Iron phosphate wastewater treatment process and system

Abstract

The application provides a treatment process and system for ferriphosphate wastewater, and belongs to the field of ferriphosphate wastewater treatment. The treatment process for ferriphosphate wastewater comprises the following steps: alkali treatment of a first mother liquor, solid-liquid separation to obtain a first filtrate; alkali treatment of a second mother liquor, solid-liquid separation to obtain a second filtrate; alkali treatment of washing water, solid-liquid separation to obtain a third filtrate; mixing of the second filtrate and the third filtrate for RO concentration and concentration to obtain a concentrated solution; mixing of the concentrated solution and the first filtrate for MVR evaporation and concentration, solid-liquid separation to obtain a waste liquid; recycling of the waste liquid to the first mother liquor for cyclic treatment; the ferriphosphate wastewater comprises a synthetic mother liquor, an aging mother liquor and washing water; the first mother liquor is composed of the synthetic mother liquor and the waste liquid; the second mother liquor is composed of the synthetic mother liquor and the aging mother liquor; through the process, the pollutants in the wastewater can be effectively removed, and the RO system can be smoothly operated.

Description

Technical Field

[0001] This invention relates to the field of ferric phosphate wastewater treatment technology, specifically to a process and system for treating ferric phosphate wastewater. Background Technology

[0002] The commonly used production process for ferric phosphate is the co-precipitation method. It utilizes ferrous sulfate, hydrogen peroxide, diammonium hydrogen phosphate, and phosphoric acid to produce high-quality ferric phosphate through processes such as synthesis, first washing, aging, and second washing. During the production process, synthesis mother liquor, first washing water, aging mother liquor, and second washing water are generated, which combine to form ferric phosphate wastewater. The synthesis mother liquor is the saturated solution separated after the raw materials are synthesized in the ferric phosphate production process. The aging mother liquor is the saturated solution separated after the synthesized impurity phase ferric phosphate has undergone a constant temperature aging process. The washing water is an aqueous solution used for separation and impurity removal, which is a mixture of first washing water and second washing water.

[0003] Typically, when treating ferric phosphate wastewater, the synthesis mother liquor and the aging mother liquor are mixed, allowing the phosphorus (P) element in the aging mother liquor to act as a precipitant and precipitate the metal elements in the synthesis mother liquor. The first wash water and the second wash water are mixed, allowing the P element in the second wash water to act as a precipitant and precipitate the metal elements in the first wash water. After pretreatment, the two types of wastewater enter an RO system for concentration and desalination, forming pure water and a concentrated liquid. The concentrated liquid enters an MVR system for evaporation and concentration. During the evaporation and concentration process, byproducts ammonium sulfate and waste liquid are generated. The waste liquid contains a large amount of P element and impurities such as Ca, Mg, F, and COD, which affect the evaporation in the MVR system. Therefore, it enters a drum dryer for drying, forming a low-value dried material.

[0004] However, due to the increasingly poor quality of raw materials, the impurities and salt content of the synthesis mother liquor will increase, making it impossible for the aged mother liquor to effectively remove metal impurities such as Ca, Mg, Mn, and Fe from the synthesis mother liquor. After the mother liquor is pretreated, it enters the RO system and mixes with the excess P element in the wash water, forming a large amount of metal precipitates, which clogs the RO system, increases the load on the RO system, and results in poor treatment effect of ferric phosphate wastewater. Therefore, it is necessary to provide a solution that can effectively remove pollutants from wastewater while ensuring the smooth operation of the RO system. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application provides a treatment process and system for ferric phosphate wastewater, aiming to solve the technical problem of how to effectively remove pollutants from wastewater while ensuring the smooth operation of the RO system.

[0006] In a first aspect, embodiments of this application provide a treatment process for ferric phosphate wastewater, comprising the following steps: alkali treatment of a first mother liquor, followed by solid-liquid separation to obtain a first filtrate; alkali treatment of a second mother liquor, followed by solid-liquid separation to obtain a second filtrate; alkali treatment of wash water, followed by solid-liquid separation to obtain a third filtrate; mixing the second and third filtrates for RO concentration to obtain a concentrate; mixing the concentrate with the first filtrate for MVR evaporation concentration, followed by solid-liquid separation to obtain waste liquid; and recycling the waste liquid back to the first mother liquor for recycling treatment; the ferric phosphate wastewater comprises a synthesis mother liquor, an aging mother liquor, and wash water; the first mother liquor is composed of the synthesis mother liquor and the waste liquid; and the second mother liquor is composed of the synthesis mother liquor and the aging mother liquor.

[0007] In the technical solution of this application embodiment, the synthesis mother liquor is divided into two parts, a first mother liquor and a second mother liquor, for processing. Since the first mother liquor does not need to be treated by the RO system, the amount of mother liquor processed by the RO system can be reduced, the impact of salt on the RO system can be reduced, and the load on the RO system can be reduced to avoid RO system blockage. On the other hand, in order to solve the problem that impurities and pollutants are not completely removed due to the first mother liquor not being treated by the RO system, the first mother liquor, the second mother liquor, and the wash water are treated and then merged into the wastewater and circulated back to the first mother liquor. The excess P in the wash water is used to further treat the synthesis mother liquor in the first mother liquor, thereby reducing the load on the RO system and effectively removing impurities and pollutants from the wastewater.

[0008] In some embodiments, the ferric phosphate wastewater is generated by the ferric phosphate coprecipitation process; the synthesis mother liquor is a saturated solution separated after the raw material synthesis, the aging mother liquor is a saturated solution separated after the synthesized impurity phase ferric phosphate undergoes a constant temperature aging process, and the wash water is an aqueous solution used for separation and impurity removal.

[0009] In this embodiment, the synthesis mother liquor has a high content of metallic impurities and high salt content, the aging mother liquor has a high content of phosphorus and high salt content, and the wash water has a low salt content but contains phosphorus. The Ca, Mg, Mn, Fe, and F impurities in the ferric phosphate wastewater can be removed by phosphorus, and the F and COD in the ferric phosphate wastewater can be removed by alkali treatment. By collecting and classifying the ferric phosphate wastewater in segments, it is beneficial to prepare the first mother liquor and the second mother liquor according to the treatment process of this application, and to utilize the wash water.

[0010] In some embodiments, the Ca content in the first mother liquor is 95-105 ppm, the Ca content in the second mother liquor is 8-12 ppm, and the Ca content in the wash water is 2-5 ppm.

[0011] In this embodiment, under the limited Ca content, it is beneficial to reduce the Ca ion content entering the MVR system, avoid clogging of the MVR system, and completely treat Ca element impurities in the ferric phosphate wastewater.

[0012] In some embodiments, the P content in the first mother liquor is 6000-6500 ppm, the P content in the second mother liquor is 700-750 ppm, and the P content in the wash water is 150-180 ppm.

[0013] In this embodiment, under the specified P content, it is beneficial to reduce the risk of RO system blockage and to completely treat P element impurities in ferric phosphate wastewater.

[0014] In some embodiments, the salt content in the first mother liquor is 100,000-130,000 mg / L, the salt content in the second mother liquor is 50,000-60,000 mg / L, and the salt content in the washing water is 6,000-7,000 mg / L.

[0015] In this embodiment, under the specified salt content, it is beneficial to reduce the risk of RO system blockage and to completely treat the salt impurities in the ferric phosphate wastewater.

[0016] In some embodiments, during the alkali pretreatment of the first mother liquor, the alkali used is lime water and / or ammonia water, and the pH value of the alkali treatment is 8-9.

[0017] In this embodiment, lime water can remove the P source in the first mother liquor, preventing P from accumulating into ammonium sulfate crystals; ammonia water can improve the utilization efficiency of the P source and reduce costs.

[0018] In some embodiments, during the alkali pretreatment of the second mother liquor, the alkali used is ammonia water, and the pH value of the alkali treatment is 8-9.

[0019] In this embodiment, ammonia can improve the utilization efficiency of the P source and reduce costs.

[0020] In some embodiments, the alkali used in the alkaline pretreatment of the wash water is ammonia water, and the pH value of the alkaline treatment is 8-9.

[0021] In this embodiment, ammonia can improve the utilization efficiency of the P source and reduce costs.

[0022] In some embodiments, the solid-liquid separation step includes, in sequence, plate and frame filter press filtration and sand filter tank filtration.

[0023] In this embodiment, solid-liquid separation can be fully achieved by using a filter press.

[0024] Secondly, embodiments of this application provide a ferric phosphate wastewater treatment system, including a first mother liquor treatment device, a second mother liquor treatment device, a wash water treatment device, an RO reverse osmosis device, an RO concentrate tank, and an MVR evaporation device; the second mother liquor treatment device and the wash water treatment device respectively convey alkali-treated second mother liquor and alkali-treated wash water to the RO reverse osmosis device through conveying pipelines; the first mother liquor treatment device conveys alkali-treated first mother liquor to the RO concentrate tank through conveying pipelines; the RO reverse osmosis device is used to collect and concentrate the mixture of alkali-treated second mother liquor and alkali-treated wash water, and is connected to the RO concentrate tank through conveying pipelines; the MVR evaporation device is connected to the RO concentrate tank and to the first mother liquor treatment device; the ferric phosphate wastewater treatment system is used to perform the ferric phosphate wastewater treatment process.

[0025] The first mother liquor treatment device includes a first mother liquor tank, a first mother liquor pretreatment reaction tank, a plate and frame filter press, and a sand filter tank connected in sequence; the second mother liquor treatment device includes a second mother liquor tank, a second mother liquor pretreatment reaction tank, a plate and frame filter press, a sand filter tank, and an ultrafiltration device connected in sequence; the wash water treatment device includes a wash water tank, a wash water pretreatment reaction tank, a plate and frame filter press, a sand filter tank, and an ultrafiltration device connected in sequence; the MVR evaporation device 6 includes an MVR system, a centrifuge, and a waste liquid tank connected in sequence, the MVR system is connected to the RO concentrate tank 5, and the waste liquid tank is connected to the first mother liquor tank.

[0026] In the technical solution of this application embodiment, the ferric phosphate wastewater treatment system implements a ferric phosphate wastewater treatment process. First, the ferric phosphate wastewater is collected into an RO concentrate tank via a three-stage treatment route. Then, the concentrate in the RO concentrate tank is transported to an MVR system for evaporation and concentration to form an MVR concentrate mother liquor. The MVR concentrate mother liquor enters a centrifuge for solid-liquid separation, forming ammonium sulfate byproduct and waste liquid. The waste liquid is then returned to the first mother liquor for recycling. The three-stage treatment route includes:

[0027] A portion of the synthetic mother liquor is used as the first mother liquor. After pH adjustment and chemical impurity removal by a mixture of lime water and ammonia water, it enters a plate and frame filter press for mud-water separation. The water produced by the plate and frame filter press is filtered through a sand filter tank and then transported to the RO concentrate tank.

[0028] Another part of the synthetic mother liquor is combined with the aged mother liquor to form a second mother liquor. After the pH is adjusted by ammonia water and chemical impurities are removed, it enters a plate and frame filter press for mud-water separation. The water produced by the plate and frame filter press is filtered through a sand filter tank. The water produced by the sand filter tank enters an ultrafiltration device for filtration. The ultrafiltration water enters an RO reverse osmosis unit for concentration and desalination, and then flows into the RO concentrate tank.

[0029] After the wash water is adjusted for pH and chemically removed with ammonia, it enters a plate and frame filter press for mud-water separation. The water produced by the plate and frame filter press is filtered through a sand filter tank. The water produced by the sand filter tank enters an ultrafiltration device for filtration. The ultrafiltration water enters an RO reverse osmosis unit for concentration and desalination, and then flows into the RO concentrate tank.

[0030] The above-mentioned treatment process for ferric phosphate wastewater effectively removes pollutants from the wastewater while reducing the processing pressure of the RO system, preventing RO equipment blockage, and lowering wastewater treatment costs.

[0031] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0033] Figure 1 This is a schematic diagram of the ferric phosphate wastewater treatment system of this application;

[0034] In the diagram: 1. First mother liquor treatment device; 2. Second mother liquor treatment device; 3. Wash water treatment device; 4. RO reverse osmosis device; 5. RO concentrate tank; 6. MVR evaporation device. Detailed Implementation

[0035] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0037] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0038] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0039] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0040] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0041] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0042] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0043] Typically, when treating ferric phosphate wastewater, the synthesis mother liquor and the aging mother liquor are mixed, allowing the phosphorus (P) element in the aging mother liquor to act as a precipitant and precipitate the metal elements in the synthesis mother liquor. The first wash water and the second wash water are mixed, allowing the P element in the second wash water to act as a precipitant and precipitate the metal elements in the first wash water. After pretreatment, the two types of wastewater enter an RO system for concentration, forming pure water and a concentrated liquid. The concentrated liquid enters an MVR system for evaporation and concentration. During the evaporation and concentration process, ammonium sulfate and waste liquid are generated as byproducts. The waste liquid contains a large amount of P element and impurities such as Ca, Mg, F, and COD, which affect the evaporation in the MVR system. Therefore, it enters a drum dryer for drying, forming a low-value dried material. However, due to the increasingly poor quality of raw materials, the impurities and salt content of the synthesis mother liquor increase, making it impossible for the aged mother liquor to effectively remove metallic impurities such as Ca, Mg, Mn, and Fe from the synthesis mother liquor. When the mother liquor mixture enters the RO system, it mixes with the excess P element in the wash water, forming a large amount of metal precipitates, which clogs the RO system, increases the load on the RO system, and results in poor treatment of ferric phosphate wastewater. Therefore, it is necessary to provide a solution that can effectively remove pollutants from wastewater while ensuring the smooth operation of the RO system.

[0044] To address the technical challenge of effectively removing pollutants from wastewater while ensuring the smooth operation of the RO system, this application provides a treatment process and system for ferric phosphate wastewater.

[0045] In a first aspect, embodiments of this application provide a treatment process for ferric phosphate wastewater, comprising the following steps: alkali treatment of a first mother liquor, followed by solid-liquid separation to obtain a first filtrate; alkali treatment of a second mother liquor, followed by solid-liquid separation to obtain a second filtrate; alkali treatment of wash water, followed by solid-liquid separation to obtain a third filtrate; mixing the second and third filtrates for RO concentration to obtain a concentrate; mixing the concentrate with the first filtrate for MVR evaporation concentration, followed by solid-liquid separation to obtain waste liquid; and recycling the waste liquid back to the first mother liquor for recycling treatment; the ferric phosphate wastewater comprises a synthesis mother liquor, an aging mother liquor, and wash water; the first mother liquor is composed of the synthesis mother liquor and the waste liquid; and the second mother liquor is composed of the synthesis mother liquor and the aging mother liquor.

[0046] In the technical solution of this application embodiment, the synthesis mother liquor is divided into two parts for treatment: a first mother liquor and a second mother liquor. One part of the synthesis mother liquor is mixed with waste liquid to form the first mother liquor, and the other part of the synthesis mother liquor is mixed with aged mother liquor to form the second mother liquor. Since the first mother liquor does not need to be treated by the RO system, the amount of mother liquor treated by the RO system can be reduced, the impact of salt on the RO system can be reduced, and the load on the RO system can be reduced to avoid RO system blockage. On the other hand, in order to solve the problem of incomplete removal of impurities and pollutants due to the first mother liquor not being treated by the RO system, the first mother liquor, the second mother liquor, and the wash water are treated and then merged into the waste liquid and recycled back to the first mother liquor. The excess phosphorus in the wash water is concentrated to form a high-phosphorus waste liquid, which is then used to further treat the synthesis mother liquor in the first mother liquor. This can effectively remove impurities and pollutants from the ferric phosphate wastewater while reducing the load on the RO system. In this application, the necessity of not requiring the first mother liquor to be treated by the RO system is that the waste liquid has a high salt content, and if the waste liquid is reused in the first mother liquor and then enters the RO system for treatment, it will cause RO system blockage.

[0047] Synthetic mother liquor, aging mother liquor, and wash water are well-known terms used by those skilled in the art when conducting conventional production using the ferric phosphate coprecipitation method.

[0048] In some embodiments, the ferric phosphate wastewater is generated by the ferric phosphate coprecipitation process; the synthesis mother liquor is a saturated solution separated after the raw material synthesis, the aging mother liquor is a saturated solution separated after the synthesized impurity phase ferric phosphate undergoes a constant temperature aging process, and the wash water is an aqueous solution used for separation and impurity removal.

[0049] In this embodiment, the synthesis mother liquor has a high content of metallic impurities and high salt content, the aging mother liquor has a high content of phosphorus and high salt content, and the wash water has a low salt content but contains phosphorus. The Ca, Mg, Mn, Fe, and F impurities in the ferric phosphate wastewater can be removed by phosphorus, and the F and COD in the ferric phosphate wastewater can be removed by alkali treatment. By collecting and classifying the ferric phosphate wastewater in segments, it is beneficial to prepare the first mother liquor and the second mother liquor according to the treatment process of this application, and to utilize the wash water.

[0050] In some embodiments, the Ca content in the first mother liquor is 95-105 ppm, the Ca content in the second mother liquor is 8-12 ppm, and the Ca content in the wash water is 2-5 ppm.

[0051] In this embodiment, under the limited Ca content, it is beneficial to reduce the Ca ion content entering the MVR system, avoid clogging of the MVR system, and completely treat Ca element impurities in the ferric phosphate wastewater.

[0052] In some embodiments, the P content in the first mother liquor is 6000-6500 ppm, the P content in the second mother liquor is 700-750 ppm, and the P content in the wash water is 150-180 ppm.

[0053] In this embodiment, under the specified P content, it is beneficial to reduce the risk of RO system blockage and to completely treat P element impurities in ferric phosphate wastewater.

[0054] In some embodiments, the salt content in the first mother liquor is 100,000-130,000 mg / L, the salt content in the second mother liquor is 50,000-60,000 mg / L, and the salt content in the washing water is 6,000-7,000 mg / L.

[0055] In this embodiment, under the specified salt content, it is beneficial to reduce the risk of RO system blockage and to completely treat the salt impurities in the ferric phosphate wastewater.

[0056] In some embodiments, during the alkali pretreatment of the first mother liquor, the alkali used is lime water and / or ammonia water, and the pH value of the alkali treatment is 8-9.

[0057] In this embodiment, lime water can precipitate and remove the P source and some impurity elements in the first mother liquor, preventing P from accumulating into ammonium sulfate crystals; adding ammonia water appropriately can increase the alkalinity, promote precipitation, improve the utilization efficiency of the P source, and reduce costs.

[0058] In some embodiments, during the alkali pretreatment of the second mother liquor, the alkali used is ammonia water, and the pH value of the alkali treatment is 8-9.

[0059] In this embodiment, ammonia can increase alkalinity, promote precipitation, improve the utilization efficiency of the P source, and reduce costs.

[0060] In some embodiments, the alkali used in the alkaline pretreatment of the wash water is ammonia water, and the pH value of the alkaline treatment is 8-9.

[0061] In this embodiment, ammonia can increase alkalinity, promote precipitation, improve the utilization efficiency of the P source, and reduce costs.

[0062] In some embodiments, the solid-liquid separation step includes, in sequence, plate and frame filter press filtration and sand filter tank filtration.

[0063] In this embodiment, solid-liquid separation can be fully achieved by using a filter press.

[0064] like Figure 1As shown in the figure, this application provides a ferric phosphate wastewater treatment system, including a first mother liquor treatment device 1, a second mother liquor treatment device 2, a wash water treatment device 3, an RO reverse osmosis device 4, an RO concentrate tank 5, and an MVR evaporator 6. The second mother liquor treatment device 2 and the wash water treatment device 3 respectively convey alkali-treated second mother liquor and alkali-treated wash water to the RO reverse osmosis device 4 through conveying pipelines. The first mother liquor treatment device 1 conveys alkali-treated first mother liquor to the RO concentrate tank 5 through conveying pipelines. The RO reverse osmosis device 4 is used to collect and concentrate the mixture of alkali-treated second mother liquor and alkali-treated wash water, and is connected to the RO concentrate tank 5 through conveying pipelines. The MVR evaporator 6 is connected to the RO concentrate tank 5 and to the first mother liquor treatment device 1. The ferric phosphate wastewater treatment system is used to perform the ferric phosphate wastewater treatment process.

[0065] The first mother liquor treatment device 1 includes a first mother liquor tank, a first mother liquor pretreatment reaction tank, a plate and frame filter press, and a sand filter tank connected in sequence; the second mother liquor treatment device 2 includes a second mother liquor tank, a second mother liquor pretreatment reaction tank, a plate and frame filter press, a sand filter tank, and an ultrafiltration device connected in sequence; the washing water treatment device 3 includes a washing water tank, a washing water pretreatment reaction tank, a plate and frame filter press, a sand filter tank, and an ultrafiltration device connected in sequence; the MVR evaporation device 6 includes an MVR system, a centrifuge, and a waste liquid tank connected in sequence, the MVR system is connected to the RO concentrate tank 5, and the waste liquid tank is connected to the first mother liquor tank.

[0066] In the technical solution of this application embodiment, the ferric phosphate wastewater treatment system implements a ferric phosphate wastewater treatment process. First, the ferric phosphate wastewater is collected into an RO concentrate tank 5 via a three-stage treatment route. Then, the concentrate in the RO concentrate tank 5 is transported to an MVR system for evaporation and concentration to form an MVR concentrate mother liquor. The MVR concentrate mother liquor enters a centrifuge for solid-liquid separation, forming ammonium sulfate byproducts and waste liquid. The waste liquid is then returned to the first mother liquor for recycling. The three-stage treatment route includes:

[0067] A portion of the synthetic mother liquor is used as the first mother liquor. After pH adjustment and chemical impurity removal by a mixture of lime water and ammonia water, it enters a plate and frame filter press for mud-water separation. The water produced by the plate and frame filter press is filtered through a sand filter tank and then transported to the RO concentrate tank 5.

[0068] Another part of the synthetic mother liquor is combined with the aged mother liquor to form a second mother liquor. After the pH is adjusted by ammonia water and chemical impurities are removed, it enters a plate and frame filter press for mud-water separation. The water produced by the plate and frame filter press is filtered through a sand filter tank. The water produced by the sand filter tank enters an ultrafiltration device for filtration. The ultrafiltration water enters the RO reverse osmosis unit 4 for concentration and desalination, and then flows into the RO concentrate tank 5.

[0069] After the wash water is adjusted for pH and chemically removed with ammonia, it enters a plate and frame filter press for mud-water separation. The water produced by the plate and frame filter press is filtered through a sand filter tank. The water produced by the sand filter tank enters an ultrafiltration device for filtration. The ultrafiltration water enters an RO reverse osmosis unit 4 for concentration and desalination, and then flows into the RO concentrate tank 5.

[0070] The above-mentioned treatment process for ferric phosphate wastewater effectively removes pollutants from the wastewater while reducing the processing pressure of the RO system, preventing RO equipment blockage, and lowering wastewater treatment costs.

[0071] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0072] Raw material source:

[0073] Ferric phosphate wastewater is generated from the ferric phosphate coprecipitation process. The synthesis mother liquor is a saturated solution separated after the raw material synthesis, the aging mother liquor is a saturated solution separated after the synthesized impurity phase ferric phosphate undergoes a constant-temperature aging process, and the wash water is an aqueous solution used for impurity removal. The synthesis mother liquor, aging mother liquor, and wash water generated in a certain workshop were used as raw materials for ferric phosphate wastewater treatment in this application embodiment. The impurity content in the synthesis mother liquor, aging mother liquor, and wash water is shown in Table 1.

[0074] Table 1. Distribution of impurities in ferric phosphate wastewater

[0075]

[0076] I. Processing Technology and System

[0077] Example 1

[0078] A ferric phosphate wastewater treatment system includes a first mother liquor treatment device 1, a second mother liquor treatment device 2, a wash water treatment device 3, an RO reverse osmosis device 4, an RO concentrate tank 5, and an MVR evaporator 6. The second mother liquor treatment device 2 and the wash water treatment device 3 respectively supply alkali-treated second mother liquor and alkali-treated wash water to the RO reverse osmosis device 4 through conveying pipelines. The first mother liquor treatment device 1 supplies alkali-treated first mother liquor to the RO concentrate tank 5 through conveying pipelines. The RO reverse osmosis device 4 is used to collect and concentrate the mixture of alkali-treated second mother liquor and alkali-treated wash water, and is connected to the RO concentrate tank 5 through conveying pipelines. The MVR evaporator 6 is connected to the RO concentrate tank 5 and the first mother liquor treatment device 1. The ferric phosphate wastewater treatment system is used to perform the ferric phosphate wastewater treatment process.

[0079] The first mother liquor treatment device 1 includes a first mother liquor tank, a first mother liquor pretreatment reaction tank, a plate and frame filter press, and a sand filter tank connected in sequence; the second mother liquor treatment device 2 includes a second mother liquor tank, a second mother liquor pretreatment reaction tank, a plate and frame filter press, a sand filter tank, and an ultrafiltration device connected in sequence; the washing water treatment device 3 includes a washing water tank, a washing water pretreatment reaction tank, a plate and frame filter press, a sand filter tank, and an ultrafiltration device connected in sequence; the MVR evaporation device 6 includes an MVR system, a centrifuge, and a waste liquid tank connected in sequence, the MVR system is connected to the RO concentrate tank 5, and the waste liquid tank is connected to the first mother liquor tank.

[0080] The process of treating ferric phosphate wastewater using the above system includes the following steps:

[0081] A portion of the synthetic mother liquor is used as the first mother liquor. After the pH is adjusted to 8.5 and chemically removed by a mixture of lime water and ammonia water in the pretreatment reaction tank of the first mother liquor, it enters the plate and frame filter press for mud-water separation. After the water produced by the plate and frame filter press is filtered by the sand filter tank, the water produced by the sand filter tank is used to obtain the first filtrate and is sent to the RO concentrate tank 5.

[0082] Another part of the synthetic mother liquor is combined with the aged mother liquor to form the second mother liquor. After the pH of the second mother liquor is adjusted to 8.5 by ammonia water and chemical impurities are removed in the pretreatment reaction tank, it enters the plate and frame filter press for mud-water separation. The water produced by the plate and frame filter press is filtered through a sand filter tank. The water produced by the sand filter tank enters the ultrafiltration equipment for filtration. The ultrafiltration water is the second filtrate.

[0083] The wash water is adjusted to pH 8.5 with ammonia water and chemically removed in the pretreatment reaction tank before entering the plate and frame filter press for mud-water separation. The water produced by the plate and frame filter press is filtered through a sand filter tank. The water produced by the sand filter tank enters the ultrafiltration equipment for filtration. The ultrafiltration water produces the third filtrate.

[0084] The second and third filtrates are fed into the RO reverse osmosis unit 4 for processing to obtain concentrated liquid and pure water. The pure water is collected in the pure water tank and the concentrated liquid is collected in the RO concentrated liquid tank 5 and mixed with the first filtrate.

[0085] The concentrate is mixed with the first filtrate and then fed into the MVR system for evaporation and concentration to form the MVR concentrated mother liquor. The MVR concentrated mother liquor is then fed into a centrifuge for solid-liquid separation to form ammonium sulfate byproduct and waste liquid. The waste liquid is then returned to the first mother liquor for recycling.

[0086] In the first mother liquor, the ratio of synthetic mother liquor to waste liquor is 8:2. The aged mother liquor in the iron phosphate wastewater and the remaining synthetic mother liquor are combined to form the second mother liquor. The distribution of impurity content in the first and second mother liquors is shown in Table 2.

[0087] Table 2. Distribution of impurity content in the first and second mother liquors of Example 1

[0088]

[0089] Example 2

[0090] A treatment process for ferric phosphate wastewater is the same as that in Example 1, except that the ratio of synthetic mother liquor to waste liquor in the first mother liquor is 9.5:0.5; the distribution of impurity content in the first and second mother liquors is shown in Table 3.

[0091] Table 3. Distribution of impurity content in the first and second mother liquors of Example 2

[0092]

[0093] Example 3

[0094] A treatment process for ferric phosphate wastewater is the same as that in Example 1, except that the ratio of synthetic mother liquor to waste liquor in the first mother liquor is 9:1. The distribution of impurity content in the first and second mother liquors is shown in Table 4.

[0095] Table 4. Distribution of impurity content in the first and second mother liquors of Example 3

[0096]

[0097] Example 4

[0098] A treatment process for ferric phosphate wastewater is the same as that in Example 1, except that the ratio of synthetic mother liquor to waste liquor in the first mother liquor is 8.5:1.5; the distribution of impurity content in the first and second mother liquors is shown in Table 5.

[0099] Table 5. Distribution of impurity content in the first and second mother liquors of Example 4

[0100]

[0101] Example 5

[0102] A treatment process for ferric phosphate wastewater is the same as that in Example 1, except that the ratio of synthetic mother liquor to waste liquid in the first mother liquor is 7:3; the distribution of impurity content in the first and second mother liquors is shown in Table 6.

[0103] Table 6. Distribution of impurity content in the first and second mother liquors of Example 5.

[0104]

[0105] II. Testing Methods

[0106] 1. The contents of metal elements, P, COD, and TDS in the first and second filtrates were tested according to GB8978-1996, and the results are shown in Table 7.

[0107] Observe the RO blockage status to determine if there is a risk of blockage. III. Analysis of Test Results for Each Implementation Example

[0108] Table 7. Distribution of impurity content in the first and second filtrates.

[0109]

[0110] In Example 1, the metals and impurities such as F and COD in the wastewater can be effectively reduced, there is no risk of RO clogging, and the energy consumption of the MVR evaporation system is low.

[0111] In Example 2, the TDS of the first mother liquor was 72160 mg / L, and the salt content was low. If it directly entered the evaporation system, the energy consumption would be high. If the first filtrate directly entered the RO system, the load pressure of the RO system would be increased.

[0112] In Examples 3 and 4, the residual calcium ion content in the first filtrate is high, which will cause equipment blockage when it enters the MVR system later. The salt content in the first filtrate is low, and it will directly enter the MVR evaporation system, resulting in high energy consumption. If the first filtrate directly enters the RO system, it will increase the load pressure on the RO system.

[0113] In Example 5, the amount of synthetic mother liquor allocated to the first mother liquor was less, while the amount allocated to the second mother liquor was more, resulting in higher metal impurities and insufficient P content in the second mother liquor, which posed a risk of blockage to the RO system.

[0114] Five sets of examples reflect the impact of different mixing ratios on the removal rate of impurity elements and the degree of fouling and energy consumption reduction in the downstream RO and MVR processes. Through five sets of mixing examples with different ratios, it can be concluded that when the ratio of synthetic mother liquor to waste liquor in the first mother liquor is 8:2, impurity elements in the wastewater can be removed better, and the energy consumption of the MVR process can be reduced to the greatest extent while minimizing the risk of downstream RO fouling.

[0115] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A treatment process for ferric phosphate wastewater, characterized in that, Includes the following steps: The first mother liquor was treated with alkali, and the first filtrate was obtained after solid-liquid separation. The second mother liquor was treated with alkali, and the second filtrate was obtained after solid-liquid separation. The washing water is treated with alkali, and the third filtrate is obtained after solid-liquid separation. The second and third filtrates were mixed and concentrated by RO to obtain a concentrated solution. The concentrated liquid is mixed with the first filtrate and concentrated by MVR evaporation. After solid-liquid separation, waste liquid is obtained. The waste liquid is recycled to the first mother liquor for recycling treatment; the ferric phosphate wastewater includes synthesis mother liquor, aging mother liquor and wash water; the first mother liquor is composed of the synthesis mother liquor and the waste liquid; the second mother liquor is composed of the synthesis mother liquor and the aging mother liquor; the ferric phosphate wastewater is generated by the ferric phosphate co-precipitation process; the synthesis mother liquor is a saturated solution separated after the raw material synthesis, the aging mother liquor is a saturated solution separated after the synthesized impurity phase ferric phosphate has undergone a constant temperature aging process, and the wash water is an aqueous solution used for separation and impurity removal.

2. The treatment process for ferric phosphate wastewater according to claim 1, characterized in that, The first mother liquor contains 95-105 ppm of Ca, the second mother liquor contains 8-12 ppm of Ca, and the wash water contains 2-5 ppm of Ca.

3. The treatment process for ferric phosphate wastewater according to claim 1, characterized in that, The first mother liquor contains 6000-6500 ppm of phosphorus, the second mother liquor contains 700-750 ppm of phosphorus, and the wash water contains 150-180 ppm of phosphorus.

4. The treatment process for ferric phosphate wastewater according to claim 1, characterized in that, The salt content in the first mother liquor is 100,000-130,000 mg / L, the salt content in the second mother liquor is 50,000-60,000 mg / L, and the salt content in the washing water is 6,000-7,000 mg / L.

5. The treatment process for ferric phosphate wastewater according to claim 1, characterized in that, In the process of alkali pretreatment of the first mother liquor, the alkali used is lime water and / or ammonia water, and the pH value of the alkali treatment is 8-9.

6. The treatment process for ferric phosphate wastewater according to claim 1, characterized in that, In the second mother liquor pretreatment process, the alkali used is ammonia water, and the pH value of the alkali treatment is 8-9.

7. The treatment process for ferric phosphate wastewater according to claim 1, characterized in that, The alkali used in the pre-treatment of the wash water is ammonia water, and the pH value of the alkali treatment is 8-9.

8. The treatment process for ferric phosphate wastewater according to claim 1, characterized in that, The solid-liquid separation steps include, in sequence, plate and frame filter press filtration and sand filter tank filtration.

9. A wastewater treatment device for ferric phosphate, characterized in that, It includes a first mother liquor treatment device (1), a second mother liquor treatment device (2), a wash water treatment device (3), an RO reverse osmosis device (4), an RO concentrate tank (5), and an MVR evaporation device (6). The second mother liquor treatment device (2) and the washing water treatment device (3) respectively transport the second filtrate and the third filtrate to the RO reverse osmosis device (4) through the conveying pipeline; the first mother liquor treatment device (1) transports the first filtrate to the RO concentrate tank (5) through the conveying pipeline; the RO reverse osmosis device (4) is used to collect and concentrate the mixture of the second filtrate and the third filtrate, and is connected to the RO concentrate tank (5) through the conveying pipeline; the MVR evaporation device (6) is connected to the RO concentrate tank (5) and to the first mother liquor treatment device (1); The ferric phosphate wastewater treatment equipment is used to perform the ferric phosphate wastewater treatment process as described in any one of claims 1 to 8.

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