Combined membrane method resourceful treatment device and process for desulfurization liquid

Abstract

The invention provides a combined membrane method resourceful treatment device and process for a desulfurization solution, and belongs to the technical field of industrial wastewater treatment. The device comprises a plate-and-frame filter press, a homogeneous membrane / reverse osmosis membrane, a nanofiltration membrane, an activated carbon decoloration tank, an evaporator, a first cooling pelleter, an ultrasonic-assisted ozone centrifugal reactor, a sulfur melting kettle, a second cooling pelleter, an ultrafiltration membrane and a bipolar membrane. By means of the synergistic effect of ultrasonic cavitation and ozone oxidation, thiosulfate is efficiently decomposed, elemental sulfur is directionally generated, and a high-quality sulfur product is obtained by matching with refining of the sulfur melting kettle; meanwhile, thiocyanate and sulfate / thiosulfate are accurately separated through a nanofiltration device, a high-purity thiocyanate product is produced through activated carbon decoloration and evaporation concentration, then bipolar membrane electrodialysis is used for directly converting sulfate into recyclable acid and alkali, various high-value resources are systematically recycled, and the method is suitable for industrial production. The problems of low resource recovery rate and insufficient product purity of the traditional process are solved.

Description

Technical Field

[0001] This invention belongs to the field of industrial wastewater treatment technology, specifically relating to a combined membrane resource recovery device and process suitable for ammonium salt and sodium salt desulfurization liquid. Background Technology

[0002] With increasingly stringent environmental policies in my country, the resource-based treatment of high-salt desulfurization wastewater has become a key challenge for the sustainable development of industries such as coal chemical, power, and steel. Wet desulfurization technology is widely used, but the desulfurization liquid it produces has a complex composition, containing various components such as thiocyanate, thiosulfate, sulfate, suspended sulfur, and catalysts. Direct discharge of such liquids not only pollutes the environment but also wastes resources.

[0003] Currently, the mainstream treatment methods each have their limitations: biochemical methods are inhibited by high salt and toxic substances, and the system is unstable; chemical oxidation methods consume a lot of reagents and easily produce salty sludge, causing secondary pollution; evaporation and crystallization methods consume a lot of energy, and the resulting mixed salt has low purity and poor utilization value, and is mostly used for hazardous waste landfill, failing to achieve resource recovery.

[0004] In terms of resource recovery, thiocyanate has high economic value, but traditional recovery processes such as solvent extraction and precipitation are complex, prone to introducing new contaminants, and difficult to guarantee product purity. Furthermore, if thiosulfates and sulfates cannot be effectively separated and converted, it not only affects product quality but also causes scaling and corrosion in the system.

[0005] Membrane separation technologies (electrodialysis, reverse osmosis, nanofiltration, etc.) have shown great potential due to their high efficiency, energy saving, and lack of phase change. However, single membrane technologies are difficult to handle complex desulfurization liquid systems: reverse osmosis has poor ion selectivity; nanofiltration concentrate requires further treatment; and traditional electrodialysis membranes are prone to fouling and have short lifespans. Therefore, optimizing and combining multiple membrane technologies and integrating them with advanced oxidation, evaporation crystallization, and other units to construct an efficient, stable, and economical resource recovery system is a key technological bottleneck that the industry urgently needs to overcome.

[0006] Existing patented technologies also have many shortcomings: CN112591969A uses ceramic membranes and multi-effect evaporation, which achieves preliminary separation of sodium thiocyanate and saves energy, but does not convert sodium thiosulfate, resulting in mixed salts with low economic value and insufficient tolerance to organic impurities; CN107352679A separates sulfur and sodium sulfate through acid hydrolysis, which simplifies the process but is complex to operate, requires high equipment corrosion resistance, and does not efficiently purify sodium thiocyanate; CN112537784A recovers sodium thiocyanate through neutralization and recrystallization, but the introduction of barium salts poses a pollution risk, and it does not treat sodium thiosulfate; CN110803731A is specifically used for extracting potassium sulfate from complexed iron desulfurization liquid, with a narrow scope of application and cannot handle complex multi-component desulfurization liquids; CN115072918A has a simple and environmentally friendly process, but only produces mixed salts, failing to achieve multi-component separation and high-value utilization, resulting in low resource recovery efficiency. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a combined membrane resource recovery device and process for desulfurization liquid. The device has a high degree of integration and a reasonable process flow, which can effectively realize the classification, recovery and conversion of water, catalyst, thiocyanate, elemental sulfur and sulfate in desulfurization liquid, and finally produce economically valuable thiocyanate products, sulfur products, dilute sulfuric acid and alkaline solution. At the same time, it realizes the reuse of water and catalyst, and truly achieves the goals of "turning waste into treasure" and "near-zero emissions".

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A combined membrane resource recovery device for desulfurization liquid includes: Plate and frame filter press: The desulfurization liquid is introduced into the feed inlet of the plate and frame filter press from the outside; the filtrate outlet of the plate and frame filter press is connected to the feed inlet of the homogeneous membrane / reverse osmosis membrane; Homogeneous membrane / reverse osmosis membrane: receives the filtrate from the plate and frame filter press; its concentrate outlet is connected to the feed inlet of the nanofiltration membrane; at the same time, the return water / deionized water interface of the homogeneous membrane / reverse osmosis membrane is connected to an external return water or deionized water source; Nanofiltration membrane: receives concentrate from homogeneous membrane / reverse osmosis membrane; its permeate outlet is connected to the feed inlet of activated carbon decolorization tank; its intercepted liquid outlet is connected to the feed inlet of centrifugal reactor. Activated carbon decolorization tank: receives the permeate from the nanofiltration membrane; its outlet is connected to the feed inlet of the evaporator; Evaporator: Receives the discharge from the activated carbon decolorization tank; its concentrated liquid outlet is connected to the feed inlet of the first cooling tablet making machine; First cooling and tableting machine: receives the concentrated liquid from the evaporator; its outlet outputs thiocyanate product. An ultrasonic-assisted ozone centrifugal reactor, which receives the intercepted liquid from a nanofiltration membrane, includes an ozone generator, a centrifugal reactor, and an ultrasonic generator. The outlet of the ozone generator is connected to the bottom aeration port of the centrifugal reactor, and the ultrasonic generator is connected to the centrifugal reactor. The sulfur paste outlet of the centrifugal reactor is connected to the feed inlet of the sulfur melting kettle, and the centrifuged clear liquid outlet of the centrifugal reactor is connected to the feed inlet of the ultrafiltration membrane. Sulfur melting kettle: receives sulfur paste from the centrifugal reactor; its outlet is connected to the inlet of the second cooling sheeting machine; The second cooling and pelletizing machine receives the discharge from the sulfur melting kettle; its outlet outputs sulfur products. Ultrafiltration membrane: receives the clear liquid from the centrifugal reactor; its product water outlet is connected to the feed inlet of the bipolar membrane; Bipolar membrane: receives the permeate from the ultrafiltration membrane; its outlet outputs sulfuric acid product and caustic soda product respectively, and is also connected to an external return water path.

[0009] Preferably, the centrifugal reactor is a vertical cylindrical structure with a conical area at the bottom center for discharging centrifugal clear liquid, and a sulfur paste outlet on the bottom side for easy collection of sulfur paste.

[0010] Preferably, the ozone generator fills the bottom of the centrifugal reactor with ozone through an aeration device, and the ultrasonic generator is connected to the inside of the centrifugal reactor through an immersion probe.

[0011] The present invention also provides a desulfurization liquid combined membrane method resource recovery treatment process using the above-mentioned device, comprising the following steps: Step 1: Pretreatment of desulfurization liquid The desulfurization liquid first enters a plate and frame filter press for pretreatment to remove sulfur particles and other suspended impurities, reducing the suspended solids content to ≤50mg / L; Step 2: Brine Concentration The clarified liquid obtained after filtration by a plate and frame filter press is concentrated by a homogeneous membrane / reverse osmosis membrane. When using a homogeneous membrane for electrodialysis, the operating voltage is 15-30V, the current density is 100-200A / m², the total salt concentration of the concentrated brine is 300-500g / L, and the total salt concentration of the reflux water after electrodialysis is less than 50g / L. When using reverse osmosis, the operating pressure is 1.5-2.5MPa, the recovery rate is 60-70%, and the permeate conductivity is less than 100μS / cm. Step 3: Nanofiltration separation The concentrated brine is then separated by a nanofiltration membrane. After separation, nanofiltration permeate and nanofiltration interception are obtained. The nanofiltration permeate includes a thiocyanate solution with a purity of ≥95%, and the nanofiltration interception includes sulfate and thiosulfate with a rejection rate of ≥95%. Step 4: Thiocyanate refining The nanofiltration permeate obtained in step 3 is decolorized in an activated carbon decolorization tank, and then evaporated and concentrated in an evaporator using single-effect evaporation to a concentration of 50-60%. Finally, it is processed by a first cooling and tableting machine to obtain a thiocyanate product with a purity of ≥98%. Step 5: Oxidation of thiosulfate The nanofiltration interception liquid obtained in step 3 enters a centrifugal reactor, with the reaction temperature controlled at 40-60℃, internal pressure at 0.8-1.2MPa, and reaction time at 20-40min. Ozone generated by an ozone generator is introduced into the bottom of the centrifugal reactor through an aeration device, with the ozone dosage calculated as 2-3 times that of thiosulfate. An ultrasonic generator produces 20-40kHz ultrasound with a power density of 100-300W / L. Under the synergistic effect of ultrasonic cavitation and ozone oxidation, thiosulfate is completely oxidized to sulfate and elemental sulfur, with an oxidation rate ≥98%. Step 6: Sulfur Recovery The elemental sulfur generated in step 5 is enriched at the bottom outer edge of the centrifugal reactor under centrifugal force. After being discharged through the sulfur discharge port, it is sent to the sulfur melting kettle for melting. Impurities are separated by gravity sedimentation to obtain liquid sulfur with a purity of ≥99%. Then, it is processed into sulfur products by a second cooling and flake making machine. Step 7: Sulfate Conversion The sulfate produced in the centrifugal reactor is further purified by ultrafiltration membrane to remove residual suspended impurities in the post-reaction supernatant, reducing the turbidity to ≤1 NTU; the purified supernatant then enters a bipolar membrane at an operating current density of 200-500 A / m², converting the sulfate into 5-10% sulfuric acid and 8-12% alkali solution with a current efficiency of 70-80%. Step 8: Resource Reuse The sulfuric acid and alkali solutions produced by the bipolar membrane are recycled into the desulfurization system process.

[0012] Preferably, in the pretreatment described in step 1, the pressure filtration is 0.6-0.8 MPa and the filtration accuracy is 5-10 μm.

[0013] Preferably, in the separation described in step 3, the operating pressure is 0.8-1.2 MPa, the temperature is 25-40℃, and the flow rate is 1-2 m / s.

[0014] Preferably, the decolorization temperature in step 4 is 60~70℃, the empty bed residence time is 15-20min, and the decolorization rate is 80-90%.

[0015] Preferably, the evaporation temperature in step 4 is 85°C.

[0016] Preferably, the melting process in step 6 is carried out at 130-150°C for 30-60 minutes.

[0017] Preferably, in the further purification process using the ultrafiltration membrane described in step 7, the operating pressure is 0.1-0.3 MPa and the temperature is 25-35℃.

[0018] Beneficial effects of the present invention Compared with existing technologies, this invention achieves resource utilization, low energy consumption, and environmental friendliness in desulfurization liquid treatment through the efficient coupling of combined membrane technology with reaction and separation units, with significant core advantages: Firstly, the efficiency and value of resource recovery are significantly improved. This invention innovatively designs an ultrasonic-assisted ozone centrifugal reactor, which, through the synergistic effect of ultrasonic cavitation and ozone oxidation, efficiently decomposes thiosulfate and directionally generates elemental sulfur. This is then combined with a sulfur melting kettle to refine high-quality sulfur products. Simultaneously, a nanofiltration device precisely separates thiocyanate from sulfate / thiosulfate. After activated carbon decolorization and evaporation concentration, a high-purity thiocyanate product is produced. Finally, bipolar membrane electrodialysis is used to directly convert sulfate into reusable acids and alkalis. This systematically recovers multiple high-value resources, solving the problems of low resource recovery rate and insufficient product purity in traditional processes.

[0019] Secondly, it completely solves the problems of secondary pollution and emissions. The entire process generates no saline sludge or mixed salt solid waste. The return water after bipolar membrane electrodialysis contains a large amount of catalyst and a small amount of sulfate, which can be directly returned to the desulfurization system for recycling, achieving near-zero wastewater discharge. Compared with the waste of reagents in chemical oxidation methods and the mixed salt pollution in evaporation crystallization methods, this invention avoids secondary pollution from the source through a closed-loop design of "separation-conversion-reuse", which meets the needs of green development.

[0020] Third, energy consumption and operating costs are significantly reduced. Homogeneous membrane electrodialysis or reverse osmosis replaces traditional high-energy-consuming evaporation and concentration. Bipolar membrane electrodialysis directly converts salts into acids and alkalis, eliminating the high-energy-consuming links of additional acid and alkali procurement or production. The application of pressure filtration and ultrafiltration units reduces membrane fouling, and ultrasound-assisted advanced oxidation improves reaction efficiency. With optimized coupling of each unit, the system can be guaranteed to operate stably for a long time, solving the pain points of high energy consumption and unstable operation of single membrane technology or traditional processes. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0022] Figure 1 This is a schematic diagram of the structure of the desulfurization liquid combined membrane resource recovery device provided in an embodiment of the present invention.

[0023] In the diagram, 1 is a plate and frame filter press, 2 is a homogeneous membrane / reverse osmosis membrane, 3 is a nanofiltration membrane, 4 is an ozone generator, 5 is a centrifugal reactor, 6 is a sulfur melting kettle, 7 is a second cooling sheet forming machine, 8 is a first cooling sheet forming machine, 9 is an evaporator, 10 is an activated carbon decolorization tank, 11 is an ultrafiltration membrane, 12 is a bipolar membrane, and 13 is an ultrasonic generator. Detailed Implementation

[0024] A combined membrane resource recovery device for desulfurization liquid, such as Figure 1As shown, it includes a plate and frame filter press 1, a homogeneous membrane / reverse osmosis membrane 2, a nanofiltration membrane 3, an activated carbon decolorization tank 10, an evaporator 9, a first cooling sheet-making machine 8, an ultrasonic-assisted ozone centrifugal reactor, a sulfur melting kettle 6, a second cooling sheet-making machine 7, an ultrafiltration membrane 11, and a bipolar membrane 12. Plate and frame filter press 1: Desulfurization liquid is introduced into the feed inlet of plate and frame filter press 1 from the outside; the filtrate outlet of plate and frame filter press 1 is connected to the feed inlet of homogeneous membrane / reverse osmosis membrane 2; the plate and frame filter press 1 receives desulfurization liquid, with a filtration accuracy of 5-10μm and a filtration pressure of 0.6-0.8MPa, and is used to remove suspended solids and sulfur particles in the desulfurization liquid; Homogeneous membrane / reverse osmosis membrane 2: Connected to the filtrate outlet of plate and frame filter press 1, receiving the filtrate from plate and frame filter press 1; its concentrate outlet is connected to the feed inlet of nanofiltration membrane 3; simultaneously, the return water / deionized water interface of homogeneous membrane / reverse osmosis membrane 2 is connected to an external return water or deionized water source; the operating voltage of the homogeneous membrane electrodialysis unit is 15-30V, and the operating pressure of the reverse osmosis unit is 1.5-2.5MPa, used to concentrate brine and increase ion concentration; Nanofiltration membrane 3: connected to the concentrate outlet of homogeneous membrane / reverse osmosis membrane 2, receiving the concentrate from homogeneous membrane / reverse osmosis membrane 2; its permeate outlet is connected to the feed inlet of activated carbon decolorization tank 10; its intercept liquid outlet is connected to the feed inlet of centrifugal reactor 5; the molecular weight cutoff is 200-300 Da, the operating pressure is 0.8-1.2 MPa, and the sulfate rejection rate is not less than 95%, used to separate thiocyanate from sulfate / thiosulfate; Activated carbon decolorization tank 10: connected to the permeate outlet of nanofiltration membrane 3, and its outlet is connected to the feed inlet of evaporator 9; granular activated carbon is used, with a filling height of 1.5-2m and an empty bed residence time of 15-20min, for decolorizing and purifying thiocyanate solution; Evaporator 9: Connected to the outlet of activated carbon decolorization tank 10, receiving the discharge from activated carbon decolorization tank 10; its concentrated liquid outlet is connected to the inlet of the first cooling tablet machine 8; it adopts a single-effect evaporator with an evaporation temperature of 85℃, and is used to evaporate and concentrate the decolorized thiocyanate solution. First cooling slicing machine 8: connected to the concentrated liquid outlet of evaporator 9, receiving the concentrated liquid of evaporator 9; its outlet outputs thiocyanate product; cooling temperature 20~30℃, using a rotary drum slicer, slice thickness 2-3mm, used to convert concentrated thiocyanate into thiocyanate product. An ultrasonic-assisted ozone centrifugal reactor is connected to the outlet of the nanofiltration membrane 3 to receive the intercepted liquid from the nanofiltration membrane 3. It includes an ozone generator 4, a centrifugal reactor 5, and an ultrasonic generator 13. The outlet of the ozone generator 4 is connected to the bottom aeration port of the centrifugal reactor 5, and ozone is introduced into the bottom of the centrifugal reactor 5 through an aeration device. The ozone output is 100-500 g / h, and the ozone concentration is 80-120 mg / L. The ultrasonic generator 13 acts on the reaction system inside the centrifugal reactor 5 through an immersion probe; the ultrasonic frequency is 20-40kHz and the power density is 100-300W / L. The sulfur paste outlet of centrifugal reactor 5 is connected to the feed inlet of sulfur melting kettle 6; the centrifuged clear liquid outlet of centrifugal reactor 5 is connected to the feed inlet of ultrafiltration membrane 11; centrifugal reactor 5 is a vertical cylindrical structure with an inner diameter of 800-1200 mm and an effective volume of 5-10 m³. ³ The bottom center has a cone-shaped area for discharging centrifuged clear liquid, and the bottom side has a discharge port for easy collection of sulfur paste; Sulfur melting kettle 6: Connected to the bottom side outlet of the centrifugal reactor 5, receiving the sulfur paste from the centrifugal reactor 5; its outlet is connected to the inlet of the second cooling sheeting machine 7; it adopts a jacketed heating method, with an operating temperature of 130-150℃ and a kettle volume of 3-5m³. ³ It is equipped with a stirring device with a rotation speed of 30-50 rpm, which is used to melt the sulfur paste; Second cooling sheet-making machine 7: connected to the outlet of sulfur melting kettle 6, receiving the discharge from sulfur melting kettle 6; its outlet outputs sulfur products; cooling temperature 20-30℃, sheet size 5×5mm; Ultrafiltration membrane 11: connected to the centrifugal clear liquid outlet at the bottom center of centrifugal reactor 5, receiving the centrifugal clear liquid from centrifugal reactor 5; its product water outlet is connected to the feed port of bipolar membrane 12; The membrane pore size is 0.01-0.1μm, the operating pressure is 0.1-0.3MPa, a hollow fiber membrane module is used, and the molecular weight cutoff is 10000Da.

[0025] Bipolar membrane 12: Connected to the product water outlet of ultrafiltration membrane 11, it receives the product water from ultrafiltration membrane 11; its outlet outputs sulfuric acid product and caustic soda product respectively, and is connected to an external return water flow path. The operating current density is 200-500A / m², and the number of membrane stacks is 30-50 pairs. It is used to convert sulfate in the clear liquid into sulfuric acid and alkali.

[0026] Preferably, the bipolar membrane system adopts an existing technology structure with a three-chamber structure for acid, alkali, and salt, each chamber equipped with an independent circulation pump and flow meter for easy adjustment and control.

[0027] The present invention also provides a desulfurization liquid combined membrane method resource recovery treatment process using the above-mentioned device, comprising the following steps: Step 1: Pretreatment of desulfurization liquid The desulfurization liquid first enters the plate and frame filter press 1 for pretreatment. The filter pressure is preferably 0.6-0.8MPa and the filtration accuracy is preferably 5-10μm to remove sulfur particles and other suspended impurities, so that the suspended solids content is reduced to ≤50mg / L. Step 2: Brine Concentration The clarified liquid obtained after filtration by plate and frame filter press 1 enters the homogeneous membrane / reverse osmosis membrane 2 for concentration. When using homogeneous membrane electrodialysis, the operating voltage is 15-30V, the current density is 100-200A / m², the total salt concentration of the concentrated brine is 300-500g / L, and the total salt concentration of the reflux water after electrodialysis is less than 50g / L. When using reverse osmosis, the operating pressure is 1.5-2.5MPa, the recovery rate is 60-70%, and the permeate conductivity is less than 100μS / cm. Step 3: Nanofiltration separation The concentrated brine is then introduced into nanofiltration membrane 3 for separation. The preferred operating pressure is 0.8-1.2 MPa, the preferred temperature is 25-40℃, and the preferred flow rate is 1-2 m / s. After separation, nanofiltration permeate and nanofiltration interception liquid are obtained. The nanofiltration permeate includes a thiocyanate solution with a purity ≥95%, and the nanofiltration interception liquid includes sulfate and thiosulfate with a rejection rate ≥95%. Step 4: Thiocyanate refining The nanofiltration permeate obtained in step 3 is decolorized sequentially in activated carbon decolorization tank 10. The decolorization temperature is preferably 60-70℃, the empty bed residence time is preferably 15-20 min, and the decolorization rate is preferably 80-90%. Then it enters evaporator 9 for evaporation and concentration. Single-effect evaporation is used, and the evaporation temperature is preferably 85℃. The concentration is concentrated to 50-60%. Finally, it is processed by the first cooling and tableting machine to obtain a thiocyanate product with a purity of ≥98%. Step 5: Oxidation of thiosulfate The nanofiltration interception liquid obtained in step 3 enters the centrifugal reactor 5, with the reaction temperature controlled at 40-60℃, internal pressure at 0.8-1.2MPa, and reaction time at 20-40min. Ozone generated by ozone generator 4 is introduced into the bottom of centrifugal reactor 5 through an aeration device, with the ozone dosage calculated as 2-3 times that of thiosulfate. Ultrasonic generator 13 generates 20-40kHz ultrasound with a power density of 100-300W / L. Under the synergistic effect of ultrasonic cavitation and ozone oxidation, thiosulfate is completely oxidized to sulfate and elemental sulfur, with an oxidation rate ≥98%. Step 6: Sulfur Recovery The elemental sulfur generated in step 5 is enriched at the bottom outer edge of the centrifugal reactor 5 under the action of centrifugal force. After being discharged through the sulfur discharge port, it is sent to the sulfur melting kettle 6. It is preferably melted at 130-150℃ for 30-60 minutes. Impurities are separated by gravity sedimentation to obtain liquid sulfur with a purity of ≥99%. Then, it is processed into sulfur products by the second cooling and flake making machine 7. Step 7: Sulfate Conversion The centrifuged clear liquid (sulfate) produced in centrifugal reactor 5 is further purified by ultrafiltration membrane 11. The operating pressure is preferably 0.1-0.3 MPa and the temperature is preferably 25-35℃. This removes residual suspended impurities from the clear liquid after the reaction, reducing the turbidity to ≤1 NTU. The purified clear liquid then enters bipolar membrane 12, where the operating current density is 200-500 A / m². This converts the sulfate into sulfuric acid of 5-10% concentration and alkali solution of 8-12% concentration, with a current efficiency of 70-80%. Step 8: Resource Reuse The sulfuric acid and alkaline solution produced by the bipolar membrane 12 are recycled to the desulfurization system process. The sulfuric acid can be used to adjust the pH value of the desulfurization solution, and the alkaline solution can be used to replenish the alkalinity of the desulfurization system. The remaining recycled water contains catalyst and sulfate (≤5g / L) and can be directly returned to the desulfurization system for recycling, achieving near-zero wastewater discharge.

[0028] According to the present invention, the bipolar membrane electrodialysis process in step 7 adopts a constant current operation mode, and the current density is automatically adjusted according to the sulfate concentration of the influent to ensure the stability of the acid and alkali concentrations of the product.

[0029] According to the present invention, the entire process system adopts a continuous operation mode, with a processing capacity of 10-50 m³ / h and an annual operating time of over 8000 hours.

[0030] This invention utilizes a combined membrane method to achieve resource utilization of high-salt desulfurization liquid, effectively solving industry pain points such as difficult discharge of desulfurization liquid, high energy consumption for treatment, and secondary pollution from mixed salt solid waste, and has significant economic and environmental benefits.

[0031] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] Example 1: This embodiment uses a high-salt desulfurization solution from a coal chemical plant. Its main components are as follows: sodium thiocyanate concentration 120-150 g / L, sodium thiosulfate concentration 20-30 g / L, sodium sulfate concentration 30-50 g / L, suspended solids concentration 200-300 mg / L, and pH value 8.5-9.5. The pilot plant has a processing capacity of 5 m³ / h and operates continuously for 72 hours.

[0033] Device operation process: The desulfurization liquid first enters a plate and frame filter press for pretreatment. The plate and frame filter press has a filtration accuracy of 8 μm and a filtration pressure of 0.7 MPa. After filtration, the suspended solids content of the clear liquid is reduced to 35 mg / L, and the sulfur particle removal rate is 99%. The filter cake produced by filtration has a volume of approximately 0.12 m³ / h and a moisture content of 65%.

[0034] After pressure filtration, the clarified liquid enters a homogeneous membrane electrodialysis unit for concentration. A laboratory-scale homogeneous membrane electrodialysis unit with 10 membrane stacks was selected, operating at 25V and a current density of 150A / m². The concentrated brine achieved a total salt concentration of 380 g / L, with sodium thiocyanate at 282 g / L, sodium thiosulfate at 30 g / L, and sodium sulfate at 68 g / L. The dilute water (return water) produced by electrodialysis had a total salt concentration of 35 g / L and was directly returned to the desulfurization system for reuse.

[0035] The concentrated brine then enters a nanofiltration membrane system for separation. The nanofiltration membrane is an NF270-2540 spiral wound membrane element, operating at a pressure of 1.0 MPa, a temperature of 35℃, and an influent flow rate of 1.5 m / s. The nanofiltration permeate flow rate is 1.9 m³ / h, with sodium thiocyanate as the main component at a concentration of 385 g / L and a purity of 98.5%. The nanofiltration intercept flow rate is 0.6 m³ / h, and the actual sulfate / thiosulfate rejection rate is 98.95%.

[0036] The nanofiltration permeate was then fed into an activated carbon decolorization tank for decolorization. The activated carbon in the decolorization tank was packed to a height of 1.5 m, using coconut shell activated carbon granules. The decolorization temperature was 65℃, the empty bed residence time was 20 min, and the decolorization rate was 85%. After decolorization, the transmittance of the solution increased from 45% to 92%.

[0037] The decolorized thiocyanate solution was concentrated in a single-effect evaporator at 85°C and a heating steam pressure of 0.3 MPa. The concentrated solution was then processed in a first cooling slicing machine at 20°C. A small rotary drum slicer was used to slice the product to a thickness of 2 mm, yielding sodium thiocyanate with a purity of 99.1% and a water content of 0.5%.

[0038] The nanofiltration interception solution entered an ultrasonic-assisted ozone centrifugal reactor for thiosulfate oxidation. The reactor had an effective volume of 8.5 m³, an ozone generator with an ozone output of 50 g / h and an ozone concentration of 100 mg / L, and an ultrasonic generator with a power density of 200 W / L and a frequency of 30 kHz. Reaction conditions were: temperature 50℃, pressure 1.0 MPa, reaction time 30 min, and pH 8.0. Under the synergistic effect of ultrasonic cavitation and ozone oxidation, the thiosulfate oxidation rate reached 99.5%, generating 6 kg / h of elemental sulfur.

[0039] The generated liquid sulfur paste, under centrifugal force (4000 rpm), accumulates on the outer bottom of the reactor and is discharged through the sulfur outlet. The sulfur paste has a solids content of 75% and is fed into a small sulfur melting kettle. The kettle has a volume of 1 m³, a temperature of 140℃, and a melting time of 45 min. The sulfur purity after melting is 99.8%. The molten sulfur then enters a second cooling and sheet-making machine, where it is cooled to 25℃ and formed into 5×5 mm sheets.

[0040] The centrifuged clarified liquid produced by the ultrasonic-assisted ozone centrifuge reactor enters the ultrafiltration membrane system for purification. The ultrafiltration membrane is a hollow fiber membrane module with a pore size of 0.05 μm and an operating pressure of 0.2 MPa. The turbidity of the ultrafiltration clarified liquid is 0.5 NTU, and the suspended solids content is 0.8 mg / L.

[0041] Ultrafiltration permeate enters a bipolar membrane electrodialysis system for sulfate conversion. The system consists of 10 pairs of bipolar membrane stacks, operating at a current density of 350 A / m². After operation, it produces 0.3 m³ / h of 10% sulfuric acid (98.5% purity) and 0.25 m³ / h of 12% sodium hydroxide solution (99.0% purity); the bipolar membrane current efficiency reaches 76.5%.

[0042] The residual effluent from bipolar membrane electrodialysis contains catalyst and a small amount of sodium sulfate (3.5 g / L), which is directly returned to the desulfurization system for recycling.

[0043] The results show that the combined membrane resource recovery process technology of the present invention is feasible, and all indicators meet the design requirements. It can effectively solve the industry pain points of difficult desulfurization liquid discharge, high energy consumption and secondary pollution of mixed salt solid waste, and has significant economic and environmental benefits.

[0044] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A combined membrane resource recovery device for desulfurization liquid, characterized in that, include: Plate and frame filter press (1): Desulfurization liquid is introduced into the feed inlet of plate and frame filter press (1) from the outside; The filtrate outlet of the plate and frame filter press (1) is connected to the feed inlet of the homogeneous membrane / reverse osmosis membrane (2); Homogeneous membrane / reverse osmosis membrane (2): Receives the filtrate from the plate and frame filter press (1); its concentrate outlet is connected to the feed inlet of the nanofiltration membrane (3); at the same time, the return water / deionized water interface of the homogeneous membrane / reverse osmosis membrane (2) is connected to an external return water or deionized water source; Nanofiltration membrane (3): receives the concentrate from the homogeneous membrane / reverse osmosis membrane (2); its permeate outlet is connected to the feed inlet of the activated carbon decolorization tank (10); its interception outlet is connected to the feed inlet of the centrifugal reactor (5); Activated carbon decolorization tank (10): receives the permeate from the nanofiltration membrane (3); its outlet is connected to the feed inlet of the evaporator (9); Evaporator (9): Receives the discharge from activated carbon decolorization tank (10); its concentrated liquid outlet is connected to the feed inlet of the first cooling tablet machine (8); First cooling sheeter (8): Receives the concentrate from evaporator (9); Its outlet outputs thiocyanate products; An ultrasonic-assisted ozone centrifugal reactor, receiving the intercepted liquid from a nanofiltration membrane (3), includes an ozone generator (4), a centrifugal reactor (5), and an ultrasonic generator (13). The outlet of the ozone generator (4) is connected to the bottom aeration port of the centrifugal reactor (5), and the ultrasonic generator (13) is connected to the centrifugal reactor (5). The sulfur paste outlet of the centrifugal reactor (5) is connected to the feed inlet of the sulfur melting kettle (6). The centrifugal clear liquid outlet of the centrifugal reactor (5) is connected to the feed inlet of the ultrafiltration membrane (11). Sulfur melting kettle (6): receives sulfur paste from centrifugal reactor (5); its outlet is connected to the inlet of the second cooling sheeting machine (7); Second cooling sheeter (7): receives the discharge from the sulfur melting kettle (6); its discharge port outputs sulfur products; Ultrafiltration membrane (11): Receives the clear liquid from the centrifugal reactor (5); Its product water outlet is connected to the feed inlet of the bipolar membrane (12); Bipolar membrane (12): Receives the product water from the ultrafiltration membrane (11); its outlet outputs sulfuric acid product and caustic soda product respectively, and is connected to an external return water flow path.

2. The combined membrane resource recovery device for desulfurization liquid according to claim 1, characterized in that, The centrifugal reactor (5) is a vertical cylindrical structure with a conical area at the bottom center for discharging centrifugal clear liquid and a sulfur paste outlet on the bottom side for easy collection of sulfur paste.

3. The combined membrane resource recovery device for desulfurization liquid according to claim 1, characterized in that, The ozone generator (4) fills the bottom of the centrifugal reactor (5) with ozone through the aeration device, and the ultrasonic generator (13) is connected to the inside of the centrifugal reactor (5) through an immersion probe.

4. A desulfurization liquid combined membrane resource recovery process using the device described in claim 1, characterized in that, Includes the following steps: Step 1: Pretreatment of desulfurization liquid The desulfurization liquid first enters the plate and frame filter press (1) for pretreatment to remove sulfur particles and other suspended impurities contained therein, so that the suspended solids content is reduced to ≤50mg / L; Step 2: Brine Concentration The clarified liquid obtained after filtration by plate and frame filter press (1) enters a homogeneous membrane / reverse osmosis membrane (2) for concentration. When using homogeneous membrane electrodialysis, the operating voltage is 15-30V, the current density is 100-200A / m², the total salt concentration of the concentrated brine is 300-500g / L, and the total salt concentration of the return water after electrodialysis is less than 50g / L. When using reverse osmosis, the operating pressure is 1.5-2.5MPa, the recovery rate is 60-70%, and the permeate conductivity is less than 100μS / cm. Step 3: Nanofiltration separation The concentrated high-concentration brine enters the nanofiltration membrane (3) for separation. After separation, nanofiltration permeate and nanofiltration interception liquid are obtained. The nanofiltration permeate includes thiocyanate solution with a purity of ≥95%. The nanofiltration interception liquid includes sulfate and thiosulfate with a rejection rate of ≥95%. Step 4: Thiocyanate refining The nanofiltration permeate obtained in step 3 is decolorized in an activated carbon decolorizing tank (10) and then enters an evaporator (9) for evaporation and concentration. Single-effect evaporation is used to concentrate it to a concentration of 50-60%. Finally, it is processed by a first cooling tablet making machine (8) to obtain a thiocyanate product with a purity of ≥98%. Step 5: Oxidation of thiosulfate The nanofiltration interception liquid obtained in step 3 enters the centrifugal reactor (5), and the reaction temperature is controlled at 40-60℃, the internal pressure is 0.8-1.2MPa, and the reaction time is 20-40min. The ozone generated by the ozone generator (4) is introduced into the bottom of the centrifugal reactor through the aeration device. The ozone dosage is calculated as 2-3 times that of thiosulfate. The ultrasonic generator (13) generates 20-40kHz ultrasonic waves with a power density of 100-300W / L. Under the synergistic effect of ultrasonic cavitation and ozone oxidation, thiosulfate is completely oxidized into sulfate and elemental sulfur, with an oxidation rate ≥98%. Step 6: Sulfur Recovery The elemental sulfur generated in step 5 is enriched at the bottom outer edge of the centrifugal reactor under the action of centrifugal force. After being discharged through the sulfur discharge port, it is sent to the sulfur melting kettle (6) for melting. Impurities are separated by gravity sedimentation to obtain liquid sulfur with a purity of ≥99%. Then, it is processed into sulfur products by the second cooling sheet making machine (7). Step 7: Sulfate Conversion The sulfate produced in the centrifugal reactor (5) is further purified by ultrafiltration membrane (11) to remove residual suspended impurities in the post-reaction clear liquid, reducing the turbidity to ≤1 NTU; the purified clear liquid enters the bipolar membrane (12) with an operating current density of 200-500 A / m², converting the sulfate into 5-10% sulfuric acid and 8-12% alkali solution with a current efficiency of 70-80%; Step 8: Resource Reuse The sulfuric acid and alkali solutions produced by the bipolar membrane are recycled into the desulfurization system process.

5. The desulfurization liquid combined membrane resource recovery process according to claim 4, characterized in that, In the pretreatment described in step 1, the pressure for filtration is 0.6-0.8 MPa and the filtration accuracy is 5-10 μm.

6. The desulfurization liquid combined membrane resource recovery process according to claim 4, characterized in that, In the separation described in step 3, the operating pressure is 0.8-1.2 MPa, the temperature is 25-40℃, and the flow rate is 1-2 m / s.

7. The desulfurization liquid combined membrane resource recovery process according to claim 4, characterized in that, The decolorization temperature in step 4 is 60~70℃, the empty bed residence time is 15-20min, and the decolorization rate is 80-90%.

8. The desulfurization liquid combined membrane resource recovery process according to claim 4, characterized in that, The evaporation temperature described in step 4 is 85°C.

9. The desulfurization liquid combined membrane resource recovery process according to claim 4, characterized in that, The melting process described in step 6 is carried out at 130-150℃ for 30-60 minutes.

10. The desulfurization liquid combined membrane resource recovery process according to claim 4, characterized in that, In step 7, the ultrafiltration membrane is used for further purification. The operating pressure is 0.1-0.3 MPa and the temperature is 25-35℃.

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