Iron removal device and iron removal method for wastewater containing complex iron

Abstract

The present application relates to wastewater treatment technical field, disclose a kind of iron-containing wastewater's iron removal device and iron removal method, including acid addition adjustment part, heating breakage part, alkali addition adjustment part and precipitation part;Acid addition adjustment part includes first adjusting tank and second adjusting tank, first adjusting tank is configured as cascade adjustment wastewater pH with second adjusting tank;Alkali addition adjustment part includes third adjusting tank and fourth adjusting tank, third adjusting tank is communicated heating breakage part, third adjusting tank is configured as cascade adjustment wastewater pH with fourth adjusting tank;Precipitation part includes flocculation tank and sedimentation tank, flocculation tank is communicated fourth adjusting tank, and precipitation part is provided with wastewater outlet;The present application gradient adjusts the pH of wastewater before and after breakage, not only avoid the waste of liquid medicine, but also more accurately control the pH of wastewater, to improve the breakage effect and the production effect of iron hydroxide, to improve the removal effect of complex iron.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to an iron removal device and method for wastewater containing complexed iron. Background Technology

[0002] Ammonia stripping wastewater accounts for the largest proportion of coking wastewater and has the most complex pollutants. It is characterized by "poor water quality, high toxicity, and difficulty in treatment". The total cyanide index in ammonia stripping wastewater can reach 20 mg / L to 100 mg / L, and the presence of cyanide can form extremely stable complex iron with iron ions in the wastewater.

[0003] In existing zero-discharge processes for coking wastewater, the biological treatment stage does not remove complexed iron from the wastewater. When the wastewater enters the reclaimed water section, some of the complexed iron, as a large molecule, is trapped in the membrane pores. On the one hand, it clogs the membrane pores, causing reverse osmosis membrane fouling and a red color on the membrane module surface; on the other hand, it is concentrated to the concentrate side, continuously accumulating in the subsequent concentrate salinization and evaporation stages. Ultimately, after the water is evaporated, the complexed iron enters the product, resulting in substandard salt quality.

[0004] Currently, there are various methods for removing complexed iron from wastewater, such as coagulation adsorption or double alkali precipitation. However, the removal efficiency of these methods is less than 25%, and some methods have a removal rate of less than 5%. The content of complexed iron in the treated wastewater is still as high as 20 mg / L to 40 mg / L, which far exceeds the influent requirements of membrane and evaporation systems. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and to propose an iron removal device and method for wastewater containing complexed iron, thereby solving the technical problems of poor removal effect of complexed iron and excessive dosage in the prior art.

[0006] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an iron removal device for wastewater containing complexed iron, comprising an acid addition regulating section, a heating and complex breaking section, an alkali addition regulating section, and a sedimentation section. The acid addition regulating section includes a first regulating tank and a second regulating tank connected in series. The first regulating tank is provided with a wastewater inlet, and the first and second regulating tanks are configured to adjust the pH of the wastewater in stages. The heating and complex breaking section includes a first heating tank and a second heating tank connected in series. The first heating tank is connected to the second regulating tank, and the first and second heating tanks are configured to sequentially heat the wastewater to a preset temperature value. The alkali addition regulating section includes a third regulating tank and a fourth regulating tank connected in series. The third regulating tank is connected to the second heating tank, and the third and fourth regulating tanks are configured to adjust the pH of the wastewater in stages. The sedimentation section includes a flocculation tank and a sedimentation pond connected in series. The flocculation tank is connected to the fourth regulating tank, and the sedimentation section is provided with a wastewater outlet.

[0007] Preferably, it further includes a dosing unit, which includes a flocculation dosing device, an alkali dosing device, and an acid dosing device. The flocculation dosing device is connected to the flocculation tank, the alkali dosing device is connected to the third regulating tank and the fourth regulating tank, and the acid dosing device is connected to the first regulating tank, the second regulating tank, the first heating tank, and the second heating tank.

[0008] Preferably, the outlets of the first regulating tank and the second regulating tank are each equipped with a first pH detection device. The first pH detection device is configured to provide feedback control over the amount of chemical added by the acid dosing device to the first regulating tank and the second regulating tank, so as to control the pH in the first regulating tank and the second regulating tank to be stable at a first preset value and a second preset value, respectively.

[0009] Preferably, the outlets of the third and fourth regulating tanks are each equipped with a second pH detection device. The second pH detection device is configured to provide feedback control over the amount of alkali dosing device added to the third and fourth regulating tanks, so as to stabilize the pH in the third and fourth regulating tanks at a third preset value and a fourth preset value, respectively.

[0010] Preferably, both the first heating tank and the second heating tank are equipped with a temperature detection device, a third pH detection device, and a heating coil. The heating coil is configured to be circulated with low-pressure steam to heat the wastewater in the corresponding tank. The temperature detection device is configured to detect the temperature of the corresponding tank to adjust and control the amount of steam introduced into the heating coil in the corresponding tank. The third pH detection device is configured to provide feedback control on the amount of chemical added by the acid dosing device to the first heating tank and the second heating tank, so as to control the pH in the first heating tank and the second heating tank to be stable at a second preset value.

[0011] The present invention also provides a method for removing iron from wastewater containing complexed iron, comprising the following steps: S1. Wastewater is introduced into the first regulating tank, and then acid is added to the first regulating tank to adjust the pH of the wastewater to a first preset value, and the wastewater is kept in the first regulating tank for a first preset time. S2. Add acid solution to the second equalization tank to adjust the pH of the wastewater to the second preset value, and control the wastewater to stay in the first equalization tank for the second preset time; S3. The wastewater temperature is heated to a first preset temperature value through the first heating tank; then the wastewater temperature is heated and maintained at the second preset temperature value through the second heating tank. S4. Add alkaline solution to the third equalization tank to adjust the pH of the wastewater to the third preset value, and control the wastewater to stay in the third equalization tank for the third preset time. S5. Add alkaline solution to the fourth regulating tank to adjust the pH of the wastewater to the fourth preset value, and control the wastewater to stay in the fourth regulating tank for the fourth preset time. S6. Add flocculant to the flocculation tank to cause iron compounds in the wastewater to precipitate in the sedimentation tank, and the clear liquid in the sedimentation tank overflows and is discharged through the wastewater outlet.

[0012] Preferably, the first preset value is 2 to 3, the second preset value is 1, the third preset value is 7, and the fourth preset value is 9 to 10; the first preset temperature is 95°C, and the second preset temperature is 98°C to 99°C.

[0013] Preferably, in step S3, acid solution is added to the first heating tank and the second heating tank so that the pH fluctuation of the wastewater during the heating process is less than 0.1.

[0014] Preferably, the flocculation tank includes a PAC reaction tank and a PAM coagulation tank connected together, the PAC reaction tank is connected to the fourth regulating tank, and the PAM coagulation tank is connected to the sedimentation tank; in step S6, PAC agent with a concentration of 10% and a dosage concentration of 50 mg / L is added to the PAC reaction tank, and PAM agent with a concentration of 0.5% and a dosage concentration of 1 mg / L is added to the PAM coagulation tank.

[0015] Preferably, a stirrer is provided in each of the first, second, third, and fourth adjustment tanks, the rotation speed of the stirrer is controlled at 50 r / min, and the first, second, third, and fourth preset times are controlled at 20 min.

[0016] Compared with the prior art, the iron removal device and method for wastewater containing complexed iron provided in this embodiment of the invention have the following advantages: In this embodiment, the pH of the wastewater is rapidly and roughly adjusted in the first adjusting tank before complex breaking, and precisely adjusted in the second adjusting tank, achieving a gradient change in the pH adjustment of the wastewater before complex breaking. In the iron removal process after complex breaking, the pH of the wastewater is rapidly and roughly adjusted in the third adjusting tank, and precisely adjusted in the fourth adjusting tank, achieving a gradient change in the pH adjustment during iron removal. This allows for better adjustment of the amount of acid and alkali added, and makes the complex breaking and iron removal reactions more complete and thorough. While improving the complex breaking and iron removal effects, it also reduces the amount of acid and alkali used. Attached Figure Description

[0017] Figure 1 This is a simplified top view of the present invention; Figure 2 This is a flowchart illustrating the present invention; Figure 3 This is a schematic diagram of the method steps of the present invention.

[0018] In the diagram: 1. Acid addition regulating section; 11. First regulating tank; 111. Wastewater inlet; 12. Second regulating tank; 2. Heated breaking section; 21. First heating tank; 22. Second heating tank; 23. Heating coil; 24. Temperature detection device; 3. Alkali addition adjustment section; 31. Third adjustment tank; 32. Fourth adjustment tank; 4. Sedimentation section; 41. Flocculation tank; 411. PAC reaction tank; 412. PAM coagulation tank; 42. Sedimentation tank; 421. Wastewater outlet; 43. Sludge transfer pump; 5. Chemical dosing section; 51. Flocculation dosing device; 511. PAC dosing device; 512. PAM dosing device; 52. Alkali dosing device; 53. Acid dosing device; 6. First pH detection device; 7. Second pH detection device; 8. Third pH detection device. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, 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.

[0020] To address the technical problems of poor removal efficiency of complexed iron and difficulty in controlling the dosage of acid and alkali solutions in existing technologies, this invention provides an iron removal device and method for wastewater containing complexed iron. This method enables gradient adjustment of pH, allowing the complexed iron in the wastewater to fully react, break down the complex, and form ferric hydroxide flocculent particles, thus facilitating subsequent precipitation reactions. This improves the iron removal efficiency while precisely controlling the dosage of acid and alkali solutions.

[0021] like Figure 1 and Figure 2 As shown, a preferred embodiment of the present invention provides an iron removal device for wastewater containing complexed iron, comprising an acid addition regulating unit 1, a heating and complex breaking unit 2, an alkali addition regulating unit 3, and a sedimentation unit 4. The acid addition regulating unit 1 includes a first regulating tank 11 and a second regulating tank 12 connected in series. The first regulating tank 11 is provided with a wastewater inlet 111. The first regulating tank 11 and the second regulating tank 12 are configured to adjust the pH of the wastewater in stages. The heating and complex breaking unit 2 includes a first heating tank 21 and a second heating tank 22 connected in series. The first heating tank 21 is connected to the second regulating tank 12. The first heating tank 21 and the second heating tank 22 are configured to sequentially heat the wastewater to a preset temperature value. The alkali addition regulating unit 3 includes a third regulating tank 31 and a fourth regulating tank 32 connected in series. The third regulating tank 31 is connected to the second heating tank 22. The third regulating tank 31 and the fourth regulating tank 32 are configured to adjust the pH of the wastewater in stages. The sedimentation section 4 includes a flocculation tank 41 and a sedimentation pond 42 connected together. The flocculation tank 41 is connected to the fourth regulating tank 32. The sedimentation section 4 is provided with a wastewater outlet 421.

[0022] Specifically, in conventional complexed iron removal processes, the addition of acid and alkali solutions is often a one-time event. This frequently leads to unstable wastewater pH, poor consistency and uniformity of pH, and insufficient subsequent reactions, severely impacting the subsequent complex-breaking and iron removal reactions, and consequently significantly affecting the removal efficiency of complexed iron. In this embodiment, before complex breaking, the wastewater pH is coarsely adjusted using a first adjusting tank 11, and then precisely controlled within the required range using a second adjusting tank 12. This gradient adjustment of the wastewater pH not only precisely controls pH changes but also reduces the amount of acid added. Furthermore, it extends the mixing time between the acid and wastewater, improving the consistency and uniformity of pH throughout the wastewater, facilitating subsequent heating and complex-breaking processes, enhancing the heating and complex-breaking effect, and providing a better foundation for subsequent iron removal. Once the wastewater's pH is adjusted to a suitable and stable acidic environment, it sequentially enters the first heating tank 21 and the second heating tank 22. The first heating tank 21 initially coarsely adjusts the wastewater temperature to near a preset value. Then, the second heating tank 22 further heats the wastewater to stabilize the temperature at the preset value, improving the stability of the wastewater temperature during the complex-breaking process and thus enhancing the complex-breaking effect. In this embodiment, heating causes the cyanide ions that generate complexed iron to volatilize, and simultaneously degrades phenols or cyanides to break the stable state of the complexed iron, generating iron ions, which facilitates the subsequent formation and precipitation of ferric hydroxide. After heating and complex breaking, the wastewater flows by gravity to the third regulating tank 31 and the fourth regulating tank 32. Alkali solution is added to the third regulating tank 31 to coarsely adjust the wastewater's pH, and to the fourth regulating tank 32 to finely adjust it, achieving gradient regulation of the wastewater's pH. This not only precisely controls the pH changes but also reduces the amount of alkali solution added. In addition, it can prolong the mixing time and mixing effect of alkaline solution and wastewater, improve the generation efficiency of ferric hydroxide flocs, thereby improving the efficiency of subsequent precipitation reaction, and ultimately improving the removal efficiency and effect of complexed iron.

[0023] In addition, it is understandable that in actual operation, in addition to temperature gradient adjustment, the first heating tank 21 and the second heating tank 22 also need to monitor the pH of the wastewater in the first heating tank 21 and the second heating tank 22 at all times and replenish acid at any time to avoid large fluctuations in the pH of the wastewater in the heating tank, which would affect the complex breaking reaction.

[0024] In one embodiment, the system further includes a dosing unit 5, which includes a flocculation dosing device 51, an alkali dosing device 52, and an acid dosing device 53. The flocculation dosing device 51 is connected to the flocculation tank 41, the alkali dosing device 52 is connected to the third regulating tank 31 and the fourth regulating tank 32, and the acid dosing device 53 is connected to the first regulating tank 11, the second regulating tank 12, the first heating tank 21, and the second heating tank 22.

[0025] Specifically, in addition to manually adding acid and alkali solutions to each tank, this embodiment, based on the aforementioned embodiments, also includes a dosing unit 5. This dosing unit 5 can add acid or alkali solutions to each tank via valves and pipes, and precisely control the dosage of acid and alkali solutions. Depending on the process section, the dosing unit 5 mainly includes an acid dosing device 53, an alkali dosing device 52, and a flocculation dosing device 51, used to store acid, alkali, and flocculants respectively. In a specific embodiment, the acid dosing device 53 includes an acid dosing tank with a volume of 5 cubic meters, which stores hydrochloric acid with a concentration of 10%. It also has two variable frequency dosing pumps corresponding to the first regulating tank 11 and the second regulating tank 12, and one variable frequency dosing pump corresponding to the first heating tank 21 and the second heating tank 22, respectively, to more accurately and quickly add hydrochloric acid to the corresponding tanks. The alkali dosing device 52 includes an alkali dosing tank with a volume of 5 cubic meters, which stores an alkali solution with a concentration of 10%. The alkali dosing tank is equipped with two variable frequency dosing pumps for the third regulating tank 31 and the fourth regulating tank 32, so that the alkali solution can be added to the corresponding tank more accurately and quickly. With the gradient control of pH before and after complex breaking, the pH of the wastewater can be controlled more accurately, while avoiding the waste of acid and alkali solutions.

[0026] Furthermore, in this embodiment, the structure of the flocculation tank 41 and the flocculation dosing device 51 vary depending on the flocculation process and the flocculant used. In a specific embodiment, iron flocculation is achieved using PAC (polyaluminum chloride) and PAM (polyacrylamide). Therefore, the flocculation tank 41 actually includes a connected PAC reaction tank 411 and a PAM coagulation tank 412, while the dosing unit 5 correspondingly includes a PAC dosing device 511 and a PAM dosing device 512. The PAC dosing device 511 includes a PAC dosing tank containing PAC agent with a concentration of 10%, and two variable frequency dosing pumps are installed in the corresponding PAC reaction tank 411. The PAM dosing device 512 includes a PAM dosing tank containing PAM agent with a concentration of 0.5%, and two variable frequency dosing pumps are also installed in the corresponding PAM coagulation tank 412.

[0027] It is understandable that stirring devices are installed in the first regulating tank 11, the second regulating tank 12, the third regulating tank 31, the fourth regulating tank 32, as well as the PAC reaction tank 411 and the PAM coagulation tank 412. These stirring devices can perform radial and axial synchronous stirring, thereby improving the mixing uniformity of wastewater with acid or alkali solutions and the mixing uniformity of wastewater with reagents, thus greatly improving the complex breaking efficiency and precipitation efficiency of complexed iron.

[0028] In one embodiment, the outlets of the first regulating tank 11 and the second regulating tank 12 are each equipped with a first pH detection device 6. The first pH detection device 6 is configured to provide feedback control for the amount of chemical added by the acid dosing device 53 to the first regulating tank 11 and the second regulating tank 12, so as to control the pH in the first regulating tank 11 and the second regulating tank 12 to be stable at a first preset value and a second preset value, respectively.

[0029] Furthermore, the outlets of the third regulating tank 31 and the fourth regulating tank 32 are each equipped with a second pH detection device 7. The second pH detection device 7 is configured to control the amount of alkali dosing device 52 dosing to the third regulating tank 31 and the fourth regulating tank 32, so as to control the pH in the third regulating tank 31 and the fourth regulating tank 32 to be stable at the third preset value and the fourth preset value, respectively.

[0030] Specifically, based on the aforementioned embodiments, this embodiment further includes a first pH detection device 6 and a second pH detection device 7. These pH detection devices can be existing testing instruments or equipment. The first pH detection device 6 is electrically connected to the acid dosing device 53, while the second pH detection device 7 is electrically connected to the alkali dosing device 52. In actual use, when the pH of the wastewater in the first regulating tank 11 and the second regulating tank 12 fluctuates, the first pH detection device 6 can quickly transmit the detected results to the central control equipment. The central control equipment can then adjust and control the operating status of each dosing pump in the acid dosing device 53, thereby accurately controlling the pH of the wastewater before complex breaking and maintaining the accuracy within ±0.1, further improving the accuracy of wastewater pH control. The second pH detection device 7 operates similarly and will not be described further here.

[0031] In one embodiment, both the first heating tank 21 and the second heating tank 22 are equipped with a temperature detection device 24, a third pH detection device 8, and a heating coil 23. The heating coil 23 is configured to be supplied with low-pressure steam to heat the wastewater in the corresponding tank. The temperature detection device 24 is configured to detect the temperature of the corresponding tank to adjust and control the amount of steam supplied to the heating coil 23 in the corresponding tank. The third pH detection device 8 is configured to provide feedback control on the amount of chemical added by the acid dosing device 53 to the first heating tank 21 and the second heating tank 22, so as to control the pH in the first heating tank 21 and the second heating tank 22 to be stable at a second preset value.

[0032] Specifically, in this embodiment, the first heating tank 21 and the second heating tank 22 are connected to the low-pressure steam in the factory area through the heating coil 23. The low-pressure steam enters the heating coil 23 inside the tank after being depressurized by valves such as the shut-off valve and pressure reducing valve installed on the pipeline, so as to indirectly heat the wastewater inside the tank. The temperature of the wastewater in the first heating tank 21 and the second heating tank 22 can be controlled by controlling the amount of low-pressure steam introduced by the valve.

[0033] In actual production, when wastewater is heated in the first heating tank 21 and the second heating tank 22 to break down the complex, not only the temperature of the wastewater affects the complex-breaking reaction, but fluctuations in the pH of the wastewater also affect the progress of the complex-breaking reaction. Based on the aforementioned embodiment, this embodiment is further equipped with a temperature detection device 24 and a third pH detection device 8 in both the first heating tank 21 and the second heating tank 22. The temperature detection device 24 detects the temperature of the corresponding tank and feeds it back to the central control equipment. The central control equipment then controls the opening of the valves on the corresponding pipelines to adjust the steam flow, ultimately achieving adjustment and control of the wastewater temperature. The third pH detection device 8 continuously monitors the pH of the wastewater in the first heating tank 21 and the second heating tank 22. When pH fluctuations occur, the central control equipment promptly starts the dosing pump to add acid to the corresponding tank, thereby ensuring that the pH of the wastewater remains stable during the heating process without fluctuations exceeding 0.1.

[0034] Furthermore, it should be noted that, in this embodiment, the entire iron removal device adopts a steel anti-corrosion cabinet structure. The main bodies of the first regulating tank 11, the second regulating tank 12, the third regulating tank 31, the fourth regulating tank 32, the first heating tank 21, the second heating tank 22, the PAC reaction tank 411, the PAM coagulation tank 412, and the sedimentation tank 42 are all made of carbon steel, with resin and fiberglass cloth alternately arranged on the outer layer of the carbon steel. At the same time, the outermost layer is coated with reinforced paint for corrosion protection. The agitators inside each tank are made of carbon steel with epoxy coal tar pitch for heavy corrosion protection. The dosing pipes and process water inlet and outlet pipes inside the tanks are made of HDPE material (high-density polyethylene).

[0035] It should also be noted that the acid addition regulating unit 1, the heating and breaking unit 2, and the alkali addition regulating unit 3 are all located on one side of the sedimentation tank 42 in the transverse direction, the flocculation tank 41 is located on one side of the sedimentation tank 42 in the longitudinal direction, and the chemical dosing unit 5 is located on the other side of the sedimentation tank 42 in the transverse direction. Furthermore, a sludge transfer pump 43 is connected to the bottom of the sedimentation tank 42, which can promptly extract large iron-containing flocs from the sedimentation tank 42, ensuring that the sedimentation tank 42 can operate stably and efficiently. In this embodiment, each tank is equipped with an air outlet, and each air outlet is connected to a tail gas treatment device (not shown in the figure) for unified treatment via a pipe.

[0036] like Figure 3 As shown, the present invention also provides a method for removing iron from wastewater containing complexed iron, comprising the following steps: S1. Wastewater is introduced into the first regulating tank 11, and then acid is added to the first regulating tank 11 to adjust the pH of the wastewater to a first preset value, and the residence time of the wastewater in the first regulating tank 11 is controlled to a first preset time. Wastewater enters the first regulating tank 11 under pressure at 0.1 MPa through the wastewater inlet 111. The stirrer in the first regulating tank 11 rotates and stirs the wastewater at a speed of 50 revolutions per minute. At the same time, the dosing pump of the acid dosing device 53 adds hydrochloric acid with a concentration of 10% to the first regulating tank 11 through the pipeline and valve body, and adjusts the opening of the corresponding valve body according to the data of the corresponding first pH detection device 6 to adjust the pH of the wastewater from 7.5 to stabilize it in the range of 2 to 3, and controls the residence time of the wastewater in the first regulating tank 11 to 20 minutes, so that the wastewater and acid are mixed evenly, improve the consistency of pH in various parts of the wastewater, provide good acidic conditions for subsequent heating and complex breaking, and also reduce the amount of acid used.

[0037] S2. Add acid solution to the second regulating tank 12 to adjust the pH of the wastewater to a second preset value, and control the wastewater to stay in the first regulating tank 11 for a second preset time. The wastewater flows by gravity from the first regulating tank 11 into the second regulating tank 12. The agitator in the second regulating tank 12 also rotates and stirs the wastewater at a speed of 50 revolutions per minute. At the same time, the dosing pump of the acid dosing device 53 adds hydrochloric acid with a concentration of 10% to the second regulating tank 12, and adjusts the opening of the corresponding valve body according to the data of the corresponding first pH detection device 6 to stabilize the pH of the wastewater at 1, and control the residence time of the wastewater in the second regulating tank 12 to 20 minutes. While accurately controlling the amount of acid solution used, it is also possible to more accurately control the pH of the wastewater when it enters the first heating tank 21, thereby improving the subsequent complex breaking effect.

[0038] S3. The wastewater temperature is heated to a first preset temperature value through the first heating tank 21; then the wastewater temperature is heated and maintained at a second preset temperature value through the second heating tank 22. After the wastewater flows into the first heating tank 21 by gravity, the external 0.7MPa 150℃ low-pressure steam is reduced to 0.2MPa through various valves on the pipeline and then enters the heating coil 23 inside the first heating tank 21, and then indirectly heats the wastewater to 95℃ through the heating coil 23. In this process, acid solution is also added to the first heating tank 21 through the acid dosing device 53. With the cooperation of the third pH detection device 8, the pH of the wastewater is kept at 1 during the heating process, and the pH fluctuation of the wastewater is controlled below ±0.1 to ensure that the complex breaking reaction can proceed smoothly. Meanwhile, 0.2MPa low-pressure steam is also introduced into the heating coil 23 inside the second heating tank 22 to heat the wastewater temperature from 95℃ to 98℃ to 99℃. The amount of low-pressure steam introduced is adjusted by the valve on the pipeline to ensure the stability of the wastewater temperature. In conjunction with the temperature detection device 24, the temperature fluctuation of the wastewater is ensured to not exceed ±1℃.

[0039] S4. Add alkaline solution to the third regulating tank 31 to adjust the pH of the wastewater to the third preset value, and control the residence time of the wastewater in the third regulating tank 31 to the third preset time. After the wastewater flows into the third regulating tank 31 by gravity, the stirrer in the third regulating tank 31 rotates at a speed of 50 revolutions per minute. At the same time, the dosing pump of the alkali dosing device 52 adds alkaline solution with a concentration of 10% to the third regulating tank 31, and adjusts the opening of the corresponding valve body according to the data of the corresponding second pH detection device 7 to stabilize the pH of the wastewater at 7, and control the residence time of the wastewater in the third regulating tank 31 to 20 minutes. While accurately controlling the amount of alkaline solution, it is also possible to better control the pH of the wastewater, thereby improving the generation efficiency of ferric hydroxide and preparing for subsequent precipitation.

[0040] S5. Add alkaline solution to the fourth regulating tank 32 to adjust the pH of the wastewater to the fourth preset value, and control the wastewater to stay in the fourth regulating tank 32 for the fourth preset time. After the wastewater has undergone pH adjustment in the second regulating tank 12, it flows into the fourth regulating tank 32 by gravity. The agitator in the fourth regulating tank 32 also rotates and stirs the wastewater at a speed of 50 revolutions per minute. At the same time, the alkali dosing device 52 also adds alkaline solution to the fourth regulating tank 32, and works in conjunction with the corresponding second pH detection device 7 to stabilize the pH of the wastewater in the fourth regulating tank 32 at 9 to 10. The residence time of the wastewater in the fourth regulating tank 32 is controlled to be 20 minutes, so that the iron ions in the wastewater can combine with hydroxide ions more quickly and fully to form ferric hydroxide, which facilitates the subsequent precipitation process. This not only saves the amount of alkaline solution used, but also makes the pH adjustment of the wastewater more precise and stable, and the production of ferric hydroxide more rapid and thorough.

[0041] S6. Add flocculant to flocculation tank 41 to cause iron compounds in the wastewater to precipitate in sedimentation tank 42. The supernatant in sedimentation tank 42 overflows and is discharged through wastewater outlet 421. In this embodiment, flocculation tank 41 includes a PAC reaction tank 411 and a PAM coagulation tank 412 connected together. The agitator in PAC reaction tank 411 rotates and stirs the wastewater at a speed of 50 revolutions per minute. PAC dosing device 511 simultaneously adds PAC agent to PAC reaction tank 411 and controls the residence time of wastewater in PAC reaction tank 411 to be 20 minutes so that ferric hydroxide can be fully adsorbed, coagulated and precipitated by polyaluminum chloride to form large particles. The agitator in the PAM coagulation tank 412 rotates at 25 revolutions per minute to further agitate the wastewater, causing the ferric hydroxide precipitate to be adsorbed into large flocs. These large flocs of ferric hydroxide are then carried by the water flow into the sedimentation tank 42 for settling. The supernatant in the sedimentation tank 42 is then discharged to downstream equipment through the wastewater outlet 421. The sedimentation tank 42 is also equipped with a sludge scraper, which rotates at an edge linear velocity of 3 m / min, controlling the surface load of the wastewater in the sedimentation tank 42 at 0.35 m³ / min. 3 / (㎡*h) to 0.4m 3 The time for wastewater to settle in the sedimentation tank 42 is controlled to be 10 minutes per square meter (㎡*h) to ensure that large flocculent particles of ferric hydroxide in the wastewater can settle sufficiently, thereby improving the iron removal efficiency.

[0042] Furthermore, the PAC reaction tank 411 is connected to the fourth equalization tank 32, and the PAM coagulation tank 412 is connected to the sedimentation tank 42; while the PAC dosing device 511 adds PAC agent with a prepared concentration of 10% and a dosage concentration of 50mg / L to the PAC reaction tank 411, and the PAM dosing device 512 adds PAM agent with a prepared concentration of 0.5% and a dosage concentration of 1mg / L to the PAM coagulation tank 412.

[0043] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and substitutions without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. An iron removal device for wastewater containing complexed iron, characterized in that, include: An acid-adding adjustment unit includes a first adjustment tank and a second adjustment tank connected in series. The first adjustment tank is provided with a wastewater inlet. The first adjustment tank and the second adjustment tank are configured to adjust the acidity and alkalinity of the wastewater in stages. The heating and breaking section includes a first heating tank and a second heating tank connected in series. The first heating tank is connected to the second adjusting tank. The first heating tank and the second heating tank are configured to sequentially heat wastewater to a preset temperature value. An alkali addition regulating unit includes a third regulating tank and a fourth regulating tank connected in series. The third regulating tank is connected to the second heating tank. The third regulating tank and the fourth regulating tank are configured to adjust the pH of the wastewater in stages. The sedimentation section includes a flocculation tank and a sedimentation pond that are connected together. The flocculation tank is connected to the fourth regulating tank. The sedimentation section is provided with a wastewater outlet.

2. The iron removal device for wastewater containing complexed iron according to claim 1, characterized in that, It also includes a dosing unit, which includes a flocculation dosing device, an alkali dosing device, and an acid dosing device. The flocculation dosing device is connected to the flocculation tank, the alkali dosing device is connected to the third regulating tank and the fourth regulating tank, and the acid dosing device is connected to the first regulating tank, the second regulating tank, the first heating tank, and the second heating tank.

3. The iron removal device for wastewater containing complexed iron according to claim 2, characterized in that, Both the first and second regulating tanks are equipped with a first pH detection device at their outlets. The first pH detection device is configured to control the amount of chemical added by the acid dosing device to the first and second regulating tanks, so as to control the pH in the first and second regulating tanks to be stable at a first preset value and a second preset value, respectively.

4. The iron removal device for wastewater containing complexed iron according to claim 2, characterized in that, The outlets of the third and fourth regulating tanks are each equipped with a second pH detection device. The second pH detection device is configured to provide feedback control over the amount of alkali dosing device added to the third and fourth regulating tanks, so as to stabilize the pH in the third and fourth regulating tanks at the third and fourth preset values, respectively.

5. The iron removal device for wastewater containing complexed iron according to claim 3, characterized in that, Both the first heating tank and the second heating tank are equipped with a temperature detection device, a third pH detection device, and a heating coil. The heating coil is configured to be circulated with low-pressure steam to heat the wastewater in the corresponding tank. The temperature detection device is configured to detect the temperature of the corresponding tank to adjust and control the amount of steam introduced into the heating coil in the corresponding tank. The third pH detection device is configured to provide feedback control on the amount of chemical added by the acid dosing device to the first heating tank and the second heating tank, so as to control the pH in the first heating tank and the second heating tank to be stable at a second preset value.

6. A method for removing iron from wastewater containing complexed iron, characterized in that, Includes the following steps: S1. Wastewater is introduced into the first regulating tank, and then acid is added to the first regulating tank to adjust the pH of the wastewater to a first preset value, and the wastewater is kept in the first regulating tank for a first preset time. S2. Add acid solution to the second equalization tank to adjust the pH of the wastewater to the second preset value, and control the wastewater to stay in the first equalization tank for the second preset time; S3. Heat the wastewater to a first preset temperature value through the first heating tank; The wastewater temperature is then heated and maintained at a second preset temperature value through a second heating tank. S4. Add alkaline solution to the third equalization tank to adjust the pH of the wastewater to the third preset value, and control the wastewater to stay in the third equalization tank for the third preset time. S5. Add alkaline solution to the fourth regulating tank to adjust the pH of the wastewater to the fourth preset value, and control the wastewater to stay in the fourth regulating tank for the fourth preset time. S6. Add flocculant to the flocculation tank to cause iron compounds in the wastewater to precipitate in the sedimentation tank, and the clear liquid in the sedimentation tank overflows and is discharged through the wastewater outlet.

7. The method for removing iron from wastewater containing complexed iron according to claim 6, characterized in that, The first preset value is 2 to 3, the second preset value is 1, the third preset value is 7, and the fourth preset value is 9 to 10; the first preset temperature is 95℃, and the second preset temperature is 98℃ to 99℃.

8. The method for removing iron from wastewater containing complexed iron according to claim 6, characterized in that, In step S3, acid solution is added to the first heating tank and the second heating tank to ensure that the pH fluctuation of the wastewater during the heating process is less than 0.

1.

9. The method for removing iron from wastewater containing complexed iron according to claim 6, characterized in that, The flocculation tank includes a PAC reaction tank and a PAM coagulation tank connected together. The PAC reaction tank is connected to the fourth regulating tank, and the PAM coagulation tank is connected to the sedimentation tank. In step S6, PAC agent with a concentration of 10% and a dosage concentration of 50 mg / L is added to the PAC reaction tank, and PAM agent with a concentration of 0.5% and a dosage concentration of 1 mg / L is added to the PAM coagulation tank.

10. The method for removing iron from wastewater containing complexed iron according to claim 6, characterized in that, A stirrer is installed in each of the first, second, third, and fourth adjustment tanks. The speed of the stirrer is controlled at 50 r / min, and the first, second, third, and fourth preset times are all controlled at 20 min.

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