Brackish water low-cost desalination device

Abstract

The invention provides a brackish water low-cost desalination device. The method comprises the following steps: repeatedly executing separation operation for preset times, wherein the separation operation comprises the following steps: extracting brackish water from a salt water lake to a raw water tank; freezing the brackish water in the raw water tank; when the freezing volume of the brackish water at the current time accounts for 1 / 3-1 / 5 of the total volume of the brackish water entering the raw water pool at the current time, the unfrozen brackish water in the raw water pool is drained back to the brackish water lake; ice melting operation is conducted on the iced brackish water in the raw water pool, and melted water obtained through the ice melting operation is discharged into a fresh water pool. The method can realize low-cost desalination of the brackish water.

Description

Technical Field

[0001] The invention belongs to the technical field of brackish water desalination, and in particular to a low-cost brackish water desalination device. Background Art

[0002] Groundwater in some areas of northwest my country is severely mineralized, resulting in a high salinity. This salty water (also known as brackish water) usually needs to be desalinated before it can be used for agricultural or domestic purposes.

[0003] Currently, mainstream technologies for brackish water desalination rely mainly on distillation and reverse osmosis. However, these methods are relatively expensive, which greatly limits the effective utilization of brackish water resources.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The first purpose of the present invention is to provide a low-cost desalination method for brackish water. The method uses a freezing method to separate desalinated water from brackish water, which can fully utilize the natural characteristics of low winter temperatures in the northwest region, requires low energy consumption, has low cost, and helps to improve the resource utilization of brackish water.

[0006] The second object of the present invention is to provide a device used in the above method, which has a simple overall structure and can achieve low-cost desalination of brackish water, thereby helping to improve the utilization rate of brackish water resources.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: A low-cost brackish water desalination method comprising: Repeating a preset number of separation operations, the separation operations comprising: Pumping brackish water from saltwater lakes to raw water tanks; Freezing the brackish water in the raw water pool; When the frozen volume of the brackish water accounts for 1 / 3 to 1 / 5 of the total volume of the brackish water entering the raw water pool, the unfrozen brackish water in the raw water pool is discharged back to the saltwater lake; The brackish water frozen in the raw water pool is subjected to an ice-melting operation, and the melted water obtained by the ice-melting operation is discharged into the fresh water pool.

[0008] The inventors took into account the fact that the winter in Northwest my country is very cold: the average temperature in winter is generally below 0°C, and the average temperature in the coldest month (January) is usually between -10°C and -25°C. The extreme minimum temperature can reach -30°C to -50°C, which is especially obvious in arid sandy areas, Gobi Desert and high-altitude areas; in addition, the temperature difference between day and night is large. Affected by strong solar radiation and surface thermal effects, the daily temperature difference is extremely large, with rapid temperature rise during the day and sharp temperature drop at night. The above method is proposed in response to the winter climate in Northwest China. Specifically, the above method can separate desalinated water from brackish water by freezing, with low energy consumption and low cost. By applying the above method to the Northwest region, low-cost desalinated brackish water can be obtained in the region by natural freezing in winter, which can provide technical support for agricultural development and domestic water use in the region, and can also provide a technical reference for brackish water desalination in other areas of the Northwest. In the above scheme, the concentrated water is discharged when the ice volume accounts for 1 / 3-1 / 5 of the total volume of the brackish water entering the raw water pool. The reason for this arrangement is that the inventors have found through research that the salt concentration in the unfrozen brine gradually increases with the formation of ice. When the ice volume reaches 1 / 3 to 1 / 5 of the total volume, the salt concentration in the unfrozen brine has reached a relatively high level. At this time, draining this part of the concentrated brine can effectively reduce the salt concentration of the remaining water. And at this time, the ice volume has reached a certain proportion, and the thickness and stability of the ice layer are sufficient to support subsequent operations, and the ice layer will not break or melt due to the drainage action. In addition, discharging the concentrated water at this stage can reduce the amount of brine that needs to be processed after the ice melts, thereby improving the efficiency of the entire desalination process.

[0009] Preferably, the step of extracting brackish water from a saltwater lake to a raw water pool comprises: Pumping brackish water from 0.1 to 0.5 m above the surface of the saltwater lake into the raw water pool; Preferably, the step of extracting brackish water from a saltwater lake to a raw water pool comprises: Brackish water is pumped from 0.2 m above the surface of the saltwater lake to the raw water pool.

[0010] In the above scheme, brackish water is extracted from a depth of 0.1 to 0.5 meters. This is because saltwater lakes typically exhibit a gradually increasing salt concentration from the lake surface to the bottom due to evaporation and salt dissolution from the lake bottom. Within the 0.1 to 0.5 meter depth range, the salt water mixes more evenly, the salt concentration is relatively stable, and close to the lake surface, it is less affected by external factors (such as rainfall, wind and waves), making extraction easier. Furthermore, within the 0.1 to 0.5 meter depth range, the water's fluidity decreases further, resulting in a more even salt distribution. The extracted brackish water has a moderate salinity, neither increasing desalination difficulties due to excessive salinity nor reducing treatment efficiency due to excessive salinity, thus meeting the process requirements for brackish water desalination. Furthermore, this depth range facilitates equipment layout and water extraction operations, eliminating the need for excessively deep pumping equipment and preventing the impact of lake bottom sediments on water quality. In a further plan, a depth of 0.2m was selected. This depth is usually located in the transition zone where the salt gradient changes. It can not only avoid possible pollution on the lake surface (such as floating objects, algae, etc.), but also obtain a relatively low salt concentration, which is suitable as raw water for brackish water desalination.

[0011] Preferably, the freezing temperature of the freezing treatment is within the range of -15°C to -20°C. When using natural freezing to desalinate brackish water, the primary purpose of selecting a freezing temperature within this range is to ensure that the salt in the water is effectively separated, thereby obtaining relatively pure fresh water. Specifically, this temperature range is chosen for the following reasons: brackish water contains a high salt content and has a lower freezing point than pure water. Pure water freezes at 0°C, while the freezing point of brackish water decreases with increasing salinity. Selecting a temperature range of -15°C to -20°C ensures that most water molecules freeze, while the salt remains in the liquid phase, thus achieving the separation of salt and water. Within this temperature range, water molecules form ice crystals, while the salt is excluded due to the ice crystal structure. This process helps separate the salt from the water, resulting in relatively pure ice crystals. If the temperature is too low, while the salt content in the ice can be further reduced, it may damage the ice crystal structure, affecting the subsequent melting process. Therefore, choosing a temperature range of -15°C to -20°C is a compromise that allows for effective salt separation without over-freezing. Furthermore, this temperature range is consistent with winter temperatures in the northwest region, allowing for direct use of natural temperatures for freezing, which helps reduce energy consumption and costs.

[0012] Preferably, the cooling method for the cooling process is natural cooling and / or cooling using a cooling device. In this embodiment, the brackish water is desalinated using natural cooling and / or cooling using a cooling device. Specifically, if the natural temperature does not reach the required cooling temperature for the cooling process, the cooling device can be used to further lower the temperature in the raw water pool so that the temperature in the raw water pool meets the temperature required for the freezing process. When the natural temperature reaches the required cooling temperature for the cooling process, the brackish water can be desalinated using only natural freezing.

[0013] Preferably, the ice melting operation is achieved by at least one of the following methods: film covering, shed covering, and electric heating. These ice melting methods are relatively mature technologies that can achieve rapid ice melting and improve desalination efficiency.

[0014] The present invention also provides a low-cost brackish water desalination device for implementing any of the above methods; the device comprises: a raw water tank, a concentrated water tank, a fresh water tank, a raw water pump, a concentrated water valve, and a fresh water valve; The raw water pump is arranged in the raw water pool, and the water inlet of the raw water pump is connected to the saltwater lake; One side of the raw water tank is connected to the concentrated water tank, and the other side is connected to the fresh water tank; the concentrated water valve is provided at the outlet of the raw water tank connected to the concentrated water tank, and the fresh water valve is provided at the outlet of the raw water tank connected to the fresh water tank; Wherein, the mineralization of water in the freshwater pool is not higher than 1g / L.

[0015] The above device has a simple structure, can realize the low-cost desalination of brackish water, and helps to improve the utilization rate of brackish water resources.

[0016] Preferably, an electric heating module is installed in the baffle on one side of the raw water pool to heat the raw water pool. By installing the electric heating module in the baffle, the raw water pool can be heated, the ice melting process can be promoted, and the efficiency of brackish water desalination can be improved.

[0017] Preferably, a solar photovoltaic inverter is further included, and the solar photovoltaic inverter is connected to the electric heating module. The solar photovoltaic inverter is used to convert light energy into electrical energy and power the electric heating module, which can further improve energy utilization efficiency and reduce costs.

[0018] Preferably, a circulation pump is provided in the concentrated water tank, and the circulation pump is used to output the concentrated water in the concentrated water tank.

[0019] Preferably, an efflux pump is provided in the fresh water pool, and an outlet of the efflux pump extends to the outside of the fresh water pool.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The above method can separate desalinated water from brackish water by freezing, requiring minimal energy and operating at a low cost. Applied to the Northwest region, this method can utilize natural freezing during winter to produce low-cost desalinated brackish water. This can provide technical support for agricultural development and domestic water use in the region, and can also serve as a technical reference for brackish water desalination in other areas of the Northwest. In the above scheme, concentrated water is discharged when the frozen volume accounts for 1 / 3-1 / 5 of the total volume of brackish water entering the raw water tank. This design is based on the inventors' research finding that the salt concentration in the unfrozen brine gradually increases with ice formation. When the frozen volume reaches 1 / 3-1 / 5 of the total volume, the salt concentration in the unfrozen brine has reached a high level. Discharging this concentrated brine effectively reduces the salt concentration of the remaining water. At this point, the frozen volume reaches a certain proportion, and the ice layer is thick and stable enough to support subsequent operations without causing the ice layer to break or melt due to drainage. Furthermore, discharging concentrated water at this stage reduces the amount of brine that needs to be processed after the ice melts, thereby improving the efficiency of the entire desalination process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present invention. The same reference symbols are used throughout the drawings to represent the same components. In the drawings: Figure 1 Schematic diagram of a low-cost brackish water desalination device provided in an embodiment of the present invention.

[0022] In the figure: 1. Raw water tank; 2. Fresh water tank; 3. External discharge pump; 4. Fresh water valve; 5. Raw water pump; 6. Concentrated water valve; 7. Circulation pump; 8. Concentrated water tank; 9. Baffle; 10. Electric heating module; 11. Solar photovoltaic inverter. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments and the accompanying drawings, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0024] Example See Figure 1 As shown, this embodiment provides a low-cost brackish water desalination device, which includes: a raw water tank 1, a concentrated water tank 8, a fresh water tank 2, a raw water pump 5, a concentrated water valve 6, and a fresh water valve 4; the raw water pump 5 is arranged in the raw water tank 1, and the water inlet of the raw water pump 5 is connected to the salt water lake; one side of the raw water tank 1 is connected to the concentrated water tank 8, and the other side is connected to the fresh water tank 2; the concentrated water valve 6 is arranged at the outlet of the raw water tank 1 connecting to the concentrated water tank 8, and the fresh water valve 4 is arranged at the outlet of the raw water tank 1 connecting to the fresh water tank 2; wherein, the mineralization of the water in the fresh water tank 2 is not higher than 1g / L.

[0025] Continue reading Figure 1 An electric heating module 10 for heating the raw water pool 1 is disposed within the baffle 9 on one side of the raw water pool 1. The number of the electric heating modules 10 can be multiple, and the multiple electric heating modules 10 can be evenly distributed in the vertical direction, so as to ensure that the ice in the raw water pool 1 is evenly heated.

[0026] Continue reading Figure 1 The device also includes a solar photovoltaic inverter 11, which is connected to the electric heating module 10.

[0027] Continue reading Figure 1 A circulating pump 7 is installed within the concentrate tank 8, which is used to output the concentrate from the concentrate tank 8. Specifically, the concentrate can be directly output to a saltwater lake. Alternatively, a three-dimensional ecological improvement model of "pond-field" water storage and diversion, combining high-standard farmland construction with supporting field canal systems, can be established, with ponds storing freshwater and concentrate aquaculture.

[0028] Continue reading Figure 1 The freshwater pool 2 is provided with an efflux pump 3, the outlet of which extends to the outside of the freshwater pool 2. For example, the water can be directly discharged into the irrigation land.

[0029] The low-cost desalination method for brackish water of this embodiment can adopt the following steps: Brackish water is pumped from 0.1-0.5 meters above the surface of the agricultural drainage saltwater lake using a raw water pump and placed in a raw water tank, where it is naturally frozen at -15°C to -25°C. When the frozen volume of the brackish water reaches 1 / 3-1 / 5 of the total volume of the brackish water entering the raw water tank, the brine valve at the bottom of the tank is opened, allowing the unfrozen brackish water to flow through the brine valve by gravity into the brine tank. (Since multiple freezing cycles form multiple ice blocks with gaps between them, and the ice blocks remain at the top due to buoyancy, this does not affect drainage.) The brackish water in the brine tank can then be pumped into the agricultural drainage saltwater lake using a circulating pump. This process is repeated until a preset number of times is reached, stopping the process. This preset number can be selected as needed. In this embodiment, the process stops when the ice volume in the raw water tank is about to fill the raw water tank.

[0030] Then, the ice is melted in the raw water pool. During the ice melting stage, various methods are adopted to melt the ice, including but not limited to film covering, roof covering, electric heating, etc. This embodiment adopts electric heating to use a solar photovoltaic inverter to convert light energy into electrical energy, power the electric heating module stored in the baffle, and use the electric heating module to melt the ice.

[0031] When the volume of melted ice in the original water pool reaches 1 / 10~1 / 2 of the total ice volume in the pool, open the fresh water valve at the bottom of the pool and let gravity drain the melted 1 / 5-2 / 5 of the water; the remaining ice in the pool continues to melt, and after all the ice in the pool has melted, it will all be input into the fresh water pool.

[0032] Example 2 The only difference between this embodiment and embodiment 1 is that the freezing temperature in this embodiment is 15°C.

[0033] Example 3 The only difference between this embodiment and embodiment 1 is that the freezing temperature in this embodiment is 25°C.

[0034] Example 4 The only difference between this embodiment and embodiment 1 is that the brackish water is discharged when the frozen volume of the brackish water reaches 1 / 3 of the total volume of the brackish water entering the raw water pool this time.

[0035] Example 5 The only difference between this embodiment and embodiment 1 is that the brackish water is discharged when the frozen volume of the brackish water reaches 1 / 5 of the total volume of the brackish water entering the raw water pool this time.

[0036] Experimental example The methods of Examples 1-5 were used to desalinate brackish water with a salinity of 10 g / L, and the salinity of the water in the corresponding freshwater pool was measured. The test results are shown in Table 1 below.

[0037] Table 1 Test results

[0038] As can be seen from the above table, the mineralization of the desalinated water obtained by the solution of the present invention can be controlled below 1g / L, meeting the salinity standard for irrigation water.

[0039] In summary, the solution of the present invention can achieve low-cost brackish water desalination, and is particularly suitable for brackish water resource utilization in the northwest region.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low-cost method for desalination of brackish water, characterized in that: include: Repeating a preset number of separation operations, the separation operations comprising: Pumping brackish water from saltwater lakes to raw water tanks; Freezing the brackish water in the raw water pool; When the frozen volume of the brackish water accounts for 1 / 3 to 1 / 5 of the total volume of the brackish water entering the raw water pool, the unfrozen brackish water in the raw water pool is discharged back to the saltwater lake; The brackish water frozen in the raw water pool is subjected to an ice-melting operation, and the melted water obtained by the ice-melting operation is discharged into the fresh water pool.

2. The method according to claim 1, characterized in that The method of extracting brackish water from the saltwater lake to the raw water pool includes: Pumping brackish water from 0.1 to 0.5 m above the surface of the saltwater lake into the raw water pool; Preferably, the step of extracting brackish water from a saltwater lake to a raw water pool comprises: Brackish water is pumped from 0.2 m above the surface of the saltwater lake to the raw water pool.

3. The method according to claim 1, characterized in that The freezing temperature of the freezing treatment is in the range of -15°C to -20°C.

4. The method according to claim 1, wherein The cooling method of the cooling treatment is natural cooling and / or cooling using a cooling device.

5. The method according to any one of claims 1 to 4, characterized in that The ice melting operation is achieved by at least one of the following methods: film covering, roof covering, and electric heating.

6. A low-cost brackish water desalination device, characterized in that: Used to implement the method described in any one of claims 1 to 5; the device comprises: a raw water tank, a concentrated water tank, a fresh water tank, a raw water pump, a concentrated water valve, and a fresh water valve; The raw water pump is arranged in the raw water pool, and the water inlet of the raw water pump is connected to the saltwater lake; One side of the raw water tank is connected to the concentrated water tank, and the other side is connected to the fresh water tank; the concentrated water valve is provided at the outlet of the raw water tank connected to the concentrated water tank, and the fresh water valve is provided at the outlet of the raw water tank connected to the fresh water tank; Wherein, the mineralization of water in the freshwater pool is not higher than 1g / L.

7. The device according to claim 6, characterized in that An electric heating module for heating the raw water pool is arranged in the baffle on one side of the raw water pool.

8. The device according to claim 7, characterized in that It also includes a solar photovoltaic inverter, which is connected to the electric heating module.

9. The device according to claim 6, characterized in that A circulation pump is provided in the concentrated water pool, and the circulation pump is used to output the concentrated water in the concentrated water pool.

10. The device according to claim 6, characterized in that An efflux pump is provided in the fresh water pool, and an outlet of the efflux pump extends to the outside of the fresh water pool.

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