A method and system for deep impurity removal of coking concentrated brine

Abstract

The application discloses a coking concentrated brine deep impurity removal method and system, comprising the following processing steps: the coking concentrated brine is subjected to 'defluorination and hardness removal precipitation + ceramic membrane filtration + enhanced defluorination + multistage advanced oxidation' treatment to obtain deep impurity removal effluent. The processing method and the processing system can effectively remove impurities (fluoride, calcium and magnesium ions, organic matter, ammonia nitrogen and the like) in water, solve the problems of incomplete impurity removal, low efficiency and high processing cost of the existing coking concentrated brine pretreatment, can guarantee stable operation of subsequent deep treatment (membrane concentration, salt separation and evaporation crystallization treatment), improve the final salt quality, and have the advantages of high efficiency, energy saving, environmental protection, safety and wide application prospect.

Description

Technical Field

[0001] This invention relates to the technical field of wastewater treatment, specifically to a method and system for deep purification of coking brine. Background Technology

[0002] The iron and steel industry encompasses a series of production processes, including sintering, coking, ironmaking, steelmaking, and rolling, and is one of the most resource- and energy-intensive industries. Coking wastewater originates from the initial cooling of coke oven gas, production water used in the coking process, and steam condensation wastewater. It is recognized both domestically and internationally as high-concentration, recalcitrant, toxic, and harmful organic wastewater. After phenol removal, ammonia stripping, biochemical treatment, and reverse osmosis reuse, a large amount of high-salt coking wastewater, i.e., concentrated coking brine, will be generated.

[0003] This type of wastewater has a highly complex composition, generally exhibiting the following characteristics: firstly, high salinity, with TDS levels typically exceeding 20,000 mg / L; secondly, complex composition, containing recalcitrant organic matter, ammonia nitrogen, phenols, cyanides, fluoride, etc.; and thirdly, high fluoride content, usually exceeding 100 mg / L. Previously, the treatment of concentrated brine in coking plants primarily relied on internal processes such as blast furnace slag flushing, steelmaking slag curing, and sintering batching. However, with the increasingly severe water resource situation and stricter environmental requirements for wastewater treatment, the government has successively introduced relevant water conservation and emission reduction policies. How to economically and effectively treat concentrated brine has become a key aspect of achieving zero discharge of coking production wastewater.

[0004] Currently, the technological approaches being explored in the coking industry mainly focus on membrane separation and evaporation crystallization, but these approaches also present numerous challenges.

[0005] 1. Initially, lime and defluorinating agents were added to remove fluoride from the coking brine, reducing the fluoride content to 10 mg / L. However, with long-term operation, calcium fluoride gradually clogged the membrane components or fluoride ions corroded and damaged the evaporator. When the fluoride ion concentration in the water is below 10 mg / L, to ensure long-term benefits and reduce the fluoride content even further, even below 1 ppm, larger doses of lime, compound defluorinating agents, and coagulants need to be added at the front end. This not only increases the cost of the chemicals but also leads to excessive defluorinating agents or coagulants and incompletely settled flocs polluting subsequent systems, creating an economic burden for the company and resulting in more harm than good. At this point, adsorption methods show a clear advantage.

[0006] 2. Coking brine is a high-salt wastewater system. When using ozone oxidation technology, the ozone has low solubility in the wastewater due to its high salt content, resulting in very low oxidation efficiency and failure to achieve the expected oxidation effect. Moreover, most of the COD in the wastewater consists of recalcitrant organic matter. Long-term operation will cause serious organic pollution to the subsequent membrane system, increase the frequency of backwashing and cleaning, reduce production efficiency, and increase operating costs.

[0007] 3. Due to the unsatisfactory removal effect of deep cleaning on pollutants such as COD, calcium and magnesium ions, and fluoride ions, scaling occurs in the evaporation system, and the mother liquor and residue often form hazardous waste salts, which cannot be effectively extracted and utilized, resulting in resource waste.

[0008] Therefore, in the treatment of coking brine, the key to deep impurity removal is to remove pollutants such as recalcitrant organic matter, ammonia nitrogen, fluoride ions, and calcium and magnesium ions, and to reduce the concentration of COD, ammonia nitrogen, and fluoride ions as much as possible. This lays the foundation for the full extraction and resource utilization of salts in subsequent deep treatment, and ensures the long-term stable operation of subsequent membrane systems or evaporation systems. This reduces the environmental and economic pressure on relevant enterprises, and ultimately achieves the goals of reducing the volume of coking wastewater, resource-based treatment, and zero discharge. Summary of the Invention

[0009] The purpose of this invention is to address the aforementioned problems by providing a comprehensive treatment method and system for coking brine, specifically targeting the deep removal of impurities from coking brine through methods such as coagulation sedimentation, adsorption exchange, and oxidative degradation. This method efficiently removes organic pollutants, ammonia nitrogen, fluorides, calcium and magnesium hardness, suspended solids, and other contaminants from the brine, laying the foundation for subsequent salt separation and improved salt quality. It overcomes the industry bottlenecks of low treatment efficiency, high treatment costs, and the inability to utilize salt resources in existing coking brine treatment systems, demonstrating the significant importance of energy conservation and emission reduction.

[0010] The technical solution adopted in this invention is as follows:

[0011] This invention discloses a method for deep purification of coking brine, comprising a defluorination and hardening precipitation unit, a ceramic membrane filtration unit, an enhanced defluorination unit, a heterogeneous Fenton oxidation unit, and an ultraviolet-enhanced electrolytic oxidation unit. The method for deep purification of coking brine includes the following processing steps:

[0012] The coking brine enters the defluorination and hardening precipitation unit. The pH of the coking brine is adjusted to 9-12 by passing sodium hydroxide solution. Fluorides, calcium and magnesium hardness and suspended solids are removed by the defluorination and hardening compound agent, resulting in the supernatant and sludge precipitate after defluorination and hardening. The supernatant enters the next treatment step.

[0013] S2: The supernatant enters the ceramic membrane filtration unit to remove suspended solids and colloidal substances from the supernatant, thus obtaining the permeate;

[0014] S3: The pH of the permeate is adjusted to 6-10 by adding sulfuric acid, and then the fluoride in the permeate is removed by the enhanced defluorination unit to obtain adsorbed effluent;

[0015] The enhanced defluorination unit includes a fluoride adsorption resin, which, through adsorption and exchange, reduces the fluoride content in the coking brine to less than 1 ppm.

[0016] S4: The adsorption effluent from coking concentrated brine is passed through a sulfuric acid solution, the pH of which is adjusted to 4-8, and then enters a heterogeneous Fenton oxidation unit. It is treated with air aeration and Fenton catalyst to remove COD from the solution and obtain Fenton oxidized effluent.

[0017] S5: The Fenton oxidation effluent enters the UV-enhanced electrolytic oxidation unit, which electrolytically oxidizes the Fenton oxidation effluent to achieve the conditions for deep treatment of influent.

[0018] The UV-enhanced electrolytic oxidation unit includes a UV-enhanced electrolytic oxidation device, which includes a UV lamp and electrodes, used to degrade ammonia nitrogen and residual COD in the water to obtain electrolytically oxidized effluent, completing the deep impurity removal of coking brine. The electrolytically oxidized effluent is then subjected to further deep treatment.

[0019] Further, in step S1, fluorides, calcium and magnesium hardness substances, and suspended solids in the coking brine are removed by adding a defluorination and hardening composite agent and a flocculant. The defluorination and hardening composite agent includes one or more of calcium chloride, sodium polyacrylate, and 2-methyl-8-hydroxyquinoline. The flocculant is polyaluminum chloride and polyacrylamide. The mass ratio of the defluorination and hardening composite agent to polyaluminum chloride and polyacrylamide is 40-50:20-30:1. The dosage of the defluorination and hardening composite agent is 300-600 mg / L, the dosage of polyaluminum chloride is 10-50 mg / L, and the dosage of polyacrylamide is 1-5 mg / L. After the defluorination and hardening precipitation treatment, the supernatant and sludge precipitate are obtained. The precipitated sludge is dewatered and transported off-site, and the supernatant enters the treatment step S2.

[0020] Further, in step S2, the ceramic membrane is an organic-inorganic composite ceramic membrane, the membrane module is in the form of hollow fiber bundles, the membrane pore size is 20-80 nm, and the ceramic membrane includes polytetrafluoroethylene, alumina, silicon dioxide, and diphenylamine, wherein the mass ratio of polytetrafluoroethylene, alumina, silicon dioxide, and diphenylamine is 120-180:1-3:1-5:1.

[0021] Furthermore, the tensile strength of the membrane fiber in the membrane module is 500-1000 N / m. 2 It has a pH tolerance range of 1-14, an applicable temperature range of 0-60℃, can tolerate sodium hypochlorite content of 10%, suspended solids of 3%, and oil content of 5000 mg / L.

[0022] Furthermore, in step S3, the fluorine adsorption resin adopts a static adsorption method, with an adsorption time of 2-4 hours. After adsorption saturation, the fluorine adsorption resin is regenerated using a regenerator, and the resulting regenerated liquid is returned to the fluorine removal and hardening precipitation unit for further treatment.

[0023] The fluorine adsorption resin is a macroporous polystyrene-divinylbenzenesulfonic acid chelating resin loaded with metallic aluminum. The preparation method of the chelating resin is to use polystyrene-divinylbenzenesulfonic acid resin as a skeleton carrier, immerse the skeleton carrier in aluminum sulfate solution and shake for 30-60 minutes, rinse with pure water 2-3 times after shaking, and then dry in an oven to obtain macroporous polystyrene-divinylbenzenesulfonic acid chelating resin loaded with metallic aluminum.

[0024] Furthermore, the concentration of the aluminum sulfate solution is 0.5-1.0 mol / L, the shaking reaction time is 12-24 h, the reaction temperature is 25-30 °C, and the aluminum metal loading rate is 50-60%; the drying time is 1-4 h, and the drying temperature is 50-60 °C.

[0025] Furthermore, the regenerant is an aluminum chloride solution with a concentration of 0.25-0.5 mol / L, the regeneration method is countercurrent regeneration, the countercurrent flow rate is 2-4 BV / h, and the regeneration time is 0.5-1.0h.

[0026] Furthermore, in step S4, air aeration is used, with an aeration intensity of 0.2-0.6 m. 3 / h, aeration time is 2-4h;

[0027] Furthermore, the Fenton catalyst is a catalyst in which iron, copper, and manganese metals are supported on an activated carbon carrier, wherein the molar ratio of iron, copper, and manganese is 1:0.8-1:0.1. The Fenton catalyst is spherical, columnar, or irregularly rhomboid in shape, with a particle size of 2-8 mm and a filling rate of 40-60%. It is a yellowish-brown opaque spherical solid with a particle size of 1-5 mm.

[0028] Further, in step S5, the UV-enhanced electrolytic oxidation unit includes a UV-enhanced electrolytic oxidation device, which includes a UV lamp and electrodes. The UV lamp is a high-pressure mercury UV lamp with a wavelength range of 350-450 nm and an irradiation intensity of 200-400 W / m². 2 The UV lamp irradiation time is 30-60 minutes; the electrode current density is 50-200 A / m. 2 The electrode is energized for 30-60 minutes.

[0029] Furthermore, the ultraviolet lamps and electrodes in the ultraviolet-enhanced electrolytic oxidation device are arranged in a grid manner, with the ultraviolet lamp area at the top of the device and the electrode area at the bottom. The Fenton oxidation effluent enters the ultraviolet-enhanced electrolytic oxidation device, is first irradiated by the ultraviolet lamp, and then enters the electrode area for electrolytic oxidation. The electrode is a double-layer cylindrical electrode with an inner anode and an outer cathode.

[0030] This invention discloses a deep impurity removal system for coking brine, comprising:

[0031] The defluorination and hardening precipitation unit allows coking brine to enter the impurity removal system through its input end, and its output end is connected to the ceramic membrane filtration unit. The defluorination and hardening unit is equipped with a device for adding defluorination and hardening composite agents and flocculants. The defluorination and hardening composite agents and flocculants are used to remove fluorides, calcium and magnesium hardening substances and suspended solids from the coking brine.

[0032] The ceramic membrane filtration unit is connected to the enhanced defluorination unit at its output end. The ceramic membrane filtration unit is used to filter suspended solids and colloidal substances in coking brine.

[0033] An enhanced defluorination unit is provided, the output of which is connected to a heterogeneous Fenton oxidation unit. The enhanced defluorination unit is equipped with a defluorination resin tank filled with fluorine adsorption resin, which is used to defluorinate the liquid that has been filtered by the ceramic membrane filtration unit.

[0034] The heterogeneous Fenton oxidation unit is connected to the UV-enhanced electrolytic oxidation unit. The heterogeneous Fenton oxidation unit is used to perform Fenton oxidation treatment on liquids that have been defluorinated by the enhanced defluorination unit.

[0035] The ultraviolet-enhanced electrolytic oxidation unit includes an ultraviolet-enhanced electrolytic oxidation device, which is used to electrolytically oxidize the liquid that has been treated by the heterogeneous Fenton oxidation unit. The output end of the ultraviolet-enhanced electrolytic oxidation unit is connected to the water outlet tank, and the treated coking brine enters the water outlet tank for further treatment.

[0036] The technical effects of this invention are as follows:

[0037] This invention provides a method and system for deep purification of coking brine, which efficiently removes organic pollutants, ammonia nitrogen, fluoride, calcium and magnesium hardness, suspended solids and other pollutants from the brine, laying the foundation for subsequent salt separation and improving salt quality. It solves the industry bottleneck problems of low efficiency, high cost and inability to utilize salt in water resources in existing coking brine treatment.

[0038] Specifically as follows:

[0039] 1. Existing wastewater defluoridation and hardness removal technologies generally involve adding lime, calcium chloride, sodium carbonate, polyaluminum chloride, or polyacrylamide to remove pollutants such as fluoride and calcium and magnesium hardness from coking brine. This method can only reduce the fluoride content to 10-20 mg / L and the calcium and magnesium hardness to 20-100 mg / L. To further reduce the fluoride content, larger doses of reagents are usually required, ultimately producing a large amount of sludge. This not only increases the cost of reagents but also leads to excessive defluoridating agents or coagulants and incompletely settled flocs polluting subsequent systems. This invention employs a composite agent composed of one or more of calcium chloride, sodium polyacrylate, and 2-methyl-8-hydroxyquinoline, along with a flocculant. Calcium chloride readily combines with fluoride ions to form calcium fluoride precipitate; sodium polyacrylate readily cross-links with divalent metal ions (such as calcium and magnesium) to form gel precipitation; and 2-methyl-8-hydroxyquinoline readily forms chelate precipitates with calcium and magnesium ions under alkaline conditions. This creates a reaction system with multiple precipitates. In this system, co-precipitation occurs between the precipitates. Under the action of the flocculant, the co-precipitation effect increases dramatically, resulting in faster and more thorough precipitation of fluoride and calcium / magnesium. The hardness in the effluent is less than 20 mg / L, and the fluoride is less than 5 mg / L. Compared with conventional technologies, the effluent quality is better, and the dosage of the agent is smaller, the sludge production is less, and the operating cost is lower.

[0040] 2. This invention enhances fluoride removal by utilizing a chelating resin with fluoride-selective functional groups, specifically a macroporous polystyrene-divinylbenzenesulfonic acid chelating resin loaded with metallic aluminum. When low-fluoride wastewater enters the resin, the metallic aluminum loaded on the resin combines with fluoride ions to form a complex, thereby removing fluoride from the water. Simultaneously, the resin, having adsorbed fluoride ions, can be recycled after regeneration. During the adsorption process, the resin only adsorbs fluoride ions and is unaffected by sulfate ions or Cl-. - Due to the influence of anions, the fluoride in the effluent is consistently reduced to below 1 ppm. This not only avoids the need to add large amounts of lime or other defluoridating agents, resulting in excessively high agent costs, but also achieves a low-cost deep defluorination effect. Furthermore, it significantly reduces the risk of scaling or corrosion when the effluent enters subsequent membrane treatment or evaporation treatment.

[0041] 3. Existing technologies using homogeneous Fenton reaction systems have strict pH requirements, requiring operation at pH=3, which increases the cost of acid-base adjustment reagents, easily forms iron sludge, produces large amounts of sludge, and causes secondary pollution. This invention employs a heterogeneous Fenton oxidation device, using air as the oxidant. Under the action of a catalyst, hydroxyl radicals, oxygen radicals, and other oxidizing substances are generated, decomposing organic matter. The catalyst is a catalyst with iron and other metals supported on a solid carrier, replacing reagents such as ferrous sulfate and hydrogen peroxide, forming an internal FFFⅢF / FFFⅢF cycle. This eliminates iron sludge production, has a wide applicable pH range, high oxidation efficiency, and reusable catalyst, achieving highly efficient COD reduction without sludge production, avoiding membrane fouling, and simultaneously reducing reagent and sludge treatment costs.

[0042] 4. Coking brine contains various organic pollutants, such as phenols, anilines, quinolines, nitrogen-containing heterocyclic compounds, and long-chain hydrocarbons. Except for phenols, most of these are recalcitrant organic compounds. When using a heterogeneous Fenton oxidation unit, the system's redox potential typically only reaches 200-400 mV. Only easily degradable organic compounds can be oxidized and degraded, such as quinones, which are the intermediate products of phenol oxidation. However, for quinones and other recalcitrant organic compounds to undergo further complete oxidation and decomposition, a higher oxidation potential (at least 400 mV) is required. Clearly, the heterogeneous Fenton oxidation unit system alone cannot meet these requirements. Therefore, by setting up an ultraviolet-enhanced electrolytic oxidation unit after the heterogeneous Fenton oxidation unit for electrolytic oxidation treatment, the electrolytic oxidation process not only... It directly or indirectly generates a large number of hydroxyl radicals and hypochlorous acid. Furthermore, due to the high concentration of chloride salts in the concentrated brine, under ultraviolet radiation, it induces the generation of even more active chlorine radicals such as ClO2· and ClO·, as well as hydroxyl radicals, significantly improving oxidation efficiency. This is because the oxidation potential of these free radicals is much higher than the standard oxidation potential (1.5-1.8V) of most recalcitrant organic matter, completely oxidizing the residual organic matter in the effluent from the heterogeneous Fenton oxidation unit into CO2 and water. Additionally, the electrolytic oxidation process generates ClO2·... - Residual chlorine substances such as HClO, ClO2·, and ClO· can oxidize ammonia nitrogen to produce N2 and water, achieving the purpose of simultaneously removing organic matter and ammonia nitrogen. Moreover, neither the heterogeneous Fenton oxidation unit nor the ultraviolet-enhanced electrolytic oxidation unit produces sludge, thus avoiding secondary pollution to the environment. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the deep impurity removal method for coking concentrated brine of the present invention;

[0044] Figure 2 This is a schematic diagram of the ultraviolet-enhanced electrolytic oxidation unit in the deep impurity removal system for coking concentrated brine of the present invention;

[0045] Figure 3 This is a schematic diagram of the adsorption process of the fluorine adsorption resin of the present invention;

[0046] In the diagram: 1-UV lamp, 2-electrode. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings.

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0049] The data used in this embodiment is a preferred solution, but it is not intended to limit the present invention.

[0050] Example

[0051] like Figure 1-3 As shown, this embodiment provides a deep impurity removal system for coking brine, including:

[0052] The defluorination and hardening precipitation unit allows coking brine to enter the impurity removal system through its input end, and its output end is connected to the ceramic membrane filtration unit. The defluorination and hardening unit is equipped with a device for adding defluorination and hardening composite agents and flocculants. The defluorination and hardening composite agents and flocculants are used to remove fluorides, calcium and magnesium hardening substances and suspended solids from the coking brine.

[0053] The ceramic membrane filtration unit is connected to the enhanced defluorination unit at its output end. The ceramic membrane filtration unit is used to filter suspended solids and colloidal substances in coking brine.

[0054] An enhanced defluorination unit is provided, the output of which is connected to a heterogeneous Fenton oxidation unit. The enhanced defluorination unit is equipped with a defluorination resin tank filled with fluorine adsorption resin, which is used to defluorinate the liquid that has been filtered by the ceramic membrane filtration unit.

[0055] The heterogeneous Fenton oxidation unit is connected to the UV-enhanced electrolytic oxidation unit. The heterogeneous Fenton oxidation unit is used to perform Fenton oxidation treatment on liquids that have been defluorinated by the enhanced defluorination unit.

[0056] The ultraviolet-enhanced electrolytic oxidation unit includes an ultraviolet-enhanced electrolytic oxidation device, which is used to electrolytically oxidize the liquid that has been treated by the heterogeneous Fenton oxidation unit. The output end of the ultraviolet-enhanced electrolytic oxidation unit is connected to the water outlet tank, and the treated coking brine enters the water outlet tank for further treatment.

[0057] In this embodiment, the processing system includes a multi-stage advanced oxidation processing unit, such as... Figure 1 As shown, it includes a heterogeneous Fenton oxidation unit. Existing technologies use a homogeneous Fenton reaction system, which has strict pH requirements, must be carried out under pH=3 conditions, increases the cost of acid-base adjustment reagents, easily forms iron sludge, produces a large amount of sludge, and causes secondary pollution.

[0058] In this embodiment, a heterogeneous Fenton oxidation device is employed, in which iron and other metals are loaded onto a solid support to act as a catalyst, replacing reagents such as ferrous sulfate and hydrogen peroxide. This forms an internal FFFⅢF / FFFⅢF cycle, which features a wide applicable pH range, reusable catalyst, high oxidant utilization, and high oxidation efficiency. Using oxygen from the air as the oxidant source, hydroxyl radicals and oxygen radicals are generated under the action of the catalyst, decomposing organic matter. This not only achieves efficient COD reduction but also avoids sludge production, preventing membrane fouling, and simultaneously reducing reagent and sludge treatment costs.

[0059] This embodiment includes an ultraviolet-enhanced electrolytic oxidation unit, which includes an ultraviolet-enhanced electrolytic oxidation device. The device includes an ultraviolet lamp and electrodes, such as... Figure 2 As shown, the UV lamps and electrodes are arranged in a compartmentalized manner, with the UV lamp area at the top and the electrode area at the bottom. The Fenton oxidation effluent enters the UV-enhanced electrolytic oxidation device, where it is first irradiated by the UV lamps before entering the electrode area for electrolytic oxidation.

[0060] In terms of the electrolytic oxidation process alone, the electrolytic oxidation reaction itself will directly or indirectly oxidize and generate a large number of hydroxyl radicals and hypochlorous acid, because the concentrated brine contains a high concentration of chloride salts.

[0061] In this embodiment, under ultraviolet radiation, more active chlorine radicals and hydroxyl radicals such as ClO2· and ClO· are induced to be generated. The oxidation potential of these strong oxidizing substances is not only higher than that of recalcitrant organic matter, but also helps to oxidize the organic matter that was not completely degraded. Moreover, these oxidizing substances have a synergistic oxidation effect with each other, which can more efficiently degrade recalcitrant organic matter into small molecules, or directly mineralize it into CO2 and water, and oxidize ammonia nitrogen to generate N2 and water without producing secondary pollution.

[0062] The water quality of a certain coking brine treated using the above-mentioned deep impurity removal system for coking brine is shown in Table 1 below:

[0063] Table 1. Water quality indicators of concentrated brine from a coking plant.

[0064]

[0065] like Figure 1As shown, this embodiment provides a method for deep purification of coking brine. The method employs a combination of a "fluoride and hardening precipitate removal unit + ceramic membrane filtration unit + enhanced fluoride removal unit + heterogeneous Fenton oxidation unit + UV-enhanced electrolytic oxidation unit" to treat the aforementioned coking brine. Specifically, the method includes the following steps:

[0066] Step 1: The coking brine enters the defluorination and hardening precipitation unit. The pH of the coking brine is adjusted to 11.5 using sodium hydroxide solution. Then, it undergoes defluorination and hardening treatment using a composite defluorination and hardening agent. The composite defluorination and hardening agent is composed of calcium chloride, sodium polyacrylate, and 2-methyl-8-hydroxyquinoline. The dosage of the composite agent is 370 mg / L, the dosage of polyaluminum chloride is 20 mg / L, and the dosage of polyacrylamide is 1.5 mg / L. After the defluorination and hardening precipitation treatment, the supernatant and sludge precipitate are obtained. The precipitated sludge is packaged and transported, while the supernatant enters the treatment step S2.

[0067] Step 2: The supernatant enters the ceramic membrane filtration unit to remove the remaining suspended solids and colloidal substances, and the permeate is obtained.

[0068] Step 3: The permeate from the ceramic membrane enters the enhanced defluorination unit to further remove the remaining fluoride, resulting in adsorbed effluent;

[0069] Step 4: The adsorbed water is adjusted to pH 6.5 with sulfuric acid solution and then enters the heterogeneous Fenton oxidation unit, where air aeration is used at an aeration intensity of 0.35 m³ / h. 3 / h, aeration time is 4h; Fenton catalyst is spherical, columnar or irregular rhomboid in shape, with a particle size of 2-8mm and a filling rate of 50%; it degrades COD in water to obtain Fenton oxidized effluent;

[0070] Step 5: The Fenton oxidation effluent enters the UV-enhanced electrolytic oxidation unit, and then into the UV-enhanced electrolytic oxidation device. The UV lamp irradiation intensity is 240W / m². 2 The UV lamp irradiation time was 30 minutes; the electrode current density was 100 A / m. 2 The electrode is energized for 30 minutes to degrade ammonia nitrogen and residual COD in the water, resulting in electrolytic oxidation effluent, which is deep impurity removal effluent. The deep impurity removal process is now complete, and the electrolytic oxidation effluent awaits further treatment.

[0071] Table 2 shows the effluent water quality of each treatment unit in the embodiments.

[0072]

[0073] Table 2 shows that after the deep purification method for coking brine, the COD in the effluent decreased to 17 mg / L, and the ammonia nitrogen concentration decreased to 1.0 mg / L; F - The concentration was reduced to 0.2 mg / L, which is less than 1 mg / L and far below the requirement of <10 mg / L for fluoride in the Integrated Wastewater Discharge Standard (GB8978-1996).

[0074] This embodiment improves upon the above method, specifically including comparative examples 1-3.

[0075] Comparative Example 1

[0076] Comparative Example 1 was conducted under the same conditions and procedures as the above treatment method. The difference was that in step one, lime, calcium chloride, and sodium carbonate were added to the defluorination and hardening precipitation unit. The dosage of lime was 720 mg / L, the dosage of calcium chloride was 560 mg / L, and the dosage of sodium carbonate was 440 mg / L. The dosage of polyaluminum chloride was 20 mg / L, and the dosage of polyacrylamide was 1.5 mg / L.

[0077] In Comparative Example 1, unlike Step 3, no enhanced fluoride removal resin was used, and the ceramic membrane permeate directly entered the oxidation unit; in Example 3, a macroporous polystyrene-divinylbenzenesulfonic acid chelating resin loaded with metallic aluminum was added.

[0078] Table 3 Comparison between the Examples and Comparative Example 1

[0079]

[0080] As shown in Table 3, the embodiment reduced the amount of defluoridation and hardening agents used in the defluorination and hardening precipitation unit, which not only reduced operating costs but also effectively reduced the risk of fouling subsequent membrane systems. In contrast, Comparative Example 1 had a large dosage of each agent and a large sludge production. Moreover, compared to Comparative Example 1, the effluent from the embodiment had a lower F content. - The concentration (0.2 mg / L) is much lower than that of the effluent in Comparative Example 1. - The concentration (15 mg / L) of calcium and magnesium ions in the effluent was much lower than that in Comparative Example 1, indicating that the effluent quality of the embodiment was better.

[0081] Comparative Example 2

[0082] Comparative Example 2 had the same conditions and operations as the above treatment method, except that in step four, a traditional Fenton oxidation device was used, and the dosage of 5% ferrous sulfate heptahydrate solution in the device was 20 mL / L, and the dosage of 30% hydrogen peroxide was 4 mL / L.

[0083] Table 4 Comparison of water quality between Example 1 and Comparative Example 2

[0084]

[0085] As shown in Table 4, comparing the examples with Comparative Example 2, the use of ferrous sulfate and hydrogen peroxide was reduced, thus lowering the cost of the reagents. Furthermore, after treatment using the methods described in the examples, the COD removal rate increased by 25% compared to Comparative Example 2, demonstrating higher oxidation efficiency and the ability to remove more organic pollutants. Therefore, the examples not only demonstrate the beneficial effects achievable by the present invention but also highlight its essential characteristics.

[0086] Comparative Example 3

[0087] Comparative Example 3 had the same conditions and operations as the above treatment method, except that in step five, no ultraviolet lamp was installed inside the electrolytic oxidation device.

[0088] Table 5 Comparison of water quality between the examples and Comparative Example 3

[0089]

[0090] As shown in Table 5, comparing the examples with Comparative Example 3, after treatment by the methods described in the examples, under the synergistic catalytic oxidation effect of ultraviolet lamp irradiation, the COD removal rate increased by about 15%, and the ammonia nitrogen removal rate increased by about 10%, which can remove organic matter and ammonia nitrogen more efficiently and thoroughly.

[0091] In summary, the treatment method and system of the present invention can effectively remove pollutants such as organic matter, ammonia nitrogen, fluoride, calcium and magnesium hardness, and suspended solids from coking brine. It not only makes full use of wastewater resources, protects the water resource environment, and reduces the amount of fresh water used, but also solves the industry bottleneck problems of low treatment efficiency and high treatment cost of existing coking brine. It lays the foundation for the full extraction and resource utilization of salts in subsequent deep treatment and ensures the long-term stable operation of subsequent membrane systems or evaporation systems.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for deep impurity removal from coking brine, characterized in that, The deep purification method for coking brine includes a defluorination and hardening precipitation unit, a ceramic membrane filtration unit, an enhanced defluorination unit, a heterogeneous Fenton oxidation unit, and an ultraviolet-enhanced electrolytic oxidation unit. The method comprises the following steps: S1: The coking brine enters the defluorination and hardening precipitation unit. The pH of the coking brine is adjusted to 9-12 by sodium hydroxide solution. Fluorides, calcium and magnesium hardening substances and suspended solids are removed by defluorination and hardening compound agent to obtain the supernatant and sludge precipitate after defluorination and hardening. The supernatant enters the next treatment step. In step S1, fluoride, calcium and magnesium hardness substances and suspended solids in coking brine are removed by adding a fluoride-removing and hardness-reducing composite agent and a flocculant. The fluoride-removing and hardness-reducing composite agent is composed of calcium chloride, sodium polyacrylate and 2-methyl-8-hydroxyquinoline, and the flocculant includes polyaluminum chloride and polyacrylamide. The mass ratio of the fluoride removal and hardening removal composite agent to polyaluminum chloride and polyacrylamide is 40-50:20-30:

1. The dosage of the fluoride removal and hardening removal composite agent is 300-600 mg / L; the dosage of polyaluminum chloride is 10-50 mg / L; and the dosage of polyacrylamide is 1-5 mg / L. S2: The supernatant enters the ceramic membrane filtration unit, where suspended solids and colloidal substances in the supernatant are filtered out to obtain the permeate; In step S2, the ceramic membrane is an organic-inorganic composite ceramic membrane, which includes polytetrafluoroethylene, alumina, silicon dioxide and diphenylamine, and the mass ratio of polytetrafluoroethylene, alumina, silicon dioxide and diphenylamine is 120-180:1-3:1-5:1; S3: Adjust the pH of the permeate to 6-10, and then remove the fluoride in the permeate through the enhanced defluorination unit to obtain adsorbed effluent; The enhanced defluorination unit includes a fluoride adsorption resin, which, through adsorption and exchange, reduces the fluoride content in the permeate to less than 1 ppm. In step S3, the adsorption time of the fluorine adsorption resin is 2-4 hours. After the adsorption is saturated, the fluorine adsorption resin is regenerated using a regenerator, and the resulting regenerated liquid is returned to the fluorine removal and hardening precipitation unit for further treatment. The fluorine adsorption resin is a macroporous polystyrene-divinylbenzenesulfonic acid chelating resin loaded with metallic aluminum. The preparation method of the chelating resin is as follows: using polystyrene-divinylbenzenesulfonic acid resin as the skeleton carrier, immersing the skeleton carrier in aluminum sulfate solution and shaking for 30-60 minutes, rinsing with pure water 2-3 times after shaking, and drying in an oven to obtain macroporous polystyrene-divinylbenzenesulfonic acid chelating resin loaded with metallic aluminum. The concentration of the aluminum sulfate solution is 0.5-1.0 mol / L, the shaking reaction time is 12-24 h, the reaction temperature is 25-30℃, and the aluminum metal fixation rate is 50-60%. The regenerant is an aluminum chloride solution with a concentration of 0.25-0.5 mol / L. The regeneration method is countercurrent regeneration with a countercurrent flow rate of 2-4 BV / h and a regeneration time of 0.5-1.0h. S4: Adjust the pH of the adsorbed effluent to 4-8, and then enter the heterogeneous Fenton oxidation unit. It is treated with air aeration and Fenton catalyst to obtain Fenton oxidized effluent. In step S4, the aeration intensity of the air aeration is 0.2-0.6 m. 3 / h, aeration time is 2-4h; The Fenton catalyst is a solid catalyst in which iron, copper, and manganese metals are supported on an activated carbon carrier, wherein the molar ratio of iron, copper, and manganese is 1:0.8-1:0.

1. The Fenton catalyst is spherical, columnar, or irregularly rhomboid in shape, with a particle size of 2-8 mm and a filling rate of 40-60%. S5: The Fenton oxidation effluent enters the UV-enhanced electrolytic oxidation unit, which electrolytically oxidizes the Fenton oxidation effluent to achieve the conditions for deep-treated influent.

2. The method for deep impurity removal from coking brine according to claim 1, characterized in that, In step S5, the UV-enhanced electrolytic oxidation unit includes a UV-enhanced electrolytic oxidation device, which includes a UV lamp (1) and an electrode (2). The UV lamp (1) is a high-pressure mercury lamp with a wavelength range of 350-450 nm and an irradiation intensity of 200-400 W / m. 2 The current density of the electrode (2) is 50-200 A / m. 2 .

3. The method for deep impurity removal from coking brine according to claim 2, characterized in that, The ultraviolet lamp (1) and the electrode (2) are arranged in a grid manner. The upper part of the device is the area of ​​the ultraviolet lamp (1) and the lower part of the device is the area of ​​the electrode (2). The Fenton oxidation effluent enters the ultraviolet enhanced electrolytic oxidation device, is first irradiated by the ultraviolet lamp (1), and then enters the area of ​​the electrode (2) for electrolytic oxidation. The electrode (2) is a double-layer cylindrical electrode with an inner anode and an outer cathode.

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