Chemical pickling waste liquid high-efficiency separation device and treatment method

Abstract

The application discloses a kind of high-efficiency separation devices and processing methods of chemical caustic cleaning waste liquid, it is related to caustic cleaning waste liquid processing technical field, including the feed unit for storing caustic cleaning waste liquid to be handled, pretreatment unit, composite demulsification and physical strengthening unit, special membrane separation unit, low-temperature catalytic oxidation unit, crystallization salt separation unit and resource recycling unit connected in series successively;The pretreatment unit is used to remove waste liquid mechanical impurities, adjust pH value and temperature;The application is cooperated by feed unit, pretreatment unit, composite demulsification and physical strengthening unit, special membrane separation unit, low-temperature catalytic oxidation unit, crystallization salt separation unit, resource recycling unit, constructs from buffer, conditioning, demulsification oil, membrane separation alkali, low-temperature oxidative degradation, salt separation crystallization and integrated processing system of whole component recycling, realizes waste liquid zero discharge, satisfies green low-carbon, ultra-low emission management and control demand of chemical industry.

Description

Technical Field

[0001] This invention belongs to the field of alkaline washing waste liquid treatment technology, specifically relating to a high-efficiency separation device and treatment method for chemical alkaline washing waste liquid. Background Technology

[0002] In mainstream chemical production fields such as petrochemicals and fine chemicals, alkaline washing is a core process for product refining, tail gas purification, and material impurity removal. It mainly uses alkaline solutions to remove impurities such as sulfides, organic acids, oils, and colloids from raw materials and products, ensuring the quality of chemical products and the stable operation of the production system. During large-scale production, this process continuously generates a large amount of chemical alkaline washing waste liquid. This waste liquid has an extremely complex composition, enriched with high concentrations of free alkali, inorganic salts, recalcitrant organic pollutants, sulfides, and heavy metal impurities. It is characterized by high pH, ​​high salinity, high COD, and strong pollutant stability. It is a typical highly polluting and recalcitrant industrial hazardous waste liquid. If it is discharged directly without effective treatment or improperly disposed of, it will cause serious environmental problems such as soil salinization, water pollution, and ecological damage.

[0003] Currently, the main treatment processes for chemical alkaline washing waste liquid include acid-base neutralization, advanced oxidation, wet oxidation, biological treatment, and single membrane separation. Among them, acid-base neutralization is simple to operate and requires low equipment investment, but it consumes a large amount of acid and alkali reagents. It can only achieve simple harmless treatment of waste liquid and cannot recover the effective alkaline components and salt resources in the waste liquid. The resource utilization rate is extremely low, and a large amount of solid waste such as salt residue and sludge will be generated after treatment, which can easily cause secondary pollution.

[0004] Advanced oxidation and wet oxidation methods can degrade most of the recalcitrant organic matter in waste liquids, but they require large equipment investment, high operating energy consumption, and large oxidant consumption. They are also poorly adaptable to complex waste liquids with high salt and high alkali, and the treatment process easily produces by-products such as bromate and residual oxidant, resulting in high operation and maintenance costs.

[0005] Biological treatment relies on microorganisms to degrade pollutants, but the high-alkalinity and high-salt waste liquid environment will inhibit the activity of microorganisms, making it difficult for the bacteria to survive, the system start-up cycle is long, and the treatment process is complicated. Not only is the separation and purification efficiency low, but it also produces residual sludge, resulting in high subsequent disposal costs.

[0006] Physical separation processes such as single membrane separation and sedimentation filtration generally suffer from problems such as incomplete separation of pollutants, easy fouling and clogging of membrane modules, and severe equipment corrosion, making it impossible to achieve graded separation and full utilization of alkali, salt, and organic matter in waste liquid.

[0007] In summary, existing single and combined treatment processes generally suffer from low separation efficiency, poor resource utilization, high operating costs, and insufficient stability, making it difficult to meet the industry's green development needs. Therefore, we propose a high-efficiency separation device and treatment method for chemical alkaline washing waste liquid. Summary of the Invention

[0008] The purpose of this invention is to provide a high-efficiency separation device and treatment method for chemical alkaline washing waste liquid, which can achieve zero discharge of waste liquid, meet the needs of green development in the industry, and solve the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A high-efficiency separation device for chemical alkaline washing waste liquid includes a feeding unit for storing alkaline washing waste liquid to be treated, a pretreatment unit, a composite demulsification and physical enhancement unit, a special membrane separation unit, a low-temperature catalytic oxidation unit, a crystallization and salt separation unit, and a resource recovery unit connected in series.

[0011] The pretreatment unit is used to remove mechanical impurities from the waste liquid and adjust the pH value and temperature.

[0012] The composite demulsification and physical reinforcement unit is used for preliminary demulsification and separation of oil phase, water phase and solid phase impurities;

[0013] The special membrane separation unit is used for the separation of regenerated alkaline solution from organic matter and inorganic salts;

[0014] The low-temperature catalytic oxidation unit is used to degrade recalcitrant organic matter, and the resulting tail gas is discharged after alkaline washing and adsorption treatment.

[0015] The crystallization and salt separation unit first separates salts by nanofiltration, and then collects the salt crystals.

[0016] The resource recycling unit is used to reuse the regenerated alkali solution and oil phase in production, achieving full-component resource recycling and zero waste discharge.

[0017] Preferably, the feeding unit includes an alkaline washing waste liquid storage tank, which is equipped with a liquid level monitoring device for real-time monitoring of the liquid level of the alkaline washing liquid in the storage tank.

[0018] Preferably, the pretreatment unit includes a waste liquid conditioning tank, a wedge-shaped screen coarse filter, and a shell-and-tube preheating heat exchanger connected in sequence. The feed end of the waste liquid conditioning tank is connected to the outlet end of the alkaline washing waste liquid storage tank. An online pH meter and a liquid level sensor are installed in the waste liquid conditioning tank. The shell-and-tube preheating heat exchanger utilizes the heat released by the reaction of the low-temperature catalytic oxidation unit to achieve heat recycling.

[0019] Preferably, the composite demulsification and physical enhancement unit includes a composite demulsification reactor, an ultrasonic-electric field synergistic enhancement device, and an inclined plate three-phase separator connected in sequence. The feed end of the composite demulsification reactor is connected to the discharge end of the shell-and-tube preheating heat exchanger. The composite demulsification reactor is equipped with a demulsifier addition component for adding demulsifier during the reaction. The oil phase discharge end of the inclined plate three-phase separator is connected to the resource recovery and recycling unit.

[0020] Preferably, the special membrane separation unit includes a ceramic ultrafiltration pre-filtration component and a PEEK strong alkali resistant nanofiltration membrane component connected in sequence. The feed end of the ceramic ultrafiltration pre-filtration component is connected to the aqueous phase discharge end of the inclined three-phase separator. The ceramic ultrafiltration pre-filtration component is used to remove minute impurities. The concentrate discharge end of the PEEK strong alkali resistant nanofiltration membrane component is connected to the feed end of the low-temperature catalytic oxidation unit. The regenerated alkali discharge end of the PEEK strong alkali resistant nanofiltration membrane component is connected to the resource recovery and reuse unit.

[0021] Preferably, the low-temperature catalytic oxidation unit includes a low-temperature fixed-bed catalytic oxidation reactor and a tail gas alkaline washing adsorption device. The inlet of the tail gas alkaline washing adsorption device is connected to the outlet of the low-temperature fixed-bed catalytic oxidation reactor. The liquid inlet of the low-temperature fixed-bed catalytic oxidation reactor is connected to the liquid outlet of the PEEK strong alkali resistant nanofiltration membrane module. The discharge end of the low-temperature fixed-bed catalytic oxidation reactor is connected to the feed end of the crystallization and salt separation unit. The low-temperature fixed-bed catalytic oxidation reactor is filled with a catalyst.

[0022] Preferably, the crystallization and salt separation unit includes a nanofiltration salt separation component, an MVR low-temperature evaporation crystallizer, and a sealed salt product collection chamber connected in sequence. The nanofiltration salt separation component is used to separate different types of salts, the MVR low-temperature evaporation crystallizer is used for salt crystallization and recovery, the sealed salt product collection chamber is used to collect salt products, and the liquid outlet of the MVR low-temperature evaporation crystallizer is connected to the feed end of the resource recovery and reuse unit.

[0023] Preferably, the resource recycling unit includes an alkali recycling tank, an oil phase recycling tank, and a condensate recycling pipeline connected in sequence. The inlet of the alkali recycling tank is connected to the outlet of the MVR low-temperature evaporation crystallizer and the outlet of the PEEK strong alkali resistant nanofiltration membrane module, respectively. The inlet of the oil phase recycling tank is also connected to the outlet of the inclined plate three-phase separator. The outlet of the condensate recycling pipeline is connected to the inlet of the waste liquid conditioning tank.

[0024] This invention also provides a method for efficient separation and treatment of chemical alkaline washing waste liquid, using the above-described efficient separation device for chemical alkaline washing waste liquid, comprising the following steps:

[0025] S1. The chemical alkaline washing waste liquid is fed into the feeding unit for buffering and pressure stabilization, and the feed flow rate fluctuation is controlled to be ≤±5%;

[0026] S2. The buffered waste liquid is sent to the pretreatment unit for treatment to complete the conditioning of water quality, impurities and temperature.

[0027] S3. The conditioned waste liquid is transferred to the composite demulsification and physical strengthening unit for preliminary demulsification, and three-phase separation of oil phase, water phase and solid phase impurities is carried out. The separated oil phase is collected and reused.

[0028] S4. The separated aqueous phase is pre-filtered and sorted through a special membrane separation unit to obtain a reusable regenerated alkali solution and a concentrated solution enriched with salts and organic matter. The regenerated alkali solution is collected and reused.

[0029] S5. The concentrate is sent to a low-temperature catalytic gasification unit, where a Cu / Mn / Ce-based supported transition metal catalyst is used to carry out a catalytic reaction to degrade the recalcitrant organic matter in the concentrate.

[0030] S6. The concentrated liquid after catalytic gasification is processed by the crystallization and salt separation unit to separate and crystallize salt products, and the crystallization mother liquor is returned to the pretreatment unit for recycling.

[0031] S7. The recovered regenerated alkali solution and oil phase are reused in chemical production processes, and the condensate generated during crystallization is recycled.

[0032] Preferably, in step S3, during the initial demulsification, a demulsifier needs to be added continuously. The mass ratio of nonionic polyether-modified silane to cationic polyacrylamide in the demulsifier is 3-4:1, the total concentration of the demulsifier is 200-400 mg / L, and the stirring reaction time is 10-15 minutes.

[0033] The present invention provides a high-efficiency separation device and treatment method for chemical alkaline washing waste liquid, which has the following advantages compared with the prior art:

[0034] 1. This invention constructs an integrated treatment system for buffering, conditioning, demulsification and oil separation, membrane alkali separation, low-temperature oxidative degradation, salt separation and crystallization, and full component recycling through the synergistic cooperation of the feeding unit, pretreatment unit, composite demulsification and physical enhancement unit, special membrane separation unit, low-temperature catalytic oxidation unit, crystallization and salt separation unit, and resource recycling unit. This system achieves zero wastewater discharge and meets the green, low-carbon and ultra-low emission control requirements of the chemical industry.

[0035] 2. This invention can initially demulsify through a composite demulsification and physical reinforcement unit, and separate oil phase, water phase and solid phase impurities in one step, realizing the graded separation of oil, free alkali, salt, water and organic matter, and improving the separation effect of emulsion;

[0036] 3. Through the setting of the resource recycling unit, this invention can recover the oil phase, regenerated alkali, and condensate. The salt products recovered by the crystallization and salt separation unit can be sold or reused, and no more waste salt residue, waste oil and waste alkali are generated, thus improving the utilization rate of resources.

[0037] 4. This invention, through the setting of a low-temperature catalytic oxidation unit, can oxidize and degrade the COD that is difficult to degrade in the concentrate. Its sulfides and nitrogen oxides are adsorbed and discharged in compliance with standards. No neutralizing agents are added throughout the process, no neutralizing salt residue is generated, and solid impurities are collected separately and disposed of in compliance with regulations, so as not to cause secondary pollution. Attached Figure Description

[0038] Figure 1 This is a structural block diagram of the separation device of the present invention;

[0039] Figure 2 This is a flowchart of the separation process of the present invention;

[0040] In the diagram: 1. Alkali washing waste liquid storage tank; 2. Waste liquid conditioning tank; 3. Wedge mesh coarse filter; 4. Shell-and-tube preheating heat exchanger; 5. Composite demulsification reactor; 6. Ultrasonic-electric field synergistic enhancement device; 7. Inclined plate three-phase separator; 8. Ceramic ultrafiltration pre-filtration module; 9. PEEK strong alkali resistant nanofiltration membrane module; 10. Low-temperature fixed bed catalytic oxidation reactor; 11. Tail gas alkali washing adsorption device; 12. Nanofiltration salt separation module; 13. MVR low-temperature evaporation crystallizer; 14. Salt product closed collection bin; 15. Alkali liquid recycling tank; 16. Oil phase recycling tank; 17. Condensate recycling pipeline network. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] This invention provides, for example Figure 1 The device shown is a high-efficiency separation device for chemical alkaline washing waste liquid, comprising a feeding unit for storing alkaline washing waste liquid to be treated, a pretreatment unit, a composite demulsification and physical enhancement unit, a special membrane separation unit, a low-temperature catalytic oxidation unit, a crystallization and salt separation unit, and a resource recovery unit connected in series.

[0043] Specifically, the feeding unit includes an alkaline washing waste liquid storage tank 1, which is equipped with a liquid level monitoring device for real-time monitoring of the liquid level of the alkaline washing liquid in the storage tank 1. The liquid level monitoring device is a submersible liquid level transmitter. The chemical alkaline washing waste liquid is first collected into the alkaline washing waste liquid storage tank 1 for temporary storage. The liquid level signal in the alkaline washing waste liquid storage tank 1 is collected in real time by the submersible liquid level transmitter, and the downstream feed booster pump is linked to adjust the discharge flow rate by frequency conversion. When the liquid level is lower than the lower limit, the pump frequency is automatically reduced; when the liquid level is higher than the upper limit, the pump output is automatically increased. The flow rate fluctuation of the waste liquid entering the pretreatment unit is controlled within ±5%, avoiding instantaneous large flow impact on demulsification and membrane separation, which may cause separation failure.

[0044] The pretreatment unit is used to remove mechanical impurities from the waste liquid and adjust the pH and temperature. The pretreatment unit includes a waste liquid conditioning tank 2, a wedge-shaped coarse filter 3, and a shell-and-tube preheating heat exchanger 4 connected in sequence. The inlet of the waste liquid conditioning tank 2 is connected to the outlet of the alkaline washing waste liquid storage tank 1, and a pump for controlling the waste liquid flow rate is installed on the connecting pipeline. An online pH meter and a liquid level sensor are installed inside the waste liquid conditioning tank 2. The shell-and-tube preheating heat exchanger 4 utilizes the exothermic reaction of the low-temperature catalytic oxidation unit to achieve heat recycling. The waste liquid first enters the waste liquid conditioning tank 2, and then acid and alkali are added via the probe of the online pH meter. The device stabilizes the pH at 10.0–12.0 to suit the subsequent demulsification and strong alkali resistant nanofiltration membrane operation. The waste liquid then enters the wedge-shaped coarse filter 3, which uses the wedge-shaped gaps to trap sand, colloids, and large mechanical impurities, preventing hard particles from scratching the downstream ceramic ultrafiltration membrane. After filtration, the waste liquid is passed through the tube side of the shell-and-tube preheating heat exchanger 4, while the shell side is fed with the high-temperature reaction effluent from the low-temperature catalytic oxidation reactor. The waste heat from the oxidation reaction is recovered through heat exchange between the tube walls, preheating the waste liquid to 40–60°C to provide the optimal temperature environment for the composite demulsification reaction. The cooled oxidation effluent then enters the subsequent deep treatment process.

[0045] The composite demulsification and physical enhancement unit is used for preliminary demulsification and separation of oil, water, and solid phase impurities. The composite demulsification and physical enhancement unit includes a composite demulsification reactor 5, an ultrasonic-electric field synergistic enhancement device 6, and an inclined plate three-phase separator 7 connected in sequence. The feed end of the composite demulsification reactor 5 is connected to the discharge end of the shell-and-tube preheating heat exchanger 4. A demulsifier dosing assembly is installed inside the composite demulsification reactor 5 for adding demulsifier during the reaction. The oil phase discharge end of the inclined plate three-phase separator 7 is connected to a resource recovery unit. Preheated waste liquid is fed into the composite demulsification reactor 5, where a metered compound is added. The demulsifier is stirred for 10–15 minutes to initially break down the oil-water emulsion micelle structure of the waste liquid. The initially demulsified waste liquid enters the ultrasonic-electric field synergistic enhancement device 6, where high-frequency ultrasonic vibration breaks up the tiny oil droplet micelles. An external DC electric field drives the oil phase droplets to directionally aggregate, further enhancing the demulsification effect. The enhanced mixture enters the inclined plate three-phase separator 7, where shallow sedimentation of the inclined plate achieves oil phase floating, water phase overflow in the middle, and solid phase impurities settling and stratifying at the bottom. The floating oil phase flows by gravity through the upper oil collection tank into the resource recovery unit oil phase recovery tank 16. The settled solid phase impurities are periodically discharged from the bottom and transported in a sealed manner, while the middle water phase is transported to the special membrane separation unit.

[0046] The special membrane separation unit is used for separating the regenerated alkali solution from organic matter and inorganic salts. The special membrane separation unit includes a ceramic ultrafiltration pre-filtration module 8 and a PEEK strong alkali-resistant nanofiltration membrane module 9 connected in sequence. The feed end of the ceramic ultrafiltration pre-filtration module 8 is connected to the aqueous phase outlet end of the inclined three-phase separator. The ceramic ultrafiltration pre-filtration module 8 is used to remove minute impurities. The concentrate outlet end of the PEEK strong alkali-resistant nanofiltration membrane module 9 is connected to the feed end of the low-temperature catalytic oxidation unit. The regenerated alkali solution outlet end of the PEEK strong alkali-resistant nanofiltration membrane module 9 is connected to the resource recovery and reuse unit. The aqueous phase from the inclined plate three-phase separator 7 first enters the ceramic ultrafiltration pre-filtration module 8. A 0.2μm pore size, alkali-resistant ceramic membrane traps residual micro-oil droplets and colloidal suspended matter. The pre-filtered water enters the PEEK alkali-resistant nanofiltration membrane module 9. The PEEK nanofiltration membrane is resistant to a strong alkaline environment of pH 0–14. The membrane sieving effect allows small molecule free alkali to pass through and form regenerated alkali solution, while large molecule organic matter and polyvalent salt ions are trapped to form a high-salt organic concentrate. The ceramic ultrafiltration trap concentrate is intermittently returned to the front-end waste liquid conditioning tank 2 for recycling and reprocessing. The PEEK nanofiltration produces regenerated alkali solution, which is transported to the alkali solution recycling tank 15. The concentrate is sent to the low-temperature catalytic oxidation unit for deep degradation. The entire membrane unit is equipped with an online chemical cleaning system, which periodically uses low-concentration alkali solution to circulate and rinse the membrane surface for contaminants.

[0047] The low-temperature catalytic oxidation unit is used to degrade recalcitrant organic compounds, and the resulting tail gas is discharged after alkaline scrubbing and adsorption treatment. The low-temperature catalytic oxidation unit includes a low-temperature fixed-bed catalytic oxidation reactor 10 and a tail gas alkaline scrubbing adsorption device 11. The tail gas alkaline scrubbing adsorption device 11 uses alkaline spraying and activated carbon adsorption to perform two-stage purification of the tail gas. The inlet of the tail gas alkaline scrubbing adsorption device 11 is connected to the outlet of the low-temperature fixed-bed catalytic oxidation reactor 10. The liquid inlet of the low-temperature fixed-bed catalytic oxidation reactor 10 is connected to the outlet of the PEEK strong alkali resistant nanofiltration membrane module 9. The outlet of the low-temperature fixed-bed catalytic oxidation reactor 10 is connected to the feed inlet of the crystallization and salt separation unit. The low-temperature fixed-bed catalytic oxidation reactor 10 is filled with a catalyst. The catalyst is a Cu / Mn / Ce composite supported transition metal catalyst. The high-salt organic concentrate produced by nanofiltration enters the low-temperature fixed-bed catalytic oxidation reactor 10. The reactor controls the reaction temperature at 60–90℃, the pressure at atmospheric pressure to 0.2MPa, and the hydraulic residence time at 20–40min. Under low temperature and mild operating conditions, the catalytic oxidation decomposes phenols, long-chain alkanes, sulfides and other recalcitrant organic compounds in the concentrate, degrading the high COD wastewater to meet the water quality standards for crystallization and desalination. The oxidation reaction produces sulfur- and nitrogen-containing volatile waste gases. The exhaust pipe at the top of the reactor is connected to the tail gas alkaline washing and adsorption device 11. The waste gas undergoes two-stage purification through alkaline spraying and activated carbon adsorption in a counter-current manner. After adsorption, the clean tail gas meets the standards and is discharged at high altitude. The sprayed circulating alkaline solution is periodically returned to the waste liquid conditioning tank 2 for reuse.

[0048] The crystallization and salt separation unit employs nanofiltration to separate salts first, followed by crystallization and collection of the salts. The unit comprises a nanofiltration salt separation component 12, an MVR low-temperature evaporator crystallizer 13, and a sealed salt product collection chamber 14, connected in sequence. The nanofiltration salt separation component 12 separates different types of salts, the MVR low-temperature evaporator crystallizer 13 recovers salt crystals, and the sealed salt product collection chamber 14 collects the salt product. The outlet of the MVR low-temperature evaporator crystallizer 13 is connected to the inlet of the resource recovery unit. Clean saline wastewater, after catalytic oxidation degradation, enters the nanofiltration salt separation component 12, where it is separated by the charge sieving effect of the nanofiltration membrane. The wastewater is separated into monovalent sodium salt and divalent sulfate to achieve the separation of different types of salts. After the salt separation, the single-component salt-containing wastewater enters the MVR low-temperature evaporation crystallizer 13, where the evaporation temperature is controlled at 55–75℃ and the vacuum degree is -0.08 to -0.09MPa. The mechanical steam is recompressed to recover the latent heat of the secondary steam, and the crystallized salt is precipitated by low-temperature evaporation. The crystallized slurry enters the salt product closed collection bin 14, where the salt material is unloaded and packaged in a closed environment to avoid salt dust pollution. The condensate produced by the MVR evaporator is transported to the condensate recycling pipeline 17, and the high-concentration crystallization mother liquor at the bottom of the evaporator flows back to the waste liquid conditioning tank 2 by gravity, where it is mixed with the newly entered waste liquid for recycling treatment.

[0049] The resource recycling unit is used to reuse the regenerated alkali solution and oil phase in production, achieving full-component resource recycling and zero waste discharge. The resource recycling unit includes an alkali solution recycling tank 15, an oil phase recycling tank 16, and a condensate recycling pipeline network 17 connected in sequence. The inlet of the alkali solution recycling tank 15 is connected to the outlet of the MVR low-temperature evaporator crystallizer 13 and the outlet of the PEEK strong alkali resistant nanofiltration membrane module 9, respectively. The inlet of the oil phase recycling tank 16 is also connected to the outlet of the inclined plate three-phase separator 7. The outlet of the condensate recycling pipeline network 17 is connected to the inlet of the waste liquid regulating tank 2. Through the alkali solution recycling tank 15, the oil phase recycling tank 16, and the condensate recycling pipeline network 17, a closed-loop resource recycling system of oil, alkali, and water is constructed, and the PEEK nanofiltration membrane product... All regenerated alkali solution is fed into alkali reuse tank 15, which is equipped with an online concentration monitoring device. Once the concentration reaches the standard, it is pumped to the alkali washing section of the chemical production for recycling. The inclined plate three-phase separator 7 separates the floating oil phase, which flows by gravity into the oil phase reuse tank 16. After settling to remove trace amounts of moisture, it is reused in the raw material pretreatment process of the unit. The clean condensate generated by the MVR evaporator is diverted through the condensate reuse pipeline network 17. Part of it is sent to the waste liquid conditioning tank 2 for pH adjustment and dilution of high-concentration waste liquid, and part of it is directly supplied to the production unit for circulating water replenishment. There are no external discharge branches in the three reuse pipelines. All recovered media are reused internally to maximize the recovery of valuable resources in the waste liquid and reduce the consumption of chemical raw materials and fresh water by the enterprise. The condensate reuse reduces the fresh water intake index of the plant area and meets the water conservation management requirements.

[0050] During operation, chemical alkaline washing waste liquid is first fed into the feeding unit for buffering and pressure stabilization to stabilize flow fluctuations; it then flows by gravity into the pretreatment unit to complete impurity interception, pH adjustment, and waste heat preheating; the conditioned waste liquid is then transported to the composite demulsification and physical enhancement unit, where chemical compound demulsification and ultrasonic electric field physical fields are used to synergistically break down the water-in-oil emulsion system of the waste liquid; a 7-layer inclined plate three-phase separator separates the oil phase and the alkaline aqueous phase; the aqueous phase enters the special membrane separation unit, where ceramic ultrafiltration intercepts tiny colloids and oil droplets to protect the membrane element, and PEEK strong alkali resistant nanofiltration membrane is used to screen and obtain reusable low-impurity regenerated alkaline solution and a concentrated solution enriched with salt and recalcitrant organic matter; the concentrated solution... The wastewater enters the low-temperature catalytic oxidation unit, where high-concentration COD is degraded by a Cu / Mn / Ce composite catalyst at low temperature. The sulfur- and nitrogen-containing tail gas generated by oxidation is purified by an alkaline washing and adsorption device before being discharged. The concentrated liquid after degradation is sent to the crystallization and salt separation unit, where a nanofiltration component separates monovalent and divalent mixed salts. The industrial salt product is then precipitated by low-temperature vacuum evaporation using an MVR system. The crystallization mother liquor is returned to the pretreatment unit for recycling and digestion. All oil phase, regenerated alkali, and condensate are recovered and uniformly incorporated into the resource recovery and reuse unit, and then transported to the alkaline washing process and circulating water system in chemical production, respectively, achieving closed-loop zero discharge of waste liquid and meeting the industry's green development requirements.

[0051] This invention also provides a method for the efficient separation and treatment of chemical alkaline washing waste liquid, using the efficient separation device for chemical alkaline washing waste liquid described above, such as... Figure 2 As shown, it includes the following steps:

[0052] S1. The chemical alkaline washing waste liquid is fed into the feeding unit for buffering and pressure stabilization, and the feed flow fluctuation is controlled to be ≤±5%. Specifically, the variable frequency feed pump is adjusted by linking the PLC control system with the submersible level transmitter to control the flow fluctuation within ±5%.

[0053] S2. The buffered waste liquid is sent to the pretreatment unit for treatment to condition the water quality, impurities and temperature. Specifically, the waste liquid enters the waste liquid conditioning tank 2 to adjust the pH value to a target pH of 10.0–12.0 to adapt to subsequent demulsification and strong alkali resistant membrane separation. Mechanical impurities are removed by the wedge mesh coarse filter 3, and then the waste liquid is preheated by the shell and tube preheating heat exchanger 4 at a temperature of 40–60℃, which is the optimal temperature range for the demulsification reaction. At the same time, the waste heat from catalytic oxidation is used to complete the pretreatment.

[0054] S3. The conditioned waste liquid is transferred to the composite demulsification and physical reinforcement unit for preliminary demulsification, and three-phase separation of oil phase, water phase, and solid impurities is performed. The separated oil phase is collected and reused. During the preliminary demulsification, a demulsifier needs to be continuously added. The mass ratio of nonionic polyether-modified silane to cationic polyacrylamide in the demulsifier is 3-4:1, and the total concentration of the demulsifier is 200-400 mg / L. The stirring reaction time is 10-15 minutes to initially break down the oil-water emulsion micelles. The effluent from the reactor flows by gravity into the ultrasonic-electric field synergistic enhancement device 6. The 4kW ultrasonic vibration combined with the 80V DC electric field causes the tiny oil droplets to collide and coalesce rapidly, greatly improving the demulsification effect. The enhanced mixture enters the inclined plate three-phase separator 7, where it settles and separates into layers by gravity. The floating oil phase flows by gravity through the upper oil collection tank into the oil phase recycling tank 16 for storage. The small amount of solid impurities at the bottom are periodically transported out for disposal by opening the pneumatic sludge discharge valve. The clarified water phase in the middle is transported to the ceramic ultrafiltration pre-filtration component 8 by the liquid level difference.

[0055] S4. The separated aqueous phase is pre-filtered and sorted through a special membrane separation unit to obtain a reusable regenerated alkali solution and a concentrated solution enriched with salts and organic matter. The regenerated alkali solution is collected and reused. That is, the aqueous phase after demulsification is filtered through a ceramic ultrafiltration pre-filtration component 8 and then enters a strong alkali resistant nanofiltration membrane component to separate the regenerated alkali solution and the concentrated solution. The regenerated alkali solution is sent to the alkali solution reuse tank 15, and the concentrated solution enters the low temperature catalytic oxidation unit.

[0056] S5. The concentrate is fed into a low-temperature catalytic gasification unit, where a Cu / Mn / Ce-based supported transition metal catalyst is used for catalytic reaction to degrade the recalcitrant organic matter in the concentrate. The reaction temperature is 60–90℃. In this low-temperature catalytic range, coking does not occur and energy consumption is low. The reaction pressure is from atmospheric pressure to 0.2MPa, and the residence time is 20–40min. The catalyst is a supported transition metal catalyst (Cu / Mn / Ce-based), which can degrade recalcitrant organic matter and ensure that the subsequent crystallization and salt separation water meets the standards. The recalcitrant organic matter is degraded under the action of the catalyst. The generated tail gas is treated by the tail gas alkaline washing and adsorption device 11 before being discharged.

[0057] S6. The concentrated liquid after catalytic gasification is subjected to salt separation and crystallization treatment through the crystallization and salt separation unit. The precipitated salt product is collected, and the crystallization mother liquor is returned to the pretreatment unit for recycling. That is, the concentrated liquid after treatment is separated into salts by nanofiltration salt separation component 12, and then enters MVR low temperature evaporation crystallizer 13 for crystallization. The evaporation temperature is 55–75℃, and the vacuum degree is -0.08 to -0.09MPa. The salt product is collected by salt product closed collection chamber 14, and the crystallization mother liquor is returned to waste liquid conditioning tank 2.

[0058] S7. The recycled alkali solution and oil phase are reused in chemical production processes, and the condensate generated during crystallization is recycled. This achieves closed-loop resource utilization of all components of the waste liquid, including oil, alkali, salt, and condensate, ultimately realizing the full-component resource utilization and efficient treatment of alkali washing waste liquid. This achieves the dual goals of environmental protection and energy conservation, reduces the company's raw material consumption and environmental protection costs, and possesses the advantages of closed-loop resource utilization.

[0059] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-efficiency separation device for chemical alkaline washing waste liquid, characterized in that: It includes a feeding unit for storing alkaline washing waste liquid to be treated, a pretreatment unit, a composite demulsification and physical enhancement unit, a special membrane separation unit, a low-temperature catalytic oxidation unit, a crystallization and salt separation unit, and a resource recycling unit, which are connected in series. The pretreatment unit is used to remove mechanical impurities from the waste liquid and adjust the pH value and temperature. The composite demulsification and physical reinforcement unit is used for preliminary demulsification and separation of oil phase, water phase and solid phase impurities; The special membrane separation unit is used for the separation of regenerated alkaline solution from organic matter and inorganic salts; The low-temperature catalytic oxidation unit is used to degrade recalcitrant organic matter, and the resulting tail gas is discharged after alkaline washing and adsorption treatment. The crystallization and salt separation unit first separates salts by nanofiltration, and then collects the salt crystals. The resource recycling unit is used to reuse the regenerated alkali solution and oil phase in production, achieving full-component resource recycling and zero waste discharge.

2. The high-efficiency separation device for chemical alkaline washing waste liquid according to claim 1, characterized in that: The feeding unit includes an alkaline washing waste liquid storage tank (1), which is equipped with a liquid level monitoring device for real-time monitoring of the liquid level of the alkaline washing liquid in the alkaline washing waste liquid storage tank (1).

3. The high-efficiency separation device for chemical alkaline washing waste liquid according to claim 2, characterized in that: The pretreatment unit includes a waste liquid conditioning tank (2), a wedge-shaped coarse filter (3), and a shell-and-tube preheating heat exchanger (4) connected in sequence. The feed end of the waste liquid conditioning tank (2) is connected to the outlet end of the alkaline washing waste liquid storage tank (1). An online pH meter and a liquid level sensor are installed in the waste liquid conditioning tank (2). The shell-and-tube preheating heat exchanger (4) utilizes the heat released by the reaction of the low-temperature catalytic oxidation unit to achieve heat recycling.

4. The high-efficiency separation device for chemical alkaline washing waste liquid according to claim 3, characterized in that: The composite demulsification and physical enhancement unit includes a composite demulsification reactor (5), an ultrasonic-electric field synergistic enhancement device (6), and an inclined plate three-phase separator (7) connected in sequence. The feed end of the composite demulsification reactor (5) is connected to the discharge end of the shell-and-tube preheating heat exchanger (4). The composite demulsification reactor (5) is equipped with a demulsifier addition component for adding demulsifier during the reaction. The oil phase discharge end of the inclined plate three-phase separator (7) is connected to the resource recycling unit.

5. The high-efficiency separation device for chemical alkaline washing waste liquid according to claim 1, characterized in that: The special membrane separation unit includes a ceramic ultrafiltration pre-filtration component (8) and a PEEK strong alkali resistant nanofiltration membrane component (9) connected in sequence. The feed end of the ceramic ultrafiltration pre-filtration component (8) is connected to the water phase discharge end of the inclined three-phase separator. The ceramic ultrafiltration pre-filtration component (8) is used to remove minute impurities. The concentrated liquid discharge end of the PEEK strong alkali resistant nanofiltration membrane component (9) is connected to the feed end of the low temperature catalytic oxidation unit. The regenerated alkali liquid discharge end of the PEEK strong alkali resistant nanofiltration membrane component (9) is connected to the resource recycling unit.

6. The high-efficiency separation device for chemical alkaline washing waste liquid according to claim 5, characterized in that: The low-temperature catalytic oxidation unit includes a low-temperature fixed-bed catalytic oxidation reactor (10) and a tail gas alkaline washing adsorption device (11). The inlet of the tail gas alkaline washing adsorption device (11) is connected to the outlet of the low-temperature fixed-bed catalytic oxidation reactor (10). The liquid inlet of the low-temperature fixed-bed catalytic oxidation reactor (10) is connected to the liquid outlet of the PEEK strong alkali resistant nanofiltration membrane module (9). The discharge end of the low-temperature fixed-bed catalytic oxidation reactor (10) is connected to the feed end of the crystallization and salt separation unit. The low-temperature fixed-bed catalytic oxidation reactor (10) is filled with a catalyst.

7. The high-efficiency separation device for chemical alkaline washing waste liquid according to claim 6, characterized in that: The crystallization and salt separation unit includes a nanofiltration salt separation component (12), an MVR low-temperature evaporation crystallizer (13), and a salt product sealed collection chamber (14) connected in sequence. The nanofiltration salt separation component (12) is used to separate different types of salts. The MVR low-temperature evaporation crystallizer (13) is used for salt crystallization and recovery. The salt product sealed collection chamber (14) is used to collect salt products. The liquid outlet of the MVR low-temperature evaporation crystallizer (13) is connected to the feed inlet of the resource recycling unit.

8. The high-efficiency separation device for chemical alkaline washing waste liquid according to claim 7, characterized in that: The resource recycling unit includes an alkali recycling tank (15), an oil phase recycling tank (16), and a condensate recycling pipeline (17) connected in sequence. The inlet of the alkali recycling tank (15) is connected to the outlet of the MVR low-temperature evaporator crystallizer (13) and the outlet of the PEEK strong alkali resistant nanofiltration membrane module (9), respectively. The inlet of the oil phase recycling tank (16) is also connected to the outlet of the inclined plate three-phase separator (7). The outlet of the condensate recycling pipeline (17) is connected to the inlet of the waste liquid conditioning tank (2).

9. A method for efficient separation and treatment of chemical alkaline washing waste liquid, using the efficient separation device for chemical alkaline washing waste liquid according to any one of claims 1-8, characterized in that: Includes the following steps: S1. The chemical alkaline washing waste liquid is fed into the feeding unit for buffering and pressure stabilization, and the feed flow rate fluctuation is controlled to be ≤±5%; S2. The buffered waste liquid is sent to the pretreatment unit for treatment to complete the conditioning of water quality, impurities and temperature. S3. The conditioned waste liquid is transferred to the composite demulsification and physical strengthening unit for preliminary demulsification, and three-phase separation of oil phase, water phase and solid phase impurities is carried out. The separated oil phase is collected and reused. S4. The separated aqueous phase is pre-filtered and sorted through a special membrane separation unit to obtain a reusable regenerated alkali solution and a concentrated solution enriched with salts and organic matter. The regenerated alkali solution is collected and reused. S5. The concentrate is sent to a low-temperature catalytic gasification unit, where a Cu / Mn / Ce-based supported transition metal catalyst is used to carry out a catalytic reaction to degrade the recalcitrant organic matter in the concentrate. S6. The concentrated liquid after catalytic gasification is processed by the crystallization and salt separation unit to separate and crystallize salt products, and the crystallization mother liquor is returned to the pretreatment unit for recycling. S7. The recovered regenerated alkali solution and oil phase are reused in chemical production processes, and the condensate generated during crystallization is recycled.

10. The method for efficient separation and treatment of chemical alkaline washing waste liquid according to claim 9, characterized in that: In step S3, during the initial demulsification, a demulsifier needs to be added continuously. The mass ratio of nonionic polyether-modified silane to cationic polyacrylamide in the demulsifier is 3-4:1, the total concentration of the demulsifier is 200-400 mg / L, and the stirring reaction time is 10-15 minutes.

Images