System for realizing zero discharge and resource utilization of coking wastewater

Abstract

The invention provides a system for realizing zero discharge and resource utilization of coking wastewater, which comprises the following steps of: performing primary treatment on coking wastewater after-treatment effluent through a primary treatment module to obtain primary produced water and primary concentrated water, and performing secondary treatment on the primary concentrated water through a secondary treatment module to obtain secondary produced water and secondary concentrated water; performing third-stage treatment on the second-stage concentrated water through a third-stage treatment module to obtain low-concentration brine, an alkaline solution and an acidic solution; according to the system for realizing zero discharge and resource utilization of the coking wastewater, primary produced water and secondary produced water obtained by the wastewater treatment process can be recycled to an industrial water system, and low-concentration brine can be recycled to a secondary reverse osmosis device in the secondary treatment module; the alkaline solution and the acid solution can be reused in a wastewater treatment process and a steelmaking and steel rolling main process of a steel mill, so that the overall recovery rate is as high as 100%, and zero emission and recycling of the coking wastewater are effectively realized in a steel-coke co-production enterprise.

Description

Technical Field

[0001] The invention relates to the technical field of coking wastewater treatment, and in particular to a system for achieving zero discharge and resource utilization of coking wastewater. Background Art

[0002] Coking wastewater mainly comes from coking, gas purification, by-product recovery and refining processes. In addition to high concentrations of inorganic pollutants such as ammonia, cyanide, and thiocyanide, coking wastewater also contains organic pollutants such as phenols, pyridine, quinoline, and polycyclic aromatic hydrocarbons (PAHs). Coking wastewater is a recognized difficult-to-treat industrial wastewater. This is mainly because the wastewater has complex components, high salt content, and contains various types of difficult-to-degrade and biologically toxic organic matter.

[0003] At present, the existing coking wastewater treatment stations have adopted a large number of biochemical treatments. This treatment system can only remove ammonia nitrogen, BOD (Biochemical Oxygen Demand), phenol, cyanide and other pollutants. It has a poor removal effect on the difficult-to-degrade COD (Chemical Oxygen Demand) and has no removal effect on salt. With the improvement of national environmental protection policy requirements, there is an urgent need for zero discharge and resource utilization of coking wastewater. For the effluent from biochemical treatment and post-treatment, zero discharge reuse and resource utilization are required. The post-treatment effluent that meets certain standards must be reused after deep treatment, and the resource utilization of salt is the only way to treat coking wastewater. At present, there are many technologies that use pure membrane method for deep treatment, but they have not been considered from the whole system, so that many technical cases have poor control of membrane water quality, inadequate concentrated water treatment, low water production rate and unstable operation. At the same time, the current zero-emission technology mainly uses evaporation and crystallization technology. When the salt is not separated, this technology will produce a large amount of miscellaneous salts that are hazardous waste, increasing disposal costs and environmental risks. When the salt is separated and recycled, it also produces a large amount of low-value sodium chloride and sodium sulfate. Due to the difficulty in disposing of them, they are stored in large quantities, causing waste of resources and environmental risks.

[0004] In view of this, it is necessary to develop a system that is technically feasible, stable in operation, and reliable in effect to achieve zero discharge and resource utilization of coking wastewater. Summary of the invention

[0005] In view of this, the present application provides a system for achieving zero discharge and resource utilization of coking wastewater, so as to solve the problem in the existing coking wastewater treatment technology that only biological treatment and post-treatment cannot meet the water quality requirements of industrial circulating cooling water make-up water and cannot achieve effective reuse of coking wastewater, and the problem that there is no reasonable way out for zero discharge of salt.

[0006] The object of the present invention is achieved through the following technical solutions: In order to achieve the above technical objectives, this application adopts the following technical solutions: The present invention provides a system for achieving zero discharge and resource utilization of coking wastewater, comprising a primary treatment module, a secondary treatment module and a tertiary treatment module connected in sequence; Among them, the primary treatment module is used to perform primary treatment on the effluent from the coking wastewater post-treatment to obtain primary produced water and primary concentrated water; the secondary treatment module is used to perform secondary treatment on the primary concentrated water to obtain secondary produced water and secondary concentrated water; the tertiary treatment module is used to perform tertiary treatment on the secondary concentrated water to obtain low-concentration brine, alkaline solution and acidic solution; both the primary produced water and the secondary produced water can be reused in the industrial water system.

[0007] Preferably, the primary treatment module comprises a primary ultrasonic catalytic oxidation tank, a primary multi-media filter, a primary self-cleaning filter, a primary ultrafiltration device and a primary reverse osmosis device connected in sequence; Among them, the first-level ultrasonic catalytic oxidation tank is used to perform a catalytic oxidation and a turbulent flow on the post-treatment effluent of the coking wastewater to form the first wastewater; the first-level multi-media filter is used to perform a filtering treatment on the first wastewater; the first-level self-cleaning filter is used to perform a secondary filtering treatment on the first wastewater; the first-level ultrafiltration device is used to perform ultrafiltration treatment on the first wastewater; the first-level reverse osmosis device is used to perform reverse osmosis treatment on the first wastewater to obtain primary produced water and primary concentrated water, and the primary produced water is transported to the produced water reuse pool.

[0008] Preferably, in the first-stage ultrasonic catalytic oxidation tank: the frequency of the ultrasonic device is 50~500kHz, the TiO2 catalyst dosage is 100~300mg / L, and the pH is set at 5~7; the filtration accuracy of the first-stage self-cleaning filter is 50μm, the design flux of the first-stage ultrafiltration device is 35~45LMH, and the design flux of the first-stage reverse osmosis device is 14~18LMH.

[0009] Preferably, the secondary treatment module comprises a secondary ultrasonic catalytic oxidation tank, a primary high-efficiency sedimentation tank, a secondary multi-media filter, a secondary self-cleaning filter, a secondary ultrafiltration device, a nanofiltration device and a secondary reverse osmosis device connected in sequence; Among them, the secondary ultrasonic catalytic oxidation tank is used to carry out secondary catalytic oxidation and secondary turbulence on the primary concentrated water to form the second wastewater; the primary high-efficiency sedimentation tank is used to remove suspended matter, organic matter and hardness in the second wastewater; the secondary multi-media filter is used to carry out primary filtration treatment on the second wastewater; the secondary self-cleaning filter is used to carry out secondary filtration treatment on the second wastewater; the secondary ultrafiltration device is used to carry out ultrafiltration treatment on the second wastewater; the nanofiltration device is used to carry out nanofiltration treatment on the second wastewater to form the third wastewater and the secondary concentrated water; the secondary reverse osmosis device is used to carry out reverse osmosis treatment on the third wastewater to obtain the secondary produced water and the secondary concentrated water, and transport the secondary produced water to the produced water reuse pool.

[0010] Preferably, in the secondary ultrasonic catalytic oxidation tank: the frequency of the ultrasonic device is 300~600kHz, the TiO2 catalyst dosage is 200~400mg / L, and the pH is set at 4~6; the filtration flow rate of the secondary multi-media filter is 8~10m / h, the design flux of the secondary ultrafiltration device is 35~40LMH, the design flux of the nanofiltration device is 10~13LMH, and the design flux of the secondary reverse osmosis device is 13~16LMH.

[0011] Preferably, the three-stage treatment module includes a secondary high-efficiency sedimentation tank, an adsorption oxidation tank, a resin hardness and carbon removal tank, and a bipolar membrane device connected in sequence; Among them, the secondary high-efficiency sedimentation tank is used to remove suspended solids, organic matter and hardness in the secondary wastewater to form the fourth wastewater; the adsorption oxidation tank is used to oxidize and remove the difficult-to-biodegrade organic matter in the fourth wastewater; the resin hardness and carbon removal tank is used to completely remove the hardness and organic matter in the fourth wastewater; the bipolar membrane device is used to prepare the fourth wastewater into an alkaline solution containing sodium hydroxide, an acidic solution containing hydrochloric acid and sulfuric acid, and low-concentration brine.

[0012] Preferably, the primary high-efficiency sedimentation tank and the secondary high-efficiency sedimentation tank both include a pH adjustment tank, a coagulation tank, a flocculation tank and a concentration sedimentation tank.

[0013] Preferably, an acid adjustment tank, an activated carbon contact tank, a reaction tank, an alkali adjustment tank and a sedimentation tank are sequentially arranged in the adsorption oxidation tank. The activated carbon in the activated carbon contact tank has an iodine value of 500-800, a methylene blue value of 10-16, and the pH of the acid adjustment tank is 2-4. Special resins for hardness removal and special resins for organic matter removal are arranged in the resin hardness removal and carbon removal tank. The hardness of the effluent is controlled below 1 mg / L, and the organic matter is controlled below 30 mg / L.

[0014] Preferably, the bipolar membrane device is used to prepare the fourth wastewater into an alkaline solution with a mass concentration of 8% to 10% and an acidic solution with a mass concentration of 8% to 11%. Preferably, the alkaline solution is respectively recycled to the primary high-efficiency sedimentation tank, the secondary high-efficiency sedimentation tank, the adsorption oxidation tank and the steelmaking process of the steel plant; the acidic solution is respectively recycled to the primary ultrasonic catalytic oxidation tank, the secondary ultrasonic catalytic oxidation tank, the adsorption oxidation tank and the steel rolling process of the steel plant; and the low-concentration brine is recycled to the secondary reverse osmosis device.

[0015] Beneficial effect: The present invention provides a system for achieving zero discharge and resource utilization of coking wastewater, which firstly performs primary treatment on the post-treatment effluent of coking wastewater through a primary treatment module to obtain primary produced water and primary concentrated water, then performs secondary treatment on the primary concentrated water through a secondary treatment module to obtain secondary produced water and secondary concentrated water, and then performs tertiary treatment on the secondary concentrated water through a tertiary treatment module to obtain low-concentration brine, alkaline solution and acidic solution; the above system for achieving zero discharge and resource utilization of coking wastewater can obtain primary produced water and secondary produced water through the wastewater treatment process, which can be reused in the industrial water system, the low-concentration brine can be reused in the secondary reverse osmosis device in the secondary treatment module, and the alkaline solution and acidic solution can be reused in the wastewater treatment process and the main steelmaking and steel rolling processes of the steel plant, so that the overall recovery rate is as high as 100%, thereby effectively enabling the steel-coke co-production enterprise to achieve zero discharge and resource utilization of coking wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A process flow chart of a system for achieving zero discharge and resource utilization of coking wastewater provided in an embodiment of the present application; In the attached figure: 100-primary processing module; 200-secondary processing module; 300-tertiary processing module. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] In the existing coking wastewater treatment technology, biological treatment and post-treatment alone cannot meet the water quality requirements of industrial circulating cooling water make-up water and cannot achieve the effective reuse of coking wastewater, and there is no reasonable way out for zero-emission salt.

[0019] The present invention uses the synergistic treatment process of pre-membrane pretreatment and three-membrane method to systematically control the water quality of the inlet and outlet water of each level of membrane components, thereby improving the water production rate and operation stability of the system as a whole. The water produced by the deep treatment system reaches and exceeds the water quality standard of Table 6.1.3 of the "Design Specification for Industrial Circulating Cooling Water Treatment" GB50050-2017 for directly using reclaimed water as supplementary water for the intercooling open system, so as to achieve the reuse of industrial new water, that is, to achieve the reuse of coking wastewater and save water resources.

[0020] At the same time, according to the demand for alkali and acid in the steel plant, the concentrated water of the membrane system is treated and the acid and alkali are produced and reused in the main process of steelmaking and rolling in the steel plant, so that the coking wastewater of the steel-coke co-production enterprise can be zero-discharged and resourced from the system. It is of great significance to protect the ecological environment and the high-quality sustainable development of the steel-coke co-production enterprise.

[0021] See also Figure 1 , Figure 1 A process flow chart of a system for achieving zero discharge and resource utilization of coking wastewater provided in an embodiment of the present application; wherein the system for achieving zero discharge and resource utilization of coking wastewater provided by the present invention comprises a primary treatment module 100, a secondary treatment module 200 and a tertiary treatment module 300 connected in sequence; Among them, the primary treatment module 100 is used to perform primary treatment on the post-treatment effluent of coking wastewater to obtain primary produced water and primary concentrated water; the secondary treatment module 200 is used to perform secondary treatment on the primary concentrated water to obtain secondary produced water and secondary concentrated water; the tertiary treatment module 300 is used to perform tertiary treatment on the secondary concentrated water to obtain low-concentration brine, alkaline solution and acidic solution; both the primary produced water and the secondary produced water can be reused in the industrial water system.

[0022] In the embodiment of the present invention, the primary treatment module 100 includes a primary ultrasonic catalytic oxidation tank, a primary multi-media filter, a primary self-cleaning filter, a primary ultrafiltration device, and a primary reverse osmosis device connected in sequence; Among them, the first-level ultrasonic catalytic oxidation tank is used to perform a catalytic oxidation and a turbulent flow on the post-treatment effluent of the coking wastewater to form the first wastewater; the first-level multi-media filter is used to perform a filtering treatment on the first wastewater; the first-level self-cleaning filter is used to perform a secondary filtering treatment on the first wastewater; the first-level ultrafiltration device is used to perform ultrafiltration treatment on the first wastewater; the first-level reverse osmosis device is used to perform reverse osmosis treatment on the first wastewater to obtain primary produced water and primary concentrated water, and the primary produced water is transported to the produced water reuse pool.

[0023] Specifically, the first-stage ultrasonic catalytic oxidation tank is mainly used to place the coking wastewater that has undergone pretreatment, biochemical treatment and post-treatment processes into the first-stage ultrasonic catalytic oxidation tank. An ultrasonic device, a TiO2 catalyst and an agitator are arranged in the tank body, and an acid addition point is arranged to perform a catalytic oxidation and a turbulent flow on the wastewater. In the first-stage ultrasonic catalytic oxidation tank: the frequency of the ultrasonic device is 50~500kHz, the dosage of the TiO2 catalyst is 100~300mg / L, and the pH is set at 5~7.

[0024] Furthermore, ultrasound can effectively stimulate chemical reactions within this frequency range, promoting the oxidation and decomposition of organic matter in the effluent from the post-treatment of coking wastewater; TiO2, as a highly efficient catalyst, can produce active substances such as strongly oxidizing hydroxyl free radicals under the action of ultrasound, and oxidize and degrade organic matter in the wastewater. The dosage within this range can ensure that there are enough catalysts to participate in the reaction and improve the oxidation effect; within this pH range, the catalyst has higher activity and can better play a catalytic role, which is also beneficial to the oxidation and decomposition of organic matter in the wastewater.

[0025] Specifically, the first wastewater enters the primary multi-media filter, and the coking wastewater is filtered using multiple layers of filter media; the first wastewater in the primary multi-media filter enters the primary self-cleaning filter, and the coking wastewater is further filtered.

[0026] Specifically, the filtration accuracy of the first-stage self-cleaning filter is 50μm, which can intercept relatively large-sized particulate matter in wastewater, such as sediment, rust, suspended solids, etc. If these impurities enter the subsequent treatment links, they may cause blockage, wear and other damages to the first-stage ultrafiltration device and the first-stage reverse osmosis device, reducing their treatment efficiency and service life.

[0027] Specifically, the first wastewater in the first-stage self-cleaning filter enters the first-stage ultrafiltration device to remove most of the suspended solids, colloids, organic matter, etc. in the first wastewater; the design flux of the first-stage ultrafiltration device is 35~45LMH. The design flux within this range can minimize the pollution rate of the ultrafiltration membrane while ensuring a certain treatment efficiency. Too high a flux may lead to faster accumulation of pollutants on the membrane surface, requiring more frequent cleaning and maintenance, and may even shorten the service life of the membrane; too low a flux will reduce the processing capacity and increase equipment investment and operating costs.

[0028] Specifically, the first wastewater in the first-stage ultrafiltration device enters the first-stage reverse osmosis device, and most of the soluble salts, colloids, organic matter and microorganisms in the first wastewater are removed to obtain first-stage produced water and first-stage concentrated water. The first-stage produced water that meets the reuse water standard is transported to the produced water reuse pool for reuse in the industrial water system, and the first-stage concentrated water is transported to the secondary treatment module 200; the design flux of the first-stage reverse osmosis device is 14~18LMH; a lower design flux can reduce the risk of reverse osmosis membrane contamination and improve the quality and stability of produced water. The reverse osmosis membrane has a high removal rate for soluble salts, small molecular organic matter, etc., but if the flux is too high, it may lead to an increase in concentration polarization on the membrane surface, making it easier for salts and impurities to accumulate on the membrane surface, affecting the quality of produced water.

[0029] In the embodiment of the present invention, the secondary treatment module 200 includes a secondary ultrasonic catalytic oxidation tank, a primary high-efficiency sedimentation tank, a secondary multi-media filter, a secondary self-cleaning filter, a secondary ultrafiltration device, a nanofiltration device, and a secondary reverse osmosis device connected in sequence; Among them, the secondary ultrasonic catalytic oxidation tank is used to carry out secondary catalytic oxidation and secondary turbulence on the primary concentrated water to form the second wastewater; the primary high-efficiency sedimentation tank is used to remove suspended matter, organic matter and hardness in the second wastewater; the secondary multi-media filter is used to carry out primary filtration treatment on the second wastewater; the secondary self-cleaning filter is used to carry out secondary filtration treatment on the second wastewater; the secondary ultrafiltration device is used to carry out ultrafiltration treatment on the second wastewater; the nanofiltration device is used to carry out nanofiltration treatment on the second wastewater to form the third wastewater and the secondary concentrated water; the secondary reverse osmosis device is used to carry out reverse osmosis treatment on the third wastewater to obtain the secondary produced water and the secondary concentrated water, and transport the secondary produced water to the produced water reuse pool.

[0030] Specifically, the primary concentrated water in the primary reverse osmosis device enters the secondary ultrasonic catalytic oxidation tank, an ultrasonic device, a TiO2 catalyst and a stirrer are arranged in the tank body, an acid addition point is arranged, and the primary concentrated water is subjected to secondary catalytic oxidation and secondary turbulence to obtain the second wastewater; the frequency of the ultrasonic device in the secondary ultrasonic catalytic oxidation tank is 300~600kHz; among them, the frequency of the secondary ultrasonic catalytic oxidation tank is higher than that of the primary ultrasonic catalytic oxidation tank, and the higher frequency ultrasonic wave can produce stronger cavitation effect and mechanical vibration, further promote the oxidation and decomposition reaction of the coking wastewater, can more effectively stimulate the activity of the TiO2 catalyst, accelerate the degradation of organic matter, and improve the treatment effect.

[0031] Specifically, the dosage of TiO2 catalyst in the secondary ultrasonic catalytic oxidation tank is 200-400 mg / L; the dosage is increased compared with the primary ultrasonic catalytic oxidation tank. This is because after the primary treatment, the remaining organic matter in the wastewater may be more difficult to degrade, and more catalysts are needed to promote the oxidation reaction. A higher catalyst dosage can provide more active sites and enhance oxidation capacity.

[0032] Specifically, the pH in the secondary ultrasonic catalytic oxidation tank is set at 4-6, where the pH value is lower than that in the primary ultrasonic catalytic oxidation tank. Within this pH range, it may be more conducive to the activity of the TiO2 catalyst and the oxidation and decomposition of specific organic matter. Different pH conditions will affect the charge properties and reaction activity of the catalyst surface. By adjusting the pH, the efficiency of the oxidation reaction can be optimized.

[0033] Specifically, the second concentrated water in the secondary ultrasonic catalytic oxidation tank enters the primary high-efficiency sedimentation tank, and the alkali, coagulant and flocculant addition points are set in the tank to remove suspended matter, organic matter and hardness in the second concentrated water.

[0034] Specifically, the second wastewater in the primary high-efficiency sedimentation tank enters the secondary multi-media filter, and the second wastewater is filtered using multiple layers of filter media. The filtration flow rate of the secondary multi-media filter is 8 to 10 m / h; this flow rate can improve the treatment efficiency while ensuring the filtration effect. The multi-media filter removes suspended matter and some organic matter in the wastewater through filter media layers of different particle sizes. The appropriate filtration flow rate can ensure that the filter media fully exerts its filtration effect while avoiding filter media blockage and excessive pressure loss.

[0035] Specifically, the second wastewater in the secondary multi-media filter enters the secondary self-cleaning filter, and the second wastewater is further filtered.

[0036] Specifically, the second wastewater in the secondary self-cleaning filter enters the secondary ultrafiltration device to remove most of the suspended solids, colloids, organic matter, etc. in the second wastewater. The design flux of the secondary ultrafiltration device is 35~40LMH; compared with the primary ultrafiltration device, the flux range is slightly different. This flux can better remove impurities such as colloids and macromolecular organic matter in the wastewater while meeting the secondary treatment requirements, and provide high-quality water for the nanofiltration and reverse osmosis devices.

[0037] Specifically, the second wastewater in the secondary ultrafiltration device enters the nanofiltration device, which removes most of the soluble divalent and trivalent salts, some soluble monovalent salts, colloids, organic matter and microorganisms in the second wastewater and produces some secondary concentrated water and third wastewater. The design flux of the nanofiltration device is 10~13LMH; the nanofiltration device is mainly used to remove divalent ions, small molecular organic matter, etc. in wastewater. A lower design flux can reduce the risk of nanofiltration membrane contamination and improve the separation performance and service life of the membrane. At the same time, it also helps to ensure the quality of produced water.

[0038] Specifically, part of the secondary concentrated water in the nanofiltration device enters the tertiary treatment module 300, and the third wastewater in the nanofiltration device enters the secondary reverse osmosis device, and most of the soluble salts, colloids, organic matter and microorganisms in the third wastewater are removed to obtain secondary produced water and secondary concentrated water. The secondary produced water is transported to the produced water reuse pool for reuse in the industrial water system because it meets the reuse water standards, and the secondary concentrated water is transported to the tertiary treatment module 300.

[0039] Furthermore, the design flux of the secondary reverse osmosis device is 13~16LMH, which is slightly lower than the flux of the primary reverse osmosis device. In the secondary treatment, since the influent water quality has been processed in multiple previous links, it may contain impurities that are more difficult to remove, so the flux needs to be reduced to ensure better removal effect and water quality. At the same time, lower flux can also reduce membrane pollution and damage and extend the service life of the membrane.

[0040] In the embodiment of the present invention, the three-stage treatment module 300 includes a secondary high-efficiency sedimentation tank, an adsorption oxidation tank, a resin hardness and carbon removal tank, and a bipolar membrane device connected in sequence; Among them, the secondary high-efficiency sedimentation tank is used to remove suspended solids, organic matter and hardness in the secondary wastewater to form the fourth wastewater; the adsorption oxidation tank is used to oxidize and remove the difficult-to-biodegrade organic matter in the fourth wastewater; the resin hardness and carbon removal tank is used to completely remove the hardness and organic matter in the fourth wastewater; the bipolar membrane device is used to prepare the fourth wastewater into an alkaline solution containing sodium hydroxide, an acidic solution containing hydrochloric acid and sulfuric acid, and low-concentration brine.

[0041] Specifically, the secondary concentrated water of the coking wastewater in the nanofiltration device and the secondary reverse osmosis device enters the secondary high-efficiency sedimentation tank to form the fourth wastewater. The tank is provided with the addition points of alkali, coagulant and flocculant to remove the suspended solids, organic matter and hardness in the secondary concentrated water; the primary high-efficiency sedimentation tank and the secondary high-efficiency sedimentation tank both include a pH adjustment tank, a coagulation tank, a flocculation tank and a concentrated sedimentation tank; wherein, the pH adjustment tank can optimize the conditions of subsequent coagulation, flocculation and other reactions by adjusting the pH value of the wastewater, and different pH values ​​will affect the existence form and reaction activity of the substances in the water, thereby affecting the precipitation effect; the coagulation tank is used to add coagulants to the wastewater to make the tiny particles and colloidal substances in the water condense into larger particles, which is convenient for subsequent precipitation and removal; the flocculation tank is used to add flocculants to the coagulated water to further promote the growth and aggregation of particles, form larger flocs, and improve the sedimentation efficiency; the concentrated sedimentation tank is used to make the flocs settle down under the action of gravity to achieve the removal of suspended solids, organic matter, hardness and other substances.

[0042] Specifically, the fourth wastewater in the secondary high-efficiency sedimentation tank enters the adsorption oxidation tank, in which an acid adjustment tank, an activated carbon contact tank, a reaction tank, an alkali adjustment tank, and a sedimentation tank are sequentially arranged, as well as acid, activated carbon, ferrous sulfate, hydrogen peroxide, alkali and flocculant addition points are sequentially arranged to oxidize and remove the difficult-to-biodegrade organic matter in the secondary concentrated water.

[0043] Furthermore, the activated carbon in the activated carbon contact tank uses an iodine value of 500-800 and a methylene blue value of 10-16; among them, activated carbon with a high iodine value usually has a larger specific surface area and rich microporous structure, which can better adsorb organic matter in wastewater. The methylene blue value reflects the adsorption capacity of activated carbon for small molecular organic matter. In this contact tank, the activated carbon removes some organic matter in the wastewater through physical adsorption.

[0044] Furthermore, the pH of the acid adjustment tank is 2-4; under this acidic condition, it is conducive to the subsequent reaction. A lower pH can promote the protonation of certain organic matter, making it easier to be adsorbed or oxidized.

[0045] Furthermore, ferrous sulfate and hydrogen peroxide are added to the adsorption oxidation tank in sequence. Ferrous sulfate reacts with hydrogen peroxide under acidic conditions to produce highly oxidizing hydroxyl radicals, which can oxidize and decompose the difficult-to-biodegrade organic matter in the wastewater. This Fenton oxidation reaction is highly efficient and rapid, and can effectively remove organic matter.

[0046] Furthermore, the alkali adjustment tank is used to adjust the pH of the wastewater to alkaline, generally to neutralize the acidic substances produced during the reaction, and also to facilitate the subsequent precipitation process; the sedimentation tank allows the precipitate generated by the reaction and the suspended matter that has not been completely removed to settle under the action of gravity to achieve solid-liquid separation. Through a series of treatment steps, the adsorption oxidation tank can effectively remove the difficult-to-biodegrade organic matter in the fourth wastewater, improve the biodegradability of the wastewater, and provide better water quality conditions for subsequent treatment.

[0047] Specifically, the fourth wastewater in the adsorption oxidation tank enters the resin hardness and carbon removal tank, in which hardness removal resin and organic matter removal resin are arranged to completely remove the hardness and organic matter in the fourth wastewater; the resin hardness and carbon removal tank is equipped with special hardness removal resin and special organic matter removal resin, and the outlet water hardness is controlled below 1 mg / L, and the organic matter is controlled below 30 mg / L.

[0048] Furthermore, hardness removal resin is mainly used to remove hardness ions in wastewater, such as calcium and magnesium ions. Through ion exchange reaction, hardness ions are adsorbed on the resin, thereby reducing the hardness of the effluent water. Controlling the effluent water hardness below 1 mg / L can effectively prevent the formation of scale in the subsequent treatment process or discharge process, protect equipment and pipelines, and reduce the impact on the environment.

[0049] Furthermore, special resins for removing organic matter are used to remove organic matter from wastewater. Such resins usually have specific functional groups that can react with organic matter through adsorption and ion exchange, thereby removing organic matter from wastewater. Controlling the organic matter in effluent to below 30 mg / L can further reduce the degree of wastewater pollution and improve water quality.

[0050] Furthermore, the resin hardness and carbon removal tank can effectively remove the hardness and organic matter in the fourth wastewater through the synergistic effect of two special resins, so that the wastewater can be further purified and provide high-quality influent water for subsequent bipolar membrane device treatment.

[0051] Specifically, the fourth wastewater in the resin hardness and carbon removal tank enters the bipolar membrane device, and a bipolar membrane system is arranged in the tank to prepare the fourth wastewater (secondary concentrated brine) into an alkaline solution of sodium hydroxide, an acidic solution of hydrochloric acid and sulfuric acid, and a low-concentration brine. The alkaline solution is respectively reused in the primary high-efficiency sedimentation tank, the secondary high-efficiency sedimentation tank, the adsorption oxidation tank and the steelmaking process of the steel plant; the acidic solution is respectively reused in the primary ultrasonic catalytic oxidation tank, the secondary ultrasonic catalytic oxidation tank, the adsorption oxidation tank and the steel rolling process of the steel plant; and the low-concentration brine is reused in the secondary reverse osmosis device.

[0052] Preferably, the bipolar membrane device is used to prepare the fourth wastewater into an alkaline solution with a mass concentration of 8% to 10% and an acidic solution with a mass concentration of 8% to 11%. Preferably, the low-concentration brine is sent to the secondary reverse osmosis device for use. The addition of low-concentration brine can adjust the inlet salinity and other water quality parameters of the secondary reverse osmosis device. To a certain extent, it can stabilize the inlet water quality, reduce the impact of inlet water quality fluctuations on the reverse osmosis membrane, and improve the operational stability and reliability of the reverse osmosis device. At the same time, incorporating low-concentration brine into the treatment process of the secondary reverse osmosis device realizes the comprehensive treatment and resource recovery of wastewater. This helps to improve the performance and efficiency of the entire system and achieve a sustainable wastewater treatment and resource utilization model.

[0053] Specifically, the primary water produced in the primary reverse osmosis device and the secondary water produced in the secondary reverse osmosis device enter the water reuse pool, the coking wastewater produced that meets the reuse standards is temporarily stored, and a lifting pump is set to deliver it to the reused water users for use.

[0054] In an embodiment of the present invention, the first-stage ultrasonic catalytic oxidation tank and the second-stage ultrasonic catalytic oxidation tank can remove most of the organic matter through catalytic oxidation to protect the subsequent membrane system. At the same time, the wastewater is turbulent through ultrasonic action and steady-state cavitation principle, which can increase the wastewater flux of the subsequent membrane and reduce fouling on the membrane surface.

[0055] In the embodiment of the present invention, the adsorption oxidation tank simultaneously adopts activated carbon adsorption and Fenton-like advanced oxidation technology. In particular, the activated carbon contact tank is placed after the acid adjustment tank, which greatly increases the adsorption effect of activated carbon on characteristic organic matter. The activated carbon adsorption and Fenton process are coupled and used. At the same time, the parameters of the activated carbon are specially set to specifically remove the organic matter mainly with 7-13C chains remaining in the secondary concentrated water.

[0056] In the embodiment of the present invention, the resin hardness and carbon removal tank reduces the hardness and organic matter remaining in the secondary concentrated water to the appropriate range of the bipolar membrane system, thereby improving the use efficiency of the bipolar membrane. Finally, the concentrated brine mainly composed of sodium chloride and sodium sulfate is separated by the bipolar membrane to produce alkali and mixed acid, which are reused in the wastewater treatment system on the one hand, and the excess alkali and acid are reused in the main steelmaking and rolling processes of the steel plant, thereby achieving a closed loop of full reuse of wastewater, zero discharge, and resource utilization of salt.

[0057] The technical solution of the present invention is now further described in conjunction with specific embodiments.

[0058] Embodiment 1: See also Figure 1 Embodiment 1 of the present invention provides a system for achieving zero discharge and resource utilization of coking wastewater, including a primary ultrasonic catalytic oxidation tank, a primary multi-media filter, a primary self-cleaning filter, a primary ultrafiltration device, a primary reverse osmosis device, a secondary ultrasonic catalytic oxidation tank, a primary high-efficiency sedimentation tank, a secondary multi-media filter, a secondary self-cleaning filter, a secondary ultrafiltration device, a nanofiltration device, a secondary reverse osmosis device, a secondary high-efficiency sedimentation tank, an adsorption oxidation tank, a resin hardness and carbon removal tank, a bipolar membrane device, and a produced water reuse tank; Among them, the first-level ultrasonic catalytic oxidation tank is connected to the first-level multi-media filter, the first-level multi-media filter is connected to the first-level self-cleaning filter, the first-level self-cleaning filter is connected to the first-level ultrafiltration device, the first-level ultrafiltration device is connected to the first-level reverse osmosis device, and the first-level reverse osmosis device is connected to the second-level ultrasonic catalytic oxidation tank and the produced water reuse tank; Among them, the secondary ultrasonic catalytic oxidation tank is connected to the primary high-efficiency sedimentation tank, the primary high-efficiency sedimentation tank is connected to the secondary multi-media filter, the secondary multi-media filter is connected to the secondary self-cleaning filter, the secondary self-cleaning filter is connected to the secondary ultrafiltration device, the secondary ultrafiltration device is connected to the nanofiltration device, the nanofiltration device is connected to the secondary reverse osmosis device and the secondary high-efficiency sedimentation tank, the secondary reverse osmosis device is connected to the produced water reuse tank and the secondary high-efficiency sedimentation tank; Among them, the secondary high-efficiency sedimentation tank is connected to the adsorption oxidation tank, the adsorption oxidation tank is connected to the resin hardness and carbon removal tank, the resin hardness and carbon removal tank is connected to the bipolar membrane device, the secondary reverse osmosis device, the first ultrasonic catalytic oxidation tank, the second ultrasonic catalytic oxidation tank, the first high-efficiency sedimentation tank, the second high-efficiency sedimentation tank and the adsorption oxidation tank.

[0059] In this embodiment 1, the water quality of the raw water of the coking wastewater is calculated by COD cr≤5000mg / L, ammonia nitrogen ≤200mg / L, total nitrogen ≤300mg / L. The raw water of coking wastewater needs to be pretreated, biochemically treated and post-treated. The effluent quality of post-treated water can easily reach the limit of direct discharge standard in Table 2 of "Emission Standard of Pollutants for Coking Chemical Industry" (GB16171-2012). The effluent of post-treatment enters this deep treatment and reuse system again. The produced water after treatment by this deep treatment and reuse system can reach and exceed the water quality standard of Table 6.1.3 of "Design Specification for Industrial Circulating Cooling Water Treatment" GB50050-2017 for direct use of recycled water as supplementary water for intercooling open system, so as to achieve the reuse of industrial new water, that is, to realize the reuse of coking wastewater and save water resources. At the same time, according to the demand for alkali and acid in the steel plant, the concentrated water of the membrane system is treated to produce acid and alkali for the main process of steelmaking and rolling in the steel plant, so as to achieve zero discharge and resource utilization of coking wastewater in steel and coke co-production enterprises from the system.

[0060] Specifically, the operating steps and specific parameters of each component in the system for achieving zero discharge and resource utilization of coking wastewater provided in Example 1 of the present invention are as follows: (1) Primary ultrasonic catalytic oxidation tank: The coking wastewater that has undergone pretreatment, biochemical treatment and post-treatment is placed in a primary ultrasonic catalytic oxidation tank. An ultrasonic device, TiO2 catalyst and a stirrer are installed in the tank body, and an acid addition point is set to perform a primary catalytic oxidation and a primary turbulence on the wastewater. The frequency of the ultrasonic device is 100~450kHz, the TiO2 catalyst dosage is 150~300mg / L, and the pH is set at 5~7.

[0061] (2) Primary multi-media filter: The coking wastewater in the intermediate water tank enters the primary multi-media filter, where suspended solids, colloids and oils are removed through multi-layer filtration, reducing the workload of the ultrafiltration membrane and extending the service life of the ultrafiltration membrane. The filter media of the multi-media filter are anthracite and graded high-quality quartz sand. The anthracite layer height is 400 mm, and the quartz sand layer height is 800 mm. The filter flow rate is 8 to 9 m / h.

[0062] (3) Primary self-cleaning filter: The coking wastewater in the primary multi-media filter enters the primary self-cleaning filter, which mainly removes suspended solids larger than 50 μm, soft impurities, and fibrous impurities in the water, effectively protecting the ultrafiltration membrane.

[0063] (4) Primary ultrafiltration device: The coking wastewater in the primary self-cleaning filter enters the primary ultrafiltration device. The external pressure hollow fiber ultrafiltration membrane element made of polymer materials is mainly used to remove suspended matter, colloids, and macromolecular organic matter in the water, and partially reduce the oil, COD and bacteria content in the water. The removal rate of suspended matter, colloidal iron and microorganisms can generally reach 98%, the effluent SDI (Silt Density Index) is ≤3, and the design flux is 35~40LMH.

[0064] (5) Primary reverse osmosis device: The coking wastewater in the primary ultrafiltration device enters the primary reverse osmosis device to remove most of the soluble salts, colloids, organic matter and microorganisms in the coking wastewater to meet the reuse water standard; the design flux is 14~16LMH, and the desalination rate is ≥97%.

[0065] (6) Secondary ultrasonic catalytic oxidation tank: The primary concentrated water in the primary reverse osmosis device enters the secondary ultrasonic catalytic oxidation tank. An ultrasonic device, TiO2 catalyst and a stirrer are installed in the tank body, and an acid addition point is set to carry out secondary catalytic oxidation and secondary turbulence on the wastewater. The frequency of the ultrasonic device is 400~600kHz, the TiO2 catalyst dosage is 300~400mg / L, and the pH is set at 4~6.

[0066] (7) Primary high-efficiency sedimentation tank: The primary concentrate in the primary advanced oxidation tank enters the primary high-efficiency sedimentation tank. Alkali, coagulant and flocculant addition points are set in the tank. The principle of high-density sedimentation is used to efficiently remove suspended solids, organic matter and hardness in the primary concentrate through return sludge inoculation.

[0067] (8) Secondary multi-media filter: The primary concentrated water of coking wastewater in the primary high-efficiency sedimentation tank enters the secondary multi-media filter, where suspended solids, colloids, oils and iron ions are removed through multi-layer filtration, reducing the workload of the ultrafiltration membrane and extending the service life of the ultrafiltration membrane. The filter media of the multi-media filter are anthracite and graded high-quality manganese sand. The anthracite layer height is 400 mm, and the manganese sand layer height is 800 mm. The filter flow rate of the filter is 8 to 9 m / h.

[0068] (9) Secondary ultrafiltration device: The primary concentrated water in the secondary self-cleaning filter enters the secondary ultrafiltration device, which uses an external pressure hollow fiber ultrafiltration membrane element made of polymer materials to mainly remove suspended matter, colloids, and macromolecular organic matter in the water, and partially reduce the oil, COD and bacteria content in the water; the removal rate of suspended matter, colloids and microorganisms can generally reach 98%, and the effluent SDI ≤3. The design flux is 35~38LMH.

[0069] (10) Nanofiltration device: The primary concentrate in the secondary ultrafiltration device enters the nanofiltration device to remove most of the soluble divalent and trivalent salts, some soluble monovalent salts, colloids, organic matter and microorganisms in the primary concentrate. The designed flux is 10~13LMH.

[0070] (11) Secondary reverse osmosis device: The primary concentrate in the nanofiltration device enters the secondary reverse osmosis device to remove most of the soluble salts, colloids, organic matter and microorganisms in the primary concentrate to meet the reuse water standards. The designed flux is 13~15LMH.

[0071] (12) Secondary high-efficiency sedimentation tank: The secondary concentrated water of coking wastewater in the nanofiltration device and the secondary reverse osmosis device enters the secondary high-efficiency sedimentation tank, which is composed of a coagulation tank, a flocculation tank and a concentrated sedimentation tank. The principle of high-density sedimentation is used to efficiently remove suspended solids, organic matter and hardness in the secondary concentrated water through return sludge inoculation.

[0072] (13) Adsorption oxidation tank: The secondary concentrate in the secondary high-efficiency sedimentation tank enters the adsorption oxidation tank, in which an acid adjustment tank, an activated carbon contact tank, a reaction tank, an alkali adjustment tank, and a sedimentation tank are sequentially arranged. Acid, activated carbon, ferrous sulfate, hydrogen peroxide, alkali, and flocculant addition points are sequentially arranged to oxidize and remove the non-biodegradable organic matter in the secondary concentrate. The iodine value of activated carbon is 500-700, the methylene blue value is 11-14, and the pH value of the acid adjustment tank is 2-4.

[0073] (14) Resin hardness removal and carbon removal tank: The secondary concentrated water in the adsorption oxidation tank enters the resin hardness removal and carbon removal tank. Hardness removal resin and organic matter removal resin are installed in the tank. The outlet water hardness is controlled below 1 mg / L and the organic matter is controlled below 30 mg / L.

[0074] (15) Bipolar membrane device: The secondary concentrated water in the resin de-hardening and de-carbonizing tank enters the bipolar membrane device. A bipolar membrane system is set in the tank to prepare the secondary concentrated brine into sodium hydroxide alkali, mixed acid of hydrochloric acid and sulfuric acid, and low-concentration brine; the alkali is recycled to the primary high-efficiency sedimentation tank, the secondary high-efficiency sedimentation tank, the adsorption oxidation tank and the steelmaking process of the steel plant, and the acid is recycled to the primary ultrasonic catalytic oxidation tank, the secondary ultrasonic catalytic oxidation tank, the adsorption oxidation tank and the steel rolling process of the steel plant. The mass concentration of the alkali is controlled at 8%~10%, and the mass concentration of the mixed acid is controlled at 8%~11%. The low-concentration brine is sent to the secondary reverse osmosis device for utilization.

[0075] In summary, different from the prior art, the present invention has the following advantages after adopting the above technical solution: (1) High recovery rate of deep treatment: The overall recovery rate is as high as 100%, which can effectively enable steel-coke co-production enterprises to achieve zero discharge of coking wastewater.

[0076] (2) Good effluent quality: The water quality of the coking wastewater after treatment can reach and exceed the water quality standard of Table 6.1.3 of the "Design Specification for Industrial Circulating Cooling Water Treatment" GB50050-2017 for directly using recycled water as make-up water for the intercooler open system, effectively achieving the reuse and zero discharge of coking wastewater.

[0077] (3) High degree of system resource utilization: According to the wastewater treatment process and the demand for alkali and acid in the steel plant, the concentrated water of the membrane system is treated and the acid and alkali produced are reused in the wastewater treatment process and the main processes of steelmaking and rolling in the steel plant, so that the coking wastewater of the steel-coke co-production enterprise can be zero-discharged and resource-utilized from the system perspective.

[0078] (4) System stability: The system adopts the membrane reuse method, especially the effective pretreatment of the water entering the membrane, which effectively removes the pollutants that are easy to cause fouling of the membrane components, protects the membrane components well, and ensures the stable operation of the entire deep treatment system.

[0079] (5) High degree of automation: The system mainly adopts membrane method and physical and chemical method technology, which can realize the full automatic operation of the system, greatly saving complex manual operations and reducing the workload of personnel.

[0080] The above are only preferred specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A system for achieving zero discharge and resource utilization of coking wastewater, characterized in that: It includes a primary processing module, a secondary processing module and a tertiary processing module connected in sequence; Among them, the primary treatment module is used to perform primary treatment on the post-treatment effluent of coking wastewater to obtain primary produced water and primary concentrated water; the secondary treatment module is used to perform secondary treatment on the primary concentrated water to obtain secondary produced water and secondary concentrated water; the tertiary treatment module is used to perform tertiary treatment on the secondary concentrated water to obtain low-concentration brine, alkaline solution and acidic solution; both the primary produced water and the secondary produced water can be reused in the industrial water system.

2. The system for achieving zero discharge and resource utilization of coking wastewater according to claim 1 is characterized in that: The primary treatment module comprises a primary ultrasonic catalytic oxidation tank, a primary multi-media filter, a primary self-cleaning filter, a primary ultrafiltration device and a primary reverse osmosis device connected in sequence; Among them, the first-level ultrasonic catalytic oxidation tank is used to perform a catalytic oxidation and a turbulent flow on the post-treatment effluent of the coking wastewater to form the first wastewater; the first-level multi-media filter is used to perform a filtering treatment on the first wastewater; the first-level self-cleaning filter is used to perform a secondary filtering treatment on the first wastewater; the first-level ultrafiltration device is used to perform an ultrafiltration treatment on the first wastewater; the first-level reverse osmosis device is used to perform a reverse osmosis treatment on the first wastewater to obtain the first-level produced water and the first-level concentrated water, and the first-level produced water is transported to the produced water reuse tank.

3. The system for achieving zero discharge and resource utilization of coking wastewater according to claim 2 is characterized in that: In the first-stage ultrasonic catalytic oxidation tank: the frequency of the ultrasonic device is 50~500kHz, the TiO2 catalyst dosage is 100~300mg / L, and the pH is set at 5~7; the filtration accuracy of the first-stage self-cleaning filter is 50μm, the design flux of the first-stage ultrafiltration device is 35~45LMH, and the design flux of the first-stage reverse osmosis device is 14~18LMH.

4. The system for achieving zero discharge and resource utilization of coking wastewater according to claim 2 is characterized in that: The secondary treatment module includes a secondary ultrasonic catalytic oxidation tank, a primary high-efficiency sedimentation tank, a secondary multi-media filter, a secondary self-cleaning filter, a secondary ultrafiltration device, a nanofiltration device and a secondary reverse osmosis device connected in sequence; Among them, the secondary ultrasonic catalytic oxidation tank is used to perform secondary catalytic oxidation and secondary turbulence on the primary concentrated water to form second wastewater; the primary high-efficiency sedimentation tank is used to remove suspended matter, organic matter and hardness in the second wastewater; the secondary multi-media filter is used to perform primary filtration treatment on the second wastewater; the secondary self-cleaning filter is used to perform secondary filtration treatment on the second wastewater; the secondary ultrafiltration device is used to perform ultrafiltration treatment on the second wastewater; the nanofiltration device is used to perform nanofiltration treatment on the second wastewater to form third wastewater and the secondary concentrated water; the secondary reverse osmosis device is used to perform reverse osmosis treatment on the third wastewater to obtain the secondary produced water and the secondary concentrated water, and transport the secondary produced water to the produced water reuse tank.

5. The system for achieving zero discharge and resource utilization of coking wastewater according to claim 4 is characterized in that: In the secondary ultrasonic catalytic oxidation pool: the frequency of the ultrasonic device is 300-600kHz, the TiO2 catalyst dosage is 200-400mg / L, and the pH is set at 4-6; the filtration flow rate of the secondary multi-media filter is 8-10m / h, the design flux of the secondary ultrafiltration device is 35-40LMH, the design flux of the nanofiltration device is 10-13LMH, and the design flux of the secondary reverse osmosis device is 13-16LMH.

6. The system for achieving zero discharge and resource utilization of coking wastewater according to claim 4 is characterized in that: The three-stage treatment module includes a secondary high-efficiency sedimentation tank, an adsorption oxidation tank, a resin hardness and carbon removal tank, and a bipolar membrane device connected in sequence; Among them, the secondary high-efficiency sedimentation tank is used to remove suspended matter, organic matter and hardness in the secondary wastewater to form the fourth wastewater; the adsorption oxidation tank is used to oxidize and remove the difficult-to-biodegrade organic matter in the fourth wastewater; the resin hardness and carbon removal tank is used to completely remove the hardness and organic matter in the fourth wastewater; the bipolar membrane device is used to prepare the fourth wastewater into the alkaline solution containing sodium hydroxide, the acidic solution containing hydrochloric acid and sulfuric acid, and the low-concentration brine.

7. The system for achieving zero discharge and resource utilization of coking wastewater according to claim 6 is characterized in that: The primary high-efficiency sedimentation tank and the secondary high-efficiency sedimentation tank both include a pH adjustment tank, a coagulation tank, a flocculation tank and a concentration sedimentation tank.

8. The system for achieving zero discharge and resource utilization of coking wastewater according to claim 6 is characterized in that: An acid adjustment tank, an activated carbon contact tank, a reaction tank, an alkali adjustment tank and a sedimentation tank are sequentially arranged in the adsorption oxidation tank. The activated carbon in the activated carbon contact tank has an iodine value of 500-800 and a methylene blue value of 10-16. The pH of the acid adjustment tank is 2-4. Special resins for hardness removal and special resins for organic matter removal are arranged in the resin hardness removal and carbon removal tank. The outlet water hardness is controlled below 1 mg / L, and the organic matter is controlled below 30 mg / L.

9. The system for achieving zero discharge and resource utilization of coking wastewater according to claim 6, characterized in that: The bipolar membrane device is used to prepare the fourth wastewater into a mass concentration of 8% to 10%, the mass concentration of the alkaline solution is 8% to 10%, and the mass concentration of the acidic solution is 8% to 11%.

10. The system for achieving zero discharge and resource utilization of coking wastewater according to claim 9, characterized in that: The alkaline solution is respectively recycled to the primary high-efficiency sedimentation tank, the secondary high-efficiency sedimentation tank, the adsorption oxidation tank and the steelmaking process of the steel plant; the acidic solution is respectively recycled to the primary ultrasonic catalytic oxidation tank, the secondary ultrasonic catalytic oxidation tank, the adsorption oxidation tank and the steel rolling process of the steel plant; the low-concentration brine is recycled to the secondary reverse osmosis device.

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