Coal-fired power plant strong brine treatment system and method

Abstract

The invention discloses a coal-fired power plant strong brine treatment system and method, and belongs to the technical field of wastewater treatment. In the invention, the water quality of the effluent of the regulating reservoir and the water quality of the inlet water of the reverse osmosis device are compared, and corresponding treatment is carried out according to condition judgment; desalting strong brine by using halophilic microorganisms, and returning desalted dilute brine to the pretreatment raw water tank for re-mixing treatment; under specific conditions, RO inlet water is subjected to catalytic oxidation treatment, continuous enrichment of organic matters in the system is controlled, pollution of the organic matters to an RO membrane is relieved, and the running stability of the system is improved; a bacteria-algae symbiotic system is established, a biological desalting system is stabilized, and the impact resistance and adaptability are improved. And the sludge obtained after biological desalination is subjected to atomization drying, and secondary solid waste is not generated.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a system and method for treating concentrated brine in a coal-fired power plant. Background Art

[0002] As an important source of electricity, coal-fired power plants occupy a prominent position in the global energy structure, but they also produce a large amount of high-salinity wastewater, including desulfurization wastewater, chemical water treatment process wastewater, ash flushing wastewater, circulating cooling system drainage, etc. These wastewaters contain high concentrations of suspended solids, heavy metals, sulfates, chloride ions and other pollutants, with complex components and great difficulty in treatment. With the increasingly stringent environmental regulations, the traditional three-unit treatment technology has been difficult to meet the new emission standards, and it is urgent to develop more efficient and environmentally friendly treatment technologies. In addition, the water volume of wastewater fluctuates greatly, which poses a challenge to the stability of the treatment system. The zero discharge target of high-salinity wastewater is a major test for existing technologies. It not only requires the treatment technology to completely remove pollutants, but also takes into account the economy and sustainability of the system. At the same time, the increasing scarcity of water resources also requires power plants to make more efforts in wastewater treatment and resource recovery. The improvement of public environmental awareness requires that wastewater treatment not only meet regulatory requirements, but also take into account social and environmental acceptability. Therefore, the treatment of high-salt wastewater from coal-fired power plants faces multiple challenges, including regulatory pressure, technical challenges, economic costs, and social responsibilities. It is necessary to comprehensively consider various factors and adopt innovative technologies and management measures to achieve stable, efficient, and economical treatment of wastewater.

[0003] The treatment technology of high-salinity wastewater from coal-fired power plants is an important part of the environmental protection work in the power industry. With the increasingly stringent environmental protection regulations, traditional treatment methods can no longer meet the current environmental protection requirements. Therefore, the industry continues to explore and apply new treatment technologies. Existing high-salinity wastewater treatment technologies mainly include pretreatment technologies such as chemical coagulation and sedimentation, membrane filtration, wastewater reduction technologies such as evaporation and membrane concentration, flue gas waste heat drying technology, rotary spray drying and other crystallization solidification technologies.

[0004] The treatment technology of high-salinity wastewater from coal-fired power plants is developing in a more efficient, environmentally friendly and economical direction. The selection of appropriate treatment technology requires comprehensive consideration of multiple factors such as wastewater quality characteristics, treatment costs, environmental protection requirements and economic feasibility. With the continuous tightening of environmental protection regulations and the improvement of public environmental awareness, future wastewater treatment technology will pay more attention to resource recovery and recycling, as well as energy conservation and emission reduction in the treatment process.

[0005] The zero-emission process route for high-salinity wastewater from traditional coal-fired power plants usually includes three main steps: pretreatment, membrane concentration and final solidification. Each step treats specific pollutants in the wastewater to achieve the goal of zero emissions.

[0006] In the pretreatment stage, the wastewater is first screened or precipitated to remove large suspended particles in the wastewater. The hardness and some heavy metals in the wastewater are then removed by double alkali chemical precipitation to protect the subsequent membrane system from damage. Next, the wastewater may pass through an adjusting tank to balance fluctuations in water quality and water volume to ensure the stable operation of subsequent treatment processes. In addition, a pH adjuster may need to be added to the adjusting tank to adjust the pH value of the wastewater to a range suitable for membrane treatment. Pretreatment may also include an oxidation step to further improve the treatability of the wastewater by adding oxidants to destroy refractory organic matter. To improve efficiency, pretreatment may also add ultrafiltration, microfiltration or ion adsorption resins.

[0007] The membrane concentration stage is the core of the entire process, usually using reverse osmosis (RO) or nanofiltration (NF) technology. Reverse osmosis membranes can effectively separate soluble salts and most organic matter in water, while nanofiltration membranes are mainly used for ions with a value of more than two, such as hardness ions, heavy metals, etc. Both technologies generally need to operate under high pressure. During the membrane concentration process, the wastewater is separated into two parts: one part is purified water that can be recycled; the other part is a concentrated liquid rich in pollutants that requires further treatment. The choice of membrane technology depends on the specific composition and treatment requirements of the wastewater. Sometimes multiple membrane technologies are used in combination to achieve more efficient pollutant removal.

[0008] The final solidification stage aims to convert the pollutants in the concentrate into a solid form for final disposal. Common solidification methods include evaporative crystallization and flue gas waste heat drying. Evaporative crystallization heats the concentrate to evaporate the water in it, leaving solid crystalline salts, which can be collected and recycled or safely disposed of according to their composition. Flue gas waste heat drying uses the heat in the flue gas of the power plant to evaporate the water in the concentrate and solidify the pollutants in fly ash or gypsum, thereby realizing the resource utilization of waste.

[0009] The advantage of the traditional zero-discharge process for wastewater from power plants lies in its efficient pollutant removal capability. However, the system investment and maintenance costs are high, and the cleaning and replacement of reagents and membranes are the main expenses. In addition, the treatment of the high-salt concentrate produced by membrane concentration is also a major challenge, and the most appropriate solidification technology needs to be selected in combination with specific environmental and economic conditions.

[0010] In general, the membrane power plant wastewater zero discharge process is a comprehensive solution that achieves efficient wastewater purification and resource utilization of pollutants through physical separation. With the continuous advancement of membrane technology and the improvement of environmental protection requirements, membrane technology is expected to play a greater role in the treatment of coal-fired power plant wastewater in the future.

[0011] Although the traditional power plant wastewater zero discharge process performs well in wastewater reuse and resource utilization, it also has some major defects and disadvantages.

[0012] The pretreatment stage is an important part of the membrane process, and its purpose is to remove suspended solids, colloidal particles and microorganisms in the wastewater to protect the membrane components from contamination and damage. However, due to the fluctuation of wastewater quality and quantity, the changes in the reagents and energy input for flocculation, sedimentation and organic matter removal are relatively lagging at this stage. Excessive reagents or untreated suspended solids and organic matter will affect the subsequent membrane concentration operation. In addition, after the wastewater is subsequently concentrated and returned to the desulfurization tower, the re-enrichment of organic matter and salt may affect the normal operation of the desulfurization tower.

[0013] In the membrane concentration stage, although membrane technology can effectively separate most pollutants in water, its separation effect on organic matter is poor. The treatment of membrane concentrated water with high salt and organic matter after concentration has always been a difficult problem.

[0014] In the final solidification stage, the secondary solid waste generated by crystallization has high storage and transportation costs, and the energy consumption required for drying is also high.

[0015] In summary, the traditional zero-discharge process for power plant wastewater has advantages in terms of treatment efficiency and resource utilization, but its economic benefits such as delayed changes in pretreatment dosing, difficulty in treating membrane concentrate, and energy consumption limit its wider application. In the future, through technological innovation and process optimization, it is expected to reduce the cost of reagent placement, improve its treatment efficiency and adaptability, and develop new membrane concentrate treatment processes, thereby promoting the application of membrane technology in the field of zero-discharge of power plant wastewater. Summary of the invention

[0016] The purpose of the present invention is to solve the problems of high reagent addition cost, difficult membrane concentrated water treatment, high operation and maintenance cost of wastewater treatment system in the zero-discharge treatment process of concentrated brine in traditional coal-fired power plants, and to provide a concentrated brine treatment system and method for coal-fired power plants.

[0017] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0018] A concentrated brine treatment system for a coal-fired power plant, the system comprising a regulating tank, a pretreatment raw water tank, a pretreatment device, a catalytic oxidation device, a reverse osmosis device, a biological desalination reactor, an ultraviolet sterilization device, and a spray drying device;

[0019] The regulating pool comprises a first water inlet, a regulating buffer zone, and a first water outlet;

[0020] The pre-treated raw water tank comprises a second water inlet, a mixing area, a reflux inlet, and a second water outlet;

[0021] The pretreatment device includes a third water inlet, a first drug inlet, a first drug distribution component, a first reaction zone, a clarification zone, a multi-media filtration component, an ultrafiltration component, and a third water outlet;

[0022] The catalytic oxidation device comprises a fourth water inlet, a second drug inlet, a second drug distribution component, a second reaction zone, and a fourth water outlet;

[0023] The reverse osmosis device comprises a fifth water inlet, a reverse osmosis membrane element, a reverse osmosis raw water tank, a produced water outlet, and a concentrated water outlet;

[0024] The biological desalination reactor comprises a sixth water inlet, a third drug inlet, a third drug distribution assembly, a third reaction zone, an aeration element, a lighting element, a reflux outlet, and a mud discharge outlet;

[0025] The ultraviolet sterilization device is an ultraviolet low-pressure mercury lamp with a wavelength of 253.7nm or an ultraviolet excimer lamp with a wavelength of 222nm, which is used to sterilize the sewage returned from the biological desalination reactor and send it back to the pretreatment raw water tank;

[0026] The spray drying device comprises a sludge inlet, an atomizing element and a drying element.

[0027] A method for treating concentrated brine using the above-mentioned concentrated brine treatment system of a coal-fired power plant, the method comprising the following steps:

[0028] (1) After the raw water to be treated is adjusted and buffered in water quality and quantity through the regulating tank, the hardness, heavy metals and suspended solids are removed through the pretreatment device, and the pretreated water meets the water inlet standard of the reverse osmosis device;

[0029] (2) Conduct TOC and TDS analysis on the effluent from the regulating tank and the influent from the reverse osmosis device respectively;

[0030] (3) When the RO inlet water TOC is less than 4*the effluent TOC of the regulating tank, and the RO inlet water TDS is less than 50000mg / L, the inlet water is directly sent to the RO device for treatment to obtain RO produced water and RO concentrated water. Among them, the RO produced water is sent to the recycled water tank as recycled water, and the RO concentrated water enters the biological desalination reactor;

[0031] When RO inlet water TOC>4* regulating tank outlet water TOC, and RO inlet water TDS<50000mg / L, the inlet water is first sent to the catalytic oxidation device to remove organic matter, and the outlet water treated by the catalytic oxidation device is sent to the reverse osmosis device for treatment to obtain RO produced water and RO concentrated water. Among them, the RO produced water is sent to the recycled water tank as recycled water, and the RO concentrated water enters the biological desalination reactor;

[0032] When the RO inlet water TDS>50000mg / L, it directly enters the RO device for treatment to obtain RO produced water and RO concentrated water. The RO produced water enters the recycled water tank, and the RO concentrated water enters the drying tower for evaporation and drying.

[0033] (4) Desalination treatment is carried out in a biological desalination reactor, nutrient solution and microorganisms are added into the biological desalination reactor, and aeration and intermittent lighting are applied, wherein the supernatant effluent of the biological desalination reactor is returned to the pretreatment raw water tank; the sludge generated by the biological desalination reactor is discharged regularly, and the discharged sludge is concentrated to obtain concentrated sludge, and the concentrated sludge is spray-dried in a drying tower, and the concentrated supernatant of the sludge is mixed with the supernatant of the biological desalination reactor, and then treated in an ultraviolet sterilization treatment unit, and then returned to the pretreatment unit for treatment.

[0034] Furthermore, in step (1), a precipitant, sodium hydroxide and sodium carbonate are added to the pretreatment device, wherein the precipitant is one of ferric sulfate, ferric chloride, PAC or PAM, and the precipitant dosage is 1-50 mg / L. Sodium hydroxide is used to adjust the pH to control the pH at 10.5-12, and the sodium carbonate dosage is 50-1000 mg / L.

[0035] Furthermore, in step (3), the catalytic oxidation device includes one or a combination of ozone catalytic oxidation, Fenton, electrocatalytic oxidation, and wet catalytic oxidation.

[0036] Furthermore, in step (3), the catalytic oxidation device adds a catalyst and an oxidant, the catalyst is one of manganese dioxide, copper oxide, iron oxide, titanium dioxide or zirconium oxide; the oxidant is one of ozone, potassium permanganate, hydrogen peroxide or potassium ferrate, wherein the dosage of manganese dioxide and copper oxide is 0.1-1g / L, the dosage of iron oxide is 0.1-3g / L, the dosage of ozone is 1-50mg / L, the dosage of potassium permanganate is 1-30mg / L, and the dosage of hydrogen peroxide is 50-1000mg / L.

[0037] Furthermore, in step (4), the nutrient solution is enriched with one or more of Cu, Zn, Co, Mn, Mo, Se, Ni, V, K, Cr, and S.

[0038] Furthermore, in step (4), the microorganisms include one or more of Nannochloropsis, Dunaliella salina, Scenedesmus obliquus, Scenedesmus acuminatus, Chlorella vulgaris, and Dunaliella, and one or more of Mobilobacterium, Acetobacter xylinum, Brevibacterium, and Coccus, and the solid content of the microorganisms is 2%-8%.

[0039] Furthermore, in step (4), the intermittent illumination is 8-14 hours of illumination followed by 8-14 hours of cessation of illumination; the illumination intensity is 1000-2000 lux.

[0040] Furthermore, in step (4), the aeration is air or carbon dioxide, or a combination of both.

[0041] Furthermore, in step (4), the outlet of the aeration element is used in one or more combinations within the third reaction zone or between the third reaction zone and the sixth water inlet.

[0042] The beneficial effects of the present invention over the prior art are as follows: the present invention provides a method for treating concentrated brine in a coal-fired power plant. After judging the key conditions of different scenarios, the industrial wastewater is desalted by specially screened microorganisms, and coupled with reverse osmosis, so that the entire system has a high recovery rate, low operating cost, and strong operating reliability. In addition, through the method provided by the present invention, the judgment of the key conditions of different scenarios can effectively improve the operating reliability and economy of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of a concentrated brine treatment system for a coal-fired power plant according to the present invention;

[0044] Figure 2 The present invention is a flow chart of the method for treating concentrated brine in a coal-fired power plant. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the protection scope of the present invention.

[0046] In the present invention, the water quality of the regulating tank outlet and the reverse osmosis device inlet is compared, and corresponding treatment is made according to the conditions; the concentrated brine is desalted by halophilic microorganisms, and the desalted dilute brine is returned to the pretreatment raw water tank for re-mixing treatment; under specific conditions, the RO inlet water is catalytically oxidized to control the continuous enrichment of organic matter in the system, alleviate the pollution of organic matter to the RO membrane, and improve the stability of the system operation; establish a bacterial-algae symbiotic system, stabilize the biological desalination system, and improve impact resistance and adaptability. The sludge discharged from the biological desalination is atomized and dried, and no secondary solid waste is generated.

[0047] The raw water to be treated enters the regulating buffer zone of the regulating tank through the first water inlet, and the water quality and quantity are adjusted and buffered. Then, it enters the pretreatment raw water tank through the first water outlet and the second water inlet. The pretreatment raw water tank contains the mixed water formed by the pretreated inlet water and the reflux after the treatment of the biological desalination reactor. Then, it enters the first reaction zone of the pretreatment device through the second water outlet and the third water inlet, and is mixed with the precipitant and hardness removal agent sent from the first drug distribution component connected to the first drug inlet to produce a precipitation reaction. Then, the wastewater enters the clarification zone, and after treatment, it passes through the multi-media filtration component and the ultrafiltration component to remove hardness, heavy metals and suspended solids, and then flows out from the third water outlet to obtain pretreated effluent, and enters the reverse osmosis device through the fifth water inlet. The TOC and TDS analysis and testing are performed on the effluent of the regulating tank and the inlet of the RO device. (1) When RO inlet water TOC>4*regulating tank effluent TOC, and RO inlet water TDS<50000mg / L, RO inlet water is first sent to the second reaction zone of the catalytic oxidation treatment device through the third water outlet and the fourth water inlet, mixed with the catalyst and oxidant sent from the second drug distribution assembly connected to the second drug inlet to undergo oxidation reaction to remove organic matter, and then sent to the reverse osmosis device through the fourth water outlet and the fifth water inlet for treatment; (2) When RO inlet water TOC<4*regulating tank effluent TOC, and RO inlet water TDS<50000mg / L, RO inlet water is directly sent to the reverse osmosis device through the third water outlet and the fifth water inlet for treatment; (3) When RO inlet water TDS>50000mg / L, RO inlet water is directly sent to the reverse osmosis device through the third water outlet and the fifth water inlet for treatment. The catalyst is one of manganese dioxide, titanium dioxide, copper oxide, iron oxide or zirconium oxide; the oxidant is one of ozone, potassium permanganate, hydrogen peroxide or potassium ferrate; the precipitant is one of ferric sulfate, ferric chloride, PAC or PAM, which is used to remove suspended solids; the first medicine dispensing component also needs to add some sodium hydroxide and sodium carbonate to remove hardness and heavy metal ions.

[0048] After the influent water enters the reverse osmosis device, it passes through the reverse osmosis membrane element to obtain product water and concentrated water. The product water flows out from the product water outlet into the reuse water tank, and the concentrated water flows out through the concentrated water outlet. When the RO inlet TDS>50000mg / L, the concentrated water is sent to the drying tower for evaporation and drying treatment; when the RO inlet TDS<50000mg / L, the concentrated water is sent to the biological desalination reactor through the sixth water inlet for desalination treatment, and the concentrated water undergoes biological reaction and desalination in the third reaction zone in an environment composed of the nutrient solution fed from the third drug distribution component connected to the third drug inlet, the intermittent light obtained from the lighting element, and the gas provided by the aeration element, and then flows out from the reflux outlet to obtain reflux water. The sludge of the biological desalination reactor flows out from the sludge discharge port regularly, enters the atomization element through the sludge inlet for atomization, and is subsequently spray-dried by the drying tower.

[0049] Embodiment 1:

[0050] A concentrated brine treatment system for a coal-fired power plant, the system comprising a regulating tank, a pretreatment raw water tank, a pretreatment device, a catalytic oxidation device, a reverse osmosis device, a biological desalination reactor, an ultraviolet sterilization device, and a spray drying device;

[0051] The regulating pool includes a first water inlet, a regulating buffer zone, and a first water outlet; the regulating buffer zone functions like a water storage tank and can regulate water quality and water quantity;

[0052] The pre-treated raw water tank comprises a second water inlet, a mixing area, a reflux inlet, and a second water outlet;

[0053] The pretreatment device includes a third water inlet, a first drug inlet, a first drug distribution component, a first reaction zone, a clarification zone, a multi-media filtration component, an ultrafiltration component, and a third water outlet; the pretreatment device is a collection of a drug addition sedimentation tank, a multi-media filter, and an ultrafiltration component, and includes three treatment units;

[0054] The catalytic oxidation device comprises a fourth water inlet, a second drug inlet, a second drug distribution component, a second reaction zone, and a fourth water outlet;

[0055] The reverse osmosis device comprises a fifth water inlet, a reverse osmosis membrane element, a reverse osmosis raw water tank, a produced water outlet, and a concentrated water outlet;

[0056] The biological desalination reactor comprises a sixth water inlet, a third drug inlet, a third drug distribution assembly, a third reaction zone, an aeration element, a lighting element, a reflux outlet, and a mud discharge outlet;

[0057] The ultraviolet sterilization device is an ultraviolet low-pressure mercury lamp with a wavelength of 253.7nm or an ultraviolet excimer lamp with a wavelength of 222nm, which is used to sterilize the sewage returned from the biological desalination reactor and send it back to the pretreatment raw water tank;

[0058] The spray drying device comprises a sludge inlet, an atomizing element and a drying element.

[0059] Embodiment 2:

[0060] A method for treating concentrated brine using the concentrated brine treatment system of a coal-fired power plant described in Example 1, the method comprising the following steps:

[0061] (1) After the raw water to be treated passes through the regulating tank to adjust the water quality and quantity, it is then passed through the pretreatment device to remove hardness, heavy metals and suspended solids. The pretreated water meets the water inlet standard of the reverse osmosis device. The role of the regulating tank in terms of water quality is to use the residence time of the regulating tank to evenly mix wastewater of different time periods and different components, prevent the occurrence of excessive differences in local water quality, and minimize the differences in water quality of each inlet.

[0062] (2) Conduct TOC and TDS analysis on the effluent from the regulating tank and the influent from the reverse osmosis device respectively;

[0063] (3) When the RO inlet water TOC is less than 4*the effluent TOC of the regulating tank, and the RO inlet water TDS is less than 50000mg / L, the inlet water is directly sent to the RO device for treatment to obtain RO produced water and RO concentrated water. Among them, the RO produced water is sent to the recycled water tank as recycled water, and the RO concentrated water enters the biological desalination reactor;

[0064] When RO inlet water TOC>4* regulating tank outlet water TOC, and RO inlet water TDS<50000mg / L, the inlet water is first sent to the catalytic oxidation device to remove organic matter, and the outlet water treated by the catalytic oxidation device is sent to the reverse osmosis device for treatment to obtain RO produced water and RO concentrated water. Among them, the RO produced water is sent to the recycled water tank as recycled water, and the RO concentrated water enters the biological desalination reactor;

[0065] When the RO inlet water TDS>50000mg / L, it directly enters the RO device for treatment to obtain RO produced water and RO concentrated water. The RO produced water enters the recycled water tank, and the RO concentrated water enters the drying tower for evaporation and drying.

[0066] (4) Desalination treatment is carried out in a biological desalination reactor, nutrient solution and microorganisms are added into the biological desalination reactor, and aeration and intermittent illumination are applied. Aeration can be continuous aeration or intermittent aeration, and the aeration volume in the wastewater can be maintained at 10-15L / h. The supernatant effluent of the biological desalination reactor is returned to the pretreatment raw water tank; the sludge generated by the biological desalination reactor is discharged regularly, and the discharged sludge is concentrated to obtain concentrated sludge. The concentrated sludge is spray-dried in a drying tower, and the concentrated supernatant of the sludge is mixed with the supernatant of the biological desalination reactor and then treated in an ultraviolet sterilization treatment unit, and then returned to the pretreatment unit for treatment.

[0067] In step (1), a precipitant, sodium hydroxide and sodium carbonate are added to the pretreatment device, wherein the precipitant is ferric sulfate and the precipitant dosage is 20 mg / L. Sodium hydroxide is used to adjust the pH to control the pH at 11 to 12, and the dosage of sodium carbonate is 100 to 200 mg / L.

[0068] In step (3), the catalytic oxidation device adds a catalyst and an oxidant, wherein the catalyst is manganese dioxide; the oxidant is hydrogen peroxide, wherein the addition amount of manganese dioxide is 0.1-1g / L, and the addition amount of hydrogen peroxide is 50-1000mg / L.

[0069] In step (4), the nutrient solution is rich in one or more of Cu, Zn, Co, Mn, Mo, Se, Ni, V, K, Cr, and S; the amount of nutrient solution added is generally between 0.01% and 3% of the volume of the wastewater, and is accurately added according to the growth conditions of the algae.

[0070] In step (4), the microorganisms include one or more of Nannochloropsis, Dunaliella salina, Scenedesmus obliquus, and one or more of Mobilobacterium and Acetobacter xylinum, and the solid content of the microorganisms is 2%-4%. Microalgae are salt-tolerant and can absorb and store salt, and the strains help the microorganisms to flocculate. The microorganisms grow, develop and reproduce in the wastewater, and the nutrient solution is also added to the wastewater.

[0071] In step (4), the intermittent illumination is to illuminate for 8-14 hours and then stop illuminating for 8-14 hours; the illumination intensity is 1000-1500 lux.

[0072] In step (4), the aeration is air.

[0073] In step (4), the outlet of the aeration element is in the third reaction zone or between the third reaction zone and the sixth water inlet, or a combination of the two. The atomization drying device includes a heating element to improve the dehydration of the sludge, and the heat source can be waste heat from a power plant.

[0074] Embodiment 3:

[0075] A method for treating concentrated brine using the concentrated brine treatment system of a coal-fired power plant described in Example 1, the method comprising the following steps:

[0076] (1) After the raw water to be treated passes through the regulating tank to adjust the water quality and quantity, it is then passed through the pretreatment device to remove hardness, heavy metals and suspended solids. The pretreated water meets the water inlet standard of the reverse osmosis device. The role of the regulating tank in terms of water quality is to use the residence time of the regulating tank to evenly mix wastewater of different time periods and different components, prevent the occurrence of excessive differences in local water quality, and minimize the differences in water quality of each inlet.

[0077] (2) Conduct TOC and TDS analysis on the effluent from the regulating tank and the influent from the reverse osmosis device;

[0078] (3) When the RO inlet water TOC is less than 4*the effluent TOC of the regulating tank, and the RO inlet water TDS is less than 50000mg / L, the inlet water is directly sent to the RO device for treatment to obtain RO produced water and RO concentrated water. Among them, the RO produced water is sent to the recycled water tank as recycled water, and the RO concentrated water enters the biological desalination reactor;

[0079] When RO inlet water TOC>4* regulating tank outlet water TOC, and RO inlet water TDS<50000mg / L, the inlet water is first sent to the catalytic oxidation device to remove organic matter, and the outlet water treated by the catalytic oxidation device is sent to the reverse osmosis device for treatment to obtain RO produced water and RO concentrated water. Among them, the RO produced water is sent to the recycled water tank as recycled water, and the RO concentrated water enters the biological desalination reactor;

[0080] When the RO inlet water TDS>50000mg / L, it directly enters the RO device for treatment to obtain RO produced water and RO concentrated water. The RO produced water enters the recycled water tank, and the RO concentrated water enters the drying tower for evaporation and drying.

[0081] (4) Desalination treatment is carried out in a biological desalination reactor, nutrient solution and microorganisms are added into the biological desalination reactor, and aeration and intermittent illumination are applied. Aeration can be continuous aeration or intermittent aeration, and the aeration volume in the wastewater can be maintained at 10-15L / h. The supernatant effluent of the biological desalination reactor is returned to the pretreatment raw water tank; the sludge generated by the biological desalination reactor is discharged regularly, and the discharged sludge is concentrated to obtain concentrated sludge. The concentrated sludge is spray-dried in a drying tower, and the concentrated supernatant of the sludge is mixed with the supernatant of the biological desalination reactor and then treated in an ultraviolet sterilization treatment unit, and then returned to the pretreatment unit for treatment.

[0082] In step (1), a precipitant, sodium hydroxide and sodium carbonate are added to the pretreatment device, wherein the precipitant is PAC, the precipitant dosage is 45-50 mg / L, sodium hydroxide is used to adjust the pH to control the pH at 11.5-12, and the sodium carbonate dosage is 500 mg / L.

[0083] In step (3), the catalytic oxidation device includes one or a combination of ozone catalytic oxidation, Fenton, electrocatalytic oxidation, and wet catalytic oxidation.

[0084] In step (3), the catalytic oxidation device adds a catalyst and an oxidant, wherein the catalyst is copper oxide; the oxidant is potassium permanganate, wherein the addition amount of copper oxide is 0.1-1 g / L, and the addition amount of potassium permanganate is 1-30 mg / L.

[0085] In step (4), the nutrient solution is rich in one or more of Cu, Zn, Co, Mn, Mo, Se, Ni, V, K, Cr, and S; the amount of nutrient solution added is generally between 8% and 1% of the volume of the wastewater, and the specific amount of nutrient solution added depends on the growth of the algae.

[0086] In step (4), the microorganisms include one or more of Chlorella vulgaris, Scenedesmus acuminatus, Chlorella vulgaris, Dunaliella, and one or more of Acetobacter xylinum, Brevibacterium, and Coccus, and the solid content of the microorganisms is 2%-8%. Microalgae are salt-tolerant and can absorb and store salt, and the strains help the microorganisms to flocculate. The microorganisms grow, develop, and reproduce in the wastewater, and the nutrient solution is also added to the wastewater.

[0087] In step (4), the intermittent illumination is to illuminate for 8-14 hours and then stop illuminating for 8-14 hours; the illumination intensity is 1000-2000 lux.

[0088] In step (4), the aeration is carbon dioxide.

[0089] In step (4), the outlet of the aeration element is in the third reaction zone or between the third reaction zone and the sixth water inlet, or a combination of the two. The atomization drying device includes a heating element to improve the dehydration of the sludge, and the heat source can be waste heat from a power plant.

[0090] The concentrated brine of the coal-fired power plant was treated using the system and method of Example 2. The specific treatment results are as follows:

[0091] The raw brine water volume of the coal-fired power plant is 70t / h, and the raw water quality is as follows:

[0092] project unit Detection value Turbidity NTU 94 TDS mg / L 18420 TOC mg / L 121 <![CDATA[Total hardness (calculated as CaCO 3 equivalent)]]> mg / L 426 <![CDATA[SiO 2 ]]> mg / L 52

[0093] First treatment

[0094] project unit Pre-treatment raw water tank Pre-treatment of effluent Reverse osmosis water Biological desalination effluent Turbidity NTU 94 0.3 0 (below the detection line) 5.8 TDS mg / L 18420 19230 821 34250 TOC mg / L 83 81 6 164 <![CDATA[Total hardness (calculated as CaCO 3 3)]]> mg / L 426 52 0.1 0.1 <![CDATA[SiO 2 ]]> mg / L 52 22 0.1 0.1

[0095] When RO inlet water TDS < 50000 mg / L, TOC < 4 * regulating tank outlet TOC

[0096] project unit Pre-treatment raw water tank Pre-treatment of effluent Reverse osmosis water Biological desalination effluent Turbidity NTU 90 0.4 0 (below the detection line) 4.6 TDS mg / L 25871 26423 947 38612 TOC mg / L 145 146 8 194 <![CDATA[Total hardness (calculated as CaCO 3 equivalent)]]> mg / L 382 54 0.2 0.1 SiO2 mg / L 59 24 0.1 0.1

[0097] When RO inlet water TDS<50000mg / L, TOC>4*TOC of regulating tank outlet water

[0098]

[0099] When RO inlet water TDS>50000mg / L

[0100] project unit Pre-treatment raw water tank Pre-treatment of effluent Reverse osmosis water Turbidity NTU 86 0.4 0 (below the detection line) TDS mg / L 54254 56740 1864 <![CDATA[Total hardness (calculated as CaCO 3 equivalent)]]> mg / L 512 61 0.4 <![CDATA[SiO 2 ]]> mg / L 55 26 0.1

Claims

1. A brine treatment system for a coal-fired power plant, characterized in that: The system includes a regulating tank, a pretreatment raw water tank, a pretreatment device, a catalytic oxidation device, a reverse osmosis device, a biological desalination reactor, an ultraviolet sterilization device, and a spray drying device; The regulating pool comprises a first water inlet, a regulating buffer zone, and a first water outlet; The pre-treated raw water tank comprises a second water inlet, a mixing area, a reflux inlet, and a second water outlet; The pretreatment device includes a third water inlet, a first drug inlet, a first drug distribution component, a first reaction zone, a clarification zone, a multi-media filtration component, an ultrafiltration component, and a third water outlet; The catalytic oxidation device comprises a fourth water inlet, a second drug inlet, a second drug distribution component, a second reaction zone, and a fourth water outlet; The reverse osmosis device comprises a fifth water inlet, a reverse osmosis membrane element, a reverse osmosis raw water tank, a produced water outlet, and a concentrated water outlet; The biological desalination reactor comprises a sixth water inlet, a third drug inlet, a third drug distribution assembly, a third reaction zone, an aeration element, a lighting element, a reflux outlet, and a mud discharge outlet; The ultraviolet sterilization device is an ultraviolet low-pressure mercury lamp with a wavelength of 253.7nm or an ultraviolet excimer lamp with a wavelength of 222nm, which is used to sterilize the sewage returned from the biological desalination reactor and send it back to the pretreatment raw water tank; The spray drying device comprises a sludge inlet, an atomizing element and a drying element.

2. A method for treating concentrated brine using the concentrated brine treatment system of a coal-fired power plant according to claim 1, characterized in that: The method comprises the following steps: (1) After the raw water to be treated is adjusted and buffered in water quality and quantity through the regulating tank, the hardness, heavy metals and suspended solids are removed through the pretreatment device, and the pretreated water meets the water inlet standard of the reverse osmosis device; (2) Conduct TOC and TDS analysis on the effluent from the regulating tank and the influent from the reverse osmosis device respectively; (3) When RO inlet water TOC < 4 * regulating tank outlet water TOC, and RO inlet water TDS <50000mg / L, the influent is directly sent to the RO device for treatment to obtain RO produced water and RO concentrated water, of which the RO produced water is sent to the recycled water tank as recycled water, and the RO concentrated water enters the biological desalination reactor; When RO inlet water TOC>4* regulating tank outlet water TOC, and RO inlet water TDS <50000mg / L, the influent is first sent to the catalytic oxidation device to remove organic matter, and the effluent treated by the catalytic oxidation device is sent to the reverse osmosis device for treatment to obtain RO produced water and RO concentrated water, among which the RO produced water is sent to the recycled water tank as recycled water, and the RO concentrated water enters the biological desalination reactor; When the RO inlet water TDS>50000mg / L, it directly enters the RO device for treatment to obtain RO produced water and RO concentrated water. The RO produced water enters the recycled water tank, and the RO concentrated water enters the drying tower for evaporation and drying. (4) Desalination treatment is carried out in a biological desalination reactor, nutrient solution and microorganisms are added into the biological desalination reactor, and aeration and intermittent lighting are applied, wherein the supernatant effluent of the biological desalination reactor is returned to the pretreatment raw water tank; the sludge generated by the biological desalination reactor is discharged regularly, and the discharged sludge is concentrated to obtain concentrated sludge, and the concentrated sludge is spray-dried in a drying tower, and the concentrated supernatant of the sludge is mixed with the supernatant of the biological desalination reactor, and then treated in an ultraviolet sterilization treatment unit, and then returned to the pretreatment unit for treatment.

3. A method for treating concentrated brine in a coal-fired power plant according to claim 2, characterized in that: In step (1), a precipitant, sodium hydroxide and sodium carbonate are added to the pretreatment device, wherein the precipitant is one of ferric sulfate, ferric chloride, PAC or PAM, and the precipitant dosage is 1-50 mg / L. Sodium hydroxide is used to adjust the pH to control the pH at 10.5-12, and the sodium carbonate dosage is 50-1000 mg / L.

4. A method for treating concentrated brine in a coal-fired power plant according to claim 2, characterized in that: In step (3), the catalytic oxidation device includes one or a combination of ozone catalytic oxidation, Fenton, electrocatalytic oxidation, and wet catalytic oxidation.

5. A method for treating concentrated brine in a coal-fired power plant according to claim 2 or 4, characterized in that: In step (3), the catalytic oxidation device adds a catalyst and an oxidant, wherein the catalyst is one of manganese dioxide, copper oxide, iron oxide, titanium dioxide or zirconium oxide; the oxidant is one of ozone, potassium permanganate, hydrogen peroxide or potassium ferrate, wherein the dosage of manganese dioxide and copper oxide is 0.1-1g / L, the dosage of iron oxide is 0.1-3g / L, the dosage of ozone is 1-50mg / L, the dosage of potassium permanganate is 1-30mg / L, and the dosage of hydrogen peroxide is 50-1000mg / L.

6. A method for treating concentrated brine in a coal-fired power plant according to claim 2, characterized in that: In step (4), the nutrient solution is rich in one or more of Cu, Zn, Co, Mn, Mo, Se, Ni, V, K, Cr, and S.

7. A method for treating concentrated brine in a coal-fired power plant according to claim 2, characterized in that: In step (4), the microorganisms include one or more of Nannochloropsis, Dunaliella salina, Scenedesmus obliquus, Scenedesmus acuminatus, Chlorella vulgaris, and Dunaliella, and one or more of Mobilobacterium, Acetobacter xylinum, Brevibacterium, and Coccus, and the solid content of the microorganisms is 2%-8%.

8. A method for treating concentrated brine in a coal-fired power plant according to claim 2, characterized in that: In step (4), the intermittent illumination is to illuminate for 8-14 hours and then stop illuminating for 8-14 hours; the illumination intensity is 1000-2000 lux.

9. A method for treating concentrated brine in a coal-fired power plant according to claim 2, characterized in that: In step (4), the aeration is air or carbon dioxide, or a combination of both.

10. A method for treating concentrated brine in a coal-fired power plant according to claim 2, characterized in that: In step (4), the outlet of the aeration element is in the third reaction zone or between the third reaction zone and the sixth water inlet, or in combination thereof.

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