CN115259516A - Iron phosphate wastewater zero-discharge treatment system and process - Google Patents
Iron phosphate wastewater zero-discharge treatment system and process Download PDFInfo
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- CN115259516A CN115259516A CN202210890848.0A CN202210890848A CN115259516A CN 115259516 A CN115259516 A CN 115259516A CN 202210890848 A CN202210890848 A CN 202210890848A CN 115259516 A CN115259516 A CN 115259516A
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- 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
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- 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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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- 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
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/20—Heavy metals or heavy metal compounds
- C02F2101/203—Iron or iron compound
Abstract
The invention discloses a ferric phosphate wastewater zero-discharge treatment system and a process, wherein the washing wastewater treatment section sequentially comprises a washing wastewater precipitation unit, a washing wastewater filtering unit, a washing wastewater ultrafiltration unit, a pre-concentration RO1 unit, a pre-concentration RO2 unit and a product water RO unit; the mother liquor treatment section sequentially comprises a synthetic mother liquor precipitation unit, a synthetic mother liquor filtration unit, a synthetic mother liquor ultrafiltration unit and a synthetic mother liquor RO concentration unit; the production section of the product salt sequentially comprises a concentration evaporation unit, an ammonium sulfate crystallization unit, an ammonium dihydrogen phosphate cooling crystallization unit and a compound fertilizer crystallization unit. Through the optimized combination of the process flows, the continuous, stable and efficient operation of the reverse osmosis system is ensured, the recovery rate of water resources is over 97.5 percent, the production of high-added-value product salts such as ammonium sulfate, ammonium dihydrogen phosphate and the like is realized, the yield of the product salts is over 80 percent, and the resource recycling is effectively realized.
Description
Technical Field
The invention relates to the technical field of industrial wastewater treatment, in particular to a ferric phosphate wastewater zero-discharge treatment system and a ferric phosphate wastewater zero-discharge treatment process in a ferric ammonium phosphate process.
Background
Under the strict policy of 'double-carbon emission reduction' in China, the use amount of new energy automobiles is increasing. The novel lithium battery is a power source of the new energy automobile. Because of low manufacturing cost and high product quality, lithium iron phosphate gradually becomes a mainstream product of the lithium battery anode material.
The ferric phosphate is a pre-driving product for synthesizing the lithium iron phosphate, and the process for preparing the lithium iron phosphate by the ferric phosphate is mature and reliable, has high utilization rate of raw materials, and gradually develops into the mainstream process for preparing the lithium iron phosphate. The current common process for industrially producing ferric phosphate is synthesized by reacting ferrous salt (such as ferrous sulfate) with ammonium hydrogen phosphate, phosphoric acid, ammonia water, hydrogen peroxide and the like, the environment for producing the ferric phosphate in the process is an acidic environment, and the generated acidic wastewater mainly comprises two parts: after raw materials of phosphate and ferric salt solution are mixed and react, the reaction slurry is subjected to filter pressing by a diaphragm to form a synthesis mother solution; the ferric phosphate filter cake is washed and purified by demineralized water to generate washing wastewater, the salt content of the washing wastewater is higher and is generally 55000-65000 mg/L, the salt content of the washing wastewater is lower and is generally 12000-15000 mg/L, the main components of the two streams of wastewater are mainly sulfate radicals, hydrogen phosphate radicals and ammonium radicals, and the washing wastewater contains heavy metal impurities such as calcium, magnesium, manganese, iron, nickel and the like. How to reasonably and effectively treat the waste water becomes a key link in enterprise production, and the waste water is an important treatment unit for controlling the cost of the iron phosphate industry in the future.
Disclosure of Invention
In order to reduce the environmental protection risk in the production process of enterprises and simultaneously realize the recycling of resources to bring certain byproduct economic benefits to the production of the enterprises, the invention provides the iron phosphate wastewater zero-discharge treatment system and process capable of ensuring the recovery of fresh water resources and chemical material (P, N and S) resources.
The application provides a zero discharge treatment system for iron phosphate wastewater, which comprises a washing wastewater treatment section, a synthetic mother liquor treatment section and a product salt production section; the washing wastewater treatment section sequentially comprises a washing wastewater precipitation unit, a washing wastewater filtering unit, a washing wastewater ultrafiltration unit, a pre-concentration RO1 unit and a pre-concentration RO2 unit, and all adjacent units are communicated through pipelines and conveyed through a water pump; the mother liquor treatment section sequentially comprises a synthetic mother liquor precipitation unit, a synthetic mother liquor filtration unit, a synthetic mother liquor ultrafiltration unit and a synthetic mother liquor RO concentration unit, and all adjacent units are communicated through a pipeline and conveyed through a water pump; the production section of the product salt sequentially comprises a concentration evaporation unit, an ammonium sulfate crystallization unit, an ammonium dihydrogen phosphate cooling crystallization unit and a compound fertilizer crystallization unit, and all adjacent units are communicated through pipelines and conveyed through a pump.
Furthermore, the washing wastewater precipitation unit is used for carrying out heavy precipitation on the washing wastewater and removing suspended matters in the washing wastewater, and the washing wastewater filtering unit is used for receiving the precipitated washing wastewater discharged by the washing wastewater precipitation unit and removing impurities in the washing wastewater; the washing wastewater ultrafiltration unit is used for receiving the clean filtrate filtered by the washing wastewater filtration unit and removing micro impurities in the washing wastewater; the pre-concentration RO1 unit is used for concentrating and desalting the washing wastewater after removing the micro impurities and generating pre-concentration RO1 concentrated water and pre-concentration RO1 fresh water, the pre-concentration RO1 concentrated water enters the pre-concentration RO2 unit for membrane separation and re-concentration to generate pre-concentration RO2 concentrated water and pre-concentration RO2 fresh water, and the pre-concentration RO2 concentrated water is conveyed to the synthetic mother liquor precipitation unit.
Further, the synthetic mother liquor precipitation unit is used for receiving the synthetic mother liquor wastewater and the pre-concentrated RO2 concentrated water, and removing heavy metals and suspended matters in the mixed liquor; the synthesis mother liquor filtering unit is used for receiving the precipitated mixed liquor discharged by the synthesis mother liquor precipitating unit and removing impurities in the mixed liquor; the synthesis mother liquor ultrafiltration unit is used for receiving the clean filtrate filtered by the synthesis mother liquor filtration unit and intercepting and removing micro impurities in the mixed liquor through an ultrafiltration membrane; the synthesis mother liquor RO concentration unit carries out mother liquor membrane separation concentration on the mixed liquid after the micro impurities are removed to generate mother liquor concentrated water and mother liquor fresh water, and the mother liquor concentrated water is conveyed to the concentration evaporation unit.
Further, the concentration evaporation unit is used for heating and evaporating the mother liquor concentrated water 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 ammonium dihydrogen phosphate cooling and crystallizing unit is used for carrying out pH adjustment and cooling crystallization on the centrifugal mother liquor, and centrifuging the supersaturated solution to obtain an ammonium dihydrogen 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 RO unit, wherein the product water RO unit is used for pre-concentrating RO1 fresh water, pre-concentrating RO2 fresh water, mother liquor fresh water, condensate of the concentration evaporation unit, condensate of the ammonium sulfate crystallization unit and condensate of the compound fertilizer crystallization unit, and generating concentrated water and qualified product water; the concentrated water returns to the pre-concentration RO1 unit, and the qualified product water returns to the iron phosphate preparation device.
Furthermore, the washing wastewater precipitation unit and the synthetic mother liquor precipitation unit are both efficient sedimentation tanks.
Also provides a process of the iron phosphate wastewater zero-discharge treatment system:
s1, pretreatment of washing wastewater and membrane concentration: pumping the washing wastewater into a washing wastewater precipitation unit, and removing heavy metal ions and suspended matters in the washing wastewater precipitation unit in a pH (potential of hydrogen) adjustment to alkalinity and coagulating sedimentation mode; the washing wastewater precipitated by the washing wastewater precipitation unit is adjusted back to weak acidity through pH, enters the washing wastewater filtering unit, and is filtered to remove impurities in the washing wastewater filtering unit; the washing wastewater is lifted by the washing wastewater filtering unit through a pump, enters the washing wastewater ultrafiltration unit, removes micro impurities in the washing wastewater, enters the pre-concentration RO1 unit, concentrates the washing wastewater in a separation and concentration mode, obtains pre-concentration RO1 concentrated water and pre-concentration RO1 fresh water, enters the pre-concentration RO2 unit, and further carries out membrane concentration and separation to obtain pre-concentration RO2 concentrated water and pre-concentration RO2 fresh water;
s2, mother liquor pretreatment and membrane concentration: combining the pre-concentrated RO2 concentrated water and the synthetic mother liquor wastewater to obtain a mixed liquid, lifting the mixed liquid to a synthetic mother liquor precipitation unit through a pump, and removing heavy metal ions and suspended matters in the washing wastewater through pH adjustment to alkalinity and a coagulating sedimentation mode; the pH of the mixed liquid precipitated by the synthetic mother liquid precipitation unit is adjusted back to weak acidity and enters the synthetic mother liquid filtration unit, and suspended matters in the mixed liquid are removed in the synthetic mother liquid filtration unit in a filtration mode; the mixed liquor is lifted by a synthetic mother liquor filtering unit through a pump, enters a synthetic mother liquor ultrafiltration unit, removes micro impurities in the mixed liquor, then is separated and concentrated by a synthetic mother liquor RO concentration unit to obtain mother liquor concentrated water and mother liquor fresh water, and the mother liquor concentrated water enters a concentration evaporation unit for continuous treatment;
s3, an evaporation concentration process: heating and evaporating mother liquor concentrated water through a concentrated liquor evaporation unit, evaporating the mother liquor concentrated water after the mother liquor concentrated water reaches a boiling point to obtain high-concentration evaporation mother liquor, and feeding the high-concentration evaporation mother liquor into an ammonium sulfate crystallization unit;
s4, 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 an ammonium dihydrogen phosphate cooling and crystallizing unit;
s5, ammonium dihydrogen phosphate crystallization process: 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 ammonium dihydrogen phosphate crystals, and centrifuging the ammonium dihydrogen phosphate crystals to obtain an ammonium dihydrogen phosphate product and a cooling mother liquor;
s6, 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 ammonium dihydrogen phosphate, allowing the mixed supersaturated solution of ammonium sulfate and ammonium dihydrogen 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 running pH of the pre-concentrated RO1 unit and the running pH of the pre-concentrated RO2 unit are 4-5, and the running pH of the product water RO unit is 6-7.
Further, in the step S2), the salt content of the mother liquor concentrated water is more than or equal to 160000mg/L, and the running pH of the synthetic mother liquor RO concentration unit is 4-5.
In summary, the present application includes at least the following advantageous technical effects:
1. the system can continuously, stably and efficiently treat the iron phosphate wastewater to produce the magnesium ammonium phosphate compound fertilizer, the ammonium sulfate evaporation crystallization process produces the I-type index product which meets GBT535-2020 Fertilizer and ammonium sulfate, the ammonium dihydrogen phosphate cooling crystallization process is arranged to produce the ammonium dihydrogen phosphate product with the purity of more than 90 percent, and the compound fertilizer can be used as a raw material for recycling, so that the resource recycling is realized to the maximum extent;
2. a large amount of condensate is generated in the evaporation and crystallization process, and the condensate is subjected to reverse osmosis separation by a product water 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. by optimizing and combining the process flow, the continuous, stable and efficient operation of a reverse osmosis system is ensured, the recovery rate of water resources is over 97.5 percent, the production of high-added-value product salts such as ammonium sulfate, ammonium dihydrogen phosphate and the like is realized, the yield of the product salts is over 80 percent, and the resource recycling is effectively realized.
Drawings
Fig. 1 is a structural block diagram of a zero discharge treatment system for iron phosphate wastewater according to the present invention.
Reference numerals are as follows: 1. a washing wastewater treatment section; 11. a washing wastewater precipitation unit; 12. a washing wastewater filtering unit; 13. a washing wastewater ultrafiltration unit; 14. a pre-concentration RO1 unit; 15. a product water RO unit; 16. a pre-concentration RO2 unit; 2. a synthetic mother liquor treatment section; 21. a synthetic mother liquor precipitation unit; 22. a synthesis mother liquor filtering unit; 23. a synthetic mother liquor ultrafiltration unit; 24. a synthesis mother liquor RO concentration unit; 3. a product salt production section; 31. a concentrated solution evaporation unit; 32. an ammonium sulfate evaporative crystallization unit; 33. ammonium dihydrogen phosphate cools the crystallization unit; 34. and (5) a compound fertilizer evaporation and 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 process system shown in fig. 1 comprises a washing wastewater treatment section 1, a synthetic mother liquor treatment section 2 and a product salt production section 3.
The washing wastewater treatment section 1 comprises a washing wastewater precipitation unit 11, a washing wastewater filtering unit 12, a washing wastewater ultrafiltration unit 13, a pre-concentration RO1 unit 14, a product water RO unit 15 and a pre-concentration RO2 unit 16 in sequence, and all adjacent units are communicated through pipelines and conveyed through a water pump. The washing wastewater precipitation unit 11 is used for removing heavy metal ions from the washing wastewater and removing suspended matters in the washing wastewater, and the washing wastewater precipitation unit 11 is a high-efficiency precipitation tank in the embodiment of the application; the washing wastewater filtering unit 12 is used for receiving the precipitated washing wastewater discharged by the washing wastewater precipitating unit 11 and further removing impurities in the precipitated washing wastewater; the washing wastewater ultrafiltration unit 13 (ultrafiltration membrane unit) is used for receiving the washing wastewater filtered by the washing wastewater filtration unit 12 and removing micro impurities in the filtered washing wastewater; the pre-concentration RO1 unit 14 is used for pre-concentrating and desalting the washing wastewater after removing the micro impurities and generating pre-concentration RO1 concentrated water and pre-concentration RO1 fresh water, and conveying the pre-concentration RO1 concentrated water to the pre-concentration RO2 unit 16 for re-concentrating and desalting and generating pre-concentration RO2 concentrated water and pre-concentration RO2 fresh water, and conveying the pre-concentration RO2 concentrated water to the synthetic mother liquor treatment section 2; the product water RO unit 15 processes fresh water generated by each stage of RO unit and condensate generated by the evaporation crystallization section 3 in a reverse osmosis mode to generate concentrated water and qualified product water. The concentrated water returns to the pre-concentration RO1 unit 14 again through the pipeline and the delivery pump, and the qualified product water returns to the iron phosphate preparation device through the pipeline and the delivery pump, so that the consumption of the iron phosphate preparation device on fresh water is saved, and the demand of enterprises on external water resources is reduced.
The synthetic mother liquor treatment section 2 comprises a synthetic mother liquor precipitation unit 21, a synthetic mother liquor filtration unit 22, a synthetic mother liquor ultrafiltration unit 23 and a synthetic mother liquor RO concentration unit 24 in sequence, and all adjacent units are communicated through pipelines and conveyed through water pumps. The synthetic mother liquor precipitation unit 21 is configured to receive the synthetic mother liquor wastewater and the pre-concentrated RO2 concentrated water, and remove heavy metal ions and suspended solids in the mixed liquor, in this embodiment, the synthetic mother liquor precipitation unit 21 is a high-efficiency precipitation tank; the synthesis mother liquor filtering unit 22 is used for receiving the mixed liquor discharged by the synthesis mother liquor precipitation unit 21 after being lined and further removing impurities in the mixed liquor; the synthesis mother liquor ultrafiltration unit 23 is used for receiving the mixed liquor filtered by the synthesis mother liquor filtration unit 22 and removing the micro impurities in the mixed liquor in an ultrafiltration mode; the synthesis mother liquor RO concentration unit 24 performs mother liquor membrane separation concentration on the mixed liquid after the removal of the micro impurities and generates mother liquor concentrated water and mother liquor fresh water, the mother liquor concentrated water is conveyed to the product salt production section 3 for the production of byproducts, and the mother liquor fresh water is conveyed to the product water RO unit 15 for separation of concentrated water and qualified product water.
The product salt production section 3 comprises a concentration evaporation unit 31, an ammonium sulfate crystallization unit 32, an ammonium dihydrogen phosphate cooling crystallization unit 33 and a compound fertilizer crystallization unit 34 in sequence, and all adjacent units are communicated through pipelines and conveyed through a water pump. The concentration evaporation unit 31 is used for heating and evaporating the mother liquor concentrated water 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 after heat is recycled, the generated condensate is conveyed to the product water RO unit 15 to separate out concentrated water and qualified 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 32 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 ammonium dihydrogen phosphate cooling and crystallizing unit 33 is used for carrying out pH adjustment and cooling crystallization on the centrifugal mother liquor, and centrifuging the supersaturated solution to obtain an ammonium dihydrogen phosphate product and a cooling mother liquor; the compound fertilizer evaporation and crystallization unit 34 is used for crystallizing the cooled mother liquor and centrifuging the supersaturated solution to obtain a compound fertilizer product (namely ammonium sulfate + ammonium dihydrogen phosphate compound fertilizer) and a compound fertilizer mother liquor.
In the present embodiment, the concentration evaporation unit 31 may employ one or more of a feed preheater, a rising film evaporator, and a falling film evaporator. The ammonium sulfate crystallization unit 32 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 RO unit 15 to separate out concentrated water and qualified 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. The ammonium dihydrogen phosphate cooling and crystallizing unit 33 sequentially comprises a pH adjusting unit, a cooling crystallizer, an ammonium dihydrogen phosphate thickener, an ammonium dihydrogen phosphate centrifuge and a tail gas processor, wherein the ammonium dihydrogen phosphate centrifuge and the tail gas processor can be selected by referring to the ammonium sulfate crystallizing unit 32. The compound fertilizer crystallization unit 34 sequentially comprises a compound fertilizer evaporator, a compound fertilizer thickener, a compound fertilizer centrifuge, a compound fertilizer mother liquor dryer and a tail gas treater, the compound fertilizer evaporator, the compound fertilizer centrifuge and the tail gas treater can refer to the ammonium sulfate crystallization unit 32, condensate generated by the compound fertilizer evaporator is conveyed to the product water RO unit 15 to separate out concentrated water and qualified product water, and the compound fertilizer mother liquor enters the compound fertilizer mother liquor dryer to obtain the compound fertilizer (mixed with compound fertilizer products obtained by centrifugation).
The iron phosphate wastewater zero-discharge treatment process system comprises the following steps:
s1, pretreatment of washing wastewater and membrane concentration: the washing wastewater of the iron phosphate device firstly enters an adjusting tank for homogenizing and equalizing the quantity, is lifted into a washing wastewater precipitation unit 11 by a pump, and is adjusted to be alkaline (pH is 9-10.5) in the washing wastewater precipitation unit 11 by pH, so as to remove heavy metal ions and suspended matters; the washing wastewater precipitated by the washing wastewater precipitation unit 11 enters the washing wastewater filtering unit 12 after the pH is adjusted back (pH: 4-5), and impurities in the washing wastewater are removed in the washing wastewater filtering unit 12 in a filtering mode (suspended matters in the effluent of the washing wastewater filtering unit 12 are below 3 mg/L); the filtrate of the washing wastewater filtering unit 12 is lifted by a water pump to enter a washing wastewater ultrafiltration unit 13 and remove pollutants such as micro impurities in the filtrate (the turbidity of the effluent of the washing wastewater ultrafiltration unit 13 is 0.2 NTU); the effluent enters a pre-concentration RO1 unit 14 after being pressurized by a lift pump and a high-pressure pump, washing wastewater is concentrated in a separation and concentration mode to obtain pre-concentration RO1 concentrated water and pre-concentration RO1 fresh water, the pre-concentration RO1 concentrated water enters a pre-concentration RO2 unit 16 for membrane separation and re-concentration to obtain pre-concentration RO2 concentrated water and pre-concentration RO2 fresh water, the concentrated RO2 concentrated water enters a synthetic mother liquor precipitation unit 21, the pre-concentration RO2 fresh water and the pre-concentration RO1 fresh water are combined and then enter a product water RO unit 15 for refined desalination treatment, the operating pH of the pre-concentration RO1 unit 14 and the pre-concentration RO2 unit 16 is 4-5, and the operating pH of the product water RO unit 15 is 6-7.
S2, mother liquor pretreatment and membrane concentration: combining the pre-concentrated RO2 concentrated water and the synthetic mother liquor wastewater, feeding the combined water and the synthetic mother liquor wastewater into a mother liquor regulating tank to obtain mixed liquid, homogenizing and homogenizing the mixed liquid, lifting the mixed liquid to a synthetic mother liquor precipitation unit 21 through a pump, regulating the pH value to be alkaline (the pH value is 9-10.5), and removing heavy metal ions and suspended matters; the mixed liquid precipitated by the synthetic mother liquid precipitation unit 21 enters the synthetic mother liquid filtering unit 22 after the pH is adjusted back (pH: 4-5), and suspended matters in the mixed liquid are removed in the synthetic mother liquid filtering unit 22 in a filtering mode (the effluent suspended matters of the synthetic mother liquid filtering unit 22 are below 3 mg/L); the filtrate of the synthesis mother liquor filtering unit 22 is lifted by a water pump to enter the synthesis mother liquor ultrafiltration unit 23 and remove the pollutants such as micro impurities in the filtrate (the turbidity of the outlet water of the synthesis mother liquor ultrafiltration unit 23 is 0.2 NTU); the filtrate of the synthetic mother liquor ultrafiltration unit 23 enters the synthetic mother liquor RO concentration unit 24 through the pressurization of a water pump and a high-pressure pump for separation and concentration to obtain mother liquor concentrated water (the salt content of the mother liquor concentrated water is more than or equal to 160000 mg/L) and mother liquor fresh water, the mother liquor concentrated water enters the rear-end evaporation concentration unit 31, the mother liquor fresh water enters the front-end product water RO unit 15 for further desalination, and the operating pH of the synthetic mother liquor RO concentration unit 24 is 4-5.
S3, an evaporation concentration process: the mother liquor concentrated water enters a concentrated liquor evaporation unit 31 for temperature rise evaporation after pH adjustment (neutral working condition), the mother liquor concentrated water starts to evaporate after reaching a boiling point, the mother liquor concentrated water is continuously concentrated and reaches a set concentration, the high-concentration evaporation mother liquor enters an ammonium sulfate crystallization unit 32 (the outlet water temperature of the high-concentration evaporation mother liquor is 99-103 ℃), and steam is condensed to form condensate and enters a product water RO unit 15.
S4, 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 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 the solution 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 an ammonium dihydrogen phosphate cooling and crystallizing unit 33;
s5, ammonium dihydrogen phosphate crystallization process: regulating the pH value of the centrifugal mother liquor to 5-6 by phosphoric acid, then cooling and crystallizing by a cooling crystallizer (the operation temperature of the cooling crystallizer is 38-42 ℃), gradually separating out ammonium dihydrogen phosphate crystals along with temperature reduction by utilizing the characteristic that the solubility difference is caused by the temperature change of ammonium dihydrogen phosphate and ammonium sulfate, pressurizing and conveying to an ammonium dihydrogen phosphate thickener by a discharge pump to regulate the quality of crystalline salt, and centrifuging by an ammonium dihydrogen phosphate centrifuge to obtain an ammonium dihydrogen phosphate product and the cooling mother liquor;
s6, compound fertilizer crystallization process: the cooled 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 ammonium dihydrogen phosphate, steam is condensed to form a condensate liquid and enters a product water RO unit 15, the mixed supersaturated solution of ammonium sulfate and ammonium dihydrogen 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 passes through a compound fertilizer mother liquor dryer to produce a compound fertilizer, and condensate water formed in the drying process enters the product water 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 ferric phosphate wastewater zero-discharge treatment process system capable of continuously, stably and efficiently running; meanwhile, the ammonium sulfate crystallization process produces products meeting GBT535-2020 type I index of fertilizer and ammonium sulfate, the ammonium dihydrogen phosphate cooling crystallization process produces ammonium dihydrogen phosphate products with purity higher than 90%, the compound fertilizer crystallization process produces compound fertilizer products, and the ammonium sulfate, the ammonium dihydrogen phosphate and the compound fertilizer products have higher market values, 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 synthetic mother liquor treatment working section (2) and a product salt production working section (3); the washing wastewater treatment section (1) sequentially comprises a washing wastewater precipitation unit (11), a washing wastewater filtering unit (12), a washing wastewater ultrafiltration unit (13), a pre-concentration RO1 unit (14) and a pre-concentration RO2 unit (16), and all adjacent units are communicated through pipelines and conveyed through a water pump; the mother liquor treatment section (2) sequentially comprises a synthetic mother liquor precipitation unit (21), a synthetic mother liquor filtration unit (22), a synthetic mother liquor ultrafiltration unit (23) and a synthetic mother liquor RO concentration unit (24), and all adjacent units are communicated through pipelines and conveyed through a water pump; the product salt production section (3) comprises a concentration evaporation unit (31), an ammonium sulfate crystallization unit (32), an ammonium dihydrogen phosphate cooling crystallization unit (33) and a compound fertilizer crystallization unit (34) in sequence, and all adjacent units are communicated through pipelines and conveyed through a pump.
2. The iron phosphate wastewater zero-discharge treatment system according to claim 1, characterized in that: the washing wastewater precipitation unit (11) is used for carrying out heavy precipitation on the washing wastewater and removing suspended matters in the washing wastewater, and the washing wastewater filtering unit (12) is used for receiving the precipitated washing wastewater discharged by the washing wastewater precipitation unit (11) and removing impurities in the washing wastewater; the washing wastewater ultrafiltration unit (13) is used for receiving the clean filtrate filtered by the washing wastewater filtration unit (12) and removing micro impurities in the washing wastewater; the pre-concentration RO1 unit (14) is used for concentrating and desalting the washing wastewater after removing the micro impurities and generating pre-concentration RO1 concentrated water and pre-concentration RO1 fresh water, the pre-concentration RO1 concentrated water enters the pre-concentration RO2 unit (16) for membrane separation and re-concentration to generate pre-concentration RO2 concentrated water and pre-concentration RO2 fresh water, and the pre-concentration RO2 concentrated water is conveyed to the synthetic mother liquor precipitation unit (21).
3. The iron phosphate wastewater zero-discharge treatment system according to claim 2, characterized in that: the synthetic mother liquor precipitation unit (21) is used for receiving the synthetic mother liquor wastewater and the pre-concentrated RO2 concentrated water and removing heavy metals and suspended matters in the mixed liquor; the synthesis mother liquor filtering unit (22) is used for receiving the precipitated mixed liquor discharged by the synthesis mother liquor precipitating unit (21) and removing impurities in the mixed liquor; the synthesis mother liquor ultrafiltration unit (23) is used for receiving the clean filtrate filtered by the synthesis mother liquor filtration unit (22) and intercepting and removing tiny impurities in the mixed liquor through an ultrafiltration membrane; the synthesis mother liquor RO concentration unit (24) performs mother liquor membrane separation concentration on the mixed liquid after the removal of the micro impurities to generate mother liquor concentrated water and mother liquor fresh water, and the mother liquor concentrated water is conveyed to the concentration evaporation unit (31).
4. The iron phosphate wastewater zero-discharge treatment system according to claim 3, characterized in that: the concentration evaporation unit (31) is used for heating and evaporating mother liquor concentrated water and preparing high-concentration evaporation mother liquor; the ammonium sulfate crystallization unit (32) 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 ammonium dihydrogen phosphate cooling and crystallizing unit (33) is used for carrying out pH adjustment and cooling crystallization on the centrifugal mother liquor, and centrifuging the supersaturated solution to obtain an ammonium dihydrogen phosphate product and a cooling mother liquor; and the compound fertilizer crystallization unit (34) 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 RO unit (15), wherein the product water RO unit (15) is used for pre-concentrating RO1 fresh water, pre-concentrating RO2 fresh water, mother liquor fresh water, condensate of the concentration evaporation unit (31), condensate of the ammonium sulfate crystallization unit (32) and condensate of the compound fertilizer crystallization unit (34), and generating concentrated water and qualified product water; the concentrated water returns to the pre-concentration RO1 unit (14), and the qualified product 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 washing wastewater precipitation unit (11) and the synthetic mother liquor precipitation unit (21) are efficient precipitation tanks.
7. The process of the iron phosphate wastewater zero-discharge treatment system according to claim 1, characterized in that:
s1, pretreatment of washing wastewater and membrane concentration: the washing wastewater is lifted into a washing wastewater precipitation unit (11) by a pump, and heavy metal ions and suspended matters in the washing wastewater are removed in the washing wastewater precipitation unit (11) by adjusting the pH value to be alkaline and in a coagulating sedimentation mode; the washing wastewater precipitated by the washing wastewater precipitation unit (11) is adjusted back to weak acidity through pH, enters the washing wastewater filtering unit (12), and is filtered in the washing wastewater filtering unit (12) to remove impurities in the washing wastewater; the washing wastewater is lifted by a washing wastewater filtering unit (12) through a pump and enters a washing wastewater ultrafiltration unit (13), micro impurities in the washing wastewater are removed, the washing wastewater enters a pre-concentration RO1 unit (14), the washing wastewater is concentrated in a separation and concentration mode, pre-concentration RO1 concentrated water and pre-concentration RO1 fresh water are obtained, the pre-concentration RO1 concentrated water enters a pre-concentration RO2 unit (16), membrane concentration and separation are further carried out, and pre-concentration RO2 concentrated water and pre-concentration RO2 fresh water are obtained;
s2, mother liquor pretreatment and membrane concentration: combining the pre-concentrated RO2 concentrated water and the synthetic mother liquor wastewater to obtain mixed liquid, and lifting the mixed liquid to a synthetic mother liquor precipitation unit (21) through a pump to remove heavy metal ions and suspended matters in the washing wastewater in a pH adjustment to alkalinity and a coagulating sedimentation mode; the pH of the mixed liquid precipitated by the synthetic mother liquid precipitation unit (21) is adjusted back to weak acidity and then enters the synthetic mother liquid filtration unit (22), and suspended matters in the mixed liquid are removed in the synthetic mother liquid filtration unit (22) in a filtration mode; the mixed liquor is lifted by a synthetic mother liquor filtering unit (22) through a pump and enters a synthetic mother liquor ultrafiltration unit (23), micro impurities in the mixed liquor are removed, then the mixed liquor is separated and concentrated through a synthetic mother liquor RO concentration unit (24), mother liquor concentrated water and mother liquor fresh water are obtained, and the mother liquor concentrated water enters a concentration evaporation unit (31) for continuous treatment;
s3, an evaporation concentration process: the mother liquor concentrated water is heated and evaporated through a concentrated liquor evaporation unit (31), the mother liquor concentrated water starts to be 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 (32);
s4, ammonium sulfate crystallization step: the high-concentration evaporation mother liquor is heated and evaporated through an ammonium sulfate crystallization evaporator, the high-concentration evaporation mother liquor is continuously concentrated to form a supersaturated ammonium sulfate solution, the supersaturated ammonium sulfate solution is centrifuged and dried to obtain an ammonium sulfate product and a centrifugal mother liquor, and the centrifugal mother liquor enters an ammonium dihydrogen phosphate cooling and crystallizing unit (33);
s5, ammonium dihydrogen phosphate crystallization process: 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 ammonium dihydrogen phosphate crystals, and centrifuging the ammonium dihydrogen phosphate crystals to obtain an ammonium dihydrogen phosphate product and a cooling mother liquor;
s6, 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 ammonium dihydrogen phosphate, allowing the mixed supersaturated solution of ammonium sulfate and ammonium dihydrogen 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 process of the iron phosphate wastewater zero-discharge treatment system according to claim 7, characterized in that: in the step S1), the running pH of the pre-concentrated RO1 unit (14) and the pre-concentrated RO2 unit (16) is 4-5, and the running pH of the product water RO unit (15) is 6-7.
9. The 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 water is more than or equal to 160000mg/L, and the running pH of the synthetic mother liquor RO concentration unit (24) is 4-5.
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| CN115818599A (en) * | 2022-12-29 | 2023-03-21 | 四川安宁铁钛股份有限公司 | Method for recycling wastewater generated in iron phosphate production |
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