Pretreatment device for iron phosphate production wastewater

Abstract

The utility model discloses a pretreatment device for iron phosphate production wastewater, which comprises a reaction sedimentation tank, a flocculation reaction tank, a second sedimentation tank, a sludge stirring device, a magnetic separation device and a water producing tank, according to the reaction sedimentation tank, sludge flows back to the reaction tank to serve as seed crystals, the crystallization reaction rate is increased, the purity and the yield of magnesium ammonium phosphate are effectively improved, meanwhile, a magnetic adsorbent is added into the flocculation reaction tank, and a baffle is arranged, so that the efficiency is improved. The magnetic adsorbent is arranged in the flocculation reaction tank, so that water flow in the flocculation reaction tank and the magnetic adsorbent can be fully and uniformly mixed under the action of the flocculation reaction tank stirrer, and the flocculation effect of magnesium ammonium phosphate crystals in the wastewater is improved by utilizing the magnetic adsorbent; sludge in the sedimentation tank is dispersed into magnetic adsorbents and sludge under the shearing action of the sludge stirring device, and the magnetic adsorbents are recycled through the magnetic separation device to achieve reutilization.

Description

Technical Field

[0001] The utility model belongs to the technical field of environmental protection sewage treatment, and particularly relates to a pretreatment device for wastewater produced in the production of iron phosphate, which is applicable to the treatment of wastewater produced in the production of iron phosphate. Background Art

[0002] With the rapid development of the new energy market, the demand for power batteries and energy storage materials is increasing. As the precursor of lithium iron phosphate, an ideal cathode material for electrodes at present, the demand for iron phosphate has also increased rapidly. In the production process of iron phosphate, processes such as synthesis and water washing are passed through, and the synthetic mother liquor and washing water produced are high-salt inorganic wastewater containing metal ions, sulfate ions, and phosphate ions at different concentrations, and the treatment is difficult. In the prior art, ammonia water is added to increase the pH of the wastewater during pretreatment to remove metal ions in the water in the form of precipitation, but the main precipitate formed is magnesium ammonium phosphate. Since the particle size of magnesium ammonium phosphate is small, it is difficult to achieve solid-liquid separation by the precipitation method, and the turbidity of the treated effluent is high, which cannot meet the water quality requirements of subsequent treatment processes. At present, the method of adding flocculants is often used to improve the precipitation efficiency of the wastewater produced in the production of iron phosphate after adding ammonia, so as to reduce the effluent turbidity. However, the precipitation effects of different flocculants vary greatly, and the dosage is large. A large amount of addition will also bring impurities, making it difficult to achieve the treatment effect. Summary of the Utility Model

[0003] The purpose of the utility model is to provide a pretreatment device for wastewater produced in the production of iron phosphate in view of the above problems existing in the prior art.

[0004] The above purpose of the utility model is achieved by the following technical means:

[0005] A pretreatment device for wastewater produced in the production of iron phosphate includes a reaction sedimentation tank, and also includes a flocculation reaction tank, a second sedimentation tank, a sludge stirring device, a magnetic separation device, and a water production tank. The reaction sedimentation tank includes a reaction tank and a first sedimentation tank. The reaction tank is arranged in the first sedimentation tank. The water inlet pipe extends into the reaction tank. The bottom of the first sedimentation tank is a first inverted cone-shaped mud hopper. The outlet of the first sedimentation tank is communicated with the inlet of the flocculation reaction tank through the water outlet pipe of the reaction sedimentation tank. The first mud hopper is communicated with the reaction tank through a return pipe, and a return pump is arranged on the return pipe. The outlet of the flocculation reaction tank is communicated with the inlet of the second sedimentation tank through the second sedimentation tank inlet pipe. The bottom of the second sedimentation tank is a second inverted cone-shaped mud hopper. The outlet of the second mud hopper is communicated with the inlet of the sludge stirring device through a sludge discharge pipe, and a first sludge discharge pump is arranged on the sludge discharge pipe. The outlet of the sludge stirring device is connected with the inlet of the magnetic separation device. The magnetic adsorbent outlet of the magnetic separation device is communicated with the flocculation reaction tank through a magnetic adsorbent return pipe. The outlet of the second sedimentation tank is communicated with the water production tank through the second sedimentation tank outlet pipe.

[0006] The tops of the reaction tank and the first sedimentation tank are both closed. The liquid level of the reaction tank is higher than that of the first sedimentation tank. A pipe mixer is provided on the inlet pipe, and the chemical dosing pipe is connected to the inlet pipe through the pipe mixer. A reaction tank agitator and a pH meter are provided in the reaction tank. The bottom of the reaction tank is open, a baffle plate is provided on the inner wall of the reaction tank, and a conical bottom baffle is provided below the reaction tank. The bottom diameter of the bottom baffle is the same as the diameter of the reaction tank. The bottom baffle is arranged on a support frame, and the support frame is fixedly connected to the inner wall of the first sedimentation tank. Flow meters are installed on both the inlet pipe and the reflux pipe.

[0007] A first inclined tube is provided between the first sedimentation tank and the reaction tank. An annular first overflow weir is provided above the first inclined tube. The first overflow weir is fixedly connected to the inner wall of the first sedimentation tank. An outlet is opened at the bottom of the first overflow weir. The outlet of the first overflow weir is connected to the inlet of the flocculation reaction tank through the outlet pipe of the reaction sedimentation tank.

[0008] As described above, a flocculation reaction tank agitator and a baffle are provided in the flocculation reaction tank. The top of the flocculation reaction tank is closed, and a chemical dosing port is provided at the top of the flocculation reaction tank.

[0009] As described above, the top of the second sedimentation tank is closed. Second inclined tubes are provided in the second sedimentation tank. The second inclined tubes are fixedly connected to the inner wall of the second sedimentation tank. An annular second overflow weir is provided above the second inclined tubes. The second overflow weir is fixedly connected to the inner wall of the second sedimentation tank. An outlet is opened at the bottom of the second overflow weir. The outlet of the second overflow weir is connected to the production tank through the outlet pipe of the second sedimentation tank. The outlet end of the inlet pipe of the second sedimentation tank is in a horn shape. A conical reflection plate is provided below the outlet end of the inlet pipe of the second sedimentation tank. The reflection plate is fixed on a second support frame, and the second support frame is fixedly connected to the inner wall of the second sedimentation tank. A branch pipe is provided on the inlet pipe of the second sedimentation tank, and the branch pipe extends outside the top of the second sedimentation tank.

[0010] As described above, the sludge stirring device is arranged on the top of the magnetic separation device. The sludge stirring device includes a sealed cylinder body, a reduction motor, and paddle blades. The sealed cylinder body is in an inverted frustum shape. An inlet of the sludge stirring device is opened at the top of the sealed cylinder body, and an outlet of the sludge stirring device is opened at the bottom of the sealed cylinder body. The reduction motor is arranged on the top of the sealed cylinder body. The rotating shaft of the reduction motor extends into the sealed cylinder body. Multiple layers of paddle blade groups are arranged on the rotating shaft. Each layer of paddle blade group includes two paddle blades located on the same horizontal line. The horizontal lines of the paddle blade groups of adjacent layers are perpendicular to each other.

[0011] As described above, a third support frame is provided at the top of the flocculation reaction tank, and the magnetic separation device is fixed on the third support frame. The magnetic separation device includes a protective housing, a guide plate, a magnetic roller, a sludge scraping plate, a sludge discharge port, and a magnetic adsorbent outlet. The protective housing is fixedly connected to the third support frame. An inlet of the magnetic separation device is provided on the protective housing. Both the magnetic roller and the reduction motor are arranged in the protective housing. The reduction motor is fixedly connected to the protective housing. The central axis of the magnetic roller is connected to the reduction motor. The guide plate is arranged between the inlet of the magnetic separation device and the magnetic roller, and the guide plate is fixedly connected to the inner bottom surface of the protective housing. A magnetic adsorbent outlet is provided on the protective housing. A sludge scraping plate is arranged between the magnetic adsorbent outlet and the magnetic roller. One side of the sludge scraping plate close to the magnetic roller is inclined upward. One end of the magnetic adsorbent return pipe is connected to the magnetic adsorbent outlet, and the other end of the magnetic adsorbent return pipe passes through the top of the flocculation reaction tank and extends into the flocculation reaction tank. A second sludge discharge pump is arranged at the sludge discharge port.

[0012] The utility model has the following beneficial effects compared with the prior art:

[0013] In the reaction sedimentation tank of the utility model, the sludge is refluxed into the reaction tank as crystal seeds to improve the reaction rate of crystallization, effectively improving the purity and yield of magnesium ammonium phosphate. At the same time, a magnetic adsorbent is added to the flocculation reaction tank, and by setting baffles, the water flow in the flocculation reaction tank and the magnetic adsorbent can be fully mixed evenly under the action of the flocculation reaction tank mixer, using the magnetic adsorbent to improve the flocculation effect of magnesium ammonium phosphate crystals in the wastewater. After sedimentation in the sedimentation tank, the sludge in the sedimentation tank is dispersed into magnetic adsorbent and sludge by the shearing action of the sludge stirring device, and the magnetic adsorbent is recovered by the magnetic separation device for reuse, having the advantages of good treatment effect and low operation cost. Description of the Drawings

[0014] Figure 1 is a schematic structural diagram of the utility model;

[0015] Reference numerals and corresponding component names:

[0016] 1 - water inlet pipe; 2 - chemical addition pipe; 3 - pipe mixer; 4 - reaction tank mixer; 5 - pH meter; 6 - reaction sedimentation tank; 7 - first inclined tube; 8 - first sludge hopper; 9 - bottom baffle; 10 - reaction tank; 11 - guide plate; 12 - reflux pump; 13 - flocculation reaction tank; 14 - chemical dosing port; 15 - flocculation reaction tank mixer; 16 - second sedimentation tank water inlet pipe; 17 - second sedimentation tank; 18 - second inclined tube; 19 - reflector; 20 - second sludge hopper; 21 - second sedimentation tank outlet pipe; 22 - product water tank; 23 - first sludge discharge pump; 24 - sludge stirring device; 25 - magnetic separation device; 26 - baffle. Detailed Embodiments

[0017] For the convenience of those of ordinary skill in the art to understand and implement the present utility model, the present utility model will be further described in detail below in conjunction with embodiments. The embodiments described herein are only used to illustrate and explain the present utility model, and are not intended to limit the present utility model.

[0018] Embodiment 1:

[0019] A pretreatment device for phosphoric acid iron production wastewater, comprising a reaction sedimentation tank 6, a flocculation reaction tank 13, a second sedimentation tank 17, a sludge stirring device 24, a magnetic separation device 25, and a water production tank 22. The reaction sedimentation tank 6 includes a reaction tank 10 and a first sedimentation tank. The reaction tank 10 is arranged in the first sedimentation tank. The water inlet pipe 1 extends into the reaction tank 10. The bottom of the first sedimentation tank is a first inverted conical sludge hopper 8. The outlet of the first sedimentation tank is communicated with the inlet of the flocculation reaction tank 13 through the outlet pipe of the reaction sedimentation tank 6. The first sludge hopper 8 is communicated with the reaction tank 10 through a reflux pipe, and a reflux pump 12 is arranged on the reflux pipe. The outlet of the flocculation reaction tank 13 is communicated with the inlet of the second sedimentation tank 17 through a second sedimentation tank inlet pipe 16. The bottom of the second sedimentation tank 17 is a second inverted conical sludge hopper 20. The outlet of the second sludge hopper 20 is communicated with the inlet of the sludge stirring device 24 through a sludge discharge pipe, and a first sludge discharge pump 23 is arranged on the sludge discharge pipe. The outlet of the sludge stirring device 24 is connected with the inlet of the magnetic separation device 25. The magnetic adsorbent outlet of the magnetic separation device 25 is communicated with the flocculation reaction tank 13 through a magnetic adsorbent reflux pipe. The outlet of the second sedimentation tank 17 is communicated with the water production tank 22 through a second sedimentation tank outlet pipe 21.

[0020] The tops of both the reaction tank 10 and the first sedimentation tank are closed. The liquid level of the reaction tank 10 is higher than that of the first sedimentation tank. A pipe mixer 3 is arranged on the water inlet pipe 1. The chemical addition pipe 2 is communicated with the water inlet pipe 1 through the pipe mixer 3. A reaction tank stirrer 4 and a pH meter 5 are arranged in the reaction tank 10. The bottom of the reaction tank 10 is open. A guide plate 11 is arranged on the inner wall of the reaction tank 10. A conical bottom baffle 9 is arranged below the reaction tank 10. The bottom diameter of the bottom baffle 9 is the same as the diameter of the reaction tank 10. The bottom baffle 9 is arranged on a support frame, and the support frame is fixedly connected with the inner wall of the first sedimentation tank. Flow meters are installed on both the water inlet pipe 1 and the reflux pipe;

[0021] A first inclined tube 7 is arranged between the first sedimentation tank and the reaction tank 10. An annular first overflow weir is arranged above the first inclined tube 7. The first overflow weir is fixedly connected with the inner wall of the first sedimentation tank. A water outlet is opened at the bottom of the first overflow weir. The water outlet of the first overflow weir (i.e., the outlet of the first sedimentation tank) is communicated with the inlet of the flocculation reaction tank 13 through the outlet pipe of the reaction sedimentation tank 6;

[0022] The phosphoric acid iron production wastewater enters the pipeline mixer 3 from the water inlet pipe 1, and ammonia water is added through the chemical dosing pipe 2. The ammonia water is mixed with the phosphoric acid iron production wastewater in the pipeline mixer 3, and after mixing, it enters the reaction tank 10 from the outlet end of the water inlet pipe 1. The pH of the reaction tank 10 is monitored by the pH meter 5, and the pH in the reaction tank 10 is adjusted to about... In the reaction tank 10, the metal precipitate and magnesium ammonium phosphate crystals formed by the reaction of the phosphoric acid iron production wastewater and ammonia water constitute the sludge. The wastewater and sludge after the reaction in the reaction tank 10 are diverted through the bottom baffle 9 and enter the first sedimentation tank. The sludge settles in the first inclined tube 7, and the settled sludge enters the first sludge hopper 8. Part of the sludge in the first sludge hopper 8 is refluxed to the reaction tank 10 through the reflux pump 12 and the reflux pipe, and the other part of the sludge is discharged to the outside of the reaction sedimentation tank 6 through the sludge discharge port.

[0023] As an implementable mode, both the water inlet pipe 1 and the reflux pipe are inserted below the liquid level of the reaction tank 10. The distance from the outlet end of the water inlet pipe 1 to the liquid level can be set to 0.2 - 0.3 m, the distance from the outlet end of the reflux pipe to the liquid level can be set to 0.5 - 1.0 m, the height difference between the bottom surface of the bottom baffle 9 and the bottom of the reaction tank 10 can be set to 5 - 10 cm, the flow rate of the reflux pipe is 50 - 100% of the flow rate of the water inlet pipe 1, the hydraulic retention time of the reaction tank 10 is 45 - 60 min, the hydraulic retention time of the first sedimentation tank is 2 - 4 h, and the surface hydraulic load of the first inclined tube 7 is 0.25 - 0.5 m 3 / (m 2 ·h), and the rotation speed of the reaction tank mixer 4 is 100 - 200 r / min.

[0024] A flocculation reaction tank 13 is provided with a flocculation reaction tank mixer 15 and a baffle 26. The top of the flocculation reaction tank 13 is closed, and a chemical dosing port 14 is provided at the top of the flocculation reaction tank 13;

[0025] As an implementable mode, the rotation speed of the flocculation reaction tank mixer 15 is 150 - 250 r / min, and the hydraulic retention time of the reaction flocculation tank is 30 - 60 min. The effluent of the reaction sedimentation tank 6 enters the flocculation reaction tank 13, and a magnetic adsorbent is added through the chemical dosing port 14 at the top of the flocculation reaction tank 13. The magnetic adsorbent undergoes a mixing reaction in the flocculation reaction tank 13, and the wastewater after the mixing reaction flows through the overflow channel under the baffle 26 and flows into the second sedimentation tank 17 through the second sedimentation tank water inlet pipe 16.

[0026] The baffle plate 26 in the flocculation reaction tank 13 can prevent the water flow entering the flocculation reaction tank 13 from directly flowing into the second sedimentation tank inlet pipe 16. Instead, blocked by the baffle plate 26, the water flows from the top of the flocculation reaction tank 13 to the bottom of the flocculation reaction tank 13. After being fully mixed with the reagent through stirring, the water then flows through the flow-through channel under the baffle plate 26 and finally enters the sedimentation tank through the second sedimentation tank inlet pipe 16.

[0027] The top of the second sedimentation tank 17 is closed. A second inclined tube 18 is arranged inside the second sedimentation tank 17. The second inclined tube 18 is fixedly connected to the inner wall of the second sedimentation tank 17. An annular second overflow weir is arranged above the second inclined tube 18. The second overflow weir is fixedly connected to the inner wall of the second sedimentation tank 17. The bottom of the second overflow weir is provided with a water outlet. The water outlet of the second overflow weir (i.e., the outlet of the second sedimentation tank 17) is communicated with the production water tank 22 through the second sedimentation tank outlet pipe 21. The outlet end of the second sedimentation tank inlet pipe 16 is in a horn shape. A conical reflector 19 is arranged below the outlet end of the second sedimentation tank inlet pipe 16. The reflector 19 is fixed on the second support frame, and the second support frame is fixedly connected to the inner wall of the second sedimentation tank 17. A branch pipe is arranged on the second sedimentation tank inlet pipe 16, and the branch pipe extends outside the top of the second sedimentation tank 17.

[0028] As an implementable mode, the surface hydraulic load of the sedimentation tank is 0.5 - 1.0 m 3 / (m 2 ·h).

[0029] The wastewater in the flocculation reaction tank 13 enters the second sedimentation tank 17 through the second sedimentation tank inlet pipe 16. After the remaining suspended solids in the wastewater are precipitated in the sedimentation tank, the suspended solids in the wastewater are effectively removed. The sludge formed after the suspended solids are precipitated enters the second sludge hopper 20. The sludge in the second sludge hopper 20 is sent to the sludge stirring device 24 by the first sludge discharge pump 23. The branch pipe plays the role of air outlet and support.

[0030] The sludge stirring device 24 is arranged on the top of the magnetic separation device 25. The sludge stirring device 24 includes a sealed cylinder body, a reduction motor, and paddle blades. The sealed cylinder body is in an inverted frustum shape. The top of the sealed cylinder body is provided with an inlet of the sludge stirring device 24, and the bottom of the sealed cylinder body is provided with an outlet of the sludge stirring device 24. The reduction motor is arranged on the top of the sealed cylinder body. The rotating shaft of the reduction motor extends into the sealed cylinder body. A multi-layer paddle blade group is arranged on the rotating shaft. Each layer of the paddle blade group includes two paddle blades located on the same horizontal straight line, and the horizontal straight lines of the adjacent layer paddle blade groups are perpendicular to each other.

[0031] As an implementable mode, the rotation speed of the reduction motor is 100 - 300 r / min.

[0032] The sludge stirring device 24 drives the paddle to rotate at a high speed through a reduction motor. The sludge and the magnetic adsorbent are separated by the shearing force generated by the paddle and the centrifugal force generated by the rotation of the sludge. The separated sludge and magnetic adsorbent flow out from the bottom outlet of the sludge stirring device 24.

[0033] A third support frame is provided at the top of the flocculation reaction tank 13. The magnetic separation device 25 is fixed on the third support frame. The magnetic separation device 25 includes a protective shell, a guide plate, a magnetic roller, a sludge scraping plate, a sludge discharge port (not shown in the figure), and a magnetic adsorbent outlet. The protective shell is fixedly connected to the third support frame. An inlet of the magnetic separation device 25 is opened on the protective shell. The magnetic roller and the reduction motor are both arranged in the protective shell. The reduction motor is fixedly connected to the protective shell. The central axis of the magnetic roller is connected to the reduction motor. The guide plate is arranged between the inlet of the magnetic separation device 25 and the magnetic roller. The guide plate is fixedly connected to the inner bottom surface of the protective shell. A magnetic adsorbent outlet is opened on the protective shell. A sludge scraping plate is arranged between the magnetic adsorbent outlet and the magnetic roller. One side of the sludge scraping plate close to the magnetic roller is inclined upward. One end of the magnetic adsorbent return pipe is connected to the magnetic adsorbent outlet. The other end of the magnetic adsorbent return pipe passes through the top of the flocculation reaction tank 13 and extends into the flocculation reaction tank 13. A second sludge pump is arranged at the sludge discharge port.

[0034] The reduction motor drives the magnetic roller to rotate. After the magnetic adsorbent and the sludge are separated for the first time by the sludge stirring device 24, they enter the magnetic separation device 25 for secondary separation. The magnetic adsorbent is adsorbed on the magnetic roller, then scraped off by the sludge scraping plate and enters the flocculation reaction tank 13 through the magnetic adsorbent return pipe. The sludge is discharged from the sludge outlet through the second sludge pump.

[0035] It should be noted that the embodiments described in the present invention are only examples to illustrate the spirit of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the described embodiments or use similar ways to replace them, but will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A pretreatment device for wastewater from iron phosphate production, comprising a reaction sedimentation tank (6), characterized in that: The invention also comprises a flocculation reaction tank (13), a second sedimentation tank (17), a sludge stirring device (24), a magnetic separation device (25), and a water production tank (22). The reaction sedimentation tank (6) comprises a reaction tank (10) and a first sedimentation tank. The reaction tank (10) is arranged in the first sedimentation tank. The water inlet pipe (1) extends into the reaction tank (10). The bottom of the first sedimentation tank is an inverted cone-shaped first mud hopper (8). The outlet of the first sedimentation tank is connected to the inlet of the flocculation reaction tank (13) through the outlet pipe of the reaction sedimentation tank (6). The first mud hopper (8) is connected to the reaction tank (10) through a reflux pipe. A reflux pump (12) is arranged on the reflux pipe. The outlet of the second sedimentation tank (13) is connected to the inlet of the second sedimentation tank (17) through the second sedimentation tank inlet pipe (16); the bottom of the second sedimentation tank (17) is a second mud hopper (20) in the shape of an inverted cone; the outlet of the second mud hopper (20) is connected to the inlet of the sludge stirring device (24) through a mud discharge pipe; a first mud discharge pump (23) is arranged on the mud discharge pipe; the outlet of the sludge stirring device (24) is connected to the inlet of the magnetic separation device (25); the magnetic adsorbent outlet of the magnetic separation device (25) is connected to the flocculation reaction tank (13) through the magnetic adsorbent reflux pipe; the outlet of the second sedimentation tank (17) is connected to the water production tank (22) through the second sedimentation tank outlet pipe (21).

2. A pretreatment device for wastewater from iron phosphate production according to claim 1, characterized in that: The tops of the reaction tank (10) and the first sedimentation tank are both closed, the liquid level of the reaction tank (10) is higher than the liquid level of the first sedimentation tank, a pipeline mixer (3) is arranged on the water inlet pipe (1), the dosing pipe (2) is connected with the water inlet pipe (1) through the pipeline mixer (3), a reaction tank stirrer (4) and a pH meter (5) are arranged in the reaction tank (10), the bottom of the reaction tank (10) is open, a guide plate (11) is arranged on the inner wall of the reaction tank (10), a conical bottom baffle (9) is arranged below the reaction tank (10), the bottom surface diameter of the bottom baffle (9) is the same as the diameter of the reaction tank (10), the bottom baffle (9) is arranged on a support frame, the support frame is fixedly connected to the inner wall of the first sedimentation tank, and flow meters are installed on the water inlet pipe (1) and the return pipe.

3. A pretreatment device for wastewater from iron phosphate production according to claim 2, characterized in that: A first inclined pipe (7) is arranged between the first sedimentation tank and the reaction tank (10), a first annular overflow weir is arranged above the first inclined pipe (7), the first overflow weir is fixedly connected to the inner wall of the first sedimentation tank, a water outlet is arranged at the bottom of the first overflow weir, and the water outlet of the first overflow weir is connected to the inlet of the flocculation reaction tank (13) through the water outlet pipe of the reaction sedimentation tank (6).

4. A pretreatment device for wastewater from iron phosphate production according to claim 1, characterized in that: The flocculation reaction tank (13) is provided with a flocculation reaction tank agitator (15) and a baffle (26). The top of the flocculation reaction tank (13) is closed, and a reagent addition port (14) is provided on the top of the flocculation reaction tank (13).

5. A pretreatment device for wastewater from iron phosphate production according to claim 1, characterized in that: The top of the second sedimentation tank (17) is closed. A second inclined pipe (18) is arranged in the second sedimentation tank (17). The second inclined pipe (18) is fixedly connected to the inner wall of the second sedimentation tank (17). A second annular overflow weir is arranged above the second inclined pipe (18). The second overflow weir is fixedly connected to the inner wall of the second sedimentation tank (17). A water outlet is provided at the bottom of the second overflow weir. The water outlet of the second overflow weir is connected to the water production tank (22) through the second sedimentation tank outlet pipe (21). The outlet end of the second sedimentation tank water inlet pipe (16) is trumpet-shaped. A conical reflecting plate (19) is arranged below the outlet end of the second sedimentation tank water inlet pipe (16). The reflecting plate (19) is fixed on a second supporting frame. The second supporting frame is fixedly connected to the inner wall of the second sedimentation tank (17). A branch pipe is arranged on the second sedimentation tank water inlet pipe (16). The branch pipe extends out of the top of the second sedimentation tank (17).

6. A pretreatment device for wastewater from iron phosphate production according to claim 1, characterized in that: The sludge stirring device (24) is arranged on the top of the magnetic separation device (25), and the sludge stirring device (24) includes a sealed cylinder, a reduction motor, and blades. The sealed cylinder is in the shape of an inverted cone, and the top of the sealed cylinder is provided with an inlet of the sludge stirring device (24), and the bottom of the sealed cylinder is provided with an outlet of the sludge stirring device (24). The reduction motor is arranged on the top of the sealed cylinder, and the rotating shaft of the reduction motor extends into the interior of the sealed cylinder. A plurality of layers of blade groups are arranged on the rotating shaft, and each layer of the blade group includes two blades located on the same horizontal straight line, and the horizontal straight lines of the blade groups of adjacent layers are perpendicular to each other.

7. A pretreatment device for wastewater from iron phosphate production according to claim 1, characterized in that: A third support frame is arranged on the top of the flocculation reaction tank (13), and the magnetic separation device (25) is fixed on the third support frame. The magnetic separation device (25) comprises a protective shell, a guide plate, a magnetic roller, a scraper plate, a mud discharge port, and a magnetic adsorbent outlet. The protective shell is fixedly connected to the third support frame. The protective shell is provided with an inlet of the magnetic separation device (25). The magnetic roller and the reduction motor are both arranged in the protective shell. The reduction motor is fixedly connected to the protective shell. The central axis of the magnetic roller is connected to the reduction motor. The guide plate is arranged between the inlet of the magnetic separation device (25) and the magnetic roller. The guide plate is fixedly connected to the inner bottom surface of the protective shell. The protective shell is provided with a magnetic adsorbent outlet. A scraper plate is arranged between the magnetic adsorbent outlet and the magnetic roller. The side of the scraper plate close to the magnetic roller is inclined upward. The magnetic adsorbent outlet is connected to one end of a magnetic adsorbent return pipe. The other end of the magnetic adsorbent return pipe passes through the top of the flocculation reaction tank (13) and extends into the flocculation reaction tank (13). A second mud discharge pump is arranged at the mud discharge port.

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