Method and system for removing COD and thallium in flue gas desulfurization wastewater

Abstract

The present application relates to a kind of method and system for removing COD and thallium in flue gas desulfurization wastewater, method includes: the water quality characteristics of flue gas desulfurization wastewater are pre-configured for removing COD and thallium in flue gas desulfurization wastewater coagulant and modified filler adsorbent, coagulant is compounded by sodium hypochlorite, sodium sulfide solution and powdered activated carbon, and modified filler adsorbent is prepared by diatomite, sodium sulfate solution and ferric chloride;Flue gas desulfurization wastewater is sent into coagulation sedimentation tank, and coagulant is added into coagulation sedimentation tank;The supernatant after being treated by coagulation sedimentation tank is sent into modified filler adsorption tower, and modified filler adsorption tower is filled with modified filler adsorbent.By the water quality characteristics of flue gas desulfurization wastewater configuration for removing COD and thallium in flue gas desulfurization wastewater coagulant, and modified filler adsorbent, after being treated, flue gas desulfurization wastewater can reach steel industry wastewater discharge standard, can be directly discharged, also can be reused according to demand.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a method and system for removing COD and thallium from flue gas desulfurization wastewater. Background Technology

[0002] The sintering flue gas from steel plants has a complex composition. After treatment by the desulfurization system, the resulting desulfurization wastewater contains various pollutants, including COD and the heavy metal thallium. Thallium is highly toxic, and if wastewater exceeding emission standards is discharged into natural water bodies, it will pose a serious threat to the ecological environment and human health. With increasing attention to thallium pollutants and the further implementation of ultra-low emission standards, the Ministry of Ecology and Environment added a new emission limit of 0.05 mg / L for total thallium in the 2020 draft amendment to the "Wastewater Discharge Standard for the Iron and Steel Industry" for public comment.

[0003] Desulfurization wastewater is typically treated using methods such as chemical precipitation, adsorption, and ion exchange. Among these, chemical precipitation is the most widely used because it can remove multiple pollutants simultaneously, ensures stable production operation, and has relatively low wastewater treatment costs. However, the COD and thallium levels in the wastewater treated by chemical precipitation generally do not meet external discharge standards, requiring secondary treatment at the enterprise's integrated water treatment center. This process is time-consuming and costly.

[0004] Therefore, there is an urgent need to develop an economical and efficient treatment process that can be implemented based on the water quality of flue gas desulfurization wastewater. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for removing COD and thallium from flue gas desulfurization wastewater, so as to solve the problems of existing flue gas desulfurization wastewater polluting the environment, having a long treatment cycle and high cost.

[0006] To achieve the above objectives, the present invention provides a method for removing COD and thallium from flue gas desulfurization wastewater, comprising:

[0007] Based on the water quality characteristics of flue gas desulfurization wastewater, a coagulant and a modified packing adsorbent for removing COD and thallium from the flue gas desulfurization wastewater are pre-prepared. The coagulant is composed of sodium hypochlorite, sodium sulfide solution and powdered activated carbon, and the modified packing adsorbent is prepared from diatomaceous earth, sodium sulfate solution and ferric chloride.

[0008] The flue gas desulfurization wastewater is sent into a coagulation sedimentation tank, and the coagulant is added to the coagulation sedimentation tank.

[0009] The supernatant after being treated in the coagulation sedimentation tank is sent to the modified packing adsorption tower, which is filled with the modified packing adsorbent.

[0010] Optionally, the method for preparing the coagulant includes:

[0011] Prepare a solution of sodium hypochlorite with a mass concentration of 15-17% and sodium sulfide with a mass concentration of 16-19% by volume to form a mixed solution at a volume ratio of 1:4-5;

[0012] Add 2-4g of the powdered activated carbon to each liter of the mixed solution, and mechanically stir for 10-16 minutes at a speed of 60-65 rpm to obtain the coagulant.

[0013] Optionally, the dosage of the coagulant is 345–782 mg / L.

[0014] Optionally, the residence time of the flue gas desulfurization wastewater in the coagulation sedimentation tank is 56 to 78 minutes.

[0015] Optionally, the preparation method of the modified filler adsorbent includes:

[0016] The diatomaceous earth with a particle size of 200-300 mesh was screened, rinsed with clean water 5-6 times, dried in a forced-air drying oven at 105℃ for 125-140 minutes, and then cooled.

[0017] Prepare a sodium sulfate solution with a mass percentage of 8-11%, add 231-321g of diatomaceous earth and 34-45g of ferric chloride to each liter of sodium sulfate solution, then place it in an autoclave and heat it to 152-278°C, react at a constant temperature for 78-89 minutes, then stop heating, cool and filter to obtain a solid substance;

[0018] The solid material is dried in the forced-air drying oven for 120-150 minutes and then cooled to room temperature to obtain the modified filler adsorbent.

[0019] Optionally, the height-to-diameter ratio of the modified packed adsorption tower is 6-7:1, and the modified packed adsorbent accounts for 87% of the total volume of the modified packed adsorption tower.

[0020] Based on the same inventive concept, the present invention also provides a system for removing COD and thallium from flue gas desulfurization wastewater, comprising:

[0021] The dosing unit is used to pre-prepare coagulants and modified packing adsorbents for removing COD and thallium from the flue gas desulfurization wastewater, based on the water quality characteristics of the wastewater. The coagulant is composed of sodium hypochlorite, sodium sulfide solution and powdered activated carbon, and the modified packing adsorbent is prepared from diatomaceous earth, sodium sulfate solution and ferric chloride.

[0022] A coagulation sedimentation tank is used to receive the flue gas desulfurization wastewater and perform coagulation treatment.

[0023] A dosing unit is used to add the coagulant into the coagulation sedimentation tank;

[0024] A modified packed adsorption tower is used to adsorb the supernatant after it has been treated by the coagulation sedimentation tank. The modified packed adsorption tower is filled with the modified packed adsorbent.

[0025] Optionally, the method for preparing the coagulant includes:

[0026] Prepare a solution of sodium hypochlorite with a mass concentration of 15-17% and sodium sulfide with a mass concentration of 16-19% by volume to form a mixed solution at a volume ratio of 1:4-5;

[0027] Add 2-4g of the powdered activated carbon to each liter of the mixed solution, and mechanically stir for 10-16 minutes at a speed of 60-65 rpm to obtain the coagulant.

[0028] Optionally, the preparation method of the modified filler adsorbent includes:

[0029] The diatomaceous earth with a particle size of 200-300 mesh was screened, rinsed with clean water 5-6 times, dried in a forced-air drying oven at 105℃ for 125-140 minutes, and then cooled.

[0030] Prepare a sodium sulfate solution with a mass percentage of 8-11%, add 231-321g of diatomaceous earth and 34-45g of ferric chloride to each liter of sodium sulfate solution, then place it in an autoclave and heat it to 152-278°C, react at a constant temperature for 78-89 minutes, then stop heating, cool and filter to obtain a solid substance;

[0031] The solid material is dried in the forced-air drying oven for 120-150 minutes and then cooled to room temperature to obtain the modified filler adsorbent.

[0032] Optionally, the system for removing COD and thallium from flue gas desulfurization wastewater further includes a primary booster pump, a secondary booster pump, and a drain pump. The primary booster pump is used to send the flue gas desulfurization wastewater into the coagulation sedimentation tank. The secondary booster pump is used to send the supernatant after treatment in the coagulation sedimentation tank into the modified packing adsorption tower. The drain pump is used to discharge the flue gas desulfurization wastewater after treatment in the modified packing adsorption tower.

[0033] In the method and system for removing COD and thallium from flue gas desulfurization wastewater provided by this invention, coagulants and modified packing adsorbents for removing COD and thallium from the flue gas desulfurization wastewater are pre-configured according to the water quality characteristics of the wastewater. First, the coagulant can remove most of the COD and thallium from the flue gas desulfurization wastewater, and then the modified packing adsorbent can further remove the residual COD and thallium from the wastewater. The treated flue gas desulfurization wastewater can meet the wastewater discharge standards of the iron and steel industry and can be directly discharged in compliance with the standards, or it can be reused as needed. Attached Figure Description

[0034] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention. Wherein:

[0035] Figure 1 This is a flowchart of a method for removing COD and thallium from flue gas desulfurization wastewater according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the structure of a system for removing COD and thallium from flue gas desulfurization wastewater according to an embodiment of the present invention.

[0037] in:

[0038] 1- Primary booster pump; 2- Coagulation sedimentation tank; 3- Dosing unit; 4- Coagulant; 5- Secondary booster pump; 6- Modified packing adsorption tower; 7- Modified packing adjuvant; 8- Drainage pump. Detailed Implementation

[0039] To make the objectives, advantages, and features of this invention clearer, the 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 in a very simplified form and use non-precise proportions, and are only used to facilitate and clearly illustrate the purpose of the embodiments of this invention. Please refer to the accompanying drawings to make the objectives, features, and advantages of this invention more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only used to complement the content disclosed in the specification, for those skilled in the art to understand and read, and are not intended to limit the implementation conditions of this invention. Any modifications to the structure, changes in proportions, or adjustments to the size, if they are the same as or similar to the effects and objectives achieved by this invention, should still fall within the scope of the technical content disclosed in this invention.

[0040] As used herein, the singular forms “a,” “an,” and “the” include plural objects unless otherwise expressly indicated. As used herein, the term “or” is generally used to include “and / or” unless otherwise expressly indicated. As used herein, the term “a number” is generally used to include “at least one” unless otherwise expressly indicated. As used herein, the term “at least two” is generally used to include “two or more” unless otherwise expressly indicated. Furthermore, the terms “first,” “second,” and “third” are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as “first,” “second,” or “third” may explicitly or implicitly include one or at least two of that feature.

[0041] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to a connection within two components or an interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0042] Please refer to Figure 1 and Figure 2 This embodiment provides a method for removing COD and thallium from flue gas desulfurization wastewater, including the following steps:

[0043] S1. Based on the water quality characteristics of flue gas desulfurization wastewater, coagulant 4 and modified packing adsorbent 7 are pre-prepared for removing COD and thallium from the flue gas desulfurization wastewater. Coagulant 4 is made of sodium hypochlorite, sodium sulfide solution and powdered activated carbon. Modified packing adsorbent 7 is made of diatomaceous earth, sodium sulfate solution and ferric chloride.

[0044] S2. Send the flue gas desulfurization wastewater into the coagulation sedimentation tank 2, and add coagulant 4 into the coagulation sedimentation tank 2.

[0045] S3. The supernatant after coagulation sedimentation tank 2 is sent to modified packing adsorption tower 6, which is filled with modified packing adsorbent 7.

[0046] This invention pre-configures a coagulant 4 and a modified packing adsorbent 7 for removing COD and thallium from flue gas desulfurization wastewater, based on the water quality characteristics of the wastewater. First, the coagulant 4 removes most of the COD and thallium from the wastewater, and then the modified packing adsorbent 7 further removes the remaining COD and thallium. The treated wastewater meets the discharge standards for wastewater from the steel industry and can be directly discharged in compliance with the standards, or it can be reused as needed.

[0047] First, execute S1, and pre-prepare coagulant 4 and modified packing adsorbent 7 for removing COD and thallium from flue gas desulfurization wastewater according to the water quality characteristics of the wastewater. Coagulant 4 is made of sodium hypochlorite, sodium sulfide solution and powdered activated carbon, and modified packing adsorbent 7 is made of diatomaceous earth, sodium sulfate solution and ferric chloride.

[0048] In this embodiment, the preparation method of coagulant 4 includes:

[0049] Prepare a solution of sodium hypochlorite with a mass concentration of 15-17% and sodium sulfide with a mass concentration of 16-19% by volume, and form a mixed solution at a volume ratio of 1:4-5.

[0050] Add 2-4g of powdered activated carbon to each liter of mixed solution, and mechanically stir for 10-16 minutes at a speed of 60-65 rpm. After stirring, coagulant 4 is obtained. The coagulant 4 prepared in this way can effectively adsorb and precipitate COD and thallium in flue gas desulfurization wastewater.

[0051] In this embodiment, the preparation method of the modified filler adsorbent 7 includes:

[0052] The diatomaceous earth with a particle size of 200-300 mesh was screened, rinsed with clean water 5-6 times, dried in a forced-air drying oven at 105℃ for 125-140 minutes, and then cooled.

[0053] Prepare a sodium sulfate solution with a mass percentage of 8-11%. Add 231-321g of diatomaceous earth and 34-45g of ferric chloride to each liter of sodium sulfate solution. Then place the solution in an autoclave, seal the autoclave, purge with nitrogen, and heat to 152-278°C. Maintain the temperature for 78-89 minutes, then stop heating. After cooling, filter to obtain a solid substance.

[0054] The solid material was dried in a forced-air drying oven for 120-150 minutes and then cooled to room temperature to obtain the modified filler adsorbent 7.

[0055] After preparing coagulant 4 and modified packing adsorbent 7, step S2 is executed to send the flue gas desulfurization wastewater into the coagulation sedimentation tank 2, and coagulant 4 is added to the coagulation sedimentation tank 2. In this embodiment, the influent water quality characteristics of the flue gas desulfurization wastewater are: COD 53-72 mg / L, thallium 3450-5413 μg / L. The flue gas desulfurization wastewater can be sent into the coagulation sedimentation tank 2 via a primary booster pump 1. Coagulant 4 is added to the coagulation sedimentation tank 2 using the dosing unit 3 at a dosage of 345-782 mg / L. The residence time of the flue gas desulfurization wastewater in the coagulation sedimentation tank 2 is 56-78 min. After passing through the coagulation sedimentation tank 2, the COD of the flue gas desulfurization wastewater is 31-45 mg / L, and the thallium is 76-95 μg / L.

[0056] Finally, step S3 is executed, sending the supernatant treated in coagulation sedimentation tank 2 into modified packing adsorption tower 6, which is filled with modified packing adsorbent 7. In this embodiment, the flue gas desulfurization wastewater enters the modified packing adsorption tower 6 via a secondary booster pump 5, and the modified packing adsorption tower 6 contains the modified packing adsorbent 7. After the entire process, the effluent COD of the flue gas desulfurization wastewater is 21–32 mg / L, and the thallium content is 33–42 μg / L, meeting the wastewater discharge standards for the iron and steel industry. It can be directly discharged through a drainage pump or reused.

[0057] Preferably, the height to diameter ratio of the modified packed adsorption tower 6 is 6-7:1, and the modified packed adsorbent 7 accounts for 87% of the total volume of the modified packed adsorption tower 6.

[0058] Based on the same technical concept, embodiments of the present invention also provide a system for removing COD and thallium from flue gas desulfurization wastewater, comprising:

[0059] The dosing unit is used to pre-prepare coagulant 4 and modified packing adsorbent 7 for removing COD and thallium from flue gas desulfurization wastewater according to the water quality characteristics of the wastewater. Coagulant 4 is made of sodium hypochlorite, sodium sulfide solution and powdered activated carbon, and modified packing adsorbent 7 is made of diatomaceous earth, sodium sulfate solution and ferric chloride.

[0060] Coagulation sedimentation tank 2 is used to coagulate and treat the wastewater from flue gas desulfurization.

[0061] Dosing unit 3 is used to add coagulant 4 into coagulation sedimentation tank 2;

[0062] The modified packed adsorption tower 6 is used to adsorb the supernatant after coagulation sedimentation tank 2. The modified packed adsorption tower 6 is filled with modified packed adsorbent 7.

[0063] Preferably, the preparation method of coagulant 4 includes:

[0064] Prepare a solution of sodium hypochlorite with a mass concentration of 15-17% and sodium sulfide with a mass concentration of 16-19% by volume, and form a mixed solution at a volume ratio of 1:4-5.

[0065] Add 2-4g of powdered activated carbon to each liter of the mixed solution, and mechanically stir for 10-16 minutes at a speed of 60-65 rpm. After stirring, coagulant 4 is obtained.

[0066] Preferably, the preparation method of the modified filler adsorbent 7 includes:

[0067] The diatomaceous earth with a particle size of 200-300 mesh was screened, rinsed with clean water 5-6 times, dried in a forced-air drying oven at 105℃ for 125-140 minutes, and then cooled.

[0068] Prepare a sodium sulfate solution with a mass percentage of 8-11%. Add 231-321g of diatomaceous earth and 34-45g of ferric chloride to each liter of sodium sulfate solution. Then place the solution in an autoclave and heat it to 152-278℃. React at this temperature for 78-89 minutes. Then stop heating, cool the solution, and filter to obtain a solid substance.

[0069] The solid material was dried in a forced-air drying oven for 120-150 minutes and then cooled to room temperature to obtain the modified filler adsorbent 7.

[0070] Preferably, the system for removing COD and thallium from flue gas desulfurization wastewater also includes a primary booster pump 1, a secondary booster pump 5, and a drainage pump. The primary booster pump 1 is used to send the flue gas desulfurization wastewater into a coagulation sedimentation tank 2. The secondary booster pump 5 is used to send the supernatant after treatment in the coagulation sedimentation tank 2 into a modified packing adsorption tower 6. The drainage pump is used to discharge the flue gas desulfurization wastewater after treatment in the modified packing adsorption tower 6.

[0071] The technical concept of the present invention will be further illustrated below through three specific embodiments.

[0072] Example 1

[0073] Coagulant 4 was prepared specifically for the water quality characteristics of flue gas desulfurization wastewater. The preparation process is as follows:

[0074] Prepare a solution of sodium hypochlorite with a mass concentration of 17% and sodium sulfide with a mass concentration of 19% by volume, and form a mixed solution at a volume ratio of 1:4 to 5.

[0075] Add 4g of powdered activated carbon to each liter of the mixed solution and mechanically stir for 16 minutes at a speed of 65 rpm to obtain coagulant 4.

[0076] Modified packing adsorbent 7 is also prepared specifically for the water quality characteristics of flue gas desulfurization wastewater. The preparation process is as follows:

[0077] Diatomaceous earth with a particle size of 300 mesh was screened, washed 6 times with clean water, dried in a 105℃ forced-air drying oven for 140 minutes, and then cooled.

[0078] Prepare a sodium sulfate solution with a mass percentage of 11%. Add 321g of diatomaceous earth and 45g of ferric chloride to each liter of sodium sulfate solution. Then place the solution in an autoclave, seal the autoclave, purge with nitrogen, and heat to 278°C. Maintain the temperature for 89 minutes, then stop heating. After cooling, filter to obtain a solid substance.

[0079] The solid material was dried in a forced-air drying oven at 105°C for 150 min and then cooled to room temperature to obtain modified filler adsorbent 7.

[0080] The influent water quality characteristics of the flue gas desulfurization wastewater are: COD is 72 mg / L and thallium is 5413 μg / L.

[0081] Flue gas desulfurization wastewater enters coagulation sedimentation tank 2 via primary booster pump 1. Coagulant 4 is added to coagulation sedimentation tank 2 at a dosage of 782 mg / L by dosing unit 3. The residence time of the flue gas desulfurization wastewater in coagulation sedimentation tank 2 is 56–78 minutes. After passing through coagulation sedimentation tank 2, the COD of the flue gas desulfurization wastewater is 45 mg / L, and the thallium content is 95 μg / L.

[0082] Subsequently, the supernatant from the coagulation sedimentation tank 2 enters the modified packing adsorption tower 6 through the secondary booster pump 5. The modified packing adsorption tower 6 contains a modified packing adsorbent 7. The height to diameter ratio of the modified packing adsorption tower 6 is 7:1. The modified packing adsorbent 7 accounts for 87% of the total volume of the modified packing adsorption tower 6. The flow velocity of the flue gas desulfurization wastewater in the modified packing adsorption tower 6 is 4 m / s.

[0083] After the entire process, the COD of the flue gas desulfurization wastewater is 32 mg / L and the thallium content is 42 μg / L, which meets the wastewater discharge standards of the iron and steel industry. It can be discharged directly in compliance with the standards, or it can be reused as needed.

[0084] Example 2

[0085] Coagulant 4 was prepared specifically for the water quality characteristics of flue gas desulfurization wastewater. The preparation process is as follows:

[0086] Prepare a 15% (w / w) sodium hypochlorite and sodium sulfide solution by mixing them in a volume ratio of 1:4 to 5 to form a mixed solution.

[0087] Add 2g of powdered activated carbon to each liter of the mixed solution and mechanically stir for 10-16 minutes at a speed of 60 rpm to obtain coagulant 4.

[0088] Modified packing adsorbent 7 is also prepared specifically for the water quality characteristics of flue gas desulfurization wastewater. The preparation process is as follows:

[0089] Diatomaceous earth with a particle size of 200 mesh was screened, rinsed 5 times with clean water, dried in a 105℃ forced-air drying oven for 125 minutes, and then cooled.

[0090] Prepare a sodium sulfate solution with a mass percentage of 8%. Add 231g of diatomaceous earth and 34g of ferric chloride to each liter of sodium sulfate solution. Then place the solution in an autoclave, seal the autoclave, purge with nitrogen, and heat to 152°C. Maintain the temperature for 78 minutes, then stop heating. After cooling, filter to obtain a solid substance.

[0091] The solid material was dried in a forced-air drying oven at 105℃ for 120 minutes and then cooled to room temperature to obtain modified filler adsorbent 7.

[0092] The influent water quality characteristics of the flue gas desulfurization wastewater are: COD is 53 mg / L and thallium is 3450 μg / L.

[0093] Flue gas desulfurization wastewater enters coagulation sedimentation tank 2 via primary booster pump 1. Coagulant 4 is added to coagulation sedimentation tank 2 by dosing unit 3 at a dosage of 456 mg / L. The residence time of the flue gas desulfurization wastewater in coagulation sedimentation tank 2 is 62 min. After passing through coagulation sedimentation tank 2, the COD of the flue gas desulfurization wastewater is 33 mg / L, and the thallium content is 79 μg / L.

[0094] Subsequently, the flue gas desulfurization wastewater enters the modified packed adsorption tower 6 via a secondary booster pump 5. The modified packed adsorption tower 6 contains modified packed adsorbent 7. The height-to-diameter ratio of the modified packed adsorption tower 6 is 6:1, and the modified packed adsorbent 7 accounts for 87% of the total volume of the modified packed adsorption tower 6. The flow velocity of the flue gas desulfurization wastewater in the modified packed adsorption tower 6 is 4 m / s.

[0095] After the entire process, the COD of the flue gas desulfurization wastewater is 23 mg / L and the thallium content is 35 μg / L, meeting the wastewater discharge standards for the iron and steel industry. It can be discharged directly in compliance with the standards or reused as needed.

[0096] Example 3

[0097] Coagulant 4 was prepared specifically for the water quality characteristics of flue gas desulfurization wastewater. The preparation process is as follows:

[0098] Prepare a 16% sodium hypochlorite and sodium sulfide solution by mixing them in a volume ratio of 1:5.

[0099] Add 3g of powdered activated carbon to each liter of the mixed solution, and mechanically stir for 13 minutes at a speed of 62 rpm to obtain coagulant 4.

[0100] Modified packing adsorbent 7 is also prepared specifically for the water quality characteristics of flue gas desulfurization wastewater. The preparation process is as follows:

[0101] Diatomaceous earth with a particle size of 200 mesh was screened, rinsed 5 times with clean water, dried in a 105℃ forced-air drying oven for 130 minutes, and then cooled.

[0102] Prepare a 9% sodium sulfate solution by mass. Add 276g of diatomaceous earth and 39g of ferric chloride to each liter of sodium sulfate solution. Then place the solution in an autoclave, seal the autoclave, purge with nitrogen, and heat to 197°C. Maintain the temperature for 82 minutes, then stop heating. After cooling, filter to obtain a solid substance.

[0103] The solid material was dried in a forced-air drying oven at 105℃ for 136 minutes and then cooled to room temperature to obtain modified filler adsorbent 7.

[0104] The influent water quality characteristics of the flue gas desulfurization wastewater are: COD is 61 mg / L and thallium is 4260 μg / L.

[0105] Flue gas desulfurization wastewater enters coagulation sedimentation tank 2 via primary booster pump 1. Coagulant 4 is added to coagulation sedimentation tank 2 by dosing unit 3 at a dosage of 557 mg / L. The residence time of the flue gas desulfurization wastewater in coagulation sedimentation tank 2 is 63 min. After passing through coagulation sedimentation tank 2, the COD of the flue gas desulfurization wastewater is 37 mg / L, and the thallium content is 81 μg / L.

[0106] Subsequently, the flue gas desulfurization wastewater enters the modified packing adsorption tower 6 through the secondary booster pump 5. The modified packing adsorption tower 6 contains modified packing adsorbent 7. The height to diameter ratio of the modified packing adsorption tower 6 is 6:1. The modified packing adsorbent 7 accounts for 87% of the total volume of the modified packing adsorption tower 6. The flow velocity of the flue gas desulfurization wastewater in the modified packing adsorption tower 6 is 4 m / s.

[0107] After the entire process, the COD of the flue gas desulfurization wastewater is 25 mg / L and the thallium content is 37 μg / L, which meets the wastewater discharge standards of the iron and steel industry. It can be discharged directly in compliance with the standards, or it can be reused as needed.

[0108] In summary, the embodiments of the present invention provide a method and system for removing COD and thallium from flue gas desulfurization wastewater. By pre-configuring coagulant 4 and modified packing adsorbent 7 for removing COD and thallium from flue gas desulfurization wastewater according to its water quality characteristics, coagulant 4 can first remove most of the COD and thallium from the flue gas desulfurization wastewater, and then modified packing adsorbent 7 can further remove the residual COD and thallium from the flue gas desulfurization wastewater. The treated flue gas desulfurization wastewater can meet the wastewater discharge standards of the iron and steel industry and can be directly discharged in compliance with the standards, or it can be reused as needed.

[0109] Furthermore, it should be understood that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method for removing COD and thallium from flue gas desulfurization wastewater, characterized in that, include: Based on the water quality characteristics of flue gas desulfurization wastewater, a coagulant and a modified packing adsorbent for removing COD and thallium from the flue gas desulfurization wastewater are pre-prepared. The coagulant is composed of sodium hypochlorite, sodium sulfide solution and powdered activated carbon, and the modified packing adsorbent is prepared from diatomaceous earth, sodium sulfate solution and ferric chloride. The flue gas desulfurization wastewater is sent into a coagulation sedimentation tank, and the coagulant is added to the coagulation sedimentation tank. The supernatant after being treated in the coagulation sedimentation tank is sent to the modified packing adsorption tower, which is filled with the modified packing adsorbent. The preparation method of the coagulant includes: Prepare a solution of sodium hypochlorite with a mass concentration of 15-17% and sodium sulfide with a mass concentration of 16-19% by volume, and form a mixed solution at a volume ratio of 1:4-5; Add 2-4 g of the powdered activated carbon to each liter of the mixed solution, and mechanically stir for 10-16 min at a speed of 60-65 rpm to obtain the coagulant. The preparation method of the modified filler adsorbent includes: The diatomaceous earth with a particle size of 200-300 mesh was screened, rinsed with clean water 5-6 times, dried in a forced-air drying oven at 105℃ for 125-140 min, and then cooled. Prepare a sodium sulfate solution with a mass percentage of 8-11%, add 231-321 g of diatomaceous earth and 34-45 g of ferric chloride to each liter of sodium sulfate solution, then place it in an autoclave and heat it to 152-278°C, react at a constant temperature for 78-89 min, then stop heating, cool and filter to obtain a solid substance; The solid material was dried in a forced-air drying oven for 120-150 min and then cooled to room temperature to obtain the modified filler adsorbent.

2. The method for removing COD and thallium from flue gas desulfurization wastewater according to claim 1, characterized in that, The dosage of the coagulant is 345~782 mg / L.

3. The method for removing COD and thallium from flue gas desulfurization wastewater according to claim 1, characterized in that, The residence time of the flue gas desulfurization wastewater in the coagulation sedimentation tank is 56-78 minutes.

4. The method for removing COD and thallium from flue gas desulfurization wastewater according to claim 1, characterized in that, The height-to-diameter ratio of the modified packing adsorption tower is 6-7:1, and the modified packing adsorbent accounts for 87% of the total volume of the modified packing adsorption tower.

5. A system for removing COD and thallium from flue gas desulfurization wastewater, characterized in that, include: The dosing unit is used to pre-prepare coagulants and modified packing adsorbents for removing COD and thallium from the flue gas desulfurization wastewater, based on the water quality characteristics of the wastewater. The coagulant is composed of sodium hypochlorite, sodium sulfide solution and powdered activated carbon, and the modified packing adsorbent is prepared from diatomaceous earth, sodium sulfate solution and ferric chloride. A coagulation sedimentation tank is used to receive the flue gas desulfurization wastewater and perform coagulation treatment. A dosing unit is used to add the coagulant into the coagulation sedimentation tank; A modified packed adsorption tower is used to adsorb the supernatant after treatment in the coagulation sedimentation tank. The modified packed adsorption tower is filled with the modified packed adsorbent. The preparation method of the coagulant includes: Prepare a solution of sodium hypochlorite with a mass concentration of 15-17% and sodium sulfide with a mass concentration of 16-19% by volume, and form a mixed solution at a volume ratio of 1:4-5; Add 2-4 g of the powdered activated carbon to each liter of the mixed solution, and mechanically stir for 10-16 min at a speed of 60-65 rpm to obtain the coagulant. The preparation method of the modified filler adsorbent includes: The diatomaceous earth with a particle size of 200-300 mesh was screened, rinsed with clean water 5-6 times, dried in a forced-air drying oven at 105℃ for 125-140 min, and then cooled. Prepare a sodium sulfate solution with a mass percentage of 8-11%, add 231-321 g of diatomaceous earth and 34-45 g of ferric chloride to each liter of sodium sulfate solution, then place it in an autoclave and heat it to 152-278°C, react at a constant temperature for 78-89 min, then stop heating, cool and filter to obtain a solid substance; The solid material was dried in a forced-air drying oven for 120-150 min and then cooled to room temperature to obtain the modified filler adsorbent.

6. The system for removing COD and thallium from flue gas desulfurization wastewater according to claim 5, characterized in that, The system for removing COD and thallium from flue gas desulfurization wastewater also includes a primary booster pump, a secondary booster pump, and a drainage pump. The primary booster pump is used to send the flue gas desulfurization wastewater into the coagulation sedimentation tank. The secondary booster pump is used to send the supernatant after treatment in the coagulation sedimentation tank into the modified packing adsorption tower. The drainage pump is used to discharge the flue gas desulfurization wastewater after treatment in the modified packing adsorption tower.

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