Phosphoric acid iron wastewater treatment method and phosphoric acid iron wastewater treatment system

Abstract

This application relates to the field of industrial wastewater treatment, and particularly to a method and a system for treating iron phosphate wastewater. The method for treating iron phosphate wastewater includes: after the washing water is pretreated and filtered, it is conveyed to a circulating concentration membrane system to obtain the concentrated water of the washing water; after the second mother liquor is pretreated and filtered, it is mixed with the concentrated water of the washing water and conveyed to a high-fold concentration membrane system to obtain a concentrated solution; the concentrated solution is subjected to MVR evaporation treatment to obtain ammonium sulfate and centrifugal mother liquor; the first mother liquor and the centrifugal mother liquor are mixed, the mixture of the first mother liquor and the centrifugal mother liquor is pretreated and filtered, and the pretreated and filtered mixture is subjected to MVR evaporation treatment. This application mixes the first mother liquor with the MVR centrifugal mother liquor for treatment, which can improve the removal rate of impurity elements and the quality of ammonium sulfate. Moreover, this application does not require the concentration treatment of the first mother liquor, reduces the treatment process of the membrane system, and has the advantage of low energy consumption.

Description

Technical Field

[0001] This application relates to the field of industrial wastewater treatment, and particularly to a method and a system for treating iron phosphate wastewater. Background Art

[0002] A large amount of iron phosphate wastewater is generated during the production of iron phosphate. The iron phosphate wastewater contains heavy metals, phosphorus, and other inorganic salts, which will seriously pollute the environment.

[0003] The iron phosphate wastewater includes washing water, a first mother liquor, and a second mother liquor. Among them, the concentration of the first mother liquor is greater than that of the second mother liquor, and the concentration of the second mother liquor is greater than that of the washing water. The existing method for treating iron phosphate wastewater is to combine the first mother liquor and the second mother liquor into a mother liquor for treatment. Due to the large fluctuation in the concentration of the iron phosphate wastewater, this method has problems such as high energy consumption, low removal rate of impurity elements, and low quality of the by-product ammonium sulfate.

[0004] Therefore, it is necessary to improve the method for treating iron phosphate wastewater. Summary of the Invention

[0005] In view of the technical problems in the background art, this application provides a method and a system for treating iron phosphate wastewater. The method for treating iron phosphate wastewater has the advantages of low energy consumption, high removal rate of impurity elements, and high quality of the by-product ammonium sulfate.

[0006] In a first aspect, an embodiment of this application provides a method for treating iron phosphate wastewater. The method for treating iron phosphate wastewater includes:

[0007] After the washing water is pretreated and filtered, it is transported to a circulating concentration membrane system to obtain the concentrated water of the washing water;

[0008] After the second mother liquor is pretreated and filtered, it is mixed with the concentrated water of the washing water and transported to a high-concentration membrane system to obtain a concentrated solution;

[0009] The concentrated solution is subjected to MVR evaporation treatment to obtain ammonium sulfate and a centrifuged mother liquor;

[0010] The first mother liquor and the centrifuged mother liquor are mixed, the mixture of the first mother liquor and the centrifuged mother liquor is pretreated and filtered, and the pretreated and filtered mixture is subjected to MVR evaporation treatment.

[0011] In the technical solution of the embodiment of the present application, by combining and processing the mixed solution of the first mother liquor and the centrifuged mother liquor, the removal rate of impurity elements can be effectively improved. Specifically, the concentration of the first mother liquor is relatively high, and the content of impurity elements is also relatively high, but the content of phosphorus element is relatively low. Since the concentration of phosphorus element in the MVR centrifuged mother liquor is relatively high, after mixing the first mother liquor with the MVR centrifuged mother liquor, it is beneficial to form phosphate precipitates of metal ion impurities that are difficult to remove in the phosphoric acid iron wastewater, which is beneficial to the removal of impurity elements. That is, the method of the present application has the advantage of a high removal rate of impurity elements. Moreover, the method of the present application can also reduce the content of miscellaneous elements in the by-product ammonium sulfate (the miscellaneous elements include calcium, magnesium, manganese, iron, aluminum, phosphorus, etc.), thereby improving the quality of ammonium sulfate. In the MVR section of the method of the present application, only one kind of high-quality ammonium sulfate is produced, and no low-quality ammonium sulfate is generated. There is no need for a low-quality ammonium sulfate drying equipment, a drum dryer, which can greatly reduce energy consumption, equipment construction investment and operation costs. At the same time, it increases the output of high-quality ammonium sulfate and improves the added value of by-products. In addition, the method of the present application does not require concentration treatment of the first mother liquor, reduces the treatment process of the membrane system, reduces the investment and operation and maintenance costs of the membrane system, and has the advantage of low energy consumption.

[0012] In some embodiments, after the washing water is pretreated and filtered and then conveyed to the circulating concentration membrane system, it further includes:

[0013] Obtaining the produced water of the washing water, and conveying the produced water of the washing water to the RO system for purification treatment to obtain pure water.

[0014] In this embodiment, by further purifying the produced water of the washing water, pure water can be obtained. That is, the method of the present application can also recycle pure water and save a large amount of water resources.

[0015] In some embodiments, the treatment method further includes: conveying the concentrated water of the washing water to the circulating concentration membrane system for re-concentration treatment.

[0016] In this embodiment, by circulating and concentrating the concentrated water of the washing water, the concentration of the concentrated water of the washing water can be increased, the amount of the solution for MVR evaporation treatment is reduced, and the energy consumption is further reduced.

[0017] In some embodiments, after the second mother liquor is pretreated and filtered and then mixed with the concentrated water of the washing water and conveyed to the high-fold concentration membrane system, it further includes:

[0018] Obtaining the membrane-produced water of the high-fold concentration membrane system, mixing the membrane-produced water with the second mother liquor, re-preprocessing and filtering, and then mixing with the concentrated water of the washing water and conveying to the high-fold concentration membrane system.

[0019] In this embodiment, by pre-treating and filtering the membrane-produced water of the high-concentration membrane system, impurity ions in the membrane-produced water can be further removed, which is beneficial to further improving the quality of the finally obtained ammonium sulfate.

[0020] In a second aspect, an embodiment of the present application provides a phosphoric acid iron wastewater treatment system, which is used to execute the phosphoric acid iron wastewater treatment method as described above. The phosphoric acid iron wastewater treatment system includes: a washing water treatment device, a circulating concentration membrane system, a second mother liquor treatment device, a high-concentration membrane system, an MVR evaporator, and a first mother liquor treatment device;

[0021] The washing water treatment device is connected to the circulating concentration membrane system, the second mother liquor treatment device is connected to the high-concentration membrane system, the concentrated water outlet of the circulating concentration membrane system is communicated with the liquid inlet of the high-concentration membrane system, the liquid outlet of the high-concentration membrane system is connected to the liquid inlet of the MVR evaporator, a centrifugal mother liquor outlet is provided on the MVR evaporator, a first mother liquor inlet and a centrifugal mother liquor inlet are provided on the first mother liquor treatment device, the centrifugal mother liquor inlet is communicated with the centrifugal mother liquor outlet on the MVR evaporator, and the liquid outlet of the first mother liquor treatment device is connected to the liquid inlet of the MVR evaporator;

[0022] The washing water treatment device is used to remove metal ions in the washing water, the circulating concentration membrane system is used to perform fixed-concentration concentration treatment on the washing water after removing metal ions, the second mother liquor treatment device is used to remove metal ions in the second mother liquor, the high-concentration membrane system is used to concentrate the second mother liquor and the concentrated water of the washing water after removing metal ions to obtain a concentrated liquid, the MVR evaporator is used to process the concentrated liquid to obtain ammonium sulfate and centrifugal mother liquor, and the first mother liquor treatment device is used to remove metal ions in the first mother liquor and the centrifugal mother liquor.

[0023] In the technical solution of the embodiment of the present application, through the first mother liquor treatment device, the first mother liquor with a lower phosphorus concentration can be mixed with the centrifugal mother liquor with a higher phosphorus concentration. At a higher phosphorus concentration, metal ion impurities that are difficult to remove can form phosphate precipitates, which can effectively improve the removal rate of impurity elements, reduce the phosphorus content in the by-product ammonium sulfate, and further improve the quality of the by-product ammonium sulfate. Moreover, since the concentration of the first mother liquor is relatively high, the present application does not need to concentrate the first mother liquor. After the first mother liquor and the centrifugal mother liquor are mixed to remove impurity elements, they can be transported to the MVR evaporator for MVR evaporation treatment. The system of the present application reduces the membrane system for concentrating the first mother liquor in the traditional system and has the advantage of lower energy consumption.

[0024] In some embodiments, the circulating concentration membrane system includes a first booster pump, a first security filter, a first high-pressure pump, a first membrane module, and a concentrated water tank connected in sequence. The circulating concentration membrane system further includes a first circulation pump and a product water tank;

[0025] The first booster pump is connected to the filtrate outlet of the washing water treatment device;

[0026] The first membrane module has a concentrated water outlet and a product water outlet. The product water outlet is communicated with the product water tank, and the product water tank is connected to the RO system;

[0027] The liquid inlet of the first circulation pump is connected to the concentrated water outlet, and the liquid outlet of the first circulation pump is connected to the liquid inlet of the first membrane module. The first circulation pump can transport the solution at the concentrated water outlet to the liquid inlet of the first membrane module for re-concentration treatment.

[0028] In this embodiment, through the first circulation pump, the solution at the concentrated water outlet can be further concentrated, the concentration of the solution at the concentrated water outlet can be increased, and the concentration of the washing water concentrated water can be controlled by controlling the flow rate of the circulation pump and the flow rate of the concentrated water discharge, so as to ensure that the ammonium sulfate concentration of the washing water concentrated water is maintained at about 10%.

[0029] In some embodiments, the high-fold concentration membrane system includes a second booster pump, a second security filter, a second high-pressure pump, a second membrane module, and a concentrated liquid tank connected in sequence. The liquid outlet of the concentrated liquid tank is connected to the liquid inlet of the MVR evaporator. The high-fold concentration membrane system further includes a circulation water tank and a second circulation pump;

[0030] The second booster pump is connected to the filtrate outlet of the second mother liquor treatment device;

[0031] The second membrane module has a membrane concentrated water outlet and a membrane product water outlet. The membrane concentrated water outlet is communicated with the concentrated liquid tank;

[0032] The circulation water tank has a concentrated washing water inlet, and the concentrated washing water inlet is communicated with the concentrated water tank in the circulating concentration membrane system;

[0033] The circulation water tank is connected to the liquid inlet on the second membrane module through the second circulation pump. The membrane product water outlet is communicated with the circulation water tank. An overflow port is provided on the circulation water tank, and the overflow port is communicated with the liquid inlet of the second mother liquor treatment device.

[0034] In this embodiment, the concentrated water of the washing water is introduced into the fresh water side of the high-concentration membrane system, which can increase the concentration of the fresh water side, reduce the osmotic pressure on the fresh water side and the concentrated water side in the high-concentration membrane system, reduce the driving force of the high-concentration membrane system, and can also concentrate the feed liquid to a higher concentration. After being treated by the high-concentration membrane system, the second mother liquor and the concentrated water of the washing water can be concentrated to a concentration of ammonium sulfate above 20%. Generally speaking, the high-concentration membrane system of the present application can concentrate the second mother liquor and the concentrated water of the washing water to a higher concentration, reduce the feed liquid volume of the MVR evaporator, and further reduce the energy consumption.

[0035] In some embodiments, the first mother liquor treatment device includes a first mother liquor adjustment tank, a first mother liquor reaction sedimentation tank, a first mother liquor intermediate water tank, and a first mother liquor intermediate water tank lift pump that are connected in sequence;

[0036] The first mother liquor adjustment tank is used to store the mixed liquid of the first mother liquor and the centrifuged mother liquor. The first mother liquor reaction sedimentation tank is used to precipitate and remove metal ions in the mixed liquid. The first mother liquor intermediate water tank is connected to the filtrate outlet of the first mother liquor reaction sedimentation tank. The first mother liquor intermediate water tank is used to store the mixed liquid from which metal ions have been removed. The first mother liquor intermediate water tank lift pump is connected to the feed inlet of the MVR evaporator. The first mother liquor intermediate water tank lift pump is used to transport the mixed liquid from which metal ions have been removed to the MVR evaporator.

[0037] In this embodiment, through the first mother liquor treatment device, the first mother liquor with a lower phosphorus concentration can be mixed with the centrifuged mother liquor with a higher phosphorus concentration. At a higher phosphorus concentration, the removal rate of impurity elements can be effectively improved, and the quality of the by-product ammonium sulfate can be further improved.

[0038] In some embodiments, the washing water treatment device, the second mother liquor treatment device, and the first mother liquor treatment device all include a precipitant dosing component, and the precipitant dosing component is used to store and dispense a precipitant.

[0039] In this embodiment, through the precipitant dosing component, the precipitant can react with the impurity elements in the mixed liquid of the washing water, the second mother liquor, the first mother liquor, and the centrifuged mother liquor, thereby removing the impurity elements and further improving the quality of the by-product ammonium sulfate.

[0040] In some embodiments, the precipitant includes ammonia water.

[0041] In this embodiment, by adding ammonia water, the metal ion impurities in the iron phosphate wastewater can be precipitated out. Specifically, the impurity iron can be precipitated out in the form of iron phosphate and iron hydroxide, the impurity magnesium can be precipitated out in the form of magnesium ammonium phosphate, and the impurity manganese can form precipitates of manganese phosphate, ammonium manganese phosphate, and manganese hydroxide and precipitate out.

[0042] The above description is only an overview of the technical solution of the present application. In order to better understand the technical means of the present application, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present application more obvious and understandable, the specific embodiments of the present application are hereinafter specifically exemplified. Brief Description of the Drawings

[0043] In order to more clearly illustrate the technical solution of the present application, the drawings used in the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0044] Figure 1 It is a schematic flow chart of the method for treating iron phosphate wastewater in an embodiment of the present application;

[0045] Figure 2 It is a schematic diagram of the iron phosphate wastewater treatment system in an embodiment of the present application;

[0046] Figure 3 It is a schematic structural diagram of the circulating concentration membrane system in an embodiment of the present application;

[0047] Figure 4 It is a schematic structural diagram of the high-concentration membrane system in an embodiment of the present application;

[0048] Figure 5 It is a schematic structural diagram of the first mother liquor treatment device in an embodiment of the present application.

[0049] Description of the reference numerals in the drawings: 100 - washing water treatment device, 200 - circulating concentration membrane system, 300 - second mother liquor treatment device, 400 - high-concentration membrane system, 500 - MVR evaporator, 600 - first mother liquor treatment device, 700 - RO system, 210 - first booster pump, 220 - first security filter, 230 - first high-pressure pump, 240 - first membrane module, 250 - concentrated water tank, 260 - first circulation pump, 270 - product water tank, 410 - second booster pump, 420 - second security filter, 430 - second high-pressure pump, 440 - second membrane module, 450 - concentrated liquid tank, 460 - circulation water tank, 470 - second circulation pump, 610 - first mother liquor adjustment tank, 620 - first mother liquor reaction sedimentation tank, 630 - first mother liquor intermediate water tank, 640 - first mother liquor intermediate water tank lift pump. Detailed Embodiments

[0050] The embodiments of the technical solution of the present application will be described in detail below with reference to the drawings. The following embodiments are only used to illustrate the technical solution of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion.

[0052] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order, or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0053] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0054] In the description of the embodiments of this application, the term "and / or" is merely a description of the associated relationship of the associated objects and indicates that three relationships can exist. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0055] In the description of the embodiments of this application, the term "a plurality" refers to more than two (including two). Similarly, "a plurality of groups" refers to more than two groups (including two groups), and "a plurality of pieces" refers to more than two pieces (including two pieces).

[0056] In the description of the embodiments of this application, the orientation or positional relationship indicated by technical terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of this application and simplifying the description, rather than indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the embodiments of this application.

[0057] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0058] The traditional method for treating ferric phosphate wastewater is to combine the first mother liquor and the second mother liquor for treatment. Since the phosphorus content in the first mother liquor and the second mother liquor is low, and some metal ions (such as manganese ions and magnesium ions) that are difficult to remove in ferric phosphate wastewater need to be removed at a higher phosphorus concentration, the traditional method for treating ferric phosphate wastewater cannot effectively remove the impurity elements in the ferric phosphate wastewater, resulting in a low removal rate of impurity elements and a low quality of the byproduct ammonium sulfate. In addition, the method also has the problem of high energy consumption. Therefore, it is of great significance to reduce energy consumption, increase the removal rate of impurity elements, and improve the quality of the byproduct ammonium sulfate.

[0059] In order to solve the technical problems of high energy consumption, low removal rate of impurity elements and low quality of by-product ammonium sulfate in the ferric phosphate wastewater treatment method, the present application provides a ferric phosphate wastewater treatment method and a ferric phosphate wastewater treatment system, wherein, by treating the wash water and the second mother liquor separately and combining the mixed liquor of the first mother liquor and the centrifugal mother liquor for treatment, it is possible to effectively reduce energy consumption, improve the removal rate of impurity elements, and improve the quality of the by-product ammonium sulfate. By mixing the first mother liquor containing a lower phosphorus concentration with the centrifugal mother liquor containing a higher phosphorus concentration, under the condition of a higher phosphorus concentration, the removal rate of impurity elements can be effectively improved, the quality of the by-product ammonium sulfate can be improved, and energy consumption can be reduced.

[0060] Please refer to Figure 1 , is a schematic diagram of a process for treating iron phosphate wastewater provided in an embodiment of the present application, and the method for treating iron phosphate wastewater comprises:

[0061] S100, after pre-treating and filtering the wash water, the wash water is transported to a circulating concentration membrane system to obtain concentrated wash water;

[0062] Specifically, pre-treating the washing water can precipitate impurity elements in the washing water; specifically, ammonia water with a concentration of 22% can be added to the washing water, and the addition ratio (the percentage of the volume of ammonia water to the volume of washing water) is 0.5 - 1.2%, and the pH range is 8 - 9. Exemplarily, the addition ratio of ammonia water can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, and the pH can be 8, 8.5 or 9. Under this condition, iron in the washing water can precipitate out in the form of iron phosphate and / or iron hydroxide, magnesium ions in the washing water can precipitate out in the form of ammonium magnesium phosphate, and manganese ions in the washing water can form precipitates of manganese phosphate, ammonium manganese phosphate, and manganese hydroxide.

[0063] Reference Figure 2 , filtering the washing water includes sand filtering and ultrafiltration treatment of the washing water, and the filtration can remove the formed precipitate. After the washing water is pre-treated and filtered, metal ions in the washing water can be removed. Specifically, metal ion impurities such as calcium, magnesium, iron, and manganese in the washing water can be removed.

[0064] After pre-treating and filtering the washing water, it is transported to a circulating concentration membrane system to obtain the concentrated water of the washing water. Through the circulating concentration membrane system, it can ensure that the ammonium sulfate concentration in the concentrated water of the washing water is controlled at 10%. The traditional membrane system needs to concentrate the washing water to an ammonium sulfate concentration of 4 - 6% in the first step, and then use the membrane system to further concentrate the above concentrated liquid to 8 - 10% in the second step. The traditional process flow is long, the process control is unstable, the equipment investment is high, and the operation energy consumption is high.

[0065] S200. After pre-treating and filtering the second mother liquor, it is mixed with the concentrated water of the washing water and transported to a high-fold concentration membrane system to obtain a concentrated solution;

[0066] Specifically, pre-treating the second mother liquor can precipitate impurity elements in the second mother liquor; specifically, ammonia water with a concentration of 22% can be added to the second mother liquor, and the addition ratio of ammonia water (the percentage of the volume of ammonia water to the volume of the second mother liquor) is 0.8 - 1.2%, and the pH range is 8 - 9. Exemplarily, the addition ratio of ammonia water can be 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, and the pH can be 8, 8.5 or 9. Under this condition, iron ions in the second mother liquor can precipitate out in the form of iron phosphate and / or iron hydroxide, magnesium ions in the second mother liquor can precipitate out in the form of ammonium magnesium phosphate, and manganese ions in the second mother liquor can form precipitates of manganese phosphate, ammonium manganese phosphate, and manganese hydroxide.

[0067] Reference Figure 2, filtering the second mother liquor includes sand filtration and ultrafiltration of the mother liquor, and the filtration can remove the formed precipitate. After the pretreatment and filtration of the second mother liquor, metal ions in the second mother liquor can be removed. Specifically, metal ion impurities such as calcium, magnesium, iron, and manganese in the second mother liquor can be removed.

[0068] After the pretreatment and filtration of the second mother liquor, it is transported together with the concentrated water of the washing water to a high-fold concentration membrane system to obtain a concentrated solution. In this application, the concentrated water of the washing water is introduced into the fresh water side of the high-fold concentration membrane system, which can increase the concentration of the fresh water side, reduce the osmotic pressure between the fresh water side and the concentrated water side in the high-fold concentration membrane system, reduce the driving force of the high-fold concentration membrane system, and is beneficial to concentrating the feed liquid to a higher concentration. In some embodiments, the ammonium sulfate concentration in the concentrated solution can reach 20%, while the ammonium sulfate concentration in the concentrated solution of the traditional membrane system is generally 12-13%.

[0069] S300. Perform MVR evaporation treatment on the concentrated solution to obtain ammonium sulfate and centrifugal mother liquor;

[0070] Furthermore, when performing MVR evaporation treatment on the concentrated solution, the concentrated solution is heated and evaporated, the water is vaporized and condensed for recovery, and the non-volatile solute ammonium sulfate is concentrated. When concentrated to a certain extent, ammonium sulfate will crystallize out to form solid particles. The solid particles are separated by centrifugation to obtain ammonium sulfate products, which can be used for the reuse of agricultural fertilizers or industrial raw materials. The mother liquor after centrifugation, that is, the centrifugal mother liquor, can be used for further treatment to achieve deeper purification and resource recovery. Generally speaking, through MVR evaporation treatment, the recycling of resources can be realized.

[0071] S400. Mix the first mother liquor and the centrifugal mother liquor, perform pretreatment and filtration on the mixed solution of the first mother liquor and the centrifugal mother liquor, and perform MVR evaporation treatment on the pretreated and filtered mixed solution.

[0072] Specifically, the concentration of the first mother liquor is relatively high and it does not need to be concentrated. Since the phosphorus content in the first mother liquor is low and the impurity content is high, and the phosphorus content in the centrifugal mother liquor is high, mixing the first mother liquor and the centrifugal mother liquor is beneficial to the removal of impurity elements in the mixed solution.

[0073] Furthermore, the pretreatment of the mixed solution of the first mother liquor and the centrifuged mother liquor can cause impurity elements to precipitate out in the form of precipitates, and the formed precipitates can be removed after filtration. Specifically, ammonia water with a concentration of 22% can be added to the mixed solution of the first mother liquor and the centrifuged mother liquor, and the addition ratio of ammonia water (the percentage of the volume of ammonia water to the sum of the volumes of the first mother liquor and the centrifuged mother liquor) is 0.8-1.2%, and the pH range is 8-9. Exemplarily, the addition ratio of ammonia water can be 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, and the pH can be 8, 8.5 or 9. Under this condition, iron ions in the mixed solution can precipitate out in the form of iron phosphate and / or iron hydroxide, magnesium ions in the mixed solution can precipitate out in the form of ammonium magnesium phosphate, and manganese ions in the mixed solution can form manganese phosphate and / or ammonium manganese phosphate and / or manganese hydroxide precipitates. By pretreating and filtering the mixed solution of the first mother liquor and the centrifuged mother liquor, calcium, magnesium, iron and manganese impurity elements in the first mother liquor and the centrifuged mother liquor can be removed, and the removal rate of impurity elements can be improved.

[0074] After the pretreatment and filtration are completed, the mixed solution contains a certain concentration of dissolved substance ammonium sulfate. Through MVR evaporation treatment, the mixed solution is heated and evaporated, the water is vaporized and condensed for recovery, while ammonium sulfate is concentrated. When concentrated to a certain extent, ammonium sulfate will crystallize out solid particles. After centrifugal separation, the separation of ammonium sulfate and the centrifuged mother liquor can be realized, and the recycling of resources can be achieved.

[0075] In this application, the first mother liquor does not need to be treated by a membrane system. It is directly mixed with the centrifuged mother liquor for pretreatment and then evaporated, which can reduce the load of the membrane system. In addition, the impurity elements calcium, magnesium, manganese and phosphorus in the centrifuged mother liquor are enriched. When mixed with the first mother liquor for pretreatment, the content of impurity elements can be reduced and the removal rate of impurity elements can be improved. After MVR evaporation treatment, there is finally only one high-quality by-product ammonium sulfate. Traditional treatment methods will produce two by-products, ammonium sulfate and low-quality ammonium sulfate. The low-quality ammonium sulfate has low value and requires a drum dryer for drying, with high energy consumption.

[0076] Generally speaking, the treatment method of this application adopts the method of separately treating the washing water and the second mother liquor and mixing and treating the first mother liquor and the centrifuged mother liquor. Since the phosphorus concentration in the centrifuged mother liquor is relatively high, the method of this application can pretreat the mixed solution under the condition of a relatively high phosphorus concentration, which can cause metal ion impurities that are difficult to remove in the iron phosphate wastewater to form phosphate precipitates, which is beneficial to the removal of impurity elements, improves the removal rate of impurity elements, reduces the phosphorus content in ammonium sulfate, and improves the quality of ammonium sulfate. Moreover, the treatment method of this application does not require the concentration treatment of the first mother liquor, reduces the process of the membrane system for treating the first mother liquor, and has the advantage of low energy consumption.

[0077] In addition, the membrane system in the existing iron phosphate wastewater treatment method includes wash water RO, mother liquor RO, concentration RO, secondary mother liquor RO, secondary wash water RO, and terminal RO, a total of 6 sets of RO. Finally, the wastewater is treated into pure water and ammonium sulfate solution with a concentration of 100 mS / cm to 130 mS / cm. Generally speaking, the existing iron phosphate wastewater treatment method has problems such as too long a process flow, too many membrane systems used, and high energy consumption. Moreover, it is impossible to further increase the concentration of the concentrated liquid, resulting in high energy consumption of the evaporator. And due to the large fluctuation of the wastewater quality, there are defects such as poor operation stability of the wash water RO and mother liquor RO. The method of this application only uses a circulating concentration membrane system and a high-concentration membrane system. The circulating concentration membrane system of this application replaces the wash water RO in the traditional method and can directly concentrate the wash water to 100 mS / cm; the high-concentration membrane system of this application replaces the mother liquor RO and concentration RO in the traditional method and can concentrate the mother liquor to more than 20%. This application reduces the number of membrane systems in the traditional treatment method, shortens the process flow, and reduces the construction investment cost and equipment maintenance management cost.

[0078] Furthermore, in the embodiment of this application, as Figure 2 shown, after the wash water is pretreated and filtered and then conveyed to the circulating concentration membrane system 200, it further includes: obtaining the produced water of the wash water, and conveying the produced water of the wash water to the RO system 700 for purification treatment to obtain pure water.

[0079] Specifically, referring to Figure 2 , conveying the produced water of the wash water to the RO system 700 for purification treatment includes: conveying the produced water of the wash water to the primary pure water RO, and after being treated by the primary pure water RO, conveying it to the secondary pure water RO. After being treated by the secondary pure water RO, pure water and membrane concentrated water are obtained. The membrane concentrated water obtained after being treated by the secondary pure water RO can be conveyed to the primary pure water RO for re-treatment, thereby improving the water recovery rate of the whole system and reducing the waste of water resources. The pure water obtained after being treated by the secondary pure water RO can be used for recycling. Thus, through further purification of the produced water of the wash water with a lower concentration, the obtained pure water can be recycled, that is, the method of this application can recycle water.

[0080] Furthermore, in the embodiment of this application, the treatment method further includes: conveying the concentrated water of the wash water to the circulating concentration membrane system 200 for re-concentration treatment. Thus, through the way of circulating and concentrating the concentrated water of the wash water, the concentration of the concentrated water of the wash water can be effectively increased. And the concentration of the solution after being treated by the circulating concentration membrane system 200 can be controlled, and the operation stability can also be improved.

[0081] Furthermore, in the embodiment of this application, as Figure 2As shown, after the second mother liquor is pretreated and filtered, it is mixed with the concentrated water of the washing water and then transported to the high-fold concentration membrane system 400. It further includes: obtaining the membrane permeate water of the high-fold concentration membrane system 400. The membrane permeate water is mixed with the second mother liquor, pretreated and filtered again, and then mixed with the concentrated water of the washing water and transported to the high-fold concentration membrane system 400.

[0082] Thus, by mixing the membrane permeate water of the high-fold concentration membrane system 400 with the second mother liquor and performing pretreatment cyclically, the impurity elements in the membrane permeate water can be precipitated out in the form of precipitation. After filtration, the impurity elements in the membrane permeate water can be further removed. Then, they are respectively transported to the high-fold concentration membrane system 400 together with the concentrated water of the washing water, which can increase the concentration on the fresh water side and concentrate the feed liquid to a higher concentration.

[0083] In a second aspect, the present application also provides a ferric phosphate wastewater treatment system. Referring to Figure 2 , the ferric phosphate wastewater treatment system is used to execute the ferric phosphate wastewater treatment method described above. The ferric phosphate wastewater treatment system includes: a washing water treatment device 100, a circulating concentration membrane system 200, a second mother liquor treatment device 300, a high-fold concentration membrane system 400, an MVR evaporator 500, and a first mother liquor treatment device 600;

[0084] The washing water treatment device 100 is connected to the circulating concentration membrane system 200. The second mother liquor treatment device 300 is connected to the high-fold concentration membrane system 400. The concentrated water outlet of the circulating concentration membrane system 200 is communicated with the liquid inlet of the high-fold concentration membrane system 400. The liquid outlet of the high-fold concentration membrane system 400 is connected to the liquid inlet of the MVR evaporator 500. The MVR evaporator 500 is provided with a centrifugal mother liquor outlet. The first mother liquor treatment device 600 is provided with a first mother liquor inlet and a centrifugal mother liquor inlet. The centrifugal mother liquor inlet is communicated with the centrifugal mother liquor outlet on the MVR evaporator 500. The liquid outlet of the first mother liquor treatment device 600 is connected to the liquid inlet of the MVR evaporator 500;

[0085] The washing water treatment device 100 is used to remove metal ions in the washing water. The circulating concentration membrane system 200 is used to perform fixed-concentration concentration treatment on the washing water after removing metal ions. The second mother liquor treatment device 300 is used to remove metal ions in the second mother liquor. The high-fold concentration membrane system 400 is used to concentrate the second mother liquor after removing metal ions and the concentrated water of the washing water to obtain a concentrated liquid. The MVR evaporator 500 is used to process the concentrated liquid to obtain ammonium sulfate and centrifugal mother liquor. The first mother liquor treatment device 600 is used to remove metal ions in the first mother liquor and the centrifugal mother liquor.

[0086] Thus, in this application, the first mother liquor treatment device 600 mixes and treats the first mother liquor and the centrifuged mother liquor. Since the phosphorus content in the centrifuged mother liquor is relatively high, it is conducive to the formation of phosphate precipitates of impurity elements in the first mother liquor and the centrifuged mother liquor. For example, precipitates of manganese phosphate, iron phosphate, and ammonium magnesium phosphate can be formed and precipitated out, improving the removal rate of impurity elements. Further, precipitating phosphorus can reduce the phosphorus content in ammonium sulfate and improve the quality of the by-product ammonium sulfate. Moreover, the problem of excessive free acid often occurs in ammonium sulfate products. The pH of the mixed solution treated by the first mother liquor treatment device 600 is greater than that of the concentrated solution. The mixed solution treated by the first mother liquor treatment device 600 is transported to the MVR evaporator 500. Thus, the system of this application can reduce the acidity of the liquid in the MVR evaporator 500 and reduce the corrosion of the MVR evaporator 500; at the same time, it can also increase the pH value of the solution in the MVR evaporator 500. The free acid can react with the alkaline solution and be consumed, reducing the free acid content in the finally obtained ammonium sulfate, improving the quality of ammonium sulfate, and increasing the value of the by-product. The system of this application also omits the membrane system for concentrating the first mother liquor and has the advantage of low energy consumption.

[0087] It should be noted that the liquid outlet of the first mother liquor treatment device 600 is connected to the liquid inlet of the MVR evaporator 500. The connection here should be understood in a broad sense. For example, it can be directly connected or indirectly connected through an intermediate medium. For example, the liquid outlet of the first mother liquor treatment device 600 can be directly connected to the liquid inlet of the MVR evaporator 500, or as Figure 2 , Figure 4 shown, the liquid outlet of the first mother liquor treatment device 600 is connected to the liquid inlet of the MVR evaporator 500 through the concentrated solution tank 450, that is, the liquid outlet of the first mother liquor treatment device 600 can be connected to the liquid inlet of the concentrated solution tank 450, and the liquid outlet of the concentrated solution tank 450 is connected to the liquid inlet of the MVR evaporator 500, so that the solution treated by the first mother liquor treatment device 600 is first combined with the concentrated solution in the concentrated solution tank 450, and the combined solution is transported to the liquid inlet of the MVR evaporator 500.

[0088] Further, in the embodiment of this application, as Figure 3 shown, the circulating concentration membrane system 200 includes a first booster pump 210, a first security filter 220, a first high-pressure pump 230, a first membrane module 240, and a concentrated water tank 250 connected in sequence. The circulating concentration membrane system 200 also includes a first circulation pump 260 and a product water tank 270;

[0089] The first booster pump 210 is connected to the filtrate outlet of the washing water treatment device 100;

[0090] The first membrane module 240 has a concentrated water outlet and a product water outlet. The product water outlet is communicated with the product water tank 270, and the product water tank 270 is connected to the RO system 700;

[0091] The inlet of the first circulation pump 260 is connected to the concentrated water outlet, and the outlet of the first circulation pump 260 is connected to the inlet of the first membrane module 240. The first circulation pump 260 can transport the solution at the concentrated water outlet to the inlet of the first membrane module 240 for re-concentration treatment.

[0092] Thus, by setting the first circulation pump 260, the concentrated water of the washing water can be circularly concentrated, the concentration of the concentrated water of the washing water can be effectively increased, and the concentration of the solution treated by the circular concentration membrane system 200 can be controlled, so that the operation can be more stable and the change of the sewage quality can be adapted.

[0093] Specifically, the first membrane module 240 includes an inter-stage booster pump. The frequency of the first high-pressure pump 230 and the inter-stage booster pump frequency converter and the operation pressure of the system can be controlled according to the inlet concentration of the first membrane module 240, so as to control the concentrated water concentration, and the system recovery rate can be controlled between 50% and 95%. The operation pressure of the circular concentration membrane system 200 of the present application is 2.3 - 5 MPa, and the washing water treated by the circular concentration membrane system 200 is concentrated to 100 mS / cm. The circular concentration membrane system 200 of the present application can adapt to the abnormal fluctuation of the sewage concentration. Since the concentration multiple of the circular concentration membrane system 200 is very high and the energy utilization rate is also very high, the energy consumption and treatment cost are further reduced.

[0094] Specifically, the first membrane module 240 includes a membrane separation system in series of multiple stages. The number of stages of the membrane separation system can be adjusted according to the use requirements. For example, the number of stages of the membrane separation system can be 3. An inter-stage booster pump is arranged between each stage of the membrane separation system. Further, the inter-stage booster pump is located between the concentrated water side of the previous stage of the membrane separation system and the inlet side of the next stage of the membrane separation system. By setting the inter-stage booster pump, a sufficient pressure difference can be ensured at both ends of the first membrane module 240, so that the fluid can pass through the membrane. The inter-stage booster pump can also ensure that the fluid enters the next stage of the membrane separation system at an appropriate flow rate and pressure, avoid excessive pressure shock, and extend the service life of the first membrane module 240.

[0095] Further, in the embodiment of the present application, as Figure 4 shown, the high-fold concentration membrane system 400 includes a second booster pump 410, a second security filter 420, a second high-pressure pump 430, a second membrane module 440 and a concentrated liquid tank 450 connected in sequence. The outlet of the concentrated liquid tank 450 is connected to the inlet of the MVR evaporator 500. The high-fold concentration membrane system 400 also includes a circulation water tank 460 and a second circulation pump 470;

[0096] The second booster pump 410 is connected to the filtrate outlet of the second mother liquor treatment device 300;

[0097] The second membrane module 440 has a membrane concentrate outlet and a membrane permeate outlet, and the membrane concentrate outlet communicates with the concentrate pool 450;

[0098] The circulation water tank 460 has a concentrated washing water inlet, and the concentrated washing water inlet communicates with the concentrated water tank 250 in the circulation and concentration membrane system 200;

[0099] The circulation water tank 460 is connected to the liquid inlet on the second membrane module 440 through the second circulation pump 470, the membrane permeate outlet communicates with the circulation water tank 460, and an overflow port is provided on the circulation water tank 460, and the overflow port communicates with the liquid inlet of the second mother liquor treatment device 300.

[0100] It should be noted that the high-concentration concentration membrane system 400 has two feed inlets and two discharge outlets. The concentrated water of the washing water and the pretreated second mother liquor are transported into the high-concentration concentration membrane system 400 from two different feed inlets. The concentrated water feed inlet of the washing water is connected to the circulation water tank 460, and the feed inlet of the pretreated second mother liquor is connected to the second booster pump 410. Thus, high-concentrated water is introduced on the fresh water side of the high-concentration concentration membrane system 400 in this application, reducing the concentration difference between the concentrated water side and the fresh water side, reducing the osmotic pressure of the membrane system. The high-concentration concentration membrane system 400 can concentrate the feed liquid to more than 20% at a relatively low pressure of 4-6 MPa.

[0101] Furthermore, the frequency of the second high-pressure pump 430 and the operating pressure of the system can be controlled according to the inlet concentration and fresh water concentration of the second membrane module 440, so as to control the concentrated water concentration. Compared with the existing iron phosphate wastewater treatment system, by setting the high-concentration concentration membrane system 400 in this application, the feed liquid volume of the MVR evaporator 500 can be reduced by more than 20%, and the energy consumption of the MVR evaporator 500 is reduced by more than 20% accordingly.

[0102] Furthermore, in the embodiment of this application, as Figure 5 shown, the first mother liquor treatment device 600 includes a first mother liquor regulation tank 610, a first mother liquor reaction and sedimentation tank 620, a first mother liquor intermediate tank 630, and a first mother liquor intermediate tank lift pump 640 connected in sequence;

[0103] The first mother liquor regulation tank 610 is used to store the mixed liquid of the first mother liquor and the centrifuged mother liquor. The first mother liquor reaction and sedimentation tank 620 is used to precipitate and remove metal ions in the mixed liquid. The first mother liquor intermediate tank 630 is connected to the filtrate outlet of the first mother liquor reaction and sedimentation tank 620. The first mother liquor intermediate tank 630 is used to store the mixed liquid from which metal ions have been removed. The first mother liquor intermediate tank lift pump 640 is connected to the feed liquid inlet of the MVR evaporator 500, and the first mother liquor intermediate tank lift pump 640 is used to transport the mixed liquid from which metal ions have been removed to the MVR evaporator 500.

[0104] Thus, through the first mother liquor treatment device 600, the removal rate of impurity elements in the first mother liquor and the centrifuged mother liquor can be improved, and the quality of ammonium sulfate can also be improved. The system of this application does not need to concentrate the first mother liquor, reducing the energy consumption. Further, the pH in the first mother liquor reaction sedimentation tank 620 can be controlled at 8.5 - 9. At this time, the impurity elements in the first mother liquor and the centrifuged mother liquor can precipitate out in the form of precipitates, generating precipitates such as magnesium ammonium phosphate, iron phosphate, and iron hydroxide. The precipitates are discharged into the pretreatment sludge tank, and after plate and frame pressure filtration, phosphate fertilizers are obtained for sale. The effluent from the first mother liquor reaction sedimentation tank 620 is connected to the first mother liquor intermediate water tank 630.

[0105] Specifically, the MVR evaporator 500 includes a triple-effect evaporator. The liquid outlet of the first mother liquor intermediate water tank lift pump 640 is connected to the liquid inlet of the triple-effect evaporator. Thus, the mixed liquid with metal ions removed can be transported to the triple-effect evaporator.

[0106] Further, in the embodiments of this application, the washing water treatment device 100, the second mother liquor treatment device 300, and the first mother liquor treatment device 600 all include a precipitant dosing component, which is used to store and dispense the precipitant. Thus, the precipitant can cause the impurity elements in the washing water, the second mother liquor, or the mixed liquid of the first mother liquor and the centrifuged mother liquor to precipitate out in the form of precipitates, which is beneficial to removing the impurity elements in the sewage and improving the quality of the by-product ammonium sulfate.

[0107] Further, in the embodiments of this application, the precipitant includes ammonia water. By adding ammonia water, the impurity elements in the sewage can precipitate out in the form of precipitates, and it is easy to remove the impurity elements from the sewage.

[0108] Please refer to Figures 1 to 5, according to one or more embodiments of the present application, the present application adopts the method of pre-treating and filtering the mixed solution of centrifuged mother liquor and the first mother liquor. Since the phosphorus concentration in the centrifuged mother liquor is relatively high, the method of the present application can form phosphate precipitates of metal ion impurities that are difficult to remove in phosphoric acid iron wastewater under the condition of a relatively high phosphorus concentration, improving the removal rate of impurity elements, reducing the phosphorus content in ammonium sulfate, and enhancing the quality of ammonium sulfate. Moreover, the circulating concentration membrane system 200 of the present application can concentrate the washing water to a specified concentration to obtain the concentrated water of the high-concentration washing water. The present application introduces the concentrated water of the washing water into the fresh water side of the high-fold concentration membrane system 400, which can increase the concentration of the fresh water side and reduce the osmotic pressure between the fresh water side and the concentrated water side of the high-fold concentration membrane system 400. On the one hand, it can reduce the driving force of the high-fold concentration membrane system 400, and on the other hand, it can concentrate the feed liquid to a higher concentration, reducing the feed liquid volume of the MVR evaporator and reducing the energy consumption of the MVR evaporation treatment. The present application can recover pure water and ammonium sulfate only by using the circulating concentration membrane system 200 and the high-fold concentration membrane system 400. The solution of the present application has the advantages of simple process flow and low energy consumption, improving the problem of too long process flows of membrane concentration and membrane purification in the existing solution. In addition, the solution of the present application also improves the problems of high energy consumption, low removal rate of impurity elements, and low quality of the by-product ammonium sulfate in the existing solution.

[0109] It should be noted that the present application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same composition and the same effect as the technical idea within the technical solution scope of the present application are included in the technical scope of the present application. In addition, within the scope of not departing from the gist of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other ways constructed by combining some constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A method for treating iron phosphate wastewater, characterized in that: The ferric phosphate wastewater treatment method comprises: After pre-treatment and filtration of the wash water, the wash water is transported to a circulating concentration membrane system to obtain concentrated water of the wash water; After pre-treatment and filtration of the second mother liquor, the second mother liquor is mixed with the concentrated water of the washing water and transported to a high-concentration membrane system to obtain a concentrated liquid; The concentrated solution is subjected to MVR evaporation treatment to obtain ammonium sulfate and a centrifugal mother liquor; mixing the first mother liquor and the centrifuged mother liquor, pre-treating and filtering the mixture of the first mother liquor and the centrifuged mother liquor, and performing MVR evaporation treatment on the pre-treated and filtered mixture; The concentration of the first mother liquor is greater than that of the second mother liquor, and the concentration of the second mother liquor is greater than that of the washing water.

2. The method for treating iron phosphate wastewater according to claim 1, characterized in that: After the wash water is pre-treated and filtered and then transported to the circulating concentration membrane system, the method further includes: The produced water of the washing water is obtained, and the produced water of the washing water is transported to the RO system for purification to obtain pure water.

3. The method for treating iron phosphate wastewater according to claim 1, characterized in that: The treatment method further comprises: conveying the concentrated water of the washing water to the circulating concentration membrane system for re-concentration treatment.

4. The method for treating iron phosphate wastewater according to any one of claims 1 to 3, characterized in that: After the second mother liquor is pretreated and filtered, and then mixed with the concentrated water of the wash water and transported to the high concentration membrane system, the method further includes: The membrane produced water of the high-concentration membrane system is obtained, and the membrane produced water is mixed with the second mother liquor, pretreated and filtered again, and then mixed with the concentrated water of the washing water and transported to the high-concentration membrane system.

5. A ferric phosphate wastewater treatment system, characterized in that: The iron phosphate wastewater treatment system is used to perform the iron phosphate wastewater treatment method according to any one of claims 1 to 4, and the iron phosphate wastewater treatment system comprises: a wash water treatment device, a circulating concentration membrane system, a second mother liquor treatment device, a high concentration membrane system, an MVR evaporator, and a first mother liquor treatment device; The wash water treatment device is connected to the circulating concentration membrane system, the second mother liquor treatment device is connected to the high concentration membrane system, the concentrated water outlet of the circulating concentration membrane system is connected to the liquid inlet of the high concentration membrane system, the liquid outlet of the high concentration membrane system is connected to the liquid inlet of the MVR evaporator, the MVR evaporator is provided with a centrifugal mother liquor outlet, the first mother liquor treatment device is provided with a first mother liquor inlet and a centrifugal mother liquor inlet, the centrifugal mother liquor inlet is connected to the centrifugal mother liquor outlet on the MVR evaporator, and the liquid outlet of the first mother liquor treatment device is connected to the liquid inlet of the MVR evaporator; The wash water treatment device is used to remove metal ions in the wash water, the circulating concentration membrane system is used to concentrate the wash water after the metal ions are removed to a fixed concentration, the second mother liquor treatment device is used to remove metal ions in the second mother liquor, the high-multiple concentration membrane system is used to concentrate the second mother liquor after the metal ions are removed and the concentrated water of the wash water to obtain a concentrated solution, the MVR evaporator is used to treat the concentrated solution to obtain ammonium sulfate and a centrifugal mother liquor, and the first mother liquor treatment device is used to remove metal ions in the first mother liquor and the centrifugal mother liquor.

6. The iron phosphate wastewater treatment system according to claim 5, characterized in that: The circulating concentration membrane system comprises a first booster pump, a first safety filter, a first high-pressure pump, a first membrane assembly and a concentrated water tank which are connected in sequence, and the circulating concentration membrane system also comprises a first circulating pump and a water production tank; The first booster pump is connected to the filtrate outlet of the wash water treatment device; The first membrane assembly has a concentrated water outlet and a produced water outlet, the produced water outlet is connected to the produced water pool, and the produced water pool is connected to the RO system; The liquid inlet of the first circulation pump is connected to the concentrated water outlet, and the liquid outlet of the first circulation pump is connected to the liquid inlet of the first membrane assembly. The first circulation pump can transport the solution from the concentrated water outlet to the liquid inlet of the first membrane assembly for re-concentration treatment.

7. The iron phosphate wastewater treatment system according to claim 5, characterized in that: The high-concentration membrane system comprises a second booster pump, a second security filter, a second high-pressure pump, a second membrane assembly and a concentrated liquid pool which are connected in sequence, wherein the liquid outlet of the concentrated liquid pool is connected to the liquid inlet of the MVR evaporator, and the high-concentration membrane system further comprises a circulating water tank and a second circulating pump; The second booster pump is connected to the filtrate outlet of the second mother liquor treatment device; The second membrane module has a membrane concentrate outlet and a membrane produced water outlet, and the membrane concentrate outlet is connected to the concentrated liquid pool; The circulating water tank is provided with a concentrated washing water inlet, and the concentrated washing water inlet is connected to the concentrated water tank in the circulating concentrated membrane system; The circulating water tank is connected to the liquid inlet on the second membrane assembly through the second circulating pump, the membrane water outlet is connected to the circulating water tank, and an overflow port is provided on the circulating water tank, and the overflow port is connected to the liquid inlet of the second mother liquid treatment device.

8. The iron phosphate wastewater treatment system according to claim 5, characterized in that: The first mother liquor treatment device comprises a first mother liquor regulating tank, a first mother liquor reaction sedimentation tank, a first mother liquor intermediate water tank and a first mother liquor intermediate water tank lifting pump which are connected in sequence; The first mother liquor regulating tank is used to store a mixed liquor of the first mother liquor and the centrifuged mother liquor, the first mother liquor reaction sedimentation tank is used to precipitate and remove metal ions in the mixed liquor, the first mother liquor water tank is connected to the filtrate outlet of the first mother liquor reaction sedimentation tank, the first mother liquor water tank is used to store the mixed liquor from which metal ions are removed, the first mother liquor water tank lift pump is connected to the liquid inlet of the MVR evaporator, and the first mother liquor water tank lift pump is used to transport the mixed liquor from which metal ions are removed to the MVR evaporator.

9. The iron phosphate wastewater treatment system according to any one of claims 5 to 8, characterized in that: The wash water treatment device, the second mother liquor treatment device and the first mother liquor treatment device all include a precipitant adding component, and the precipitant adding component is used to store and add the precipitant.

10. The iron phosphate wastewater treatment system according to claim 9, characterized in that: The precipitant includes aqueous ammonia.

Images