A device and method for deep treatment of organic matter in coal chemical reverse osmosis membrane filtered concentrated water

Abstract

A device and method for deep treatment of organic matter in reverse osmosis membrane filtration concentrate from coal chemical industry are disclosed. This invention relates to a device and method for treating membrane filtration concentrate, aiming to solve the technical problems of easy scaling, high energy consumption, and long treatment time in existing membrane filtration concentrate treatment methods. The device of this invention includes a heat exchanger, an advanced oxidation tank, an electrocoagulation coupled electro-oxidation tank, and a sedimentation tank connected in sequence. A persulfate dosing system is connected to the advanced oxidation tank. Simultaneously, the electrocoagulation coupled electro-oxidation tank and the sedimentation tank are connected to the advanced oxidation tank via reflux pipes. Through the combination of advanced oxidation and electrocoagulation coupled electro-oxidation, thermal activation and Fe... 2+ Ion activation generates sulfate free radicals, which react with existing chloride ions to produce active chlorine. This oxidizes and degrades recalcitrant organic matter in the reverse osmosis concentrate, reducing scaling problems in subsequent evaporation and crystallization systems and completely separating organic matter from the crystalline salt. This invention can be used in the field of wastewater treatment.

Description

Technical Field

[0001] This invention relates to an apparatus and method for deep treatment of membrane filtration concentrate, belonging to the field of wastewater treatment. Background Technology

[0002] Wastewater generated during the production process of coal chemical enterprises needs to be recycled. However, the high-salinity wastewater mainly comes from the reverse osmosis concentrate produced by the membrane separation unit. This concentrate is characterized by extremely high organic content, high salt content, poor biodegradability, and complex composition, making it difficult to completely degrade through biological treatment. Existing methods for evaporating and crystallizing high-salinity wastewater can not only recycle the wastewater but also recover crystalline salt as a byproduct from the concentrate, and the large amount of waste heat generated during the evaporation and crystallization process can be recovered. However, during the evaporation process, as the crystalline salt precipitates, high concentrations of organic matter also remain in the solid. Even if more than 80% of sodium chloride and sodium sulfate can be recovered from the crystalline salt, it is classified as hazardous waste due to the presence of organic impurities, resulting in high disposal costs. Furthermore, the large amount of scaling generated leads to instability in the subsequent evaporation and crystallization system, requiring frequent cleaning or equipment replacement, increasing operating and management costs. How to deeply treat the reverse osmosis concentrate to minimize the concentration of organic matter, reduce scaling on the evaporator surface, and enable the resource utilization of crystalline salt is a critical issue that urgently needs to be addressed.

[0003] Currently, the main technologies for advanced treatment of membrane filtration concentrate include membrane distillation, electrodialysis, constructed wetlands, and advanced oxidation. Among these, membrane distillation equipment is simple and can utilize locally sourced plant steam as an energy source, but its efficiency is easily reduced by scaling during actual operation. Newer forms of electrodialysis, such as frequent polarity reversal electrodialysis and bipolar membrane electrodialysis, exhibit good corrosion resistance and are suitable for concentrating inorganic salt wastewater, but their energy consumption and operating costs are high. Constructed wetlands offer advantages such as low cost and simultaneous removal of organic matter and heavy metals, but system construction is time-consuming and lacks additional benefits. Advanced oxidation processes are widely used, but in-depth research on their application in coal chemical industry is lacking, and uneconomical operation is also a factor limiting their practical engineering application. Summary of the Invention

[0004] This application aims to address the technical problems of existing membrane filtration concentrate treatment methods, such as easy scaling, high energy consumption, and long treatment time, by providing a device and method for deep treatment of organic matter in coal chemical reverse osmosis membrane filtration concentrate. The device of this invention utilizes a combination of advanced oxidation and electrocoagulation coupled with electro-oxidation, taking advantage of thermal activation and Fe... 2+Ion activation generates sulfate radicals, which react with existing chloride ions to produce active chlorine. This oxidizes and degrades recalcitrant organic matter in the reverse osmosis concentrate, reducing scaling issues in the subsequent evaporation and crystallization system. Organic matter is completely separated from the crystalline salt, improving its quality. Waste heat generated during evaporation and crystallization is recovered and used to thermally activate the PDS, improving resource utilization and reducing operating costs. Simultaneously, sludge and ferrous ions generated from electrocoagulation and electrooxidation are recycled for catalytic advanced oxidation reactions, achieving clean production with resource utilization and zero discharge of high-salinity wastewater.

[0005] The apparatus for deep treatment of organic matter in the concentrated water of reverse osmosis membrane filtration in coal chemical industry of the present invention includes a heat exchanger 1, a persulfate dosing system 2, an advanced oxidation tank 3, an electrocoagulation coupled electro-oxidation tank 4, and a sedimentation tank 5;

[0006] The heat exchanger 1 consists of an internal coil 1-1 and an outer casing 1-2. The internal coil 1-1 is a bent pipe. A steam inlet is provided at the bottom of the outer casing 1-2. Steam is introduced into the outer casing 1-2 to heat the water inside the internal coil 1-1. The bent pipe increases the residence time of the water in the heat exchanger, which helps to ensure sufficient heat exchange.

[0007] The persulfate dosing system 2 consists of a persulfate storage tank 2-1, a dosing pump 2-2, and a dosing pipeline 2-3. The persulfate storage tank 2-1 is sealed to prevent the persulfate from oxidizing upon contact with air.

[0008] The advanced oxidation tank 3 has an inlet 3-1 and a reflux liquid inlet 3-2 on its side wall, an outlet 3-3 on the upper part of the opposite side tank wall, a sludge discharge port 3-4 at the conical bottom of the tank, and a first hydraulic stirring device 3-5 inside the tank; the heat exchanger 1 is connected to the inlet 3-1 of the advanced oxidation tank 3 by an internal coil 1-1; the persulfate storage tank 2-1 is connected to the advanced oxidation tank 3 by a dosing pump 2-2 and a dosing pipe 2-3.

[0009] A cathode plate 4-1 and an anode plate 4-2 are arranged opposite each other in an electrocoagulation coupled electrooxidation tank 4. Multiple sets of bipolar plates 4-3, perpendicular to the cathode plate 4-1 and anode plate 4-2 and arranged at equal intervals, are fixed between the cathode plate 4-1 and anode plate 4-2 by a support frame. The cathode plate 4-1 and anode plate 4-2 are connected to the positive and negative terminals of a DC power supply 4-4. The main electrode surfaces of the multiple sets of bipolar plates 4-3 are parallel to the electric field lines formed by the cathode and anode. An inlet 4-5 is provided on the upper part of the side wall of the electrocoagulation coupled electrooxidation tank 4, and a connecting outlet 4-6 is provided in the middle of the opposite side wall. A reflux outlet 4-7 is provided at the bottom of the tank. The reflux outlet 4-7 is connected to the reflux inlet 3-2 of the advanced oxidation tank 3 through a pipe, and a reflux pump 4-8 and a reflux control valve 4-9 are provided on the pipe. A second hydraulic stirring device 4-10 is also provided below the cathode plate 4-1 and anode plate 4-2.

[0010] A connecting inlet 5-1 is provided in the middle of the side wall of the sedimentation tank 5, which is connected to the connecting outlet 4-6 of the electrocoagulation coupled electro-oxidation tank 4; an overflow outlet 5-2 is provided on the upper part of the opposite side wall of the sedimentation tank 5; a sludge discharge pipe 5-3 is provided at the conical bottom of the sedimentation tank 5; a branch pipe is provided on the sludge discharge pipe 5-3 and connected to the return liquid inlet 3-2 of the advanced oxidation tank 3; a floc return pump 5-4 and a floc return control valve 5-5 are provided on the branch pipe; the branch pipe puts part of the flocs generated by electrocoagulation at the bottom of the sedimentation tank 5 into the advanced oxidation tank, and the other part is discharged from the system through the sludge discharge pipe 5-3.

[0011] Furthermore, the inner surfaces of the built-in coil 1-1 and the delivery pipe of the heat exchanger 1 are coated with Teflon to prevent corrosion.

[0012] Furthermore, a filter screen is installed at the outlet 3-3 to trap the flocs and discharge them through the sludge discharge port 3-4 at the lower end.

[0013] Furthermore, the cathode plate 4-1 in the electrocoagulation coupled electrooxidation cell 4 is a graphite electrode, carbon felt, stainless steel electrode, carbon plate, or titanium plate; the anode plate 4-2 is a coated titanium anode, lead dioxide electrode, or carbon plate electrode; and the bipolar electrode 4-3 is a rectangular iron plate. The bipolar electrode is a consumable electrode, which is replaced periodically and is easy to operate, enabling the synergistic removal of pollutants by electrocoagulation and electrooxidation.

[0014] Furthermore, the upper part of the sedimentation tank 5 is cylindrical and the lower part is conical, and inclined tube packing 5-6 is installed below the overflow outlet 5-2.

[0015] Furthermore, the device for deep treatment of organic matter in coal chemical reverse osmosis membrane filter concentrate also includes an evaporator crystallizer 6. The steam generated by the evaporator crystallizer 6 is input into the heat exchanger 1 through a pipeline to heat the treated membrane filter concentrate.

[0016] The method for deep treatment of organic matter in the concentrate from reverse osmosis membrane filtration in coal chemical industry using the above-mentioned device is carried out according to the following steps:

[0017] 1. The concentrated water from the reverse osmosis membrane is fed into the built-in coil 1-1 of the heat exchanger 1 and heated to 80-90°C by steam. It then enters the advanced oxidation tank 3. Persulfate from the persulfate storage tank 2-1 is added to the advanced oxidation tank 3 through the dosing pump 2-2 and the dosing pipe 2-3. At the same time, the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 and the flocs returned from the sedimentation tank 5 also enter the advanced oxidation tank 3. The reflux ratio of the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 is 50%-100%, and the reflux ratio of the flocs returned from the sedimentation tank 5 is 90%-100%. The stirring speed is 1400-1500 rpm, and the hydraulic residence time of the concentrated water from the reverse osmosis membrane in the advanced oxidation tank 3 is 0.5-2 hours. In this step, under the combined action of thermal radiation and ferrous ions contained in the reflux water, the persulfate decomposes rapidly, generating sulfate free radicals that oxidize organic matter. The large amount of chloride ions and sulfate free radicals present in the reverse osmosis concentrate react to generate chlorine-containing free radicals, which also participate in the degradation of organic matter and Fe. 2+ The activated sulfite system and the thermally activated sulfite system form three microscopic advanced oxidation systems, and the synergistic effect greatly promotes the degradation of organic matter. In addition, the flocs generated by electrocoagulation are collected in the sedimentation tank and then fed into the advanced oxidation tank to further enhance the oxidation effect.

[0018] Second, the concentrated water from the reverse osmosis membrane then enters the electrocoagulation coupled electro-oxidation tank 4, with the DC power supply current density set to 20–200 mA / cm². 2 The stirring rate is 1400–1500 rpm, and the hydraulic residence time of the reverse osmosis concentrate in the electrocoagulation coupled electrooxidation tank 4 is 0.5–3 h. In this step, water flows into the electrocoagulation coupled electrooxidation tank, and the anode and cathode connected to the external power supply serve as driving electrodes. The side of the anode facing the bipolar electrode is polarized into the cathode region, and the side facing the cathode is polarized into the anode region. Under the polarization effect of the electric field, a large amount of flocculant and active free radicals are generated, and electrocoagulation and electrochemical oxidation occur simultaneously. According to the principle of electrocoagulation, the iron at the anode end loses electrons to generate ions, and OH groups generated at the cathode... - Iron hydroxides are formed, which complex with water to form flocs. These flocs remove organic matter through physical adsorption, coordination adsorption, bridging, co-precipitation, and charge neutralization. Electro-oxidation reactions occur at the cathode and anode, where organic matter is directly or indirectly oxidized on the anode surface and degraded by the strong oxidizing free radicals generated during the anode surface oxidation reaction.

[0019] 3. After the concentrated water from the reverse osmosis membrane enters the sedimentation tank 5, the electrocoagulated flocs settle at the bottom to form iron-containing sludge. Part of it is reused in the advanced oxidation tank and part is discharged. The treated water is discharged through the overflow outlet 5-2, thus completing the deep treatment of organic matter in the concentrated water from the reverse osmosis membrane in coal chemical industry.

[0020] This invention heats the concentrated water from reverse osmosis membrane filtration at a controlled temperature of 80–90°C. Excessively low pH is detrimental to the stable existence of iron hydroxide; the products of thermally activated persulfate (PDS) can adjust the conductivity and pH of the concentrated water, making the solution slightly alkaline. The bipolar electrodes in the electrocoagulation-coupled electro-oxidation tank are consumable electrodes, requiring periodic replacement, and are easy to operate, enabling synergistic removal of pollutants through electrocoagulation and electro-oxidation. The flocs produced by electrocoagulation are mainly α-FeOOH, γ-FeOOH, Fe3O4, and rust (GRs). Rust exhibits the best adsorption effect; the large amount of chloride ions present in the water ensures the stable existence of rust and produces the highest floc yield. Rust has better pH adaptability and buffering effect, broadening the pH range of advanced oxidation reactions without the need for additional acid or alkali reagents. The flocs flow into the sedimentation tank with the water flow, reducing in-situ deposition of flocs, preventing electrode passivation, and improving the working efficiency of the electrode plates.

[0021] The process and principle of organic matter removal in the concentrated water filtered by the reverse osmosis membrane of this invention are as follows:

[0022] The process involves generating highly oxidizing active groups such as hydroxyl radicals and sulfate radicals through advanced oxidation, which destroy the long carbon chains and complex functional group structures of organic pollutants. Then, electrocoagulation produces iron hydroxide flocs that can effectively adsorb and complex small organic molecule pollutants, thereby achieving rapid and efficient water treatment.

[0023] In the advanced oxidation tank, the peroxy bonds in persulfate can break under thermal radiation, generating sulfate radicals, which destroy the structure of recalcitrant organic matter and convert it into small molecules. The reaction process is shown in formula (1). Ferrous ions, as electron donors, can catalyze the generation of sulfate radicals from PDS, as shown in formula (2). Chloride ions in the reverse osmosis concentrate can react with SO42-. ·- The reaction generates chlorine-containing free radicals, including Cl. · ClHO ·- Cl2 ·- They participate in the degradation of organic matter, as shown in formulas (3) to (5).

[0024] S2O8 2- +heat→2SO4 ·- (1)

[0025] S2O8 2- +Fe 2+ →Fe 2+ +SO4·- +SO4 2- (2)

[0026] SO4 ·- +Cl - →Cl · +SO4 2- (3)

[0027] Cl · +OH→ClHO · (4)

[0028] Cl · +Cl - →Cl2 ·- (5)

[0029] In the electro-oxidation coupled electrocoagulation tank, the bipolar electrode is polarized under the drive of the anode and cathode. Fe(II) is precipitated at the anode end, and hydrolysis is performed to form iron hydroxide coagulant, which adsorbs organic pollutants in the water. The specific reaction process is shown in formulas (6) to (12). Electrochemical oxidation reaction occurs at the cathode end and the DSA anode. Organic pollutants directly lose electrons at the DSA anode and are converted into non-toxic and easily biodegradable substances, or undergo indirect oxidation. The large amount of chloride ions in the reverse osmosis concentrate acts as a catalyst to generate highly oxidizing active chlorine·Cl and ClO. - Oxidation is achieved by Cl2.

[0030] Fe→Fe(II)+2e - (6)

[0031] Fe(II)→Fe(III)+e - (7)

[0032] 2Fe(II) + 2H₂O + O 2(g) →Fe(III)+4OH - (8)

[0033] Fe(II) + 2OH - →Fe(OH) 2(s) (9)

[0034] Fe(III) + 3OH - →Fe(OH) 3(s) (10)

[0035] 4Fe(II) + 10H₂O + O 2(g) →4Fe(OH) 3(s) +8H + (11)

[0036] Fe(OH) 3(s) +2OH- →Fe(OH)4 - (aq) +e - (12)

[0037] The innovations and beneficial effects of this invention are as follows:

[0038] I. This invention includes processes such as thermally activated PDS oxidation, electrocoagulation, and electrochemical oxidation. It utilizes a combined free radical-electrocoagulation reaction to remove recalcitrant organic matter from wastewater. It has a good treatment effect on reverse osmosis concentrate with extremely high organic matter content, high salt content, poor biodegradability, and complex composition. It can overcome the technical difficulties of zero discharge in coal chemical industry and effectively reduce the concentration of organic matter in high-salt wastewater.

[0039] Second, this invention completely separates organic matter from the crystalline salt product, improving the quality and purity of the crystalline salt for export, rendering difficult-to-process mixed salts harmless and resource-efficient, reducing environmental pollution and increasing enterprise economic benefits. Simultaneously, the removal of organic matter also reduces scaling in the evaporator, improving the system's heat exchange efficiency and operational stability.

[0040] Third, this invention can utilize the waste heat generated during evaporation and crystallization to thermally activate persulfate, efficiently producing sulfate free radicals to degrade organic matter, thus providing a new approach for the recovery and utilization of waste heat from evaporators. Simultaneously, it utilizes the generated SO4· - It reacts with the large amount of chloride ions already present in the concentrated water to generate highly reactive Cl· and ClHO·. - Cl2· - It oxidizes and degrades recalcitrant organic matter in concentrated water, and reacts with SO4· - Multiple microscopic advanced oxidation systems are formed in the advanced oxidation pool to synergistically degrade organic matter.

[0041] IV. This invention enables a green, circular, and energy-saving process. Besides waste heat, this invention innovatively and effectively reuses the ferrous ions and iron hydroxide flocs generated in the electrocoagulation coupled electrooxidation tank in the advanced oxidation tank. Ferrous ions activate PDS to produce SO4· - Iron oxide flocs can adsorb organic matter and act as catalysts to enhance the generation of active substances, broadening the pH operating range and providing a new approach for the treatment of flocs generated by electrocoagulation. By utilizing reflux and reuse systems, the products from the wastewater treatment process are fully utilized, enhancing the generation and oxidation of free radicals, which is beneficial for energy conservation and emission reduction. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the device for deep treatment of organic matter in the concentrated water from the reverse osmosis membrane filter of coal chemical industry according to the present invention;

[0043] Figure 2This is a schematic diagram of the persulfate dosing system 2 and the advanced oxidation tank 3;

[0044] Figure 3 This is a schematic diagram of the structure of the electrocoagulation coupled electrooxidation cell 4;

[0045] Figure 4 This is a schematic diagram of the sedimentation tank 5.

[0046] In the picture:

[0047] Includes: 1. Heat exchanger; 1-1. Built-in coil; 1-2. Outer casing; 2. Persulfate dosing system; 2-1. Persulfate storage tank; 2-2. Dosing pump; 2-3. Dosing pipeline; 3. Advanced oxidation tank; 3-1. Inlet; 3-2. Return liquid inlet; 3-3. Outlet; 3-4. Sludge discharge port; 3-5. First hydraulic stirring device; 4. Electrocoagulation coupled electro-oxidation tank; 4-1. Cathode plate; 4-2. 4-3 is the anode plate, 4-4 is the bipolar plate, 4-5 is the DC power supply, 4-6 is the water inlet, 4-7 is the reflux outlet, 4-8 is the reflux pump, 4-9 is the reflux control valve, 4-10 is the second hydraulic stirring device, 5 is the sedimentation tank, 5-1 is the reflux inlet, 5-2 is the overflow outlet, 5-3 is the sludge discharge pipe, 5-4 is the floc reflux pump, 5-5 is the floc reflux control valve, and 6 is the evaporator crystallizer. Detailed Implementation

[0048] The beneficial effects of the present invention are verified using the following examples:

[0049] Example 1: The device for deep treatment of organic matter in the concentrated water of reverse osmosis membrane filtration in coal chemical industry in this example consists of a heat exchanger 1, a persulfate dosing system 2, an advanced oxidation tank 3, an electrocoagulation coupled electro-oxidation tank 4, a sedimentation tank 5, and an evaporator crystallizer 6;

[0050] The heat exchanger 1 consists of an internal coil 1-1 and an outer casing 1-2. The internal coil 1-1 is a bent pipe. A steam inlet is located at the bottom of the outer casing 1-2, which is connected to the steam outlet of the evaporator crystallizer 6. Steam is introduced into the outer casing 1-2 to heat the water inside the internal coil 1-1. The bent pipe increases the residence time of the water in the heat exchanger, which helps to ensure sufficient heat exchange. The steam generated by the evaporator crystallizer 6 is used to heat the treated membrane filter concentrate, realizing waste heat utilization. The inner surfaces of the internal coil 1-1 and the conveying pipe of the heat exchanger 1 are coated with Teflon to prevent corrosion.

[0051] The persulfate dosing system 2 consists of a persulfate storage tank 2-1, a dosing pump 2-2, and a dosing pipeline 2-3. The persulfate storage tank 2-1 is sealed to prevent the persulfate from oxidizing upon contact with air.

[0052] The advanced oxidation tank 3 has an inlet 3-1 and a reflux liquid inlet 3-2 on its side wall, an outlet 3-3 on the upper part of the opposite side tank wall, a sludge discharge port 3-4 at the conical bottom, and a first hydraulic stirring device 3-5 inside the tank. The heat exchanger 1 is connected to the inlet 3-1 of the advanced oxidation tank 3 by an internal coil 1-1. The persulfate storage tank 2-1 is connected to the advanced oxidation tank 3 through a dosing pump 2-2 and a dosing pipe 2-3. The outlet 3-3 is equipped with a filter screen to trap the flocs and discharge them through the sludge discharge port 3-4 at the lower end.

[0053] A cathode plate 4-1 and an anode plate 4-2 are arranged opposite each other in an electrocoagulation coupled electrooxidation cell 4. Four bipolar plates 4-3, perpendicular to the cathode plate 4-1 and anode plate 4-2 and arranged at equal intervals, are fixed between the cathode plate 4-1 and anode plate 4-2 by a support frame. The cathode plate 4-1 and anode plate 4-2 are connected to the positive and negative terminals of a DC power supply 4-4. The main electrode surfaces of the multiple sets of bipolar plates 4-3 are parallel to the electric field lines formed by the cathode and anode. The cathode plate 4-1 is a graphite electrode, the anode plate 4-2 is a coated titanium anode, and the bipolar plates 4-3 are rectangular iron plates. The distance between the cathode plate 4-1 and the anode plate 4-2 is 2cm, and the distance between the bipolar plates 4-3 is 0.5cm. An inlet 4-5 is provided on the upper part of the side wall of the electrocoagulation coupled electro-oxidation tank 4, and a connecting outlet 4-6 is provided in the middle of the opposite side wall. A reflux outlet 4-7 is provided at the bottom of the tank. The reflux outlet 4-7 is connected to the reflux inlet 3-2 of the advanced oxidation tank 3 through a pipe, and a reflux pump 4-8 and a reflux control valve 4-9 are provided on the pipe. A second hydraulic stirring device 4-10 is also provided below the cathode plate 4-1 and the anode plate 4-2.

[0054] The upper part of the sedimentation tank 5 is cylindrical and the lower part is conical. A connecting inlet 5-1 is set in the middle of the side wall of the sedimentation tank 5, which is connected to the connecting outlet 4-6 of the electrocoagulation coupled electro-oxidation tank 4. An overflow outlet 5-2 is set on the upper part of the opposite side wall of the sedimentation tank 5. Inclined tube packing 5-6 is set below the overflow outlet 5-2. A sludge discharge pipe 5-3 is set at the conical bottom of the sedimentation tank 5. A branch pipe is set on the sludge discharge pipe 5-3 and connected to the return liquid inlet 3-2 of the advanced oxidation tank 3. A floc return pump 5-4 and a floc return control valve 5-5 are set on the branch pipe. The branch pipe returns part of the flocs generated by electrocoagulation at the bottom of the sedimentation tank 5 to the advanced oxidation tank, and the other part is discharged from the system through the sludge discharge pipe 5-3.

[0055] The apparatus of Example 1 was used for deep treatment of organic matter in the concentrate from the reverse osmosis membrane filtration of coal chemical industry. The water quality indicators of the concentrate were as follows: pH = 7.83, COD: 500 mg / L, Cl... - The concentration was 14747.2 mg / L. The effective area of ​​the electrode in the electrocoagulation coupled electrooxidation cell was 6.25 cm² (2.5 cm × 2.5 cm). The specific method is as follows:

[0056] 1. The reverse osmosis membrane filtrate concentrate is fed into the built-in coil 1-1 of the heat exchanger 1 and heated to 80°C by steam. It then enters the advanced oxidation tank 3. The potassium persulfate in the storage tank 2-1 is added to the advanced oxidation tank 3 through the dosing pump 2-2 and the dosing pipe 2-3 at a concentration of 10 mmol / L. At the same time, the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 and the flocs returned from the sedimentation tank 5 also enter the advanced oxidation tank 3. The reflux ratio of the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 is 50%, and the reflux ratio of the flocs returned from the sedimentation tank 5 is 100%. The stirring speed is 1500 rpm, and the hydraulic retention time of the reverse osmosis membrane filtrate concentrate in the advanced oxidation tank 3 is 0.5 h.

[0057] Second, the concentrated water from the reverse osmosis membrane then enters the electrocoagulation coupled electro-oxidation tank 4, with a stirring rate of 1500 rpm and a current density of 200 mA / cm². 2 Under the condition of hydraulic retention for 1 hour, the treatment was carried out;

[0058] 3. After the concentrated water from the reverse osmosis membrane enters the sedimentation tank 5, the electrocoagulated flocs settle at the bottom to form iron-containing sludge. Part of it is reused in the advanced oxidation tank, and part of it is discharged. The treated water is discharged through the overflow outlet 5-2 and enters the evaporator crystallizer 6 for evaporation and crystallization treatment.

[0059] In this embodiment, the treated water discharged through overflow outlet 5-2 in step three showed a COD removal rate of 91.4%.

[0060] Example 2: The apparatus for deep treatment of organic matter in the concentrate from reverse osmosis membrane filtration in coal chemical industry in this example differs from that in Example 1 in that the cathode plate 4-1 in the electrocoagulation coupled electro-oxidation cell 4 is made of carbon felt, and the anode plate 4-2 is a coated titanium electrode. Everything else is the same as in Example 1.

[0061] The apparatus of Example 2 was used for deep treatment of organic matter in the concentrate from the reverse osmosis membrane filtration of coal chemical industry. The water quality indicators of the concentrate were as follows: pH = 7.83, COD: 500 mg / L, Cl... - The concentration was 14747.2 mg / L. The specific method is as follows:

[0062] 1. The reverse osmosis membrane filtrate concentrate is fed into the built-in coil 1-1 of the heat exchanger 1 and heated to 80°C by steam. It then enters the advanced oxidation tank 3. The potassium persulfate in the storage tank 2-1 is added to the advanced oxidation tank 3 through the dosing pump 2-2 and the dosing pipe 2-3 at a concentration of 10 mmol / L. At the same time, the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 and the flocs returned from the sedimentation tank 5 also enter the advanced oxidation tank 3. The reflux ratio of the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 is 50%, and the reflux ratio of the flocs returned from the sedimentation tank 5 is 100%. The stirring speed is 1500 rpm, and the hydraulic retention time of the reverse osmosis membrane filtrate concentrate in the advanced oxidation tank 3 is 1 hour.

[0063] Second, the concentrated water from the reverse osmosis membrane then enters the electrocoagulation coupled electro-oxidation tank 4, with a stirring rate of 1500 rpm and a current density of 200 mA / cm². 2 Under the condition of hydraulic retention for 1 hour, the treatment was carried out;

[0064] 3. After the concentrated water from the reverse osmosis membrane enters the sedimentation tank 5, the electrocoagulated flocs settle at the bottom to form iron-containing sludge. Part of it is reused in the advanced oxidation tank, and part of it is discharged. The treated water is discharged through the overflow outlet 5-2 and enters the evaporator crystallizer 6 for evaporation and crystallization treatment.

[0065] In this embodiment, the water discharged through overflow outlet 5-2 in step three achieves a COD removal rate of 91% after treatment in the electrocoagulation coupled electrooxidation tank for 0.5 hours, and a COD removal rate of 100% after treatment in the electrocoagulation coupled electrooxidation tank for 1 hour. When the DSA electrode of anode plate 4-2 is replaced with a boron-doped diamond electrode (BDD electrode), the COD removal rate of the water discharged through overflow outlet 5-2 in step three reaches 85.0% after treatment in the electrocoagulation coupled electrooxidation tank for 1 hour.

[0066] Example 3: The apparatus for deep treatment of organic matter in the concentrated water from the reverse osmosis membrane in coal chemical industry in this example differs from that in Example 1 in that the cathode plate 4-1 in the electrocoagulation coupled electro-oxidation cell 4 is a titanium plate electrode, the anode plate 4-2 is a coated titanium anode, and there is no evaporator crystallizer 6 in this system. Everything else is the same as in Example 1.

[0067] The apparatus described in Example 3 was used to treat leachate from a landfill. The leachate quality parameters were as follows: pH = 8.00 ± 0.20, COD: 10000 mg / L, Cl... - The concentration was 5041.6 mg / L. The specific method is as follows:

[0068] 1. The landfill leachate is fed into the built-in coil 1-1 of the heat exchanger 1. Steam is introduced to heat the leachate in the built-in coil 1-1 to 80°C. Then the leachate enters the advanced oxidation tank 3. The potassium persulfate in the storage tank 2-1 is added to the advanced oxidation tank 3 through the dosing pump 2-2 and the dosing pipe 2-3 at a concentration of 60 mmol / L. At the same time, the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 and the flocs returned from the sedimentation tank 5 also enter the advanced oxidation tank 3. The return ratio of the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 is 100%, and the return ratio of the flocs returned from the sedimentation tank 5 is 100%. The stirring speed is 1500 rpm, and the hydraulic retention time of the leachate in the advanced oxidation tank 3 is 0.5 h.

[0069] Second, the leachate then enters the electrocoagulation coupled electro-oxidation tank 4, with a stirring rate of 1500 rpm and a current density of 20 mA / cm³. 2 The treatment was carried out under the condition of a hydraulic retention time of 240 minutes;

[0070] 3. After the leachate enters the sedimentation tank 5, the electrocoagulated flocs settle at the bottom to form iron-containing sludge. Part of it is reused in the advanced oxidation tank and part is discharged. The treated water is discharged through the overflow outlet 5-2, thus completing the treatment of landfill leachate.

[0071] In this embodiment, the treated water discharged through overflow outlet 5-2 in step three showed a COD removal rate of 85.0%.

[0072] Example 4: The device for deep treatment of organic matter in the concentrated water of reverse osmosis membrane in coal chemical industry in this example differs from the device in Example 1 in that: the cathode plate 4-1 in the electrocoagulation coupled electro-oxidation tank 4 is a stainless steel electrode, the anode plate 4-2 is a lead dioxide electrode, and there is no evaporator crystallizer 6 in this system. Otherwise, it is the same as in Example 1.

[0073] The apparatus described in Example 4 was used to treat leachate collected from a municipal landfill. The leachate water quality indicators were as follows: pH = 6.40 ± 0.05, COD: 8580 ± 200 mg / L, TOC: 3240 ± 50 mg / L, Cl... - 2400.0 mg / L. The specific method is as follows:

[0074] 1. The leachate is fed into the built-in coil 1-1 of the heat exchanger 1 and heated to 80°C by steam. It then enters the advanced oxidation tank 3. The potassium persulfate in the storage tank 2-1 is added to the advanced oxidation tank 3 through the dosing pump 2-2 and the dosing pipe 2-3 at a concentration of 10 mmol / L. At the same time, the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 and the flocs returned from the sedimentation tank 5 also enter the advanced oxidation tank 3. The return ratio of the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 is 100%, and the return ratio of the flocs returned from the sedimentation tank 5 is 100%. The stirring speed is 1500 rpm, and the hydraulic retention time of the leachate in the advanced oxidation tank 3 is 2 hours.

[0075] Second, the leachate then enters the electrocoagulation coupled electro-oxidation tank 4, with a stirring rate of 1500 rpm and a current density of 30 mA / cm³. 2 Treatment was carried out under the condition of a hydraulic retention time of 2.5 hours;

[0076] 3. After the leachate enters the sedimentation tank 5, the electrocoagulated flocs settle at the bottom to form iron-containing sludge. Part of it is reused in the advanced oxidation tank and part is discharged. The treated water is discharged through the overflow outlet 5-2, thus completing the treatment of landfill leachate.

[0077] In this embodiment, the treated water discharged through overflow outlet 5-2 in step three was tested and found to have a COD removal rate of 95.6% and a TOC removal rate of 90.5%.

[0078] Example 5: The device for deep treatment of organic matter in the concentrated water of reverse osmosis membrane in coal chemical industry in this example differs from the device in Example 1 in that: the cathode plate 4-1 in the electrocoagulation coupled electro-oxidation cell 4 is a titanium plate electrode, the anode plate 4-2 is a coated titanium electrode, and there is no evaporator crystallizer 6 in this system. Otherwise, it is the same as in Example 1.

[0079] The apparatus described in Example 5 was used to treat the biochemical effluent from a coking plant's wastewater after secondary sedimentation. The water quality parameters of the biochemical effluent were as follows: pH = 8.80 ± 0.60, COD: 177 mg / L, TOC: 145 mg / L. The specific method is as follows:

[0080] 1. The biochemical effluent is fed into the built-in coil 1-1 of the heat exchanger 1 and heated to 80°C by steam. It then enters the advanced oxidation tank 3. The potassium persulfate in the storage tank 2-1 is added to the advanced oxidation tank 3 through the dosing pump 2-2 and the dosing pipe 2-3 at a concentration of 10 mmol / L. At the same time, the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 and the flocs returned from the sedimentation tank 5 also enter the advanced oxidation tank 3. The reflux ratio of the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 is 100%, and the reflux ratio of the flocs returned from the sedimentation tank 5 is 100%. The stirring speed is 1500 rpm, and the hydraulic retention time of the biochemical effluent in the advanced oxidation tank 3 is 0.5 h.

[0081] Second, the biochemically treated effluent then enters the electrocoagulation coupled electro-oxidation tank 4, where a stirring rate of 1500 rpm and a current density of 30 mA / cm³ are maintained. 2 Treatment was carried out under the condition of a hydraulic retention time of 0.5 h;

[0082] 3. After the biochemical effluent enters the sedimentation tank 5, the electrocoagulated flocs settle at the bottom to form iron-containing sludge. Part of it is reused in the advanced oxidation tank and part is discharged. The treated water is discharged through the overflow outlet 5-2, completing the treatment of the biochemical effluent.

[0083] In this embodiment, the treated water discharged through overflow outlet 5-2 in step three showed a COD removal rate of 60.0% and a TOC removal rate of 54.0%. This is because the coking wastewater lacks Cl... - It cannot produce highly reactive Cl· and ClHO· - Cl2· - The COD removal rate of this embodiment is significantly lower than that of Examples 1-4 due to the synergistic oxidation of chlorine-containing free radicals to recalcitrant organic matter.

[0084] Example 6: The apparatus for deep treatment of organic matter in the concentrated water from the reverse osmosis membrane filter of coal chemical industry in this example differs from the apparatus in Example 1 in that: the cathode plate 4-1 and the anode plate 4-2 in the electrocoagulation coupled electro-oxidation cell 4 are carbon plate electrodes, and the effective area of ​​the electrodes is 12.5 cm². 2 (5cm×2.5cm), and the system does not have an evaporator crystallizer 6, otherwise it is the same as in Example 1.

[0085] The apparatus of Example 6 was used to treat simulated wastewater prepared according to the actual wastewater salinity composition and typical organic compound 2-methoxyphenol (MOP) of a coal chemical plant. The simulated wastewater quality indicators were as follows: pH = 12.00 ± 0.20, MOP: 200 mg / L, Cl... - 15000.0 mg / L. The specific method is as follows:

[0086] 1. Simulated wastewater is fed into the built-in coil 1-1 of heat exchanger 1 and heated to 80°C by steam. It then enters the advanced oxidation tank 3. Potassium persulfate in the persulfate storage tank 2-1 is added to the advanced oxidation tank 3 through the dosing pump 2-2 and the dosing pipe 2-3 at a concentration of 10 mmol / L. At the same time, the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 and the flocs returned from the sedimentation tank 5 also enter the advanced oxidation tank 3. The return ratio of the liquid returned from the electrocoagulation coupled electro-oxidation tank 4 is 100%, and the return ratio of the flocs returned from the sedimentation tank 5 is 100%. The stirring speed is 1500 rpm, and the hydraulic retention time of the simulated wastewater in the advanced oxidation tank 3 is 0.5 h.

[0087] Second, the simulated wastewater then enters the electrocoagulation coupled electro-oxidation tank 4, with a stirring speed of 1500 rpm and a current density of 100 mA / cm³. 2 Treatment was carried out under the condition of a hydraulic retention time of 3 hours;

[0088] 3. After the simulated wastewater enters the sedimentation tank 5, the electrocoagulated flocs settle at the bottom to form iron-containing sludge. Part of the sludge is reused in the advanced oxidation tank, and part of it is discharged. The treated water is discharged through the overflow outlet 5-2, thus completing the treatment of the simulated wastewater.

[0089] In this embodiment, the treated water discharged through overflow outlet 5-2 in step three showed an MOP removal rate of 98.0% upon testing.

Claims

1. A method for deep treatment of organic matter in concentrated water from reverse osmosis membrane filters in coal chemical industry, characterized in that, This method is performed according to the following steps; I. A device for deep treatment of organic matter in the concentrated water of reverse osmosis membrane in coal chemical industry, including a heat exchanger (1), a persulfate dosing system (2), an advanced oxidation tank (3), an electrocoagulation coupled electro-oxidation tank (4), and a sedimentation tank (5). The heat exchanger (1) consists of an internal coil (1-1) and an outer casing (1-2). The internal coil (1-1) is a bent pipe. A steam inlet is provided at the bottom of the outer casing (1-2). The persulfate dosing system (2) consists of a persulfate storage tank (2-1), a dosing pump (2-2), and a dosing pipeline (2-3). The persulfate storage tank (2-1) is sealed to prevent the persulfate from oxidizing upon contact with air. The advanced oxidation tank (3) has an inlet (3-1) and a reflux liquid inlet (3-2) on its side wall, an outlet (3-3) on the upper part of the opposite side tank wall, a sludge discharge port (3-4) at the bottom of the conical tank, and a first hydraulic stirring device (3-5) inside the tank; the heat exchanger (1) is connected to the inlet (3-1) of the advanced oxidation tank (3) by a built-in coil (1-1); the persulfate storage tank (2-1) is connected to the advanced oxidation tank (3) by a dosing pump (2-2) and a dosing pipe (2-3); In the electrocoagulation coupled electro-oxidation cell (4), opposite cathode plates (4-1) and anode plates (4-2) are set up. Multiple sets of bipolar plates (4-3) arranged at equal intervals and perpendicular to the cathode plates (4-1) and anode plates (4-2) are fixed between the cathode plates (4-1) and anode plates (4-2) by a support frame. The cathode plates (4-1) and anode plates (4-2) are connected to the positive and negative terminals of the DC power supply (4-4). The main electrode surfaces of the multiple sets of bipolar plates (4-3) are parallel to the electric field lines formed by the cathode and anode. An inlet (4-5) is provided on the upper side wall of the electrocoagulation coupled electro-oxidation tank (4), and a connecting outlet (4-6) is provided in the middle of the opposite side wall; a reflux outlet (4-7) is provided at the bottom of the tank; the reflux outlet (4-7) is connected to the reflux inlet (3-2) of the advanced oxidation tank (3) through a pipe, and a reflux pump (4-8) and a reflux control valve (4-9) are provided on the pipe; a second hydraulic stirring device (4-10) is also provided below the cathode plate (4-1) and the anode plate (4-2); A connecting inlet (5-1) is provided in the middle of the side wall of the sedimentation tank (5), and the connecting inlet (5-1) is connected to the connecting outlet (4-6) of the electrocoagulation coupled electro-oxidation tank (4); an overflow outlet (5-2) is provided on the upper part of the opposite side wall of the sedimentation tank (5); a sludge discharge pipe (5-3) is provided at the conical bottom of the sedimentation tank (5); a branch pipe is provided on the sludge discharge pipe (5-3) and connected to the return liquid inlet (3-2) of the advanced oxidation tank (3); a floc return pump (5-4) and a floc return control valve (5-5) are provided on the branch pipe. The reverse osmosis membrane filtrate concentrate is fed into the built-in coil (1-1) of the heat exchanger (1), heated to 80~90℃ by steam, and then fed into the advanced oxidation tank (3). Persulfate in the persulfate storage tank (2-1) is added into the advanced oxidation tank (3) through the addition pump (2-2) and the addition pipe (2-3). At the same time, the liquid returned from the electrocoagulation coupled electro-oxidation tank (4) and the flocs returned from the sedimentation tank (5) also enter the advanced oxidation tank (3). The return ratio of the liquid returned from the electrocoagulation coupled electro-oxidation tank (4) is 50%~100%, and the return ratio of the flocs returned from the sedimentation tank (5) is 90%~100%. The stirring speed is 1400~1500rpm, and the hydraulic residence time of the reverse osmosis membrane filtrate concentrate in the advanced oxidation tank (3) is 0.5~2h.

2. Then, the concentrated water from the reverse osmosis membrane enters the electrocoagulation coupled electro-oxidation tank (4), and the current density of the DC power supply is set to 20~200 mA / cm. 2 The stirring rate is 1400~1500rpm, and the hydraulic retention time of the reverse osmosis concentrate in the electrocoagulation coupled electro-oxidation tank (4) is 0.5~3h; 3. After the concentrated water from the reverse osmosis membrane enters the sedimentation tank (5), the electrocoagulated flocs settle at the bottom to form iron-containing sludge. Part of it is reused in the advanced oxidation tank, and part of it is discharged. The treated water is discharged through the overflow outlet (5-2), thus completing the deep treatment of organic matter in the concentrated water from the reverse osmosis membrane of coal chemical industry.

2. The method for deep treatment of organic matter in concentrated water from reverse osmosis membrane filtration in coal chemical industry according to claim 1, characterized in that, The built-in coil (1-1) and the inner surface of the delivery pipe of the heat exchanger (1) are coated with Teflon.

3. A method for deep treatment of organic matter in concentrated water from reverse osmosis membrane filtration in coal chemical industry according to claim 1 or 2, characterized in that, A filter screen is installed at the water outlet (3-3).

4. A method for deep treatment of organic matter in concentrated water from reverse osmosis membrane filtration in coal chemical industry according to claim 1 or 2, characterized in that, The cathode plate (4-1) in the electrocoagulation coupled electro-oxidation cell (4) is a graphite electrode, carbon felt, stainless steel electrode, carbon plate or titanium plate; the anode plate (4-2) is a coated titanium anode, lead dioxide electrode or carbon plate electrode; the bipolar plate (4-3) is a rectangular iron plate.

5. A method for deep treatment of organic matter in concentrated water from reverse osmosis membrane filtration in coal chemical industry according to claim 1 or 2, characterized in that, The upper part of the sedimentation tank (5) is cylindrical and the lower part is conical.

6. A method for deep treatment of organic matter in concentrated water from reverse osmosis membrane filtration in coal chemical industry according to claim 1 or 2, characterized in that, Inclined tube packing (5-6) is installed below the overflow outlet (5-2) of the sedimentation tank (5).

7. A method for deep treatment of organic matter in concentrated water from reverse osmosis membrane filtration in coal chemical industry according to claim 1 or 2, characterized in that, The device for deep treatment of organic matter in coal chemical reverse osmosis membrane filter concentrate also includes an evaporator crystallizer (6), and the steam pipe of the evaporator crystallizer (6) is connected to the bottom of the outer casing (1-2) of the heat exchanger (1) with a steam inlet.

Images