Double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and phosphorus recovery method

Abstract

The present application relates to sewage treatment and resource technology field, specifically relates to a kind of double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and phosphorus recovery method, crystallization reactor includes reactor body, flow guide barrel assembly is arranged in the inside of reactor body and coaxially arranged with reactor body, water distribution pipeline assembly, precipitant delivery pipeline assembly and crystal discharge pipeline assembly extend to the inside of reactor body;It also includes double-impeller assembly arranged in the inside of reactor body;Through the synergistic effect of inner and outer double-impeller, the fluid mixing and material circulation in the inside of reactor body are greatly enhanced, the generation of crystallization nucleus and the sustained growth of particle are effectively promoted, the sustained growth and efficient classification of crystalline particle are realized;Again, the forced internal circulation channel constructed by flow guide barrel assembly enables fine crystal particles to repeatedly backflow to reaction zone to continue growing, significantly reduces the loss of fine crystal particles with effluent, and improves the recovery rate of phosphorus.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sewage treatment and resource utilization, and particularly relates to a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and a phosphorus recovery method. BACKGROUND

[0002] The main cause of eutrophication of water bodies is that the content of nitrogen and phosphorus in water exceeds the standard; among them, excessive phosphorus discharge is the key factor causing this problem. Generally, when the total phosphorus concentration in the water body reaches 0.02 mg / L, the ecological balance of the water environment will be destroyed, thereby affecting the stability and health of the entire ecological system. In order to effectively curb the eutrophication of water bodies, the city sewage treatment plant needs to remove nitrogen and phosphorus in sewage while removing organic pollutants in sewage. With the rapid development of social economy, the problem of eutrophication of water bodies is becoming increasingly serious, while the phosphorus resource is becoming increasingly scarce; since phosphorus is a key non-renewable resource in agricultural production, industry and new energy, the phosphorus recovery technology has attracted widespread attention. One of the mainstream methods of phosphorus recovery is to recover and utilize the phosphorus in wastewater in the form of struvite (NH4)3PO4· MgSO4· 6H2O) and the like through a crystallization reactor.

[0003] The existing crystallization reactor still has significant defects in actual application; for example, under the action of high upflow velocity of the crystallization reactor, fine particles generated in the crystallization process are easily entrained by the effluent, thereby causing problems such as decrease of effluent quality and decrease of phosphorus recovery efficiency. In addition, the traditional single reaction zone or single-impeller stirring crystallizer is difficult to achieve balance between crystallization nucleus generation and particle growth, and in actual operation, phenomena such as excessive growth of crystals leading to decrease of reaction surface area or too small particles being lost with water flow often occur. In order to solve the above problems, the industry usually adopts auxiliary measures such as external side flow reactor, filter tank or addition of coagulant; however, these methods often increase the complexity and operation cost of the crystallization reaction system, and the effect that can be achieved is very limited, and it is difficult to fundamentally solve the defects of the crystallization reactor.

[0004] The present application provides a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and a phosphorus recovery method to solve the problems of low phosphorus recovery efficiency of the existing crystallization reactor and difficulty in achieving balance between crystallization nucleus generation and particle growth in the prior art. SUMMARY

[0005] The present application aims to provide a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and a phosphorus recovery method to solve the problems of low phosphorus recovery efficiency of the existing crystallization reactor and difficulty in achieving balance between crystallization nucleus generation and particle growth in the prior art.

[0006] The technical solution of the present application is: a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery, comprising:​

[0007] a reactor body for containing fluid formed by mixing phosphorus-containing wastewater and a precipitant;

[0008] a draft tube assembly arranged inside the reactor body, a first gradient space being formed inside the draft tube assembly, and a second gradient space being formed outside the draft tube assembly;

[0009] a pipeline structure including a water distribution pipeline assembly extending to the first gradient space, a precipitant delivery pipeline assembly extending to the second gradient space, and a crystal discharge pipeline assembly communicating with the upper end of the first gradient space;

[0010] a double-impeller assembly coaxially arranged with the draft tube assembly, including impeller sets with opposite inclining directions; under the rotating state of the double-impeller assembly, the fluid is circulated and reciprocally flowed in and out of the draft tube assembly, and the phosphorus-containing wastewater forms a concentration gradient in the first gradient space, and the precipitant forms a concentration gradient in the second gradient space.

[0011] Preferably, the double-impeller assembly further includes an impeller main shaft, and the impeller sets include an impeller connecting part, a plurality of inner impellers, and a plurality of outer impellers.

[0012] One end of each of the plurality of inner impellers is fixedly connected to the impeller main shaft at the same inclining angle, and the other end is fixedly connected to the inner side wall of the impeller connecting part; one end of each of the plurality of outer impellers is fixedly connected to the outer side wall of the impeller connecting part at the same inclining angle; and the inclining direction of the inner impellers is opposite to that of the outer impellers.

[0013] Preferably, the draft tube assembly includes an upper draft tube and a lower draft tube.

[0014] The upper draft tube and the lower draft tube are fixedly arranged inside the reactor body by a draft tube support.

[0015] The input end of the crystal discharge pipeline assembly and the output end of the water distribution pipeline assembly are arranged inside the upper draft tube; and the impeller sets are arranged between the upper draft tube and the lower draft tube.

[0016] Preferably, the output end of the water distribution pipeline assembly and the output end of the precipitant delivery pipeline assembly are configured as annular pipeline structures and are arranged inside the upper draft tube and outside the lower draft tube, respectively.

[0017] The central axis of the annular pipeline structure and the central axis of the input end of the crystal discharge pipeline assembly are coaxially arranged with the reactor body.

[0018] Preferably, the water distribution pipe assembly comprises a water distribution pipe and a water distributor; the water distributor is arranged inside the draft tube assembly; one end of the water distribution pipe is in communication with the water distributor, and the other end penetrates through the side wall of the reactor body and is in communication with an external wastewater source;

[0019] The precipitant delivery pipe assembly comprises a precipitant pipe and an annular precipitant distributor;

[0020] The annular precipitant distributor is sleeved on the lower draft tube; one end of the precipitant pipe is in communication with the annular precipitant distributor, and the other end penetrates through the side wall of the reactor body and is in communication with an external precipitant source;

[0021] The water distributor and the annular precipitant distributor are configured as the annular pipeline structure.

[0022] Preferably, the crystal discharge pipe assembly comprises a discharge pipe and a crystal collection port;

[0023] The crystal collection port is arranged inside the draft tube assembly; one end of the discharge pipe is in communication with the crystal collection port, and the other end penetrates through the side wall of the reactor body and is in communication with an external crystal collection device.

[0024] Preferably, a plurality of inclined plates are arranged on the inner side wall of the reactor body, and the outer wall surface of the inclined plate is configured as a sedimentation surface for fluid to sink along a flow path.

[0025] The application also provides a phosphorus recovery method, which adopts the above-mentioned crystallization reactor to perform phosphorus recovery operation.

[0026] The method comprises the following steps:

[0027] S1, delivering wastewater and a precipitant into the interior of the reactor body, and starting the double-impeller assembly to promote the circulation of the liquid in the interior of the reactor body in and out of the draft tube assembly;

[0028] S2, controlling the delivery amount of the wastewater and the precipitant, and controlling the rotating speed of the double-impeller assembly, performing a crystallization reaction, and then discharging the crystals generated in the interior of the reactor body.

[0029] Preferably, in the step S2, the pH value of the liquid in the interior of the reactor body is controlled within the range of 8.5-9.5 during the crystallization reaction.

[0030] Preferably, in the step S2, the molar ratio of Ca to P in the liquid in the interior of the reactor body is controlled within the range of 1.5-2.0 during the crystallization reaction.

[0031] Compared with the prior art, the application has the following advantages:

[0032] The application provides a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and a phosphorus recovery method. BRIEF DESCRIPTION OF DRAWINGS

[0033] The application will be further described below in combination with the drawings and examples:

[0034] Figure 1 The application provides a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and a phosphorus recovery method.

[0035] Figure 2 The application provides a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and a phosphorus recovery method.

[0036] Figure 3 The application provides a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and a phosphorus recovery method.

[0037] Figure 4 The application provides a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and a phosphorus recovery method.

[0038] Figure 5 The application provides a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and a phosphorus recovery method.

[0039] Figure 6 The application provides a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery and a phosphorus recovery method.

[0040] Wherein: 1, reactor body; 2, draft tube assembly; 21, upper draft tube; 22, lower draft tube; 23, draft tube support; 3, water distribution pipeline assembly; 31, water distribution pipeline; 32, water distributor; 4, precipitant delivery pipeline assembly; 41, precipitant pipeline; 42, annular precipitant distributor; 5, crystal discharge pipeline assembly; 51, discharge pipeline; 52, crystal collection port; 6, double-impeller assembly; 61, impeller set; 611, inner impeller; 612, impeller connecting portion; 613, outer impeller; 62, impeller main shaft; 7, swash plate; 8, sight glass. DETAILED DESCRIPTION

[0041] The content of the present application will be further described in detail below in combination with specific embodiments:

[0042] In the description of the present application, it should be understood that the terms "upper", "lower", "outer", "inner", "side", "bottom" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0043] As Figure 1 shown, a double-impeller forced internal circulation type crystallization reactor for phosphorus recovery includes a reactor body 1, a draft tube assembly 2, and a pipeline structure composed of a water distribution pipeline assembly 3, a precipitant delivery pipeline assembly 4, and a crystal discharge pipeline assembly 5; wherein the draft tube assembly 2 is arranged inside the reactor body 1 and coaxially arranged with the reactor body 1, a first gradient space is formed inside the draft tube assembly 2, and a second gradient space is formed outside the draft tube assembly 2; the output end of the water distribution pipeline assembly 3, the output end of the precipitant delivery pipeline assembly 4, and the input end of the crystal discharge pipeline assembly 5 extend to the inside of the reactor body 1, the input end of the water distribution pipeline assembly 3, the input end of the precipitant delivery pipeline assembly 4, and the output end of the crystal discharge pipeline assembly 5 are respectively connected to an external wastewater source, a precipitant source, and a crystal collection device, for delivering phosphorus-containing wastewater and precipitant to the inside of the reactor body 1, and discharging the crystals formed by the crystallization reaction inside the reactor body 1 with the water flow.

[0044] The crystallization reactor also comprises a double impeller assembly 6; the double impeller assembly 6 is arranged inside the reactor body 1; the double impeller assembly 6 comprises an impeller main shaft 62 and an impeller group 61 with opposite inclined directions; the axis of the impeller main shaft 62 coincides with the axis of the reactor body 1; the impeller group 61 is arranged at one end of the impeller main shaft 62, and the other end of the impeller main shaft 62 penetrates through the bottom wall of the reactor body 1 and is connected with external driving devices; the liquid inside the reactor body 1 is stirred and continuously circulated in a specific circulation path. At the same time, under the rotating state of the double impeller assembly, the phosphorus-containing wastewater forms a concentration gradient in the first gradient space, and the precipitant forms a concentration gradient in the second gradient space. The crystallization reactor can also be electrically connected with an external monitoring and control system, and the start and stop of the crystallization reactor, the input of the wastewater and the precipitant in the reactor body 1, the output of the crystals, etc. are regulated by the monitoring and control system.

[0045] Specifically, the impeller group 61 comprises an impeller connecting part 612, a plurality of inner impellers 611 and a plurality of outer impellers 613; as shown in Figure 2As shown, from the direction of the impeller main shaft 62 towards the inner impeller 611 connecting surface, the one end of each of the plurality of inner impellers 611 is fixedly connected with the impeller main shaft 62 in the same inclined direction and at the same inclined angle, and the other end is fixedly connected with the inner side wall of the impeller connecting part 612; the inner impeller 611 is located close to the central axis of the reactor body 1, and is mainly responsible for stirring the liquid in the reaction zone, diluting the phosphate in the wastewater, and forming a certain concentration gradient of the phosphate in the draft tube assembly 2 to increase the area of the supersaturated region in the reaction zone, effectively promoting the uniform distribution of reactants and the generation of crystal nuclei. The inclined design of the inner impeller 611 can effectively guide the flow of liquid during rotation, optimize the flow path and mixing effect of the liquid in the reactor, ensure that the wastewater and the precipitator can fully contact and react, and create a specific fluid dynamics environment. The one end of each of the plurality of outer impellers 613 is fixedly connected with the outer side wall of the impeller connecting part 612 at the same inclined angle; the outer impeller 613 is located close to the side wall of the reactor body 1, and is used to enhance the overall circulation of the liquid and promote the reflux of large particle crystals to the reaction zone to promote their further growth; at the same time, it can be used to dilute the calcium ions in the precipitator, so that the calcium ions in the liquid form a certain concentration gradient in the draft tube assembly 2. Through this unique double-impeller structure design and specific connection method, the inner impeller 611 and the outer impeller 613 can rotate synchronously under the drive of the impeller main shaft 62, realizing collaborative work. Moreover, the inclined direction of the outer impeller 613 is opposite to that of the inner impeller 611; this reverse inclined design can generate fluid dynamics in opposite directions during impeller rotation, thereby circulating the liquid in the reactor body 1, significantly enhancing the mixing and disturbance effect of the liquid, and promoting the progress of the crystallization reaction. In order to better dilute the wastewater and the precipitator delivered into the reactor body 1 to build more precise calcium and phosphorus concentration gradients, and better control the circulation flow path, the output end of the water distribution pipe assembly 3, the output end of the precipitator delivery pipe assembly 4, and the input end of the crystal discharge pipe assembly 5 are coaxially arranged with the reactor body 1.

[0046] The output end of the water distribution pipe assembly 3 and the input end of the crystal discharge pipe assembly 5 are arranged in the interior of the draft tube assembly 2, and the input end of the crystal discharge pipe assembly 5 is arranged above the output end of the water distribution pipe assembly 3; the output end of the precipitant conveying pipe assembly 4 is arranged below the output end of the water distribution pipe assembly 3; and the impeller set 61 is arranged at a position between the output end of the precipitant conveying pipe assembly 4 and the output end of the water distribution pipe assembly 3. A forced internal circulation channel is formed in the interior of the reactor body 1 by the draft tube assembly 2, and under the agitation of the impeller set 61, the liquid in the interior of the reactor body 1 forms a specific circulation flow path; that is, the liquid in the interior of the reactor body 1 and the precipitant enter the interior of the draft tube assembly 2 from the bottom of the reactor body 1, flow upward along the draft tube assembly 2, mix with and react with the wastewater in the interior of the draft tube assembly 2, overflow from the opening at the upper end of the draft tube assembly 2 to the outside of the draft tube assembly 2 after flowing to the upper end of the draft tube assembly 2, and then return to the bottom of the reactor body 1 under the action of gravity and fluid dynamics, to continue the circulation flow; and the region in the interior of the draft tube assembly 2, where the upward-flowing precipitant contacts the wastewater, is defined as the reaction zone, that is, the upper part of the interior of the draft tube assembly 2 is defined as the reaction zone. The continuous circulation of the liquid in the interior of the reactor is realized by the draft tube assembly 2, so that the crystal particles formed by crystallization pass through the reaction zone multiple times in the reactor body 1; and the precipitant and the phosphorus element have the maximum supersaturation in the reaction zone, which increases the driving force for crystallization, improves the crystallization efficiency and the uniformity of the particles.

[0047] In detail, the draft tube assembly 2 includes an upper draft tube 21 and a lower draft tube 22; as shown in the drawings, Figure 3 The upper draft tube 21 and the lower draft tube 22 are fixedly arranged in the interior of the reactor body 1 by a draft tube support 23; the input end of the crystal discharge pipe assembly 5 and the output end of the water distribution pipe assembly 3 are arranged in the interior of the upper draft tube 21; the impeller set 61 is arranged between the upper draft tube 21 and the lower draft tube 22; and the output end of the precipitant conveying pipe assembly 4 is sleeved on the lower draft tube 22. Specifically, as shown in the drawings, Figure 5As shown, the water distribution pipe assembly 3 comprises a water distribution pipe 31 and a water distributor 32; the water distributor 32 is arranged inside the draft tube assembly 2; one end of the water distribution pipe 31 is in communication with the water distributor 32, and the other end penetrates through the side wall of the reactor body 1 and is in communication with an external wastewater source; the water distributor 32 can be annular or of other shapes; the precipitant delivery pipe assembly 4 comprises a precipitant pipe 41 and an annular precipitant distributor 42; the annular precipitant distributor 42 is sleeved on the lower draft tube 22; one end of the precipitant pipe 41 is in communication with the annular precipitant distributor 42, and the other end penetrates through the side wall of the reactor body 1 and is in communication with an external precipitant source. The crystal discharge pipe assembly 5 comprises a discharge pipe 51 and a crystal collection port 52; the crystal collection port 52 is arranged inside the draft tube assembly 2; one end of the discharge pipe 51 is in communication with the crystal collection port 52, and the other end penetrates through the side wall of the reactor body 1 and is in communication with an external crystal collection device.

[0048] As shown in Figure 6 The reactor body 1 is further provided with a plurality of inclined plates 7 on the inner side wall; the inclined plates 7 are arranged above the liquid flow path and are used to form an inclined settling surface, so that the fine apatite crystalline particles suspended in the reactor can more easily settle, gather and slide to the bottom of the reactor or the reflux area when passing through the inclined plate 7 area under the joint action of gravity and liquid flow, thereby further reducing the loss of fine particles with the effluent, improving the classification effect of the particles and the purity of the final product. The addition of the inclined plates 7 optimizes the settling path of the particles and strengthens the solid-liquid separation capacity of the equipment, which helps to obtain apatite recovery products with more uniform particle size and higher purity. More preferably, the inclined directions of the plurality of inclined plates 7 are the same as the inclined direction of the outer impeller 613. In addition, the reactor body 1 is provided with a sight glass 8. The addition of the sight glass 8 on the reactor body 1 can be used for real-time observation of the crystallization process, liquid flow state and particle settling in the reactor, etc. The arrangement of the sight glass 8 facilitates the process monitoring and adjustment of the operator without opening the equipment, which helps to discover and handle abnormal situations in time, thereby ensuring the stability of the apatite crystallization reaction and the product quality.

[0049] The application also provides a phosphorus recovery method, which is implemented by using the above-mentioned double-impeller forced internal circulation type crystallization reactor for phosphorus recovery operation, and specifically comprises the following steps:

[0050] S1: the wastewater is transported into the reactor body by the water distribution pipe assembly, and the precipitant is transported into the reactor body by the precipitant pipe assembly; in the process of transporting the wastewater and the precipitant into the reactor body, the double-impeller assembly is started synchronously, the liquid in the reactor body is agitated by the inner impeller and the outer impeller, the liquid is caused to form a circulating flow state in the reactor, so that the wastewater and the precipitant can be fully mixed, and a preliminary crystallization reaction is carried out in the reaction zone in the draft tube assembly. The precipitant is a compound solution or a mixture solution of a calcium source such as calcium hydroxide and / or calcium chloride; a small amount of apatite or similar material can also be added as a seed crystal to promote crystallization.

[0051] S2: the transport amount of the wastewater and the precipitant is accurately controlled according to actual needs, and the rotating speed of the double-impeller assembly is reasonably adjusted, and a crystallization reaction is carried out; by adjusting the transport amount of the wastewater and the precipitant and the rotating speed of the double-impeller assembly, suitable conditions are created for the crystallization reaction, and the crystallization reaction can be carried out efficiently and stably, and the phosphorus in the water is crystallized in the form of apatite; after the crystal particles formed in the crystallization reaction reach the target particle size, the crystals generated in the reactor body are separated and collected through the crystal discharge pipe assembly. In the process of the crystallization reaction, the molar ratio of Ca and P in the liquid in the reactor body needs to be controlled in the range of 1.5-2.0; and the molar ratio of Ca and P in the liquid in the reactor body is preferably 1.67; the PH value of the liquid in the reactor body also needs to be controlled in the range of 8.5-9.5; the reaction temperature of the crystallization reaction can be normal temperature, and the reaction time is preferably controlled in the range of 30-120 minutes. In the entire crystallization process, the pH value, the concentration gradient of calcium ions and phosphate ions in the liquid, and the amount of induced crystal seeds of the crystallization reaction can be adjusted according to the water quality and the recovery target, and the stirring intensity, the circulation flow rate and the reaction time can be flexibly adjusted, so as to ensure the efficiency and stability of the process. The double-impeller structure ensures that the wastewater and the precipitant are fully mixed and circulated, the fine crystalline particles can be backflowed to the reaction zone for continuous growth, and finally the apatite product with high purity and uniform particle size is obtained.

[0052] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. It is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or basic characteristics of the present application, therefore, no matter from which point of view, the examples should be regarded as exemplary and non-limiting, the scope of the present application is defined by the appended claims rather than the above description, therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application.

Claims

1. A double-impeller forced internal circulation crystallization reactor for phosphorus recovery, characterized in that, include: The reactor body (1) is used to contain the fluid formed by mixing phosphorus-containing wastewater and precipitant; A flow guide tube assembly (2) is disposed inside the reactor body (1). A first gradient space is formed inside the flow guide tube assembly (2), and a second gradient space is formed outside the flow guide tube assembly (2). The pipeline structure includes a water distribution pipeline assembly (3) extending to the first gradient space, a precipitant delivery pipeline assembly (4) extending to the second gradient space, and a crystal discharge pipeline assembly (5) connected to the upper end of the first gradient space. The double impeller assembly (6) is coaxially arranged with the guide tube assembly (2) and includes an impeller group (61) with opposite tilt directions. When the double impeller assembly (6) is rotating, the driving fluid circulates back and forth inside and outside the guide tube assembly (2) and makes the phosphorus-containing wastewater form a concentration gradient in the first gradient space and the precipitant form a concentration gradient in the second gradient space. The dual impeller assembly (6) further includes an impeller main shaft (62); the impeller group (61) includes an impeller connecting part (612), a plurality of inner impellers (611), and a plurality of outer impellers (613). One end of each of the plurality of inner impellers (611) is fixedly connected to the impeller main shaft (62) at the same inclination angle, and the other end is fixedly connected to the inner sidewall of the impeller connecting part (612); one end of each of the plurality of outer impellers (613) is fixedly connected to the outer sidewall of the impeller connecting part (612) at the same inclination angle; the inclination direction of the inner impellers (611) is opposite to the inclination direction of the outer impellers (613); The guide tube assembly (2) includes an upper guide tube (21) and a lower guide tube (22); the upper guide tube (21) and the lower guide tube (22) are both fixedly installed inside the reactor body (1) by a guide tube support (23); the input end of the crystal discharge pipe assembly (5) and the output end of the water distribution pipe assembly (3) are both installed inside the upper guide tube (21); the impeller assembly (61) is installed between the upper guide tube (21) and the lower guide tube (22).

2. The phosphorus recovery double-impeller forced internal circulation crystallization reactor according to claim 1, characterized in that: The output end of the water distribution pipe assembly (3) and the output end of the precipitant conveying pipe assembly (4) are both constructed as ring pipe structures and are respectively arranged inside the upper guide tube (21) and outside the lower guide tube (22); The central axis of the annular pipeline structure and the central axis of the input end of the crystal discharge pipeline assembly (5) are both coaxially set with the reactor body (1).

3. The phosphorus recovery double-impeller forced internal circulation crystallization reactor according to claim 2, characterized in that: The water distribution pipe assembly (3) includes a water distribution pipe (31) and a water distributor (32); one end of the water distribution pipe (31) is connected to the water distributor (32), and the other end passes through the side wall of the reactor body (1) and is connected to an external wastewater source. The precipitant delivery pipeline assembly (4) includes a precipitant pipeline (41) and an annular precipitant distributor (42); one end of the precipitant pipeline (41) is connected to the annular precipitant distributor (42), and the other end passes through the side wall of the reactor body (1) and is connected to an external precipitant source; The water distributor (32) and the annular precipitant distributor (42) are configured as an annular pipeline structure.

4. A double-impeller forced internal circulation crystallization reactor for phosphorus recovery according to claim 3, characterized in that: The crystal discharge pipe assembly (5) includes a discharge pipe (51) and a crystal collection port (52); the crystal collection port (52) is located inside the guide tube assembly (2); one end of the discharge pipe (51) is connected to the crystal collection port (52), and the other end passes through the side wall of the reactor body (1) and is connected to an external crystal collection device.

5. A double-impeller forced internal circulation crystallization reactor for phosphorus recovery according to claim 1, characterized in that: The reactor body (1) has several inclined plates (7) on its inner sidewall, and the outer wall surface of the inclined plates (7) is configured as a settling surface for the fluid to sink along the flow path.

6. A method for phosphorus recovery, characterized in that: Phosphorus recovery operation using the crystallization reactor described in any one of claims 1-5 includes the following steps: S1. Wastewater and precipitant are delivered into the reactor body. At the same time, the double impeller assembly is started to promote the circulation of liquid inside the reactor body in and out of the guide tube assembly. S2. Regulate the flow rate of wastewater and precipitant, and adjust the rotation speed of the double impeller assembly to carry out the crystallization reaction. Afterward, discharge the crystals generated inside the reactor body.

7. A phosphorus recovery method according to claim 6, characterized in that: In step S2, during the crystallization reaction, the pH value of the liquid inside the reactor body is controlled within the range of 8.5 to 9.

5.

8. A phosphorus recovery method according to claim 7, characterized in that: In step S2, during the crystallization reaction, the molar ratio of Ca to P in the liquid inside the reactor body is controlled within the range of 1.5 to 2.0.

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