Method for treating coal chemical membrane concentrated water by utilizing electrooxidation

Abstract

The invention provides a method for treating coal chemical industry membrane concentrated water by electrooxidation, which comprises the following steps: firstly, feeding coal chemical industry membrane concentrated liquor into a hardness removal system unit, removing calcium and magnesium ions enriched by membrane concentration to obtain hardness-removed effluent, then feeding the hardness-removed effluent into an electrooxidation system 1, degrading refractory organic matters and ammonia nitrogen in the membrane concentrated liquor to obtain up-to-standard discharge effluent, and finally discharging the up-to-standard discharge effluent. Feeding the discharged water reaching the standard into an electrodialysis unit, further concentrating the salt to obtain electrodialysis fresh water and electrodialysis concentrated water, feeding the electrodialysis fresh water into a reverse osmosis unit to obtain reverse osmosis produced water and reverse osmosis concentrated water, feeding the electrodialysis concentrated water into an electrooxidation system 2, further removing concentrated organic matters and ammonia nitrogen pollutants, and recycling the electrodialysis concentrated water. And finally, the effluent of the electrooxidation system 2 is fed into a quality-divided crystallization unit to obtain industrial-grade sodium sulfate and industrial-grade sodium chloride, so that the coal chemical industry concentrated solution is discharged after reaching the standard, and meanwhile, water resources in the coal chemical industry concentrated solution are effectively recycled for system reuse.

Description

Technical Field

[0001] The present invention belongs to the technical field of industrial wastewater treatment, and particularly relates to a method for treating coal chemical membrane concentrate by electrooxidation. Background Art

[0002] Wastewater in the coal chemical industry is generated in the production process and usually contains a large amount of toxic substances such as phenolic substances, polycyclic aromatic compounds and heterocyclic compounds. The state has continuously improved the discharge standards for wastewater from various industrial sectors, and at the same time requires enterprises to recycle the produced wastewater according to their own water use needs to achieve energy conservation and emission reduction.

[0003] Wastewater from coal chemical enterprises is treated by a biochemical + membrane treatment method; the biochemical process has a good removal effect on most COD and ammonia nitrogen, but has a poor treatment effect on refractory organic compounds such as quinoline, indole, pyridine, carbazole, etc. After membrane concentration treatment, refractory organic compounds are enriched, increasing the treatment difficulty of coal chemical wastewater membrane concentrate.

[0004] Currently, for the treatment of coal chemical membrane concentrate, treatment methods such as Fenton oxidation, activated carbon adsorption, wet catalytic oxidation, and ozone are used; however, methods such as Fenton oxidation and activated carbon adsorption will generate a large amount of hazardous waste; wet catalytic oxidation uses high temperature and pressure and hydrogen peroxide, and there are great safety hazards during the operation process and it is difficult to effectively meet the standards; ozone treatment for coal chemical membrane concentrate has limited pollutant removal effect. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problem that it is difficult to effectively and fully treat coal chemical membrane concentrate in the prior art, and provide a method for treating coal chemical membrane concentrate by electrooxidation;

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A method for treating coal chemical membrane concentrate by electrooxidation, characterized by comprising:

[0007] S1: Feed the coal chemical membrane concentrate into a hard removal system unit to remove calcium and magnesium ions enriched by membrane concentration, and obtain hard removal effluent;

[0008] S2: Feed the hard removal effluent obtained in step S1 into an electrooxidation 1 system to degrade refractory organic compounds and ammonia nitrogen in the membrane concentrate, and obtain effluent meeting the discharge standards;

[0009] S3: Feed the effluent meeting the discharge standards obtained in step S2 into an electrodialysis unit for further concentration of salts, and obtain electrodialysis fresh water and electrodialysis concentrate;

[0010] S4: Feed the electrodialysis fresh water obtained in step S3 into the reverse osmosis unit to obtain reverse osmosis product water and reverse osmosis concentrate. Among them, the reverse osmosis product water is used for reclaimed water reuse, and the reverse osmosis concentrate is recycled back to the electrodialysis unit for further concentration;

[0011] S5: Feed the electrodialysis concentrate obtained in step S3 into the electro-oxidation 2 system to further remove the concentrated organic matter and ammonia nitrogen pollutants to obtain the effluent of the electro-oxidation 2 system;

[0012] S6: Feed the effluent of the electro-oxidation 2 system obtained in step S5 into the fractional crystallization unit to obtain industrial-grade sodium sulfate and industrial-grade sodium chloride. Among them, the evaporation condensate water in the fractional crystallization process is used for reclaimed water reuse.

[0013] Further, the hard removal system unit uses the double-alkali method coupled with hard removal resin to remove calcium and magnesium ions in the membrane concentrate, so that the Ca in the hard removal effluent obtained after being treated by the hard removal system unit 2+ <50 mg / L, Mg 2+ <50 mg / L.

[0014] Further, the cathode and anode of the electro-oxidation 1 system are arranged in a spaced-apart manner, and each electrolytic chamber composed of a cathode and an anode has an independent inlet and outlet pipeline, so that the organic matter can effectively contact the anode surface and be oxidized and degraded.

[0015] Further, the anode of the electro-oxidation 1 system is a thin-film diamond electrode, and the cathode of the electro-oxidation 1 system is a stainless steel or titanium electrode.

[0016] Further, the electrodialysis unit uses anion and cation homogeneous electrodialysis membranes to simultaneously enrich anions and cations. The electrodialysis concentrate is enriched to TDS≥50000 mg / L, and the indoor salt content TDS of the electrodialysis fresh water ≤3000 mg / L.

[0017] Further, the reverse osmosis unit is a spiral-wound reverse osmosis, disk tube reverse osmosis or high-pressure reverse osmosis.

[0018] Further, the anode of the electro-oxidation 2 system is a thin-film diamond electrode or a coated electrode.

[0019] Further, the fractional crystallization unit performs evaporation concentration and fractional crystallization treatment on the effluent of the electro-oxidation 2 system. During the fractional crystallization process, sodium chloride is precipitated by evaporation crystallization, and the condensate water generated during the evaporation crystallization process is used for reclaimed water reuse. Then, the effluent of the electro-oxidation 2 system after evaporation is treated by freeze crystallization to precipitate sodium sulfate and obtain mother liquor, and then the mother liquor is subjected to evaporation crystallization and freeze crystallization.

[0020] Furthermore, both the electro-oxidation 1 system and the electro-oxidation 2 system are equipped with an electro-oxidation cleaning system, which is used to perform pickling regularly during the electro-oxidation operation to remove the scale layer deposited on the cathode surface due to the electrolysis process.

[0021] Beneficial effects: Based on the usual treatment of coal chemical wastewater, the present invention uses hard removal and electro-oxidation treatment means for the membrane concentrate generated by the membrane system, enabling the coal chemical concentrate to meet the discharge standards; aiming at the water shortage characteristics of coal chemical enterprises in inland areas, for the membrane concentrate that meets the discharge standards, a combined process is used for fractional crystallization treatment, and at the same time, the internal water resources are effectively recovered for system reuse, realizing the resource treatment of coal chemical wastewater and providing an effective treatment means for the resource treatment of coal chemical wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the process flow chart of the present invention;

[0023] Figure 2 is the schematic diagram of electro-oxidation of the present invention;

[0024] Figure 3 is the schematic diagram of fractional crystallization of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following further explains the present invention with reference to the accompanying drawings.

[0026] As Figure 1 shown, the present invention provides a method for treating coal chemical membrane concentrate by electro-oxidation, including:

[0027] S1: Feed the coal chemical membrane concentrate into the hard removal system unit to remove the calcium and magnesium ions enriched by membrane concentration, and obtain the hard removal effluent.

[0028] S2: Feed the hard removal effluent obtained in step S1 into the electro-oxidation 1 system to degrade the refractory organic matter and ammonia nitrogen in the membrane concentrate, and obtain the effluent meeting the discharge standards.

[0029] S3: Feed the effluent meeting the discharge standards obtained in step S2 into the electrodialysis unit for further concentration of salts, and obtain electrodialysis fresh water and electrodialysis concentrated water.

[0030] S4: Feed the electrodialysis fresh water obtained in step S3 into the reverse osmosis unit to obtain reverse osmosis product water and reverse osmosis concentrated water. Among them, the reverse osmosis product water is used for reusing intermediate water, and the reverse osmosis concentrated water is recycled to the electrodialysis unit for further concentration.

[0031] S5: Feed the electrodialysis concentrated water obtained in step S3 into the electro-oxidation 2 system to further remove the concentrated organic matter and ammonia nitrogen pollutants, and obtain the effluent of the electro-oxidation 2 system.

[0032] S6: Feed the effluent of the electro-oxidation 2 system obtained in step S5 into a fractional crystallization unit to obtain industrial-grade sodium sulfate and industrial-grade sodium chloride. During the fractional crystallization process, the evaporated and condensed water is recycled as reclaimed water.

[0033] In step 1, the hardening removal system unit uses the double-alkali method coupled with hardening removal resin to remove calcium and magnesium ions in the membrane concentrate. After being treated by the hardening removal system unit, the Ca in the effluent after hardening removal is 2+ < 50 mg / L, and Mg 2+ < 50 mg / L.

[0034] As Figure 2 shown, in step 2, the cathode and anode of the electro-oxidation 1 system are arranged in a spaced-apart manner, and each electrolytic chamber composed of a cathode and an anode has independent inlet and outlet pipes, enabling organic substances to effectively contact the anode surface and be oxidized and degraded. The anode of the electro-oxidation 1 system is a thin-film diamond electrode, and the cathode of the electro-oxidation 1 system is a stainless steel or titanium electrode. After being treated by the electro-oxidation 1 system, the pollutants in the coal chemical concentrate can reach the first-class discharge standard of the Comprehensive Wastewater Discharge Standard, where COD ≤ 100 mg / L and ammonia nitrogen ≤ 15 mg / L.

[0035] In step 3, the electrodialysis unit uses homogeneous anion and cation electrodialysis membranes to simultaneously enrich anions and cations, obtaining electrodialysis concentrated water with TDS ≥ 50000 mg / L and the indoor salt content TDS of electrodialysis fresh water ≤ 3000 mg / L.

[0036] In step 4, the reverse osmosis unit is a spiral-wound reverse osmosis, disk tube reverse osmosis, or high-pressure reverse osmosis.

[0037] In step 5, the anode of the electro-oxidation 2 system is a thin-film diamond electrode or a coated electrode.

[0038] As Figure 3 shown, in step 6, the fractional crystallization unit performs evaporation concentration and fractional crystallization treatment on the effluent of the electro-oxidation 2 system. During the fractional crystallization process, sodium chloride is precipitated by evaporation crystallization, and the condensed water generated during the evaporation crystallization process is recycled as reclaimed water. Then, sodium sulfate is precipitated from the effluent of the electro-oxidation 2 system after evaporation through freeze crystallization, and mother liquor is obtained. The mother liquor is then subjected to evaporation crystallization and freeze crystallization until no more mother liquor is generated.

[0039] During the above process, both the electro-oxidation 1 system and the electro-oxidation 2 system are equipped with an electro-oxidation cleaning system, which is used to perform pickling regularly during the electro-oxidation operation to remove the scale layer deposited on the cathode surface due to the electrolysis process. The scale layer is a scale layer such as calcium carbonate and magnesium hydroxide. Reducing agents need to be added to the standard discharge water and the effluent of the electro-oxidation 2 system to make the ORP value in the standard discharge water and the effluent of the electro-oxidation 2 system ≤ 200 mv. The reducing agent can be a chemical substance with reducing properties such as sodium sulfite and sodium pyrosulfate. The reclaimed water produced in the processes of step S4 and step S6 meets the requirements in Table 1 of "Urban Wastewater Reuse - Industrial Water Quality" (GB / T 19923 - 2024), where: COD ≤ 50 mg / L, ammonia nitrogen ≤ 5 mg / L, dissolved total solids ≤ 1000 mg / L, Cl - ≤ 250 mg / L, SO 4 2- ≤ 250 mg / L.

[0040] Example 1:

[0041] Using the method of the present invention to treat the reverse osmosis membrane concentrate in the treatment process of a certain coal chemical wastewater, COD = 500 - 700 mg / L, NH 3 -N = 50 - 150 mg / L, Cl - = 5000 - 10000 mg / L, SO 4 2- After being treated by the electro-oxidation 2 system with BDD as the anode, the current density is controlled at 400 - 600 A / m 2 , and the voltage is controlled at 5 - 7 V. After electro-oxidation treatment, the COD in it < 100 mg / L and the ammonia nitrogen < 5 mg / L. The effluent meets the first-class discharge standard of "Integrated Wastewater Discharge Standard", where COD ≤ 100 mg / L and ammonia nitrogen ≤ 15 mg / L.

[0042] Example 2:

[0043] Using the method of the present invention to treat the reverse osmosis secondary concentrate in the treatment process of a certain coal chemical wastewater, COD = 350 - 550 mg / L, TDS = 25000 - 33000 mg / L, NH 3 -N = 50 - 100 mg / L. This membrane concentrate is treated by the electro-oxidation 1 system, and the electrolysis current density is 550 A / m 2 . The COD in the effluent is 60 - 80 mg / L and the ammonia nitrogen < 5 mg / L. A reducing agent is added to make the ORP value ≤ 200 mv, and it is fed into the electrodialysis unit, and the current density is controlled at 200 - 300 A / m 2, the voltage is 60 - 70V, the COD of the effluent from the fresh water chamber is 30 - 50mg / L, the TDS is 2000 - 5000mg / L, the COD of the effluent from the concentrated water chamber is 150 - 200mg / L, and the TDS is 100000 - 130000mg / L. After the effluent from the fresh water chamber is concentrated by reverse osmosis, the reverse osmosis product water enters the reclaimed water reuse system, and the concentrated water enters the electrodialysis for further concentration; the concentrated water from the electrodialysis is treated by electrooxidation to make the COD in it < 60mg / L, and then it is evaporated and concentrated. Sodium sulfate is precipitated by the freezing method, sodium chloride is produced by evaporation and concentration crystallization, and the evaporation condensate water enters the reclaimed water reuse system.

[0044] Based on the usual treatment of coal chemical wastewater, the present invention adopts the means of hardness removal and electrooxidation treatment for the membrane concentrate generated by the membrane system, so that the coal chemical concentrate can meet the discharge standards; aiming at the water shortage characteristics of coal chemical enterprises in inland areas, the qualified membrane concentrate is treated by a combined process for mass crystallization treatment, and at the same time, the water resources in it are effectively recovered for system reuse, realizing the resource treatment of coal chemical wastewater and providing an effective treatment means for the resource treatment of coal chemical wastewater.

[0045] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for treating coal chemical membrane concentrate by electro-oxidation, characterized in that: include: S1: The coal chemical membrane concentrate enters the hardness removal system unit to remove the calcium and magnesium ions concentrated and enriched by the membrane to obtain hardness-removed effluent; S2: sending the de-hardened effluent obtained in step S1 to the electro-oxidation system 1 to degrade the refractory organic matter and ammonia nitrogen in the membrane concentrate to obtain effluent that meets the discharge standards; S3: sending the qualified discharge water obtained in step S2 to an electrodialysis unit for further concentration of salt to obtain electrodialysis fresh water and electrodialysis concentrated water; S4: sending the electrodialysis fresh water obtained in step S3 to a reverse osmosis unit to obtain reverse osmosis product water and reverse osmosis concentrated water, wherein the reverse osmosis product water is reused as reclaimed water, and the reverse osmosis concentrated water is returned to the electrodialysis unit for further concentration; S5: sending the electrodialysis concentrated water obtained in step S3 to the electro-oxidation system 2 to further remove the concentrated organic matter and ammonia nitrogen pollutants to obtain the effluent of the electro-oxidation system 2; S6: The effluent from the electro-oxidation system 2 obtained in step S5 is sent to a fractionation crystallization unit to obtain industrial-grade sodium sulfate and industrial-grade sodium chloride, wherein the evaporated condensed water during the fractionation crystallization process is reused as reclaimed water.

2. The method for treating coal chemical membrane concentrate by electro-oxidation according to claim 1, characterized in that: The hardness removal system unit uses a double alkali method coupled with a hardness removal resin to remove calcium and magnesium ions in the membrane concentrate, so that the hardness removal effluent obtained after treatment by the hardness removal system unit contains Ca 2+ <50mg / L、Mg 2+ <50mg / L.

3. The method for treating coal chemical membrane concentrate by electro-oxidation according to claim 1, characterized in that: The cathode and anode of the electro-oxidation system are arranged in an intermittent manner, and each electrolysis chamber composed of the cathode and anode has an independent water inlet and outlet pipe, so that organic matter can effectively contact the anode surface and be oxidized and degraded.

4. The method for treating coal chemical membrane concentrate by electro-oxidation according to claim 3, characterized in that: The anode of the electro-oxidation system 1 is a thin film diamond electrode, and the cathode of the electro-oxidation system 1 is a stainless steel or titanium electrode.

5. The method for treating coal chemical membrane concentrate by electro-oxidation according to claim 1, characterized in that: The electrodialysis unit adopts anion and cation homogeneous electrodialysis membrane to simultaneously enrich anions and cations. The electrodialysis concentrated water is enriched to a TDS of ≥50000 mg / L, and the indoor salt content TDS of the electrodialysis fresh water is ≤3000 mg / L.

6. The method for treating coal chemical membrane concentrate by electro-oxidation according to claim 1, characterized in that: The reverse osmosis unit is a spiral reverse osmosis, a disc-tube reverse osmosis or a high-pressure reverse osmosis.

7. The method for treating coal chemical membrane concentrate by electro-oxidation according to claim 1, characterized in that: The anode of the electro-oxidation system is a thin film diamond electrode or a coated electrode.

8. The method for treating coal chemical membrane concentrate by electro-oxidation according to claim 1, characterized in that: The fractionation crystallization unit performs evaporation, concentration, fractionation and crystallization treatment on the effluent from the electro-oxidation system 2. During the fractionation and crystallization process, sodium chloride is precipitated by evaporation and crystallization. The condensed water generated in the evaporation and crystallization process is reused as reclaimed water. The effluent from the electro-oxidation system 2 is then treated by freezing crystallization to precipitate sodium sulfate and obtain a mother liquor, which is then subjected to evaporation and crystallization and freezing crystallization.

9. The method for treating coal chemical membrane concentrate by electro-oxidation according to claim 1, characterized in that: The electro-oxidation system 1 and the electro-oxidation system 2 are both equipped with an electro-oxidation cleaning system for periodically performing acid washing to remove the scale layer deposited on the cathode surface due to the electrolysis process during the electro-oxidation operation.

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