Iron phosphate wastewater treatment method and system

Abstract

The invention provides an iron phosphate wastewater treatment method and system, and belongs to the field of wastewater treatment.The iron phosphate wastewater treatment method comprises the steps that ammonium sulfate in wastewater is separated out through an MVR evaporation device, and then primary precipitation is conducted by adjusting the pH value to remove heavy metal impurities; then adding ammonia water for secondary precipitation and filtration to further remove phosphate radical impurities; then adding lime to carry out three-stage precipitation filtration to remove fluorine element; and finally, carrying out ammonia removal treatment on the obtained tail liquid, returning to the first step of working procedure, and carrying out repeated treatment again. Wherein the generated ammonia gas is used for secondary precipitation filtration; the mode of directly recovering resources in the iron phosphate wastewater through the cooperation of a high-temperature treatment method and a fractional precipitation method is beneficial to avoiding heat value waste, and the energy consumption cost for subsequent treatment of the tail liquid and the use cost of the reagent dosage in a tail gas recovery system are reduced.

Description

Technical Field

[0001] The present application relates to the technical field of wastewater treatment, and in particular to a method and system for treating iron phosphate wastewater. Background Art

[0002] Iron phosphate wastewater is wastewater generated during the production process of lithium battery materials. It contains N, P, S, Ca, Mg, Fe, Mn and other elements. If it is discharged directly without treatment, it will not only waste resources, but also cause serious environmental pollution. In the prior art, the following treatment methods are usually used for iron phosphate wastewater:

[0003] Iron phosphate wastewater is evaporated by MVR to form a high-concentration tail liquid, which is first cooled and crystallized to separate some phosphate salts, and then passed through a dryer to dry and crystallize the separated mother liquor. This process involves a large amount of heat removal and requires the use of cooling equipment (such as cooling towers, chillers, etc.), which consumes a lot of electricity or cooling water. In the MVR evaporation device, the wastewater has been heated to a high temperature to promote water evaporation, and the cooling and crystallization process requires the removal of this heat, which is equivalent to partially offsetting the energy invested in the evaporation process, and the repeated energy consumption of evaporation and crystallization. In addition, the cooling and crystallization and drying and crystallization processes require precise control of parameters such as temperature and time. The operation is relatively complicated and has high technical requirements for operators.

[0004] In view of this, it is necessary to design a method and system for treating iron phosphate wastewater to solve the above problems. Summary of the invention

[0005] In view of the technical problems existing in the background technology, the present application provides a method and system for treating iron phosphate wastewater. The method and system for treating iron phosphate wastewater have stable operation, and while reducing the energy consumption cost of wastewater treatment, they can also reduce the cost of using the dosage of reagents in the entire system.

[0006] In a first aspect, the present invention provides a method for treating iron phosphate wastewater, comprising the following steps:

[0007] S1, performing MVR evaporation and concentration on the iron phosphate wastewater to obtain a first tail liquid;

[0008] S2, treating the first tail liquid with alkali to obtain a second tail liquid after solid-liquid separation;

[0009] S3, treating the second tail liquid with alkali to obtain a third tail liquid after solid-liquid separation;

[0010] S4, treating the third tail liquid with alkali to obtain a fourth tail liquid after solid-liquid separation;

[0011] S5, removing ammonia from the fourth tail liquid and returning to step S1.

[0012] In the technical solution of the embodiment of the present application, high temperature treatment and step-by-step precipitation methods are used for resource recovery, and the impurity elements in the wastewater are separated separately to facilitate recycling and reuse in subsequent processes.

[0013] In some embodiments, in the step of treating the first tail liquid with alkali, the alkali used is magnesium oxide.

[0014] In this embodiment, by using magnesium oxide as an alkali source for primary precipitation filtration, not only can the metal impurities in the first tail liquid be removed, but also the subsequent precipitation of phosphate impurities can be facilitated.

[0015] In some embodiments, in the step of treating the second tail liquid with alkali, the alkali used is aqueous ammonia.

[0016] In this embodiment, by using ammonia water as an alkali source for secondary precipitation and filtration, phosphate impurities are removed in the form of magnesium ammonium phosphate precipitates, so that the flocs of the precipitate formed are larger and easier to settle and filter; in addition, due to the volatility of ammonia, it can be separated from other elements by heating, avoiding the addition of other impurity elements and making the entire treatment system simpler.

[0017] By removing phosphate impurities in the form of magnesium ammonium phosphate precipitation, the phosphate in the wastewater can be efficiently removed to form an insoluble precipitate, thereby reducing the phosphorus content in the wastewater.

[0018] In some embodiments, the second tail liquid is treated with alkali to obtain magnesium ammonium phosphate precipitate after solid-liquid separation; the magnesium ammonium phosphate precipitate is calcined, and the ammonia gas generated by the calcination is directly introduced into the second tail liquid or used to prepare the ammonia water.

[0019] In this embodiment, the obtained magnesium ammonium phosphate precipitate is calcined, ammonia is recovered and used as an alkali source for secondary precipitation and filtration, and recycled, thereby reducing the energy consumption cost of subsequent treatment of the tail liquid and the cost of using the amount of reagents in the system.

[0020] In some embodiments, in the step of alkali treating the third tail liquid, the alkali used is lime.

[0021] In this embodiment, lime is used as an alkali source for three-stage precipitation and filtration, lime is added to the third tail liquid, and calcium phosphate and calcium fluoride precipitates are formed with the P element and F, and COD in the third tail liquid is adsorbed. In this way, not only can the phosphate radicals that have not been completely precipitated be further precipitated and removed, but the fluorine can also be removed in the form of calcium fluoride precipitates. The remaining phosphate radicals can be removed in the form of calcium phosphate precipitates.

[0022] In some embodiments, in step S2, the pH value of the alkali treatment is 5.0 to 5.5; and or

[0023] In step S3, the pH value of the alkali treatment is 8.0 to 8.5; and or

[0024] In the step S4, the pH value of the alkali treatment is 9-11.

[0025] In this embodiment, by controlling the amount of alkali added in each step, the pH value in the reaction is maintained within the respective range, so that the corresponding target product is formed in each reaction, and the reaction is ensured to be more complete, which is beneficial to sufficient precipitation of each reaction.

[0026] In some embodiments, the method for removing ammonia in S5 includes stripping, and the ammonia gas generated by the stripping is introduced into the second tail liquid or used to prepare the ammonia water.

[0027] In this embodiment, the stripping method is used to remove ammonia nitrogen. Compared with other methods of removing ammonia nitrogen, the ammonia nitrogen concentration in the wastewater can be reduced to a lower level, meet more stringent emission standards, and have lower operating costs; the stripping system is relatively simple, easy to operate and maintain, does not require complex chemical treatment processes, and the stripping method will not cause secondary pollution to the environment; in addition, the generated ammonia gas can also be used as an alkali source for secondary precipitation and filtration, so that it can be recycled to further reduce production costs. At the same time, due to the presence of the pre-step of MVR evaporation and concentration, the step-by-step precipitation process is carried out in a high temperature environment throughout the process, and no additional heat source is required for the ammonia nitrogen stripping process.

[0028] In a second aspect, the embodiment of the present application provides a ferric phosphate wastewater treatment system, which uses the above-mentioned ferric phosphate wastewater treatment method to treat ferric phosphate wastewater.

[0029] The iron phosphate wastewater treatment system comprises an MVR evaporation device, a separation device, a multi-stage precipitation and filtration device and a deammoniation device connected in sequence;

[0030] The outlet of the deammoniation device is connected to the MVR evaporation device, and the outlet of the separation device is also connected to the MVR evaporation device.

[0031] In the technical solution of the embodiment of the present application, an MVR evaporation device, a separation device, a multi-stage precipitation and filtration device and a deamination device are arranged to be connected in sequence, and the outlets of the deamination device and the separation device are connected to the MVR evaporation device. In this way, the impurity elements that are not fully treated in the above-mentioned iron phosphate wastewater treatment method can be returned to the system for treatment, so as to fully recycle the wastewater.

[0032] In some embodiments, the multi-stage precipitation and filtration device includes a primary precipitation and filtration unit, a secondary precipitation and filtration unit, and a tertiary precipitation and filtration unit connected in sequence, and the deammoniation device includes a deammoniation tank and a sand filter tank; the outlet of the deammoniation tank is connected to the inlet of the secondary precipitation and filtration unit. The secondary precipitation and filtration unit is also connected to the inlet of the calcination system, and the outlet of the calcination system is connected to the inlet of the secondary precipitation and filtration unit.

[0033] In this embodiment, by setting up a multi-stage sedimentation and filtration device, the various elements in the wastewater can be fully separated, which is beneficial to the subsequent classification and recycling of different substances; by connecting the outlets of the deammoniation tank and the calcination system to the inlet of the secondary sedimentation and filtration unit, the recycling of ammonia in the above-mentioned iron phosphate wastewater treatment method can be met.

[0034] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 This is a schematic diagram of the structure of the iron phosphate wastewater treatment system in the embodiment of the present application. DETAILED DESCRIPTION

[0037] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians 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" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0039] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0040] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0041] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0042] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0043] In the description of the embodiments of the present application, the technical terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the embodiments of the present application.

[0044] 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.

[0045] The existing method for treating iron phosphate wastewater is to first separate part of the phosphate salts by cooling and crystallizing, and then dry and crystallize the separated mother liquor. This method has high energy consumption costs in the cooling process and evaporation process. Therefore, it is particularly important to recycle the resources in iron phosphate wastewater with high efficiency and low energy consumption.

[0046] In order to solve the above-mentioned technical problems, the present application provides a method and system for treating iron phosphate wastewater, wherein different impurity elements in the wastewater are separated separately by high-temperature treatment with the help of an MVR evaporation device and a step-by-step precipitation method, and the generated ammonia gas is recycled for use in the precipitation and filtration process, thereby achieving the technical effect of reducing the energy consumption cost of subsequent treatment of the tail liquid while reducing the cost of using the amount of reagents in the system.

[0047] The iron phosphate wastewater treatment method disclosed in the embodiment of the present application can be used, but is not limited to, in industrial fields such as chemical industry, metallurgy, and environmental protection. The treatment method disclosed in the present application can be used, which is beneficial to improving wastewater treatment efficiency, reducing environmental pollution, and realizing the economical utilization of resources.

[0048] The iron phosphate wastewater treatment system provided in the embodiment of the present application can be, but is not limited to, the treatment of iron phosphate wastewater, the denitrification of ammonia-containing wastewater, the removal of heavy metal ions, etc. The iron phosphate wastewater treatment system can include an MVR evaporation device, a separation device, a multi-stage precipitation and filtration device, and a deammoniation device. For example, the MVR evaporation device can include a compressor, a heating chamber, and an evaporator, etc. The multi-stage precipitation and filtration device can include a primary precipitation and filtration unit, a secondary precipitation and filtration unit, and a tertiary precipitation and filtration unit, etc.; the primary precipitation and filtration unit can include a primary precipitation tank and a primary filtration tank, etc.

[0049] For the convenience of description, the following embodiments are described by taking a method and system for treating iron phosphate wastewater according to an embodiment of the present application as an example.

[0050] In a first aspect, an embodiment of the present application provides a method for treating iron phosphate wastewater, which is used to recycle resources in the iron phosphate wastewater, comprising the following steps:

[0051] S1, performing MVR evaporation and concentration on the iron phosphate wastewater to obtain a first tail liquid;

[0052] S2, treating the first tail liquid with alkali to obtain a second tail liquid after solid-liquid separation;

[0053] S3, treating the second tail liquid with alkali to obtain a third tail liquid after solid-liquid separation;

[0054] S4, treating the third tail liquid with alkali to obtain a fourth tail liquid after solid-liquid separation;

[0055] S5, removing ammonia from the fourth tail liquid and returning to step S1.

[0056] First, the iron phosphate wastewater is separated into by-product ammonium sulfate and the first tail liquid through MVR evaporation and concentration. The main components of the first tail liquid are ammonia nitrogen, sulfate, phosphate, COD, F and metal impurities such as calcium, magnesium, manganese, and iron. Then, the impurities in the wastewater are removed by adjusting the pH value in steps. The first tail liquid is treated with alkali to remove heavy metal impurities in the first tail liquid and reduce the content of harmful components; the second tail liquid is then treated with alkali to remove phosphate impurities in the second tail liquid, reducing the burden of subsequent treatment; the third tail liquid is then treated with alkali to remove fluorine elements in the third tail liquid and reduce the harm of wastewater to the environment; finally, the treated fourth tail liquid is treated for ammonia removal and returned to the first step, and the above-mentioned repeated treatment is performed again to avoid insufficient resource recovery. Compared with the low-temperature crystallization method used in the prior art to recover phosphate, this method uses high-temperature treatment throughout the process and cooperates with the step-by-step precipitation method to recover the resources in the iron phosphate wastewater. This not only avoids the waste of calorific value, reduces the energy consumption cost of subsequent treatment of the tail liquid, reduces the cost of using the dosage of the agent in the system, but also reduces the pollution to the environment. It has good environmental benefits, reduces production costs, and improves the economic benefits of the enterprise.

[0057] Furthermore, in an embodiment of the present application, in the step of alkali treatment of the first tail liquid, the alkali used is magnesium oxide; since the first tail liquid has a high salt content and a low pH value, a large amount of phosphate forms a phosphate buffer system. In order to reduce the amount of ammonia water used, magnesium oxide is used in the first stage of the step-by-step precipitation to remove impurities while supplementing the magnesium source, which facilitates the recovery of phosphate salts to form magnesium ammonium phosphate in the second stage, and the ammonia gas recovered by the subsequent calcination of magnesium ammonium phosphate can further reduce the amount of external ammonia water used.

[0058] Further, in the embodiment of the present application, in the step of alkali treatment of the second tail liquid, the alkali used is ammonia water; the ammonia water is used as the alkali source to precipitate the second tail liquid, so that the original Mg in the tail liquid and the Mg dissolved in magnesium oxide form a magnesium ammonium phosphate precipitate, and the phosphorus source and Mg in the tail liquid are recovered in the form of magnesium ammonium phosphate precipitate (Mg 2+ +NH4 + +PO4 3-→MgNH4PO4↓), so that the flocs of the precipitate formed are larger and easy to settle and filter; in addition, due to the volatility of ammonia, the product can be separated from other elements by heating. Compared with the use of other alkali sources, no other reagents are needed, and the addition of other impurity elements is avoided, making the entire treatment system simpler, and the ammonia gas recovered by the subsequent calcination of magnesium ammonium phosphate can be directly introduced into the second tail liquid or used to prepare ammonia water, further reducing the amount of added ammonia water. By removing phosphate impurities in the form of magnesium ammonium phosphate precipitation, the phosphate in the wastewater can be efficiently removed to form an insoluble precipitate, thereby reducing the phosphorus content in the wastewater.

[0059] Furthermore, in an embodiment of the present application, the second tail liquid is treated with alkali, and magnesium ammonium phosphate precipitate is obtained after solid-liquid separation; the magnesium ammonium phosphate precipitate is calcined, and the ammonia generated by the calcination is directly introduced into the second tail liquid or used to prepare the ammonia water; the recovered ammonia is recycled, thereby reducing the energy consumption cost of subsequent treatment of the tail liquid and the cost of using the dosage of the reagent in the system.

[0060] Further, in the embodiment of the present application, in the step of alkali treatment of the third tail liquid, the alkali used is lime, and the temperature in the system is 60°C to 70°C. At this time, the third tail liquid contains a large amount of P element, sulfate, ammonia nitrogen, F, and COD. Lime is added to the third tail liquid to form calcium phosphate and calcium fluoride precipitation with P element and F, and the COD in the third tail liquid is adsorbed, so that not only the phosphate that has not been completely precipitated can be further precipitated and removed, but also the fluorine can be removed in the form of calcium fluoride precipitation, and the removal method of the remaining phosphate includes removal in the form of calcium phosphate precipitation.

[0061] Further, in the embodiment of the present application, in the step S2, the pH value of the alkali treatment is 5.0 to 5.5; and or

[0062] In step S3, the pH value of the alkali treatment is 8.0 to 8.5; and or

[0063] In the step S4, the pH value of the alkali treatment is 9-11.

[0064] By controlling the amount of alkali added in each step, the pH value in the reaction is maintained within the respective range, so that the corresponding target product is formed in each reaction, and the reaction is ensured to be more complete, which is beneficial to the sufficient precipitation of each reaction.

[0065] Furthermore, in the embodiment of the present application, the method for removing ammonia in S5 includes stripping, and the ammonia gas generated by stripping is introduced into the second tail liquid or used to prepare the ammonia water. Finally, the stripping method is used to remove ammonia nitrogen. Compared with other methods of removing ammonia nitrogen, the ammonia nitrogen concentration in the wastewater can be reduced to a lower level, meet more stringent emission standards, and have a lower operating cost; the stripping system is relatively simple, easy to operate and maintain, does not require a complex chemical treatment process, and the stripping method will not cause secondary pollution to the environment; in addition, the generated ammonia gas can also be used as an alkali source for precipitation and filtration again, so that it can be recycled to further reduce production costs.

[0066] Furthermore, in the present application, due to the presence of the MVR evaporation and concentration pre-step, the step-by-step precipitation process is carried out in a high-temperature environment, thereby avoiding the waste of phosphate recovery exceeding the calorific value in the traditional process by low-temperature crystallization, and no additional heat source is required in the ammonia nitrogen stripping process.

[0067] Please refer to Figure 1 , Figure 1 A schematic diagram of the structure of an iron phosphate wastewater treatment system provided in some embodiments of the present application.

[0068] In a second aspect, the present application also provides an iron phosphate wastewater treatment system, which is used to treat iron phosphate wastewater using the above-mentioned iron phosphate wastewater treatment method, and includes an MVR evaporation device, a separation device, a multi-stage precipitation and filtration device, and a deammoniation device connected in sequence;

[0069] The outlet of the deammoniation device is connected to the MVR evaporation device, and the outlet of the separation device is also connected to the MVR evaporation device.

[0070] The MVR evaporation device comprises an MVR evaporation device connected to the separation device, and a centrifuge connected to the outlet of the MVR evaporation device;

[0071] The separation device comprises a separation tank connected to the outlet of the MVR evaporation device; the separation tank is connected to the MVR evaporation device;

[0072] In this way, the impurity elements that are not fully treated in the above-mentioned iron phosphate wastewater treatment method can be returned to the system for treatment, so as to fully recycle the wastewater.

[0073] Further, in the embodiments of the present application, Figure 1As shown, the multi-stage sedimentation and filtration device includes a primary sedimentation and filtration unit, a secondary sedimentation and filtration unit and a tertiary sedimentation and filtration unit which are connected in sequence; the deammoniation device includes a deammoniation tank and a sand filter tank; the outlet of the deammoniation tank is connected to the inlet of the secondary sedimentation tank in the secondary sedimentation and filtration unit; the secondary sedimentation and filtration unit is also connected to the inlet of the calcination system, and the outlet of the calcination system is connected to the inlet of the secondary sedimentation tank in the secondary sedimentation and filtration unit.

[0074] The primary sedimentation and filtration unit comprises a primary sedimentation tank connected to the outlet of the separation tank, and a primary filtration tank connected to the outlet of the primary sedimentation tank; the secondary sedimentation and filtration unit comprises a secondary sedimentation tank connected to the outlet of the primary filtration tank, and a secondary filtration tank connected to the outlet of the secondary sedimentation tank; the tertiary sedimentation and filtration unit comprises a tertiary sedimentation tank connected to the outlet of the secondary filtration tank, and a tertiary filtration tank connected to the outlet of the tertiary sedimentation tank;

[0075] Specifically, the first tail liquid separated by MVR evaporation and concentration is first subjected to primary precipitation in a primary sedimentation tank by adjusting the pH value. After the precipitation is completed, the heavy metal impurities in the wastewater are removed in the primary filtration tank to reduce the content of harmful components in the wastewater, thereby obtaining a second tail liquid. Then, the second tail liquid is subjected to secondary precipitation in a secondary sedimentation tank by adjusting the pH value. After the precipitation is completed, the phosphate impurities in the wastewater are further removed in the secondary filtration tank, thereby reducing the burden of subsequent treatment and obtaining a third tail liquid. Subsequently, the third tail liquid is subjected to tertiary precipitation in a tertiary sedimentation tank by adjusting the pH value. After the precipitation is completed, the fluorine element in the wastewater is removed in the tertiary filtration tank to reduce the harm of the wastewater to the environment. In this way, the recovery of resources in the iron phosphate wastewater is maximized through the step-by-step precipitation method.

[0076] The following is an explanation of the working process of a method and system for treating iron phosphate wastewater provided by the present application: Figure 1 As shown,

[0077] S1, evaporating and concentrating the iron phosphate wastewater through an MVR evaporation device, and separating the byproduct ammonium sulfate and the first tail liquid through a centrifuge;

[0078] S2, the first tail liquid enters the separation tank, the separated semi-crystalline solution is returned to the MVR evaporation equipment for reprocessing, and the supernatant in the separation tank enters the primary sedimentation tank; then magnesium oxide is added to the primary sedimentation tank to consume the acidity of the first tail liquid (MgO+2H + →Mg 2+ +H2O), and adjust the pH value of the solution to 5.0-5.5 for precipitation. After the precipitation is completed, it enters the primary filtration tank for solid-liquid separation to remove metal impurities in the first tail liquid to obtain a second tail liquid;

[0079] S3, the second tail liquid enters the secondary sedimentation tank, ammonia water is added to the secondary sedimentation tank, and the pH value of the solution is adjusted to 8.0-8.5 for precipitation. After the precipitation is completed, it enters the secondary filtration tank for solid-liquid separation to obtain the third tail liquid, wherein the precipitate is magnesium ammonium phosphate precipitate; at the same time, the magnesium ammonium phosphate precipitate is calcined through a dryer and a roller kiln to generate magnesium hydrogen phosphate and ammonia, and the generated ammonia is directly introduced into the second tail liquid or used to prepare the ammonia water;

[0080] S4, the third tail liquid enters the tertiary sedimentation tank, then lime solution is added to the tertiary sedimentation tank, and the pH value of the solution is adjusted to 9-11, forming calcium phosphate and calcium fluoride precipitation with P element and F, and adsorbing COD in the tail liquid at the same time. After the precipitation is completed, it enters the tertiary filtration tank for solid-liquid separation to obtain the fourth tail liquid, wherein the filtration can obtain white phosphate fertilizer byproduct;

[0081] S5, the fourth tail liquid enters the deammonification tank for stripping to remove ammonia, and then enters the sand filter tank for filtration. The filtered solution enters the MVR evaporation equipment to continue the S1 process, and the ammonia gas produced by stripping is introduced into the second tail liquid or used to prepare the ammonia water.

[0082] Please also read Figure 1 According to one or more embodiments of the present application, the method for treating iron phosphate wastewater provided by the present application includes: firstly separating the ammonium sulfate in the wastewater through an MVR evaporation device, and then performing primary precipitation by adjusting the pH value to remove heavy metal impurities in the wastewater; then adding ammonia water for secondary precipitation filtration to further remove phosphate impurities in the iron phosphate wastewater; then adding lime for tertiary precipitation filtration to remove fluorine elements in the wastewater; finally, the fourth tail liquid obtained is subjected to ammonia removal treatment and returned to the first step, and the above-mentioned repeated treatment is performed again to avoid insufficient resource recovery; the ammonia generated is reused in the secondary precipitation filtration; this method of directly recovering resources in the iron phosphate wastewater through high-temperature treatment and coordinated step-by-step precipitation method not only avoids the waste of calorific value, reduces the energy consumption cost of subsequent treatment of the tail liquid, reduces the cost of using the dosage of the reagent in the system, but also reduces the pollution to the environment, and has good environmental benefits.

[0083] In addition, the iron phosphate wastewater treatment system provided in the present application is composed of an MVR evaporation device, a separation device, a multi-stage sedimentation and filtration device and a deammoniation device connected in sequence, wherein the outlets of the deammoniation device and the separation device are also connected to the MVR evaporation device, thereby forming a complete iron phosphate wastewater treatment system to meet the recovery and utilization of ammonia in the iron phosphate wastewater treatment method provided above.

[0084] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and the same effect as the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for treating iron phosphate wastewater, It is characterized in that The steps include: S1, performing MVR evaporation and concentration on the iron phosphate wastewater to obtain a first tail liquid; S2, treating the first tail liquid with alkali to obtain a second tail liquid after solid-liquid separation; S3, treating the second tail liquid with alkali to obtain a third tail liquid after solid-liquid separation; S4, treating the third tail liquid with alkali to obtain a fourth tail liquid after solid-liquid separation; S5, removing ammonia from the fourth tail liquid and returning to step S1.

2. The method for treating iron phosphate wastewater according to claim 1, It is characterized in that In the step of treating the first tail liquid with alkali, the alkali used is magnesium oxide.

3. The method for treating iron phosphate wastewater according to claim 1, It is characterized in that In the step of treating the second tail liquid with an alkali, the alkali used is aqueous ammonia.

4. The method for treating iron phosphate wastewater according to claim 3, It is characterized in that treating the second tail liquid with alkali to obtain magnesium ammonium phosphate precipitate after solid-liquid separation; The magnesium ammonium phosphate precipitate is calcined, and the ammonia generated by the calcination is directly introduced into the second tail liquid or used to prepare the ammonia water.

5. The method for treating iron phosphate wastewater according to claim 1, It is characterized in that In the step of treating the third tail liquid with alkali, the alkali used is lime.

6. The method for treating iron phosphate wastewater according to claim 1, It is characterized in that In the step S2, the pH value of the alkali treatment is 5.0 to 5.5; and or In step S3, the pH value of the alkali treatment is 8.0 to 8.5; and or In the step S4, the pH value of the alkali treatment is 9-11.

7. The method for treating iron phosphate wastewater according to claim 3, It is characterized in that The method for removing ammonia in S5 includes stripping, and the ammonia gas generated by stripping is introduced into the second tail liquid or used to prepare the ammonia water.

8. A ferric phosphate wastewater treatment system, It is characterized in that The ferric phosphate wastewater is treated by the ferric phosphate wastewater treatment method as described in any one of claims 1 to 7 above. The iron phosphate wastewater treatment system comprises an MVR evaporation device, a separation device, a multi-stage precipitation and filtration device and a deammoniation device connected in sequence; The outlet of the deammoniation device is connected to the MVR evaporation device, and the outlet of the separation device is also connected to the MVR evaporation device.

9. The iron phosphate wastewater treatment system according to claim 8, It is characterized in that The multi-stage sedimentation and filtration device comprises a primary sedimentation and filtration unit, a secondary sedimentation and filtration unit and a tertiary sedimentation and filtration unit connected in sequence, and the deammonification device comprises a deammonification tank and a sand filter tank; the outlet of the deammonification tank is connected to the inlet of the secondary sedimentation and filtration unit.

10. The iron phosphate wastewater treatment system according to claim 8, It is characterized in that The secondary precipitation and filtration unit is also connected to the inlet of the calcination system, and the outlet of the calcination system is connected to the inlet of the secondary precipitation and filtration unit.

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