111 to evenly distribute and spray the lean liquid introduced into the tower body 11. The swirl plate 112 It is installed below the lean liquid distributor 111 on each layer. When the raw gas entering from the lower part of the tower body 11 passes through the swirl plate 112 from bottom to top, the airflow rotates due to the blade guiding effect of the swirl plate 112. The rotated airflow can more fully contact with the lean liquid sprayed from above in countercurrent. The lean liquid distributor 111 and the swirl plate 112 are prior art and will not be described in detail here. Pressure sensors 115 are provided above and below the inner wall of the tower body 11 to monitor the pressure difference between the upper and lower parts of the tower body 11.

[0030] The scraper 113 is symmetrically installed on the upper and lower sides of the swirl plate 112, and a plurality of scrapers 113 are evenly arranged on each side along the circumference of the tower body 11. The scraper 113 is rotatably connected to the middle of the swirl plate 112 through a connecting rod, and the scraper 113 abuts against the inner wall of the tower body 11. The scraper 113 rotates under the driving of the rotating airflow passing through the swirl plate 112, so that the inner wall of the tower body 11 can be cleaned during the countercurrent contact between the raw gas and the lean amine liquid, thereby preventing the secondary salt from being deposited on the inner wall of the tower body 11; the filter membrane 116 is arranged at the bottom of the tower body 11, and the filter membrane 116 covers the tower body The bottom of the desulfurization tower 11 is divided into a high-salt amine liquid area and a low-salt amine liquid area, wherein the high-salt amine liquid area is above the filter membrane 116, and the low-salt amine liquid area is below the filter membrane 116. The rich amine liquid and secondary salts produced by the desulfurization reaction at the upper part of the desulfurization tower 1 are gathered in the high-salt amine liquid area above the filter membrane 116 to form a high-salt amine liquid. The agitator 114 is arranged in the high-salt amine liquid area. The agitator 114 is rotatably connected to the bottom of the tower body 11. A driving motor is installed at the bottom of the tower body 11 to drive the agitator 114 to rotate. The agitator 114 ensures that the secondary salts are in a solution state instead of being deposited at the bottom of the tower body 11. The automatic salt discharge device comprises a cyclone 1 41 and a cyclone 2 411, which are respectively arranged on both sides of the outside of the tower body 11, and the inlets of the cyclone 1 41 and the cyclone 2 411 are both connected to the high-salt amine liquid area above the filter membrane 116, and the connecting pipes between the cyclone 1 41 and the cyclone 2 411 and the high-salt amine liquid area are respectively provided with a valve 1 412 and a valve 2 413, and the overflow ports at the top of the cyclone 1 41 and the cyclone 2 411 are both connected to the low-salt amine liquid area below the filter membrane 116, and the high-salt amine liquid enters the cyclone 1 or cyclone 41. After passing through cyclone 1411, the desulfurization tower 1 is separated into low-salt amine liquid and concentrated salt slurry through cyclone action. The low-salt amine liquid overflows into the low-salt amine liquid area and flows out from the bottom outlet of the tower body 11, and the concentrated salt slurry flows out from the outlet at the bottom of cyclone 141 or cyclone 2411. An amine liquid inlet 117 is provided on the side of the low-salt amine liquid area of ​​the desulfurization tower 1. When the pressure difference inside the desulfurization tower 1 detected by the pressure sensor 115 is too large, the opening of valve 1412 or valve 2413 is reduced to reduce the inlet flow of cyclone 141 or cyclone 2411, thereby ensuring the pressure balance inside the desulfurization tower 1.

[0031] Furthermore, the automatic salt discharge device also includes an amine liquid replenishing tank 4, a reactor 1 43, a reactor 2 431, a replenishing liquid return valve 46 and a liquid inlet flowmeter 48. The inlets of the reactor 1 43 and the reactor 2 431 are respectively connected to the outlets at the bottom of the cyclone 1 41 and the cyclone 2 411, respectively, for desalting the concentrated salt slurry flowing out of the outlets at the bottom of the cyclone 1 41 and the cyclone 2 411, respectively. The liquid outlet flowmeter 1 42 is installed on the connecting pipe between the cyclone 1 41 and the reactor 1 43, and the liquid outlet flowmeter 2 421 is installed between the cyclone 2 411 and the reactor 2 431. The outlets of the reactor 1 43 and the reactor 2 431 are connected to the buffer tank 1 44 and the buffer tank 2 441 respectively, and the other outlets of the reactor 1 43 and the reactor 2 431 are connected to the sulfur storage tank 23, and the outlets of the buffer tank 1 44 and the buffer tank 2 441 are connected to the liquid inlet pump 1 45 and the liquid inlet pump 2 451, and the outlets of the liquid inlet pump 1 45 and the liquid inlet pump 2 451 are connected to the amine liquid inlet port 117, and the liquid inlet flowmeter 48 is arranged on the connecting pipe of the amine liquid inlet port 117; the amine liquid replenishing tank 4 is connected to the replenishing pump 47 and the return pump 47 respectively. The liquid pump 471, the replenishing and returning liquid valve 46 is a four-position four-way solenoid valve, the replenishing and returning liquid valve 46 includes a replenishing port, a return liquid port, a liquid inlet 1 and a liquid inlet 2, the replenishing port is connected to the outlet of the replenishing and returning liquid pump 47, the return liquid port is connected to the inlet of the return liquid pump 471, the liquid inlet 1 is connected to the liquid inlet pump 1 45, a regulating valve 1 49 is arranged on the connecting pipeline between the liquid inlet 1 and the liquid inlet pump 1 45, the liquid inlet 2 is connected to the liquid inlet pump 2 451, a regulating valve 2 491 is arranged on the connecting pipeline between the liquid inlet 2 and the liquid inlet pump 2 451, the opening of the regulating valve 1 49 and the regulating valve 2 491 is adjustable, and the replenishing and returning liquid valve 46 is from left to right. They are respectively located at four positions, recorded as the first position, the second position, the third position and the fourth position. When the liquid replenishment valve 46 is located at the first position, the liquid replenishment port is connected with the liquid inlet port 1, and the liquid replenishment pump 47 is connected with the liquid inlet pump 1 45. When the liquid replenishment valve 46 is located at the second position, the liquid inlet port 1 is connected with the liquid return port, and the liquid return pump 471 is connected with the liquid inlet pump 1 45. When the liquid replenishment valve 46 is located at the third position, the liquid replenishment port is connected with the liquid inlet port 2, and the liquid replenishment pump 47 is connected with the liquid inlet pump 2 451. When the liquid replenishment valve 46 is located at the fourth position, the liquid inlet port 2 is connected with the liquid return port, and the liquid return pump 471 is connected with the liquid inlet pump 2 451.

[0032] The cyclone 1 41 and the cyclone 2 411 work in a time-series alternating manner. When the cyclone 1 41 is working, the cyclone 2 411 is closed, and the high-salt amine liquid in the high-salt amine liquid area at the bottom of the desulfurization tower 1 enters the cyclone 1 41 to separate the concentrated salt slurry. The concentrated salt slurry flows out from the bottom of the cyclone 1 41 and enters the reactor 1 43 for desalination reaction. At this time, the desalination reaction in the reactor 2 431 has been completed. The concentrated salt slurry is converted into low-salt amine liquid after desalination and enters the buffer tank 2 441. The liquid inlet pump 2 451 is started to pump the amine liquid in the buffer tank 2 441 to the bottom of the desulfurization tower 1 again. The liquid outlet flow meter 42 and the liquid inlet flow meter 48 monitor the concentrated salt slurry flow rate flowing out from the bottom of the cyclone 41 and the amine liquid flow rate returning to the desulfurization tower 1 respectively. When the concentrated salt slurry flow rate is greater than the reflux amine liquid flow rate, the valve core of the return liquid valve 46 moves to the first position, the liquid replenishment pump 47 starts, and the amine liquid replenishment tank 4 replenishes amine liquid to the amine liquid inlet 117. When the concentrated salt slurry flow rate is less than the reflux amine liquid flow rate, the valve core of the return liquid valve 46 moves to the second position, the liquid return pump 471 starts, and the excess amine liquid in front of the amine liquid inlet 117 returns to the amine liquid replenishment tank 4; similarly, the cyclone When the first 41 is closed, the cyclone second 411 works, the reactor second 431 performs desalination reaction, the liquid inlet pump 1 45 is started, and the amine liquid in the buffer tank 44 is pumped back to the bottom of the desulfurization tower 1, and the liquid outlet flow meter 2 421 monitors the flow of the concentrated salt slurry flowing out from the bottom of the second cyclone 411. When the flow of the concentrated salt slurry is greater than the flow of the refluxed amine liquid, the valve core of the return liquid valve 46 moves to the third position, the liquid replenishment pump 47 is started, and the amine liquid replenishment tank 4 replenishes amine liquid to the amine liquid inlet 117. When the flow of the concentrated salt slurry is less than the flow of the refluxed amine liquid, the valve core of the return liquid valve 46 moves to the fourth position. The return pump 471 is started, and the excess amine liquid in front of the amine liquid inlet 117 is returned to the amine liquid replenishing tank 4. The opening of the regulating valve 49 or the regulating valve 2 491 is adjusted according to the flow difference between the concentrated salt slurry flow and the reflux amine liquid flow; through the alternating operation of the cyclone 1 41 and the cyclone 2 411, sufficient reaction time is given to the desalination reaction, ensuring that the desulfurization tower 1 can obtain stable reflux amine liquid, and realizing automatic salt discharge of the desulfurization tower 1 in the working state. The amine liquid replenishing tank 4 is used to replenish or recover the amine liquid for the amine liquid inlet 117, ensuring the balance of the inlet and outlet flows at the bottom of the desulfurization tower 1.

[0033] Further, the dehydration device adopts a molecular sieve dehydration process, and the molecular sieve dehydration tower in the molecular sieve dehydration process can be selected as a double-tower molecular sieve or a multi-tower molecular sieve. In this example, a double-tower molecular sieve is adopted, and the dehydration device includes a dehydration tower 1 3, a dehydration tower 2 31 and a molecular sieve regeneration device. The top inlets of the dehydration tower 1 3 and the dehydration tower 2 31 are both connected to the outlet of the amine absorber 14, and the bottom outlets of the dehydration tower 1 3 and the dehydration tower 2 31 are both connected to the inlet of the gas storage tank 7, and the outlet of the gas storage tank 7 is connected to the liquefaction device 8. The desulfurized gas after desulfurization treatment enters dehydration tower 1 3 for dehydration treatment. At this time, dehydration tower 2 31 is regenerated by a molecular sieve regeneration device. Similarly, after the regeneration treatment of dehydration tower 2 31 is completed, the desulfurized gas enters dehydration tower 2 31 for dehydration treatment. Dehydration tower 1 3 is regenerated. After dehydration treatment, the desulfurized gas obtains dry natural gas. The dry natural gas enters the gas storage tank 7 and enters the liquefaction device 8 together with the hydrocarbon gas flashed out by the flash device 12 for natural gas liquefaction treatment to finally obtain liquefied natural gas.

[0034] Further, the molecular sieve regeneration device includes a compressor 5, a regeneration gas heat exchanger 51, a primary heater 52, a secondary heater 53, a primary reversing valve 54 and a secondary reversing valve 55. The heating side of the regeneration gas heat exchanger 51 is provided with a regeneration gas heating channel, and the cooling side of the regeneration gas heat exchanger 51 is provided with a regeneration gas cooling channel. The inlet end of the regeneration gas heating channel is connected to the outlet end of the compressor 5. The primary reversing valve 54 is a two-position three-way solenoid valve. The primary reversing valve 54 includes a primary air inlet, a first air outlet and a second air outlet. The primary air inlet is connected to the outlet end of the regeneration gas heating channel, the first air outlet is connected to the bottom inlet of the dehydration tower 1 3 and the dehydration tower 2 31, and the second air outlet is connected to the inlet of the primary heater 52. When the valve core of the primary reversing valve 54 is in the left position, the primary air inlet is connected to the first air outlet, and when the valve core of the primary reversing valve 54 is in the right position, the primary air inlet is connected to the second air outlet; the secondary reversing valve 55 is a two-position three-way solenoid valve. The three-way solenoid valve, the secondary reversing valve 55 includes a secondary air inlet, a third air outlet and a fourth air outlet. The secondary air inlet is connected to the outlet of the primary heater 52, the third air outlet is connected to the bottom inlet of the dehydration tower 1 3 and the dehydration tower 2 31, and the fourth air outlet is connected to the inlet of the secondary heater 53. When the valve core of the secondary reversing valve 55 is located at the left position, the secondary air inlet is connected to the third air outlet. When the valve core of the secondary reversing valve 55 is located at the right position, the secondary air inlet is connected to the fourth air outlet. The outlet of the secondary heater 53 is connected to the bottom inlet of the dehydration tower 1 3 and the dehydration tower 2 31; the inlet end of the regenerated gas cooling channel is connected to the top outlet of the dehydration tower 1 3 and the dehydration tower 2 31 respectively, and the outlet end of the regenerated gas cooling channel is connected to a cooler 56, and the outlet end of the cooler 56 is connected to a water separator 57, and the outlet of the water separator 57 is connected to the inlet end of the compressor 5, and the other outlet of the water separator 57 is connected to the inlet end of the compressor 5 and the sulfur recovery device 6.

[0035] The molecular sieve regeneration device has three working states, namely low-temperature regeneration, medium-temperature regeneration and high-temperature regeneration working states. In the low-temperature regeneration working state, the valve core of the first-stage reversing valve 54 is located at the left position, the valve core of the second-stage reversing valve 55 is located at the left position, and the outlet end of the regeneration gas heating channel of the regeneration gas heat exchanger 51 is connected with the bottom inlet of the dehydration tower 1 3 and the dehydration tower 2 31; in the medium-temperature regeneration working state, the valve core of the first-stage reversing valve 54 is located at the right position, the valve core of the second-stage reversing valve 55 is located at the left position, the outlet end of the regeneration gas heating channel of the regeneration gas heat exchanger 51 is connected with the inlet end of the first-stage heater 52, and the first-stage heater The outlet end of 52 is connected with the bottom inlet of dehydration tower 1 3 and dehydration tower 2 31, and the regeneration gas heating channel is connected in series with the first-level heater 52; in the high-temperature regeneration state, the valve core of the first-level reversing valve 54 is located at the right position, the valve core of the second-level reversing valve 55 is located at the right position, the outlet end of the regeneration gas heating channel of the regeneration gas heat exchanger 51 is connected with the inlet end of the first-level heater 52, the outlet end of the first-level heater 52 is connected with the inlet end of the second-level heater 53, the outlet end of the second-level heater 53 is connected with the bottom inlet of dehydration tower 1 3 and dehydration tower 2 31, and the regeneration gas heating channel is connected in series with the first-level heater 52 and the second-level heater 53 step by step.

[0036] After being pressurized by the compressor 5, the cold regenerated gas enters the regeneration gas heat exchanger 51 for heat exchange and temperature rise to obtain low-temperature regenerated gas. When the molecular sieve begins to be regenerated through the molecular sieve regeneration device, it is necessary to perform three stages of step-by-step temperature rise, namely, the low-temperature stage, the medium-temperature stage and the high-temperature stage. In the low-temperature stage, the molecular sieve regeneration device is in a low-temperature regeneration working state. The low-temperature regenerated gas after heat exchange and temperature rise through the regeneration gas heat exchanger 51 directly enters the dehydration tower 1 3 or the dehydration tower 2 31, so that the temperature of the molecular sieve in the tower is increased until the free water on the surface and in the macropores of the molecular sieve is desorbed; in the medium-temperature stage, the molecular sieve regeneration device is in a medium-temperature regeneration working state. The low-temperature regenerated gas after heat exchange and temperature rise through the regeneration gas heat exchanger 51 enters the primary heater 52 for further heating to obtain medium-temperature regenerated gas. The medium-temperature regenerated gas enters the dehydration tower 1 3 or the dehydration tower 2 31, so that the temperature of the molecular sieve in the tower is further increased until the bound water in the micropores of the molecular sieve is desorbed; in the high-temperature stage, the molecular sieve regeneration device is in a high-temperature regeneration working state. After the low-temperature regeneration gas is heated by heat exchange in the heat exchanger 51, it enters the primary heater 52 and the secondary heater 53 in turn for further heating to obtain high-temperature regeneration gas. The high-temperature regeneration gas enters the dehydration tower 1 3 or the dehydration tower 2 31, so that the temperature of the molecular sieve in the tower is further increased until the residual water in the molecular sieve is fully desorbed. At the same time, the residual sulfur components in the molecular sieve that have not been removed by the desulfurization device are desorbed together. By stepwise heating the molecular sieve in three different heating stages, the thermal stress damage in the thermal regeneration process of the molecular sieve can be reduced, the service life of the molecular sieve can be extended, and the energy consumption in the heating process of the regeneration gas can also be reduced. The regeneration gas leaving the dehydration tower 1 3 or the dehydration tower 2 31 enters the regeneration gas heat exchanger 51 for heat exchange and cooling, enters the cooler 56 for further cooling, and then enters the water separator 57. The water separator 57 separates the water in the regeneration gas and the carried desorbed sulfur to obtain cold regeneration gas. The cold regeneration gas returns to the inlet end of the compressor 5 again, and the desorbed sulfur and the sulfur components in the sulfur storage tank 23 enter the sulfur recovery device 6 for recovery treatment.

[0037] The present invention also provides a method for dehydrating and desulfurizing liquefied natural gas using the above-mentioned method, which is applied to the above-mentioned dehydrating and desulfurizing system for liquefied natural gas, and comprises the following steps: S1: The raw gas enters the desulfurization tower 1 and contacts with the lean amine liquid sprayed from top to bottom in the tower in countercurrent to undergo a desulfurization reaction to remove the sulfur component to obtain desulfurized gas. The lean amine liquid that adsorbs the sulfur component is converted into rich amine liquid. The secondary salts produced by the desulfurization reaction and the rich amine liquid gather in the high-salt amine liquid area to form a high-salt amine liquid. S2 and S5 are executed alternately during the desulfurization process. S2: Close the cyclone 411, start the cyclone 41, the high-salt amine solution flows out from the bottom of the cyclone 41 and enters the reactor 43 for desalination reaction, start the liquid inlet pump 451, and the amine solution in the buffer tank 441 returns to the bottom of the desulfurization tower 1. The liquid outlet flowmeter 42 and the liquid inlet flowmeter 48 monitor the outlet flow of the cyclone 41 and the inlet flow of the amine solution inlet 117 respectively. If the outlet flow of the cyclone 41 is greater than the inlet flow of the amine solution inlet 117, execute S3; if the outlet flow of the cyclone 41 is less than or equal to the inlet flow of the amine solution inlet 117, execute S4; Among them, when the pressure difference inside the desulfurization tower 1 is too large, liquid blocking will occur, affecting the stable operation of the desulfurization tower 1. When the pressure difference inside the tower is too small, it will affect the desulfurization efficiency. Therefore, it is very important to ensure the stability of the pressure difference inside the desulfurization tower 1. This embodiment adjusts the pressure difference inside the tower by adjusting the salt slurry flow rate flowing out of the desulfurization tower 1, ensuring that the desulfurization tower 1 can maintain a stable pressure difference inside the tower during the automatic salt discharge process.

[0038] S3: The liquid replenishment valve 46 is adjusted to connect the liquid replenishment pump 47 with the liquid inlet pump 45, the liquid replenishment pump 47 is started, the liquid return pump 471 is closed, and the amine liquid replenishment tank 4 replenishes amine liquid to the amine liquid inlet 117; S4: the liquid replenishment valve 46 is adjusted to connect the liquid return pump 471 with the liquid inlet pump 45, the liquid replenishment pump 47 is closed, the liquid return pump 471 is started, and the excess amine liquid in front of the amine liquid inlet 117 is returned to the amine liquid replenishment tank 4; S5: close the cyclone 1 41, start the cyclone 2 411, the high-salt amine solution flows out from the bottom of the cyclone 2 411 into the reactor 2 431 for desalination reaction, start the liquid inlet pump 1 45, the amine solution in the buffer tank 1 44 returns to the bottom of the desulfurization tower 1, the liquid outlet flowmeter 2 421 and the liquid inlet flowmeter 48 monitor the outlet flow of the cyclone 2 411 and the inlet flow of the amine solution inlet 117 respectively, if the outlet flow of the cyclone 2 411 is greater than the inlet flow of the amine solution inlet 117, execute S6; if the outlet flow of the cyclone 2 411 is less than or equal to the inlet flow of the amine solution inlet 117, execute S7; S6: The liquid replenishment valve 46 is adjusted to connect the liquid replenishment pump 47 with the second liquid inlet pump 451, the liquid replenishment pump 47 is started, the liquid return pump 471 is closed, and the amine liquid replenishment tank 4 replenishes amine liquid to the amine liquid inlet 117; S7: the liquid replenishment valve 46 is adjusted to the liquid return pump 471 and the liquid inlet pump 2 451 are connected, the liquid replenishment pump 47 is closed, the liquid return pump 471 is started, and the excess amine liquid in front of the amine liquid inlet 117 is returned to the amine liquid replenishment tank 4; Among them, in order to ensure that the desulfurization reaction in the desulfurization tower 1 can still operate normally during the automatic salt discharge process of the desulfurization tower 1, it is required that the inlet and outlet flow rates from the bottom of the desulfurization tower 1 are roughly the same. By alternately executing S2 and S5, the desulfurization tower 1 can continuously carry out the salt slurry discharge, desalination reaction and amine liquid intake process. At the same time, the amine liquid replenishing tank 4 is used to replenish or recover the amine liquid for the amine liquid inlet 117, ensuring the inlet and outlet flow balance at the bottom of the desulfurization tower 1.

[0039] S8: The rich amine liquid flows from the bottom of the desulfurization tower 1 into the amine liquid regeneration device for regeneration and then returns to the desulfurization tower 1. The hydrocarbon gas flashed out by the amine liquid regeneration device in the process of treating the amine liquid enters the fuel gas storage tank 7. The desulfurized gas enters the amine absorber 14 from the top of the desulfurization tower 1 to remove the small amount of amine liquid carried and then enters the dehydration device for dehydration treatment. The dehydration tower 1 3 and the dehydration tower 2 31 in the dehydration device alternately perform dehydration and regeneration processes. When the desulfurized gas enters the dehydration tower 1 3 for dehydration treatment, the dehydration tower 2 31 is regenerated by the molecular sieve regeneration device; after the regeneration treatment of the dehydration tower 2 31 is completed, the desulfurized gas enters the dehydration tower 2 31 for dehydration treatment, and the dehydration tower 1 3 is regenerated; S9: After being pressurized by the compressor 5, the cold regeneration gas enters the regeneration gas heat exchanger 51 for heat exchange and temperature increase. The primary reversing valve 54 and the secondary reversing valve 55 are adjusted to gradually increase the temperature of the molecular sieve. The temperature increase process goes through a low temperature stage, a medium temperature stage and a high temperature stage respectively. In the low temperature stage, the valve core of the first reversing valve 54 is adjusted to the left position, the first air inlet is connected to the first air outlet, the valve core of the second reversing valve 55 is adjusted to the left position, the second air inlet is connected to the third air outlet, and the low temperature regeneration gas after heat exchange and temperature increase in the regeneration gas heat exchanger 51 enters the dehydration tower 1 3 or the dehydration tower 2 31, and the temperature of the molecular sieve in the tower is increased to the point where the free water on the surface of the molecular sieve and in the macropores is desorbed; In the medium temperature stage, the valve core of the first reversing valve 54 is adjusted to the right position, the first air inlet is connected with the second air outlet, and the low-temperature regeneration gas after heat exchange and temperature increase in the regeneration gas heat exchanger 51 enters the first heater 52 and is further heated to obtain medium-temperature regeneration gas. The medium-temperature regeneration gas enters the dehydration tower 1 3 or the dehydration tower 2 31, so that the temperature of the molecular sieve in the tower is further increased until the bound water in the micropores of the molecular sieve is desorbed; In the high-temperature stage, the valve core of the secondary reversing valve 55 is adjusted to the right position, the secondary air inlet is connected with the fourth air outlet, and the low-temperature regenerated gas after heat exchange and temperature increase in the regenerated gas heat exchanger 51 successively enters the primary heater 52 and the secondary heater 53 to obtain high-temperature regenerated gas after further temperature increase. The high-temperature regenerated gas enters the dehydration tower 1 3 or the dehydration tower 2 31, so that the temperature of the molecular sieve in the tower is further increased until the residual water in the molecular sieve is fully desorbed, and at the same time, the residual sulfur components in the molecular sieve that have not been removed by the desulfurization device are desorbed together; Among them, by adjusting the first-level reversing valve 54 and the second-level reversing valve 55, adjusting the number of heaters involved in the heating of the regenerated gas, and performing step-by-step heating of the molecular sieve in three different heating stages, the thermal stress damage of the molecular sieve during the thermal regeneration process can be reduced, the service life of the molecular sieve can be extended, and the energy consumption when heating the regenerated gas can also be reduced.

[0040] S10: the regeneration gas after heat exchange with the molecular sieve enters the regeneration gas heat exchanger 51 for heat exchange and cooling, and then enters the water separator 57 after further cooling through the cooler 56. The water separator 57 separates the water in the regeneration gas and the desorbed sulfur carried by the regeneration gas to obtain cold regeneration gas. The cold regeneration gas returns to the inlet end of the compressor 5 again, and the desorbed sulfur and the sulfur-containing components in the sulfur storage tank 23 enter the sulfur recovery device 6 for recovery treatment; S11: After dehydration, the desulfurized gas is treated to obtain dry natural gas, which enters the fuel gas storage tank 7 and enters the liquefaction device 8 together with the hydrocarbon gas flashed out from the amine liquid regeneration device for natural gas liquefaction treatment to finally obtain liquefied natural gas.

[0041] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A dehydration and desulfurization treatment system for liquefied natural gas, characterized in that: The invention comprises a desulfurization device, a dehydration device and an automatic salt discharge device, wherein the desulfurization device is connected to the dehydration device, and the automatic salt discharge device is connected to the desulfurization device. The automatic salt discharge device comprises a cyclone 1 (41) and a cyclone 2 (411) which work in a time-sequential alternating manner. The dehydration device comprises a molecular sieve regeneration device, and the molecular sieve regeneration device comprises a regeneration gas heat exchanger (51), a first-stage heater (52) and a second-stage heater (53). The regeneration gas heat exchanger (51), the first-stage heater (52) and the second-stage heater (53) are connected in series step by step.

2. A liquefied natural gas dehydration and desulfurization treatment system according to claim 1, characterized in that: The desulfurization device comprises a desulfurization tower (1), the desulfurization tower (1) comprising a tower body (11) and a filter membrane (116), the filter membrane (116) being arranged at the bottom of the tower body (11), the filter membrane (116) dividing the bottom of the tower body (11) into a high-salt amine liquid area and a low-salt amine liquid area, a cyclone 1 (41) and a cyclone 2 (411) being arranged on both sides outside the tower body (11), the inlets of the cyclone 1 (41) and the cyclone 2 (411) being both connected to the high-salt amine liquid area above the filter membrane (116), the overflow ports at the top of the cyclone 1 (41) and the cyclone 2 (411) being both connected to the low-salt amine liquid area below the filter membrane (116), and the desulfurization tower (1) being provided with an amine liquid inlet (117) at the side of the low-salt amine liquid area.

3. A liquefied natural gas dehydration and desulfurization treatment system according to claim 2, characterized in that: The automatic salt discharge device further comprises a reactor 1 (43), a reactor 2 (431) and a liquid inlet flowmeter (48); the inlets of the reactor 1 (43) and the reactor 2 (431) are respectively connected to the outlets at the bottom of the cyclone 1 (41) and the cyclone 2 (411); a liquid outlet flowmeter 1 (42) is arranged on the connecting pipe between the cyclone 1 (41) and the reactor 1 (43); a liquid outlet flowmeter 2 (421) is arranged on the connecting pipe between the cyclone 2 (411) and the reactor 2 (431); the outlets of the reactor 1 (43) and the reactor 2 (431) are respectively connected to a liquid inlet pump 1 (45) and a liquid inlet pump 2 (451); the outlets of the liquid inlet pump 1 (45) and the liquid inlet pump 2 (451) are both connected to the amine liquid inlet (117); and the liquid inlet flowmeter (48) is arranged on the connecting pipe of the amine liquid inlet (117).

4. A liquefied natural gas dehydration and desulfurization treatment system according to claim 3, characterized in that: The automatic salt discharge device also includes an amine liquid replenishing tank (4) and a replenishing and returning liquid valve (46). The amine liquid replenishing tank (4) is respectively connected to a replenishing pump (47) and a returning liquid pump (471). The replenishing and returning liquid valve (46) includes a replenishing port, a returning liquid port, a first liquid inlet, and a second liquid inlet. The replenishing port is connected to the outlet of the replenishing pump (47), the returning liquid port is connected to the inlet of the returning liquid pump (471), the first liquid inlet is connected to the first liquid inlet pump (45), and the second liquid inlet is connected to the second liquid inlet pump (451).

5. A liquefied natural gas dehydration and desulfurization treatment system according to claim 2, characterized in that: The desulfurization tower (1) further comprises a lean liquid distributor (111), a swirl plate (112), a scraper (113) and an agitator (114). The agitator (114) is arranged in a high-salt amine liquid area. The agitator (114) is rotatably connected to the bottom of the tower body (11). The lean liquid distributor (111) is installed in the tower body (11). The lean liquid distributor (111) is provided with multiple layers from bottom to top. The swirl plate (112) is installed below each layer of the lean liquid distributor (111). The scraper (113) is symmetrically installed on the upper and lower sides of the swirl plate (112). Multiple scrapers (113) are evenly arranged on each side along the circumference of the tower body (11). The scraper (113) is rotatably connected to the middle of the swirl plate (112) through a connecting rod. The scraper (113) abuts against the inner wall of the tower body (11).

6. A liquefied natural gas dehydration and desulfurization treatment system according to claim 2, characterized in that: The molecular sieve regeneration device further comprises a primary reversing valve (54) and a secondary reversing valve (55), wherein the primary reversing valve (54) comprises a primary air inlet, a first air outlet and a second air outlet, wherein the primary air inlet is connected to the outlet end of the heating side of the regeneration gas heat exchanger (51), and the second air outlet is connected to the inlet of the primary heater (52), and the secondary reversing valve (55) comprises a secondary air inlet, a third air outlet and a fourth air outlet, wherein the secondary air inlet is connected to the outlet of the primary heater (52), and the fourth air outlet is connected to the inlet of the secondary heater (53).

7. A liquefied natural gas dehydration and desulfurization treatment system according to claim 6, characterized in that: The dehydration device further comprises a dehydration tower 1 (3) and a dehydration tower 2 (31); the bottom inlets of the dehydration tower 1 (3) and the dehydration tower 2 (31) are respectively connected to the first air outlet, the third air outlet and the outlet of the secondary heater (53); the top outlets of the dehydration tower 1 (3) and the dehydration tower 2 (31) are connected to the cooling side inlet of the regeneration gas heat exchanger (51); the heating side inlet of the regeneration gas heat exchanger (51) is connected to the compressor (5); the cooling side outlet of the regeneration gas heat exchanger (51) is connected to the cooler (56); the outlet of the cooler (56) is connected to the water separator (57); the outlet of the water separator (57) is connected to the inlet of the compressor (5).

8. A liquefied natural gas dehydration and desulfurization treatment system according to claim 2, characterized in that: The desulfurization device further comprises an amine liquid regeneration device, the amine liquid regeneration device comprising a flash device (12), a lean-rich liquid heat exchanger (13) and a regeneration tower (2), the bottom outlet of the desulfurization tower (1) being connected to the inlet of the flash device (12), the bottom outlet of the flash device (12) being connected to the inlet end of the lean-rich liquid heat exchanger (13), the outlet end of the lean-rich liquid heat exchanger (13) being connected to the upper inlet of the regeneration tower (2), the bottom outlet of the regeneration tower (2) being connected to the lean-rich liquid heat exchanger (13), the outlet end of the lean-rich liquid heat exchanger (13) being connected to a regeneration pump (24), and the outlet end of the regeneration pump (24) being connected to the upper part of the desulfurization tower (1).

9. A liquefied natural gas dehydration and desulfurization treatment system according to claim 7, characterized in that: The top inlets of the dehydration tower 1 (3) and the dehydration tower 2 (31) are both connected to the top outlet of the desulfurization tower (1), the bottom outlets of the dehydration tower 1 (3) and the dehydration tower 2 (31) are connected to a gas storage tank (7), and the outlet of the gas storage tank (7) is connected to a liquefaction device (8).

10. A method for dehydration and desulfurization of liquefied natural gas, applied to the dehydration and desulfurization system for liquefied natural gas according to any one of claims 1 to 9, characterized in that: The steps include: S1: The raw gas enters the desulfurization tower (1) and contacts with the lean amine liquid sprayed from top to bottom in the tower in countercurrent to undergo a desulfurization reaction to remove the sulfur components to obtain desulfurized gas. The lean amine liquid that adsorbs the sulfur components is converted into rich amine liquid. The secondary salts produced by the desulfurization reaction and the rich amine liquid gather in the high-salt amine liquid area to form a high-salt amine liquid. During the desulfurization process, S2 and S5 are performed alternately; S2: Close cyclone 2 (411), start cyclone 1 (41), high-salt amine liquid passes through cyclone 1 (41) and enters reactor 1 (43) for desalination reaction, start inlet pump 2 (451), low-salt amine liquid in buffer tank 2 (441) returns to the bottom of desulfurization tower (1), outlet flow meter 1 (42) and inlet flow meter (48) monitor the outlet flow of cyclone 1 (41) and the inlet flow of amine liquid inlet (117) respectively. If the outlet flow of cyclone 1 (41) is greater than the inlet flow of amine liquid inlet (117), execute S3; if the outlet flow of cyclone 1 (41) is less than or equal to the inlet flow of amine liquid inlet (117), execute S4; S3: the liquid replenishment valve (46) is adjusted to connect the liquid replenishment pump (47) to the liquid inlet pump 1 (45), the liquid replenishment pump (47) is started, the liquid return pump (471) is closed, and the amine liquid replenishment tank (4) replenishes amine liquid to the amine liquid inlet (117); S4: the liquid return valve (46) is adjusted to connect the liquid return pump (471) with the liquid inlet pump 1 (45), the liquid replenishment pump (47) is closed, the liquid return pump (471) is started, and the excess amine liquid in front of the amine liquid inlet (117) is returned to the amine liquid replenishment tank (4); S5: close the cyclone 1 (41), start the cyclone 2 (411), the high-salt amine liquid passes through the cyclone 2 (411) and enters the reactor 2 (431) for desalination reaction, start the liquid inlet pump 1 (45), and the amine liquid in the buffer tank 1 (44) returns to the bottom of the desulfurization tower (1), and the outlet flow meter 2 (421) and the inlet flow meter (48) respectively monitor the outlet flow of the cyclone 2 (411) and the inlet flow of the amine liquid inlet (117). If the outlet flow of the cyclone 2 (411) is greater than the inlet flow of the amine liquid inlet (117), execute S6; if the outlet flow of the cyclone 2 (411) is less than or equal to the inlet flow of the amine liquid inlet (117), execute S7; S6: the liquid replenishment valve (46) is adjusted to connect the liquid replenishment pump (47) with the second liquid inlet pump (451), the liquid replenishment pump (47) is started, the liquid return pump (471) is closed, and the amine liquid replenishment tank (4) replenishes amine liquid to the amine liquid inlet (117); S7: the liquid replenishment valve (46) is adjusted to connect the liquid return pump (471) with the second liquid inlet pump (451), the liquid replenishment pump (47) is closed, the liquid return pump (471) is started, and the excess amine liquid in front of the amine liquid inlet (117) is returned to the amine liquid replenishment tank (4); S8: The rich amine liquid flows from the bottom of the desulfurization tower (1) into the amine liquid regeneration device for regeneration and then returns to the desulfurization tower (1). The desulfurized gas enters the dehydration device for dehydration. The dehydration tower 1 (3) and the dehydration tower 2 (31) in the dehydration device perform dehydration and regeneration processes alternately. S9: After being pressurized by the compressor (5), the cold regeneration gas enters the regeneration gas heat exchanger (51) for heat exchange and temperature increase to obtain low-temperature regeneration gas. The primary reversing valve (54) and the secondary reversing valve (55) are adjusted to gradually increase the temperature of the molecular sieve. The temperature increase process goes through a low-temperature stage, a medium-temperature stage and a high-temperature stage respectively. S10: the regeneration gas after heat exchange with the molecular sieve enters the regeneration gas heat exchanger (51) for heat exchange and cooling, and then enters the water separator (57) for further cooling to obtain cold regeneration gas. The cold regeneration gas returns to the inlet end of the compressor (5) again; S11: After dehydration, the desulfurized gas is dehydrated to obtain dry natural gas, which enters the gas storage tank (7) and then enters the liquefaction device (8) for natural gas liquefaction treatment to finally obtain liquefied natural gas.

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