Phosphorus recycling device for ultra-low concentration phosphorus-containing wastewater

Abstract

The application discloses a phosphorus recycling device for ultra-low-concentration phosphorus-containing wastewater. The application comprises the following steps: 1, adding calcium hydroxide solution into the ultra-low-concentration phosphorus-containing wastewater, and stirring and reacting in a reaction tank; 2, circulating a part of the slurry obtained in the step 1 to the front end of the reaction tank, and adding an arsenic removal agent into another part of the slurry; 3, carrying out sedimentation and solid-liquid separation of the slurry after the arsenic removal agent is added in a deep-cone reactor, and obtaining a semi-finished product clear liquid; 4, mixing and stirring the semi-finished product clear liquid and the calcium hydroxide solution in a neutralization tank again, and obtaining a reaction slurry; 5, carrying out sedimentation and separation of the reaction slurry in a clarification tank, and obtaining a calcium hydrogen phosphate semi-finished product; 6, conveying the calcium hydrogen phosphate semi-finished product to a drying and dewatering system, and carrying out pressure filtration and dewatering treatment; and 7, crushing and drying the calcium hydrogen phosphate semi-finished product after the pressure filtration and dewatering, and obtaining a finished product calcium hydrogen phosphate.

Description

Technical Field

[0001] This application relates to the field of phosphating technology, and in particular to a phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater. Background Technology

[0002] Currently, the wet-process phosphoric acid production process is the mainstream phosphoric acid preparation process in the phosphorus chemical industry and is widely used in actual industrial production. This process produces phosphoric acid by reacting phosphate rock with sulfuric acid. During the reaction, purification, and post-treatment stages, a large amount of phosphorus-containing wastewater is continuously generated. Although the phosphorus content in this wastewater is relatively low, the large volume and stable concentration mean that without effective treatment or recycling, it will result in a waste of phosphorus resources and pose environmental pollution risks.

[0003] To address the aforementioned problem of treating phosphorus-containing wastewater, existing technologies typically employ methods such as chemical precipitation and neutralization reactions. Some processes can simultaneously produce byproducts such as dicalcium phosphate, enabling preliminary resource recovery and utilization. However, due to limitations in arsenic removal efficiency, reaction control conditions, and precipitation separation performance, these methods still have significant room for improvement in phosphorus recovery efficiency. This is particularly true when treating ultra-low concentration phosphorus-containing wastewater, where phosphorus recovery rates are generally low, impacting resource utilization and product quality.

[0004] Therefore, there is an urgent need to provide an improved method for treating ultra-low concentration phosphorus-containing wastewater, so as to significantly improve the efficiency of phosphorus recovery and utilization, reduce the residual phosphorus content in wastewater, reduce the emission burden, and thus achieve a more efficient resource recycling goal. Utility Model Content

[0005] This application provides a phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater. The technical solution in this application is described below:

[0006] This application provides a phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater, comprising:

[0007] Defluorination tank, arsenic removal agent dosing port, deep cone reaction tank, neutralization tank, clarification tank, filter press and drying equipment;

[0008] The defluorination tank is used to receive phosphorus-containing wastewater and add calcium hydroxide solution for stirring and reaction to form an initial slurry. The arsenic removal agent inlet is located at the front end or top of the defluorination tank and is used to add arsenic removal agent to the initial slurry.

[0009] The deep cone reaction tank is connected to the defluorination tank and is used to carry out a sedimentation reaction of the initial slurry to obtain a supernatant.

[0010] The neutralization tank is connected to the deep cone reaction tank and is used to add calcium hydroxide solution to the supernatant for a secondary reaction, adjust the pH value, and generate a neutralized slurry.

[0011] The clarification tank is connected to the neutralization tank and is used to perform solid-liquid separation of the neutralization slurry to obtain dicalcium phosphate semi-finished product and wastewater clear liquid.

[0012] The filter press is connected to the clarification tank and is used to filter and dehydrate the dicalcium phosphate semi-finished product to reduce its dry basis moisture content to less than 30%.

[0013] The drying device is connected to the filter press and is used to dry the dehydrated dicalcium phosphate semi-finished product to obtain the final product, dicalcium phosphate.

[0014] Optionally, a circulation pipeline is provided between the defluorination tank and the deep cone reaction tank to return a portion of the initial slurry to the front end of the defluorination tank.

[0015] Optionally, the defluorination tank is equipped with a stirring device.

[0016] Optionally, the clarification tank is an inclined tube sedimentation clarification tank.

[0017] Optionally, the filter press is a plate and frame filter press.

[0018] Optionally, the drying apparatus includes a hot air drying oven or a rotary drying device.

[0019] Optionally, the arsenic removal agent dosing port is equipped with a metering pump.

[0020] Optionally, the bottom of the deep cone reaction tank is provided with a flocculant dosing port to promote floc formation during the initial slurry settling process.

[0021] Optionally, both the defluorination tank and the neutralization tank are made of corrosion-resistant materials, such as polypropylene, polyvinyl chloride, or 316L stainless steel.

[0022] Optionally, a flow rate regulating device is provided between the defluorination tank and the arsenic removal agent dosing port to control the residence time of the wastewater and the arsenic removal agent mixture.

[0023] As can be seen from the above technical solutions, this application has the following advantages:

[0024] 1. This device is designed for ultra-low concentration phosphorus-containing wastewater and can achieve effective phosphorus recovery even when the phosphorus content is low. Compared with traditional solutions that are only applicable to medium and high concentration wastewater, it expands the scope of application and improves the phosphorus resource recovery rate.

[0025] 2. First, common impurities (such as fluoride and arsenic) in wastewater are effectively removed through the reaction of calcium hydroxide in the defluorination tank and the addition of dearsenic removal agent. Then, the solid phase precipitation is accelerated through the efficient sedimentation effect of the deep cone reaction tank. After neutralization and pH adjustment, the wastewater enters the clarification tank, where phosphorus is efficiently separated in the form of dicalcium phosphate. The overall design has good process continuity and stage synergy, maximizing the phosphorus separation effect.

[0026] 3. The device adopts a seven-stage processing structure from pretreatment to solid-liquid separation to finished product drying. Each module has a clear function and a smooth process, which not only ensures processing efficiency, but also helps the system to operate stably and maintain its management.

[0027] 4. After processing by a pressure filter and drying device, the final product is dried dicalcium phosphate, which can be used for industrial or agricultural purposes (such as fertilizer additives), realizing the resource utilization of waste and conforming to the direction of green circular economy.

[0028] 5. The treated wastewater has removed most of the pollutants such as phosphorus, fluorine, and arsenic, reducing the load on downstream wastewater treatment facilities and improving the overall environmental protection efficiency. Attached Figure Description

[0029] Figure 1 This is a schematic flowchart of an embodiment of the phosphorus recovery and utilization method for ultra-low concentration phosphorus-containing wastewater provided in this application;

[0030] Figure 2 This is a schematic diagram of an embodiment of the phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater provided in this application. Detailed Implementation

[0031] In this application, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and other terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to describe the relative positional relationship between the components or parts and do not specifically limit the specific installation orientation of each component or part.

[0032] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0033] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; 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, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0034] Furthermore, the structures, proportions, sizes, etc., drawn in the accompanying drawings of this application are only used to complement the content disclosed in the specification for those skilled in the art to understand and read, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modification to the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects and purposes that this application can produce, should still fall within the scope of the technical content disclosed in this application.

[0035] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] See Figure 1 This application first provides an embodiment of a method for phosphorus recovery and utilization from ultra-low concentration phosphorus-containing wastewater, including:

[0037] Step 1: Add calcium hydroxide solution to ultra-low concentration phosphorus-containing wastewater, stir and react in a reaction tank, and adjust the pH value to 3.5 to 3.7 hours. The reaction time is 1 to 2 hours. The phosphorus content of the ultra-low concentration phosphorus-containing wastewater is 0.8% to 1.3%, the concentration of the calcium hydroxide solution is 15%, and the CaO content in the calcium hydroxide is 85% to 95%.

[0038] A calcium hydroxide solution was added to the ultra-low concentration phosphorus-containing wastewater, and the mixture was stirred and reacted in a reaction tank. During the stirring reaction, the pH value was continuously monitored and adjusted to 3.5 to 3.7, and the reaction time was maintained for 1 to 2 hours. This pH range is conducive to the initial reaction of some soluble phosphorus and calcium ions in the wastewater, while also providing suitable acidic environmental conditions for the subsequent separation of arsenic. The calcium hydroxide solution used in this step had a concentration of 15% and a CaO content of 85% to 95%. Reaction under these conditions helps to improve reaction efficiency and control the stability of the slurry composition.

[0039] Step 2: A portion of the slurry obtained in Step 1 is recycled back to the front end of the reaction tank for circulation, and an arsenic removal agent is added to the other portion of the slurry for reaction in the defluorination tank;

[0040] The slurry obtained in step 1 is divided into two parts. One part is returned to the front end of the reaction tank through a circulation pipeline to enhance the mixing uniformity of the slurry and stabilize the reaction conditions in the upstream section. The other part of the slurry is introduced into the defluorination tank, where a pre-prepared arsenic removal agent is added. The reaction takes place in this tank, where the arsenic removal agent reacts with the arsenic in the slurry to form insoluble arsenic compounds, thereby achieving arsenic removal. The reaction environment in this step is maintained within the acidic range, which is conducive to the efficient reaction of the arsenic removal agent.

[0041] Step 3: The slurry after adding the arsenic removal agent is subjected to sedimentation and solid-liquid separation in a deep cone reactor to obtain a semi-finished clear liquid, wherein the phosphorus content of the semi-finished clear liquid is 0.7% to 1.05% and the fluorine content is 0.0050% to 0.0090%;

[0042] After arsenic removal, the slurry is transported to a deep cone reactor for sedimentation. Gravity separation causes solid impurities to settle to the bottom, and a semi-finished clear liquid is obtained from the upper layer. The phosphorus content in this clear liquid is controlled between 0.7% and 1.05%, and the fluorine content is between 0.0050% and 0.0090%, providing relatively pure raw materials for subsequent reactions.

[0043] Step 4: Mix the semi-finished product clear liquid with calcium hydroxide solution again in a neutralization tank, adjust the pH value to 5.7 to 6.2, and react for 2 hours to obtain a reaction slurry;

[0044] The semi-finished product solution obtained in step 3 is mixed and stirred again with the calcium hydroxide solution in a neutralization tank, and the pH value is adjusted to 5.7 to 6.2. This pH range is suitable for the formation of dicalcium phosphate while inhibiting the precipitation of other impurities. The mixing reaction time is 2 hours to ensure that calcium and phosphorus react fully to form a precipitate. The concentration of the calcium hydroxide solution used in this step is still 15%, and the CaO content is 85% to 95%.

[0045] Step 5: The reaction slurry is settled and separated in a clarification tank to obtain a semi-finished product of dicalcium phosphate;

[0046] After neutralization, the slurry is introduced into a clarification tank for sedimentation and separation. The dicalcium phosphate crystals gradually aggregate and settle to the bottom of the tank, forming a semi-finished sludge. This semi-finished dicalcium phosphate is relatively moist, but already possesses a high phosphorus content and purity.

[0047] Step 6: The semi-finished dicalcium phosphate is transported to a drying and dehydration system for pressure filtration and dehydration treatment, so that the moisture content of the dry dicalcium phosphate is less than 30%.

[0048] The semi-finished dicalcium phosphate obtained from sedimentation is pumped into a drying and dehydration system, where it is dehydrated using a filter press. The goal of this step is to reduce the dry basis moisture content of the dicalcium phosphate to below 30%, providing a foundation for the physical stability and storage and transportability of the final product.

[0049] Step 7: Crush and dry the semi-finished dicalcium phosphate after pressure filtration and dehydration to obtain the finished dicalcium phosphate.

[0050] The dehydrated dicalcium phosphate semi-finished product is crushed to adjust the particle size to the required range, and then further sent to a drying device for drying to remove residual moisture, finally obtaining finished dicalcium phosphate that meets product quality standards.

[0051] In an optional embodiment, the arsenic removal agent is sodium sulfide, ferric trisulfide, or a mixture of the two.

[0052] In an optional embodiment, the arsenic removal agent is selected from sodium sulfide, ferric trisulfide, or a mixture of the two. The above-mentioned arsenic removal agent has good selective precipitation effect and can effectively form insoluble arsenic compounds with arsenic in wastewater, thereby achieving efficient removal of arsenic.

[0053] In an optional embodiment, the calcium hydroxide solution added in step 1 is 5% to 10% of the total mass of the wastewater.

[0054] In an optional embodiment, the calcium hydroxide solution added in step 1 is 5% to 10% of the total mass of the wastewater. By controlling the addition ratio of calcium hydroxide, the Ca²⁺ concentration in the system is adapted to the initial precipitation conditions of phosphorus, while avoiding excessive addition that could lead to excessively high pH or waste of raw materials, thus optimizing reaction efficiency and economy.

[0055] See Figure 2 This application provides a phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater, comprising:

[0056] Defluorination tank 01, arsenic removal agent dosing port 02, deep cone reaction tank 03, neutralization tank 05, clarification tank 06, filter press device 07, and drying device 04;

[0057] The defluorination tank 01 is used to receive phosphorus-containing wastewater and add calcium hydroxide solution for stirring and reaction to form an initial slurry. The arsenic removal agent inlet 02 is set at the front end or the top of the defluorination tank 01 and is used to add arsenic removal agent to the initial slurry.

[0058] The deep cone reaction tank 03 is connected to the defluorination tank 01 and is used to perform a sedimentation reaction on the initial slurry to obtain a supernatant.

[0059] The neutralization tank 05 is connected to the deep cone reaction tank 03 and is used to add calcium hydroxide solution to the supernatant for a secondary reaction, adjust the pH value, and generate a neutralized slurry.

[0060] The clarification tank 06 is connected to the neutralization tank 05 and is used to perform solid-liquid separation of the neutralization slurry to obtain dicalcium phosphate semi-finished product and wastewater clear liquid.

[0061] The filter press 07 is connected to the clarification tank 06 and is used to filter and dehydrate the dicalcium phosphate semi-finished product to reduce its dry basis moisture content to less than 30%.

[0062] The drying device 04 is connected to the filter press 07 and is used to dry the dehydrated dicalcium phosphate semi-finished product to obtain the final product dicalcium phosphate.

[0063] In one embodiment, such as Figure 2 As shown, this application provides a process apparatus for treating ultra-low concentration phosphorus-containing wastewater and realizing phosphorus recovery. The apparatus includes a defluorination tank 01, a deep cone reaction tank 03, a neutralization tank 05, a clarification tank 06, a filter press device 07, and a drying device 04 connected in sequence, and also includes an arsenic removal agent dosing port 02 provided on the defluorination tank 01.

[0064] The defluorination tank 01 is designated as the first reaction unit, featuring an inlet, a stirring device 09, and a chemical dosing port. Specifically, it receives phosphorus-containing wastewater and adds calcium hydroxide solution to it, allowing the wastewater and alkaline solution to undergo a preliminary mixing reaction. The reaction tank is equipped with a stirring structure to ensure thorough mixing of calcium hydroxide and wastewater and to adjust the pH to a preset range (e.g., 3.5~3.7). The arsenic removal agent dosing port 02 is preferably located at the front or top of the defluorination tank 01, facilitating the addition of sodium sulfide, ferric trisulfide, or mixtures thereof in liquid or solid form to the reaction system, promoting the removal of arsenic from the wastewater.

[0065] The deep cone reaction tank 03 is connected to the discharge end of the defluorination tank 01 and is specifically used for gravity sedimentation treatment of the initial slurry. The bottom of the tank has a cone-shaped structure, which is conducive to the sedimentation of flocs and the collection of sludge, while the upper part can collect the supernatant, achieving preliminary solid-liquid separation. By adjusting the residence time and cone structure parameters, the sedimentation efficiency and the clarity of the supernatant can be effectively improved.

[0066] Neutralization tank 05 is used for a secondary alkali adjustment reaction of the supernatant after treatment by deep cone reaction tank 03. It is connected to the supernatant outlet of deep cone reaction tank 03 and is equipped with a second calcium hydroxide dosing system. During the reaction, the alkali solution and supernatant are thoroughly mixed by a stirrer, and the pH of the system is adjusted to approximately 5.7-6.2 to promote the precipitation of phosphorus as calcium hydrogen phosphate.

[0067] The clarification tank 06 is connected to the neutralization tank 05 and is used to further settle and separate the neutralized slurry produced after the above reaction. The clarification tank 06 has a cylindrical conical bottom structure and is equipped with an overflow outlet and a bottom slag discharge outlet. The upper part recovers the clarified water, and the lower part collects the formed dicalcium phosphate sludge, which is the dicalcium phosphate semi-finished product.

[0068] The filter press device 07 is used to mechanically filter and dewater the dicalcium phosphate semi-finished product conveyed from the bottom of the clarification tank 06. The device can be a plate and frame filter press or a belt filter press. The dry basis moisture content of the material obtained after dewatering is controlled below 30%, which facilitates subsequent processing and transportation.

[0069] The drying device 04 is located after the filter press 07 and is used to dry the semi-finished dicalcium phosphate after filter press to achieve a stable finished product form. This device can be a rotary dryer, belt dryer, or airflow drying system, and can be combined with a temperature control system to precisely control the temperature and time parameters during the drying process, ultimately obtaining a dicalcium phosphate product with lower moisture content and stable form.

[0070] In actual operation, the various units are connected by conveying pipelines, and a pumping system can be set up when necessary to improve the slurry transfer efficiency. At the same time, to improve the stability of system operation, online pH meters, level gauges and automatic valves can be installed at key nodes to realize closed-loop control and automated management of the process.

[0071] In an optional embodiment, a circulation pipeline 08 is provided between the defluorination tank 01 and the deep cone reaction tank 03 for returning a portion of the initial slurry to the front end of the defluorination tank 01.

[0072] In an optional embodiment, a circulation pipeline 08 is provided between the defluorination tank 01 and the deep cone reaction tank 03 for returning a portion of the initial slurry to the front end of the defluorination tank 01. This circulation pipeline 08 is connected to the feed end of the defluorination tank 01 via a return port located in the middle or bottom of the deep cone reaction tank 03, and the slurry return is achieved by a booster pump or gravity flow. This structure helps improve the mixing uniformity and reaction efficiency of the reaction system, while also stabilizing the concentration of suspended particles in the reaction tank and promoting the full utilization of reactants.

[0073] In an optional embodiment, the defluorination tank 01 is equipped with a stirring device 09.

[0074] In an optional embodiment, the defluorination tank 01 is equipped with a stirring device 09. This stirring device 09 can be a mechanical stirrer structure, including a drive motor, stirring shaft, and impeller, and is located at the top or side wall of the reaction tank. It is used to thoroughly mix the wastewater and calcium hydroxide solution, enhancing the reaction rate and preventing solid deposition. The reaction conditions can be precisely controlled by adjusting the stirring speed, making it suitable for wastewater systems with high viscosity or high solids content.

[0075] In an optional embodiment, the clarification tank 06 is an inclined tube sedimentation clarification tank.

[0076] In an optional embodiment, the clarifier 06 is an inclined tube sedimentation clarifier. The clarifier 06 is internally equipped with inclined tube assemblies at an angle of 45°~60°, forming multiple settling channels to shorten the settling path of flocs, improve settling efficiency, and enhance the quality of clarified water. This structure enables high-throughput solid-liquid separation within a limited volume, and is particularly suitable for treating neutralized slurries containing fine suspended particles.

[0077] In an optional embodiment, the filter press 07 is a plate and frame filter press.

[0078] In an optional embodiment, the filter press device 07 is a plate and frame filter press. This device uses multiple sets of filter plates and frames arranged alternately to form filter chambers, which, together with filter cloth, perform solid-liquid separation. It is suitable for dewatering high-concentration suspensions. The material is fed into the filter chamber by a feed pump. Under pressure, the liquid passes through the filter cloth and is discharged, while the solid remains in the filter chamber to form a filter cake. The filter plates can be opened and closed via a hydraulic system, facilitating filter cake unloading and equipment cleaning. The entire machine has a mature structure and operates stably and reliably.

[0079] In an optional embodiment, the drying apparatus 04 includes a hot air drying oven or a rotary drying device.

[0080] In an optional embodiment, the drying device 04 includes a hot air drying oven or a rotary drying device. The hot air drying oven utilizes high-temperature air in direct contact with the material to achieve rapid moisture evaporation, making it suitable for large-scale continuous production. The rotary drying device has a cylindrical structure with internal spiral propulsion blades. The material advances slowly within the rotating cylinder and is heated by hot air, making it suitable for processing granular or powdery materials, resulting in uniform drying and high production capacity.

[0081] In an optional embodiment, the arsenic removal agent dosing port 02 is equipped with a metering pump 10.

[0082] In an optional embodiment, the arsenic removal agent dosing port 02 is equipped with a metering pump 10. This metering pump 10 is an adjustable flow type with automatic quantitative control, allowing the dosage to be set according to the initial arsenic concentration in the wastewater, thus achieving precise dosing of the arsenic removal agent. Combined with an automatic control system, the dosing rate can be adjusted in real time based on pH value or redox potential, improving the system's responsiveness and treatment efficiency.

[0083] In an optional embodiment, the bottom of the deep cone reaction tank 03 is provided with a flocculant inlet 11 to promote floc formation during the initial slurry settling process.

[0084] In an optional embodiment, both the defluorination tank 01 and the neutralization tank 05 are made of corrosion-resistant materials, such as polypropylene, polyvinyl chloride, or 316L stainless steel.

[0085] In an optional embodiment, a flow rate regulating device 12 is provided between the defluorination tank 01 and the arsenic removal agent dosing port 02 to control the residence time of the wastewater and the arsenic removal agent mixture.

[0086] It should be noted that the above description of the disclosed embodiments enables those skilled in the art to implement or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater, characterized in that, include: Defluorination tank, arsenic removal agent dosing port, deep cone reaction tank, neutralization tank, clarification tank, filter press and drying equipment; The defluorination tank is used to receive phosphorus-containing wastewater and add calcium hydroxide solution for stirring and reaction to form an initial slurry. The arsenic removal agent inlet is located at the front end or top of the defluorination tank and is used to add arsenic removal agent to the initial slurry. The deep cone reaction tank is connected to the defluorination tank and is used to carry out a sedimentation reaction of the initial slurry to obtain a supernatant. The neutralization tank is connected to the deep cone reaction tank and is used to add calcium hydroxide solution to the supernatant for a secondary reaction, adjust the pH value, and generate a neutralized slurry. The clarification tank is connected to the neutralization tank and is used to perform solid-liquid separation of the neutralization slurry to obtain dicalcium phosphate semi-finished product and wastewater clear liquid. The filter press is connected to the clarification tank and is used to filter and dehydrate the dicalcium phosphate semi-finished product to reduce its dry basis moisture content to less than 30%. The drying device is connected to the filter press and is used to dry the dehydrated dicalcium phosphate semi-finished product to obtain the final product, dicalcium phosphate.

2. The phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater according to claim 1, characterized in that, A circulation pipeline is provided between the defluorination tank and the deep cone reaction tank to return a portion of the initial slurry to the front end of the defluorination tank.

3. The phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater according to claim 1, characterized in that, The defluorination tank is equipped with a stirring device.

4. The phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater according to claim 1, characterized in that, The clarification tank is an inclined tube sedimentation clarification tank.

5. The phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater according to claim 1, characterized in that, The filter press is a plate and frame filter press.

6. The phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater according to claim 1, characterized in that, The drying device includes a hot air drying oven or a rotary drying device.

7. The phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater according to claim 1, characterized in that, The arsenic removal agent dosing port is equipped with a metering pump.

8. The phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater according to claim 1, characterized in that, The bottom of the deep cone reaction tank is equipped with a flocculant dosing port to promote floc formation during the initial slurry settling process.

9. The phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater according to claim 1, characterized in that, Both the defluorination tank and the neutralization tank are made of corrosion-resistant materials, such as polypropylene, polyvinyl chloride, or 316L stainless steel.

10. The phosphorus recovery and utilization device for ultra-low concentration phosphorus-containing wastewater according to claim 1, characterized in that, A flow rate regulating device is provided between the defluorination tank and the arsenic removal agent dosing port to control the residence time of the wastewater and the arsenic removal agent mixture.

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