A method and device for pretreating power plant desulfurization wastewater

Abstract

The application discloses a power plant desulfurization wastewater pretreatment method and device, and relates to the technical field of water pollution. The power plant desulfurization wastewater pretreatment method comprises the following steps: S1, wastewater homogenization adjustment: collecting power plant desulfurization wastewater, and sending the wastewater into an adjusting tank for aeration stirring treatment; S2, neutralization, impurity and heavy metal removal: sending the wastewater into a treatment device, adjusting the wastewater pH, and adding corresponding reagents; S3, coagulation and flocculation sedimentation: adding inorganic coagulants and anionic polyacrylamide to the reacted wastewater; and S4, water quality readjustment and fine filtration: adding dilute hydrochloric acid to the supernatant of a clarifying tank. The power plant desulfurization wastewater pretreatment method and device can suck the added substances in the feeding inlet into the moving box, gradually put the added substances in the moving box into the reaction box during the upward movement of the moving box, and expand the contact area of the added substances and the wastewater in the reaction box.

Description

Technical Field

[0001] This invention relates to the field of water pollution technology, specifically to a pretreatment method and apparatus for desulfurization wastewater from power plants. Background Technology

[0002] The desulfurization wastewater from the power plant comes from the wet desulfurization system of the coal-fired unit. In order to control the concentration of impurities in the slurry, the water quality is complex and has the characteristics of high salt, high suspended solids, heavy metals and corrosive ions, which poses a high risk of water pollution. It needs to be specially treated and cannot be directly discharged to avoid water pollution.

[0003] Chinese patent application number 202211270163.2 discloses a pretreatment method and apparatus for desulfurization wastewater from a biomass power plant, comprising the following steps: S1: continuously feeding desulfurization wastewater into a coagulation sedimentation tank, and sequentially adding 32% sodium hydroxide solution, 20% sodium carbonate solution, 10% polyferric sulfate solution, and 0.1% polyacrylamide solution to the desulfurization wastewater to allow calcium and magnesium ions, impurities, and suspended solids in the desulfurization wastewater to settle; S2: pressurizing the settled desulfurization wastewater by a pump and then sending it to a plate and frame filter press for filtration; S3: obtaining clear wastewater through continuous filtration by the plate and frame filter press, and adjusting the pH of the wastewater to 4-6 with concentrated sulfuric acid; S4: uniformly pressurizing the wastewater and sending it to an MVR evaporator for evaporation and concentration treatment;

[0004] In the existing pretreatment process of desulfurization wastewater from power plants, some additives are added to the wastewater treatment pond. These additives are often added from the top of the wastewater, which causes the additives to mix with the wastewater too slowly, thus affecting the overall pretreatment efficiency of the wastewater. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a pretreatment method and apparatus for power plant desulfurization wastewater, thereby solving the problems mentioned in the background section.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a pretreatment method for power plant desulfurization wastewater, comprising the following steps:

[0007] S1. Wastewater homogenization and conditioning: Collect desulfurization wastewater from the power plant and send it to the conditioning tank for aeration and stirring treatment to balance the wastewater quality and quantity, inhibit the deposition of gypsum particles, and complete the pre-treatment homogenization and buffering of wastewater.

[0008] S2. Neutralization and Heavy Metal Removal: The homogenized wastewater is sent into the treatment device, and lime slurry is added to adjust the pH of the wastewater to 9.0-9.3. Fluoride ions, some calcium and magnesium hardness, and conventional heavy metal ions in the wastewater are removed by precipitation. Then, organic sulfur agents are added to deeply chelate and precipitate the residual mercury, cadmium, and other difficult-to-remove heavy metals in the wastewater.

[0009] S3. Coagulation and flocculation sedimentation: Inorganic coagulant is added to the wastewater after the reaction for destabilization and coagulation, and then anionic polyacrylamide is added for flocculation and agglomeration, so that the fine impurities and sediments in the water form large flocs; then it is sent to the clarification tank to complete solid-liquid separation, the settled sludge is discharged into the sludge treatment system, and the supernatant overflow is collected.

[0010] S4. Water quality readjustment and fine filtration: Add dilute hydrochloric acid to the supernatant of the clarifier to adjust the pH to 7.0-8.0 to complete the water quality neutralization and readjustment; finally, remove residual fine suspended solids through multi-media filtration to obtain compliant pretreated water.

[0011] Preferably, in step S2, the lime slurry is a calcium hydroxide solution, the pH of the wastewater is maintained stably at 9.0-9.3, and the reaction is allowed to proceed for a period of time; the organic sulfur agent is TMT-15, and the heavy metal chelation reaction is allowed to proceed for a period of time.

[0012] Preferably, in step S3, the inorganic coagulant is polyferric sulfate, which is rapidly stirred and coagulated for a period of time; after the anionic polyacrylamide is added, it is slowly flocculated and held for a period of time (minutes); the bottom sludge separated in the clarifier is sent to the sludge tank, and after being dewatered by a plate and frame filter press, the sludge cake is transported off-site for disposal, and the filter press filtrate is returned to the wastewater collection end for recycling.

[0013] A pretreatment device for desulfurization wastewater from a power plant includes a reaction tank. An inlet is fixedly connected to the top of the reaction tank, and a drain outlet is fixedly connected to the outer wall of the reaction tank. A feeding mechanism is installed inside the reaction tank, and a pushing mechanism is fixedly connected to the outer wall of the feeding mechanism. The feeding mechanism includes a drive motor, which is fixedly connected to the bottom of the reaction tank. A threaded rod is fixedly connected to the top output shaft of the drive motor. A movable box is movably connected to the outer wall of the threaded rod. A telescopic hose is fixedly connected to the top of the movable box, and a feeding inlet is fixedly connected to the top of the telescopic hose, which is also fixedly connected to the top of the reaction tank.

[0014] Preferably, a first limiting component is fixedly connected to the outer wall of the movable box, a second limiting component is provided inside the threaded rod at the bottom of the feeding inlet, an extension plate is fixedly connected to the outer wall of the movable box outside the first limiting component, and a blade is movably connected to the bottom of the extension plate.

[0015] Preferably, the first limiting component includes a discharge pipe, which is fixedly connected to the outer wall of the movable box. A discharge plate is provided on the outer side of the discharge pipe, and a first limiting ring is fixedly connected to the side of the discharge plate near the movable box. The first limiting ring is movably connected inside the movable box.

[0016] Preferably, the second limiting component includes a discharge ring, which is fixedly connected to the inner wall of the telescopic hose. A discharge plate is provided at the bottom of the discharge ring, and a second limiting ring is fixedly connected to the top of the discharge plate. The second limiting ring is movably connected inside the telescopic hose.

[0017] Preferably, the pushing mechanism includes an extension rod, which is fixedly connected to the outer wall of the movable box. A guide protrusion is fixedly connected to the inner wall of the reaction chamber, and the guide protrusion is movably connected to the extension rod. A pushing component is movably connected to the outer wall of the extension rod, and a stirring rod is fixedly connected to the outer wall of the telescopic hose at the bottom of the pushing component.

[0018] Preferably, the pushing component includes a fixed frame, which is movably connected to the outer wall of the extension rod. A gathering net is fixedly connected inside the fixed frame. A limiting angle component is provided on the outer wall of the extension rod at a corresponding position of the fixed frame. A support plate is provided on the inner wall of the extension rod at the bottom of the fixed frame.

[0019] Preferably, the angle limiting assembly includes a top baffle, which is fixedly connected to the outer wall of the extension rod at the top of the fixed frame, and a bottom baffle is fixedly connected to the outer wall of the extension rod at the bottom of the fixed frame.

[0020] This invention provides a method and apparatus for pretreatment of desulfurization wastewater from power plants. It has the following beneficial effects:

[0021] 1. The pretreatment method and apparatus for desulfurization wastewater of the power plant involves drawing the additives from the feed inlet into a moving box. As the moving box moves upward, it gradually introduces the additives into the reaction tank, thereby increasing the contact area between the additives and the wastewater inside the reaction tank, improving the reaction efficiency, and thus enhancing the wastewater treatment efficiency.

[0022] 2. The pretreatment method and device for desulfurization wastewater of the power plant promotes the downward movement of flocculated and precipitated substances through the mesh structure within the component, causing hydroxide and calcium fluoride particles to converge and accumulate at the bottom. This promotes the reaction of the organic sulfur reagent TMT-15 with dissolved heavy metal ions, improves reagent utilization, and further enhances the wastewater treatment efficiency.

[0023] 3. The pretreatment method and device for desulfurization wastewater of the power plant: the additives discharged through the discharge pipe diffuse to the surroundings through the agitation of the blades. When the collection net moves, it agitates the additives diffused into the wastewater simultaneously. The up-and-down agitation method can prevent the substances from stratifying, thereby improving the efficiency of the mixing reaction and the treatment efficiency of the wastewater. Attached Figure Description

[0024] Figure 1 This is a front-view stereoscopic structural diagram of the present invention;

[0025] Figure 2 This is a schematic diagram of the three-dimensional structure of the back side of the present invention;

[0026] Figure 3 for Figure 1 Schematic diagram of cross-section structure;

[0027] Figure 4 for Figure 3 Enlarged structural diagram of section A in the middle;

[0028] Figure 5 for Figure 3 Enlarged structural diagram of section B in the middle;

[0029] Figure 6 for Figure 3 Enlarged structural diagram of section C;

[0030] Figure 7 This is a schematic diagram of the movable box structure of the present invention;

[0031] Figure 8 This is a schematic diagram of the aggregation network structure of the present invention;

[0032] Figure 9 for Figure 8 Enlarged structural diagram of section D in the middle.

[0033] In the diagram: 1. Reaction chamber; 2. Water inlet; 3. Drain outlet; 4. Feeding mechanism; 41. Drive motor; 42. Telescopic hose; 43. Feeding inlet; 44. Threaded rod; 45. Moving box; 46. First limiting component; 461. Discharge plate; 462. Discharge pipe; 463. First limiting ring; 47. Second limiting component; 471. Inlet plate; 472. Inlet ring; 473. Second limiting ring; 48. Blade; 49. Extension plate; 5. Aggregating mechanism; 51. Extension rod; 52. Guide protrusion; 53. Stirring rod; 54. Pushing component; 541. Fixing frame; 542. Aggregating net; 543. Angle limiting component; 5431. Top baffle; 5432. Bottom baffle; 544. Support plate. Detailed Implementation

[0034] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0035] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0036] Example 1: Please refer to Figure 1-2 This invention provides a technical solution: a pretreatment method and apparatus for power plant desulfurization wastewater, comprising the following steps:

[0037] S1. Wastewater homogenization and conditioning: Collect desulfurization wastewater from the power plant and send it to the conditioning tank for aeration and stirring treatment to balance the wastewater quality and quantity, inhibit the deposition of gypsum particles, and complete the pre-treatment homogenization and buffering of wastewater.

[0038] S2. Neutralization and Heavy Metal Removal: The homogenized wastewater is sent into the treatment device, and lime slurry is added to adjust the pH of the wastewater to 9.0-9.3. Fluoride ions, some calcium and magnesium hardness, and conventional heavy metal ions in the wastewater are removed by precipitation. Then, organic sulfur agents are added to deeply chelate and precipitate the residual mercury, cadmium, and other difficult-to-remove heavy metals in the wastewater.

[0039] S3. Coagulation and flocculation sedimentation: Inorganic coagulant is added to the wastewater after the reaction for destabilization and coagulation, and then anionic polyacrylamide is added for flocculation and agglomeration, so that the fine impurities and sediments in the water form large flocs; then it is sent to the clarification tank to complete solid-liquid separation, the settled sludge is discharged into the sludge treatment system, and the supernatant overflow is collected.

[0040] S4. Water quality readjustment and fine filtration: Add dilute hydrochloric acid to the supernatant of the clarifier to adjust the pH to 7.0-8.0 to complete the water quality neutralization and readjustment; finally, remove residual fine suspended solids through multi-media filtration to obtain compliant pretreated water.

[0041] In step S2, the lime slurry is a calcium hydroxide solution with a mass fraction of 5%-20%, the pH of the wastewater is kept stable at 9.0-9.3, and the reaction residence time is 20-30 minutes; the organic sulfur agent is TMT-15, with a mass fraction of 2% after dilution, and the dosage is 20-50 mL / m³ of wastewater, and the heavy metal chelation reaction residence time is 15-20 minutes.

[0042] In step S3, the inorganic coagulant is polyferric sulfate, with a dosage of 50-100 mg / L, and the mixture is rapidly stirred and coagulated for 10-15 minutes; the anionic polyacrylamide is prepared as a 0.1% dilute solution, with a dosage of 2-5 mg / L, and the mixture is slowly flocculated for 10-15 minutes; the bottom sludge separated from the clarifier is sent to the sludge tank, and after dewatering by a plate and frame filter press, the sludge cake is transported off-site for disposal, and the filtrate is returned to the wastewater collection end for recycling treatment.

[0043] First, collect the desulfurization wastewater from the power plant and send it to the equalization tank for aeration and stirring to balance the wastewater quality and quantity, while inhibiting the deposition of gypsum particles. This completes the pre-treatment homogenization and buffering of the wastewater before it is sent into the treatment device.

[0044] Lime slurry with a mass fraction of 5%-20% calcium hydroxide solution is added to the treatment device to adjust the pH of the wastewater to 9.0-9.3, which precipitates and removes fluoride ions, some calcium and magnesium hardness, and conventional heavy metal ions from the wastewater; then TMT-15 organic sulfur reagent is added, in which the mass fraction of TMT-15 after dilution is 2%, and the dosage is 20-50 mL / m³ of wastewater. The heavy metal chelation reaction is held for 15-20 minutes to deeply chelate and precipitate residual mercury, cadmium, and other difficult-to-remove heavy metals in the wastewater.

[0045] Add 50-100 mg / L of polyferric sulfate (an inorganic coagulant) to the reacted wastewater for destabilization and coagulation. Stir and coagulate rapidly for 10-15 minutes. Then add 2-5 mg / L of 0.1% dilute anionic polyacrylamide solution for flocculation and agglomeration. Flocculate slowly for 10-15 minutes to form large flocs from fine impurities and precipitates in the water. The wastewater is then sent to a clarification tank for solid-liquid separation. The settled sludge is discharged into the sludge treatment system, and the supernatant overflows and is collected.

[0046] Finally, dilute hydrochloric acid was added to the supernatant in the clarifier to adjust the pH to 7.0-8.0, completing the water quality neutralization and readjustment; finally, residual fine suspended solids were removed by multi-media filtration to obtain compliant pretreated water.

[0047] Example 2: Please refer to Figure 1-8 Based on Embodiment 1, the present invention provides a technical solution:

[0048] A pretreatment device for desulfurization wastewater from a power plant includes a reaction tank 1, with an inlet 2 fixedly connected to the top of the reaction tank 1 and a drain outlet 3 fixedly connected to the outer wall of the reaction tank 1. A feeding mechanism 4 is installed inside the reaction tank 1, and a pushing mechanism 5 is fixedly connected to the outer wall of the feeding mechanism 4. The feeding mechanism 4 includes a drive motor 41, which is fixedly connected to the bottom of the reaction tank 1. A threaded rod 44 is fixedly connected to the top output shaft of the drive motor 41. A movable box 45 is movably connected to the outer wall of the threaded rod 44. A telescopic hose 42 is fixedly connected to the top of the movable box 45, and a feeding inlet 43 is fixedly connected to the top of the telescopic hose 42. The feeding inlet 43 is fixedly connected to the top of the reaction tank 1. The bottom of the drain outlet 3 is connected to a corresponding valve, allowing the wastewater inside the reaction tank 1 to be sent into a clarification tank by opening the valve. The material inside the reaction tank 1 that needs to contact the wastewater is selected as an acid and alkali resistant polymer material.

[0049] Wastewater can be added into the reaction tank 1 through inlet 2. Additives to be added into the reaction tank 1 are added into the feeding inlet 43. During the reaction stage, the drive motor 41 drives the threaded rod 44 to rotate, causing the moving box 45 to be driven by the threads on the surface of the feeding inlet 43. The moving box 45 is restricted from rotating by the pushing mechanism 5, allowing it to move up and down along the outer wall of the feeding inlet 43. When the moving box 45 moves upward, the telescopic hose 42 contracts and shortens. Simultaneously, the second limiting component 47 prevents the gas and liquid inside the telescopic hose 42 from escaping upward. Because the moving box 45 moves, the holes inside the telescopic hose 42 will pass through the first limiting component on the outer wall of the moving box 45. After component 46 is discharged, the moving box 45 moves to the top and the drive motor 41 rotates in the opposite direction, causing the moving box 45 to be driven in the opposite direction by the threaded rod 44, making the moving box 45 move downward. The first limiting component 46 can prevent gaseous and liquid substances from being sucked into the moving box 45 through the first limiting component 46. During this process, a negative pressure is generated inside the moving box 45 and the telescopic hose 42. The additives inside the feeding inlet 43 are sucked into the moving box 45 through the second limiting component 47. Then, during the upward movement of the moving box 45, the additives inside the moving box 45 are gradually put into the reaction chamber 1, expanding the contact area between the additives and the wastewater inside the reaction chamber 1, and improving the reaction efficiency.

[0050] The outer wall of the movable box 45 is fixedly connected to a first limiting component 46. The inside of the threaded rod 44 is provided with a second limiting component 47 located at the bottom of the feeding inlet 43. The outer wall of the movable box 45 is fixedly connected to an extension plate 49 located outside the first limiting component 46. The bottom of the extension plate 49 is movably connected to a blade 48.

[0051] When the moving box 45 moves up and down inside the reaction chamber 1, it will drive the blade 48 to move inside the reaction chamber 1 through the extension plate 49. During this process, the wastewater liquid inside the reaction chamber 1 will flow relative to the blade 48, which will push the blade 48 to rotate. The rotation of the blade 48 will agitate the wastewater. The additives discharged through the first limiting component 46 will be agitated at the blade 48, further promoting the reaction speed between the additives and the wastewater.

[0052] The first limiting component 46 includes a discharge pipe 462, which is fixedly connected to the outer wall of the movable box 45. A discharge plate 461 is provided on the outer side of the discharge pipe 462. A first limiting ring 463 is fixedly connected to the side of the discharge plate 461 near the movable box 45. The first limiting ring 463 is movably connected inside the movable box 45.

[0053] When the internal pressure of the movable box 45 is too high, it will push the discharge plate 461 outward, and under the restriction of the first limiting ring 463, a gap will be formed between the discharge plate 461 and the discharge pipe 462, so as to squeeze the material inside the movable box 45 into the reaction chamber 1. When a negative pressure is formed inside the movable box 45, the liquid pressure inside the reaction chamber 1 will push the discharge plate 461 to seal the outer end of the discharge pipe 462, thereby preventing wastewater inside the reaction chamber 1 from entering the movable box 45 through the outer end of the discharge pipe 462.

[0054] The second limiting component 47 includes an inlet ring 472, which is fixedly connected to the inner wall of the telescopic hose 42. An inlet piece 471 is provided at the bottom of the inlet ring 472, and a second limiting ring 473 is fixedly connected to the top of the inlet piece 471. The second limiting ring 473 is movably connected inside the telescopic hose 42.

[0055] When the internal pressure of the movable box 45 is too high, the air pressure inside the movable box 45 will push the discharge plate 471 upward, and make the discharge plate 471 fit with the discharge ring 472, thereby blocking the cross section of the telescopic hose 42 and preventing the gas and liquid from pushing out the additive inside the feeding inlet 43.

[0056] When a negative pressure is formed inside the movable box 45, the external air pressure will push the discharge plate 471 downward. Under the restriction of the second limiting ring 473, the discharge plate 471 and the discharge ring 472 maintain a gap, so that the additive inside the feeding inlet 43 enters the movable box 45 through the telescopic hose 42.

[0057] Example 3: Please refer to Figure 1-9 Based on Embodiment 1 and Embodiment 2, the present invention provides a technical solution:

[0058] The pushing mechanism 5 includes an extension rod 51, which is fixedly connected to the outer wall of the movable box 45. A guide protrusion 52 is fixedly connected to the inner wall of the reaction chamber 1, and the guide protrusion 52 is movably connected to the extension rod 51. A pushing assembly 54 is movably connected to the outer wall of the extension rod 51. A stirring rod 53 is fixedly connected to the outer wall of the telescopic hose 42 at the bottom of the pushing assembly 54.

[0059] The extension rod 51 and the guide protrusion 52 work together to hold the movable box 45 in place, preventing the movable box 45 from being rotated.

[0060] When the drive motor 41 drives the threaded rod 44 to rotate, the threaded rod 44 can drive the stirring rod 53 on its outer wall to rotate, thereby pushing the wastewater inside the reaction tank 1 to rotate and flow. At the same time, the drive motor 41 will rotate in the opposite direction intermittently, which further enables the stirring rod 53 to repeatedly stir the wastewater inside the reaction tank 1, thereby improving the mixing effect of wastewater and added substances.

[0061] In addition, as the moving box 45 moves upward, it simultaneously drives the pushing component 54 to move upward. When the moving box 45 moves downward, the pushing component 54 pushes the flocculated and precipitated substances downward through the mesh structure. Before the addition of the organic sulfur reagent TMT-15, the hydroxide and calcium fluoride particles converge downward and are enriched at the bottom, which can promote the reaction of the organic sulfur reagent TMT-15 with dissolved heavy metal ions, improve the reagent utilization rate, and further improve the wastewater treatment efficiency.

[0062] The pushing component 54 includes a fixed frame 541, which is movably connected to the outer wall of the extension rod 51. A gathering net 542 is fixedly connected inside the fixed frame 541. A limiting angle component 543 is set on the outer wall of the extension rod 51 at the corresponding position of the fixed frame 541. A support plate 544 is set on the inner wall of the extension rod 51 at the bottom of the fixed frame 541. When the fixed frame 541 moves to the bottom with the moving box 45, the support plate 544 will support the outermost edge of the fixed frame 541 to avoid interference caused by the rotation of the stirring rod 53 at the bottom of the fixed frame 541.

[0063] When the moving box 45 and the extension rod 51 move upward, the gathering net 542 will be affected by the flow resistance, causing the fixed frame 541 to deflect downward. Under the restriction of the angle limiting component 543, the fixed frame 541 will be close to the vertical state, so that the flocculated and precipitated substances will move downward along the formed slope on the surface of the gathering net 542. Then the moving box 45 moves downward, the gathering net 542 will be affected by the flow resistance, and under the restriction of the angle limiting component 543, it will change to a horizontal state. The gathering net 542 will push the flocculated and precipitated substances downward, and make them converge and accumulate at the bottom.

[0064] In addition, as a large-area mesh structure, the additives discharged through the discharge pipe 462 will spread to the surroundings through the stirring of the blades 48. During the up-and-down movement of the aggregated net 542, the additives diffused into the wastewater will be stirred simultaneously, and the up-and-down stirring method can avoid the stratification of the substances, thereby improving the efficiency of the mixing reaction.

[0065] The angle limiting assembly 543 includes a top baffle 5431, which is fixedly connected to the outer wall of the extension rod 51 at the top of the fixed frame 541. A bottom baffle 5432 is fixedly connected to the outer wall of the extension rod 51 at the bottom of the fixed frame 541.

[0066] When the fixed frame 541 deflects downward, the bottom baffle 5432 supports the bottom of the fixed frame 541, so that the fixed frame 541 maintains a certain angle with the vertical direction, which makes it easier for the flow resistance to push the gathering net 542 to a horizontal state. When the fixed frame 541 deflects upward, the top baffle 5431 restricts the deflection angle of the fixed frame 541, so that the gathering net 542 remains in a horizontal state.

[0067] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A pretreatment method for desulfurization wastewater from a power plant, characterized in that: Includes the following steps: S1. Wastewater homogenization and conditioning: Collect desulfurization wastewater from the power plant and send it to the conditioning tank for aeration and stirring treatment to balance the wastewater quality and quantity, inhibit the deposition of gypsum particles, and complete the pre-treatment homogenization and buffering of wastewater. S2. Neutralization and Heavy Metal Removal: The homogenized wastewater is sent into the treatment device, and lime slurry is added to adjust the pH of the wastewater to 9.0-9.

3. Fluoride ions, some calcium and magnesium hardness, and conventional heavy metal ions in the wastewater are removed by precipitation. Then, organic sulfur agents are added to deeply chelate and precipitate the residual mercury, cadmium, and other difficult-to-remove heavy metals in the wastewater. S3. Coagulation and flocculation sedimentation: Inorganic coagulant is added to the wastewater after the reaction for destabilization and coagulation, and then anionic polyacrylamide is added for flocculation and agglomeration, so that the fine impurities and sediments in the water form large flocs. The sludge is then sent to a clarifier to complete solid-liquid separation. The settled sludge is discharged into the sludge treatment system, and the supernatant overflows and is collected. S4. Water quality readjustment and fine filtration: Add dilute hydrochloric acid to the supernatant of the clarifier to adjust the pH to 7.0-8.0 to complete the water quality neutralization and readjustment; finally, remove residual fine suspended solids through multi-media filtration to obtain compliant pretreated water.

2. The pretreatment method for power plant desulfurization wastewater according to claim 1, characterized in that: In step S2, the lime slurry is made of calcium hydroxide solution, the pH of the wastewater is kept stable at 9.0-9.3, and the reaction is allowed to proceed for a period of time; the organic sulfur reagent is TMT-15, and the heavy metal chelation reaction is allowed to proceed for a period of time.

3. The pretreatment method for power plant desulfurization wastewater according to claim 1, characterized in that: In step S3, the inorganic coagulant is polyferric sulfate, and the mixture is rapidly stirred and allowed to stand for a period of time to coagulate. After the anionic polyacrylamide is added, it undergoes slow flocculation and remains for a period of time (minutes). The bottom sludge separated in the clarifier is sent to the sludge tank, and after being dewatered by a plate and frame filter press, the sludge cake is transported off-site for disposal, while the filter filtrate is returned to the wastewater collection end for recycling.

4. A pretreatment device for power plant desulfurization wastewater, used in the pretreatment method for power plant desulfurization wastewater according to claim 1, comprising a reaction tank (1), characterized in that: The reaction chamber (1) is fixedly connected to a water inlet (2) at the top and a drain outlet (3) at the outer wall of the reaction chamber (1). The reaction chamber (1) is equipped with a feeding mechanism (4) inside. The feeding mechanism (4) is fixedly connected to a pushing mechanism (5) at the outer wall of the feeding mechanism (4). The feeding mechanism (4) includes a drive motor (41). The drive motor (41) is fixedly connected to the bottom of the reaction chamber (1). The output shaft at the top of the drive motor (41) is fixedly connected to a threaded rod (44). The outer wall of the threaded rod (44) is movably connected to a movable box (45). The top of the movable box (45) is fixedly connected to a telescopic hose (42). The top of the telescopic hose (42) is fixedly connected to a feeding inlet (43), and the feeding inlet (43) is fixedly connected to the top of the reaction chamber (1).

5. The pretreatment device for power plant desulfurization wastewater according to claim 4, characterized in that: The outer wall of the movable box (45) is fixedly connected to a first limiting component (46), and the inside of the threaded rod (44) is provided with a second limiting component (47) at the bottom of the feeding inlet (43). The outer wall of the movable box (45) is fixedly connected to an extension plate (49) outside the first limiting component (46), and the bottom of the extension plate (49) is movably connected to a blade (48).

6. The pretreatment device for power plant desulfurization wastewater according to claim 5, characterized in that: The first limiting component (46) includes a discharge pipe (462), which is fixedly connected to the outer wall of the movable box (45). A discharge plate (461) is provided on the outer side of the discharge pipe (462). A first limiting ring (463) is fixedly connected to the side of the discharge plate (461) near the movable box (45). The first limiting ring (463) is movably connected inside the movable box (45).

7. The pretreatment device for power plant desulfurization wastewater according to claim 5, characterized in that: The second limiting component (47) includes an inlet ring (472) which is fixedly connected to the inner wall of the telescopic hose (42). An inlet plate (471) is provided at the bottom of the inlet ring (472), and a second limiting ring (473) is fixedly connected to the top of the inlet plate (471). The second limiting ring (473) is movably connected inside the telescopic hose (42).

8. A pretreatment device for power plant desulfurization wastewater according to claim 4, characterized in that: The pushing mechanism (5) includes an extension rod (51), which is fixedly connected to the outer wall of the movable box (45). A guide protrusion (52) is fixedly connected to the inner wall of the reaction chamber (1), and the guide protrusion (52) is movably connected to the extension rod (51). A pushing assembly (54) is movably connected to the outer wall of the extension rod (51). A stirring rod (53) is fixedly connected to the outer wall of the telescopic hose (42) at the bottom of the pushing assembly (54).

9. A pretreatment device for power plant desulfurization wastewater according to claim 8, characterized in that: The pushing component (54) includes a fixed frame (541), which is movably connected to the outer wall of the extension rod (51). A gathering net (542) is fixedly connected inside the fixed frame (541). A limiting angle component (543) is provided on the outer wall of the extension rod (51) at the corresponding position of the fixed frame (541). A support plate (544) is provided on the inner wall of the extension rod (51) at the bottom of the fixed frame (541).

10. A pretreatment device for power plant desulfurization wastewater according to claim 9, characterized in that: The angle limiting assembly (543) includes a top baffle (5431), which is fixedly connected to the outer wall of the extension rod (51) at the top of the fixed frame (541), and a bottom baffle (5432) is fixedly connected to the outer wall of the extension rod (51) at the bottom of the fixed frame (541).

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