Desulfurization wastewater treatment method and system

Abstract

The application provides a desulfurization wastewater treatment method and system, and belongs to the field of wastewater treatment. The desulfurization wastewater treatment method comprises the following steps: adjusting the pH value of desulfurization wastewater to 7.0-7.5; adding a modified inorganic-organic coagulant to the desulfurization wastewater with the pH value of 7.0-7.5 for treatment, and then performing filtration treatment to obtain product water; and performing adsorption treatment on the product water by using modified filter material to obtain drainage. The modified inorganic-organic coagulant can effectively reduce or eliminate the ξ potential of colloids in the wastewater, and the colloids are coagulated through electric neutralization, adsorption bridging and roll-sweeping, and then thallium and total chromium are removed through sedimentation separation. The modified filter material can adsorb thallium and total chromium in the desulfurization wastewater by being filled in a filter tower, and can further remove thallium and total chromium in the desulfurization wastewater, so that the content of thallium and total chromium in the drainage after the desulfurization wastewater treatment reaches the discharge standard.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a method and system for treating desulfurization wastewater. Background Technology

[0002] Flue gas desulfurization (FGD) is the most effective and widely used technology for controlling SO2 emissions in coal-fired power plants. Its basic principle is that SO2 in flue gas is essentially acidic and can be removed by reacting with appropriate alkaline substances. The most commonly used alkaline substances include limestone (calcium carbonate, CaCO3), quicklime (calcium oxide, CaO), and hydrated lime (calcium hydroxide, Ca(OH)2). To maintain the desulfurization performance of the system and achieve ultra-clean SO2 emissions from the flue gas, the desulfurization slurry must be continuously replenished and renewed, while wastewater containing large amounts of heavy metal ions and chloride ions must be treated before discharge. With the implementation of a series of policies and regulations on water pollution control, achieving standard wastewater discharge has become one of the important tasks for coal-fired power plants.

[0003] The composition of desulfurization wastewater is greatly affected by factors such as the type of coal used in coal-fired power plants, the purity of limestone, the desulfurization oxidation air volume, the chloride ion control concentration and concentration ratio of the absorption tower. Therefore, the composition of desulfurization wastewater from the same equipment can vary significantly at different effluent times.

[0004] Desulfurization wastewater can generally meet the requirements for saline water reuse by undergoing a three-stage process of neutralization-sedimentation-coagulation. This three-stage pretreatment process achieves a heavy metal removal rate of over 95% and a suspended solids removal rate of up to 90% in desulfurization wastewater.

[0005] The triple-tank process is not very effective in removing thallium and total chromium. The wastewater discharged after desulfurization treatment still contains excessive amounts of thallium and total chromium. Direct discharge of this wastewater causes environmental pollution.

[0006] It should be noted that the information disclosed in the background section of this invention is intended only to enhance the understanding of the general background of this invention, and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a method and system for treating desulfurization wastewater, so as to solve the technical problem that the effluent after desulfurization wastewater treatment still contains excessive amounts of thallium and total chromium.

[0008] To solve the above-mentioned technical problems, the present invention provides a method for treating desulfurization wastewater, comprising:

[0009] Adjust the pH of the desulfurization wastewater to 7.0–7.5;

[0010] After adding a modified inorganic-organic coagulant to desulfurization wastewater with a pH of 7.0-7.5 for treatment, and then filtering it, product water is obtained.

[0011] The produced water is then subjected to adsorption treatment with modified filter media to obtain wastewater.

[0012] Preferably, adjusting the pH of the desulfurization wastewater to between 7.0 and 7.5 includes:

[0013] Lime is added to the desulfurization wastewater to adjust its pH to 7.0–7.5.

[0014] Preferably, adding lime to the desulfurization wastewater to adjust its pH to 7.0–7.5 includes:

[0015] The desulfurization wastewater is transported to the first mixing zone, and lime is added to the first mixing zone to adjust the pH of the desulfurization wastewater to 7.0-7.5. The first mixing zone is equipped with a first mixer, and the mixing speed of the first mixer is 45-65 rpm. The residence time of the desulfurization wastewater in the first mixing zone is 1.5-3.5 min, and the mass concentration of the lime is 16-25%.

[0016] Preferably, the modified inorganic-organic coagulant is prepared by:

[0017] Prepare iron ion solutions with a mass concentration of 7–12% and sulfide ion solutions with a mass concentration of 9–15%, respectively.

[0018] A mixed solution is formed by mixing iron ion solution and sulfur ion solution in a volume ratio of 1:2 to 3.

[0019] Add 0.01–0.05 g of polyethyleneimine to the mixed solution, react at 35–39 °C for a certain time, and then cool to obtain the modified inorganic-organic coagulant.

[0020] Preferably, the iron ion solution is a ferric sulfate solution, and the sulfide ion solution is a sodium sulfide solution.

[0021] Preferably, after adding a modified inorganic-organic coagulant to the desulfurization wastewater with a pH of 7.0-7.5 for treatment, and then filtering it, the resulting product water includes:

[0022] Desulfurization wastewater with a pH of 7.0–7.5 is transported to the second mixing zone, and a modified inorganic-organic coagulant is added to the second mixing zone to obtain flocculation and sedimentation.

[0023] The flocculated sediment is transported to an inclined plate sedimentation zone for filtration to obtain product water.

[0024] Preferably, the dosage of the modified inorganic-organic coagulant is 325-653 mg / L, the second mixing zone is equipped with a second mixer, the mixing speed of the second mixer is 65-75 rpm, and the residence time of the desulfurization wastewater in the second mixing zone is 3-7 min.

[0025] Preferably, the modified filter material is prepared by:

[0026] Coal-based activated carbon, manganese sand filler, and vermiculite filler are mixed in a solid-solid ratio of 5 to 9:7:1 to obtain a mixture, wherein the particle size of the coal-based activated carbon is 50 to 100 mesh, the particle size of the manganese sand filler is 50 to 100 mesh, and the particle size of the vermiculite filler is 50 to 100 mesh.

[0027] The mixture is irradiated with microwave power of 500-600W for 45-60 minutes to form the modified filter material.

[0028] Preferably, the wastewater is subjected to adsorption treatment with modified filter media to obtain wastewater, which includes:

[0029] The produced water is transported to a filter tower for adsorption treatment. The filter tower is filled with modified filter media, which accounts for 85-95% of the total volume of the filter tower. The produced water stays in the filter tower for 36-42 minutes.

[0030] Based on the same inventive concept, the present invention also provides a desulfurization wastewater treatment system, comprising:

[0031] The first mixing zone is used to adjust the pH of the desulfurization wastewater to 7.0–7.5;

[0032] The second mixing zone is used to add modified inorganic-organic coagulants to desulfurization wastewater with a pH of 7.0 to 7.5 for treatment, followed by filtration to obtain product water;

[0033] A filter tower, filled with modified filter media, is used to adsorb the produced water through the modified filter media to obtain wastewater.

[0034] Compared with the prior art, the desulfurization wastewater treatment method of the present invention has the following advantages:

[0035] This invention adjusts the pH of desulfurization wastewater to 7.0–7.5. After adding a modified inorganic-organic coagulant to the desulfurization wastewater at a pH of 7.0–7.5, it undergoes filtration to obtain permeable water. This permeable water is then subjected to adsorption treatment with modified filter media to obtain wastewater. Thus, the desulfurization wastewater treatment method provided by this invention effectively reduces or eliminates the zeta potential of colloids in the wastewater by adding a modified inorganic-organic coagulant. This coagulant causes colloid coagulation through charge neutralization, adsorption bridging, and sweeping, followed by precipitation separation to remove thallium and total chromium. By setting up a filter tower and filling it with modified filter media, the modified filter media can adsorb thallium and total chromium from the desulfurization wastewater, further removing them. This ensures that the thallium and total chromium content in the treated wastewater meets discharge standards, preventing direct discharge and environmental pollution. It can simultaneously remove thallium and total chromium, with stable and efficient treatment results, low production and operating costs, and simple operation, making it an environmentally friendly and green treatment method.

[0036] The desulfurization wastewater treatment system and the desulfurization wastewater treatment method provided by this invention belong to the same inventive concept. Therefore, the desulfurization wastewater treatment system provided by this invention has at least all the advantages of the desulfurization wastewater treatment method provided by this invention, and can ensure that the content of thallium and total chromium in the effluent after desulfurization wastewater treatment meets the discharge standards, thus avoiding direct discharge of effluent and causing pollution to the environment. Attached Figure Description

[0037] Figure 1 This is a flowchart of a desulfurization wastewater treatment method provided in one embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the overall structure of the desulfurization wastewater treatment system provided in one embodiment of the present invention;

[0039] In the picture,

[0040] 1- Primary booster pump; 2- Processing unit;

[0041] 21-First mixing zone; 22-Second mixing zone;

[0042] 23- Inclined plate sedimentation zone; 3- Lime dosing system;

[0043] 4- Coagulant dosing system; 5- Modified inorganic-organic coagulant;

[0044] 6-Secondary booster pump; 7-Filter tower;

[0045] 8-Modified filter media; 9-Drain pump. Detailed Implementation

[0046] To make the objectives, advantages, and features of the present invention clearer, the desulfurization wastewater treatment method and system proposed by the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention. It should be understood that the accompanying drawings do not necessarily show the specific structure of the present invention to scale, and the illustrative features used to illustrate certain principles of the present invention in the accompanying drawings are also drawn in a slightly simplified manner. Specific design features of the present invention disclosed herein, including, for example, specific dimensions, orientations, positions, and shapes, will be determined in part by the specific environment in which they are applied and used. Furthermore, in the embodiments described below, the same reference numerals are sometimes used across different drawings to denote the same parts or parts having the same function, and their repeated descriptions are omitted. In this specification, similar reference numerals and letters are used to denote similar items; therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0048] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0049] The core idea of ​​this invention is to provide a desulfurization wastewater treatment method that can effectively remove thallium and total chromium from the desulfurization wastewater, so that the content of thallium and total chromium in the effluent after desulfurization wastewater treatment meets the discharge standards, thus avoiding direct discharge of effluent and causing pollution to the environment.

[0050] To achieve the above-mentioned goals, this invention provides a method for treating desulfurization wastewater, referring to... Figures 1 to 2A specific embodiment of a desulfurization wastewater treatment method is disclosed. The desulfurization wastewater treatment method includes the following steps S1 to S3.

[0051] Step S1: Adjust the pH of the desulfurization wastewater to 7.0-7.5.

[0052] Specifically, refer to Figure 1 and Figure 2 As shown, the desulfurization wastewater has a pH of 3.9–5.1, thallium concentration of 2350–4590 μg / L, and total chromium concentration of 3.6–19.2 mg / L. Desulfurization wastewater discharged from the power plant or other plant areas is transported to the first mixing zone 21 in the treatment unit 2 via a primary booster pump 1. The first mixing zone 21 is equipped with a first mixer for mixing the materials. Next, lime is transported to the first mixing zone 21 via a lime dosing system 3. The lime and desulfurization wastewater are thoroughly mixed by the first mixer, and the pH of the desulfurization wastewater is adjusted to within the range of 7.0–7.5 using lime.

[0053] The residence time of the desulfurization wastewater in the first mixing zone 21 is 1.5–3.5 minutes, and the mixing speed of the first mixer is 45–65 rpm. The lime dosing system 3 includes a reagent tank, a dosing pump, and an automatic control system. The reagent tank of the lime dosing system 3 contains lime with a mass concentration of 16–25%, which is added to the first mixing zone 21 via the dosing pump. A pH meter is located at the outlet of the first mixing zone 21. The automatic control system of the lime dosing system controls the amount of lime added via the pH meter, maintaining the pH of the desulfurization wastewater at the outlet of the first mixing zone 21 between 7.0 and 7.5. It should be noted that since the reagent tank, dosing pump, and automatic control system in the lime dosing system 3 are existing technologies, their structure and working principle are well-known to those skilled in the art and will not be described in detail here.

[0054] Step S2: After adding a modified inorganic-organic coagulant to the desulfurization wastewater with a pH of 7.0-7.5 for treatment, the wastewater is then filtered to obtain the permeable water.

[0055] Specifically, refer to Figure 1 and Figure 2As shown, desulfurization wastewater with a pH of 7.0–7.5 is transported to the second mixing zone 22 in treatment device 2. Modified inorganic-organic coagulant 5 is added to the second mixing zone 22 to achieve flocculation and sedimentation. After the pH of the desulfurization wastewater is adjusted to between 7.0 and 7.5 in the first mixing zone 21, it is transported to the second mixing zone 22 via overflow. The second mixing zone 22 is equipped with a second mixer for mixing the materials. The coagulant dosing system 4 is also equipped with a reagent tank, a dosing pump, and an automatic control system. The reagent tank of the coagulant dosing system 4 contains modified inorganic-organic coagulant 5. The modified inorganic-organic coagulant 5 is added to the second mixing zone 22 via the dosing pump of the coagulant dosing system 4 to achieve flocculation and sedimentation. The dosage of modified inorganic-organic coagulant 5 is 325–653 mg / L. The residence time of the desulfurization wastewater in the second mixing zone 22 is 3-7 minutes, and the mixing speed of the second mixer is 65-75 rpm. It should be noted that since the reagent tank, dosing pump and automatic control system in the coagulant dosing system 4 are existing technologies, their structure and working principle are already well known to those skilled in the art, and will not be described in detail here.

[0056] This embodiment describes the development and preparation of a modified inorganic-organic coagulant tailored to the characteristics of desulfurization wastewater. The preparation method of the modified inorganic-organic coagulant is as follows:

[0057] First, prepare iron ion solutions with a mass concentration of 7-12% and sulfide ion solutions with a mass concentration of 9-15% respectively;

[0058] Next, iron ion solution and sulfur ion solution with a volume ratio of 1:2 to 3 are mixed to form a mixed solution;

[0059] Finally, 0.01–0.05 g of polyethyleneimine was added to the mixed solution, and the mixture was reacted at a constant temperature of 35–39°C for 3–4.5 h. After cooling, the modified inorganic-organic coagulant 5 was obtained.

[0060] It should be noted that the iron ion solution can be a ferric sulfate solution, ferric chloride solution, or other solutions containing iron ions. The sulfide ion solution can be a sodium sulfide solution, potassium sulfide solution, or other sulfide ion solutions. However, to avoid introducing other impurities into the wastewater, in this embodiment, the iron ion solution is preferably a ferric sulfate solution, and the sulfide ion solution is preferably a sodium sulfide solution.

[0061] The prepared modified inorganic-organic coagulant 5 can effectively reduce or eliminate the zeta potential of colloids in water, and cause colloid coagulation through charge neutralization, adsorption bridging and sweeping effects, resulting in flocculation and sedimentation. This modified inorganic-organic coagulant 5 can simultaneously remove thallium and total chromium.

[0062] Next, the flocculated sediment is conveyed to the inclined plate sedimentation zone 23 in the treatment device 2 for filtration to obtain permeable water. The flocculated sediment flows from the outlet of the second stirring zone 22 into the inclined plate sedimentation zone 23 for filtration, obtaining permeable water and sediment. The residence time of the wastewater in the inclined plate sedimentation zone 23 is 38–53 minutes, and the length of the inclined plate (i.e., Figure 2 The length of 'a' is 1-1.2m, and the spacing between the inclined plates is (i.e., Figure 2 The length (b) is between 0.8 and 1 cm, and the inclined plate forms a 57-degree angle with the horizontal plane (i.e., Figure 2 (At the mid-β angle), the water depth in the upper layer of the inclined plate is 0.4-0.7m, and the bottom buffer zone height is 0.8-0.9m. Gravity sludge removal is adopted, 1-2 times per day.

[0063] Flocculation and sedimentation filtration can initially remove thallium and total chromium from wastewater. Testing of the permeate at the outlet of inclined plate sedimentation zone 23 showed that after two stages of stirred-inclined plate coagulation sedimentation, the power plant desulfurization wastewater had a pH of 7.1–7.5, thallium levels of 57–73 μg / L, and total chromium levels of 0.1–0.2 mg / L. These data indicate a significant reduction in the content of thallium and total chromium in the wastewater.

[0064] Step S3: The produced water is subjected to adsorption treatment by modified filter media to obtain wastewater.

[0065] Specifically, refer to Figure 1 and Figure 2 As shown, the permeate enters the filter tower 7 via a secondary booster pump 6. The filter tower 7 is filled with modified filter media 8 to transport the permeate to the filter tower 7 for adsorption treatment. The modified filter media 8 occupies 85-95% of the total volume of the filter tower 7, and the residence time of the permeate in the filter tower 7 is 36-42 minutes.

[0066] The modified filter media 8 in this embodiment is prepared according to the characteristics of power plant desulfurization wastewater. The specific preparation process is as follows:

[0067] First, select coal-based activated carbon with a particle size of 50-100 mesh, manganese sand filler with a particle size of 50-100 mesh, and vermiculite filler with a particle size of 50-100 mesh.

[0068] Next, coal-based activated carbon, manganese sand filler, and vermiculite filler are mixed in a solid-solid ratio of 5–9:7:1 to obtain a mixture. To improve the uniformity of the mixture, it is stirred for 15–20 minutes at a stirring speed of 40–50 rpm.

[0069] Finally, the mixed solids are irradiated with microwave power of 500-600W for 45-60 minutes to form modified filter media 8. Modified filter media 8 has a surface area of ​​462-670 m² / L and can adsorb thallium and total chromium in power plant desulfurization wastewater.

[0070] After passing through filter tower 7, the thallium and total chromium in the product water meet the standards, with a pH of 7.0–7.7, thallium concentration of 34–47 μg / L, and total chromium concentration of 0.05–0.07 mg / L. Subsequently, the wastewater is discharged through drainage pump 9.

[0071] The desulfurization wastewater treatment method provided in this embodiment involves adding a modified inorganic-organic coagulant 5 to the wastewater. This modified inorganic-organic coagulant 5 effectively reduces or eliminates the zeta potential of colloids in the wastewater, causing colloid coagulation through charge neutralization, adsorption bridging, and sweeping. Thallium and total chromium are then removed through precipitation separation. A filter tower 7 is installed and filled with modified filter media 8. The modified filter media 8 adsorbs thallium and total chromium from the desulfurization wastewater, further removing them. This ensures that the thallium and total chromium content in the treated wastewater meets discharge standards, preventing direct discharge and environmental pollution. Furthermore, it simultaneously removes thallium and total chromium, offering stable and efficient treatment results with low operating costs and simple operation, making it an environmentally friendly and green treatment method.

[0072] To achieve the above-mentioned goals, this embodiment also discloses a desulfurization wastewater treatment system, including a first stirring zone 21 for adjusting the pH of the desulfurization wastewater to 7.0–7.5. A second stirring zone 22 is used to add a modified inorganic-organic coagulant to the desulfurization wastewater with a pH of 7.0–7.5 for treatment, followed by filtration to obtain permeable water. A filter tower 7, filled with modified filter media 8, is used to adsorb the permeable water through the modified filter media 8 to obtain effluent.

[0073] Desulfurization wastewater discharged from power plants or other plant areas is transported to the first mixing zone 21 in the treatment unit 2 via a primary booster pump 1. The first mixing zone 21 is equipped with a first mixer for mixing the materials. Next, lime is transported to the first mixing zone 21 via a lime dosing system 3. The lime and desulfurization wastewater are thoroughly mixed by the first mixer, and the pH of the desulfurization wastewater is adjusted to within the range of 7.0–7.5 using lime. The desulfurization wastewater with a pH of 7.0–7.5 is then transported to the second mixing zone 22 in the treatment unit 2, where a modified inorganic-organic coagulant 5 is added to achieve flocculation and sedimentation. After the pH of the desulfurization wastewater is adjusted to between 7.0 and 7.5 in the first mixing zone 21, it is overflowed into the second mixing zone 22. The second mixing zone 22 is equipped with a second mixer for mixing the materials. The coagulant dosing system 4 is also equipped with a reagent tank, a dosing pump, and an automatic control system. The reagent tank of the coagulant dosing system 4 contains modified inorganic-organic coagulant 5. The modified inorganic-organic coagulant 5 is added to the second mixing zone 22 via the dosing pump of the coagulant dosing system 4, resulting in flocculation and sedimentation. Next, the flocculated sediment is transported to the inclined plate sedimentation zone 23 in the treatment device 2 for filtration treatment, yielding permeable water. The flocculated sediment overflows from the outlet of the second mixing zone 22 into the inclined plate sedimentation zone 23 for filtration treatment, yielding permeable water and sediment. The permeable water enters the filter tower 7 via a secondary booster pump 6. The filter tower 7 is filled with modified filter media 8 to transport the permeable water for adsorption treatment. After passing through the filter tower 7, the thallium and total chromium in the permeable water meet the standards, with a pH of 7.0–7.7, thallium levels of 34–47 μg / L, and total chromium levels of 0.05–0.07 mg / L. Subsequently, the wastewater is discharged via a drainage pump 9.

[0074] Furthermore, in the desulfurization wastewater treatment system provided in this embodiment, a modified inorganic-organic coagulant was developed and prepared. The preparation method of the modified inorganic-organic coagulant is as follows:

[0075] First, prepare iron ion solutions with a mass concentration of 7-12% and sulfide ion solutions with a mass concentration of 9-15% respectively;

[0076] Next, iron ion solution and sulfur ion solution with a volume ratio of 1:2 to 3 are mixed to form a mixed solution;

[0077] Finally, 0.01–0.05 g of polyethyleneimine was added to the mixed solution, and the mixture was reacted at a constant temperature of 35–39°C for 3–4.5 h. After cooling, the modified inorganic-organic coagulant 5 was obtained.

[0078] Furthermore, in the desulfurization wastewater treatment system provided in this embodiment, modified filter media 8 was developed and prepared. The preparation method of modified filter media 8 is as follows:

[0079] First, select coal-based activated carbon with a particle size of 50-100 mesh, manganese sand filler with a particle size of 50-100 mesh, and vermiculite filler with a particle size of 50-100 mesh.

[0080] Next, coal-based activated carbon, manganese sand filler, and vermiculite filler are mixed in a solid-solid ratio of 5–9:7:1 to obtain a mixture. To improve the uniformity of the mixture, it is stirred for 15–20 minutes at a stirring speed of 40–50 rpm.

[0081] Finally, the mixed solids are irradiated with microwave power of 500-600W for 45-60 minutes to form modified filter media 8. Modified filter media 8 has a surface area of ​​462-670 m² / L and can adsorb thallium and total chromium in power plant desulfurization wastewater.

[0082] The desulfurization wastewater treatment system and the desulfurization wastewater treatment method provided in this embodiment belong to the same inventive concept. Therefore, the desulfurization wastewater treatment system provided in this embodiment has at least all the advantages of the desulfurization wastewater treatment method provided in this embodiment. It can ensure that the content of thallium and total chromium in the effluent after desulfurization wastewater treatment meets the discharge standards, thus avoiding direct discharge of effluent and causing pollution to the environment.

[0083] Example 1

[0084] Take desulfurization wastewater discharged from power plants as an example, which has a pH of 4.3, a thallium concentration of 3680 μg / L, and a total chromium concentration of 11.5 mg / L.

[0085] The desulfurization wastewater is transported to the first mixing zone 21 via a primary booster pump 1. The residence time of the desulfurization wastewater in the first mixing zone 21 is 2.7 minutes, and the mixing speed of the first mixer is 515 rpm. The lime dosing system 3 contains lime with a mass concentration of 21% in its reagent tank, and the lime is added to the first mixing zone 21 via its dosing pump. A pH meter is located at the outlet of the first mixing zone 21. The lime dosing automatic control system controls the lime dosing amount through the pH meter to maintain the pH of the desulfurization wastewater at the outlet of the first mixing zone 21 at 7.3.

[0086] Desulfurization wastewater with a pH of 7.3 flows into the second mixing zone 22 through the outlet of the first mixing zone 21. The residence time in the second mixing zone 22 is 5 minutes, and the mixing speed of the second mixer is 70 rpm. The reagent tank of the coagulant dosing system 4 contains modified inorganic-organic coagulant 5. The modified inorganic-organic coagulant 5 is added to the second mixing zone 22 via the dosing pump of the coagulant dosing system 4, resulting in flocculation and sedimentation. The dosage of modified inorganic-organic coagulant 5 is 503 mg / L.

[0087] Then, the flocculated sediment flows into the inclined plate sedimentation zone 23 through the outlet of the second mixing zone 22. The residence time of the flocculated sediment in the inclined plate sedimentation zone 23 is 42 minutes. The length of the inclined plate is 1.1m, the spacing between the inclined plates should be 0.9cm, the inclined plates are at a 57-degree angle to the horizontal plane, the water depth of the upper layer of the inclined plate is 0.5m, the bottom buffer zone height is 0.8m, and gravity sludge removal is used twice a day.

[0088] The preparation method of the modified inorganic-organic coagulant is as follows: 1) Prepare an 8% (w / w) ferric sulfate solution and an 11% (w / w) sodium sulfide solution. 2) Mix the ferric sulfate solution and sodium sulfide solution at a volume ratio of 1:3 to form a mixed solution, and place the mixed solution in a reactor. 3) Add 0.03 g of polyethyleneimine to each liter of the mixed solution, heat the reactor to 37°C, mechanically stir at 50 rpm, and react at a constant temperature for 4 hours. After cooling, the modified inorganic-organic coagulant is obtained. The prepared modified inorganic-organic coagulant can effectively reduce or eliminate the zeta potential of colloids in water, causing colloid coagulation through charge neutralization, adsorption bridging, and sweeping effects, and then removing thallium and total chromium through precipitation separation.

[0089] After passing through the first mixing zone 21, the second mixing zone 22, and the inclined plate sedimentation zone 23, product water is obtained. The test results show that the product water quality is pH 3, thallium is 61 μg / L, and total chromium is 0.1 mg / L.

[0090] The permeate is then pumped into filter tower 7 via a secondary booster pump 6. Filter tower 7 is filled with modified filter media 8. Modified filter media 8 occupies 90% of the total volume of filter tower 7, and the permeate stays in filter tower 7 for 39 minutes.

[0091] The modified filter media 8 in this embodiment is prepared according to the characteristics of power plant desulfurization wastewater. The specific preparation process is as follows:

[0092] 1) Select coal-based activated carbon with a particle size of 80 mesh, manganese sand filler with a particle size of 80 mesh, and vermiculite filler with a particle size of 80 mesh. 2) Mix the coal-based activated carbon, manganese sand filler, and vermiculite filler in a solid-solid ratio of 7:7:1, and stir for 17 minutes at a stirring speed of 45 rpm. 3) Irradiate the mixed solid mixture with a microwave power of 550W for 55 minutes to form modified filter media 8. Modified filter media 8 has a surface area of ​​567 m² / L and is used to adsorb thallium and total chromium in the produced water.

[0093] After passing through filter tower 7, the wastewater is obtained. Testing shows that the thallium and total chromium levels in the wastewater meet the standards, with a pH of 7.4, thallium concentration of 39 μg / L, and total chromium concentration of 0.06 mg / L.

[0094] Subsequently, the qualified drainage is discharged through drainage pump 9.

[0095] Example 2

[0096] Take desulfurization wastewater discharged from power plants as an example, which has a pH of 3.9, a thallium concentration of 2350 μg / L, and a total chromium concentration of 3.6 mg / L.

[0097] The desulfurization wastewater is transported to the first mixing zone 21 via a primary booster pump 1. The residence time of the desulfurization wastewater in the first mixing zone 21 is 3.5 minutes, and the mixing speed of the first mixer is 65 rpm. The lime dosing system 3 contains lime with a mass concentration of 25%, and the lime is added to the first mixing zone 21 via a dosing pump. A pH meter is located at the outlet of the first mixing zone 21. The lime dosing automatic control system controls the lime dosing amount through the pH meter, maintaining the pH of the desulfurization wastewater at the outlet of the first mixing zone 21 at 7.0.

[0098] Desulfurization wastewater with a pH of 7.0 flows into the second mixing zone 22 through the outlet of the first mixing zone 21. The residence time in the second mixing zone 22 is 3 minutes, and the mixing speed of the second mixer is 65 rpm. The reagent tank of the coagulant dosing system 4 contains modified inorganic-organic coagulant 5. The modified inorganic-organic coagulant 5 is added to the second mixing zone 22 via the dosing pump of the coagulant dosing system 4, resulting in flocculation and sedimentation. The dosage of modified inorganic-organic coagulant 5 is 325 mg / L.

[0099] Then, the flocculated sediment flows into the inclined plate sedimentation zone 23 through the outlet of the second mixing zone 22. The residence time of the flocculated sediment in the inclined plate sedimentation zone 23 is 38 minutes. The length of the inclined plate is 1.0 m, the spacing between the inclined plates should be 0.8 cm, the inclined plates are at a 57-degree angle to the horizontal plane, the water depth of the upper layer of the inclined plate is 0.4 m, the bottom buffer zone height is 0.8 m, and gravity sludge removal is used once a day.

[0100] The preparation method of the modified inorganic-organic coagulant is as follows: 1) Prepare a 7% (w / w) ferric sulfate solution and a 9% (w / w) sodium sulfide solution. 2) Mix the ferric sulfate solution and sodium sulfide solution at a volume ratio of 1:2 to form a mixed solution, and place the mixed solution in a reactor. 3) Add 0.01g of polyethyleneimine to each liter of the mixed solution, heat the reactor to 35℃, mechanically stir at 45 rpm, and react at a constant temperature for 3 hours. After cooling, the modified inorganic-organic coagulant is obtained. The prepared modified inorganic-organic coagulant can effectively reduce or eliminate the zeta potential of colloids in water, and cause colloid coagulation through charge neutralization, adsorption bridging, and sweeping effects, and then remove thallium and total chromium through precipitation separation.

[0101] After passing through the first mixing zone 21, the second mixing zone 22, and the inclined plate sedimentation zone 23, product water is obtained. The product water quality is as follows: pH 7.1, thallium 57 μg / L, and total chromium 0.1 mg / L.

[0102] The permeate is then pumped into filter tower 7 via a secondary booster pump 6. Filter tower 7 is filled with modified filter media 8. Modified filter media 8 occupies 85% of the total volume of filter tower 7, and the permeate stays in filter tower 7 for 36 minutes.

[0103] The modified filter media 8 in this embodiment is prepared according to the characteristics of power plant desulfurization wastewater. The specific preparation process is as follows:

[0104] 1) Select coal-based activated carbon (50 mesh), manganese sand filler (50 mesh), and vermiculite filler (50 mesh). 2) Mix the coal-based activated carbon, manganese sand filler, and vermiculite filler in a solid-solid ratio of 5:7:1, and stir for 15 minutes at a stirring speed of 40 rpm. 3) Irradiate the mixed solid mixture with a microwave power of 500W for 45 minutes to form modified filter media 8. Modified filter media 8 has a surface area of ​​462 m² / L and is used to adsorb thallium and total chromium in the produced water.

[0105] After passing through filter tower 7, the wastewater is obtained. Testing shows that the thallium and total chromium levels in the wastewater meet the standards, with a pH of 7.1, thallium concentration of 34 μg / L, and total chromium concentration of 0.05 mg / L.

[0106] Subsequently, the qualified drainage is discharged through drainage pump 9.

[0107] Example 3

[0108] Take desulfurization wastewater discharged from a power plant as an example, which has a pH of 5.1, a thallium concentration of 4590 μg / L, and a total chromium concentration of 19.2 mg / L.

[0109] The desulfurization wastewater is transported to the first mixing zone 21 via a primary booster pump 1. The residence time of the desulfurization wastewater in the first mixing zone 21 is 1.5 minutes, and the mixing speed of the first mixer is 45 rpm. The lime dosing system 3 contains lime with a mass concentration of 16%, and the lime is added to the first mixing zone 21 via a dosing pump. A pH meter is located at the outlet of the first mixing zone 21. The lime dosing automatic control system controls the lime dosing amount through the pH meter, maintaining the pH of the desulfurization wastewater at the outlet of the first mixing zone 21 at 7.5.

[0110] Desulfurization wastewater with a pH of 7.0 flows into the second mixing zone 22 through the outlet of the first mixing zone 21. The residence time in the second mixing zone 22 is 7 minutes, and the mixing speed of the second mixer is 75 rpm. The reagent tank of the coagulant dosing system 4 contains modified inorganic-organic coagulant 5. The modified inorganic-organic coagulant 5 is added to the second mixing zone 22 via the dosing pump of the coagulant dosing system 4, resulting in flocculation and sedimentation. The dosage of modified inorganic-organic coagulant 5 is 653 mg / L.

[0111] Then, the flocculated sediment flows into the inclined plate sedimentation zone 23 through the outlet of the second mixing zone 22. The residence time of the flocculated sediment in the inclined plate sedimentation zone 23 is 53 minutes. The length of the inclined plate is 1.2m, the spacing between the inclined plates should be 1.0cm, the inclined plates are at an angle of 57 degrees to the horizontal plane, the water depth of the upper layer of the inclined plate is 0.7m, the bottom buffer zone height is 0.9m, and gravity sludge removal is used twice a day.

[0112] The preparation method of the modified inorganic-organic coagulant is as follows: 1) Prepare a 12% (w / w) ferric sulfate solution and a 15% (w / w) sodium sulfide solution. 2) Mix the ferric sulfate solution and sodium sulfide solution at a volume ratio of 1:3 to form a mixed solution, and place the mixed solution in a reactor. 3) Add 0.05 g of polyethyleneimine to each liter of the mixed solution, heat the reactor to 39°C, mechanically stir at 55 rpm, and react at a constant temperature for 4.5 h. After cooling, the modified inorganic-organic coagulant is obtained. The prepared modified inorganic-organic coagulant can effectively reduce or eliminate the zeta potential of colloids in water, and cause colloid coagulation through charge neutralization, adsorption bridging, and sweeping action, and then remove thallium and total chromium through precipitation separation.

[0113] After passing through the first mixing zone 21, the second mixing zone 22, and the inclined plate sedimentation zone 23, product water is obtained. The test results show that the product water quality is pH 7.5, thallium 73 μg / L, and total chromium 0.2 mg / L.

[0114] The permeate is then pumped into filter tower 7 via a secondary booster pump 6. Filter tower 7 is filled with modified filter media 8. Modified filter media 8 occupies 95% of the total volume of filter tower 7, and the permeate stays in filter tower 7 for 42 minutes.

[0115] The modified filter media 8 in this embodiment is prepared according to the characteristics of power plant desulfurization wastewater. The specific preparation process is as follows:

[0116] 1) Select coal-based activated carbon (100 mesh), manganese sand filler (100 mesh), and vermiculite filler (100 mesh). 2) Mix the coal-based activated carbon, manganese sand filler, and vermiculite filler in a solid-solid ratio of 9:7:1, and stir for 20 minutes at a stirring speed of 50 rpm. 3) Irradiate the mixed solid under microwave power of 600W for 60 minutes to form modified filter media 8. Modified filter media 8 has a surface area of ​​670 m². 2 / L, used to adsorb thallium and total chromium in the product water.

[0117] After passing through filter tower 7, the wastewater is obtained. Testing shows that the thallium and total chromium levels in the wastewater meet the standards, with a pH of 7.7, thallium concentration of 47 μg / L, and total chromium concentration of 0.07 mg / L.

[0118] Subsequently, the qualified drainage is discharged through drainage pump 9.

[0119] The desulfurization wastewater treatment method and system disclosed in this embodiment can simultaneously remove thallium and total chromium, with stable and efficient treatment effects, low production and operating costs, and simple operation. It is an environmentally friendly and green treatment method.

[0120] Of course, those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Any modifications or variations of the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

[0121] In summary, the above embodiments have provided detailed descriptions of different configurations of desulfurization wastewater treatment methods and systems. Of course, the above descriptions are only descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention in any way. The present invention includes but is not limited to the configurations listed in the above embodiments. Those skilled in the art can draw inferences from the above embodiments. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method for treating desulfurization wastewater, characterized in that, include: Lime is added to the desulfurization wastewater to adjust its pH to 7.0-7.5; After adding a modified inorganic-organic coagulant to the desulfurization wastewater with a pH of 7.0~7.5 for treatment, and then filtering it, the treated water is obtained. The produced water is then subjected to adsorption treatment with modified filter media to obtain wastewater; The preparation method of the modified inorganic-organic coagulant is as follows: Prepare iron ion solutions with a mass concentration of 7-12% and sulfide ion solutions with a mass concentration of 9-15% respectively; A mixed solution is formed by mixing an iron ion solution and a sulfur ion solution in a volume ratio of 1:2~3, wherein the iron ion solution is a ferric sulfate solution and the sulfur ion solution is a sodium sulfide solution. Add 0.01~0.05g of polyethyleneimine to each liter of the mixed solution, react at 35~39℃ for a certain time, and then cool to obtain the modified inorganic-organic coagulant; The method for preparing the modified filter material is as follows: Coal-based activated carbon, manganese sand filler, and vermiculite filler are mixed in a solid-solid ratio of 5 to 9:7:1 to obtain a mixture, wherein the particle size of the coal-based activated carbon is 50 to 100 mesh, the particle size of the manganese sand filler is 50 to 100 mesh, and the particle size of the vermiculite filler is 50 to 100 mesh. The mixture is irradiated with microwave power of 500~600W for 45~60 minutes to form the modified filter material.

2. The desulfurization wastewater treatment method according to claim 1, characterized in that, Adding lime to desulfurization wastewater to adjust its pH to 7.0-7.5 includes: The desulfurization wastewater is transported to the first mixing zone, and lime is added to the first mixing zone to adjust the pH of the desulfurization wastewater to 7.0~7.

5. The first mixing zone is equipped with a first mixer, and the mixing speed of the first mixer is 45~65 rpm. The residence time of the desulfurization wastewater in the first mixing zone is 1.5~3.5 min, and the mass concentration of the lime is 16~25%.

3. The desulfurization wastewater treatment method according to claim 2, characterized in that, After adding a modified inorganic-organic coagulant to the desulfurization wastewater with a pH of 7.0-7.5 for treatment, and then filtering it, the resulting product water includes: Desulfurization wastewater with a pH of 7.0~7.5 is transported to the second mixing zone, and a modified inorganic-organic coagulant is added to the second mixing zone to obtain flocculation and sedimentation. The flocculated sediment is transported to an inclined plate sedimentation zone for filtration to obtain product water.

4. The desulfurization wastewater treatment method according to claim 3, characterized in that, The dosage of the modified inorganic-organic coagulant is 325~653 mg / L. A second mixer is installed in the second mixing zone. The mixing speed of the second mixer is 65~75 rpm. The residence time of the desulfurization wastewater in the second mixing zone is 3~7 min.

5. The desulfurization wastewater treatment method according to claim 1, characterized in that, The wastewater is treated by adsorption using modified filter media to obtain wastewater, which includes: The produced water is transported to a filter tower for adsorption treatment. The filter tower is filled with modified filter media, which accounts for 85-95% of the total volume of the filter tower. The produced water stays in the filter tower for 36-42 minutes.

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