A phosphogypsum leachate resourceful treatment system and method

Abstract

The application belongs to the field of industrial wastewater treatment, and discloses a phosphogypsum leachate resource treatment system and method. The system comprises an alkali adjusting reaction unit, a nanofiltration unit, a fluorine recovery unit, a reverse osmosis unit and a phosphorus recovery unit. The application solves the technical problem that the purity and yield of the phosphorus resource recovery product in the phosphogypsum leachate are low due to the interference of fluorine ions.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment, and more specifically, relates to a system and method for the resource utilization treatment of phosphogypsum leachate. Background Technology

[0002] The wet-process phosphoric acid production process involves reacting phosphate rock powder with inorganic acids such as sulfuric acid, separating the resulting crude phosphoric acid, and then purifying it to obtain the final phosphoric acid product. This method is 20-30% cheaper than the thermal process for phosphoric acid production, and the purity of the product is comparable. It has gradually become the dominant process in phosphoric acid production. Phosphogypsum is a byproduct of the wet-process phosphoric acid production; approximately 4-5 tons of phosphogypsum are produced for every ton of phosphoric acid produced. The main component of phosphogypsum is calcium sulfate, but it also contains calcium and magnesium ions, phosphate ions, fluoride ions, ammonia nitrogen, and other components. After sedimentation and rainwater washing, it produces a highly acidic phosphogypsum leachate containing a large number of impurity ions. Direct discharge of this leachate would cause significant pollution to the environment.

[0003] Due to the complex composition of phosphogypsum leachate, most existing enterprises currently use precipitation methods for treatment. For example, patent application number 202410281662.4 proposes a multi-stage lime slurry method for treating phosphogypsum leachate, where fluoride and phosphate ions are simultaneously precipitated as calcium fluorophosphate. After solid-liquid separation with the addition of a coagulant, regenerated defluorinated and dephosphorized permeable water and fluoride- and phosphorus-containing sludge are obtained, which require further sludge treatment. In addition, there are schemes for resource recovery of phosphorus from phosphogypsum leachate. For example, patent applications 202110155376.X and 202111051702.8 both propose using the magnesium ammonium phosphate method to recover phosphorus resources from phosphogypsum leachate. However, due to the large presence of fluoride ions, magnesium fluoride precipitate inevitably mixes into the recovered magnesium ammonium phosphate, resulting in low purity of the recovered magnesium ammonium phosphate. Patent application number 202310547637.1 proposes to first add lime to the phosphogypsum leachate to precipitate fluoride ions. However, the phosphogypsum leachate is strongly acidic and contains a large amount of phosphorus. At this time, the added calcium will form calcium fluorophosphate precipitate together with fluoride ions and phosphate ions, resulting in a large loss of phosphate ions that cannot be recovered.

[0004] Therefore, how to remove the interference of fluoride ions on phosphate resource recovery and improve the purity and yield of phosphorus resource recovery products in phosphogypsum leachate has become an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a resource recovery system and method for phosphogypsum leachate. This invention solves the technical problem of low purity and yield of phosphorus resource recovery products from phosphogypsum leachate due to the interference of fluoride ions.

[0006] To achieve the above objectives, the present invention provides a resource recovery system for phosphogypsum leachate, the system comprising: an alkali adjustment reaction unit, a nanofiltration unit, a fluoride recovery unit, a reverse osmosis unit, and a phosphorus recovery unit;

[0007] The alkali adjustment reaction unit includes a phosphogypsum leachate feed pump, a liquid alkali feed pump, an alkali adjustment reaction vessel, and an alkali adjustment solid-liquid separation device; the nanofiltration unit includes a nanofiltration high-pressure feed pump and a nanofiltration membrane column; the fluorine recovery unit includes a calcium salt feed pump, a fluorine recovery reaction vessel, and a fluorine recovery solid-liquid separation device; the reverse osmosis unit includes a reverse osmosis high-pressure feed pump and a reverse osmosis membrane column; the phosphorus recovery unit includes a magnesium salt feed pump, an ammonium salt feed pump, a phosphorus recovery reaction vessel, and a phosphorus recovery solid-liquid separation device;

[0008] The alkali adjustment reactor is equipped with an upper and middle feed inlet and a bottom discharge outlet; the outlet of the liquid alkali feed pump is divided into three streams, with the outlet of the phosphogypsum leachate feed pump and the first stream of the liquid alkali feed pump connected to the upper and middle feed inlet of the alkali adjustment reactor; the bottom discharge outlet of the alkali adjustment reactor is connected to the inlet of the alkali adjustment solid-liquid separation device; the alkali adjustment solid-liquid separation device is equipped with a filtrate outlet and a filter residue outlet; the filtrate outlet of the alkali adjustment solid-liquid separation device is connected to the inlet of the nanofiltration membrane column through a nanofiltration high-pressure feed pump; the nanofiltration membrane column is equipped with a nanofiltration permeate outlet and a nanofiltration concentrate outlet;

[0009] The fluorine recovery reactor is equipped with an upper-middle inlet and a bottom outlet; the nanofiltration permeate outlet, the calcium salt feed pump outlet, and the second stream of the liquid alkali feed pump outlet are connected to the upper-middle inlet of the fluorine recovery reactor; the bottom outlet of the fluorine recovery reactor is connected to the inlet of the fluorine recovery solid-liquid separation device; the fluorine recovery solid-liquid separation device is equipped with a calcium fluoride product outlet and a filtrate outlet; the filtrate outlet of the fluorine recovery solid-liquid separation device is connected to the inlet of the reverse osmosis membrane column via a reverse osmosis high-pressure feed pump; the reverse osmosis membrane column is equipped with a reverse osmosis permeate outlet and a reverse osmosis concentrate outlet;

[0010] The phosphorus recovery reactor is provided with an upper and middle feed inlet and a bottom discharge outlet; the third stream of the nanofiltration concentrate outlet, reverse osmosis concentrate outlet, magnesium salt feed pump outlet, ammonium salt feed pump outlet, and liquid alkali feed pump outlet is connected to the upper and middle feed inlet of the phosphorus recovery reactor; the bottom discharge outlet of the phosphorus recovery reactor is connected to the inlet of the phosphorus recovery solid-liquid separation device; the phosphorus recovery solid-liquid separation device is provided with an ammonium magnesium phosphate product outlet and a filtrate outlet.

[0011] According to the present invention, preferably, the filter residue outlet and the reverse osmosis permeate outlet of the alkali-adjusting solid-liquid separation device are connected to the outside of the system.

[0012] According to the present invention, preferably, the alkali adjustment reactor, the fluorine recovery reactor, and the phosphorus recovery reactor are all equipped with stirring equipment.

[0013] According to the present invention, preferably, the alkali adjustment solid-liquid separation device, the fluorine recovery solid-liquid separation device, and the phosphorus recovery solid-liquid separation device are each independently a plate and frame filter press and / or a belt vacuum filter.

[0014] According to the present invention, preferably, the membrane module of the nanofiltration membrane column and the membrane module of the reverse osmosis membrane column are each independently made of polyamide and / or PVDF material.

[0015] According to the present invention, preferably, the nanofiltration membrane column and the reverse osmosis membrane column each independently adopt a disc tube type and / or spiral wound structure.

[0016] According to the present invention, preferably, the inlet of the phosphogypsum leachate feed pump is connected to a phosphogypsum leachate feed device.

[0017] According to the present invention, preferably, the inlet of the liquid alkali feed pump is connected to a liquid alkali feed device.

[0018] According to the present invention, preferably, the inlet of the calcium salt feed pump is connected to a calcium salt feed device.

[0019] According to the present invention, preferably, the inlet of the magnesium salt feed pump is connected to a magnesium salt feed device.

[0020] According to the present invention, preferably, the inlet of the ammonium salt feed pump is connected to an ammonium salt feed device.

[0021] Another aspect of the present invention provides a method for the resource utilization treatment of phosphogypsum leachate, the method employing the above-described system and comprising the following steps:

[0022] S1. Alkali Adjustment: In the alkali adjustment reactor, the pH of the phosphogypsum leachate is adjusted using liquid alkali to obtain the alkali adjustment reactor system; the alkali adjustment reactor system is then subjected to solid-liquid separation to obtain alkali adjustment filtrate and alkali adjustment filter residue.

[0023] S2, Nanofiltration desalination: The alkaline filtrate is subjected to nanofiltration to obtain nanofiltration permeate and nanofiltration concentrate;

[0024] S3. Fluorine Resource Recovery: The nanofiltration permeate, liquid alkali, and calcium salt are fed into a fluorine recovery reactor for mixing and reaction to obtain the fluorine recovery reactor system; the fluorine recovery reactor system is subjected to solid-liquid separation to obtain recovered calcium fluoride product and fluorine recovery filtrate;

[0025] S4. Reverse osmosis concentration: The fluoride recovery filtrate is subjected to reverse osmosis to obtain reverse osmosis permeate and reverse osmosis concentrate.

[0026] S5. Phosphorus Resource Recovery: The reverse osmosis concentrate, nanofiltration concentrate, magnesium salt, ammonium salt, and liquid alkali are fed into the phosphorus recovery reactor for mixing and reaction to obtain the phosphorus recovery reactor system; the phosphorus recovery reactor system is subjected to solid-liquid separation to obtain recovered magnesium ammonium phosphate product and phosphorus recovery filtrate.

[0027] According to the present invention, preferably, in step S1:

[0028] The liquid alkali and phosphogypsum leachate are mixed and stirred in the alkali adjustment reactor, and the pH of the system in the alkali adjustment reactor is adjusted to 3-4 by using the liquid alkali.

[0029] The residence time of the system in the alkali adjustment reactor is 10-30 minutes.

[0030] The alkali-adjusting filter residue is discharged from the system.

[0031] According to the present invention, preferably, in step S2, the water production rate of the nanofiltration is 80-85%.

[0032] According to the present invention, preferably, in step S3:

[0033] The nanofiltration permeate, liquid alkali, and calcium salt are mixed and stirred in the fluoride recovery reactor, and the liquid alkali is used to make the pH of the system in the fluoride recovery reactor 6-7.

[0034] The amount of calcium salt added is based on the amount of Ca in the fluorine recovery reactor. 2+ With F - The molar ratio (0.45-0.5):1 is determined;

[0035] The residence time of the system in the fluorine recovery reactor is 10-30 minutes.

[0036] According to the present invention, preferably, in step S4:

[0037] The reverse osmosis has a water production rate of 85-90%;

[0038] The reverse osmosis permeate is discharged from the system after meeting the standards.

[0039] According to the present invention, preferably, in step S5:

[0040] The reverse osmosis concentrate, nanofiltration concentrate, magnesium salt, ammonium salt and liquid alkali are mixed and stirred in the phosphorus recovery reactor, and the pH of the system in the phosphorus recovery reactor is made to be 8-9 by using liquid alkali.

[0041] The amounts of ammonium salt and magnesium salt added are based on the amount of Mg in the phosphorus recovery reactor. 2+ NH 4+ and PO4 3-The molar ratio (1-1.05):(1-1.05):1 is determined;

[0042] The residence time of the system in the phosphorus recovery reactor is 10-60 min.

[0043] In this invention, the liquid alkali is a sodium hydroxide aqueous solution with a concentration of 10-350 g / L; the calcium salt is a calcium chloride aqueous solution with a concentration of 10-350 g / L; the magnesium salt is a magnesium chloride aqueous solution with a concentration of 10-350 g / L and / or a magnesium sulfate aqueous solution with a concentration of 10-300 g / L; and the ammonium salt is an ammonium chloride aqueous solution with a concentration of 10-300 g / L and / or an ammonium sulfate aqueous solution with a concentration of 10-450 g / L.

[0044] The beneficial effects of the technical solution of the present invention are as follows:

[0045] This invention solves the technical problem that the purity and yield of phosphorus resource recovery products from phosphogypsum leachate are low due to the interference of fluoride ions.

[0046] This invention employs a combination of chemical precipitation and membrane separation to obtain permeate from phosphogypsum leachate that meets the GB 8978-1996 standard for discharge or reuse, with a permeate yield of 70-75%.

[0047] This invention separates fluoride and phosphate ions in phosphogypsum leachate by nanofiltration at a specific pH and recovers them separately, resulting in recovered calcium fluoride with a purity of over 95% and recovered magnesium ammonium phosphate with a purity of over 97-98%, greatly increasing the added value.

[0048] This invention recovers the relatively high proportions of fluoride ions and phosphate ions separately, thereby reducing the amount of sludge, lowering sludge disposal costs, saving costs, and generating new revenue.

[0049] Other features and advantages of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0050] The above and other objects, features and advantages of the present invention will become more apparent from the more detailed description of exemplary embodiments of the invention in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of the invention.

[0051] Figure 1 A schematic diagram of a phosphogypsum leachate resource utilization system provided by the present invention is shown.

[0052] The annotations in the attached figures are explained as follows:

[0053] 101-Phosphogypsum leachate feed pump; 102-Liquid alkali feed pump; 103-Alkali conditioning reaction vessel; 104-Alkali conditioning solid-liquid separation device; 105-Alkali conditioning filter residue; 106-Alkali conditioning filtrate;

[0054] 201-Nanofiltration high-pressure feed pump; 202-Nanofiltration membrane column; 203-Nanofiltration feed water; 204-Nanofiltration permeate; 205-Nanofiltration concentrate;

[0055] 301 - Calcium salt feed pump; 302 - Fluorine recovery reactor; 303 - Fluorine recovery solid-liquid separation device; 304 - Recovered calcium fluoride product; 305 - Fluorine recovery filtrate;

[0056] 401 - Reverse osmosis high-pressure feed pump; 402 - Reverse osmosis membrane column; 403 - Reverse osmosis feed water; 404 - Reverse osmosis permeate; 405 - Reverse osmosis concentrate;

[0057] 501 - Magnesium salt feed pump; 502 - Ammonium salt feed pump; 503 - Phosphorus recovery reactor; 504 - Phosphorus recovery solid-liquid separation device; 505 - Recovered magnesium ammonium phosphate product; 506 - Phosphorus recovery filtrate;

[0058] 601-Phosphogypsum leachate feeding device; 602-Liquid alkali feeding device; 603-Calcium salt feeding device; 604-Magnesium salt feeding device; 605-Ammonium salt feeding device. Detailed Implementation

[0059] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0060] In the following embodiments:

[0061] The phosphogypsum leachate being treated was phosphogypsum leachate generated on-site by a wet-process phosphoric acid production enterprise in Yunnan Province. The water quality conditions are shown in Table 1.

[0062] Table 1

[0063] name pH <![CDATA[SO4 2- mg / L]]> TP mg / L <![CDATA[F - mg / L]]> <![CDATA[Ca 2+ mg / L]]> <![CDATA[Mg 2+ mg / L]]> Phosphogypsum leachate 1.8 6509 8200 2007 337 301

[0064] Ca 2+ Mg 2+ The detection method used was EDTA titration.

[0065] F - The detection method employs the ion-selective electrode method;

[0066] pH values ​​were measured using a pH meter.

[0067] The nitric acid washing method is used for testing the recovered magnesium ammonium phosphate products.

[0068] Water quality testing shall be conducted in accordance with the national standard GB 8978-1996;

[0069] Purity testing of recycled calcium fluoride products shall be performed in accordance with the national standard GB / T 27804-2011.

[0070] Example 1

[0071] This embodiment provides a resource utilization system for phosphogypsum leachate, such as... Figure 1 As shown, the system includes: an alkali adjustment reaction unit, a nanofiltration unit, a fluorine recovery unit, a reverse osmosis unit, and a phosphorus recovery unit;

[0072] The alkali adjustment reaction unit includes a phosphogypsum leachate feed pump 101, a liquid alkali feed pump 102, an alkali adjustment reaction vessel 103 (10L volume), and an alkali adjustment solid-liquid separation device 104; the nanofiltration unit includes a nanofiltration high-pressure feed pump 201 and a nanofiltration membrane column 202; the fluorine recovery unit includes a calcium salt feed pump 301, a fluorine recovery reaction vessel 302 (10L volume), and a fluorine recovery solid-liquid separation device 303; the reverse osmosis unit includes a reverse osmosis high-pressure feed pump 401 and a reverse osmosis membrane column 402; the phosphorus recovery unit includes a magnesium salt feed pump 501, an ammonium salt feed pump 502, a phosphorus recovery reaction vessel 503 (5L volume), and a phosphorus recovery solid-liquid separation device 504;

[0073] The alkali adjustment reactor 103 is provided with an upper-middle feed inlet and a bottom discharge outlet; the outlet of the liquid alkali feed pump 102 is divided into three streams, the outlet of the phosphogypsum leachate feed pump 101 and the first stream of the liquid alkali feed pump 102 are connected to the upper-middle feed inlet of the alkali adjustment reactor 103; the bottom discharge outlet of the alkali adjustment reactor 103 is connected to the inlet of the alkali adjustment solid-liquid separation device 104; the alkali adjustment solid-liquid separation device 104 is provided with a filtrate outlet and a filter residue outlet; the filter residue outlet of the alkali adjustment solid-liquid separation device 104 is connected to the outside of the system, and the filtrate outlet of the alkali adjustment solid-liquid separation device 104 is connected to the inlet of the nanofiltration membrane column 202 through the nanofiltration high-pressure feed pump 201; the nanofiltration membrane column 202 is provided with a nanofiltration permeate outlet and a nanofiltration concentrate outlet;

[0074] The fluorine recovery reactor 302 is provided with an upper-middle inlet and a bottom outlet; the nanofiltration permeate outlet, the outlet of the calcium salt feed pump 301, and the second stream of the liquid alkali feed pump 102 are connected to the upper-middle inlet of the fluorine recovery reactor 302; the bottom outlet of the fluorine recovery reactor 302 is connected to the inlet of the fluorine recovery solid-liquid separation device 303; the fluorine recovery solid-liquid separation device 303 is provided with a calcium fluoride product outlet and a filtrate outlet; the filtrate outlet of the fluorine recovery solid-liquid separation device 303 is connected to the inlet of the reverse osmosis membrane column 402 through a reverse osmosis high-pressure feed pump 401; the reverse osmosis membrane column 402 is provided with a reverse osmosis permeate outlet and a reverse osmosis concentrate outlet; the reverse osmosis permeate outlet is connected to the outside of the system;

[0075] The phosphorus recovery reactor 503 is provided with an upper and middle feed inlet and a bottom discharge outlet; the third stream of the nanofiltration concentrate outlet, reverse osmosis concentrate outlet, magnesium salt feed pump outlet, ammonium salt feed pump outlet, and liquid alkali feed pump outlet is connected to the upper and middle feed inlet of the phosphorus recovery reactor 503; the bottom discharge outlet of the phosphorus recovery reactor 503 is connected to the inlet of the phosphorus recovery solid-liquid separation device 504; the phosphorus recovery solid-liquid separation device 504 is provided with an ammonium magnesium phosphate product outlet and a filtrate outlet.

[0076] The alkali adjustment reactor 103, fluorine recovery reactor 302, and phosphorus recovery reactor 503 are all equipped with stirring devices; the alkali adjustment solid-liquid separation device 104, fluorine recovery solid-liquid separation device 303, and phosphorus recovery solid-liquid separation device 504 are all plate and frame filter presses; the membrane modules of the nanofiltration membrane column 202 and the reverse osmosis membrane column 402 are each independently made of polyamide and / or PVDF material; the reverse osmosis membrane column 402 adopts a disc tube and / or spiral wound structure.

[0077] The inlet of the phosphogypsum leachate feed pump 101 is connected to the phosphogypsum leachate feed device 601; the inlet of the liquid alkali feed pump 102 is connected to the liquid alkali feed device 602; the inlet of the calcium salt feed pump 301 is connected to the calcium salt feed device 603; the inlet of the magnesium salt feed pump 501 is connected to the magnesium salt feed device 604; and the inlet of the ammonium salt feed pump 502 is connected to the ammonium salt feed device 605.

[0078] This embodiment also provides a method for the resource utilization of phosphogypsum leachate, which uses the above-described system and includes the following steps:

[0079] S1. Alkali Adjustment: In the alkali adjustment reactor 103, the stirring equipment is turned on at 100 r / min, and the feed is carried out at a residence time of 15 min. The feed rate of liquid alkali is 0.35 L / h, and the feed rate of phosphogypsum leachate is 32 L / h. The pH of the phosphogypsum leachate is adjusted using liquid alkali (in this embodiment, the liquid alkali used is a 300 g / L sodium hydroxide aqueous solution) to obtain the system in the alkali adjustment reactor with a pH of 3.6. The system in the alkali adjustment reactor is subjected to plate and frame filter press filtration to obtain alkali adjustment filtrate 106 (water quality is shown in Table 2) and alkali adjustment filter residue (26 g / h) 105. The alkali adjustment filter residue 105 is discharged from the system.

[0080] Table 2

[0081] name pH <![CDATA[SO4 2- mg / L]]> TP mg / L <![CDATA[F - mg / L]]> <![CDATA[Ca 2+ mg / L]]> <![CDATA[Mg 2+ mg / L]]> Alkali-adjusting filtrate 3.6 6201 7565 1741 5.1 21

[0082] S2. Nanofiltration desalination: Nanofiltration is performed on the alkali-adjusting filtrate 106, and the water production rate is controlled at 85% to obtain nanofiltration permeate 204 and nanofiltration concentrate 205. The water quality is shown in Table 3.

[0083] Table 3

[0084] name pH <![CDATA[SO4 2- mg / L]]> TP mg / L <![CDATA[F - mg / L]]> <![CDATA[Ca 2+ mg / L]]> <![CDATA[Mg 2+ mg / L]]> Nanofiltration permeate 3.6 18.3 1.2 2032 1.1 3.2 Nanofiltration concentrate 3.6 30895 37783 2.3 24.8 92

[0085] S3. Fluorine Resource Recovery: Start the stirring equipment at 100 r / min, feed at a residence time of 15 min, feed rate of nanofiltration permeate 204 is 27 L / h, feed rate of calcium chloride aqueous solution (concentration 300 g / L) is 0.52 L / h, feed rate of liquid alkali is 0.16 L / h. The nanofiltration permeate 204, liquid alkali and calcium chloride aqueous solution are fed into the fluorine recovery reactor 302 for mixing and reaction, resulting in a fluorine recovery reactor system with a pH of 6.6. Solid-liquid separation is performed on the fluorine recovery reactor system to obtain recovered calcium fluoride product 304 (98 g / h, purity 95.1%, yield 92.3%) and fluorine recovery filtrate 305 (water quality see Table 4).

[0086] Table 4

[0087] name pH <![CDATA[SO4 2- mg / L]]> TP mg / L <![CDATA[F - mg / L]]> <![CDATA[Ca 2+ mg / L]]> <![CDATA[Mg 2+ mg / L]]> Fluorine recovery filtrate 6.6 18.1 0.7 6.3 7.5 2.3

[0088] S4. Reverse osmosis concentration: The fluoride recovery filtrate 305 is subjected to reverse osmosis, and the water production rate is controlled at 87% to obtain reverse osmosis permeate 404 and reverse osmosis concentrate 405. The water quality is shown in Table 5.

[0089] Table 5

[0090] name pH <![CDATA[SO4 2- mg / L]]> TP mg / L <![CDATA[F - mg / L]]> <![CDATA[Ca 2+ mg / L]]> <![CDATA[Mg 2+ mg / L]]> Reverse osmosis permeate 6.6 1.3 0 0.3 0.2 0.3 Reverse osmosis concentrate 6.6 89.3 3.2 28.3 27.8 9.2

[0091] S5. Phosphorus Resource Recovery: Start the stirring equipment at 100 r / min, feed at a residence time of 30 min, with the following feed rates: reverse osmosis concentrate 405 at 3.8 L / h, nanofiltration concentrate 205 at 4.8 L / h, magnesium sulfate aqueous solution (250 g / L) at 0.7 L / h, ammonium sulfate aqueous solution (250 g / L) at 0.4 L / h, and liquid alkali at 0.05 L / h. Introduce the reverse osmosis concentrate 405, nanofiltration concentrate 205, magnesium sulfate aqueous solution, ammonium sulfate aqueous solution, and liquid alkali into the phosphorus recovery reactor 503 for mixing and reaction, resulting in a phosphorus recovery reactor system with a pH of 8.6. Perform solid-liquid separation on the phosphorus recovery reactor system to obtain recovered magnesium ammonium phosphate product 505 (203 g / h, purity 97.6%, yield 91.2%) and phosphorus recovery filtrate 506.

[0092] Example 2

[0093] The only difference between this embodiment and Embodiment 1 is that:

[0094] The nanofiltration permeate rate was controlled at 81%.

[0095] The purity of the recovered calcium fluoride product 304 was 95.5%, and the yield was 90.4%.

[0096] The reverse osmosis permeate rate is controlled at 90%.

[0097] The purity of the recovered magnesium ammonium phosphate product 505 was 97.1%, and the yield was 92.6%.

[0098] Table 6

[0099] name pH <![CDATA[SO4 2- mg / L]]> TP mg / L <![CDATA[F - mg / L]]> <![CDATA[Ca 2+ mg / L]]> <![CDATA[Mg 2+ mg / L]]> Alkali-adjusting filtrate 3.6 6201 7565 1741 5.1 21 Nanofiltration permeate 3.6 12.2 0.9 2118 1.0 2.8 Nanofiltration concentrate 3.6 24390 29816 4.3 19.6 73.1 Fluorine recovery filtrate 6.6 11.9 0.8 6.1 7.2 2.6 Reverse osmosis permeate 6.6 0.8 0 0.3 0.5 0.2 Reverse osmosis concentrate 6.6 71.1 4.5 25.6 38.8 10.9

[0100] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A resource utilization system for phosphogypsum leachate, characterized in that, The system includes: an alkali adjustment reaction unit, a nanofiltration unit, a fluorine recovery unit, a reverse osmosis unit, and a phosphorus recovery unit; The alkali adjustment reaction unit includes a phosphogypsum leachate feed pump, a liquid alkali feed pump, an alkali adjustment reaction vessel, and an alkali adjustment solid-liquid separation device; the nanofiltration unit includes a nanofiltration high-pressure feed pump and a nanofiltration membrane column; the fluorine recovery unit includes a calcium salt feed pump, a fluorine recovery reaction vessel, and a fluorine recovery solid-liquid separation device; the reverse osmosis unit includes a reverse osmosis high-pressure feed pump and a reverse osmosis membrane column; the phosphorus recovery unit includes a magnesium salt feed pump, an ammonium salt feed pump, a phosphorus recovery reaction vessel, and a phosphorus recovery solid-liquid separation device; The alkali adjustment reactor is equipped with an upper and middle feed inlet and a bottom discharge outlet; the outlet of the liquid alkali feed pump is divided into three streams, with the outlet of the phosphogypsum leachate feed pump and the first stream of the liquid alkali feed pump connected to the upper and middle feed inlet of the alkali adjustment reactor; the bottom discharge outlet of the alkali adjustment reactor is connected to the inlet of the alkali adjustment solid-liquid separation device; the alkali adjustment solid-liquid separation device is equipped with a filtrate outlet and a filter residue outlet; the filtrate outlet of the alkali adjustment solid-liquid separation device is connected to the inlet of the nanofiltration membrane column through a nanofiltration high-pressure feed pump; the nanofiltration membrane column is equipped with a nanofiltration permeate outlet and a nanofiltration concentrate outlet; The fluorine recovery reactor is equipped with an upper-middle inlet and a bottom outlet; the nanofiltration permeate outlet, the calcium salt feed pump outlet, and the second stream of the liquid alkali feed pump outlet are connected to the upper-middle inlet of the fluorine recovery reactor; the bottom outlet of the fluorine recovery reactor is connected to the inlet of the fluorine recovery solid-liquid separation device; the fluorine recovery solid-liquid separation device is equipped with a calcium fluoride product outlet and a filtrate outlet; the filtrate outlet of the fluorine recovery solid-liquid separation device is connected to the inlet of the reverse osmosis membrane column via a reverse osmosis high-pressure feed pump; the reverse osmosis membrane column is equipped with a reverse osmosis permeate outlet and a reverse osmosis concentrate outlet; The phosphorus recovery reactor is provided with an upper and middle feed inlet and a bottom discharge outlet; the third stream of the nanofiltration concentrate outlet, reverse osmosis concentrate outlet, magnesium salt feed pump outlet, ammonium salt feed pump outlet, and liquid alkali feed pump outlet is connected to the upper and middle feed inlet of the phosphorus recovery reactor; the bottom discharge outlet of the phosphorus recovery reactor is connected to the inlet of the phosphorus recovery solid-liquid separation device; the phosphorus recovery solid-liquid separation device is provided with an ammonium magnesium phosphate product outlet and a filtrate outlet.

2. The phosphogypsum leachate resource utilization system according to claim 1, wherein, The filter residue outlet and reverse osmosis permeate outlet of the alkali-adjusting solid-liquid separation device are connected to the outside of the system.

3. The phosphogypsum leachate resource utilization system according to claim 1, wherein, The alkali adjustment reactor, fluorine recovery reactor, and phosphorus recovery reactor are all equipped with stirring equipment; The alkali adjustment solid-liquid separation device, the fluorine recovery solid-liquid separation device, and the phosphorus recovery solid-liquid separation device are each independently a plate and frame filter press and / or a belt vacuum filter. The membrane modules of the nanofiltration membrane column and the reverse osmosis membrane column are each independently made of polyamide and / or PVDF material; The nanofiltration membrane column and the reverse osmosis membrane column each independently adopt a disc tube type and / or spiral wound structure.

4. The phosphogypsum leachate resource utilization system according to claim 1, wherein, The inlet of the phosphogypsum leachate feed pump is connected to a phosphogypsum leachate feed device. The inlet of the liquid alkali feed pump is connected to a liquid alkali feed device; The calcium salt feed pump is connected to a calcium salt feed device at its inlet; The inlet of the magnesium salt feed pump is connected to a magnesium salt feed device. The inlet of the ammonium salt feed pump is connected to an ammonium salt feed device.

5. A method for resource-based treatment of phosphogypsum leachate, characterized in that, The method employs the system described in any one of claims 1-4 and includes the following steps: S1. Alkali Adjustment: In the alkali adjustment reactor, the pH of the phosphogypsum leachate is adjusted using liquid alkali to obtain the alkali adjustment reactor system; the alkali adjustment reactor system is then subjected to solid-liquid separation to obtain alkali adjustment filtrate and alkali adjustment filter residue. S2, Nanofiltration desalination: The alkaline filtrate is subjected to nanofiltration to obtain nanofiltration permeate and nanofiltration concentrate; S3. Fluorine Resource Recovery: The nanofiltration permeate, liquid alkali, and calcium salt are fed into a fluorine recovery reactor for mixing and reaction to obtain the fluorine recovery reactor system; the fluorine recovery reactor system is subjected to solid-liquid separation to obtain recovered calcium fluoride product and fluorine recovery filtrate; S4. Reverse osmosis concentration: The fluoride recovery filtrate is subjected to reverse osmosis to obtain reverse osmosis permeate and reverse osmosis concentrate. S5. Phosphorus Resource Recovery: The reverse osmosis concentrate, nanofiltration concentrate, magnesium salt, ammonium salt, and liquid alkali are fed into the phosphorus recovery reactor for mixing and reaction to obtain the phosphorus recovery reactor system; the phosphorus recovery reactor system is subjected to solid-liquid separation to obtain recovered magnesium ammonium phosphate product and phosphorus recovery filtrate.

6. The method for resource utilization of phosphogypsum leachate according to claim 5, wherein, In step S1: The liquid alkali and phosphogypsum leachate are mixed and stirred in the alkali adjustment reactor, and the pH of the system in the alkali adjustment reactor is adjusted to 3-4 by using the liquid alkali. The system in the alkali-adjusting reactor has a residence time of 10-30 minutes; the alkali-adjusting filter residue is discharged from the system.

7. The method for resource utilization of phosphogypsum leachate according to claim 5, wherein, In step S2, the water production rate of the nanofiltration is 80-85%.

8. The method for resource utilization of phosphogypsum leachate according to claim 5, wherein, In step S3: The nanofiltration permeate, liquid alkali, and calcium salt are mixed and stirred in the fluoride recovery reactor, and the liquid alkali is used to make the pH of the system in the fluoride recovery reactor 6-7. The amount of calcium salt added is based on the amount of Ca in the fluorine recovery reactor. 2+ With F - The molar ratio (0.45-0.5):1 is determined; The residence time of the system in the fluorine recovery reactor is 10-30 minutes.

9. The method for resource utilization of phosphogypsum leachate according to claim 5, wherein, In step S4: The reverse osmosis has a water production rate of 85-90%; The reverse osmosis permeate is discharged from the system after meeting the standards.

10. The method for resource utilization of phosphogypsum leachate according to claim 5, wherein, In step S5: The reverse osmosis concentrate, nanofiltration concentrate, magnesium salt, ammonium salt and liquid alkali are mixed and stirred in the phosphorus recovery reactor, and the pH of the system in the phosphorus recovery reactor is made to be 8-9 by using liquid alkali. The amounts of ammonium salt and magnesium salt added are based on the amount of Mg in the phosphorus recovery reactor. 2+ NH 4+ and PO4 3- The molar ratio (1-1.05):(1-1.05):1 is determined; The residence time of the system in the phosphorus recovery reactor is 10-60 min.

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