A treatment method for removing mercury and lead from desulfurization wastewater in power plants

Abstract

The present invention belongs to the technical field of water treatment, and specifically relates to a treatment method for removing mercury and lead in desulfurization wastewater from a power plant, comprising the following steps: (1) the desulfurization wastewater from the power plant enters a modified zeolite adsorption tower, wherein the modified zeolite adsorption tower is internally provided with an organic modified zeolite, and the organic modified zeolite accounts for 87-91% of the volume of the entire modified zeolite adsorption tower; (2) the effluent from the modified zeolite adsorption tower enters a ceramic microfiltration membrane system, wherein the operating pressure is 0.11-0.14 MPa, the filter pore size is 0.1-0.2 μm, the cross-flow velocity is 3.1-3.3 m / s, and the flux is 78-89 L / (m 2 h); (3) The effluent from the ceramic microfiltration membrane system is discharged or injected into the zero-discharge system for desulfurization wastewater. The present invention develops an economical and efficient resource recovery process with recycling, energy conservation and emission reduction as the main tasks to reduce environmental pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a treatment method for removing mercury and lead from desulfurization wastewater in a power plant. Background Art

[0002] Currently, the primary desulfurization method used in coal-fired power plants is limestone-gypsum wet desulfurization. This mature technology is suitable for large-capacity units and offers stable system operation, adaptability to a wide range of coal types and unit loads, rapid desulfurization reaction rates, and comprehensive utilization of the desulfurization byproduct, gypsum. Currently, coal-fired power plants generally use a three-stage desulfurization process to control heavy metal emissions. However, with increasingly stringent emission standards, existing processes are unable to meet these requirements, resulting in excessive levels of mercury and lead in desulfurization wastewater.

[0003] The present invention targets desulfurization wastewater treated by the triple-tank process. However, to date, there is no process for deep treatment of mercury and lead in desulfurization wastewater. The purpose of the present invention is to develop an economical and efficient resource treatment process based on the water quality and quantity of desulfurization wastewater, with recycling, energy saving and emission reduction as the main tasks, to reduce environmental pollution. Summary of the Invention

[0004] The purpose of the present invention is to provide a treatment method for removing mercury and lead in desulfurization wastewater from a power plant, wherein the treatment object is the desulfurization wastewater after treatment by a triple-tank process.

[0005] The present invention is a technical solution for the deep treatment of desulfurization wastewater, which is as follows:

[0006] A method for removing mercury and lead from desulfurization wastewater in a power plant comprises the following steps:

[0007] (1) The desulfurization wastewater from the power plant enters a modified zeolite adsorption tower, which has an organic modified zeolite built in. The organic modified zeolite occupies 87-91% of the volume of the entire modified zeolite adsorption tower;

[0008] The water quality characteristics of the desulfurization wastewater from the power plant are as follows: pH 6.8-8.5, conductivity 15200-31670 μS / cm, mercury ion 0.08-0.16 mg / L, and lead ion 2.1-3.4 mg / L.

[0009] The organic modified zeolite is prepared by soaking and cleaning natural zeolite in a calcium hydroxide solution, then soaking and centrifuging the zeolite in a 4-acetamido-aniline hydrochloride solution at a solid-liquid ratio of 1:12 to 17, and finally soaking and centrifuging the zeolite in a zinc acetate solution.

[0010] (2) The effluent from the modified zeolite adsorption tower enters the ceramic microfiltration membrane system with an operating pressure of 0.11-0.14 MPa, a filtration pore size of 0.1-0.2 μm, a cross-flow velocity of 3.1-3.3 m / s, and a flux of 78-89 L / (m 2 h);

[0011] (3) The effluent from the ceramic microfiltration membrane system is discharged or injected into the desulfurization wastewater zero discharge system.

[0012] Furthermore, in step (1), the residence time of the desulfurized wastewater in the modified zeolite adsorption tower is 17 to 26 minutes.

[0013] Furthermore, after passing through the mixed organic modified zeolite adsorption tower, the water quality of the desulfurization wastewater is 0.03-0.05 mg / L for mercury ions and 0.4-0.6 mg / L for lead ions.

[0014] Furthermore, in step (1), the natural zeolite has a particle size of 0.1 to 0.2 mm and a specific surface area of ​​225.2 to 281.5 m 2 / g.

[0015] Furthermore, in step (1), the concentration of the calcium hydroxide solution is 0.2 to 0.7 mol / L, and the zeolite is oscillated therein for 4 to 6 hours, during which the indoor temperature is maintained at 20 to 26° C., and then dried at 105° C. and naturally cooled.

[0016] Furthermore, in step (1), the concentration of the 4-acetamido-aniline hydrochloride solution is 0.01 to 0.03 mol / L, the zeolite is immersed in the 4-acetamido-aniline hydrochloride solution, shaken at 45 to 55° C. for 8 to 12 hours, centrifuged and filtered, and the solid portion is rinsed 3 to 6 times with deionized water, dried at 75° C., and naturally cooled to form an acetamido-modified zeolite.

[0017] Furthermore, the concentration of the zinc acetate solution is 0.5 to 0.8 mol / L, and the zeolite is immersed in the zinc acetate solution at a solid-liquid ratio of 1:7 to 12; the mixture is shaken at 50 to 65° C. for 13 to 16 hours, centrifuged, and filtered, and the solid portion is rinsed with deionized water 3 to 6 times, dried at 70° C., and naturally cooled to form a mixed organic-modified zeolite.

[0018] According to the method for removing mercury and lead from desulfurization wastewater in a power plant according to the present invention, the specific surface area of ​​the organic modified zeolite is 633.2 to 679.6 m 2 / g. Detailed description of the invention:

[0020] The water quality characteristics of the desulfurization wastewater from the power plant are as follows: pH 6.8-8.5, conductivity 15200-31670 μS / cm, mercury ion 0.08-0.16 mg / L, and lead ion 2.1-3.4 mg / L.

[0021] A treatment system for removing mercury and lead from power plant wastewater comprises a water inlet pump, a modified zeolite adsorption tower, mixed organic modified zeolite, a primary water inlet pump, a microfiltration membrane system, and a water outlet pump.

[0022] The power plant's desulfurization wastewater enters the modified zeolite adsorption tower via an inlet pump. The mixed organic modified zeolite accounts for 87-91% of the total adsorption volume of the modified zeolite. The desulfurization wastewater resides in the modified zeolite adsorption tower for 17-26 minutes. After passing through the mixed organic modified zeolite adsorption tower, the desulfurization wastewater has a mercury ion concentration of 0.03-0.05 mg / L and a lead ion concentration of 0.4-0.6 mg / L.

[0023] The mixed modified zeolite of the present invention is prepared according to the characteristics of desulfurization wastewater from power plants. 1) Select natural zeolite with a particle size of 0.1 to 0.2 mm and a specific surface area of ​​225.2 to 281.5 m 2 / g. The zeolite was shaken in a 0.2-0.7 mol / L calcium hydroxide solution for 4-6 hours, maintaining the room temperature at 20-26°C, then dried at 105°C and allowed to cool naturally. Soaking and cleaning with calcium hydroxide can remove impurities blocking the zeolite pores, unblocking the pores and making the pores and channels smoother. 2) Prepare a 0.01-0.03 mol / L 4-acetamido-aniline hydrochloride solution and soak the zeolite in the 4-acetamido-aniline hydrochloride solution at a solid-to-liquid ratio of 1:12-17. Oscillate at 45-55°C for 8-12 hours, centrifuge, filter, rinse the solid portion with deionized water 3-6 times, dry at 75°C, and cool naturally to form the acetamido-modified zeolite. 3) Prepare a 0.5-0.8 mol / L zinc acetate solution and soak the zeolite in the zinc acetate solution at a solid-to-liquid ratio of 1:7-12. Under the condition of 50-65℃, shake for 13-16h, centrifuge and filter, rinse the solid part with deionized water 3-6 times, dry at 70℃, and cool naturally to form mixed organic modified zeolite. After mixed organic modification, the specific surface area of ​​zeolite is increased, resulting in an increase in the ability of modified zeolite to adsorb heavy metals. The specific surface area of ​​mixed organic modified zeolite is 633.2-679.6m 2 / g.

[0024] Subsequently, the first-stage water inlet pump pumps the desulfurization wastewater into the ceramic microfiltration membrane system. The operating pressure is 0.11-0.14 MPa, the filtration pore size is 0.1-0.2 μm, the cross-flow velocity is 3.1-3.3 m / s, and the flux is 78-89 L / (m 2h). After treatment with the microfiltration membrane, the desulfurization wastewater has a pH of 6.8-8.5, a conductivity of 15350-32180 μS / cm, a mercury ion concentration of 0.01-0.02 mg / L, and a lead ion concentration of 0.3-0.5 mg / L.

[0025] The desulfurization wastewater is then discharged by the outlet pump or pumped into the desulfurization wastewater zero discharge system.

[0026] Beneficial technical effects of the present invention:

[0027] This invention develops an economical and efficient resource-based treatment process based on the quality and quantity of desulfurization wastewater. It prioritizes recycling, energy conservation, and emission reduction, thereby reducing environmental pollution. The invention transforms the original desulfurization wastewater from a power plant with a pH of 6.8-8.5, a conductivity of 15,200-31,670 μS / cm, mercury ion levels of 0.08-0.16 mg / L, and lead ion levels of 2.1-3.4 mg / L into a treated desulfurization wastewater with a pH of 6.8-8.5, a conductivity of 15,350-32,180 μS / cm, mercury ion levels of 0.01-0.02 mg / L, and lead ion levels of 0.3-0.5 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 : A treatment system for removing mercury and lead from power plant wastewater;

[0029] Including: water inlet pump-1, modified zeolite adsorption tower-2, mixed organic modified zeolite-3, first-stage water inlet pump-4, microfiltration membrane system-5, water outlet pump-6. DETAILED DESCRIPTION

[0030] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0031] Embodiment 1:

[0032] The water quality characteristics of the desulfurization wastewater from the power plant are as follows: pH 8.3, conductivity 29870 μS / cm, mercury ion 0.16 mg / L, and lead ion 3.2 mg / L.

[0033] A treatment system for removing mercury and lead from power plant wastewater comprises a water inlet pump, a modified zeolite adsorption tower, mixed organic modified zeolite, a primary water inlet pump, a microfiltration membrane system, and a water outlet pump.

[0034] The power plant's desulfurization wastewater enters the modified zeolite adsorption tower via an inlet pump. The mixed organic modified zeolite accounts for 91% of the total adsorption volume of the modified zeolite. The desulfurization wastewater's residence time in the modified zeolite adsorption tower is 26 minutes. After passing through the mixed organic modified zeolite adsorption tower, the desulfurization wastewater has a mercury ion concentration of 0.05 mg / L and a lead ion concentration of 0.6 mg / L.

[0035] The mixed modified zeolite of the present invention is prepared according to the characteristics of desulfurization wastewater from power plants. 1) Select natural zeolite with a particle size of 0.2 mm and a specific surface area of ​​275.3 m 2 / g. The zeolite was shaken in a 0.6 mol / L calcium hydroxide solution for 6 hours, maintaining the room temperature at 25°C. It was then dried at 105°C and allowed to cool naturally. Soaking and cleaning with calcium hydroxide removes impurities blocking the zeolite pores, unblocking the channels and making the pores and channels smoother. 2) Prepare a 0.03 mol / L 4-acetamido-aniline hydrochloride solution and soak the zeolite in it at a solid-to-liquid ratio of 1:16. Shake at 55°C for 12 hours, centrifuge, filter, rinse the solids six times with deionized water, dry at 75°C, and cool naturally to form the acetamido-modified zeolite. 3) Prepare a 0.8 mol / L zinc acetate solution and soak the zeolite in it at a solid-to-liquid ratio of 1:12. Shake at 65°C for 16 hours, centrifuge, filter, rinse the solids five times with deionized water, dry at 70°C, and cool naturally to form the mixed organic-modified zeolite. After mixed organic modification, the specific surface area of ​​zeolite is increased, resulting in an increase in the ability of modified zeolite to adsorb heavy metals. The specific surface area of ​​mixed organic modified zeolite is 676.2m 2 / g.

[0036] Subsequently, the first-stage water inlet pump pumps the desulfurization wastewater into the ceramic microfiltration membrane system. The operating pressure is 0.14MPa, the filtration pore size is 0.2μm, the cross-flow velocity is 3.3m / s, and the flux is 88L / (m 2 h). After treatment with the microfiltration membrane, the desulfurization wastewater had a pH of 8.4, a conductivity of 30100 μS / cm, a mercury ion content of 0.02 mg / L, and a lead ion content of 0.5 mg / L.

[0037] The desulfurization wastewater is then discharged by the outlet pump or pumped into the desulfurization wastewater zero discharge system.

[0038] Example 2

[0039] The water quality characteristics of the desulfurization wastewater from the power plant are as follows: pH 6.8, conductivity 15900 μS / cm, mercury ion 0.08 mg / L, and lead ion 2.1 mg / L.

[0040] A treatment system for removing mercury and lead from power plant wastewater comprises a water inlet pump, a modified zeolite adsorption tower, mixed organic modified zeolite, a primary water inlet pump, a microfiltration membrane system, and a water outlet pump.

[0041] The power plant's desulfurization wastewater enters the modified zeolite adsorption tower via an inlet pump. The mixed organic modified zeolite accounts for 87% of the total adsorption volume of the modified zeolite. The desulfurization wastewater's residence time in the modified zeolite adsorption tower is 17 minutes. After passing through the mixed organic modified zeolite adsorption tower, the desulfurization wastewater's water quality is 0.03 mg / L mercury ions and 0.4 mg / L lead ions.

[0042] The mixed modified zeolite of the present invention is prepared according to the characteristics of desulfurization wastewater from power plants. 1) Select natural zeolite with a particle size of 0.1 mm and a specific surface area of ​​233.1 m 2 / g. The zeolite was shaken in a 0.2 mol / L calcium hydroxide solution for 4 hours, maintaining the room temperature at 20°C. It was then dried at 105°C and allowed to cool naturally. Soaking and cleaning with calcium hydroxide removes impurities blocking the zeolite pores, unblocking the channels and making the pores and channels smoother. 2) Prepare a 0.01 mol / L 4-acetamido-aniline hydrochloride solution and soak the zeolite in it at a solid-to-liquid ratio of 1:12. Shake at 45°C for 8 hours, centrifuge, filter, rinse the solids three times with deionized water, dry at 75°C, and cool naturally to form the acetamido-modified zeolite. 3) Prepare a 0.5 mol / L zinc acetate solution and soak the zeolite in it at a solid-to-liquid ratio of 1:7. Shake at 50°C for 13 hours, centrifuge, filter, rinse the solids three times with deionized water, dry at 70°C, and cool naturally to form the mixed organic-modified zeolite. After mixed organic modification, the specific surface area of ​​zeolite is increased, resulting in an increase in the ability of modified zeolite to adsorb heavy metals. The specific surface area of ​​mixed organic modified zeolite is 641.1m 2 / g.

[0043] Subsequently, the first-stage water inlet pump pumps the desulfurization wastewater into the ceramic microfiltration membrane system. The operating pressure is 0.11MPa, the filtration pore size is 0.2μm, the cross-flow velocity is 3.1m / s, and the flux is 83L / (m 2 h). After treatment with the microfiltration membrane, the desulfurization wastewater had a pH of 6.9, a conductivity of 16900 μS / cm, mercury ions of 0.01 mg / L, and lead ions of 0.3 mg / L.

[0044] The desulfurization wastewater is then discharged by the outlet pump or pumped into the desulfurization wastewater zero discharge system.

[0045] In summary, the present invention proposes a method for deep treatment of desulfurization wastewater for the first time, so the present invention belongs to a green and environmentally friendly production process system.

[0046] Of course, those skilled in the art should realize that the above embodiments are only used to illustrate the present invention and are not used to limit the present invention. As long as they are within the scope of the essential spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for removing mercury and lead from desulfurization wastewater in power plants, characterized in that: The steps include: (1) The desulfurization wastewater from the power plant enters a modified zeolite adsorption tower, which has an organic modified zeolite built in. The organic modified zeolite occupies 87-91% of the volume of the entire modified zeolite adsorption tower; The organic modified zeolite is prepared by soaking and cleaning natural zeolite in a calcium hydroxide solution, then soaking and centrifuging the zeolite in a 4-acetamido-aniline hydrochloride solution at a solid-liquid ratio of 1:12 to 17, and finally soaking and centrifuging the zeolite in a zinc acetate solution. (2) The effluent from the modified zeolite adsorption tower enters the ceramic microfiltration membrane system with an operating pressure of 0.11-0.14 MPa, a filtration pore size of 0.1-0.2 μm, a cross-flow velocity of 3.1-3.3 m / s, and a flux of 78-89 L / (m 2 h); (3) The effluent from the ceramic microfiltration membrane system is discharged or injected into the desulfurization wastewater zero discharge system.

2. A method for removing mercury and lead from desulfurization wastewater in a power plant according to claim 1, characterized in that: In step (1), the residence time of the desulfurized wastewater in the modified zeolite adsorption tower is 17 to 26 minutes.

3. The method for removing mercury and lead from desulfurization wastewater in a power plant according to claim 1, characterized in that: After passing through the mixed organic modified zeolite adsorption tower, the water quality of the desulfurization wastewater is 0.03-0.05 mg / L for mercury ions and 0.4-0.6 mg / L for lead ions.

4. The method for removing mercury and lead from desulfurization wastewater in a power plant according to claim 1, characterized in that: In step (1), the natural zeolite has a particle size of 0.1 to 0.2 mm and a specific surface area of ​​225.2 to 281.5 m 2 / g.

5. A method for removing mercury and lead from desulfurization wastewater in a power plant according to claim 1, characterized in that: In step (1), the concentration of the calcium hydroxide solution is 0.2-0.7 mol / L, and the zeolite is oscillated therein for 4-6 hours, during which the room temperature is maintained at 20-26° C., and then dried at 105° C. and cooled naturally.

6. A method for removing mercury and lead from desulfurization wastewater in a power plant according to claim 1, characterized in that: In step (1), the concentration of the 4-acetamido-aniline hydrochloride solution is 0.01 to 0.03 mol / L. The zeolite is immersed in the 4-acetamido-aniline hydrochloride solution and shaken at 45 to 55° C. for 8 to 12 hours. The mixture is centrifuged and filtered. The solid portion is rinsed 3 to 6 times with deionized water, dried at 75° C., and naturally cooled to form an acetamido-modified zeolite.

7. A method for removing mercury and lead from desulfurization wastewater in a power plant according to claim 1, characterized in that: The concentration of the zinc acetate solution is 0.5-0.8 mol / L, and the zeolite is immersed in the zinc acetate solution at a solid-liquid ratio of 1:7-12; the mixture is shaken at 50-65° C. for 13-16 hours, centrifuged, and filtered, and the solid portion is rinsed with deionized water 3-6 times, dried at 70° C., and naturally cooled to form a mixed organic modified zeolite.

8. The method for removing mercury and lead from desulfurization wastewater in a power plant according to claim 1, characterized in that: The specific surface area of ​​the organic modified zeolite is 633.2 to 679.6 m 2 / g.

9. The method for removing mercury and lead from desulfurization wastewater in a power plant according to claim 1, characterized in that: After treatment with microfiltration membrane, the desulfurization wastewater has a pH of 6.8-8.5, a conductivity of 15350-32180 μS / cm, mercury ions of 0.01-0.02 mg / L, and lead ions of 0.3-0.5 mg / L.

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