Device for high-value recovery of phosphorus from sewage and method for operating the same

Abstract

This application provides a wastewater phosphorus high-value recovery device and its operation method, belonging to the field of wastewater treatment and resource recovery technology. The wastewater phosphorus high-value recovery device includes: a membrane separation unit for solid-liquid separation and phosphate concentration of phosphorus-containing wastewater; a crystallization unit including a crystallization tank group, a dosing module, a detection module, and a control console, wherein the dosing module is connected to the crystallization tank group, the detection module is located within the crystallization tank group, and the control console is electrically connected to both the dosing module and the detection module; the crystallization unit is used for graded crystallization of the phosphorus-containing wastewater treated by the membrane separation unit to recover phosphate crystals; and a high-value preparation unit including a grinding module, a drying module, and a calcination module connected in sequence, used to prepare the recovered phosphate crystals into phosphate products.

Description

Technical Field

[0001] This application relates to the field of wastewater treatment and resource recycling technology, specifically to a wastewater phosphorus high-value recovery device and its operation method. Background Technology

[0002] Phosphorus is an indispensable core nutrient element for agricultural production and is also a non-renewable mineral resource. According to relevant research data, existing phosphate rock reserves can only sustain industrial mining and application for 50-100 years. The shortage of phosphorus resources has become a significant factor restricting the development of agriculture and related industries. Urban sewage sludge, as a terminal product of wastewater treatment systems, has a good adsorption and enrichment effect on phosphorus in wastewater, capable of adsorbing approximately 90% of the phosphorus in wastewater annually. Its dry basis phosphorus content can reach 2%-5%, comparable to the phosphorus content of low- to medium-grade phosphate rock. Therefore, the recovery and utilization of phosphorus resources from sewage sludge and phosphorus-containing wastewater has become a research hotspot and important development direction in the fields of resource regeneration and wastewater treatment.

[0003] Among existing wastewater and sludge phosphorus recovery technologies, chemical precipitation has become a more engineering-feasible technique in the field of phosphorus recovery due to its advantages such as high technological maturity, low difficulty in engineering application, stable and controllable phosphorus recovery efficiency, resource utilization of recovered products, and great potential for technological improvement. Currently, research on technological improvements to chemical precipitation mainly focuses on reagent innovation, process parameter optimization, and enhancing environmental and economic benefits. Related improvement methods mainly include selecting inexpensive and readily available metal salt reagents to reduce costs and increase efficiency, combining multiple processes to improve treatment effects, and using specialized equipment such as fluidized bed crystallizers and sequencing batch reactors to improve phosphate crystallization efficiency and reduce reactor clogging risks.

[0004] However, existing chemical precipitation methods still have many technical shortcomings in the actual industrial operation of phosphorus recovery, which need to be addressed. Specifically, these include: high reagent consumption leading to high operating costs; impurities such as organic matter in wastewater and sludge easily interfering with the phosphate crystallization process and reducing the purity of the recovered products; secondary pollution easily generated during process operation, increasing the burden of subsequent treatment; and poor coordination between process units, making it difficult to achieve continuous and efficient operation of the phosphorus recovery process. These problems seriously limit the large-scale promotion and application of this technology.

[0005] Therefore, developing a technical solution that can reduce reagent consumption, minimize impurity interference, improve process synergy, and achieve high-value recovery of phosphorus resources is of great practical significance for promoting the industrialization of phosphorus recovery from wastewater and sludge and alleviating the phosphorus resource shortage problem. Summary of the Invention

[0006] This application provides a wastewater phosphorus high-value recovery device and its operation method, in order to at least partially solve the above-mentioned technical problems. The specific technical solution provided by this application is as follows.

[0007] As a first aspect of this application, a wastewater phosphorus high-value recovery device is provided, including a membrane separation unit, a crystallization unit, and a high-value preparation unit.

[0008] The membrane separation unit is used for solid-liquid separation and phosphate concentration in phosphorus-containing wastewater.

[0009] The inlet of the crystallization unit is connected to the outlet of the membrane separation unit. The crystallization unit includes a crystallization tank assembly, a dosing module, a detection module, and a control console. The dosing module is connected to the crystallization tank assembly, the detection module is located within the crystallization tank assembly, and the control console is electrically connected to both the dosing module and the detection module. The crystallization unit is used for the graded crystallization of phosphorus-containing wastewater treated by the membrane separation unit to recover phosphate crystals.

[0010] The feed end of the high-value preparation unit is connected to the discharge end of the crystallization unit. The high-value preparation unit includes a grinding module, a drying module, and a calcination module connected in sequence, used to prepare the recovered phosphate crystals into phosphate products.

[0011] As a second aspect of this application, a method for operating a wastewater phosphorus high-value recovery device is provided, comprising: solid-liquid separation and phosphate concentration of phosphorus-containing wastewater through a membrane separation unit to obtain a phosphorus-rich concentrate; transporting the phosphorus-rich concentrate to a crystallization unit, and, based on data collected by a detection module, controlling a dosing module via a control console to add metal ions and acid-base regulators in stages to regulate crystallization conditions and achieve graded crystallization of phosphate and recovery of phosphate crystals; transporting the recovered phosphate crystals to a high-value preparation unit, and, after grinding, drying, and calcination, obtaining lithium iron phosphate or calcium iron phosphate.

[0012] In this embodiment, the wastewater phosphorus high-value recovery device and operation method utilize a membrane separation unit to complete solid-liquid separation and phosphate concentration of phosphorus-containing wastewater, providing a stable phosphorus-rich concentrate for subsequent crystallization. The crystallization unit, relying on the coordinated operation of the control console, detection module, and dosing module, can precisely control the crystallization conditions and achieve graded crystallization of phosphate, efficiently recovering phosphate crystals. The high-value preparation unit, through integrated grinding, drying, and calcination, prepares phosphate crystals into lithium iron phosphate or calcium iron phosphate. Overall, it achieves stable recovery and high-value conversion of phosphorus resources in phosphorus-containing wastewater. The device has strong structural synergy, the method process is highly controllable, and the phosphorus resource utilization effect is stable and reliable. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the wastewater phosphorus high-value recovery device in the embodiments of this application;

[0014] Figure 2 This is a top-down schematic diagram of the crystallization pool group in the embodiments of this application;

[0015] Figure 3 for Figure 2 A schematic diagram of the cross-section of the intermediate crystallization pool group along the AA direction;

[0016] Figure 4 for Figure 1 The flowchart shown is the operation method of the wastewater phosphorus high-value recovery device;

[0017] Figure 5 This is a scanning electron microscope image of the crude vivianite recovered in Example 1 of this application;

[0018] Figure 6 This is a scanning electron microscope image of the crude iron phosphate recovered in Example 1 of this application;

[0019] Figure 7 The X-ray diffraction pattern of the lithium iron phosphate material prepared in Example 1 of this application is shown.

[0020] Figure 8 This is a scanning electron microscope image of the calcium iron phosphate material prepared in Example 1 of this application.

[0021] The reference numerals in the above figures are explained as follows:

[0022] 1- Membrane separation unit;

[0023] 11-Ultrafiltration membrane module; 111-First inlet water line; 112-First membrane pressure gauge; 113-First inlet water pump; 114-First filtrate line; 115-First reflux line;

[0024] 12-Nanofiltration membrane module; 121-Second inlet water line; 122-Second membrane pressure gauge; 123-Second inlet water pump; 124-Second filtrate line; 125-Second return line;

[0025] 13-Water inlet tank;

[0026] 14-Intermediate tank; 141-Third inlet water pipe; 142-Third inlet water pump; 143-Regulating pipe;

[0027] 2-Crystallization unit;

[0028] 21-Crystallization pool group;

[0029] 211-First stage reaction tank; 2111-First crystal growth zone; 2112-First crystal nucleation zone; 2113-First crystal precipitation zone; 21131-Liquid outlet of the first crystal precipitation zone;

[0030] 212 - Secondary reaction tank; 2121 - Second crystal growth zone; 2122 - Second crystal nucleation zone; 2123 - Second crystal precipitation zone; 21231 - Liquid outlet of the second crystal precipitation zone;

[0031] 213 - Tertiary reaction tank; 2131 - Third crystal growth zone; 2132 - Third crystal precipitation zone; 21321 - Liquid outlet of the third crystal precipitation zone;

[0032] 214 - First stirring module;

[0033] 215 - Circulation channels;

[0034] 22-Dosing module;

[0035] 221-Alkali addition tank; 2211-Alkali addition pipeline; 2212-Alkali addition pump;

[0036] 222 - Acid tank; 2221 - Acid pipeline; 2222 - Acid pump;

[0037] 223-Dosing tank; 2231-Dosing pipeline; 2232-Dosing pump;

[0038] 224 - Second stirring module;

[0039] 23-Detection module; 231-pH detection electrode; 232-Redox potential detection electrode; 233-Temperature detection electrode; 234-Conductivity detection electrode;

[0040] 24-Console;

[0041] 25-Y type filter;

[0042] 26 - Collection bucket;

[0043] 3-High-value preparation unit;

[0044] 31-Grinding module; 32-Drying module; 33-Calcination module. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0046] In realizing the concept of this application, it was found that existing wastewater phosphorus recovery technologies generally suffer from problems such as high reagent consumption, impurities interfering with crystallization, poor process synergy, and low purity and added value of recovered products, making it difficult to achieve efficient recovery and high-value utilization of phosphorus resources. Based on this, this application provides a wastewater phosphorus high-value recovery device. By integrating a membrane separation unit, a crystallization unit, and a high-value preparation unit, and employing a control console with a linkage detection module and a dosing module for intelligent control, combined with the structured design of the crystallization tank group, it achieves efficient impurity removal and concentration of phosphorus-containing wastewater, precise phosphate classification and crystallization, and high-value product preparation, effectively improving phosphorus recovery efficiency and the economic value of the products.

[0047] Figure 1 This is a schematic diagram of the wastewater phosphorus high-value recovery device in the embodiments of this application.

[0048] As the first aspect of this application, a wastewater phosphorus high-value recovery device is provided, such as... Figure 1 As shown, it includes a membrane separation unit 1, a crystallization unit 2, and a high-value preparation unit 3.

[0049] Among them, membrane separation unit 1 is used for solid-liquid separation and phosphate concentration of phosphorus-containing wastewater.

[0050] The inlet of crystallization unit 2 is connected to the outlet of membrane separation unit 1. The crystallization unit includes a crystallization tank assembly 21, a dosing module 22, a detection module 23, and a control console 24. The dosing module 22 is connected to the crystallization tank assembly 21, the detection module 23 is located within the crystallization tank assembly 21, and the control console 24 is electrically connected to both the dosing module 22 and the detection module 23. Crystallization unit 2 is used for graded crystallization of phosphorus-containing wastewater treated by membrane separation unit 1 to recover phosphate crystals.

[0051] The feed end of the high-value preparation unit 3 is connected to the discharge end of the crystallization unit 2. The high-value preparation unit includes a grinding module 31, a drying module 32, and a calcination module 33 connected in sequence, which are used to prepare the recovered phosphate crystals into phosphate products.

[0052] In this embodiment, the wastewater phosphorus high-value recovery device adopts an integrated interconnected structure. The membrane separation unit 1 can complete the solid-liquid separation and phosphate concentration of phosphorus-containing wastewater, providing stable feeding conditions for the crystallization reaction. The crystallization unit 2 coordinates the detection module 23 and the dosing module 22 through the control console 24, which can accurately regulate the reaction environment in the crystallization tank group 21 and reliably realize the graded crystallization and crystal recovery of phosphate. The high-value preparation unit 3 can prepare the recovered phosphate crystals into phosphate products through the sequential cooperation of the grinding module 31, the drying module 32, and the calcination module 33. The overall layout of the device is reasonable and the control is precise, which can stably realize the recovery and resource utilization of phosphorus resources in phosphorus-containing wastewater.

[0053] Figure 2 This is a top-down schematic diagram of the crystallization pool group in the embodiments of this application.

[0054] In some embodiments, such as Figure 2 As shown, the crystallization tank group 21 is a graded crystallization tank group 21, specifically including multiple reaction tanks connected in sequence. Further, along the flow direction of the phosphorus-containing wastewater, the reaction tanks are sequentially a primary reaction tank 211, a secondary reaction tank 212, and a tertiary reaction tank 213.

[0055] For example, such as Figure 2 As shown, the number of reaction tanks can be, for example, nine; multiple reaction tanks can be used. Figure 2 The arrangement shown can also be other reasonable arrangements such as linear arrangement, ring arrangement, or matrix arrangement, and this application does not make any special limitation on this. The number of primary reaction tanks 211 can be, for example, 2; the number of secondary reaction tanks 212 can be, for example, 3; and the number of tertiary reaction tanks 213 can be, for example, 4.

[0056] The staged design of the reaction tanks is specifically tailored to the crystallization stage reaction characteristics of vivianite, ferric phosphate, and calcium phosphate. Specifically: the primary reaction tank 211 is mainly used to meet the requirements of reaction volume and residence time during the induced nucleation stage of vivianite or ferric phosphate, promoting uniform crystal nucleation and reducing premature nucleus loss, thus providing sufficient space for crystallization reaction. The secondary reaction tank 212 is used for the crystal growth stage, optimizing hydraulic conditions and the reaction environment to reduce ineffective collisions between crystals, promoting crystal size differentiation and uniform growth. The system is adapted to the growth and enrichment stages of lapis lazuli or ferric phosphate, providing ample space for crystal growth. The two work together to achieve graded recovery of the mainstream phosphate products (lapis lazuli / ferric phosphate). The tertiary reaction tank 213 is used for deep recovery of phosphorus resources, and is used to directionally complete the generation and collection of calcium phosphate crystals. It mainly serves the precipitation enrichment and reaction tailing in the later stage of the crystallization reaction, and increases the conversion probability of calcium phosphate crystals by appropriately reducing the volume of the reaction tank. Through this segmented crystallization design, the step-by-step separation and graded collection of different phosphate crystals are achieved, effectively improving crystal purity and the total recovery rate of phosphorus resources.

[0057] Figure 3 for Figure 2 A schematic diagram of the cross-section of the central crystallization pool group along the AA direction.

[0058] In some embodiments, such as Figure 3As shown, the primary reaction tank 211 includes, from top to bottom, a first crystal growth region 2111, a first crystal nucleation region 2112, and a first crystal precipitation region 2113 along the liquid flow direction. The secondary reaction tank 212 includes, from top to bottom, a second crystal growth region 2121, a second crystal nucleation region 2122, and a second crystal precipitation region 2123 along the liquid flow direction. The tertiary reaction tank 213 includes, from top to bottom, a third crystal growth region 2131 and a third crystal precipitation region 2132 along the liquid flow direction.

[0059] In this embodiment, the primary reaction tank 211 and the secondary reaction tank 212 are used to recover phosphate crystals such as lapis lazuli or ferric phosphate. Their crystallization requires a complete process of crystal nucleation, crystal growth, and sedimentation enrichment. Therefore, a crystal nucleation zone, a crystal growth zone, and a crystal precipitation zone are set from top to bottom to provide dedicated space for crystal nucleation, crystal growth, and crystal collection, ensuring crystal particle size and purity. The tertiary reaction tank 213 is used to recover calcium phosphate, which belongs to the deep phosphorus recovery stage. At this time, the phosphorus concentration in the phosphorus-containing wastewater is low, and crystal nuclei can be generated quickly and grow directly. There is no need to set up a separate nucleation zone. Only the crystal growth zone and the crystal precipitation zone are retained to complete the growth and collection of calcium phosphate. This simplifies the structure and improves the collection efficiency while ensuring the recovery effect.

[0060] In some embodiments, such as Figure 3 As shown, the first crystal growth region 2111, the second crystal growth region 2121, and the third crystal growth region 2131 all have a frustum-shaped structure; the first crystal nucleation region 2112 and the second crystal nucleation region 2122 both have a frustum-shaped structure. The first crystal precipitation region 2113, the second crystal precipitation region 2123, and the third crystal precipitation region 2132 all have a conical structure. The cross-sectional diameters of the primary reaction tank 211, the secondary reaction tank 212, and the tertiary reaction tank 213 gradually decrease from top to bottom along the liquid flow direction.

[0061] In this embodiment, the crystal growth zone is truncated pyramidal in shape, which provides a stable space for crystal to float and grow, ensuring that the crystal develops and grows fully; the crystal nucleation zone is truncated cone-shaped, which can optimize the mixing effect of the reagents and the flow field distribution, and promote the uniform and stable generation of crystal nuclei; the crystal precipitation zone is conical, which facilitates the rapid settling, enrichment and centralized collection of crystals; the cross-sectional diameter of each reaction tank gradually decreases from top to bottom along the liquid flow direction, which can match the flow rate changes in the crystallization process, strengthen the synergistic effect of nucleation, growth and precipitation, and improve the phosphate crystallization efficiency and crystal purity.

[0062] Furthermore, continue as Figure 3As shown, the height ratio of the first crystal growth region 2111, the first crystal nucleation region 2112, and the first crystal precipitation region 2113 is (1.5-2.5):(2.5-3.5):(2.5-3.5), preferably 2:3:3. This ratio is used for inducing nucleation and initial growth of crystal nuclei in the early stage of crystallization, providing sufficient reaction space and hydraulic residence time for nucleation and early crystal growth. At the same time, the larger crystal precipitation region can settle and remove organic matter and suspended impurities in the influent, reducing interference with subsequent crystallization. The height ratio of the second crystal growth region 2121, the second crystal nucleation region 2122, and the second crystal precipitation region 2123 is (1.5-2.5):(2.5-3.5):(1.5-2.5), preferably 2:3:2. This ratio is used for further crystal growth and sedimentation separation, improving the utilization efficiency of the crystal growth region by reducing the volume of the crystal precipitation region. The height ratio of the third crystal growth region 2131 to the third crystal precipitation region 2132 is (1.5-2.5):(2.5-3.5), preferably 2:3, for enrichment and collection of precipitation products at the end of crystallization.

[0063] In some embodiments, the liquid outlets of the first crystal precipitation zone 2113, the second crystal precipitation zone 2123, and the third crystal precipitation zone 2132 (i.e., the liquid outlets of the first crystal precipitation zone 21131, the second crystal precipitation zone 21231, and the third crystal precipitation zone 21321) are respectively connected to Y-type filters 25.

[0064] Furthermore, the discharge end of the Y-type filter 25 is connected to the high-value preparation unit 3. The Y-type filter 25 is used to filter and retain the crystal concentrate discharged from each crystal precipitation zone (i.e., the first crystal precipitation zone 2113, the second crystal precipitation zone 2123, and the third crystal precipitation zone 2132), which can effectively enrich large phosphate crystals in the crystal concentrate, filter out fine impurities remaining in the crystal concentrate, and ensure the purity of phosphate crystals entering the high-value preparation unit.

[0065] Furthermore, a collection tank 26 is provided between the Y-type filter 25 and the high-value preparation unit 3. The collection tank 26 is used to receive the phosphate crystals enriched by the Y-type filter 25, realizing the centralized temporary storage and unified transportation of the crystals, providing a continuous and stable raw material supply for subsequent high-value preparation, and ensuring the continuous and stable operation of the entire phosphorus recovery and resource-based preparation process.

[0066] In some embodiments, the material of the reaction tank can be flexibly selected according to the actual application conditions. Specifically, stainless steel can be used, and a polyurea anti-corrosion coating is sprayed on its inner surface to adapt to the water intake requirements of different water quality environments.

[0067] In some embodiments, the detection module 23 includes a pH detection electrode 231, a redox potential detection electrode 232, a temperature detection electrode 233, and a conductivity detection electrode 234.

[0068] Furthermore, the detection module 23 is respectively disposed in the first crystal growth region 2111, the first crystal nucleation region 2112, the second crystal growth region 2121, the second crystal nucleation region 2122, the third crystal growth region 2131 and the third crystal precipitation region 2132.

[0069] Furthermore, the pH detection electrode 231 and the redox potential detection electrode 232 are respectively disposed in the first crystal growth region 2111, the first crystal nucleation region 2112, the second crystal growth region 2121, the second crystal nucleation region 2122, the third crystal growth region 2131, and the third crystal precipitation region 2132. The temperature detection electrode 233 is disposed in the first crystal growth region 2111, the second crystal growth region 2121, and the third crystal growth region 2131. The conductivity detection electrode 234 is disposed in the first crystal nucleation region 2112, the second crystal nucleation region 2122, and the third crystal precipitation region 2132.

[0070] In this embodiment, by precisely setting the pH detection electrode 231, the oxidation-reduction potential (ORP) detection electrode 232, the temperature detection electrode 233, and the conductivity detection electrode 234 in each crystal growth zone, crystal nucleation zone, and crystal precipitation zone according to functional requirements, the relevant performance indicators of each zone in the entire crystallization process can be collected in real time and comprehensively. This provides accurate data for the control console 24 to regulate the crystallization process, ensuring that the crystallization conditions in each zone are stable and controllable, effectively matching the graded crystallization requirements of different phosphates, improving the regulation accuracy and reaction stability of the crystallization process, and ensuring the efficient and stable generation and recovery of phosphate crystals.

[0071] In some embodiments, each reaction tank is further provided with a first stirring module 214 and a flow pipe 215. The first stirring module 214 is disposed inside the crystal growth region of each reaction tank; the flow pipe 215 is arranged around the tank wall of each reaction tank, with one end extending to the middle part of the reaction tank and the other end connected to the adjacent preceding reaction tank.

[0072] In this embodiment, the first stirring module 214 and the flow pipe 215 installed in each reaction tank can work together to optimize the crystallization reaction environment. The first stirring module 214 can fully stir and mix the reagent and phosphorus-containing wastewater in the crystal growth zone to ensure that the reaction materials are mixed evenly. The flow pipe 215 can stabilize the inlet flow rate and guide the flow of phosphorus-containing wastewater, so as to promote the reagent to be fully mixed and reacted in the crystal nucleation zone. At the same time, it can effectively block the direct contact between metal ions and the upper air, avoid the oxidation of metal ions, significantly improve the uniformity, stability and controllability of the crystallization reaction, and ensure the efficient and stable generation of phosphate crystals.

[0073] In some embodiments, the dosing module 22 includes an alkali dosing tank 221, an acid dosing tank 222, and a chemical dosing tank 223. Specifically, the alkali dosing tank 221 is used to store a solution prepared using an alkali adjuster, which may be sodium hydroxide, potassium hydroxide, or sodium carbonate; the acid dosing tank 222 is used to store a solution prepared using an acid adjuster, which may be hydrochloric acid, aminosulfonic acid, or methanesulfonic acid; and the chemical dosing tank 223 is used to store a solution prepared using a metal ion reagent, which may be Ca2+, Ca2+, or ... 2+ Pharmaceuticals, Fe 2+ Pharmaceuticals, Fe 3+ Chemicals, etc. Multiple dosing tanks 223 can be installed according to the different requirements of the water quality composition and crystallization reaction process of phosphorus-containing wastewater. Examples include Ca... 2+ Dosing tank, Fe 2+ Dosing tank, Fe 3+ Dosing tanks, etc., are designed to meet the metal ion dosing requirements of different phosphate crystallization reactions.

[0074] Furthermore, the alkali addition tank 221 is connected to each reaction tank via alkali addition pipeline 2211, and an alkali addition pump 2212 is installed on the alkali addition pipeline 2211; the acid addition tank 222 is connected to each reaction tank via acid addition pipeline 2221, and an acid addition pump 2222 is installed on the acid addition pipeline 2221; the chemical addition tank 223 is connected to each reaction tank via chemical addition pipeline 2231, and a chemical addition pump 2232 is installed on the chemical addition pipeline 2231.

[0075] In this embodiment, by setting up an alkali addition tank 221, an acid addition tank 222, and a chemical addition tank 223, and connecting them with independent pipelines (i.e., alkali addition pipeline 2211, acid addition pipeline 2221, and chemical addition pipeline 2231) and dosing pumps (i.e., alkali addition pump 2212, acid addition pump 2222, and chemical addition pump 2232) to each reaction tank, the pH value of phosphorus-containing wastewater can be precisely controlled according to the crystallization requirements of different reaction tanks, while Ca is added in a targeted manner. 2+ Fe 2+ Fe 3+ The addition of metal ions enables precise control of dosage and acceleration rate, adapting to the differentiated crystallization reaction conditions of different phosphates such as lapis lazuli, iron phosphate, and calcium phosphate, ensuring stable and controllable crystallization processes in each reaction tank, and effectively improving the purity of phosphate crystals and the efficiency of graded recovery.

[0076] In some embodiments, the dosing module 22 further includes a second stirring module 224, which is respectively disposed inside the alkali addition tank 221, the acid addition tank 222 and the dosing tank 223, and continuously and uniformly stirs the acid-base regulator and metal ion agent in the alkali addition tank 221, the acid addition tank 222 and the dosing tank 223.

[0077] In this embodiment, the dosing module 22, detection module 23, and control console 24 form a closed-loop linkage control system. The detection module 23 can collect relevant performance indicators such as pH, redox potential, temperature, and conductivity of different functional zones of each reaction tank in real time and transmit them to the control console 24. Based on the preset crystallization reaction parameter thresholds of lapis lazuli, ferric phosphate, and calcium phosphate, the start-stop status and dosing rate of the dosing pumps such as the alkali pump 2212, acid pump 2222, and dosing pump 2232, as well as the start-stop status and stirring rate of the first stirring module 214 in each reaction tank, can achieve precise and dynamic adjustment of the crystallization reaction environment in each reaction tank. This ensures that lapis lazuli, ferric phosphate, and calcium phosphate complete graded crystallization under suitable physicochemical conditions, effectively improving the purity and recovery rate of phosphate crystals, while avoiding waste caused by excessive dosing of reagents, and enhancing the controllability and stability of the entire crystallization process.

[0078] In some embodiments, the membrane separation unit 1 includes an ultrafiltration membrane module 11 and a nanofiltration membrane module 12 connected in sequence; wherein, the ultrafiltration membrane module 11 is used for solid-liquid separation of phosphorus-containing wastewater, and the nanofiltration membrane module 12 is used for phosphate concentration of phosphorus-containing wastewater.

[0079] Specifically, the ultrafiltration membrane module 11 is mainly used to remove organic matter, colloids and suspended impurities from phosphorus-containing wastewater, reducing their interference with subsequent crystallization reactions. According to the distribution characteristics of organic matter in phosphorus-containing wastewater, macromolecular organic matter is mainly concentrated above 30kDa, while among small molecule organic matter, about 30% are above 8kDa, about 60% are above 5kDa, and about 99% are above 1kDa. After screening, the ultrafiltration membrane with a molecular weight cutoff of 5kDa has better comprehensive performance under 0.05MPa conditions, with a phosphate permeability >99%, a rejection rate <1%, and a total organic carbon (TOC) content of the treated phosphorus-containing wastewater below 600mg / L. The nanofiltration membrane module 12 utilizes the selective separation of ions, as well as the polymerization form and charge characteristics of phosphate, to allow some impurity ions to pass through the nanofiltration membrane while retaining calcium, magnesium, iron, and phosphate ions. The selected nanofiltration membrane has a molecular weight cutoff of 100-300 Da and a high phosphate rejection capacity of 90%-95%, thereby concentrating the system and increasing the phosphate concentration, which in turn promotes the formation of target phosphate minerals and improves phosphorus recovery efficiency.

[0080] For example, the ultrafiltration membrane module 11 is made of stainless steel, and its structure consists of a polyvinyl chloride (PVC) frame, a stainless steel inner support, and ultrafiltration membrane material stacked layer by layer and assembled by nylon screws; wherein the ultrafiltration membrane can be made of polyvinylidene fluoride (PVDF). The nanofiltration membrane module 12 is also made of stainless steel, and its structure is the same as that of the ultrafiltration membrane module 11, consisting of a PVC frame, a stainless steel inner support, and nanofiltration membrane material assembled by nylon screws; wherein the nanofiltration membrane can be made of polyethersulfone (PES).

[0081] In some embodiments, the membrane separation unit 1 further includes an inlet tank 13 and an intermediate tank 14. The inlet tank 13 stores phosphorus-containing wastewater, as well as the concentrate from the ultrafiltration membrane module 11 and the permeate from the nanofiltration membrane module 12. The intermediate tank 14 stores the permeate from the ultrafiltration membrane module 11 and the concentrate from the nanofiltration membrane module 12. The material and shape of the inlet tank 13 and the intermediate tank 14 are not limited; for example, they can be made of polyvinyl chloride or stainless steel, and can be circular or square.

[0082] In some embodiments, the inlet of the ultrafiltration membrane module 11 is connected to the water tank 13 via a first water inlet pipe 111, and a first membrane pressure gauge 112 and a first water inlet pump 113 are provided on the first water inlet pipe 111; the permeate outlet of the ultrafiltration membrane module 11 is connected to the intermediate tank 14 via a first filtrate pipe 114; and the concentrate outlet of the ultrafiltration membrane module 11 is connected to the water tank 13 via a first reflux pipe 115.

[0083] Specifically, the ultrafiltration membrane module 11 employs a cross-flow filtration process to remove large particulate impurities and macromolecular organic matter from phosphorus-containing wastewater, yielding permeate and concentrate from the ultrafiltration membrane module 11. The permeate from the ultrafiltration membrane module 11 is transported to the intermediate tank 14 via the first filtrate pipeline 114. A first membrane pressure gauge 112 is installed on the first filtrate pipeline 114 via a three-way connector to monitor the membrane filtration pressure in the pipeline in real time. The concentrate from the ultrafiltration membrane module 11 is transported to the inlet tank 13 via the first return pipeline 115, achieving cyclic filtration treatment of phosphorus-containing wastewater.

[0084] In some embodiments, the inlet of the nanofiltration membrane module 12 is connected to the intermediate tank 14 via the second inlet water pipe 121, and the second inlet water pipe 121 is provided with a second membrane pressure gauge 122 and a second inlet water pump 123; the concentrate outlet of the nanofiltration membrane module 12 is connected to the intermediate tank 14 via the second filtrate pipe 124; and the permeate outlet of the nanofiltration membrane module 12 is connected to the inlet water tank 13 via the second return pipe 125.

[0085] Specifically, the nanofiltration membrane module 12 employs a cross-flow filtration process to concentrate phosphates in phosphorus-containing wastewater and the concentrate from the ultrafiltration membrane module 11, yielding the permeate and concentrate of the nanofiltration membrane module 12. The concentrate from the nanofiltration membrane module 12 can be directly used for subsequent phosphate crystallization recovery. Simultaneously, this concentration process reduces the binding energy required for phosphate crystallization, providing favorable conditions for crystal nucleus formation. The concentrate from the nanofiltration membrane module 12 is transported to the intermediate tank 14 via a second filtrate pipeline 124. A second membrane pressure gauge 122 is installed on the second filtrate pipeline 124 via a three-way connector to monitor the membrane filtration pressure in the pipeline in real time. The permeate from the nanofiltration membrane module 12 is transported to the inlet tank 13 via a second return pipeline 125, achieving cyclic filtration treatment of the phosphorus-containing wastewater.

[0086] In some embodiments, the intermediate tank 14 is connected to the crystallization tank group 21 via a third inlet water pipe 141, and a third inlet water pump 142 is provided on the third inlet water pipe 141. The third inlet water pump 142 is used to stably transport the permeate of the ultrafiltration membrane module 11 and the concentrate of the nanofiltration membrane module 12 temporarily stored in the intermediate tank 14 to the crystallization tank group 21 for subsequent phosphate fractionation crystallization reaction.

[0087] In some embodiments, the intermediate tank 14 is connected to the dosing module 22 via the regulating pipeline 143, so that the dosing module 22 can accurately add acid-base regulators or metal ion agents into the intermediate tank 14, and pre-regulate the pH value and ion concentration of the permeate of the ultrafiltration membrane module 11 and the concentrate of the nanofiltration membrane module 12 in the intermediate tank 14, so as to provide suitable physicochemical preconditions for the subsequent crystallization reaction of the crystallization pool group 21.

[0088] In some embodiments, the high-value preparation unit 3 includes a grinding module 31, a drying module 32, and a calcination module 33. Each functional module can be selected from conventional process equipment in the art. For example, the grinding module 31 can be a ball mill, the drying module 32 can be a drying oven, and the calcination module 33 can be a tube furnace. This application does not limit the specific equipment type of each functional module.

[0089] Specifically, the ball mill is used to mix recovered phosphate crystals (such as lapis lazuli, iron phosphate, and calcium phosphate) with auxiliary materials, and at the same time, the ball milling action refines large mineral particles in the mixed system into small crystal particles; the drying oven is used to dehydrate and dry the ground mixture to remove free water from the system; and the tube furnace is used to heat and calcine the dried material to form a final product of high value.

[0090] Figure 4 for Figure 1 The diagram shows the operation method of the wastewater phosphorus high-value recovery device.

[0091] As a second aspect of this application, an operating method for a wastewater phosphorus high-value recovery device is provided, such as... Figure 4 As shown, it includes steps S1-S3.

[0092] Step S1: Phosphorus-containing wastewater undergoes solid-liquid separation and phosphate concentration in membrane separation unit 1 to obtain phosphorus-rich concentrate.

[0093] Step S2: The phosphorus-rich concentrate is transported to the crystallization unit 2. Based on the data collected by the detection module 23, the dosing module 22 is controlled by the control console 24 to add metal ions and acid-base regulators in stages, thereby adjusting the crystallization conditions to achieve phosphate stage crystallization and recover phosphate crystals.

[0094] Step S3: The recovered phosphate crystals are transported to the high-value preparation unit 3, where they are ground, dried, and calcined to obtain lithium iron phosphate or calcium iron phosphate.

[0095] In the embodiments of this application, the operation method of the wastewater phosphorus high-value recovery device provided by this application first completes the solid-liquid separation and phosphate concentration of phosphorus-containing wastewater through membrane separation unit 1, providing a high-concentration, low-impurity phosphorus-rich concentrate for subsequent crystallization reaction, laying the foundation for efficient crystallization; then, with the closed-loop linkage of detection module 23, control console 24 and dosing module 22 in crystallization unit 2, metal ions and acid-base regulators are added in stages according to real-time monitoring data, and crystallization conditions are precisely controlled to achieve graded crystallization and efficient recovery of different phosphates, ensuring crystal purity; finally, through a series of treatments of grinding, drying and calcination in high-value preparation unit 3, the recovered phosphate crystals are directionally converted into high-value-added products such as lithium iron phosphate or calcium iron phosphate. The whole method forms a complete technical link of "pretreatment-graded crystallization-high-value conversion", which not only realizes the deep recovery and graded utilization of phosphorus resources, significantly improves the phosphorus recovery rate and product added value, but also reduces reagent waste and by-product generation through precise control, and enhances the controllability, stability and economy of the operation process, providing an efficient and feasible technical solution for the resource-based and high-value recovery of wastewater phosphorus resources.

[0096] In some embodiments, the specific implementation process of step S1 is as follows: the first inlet pump 113 and the second inlet pump 123 are turned on, and the phosphorus-containing wastewater flows through the ultrafiltration membrane module 11 to intercept and remove large particulate impurities and macromolecular organic matter; then, the permeate of the ultrafiltration membrane module 11 is concentrated with phosphate through the nanofiltration membrane module 12, and the concentrated phosphorus-rich concentrate is transported to the intermediate tank 14 for temporary storage.

[0097] During the operation of membrane separation unit 1, the transmembrane pressure difference (TMP) of ultrafiltration membrane module 11 and nanofiltration membrane module 12 is monitored in real time by the first membrane pressure gauge 112 and the second membrane pressure gauge 122. When the transmembrane pressure difference (TMP) reaches the preset threshold, the ultrafiltration membrane element and nanofiltration membrane element are replaced in time, and the contaminated membrane element is subjected to physical cleaning and chemical cleaning in sequence to remove reversible and irreversible fouling on the membrane surface. The membrane element after cleaning can be put back into use.

[0098] In some embodiments, the specific implementation process of step S2 is as follows.

[0099] (1) Pretreatment of phosphorus-rich concentrate.

[0100] First, turn on the second stirring module 224 in the dosing module 22 to fully stir the acid-base regulator and metal ion reagent in the alkali tank 221, acid tank 222 and dosing tank 223 to ensure that all kinds of reagents are mixed evenly and have a stable and consistent concentration.

[0101] During the cross-flow filtration process of the nanofiltration membrane module 12, the alkali addition pump 2212, acid addition pump 2222, and chemical addition pump 2232 are simultaneously activated in real time. The control console 24 precisely adds acid-base regulators and metal ion reagents to the intermediate tank 14 according to a preset reagent dosing program, thereby controlling the concentration ratio of metal ions to phosphate and the pH value within the intermediate tank 14 to stabilize it within the target range for phosphate crystallization. Simultaneously, the cross-flow filtration effect of the nanofiltration membrane module 12 continuously promotes a gradual increase in the phosphate concentration of the phosphorus-rich concentrate in the intermediate tank 14, thereby increasing the supersaturation of the phosphate system. Furthermore, the nanofiltration membrane effectively reduces the binding energy required for phosphate crystallization, ultimately achieving directional nucleation of phosphate crystals under controlled conditions.

[0102] (2) Transport of phosphorus-rich concentrate and pretreatment in reaction tank.

[0103] When the volume of the concentrate in the nanofiltration membrane module 12 is concentrated to 30% of its original volume, the third inlet pump 142 is turned on to input the pretreated phosphorus-rich concentrate in the intermediate tank 14 into the reaction tank of the crystallization tank group 21 at a rate of 200-250 L / H; at the same time, the first stirring module 214 is turned on to promote the full mixing of phosphorus-rich concentrate and metal ions in each reaction tank, and based on the hierarchical structure design of each reaction tank, to provide a suitable environment for the growth and precipitation of phosphate crystals.

[0104] (3) Dynamic control of crystallization conditions.

[0105] The control console 24 continuously monitors the stability of pH, ORP, conductivity, and temperature in each reaction tank. Based on the monitoring data, it judges the crystallization reaction status and controls the dosing module 22 to add acid-base regulators and metal ion agents to the reaction tank as needed, accurately adjusting the relevant performance indicators to the corresponding crystal formation range to ensure the graded crystallization effect.

[0106] (4) Targeted drug addition achieves graded crystallization.

[0107] Depending on the target phosphate crystallization product, the addition of acid-base regulators and metal ion agents includes the following two schemes.

[0108] The first option is to add Fe to the phosphorus-rich concentrate in intermediate tank 14. 2+ Alkali is added to control the Fe:P molar ratio in the phosphorus-rich concentrate to 1.5-2.0:1 and the pH to 7.7-7.8, recovering crude blue iron ore; subsequently, Ca is added to the intermediate reaction tank of crystallization tank group 21. 2+ The solution is mixed with alkali, and the Ca:P molar ratio of the remaining phosphorus-rich concentrate in the intermediate reaction tank is controlled to be 2-3:1 and the pH is 9-9.1. Crude calcium phosphate is recovered, which contains lapis lazuli or ferric sulfate.

[0109] The second option is to add Fe to the phosphorus-rich concentrate in intermediate tank 14. 3+ The solution is acidified, and the Fe:P molar ratio in the phosphorus-rich concentrate is controlled at 1.0-1.4:1, and the pH is controlled at 1.7-1.8 to recover crude iron phosphate. Subsequently, Ca is added to the intermediate reaction tank of crystallization tank group 21. 2+ The solution is mixed with alkali, and the Ca:P molar ratio of the remaining phosphorus-rich concentrate in the intermediate reaction tank is controlled to be 2-3:1 and the pH is 9-9.1. Crude calcium phosphate is recovered, which contains lapis lazuli or ferric sulfate.

[0110] (5) Crystal collection and process feedback regulation.

[0111] According to the theoretical crystal growth cycle of phosphate crystals, the concentrated crystal liquid in the crystal precipitation zone of each reaction tank is discharged from the corresponding concentrated liquid outlet (i.e., the outlet 21131 of the first crystal precipitation zone, the outlet 21231 of the second crystal precipitation zone, and the outlet 21321 of the third crystal precipitation zone) at regular intervals. After being filtered through the Y-type filter 25, the phosphate crystals are collected into the collection tank 26.

[0112] The control console 24 records and analyzes parameters such as the yield, sedimentation state, and particle size change of phosphate crystals per unit time in the collection tank 26 in real time, and judges the current crystallization process status based on the above parameters (determining whether the crystallization process is in a state of strong nucleation or insufficient growth):

[0113] (a) When the phosphate crystal production per unit time is lower than the set threshold, the control console 24 increases the operating load of the nanofiltration membrane module 12 or extends the hydraulic residence time of the reaction tank, and adjusts the dosing rate of the alkali pump 2212, acid pump 2222 and chemical pump 2232 in conjunction to restore the pH, the molar ratio of metal ions to phosphate to the preset crystallization range.

[0114] (b) When the crystal settling rate decreases or the crystal size tends to be finer, the control console 24 reduces the instantaneous supersaturation formation rate and extends the crystal growth time by adjusting the flow rate of the third water pump 142 and the operating parameters of the first stirring module 214, so that the crystallization process is transformed from nucleation-dominated to crystal growth-dominated.

[0115] (c) When the fluctuation of crystal production per unit time exceeds the preset range, the control console 24 performs coordinated correction on the dosing rate of the alkali pump 2212, acid pump 2222 and chemical pump 2232 and the operating load of the nanofiltration membrane module 12, so that the crystallization load and the reaction residence time are matched.

[0116] Through the closed-loop feedback regulation based on the behavior of crystallization products, the load adaptive control of crystallization unit 2 is achieved, ensuring that phosphate crystals complete the nucleation, growth and precipitation processes sequentially and orderly in different reaction tanks.

[0117] In some embodiments, the specific implementation process of step S3 is as follows: the recovered crude blue iron ore or crude iron phosphate is mixed with ammonium dihydrogen phosphate, lithium carbonate, and glucose, and then calcined after grinding and drying to obtain lithium iron phosphate; the recovered crude calcium phosphate is calcined to obtain calcium iron phosphate.

[0118] Specifically, the process of preparing lithium iron phosphate using crude blue iron ore or crude iron phosphate as raw materials is as follows.

[0119] (1) The crude blue iron ore or crude iron phosphate recovered from crystallization unit 2 is thoroughly mixed with ammonium dihydrogen phosphate and lithium carbonate at a Fe:P:Li molar ratio of 1:1:1 to obtain a mixture; at the same time, 10-15% glucose by mass and 1.5 times the volume of the above mixture are added and stirred until the mixture is uniform to obtain a mixed liquid.

[0120] (2) Place the mixture in an agate ball mill and ball mill at a speed of 300-350 rpm for 10-12 hours. In the early stage of grinding, the viscosity of the slurry should be observed in real time and the amount of ethanol added should be dynamically adjusted to avoid the slurry becoming viscous due to too little ethanol or the slurry becoming loose due to too much ethanol, so as to ensure the mixing effect of the materials.

[0121] (3) Place the ball-milled mixture into a drying oven and dry it at 60-80℃ to completely remove ethanol from the system and prevent ethanol from volatilizing during subsequent calcination and affecting the purity of the product, so as to obtain the precursor material.

[0122] (4) The precursor material is transferred to a tube furnace under argon atmosphere protection, heated at 430-470℃ for 4-6 hours, and then heated to 700℃ for 6-10 hours. After calcination, it is cooled and dried to obtain powdered lithium iron phosphate material.

[0123] The process of preparing calcium iron phosphate from crude calcium phosphate includes: placing the crude calcium phosphate containing lapis lazuli or ferric sulfate recovered from crystallization unit 2 directly into a tube furnace, heating it to 700-800℃, and calcining it for 3-4 hours to obtain calcium iron phosphate material.

[0124] To at least partially address the technical deficiencies in existing technologies, such as the lack of a complete high-value phosphorus recovery process from wastewater and insufficient phosphorus recovery purity and economic efficiency, this application provides a wastewater phosphorus high-value recovery device and its operation method, the core technical logic and implementation path of which are as follows.

[0125] The system integrates membrane separation, crystallization, and high-value conversion into a complete technological chain, adapting to the phosphorus recovery needs of various wastewater treatments. The membrane separation unit plays a dual role: firstly, it separates most organic matter through ultrafiltration, reducing its adsorption and complexation interference with phosphates while removing large particulate impurities; secondly, it concentrates the phosphorus-containing solution through nanofiltration, increasing the phosphate concentration to meet the supersaturation requirements for crystallization, and also lowering the activation energy of phosphate crystallization to promote spontaneous crystal nucleation, laying the foundation for subsequent crystallization. The crystallization unit, as the core of resource recovery, achieves stepwise addition of acid-base regulators and metal ion reagents through intelligent control. It utilizes multiple reaction tanks to construct a gradient separation system to address the problem of fluctuating phosphorus quality in wastewater. Based on the thermodynamics and kinetics of crystal nucleation, and relying on the "heterogeneous nucleation-growth-precipitation" mechanism, it provides sufficient time for crystal nucleation, primary growth, secondary growth purification, and precipitation recovery in different reaction tanks. At the same time, it utilizes buoyancy and gravity to promote the natural growth and enrichment of crystal nuclei, while small crystals enter subsequent reaction tanks with the influent flow rate to continue growing, avoiding pipeline blockage and gradually reducing the concentration of impurities such as organic matter in the system. Ultimately, it achieves high-quality recovery of phosphate crystals such as blue iron ore, iron phosphate, and calcium phosphate, upgrading the traditional powdery coarse recovery to millimeter-level fine ore recovery. The high-value preparation module targets the graded recovery of phosphate crystals and performs targeted conversion through differentiated processes: lithium iron phosphate materials are prepared by using lapis lazuli or crude iron phosphate as raw materials through batching, mixing, grinding, drying and segmented calcination; calcium iron phosphate materials are prepared by using crude calcium phosphate containing lapis lazuli or iron sulfate as raw materials through high-temperature calcination, which greatly improves the economic value of the recovered products.

[0126] The beneficial effects of this invention are as follows: First, through the synergistic effect of ultrafiltration to remove organic matter and multi-stage reaction tank gradient impurity removal, the interference of impurities on phosphate crystallization is significantly reduced, providing a clean system for the generation of high-quality crystals. Second, the combination of the concentration function of nanofiltration membrane and the reduction of crystallization activation energy not only increases the supersaturation of phosphate to promote crystal growth, but also reduces reagent consumption and the risk of secondary pollution, lowers operating costs, and enhances technical and economic feasibility. Third, based on the natural dynamic mechanism of "nucleation-growth-precipitation" and intelligent flow control, process blockage problems are avoided, system synergy and operational stability are improved, and a closed-loop recovery process chain is formed. Fourth, the upgrade of phosphorus resources from crude recovery to high-value materials is realized, obtaining high-value-added products such as lithium iron phosphate and calcium iron phosphate, promoting the industrialization and large-scale application of wastewater phosphorus recovery. Fifth, the entire process is characterized by low energy consumption and simple process flow. Through multi-stage stepwise addition of metal ions, the efficient recovery of various types of phosphate crystals is achieved, with high mineral purity and high value density, taking into account both resource energy utilization and innovation, filling the technological gap in high-value recovery of wastewater phosphorus.

[0127] The present application is further illustrated below through embodiments and related test experiments. In the detailed description below, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present application. However, it is apparent that one or more embodiments may be implemented without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict. All instruments, consumables, and reagents used in the following embodiments are commercially available unless otherwise specified.

[0128] Example 1

[0129] This embodiment 1 utilizes, as follows Figure 1 The wastewater phosphorus high-value recovery device shown is used to recover phosphate crystals from phosphorus-containing wastewater.

[0130] In this embodiment, the effective volume of the primary reaction tank 211 is 500L. The first crystal growth region 2111 has a frustum-shaped structure with an upper boundary diameter of 1m, a lower boundary diameter of 0.7m, and a vertical height of 0.4m; the first crystal nucleation region 2112 has a frustum-shaped structure with an upper boundary diameter of 0.7m, a lower boundary diameter of 0.5m, and a vertical height of 0.6m; and the first crystal precipitation region 2113 has a conical structure with an upper boundary diameter of 0.5m and a vertical height of 0.6m. The primary reaction tank 211 is mainly used for inducing nucleation and initial crystal growth in the early stages of crystallization, providing sufficient reaction space and residence time for nucleation and early crystal growth. The first crystal precipitation region 2113 can also be used to settle and remove some organic matter and suspended impurities from the influent, reducing their interference with the subsequent crystallization process in the reaction tank.

[0131] The effective volume of the secondary reaction tank 212 is 300L. The second crystal growth region 2121 has a frustum-shaped structure with an upper boundary diameter of 0.8m, a lower boundary diameter of 0.4m, and a vertical height of 0.4m; the second crystal nucleation region 2122 has a frustum-shaped structure with an upper boundary diameter of 0.4m, a lower boundary diameter of 0.2m, and a vertical height of 0.6m; and the second crystal precipitation region 2123 has a conical structure with an upper boundary diameter of 0.2m and a vertical height of 0.4m. The secondary reaction tank 212 is mainly used for further crystal growth and sedimentation separation, and by appropriately reducing the volume of the second crystal precipitation region 2123, the utilization efficiency of the crystal growth region is improved.

[0132] The effective volume of the three-stage reaction tank 213 is 150L. The third crystal growth zone 2131 has a frustum-shaped structure with an upper boundary diameter of 0.6m, a lower boundary diameter of 0.3m, and a vertical height of 0.4m; the third crystal precipitation zone 2132 has a conical structure with an upper boundary diameter of 0.3m and a vertical height of 0.6m. The three-stage reaction tank 213 is mainly used for the enrichment and collection of the precipitation products at the end of crystallization.

[0133] In this embodiment, the total volume of the reaction tank is 2500L, designed primarily based on the requirements for high-purity recovery of ferric phosphate and lapis lazuli crystals. The initial influent flow rate is set at 100-300L / h. According to the pilot-scale test results, the nucleation time for lapis lazuli is approximately 1-2 hours, the crystal growth time is approximately 2-6 hours, and the total reaction time is approximately 2.5-8 hours. Therefore, the device volume must meet the maximum residence time requirement. The nucleation time for ferric phosphate from induction to crystal maturation is approximately 1.5-6 hours, which also falls within the design residence time range of this device. The nucleation time for hydroxyapatite is approximately 0.5-4 hours, and the crystal growth time is approximately 4-24 hours. Although it has high requirements for reaction volume and residence time, since it is not the primary target product of this device design, its complete crystal growth process is not used as the basis for the device volume design. Instead, its precipitation effect is mainly utilized to reduce the phosphate content in the solution to achieve comprehensive phosphate recovery.

[0134] The phosphorus-containing wastewater used in this embodiment has the following parameters: COD 400-500 mg / L, SCOD 150-200 mg / L, total dissolved phosphorus 55-60 mg / L, orthophosphate 50-53 mg / L, and pH 6.7-6.8.

[0135] Furthermore, such as Figure 1 The operation process of the wastewater phosphorus high-value recovery device shown is as follows.

[0136] The first inlet pump 113 is turned on to draw phosphorus-containing wastewater from the inlet tank 13. The wastewater is then filtered through the ultrafiltration membrane module 11 to remove organic matter and large particles. The resulting permeate flows into the intermediate tank 14. The permeate from the ultrafiltration membrane module 11 contains PO4. 3- The concentration of phosphate was 48-51 mg / L, the pH was 6.7-6.8, and the final volume accounted for 70-80% of the influent volume of the phosphorus-containing wastewater. When the water level in the intermediate tank 14 reached the appropriate level, the second influent pump 123 was turned on to extract the permeate from the ultrafiltration membrane module 11 in the intermediate tank 14. The phosphate was then concentrated by cross-flow filtration through the nanofiltration membrane module 12. The final volume of the concentrated solution accounted for 20-30% of the permeate volume of the ultrafiltration membrane module 11. The PO4 in the concentrated solution of the nanofiltration membrane module 12 was... 3- The concentration is 150-160 mg / L, and the pH is 6.7-6.8. When the TMP of the first membrane pressure gauge 112 exceeds 0.2 MPa, replace the ultrafiltration fouling membrane; when the TMP of the second membrane pressure gauge 122 exceeds 0.75 MPa, replace the nanofiltration fouling membrane. Perform physical and chemical cleaning (NaClO and citric acid) on the fouling membrane to remove reversible and irreversible fouling, and reuse it.

[0137] To ensure sufficient mixing of phosphate and metal particles and to form optimal reaction conditions for the final formation of high-quality phosphate minerals, when the volume of the concentrated liquid in the nanofiltration membrane module 12 reaches 20-30% of the volume of the permeate in the ultrafiltration membrane module 11, the third inlet water pump 142 is turned on, and the alkali pump 2212, acid pump 2222, and chemical pump 2232, as well as the first stirring module 214 in all reaction tanks of the crystallization tank group 21, are turned on simultaneously.

[0138] When the initial recovery product is vivianite, Fe is added to intermediate container 14. 2+ Add alkali to ensure the Fe:P molar ratio of the phosphorus-rich concentrate in intermediate tank 14 is 1.5:1 and the pH is 7.7-7.8. Maintain the orthophosphate concentration in the intermediate reaction tank at 10-20 mg / L, and add Ca to the intermediate reaction tank. 2+ Alkali is added to ensure that the Ca:P molar ratio of the phosphorus-rich concentrate in the intermediate reaction tank is 3:1 and the pH is 9-9.1, which is used to recover the remaining phosphate. The orthophosphate in the effluent of crystallization tank group 21 is stable at 0-2 mg / L.

[0139] When the initial recovery product is ferric phosphate, Fe is added to intermediate tank 44. 3+ Add acid to ensure the Fe:P molar ratio of the phosphorus-rich concentrate in intermediate tank 14 is 1.2:1 and the pH is 1.7-1.8. Maintain the orthophosphate concentration in the intermediate reaction tank at 10-25 mg / L. Add Ca to the intermediate reaction tank. 2+Alkali is added to ensure that the Ca:P molar ratio of the phosphorus-rich concentrate in the intermediate reaction tank is 3:1 and the pH is 9-9.1, which is used to recover the remaining phosphate. The orthophosphate in the effluent of crystallization tank group 21 is stable at 0-2 mg / L.

[0140] In this embodiment, the wastewater phosphorus high-value recovery device first adopts a blue iron ore + calcium phosphate recovery scheme. After nearly 60 days of continuous operation, the phosphate concentrated from the wastewater is treated by crystallization unit 2. The phosphate removal rate of the blue iron ore crystallization part is stable at over 94%, the phosphate removal rate of the calcium phosphate crystallization part is stable at over 90%, and the total phosphate removal rate is over 98%. The content of crude blue iron ore in the crystal concentrate at the bottom of each reaction tank in crystallization tank group 21 is on average over 0.78 g / g, and the content of crude calcium phosphate is on average over 0.70 g / g.

[0141] In this embodiment, the wastewater phosphorus high-value recovery device adopts an iron phosphate + calcium phosphate recovery scheme. After nearly 60 days of continuous operation, the phosphate concentrated from the wastewater is treated by the crystallization unit 2. The phosphate removal rate of the iron phosphate crystallization part is stable at over 85%, the phosphate removal rate of the calcium phosphate crystallization part is stable at over 90%, and the total phosphate removal rate is over 95%. The content of crude iron phosphate in the crystal concentrate at the bottom of each reaction tank in the crystallization tank group 21 is on average over 0.83 g / g, and the content of crude calcium phosphate is on average over 0.70 g / g.

[0142] Figure 5 This is a scanning electron microscope image of the crude vivianite recovered in Example 1 of this application.

[0143] like Figure 5 As shown, the crude vivianite is evenly distributed with clearly distinguishable crystal grains and diverse morphologies: it is mainly composed of radially clustered crystals, with slender needle / rod-shaped crystals radiating outward from the center; it also contains platy / plate-like crystals and crystals with cross-symmetric structures, with sizes ranging from tens to hundreds of micrometers. The crystal outlines are clear, the edges are distinct, the dispersion is good, there is no obvious adhesion, the crystallinity is high, and there is little interference from impurities, providing a high-quality raw material foundation for subsequent high-value preparation.

[0144] Figure 6 This is a scanning electron microscope image of the crude iron phosphate recovered in Example 1 of this application.

[0145] like Figure 6 As shown, crude iron phosphate mainly exhibits an irregular blocky structure with particle sizes ranging from nanometers to micrometers. The primary particles are approximately 100-300 nm in size and further aggregate to form micrometer-scale secondary structures. The particle surfaces are rough, lacking clear crystal planes and regular geometric morphologies, resulting in low crystallinity and the formation of multi-level iron phosphate aggregates, requiring further heating and shaping.

[0146] Crude lapis lazuli and crude iron phosphate were thoroughly mixed with ammonium dihydrogen phosphate and lithium carbonate at a Fe:P:Li molar ratio of 1:1:1 to obtain a mixture. Simultaneously, 10-15% glucose and 1.5 times the volume of ethanol were added to the mixture, and the mixture was stirred until homogeneous to obtain a homogeneous solution. The solution was then placed in an agate ball mill and milled at 320 rpm for 10 hours. The milled solution was then placed in a drying oven and dried at 60-80℃ to remove ethanol, yielding a precursor material. Finally, the precursor material was placed in a tube furnace under an argon atmosphere, heated at 450℃ for 4 hours, then increased to 700℃ for 6 hours. After cooling and drying, powdered lithium iron phosphate material was obtained.

[0147] Figure 7 This is an X-ray diffraction pattern of the lithium iron phosphate material prepared in Example 1 of this application.

[0148] like Figure 7 As shown, the peak positions of the lithium iron phosphate sample prepared in Example 1 are highly consistent with those of the standard card. The peaks are sharp and have high intensity, indicating that the prepared lithium iron phosphate samples all have a highly crystalline pure phase LiFePO4 structure with no obvious impurities, which meets the phase purity requirements of high-value battery materials.

[0149] Crude calcium phosphate containing lapis lazuli or iron phosphate was placed in a tube furnace and heated to 900°C at a heating rate of 10°C / min, and calcined for 3 hours to obtain calcium iron phosphate material.

[0150] Figure 8 This is a scanning electron microscope image of the calcium iron phosphate material prepared in Example 1 of this application.

[0151] like Figure 8 As shown, the calcium iron phosphate material prepared in Example 1 consists of a large number of spherical / near-spherical particles with particle sizes ranging from tens to hundreds of nanometers. There is a certain degree of soft agglomeration between the particles, but no obvious hard agglomeration or adhesion. The particle outlines are clear and the surface is dense, with no obvious amorphous impurities or impurity phases covering them. This indicates that the calcium iron phosphate material prepared by calcination has good crystallinity and uniform phase, providing a high-quality microstructure basis for subsequent high-value applications.

[0152] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this application. It should be understood that the above descriptions are merely specific embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A wastewater phosphorus high-value recovery device, characterized in that, include: Membrane separation unit for solid-liquid separation and phosphate concentration in phosphorus-containing wastewater; A crystallization unit, wherein the inlet end of the crystallization unit is connected to the outlet end of the membrane separation unit, the crystallization unit includes a crystallization tank group, a dosing module, a detection module, and a control console. The dosing module is connected to the crystallization tank group, the detection module is disposed within the crystallization tank group, and the control console is electrically connected to both the dosing module and the detection module. The crystallization unit is used to perform graded crystallization on phosphorus-containing wastewater treated by the membrane separation unit to recover phosphate crystals; and The high-value preparation unit is connected to the feed end of the crystallization unit. The high-value preparation unit includes a grinding module, a drying module and a calcination module connected in sequence, which are used to prepare the recovered phosphate crystals into phosphate products.

2. The wastewater phosphorus high-value recovery device according to claim 1, characterized in that, The crystallization pool group includes multiple reaction pools connected in sequence; Along the flow direction of the phosphorus-containing wastewater, the reaction tanks are sequentially classified as a primary reaction tank, a secondary reaction tank, and a tertiary reaction tank.

3. The wastewater phosphorus high-value recovery device according to claim 2, characterized in that, The primary reaction tank includes, from top to bottom, a first crystal growth zone, a first crystal nucleation zone, and a first crystal precipitation zone along the liquid flow direction; The secondary reaction tank includes, from top to bottom, a second crystal growth zone, a second crystal nucleation zone, and a second crystal precipitation zone along the liquid flow direction; The three-stage reaction tank includes a third crystal growth zone and a third crystal precipitation zone from top to bottom along the liquid flow direction; Preferably, the liquid outlets of the first crystal precipitation zone, the second crystal precipitation zone, and the third crystal precipitation zone are respectively connected to Y-type filters; The discharge end of the Y-type filter is connected to the high-value preparation unit.

4. The wastewater phosphorus high-value recovery device according to claim 3, characterized in that, The first crystal growth region, the second crystal growth region, and the third crystal growth region are all frustum-shaped structures; Both the first crystal nucleation region and the second crystal nucleation region are frustum-shaped structures; The first crystal precipitation region, the second crystal precipitation region, and the third crystal precipitation region are all conical structures; The cross-sectional diameters of the primary reaction tank, the secondary reaction tank, and the tertiary reaction tank gradually decrease from top to bottom along the liquid flow direction.

5. The wastewater phosphorus high-value recovery device according to claim 3, characterized in that, The height ratio of the first crystal growth region, the first crystal nucleation region, and the first crystal precipitation region is (1.5-2.5):(2.5-3.5):(2.5-3.5); The height ratio of the second crystal growth region, the second crystal nucleation region, and the second crystal precipitation region is (1.5-2.5):(2.5-3.5):(1.5-2.5); The height ratio of the third crystal growth region to the third crystal precipitation region is (1.5-2.5):(2.5-3.5).

6. The wastewater phosphorus high-value recovery device according to claim 2, characterized in that, The detection module includes a pH detection electrode, a redox potential detection electrode, a temperature detection electrode, and a conductivity detection electrode; and / or The reaction tank is also equipped with a first stirring module and a flow pipe; The flow pipe is arranged around the wall of the reaction tank, with one end extending to the middle part of the reaction tank and the other end connected to the adjacent preceding reaction tank.

7. The wastewater phosphorus high-value recovery device according to claim 1, characterized in that, The membrane separation unit includes an ultrafiltration membrane module and a nanofiltration membrane module connected in sequence. The ultrafiltration membrane module is used for solid-liquid separation of the phosphorus-containing wastewater, and the nanofiltration membrane module is used for phosphate concentration of the phosphorus-containing wastewater.

8. A method for operating a wastewater phosphorus high-value recovery device as described in any one of claims 1-7, characterized in that, include: Phosphorus-containing wastewater undergoes solid-liquid separation and phosphate concentration in a membrane separation unit to obtain a phosphorus-rich concentrate. The phosphorus-rich concentrate is transported to the crystallization unit. Based on the data collected by the detection module, the dosing module is controlled by the control console to add metal ions and acid-base regulators in stages, thereby adjusting the crystallization conditions to achieve phosphate stage crystallization and recover phosphate crystals. The recovered phosphate crystals are transported to the high-value preparation unit, where they are ground, dried, and calcined to obtain lithium iron phosphate or calcium iron phosphate.

9. The operating method according to claim 8, characterized in that, The staged addition of metal ions and acid-base adjusters includes: Fe is added to the phosphorus-rich concentrate 2+ and alkali, the molar ratio of Fe:P in the phosphorus-rich concentrate is controlled to be 1.5-2.0:1, the pH is controlled to be 7.7-7.8, and a crude vivianite is recovered; or Add Fe to the phosphorus-rich concentrate 3+ The solution is acidified, and the Fe:P molar ratio in the phosphorus-rich concentrate is controlled to be 1.0-1.4:1 and the pH to be 1.7-1.8, so as to recover crude iron phosphate. Ca was subsequently added to the reaction tank. 2+ The solution is mixed with alkali, and the Ca:P molar ratio of the remaining phosphorus-rich concentrate in the reaction tank is controlled to be 2-3:1 and the pH to be 9-9.

1. Crude calcium phosphate is recovered, wherein the crude calcium phosphate contains lapis lazuli or ferric sulfate.

10. The operating method according to claim 9, characterized in that, The lithium iron phosphate is prepared by the following method: The crude lapis lazuli or crude iron phosphate is mixed with ammonium dihydrogen phosphate, lithium carbonate, and glucose, and then ground, dried, and calcined to obtain lithium iron phosphate; and / or The calcium iron phosphate is prepared by the following method: The crude calcium phosphate was calcined to obtain calcium iron phosphate.

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