Highly mineralized water desalination treatment system based on open-pit mine dump and desalination method

Abstract

The application discloses a high-mineralization water desalination treatment system and method based on a strip mine dump, and utilizes the stripping material of the strip mine and the wide site of the dump to construct a freeze-thaw cycle desalination system, which is divided into a plurality of freeze-thaw sub-pools to improve the system processing capacity and arrangement flexibility; the high-mineralization water is changed into ice with lower salinity and water with higher salt content by fully utilizing the cold climate condition in the northern region in winter, and the ice is further melted into fresh water by using the waste heat of the mine area or seasonal temperature rise. The application utilizes the natural freeze-thaw cycle process to realize the quality and quantity utilization of the high-mineralization water, does not need to add chemical reagents and special equipment, has strong adaptability to water quality, low technical difficulty, small investment and low operation cost; the large-scale freeze-thaw pool is constructed by using the strip mine dump, has large capacity and high efficiency, does not need to newly occupy land, and has small influence on the ecological environment of the mine area.

Description

Technical Field

[0001] This invention relates to a high-mineralization water desalination system, specifically to a high-mineralization water desalination system and method based on an open-pit mine spoil heap. Background Technology

[0002] In some areas of Northwest my country, groundwater mineralization is severe, with high salt content. When open-pit mining is conducted in these areas, the direct discharge of groundwater from the mining area leads to severe soil salinization, impacting ecological security. If coal washing operations are also carried out in the mining area, the salt content of the coal washing wastewater will further increase, making it difficult to remove salt ions through simple purification, thus exacerbating the mineralization of water resources. Currently, the relatively mature saline water desalination technologies are reverse osmosis membrane methods and distillation methods. However, their application in open-pit mining still faces problems such as poor material adaptability, high energy consumption, high desalination costs, high technical requirements, and low conversion rates. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a high-mineralization water desalination system and method based on open-pit mine spoil heaps. The desalination system has low desalination cost and low technical requirements, making it suitable for desalination in open-pit mines in Northwest China.

[0004] To achieve the above objectives, the present invention provides the following technical solution: an open-pit mine spoil heap for easy desalination of highly mineralized water.

[0005] A construction platform is laid on the top surface of the uppermost step of the open-pit mine spoil heap. When the top surface of the construction platform is 5-8m away from the final design height of the open-pit mine spoil heap, a water-blocking layer is laid. An isolation layer is laid on top of the water-blocking layer using concrete and waterproof cloth. Isolation walls are set around the perimeter of the isolation layer to form a freeze-thaw pool.

[0006] Inside the freeze-thaw pool, a drainage ditch is set along the center line of the two long side isolation walls. The height of the drainage ditch is higher than the isolation walls. The drainage ditch divides the freeze-thaw pool into two freeze-thaw sub-pools. The freeze-thaw sub-pools are connected to the drainage ditch through valves. The overflow outlet and the combined interface of the drainage ditch are both located outside the isolation walls. The combined interface is divided into three interfaces: a saline water interface, a fresh water interface, and a raw water interface. The saline water interface is connected to the saline water storage tank, the fresh water interface is connected to the fresh water storage tank, the raw water interface is connected to the raw water storage tank, and the overflow outlet is connected to the raw water storage tank.

[0007] A U-shaped heating pipe is densely laid on the bottom plate of the freeze-thaw sub-pool, with both the heating pipe outlet and the heating pipe inlet located outside the freeze-thaw sub-pool.

[0008] Furthermore, the isolation wall consists of an outer wall and a core wall, with the core wall longitudinally located inside the outer wall. The core wall has a rectangular cross-section with a height of 2-3m and a width of 0.5-1m, and is constructed using concrete and waterproof fabric. The outer wall has a trapezoidal cross-section with a top width of 3-4m and a bottom width of 6-8m.

[0009] Furthermore, a partition wall is constructed in the freeze-thaw pool, with both ends of the partition wall connected to an isolation wall and a drainage ditch, respectively, dividing the freeze-thaw pool into several freeze-thaw sub-pools. Each freeze-thaw sub-pool is connected to the drainage ditch through a valve.

[0010] Furthermore, the isolation layer is inclined with a slope of 5-10‰, the combined interface of the drainage ditch is lower than the overflow outlet, and within a single freeze-thaw sub-pool, the connection point with the drainage ditch is lower than other areas.

[0011] A method for desalination of high-mineralized water includes the following steps: Every winter, high-mineralized water is injected into the drainage ditch through the raw water interface. Valves are opened sequentially from low to high to inject high-mineralized water into the freeze-thaw sub-pools. Once the freeze-thaw sub-pools are full of high-mineralized water, the corresponding valves are closed. This process continues until all freeze-thaw sub-pools are full. Injection of high-mineralized water into the drainage ditch is then stopped, and excess high-mineralized water is returned to the raw water storage tank.

[0012] Step 2: Let the highly mineralized water in the freeze-thaw pool freeze;

[0013] Step 3: After the high-mineralized water in the freeze-thaw pool freezes to half the depth of the water injection, open the valve and the saline water inlet to discharge all the liquid water in the freeze-thaw pool into the saline water storage tank for later use. The frozen ice blocks will naturally fall to the bottom of the freeze-thaw pool.

[0014] Step 4: After the liquid water in the freeze-thaw tanks has been completely drained, close the valves and overflow outlets, and inject the treated water from the mine wastewater treatment plant into the heating pipeline to heat each freeze-thaw tank, so that the ice blocks melt into fresh water.

[0015] Step 5: When the fresh water depth in the freeze-thaw sub-pool reaches 10cm, open the valve and fresh water interface to divert some of the fresh water formed by melting ice to the fresh water storage tank for later use. Only a small amount of water is left in the freeze-thaw sub-pool for heat conduction. The heating pipeline continuously supplies heat to the ice in the freeze-thaw sub-pool to melt the remaining ice. Repeatedly open and close the valve to drain fresh water until all the ice melts.

[0016] Step Six: After all the desalinated water has been released, close the valve and repeat steps one to five to achieve repeated high-mineralized water desalination treatment until the desalination requirements are met.

[0017] Compared with existing technologies, this invention does not add any chemical reagents. The highly mineralized water is partially frozen, and after the frozen portion thaws, the salt content in the water decreases significantly, while the salt content in the unfrozen portion increases significantly. This invention fully utilizes the low winter temperatures of Northwest China, employing a freeze-thaw method to solve the desalination problem of mineralized water over a vast area of ​​open-pit mines. The desalination process efficiently utilizes atmospheric temperature and the residual temperature of open-pit mine wastewater, resulting in low energy consumption and low cost. The engineering construction is simple, with low technical difficulty, facilitating unmanned operation without increasing the burden on enterprises. It does not occupy additional surface land and does not increase enterprise production costs. The freeze-thaw sub-pools are flexibly arranged, enabling continuous operation and high system efficiency. The heating pipelines are arranged in a loop from low to high temperature, maximizing the use of the energy of the high-temperature water, accelerating ice melting, and improving system circulation efficiency. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the cross-section of the present invention;

[0019] Figure 2 This is a top view of the present invention;

[0020] Figure 3 for Figure 1 Schematic diagram of the BB section in the diagram;

[0021] Figure 4 for Figure 1 Schematic diagram of section AA in the diagram;

[0022] Figure 5 This is a schematic diagram of the heating pipeline layout of the present invention;

[0023] In the diagram: 1. Waste dump, 2. Construction platform, 3. Water barrier layer, 4. Mining area surface, 5. Isolation layer, 6. Isolation wall, 7. Freeze-thaw pool, 8. Core wall, 9. Outer wall, 10. Drainage ditch, 11. Overflow outlet, 12. Freeze-thaw sub-pool, 13. Valve, 14. Saltwater inlet, 15. Freshwater inlet, 16. Raw water inlet, 17. Heating pipe, 18. Heating pipe outlet, 19. Heating pipe inlet. Detailed Implementation

[0024] The invention will now be further described with reference to the accompanying drawings.

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] like Figure 1 and Figure 2As shown, this invention provides a technical solution: a construction platform 2 is laid on the top surface of the uppermost step of the open-pit mine spoil heap 1, which is closest to the mine's wastewater treatment plant. The parameters of the construction platform 2 should meet the layout requirements of the freeze-thaw pond 7 and the water storage tank system. The construction platform 2 should be at least 1000m long and at least 500m wide to ensure that the freeze-thaw pond 7 has a certain water storage capacity; the capacity of the freeze-thaw pond 7 should meet the requirements for treating highly mineralized water throughout the year.

[0027] S = V * k r / h=Q*m*k r / (n*h)

[0028] In the formula: S is the net construction area of ​​freeze-thaw pool 7, in m². 2 V represents the annual volume of water requiring freeze-thaw cycle treatment, in meters. 3 / a;k r Let m be the coefficient of water expansion after freezing. 2 h represents the designed single freeze-thaw cycle treatment water depth, in meters; Q represents the annual wastewater treatment volume, in meters. 3 / a; m represents the number of times high-mineralized wastewater requires freeze-thaw cycle treatment; n represents the number of times the freeze-thaw tank is used annually.

[0029] The construction platform 2 is equipped with a freeze-thaw pool 7 and a water storage system. The water storage system includes three sets of storage pools: saline water (concentrated high-mineralized water), fresh water (water with lower mineralization after freeze-thaw cycles), and raw water (high-mineralized raw water after turbidity reduction and purification at the wastewater treatment plant). The raw water storage pool should meet the water storage capacity requirements during the non-freezing period (approximately equal to Q). The fresh water storage pool is designed as a tiered pool according to the needs of differentiated utilization. The saline water storage pool has at least two capacities, one of which is used to store ultra-high-mineralized water to meet the requirement of not freezing at -10℃ in winter.

[0030] If there are multiple wastewater treatment plants in the mining area, and the distances are too great to choose between, Platform 2 should be planned and constructed near a wastewater treatment plant with a large treatment capacity to ensure a sufficient supply of purified water. When the top surface of Platform 2 is approximately 5m above the final design height of the open-pit mine spoil heap 1, the disposal of ordinary materials should cease. First, a 1-2m thick layer of sand and gravel should be disposed of as the basic permeable layer. Then, a material with high viscosity in the mining area, which has good compaction after water contact and can block water seepage, should be selected as the disposal material to lay the water-blocking layer 3. The thickness of the water-blocking layer 3 should be approximately 3m. Moderate watering and compaction using engineering machinery should be carried out to ensure density. Above the water-blocking layer 3, an isolation layer 5 should be laid using concrete and waterproof fabric. This type of isolation layer 5 can achieve near-absolute water isolation, preventing vertical seepage. The thickness of the isolation layer 5 should be 0.3-0.5m. The final height of the open-pit mine spoil heap 1 should not exceed the surface height 4 of the mining area to reduce energy waste caused by subsequent increases in water resource elevation.

[0031] An isolation wall 6 is installed on the isolation layer 5, forming a freeze-thaw pool 7 around it. The isolation wall 6 consists of an outer wall 9 and a core wall 8, with the core wall 8 longitudinally positioned inside the outer wall 9. The core wall 8 is a rectangle with a cross-sectional height of 2-3m and a width of 0.5m, constructed using concrete and waterproof fabric, and is integrated with the bottom isolation layer 5. The outer wall 9 is constructed using the same process as the waterproof layer 3 and has a trapezoidal cross-section, with a top width of approximately 2m, a bottom width of 6-8m, an inner slope of 45°-60°, and an outer slope of 35°-45°. After construction, the outer wall 9 is compacted with water to maintain its airtightness.

[0032] Within the freeze-thaw pool 7, a drainage ditch 10 is constructed along the centerline of the two long-side isolation walls 6. When the freeze-thaw pool 7 is large, multiple drainage ditches 10 can be constructed. The height of the drainage ditch 10 is 0.5-1m greater than the height of the isolation walls 6. The drainage ditch 10 divides the freeze-thaw pool 7 into two sub-frozen pools 12. If necessary, partition walls can also be constructed within the freeze-thaw pool 7. These partition walls are constructed using the same process as the drainage ditch 10 and include anti-corrosion agents to prevent freeze-thaw damage. The partition walls are connected at both ends to the isolation walls 6 and the drainage ditch 10, respectively, dividing the freeze-thaw pool 7 into several sub-frozen pools 12. The width of each freeze-thaw sub-pool 12 is not less than 100m, ensuring that each freeze-thaw sub-pool 12 has a certain water storage capacity. Each freeze-thaw sub-pool 12 is connected to the drainage ditch 10 through a valve 13. The overflow outlet 11 and the combined interface of the drainage ditch are both set outside the isolation wall 6. The combined interface of the drainage ditch is divided into three interfaces, namely the saline water interface 14, the fresh water interface 15 and the raw water interface 16. The saline water interface 14 is connected to the saline water storage tank, the fresh water interface 15 is connected to the fresh water storage tank, the raw water interface 16 is connected to the raw water storage tank, and the overflow outlet 11 is connected to the raw water storage tank.

[0033] like Figure 3 and Figure 4 As shown, the isolation layer 5 is designed to be inclined with a slope of 5-10‰. The direction of the combined interface of the drainage ditch is lower than that of the overflow outlet 11, and the combined interface is located at the lower part of the drainage ditch 10, while the overflow outlet 11 is located at the upper part of the drainage ditch 10. In a single freeze-thaw sub-pool 12, the connection position with the drainage ditch 10 is lower than that of other areas, thus ensuring that water can converge to the combined interface of the drainage ditch.

[0034] like Figure 5 As shown, a U-shaped heating pipe network 17 is densely laid on the bottom plate of the freeze-thaw sub-pool 12. The pipe network should meet the requirements of freeze resistance and rapid heat transfer. The heating pipe outlet 18 is located outside the freeze-thaw sub-pool 12 and is the highest point of the freeze-thaw sub-pool 12; the heating pipe inlet 19 is located outside the freeze-thaw sub-pool 12 and is the lowest point of the freeze-thaw sub-pool 12. Therefore, the heating pipe network 17 needs to be introduced along the drainage ditch 10.

[0035] Every winter, high-mineralized water is injected into the drainage ditch 10 through the raw water interface 16. Then, the valves 13 connecting the drainage ditch 10 and the freeze-thaw sub-pools 12 are opened sequentially from low to high to inject high-mineralized water into the freeze-thaw sub-pools 12. When the water level reaches 80% of the height of the isolation wall 6, the freeze-thaw sub-pools 12 are considered full. The valves 13 of the freeze-thaw sub-pools 12 that are full of high-mineralized water are closed. After all the freeze-thaw sub-pools 12 are full, the injection of high-mineralized water into the drainage ditch 10 is stopped. The excess high-mineralized water flows back to the raw water storage tank through the raw water interface 16. If the injection volume is too large and may overflow the freeze-thaw sub-pools 12, the overflow port 11 is opened to guide the high-mineralized water back to the raw water storage tank.

[0036] The high-mineralized water in the freeze-thaw sub-pool 12 is left to freeze. Preferably, to accelerate the freezing of the high-mineralized water, ultra-high-mineralized water at a temperature below -5°C can be injected into the heating pipe 17 to cool the water in the freeze-thaw sub-pool 12 from both the top and bottom. After the frozen thickness of the mineralized water in the freeze-thaw sub-pool 12 reaches half of the injection depth, the valve 13 connecting the drainage channel 10 to the freeze-thaw sub-pool 12 and the saline water interface 14 are opened to discharge all the liquid water in the freeze-thaw sub-pool 12 into the saline water storage tank for later use. The frozen ice blocks fall naturally to the bottom of the freeze-thaw sub-pool 12. Throughout the water injection and freezing process, the overflow port 11 is kept open to avoid stress damage caused by changes in air pressure in the drainage channel 10 due to temperature changes.

[0037] After the liquid saline water in the freeze-thaw sub-pool 12 is discharged, a small amount of high-temperature fresh water is injected through the fresh water interface 15 to fill the gaps between the ice and the bottom of the pool, which plays a role in transferring heat and promoting the melting of the ice. After the water injection is completed, the valves 13 of each freeze-thaw sub-pool 12 and the overflow port 11 of the drainage ditch 10 are closed in sequence. At the same time, high-temperature water treated by the mine wastewater treatment plant is injected into the heating pipeline 17 to heat each freeze-thaw sub-pool 12, so that the ice melts into fresh water.

[0038] When the freshwater depth in the freeze-thaw sub-pool 12 reaches 10cm, the valve 13 connecting the drainage ditch 10 to the freeze-thaw sub-pool 12 and the freshwater inlet 15 are opened to divert some of the freshwater formed by melting ice to the freshwater storage tank for later use. Only a small amount of water is retained in the freeze-thaw sub-pool 12 for heat conduction. The heating pipe 17 continuously supplies heat to the ice in the freeze-thaw sub-pool 12 to melt the remaining ice. The valve 13 is repeatedly opened and closed to drain freshwater until all the ice melts. During the ice melting process, the freshwater inlet 15 is in a normally open state, which also serves to regulate the air pressure in the drainage ditch 10.

[0039] After all the desalinated water in the freeze-thaw sub-pool 12 is discharged, valve 13 is closed. After all the fresh water in the freeze-thaw sub-pool 12 is discharged, the fresh water inlet 15 is closed, thus completing one freeze-thaw cycle desalination of high-mineralized water.

[0040] Repeat the above steps to achieve desalination of all high-mineralization raw water. Alternatively, high-mineralization water can be repeatedly treated until it meets the requirements for freshwater use. Preferably, the last freeze-thaw cycle desalination of the year can use the maximum capacity of the freeze-thaw tank, utilizing seasonal natural warming to melt ice blocks, further reducing the desalination cost of high-mineralization raw water.

[0041] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-mineralization water desalination system based on open-pit mine spoil heaps, characterized in that: A construction platform (2) is laid on the top surface of the uppermost step of the open-pit mine spoil heap (1). When the top surface of the construction platform (2) is 5-8m away from the final design height of the open-pit mine spoil heap (1), a water-blocking layer (3) is laid. An isolation layer (5) is laid on top of the water-blocking layer (3) using concrete and waterproof cloth. An isolation wall (6) is set around the perimeter of the isolation layer (5), and a freeze-thaw pool (7) is formed by the isolation wall (6). Inside the freeze-thaw pool (7), a drainage ditch (10) is set along the center line of the two long side isolation walls (6). The height of the drainage ditch (10) is higher than that of the isolation wall (6). The drainage ditch (10) divides the freeze-thaw pool (7) into two freeze-thaw sub-pools (12). The freeze-thaw sub-pools (12) and the drainage ditch (10) are connected through a valve (13). The overflow port (11) of the drainage ditch and the combined interface of the drainage ditch are both set outside the isolation wall (6). The combined interface is divided into three interfaces, namely the saline water interface (14), the fresh water interface (15) and the raw water interface (16). The saline water interface (14) is connected to the saline water storage tank, the fresh water interface (15) is connected to the fresh water storage tank, the raw water interface (16) is connected to the raw water storage tank, and the overflow port (11) is connected to the raw water storage tank. A spiral heating pipe (17) is densely laid on the bottom plate of the freeze-thaw sub-pool (12). Water treated by the mine sewage treatment plant is injected into the heating pipe (17). The outlet (18) and inlet (19) of the heating pipe are both located outside the freeze-thaw sub-pool (12). A partition wall is constructed in the freeze-thaw pool (7), with the two ends of the partition wall connected to the isolation wall (6) and the drainage ditch (10) respectively, dividing the freeze-thaw pool (7) into several freeze-thaw sub-pools (12), and each freeze-thaw sub-pool (12) is connected to the drainage ditch (10) through a valve (13).

2. The high-mineralization water desalination system based on an open-pit mine spoil heap as described in claim 1, characterized in that: The isolation wall (6) consists of an outer wall (9) and a core wall (8). The core wall (8) is longitudinally located inside the outer wall (9). The core wall (8) has a cross-section that is 2-3m high and 0.5-1m wide and is constructed using concrete and waterproof cloth. The outer wall (9) has a cross-section that is trapezoidal with a top width of 3-4m and a bottom width of 6-8m.

3. The high-mineralization water desalination system based on an open-pit mine spoil heap as described in claim 1, characterized in that: The isolation layer (5) is inclined with a slope of 5-10‰. The combined interface of the drainage ditch is lower than the overflow outlet (11). In a single freeze-thaw sub-pool (12), the connection position with the drainage ditch (10) is lower than that of other areas.

4. A desalination method based on a high-mineralization water desalination system in an open-pit mine spoil heap, as described in any one of claims 1-3, characterized in that: Step 1: Every winter, high-mineralized water is injected into the drainage ditch (10) through the raw water interface (16). Valves (13) are opened sequentially from low to high to inject high-mineralized water into the freeze-thaw sub-pool (12). Once the freeze-thaw sub-pool (12) is filled with high-mineralized water, the corresponding valves (13) are closed. After all the freeze-thaw sub-pools (12) are filled, the injection of high-mineralized water into the drainage ditch (10) is stopped, and the excess high-mineralized water is returned to the raw water storage tank. Step 2: Let the highly mineralized water in the freeze-thaw sub-pool (12) freeze and wait for it to freeze; Step 3: After the high mineralized water in the freeze-thaw sub-pool (12) freezes to half the depth of the water injection, open the valve (13) and the salt water inlet (14) to discharge all the liquid water in the freeze-thaw sub-pool (12) into the salt water storage tank for later use. The frozen ice blocks will fall naturally to the bottom of the freeze-thaw sub-pool (12). Step 4: After the liquid water in the freeze-thaw sub-pool (12) has been completely drained, close the valve (13) and the overflow port (11), and inject the water treated by the mine sewage treatment plant into the heating pipeline (17) to heat each freeze-thaw sub-pool (12) at the same time, so that the ice blocks melt into fresh water; Step 5: When the fresh water depth in the freeze-thaw sub-pool (12) reaches 10cm, open the valve (13) and the fresh water inlet (15) to divert some of the fresh water formed by melting ice to the fresh water storage tank for later use. Only a small amount of water is left in the freeze-thaw sub-pool (12) for heat conduction. The heating pipe (17) continuously supplies heat to the ice in the freeze-thaw sub-pool (12) to melt the remaining ice. Repeatedly open and close the valve (13) to drain the fresh water until all the ice melts. Step 6: After all the desalinated water has been released, close the valve (13) and repeat steps one to five to achieve repeated high-mineralized water desalination treatment until the desalination requirements are met.

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