A phosphogypsum stockyard drainage system

Abstract

This invention provides a drainage system for phosphogypsum stockpiles, including an initial dam. The initial dam slope has multiple seepage ditches along the slope direction, each with multiple vertical drainage installation slots distributed along its length. A converging ditch parallel to the seepage ditches is located on the slope, and the lower ends of the seepage ditches are connected to the converging ditch. The surfaces of the initial dam, seepage ditches, vertical drainage installation slots, and converging ditch are all covered with impermeable membranes. Vertically upward-facing perforated drainage pipes, multiple of which are connected end-to-end, are installed in the vertical drainage installation slots, covered with geotextile sleeves and filter sleeves. The seepage ditches, vertical drainage installation slots, and converging ditch are filled with granular aggregate to fix the perforated drainage pipes. A geotextile layer covers the granular aggregate on the initial dam slope, and a filter layer is laid on top. A collection pond is located outside the initial dam, lined with an impermeable membrane, and the converging ditch is connected to the collection pond via the drainage pipes. This invention increases vertical drainage capacity, forming a three-dimensional drainage network, maximizing drainage efficiency, and can cope with larger rainfall or seepage events.

Description

Technical Field

[0001] This invention belongs to the field of chemical solid waste storage technology and relates to a phosphogypsum storage drainage system. Background Technology

[0002] In the phosphorus chemical production process, phosphogypsum, as a major byproduct of the wet-process phosphoric acid production, is generated in large quantities and contains a certain amount of soluble phosphorus, fluorine, and heavy metals, among other harmful substances. To ensure environmental safety, phosphogypsum is usually transported to dedicated stockpiles for storage and disposal. However, phosphogypsum stockpiles are characterized by high water content, low permeability, and poor long-term stability. Under the influence of rainfall infiltration and their own water retention capacity, large amounts of leachate easily accumulate within the stockpile. If this leachate cannot be effectively drained in a timely manner, it will not only raise the phreatic line within the stockpile, reducing slope stability and increasing the risk of dam failure, but may also cause harmful components to leak out with the leachate, polluting the surrounding soil and groundwater environment.

[0003] To control internal moisture, maintain site stability, and reduce environmental pollution, drainage systems are commonly used in engineering practice to drain leachate from phosphogypsum stockpiles. Traditional drainage systems are typically located at the bottom of the stockpile and consist of horizontally laid gravel blind drains, geotextile-wrapped drainage pipes, or composite drainage nets, forming a bottom horizontal drainage layer. This structure primarily collects leachate that seeps from top to bottom and guides it to collection wells or treatment facilities via a pipeline system. However, as stockpiles expand, their height often reaches tens of meters or even higher, making reliance solely on the bottom horizontal drainage layer significantly limited: its pumping radius is limited, making it difficult to effectively cover the entire cross-section of the stockpile; leachate in the central area must overcome a long seepage path and significant flow resistance to reach the bottom drainage layer, easily stagnating in the upper and middle parts of the stockpile, leading to a significant rise in the phreatic line. Especially under conditions of heavy rainfall or uneven stockpile density, localized saturation zones are more likely to form, further exacerbating the risk of stockpile instability. Therefore, existing systems that primarily rely on bottom horizontal drainage suffer from insufficient vertical drainage capacity and low drainage efficiency when dealing with tall phosphogypsum piles. There is an urgent need to introduce a new drainage structure that also takes into account vertical drainage function in order to effectively control the seepage field inside the pile. Summary of the Invention

[0004] The purpose of this invention is to provide a phosphogypsum stockpile drainage system that increases vertical drainage capacity, forms a three-dimensional drainage network, maximizes drainage efficiency, and can cope with larger rainfall or seepage events.

[0005] To solve the above-mentioned technical problems, the present invention provides a phosphogypsum stockpile drainage system, including an initial dam for the phosphogypsum stockpile. The initial dam has multiple seepage channels along its slope direction. Each seepage channel has multiple vertical drainage installation slots distributed along its length. A converging channel parallel to the seepage channels is formed at the slope of the initial dam. The lower end of each seepage channel is connected to the converging channel. An impermeable membrane is laid on the surface of the initial dam, each seepage channel, each vertical drainage installation slot, and the converging channel.

[0006] Each vertical drainage installation trench is equipped with a vertically upward-oriented mesh drainage pipe. Multiple mesh drainage pipes are connected end to end inside the vertical drainage installation trench. Each mesh drainage pipe is covered with a geotextile sleeve, and each mesh drainage pipe is covered with a filter sleeve outside the corresponding geotextile sleeve.

[0007] Each seepage channel, each vertical drainage installation trench, and the collection trench are filled with granular aggregate. The mesh seepage pipe in the vertical drainage installation trench is fixed by the granular aggregate. The slope of the initial dam of the phosphogypsum stockpile is covered with a geotextile layer that covers the granular aggregate, and a filter layer is laid on the upper surface of the geotextile layer.

[0008] A collection pond is set up outside the initial dam of the phosphogypsum stockpile. The inner surface of the collection pond is covered with an impermeable membrane. The collection ditch is connected to a drainage pipe that connects to the collection pond.

[0009] By adopting the above technical solution, under the action of rainfall or seepage, the water accumulated on the surface of the phosphogypsum pile is first filtered through the filter layer and geotextile layer, reducing the entry of large particles into the system. Subsequently, the water seeps into the graded sand and gravel protective layer and flows downward along the perforated drainage pipes in the vertical drainage trench. The perforated drainage pipes are double-wrapped by the geotextile sleeve and the filter sleeve, effectively preventing soil particles from entering the pipe, while allowing water to seep in through the mesh of the pipe wall, forming a vertical drainage channel. Multiple perforated drainage pipes are connected end to end by mesh connecting pipes to form a continuous drainage path, ensuring that the leachate can be smoothly transported downward to the drainage ditch.

[0010] The granular aggregate in the seepage channel further filters the leachate, accelerates the drainage and consolidation of phosphogypsum, prevents pipe blockage, and guides it to the collection channel, and then transports it to the collection pool outside the initial dam of the phosphogypsum stockpile through the drainage pipe.

[0011] This system, through the combination of vertical mesh drainage pipes and horizontal drainage ditches and converging ditches, forms a three-dimensional drainage network, which significantly improves the drainage efficiency of phosphogypsum piles, effectively lowers the phlogiston line inside the pile, enhances slope stability, and reduces the risk of harmful components leaking out. It is suitable for the leachate drainage needs of tall phosphogypsum piles.

[0012] The present invention is further configured such that the geomembrane is an HDPE membrane, and the thickness of the HDPE membrane is ≥1.5mm.

[0013] The present invention is further configured such that the upper end of each mesh drainage tube is a mesh connecting tube with an outer diameter matching the inner diameter, the upper end of the mesh connecting tube is open, and the upper mesh drainage tube is connected to the lower mesh connecting tube.

[0014] The present invention is further configured such that both the geotextile sleeve and the filter sleeve cover the upper opening of the mesh connecting tube.

[0015] The invention is further configured such that a support ring is provided outward at the lower edge of the bottommost mesh permeable drainage pipe.

[0016] The present invention is further configured such that a graded sand and gravel protective layer is provided between the geotextile layer and the impermeable membrane.

[0017] The present invention is further configured such that the granular aggregate is granite aggregate.

[0018] The present invention is further configured such that a collection trough is provided on the slope of the initial dam of the phosphogypsum stockpile at the middle of the collection ditch, an impermeable membrane is laid at the bottom of the collection trough, and the upper end of the drainage pipe extends into the collection trough.

[0019] The present invention is further configured such that at least one collection tank is provided, each collection tank is connected to the drainage pipe through a diversion pipe, each diversion pipe is provided with a valve, and a water pump is connected to the middle of each diversion pipe.

[0020] The invention is further configured such that each collection pool is divided into settling chambers distributed in a direction away from the diversion pipe, and a seepage port is provided at the upper part between every two settling chambers.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention constructs a three-dimensional drainage network by setting up seepage ditches, vertical drainage installation trenches, and collection ditches on the slope of the initial dam of a phosphogypsum stockpile, and combining them with structures such as perforated seepage pipes, geotextile sleeves, filter sleeves, and granular aggregates. This design not only increases vertical drainage capacity, maximizing drainage efficiency, but also effectively copes with larger rainfall or seepage events. Compared to traditional systems that rely solely on the bottom horizontal drainage layer, this invention can more comprehensively cover the entire cross-section of the stockpile, reducing the retention of leachate in the upper part of the stockpile, thereby significantly lowering the phreatic line and improving slope stability. Simultaneously, through multiple filtration and seepage prevention measures, this invention also reduces the risk of harmful component leakage, which is of great significance for protecting the surrounding soil and groundwater environment. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0024] Figure 2 Used to demonstrate the distribution of geomembrane, graded sand and gravel protective layer, geotextile layer and filter layer;

[0025] Figure 3 Used to demonstrate the seepage ditches, vertical drainage installation trenches, collection ditches, and collection channels on the initial dam slope of the phosphogypsum stockpile;

[0026] Figure 4 Used to demonstrate the connection between two mesh drainage pipes;

[0027] Figure 5 It is used to display the geotextile sleeve and filter sleeve outside the mesh drainage pipe.

[0028] The components include: 1. Initial dam for phosphogypsum stockpile; 2. Drainage ditch; 3. Vertical drainage installation trench; 4. Convergence ditch; 5. Convergence channel; 6. Impermeable membrane; 7. Mesh drainage pipe; 8. Mesh connecting pipe; 9. Support ring; 10. Geotextile sleeve; 11. Filter sleeve; 12. Granular aggregate; 13. Graded sand and gravel protective layer; 14. Geotextile layer; 15. Filter layer; 16. Collection pool; 17. Drainage pipe; 18. Diversion pipe; 19. Valve; 20. Water pump; 21. Settlement chamber; 22. Infiltration outlet. Detailed Implementation

[0029] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a further detailed explanation of the phosphogypsum landfill drainage system proposed in this invention. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, used only to facilitate and clarify the illustration of the embodiments of this invention. The same or similar reference numerals in the drawings represent the same or similar components.

[0030] Example, refer to Figure 1-5 A phosphogypsum stockpile drainage system includes an initial dam 1 for the phosphogypsum stockpile. Multiple seepage channels 2 are formed along the slope of the initial dam 1. Multiple vertical drainage installation trenches 3, distributed along the length of each seepage channel 2, are formed on the slope of the initial dam 1. A converging channel 4, parallel to the seepage channels 2, is formed at the bottom of the initial dam 1. The lower end of each seepage channel 2 is connected to the converging channel 4. A converging trough 5 is formed in the middle of the converging channel 4 on the slope of the initial dam 1. An impermeable membrane 6, which is an HDPE membrane, is laid on the surface of the initial dam 1, each seepage channel 2, each vertical drainage installation trench 3, the converging channel 4, and the converging trough 5. The HDPE membrane thickness is ≥1.5 mm.

[0031] Each vertical drainage installation trench 3 is equipped with a vertically upward-facing mesh drainage pipe 7. Multiple mesh drainage pipes 7 are connected end to end inside the vertical drainage installation trench 3. The upper end of each mesh drainage pipe 7 is a mesh connecting pipe 8 with an outer diameter matching the inner diameter. The upper end of the mesh connecting pipe 8 is open. The upper mesh drainage pipe 7 is connected to the lower mesh connecting pipe 8. The lower edge of the lowermost mesh drainage pipe 7 is provided with a support ring 9. Each mesh drainage pipe 7 is covered with a geotextile sleeve 10. Each mesh drainage pipe 7 is covered with a filter sleeve 11 outside the corresponding geotextile sleeve 10. The geotextile sleeve 10 and the filter sleeve 11 both cover the upper opening of the mesh connecting pipe 8. The number of perforated drainage pipes 7 is gradually increased according to the thickness of the phosphogypsum pile to ensure that the upper part of the perforated drainage pipes 7 always leaks above the phosphogypsum pile, so that the water on the surface of the phosphogypsum can also be quickly drained downward through the perforated drainage pipes 7, reducing its downward infiltration through the phosphogypsum.

[0032] Each seepage channel 2, each vertical drainage installation trench 3, the collection trench 4, and the collection trench 5 are filled with granular aggregate 12 made of granite aggregate. The mesh seepage pipe 7 in the vertical drainage installation trench 3 is fixed by the granular aggregate 12. The granular aggregate 12 can effectively filter the seepage water, accelerate the drainage and consolidation of phosphogypsum, and prevent pipe blockage. The slope of the initial dam 1 of the phosphogypsum stockpile is covered with a graded sand and gravel protective layer 13 that covers the granular aggregate 12. The graded sand and gravel protective layer 13 is used to prevent the geotextile material from being punctured. A geotextile layer 14 is laid on the upper surface of the graded sand and gravel protective layer 13, and a filter layer 15 is laid on the upper surface of the geotextile layer 14.

[0033] Two collection pools 16 are installed outside the initial dam 1 of the phosphogypsum stockpile. The inner surface of the collection pools 16 is covered with an impermeable membrane 6, and the collection channel 5 is connected to the outward drainage pipe 17. Each collection pool 16 is connected to the drainage pipe 17 through a branch pipe 18. Each branch pipe 18 is equipped with a valve 19, and a water pump 20 is connected to the middle of each branch pipe 18. Each collection pool 16 is divided into settling chambers 21 distributed away from the branch pipe 18. A seepage port 22 is opened at the top between every two settling chambers 21. As the seepage water continuously passes through the settling chambers 21, the sediment in the seepage water can gradually settle and settle. When the sediment inside a collection pool 16 needs to be cleaned, the valve 19 corresponding to that collection pool 16 is closed to stop the seepage water from entering.

[0034] Working principle: Under rainfall or seepage, the water on the surface of the phosphogypsum pile is first filtered through the filter layer 15 and the geotextile layer 14, reducing the entry of large particles into the system. Subsequently, the water seeps into the graded sand and gravel protective layer 13 and flows downwards along the perforated drainage pipes 7 in the vertical drainage trench 3. The perforated drainage pipes 7 are double-wrapped by the geotextile sleeve 10 and the filter sleeve 11, effectively preventing soil particles from entering the pipe while allowing water to seep in through the mesh of the pipe wall, forming a vertical drainage channel. Multiple perforated drainage pipes 7 are connected end-to-end by perforated connecting pipes 8, forming a continuous drainage path to ensure that the leachate can be smoothly transported downwards to the drainage trench 2.

[0035] The granular aggregate 12 within the seepage channel 2 further filters the leachate, accelerating the drainage and consolidation of the phosphogypsum, preventing pipe blockage, and guiding its flow to the collection channel 4. The collection channel 4 concentrates the leachate from each seepage channel 2 into the collection trough 5, and then transports it through the drainage pipe 17 to the collection pool 16 outside the initial dam 1 of the phosphogypsum stockpile. The settling chamber 21 within the collection pool 16 is designed to allow impurities to gradually settle during the flow of the leachate, while the seepage outlet 22 allows the upper layer of clear water to enter the next settling chamber 21, achieving solid-liquid separation. When a collection pool 16 needs cleaning, the valve 19 on the corresponding diversion pipe 18 is closed to stop the flow of seepage water, allowing maintenance operations to be performed, while the other collection pool 16 can continue to operate, ensuring the continuity of system operation.

[0036] The system forms a three-dimensional drainage network by combining vertical mesh drainage pipes 7 with horizontal drainage ditches 2 and converging ditches 4, which significantly improves the drainage efficiency of phosphogypsum piles, effectively lowers the phlogiston line inside the pile, enhances slope stability, and reduces the risk of harmful components leaking out. It is suitable for the leachate drainage needs of tall phosphogypsum piles.

[0037] It should also be noted that all terms such as "set up" and similar descriptive words in this application (especially the specification) indicate that two structures have or exist a connection relationship. However, the specific means by which the two are connected are not limited in detail, and are usually conventional connection methods. That is, the means should be understood as prior art and do not need to be elaborated. For example, "m is set up with n" only indicates that structure m has structure n, and whether the two are connected by welding, riveting, adhesive, or integral molding is within the scope of protection of this application. Similarly, "x is rotatably set up with y" only indicates that y and x can rotate relative to each other, and whether the two are connected by a bearing, or whether y directly passes through x and is rotatably connected to x, or other feasible methods, are all within the scope of protection of this application.

[0038] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A phosphogypsum dump drainage system, comprising an initial dam (1) for the phosphogypsum dump, characterized in that, The slope of the initial dam (1) of the phosphogypsum stockpile has multiple seepage ditches (2) set along its slope direction. On each seepage ditches (2), multiple vertical drainage installation grooves (3) are set along its length direction. At the slope of the initial dam (1) of the phosphogypsum stockpile, a convergence ditch (4) parallel to the seepage ditches (2) is set. The lower end of each seepage ditches (2) is connected to the convergence ditch (4). The surfaces of the initial dam (1), each seepage ditches (2), each vertical drainage installation groove (3) and the convergence ditch (4) are all covered with an impermeable membrane (6). Each vertical drainage installation trench (3) is equipped with a vertically upward mesh drainage pipe (7). Multiple mesh drainage pipes (7) are connected end to end in the vertical drainage installation trench (3). Each mesh drainage pipe (7) is covered with a geotextile sleeve (10), and each mesh drainage pipe (7) is covered with a filter sleeve (11) on the corresponding geotextile sleeve (10). Each seepage channel (2), each vertical drainage installation trench (3) and the converging trench (4) are filled with granular aggregate (12). The mesh seepage pipe (7) in the vertical drainage installation trench (3) is fixed by the granular aggregate (12). The slope of the initial dam (1) of the phosphogypsum stockpile is covered with a geotextile layer (14) covering the granular aggregate (12). The upper surface of the geotextile layer (14) is covered with a filter layer (15). A collection pool (16) is provided outside the initial dam (1) of the phosphogypsum stockpile. The inner surface of the collection pool (16) is covered with an impermeable membrane (6). The converging ditch (4) is connected to a drainage pipe (17) that is connected to the collection pool (16) to the outside.

2. The phosphogypsum stockpile drainage system according to claim 1, characterized in that, The geomembrane (6) is an HDPE membrane, and the thickness of the HDPE membrane is ≥1.5mm.

3. The phosphogypsum stockpile drainage system according to claim 1, characterized in that, Each mesh drainage tube (7) has a mesh connecting tube (8) at its upper end with an outer diameter matching the inner diameter. The upper end of the mesh connecting tube (8) is open, and the upper mesh drainage tube (7) is connected to the lower mesh connecting tube (8).

4. The phosphogypsum stockpile drainage system according to claim 3, characterized in that, Both the geotextile sleeve (10) and the filter sleeve (11) cover the upper opening of the mesh connecting tube (8).

5. The phosphogypsum stockpile drainage system according to claim 3, characterized in that, A support ring (9) is provided on the lower edge of the bottom mesh drainage pipe (7).

6. The phosphogypsum stockpile drainage system according to claim 1, characterized in that, A graded sand and gravel protective layer (13) is provided between the geotextile layer (14) and the impermeable membrane (6).

7. The phosphogypsum stockpile drainage system according to claim 1, characterized in that, The granular aggregate (12) is granite aggregate.

8. The phosphogypsum stockpile drainage system according to claim 1, characterized in that, The slope of the initial dam (1) of the phosphogypsum stockpile is provided with a collection trough (5) in the middle of the collection ditch (4). The bottom of the collection trough (5) is covered with an impermeable membrane (6), and the upper end of the drainage pipe (17) extends into the collection trough (5).

9. A phosphogypsum stockpile drainage system according to claim 1, characterized in that, At least one collection tank (16) is provided. Each collection tank (16) is connected to the drainage pipe (17) through a diversion pipe (18). Each diversion pipe (18) is equipped with a valve (19). A water pump (20) is connected to the middle of each diversion pipe (18).

10. A phosphogypsum stockpile drainage system according to claim 9, characterized in that, Each collection pool (16) is divided into settling chambers (21) distributed in a direction away from the diversion pipe (18), and a seepage port (22) is provided in the upper part between each pair of settling chambers (21).

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