A seawater desalination system

Abstract

The present application relates to the technical field of seawater desalination treatment, and provides a seawater desalination system, which comprises an evaporation subsystem, a membrane distillation subsystem and a coupling subsystem; the evaporation subsystem comprises a material inlet, a material outlet, a steam inlet and a steam outlet, the steam inlet is communicated with one end of a first pipeline, the steam outlet is communicated with one end of a second pipeline, the material outlet is communicated with a membrane distillation concentration unit of the membrane distillation subsystem through a third pipeline, the membrane distillation concentration unit is communicated with a condensation unit and one end of a fourth pipeline, and the coupling subsystem comprises a steam ejector pump group, the steam ejector pump group is installed on the first pipeline, and the other end of the second pipeline and / or the fourth pipeline is communicated with the steam ejector pump group; the seawater is concentrated and distilled twice, the efficiency of seawater treatment is greatly improved, the low-temperature and low-pressure steam discharged from the evaporation subsystem and the membrane distillation subsystem is recycled and utilized, the efficient utilization of low-grade energy is realized, and the overall energy consumption of the system is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of seawater desalination treatment, and particularly relates to a seawater desalination system. BACKGROUND

[0002] Fresh water is one of the basic materials for human society to survive and develop. Fresh water resource shortage has become an important factor affecting the sustainable development of the world economy and society, and has attracted the general attention of the whole society. Actively promoting seawater desalination technology and getting water from the sea have become the consensus of the world today.

[0003] Seawater desalination, also known as seawater desalination, is a technology and process for separating salt and water in seawater. Seawater desalination has also become one of the most effective measures to solve the current water shortage problem in coastal areas. It can be predicted that with the continuous development of economy and the improvement of people's living standards, the contradiction between supply and demand of fresh water resources will become increasingly acute, and seawater desalination as an effective means to solve the shortage of fresh water resources will become more and more important.

[0004] At present, low-temperature multi-effect distillation technology is widely used for seawater desalination treatment. Low-temperature multi-effect distillation technology uses waste heat or low-quality steam from power plants and chemical plants to distill seawater in a series of falling film evaporators at a lower temperature (less than 70 DEG C). A certain amount of steam is input through multiple evaporation and condensation to obtain distilled water with multiple times of input steam. In the low-temperature multi-effect distillation technology, each evaporator is also called "effect". The product water quality of this technology is high, and the salt content of the desalinated water can be less than 10 mg / L.

[0005] However, it is found in actual treatment process that the existing low-temperature multi-effect distillation technology is difficult to further concentrate and distill seawater, so the efficiency of seawater desalination treatment is not high, and most of the non-condensable gas discharged from the vacuum device of the low-temperature multi-effect distillation seawater desalination system is steam. However, due to its low temperature and pressure, it cannot be directly reused, and is generally discharged, causing waste of resources and energy. SUMMARY

[0006] (I) Technical problem to be solved

[0007] The purpose of the present application is to provide a seawater desalination system to solve the problem that the low-temperature multi-effect distillation technology currently used for seawater desalination treatment has a low concentration ratio and is difficult to reuse the steam generated in the treatment process.

[0008] (II) Technical scheme

[0009] In order to solve the above technical problems, the present application provides a seawater desalination system,

[0010] The system comprises an evaporation subsystem, a membrane distillation subsystem and a coupling subsystem.

[0011] The evaporation subsystem is used for evaporative concentration of seawater, and comprises a material inlet, a material outlet, a steam inlet and a steam outlet.

[0012] The membrane distillation subsystem comprises a membrane distillation concentration unit and a condensation unit, and the material inlet of the membrane distillation concentration unit is connected to the other end of the third pipeline.

[0013] The coupling subsystem comprises a steam ejector pump group, which is installed on the first pipeline, and the other end of the second pipeline and / or the other end of the fourth pipeline is connected to the steam ejector pump group.

[0014] Preferably, the coupling subsystem further comprises a steam compressor group, which is installed on the first pipeline between the steam ejector pump group and the evaporation subsystem.

[0015] Preferably, the coupling subsystem further comprises a pressure stabilizer, which is connected to the other end of the second pipeline and / or the other end of the fourth pipeline and the steam ejector pump group.

[0016] Preferably, the evaporation subsystem comprises a plurality of falling film evaporators connected in series, wherein the steam inlet of the falling film evaporator at the first effect is connected to the one end of the first pipeline, the steam outlet of each falling film evaporator is connected to the steam inlet of the falling film evaporator at the next effect through a first steam conveying pipe, and the steam outlet and the material outlet of the falling film evaporator at the last effect are connected to the other end of the second pipeline and the third pipeline, respectively.

[0017] The condensate outlet of each falling film evaporator is connected to a fifth pipeline through a corresponding short connecting pipe, and each falling film evaporator between the first effect and the last effect is provided with a corresponding flash evaporator, which is installed at the joint of the short connecting pipe and the fifth pipeline of the corresponding effect, and the steam outlet of each flash evaporator is connected to the middle part of the first steam conveying pipe of the corresponding falling film evaporator through a second steam conveying pipe.

[0018] Preferably, in the present application, the material inlet of the falling film evaporator at the first effect is connected to one end of the sixth pipeline, the first condenser is installed on the sixth pipeline, one heat exchange channel of the first condenser is connected to the sixth pipeline, and the other heat exchange channel of the first condenser is connected to one end of the fifth pipeline; the falling film evaporator at the last effect is connected to the other heat exchange channel of the first condenser through the first steam conveying pipeline.

[0019] Preferably, in the present application, the falling film evaporator at each effect between the first effect and the last effect is provided with a corresponding preheater, the preheater is installed on the sixth pipeline, the sixth pipeline is connected to one heat exchange channel of each preheater, and the falling film evaporator at each effect is connected to the other heat exchange channel of the preheater corresponding to the falling film evaporator at the next effect through the first steam conveying pipeline.

[0020] Preferably, in the present application, the membrane distillation concentrating unit comprises a plurality of membrane distillation assemblies connected in series, the material inlet of the membrane distillation assembly at the first effect is connected to the other end of the third pipeline, and the material outlet of each membrane distillation assembly is connected to the material inlet of the membrane distillation assembly at the next effect through an adapter pipeline.

[0021] The steam outlet of the membrane distillation assembly at the first effect is connected to one end of the fourth pipeline, and the steam outlet of the membrane distillation assembly at each other effect is connected to the condensing unit.

[0022] Preferably, in the present application, the condensing unit comprises a second condenser, a third steam conveying pipeline and a seventh pipeline.

[0023] The third pipeline or the adapter pipeline corresponding to the material inlet end of each membrane distillation assembly is respectively provided with one second condenser.

[0024] The third pipeline or the adapter pipeline is connected to one heat exchange channel of the second condenser.

[0025] One end of the other heat exchange channel of each second condenser is connected to the steam outlet of the membrane distillation assembly at the next effect through the third steam conveying pipeline, and the other end of the other heat exchange channel of each second condenser is connected to the seventh pipeline.

[0026] Preferably, in the present application, the condensing unit further comprises an eighth pipeline, one end of the eighth pipeline is connected to the first pipeline between the steam compressor set and the evaporation subsystem, the other end of the eighth pipeline is connected to one end of the other heat exchange channel of the second condenser at the last effect, and the other end of the other heat exchange channel of the second condenser at the last effect is connected to the seventh pipeline.

[0027] Preferably, the condensing unit in the application further comprises a third condenser and a ninth pipeline, one end of the ninth pipeline is communicated with the steam outlet of the primary effect membrane distillation assembly, the other end of the ninth pipeline is communicated with the seventh pipeline; the third condenser is installed on the ninth pipeline.

[0028] (III) Technical effects

[0029] The seawater desalination system provided by the application, when performing seawater desalination treatment, firstly, after the high-temperature and high-pressure power steam is introduced into the evaporation subsystem through the first pipeline and the pretreated seawater is injected into the material inlet of the evaporation subsystem, the seawater is evaporated and concentrated for the first time by the evaporation subsystem, then, the concentrated seawater treated by the evaporation subsystem is transferred to the membrane distillation concentration unit in the membrane distillation subsystem, the concentrated seawater is concentrated again by the membrane distillation concentration unit, the seawater after concentration is discharged, and the steam generated in the concentration process of the membrane distillation concentration unit is introduced into the condensing unit in the membrane distillation subsystem, and the condensed fresh water is obtained after the condensing treatment of the condensing unit; at the same time, during the whole treatment process, the last-effect deficient gas output by the evaporation subsystem and / or part of the steam output by the membrane distillation subsystem is returned to the steam ejector pump set in the coupling subsystem, and the steam ejector pump set is used to transport the steam together with the power steam to the evaporation subsystem again and participate in the seawater desalination treatment in the next cycle.

[0030] As can be seen from the above, the seawater is concentrated and distilled twice by the evaporation subsystem and the membrane distillation subsystem, which greatly improves the efficiency of seawater treatment, and the low-temperature and low-pressure steam discharged from the evaporation subsystem and the membrane distillation subsystem is recycled and utilized to provide energy for the treatment process of the evaporation subsystem and the membrane distillation subsystem, realizing efficient utilization of low-grade energy and reducing the overall energy consumption of the system. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the application or the technical solutions in the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0032] Figure 1 The structure diagram of the seawater desalination system shown in the embodiments of the application.

[0033] In the diagram: Ⅰ-Evaporation subsystem, Ⅱ-Membrane distillation subsystem, Ⅲ-Coupled subsystem, 1-First pipeline, 2-Second pipeline, 3-Third pipeline, 4-Fourth pipeline, 5-Fifth pipeline, 6-Sixth pipeline, 7-Seventh pipeline, 8-Eighth pipeline, 9-Ninth pipeline, 10-Steam ejector pump unit, 11-Steam compressor unit, 12-Pressure stabilizer, 13-Falling film evaporator, 14-First steam delivery pipe, 15-Flash evaporator, 16-Second steam delivery pipe, 17-First condenser, 18-Membrane distillation assembly, 19-Transfer pipe, 20-Second condenser, 21-Third steam delivery pipe, 22-Third condenser, 23-Preheater. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] See Figure 1 This embodiment provides a seawater desalination system.

[0037] It includes evaporation subsystem I, membrane distillation subsystem II, and coupling subsystem III;

[0038] Evaporation subsystem I is used to exchange heat between the introduced power steam and seawater, and to evaporate and concentrate the seawater. Evaporation subsystem I includes a material inlet, a material outlet, a steam inlet, and a steam outlet. The steam inlet is connected to one end of the first pipeline 1, the steam outlet is connected to one end of the second pipeline 2, and the material outlet is connected to one end of the third pipeline 3.

[0039] The membrane distillation subsystem II comprises a membrane distillation concentrating unit and a condensing unit, the material inlet of the membrane distillation concentrating unit is communicated with the other end of the third pipeline 3, the steam outlet of the membrane distillation concentrating unit is communicated with the condensing unit and one end of the fourth pipeline 4, wherein the condensing unit condenses the steam output by the membrane distillation concentrating unit in the process of concentrating seawater to output fresh water.

[0040] The coupling subsystem III comprises a steam ejector pump group 10, the steam ejector pump group 10 is installed on the first pipeline 1, and the other end of the second pipeline 2 and / or the other end of the fourth pipeline 4 is communicated with the steam ejector pump group 10.

[0041] As shown by the structure, Figure 1 As shown by the structure, when the seawater is desalinated, the high-temperature and high-pressure power steam is input into the steam inlet of the evaporation subsystem I through the first pipeline 1, the pretreated seawater is injected into the material inlet of the evaporation subsystem I, then the seawater is evaporated and concentrated by the evaporation subsystem I for the first time, the concentrated seawater output by the evaporation subsystem I is transferred to the membrane distillation concentrating unit in the membrane distillation subsystem II through the third pipeline 3, the concentrated seawater is concentrated again by the membrane distillation concentrating unit, the concentrated seawater is discharged, the steam generated in the concentrating process of the membrane distillation concentrating unit is input into the condensing unit, the condensed fresh water is obtained after the condensing treatment of the condensing unit, and the released condensing heat is used as the preheating heat source of the previous membrane distillation assembly; in the whole process, the last-effect exhaust gas output by the evaporation subsystem I and / or part of the steam output by the membrane distillation subsystem II is returned to the steam ejector pump group 10 in the coupling subsystem III, and the steam ejector pump group 10 sends the steam together with the power steam to the evaporation subsystem I again and participates in the seawater desalination treatment in the next cycle.

[0042] As shown above, the seawater is concentrated and distilled twice by the evaporation subsystem I and the membrane distillation subsystem II, so that the efficiency of seawater treatment is greatly improved, the low-temperature and low-pressure steam discharged by the evaporation subsystem I and the membrane distillation subsystem II is recycled by the coupling subsystem III, energy is provided for the seawater desalination process of the evaporation subsystem I and the membrane distillation subsystem II, and efficient use of low-grade energy is realized.

[0043] Further, the coupling subsystem III comprises a steam compressor group 11, and the steam compressor group 11 is installed on the first pipeline 1 between the steam ejector pump group 10 and the evaporation subsystem I.

[0044] Specifically, the steam ejector pump set 10, in operation, sucks steam from the second pipeline 2 and / or the fourth pipeline 4, mixes the steam with motive steam and pumps the mixed steam out, achieving the purpose of primary enthalpy increase, and the mixed steam is compressed again by the steam compressor set 11 during the delivery in the first pipeline 1, i.e. secondary enthalpy increase, to provide high-temperature and high-pressure steam for the evaporation subsystem I and the membrane distillation subsystem II, thereby realizing efficient utilization of low-grade energy.

[0045] Further, the coupling subsystem III in the embodiment further comprises a pressure stabilizer 12, wherein the pressure stabilizer 12 can adopt a closed air chamber; the other end of the second pipeline 2 and the other end of the fourth pipeline 4 are communicated with the pressure stabilizer 12, and the pressure stabilizer 12 is communicated with the steam ejector pump set 10 through a pipeline.

[0046] Specifically, in operation, the pressure stabilizer 12 not only can transfer and store the steam delivered by the second pipeline 2 and the fourth pipeline 4, but also can stabilize the pressure of the steam delivered by the second pipeline 2 and the fourth pipeline 4, so as to facilitate the steam ejector pump set 10 to suck the steam stored in the pressure stabilizer 12 in operation.

[0047] Further, the evaporation subsystem I in the embodiment comprises a plurality of falling film evaporators 13 connected in series, wherein the steam inlet of the falling film evaporator located at the first effect is communicated with one end of the first pipeline 1, the steam outlet of each falling film evaporator is communicated with the steam inlet of the falling film evaporator located at the next effect through a first steam delivery pipe 14, the steam outlet of the falling film evaporator located at the last effect is communicated with one end of the second pipeline 2, and the material outlet of the falling film evaporator located at the last effect is communicated with one end of the third pipeline 3. The condensate outlet of each falling film evaporator is communicated with the fifth pipeline 5 through a corresponding short connecting pipe, and each falling film evaporator located between the first effect and the last effect is provided with a corresponding flash evaporator 15, each flash evaporator is installed at the joint of the short connecting pipe of the corresponding effect and the fifth pipeline 5, and the steam outlet of each flash evaporator is communicated with the middle part of the first steam delivery pipe 14 of the corresponding falling film evaporator through a second steam delivery pipe 16.

[0048] Specifically, when the seawater is treated, the pretreated seawater enters the first falling film evaporator, and is uniformly distributed on the pipeline of the falling film evaporator by the film distributor. The motive steam enters the heat exchange pipeline of the first falling film evaporator after passing through the steam ejector pump set 10 and the steam compressor set 11, exchanges heat with the pretreated seawater entering the first falling film evaporator, and the secondary steam generated by the heat exchange enters the heat exchange pipeline of the next falling film evaporator adjacent to the first falling film evaporator to serve as the heat source of the next falling film evaporator. The seawater not evaporated after the preliminary concentration of the first falling film evaporator enters the next falling film evaporator to be further evaporated and concentrated. The condensed water generated by the heat exchange is discharged into the flash evaporator 15 to flash, and the flash evaporator 15 supplies steam to the next falling film evaporator. In this way, the condensed water formed by the condensation of each falling film evaporator is flashed by the flash evaporator 15, and the flashed steam is supplied to the next falling film evaporator, and the unflashed part is discharged as condensed water. The exhaust steam of the last falling film evaporator of the evaporation subsystem I is introduced into the steam ejector pump set 10 again, and enters the heat exchange pipeline of the first falling film evaporator again through the steam compressor set 12. The concentrated seawater of the last falling film evaporator enters the membrane distillation subsystem II.

[0049] Further, in the embodiment, one end of the sixth pipeline 6 is connected to the material inlet of the first falling film evaporator, the first condenser 17 is installed on the sixth pipeline 6, one heat exchange channel of the sixth pipeline 6 is connected to the first condenser 17, and the other heat exchange channel of the first condenser 17 is connected to one end of the fifth pipeline 5. Therefore, the first condenser 17 can preheat the pretreated seawater by using the condensed water output by the last falling film evaporator of the evaporation subsystem I.

[0050] At the same time, the other heat exchange channel of the first condenser 17 is connected to the first steam delivery pipeline 14 of the last falling film evaporator, so that the first condenser 17 can also preheat the pretreated seawater by using the exhaust steam output by the last falling film evaporator of the evaporation subsystem I.

[0051] Further, in the embodiment, the falling film evaporator between the first falling film evaporator and the last falling film evaporator is provided with a corresponding preheater 23, the preheater 23 is installed on the sixth pipeline 6, the sixth pipeline 6 is connected to one heat exchange channel of each preheater, and the first steam delivery pipeline 14 of each falling film evaporator 13 is connected to the other heat exchange channel of the preheater 23 corresponding to the next falling film evaporator 13.

[0052] Specifically, since each effect's flash evaporator 15 is communicated with the middle part of the first steam delivery pipe 14 of the corresponding effect's falling film evaporator 13 through the second steam delivery pipe 16 on it, and each effect's falling film evaporator 13 is communicated with the preheater 23 corresponding to the next effect's falling film evaporator 13 through the first steam delivery pipe 14, each effect's preheater 23 receives the excess steam from the previous effect's falling film evaporator 13 and flash evaporator 15, and preheats the pretreated seawater.

[0053] Further, the membrane distillation concentrating unit in the embodiment includes a plurality of membrane distillation assemblies 18 connected in series, the material inlet of the membrane distillation assembly in the first effect is communicated with the other end of the third pipeline 3, the material outlet of each effect's membrane distillation assembly is communicated with the material inlet of the next effect's membrane distillation assembly through the adapter pipe 19; the steam outlet of the membrane distillation assembly in the first effect is communicated with one end of the fourth pipeline 4, and the steam outlet of the other effect's membrane distillation assembly is communicated with the condensing unit. The steam generated by each membrane distillation assembly in the process of concentrating seawater is condensed by the condensing unit to prepare fresh water.

[0054] Specifically, when the membrane distillation subsystem II further processes seawater, the last effect's concentrated seawater output by the evaporation subsystem I is sequentially subjected to membrane distillation concentration treatment by each effect's membrane distillation assembly 18. Since the permeation side of each effect's membrane distillation assembly 18 is under negative pressure, in the process of membrane concentration, water molecules in the concentrated seawater evaporate and vaporize, pass through the micropores of the hydrophobic membrane, and the non-volatile ions and molecules cannot pass through the hydrophobic membrane, thereby realizing preliminary concentration of the concentrated seawater. The preliminarily concentrated concentrated seawater enters the next effect's membrane distillation assembly 18 and is subjected to separation and concentration again, and so on. The water vapor generated by each effect's membrane distillation assembly 18 in the process of treatment enters the condensing unit, and the water vapor is condensed by the condensing unit to prepare fresh water. The water vapor output by the membrane distillation assembly in the first effect is recycled to the steam ejector pump set 10 through the fourth pipeline 4, and is subjected to enthalpy increase and reuse by the steam ejector pump set 10.

[0055] Further, the condensing unit in the embodiment includes a second condenser 20, a third steam delivery pipe 21 and a seventh pipeline 7. A second condenser 20 is respectively installed on the third pipeline 3 or the adapter pipe 19 corresponding to the material inlet end of each effect's membrane distillation assembly 18. The third pipeline 3 or the adapter pipe 19 is communicated with one of the heat exchange channels of the second condenser 20. One end of the other heat exchange channel of each effect's second condenser 20 is communicated with the steam outlet of the next effect's membrane distillation assembly 18 through the third steam delivery pipe 21, and the other end of the other heat exchange channel of each effect's second condenser 20 is communicated with the seventh pipeline 7.

[0056] Specifically, the concentrated seawater outputted by the evaporation subsystem I absorbs the condensation heat released by the steam outputted by the second effect membrane distillation assembly 18 when passing through the second condenser 20 of the first effect, and then enters the membrane distillation assembly 18 of the first effect for membrane distillation concentration treatment. After the preliminary concentrated seawater absorbs the heat released by the steam generated by the membrane distillation assembly 18 of the third effect, the seawater enters the membrane distillation assembly 18 of the second effect for separation and concentration. In this way, the steam generated by the membrane distillation assembly 18 of the nth effect (the membrane distillation assembly 18 of the last effect, n is a natural number greater than or equal to 3) is condensed in the second condenser 20 between the (n-1)th effect and the nth effect, and the released condensation heat is used as the heat source of the membrane distillation assembly 18 of the (n-1)th effect to heat the concentrated seawater entering the (n-1)th effect. During the entire process, the fresh water generated by the second condenser 20 of each effect is collected by the seventh pipeline 7.

[0057] Further, the condensation unit in the embodiment further comprises an eighth pipeline 8, one end of the eighth pipeline 8 is connected to the first pipeline 1 between the steam ejector pump set 10 and the evaporation subsystem I, and the other end of the eighth pipeline 8 is connected to one end of the other heat exchange channel of the second condenser 20 of the last effect. The other end of the other heat exchange channel of the second condenser 20 of the last effect is connected to the seventh pipeline 7.

[0058] Therefore, the steam with twice increased enthalpy by the steam ejector pump set 10 and the steam compressor set 11 can be supplied to the second condenser 20 of the last effect through the eighth pipeline 8 to provide heat to the seawater delivered to the membrane distillation assembly 18 of the last effect, and the fresh water generated by condensation in the second condenser 20 of the last effect is recovered to the seventh pipeline 7.

[0059] Further, the condensation unit in the embodiment further comprises a third condenser 22 and a ninth pipeline 9, the steam outlet of the membrane distillation assembly 18 of the first effect is connected to one end of the ninth pipeline 9, and the other end of the ninth pipeline 9 is connected to the seventh pipeline 7. The third condenser 22 is installed on the ninth pipeline 7, so that the steam outputted by the membrane distillation assembly 18 of the first effect can also be condensed by the third condenser 22 to recover fresh water, and the fresh water is delivered to the seventh pipeline 7.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some technical features. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A seawater desalination system, characterized in that, it comprises an evaporation subsystem, a membrane distillation subsystem and a coupling subsystem; the evaporation subsystem is used for evaporative concentration of seawater, and comprises a material inlet, a material outlet, a steam inlet and a steam outlet, the steam inlet is communicated with one end of a first pipeline, the steam outlet is communicated with one end of a second pipeline, and the material outlet is communicated with one end of a third pipeline; the membrane distillation subsystem comprises a membrane distillation concentration unit and a condensation unit, the material inlet of the membrane distillation concentration unit is communicated with the other end of the third pipeline, and the steam outlet of the membrane distillation concentration unit is communicated with the condensation unit and one end of a fourth pipeline; the coupling subsystem comprises a steam ejector pump group, the steam ejector pump group is installed on the first pipeline, and the other end of the second pipeline and the other end of the fourth pipeline are communicated with the steam ejector pump group; the membrane distillation concentration unit comprises a plurality of membrane distillation assemblies connected in series, the material inlet of the membrane distillation assembly located at the first effect is communicated with the other end of the third pipeline, the material outlet of each effect of the membrane distillation assembly is communicated with the material inlet of the membrane distillation assembly of the next effect through an adapter pipe, and the steam outlet of the membrane distillation assembly located at the first effect is communicated with one end of the fourth pipeline, and the steam outlet of the membrane distillation assembly of other effects is communicated with the condensation unit; the condensation unit comprises a second condenser, a third steam conveying pipe and a seventh pipeline, one second condenser is installed on the third pipeline or the adapter pipe corresponding to the material inlet end of each effect of the membrane distillation assembly, the third pipeline or the adapter pipe is communicated with one heat exchange channel of the second condenser, one end of the other heat exchange channel of each effect of the second condenser is communicated with the steam outlet of the membrane distillation assembly of the next effect through the third steam conveying pipe, and the other end of the other heat exchange channel of each effect of the second condenser is communicated with the seventh pipeline; the coupling subsystem further comprises a steam compressor group, and the steam compressor group is installed on the first pipeline between the steam ejector pump group and the evaporation subsystem; the evaporation subsystem comprises a plurality of falling film evaporators connected in series, wherein the steam inlet of the falling film evaporator located at the first effect is communicated with one end of the first pipeline, the steam outlet of each effect of the falling film evaporator is communicated with the steam inlet of the falling film evaporator of the next effect through a first steam conveying pipe, and the steam outlet and the material outlet of the falling film evaporator located at the last effect are correspondingly communicated with one end of the second pipeline and one end of the third pipeline; the condensation unit further comprises an eighth pipeline, one end of the eighth pipeline is communicated with the first pipeline between the steam compressor group and the evaporation subsystem, the other end of the eighth pipeline is communicated with one end of the other heat exchange channel of the second condenser located at the last effect, and the other end of the other heat exchange channel of the second condenser located at the last effect is communicated with the seventh pipeline. The condensing unit further comprises a third condenser and a ninth pipeline, one end of the ninth pipeline is communicated with a steam outlet of the membrane distillation assembly of the first effect, the other end of the ninth pipeline is communicated with the seventh pipeline, and the third condenser is installed on the ninth pipeline.

2. The seawater desalination system according to claim 1, characterized in that, The coupling subsystem further comprises a pressure stabilizer, one end of the second pipeline and one end of the fourth pipeline are communicated with the pressure stabilizer, and the pressure stabilizer is communicated with the steam ejector pump group.

3. The seawater desalination system according to claim 1 or 2, characterized in that, The condensing water outlet of the falling film evaporator of each effect is communicated with a fifth pipeline through a corresponding short connecting pipe, the falling film evaporator of each effect between the first effect and the last effect is provided with a corresponding flash evaporator, the flash evaporator of each effect is installed at the joint of the short connecting pipe of the corresponding effect and the fifth pipeline, and the steam outlet of the flash evaporator of each effect is communicated with the middle part of the first steam conveying pipe of the falling film evaporator of the corresponding effect through a second steam conveying pipe.

4. The seawater desalination system according to claim 3, characterized in that, The material inlet of the falling film evaporator of the first effect is communicated with one end of a sixth pipeline, the sixth pipeline is provided with a first condenser, the sixth pipeline is communicated with one heat exchange channel of the first condenser, and the other heat exchange channel of the first condenser is communicated with one end of the fifth pipeline; the first steam conveying pipe of the falling film evaporator of the last effect is communicated with the other heat exchange channel of the first condenser.

5. The seawater desalination system according to claim 4, characterized in that, The falling film evaporator of each effect between the first effect and the last effect is provided with a corresponding preheater, the preheater is installed on the sixth pipeline, the sixth pipeline is respectively communicated with one heat exchange channel of each preheater, and the first steam conveying pipe of the falling film evaporator of each effect is communicated with the other heat exchange channel of the preheater corresponding to the falling film evaporator of the next effect.

Images