Phosphogypsum leachate resourceful treatment system and method

Abstract

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

Description

Technical Field

[0001] The present invention belongs to the field of industrial wastewater treatment, and more specifically, relates to a system and method for resource processing of phosphogypsum leachate. Background Art

[0002] The wet phosphoric acid production process is to react phosphate rock powder with inorganic acids such as sulfuric acid, separate crude phosphoric acid, and then purify it to obtain phosphoric acid products. This method is 20-30% cheaper than thermal phosphoric acid, and the product purity is comparable to that of thermal phosphoric acid. It has gradually occupied a dominant position in the phosphoric acid production process. Phosphogypsum is a by-product of wet phosphoric acid. For every ton of phosphoric acid produced, about 4-5 tons of phosphogypsum are produced. The main component of phosphogypsum is calcium sulfate. In addition, it also contains calcium and magnesium ions, phosphate, fluoride ions, ammonia nitrogen and other components. After sedimentation and rainwater washing, a strongly acidic phosphogypsum leachate containing a large amount of impurity ions will be obtained. If it is directly discharged, it will cause huge pollution to the ecological environment.

[0003] Due to the complex composition of phosphogypsum leachate, most existing companies currently use precipitation methods for treatment. For example, patent application No. 202410281662.4 proposes a multi-stage lime milk method for the treatment of phosphogypsum leachate, in which the fluoride ions and phosphate ions are simultaneously precipitated in the form of calcium fluorophosphate, and a coagulant is added for solid-liquid separation to obtain regenerated water and fluorine-containing and phosphorus-containing sludge that can be discharged after fluoride and phosphorus removal. The sludge needs to be treated again. In addition, there are also schemes for resource recovery of phosphorus in phosphogypsum leachate. For example, patent applications No. 202110155376.X and 202111051702.8 both propose the use of magnesium ammonium phosphate to recover phosphorus resources in phosphogypsum leachate. However, due to the presence of a large amount of fluoride ions, magnesium fluoride precipitate is inevitably mixed into the recovered magnesium ammonium phosphate, resulting in a low purity of the recovered magnesium ammonium phosphate. Patent application No. 202310547637.1 proposes to first add lime to the phosphogypsum leachate to precipitate fluoride ions, but the phosphogypsum leachate is strongly acidic and contains a large amount of phosphorus. At this time, the calcium added will form calcium fluorophosphate precipitate together with fluoride ions and phosphate ions, causing a large amount of phosphate loss that cannot be recovered.

[0004] Therefore, how to remove the interference of fluoride ions on phosphate resource utilization and improve the purity and yield of phosphorus resource recovery products in phosphogypsum leachate has become a problem that needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to provide a system and method for resource processing of phosphogypsum leachate in view of the deficiencies of the prior art. The present invention solves the technical problem that the purity and yield of phosphorus resource recovery products in phosphogypsum leachate are low due to the interference of fluoride ions.

[0006] In order to achieve the above-mentioned object, the present invention provides a resource processing system for phosphogypsum leachate, the system comprising: an alkali adjustment reaction unit, a nanofiltration unit, a fluorine recovery unit, a reverse osmosis unit and a phosphorus recovery unit;

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

[0008] The alkali adjustment reactor is provided with a middle-upper feed port and a bottom discharge port; the outlet of the liquid alkali feed pump is divided into three branches, and the outlet of the phosphogypsum leachate feed pump and the first branch of the outlet of the liquid alkali feed pump are connected to the middle-upper feed port of the alkali adjustment reactor; the bottom discharge port 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 provided with a filtrate outlet and a filter residue outlet; the filtrate outlet of the alkali adjustment solid-liquid separation device is connected to the water inlet of the nanofiltration membrane column through a nanofiltration high-pressure feed pump; the nanofiltration membrane column is provided with a nanofiltration produced water outlet and a nanofiltration concentrated water outlet;

[0009] The fluorine recovery reactor is provided with a middle-upper feed port and a bottom discharge port; the nanofiltration water output outlet, the calcium salt feed pump outlet and the second outlet of the liquid alkali feed pump are connected to the middle-upper feed port of the fluorine recovery reactor; the bottom discharge port 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 provided 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 water inlet of the reverse osmosis membrane column through a reverse osmosis high-pressure feed pump; the reverse osmosis membrane column is provided with a reverse osmosis water output outlet and a reverse osmosis concentrated water outlet;

[0010] The phosphorus recovery reactor is provided with a middle-upper feed port and a bottom discharge port; the third of the nanofiltration concentrated water outlet, the reverse osmosis concentrated water outlet, the magnesium salt feed pump outlet, the ammonium salt feed pump outlet and the liquid alkali feed pump outlet is connected to the middle-upper feed port of the phosphorus recovery reactor; the bottom discharge port 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 a magnesium ammonium phosphate product outlet and a filtrate outlet.

[0011] According to the present invention, preferably, the filter residue outlet and the reverse osmosis water outlet of the alkali adjustment 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 provided with a stirring device.

[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 components of the nanofiltration membrane column and the membrane components of the reverse osmosis membrane column are independently made of polyamide and / or PVDF.

[0015] According to the present invention, preferably, the nanofiltration membrane column and the reverse osmosis membrane column each independently adopt a disc-tube and / or coiled 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 caustic soda feed pump is connected to a liquid caustic soda feed device.

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

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

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

[0021] Another aspect of the present invention provides a method for resource processing of phosphogypsum leachate, the method adopting the above-mentioned system comprises the following steps:

[0022] S1. Alkali adjustment: In an alkali adjustment reactor, the pH of the phosphogypsum leachate is adjusted by using liquid alkali to obtain a system in the alkali adjustment reactor; solid-liquid separation is performed on the system in the alkali adjustment reactor to obtain an alkali adjustment filtrate and an alkali adjustment filter residue;

[0023] S2, nanofiltration salt separation: performing nanofiltration on the alkali adjustment filtrate to obtain nanofiltration product water and nanofiltration concentrated water;

[0024] S3, fluorine resource recovery: sending the nanofiltration produced water, liquid alkali and calcium salt into a fluorine recovery reactor for mixing and reacting to obtain a system in the fluorine recovery reactor; performing solid-liquid separation on the system in the fluorine recovery reactor to obtain a recovered calcium fluoride product and a fluorine recovery filtrate;

[0025] S4, reverse osmosis concentration: performing reverse osmosis on the fluorine recovery filtrate to obtain reverse osmosis product water and reverse osmosis concentrated water;

[0026] S5. Phosphorus resource recovery: sending the reverse osmosis concentrated water, nanofiltration concentrated water, magnesium salt, ammonium salt and liquid alkali into a phosphorus recovery reactor for mixing and reacting to obtain a system in the phosphorus recovery reactor; performing solid-liquid separation on the system in the phosphorus recovery reactor to obtain a recovered magnesium ammonium phosphate product and a phosphorus recovery filtrate.

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

[0028] Mixing and stirring the liquid alkali and the phosphogypsum leachate in the alkali adjustment reactor, and using the liquid alkali to adjust the pH of the system in the alkali adjustment reactor to 3-4;

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

[0030] The alkali adjustment filter residue is discharged out of 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 product water, liquid alkali and calcium salt are mixed and stirred in the fluorine recovery reactor, and the pH of the system in the fluorine recovery reactor is adjusted to 6-7 by using the liquid alkali;

[0034] The amount of calcium salt added is based on the amount of Ca 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 in the fluorine recovery reactor is 10-30 minutes.

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

[0037] The water production rate of the reverse osmosis is 85-90%;

[0038] The reverse osmosis produced water that meets the standards is discharged out of the system.

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

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

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

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

[0043] In the present 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; 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] The invention solves the technical problem that the purity and yield of phosphorus resource recovery products in phosphogypsum leachate are low due to the interference of fluoride ions.

[0046] The present invention adopts a combination of chemical precipitation and membrane separation to obtain produced water meeting the GB 8978-1996 standard from phosphogypsum leachate for discharge or reuse, with a water production rate of 70-75%.

[0047] The present invention separates fluoride ions and phosphate ions in phosphogypsum leachate by nanofiltration at a specific pH and recycles them respectively, thereby obtaining recovered calcium fluoride with a purity of more than 95% and recovered magnesium ammonium phosphate with a purity of more than 97-98%, thereby greatly improving the added value.

[0048] After the present invention recycles the fluoride ions and phosphates which account for a relatively high proportion, the amount of sludge is reduced, thereby reducing the sludge disposal fee, saving costs and generating new income.

[0049] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0052] The following are the descriptions of the reference numerals:

[0053] 101-phosphogypsum leachate feed pump; 102-liquid alkali feed pump; 103-alkali adjustment reactor; 104-alkali adjustment solid-liquid separation device; 105-alkali adjustment filter residue; 106-alkali adjustment filtrate;

[0054] 201-nanofiltration high-pressure feed pump; 202-nanofiltration membrane column; 203-nanofiltration influent; 204-nanofiltration produced water; 205-nanofiltration concentrated water;

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

[0056] 401-reverse osmosis high pressure feed pump; 402-reverse osmosis membrane column; 403-reverse osmosis water inlet; 404-reverse osmosis produced water; 405-reverse osmosis concentrated water;

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

[0058] 601-phosphogypsum leachate feeding device; 602-liquid caustic soda feeding device; 603-calcium salt feeding device; 604-magnesium salt feeding device; 605-ammonium salt feeding device. DETAILED DESCRIPTION

[0059] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0060] In the following embodiments:

[0061] The treated phosphogypsum leachate was produced on-site by a wet-process phosphoric acid production enterprise in Yunnan, and 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 adopts EDTA titration method;

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

[0066] The pH value was tested using a pH meter;

[0067] The nitric acid pickling method is used for the detection of the recovered magnesium ammonium phosphate product;

[0068] Water quality testing is carried out in accordance with the national standard GB 8978-1996;

[0069] The purity test of the recovered calcium fluoride product shall be carried out in accordance with the national standard GB / T 27804-2011.

[0070] Example 1

[0071] This embodiment provides a phosphogypsum leachate resource treatment system, 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 reactor 103 (volume 10L) 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 reactor 302 (volume 10L) 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 reactor 503 (volume 5L) and a phosphorus recovery solid-liquid separation device 504;

[0073] The alkali adjustment reactor 103 is provided with a middle-upper feed port and a bottom discharge port; the outlet of the liquid alkali feed pump 102 is divided into three streams, and the outlet of the phosphogypsum leachate feed pump 101 and the first stream of the outlet of the liquid alkali feed pump 102 are connected to the middle-upper feed port of the alkali adjustment reactor 103; the bottom discharge port 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 water 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 produced water outlet and a nanofiltration concentrated water outlet;

[0074] The fluorine recovery reactor 302 is provided with a middle-upper feed port and a bottom discharge port; the nanofiltration water output outlet, the outlet of the calcium salt feed pump 301 and the second outlet of the liquid alkali feed pump 102 are connected to the middle-upper feed port of the fluorine recovery reactor 302; the bottom discharge port 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 water 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 water output outlet and a reverse osmosis concentrated water outlet; the reverse osmosis water output outlet is connected to the outside of the system;

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

[0076] The alkali adjustment reactor 103, the fluorine recovery reactor 302 and the phosphorus recovery reactor 503 are all provided with stirring equipment; the alkali adjustment solid-liquid separation device 104, the fluorine recovery solid-liquid separation device 303 and the phosphorus recovery solid-liquid separation device 504 are all plate and frame filter presses; the membrane components of the nanofiltration membrane column 202 and the membrane components of the reverse osmosis membrane column 402 are each independently made of polyamide and / or PVDF; the reverse osmosis membrane column 402 adopts a disc tube and / or roll 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; 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 resource processing of phosphogypsum leachate, which uses the above system and includes the following steps:

[0079] S1, alkali adjustment: in the alkali adjustment reactor 103, the stirring device is turned on at 100r / min, the material is fed according to the residence time of 15min, the feeding rate of liquid alkali is 0.35L / h, the feeding rate of phosphogypsum leachate is 32L / h, and the pH of the phosphogypsum leachate is adjusted by liquid alkali (the liquid alkali used in this embodiment is a sodium hydroxide aqueous solution with a concentration of 300g / L) to obtain a 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 pressing to obtain an alkali adjustment filtrate 106 (water quality is shown in Table 2) and an alkali adjustment filter residue (26g / 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 Filtrate 3.6 6201 7565 1741 5.1 21

[0082] S2, nanofiltration salt separation: the alkali adjustment filtrate 106 is subjected to nanofiltration, and the water production rate is controlled to be 85%, to obtain nanofiltration product water 204 and nanofiltration concentrated water 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 water production 3.6 18.3 1.2 2032 1.1 3.2 Nanofiltration concentrated water 3.6 30895 37783 2.3 24.8 92

[0085] S3, fluorine resource recovery: start the stirring device at 100r / min, feed according to the residence time of 15min, the feed rate of nanofiltration water 204 is 27L / h, the feed rate of calcium chloride aqueous solution (concentration 300g / L) is 0.52L / h, and the feed rate of liquid alkali is 0.16L / h, and the nanofiltration water 204, liquid alkali and calcium chloride aqueous solution are sent into the fluorine recovery reactor 302 for mixing and reaction to obtain the system in the fluorine recovery reactor, with a pH of 6.6; perform solid-liquid separation on the system in the fluorine recovery reactor to obtain the recovered calcium fluoride product 304 (98g / h, purity 95.1%, yield 92.3%) and the fluorine recovery filtrate 305 (water quality is shown in 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]]> Fluoride recovery filtrate 6.6 18.1 0.7 6.3 7.5 2.3

[0088] S4, reverse osmosis concentration: the fluorine recovery filtrate 305 is subjected to reverse osmosis, and the water production rate is controlled to be 87%, to obtain reverse osmosis produced water 404 and reverse osmosis concentrated water 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 water 6.6 1.3 0 0.3 0.2 0.3 Reverse osmosis concentrated water 6.6 89.3 3.2 28.3 27.8 9.2

[0091] S5. Phosphorus resource recovery: start the stirring device at 100 r / min, feed according to the residence time of 30 min, the feed rate of the reverse osmosis concentrated water 405 is 3.8 L / h, the feed rate of the nanofiltration concentrated water 205 is 4.8 L / h, the feed rate of the magnesium sulfate aqueous solution (250 g / L) is 0.7 L / h, the feed rate of the ammonium sulfate aqueous solution (250 g / L) is 0.4 L / h, and the feed rate of the liquid caustic soda is 0.05 L / h. The reverse osmosis concentrated water 405, the nanofiltration concentrated water 205, the magnesium sulfate aqueous solution, the ammonium sulfate aqueous solution and the liquid caustic soda are fed into the phosphorus recovery reactor 503 for mixing and reaction to obtain a system in the phosphorus recovery reactor with a pH of 8.6; perform solid-liquid separation on the system in the phosphorus recovery reactor to obtain a recovered magnesium ammonium phosphate product 505 (203 g / h, purity 97.6%, yield 91.2%) and a phosphorus recovery filtrate 506.

[0092] Example 2

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

[0094] The nanofiltration water production rate was controlled to be 81%;

[0095] The purity of the recovered calcium fluoride product 304 is 95.5% and the yield is 90.4%;

[0096] Control the reverse osmosis water production rate to 90%;

[0097] The purity of the recovered magnesium ammonium phosphate product 505 is 97.1%, and the yield is 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 Filtrate 3.6 6201 7565 1741 5.1 21 Nanofiltration water production 3.6 12.2 0.9 2118 1.0 2.8 Nanofiltration concentrated water 3.6 24390 29816 4.3 19.6 73.1 Fluoride recovery filtrate 6.6 11.9 0.8 6.1 7.2 2.6 Reverse osmosis water 6.6 0.8 0 0.3 0.5 0.2 Reverse osmosis concentrated water 6.6 71.1 4.5 25.6 38.8 10.9

[0100] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A phosphogypsum leachate resource treatment system, characterized in that: The system comprises: 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 comprises a phosphogypsum leachate feed pump, a liquid alkali feed pump, an alkali adjustment reactor and an alkali adjustment solid-liquid separation device; the nanofiltration unit comprises a nanofiltration high-pressure feed pump and a nanofiltration membrane column; the fluorine recovery unit comprises a calcium salt feed pump, a fluorine recovery reactor and a fluorine recovery solid-liquid separation device; the reverse osmosis unit comprises a reverse osmosis high-pressure feed pump and a reverse osmosis membrane column; the phosphorus recovery unit comprises a magnesium salt feed pump, an ammonium salt feed pump, a phosphorus recovery reactor and a phosphorus recovery solid-liquid separation device; The alkali adjustment reactor is provided with a middle-upper feed port and a bottom discharge port; the outlet of the liquid alkali feed pump is divided into three branches, and the outlet of the phosphogypsum leachate feed pump and the first branch of the outlet of the liquid alkali feed pump are connected to the middle-upper feed port of the alkali adjustment reactor; the bottom discharge port 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 provided with a filtrate outlet and a filter residue outlet; the filtrate outlet of the alkali adjustment solid-liquid separation device is connected to the water inlet of the nanofiltration membrane column through a nanofiltration high-pressure feed pump; the nanofiltration membrane column is provided with a nanofiltration produced water outlet and a nanofiltration concentrated water outlet; The fluorine recovery reactor is provided with a middle-upper feed port and a bottom discharge port; the nanofiltration water output outlet, the calcium salt feed pump outlet and the second outlet of the liquid alkali feed pump are connected to the middle-upper feed port of the fluorine recovery reactor; the bottom discharge port 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 provided 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 water inlet of the reverse osmosis membrane column through a reverse osmosis high-pressure feed pump; the reverse osmosis membrane column is provided with a reverse osmosis water output outlet and a reverse osmosis concentrated water outlet; The phosphorus recovery reactor is provided with a middle-upper feed port and a bottom discharge port; the third of the nanofiltration concentrated water outlet, the reverse osmosis concentrated water outlet, the magnesium salt feed pump outlet, the ammonium salt feed pump outlet and the liquid alkali feed pump outlet is connected to the middle-upper feed port of the phosphorus recovery reactor; the bottom discharge port 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 a magnesium ammonium phosphate product outlet and a filtrate outlet.

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

3. The phosphogypsum leachate resource processing system according to claim 1, wherein: The alkali adjustment reactor, fluorine recovery reactor and phosphorus recovery reactor are all provided 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 assembly of the nanofiltration membrane column and the membrane assembly of the reverse osmosis membrane column are independently made of polyamide and / or PVDF; The nanofiltration membrane column and the reverse osmosis membrane column each independently adopt a disc-tube type and / or a roll type structure.

4. The phosphogypsum leachate resource processing 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 caustic soda feed pump is connected with a liquid caustic soda feed device; The inlet of the calcium salt feeding pump is connected to a calcium salt feeding device; The inlet of the magnesium salt feed pump is connected to a magnesium salt feeding device; The inlet of the ammonium salt feeding pump is connected with an ammonium salt feeding device.

5. A method for resource processing of phosphogypsum leachate, characterized in that: The method adopts the system according to any one of claims 1 to 4, comprising the following steps: S1. Alkali adjustment: In an alkali adjustment reactor, the pH of the phosphogypsum leachate is adjusted by using liquid alkali to obtain a system in the alkali adjustment reactor; solid-liquid separation is performed on the system in the alkali adjustment reactor to obtain an alkali adjustment filtrate and an alkali adjustment filter residue; S2, nanofiltration salt separation: performing nanofiltration on the alkali adjustment filtrate to obtain nanofiltration product water and nanofiltration concentrated water; S3, fluorine resource recovery: sending the nanofiltration produced water, liquid alkali and calcium salt into a fluorine recovery reactor for mixing and reacting to obtain a system in the fluorine recovery reactor; performing solid-liquid separation on the system in the fluorine recovery reactor to obtain a recovered calcium fluoride product and a fluorine recovery filtrate; S4, reverse osmosis concentration: performing reverse osmosis on the fluorine recovery filtrate to obtain reverse osmosis product water and reverse osmosis concentrated water; S5. Phosphorus resource recovery: sending the reverse osmosis concentrated water, nanofiltration concentrated water, magnesium salt, ammonium salt and liquid alkali into a phosphorus recovery reactor for mixing and reacting to obtain a system in the phosphorus recovery reactor; performing solid-liquid separation on the system in the phosphorus recovery reactor to obtain a recovered magnesium ammonium phosphate product and a phosphorus recovery filtrate.

6. The method for resource recovery of phosphogypsum leachate according to claim 5, wherein: In step S1: Mixing and stirring the liquid alkali and the phosphogypsum leachate in the alkali adjustment reactor, and using the liquid alkali to adjust the pH of the system in the alkali adjustment reactor to 3-4; The residence time of the system in the alkali adjustment reactor in the alkali adjustment reactor is 10-30 minutes; and the alkali adjustment filter residue is discharged out of the system.

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

9. The method for resource recovery of phosphogypsum leachate according to claim 5, wherein: In step S4: The water production rate of the reverse osmosis is 85-90%; The reverse osmosis produced water that meets the standards is discharged out of the system.

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

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