A phosphogypsum leachate resource recovery system

Abstract

The utility model relates to a kind of phosphogypsum percolate resource recovery system, it is related to industrial wastewater treatment and resource recovery technical field, including phosphogypsum percolate raw water tank, primary sedimentation defluorination unit, secondary sedimentation phosphorus removal unit and membrane purification treatment and membrane concentration unit connected by pipeline sequentially, primary sedimentation defluorination unit includes first solid-liquid separation device and first reaction tank, and first reaction tank is equipped with pH meter one for monitoring and adjusting pH and dosing device one, secondary sedimentation phosphorus removal unit includes second solid-liquid separation device and second reaction tank, and second reaction tank is equipped with pH meter two for monitoring and adjusting pH and dosing device two, and membrane purification treatment and membrane concentration unit includes ultrafiltration device, acid-resistant nanofiltration device, acid-resistant reverse osmosis device, phosphoric acid concentrated solution storage tank and water production reuse pool.The utility model realizes the effective recovery of phosphorus and fluorine resources in phosphogypsum percolate and the reuse of waste water, solves the problem of treating strong acidic high-impurity percolate, and has both environmental benefits and economic benefits.

Description

Technical Field

[0001] This utility model relates to the field of industrial wastewater treatment and resource recovery technology, and in particular to a resource recovery system for phosphogypsum leachate. Background Technology

[0002] Phosphogypsum is a large-scale industrial solid waste generated during the wet-process phosphoric acid production. The leachate from phosphogypsum stockpiles has a complex composition, containing high concentrations of phosphoric acid, fluoride ions, and various heavy metals and impurities, and is highly acidic (typically with a low pH). Improper treatment can lead to severe water and soil pollution. Currently, the main treatment method for phosphogypsum leachate is neutralization and precipitation followed by discharge to meet standards, which fails to effectively recover the phosphorus resources, resulting in resource waste and high treatment costs.

[0003] In existing technologies, directly using membrane methods to treat phosphogypsum leachate is prone to problems such as fluoride scaling, suspended solids clogging, and strong acid corrosion, leading to rapid membrane element failure and unstable system operation. Therefore, developing a phosphogypsum leachate treatment system that can efficiently recover phosphorus resources, enable wastewater reuse, and operate stably is of great significance. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a resource recovery system for phosphogypsum leachate, which realizes the effective recovery of phosphorus and fluorine resources in phosphogypsum leachate and the reuse of wastewater, overcomes the problem of treating highly acidic and high-impurity leachate, and has both environmental and economic benefits.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: A phosphogypsum leachate resource recovery system includes the following components connected sequentially via pipelines: The raw water tank for phosphogypsum leachate is used to store phosphogypsum leachate. The primary sedimentation defluorination unit includes a primary reaction tank and a first solid-liquid separation device. The primary reaction tank is equipped with a pH meter and a dosing device for monitoring and adjusting the pH. Using the dosing device and based on feedback from the pH meter, the pH of the system is precisely controlled between 3 and 4. Under these conditions, fluoride ions react with calcium ions to form calcium fluoride precipitate. The mixture then flows into the first solid-liquid separation device for solid-liquid separation. The secondary sedimentation phosphorus removal unit includes a secondary reaction tank and a second solid-liquid separation device. The effluent from the first solid-liquid separation device flows into the secondary reaction tank. The secondary reaction tank is equipped with a pH meter (II) and a dosing device (II) for monitoring and adjusting the pH. The pH of the primary effluent is adjusted to 7-9, causing phosphate ions to precipitate as calcium phosphate. Through the dosing device (II) and based on feedback from the pH meter (II), the pH of the system is raised to 7-9. Under these alkaline conditions, phosphate ions in the solution react with calcium ions to form calcium phosphate precipitate. The mixture then enters the second solid-liquid separation device for solid-liquid separation. The membrane purification and concentration unit includes an ultrafiltration unit, an acid-resistant nanofiltration unit, an acid-resistant reverse osmosis unit, a phosphoric acid concentrate storage tank, and a permeate reuse tank. The inlet of the ultrafiltration unit is connected to the outlet of the second solid-liquid separation unit, the outlet of the ultrafiltration unit is connected to the inlet of the acid-resistant nanofiltration unit, the permeate outlet of the acid-resistant nanofiltration unit is connected to the inlet of the acid-resistant reverse osmosis unit, the concentrate outlet of the acid-resistant reverse osmosis unit is connected to the phosphoric acid concentrate storage tank, and the permeate outlet of the acid-resistant reverse osmosis unit is connected to the permeate reuse tank. The ultrafiltration unit removes residual micro-suspended solids, colloids, and other substances from the water to ensure that the SDI (Soil Discharge Index) of the effluent meets the feed water requirements of the subsequent nanofiltration membrane. The acid-resistant nanofiltration unit can efficiently retain residual polyvalent metal ions (such as iron, calcium, magnesium, etc.), some sulfate ions, and organic matter, while allowing phosphoric acid and some monovalent ions to permeate. The acid-resistant reverse osmosis unit is used for final concentration.

[0006] Preferably, an intermediate water tank is provided between the second solid-liquid separation device and the ultrafiltration device, and the filtrate in the intermediate water tank is pumped to the ultrafiltration device.

[0007] Preferably, the first solid-liquid separation device and the second solid-liquid separation device are plate and frame filter presses, chamber filter presses, or centrifuges.

[0008] Preferably, the first solid-liquid separation device separates calcium fluoride filter mud, which can be sold or disposed of safely, while the second solid-liquid separation device separates calcium phosphate filter cake, which is connected to a conveying device to transport the calcium phosphate filter cake back to the phosphoric acid production slurry tank for reuse as raw material.

[0009] Preferably, the ultrafiltration device is a column ultrafiltration membrane, tubular ultrafiltration membrane, or ceramic ultrafiltration membrane device, with a molecular weight cutoff of 50,000 to 150,000 Daltons.

[0010] Preferably, the membrane material of the acid-resistant nanofiltration device is sulfonated polyethersulfone or polypiperazine amide, or a composite membrane specially modified for acid resistance, with a molecular weight cutoff of 150-400 Daltons and an operating pH range of 0-4.

[0011] Preferably, the concentrate outlet of the acid-resistant nanofiltration device is connected to the phosphoric acid production slurry preparation tank, and the concentrate outlet outputs nanofiltration concentrate containing impurities, which is then returned to the upstream phosphoric acid production slurry preparation tank for reuse.

[0012] Preferably, the membrane material of the acid-resistant reverse osmosis device is a polyamide composite membrane that has undergone special acid-resistant modification, and its operating pH range is 1-5.

[0013] Preferably, the first dosing device is a lime slurry dosing device, and the second dosing device is a lime slurry and sodium hydroxide dosing device, that is, a combination dosing device for lime slurry and sodium hydroxide.

[0014] The advantages of this invention are as follows: 1. Significantly improved resource recovery efficiency: Through a two-stage chemical sedimentation process, filter mud mainly composed of calcium fluoride and calcium phosphate, which can be used as a raw material for phosphoric acid production, were successfully separated and recovered, achieving preliminary separation and efficient recovery of fluorine and phosphorus resources. Finally, using an acid-resistant membrane combination process, a pure phosphoric acid solution with a concentration of approximately 10% was obtained. This solution has high value and can be directly reused in production, effectively realizing the resource utilization of phosphogypsum leachate.

[0015] 2. Stable and Reliable Membrane System: An innovative process flow of "pretreatment (two-stage sedimentation + ultrafiltration) + acid-resistant nanofiltration + acid-resistant reverse osmosis" has been constructed. The first-stage fluoride removal is carried out under acidic conditions, effectively avoiding phosphorus co-precipitation loss. The subsequent acid-resistant nanofiltration acts as a core barrier, efficiently retaining multivalent ions, organic matter, and other impurities in an acidic environment, significantly reducing the risk of fouling and scaling in the subsequent acid-resistant reverse osmosis, and ensuring the long-term stable operation of the entire membrane system in a strongly acidic environment.

[0016] 3. Win-win situation for both environmental and economic benefits: The system ultimately produces high-quality purified water, which can be reused in production processes or used as clean water in the plant area, achieving "zero discharge" or significant reduction of wastewater, resulting in significant environmental benefits. At the same time, the recovered phosphoric acid products create direct economic value, effectively offsetting some of the operating costs, and achieving an organic combination of environmental governance and economic benefits.

[0017] 4. Compact process and high degree of automation: Each unit is connected sequentially via pipelines, supporting continuous or semi-continuous operation. Through the linkage control of the pH meter and the dosing device, precise automatic adjustment of the pH value is achieved, significantly reducing manual labor intensity and ensuring the stability and reliability of the treatment effect. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structural principle of this utility model.

[0019] Explanation of key component symbols in the diagram: 1. Raw water tank for phosphogypsum leachate; 2. Primary reaction tank; 3. First solid-liquid separation device; 4. Secondary reaction tank; 5. Second solid-liquid separation device; 6. Intermediate water tank; 7. Ultrafiltration device; 8. Acid-resistant nanofiltration device; 9. Acid-resistant reverse osmosis device; 10. Phosphate concentrate storage tank; 11. Permeate reuse tank; 12. Calcium fluoride filter mud; 13. Calcium phosphate filter cake; 14. Nanofiltration concentrate. Detailed Implementation

[0020] To more clearly illustrate this utility model, the following description, in conjunction with the accompanying drawings, will provide further details.

[0021] Example 1: As Figure 1 As shown, a phosphogypsum leachate resource recovery system includes the following components connected sequentially via pipelines: 1. Raw water tank for phosphogypsum leachate, used to store phosphogypsum leachate; The primary sedimentation defluorination unit includes a primary reaction tank 2 and a first solid-liquid separation device 3. The primary reaction tank is equipped with a pH meter 1 for monitoring and adjusting pH and a dosing device 1. The secondary sedimentation phosphorus removal unit includes a secondary reaction tank 4 and a second solid-liquid separation device 5. The secondary reaction tank is equipped with a pH meter 2 for monitoring and adjusting pH and a dosing device 2. The membrane purification and concentration unit includes an ultrafiltration unit 7, an acid-resistant nanofiltration unit 8, an acid-resistant reverse osmosis unit 9, a phosphoric acid concentrate storage tank 10, and a permeate reuse tank 11. The inlet of the ultrafiltration unit 7 is connected to the outlet of the second solid-liquid separation unit 5, the outlet of the ultrafiltration unit 7 is connected to the inlet of the acid-resistant nanofiltration unit 8, the permeate outlet of the acid-resistant nanofiltration unit 8 is connected to the inlet of the acid-resistant reverse osmosis unit 9, the concentrate outlet of the acid-resistant reverse osmosis unit 9 is connected to the phosphoric acid concentrate storage tank 10, and the permeate outlet of the acid-resistant reverse osmosis unit 9 is connected to the permeate reuse tank 11.

[0022] Example 2: Combination Figure 1 As shown, based on Embodiment 1, an intermediate water tank 6 is provided between the second solid-liquid separation device 5 and the ultrafiltration device 7, and the filtrate in the intermediate water tank 6 is pumped to the ultrafiltration device 7.

[0023] Example 3: Based on Example 1 or Example 2, the first solid-liquid separation device 3 and the second solid-liquid separation device 5 are plate and frame filter presses, chamber filter presses or centrifuges.

[0024] The first solid-liquid separation device 3 separates calcium fluoride filter mud 12, which can be sold or disposed of safely. The second solid-liquid separation device 5 separates calcium phosphate filter cake 13, which is connected to a conveying device to transport the calcium phosphate filter cake 13 back to the phosphoric acid production slurry tank for reuse as raw material.

[0025] Example 4: Based on Example 1, Example 2 or Example 3, the ultrafiltration device 7 is a column ultrafiltration membrane, tubular ultrafiltration membrane or ceramic ultrafiltration membrane device, the membrane material of the acid-resistant nanofiltration device 8 is sulfonated polyethersulfone or polypiperazine amide, and the membrane material of the acid-resistant reverse osmosis device 9 is an acid-resistant modified polyamide composite membrane.

[0026] The concentrated water outlet of the acid-resistant nanofiltration device 8 is connected to the phosphoric acid production slurry preparation tank, and the nanofiltration concentrated water 14 is returned to the upstream phosphoric acid production slurry preparation tank for reuse.

[0027] Example 5: Based on the above examples, the first dosing device is a lime slurry dosing device, and the second dosing device is a lime slurry and sodium hydroxide dosing device.

[0028] The work process is as follows: 1. As shown in Figure 1, the phosphogypsum leachate in the raw water tank 1 first flows into the primary reaction tank 2. Using a dosing device (e.g., adding lime slurry) and based on feedback from a pH meter, the pH of the system is precisely controlled between 3 and 4. Under these conditions, fluoride ions react with calcium ions to form calcium fluoride precipitate. The mixture then flows into the first solid-liquid separation device 3 (e.g., a plate and frame filter press) for solid-liquid separation. The resulting calcium fluoride filter mud 12 can be sold or safely disposed of.

[0029] 2. The effluent from the first solid-liquid separation unit 3 flows into the secondary reaction tank 4, where it is dosing via a second dosing device (e.g., adding lime slurry and sodium hydroxide solution), and the pH of the system is raised to 7-9 based on feedback from the second pH meter. Under these alkaline conditions, phosphate ions in the solution react with calcium ions to form calcium phosphate precipitate. The mixture then enters the second solid-liquid separation unit 5, and the separated calcium phosphate filter cake 13 is returned to the front end of phosphoric acid production (phosphoric acid production slurry tank) via a conveying device for reuse as raw material.

[0030] 3. The filtrate from the second solid-liquid separation device 5 flows into the intermediate water tank 6, and is then pumped to the ultrafiltration device 7. The ultrafiltration device 7 is used to remove residual micro-suspended solids, colloids, and other substances in the water to ensure that the SDI (Soil Degradation Index) of the effluent meets the feed water requirements of the subsequent nanofiltration membrane.

[0031] 4. Ultrafiltration permeate flows into the acid-resistant nanofiltration unit 8. The acid-resistant nanofiltration membrane operates under acidic conditions, effectively retaining residual polyvalent metal ions (such as iron, calcium, magnesium, etc.), some sulfate ions, and organic matter, while allowing phosphoric acid and some monovalent ions to pass through. The nanofiltration concentrate 14 contains high concentrations of impurities and phosphoric acid, which is recycled back to the pre-treatment slurry tank of the phosphoric acid production process. The permeate from the nanofiltration process is the purified phosphoric acid solution.

[0032] 5. The permeate from the acid-resistant nanofiltration unit 8 flows into the acid-resistant reverse osmosis unit 9 for final concentration. The acid-resistant reverse osmosis membrane can withstand low pH environments, concentrating the phosphoric acid solution to a concentration of 8-12%, which is then stored in the phosphoric acid concentrate storage tank 10 and can be reused in the production system. The product water produced by the acid-resistant reverse osmosis unit 9 is high-quality pure water, which flows into the product water reuse tank 11 and can be directly reused in the production process or other water usage points.

[0033] The above description is only a specific embodiment of the present utility model, but the structural features of the present utility model are not limited thereto. The present utility model can be used in similar products. Any changes or modifications made by those skilled in the art within the scope of the present utility model are covered by the patent scope of the present utility model.

Claims

1. A resource recovery system for phosphogypsum leachate, characterized in that, Including those connected sequentially via pipes: The raw water tank for phosphogypsum leachate (1) is used to store phosphogypsum leachate. The primary sedimentation defluorination unit includes a primary reaction tank (2) and a first solid-liquid separation device (3). The primary reaction tank is equipped with a pH meter and a dosing device for monitoring and adjusting pH. The secondary sedimentation phosphorus removal unit includes a secondary reaction tank (4) and a second solid-liquid separation device (5). The secondary reaction tank is equipped with a pH meter and a dosing device for monitoring and adjusting pH. The membrane purification and concentration unit includes an ultrafiltration device (7), an acid-resistant nanofiltration device (8), an acid-resistant reverse osmosis device (9), a phosphoric acid concentrate storage tank (10), and a permeate reuse tank (11). The inlet of the ultrafiltration device (7) is connected to the outlet of the second solid-liquid separation device (5), the outlet of the ultrafiltration device (7) is connected to the inlet of the acid-resistant nanofiltration device (8), the permeate of the acid-resistant nanofiltration device (8) is connected to the inlet of the acid-resistant reverse osmosis device (9), the concentrate outlet of the acid-resistant reverse osmosis device (9) is connected to the phosphoric acid concentrate storage tank (10), and the permeate outlet of the acid-resistant reverse osmosis device (9) is connected to the permeate reuse tank (11).

2. The phosphogypsum leachate resource recovery system according to claim 1, characterized in that, An intermediate water tank (6) is provided between the second solid-liquid separation device (5) and the ultrafiltration device (7), and the filtrate in the intermediate water tank (6) is pumped to the ultrafiltration device (7).

3. The phosphogypsum leachate resource recovery system according to claim 1, characterized in that, The first solid-liquid separation device (3) and the second solid-liquid separation device (5) are plate and frame filter presses, chamber filter presses or centrifuges.

4. The phosphogypsum leachate resource recovery system according to claim 3, characterized in that, The first solid-liquid separation device (3) separates calcium fluoride filter mud (12), which is sold or disposed of safely. The second solid-liquid separation device (5) separates calcium phosphate filter cake (13), which is connected to a conveying device to transport the calcium phosphate filter cake (13) back to the phosphoric acid production slurry tank for reuse as raw material.

5. The phosphogypsum leachate resource recovery system according to claim 1, characterized in that, The ultrafiltration device (7) is a column-type ultrafiltration membrane.

6. The phosphogypsum leachate resource recovery system according to claim 1, characterized in that: The membrane material of the acid-resistant nanofiltration device (8) is sulfonated polyethersulfone or polypiperazine amide.

7. The phosphogypsum leachate resource recovery system according to claim 6, characterized in that, The concentrated water outlet of the acid-resistant nanofiltration device (8) is connected to the phosphoric acid production slurry preparation tank, and the nanofiltration concentrated water (14) is returned to the upstream phosphoric acid production slurry preparation tank for reuse.

8. The phosphogypsum leachate resource recovery system according to claim 1, characterized in that, The membrane material of the acid-resistant reverse osmosis device (9) is an acid-resistant modified polyamide composite membrane.

9. A resource recovery system for phosphogypsum leachate according to any one of claims 1-8, characterized in that, The first dosing device is a lime slurry dosing device, and the second dosing device is a lime slurry and sodium hydroxide dosing device.

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