Brackish water desalination system and method

Abstract

The invention relates to the technical field of brackish water desalination, and discloses a brackish water desalination system and method.The system comprises a primary water treatment device, a secondary water treatment device, a freezing pond, a tertiary water treatment device and a quaternary water treatment device, the secondary water treatment device is connected with the primary water treatment device, the secondary water treatment device is suitable for separating tail water, the freezing pool is connected with the secondary water treatment device, the tertiary water treatment device is connected with the freezing pool, and the quaternary water treatment device is connected with the tertiary water treatment device. The tail water is sequentially subjected to multi-stage separation and purification of the second-stage water treatment device, the freezing pool, the third-stage water treatment device and the fourth-stage water treatment device, salt and alkali in the tail water can be separated out, tail water treatment is achieved, the final product only comprises salt, alkali and water, and the tail water treatment device has the advantages of being simple in structure and good in tail water treatment effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of brackish water desalination, in particular to a brackish water desalination system and method. BACKGROUND

[0002] Brackish water is a type of natural water body, which is characterized by a high concentration of salt and minerals in the water, but the salinity is lower than the average concentration of seawater, usually the total dissolved solids (TDS) content is between 1 gram / liter to 10 grams / liter. Compared with clear fresh water, this type of water body often appears turbid, the entrance has obvious bitterness, and long-term drinking will cause electrolyte imbalance in the body.

[0003] In the prior art, brackish water desalination usually uses water treatment equipment based on reverse osmosis technology, and uses multi-effect distillation, electrodialysis and reverse osmosis method to desalinate and treat brackish water, but the tail water of brackish water needs to be reasonably treated, and the higher the concentration of brackish water, the more difficult it is to dispose of the tail water and the higher the cost. SUMMARY

[0004] Therefore, the present application provides a brackish water desalination system and method to solve the problem of tail water treatment after brackish water desalination in the prior art.

[0005] In a first aspect, the present application provides a brackish water desalination system, comprising a primary water treatment device, a secondary water treatment device, a freezing pool, a tertiary water treatment device and a quaternary water treatment device, the primary water treatment device is adapted to separate brackish water into purified water and tail water, the secondary water treatment device is connected with the primary water treatment device, the secondary water treatment device is adapted to concentrate and separate part of the tail water, the freezing pool is connected with the secondary water treatment device, the tertiary water treatment device is connected with the freezing pool, and the quaternary water treatment device is connected with the tertiary water treatment device and adapted to classify salt and alkali in the tail water.

[0006] Beneficial effects: the present application separates brackish water into purified water and tail water in the primary water treatment device, and the tail water is sequentially subjected to multi-stage separation and purification in the secondary water treatment device, the freezing pool, the tertiary water treatment device and the quaternary water treatment device, so that salt and alkali in the tail water can be separated, the treatment of the tail water is realized, and the final product only contains salt, alkali and water, which has the advantages of simple structure and good tail water treatment effect.

[0007] In an alternative embodiment, the brackish water desalination system further comprises a heater, a regenerator and a heat supply heat pump, the heater is connected with the primary water treatment device and the secondary water treatment device, the regenerator is connected with the secondary water treatment device and the freezing pool, and the heat supply heat pump is connected with the regenerator and the heater.

[0008] Beneficial effects: The heater of the application can heat the separated tail water of the primary water treatment device to further concentrate, which is convenient for subsequent process to separate salt and alkali in the tail water, the heat recovery unit can recover heat of the tail water in the secondary water treatment device, and part of the heat is transported to the heater by the heat supply heat pump, so that the heat is recycled and utilization, and the energy efficiency of the system is improved.

[0009] In an alternative embodiment, the brackish water desalination system further comprises a cooler and a cold source, the cooler is connected with the secondary water treatment device and the freezing pool, and the cold source is connected with the cooler.

[0010] Beneficial effects: The cooler of the application can cool the tail water output by the secondary water treatment device, so as to be treated in the freezing pool, and the external cold source can improve the energy efficiency of the system.

[0011] In an alternative embodiment, the brackish water desalination system further comprises a cooler and a cold source, the cooler is connected with the secondary water treatment device and the freezing pool, and the cold source is connected with the cooler.

[0012] Beneficial effects: The cooler of the application can cool the tail water output by the secondary water treatment device, so as to be treated in the freezing pool, and the external cold source can improve the energy efficiency of the system.

[0013] In an alternative embodiment, the brackish water desalination system further comprises a buffer tank and a final water treatment device, the buffer tank is connected with the primary water treatment device and the secondary water treatment device, the final water treatment device is connected with the buffer tank, the primary water treatment device and the fourth water treatment device, and a circulating loop is formed between the final water treatment device and the primary water treatment device.

[0014] Beneficial effects: The buffer tank of the application can collect the purified water separated by the primary water treatment device and the secondary water treatment device, and the final water treatment device can strengthen the quality adjustment of the outlet water, so that the outlet water reaches the level of drinking water or deionized water.

[0015] In an alternative embodiment, the freezing pool comprises a pool body, a first hydrophobic grid, a heat exchange coil and a first conveying device, the pool body is connected with the secondary water treatment device and the third water treatment device, the first hydrophobic grid is arranged in the pool body, the heat exchange coil is arranged in the pool body and located below the first hydrophobic grid, and the first conveying device is arranged in the pool body and located above the first hydrophobic grid.

[0016] Beneficial effects: In the application, the temperature in the pool body is between the freezing point of the concentrated brackish water and zero degree, when the concentrated brackish water enters the pool body, it is cooled to the freezing point range first, at this time, the solubility of the alkali component in the brackish water is reduced and begins to be preliminarily precipitated, and the alkali crystal is floated on the surface of the brackish water and is transported away by the first conveying device.

[0017] In an alternative embodiment, the secondary water treatment device comprises a first shell, a first microporous membrane, a first water distributor and a condensing assembly, the first shell has an empty cavity inside, the first shell is connected with the primary water treatment device and the freezing pool, the first microporous membrane is arranged in the first shell, the first water distributor is arranged in the first shell below the first microporous membrane, the first water distributor is connected with the primary water treatment device, and the condensing assembly is arranged in the first shell above the first microporous membrane.

[0018] Beneficial effects: In the present application, the secondary water treatment adopts a low-pressure medium-low-temperature flash evaporation method, and energy recovery and preheating of the brackish water are performed before and after the method by using a heating heat pump, so as to ensure the highest energy efficiency under the condition of no external heat source driving. The built-in first microporous membrane can ensure the rapid screening of water vapor and brackish water under the condition of low resistance.

[0019] In an alternative embodiment, the tertiary water treatment device comprises a second shell, a second microporous membrane, a second water distributor, a second hydrophobic grid and a second conveying device, the second shell has an empty cavity inside, the second shell is connected with the freezing pool and the fourth water treatment device, the second microporous membrane is arranged in the second shell, the second water distributor is arranged in the second shell below the second microporous membrane, the second water distributor is connected with the freezing pool, the second hydrophobic grid is arranged in the second shell below the second water distributor, and the second conveying device is arranged above the second hydrophobic grid.

[0020] Beneficial effects: In the present application, the tertiary water treatment adopts a freezing method, the second water distributor is built-in to rapidly atomize the low-temperature brackish water, and the second microporous membrane screens water vapor and small droplets. In this process, the brackish water is further concentrated above its freezing point. At this time, by taking advantage of the feature that the solubility of alkali components in brackish water decreases at low temperatures, most of the alkali components are precipitated.

[0021] In an alternative embodiment, the fourth water treatment device comprises a water evaporation pool, a ceiling and a water draining plate, the water evaporation pool is provided with an inner wall, the inner wall divides the water evaporation pool into a salt evaporation area and a condensed water collection area, the salt evaporation area is connected with the cold trap, the ceiling is arranged at the top of the water evaporation pool, and the water draining plate is arranged at the top of the condensed water collection area.

[0022] Beneficial effects: In the present application, the fourth water treatment adopts an air-drying method, the top of the water evaporation pool is provided with a ceiling, concentrated brine is rapidly evaporated by sunlight, condensed water is recovered from the ceiling to the condensed water collection area, and brackish water becomes salt after evaporation in the salt evaporation area.

[0023] In a second aspect, the present application further provides a method for desalination of brackish water, which is applied to the above-mentioned brackish water desalination system and comprises the following steps: Separating and desalinating the brackish water by inputting the brackish water into the primary water treatment device; The purified water in the primary water treatment device is input into the buffer tank, and the primary concentrated brackish water is input into the heater for heating, and then the heated water is input into the secondary water treatment device; The purified water in the secondary water treatment device is input into the buffer tank, and the further concentrated brackish water is input into the cooler; The cooled concentrated brackish water is input into the brackish water freezing pool, and the alkali component crystals separated from the brackish water are discharged; The frozen brackish water is input into the tertiary water treatment device, and the separated alkali crystals are discharged, and the saturated concentrated salt water is input into the quaternary water treatment device; The saturated concentrated salt water in the quaternary water treatment device is dehydrated to form salt crystals, and the separated purified water is input into the final water treatment device. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0025] Figure 1 A schematic diagram of a brackish water desalination system according to an embodiment of the present application; Figure 2 A schematic diagram of a brackish water desalination system according to an embodiment of the present application, including a primary water treatment device, a buffer tank, a final water treatment device and a secondary water treatment device; Figure 3 A schematic diagram of a freezing pool in a brackish water desalination system according to an embodiment of the present application; Figure 4 A schematic diagram of a tertiary water treatment device in a brackish water desalination system according to an embodiment of the present application; Figure 5 A flowchart of a brackish water desalination method according to an embodiment of the present application.

[0026] Explanation of reference signs: 1, primary water treatment device; 101, first brackish water inlet; 102, first concentrated brackish water outlet; 103, first purified water outlet; 2, secondary water treatment device; 201, first shell; 202, first microporous membrane; 203, first water distributor; 204, condensing assembly; 2041, condensing coil; 2042, condensing water tray; 2043, condensing cold source; 205, first water inlet; 206, condensing water outlet; 207, first water outlet; 3, freezing pool; 301, pool body; 302, first hydrophobic grid; 303, heat exchange coil; 304, first conveying device; 305, chilled water inlet; 306, chilled water outlet; 307, brackish water freezing pool alkali crystal outlet; 308, frozen brackish water outlet; 4, three-stage water treatment device; 401, second shell; 402, second microporous membrane; 403, second water distributor; 404, second hydrophobic grid; 405, second conveying device; 406, second water inlet; 407, dry air inlet; 408, dry air outlet; 409, alkali crystal outlet discharge; 410, second water outlet; 5, four-stage water treatment device; 501, solar evaporation pool; 5011, inner wall; 5012, outer wall; 502, ceiling; 503, inverted water plate; 504, solar salt area; 505, condensed water collection area; 506, water intake pipe; 6, heater; 7, heat exchanger; 8, heat supply heat pump; 9, cooler; 10, cold source; 11, cooler; 12, refrigeration heat pump; 13, buffer tank; 131, first-stage purified water collection inlet; 132, second-stage purified water collection inlet; 133, purified water collection outlet; 14, final-stage water treatment device; 141, final-stage water treatment device water inlet; 142, final-stage water treatment device wastewater outlet; 143, final-stage water treatment device pure water outlet; 15, first three-way valve; 16, second three-way valve; 17, third three-way valve. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0028] The embodiments of the present application will be described below with reference to the drawings. Figures 1 to 5

[0029] According to the embodiments of the present application, in one aspect, as Figures 1 to 4 ​As shown, a brackish water desalination system is provided, comprising a primary water treatment device 1, a secondary water treatment device 2, a freezing pool 3, a tertiary water treatment device 4 and a quaternary water treatment device 5, the primary water treatment device 1 is adapted to separate the brackish water into purified water and tail water, the secondary water treatment device 2 is connected with the primary water treatment device 1, the secondary water treatment device 2 is adapted to concentrate and separate part of the tail water, the freezing pool 3 is connected with the secondary water treatment device 2, the tertiary water treatment device 4 is connected with the freezing pool 3, and the quaternary water treatment device 5 is connected with the tertiary water treatment device 4, and is adapted to separate the salt and alkali in the tail water.

[0030] Specifically, as shown in the embodiment, the primary water treatment device 1 comprises a primary brackish water inlet 101, a primary concentrated brackish water outlet 102 and a primary purified water outlet 103, the primary brackish water inlet 101 is used to input the brackish water into the primary water treatment device 1, the primary concentrated brackish water outlet 102 is connected with the secondary water treatment device 2, and is used to input the separated tail water into the secondary water treatment device 2, and the primary purified water outlet 103 is used to output the purified water. Figure 2

[0031] In the embodiment, the primary water treatment device 1 is not limited, for example, the primary water treatment device 1 in the embodiment can adopt a reverse osmosis membrane assembly, and the purified water separated by the primary water treatment device 1 can reach the irrigation level, which can reduce the water cost for irrigation.

[0032] In the embodiment, the primary water treatment device 1, the secondary water treatment device 2, the freezing pool 3, the tertiary water treatment device 4 and the quaternary water treatment device 5 are connected in sequence, and the tail water separated in the primary water treatment device 1 is sequentially subjected to re-separation in the secondary water treatment device 2, the freezing pool 3, the tertiary water treatment device 4 and the quaternary water treatment device 5. The secondary water treatment device 2 is used to separate the purified water in the tail water output by the primary water treatment device 1 again, which can strengthen the concentration of the tail water, the freezing pool 3 is set at a temperature between the freezing point of the concentrated brackish water and zero degrees, at which time the alkali components in the tail water can be crystallized and separated out, the tertiary water treatment device 4 is used to finely screen the alkali components in the tail water output by the secondary water treatment device 2, and separate the purified water therefrom, and the quaternary water treatment device 5 is used to dehydrate the tail water output by the tertiary water treatment device 4 to form salt and alkali crystals.

[0033] The present application separates the purified water and the tail water of the brackish water in the primary water treatment device 1, and the tail water is sequentially subjected to multi-stage separation and purification in the secondary water treatment device 2, the freezing pool 3, the tertiary water treatment device 4 and the quaternary water treatment device 5, so that the salt and alkali in the tail water can be separated, the tail water is treated, and the final product only has salt, alkali and water, which has the advantages of simple structure and good tail water treatment effect.

[0034] In one embodiment, as shown in Figure 1 ​As shown, the brackish water desalination system further comprises a heater 6, a regenerator 7 and a heat supply heat pump 8, the heater 6 is connected with the primary water treatment device 1 and the secondary water treatment device 2, the regenerator 7 is connected with the secondary water treatment device 2 and the freezing pool 3, and the heat supply heat pump 8 is connected with the regenerator 7 and the heater 6.

[0035] Specifically, in the embodiment, the heater 6 is arranged between the first-stage concentrated brackish water outlet 102 of the primary water treatment device 1 and the secondary water treatment device 2, the regenerator 7 is arranged between the secondary water treatment device 2 and the tertiary water treatment device 4, and the heat supply heat pump 8 is connected between the heater 6 and the regenerator 7.

[0036] In the embodiment, the tail water after primary concentration is heated by the heater 6 and then enters the secondary water treatment device 2, the tail water after further concentration enters the regenerator 7 for heat recovery, the heat recovered by the regenerator 7 is used as a heat source, the heat is heated by the heat supply heat pump 8 and then sent to the heater 6, and the heat is used for preheating the brackish water entering the secondary water treatment device 2.

[0037] In the embodiment, the heater 6 is arranged to heat the separated tail water of the primary water treatment device 1 for further concentration, which facilitates the separation of salt and alkali in the tail water in the subsequent process, the regenerator 7 is arranged to recover heat of the tail water in the secondary water treatment device 2, part of the heat is sent to the heater 6 by the heat supply heat pump 8, the heat is recovered and utilized, and the energy efficiency of the system is improved.

[0038] In one embodiment, as shown in Figure 1 As shown, the brackish water desalination system further comprises a cooler 9 and a cold source 10, the cooler 9 is connected with the secondary water treatment device 2 and the freezing pool 3, and the cold source 10 is connected with the cooler 9.

[0039] Specifically, in the embodiment, the cooler 9 is arranged between the regenerator 7 and the freezing pool 3, the tail water after two-stage concentration is cooled by the cooler 9, the heat is taken away by the cold source 10, the cooled tail water is input into the freezing pool 3.

[0040] In the embodiment, the cold source 10 is not limited, for example, in the embodiment, the cold source 10 can be natural air cooling, a cooling tower, process waste water, underground water and the like.

[0041] In the embodiment, the cooler 9 is arranged to cool the tail water output by the secondary water treatment device 2, so that the tail water is treated by freezing in the freezing pool 3, and the external cold source 10 can improve the energy efficiency of the system.

[0042] In one embodiment, as shown in Figure 1 As shown, the brackish water desalination system further comprises a cooler 9 and a cold source 10, the cooler 9 is connected with the secondary water treatment device 2 and the freezing pool 3, and the cold source 10 is connected with the cooler 9.

[0043] Specifically, the temperature of the tail water (saturated concentrated brine) of the freezing pool 3 and the tertiary water treatment device 4 is low in the embodiment, and the cold energy of the saturated concentrated brine is recovered by the back cooling device 11 after being discharged, and then is cooled by the refrigeration heat pump 12, so that the cold energy is sent into the freezing pool 3 to preliminarily remove alkali from the tail water entering the tertiary water treatment device 4.

[0044] The back cooling device 11 is arranged in the embodiment, and part of the heat in the tertiary water treatment device 4 is recovered and is sent to the freezing pool 3 by the refrigeration heat pump 12, so that the heat is recycled and used, and the energy efficiency of the system is improved.

[0045] In one embodiment, as shown in Figure 1 and Figure 2 The brackish water desalination system further includes a buffer tank 13 and a final water treatment device 14, the buffer tank 13 is connected with the primary water treatment device 1 and the secondary water treatment device 2, the final water treatment device 14 is connected with the buffer tank 13, the primary water treatment device 1 and the fourth water treatment device 5, and a circulating loop is formed between the final water treatment device 14 and the primary water treatment device 1.

[0046] Specifically, the buffer tank 13 is used for collecting purified water separated by the primary water treatment device 1 and the secondary water treatment device 2 in the embodiment, and the buffer tank 13 includes a first purified water collection inlet 131, a second purified water collection inlet 132 and a purified water collection outlet 133, the first purified water collection inlet 131 is connected with the first purified water outlet 103, the second purified water collection inlet 132 is connected with the secondary water treatment device 2, and the purified water collection outlet 133 is connected with the final water treatment device 14.

[0047] In the embodiment, the final water treatment device 14 includes a final water treatment device water inlet 141, a final water treatment device waste water outlet 142 and a final water treatment device pure water outlet 143, the final water treatment device water inlet 141 is connected with the purified water collection outlet 133, the final water treatment device waste water outlet 142 is connected with the first brackish water inlet 101 and forms a circulating loop, the water output from the final water treatment device waste water outlet 142 can be input into the primary water treatment device 1 again for treatment, and the final water treatment device pure water outlet 143 can output drinking water or deionized water of a pure water level.

[0048] In the embodiment, the brackish water separated by the buffer tank 13 and the fourth water treatment device 5 can be further purified by the final water treatment device 14, and reference water or deionized water can be produced on demand, the final water treatment device 14 can adopt a membrane method to separate tail water, and a small amount of tail water can be generated, and the generated small amount of tail water can be returned to the primary water treatment device 1 again for filtration.

[0049] In this embodiment, a third tee 17 is provided at the primary brackish water inlet 101. The third tee 17 is used to connect the external water source, the primary water treatment device 1 and the final water treatment device 14.

[0050] The present invention provides a buffer tank 13 to collect purified water separated by the primary water treatment device 1 and the secondary water treatment device 2, and a final water treatment device 14 to enhance the quality adjustment of the effluent so that it reaches the level of drinking water or deionized water.

[0051] In one embodiment, such as Figure 1 and Figure 3 As shown, the freezing tank 3 includes a tank body 301, a first drainage grid 302, a heat exchange coil 303, and a first conveying device 304. The tank body 301 is connected to the secondary water treatment device 2 and the tertiary water treatment device 4. The first drainage grid 302 is installed inside the tank body 301. The heat exchange coil 303 is installed inside the tank body 301 and located below the first drainage grid 302. The first conveying device 304 is installed inside the tank body 301 and located above the first drainage grid 302.

[0052] Specifically, in this embodiment, the heat exchange coil 303 is located at the bottom of the tank 301. The heat exchange coil 303 can be concealed and cools the water in the freezing tank 301 through radiation and convection heat exchange. The first hydrophobic grid 302 is located at the bottom of the tank 301 and above the heat exchange coil 303. When the water temperature drops, alkali crystallizes and precipitates. Due to its low density, it floats on the water surface. Over a certain period of time, enough alkali gradually accumulates. The first hydrophobic grid 302 moves upward, separating the alkali crystals from the water. The crystals are then collected by a scraper or spiral feeding device and discharged from the tank 301 through the first conveying device 304. In this embodiment, the first conveying device 304 can be a sewage pump or a conveyor belt.

[0053] In this embodiment, the freezing tank 3 further includes a chilled water inlet 305, a chilled water outlet 306, a brackish water freezing tank alkali crystal outlet 307, and a chilled brackish water outlet 308. One end of the chilled water inlet 305 and the chilled water outlet 306 is connected to the refrigeration heat pump 12, and the other end is connected to the heat exchange coil 303, respectively. In this embodiment, the heat exchange coil 303 is not specifically limited; for example, in this instance, the heat exchange coil 303 is a heat exchange coil 303 with a superhydrophobic membrane. The first conveying device 304 is positioned above the first hydrophobic grid 302, and the heat exchange coil 303 is positioned below the first conveying device 304.

[0054] In this embodiment, the tail water (concentrated brackish water) cooled by the cooler 9 enters the freezing pool 3, the operating temperature of which is selected between the freezing point of the concentrated brackish water and zero degrees, at which time the alkali components in the tail water are crystallized and precipitated, the first hydrophobic grid 302 is a moving mechanism, the bottom of which pushes the precipitated alkali crystals to the first conveying device 304, and then the alkali crystals are discharged 409 from the alkali crystal outlet 307 of the freezing brackish water pool, and the frozen brackish water is input into the tertiary water treatment device 4 from the frozen brackish water outlet 308.

[0055] In this embodiment, the temperature in the pool body 301 is between the freezing point of the concentrated brackish water and zero degrees, and when the concentrated brackish water enters the pool body 301, it is first cooled to the freezing point range, at which time the solubility of the alkali components in the brackish water decreases and begins to be preliminarily precipitated, and the alkali crystals float on the surface of the brackish water and are removed by the first conveying device 304.

[0056] In one embodiment, as shown in Figure 1 and Figure 2 The secondary water treatment device 2 includes a first shell 201, a first microporous membrane 202, a first water distributor 203, and a condensing assembly 204. The first shell 201 is internally hollow, and is connected to the primary water treatment device 1 and the freezing pool 3. The first microporous membrane 202 is arranged in the first shell 201. The first water distributor 203 is arranged in the first shell 201 and is located below the first microporous membrane 202. The first water distributor 203 is connected to the primary water treatment device 1. The condensing assembly 204 is arranged in the first shell 201 and is located above the first microporous membrane 202.

[0057] Specifically, in this embodiment, the tail water passing through the heater 6 enters the secondary water treatment device 2 through the first water inlet 205 on the first shell 201, and is atomized by the first water distributor 203. Due to the negative pressure inside the first shell 201, the water in the atomized tail water quickly changes into water vapor, and the tail water is further concentrated. The water vapor dispersed in the air is screened by the first microporous membrane 202, and is condensed and collected by the condensing assembly 204. The purified water enters the buffer tank 13 through the condensing water outlet 206 in the first shell 201, and the condensing water outlet 206 is connected to the secondary purified water collection inlet 132. The further concentrated tail water is conveyed to the regenerator 7 through the first water outlet 207 at the bottom of the first shell 201.

[0058] In this embodiment, the condensation assembly 204 includes a condensation coil 2041, a condensate pan 2042, and a condensation source 2043. The condensation coil 2041 is located near the top inside the first housing 201. The condensate pan 2042 is located below the condensation coil and above the first microporous membrane 202. A condensate outlet 206 is located on the condensate pan 2042. The condensation source 2043 is connected to the condensation coil 2041. The condensation source 2043 can be natural air cooling, a cooling tower, process waste water, groundwater, etc. Water vapor condenses on the surface of the condensation coil 2041 and falls into the condensate pan 2042, and is then transported to the secondary purified water collection inlet 132 via the condensate outlet 206.

[0059] In this invention, the secondary water treatment device 2 adopts a low-pressure, medium-low temperature flash evaporation method. It uses a heat pump 8 before and after the device to recover energy and preheat brackish water, so as to ensure the highest energy efficiency under the condition of no external heat source. Its built-in first microporous membrane 202 can ensure rapid sieving of water vapor and brackish water under low resistance conditions.

[0060] In one embodiment, such as Figure 1 and Figure 4 As shown, the three-stage water treatment device 4 includes a second housing 401, a second microporous membrane 402, a second water distributor 403, a second hydrophobic grid 404, and a second conveying device 405. The second housing 401 has an internal cavity and is connected to the chilled tank 3 and the four-stage water treatment device 5. The second microporous membrane 402 is disposed inside the second housing 401. The second water distributor 403 is disposed inside the second housing 401 and located below the second microporous membrane 402. The second water distributor 403 is connected to the chilled tank 3. The second hydrophobic grid 404 is disposed inside the second housing 401 and located below the second water distributor 403. The second conveying device 405 is disposed above the second hydrophobic grid 404.

[0061] Specifically, in this embodiment, the chilled brackish water is fed into the second water distributor 403 through the second inlet 406 on the second housing 401 from the chilled brackish water outlet 308 for atomization. The water in the atomized brackish water is converted into water vapor, and the small droplets are cooled again to achieve further dealkalization. The water vapor dispersed in the air is filtered by the second microporous membrane 402 and output by the dry air outlet 408 located above the second microporous membrane 402 on the second housing 401. The small droplets are further evaporated and expanded and then collected at the bottom of the second housing 401. The second hydrophobic grid 404 is also a moving mechanism to further concentrate the alkaline components in the expanded and cooled concentrated brackish water and precipitate them to make it into saturated concentrated brine. The alkaline crystals that can be precipitated are pushed onto the second conveying device 405 by the scraper above the second hydrophobic grid 404 and discharged through the alkaline crystal outlet 409 on the side of the second housing 401. The saturated concentrated brine is transported to the cooler 11 through the second water outlet 410 at the bottom of the second housing 401. The second outlet is equipped with a filter.

[0062] In this embodiment, the second shell 401 side is provided with a dry air inlet 407, which is located above the second microporous membrane 402 and is arranged opposite to the dry air outlet 408. The dry air inlet 407 inputs dry air, and the water vapor in the second shell 401 is output from the dry air outlet 408.

[0063] In this embodiment, the third water treatment device 4 is externally provided with a second three-way valve 16 connected with the alkali crystal outlet and the brackish water freezing pool 3 alkali crystal outlet.

[0064] In this embodiment, the third water treatment device 4 adopts a freezing method, the second water distributor 403 is built-in to quickly atomize the low-temperature brackish water, and the second microporous membrane 402 screens water vapor and small droplets. In this process, the brackish water is further concentrated above its freezing point. At this time, by taking advantage of the low solubility of alkali components at low temperatures, most of the alkali components are precipitated.

[0065] In one embodiment, as shown in Figure 1 The fourth water treatment device 5 includes a water evaporation pool 501, a ceiling 502, and a water deflection plate 503. The water evaporation pool 501 is internally provided with an inner wall 5011, which divides the water evaporation pool 501 into a salt evaporation area 504 and a condensed water collection area 505. The salt evaporation area 504 is connected with the third water treatment device 4. The ceiling 502 is arranged at the top of the water evaporation pool 501. The water deflection plate 503 is arranged at the top of the condensed water collection area 505.

[0066] Specifically, in this embodiment, the water evaporation pool 501 includes an outer wall 5012 and an inner wall 5011. The condensed water collection area 505 is formed between the outer wall 5012 and the inner wall 5011. The salt evaporation area 504 is formed between the two inner walls 5011. The ceiling 502 is installed at the top of the outer wall 5012. In this embodiment, the ceiling 502 adopts an arched high-transmittance inflatable film. The inner side of the top of the outer wall 5012 is provided with the water deflection plate 503. The water deflection plate 503 is inclined downward and has a gap with the inner wall 5011 to allow the condensed water to flow into the condensed water collection area 505. The water deflection plate 503 can play a role in guiding and reducing evaporation.

[0067] In this embodiment, the saturated concentrated brine warmed by the aftercooler 11 enters the salt evaporation area 504. Due to the greenhouse effect, heat is concentrated in the fourth water treatment device 5. The saturated concentrated brine is dehydrated in the salt evaporation area 504 to form salt crystals for sale. Water vapor is concentrated on the inner surface of the ceiling 502 and is guided by the water deflection plate 503 to the condensed water collection area 505. The purified water from the buffer tank 13 is combined with the condensed water in the condensed water collection area 505 through the water taking pipe 506. The combined water flows into the final water treatment device 14 through the first three-way valve 15, is further purified, and is used or sold.

[0068] The fourth-stage water treatment device 5 in the application adopts the sunning method, the top of the sunning pool 501 is provided with a roof 502, the concentrated brine is rapidly evaporated by sunlight, and the condensed water is recovered to the condensed water collecting area 505 from the roof 502, and the brackish water is changed into salt after evaporation in the sunning area 504.

[0069] In the embodiment, the devices are connected through pipelines.

[0070] According to the embodiment of the application, on the other hand, as Figure 5 shown, a brackish water desalination method is also provided, which is applied to the brackish water desalination system of the embodiment and includes the following steps. S1: The brackish water is input into the primary water treatment device 1 for separation and desalination.

[0071] Specifically, in the embodiment, the brackish water raw water is input into the primary water treatment device 1 through the first-stage brackish water inlet 101 for separation and desalination into purified water and tail water.

[0072] S2: The purified water in the primary water treatment device 1 is input into the buffer tank 13, the primary concentrated brackish water is input into the heater 6 for heating, and the heated brackish water is input into the secondary water treatment device 2.

[0073] Specifically, in the embodiment, the purified water in the primary water treatment device 1 is input into the first-stage purified water collecting inlet 131 through the first-stage purified water outlet 103, the primary concentrated brackish water tail water is input into the heater 6 through the first-stage concentrated brackish water outlet 102 for heating, the heated brackish water tail water is input into the first water distributor 203 through the first water inlet 205, is atomized through the first water distributor 203, the water in the tail water is rapidly changed into water vapor after atomization, the tail water is further concentrated, and the water vapor dispersed in the air passes through the first microporous membrane 202.

[0074] S3: The purified water in the secondary water treatment device 2 is input into the buffer tank 13, and the further concentrated brackish water is input into the cooler 9.

[0075] Specifically, in the embodiment, the water vapor in the secondary water treatment device 2 is condensed on the condensing coil 2041 and falls to the condensing water disc 2042, is then transported to the second-stage purified water collecting inlet 132 through the condensing water outlet 206, and the concentrated tail water screened out by the first microporous membrane 202 is transported to the heat regenerator 7 through the first water outlet 207, the tail water in the heat regenerator 7 still has a higher heat, and the tail water is heat-exchanged with the heat supply heat pump 8, the heat supply heat pump 8 transports the recovered heat to the heater 6, and the cooled tail water in the heat regenerator 7 is input into the cooler 9 for further cooling.

[0076] S4: The cooled concentrated brackish water is input into the brackish water freezing pool 3, and the alkali component crystals separated out from the brackish water are discharged.

[0077] Specifically, the tail water after further cooling in the embodiment is input into the freezing pool 3, and the alkali components in the tail water are crystallized and separated out on the first hydrophobic grid 302, and are transported out of the freezing pool 3 by the first conveying device 304.

[0078] S5: The freezing brackish water is input into the third water treatment device 4, the separated-out alkali crystals are discharged, and the saturated concentrated brine is input into the fourth water treatment device 5.

[0079] Specifically, the remaining freezing brackish water in the freezing pool 3 in the embodiment is input into the second water inlet 406 through the freezing brackish water outlet 308, and is input into the second water distributor 403 again to be atomized again, the water vapor dispersed in the air passes through the second microporous membrane 402, and is output to the water inlet 141 of the final water treatment device through the dry air outlet 408 above the second microporous membrane 402 of the second shell 401, the alkali components in the concentrated brackish water screened out below the second microporous membrane 402 are further separated out, so that the concentrated brackish water becomes saturated concentrated brine, the alkali crystals capable of being separated out are pushed to the second conveying device 405 by the second hydrophobic grid 404, are discharged through the alkali crystal outlet 409 on the side of the second shell 401, and the saturated concentrated brine is conveyed to the cold reservoir 11 through the second water outlet 410 at the bottom of the second shell 401, the cold reservoir 11 exchanges heat with the refrigeration heat pump 12, absorbs the cold energy in the saturated concentrated brine, the refrigeration heat pump 12 conveys the cold energy back to the freezing pool 3, and the saturated concentrated brine after being warmed up enters the solar evaporation area 504 in the fourth water treatment device 5.

[0080] S6: The saturated concentrated brine in the fourth water treatment device 5 is dehydrated to form salt crystals, and the separated-out purified water is input into the final water treatment device 14.

[0081] Specifically, the saturated concentrated brine in the solar evaporation area 504 in the embodiment is dehydrated to form salt crystals under the sunlight, the water vapor is gathered on the inner surface of the ceiling 502, is guided to the condensate water collection area 505 through the water guide plate 503, and is input into the final water treatment device 14 together with the purified water from the buffer tank 13 through the first three-way valve 15.

[0082] Although the embodiments of the present application are described in conjunction with the drawings, various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and changes fall within the scope defined by the appended claims.

Claims

1. A brackish water desalination system, characterized by, Comprising: a primary water treatment device (1) adapted to separate brackish water into purified water and tail water; a secondary water treatment device (2) connected with the primary water treatment device (1), adapted to concentrate and separate part of the tail water; a freezing pool (3) connected with the secondary water treatment device (2); a tertiary water treatment device (4) connected with the freezing pool (3); a quaternary water treatment device (5) connected with the tertiary water treatment device (4), adapted to separate salt and alkali in the tail water.

2. The brackish water desalination system of claim 1, wherein, Further comprising: a heater (6) connected with the primary water treatment device (1) and the secondary water treatment device (2); a regenerator (7) connected with the secondary water treatment device (2) and the freezing pool (3); a heat supply heat pump (8) connected with the regenerator (7) and the heater (6).

3. The brackish water desalination system of claim 1, wherein, Further comprising: a cooler (9) connected with the secondary water treatment device (2) and the freezing pool (3); a cold source (10) connected with the cooler (9).

4. The brackish water desalination system of claim 1, wherein, Further comprising: a sub-cooler (11) connected with the tertiary water treatment device (4) and the quaternary water treatment device (5); a refrigeration heat pump (12) connected with the sub-cooler (11) and the freezing pool (3).

5. The brackish water desalination system of claim 1, wherein, Further comprising: a buffer tank (13) connected with the primary water treatment device (1) and the secondary water treatment device (2); a final water treatment device (14) connected with the buffer tank (13), the primary water treatment device (1) and the quaternary water treatment device (5), forming a circulation loop between the primary water treatment device (1) and the final water treatment device (14).

6. The brackish water desalination system of claim 1, wherein, The freezing pool (3) comprises: a pool body (301) connected with the secondary water treatment device (2) and the tertiary water treatment device (4); a first water-blocking grid (302) arranged in the pool body (301); a heat exchange coil (303) arranged in the pool body (301) below the first water-blocking grid (302); a first conveying device (304) arranged in the pool body (301) above the first water-blocking grid (302).

7. The brackish water desalination system of claim 1, wherein, The secondary water treatment device (2) comprises: a first shell (201) with an empty cavity inside, connected with the primary water treatment device (1) and the freezing pool (3); a first microporous membrane (202) arranged in the first shell (201); A first water distributor (203) is arranged in the first shell (201) below the first microporous membrane (202), and is connected with the primary water treatment device (1); A condensing assembly (204) is arranged in the first shell (201) above the first microporous membrane (202).

8. The brackish water desalination system of claim 1, wherein, The tertiary water treatment device (4) comprises: A second shell (401) is internally hollow, and is connected with the freezing pool (3) and the quaternary water treatment device (5); A second microporous membrane (402) is arranged in the second shell (401); A second water distributor (403) is arranged in the second shell (401) below the second microporous membrane (402), and is connected with the freezing pool (3); A second water-repellent grid (404) is arranged in the second shell (401) below the second water distributor (403); A second conveying device (405) is arranged above the second water-repellent grid (404).

9. The brackish water desalination system of claim 1, wherein, The quaternary water treatment device (5) comprises: A water evaporation pool (501) is internally provided with an inner wall (5011) for separating the water evaporation pool (501) into a salt evaporation area (504) and a condensate water collecting area (505), and the salt evaporation area (504) is connected with the tertiary water treatment device (4); A roof (502) is arranged on the top of the water evaporation pool (501); A water deflector (503) is arranged on the top of the condensate water collecting area (505).

10. A method of brackish water desalination applied to the brackish water desalination system according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: Brackish water is input into the primary water treatment device (1) for desalination; Purified water in the primary water treatment device (1) is input into a buffer tank (13), and the primary concentrated brackish water is input into a heater (6) for heating, and then is input into the secondary water treatment device (2) after heating; Purified water in the secondary water treatment device (2) is input into the buffer tank (13), and the further concentrated brackish water is input into a cooler (9); The cooled concentrated brackish water is input into a brackish water freezing pool (3), and the alkali component crystals separated from the brackish water are discharged; The frozen brackish water is input into the tertiary water treatment device (4), and the separated alkali crystals are discharged, and the saturated concentrated brine is input into the quaternary water treatment device (5); The saturated concentrated brine in the quaternary water treatment device (5) is dehydrated to form salt crystals, and the separated purified water is input into the final water treatment device (14).

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