CN115010309A - Iron phosphate wastewater zero-discharge treatment system and treatment process - Google Patents
Iron phosphate wastewater zero-discharge treatment system and treatment process Download PDFInfo
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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- C02F9/00—Multistage treatment of water, waste water or sewage
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- C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
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- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
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- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
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- C—CHEMISTRY; METALLURGY
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- C02F2001/007—Processes including a sedimentation step
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Abstract
The invention discloses a ferric phosphate wastewater zero-discharge treatment system and a process method, wherein a washing wastewater treatment section sequentially comprises a first sedimentation tank, a first V-shaped filter tank, a first UF unit and a first material separation membrane unit; the mother liquor treatment section sequentially comprises a second sedimentation tank, a second V-shaped filter tank, a second UF unit and a second material separation membrane unit; the production section of the product salt sequentially comprises a de-hardening sedimentation tank, a concentration and evaporation unit, an ammonium sulfate crystallization unit, a monoammonium phosphate cooling and crystallization unit and a compound fertilizer crystallization unit. Through the optimized combination of the process flows, the continuous and efficient operation of a reverse osmosis system is ensured, the recovery rate of product water is also ensured to reach more than 99%, the production of high-added-value crystallized salt products such as ammonium sulfate, monoammonium phosphate and the like is realized, the recovery rate of the crystallized salt is more than 85%, the comprehensive operation cost is reduced by 30-60%, the burden of production enterprises can be effectively reduced, and the resource recycling is realized to the maximum extent.
Description
Technical Field
The invention relates to the field of wastewater treatment technology, in particular to a zero-discharge treatment system and a zero-discharge treatment process for iron phosphate wastewater.
Background
With the popularization of new energy automobiles, the demand of lithium batteries is increasing, wherein lithium iron phosphate has a stable P-O bond in a crystal, does not cause structural collapse and heating or produce strong oxide at overshoot and high temperature, and has a long cycle life, so the lithium iron phosphate is the most potential lithium battery cathode material at present.
The process for preparing lithium iron phosphate from iron phosphate is simple, high in raw material utilization rate and good in repeatability, and gradually develops into the mainstream process for preparing lithium iron phosphate. Two ways of industrially producing the iron phosphate are adopted, namely, purified phosphoric acid is used to react with ferrous sulfate; secondly, the phosphate reacts with ferrous sulfate, and the common phosphate is monoammonium phosphate. The environment for producing the iron phosphate is an acid environment, and the produced acid wastewater mainly comprises two streams: after raw material phosphate and ferric salt solution are mixed and reacted, the reaction slurry is subjected to filter pressing by a diaphragm to form synthetic mother liquor; and washing and purifying the iron phosphate filter cake by using demineralized water to generate washing wastewater, wherein the salt content of the iron phosphate filter cake is higher and is generally 60000-80000 mg/L, and the salt content of the iron phosphate filter cake is lower and is generally 12000-30000 mg/L, the washing wastewater is wastewater mainly containing sulfate and phosphate and contains impurities such as hardness, iron, aluminum and the like. Because the waste water contains sulfate and phosphate with higher utilizable value and the waste water treatment device accounts for about 30 percent of the total investment, the selection of the waste water treatment process directly influences the investment and operation cost of the whole project and is a competitive point for cost control of various manufacturers in the future.
At present, the main process for treating the iron phosphate wastewater comprises the following steps: pretreatment (pH adjustment) + UF + RO + resin + ammonium sulfate evaporative crystallization + mixed salt (ammonium sulfate + ammonium phosphate), partial sulfate or phosphate will precipitate out in the form of sludge after pH adjustment, which is not beneficial to product recovery, resin selection is difficult due to high salt content and the regenerated waste liquid is difficult to treat, the evaporation crystallization scale is large, which causes high investment, the produced mixed salt is low in selling price, and the operation cost is not beneficial to control.
Disclosure of Invention
In order to solve the problems that products are not easy to recycle and the operation cost is high, the invention provides the iron phosphate wastewater zero-discharge treatment system and the treatment process which can ensure product water recycling, high value-added product salt output and low investment.
The application provides a zero discharge treatment system for iron phosphate wastewater, which comprises a washing wastewater treatment section, a mother liquor treatment section and a product salt production section; the washing wastewater treatment section sequentially comprises a first sedimentation tank, a first V-shaped filter tank, a first UF unit and a first material separation membrane unit, and all adjacent parts are communicated through pipelines and mutually conveyed through a pump; the mother liquor treatment section sequentially comprises a second sedimentation tank, a second V-shaped filter tank, a second UF unit and a second material separation membrane unit, and all adjacent parts are communicated through pipelines and mutually conveyed through a pump; the product salt production section comprises a hard-removing sedimentation tank, a concentration evaporation unit, an ammonium sulfate crystallization unit, a monoammonium phosphate cooling crystallization unit and a compound fertilizer crystallization unit in sequence, and all adjacent parts are communicated through pipelines and are conveyed mutually through a pump.
Furthermore, the first sedimentation tank is used for filtering the washing wastewater and removing suspended matters in the washing wastewater, and the first V-shaped filter tank is used for receiving the washing wastewater discharged by the first sedimentation tank and removing impurities in the washing wastewater; the first UF unit is used for receiving the washing wastewater filtered by the first V-shaped filter and removing micro impurities in the washing wastewater; the first material separation membrane unit is used for concentrating and desalting the washing wastewater after removing the micro impurities to generate washing concentrated solution and washing fresh water solution, and conveying the washing concentrated solution to the second sedimentation tank.
Further, the second sedimentation tank is used for receiving the mother liquor and the washing concentrated solution and removing suspended matters in the mixed solution; the second V-shaped filter is used for receiving the mixed liquid discharged by the second sedimentation tank and removing impurities in the mixed liquid; the second UF unit is used for receiving the mixed liquid filtered by the second V-shaped filter and removing tiny impurities in the mixed liquid in an ultrafiltration mode; and the second material separation membrane unit is used for separating and concentrating the mother liquid material of the mixed liquid after the micro impurities are removed to generate a mother liquid concentrated solution and a mother liquid light water solution, and the mother liquid concentrated solution is conveyed to the hardness removal sedimentation tank to produce byproducts.
Further, the de-hardening sedimentation tank is used for receiving the mother liquor concentrated solution and ammonia water or liquid ammonia, adjusting the pH of the mother liquor concentrated solution and forming magnesium ammonium phosphate; the concentration evaporation unit is used for heating and evaporating the mother liquor concentrated solution after hardness removal, and preparing high-concentration evaporation mother liquor; the ammonium sulfate crystallization unit is used for heating and evaporating the high-concentration evaporation mother liquor, and centrifuging and drying the supersaturated solution to obtain an ammonium sulfate product and a centrifugal mother liquor; the monoammonium phosphate cooling crystallization unit is used for carrying out pH adjustment and cooling crystallization on the centrifugal mother liquor, and centrifuging the supersaturated solution to obtain a monoammonium phosphate product and a cooling mother liquor; and the compound fertilizer crystallization unit is used for cooling the mother liquor and centrifuging the supersaturated solution to obtain a compound fertilizer product and a compound fertilizer mother liquor.
Further, the washing wastewater treatment section also comprises a product water refining RO unit, wherein the product water refining RO unit is used for washing water dilute water liquid, mother liquid dilute water liquid, condensate of a concentration evaporation unit, condensate of an ammonium sulfate crystallization unit and condensate of a compound fertilizer crystallization unit, and generating refined concentrated water and refined produced water; the refined concentrated water returns to the first material separation membrane unit, and the refined produced water returns to the iron phosphate preparation device.
Further, the first sedimentation tank is an inclined plate sedimentation tank, and the second sedimentation tank and the hardness removal sedimentation tank are inclined plate sedimentation tanks.
The treatment process of the iron phosphate wastewater zero-discharge treatment system comprises the following steps:
s1, pretreatment of washing wastewater and membrane concentration process: lifting the wastewater into a first sedimentation tank by a pump, and removing suspended matters in the washing wastewater in the first sedimentation tank in a standing mode; washing wastewater enters a first V-shaped filter tank from a first sedimentation tank in a self-flowing mode, and impurities in the washing wastewater are removed in the first V-shaped filter tank in a filtering mode; the washing wastewater is lifted by the first V-shaped filter tank through a pump to enter a first UF unit, micro impurities in the washing wastewater are removed, the washing wastewater enters a first material separation membrane unit, and the washing wastewater is concentrated in a separation and concentration mode to obtain a washing concentrated solution and a washing fresh water solution;
s2, mother liquor pretreatment and membrane concentration working procedures: mixing the washing concentrated solution and the mother solution to obtain a mixed solution, lifting the mixed solution to a second sedimentation tank by a pump, and removing suspended matters in the mixed solution in a standing mode; the mixed liquid enters a second V-shaped filter from a second sedimentation tank in a self-flowing mode, and suspended matters in the mixed liquid are removed in the second V-shaped filter in a filtering mode; the washing wastewater is lifted by the second V-shaped filter tank through the pump and enters the second UF unit, micro impurities in the washing wastewater are removed, then the mixed liquid is separated and concentrated through the second material separation membrane unit, mother liquid concentrated solution and mother liquid fresh water solution are obtained, and the mother liquid concentrated solution enters the hardness removal sedimentation tank for continuous treatment;
s3, hard sediment removal step: adding ammonia water or liquid ammonia into the de-hardening sedimentation tank to adjust the pH value of the mother liquor concentrated solution to 8-9 to form magnesium ammonium phosphate sediment;
s4, evaporation and concentration step: the mother liquor concentrated solution after hardness removal is subjected to temperature rise evaporation through a concentrated solution evaporation unit, the mother liquor concentrated solution starts to evaporate after reaching the boiling point to obtain high-concentration evaporation mother liquor, and the high-concentration evaporation mother liquor enters an ammonium sulfate crystallization unit;
s5, ammonium sulfate crystallization step: heating and evaporating the high-concentration evaporation mother liquor through an ammonium sulfate crystallization evaporator, continuously concentrating the high-concentration evaporation mother liquor to form a supersaturated ammonium sulfate solution, centrifuging and drying the supersaturated ammonium sulfate solution to obtain an ammonium sulfate product and a centrifugal mother liquor, and feeding the centrifugal mother liquor into a monoammonium phosphate cooling and crystallizing unit;
s6, monoammonium phosphate crystallization step: after the pH value of the centrifugal mother liquor is adjusted to 5-6, cooling and crystallizing the centrifugal mother liquor through a cooling crystallizer to separate out monoammonium phosphate crystals, and centrifuging the monoammonium phosphate crystals to obtain monoammonium phosphate products and cooling mother liquor;
s7, compound fertilizer crystallization process: and (3) heating and evaporating the cooled mother liquor through a compound fertilizer evaporator to form a mixed supersaturated solution of ammonium sulfate and monoammonium phosphate, allowing the mixed supersaturated solution of ammonium sulfate and monoammonium phosphate to pass through a compound fertilizer centrifuge to obtain a compound fertilizer product and a compound fertilizer mother liquor, and allowing the compound fertilizer mother liquor to pass through a compound fertilizer mother liquor dryer to produce a compound fertilizer.
Further, in the step S1), the operating pH of the first material separation membrane unit and the product water refining RO unit is 4-5.
Further, in the step S2), the salt content of the mother liquor concentrated solution is more than or equal to 180000mg/L, and the operating pH value of the second material separation membrane unit is 4-5.
In summary, the present application includes at least the following advantageous technical effects:
1. the system can continuously and efficiently treat the iron phosphate wastewater, simultaneously cancels a pretreatment pH adjusting unit in the treatment process, adopts a material separation membrane aiming at the acidic wastewater, adopts a precipitation process to replace a resin hardness removing process before evaporation crystallization to produce the magnesium ammonium phosphate compound fertilizer, and produces the ammonium sulfate according with GBT535-2020 Fertilizer and ammonium sulfate through the evaporation crystallization process
The I type index product is provided with a monoammonium phosphate cooling and crystallizing procedure, and a monoammonium phosphate product with the purity of more than 90% is produced, so that the process can reduce the investment cost, the product yield is good, the running cost can be reduced, and the resource recycling is realized to the greatest extent;
2. a large amount of condensate is generated in the evaporation and crystallization process, and the condensate is subjected to reverse osmosis filtration by the product water refining RO unit, so that the condensate can be recycled to the previous production, the production cost is further reduced, the condensate can be fully treated, and the discharge of pollutants is reduced;
3. through the optimized combination of the process flows, the continuous and efficient operation of a reverse osmosis system is ensured, the recovery rate of product water is also ensured to reach more than 99%, the production of high-added-value crystallized salt products such as ammonium sulfate, monoammonium phosphate and the like is realized, the recovery rate of the crystallized salt is more than 85%, the comprehensive operation cost is reduced by 30-60%, the burden of production enterprises can be effectively reduced, and the resource recycling is realized to the maximum extent.
Drawings
Fig. 1 is a block diagram of a zero discharge treatment system for iron phosphate wastewater according to an embodiment of the present application.
Reference numerals: 1. a washing wastewater treatment section; 11. a first sedimentation tank; 12. a first V-shaped filter chamber; 13. a first UF unit; 14. a first material separation membrane unit; 15. a product water refining RO unit; 2. a mother liquor treatment section; 21. a second sedimentation tank; 22. a second V-shaped filter chamber; 23. a second UF unit; 24. a second material separation membrane unit; 3. a product salt production section; 31. a hardness removal sedimentation tank; 32. a concentrated solution evaporation unit; 33. an ammonium sulfate crystallization unit; 34. a monoammonium phosphate cooling and crystallizing unit; 35. and (4) a compound fertilizer crystallization unit.
Detailed Description
The present application is described in further detail below with reference to fig. 1. The iron phosphate wastewater zero-discharge treatment system shown in fig. 1 comprises a washing wastewater treatment section 1, a mother liquor treatment section 2 and a product salt production section 3.
The washing wastewater treatment section 1 comprises a first sedimentation tank 11, a first V-shaped filter tank 12, a first UF unit 13, a first material separation membrane unit 14 and a product water refining RO unit 15 in sequence, and all adjacent parts are communicated through pipelines and mutually conveyed through pumps. Wherein, the first sedimentation tank 11 is used for filtering the washing wastewater and removing suspended matters in the washing wastewater, and in the embodiment of the present application, the first sedimentation tank 11 is an inclined plate sedimentation tank. The first V-shaped filter tank 12 is used for receiving the washing wastewater discharged by the first sedimentation tank 11 and further removing impurities in the washing wastewater; the first UF unit 13 (ultrafiltration membrane unit) is used for receiving the washing wastewater filtered by the first V-shaped filter 12 and removing tiny impurities in the washing wastewater; the first material separation membrane unit 14 (reverse osmosis membrane and nanofiltration membrane combined unit) is used for concentrating and desalting the washing wastewater after removing the micro impurities to generate a washing concentrated solution (namely material separation membrane concentrated water) and a washing fresh water solution (namely material separation membrane produced water), and conveying the washing concentrated solution to the mother liquor treatment section 2; the filtering diameter of the product water refining RO unit 15 is smaller than that of the first material separation membrane unit 14 on average, and the product water refining RO unit 15 concentrates the washing water dilute liquid of the first material separation membrane unit 14 by a reverse osmosis mode and generates refined concentrated water and refined produced water. The refined concentrated water returns to the first material separation membrane unit 14 again through the pipeline and the delivery pump, and the refined produced water returns to the iron phosphate preparation device through the pipeline and the delivery pump, so that the sewage can be fully treated and utilized.
The mother liquor treatment section 2 comprises a second sedimentation tank 21, a second V-shaped filter 22, a second UF unit 23 and a second material separation membrane unit 24 in sequence, and all the adjacent components are communicated through pipelines and mutually conveyed through a pump. The second sedimentation tank 21 is configured to receive the mother liquor and the washing concentrate, and remove suspended matters in the mixed liquor, in this embodiment, the second sedimentation tank 21 is an inclined plate sedimentation tank; the second V-shaped filter 22 is used for receiving the mixed liquid discharged from the second sedimentation tank 21 and further removing impurities in the mixed liquid; the second UF unit 23 is configured to receive the mixed liquid filtered by the second V-shaped filter 22, and remove the fine impurities in the mixed liquid by an ultrafiltration mode; the second material separation membrane unit 24 separates and concentrates the mother liquid material of the mixed liquid after the removal of the micro impurities to generate mother liquid concentrated solution and mother liquid fresh water solution, the mother liquid concentrated solution is conveyed to the product salt production section 3 to produce byproducts, and the mother liquid fresh water solution is conveyed to the product water refining RO unit 15 to separate refined concentrated solution and refined product water.
The product salt production section 3 comprises a hard removal sedimentation tank 31, a concentration evaporation unit 32, an ammonium sulfate crystallization unit 33, a monoammonium phosphate cooling crystallization unit 34 and a compound fertilizer crystallization unit 35 in sequence, and all adjacent parts are communicated through pipelines and are mutually conveyed through pumps. The de-hardening sedimentation tank 31 is used for receiving the mother liquor concentrated solution and ammonia water or liquid ammonia, adjusting the pH of the mother liquor concentrated solution and forming magnesium ammonium phosphate; the concentration evaporation unit 32 is used for heating and evaporating the mother liquor concentrated solution after hardness removal, and preparing high-concentration evaporation mother liquor, steam generated by the high-concentration evaporation mother liquor can be used as a secondary heat source, and the condensate generated after heat is recycled is conveyed to the product water refining RO unit 15 to separate refined concentrated water and refined product water, so that the use amount of fresh steam can be reduced, and the secondary steam can be fully utilized and treated; the ammonium sulfate crystallization unit 33 is used for heating and evaporating the high-concentration evaporation mother liquor, and centrifuging and drying the supersaturated solution to obtain an ammonium sulfate product and a centrifugal mother liquor; the monoammonium phosphate cooling and crystallizing unit 34 is used for carrying out pH adjustment and cooling crystallization on the centrifugal mother liquor, and centrifuging the supersaturated solution to obtain a monoammonium phosphate product and a cooling mother liquor; the compound fertilizer crystallization unit 35 is used for cooling the mother liquor and centrifuging the supersaturated solution to obtain a compound fertilizer product (namely ammonium sulfate + monoammonium phosphate compound fertilizer) and a compound fertilizer mother liquor.
In the present embodiment, the concentration evaporation unit 32 may employ one or more of a feed preheater, a rising film evaporator, and a falling film evaporator. The ammonium sulfate crystallization unit 33 sequentially comprises an ammonium sulfate evaporator, an ammonium sulfate thickener, an ammonium sulfate centrifuge, an ammonium sulfate dryer and a tail gas processor, wherein the ammonium sulfate evaporator can adopt an MED evaporator or an MVR evaporator, in the invention, the MVR forced circulation evaporator is selected, and condensate generated by the ammonium sulfate evaporator is conveyed to the product water refining RO unit 15 to separate refined concentrated water and refined product water; the ammonium sulfate centrifuge adopts one or two of a cyclone and a centrifuge, the centrifuge is selected in the invention, the ammonium sulfate dryer adopts a vibration drying fluidized bed or a hot air dryer, and the tail gas processor adopts the combination of a cyclone dust collector and a washing tower. Monoammonium phosphate cooling crystallization unit 34 includes PH adjusting unit, cooling crystallizer, monoammonium phosphate thickener, monoammonium phosphate centrifuge and tail gas treater in proper order, but ammonium sulfate crystallization unit 33 can be referred to in the chooseing of monoammonium phosphate centrifuge and tail gas treater. The compound fertilizer crystallizing unit 35 sequentially comprises a compound fertilizer evaporator, a compound fertilizer thickener, a compound fertilizer centrifuge, a compound fertilizer mother liquor dryer and a tail gas processor, the compound fertilizer evaporator, the compound fertilizer centrifuge and the tail gas processor can refer to the ammonium sulfate crystallizing unit 33, condensate generated by the compound fertilizer evaporator is conveyed to the product water refining RO unit 15 to separate refined concentrated water and refined produced water, the compound fertilizer mother liquor enters the compound fertilizer mother liquor dryer to obtain a compound fertilizer product (mixed with the compound fertilizer product obtained by centrifuging), and the compound fertilizer mother liquor dryer adopts a roller dryer to produce the compound fertilizer.
The treatment process adopting the iron phosphate wastewater zero-discharge treatment system comprises the following steps:
s1, pretreatment of washing wastewater and membrane concentration process: the washing wastewater of the iron phosphate device firstly enters an adjusting tank for homogenizing and equalizing the quantity, then is lifted into a first sedimentation tank 11 through a pump, and suspended matters in the washing wastewater are removed in the first sedimentation tank 11 through a standing mode (the effluent suspended matters of the first sedimentation tank 11 are below 10mg/L, the suspended matters mainly comprise iron phosphate and iron filings which are not completely reacted, and the suspended matters can return to an iron phosphate preparation device); washing wastewater enters a first V-shaped filter 12 from a first sedimentation tank 11 in a self-flowing mode, and impurities in the washing wastewater are removed in the first V-shaped filter 12 in a filtering mode (the suspended matters in the effluent of the first V-shaped filter 12 are below 3 mg/L); the washing wastewater is lifted by the first V-shaped filter 12 through a pump to enter the first UF unit 13 and remove pollutants such as micro impurities in the washing wastewater (the turbidity of the water discharged by the first UF unit 13 is 0.2 NTU);
and pressurizing the effluent by a material separation membrane lift pump and a high-pressure pump, feeding the effluent into a first material separation membrane unit 14, concentrating the washing wastewater in a separation and concentration mode to obtain a washing concentrated solution and a washing fresh water solution, feeding the washing concentrated solution into a second sedimentation tank 21, feeding the washing fresh water solution into a product water refining RO unit 15 for secondary concentration and salt extraction, and controlling the operating pH of the first material separation membrane unit 14 and the product water refining RO unit 15 to be 4-5.
S2, mother liquor pretreatment and membrane concentration working procedures: mixing the washing concentrated solution and the mother solution, feeding the mixed solution and the mother solution into an adjusting tank to obtain a mixed solution with average value, lifting the mixed solution to a second sedimentation tank 21 through a pump, and removing suspended matters in the mixed solution in a standing mode (the suspended matters in the effluent of the second sedimentation tank 21 are less than 10mg/L, the suspended matters are mainly iron phosphate and unreacted scrap iron, and the suspended matters can return to an iron phosphate preparation device); the mixed liquid enters a second V-shaped filter 22 from a second sedimentation tank 21 in a self-flowing mode, and suspended matters in the mixed liquid are removed in the second V-shaped filter 22 in a filtering mode (the suspended matters in the effluent of the second V-shaped filter 22 are below 3 mg/L); the washing wastewater is lifted by the second V-shaped filter 22 through a pump to enter the second UF unit 23 and remove pollutants such as micro impurities in the washing wastewater (the turbidity of the water discharged by the second UF unit 23 is 0.2 NTU);
and separating the concentrated mixed liquid by a second material separation membrane unit 24 to obtain a mother liquid concentrated solution (the salt content of the mother liquid concentrated solution is more than or equal to 180000mg/L) and a mother liquid fresh water solution, wherein the mother liquid concentrated solution enters a hardness removal sedimentation tank 31 for continuous treatment, the mother liquid fresh water solution enters a product water refining RO unit 15 for further desalination, and the operating pH of the second material separation membrane unit 24 is 4-5.
S3, hard sediment removal step: the pH value of the mother liquor concentrated solution (the ammonia water is selected in the embodiment of the application) is adjusted to 8-9 by adding ammonia water or liquid ammonia into the de-hardening sedimentation tank 31, and magnesium ammonium phosphate sediment can be formed in the de-hardening sedimentation tank 31.
S4, evaporation and concentration step: the mother liquor concentrated solution after hardness removal is subjected to temperature rise evaporation through a concentrated solution evaporation unit 32, the mother liquor concentrated solution starts to evaporate after reaching a boiling point, the mother liquor concentrated solution is continuously concentrated and reaches a set concentration, the high-concentration evaporation mother liquor enters an ammonium sulfate crystallization unit 33 (the outlet water temperature of the high-concentration evaporation mother liquor is 99-103 ℃), and steam is condensed to form a condensate and enters a product water refining RO unit 15.
S5, ammonium sulfate crystallization step: heating and evaporating the high-concentration evaporation mother liquor through an ammonium sulfate crystallization evaporator (the operating temperature of the ammonium sulfate crystallization evaporator is 97-100 ℃), continuously concentrating the high-concentration evaporation mother liquor and forming a supersaturated ammonium sulfate solution, condensing steam to form a condensate, feeding the condensate into a product water refining RO unit 15, pressurizing and conveying the supersaturated ammonium sulfate solution to an ammonium sulfate thickener through a discharge pump to blend the quality of crystallized salt, centrifuging and drying through an ammonium persulfate centrifuge and an ammonium sulfate dryer to obtain an ammonium sulfate product and centrifugal mother liquor, and feeding the centrifugal mother liquor into a monoammonium phosphate cooling and crystallizing unit 34;
s6, monoammonium phosphate crystallization step: after the pH value of the centrifugal mother liquor is adjusted to 5-6, cooling crystallization is carried out through a cooling crystallizer (the operation temperature of the cooling crystallizer is 38-42 ℃), monoammonium phosphate crystals are gradually separated out along with temperature reduction by utilizing the characteristic that the solubility difference is caused by the temperature change of monoammonium phosphate and ammonium sulfate, the monoammonium phosphate crystals are pressurized through a discharge pump and are conveyed to a monoammonium phosphate thickener to be blended with the quality of crystallized salt, and then the monoammonium phosphate products and the cooling mother liquor are obtained through centrifugation through the monoammonium phosphate centrifuge;
s7, compound fertilizer crystallization process: the cooling mother liquor is heated and evaporated through a compound fertilizer evaporator (the operating temperature of the compound fertilizer evaporator is 100-103 ℃) to form a mixed supersaturated solution of ammonium sulfate and monoammonium phosphate, the steam is condensed to form a condensate to enter a product water refining RO unit 15, the mixed supersaturated solution of ammonium sulfate and monoammonium phosphate is pressurized and conveyed to the compound fertilizer thickener through a discharge pump to regulate the quality of crystalline salt, a compound fertilizer product and a compound fertilizer mother liquor are obtained through a compound fertilizer centrifuge, the compound fertilizer mother liquor is used for producing a compound fertilizer through a compound fertilizer mother liquor dryer, and condensate water formed in the drying process enters the product water refining RO unit 15.
The implementation principle of the iron phosphate wastewater zero-discharge treatment process and system provided by the embodiment of the application is as follows: the application provides a zero-discharge treatment process and a zero-discharge treatment system for iron phosphate wastewater, which have low investment cost and low operation cost, the system maintains an acidic operation condition, an acid-resistant material separation membrane aiming at the acidic wastewater is adopted, and a precipitation process is adopted to replace a resin hardness removal procedure before evaporative crystallization to produce a magnesium ammonium phosphate compound fertilizer;
meanwhile, the ammonium sulfate crystallization process produces a product meeting GBT535-2020 type I index of fertilizer and ammonium sulfate, the monoammonium phosphate cooling crystallization process produces a monoammonium phosphate product with the purity of more than 90%, the compound fertilizer crystallization process produces a compound fertilizer product, and the magnesium ammonium phosphate compound fertilizer, the ammonium sulfate, the monoammonium phosphate and the compound fertilizer product have high market value, so that the investment cost and the operation cost can be reduced, the resource recycling can be realized to the greatest extent, and the emission of pollutants is reduced.
The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.
Claims (9)
1. The utility model provides an iron phosphate waste water zero release processing system which characterized in that: comprises a washing wastewater treatment working section (1), a mother liquor treatment working section (2) and a product salt production working section (3); the washing wastewater treatment section (1) sequentially comprises a first sedimentation tank (11), a first V-shaped filter (12), a first UF unit (13) and a first material separation membrane unit (14), and all adjacent parts are communicated through pipelines and mutually conveyed through a pump; the mother liquor treatment section (2) sequentially comprises a second sedimentation tank (21), a second V-shaped filter (22), a second UF unit (23) and a second material separation membrane unit (24), and all adjacent parts are communicated through pipelines and are mutually conveyed through a pump; the product salt production section (3) comprises a de-hardening sedimentation tank (31), a concentration evaporation unit (32), an ammonium sulfate crystallization unit (33), a monoammonium phosphate cooling crystallization unit (34) and a compound fertilizer crystallization unit (35) in sequence, and all adjacent parts are communicated through pipelines and are conveyed mutually through a pump.
2. The iron phosphate wastewater zero-discharge treatment system according to claim 1, characterized in that: the first sedimentation tank (11) is used for filtering the washing wastewater and removing suspended matters in the washing wastewater, and the first V-shaped filter (12) is used for receiving the washing wastewater discharged by the first sedimentation tank (11) and removing impurities in the washing wastewater; the first UF unit (13) is used for receiving the washing wastewater filtered by the first V-shaped filter (12) and removing tiny impurities in the washing wastewater; the first material separation membrane unit (14) is used for concentrating and desalting the washing wastewater after removing the micro impurities to generate a washing concentrated solution and a washing dilute solution, and conveying the washing concentrated solution to the second sedimentation tank (21).
3. The iron phosphate wastewater zero-discharge treatment system according to claim 2, characterized in that: the second sedimentation tank (21) is used for receiving the mother liquor and the washing concentrated solution and removing suspended matters in the mixed solution; the second V-shaped filter tank (22) is used for receiving the mixed liquid discharged by the second sedimentation tank (21) and removing impurities in the mixed liquid; the second UF unit (23) is used for receiving the mixed liquid filtered by the second V-shaped filter (22) and removing tiny impurities in the mixed liquid in an ultrafiltration mode; the second material separation membrane unit (24) separates and concentrates mother liquid materials of the mixed liquid after the micro impurities are removed to generate mother liquid concentrated solution and mother liquid light water solution, and the mother liquid concentrated solution is conveyed to the hardness removal sedimentation tank (31) to produce byproducts.
4. The iron phosphate wastewater zero-discharge treatment system according to claim 3, characterized in that: the de-hardening sedimentation tank (31) is used for receiving the mother liquor concentrated solution and ammonia water or liquid ammonia, adjusting the pH of the mother liquor concentrated solution and forming magnesium ammonium phosphate; the concentration evaporation unit (32) is used for heating and evaporating the mother liquor concentrated solution after hardness removal and preparing high-concentration evaporation mother liquor; the ammonium sulfate crystallization unit (33) is used for heating and evaporating the high-concentration evaporation mother liquor, and centrifuging and drying the supersaturated solution to obtain an ammonium sulfate product and centrifugal mother liquor; the monoammonium phosphate cooling and crystallizing unit (34) is used for carrying out pH adjustment and cooling crystallization on the centrifugal mother liquor, and centrifuging the supersaturated solution to obtain a monoammonium phosphate product and a cooling mother liquor; and the compound fertilizer crystallization unit (35) is used for cooling the mother liquor and centrifuging the supersaturated solution to obtain a compound fertilizer product and a compound fertilizer mother liquor.
5. The iron phosphate wastewater zero-discharge treatment system according to claim 4, characterized in that: the washing wastewater treatment section (1) also comprises a product water refining RO unit (15), wherein the product water refining RO unit (15) is used for washing a fresh water solution, a mother liquid fresh water solution, a condensate of a concentration evaporation unit (32), a condensate of an ammonium sulfate crystallization unit (33) and a condensate of a compound fertilizer crystallization unit (35) and generating refined concentrated water and refined produced water; the refined concentrated water returns to the first material separation membrane unit (14), and the refined produced water returns to the iron phosphate preparation device.
6. The iron phosphate wastewater zero-discharge treatment system according to claim 1, characterized in that: the first sedimentation tank (11) is an inclined plate sedimentation tank, and the second sedimentation tank (21) and the hardness removing sedimentation tank (31) are inclined plate sedimentation tanks.
7. The treatment process of the iron phosphate wastewater zero-discharge treatment system according to claim 1, characterized by comprising the following steps: the method comprises the following steps:
s1, pretreatment of washing wastewater and membrane concentration process: the wastewater is lifted into a first sedimentation tank (11) by a pump, and suspended matters in the washing wastewater are removed in the first sedimentation tank (11) in a standing mode; washing wastewater enters a first V-shaped filter tank (12) from a first sedimentation tank (11) in a self-flowing mode, and impurities in the washing wastewater are removed in the first V-shaped filter tank (12) in a filtering mode; the washing wastewater is lifted by a first V-shaped filter (12) through a pump, enters a first UF unit (13), removes micro impurities in the washing wastewater, enters a first material separation membrane unit (14), and is concentrated in a separation and concentration mode to obtain washing concentrated solution and washing fresh water solution;
s2, mother liquor pretreatment and membrane concentration working procedures: mixing the washing concentrated solution and the mother solution to obtain a mixed solution, lifting the mixed solution to a second sedimentation tank (21) by a pump, and removing suspended matters in the mixed solution in a standing mode; the mixed liquid enters a second V-shaped filter tank (22) from a second sedimentation tank (21) in a self-flowing mode, and suspended matters in the mixed liquid are removed in the second V-shaped filter tank (22) in a filtering mode; the washing wastewater is lifted by a second V-shaped filter (22) through a pump and enters a second UF unit (23) to remove micro impurities in the washing wastewater, then a second material separation membrane unit (24) is used for separating and concentrating mixed liquid to obtain mother liquid concentrated solution and mother liquid fresh water solution, and the mother liquid concentrated solution enters a hardness removal sedimentation tank (31) for continuous treatment;
s3, hard sediment removal step: ammonia water or liquid ammonia is added into the de-hardening sedimentation tank (31) to adjust the pH value of the mother liquor concentrated solution to 8-9 so as to form magnesium ammonium phosphate sediment;
s4, evaporation and concentration step: the mother liquor concentrated solution after hardness removal is heated and evaporated by a concentrated solution evaporation unit (32), the concentrated solution of the mother liquor is evaporated after reaching the boiling point to obtain high-concentration evaporation mother liquor, and the high-concentration evaporation mother liquor enters an ammonium sulfate crystallization unit (33);
s5, ammonium sulfate crystallization step: heating and evaporating the high-concentration evaporation mother liquor through an ammonium sulfate crystallization evaporator, continuously concentrating the high-concentration evaporation mother liquor to form a supersaturated ammonium sulfate solution, centrifuging and drying the supersaturated ammonium sulfate solution to obtain an ammonium sulfate product and a centrifugal mother liquor, and feeding the centrifugal mother liquor into a monoammonium phosphate cooling and crystallizing unit (34);
s6, monoammonium phosphate crystallization step: after the pH value of the centrifugal mother liquor is adjusted to 5-6, cooling and crystallizing the centrifugal mother liquor through a cooling crystallizer to separate out monoammonium phosphate crystals, and centrifuging the monoammonium phosphate crystals to obtain monoammonium phosphate products and cooling mother liquor;
s7, compound fertilizer crystallization process: and (3) heating and evaporating the cooled mother liquor through a compound fertilizer evaporator to form a mixed supersaturated solution of ammonium sulfate and monoammonium phosphate, allowing the mixed supersaturated solution of ammonium sulfate and monoammonium phosphate to pass through a compound fertilizer centrifuge to obtain a compound fertilizer product and a compound fertilizer mother liquor, and allowing the compound fertilizer mother liquor to pass through a compound fertilizer mother liquor dryer to produce a compound fertilizer.
8. The treatment process of the iron phosphate wastewater zero-discharge treatment system according to claim 7, characterized in that: in the step S1), the operating pH of the first material separation membrane unit (14) and the product water refining RO unit (15) is 4-5.
9. The treatment process of the iron phosphate wastewater zero-discharge treatment system according to claim 7, characterized in that: in the step S2), the salt content of the mother liquor concentrated solution is more than or equal to 180000mg/L, and the operating pH value of the second material separation membrane unit (24) is 4-5.
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