Low temperature multi-effect seawater desalination system

Abstract

The application discloses a low-temperature multi-effect seawater desalination system, wherein a booster pump and a heater are arranged in the low-temperature multi-effect seawater desalination system; suction steam is sequentially subjected to pressure boosting of the booster pump and heating of the heater; the temperature and the pressure are increased to form new suction steam; the new suction steam is mixed with power steam in a steam ejector group to form heated steam; the power steam is prevented from being directly mixed with the suction steam; the power steam flow is reduced; and the energy consumption is reduced. The application uses cooling seawater for cooling the last-effect secondary steam as feed seawater in a multi-effect evaporator group, reduces the loss of available energy, and improves the production efficiency. The application arranges a common module and a standby module in the steam ejector group, thereby ensuring the stability of system operation. The low-temperature seawater desalination system is simple in structure, small in scale and stable in operation, and is suitable for areas with small areas or small populations.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of seawater desalination, in particular to a low-temperature multi-effect seawater desalination system. BACKGROUND

[0002] The world is seriously short of fresh water, and seawater desalination can effectively alleviate this problem. Low-temperature multi-effect seawater desalination is one of the main methods of seawater desalination. Low-temperature multi-effect seawater desalination technology is a seawater desalination technology that inputs a certain amount of power steam, and through multiple evaporation and condensation, obtains distilled water that is multiple times the heating steam. In a low-temperature multi-effect seawater desalination system, the equipment normally operates under vacuum, and the absolute pressure is between 7-28 kpa / a. The pressure and temperature of the first effect evaporation chamber are the highest, and the pressure and temperature of each subsequent effect evaporation chamber decrease in turn. At present, a large amount of high-temperature and high-pressure power steam is mixed with low-temperature and low-pressure secondary steam of the last effect, i.e. suction steam, in a steam ejector to form heating steam with appropriate pressure and temperature. The heating steam is used to heat and phase change seawater, which not only consumes a large amount of power steam but also has low efficiency. The loss of available energy accounts for more than half of the total loss. The cooling seawater that cools the secondary steam of the last effect also carries away about 10% of the available energy of the system, resulting in low efficiency of the low-temperature multi-effect seawater desalination system. At present, most of the research is on low-temperature multi-effect devices with large water production, which have large scale and complex structure. There is little research on small low-temperature multi-effect devices suitable for water-deficient areas. For islands, coastal villages, offshore drilling platforms and other areas with small area or few people but need, there is an urgent need for a small low-temperature multi-effect seawater desalination device that can produce enough water and run stably. SUMMARY

[0003] In view of the defects in the prior art, the present application provides a low-temperature multi-effect seawater desalination system to solve the technical problems of low energy utilization and complex structure of the low-temperature multi-effect seawater desalination system in the prior art.

[0004] To achieve the above object, the application provides the following technical scheme: a low-temperature multi-effect seawater desalination system, comprising a raw seawater pump, a multi-effect evaporator group, a condenser, and a steam ejector group, the low-temperature multi-effect seawater desalination system further comprising a booster pump and a heater, the multi-effect evaporator group comprising a plurality of evaporators connected in series, the steam ejector group comprising a plurality of ejector modules connected in parallel, part of the steam generated by the last evaporator forming suction steam, the suction steam being delivered to the booster pump to be pressurized to form pressurized suction steam, the pressurized suction steam being heat-exchanged in the heater to form new suction steam, the temperature and pressure of the new suction steam being higher than those of the suction steam, the new suction steam being mixed with motive steam in the steam ejector group to form heated steam, the heated steam entering the multi-effect evaporator group to cause the phase change of the raw seawater to be desalinated, the remaining part of the steam generated by the last evaporator being delivered to the condenser to heat the raw seawater delivered by the raw seawater pump into feed seawater, the feed seawater being delivered to the multi-effect evaporator group.

[0005] In an embodiment, the heater is a heat exchanger, and a heating medium inlet of the heater is connected with a first-effect fresh water outlet of a first-effect evaporator.

[0006] In an embodiment, a heating medium outlet one and a heating medium outlet two are arranged on the heater, the heating medium outlet one being connected with a boiler, and the heating medium outlet two being connected with a product water collecting device.

[0007] In an embodiment, the low-temperature multi-effect seawater desalination system further comprises a concentrated brine pump and a product water pump, the concentrated brine pump being used to discharge the concentrated brine generated by the multi-effect evaporator group from the system, and the product water pump being used to discharge the fresh water generated by the system from the system.

[0008] In an embodiment, the multi-effect evaporator group comprises a first-effect evaporator and a second-effect evaporator, and the steam ejector group comprises a first ejector module and a second ejector module, the first ejector module and the second ejector module being identical in structure.

[0009] In one embodiment, the first ejector module includes a steam ejector A, and the second ejector module includes a steam ejector B. The power steam inlets of both steam ejector A and steam ejector B are connected to power steam pipelines. The new suction steam inlets of both steam ejector A and steam ejector B are connected to the outlet of the new suction steam of the heater. The heating steam outlets of steam ejector A and steam ejector B are respectively connected to the two inlets of a three-way valve. Valves are installed at both the power steam inlet and the new suction steam inlet of steam ejector A and steam ejector B. The outlet of the three-way valve is connected to the heating steam inlet of the first-effect evaporator chamber. The first-effect secondary steam outlet of the first-effect evaporator chamber is connected to the first-effect secondary steam outlet of the second-effect evaporator chamber. The system is as follows: the concentrated brine outlet of the first-effect evaporator is connected to the concentrated brine inlet of the first-effect evaporator; the steam outlet of the second-effect evaporator is connected to the steam inlet of the condenser and the inlet of the booster pump via pipes; the concentrated brine outlet of the second-effect evaporator is connected to the concentrated brine pump; the raw seawater inlet of the condenser is connected to the outlet of the raw seawater pump; the feed seawater outlet of the condenser is connected to the first feed seawater inlet of the first-effect evaporator and the second feed seawater inlet of the second-effect evaporator via feed seawater pipes; the new suction steam inlet of the heater is connected to the outlet of the booster pump; the heating medium outlet of the heater, the fresh water outlet of the second-effect evaporator, and the product water outlet of the condenser are connected to the product water pump via pipes.

[0010] In one embodiment, all valves are solenoid valves, the three-way valve is a two-position three-way solenoid valve, and the booster pump is a centrifugal booster pump.

[0011] In one embodiment, the heater is a mixing chamber type heater, and the inlet of the heater's heating medium is connected to a power steam pipe.

[0012] In one embodiment, the heater is a heat exchanger, the heater heating medium inlet is connected to a power steam pipeline, and the heater heating medium outlet is connected to either a boiler or a product water insulation system.

[0013] Compared with the prior art, the beneficial effects of this application are as follows:

[0014] The application sets a booster pump and a heater in the low-temperature multi-effect seawater desalination system, the steam is pumped to be pressurized by the booster pump and heated by the heater, the temperature and pressure are improved to form new pumping steam, the new pumping steam is mixed with power steam in the steam ejector group to form heated steam, the direct mixing of the power steam and the pumping steam is avoided, the flow of the power steam is reduced, and the energy consumption is reduced, the cooling seawater for cooling the last-effect secondary steam is used as the feed seawater in the multi-effect evaporator group, the loss of available energy is reduced, and the production efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.

[0016] Figure 1 FIG. 1 is a schematic diagram of a low-temperature multi-effect seawater desalination system in Embodiment One of the application;

[0017] Figure 2 FIG. 2 is a schematic diagram of a low-temperature multi-effect seawater desalination system in Embodiment Two of the application;

[0018] Figure 3 FIG. 3 is a schematic diagram of a low-temperature multi-effect seawater desalination system in Embodiment Three of the application;

[0019] Figure 4 FIG. 4 is a schematic diagram of a low-temperature multi-effect seawater desalination system in Embodiment Four of the application.

[0020] The drawings show that: 1, raw seawater pump; 2, condenser; 3, one-effect evaporation chamber; 4, two-effect evaporation chamber; 5, booster pump; 6, heater; 7, steam ejector A; 8, steam ejector B; 9, three-way valve; 10, concentrated brine pump; 11, product water pump; 12-15, valve. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the application more clear, the following will combine the drawings in the embodiments of the application to clearly and completely describe the technical solutions in the embodiments of the application. Obviously, the described embodiments are some of the embodiments of the application, not all the embodiments. The components of the embodiments of the application described and shown in the drawings can be arranged and designed in various different configurations.

[0022] The following detailed description of embodiments of the application in the drawings provided is not intended to limit the scope of the application claimed, but merely represents selected embodiments of the application. Based upon the embodiments in the present application, all other embodiments that a person of ordinary skill in the art obtains without making creative efforts, fall within the scope of the present application.

[0023] Embodiment one

[0024] A low-temperature multi-effect seawater desalination system, comprising a raw seawater pump 1, a condenser 2, a multi-effect evaporator group, a steam ejector group, a booster pump 5, a heater 6, a concentrated brine pump 10 and a product water pump 11, the multi-effect evaporator group comprising a plurality of evaporating chambers connected in series, part of the steam generated by the last evaporating chamber forming suction steam, the suction steam being delivered to the booster pump 5 to be pressurized to form pressurized suction steam, the pressurized suction steam being heat exchanged in the heater 6 to form new suction steam, the new suction steam being mixed with motive steam in the steam ejector group to form heated steam, the heated steam entering the multi-effect evaporator group to cause the phase change of the feed seawater to be desalinated, the remaining part of the steam generated by the last evaporating chamber being delivered to the condenser 2 to heat the raw seawater delivered by the raw seawater pump 1 into feed seawater, the feed seawater being delivered to the multi-effect evaporator group, the produced fresh water and concentrated brine being discharged from the system by the product water pump 11 and the concentrated brine pump 10 respectively.

[0025] As Figure 1As shown, the multi-effect evaporator group in the embodiment includes an evaporator chamber 3 and an evaporator chamber 4, the heater 6 is a heat exchanger, the steam ejector group includes a first ejector module and a second ejector module, the first ejector module and the second ejector module are connected in parallel, the first ejector module and the second ejector module are the same in structure, the first ejector module includes a steam ejector A 7, the second ejector module includes a steam ejector B 8, the motive steam inlets of the steam ejector A 7 and the steam ejector B 8 are connected with a motive steam pipeline, the motive steam inlets of the steam ejector A 7 and the steam ejector B 8 are connected with a motive steam outlet of the heater 6, the heating steam outlets of the steam ejector A and the steam ejector B are connected with two inlets of a three-way valve 9 respectively, the motive steam inlets and the motive steam inlets of the steam ejector A and the steam ejector B are respectively provided with valves 12, 13, 14 and 15, an outlet of the three-way valve 9 is connected with a heating steam inlet of the evaporator chamber 3, a first secondary steam outlet of the evaporator chamber 3 is connected with a first secondary steam inlet of the evaporator chamber 4, a first concentrated brine outlet of the evaporator chamber 3 is connected with a first concentrated brine inlet of the evaporator chamber 4, a first fresh water outlet of the evaporator chamber 3 is connected with a heating medium inlet of the heater 6, a steam outlet of the evaporator chamber 4 is connected with a steam inlet of the condenser 2 and an inlet of the booster pump 5 through pipelines respectively, a concentrated brine outlet of the evaporator chamber 4 is connected with the concentrated brine pump 10, a raw seawater inlet of the condenser 2 is connected with an outlet of the raw seawater pump 1, a raw seawater outlet of the condenser 2 is connected with a first raw seawater inlet of the evaporator chamber 3 and a second raw seawater inlet of the evaporator chamber 4 through a raw seawater pipeline; a motive steam inlet of the heater 6 is connected with an outlet of the booster pump 5, the heating medium outlet of the heater 6 in the embodiment has two, a heating medium outlet one is connected with a boiler, a heating medium outlet two, a second fresh water outlet of the evaporator chamber 4 and a product water outlet of the condenser 3 are connected with the product water pump 11 through pipelines. In order to facilitate the opening of the valve, the valve is an electromagnetic valve, the three-way valve is a two-position three-way electromagnetic valve, and the booster pump 5 is a centrifugal booster pump.

[0026] The operation process of the low-temperature multi-effect seawater desalination device in the embodiment is as follows:

[0027] The raw seawater enters the condenser 2 through the raw seawater pump 1, exchanges heat with part of the new second-effect secondary steam in the condenser 2 to form feed seawater, and the feed seawater enters the first-effect evaporation chamber 3 and the second-effect evaporation chamber 4 through the feed seawater pipeline; in the first-effect evaporation chamber 3, the feed seawater exchanges heat with the heating steam to generate the first-effect secondary steam and the first-effect concentrated brine, and the heating steam condenses into high-temperature fresh water which enters the heater 6; the first-effect secondary steam and the first-effect concentrated brine both enter the second-effect evaporation chamber 4; in the second-effect evaporation chamber 4, the feed seawater exchanges heat with the first-effect secondary steam to generate the second-effect secondary steam and the second-effect concentrated brine, the first-effect secondary steam condenses into fresh water, and part of the first-effect concentrated brine flashes to generate steam which mixes with the second-effect secondary steam to form new second-effect secondary steam, and the remaining part of the first-effect concentrated brine mixes with the second-effect concentrated brine to form concentrated brine which is discharged from the system through the concentrated brine pump 10; part of the new second-effect secondary steam enters the condenser 3 to exchange heat with the raw seawater to form fresh water, and the remaining part of the new second-effect secondary steam is suction steam; because the low-temperature multi-effect seawater desalination system normally operates in a vacuum state, and the pressure and temperature of the first-effect evaporation chamber are the highest, and the pressure and temperature of each subsequent evaporation chamber decrease in turn, the temperature of the high-temperature fresh water generated by the first-effect evaporation chamber 3 is higher than the temperature of the suction steam, the suction steam enters the booster pump 5 to be pressurized to form pressurized suction steam, the pressurized suction steam exchanges heat with the high-temperature fresh water in the heater 6 to form new suction steam, and the temperature and pressure of the new suction steam are higher than those of the suction steam; part of the fresh water discharged from the heater 6 continues to circulate in the boiler, and the remaining part of the fresh water is combined with the fresh water generated by the second-effect evaporation chamber 4 and the fresh water generated by the condenser 2, and is discharged from the system through the product water pump 11.

[0028] The first ejector module is a normal module, and the second ejector module is a standby module; when the first ejector module can normally operate, all valves in the second ejector module are closed, the interface between the three-way valve 9 and the steam ejector B 8 is closed, all valves in the first ejector module are opened, the interface between the three-way valve 9 and the steam ejector A 7 is opened, the new suction steam discharged from the heater 6 enters the steam ejector A 7, mixes with the power steam generated by the boiler in the steam ejector A 7 to form heating steam which enters the first-effect evaporation chamber 3; when the first ejector module cannot normally operate due to failure, all valves in the first ejector module are closed, the interface between the three-way valve 9 and the steam ejector A 7 is closed, all valves in the second ejector module are opened, the interface between the three-way valve 9 and the steam ejector B 8 is opened, the new suction steam discharged from the heater 6 enters the steam ejector B 8, mixes with the power steam generated by the boiler in the steam ejector B 8 to form heating steam which enters the first-effect evaporation chamber 3.

[0029] The daily production of the low-temperature multi-effect seawater desalination system in this embodiment is taken as an example to calculate and analyze 15 tons of fresh water.

[0030] The following mathematical model is established:

[0031] ①Mass conservation

[0032] F i = B i + D i

[0033] ②Salinity conservation

[0034] F i X f = B i X bi

[0035] ③Heat conservation

[0036] D i-1 Δh i-1 = F i C p (T i -T f ) + D i Δh i

[0037] ④Secondary steam temperature

[0038] T vi = T i -BPE i

[0039] ⑤Condenser model

[0040] (D2+d b -M ev )Δh2= (M cw +F1+F2)C p (T f -T cw )

[0041] ⑥Flash tank model

[0042] B1C p (T1-T2) = d b Δh

[0043] In the formula:

[0044] F - feed seawater flow rate, kg / h;

[0045] B - concentrated brine flow rate, kg / h;

[0046] D - secondary steam flow rate, ℃;

[0047] X f - supply seawater salinity, g / kg;

[0048] X b - concentrated brine salinity, g / kg;

[0049] Ah - latent heat, °C;

[0050] T - effectiveness temperature, °C;

[0051] T f - feed seawater temperature, °C;

[0052] T v - secondary steam temperature, °C;

[0053] BPE - boiling point elevation, °C;

[0054] d b - concentrated brine flash quantity, kg / h;

[0055] M ev - suction steam flow, kg / h;

[0056] M cw - cooling seawater flow, kg / h;

[0057] T cw - feed seawater temperature, °C;

[0058] C P - specific heat at constant pressure, J / (kg-K)

[0059] i - effect number.

[0060] The exergy losses of each module of the system are solved by the following mathematical model.

[0061] ① Evaporator

[0062] Ex dest = Ex F + Ex D - Ex f - Ex d - Ex B ② Brine flash tank

[0063] Ex dest = Ex B - Ex d′ - Ex B′

[0064] ③ Steam jet pump

[0065] Ex dest = Ex M + Ex ev - Ex D

[0066] ④ Condenser

[0067] Ex dest = Excw +Ex d′ +Ex d” -Ex F In the formula:

[0068] Ex - available energy;

[0069] - available energy loss of each module;

[0070] Subscript:

[0071] F - feed seawater;

[0072] D - heating steam;

[0073] f - heating steam condensate;

[0074] d - secondary steam;

[0075] B - concentrated brine;

[0076] d' - flash tank secondary steam;

[0077] B' - flashed concentrated brine;

[0078] M - power steam;

[0079] ev - extraction steam;

[0080] cw - raw seawater;

[0081] d" - final effect secondary steam.

[0082] The design conditions of the low-temperature multi-effect seawater desalination system in the present embodiment are as follows: heating steam temperature 60℃, secondary evaporation chamber temperature 54℃, feed seawater temperature 51℃, raw seawater temperature 25℃, feed seawater salinity 35g / kg, and discharge concentrated brine salinity 69g / kg. The operating parameters of the low-temperature multi-effect seawater desalination system in the present embodiment are shown in Table 1:

[0083] Table 1 Operating parameters of the present embodiment

[0084]

[0085] The available energy analysis of the low-temperature multi-effect seawater desalination system in the present embodiment is shown in Table 2:

[0086] Table 2 Available energy analysis of the present embodiment

[0087]

[0088]

[0089] In the low-temperature multi-effect seawater desalination system in the prior art, the suction steam directly enters the steam ejector group to mix with the motive steam to form heating steam, and part of the cooling seawater that cools the last-effect secondary steam is discharged. The low-temperature multi-effect seawater desalination system in the prior art adopts the same design condition as the present application, and the daily output is also 15 tons of fresh water. The operating parameters of the low-temperature multi-effect seawater desalination system in the prior art are shown in Table 3:

[0090] Table 3 Operating parameters of the system based on the prior art

[0091]

[0092] The available energy analysis of the low-temperature multi-effect seawater desalination system in the prior art is shown in Table 4:

[0093] Table 4 Available energy analysis of the system based on the prior art

[0094]

[0095]

[0096] By comparing Table 1 and Table 3, it can be found that under the same operating condition, compared with the scheme based on the prior art, the motive steam flow is reduced by 36.07%, and the water production ratio is increased by 56.62%. By analyzing Table 2 and Table 4, it can be found that under the same operating condition, compared with the scheme based on the prior art, the available energy consumed by the motive steam to produce each ton of product water is reduced by 36.74%, the available energy consumed is reduced by 30.18%, and the available energy loss caused by the cooling seawater discharged by the system to produce each ton of product water is almost zero.

[0097] By establishing mathematical models for the system scheme based on the prior art and the scheme of the present application and solving them, the corresponding system operating parameters are obtained, and the specific results are shown in Table 5.

[0098] Table 5 Comparison of system operating performance between the system scheme based on the prior art and the scheme of the present application

[0099]

[0100] By analyzing Table 5, it can be found that after applying the scheme of the present application, compared with the system scheme based on the prior art, the motive steam flow is reduced by about 36%, and the cooling seawater flow is almost zero under ideal conditions, which shows that the energy utilization rate of the low-temperature multi-effect device is greatly improved after applying the scheme of the present application.

[0101] Example Two

[0102] As Figure 2As shown, the difference between this embodiment and embodiment one is the heater 6. In this embodiment, the heater 6 is a heat exchanger. The heater 6 is provided with a heating medium outlet. The heating medium outlet, the second-effect fresh water outlet of the second-effect evaporation chamber 4 and the product water outlet of the condenser 3 are connected to the product water pump 11 through pipes.

[0103] Example 3

[0104] like Figure 3 As shown, the difference between this embodiment and Embodiment 1 is the heater 6 and the first-effect evaporation chamber 3. In this embodiment, the heater 6 is a mixing chamber type heater. The heater 6 is provided with a heating medium inlet, a new suction steam inlet, and a new suction steam outlet. The heating medium inlet is connected to the power steam pipeline. The new suction steam inlet of the heater 6 is connected to the outlet of the booster pump 5. The new suction steam inlets of steam ejector A7 and steam ejector B8 are both connected to the new suction steam outlet of the heater 6. The power steam mixes with the booster suction steam in the heater 6 to form new suction steam. The first-effect fresh water outlet of the first-effect evaporation chamber 3, the second-effect fresh water outlet of the second-effect evaporation chamber 4, and the product water outlet of the condenser 3 are connected to the product water pump 11 through pipelines.

[0105] Example 4

[0106] like Figure 4 As shown, the difference between this embodiment and embodiment one is the heater 6 and the first-effect evaporation chamber 3. In this embodiment, the heater 6 is a heat exchanger type heater, which is provided with a heating medium inlet, a heating medium outlet, a new extraction steam inlet, and a new extraction steam outlet. The heating medium inlet is connected to the power steam pipeline. The power steam exchanges heat with the pressurized extraction steam in the heater 6 to form new extraction steam. When the heating medium outlet is connected to the boiler, the heat-exchanged power steam either returns to the boiler for reheating. When the heating medium outlet is connected to the product water insulation system, the heat-exchanged power steam is used to insulate the product water.

[0107] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A low-temperature multi-effect seawater desalination system, comprising a raw seawater pump, a multi-effect evaporator group, a condenser, and a steam ejector group, characterized in that, The low-temperature multi-effect seawater desalination system also includes a booster pump and a heater. The multi-effect evaporator group includes multiple evaporation chambers connected in series, and the steam ejector group includes multiple ejector modules connected in parallel. Part of the steam generated by the last-effect evaporator chamber forms suction steam, which is then transported to the booster pump for pressurization to form pressurized suction steam. The pressurized suction steam is heated in the heater to form new suction steam. The temperature and pressure of the new suction steam are higher than those of the original suction steam. The new suction steam is mixed with the motive steam in the steam ejector group to form heating steam. The heating steam enters the multi-effect evaporator group to desalinate the feed seawater through phase change. The remaining steam generated by the last-effect evaporator chamber is transported to the condenser to heat the feed seawater pumped by the feed seawater pump. The feed seawater is transported to a multi-effect evaporator assembly, which includes a first-effect evaporator chamber and a second-effect evaporator chamber. In the first-effect evaporator chamber, the feed seawater exchanges heat with heating steam to generate first-effect secondary steam and first-effect concentrated brine. Both the first-effect secondary steam and the first-effect concentrated brine enter the second-effect evaporator chamber. In the second-effect evaporator chamber, the feed seawater exchanges heat with the first-effect secondary steam to generate second-effect secondary steam and second-effect concentrated brine. The first-effect secondary steam condenses into fresh water, and part of the first-effect concentrated brine flashes to generate steam, which mixes with the second-effect secondary steam to form new second-effect secondary steam. The remaining part of the first-effect concentrated brine mixes with the second-effect concentrated brine to form concentrated brine. The heater is a heat exchanger, and the inlet of the heater is connected to the first-effect fresh water outlet of the first-effect evaporator chamber.

2. The low-temperature multi-effect seawater desalination system according to claim 1, characterized in that, The heater is provided with a heating medium outlet one and a heating medium outlet two. The heating medium outlet one is connected to the boiler, and the heating medium outlet two is connected to the product water collection device.

3. The low-temperature multi-effect seawater desalination system according to claim 2, characterized in that, The low-temperature multi-effect seawater desalination system also includes a concentrated brine pump and a product water pump. The concentrated brine pump is used to discharge the concentrated brine produced by the multi-effect evaporator group from the system, and the product water pump is used to discharge the fresh water produced by the system from the system.

4. The low-temperature multi-effect seawater desalination system according to claim 3, characterized in that, The steam ejector assembly includes a first ejector module and a second ejector module, and the first ejector module and the second ejector module have the same structure.

5. The low-temperature multi-effect seawater desalination system according to claim 4, characterized in that, The first ejector module includes steam ejector A, and the second ejector module includes steam ejector B. The power steam inlets of both steam ejector A and steam ejector B are connected to power steam pipelines. The new suction steam inlets of both steam ejector A and steam ejector B are connected to the outlet of the new suction steam of the heater. The heating steam outlets of steam ejector A and steam ejector B are respectively connected to the two inlets of a three-way valve. Valves are installed at both the power steam inlet and the new suction steam inlet of steam ejector A and steam ejector B. The outlet of the three-way valve is connected to the heating steam inlet of the first-effect evaporator chamber. The first-effect secondary steam outlet of the first-effect evaporator chamber is connected to the first-effect secondary steam inlet of the second-effect evaporator chamber. The concentrated brine outlet of the first-effect evaporator is connected to the concentrated brine inlet of the first-effect evaporator. The steam outlet of the second-effect evaporator is connected to the steam inlet of the condenser and the inlet of the booster pump via pipelines. The concentrated brine outlet of the second-effect evaporator is connected to the concentrated brine pump. The raw seawater inlet of the condenser is connected to the outlet of the raw seawater pump. The feed seawater outlet of the condenser is connected to the first feed seawater inlet of the first-effect evaporator and the second feed seawater inlet of the second-effect evaporator via feed seawater pipelines. The new suction steam inlet of the heater is connected to the outlet of the booster pump. The heating medium outlet of the heater, the fresh water outlet of the second-effect evaporator, and the product water outlet of the condenser are connected to the product water pump via pipelines.

6. The low-temperature multi-effect seawater desalination system according to claim 5, characterized in that, All valves are solenoid valves, the three-way valve is a two-position three-way solenoid valve, and the booster pump is a centrifugal booster pump.

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