A method for rapid demulsification and oil removal of high-oil-content emulsified wastewater based on coupling of pulsed electric field and spiral microchannels

Abstract

The application belongs to the technical field of sewage treatment, and discloses a high-oil-emulsified wastewater rapid demulsification and oil removal method based on coupling of a pulse electric field and a spiral microchannel. In view of the problems of difficulty in demulsification and low oil removal efficiency of high-oil-emulsified wastewater, the application proposes to apply a composite waveform pulse electric field superimposed by a square wave, a triangular wave and a sine wave to a double-spiral nested microchannel electrode system, to accelerate coalescence and separation of oil droplets by using the composite waveform of the composite waveform pulse electric field and the limited action of the double-spiral nested microchannel, and to realize rapid demulsification and oil removal in combination with subsequent air flotation and activated carbon adsorption steps loaded with nano iron. The high-oil-emulsified wastewater rapid demulsification and oil removal method introduces an innovative mode of coupling of a composite waveform pulse electric field and a double-spiral nested microchannel, greatly shortens the demulsification and oil removal time, improves the processing speed, and is particularly suitable for scenes requiring rapid processing of high-oil-emulsified wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology and relates to a rapid demulsification and oil removal method for high-oil-content emulsified wastewater based on the coupling of pulsed electric field and spiral microchannel. Background Technology

[0002] The generation of high-oil-content emulsified wastewater is increasing daily in industrial production and daily life, posing a serious threat to the environment. High-oil-content emulsified wastewater mainly originates from industries such as oil extraction, refining, chemical processing, and food processing. It is characterized by small oil droplet size, high degree of emulsification, and strong stability, making it difficult to treat effectively using traditional physical, chemical, and biological methods. Therefore, developing efficient and rapid technologies for treating high-oil-content emulsified wastewater is of significant practical importance.

[0003] Currently, domestic and international treatment methods for high-oil-content emulsified wastewater include physical, chemical, and biological methods. Physical methods mainly include gravity separation, centrifugal separation, filtration, and flotation. These methods are simple to operate and low-cost, but their treatment effects are limited and often fail to meet discharge standards. Chemical methods mainly include coagulation sedimentation, oxidation-reduction, and electrolysis. These methods have better treatment effects, but require large amounts of chemical reagents, which can cause secondary pollution. Biological methods mainly include activated sludge processes and biofilm processes. These methods offer stable treatment effects and low costs, but have long treatment cycles and require high water quality standards.

[0004] In recent years, with the continuous development of science and technology, a number of new technologies for treating high-oil-content emulsified wastewater have emerged, such as pulsed electric field demulsification, microchannel technology, and membrane separation technology. Pulsed electric field demulsification utilizes the effect of a pulsed electric field to cause oil droplets to coalesce and separate, thereby achieving the purpose of demulsification and oil removal. Microchannel technology utilizes the special structure and hydrodynamic properties of microchannels to accelerate the coalescence and separation of oil droplets, improving treatment efficiency. Membrane separation technology utilizes the selective permeability of membranes to separate oil droplets from water, thereby achieving the purpose of oil removal.

[0005] However, these novel technologies still face some challenges in practical applications, such as the high energy consumption of pulsed electric field demulsification, the limited processing capacity of microchannel technology, and severe membrane fouling in membrane separation technology. Therefore, how to organically combine these novel technologies to develop an efficient, rapid, and energy-saving method for treating high-oil-content emulsified wastewater is currently a hot research topic and a difficult challenge.

[0006] Regarding related patents, patent "A high-oil-content emulsified wastewater treatment process based on electrochemistry" (CN120943465A) proposes a single-electric-field demulsification method, which uses an electric field to treat wastewater. However, it employs direct current operation, resulting in limited demulsification effect and difficulty in handling complex high-oil-content emulsified wastewater. Patent "A high-oil-content emulsified wastewater demulsification and separation device" (CN220745619U) uses reflux dilution and variable-diameter mixing reaction to effectively modify and promote wastewater demulsification. However, its structural design is not reasonable, and its effect on oil droplet aggregation and separation is not significant, resulting in low treatment efficiency. Patent "A continuous pretreatment method for maleic anhydride emulsified wastewater" is designed for pretreatment of high-oil-content emulsified wastewater generated in the process of preparing maleic anhydride by n-butane oxidation. However, it focuses on removing chemical oxygen demand (COD) from the water and lacks attention to oil removal.

[0007] In summary, the current research and technical solutions still have significant shortcomings, as detailed below: 1) Existing demulsification techniques mostly employ a single method, making it difficult to fully utilize the advantages of various techniques, resulting in unsatisfactory treatment effects; 2) Some technologies suffer from problems such as high energy consumption, limited processing capacity, and severe membrane fouling, which increase processing costs and difficulty; 3) The lack of efficient collaborative treatment models makes it impossible to achieve rapid and efficient treatment of high-oil-content emulsified wastewater. Summary of the Invention

[0008] This invention addresses the problems existing in the prior art. Theoretically, it is based on the polarization and coalescence effects of a pulsed electric field on oil droplets, and the unique confinement effect of a spiral microchannel. According to electrodynamic principles, a pulsed electric field can generate polarized charges on the surface of oil droplets, thereby promoting mutual attraction and coalescence between them. The spiral structure of the spiral microchannel induces spiral flow in the fluid, increasing the probability of collisions between oil droplets and further accelerating their coalescence. Simultaneously, the composite waveform pulsed electric field is composed of superimposed square waves, triangular waves, and sine waves; the combination of different waveforms can generate a more complex electric field distribution, resulting in a more diversified effect on the oil droplets and improving the demulsification effect.

[0009] This invention innovatively combines a composite waveform pulsed electric field with a double-helix nested microchannel. By precisely controlling the parameters of the composite waveform pulsed electric field, such as pulse frequency, electric field strength, and duration, as well as the structural parameters of the double-helix nested microchannel, such as the diameter of the inner helix microchannel, the diameter of the outer helix microchannel, and the helix spacing, rapid demulsification and oil removal of highly oily emulsified wastewater can be achieved. This coupling mode fully leverages the synergistic effect of the pulsed electric field and the helical microchannel, significantly improving treatment efficiency.

[0010] The technical solution of the present invention: A rapid demulsification and oil removal method for high-oil-content emulsified wastewater based on pulsed electric field and spiral microchannel coupling includes the following steps: Step 1: Construct a double-helix nested microchannel electrode system; The double-helix nested microchannel electrode system includes an inlet 1, a pre-electrocatalytic cathode 2, a pre-electrocatalytic anode 3, a pre-connecting terminal 4, an outer spiral microchannel 5, an inner spiral microchannel 6, a post-electrocatalytic cathode 7, a post-electrocatalytic anode 8, a post-connecting terminal 9, an outlet 10, a connecting rod 11, and a base 12. The inlet 1 is embedded in the cavity between the pre-catalytic cathode 2 and the pre-catalytic anode 3. The pre-catalytic cathode 2 and the pre-catalytic anode 3 are separated and connected by a silicone flange gasket, and a cavity exists between them. The cathode wire and anode wire led out from the pre-terminal terminal 4 are respectively connected to the pre-catalytic cathode 2 and the pre-catalytic anode 3 to provide a composite waveform pulsed electric field. One end of the outer spiral microchannel 5 and the inner spiral microchannel 6 are both connected to the outlet of the pre-catalytic anode 3. The outer spiral microchannel 5 is wound around the inner spiral microchannel 6, with the two spiraling in clockwise and counterclockwise directions, respectively. The outer spiral microchannel 5 and the inner spiral microchannel 6 extend axially and are connected at the other end to the inlet of the post-electrocatalytic cathode 7. The post-electrocatalytic cathode 7 and the post-electrocatalytic anode 8 are separated and fixed by a silicone flange gasket, and there is a cavity reaction zone between them. The cathode wire and anode wire led out through the post-terminal 9 are respectively connected to the post-electrocatalytic cathode 7 and the post-electrocatalytic anode 8 to provide a composite waveform pulse electric field. The post-electrocatalytic anode 8 is connected to the outlet 10. The pre-electrocatalytic anode 3 and the post-electrocatalytic cathode 7 are fixed by a connecting rod 11 and supported by a base 12. Step 2: Control the temperature at 20~30℃ and the pH value at 6~8. Introduce the high oil content emulsified wastewater into the cavity between the pre-electrocatalytic cathode 2 and the pre-electrocatalytic anode 3 through the inlet 1 at a flow rate of 0.5~2L / min. Apply a composite waveform pulsed electric field to perform electrochemical oil separation pretreatment to achieve preliminary oil-water separation. Step 3: The charged, high-oil-content emulsified wastewater, after preliminary oil-water separation, penetrates the cavity between the pre-electrocatalytic cathode 2 and the pre-electrocatalytic anode 3 and enters the outer spiral microchannel 5 and the inner spiral microchannel 6 in parallel. Under the throttling effect, it flows in a counter-current high-speed swirling motion. Under the action of supergravity, it further achieves oil-water separation. Then, under the violent impact in the cavity reaction zone between the post-electrocatalytic cathode 7 and the post-electrocatalytic anode 8, a composite waveform pulsed electric field is applied again for deep electrochemical treatment. Step 4: Introduce the high-oil-content emulsified wastewater treated in Step 3 into the dissolved air flotation (DAF) tank, and introduce air into the DAF tank at a flow rate of 0.1~0.5 m³ / h. 3 / h, the flotation time is 10~20min, so that the oil droplets float to the water surface; Step 5: Introduce the high oil content emulsified wastewater after air flotation into an activated carbon adsorption column loaded with nano-iron. The height of the activated carbon adsorption column is 50~100cm, the inner diameter is 10~20cm, the flow rate of the high oil content emulsified wastewater is 0.1~0.5L / min, and the adsorption time is 20~40min. Step 6: Conduct water quality testing on the treated high-oil-content emulsified wastewater. The testing items include oil content, chemical oxygen demand, and suspended solids content. If the water quality meets the discharge standards, the wastewater will be discharged or reused. If the water quality does not meet the discharge standards, it will be returned to inlet 1 for retreatment until the water quality meets the discharge standards.

[0011] In step 1, the inner diameter of the inner spiral microchannel 6 is 1~3mm, the inner diameter of the outer spiral microchannel 7 is 3~5mm, and the spiral spacing is 2~4mm; further, the inner diameter of the inner spiral microchannel 6 is preferably 2mm, the inner diameter of the outer spiral microchannel 7 is preferably 4mm, and the spiral spacing is preferably 3mm.

[0012] In step 1, the pre-catalytic cathode 2, pre-catalytic anode 3, post-catalytic cathode 7, and post-catalytic anode 8 are all made of stainless steel. The spacing between the pre-catalytic cathode 2 and the pre-catalytic anode 3, as well as between the post-catalytic cathode 7 and the post-catalytic anode 8, is 5~10mm.

[0013] In step 2, the composite waveform is composed of a square wave, a triangular wave, and a sine wave superimposed, with a duty cycle of 3:2:1, a pulse frequency of 100~500Hz, an electric field strength of 500~1500V / m, and an action time of 5~15min; furthermore, the pulse frequency of the composite waveform pulse electric field is preferably 300Hz, the electric field strength is preferably 1000V / m, and the action time is preferably 10min.

[0014] In step 3, the composite waveform is composed of a square wave, a triangular wave, and a sine wave superimposed, with a duty cycle of 5:2:1, a pulse frequency of 100~500Hz, an electric field strength of 500~1500V / m, and an action time of 5~15min; furthermore, the pulse frequency of the composite waveform pulse electric field is preferably 300Hz, the electric field strength is preferably 1000V / m, and the action time is preferably 10min.

[0015] In step 5, the height of the activated carbon adsorption column loaded with nano-iron is 80cm, the inner diameter is 15cm, and the wastewater flow rate is 0.3L / min.

[0016] The double-helix nested microchannel electrode system, flotation tank, and activated carbon adsorption column loaded with nano-iron should be cleaned and maintained regularly. The cleaning cycle is 10 to 30 days and the cleaning time is 1 to 3 hours.

[0017] The beneficial effects of this invention are: (1) The present invention adopts an innovative mode of coupling composite waveform pulse electric field with double helix nested microchannel, which greatly shortens the demulsification and oil removal time, improves the processing speed, and can quickly treat high oil content emulsified wastewater.

[0018] (2) This method combines multiple treatment methods such as pulsed electric field, spiral microchannel, air flotation and activated carbon adsorption, giving full play to the advantages of each technology, and the treatment effect is significant. It can effectively reduce the oil content and chemical oxygen demand in wastewater.

[0019] (3) The processing of the present invention is relatively simple, has low energy consumption, and generates less secondary pollution, which meets environmental protection requirements and has good application prospects. Attached Figure Description

[0020] Figure 1 This is a process flow diagram of a rapid demulsification and oil removal method for high-oil-content emulsified wastewater based on the coupling of pulsed electric field and spiral microchannel; Figure 2 The waveform diagram is shown below; Figure 3 This is a schematic diagram of the structure of a spiral microchannel.

[0021] In the diagram: 1. Inlet, 2. Pre-electrocatalytic cathode, 3. Pre-electrocatalytic anode, 4. Pre-connection terminal, 5. Outer spiral microchannel, 6. Inner spiral microchannel, 7. Post-electrocatalytic cathode, 8. Post-electrocatalytic anode, 9. Post-connection terminal, 10. Outlet, 11. Connecting rod, 12. Base. Detailed Implementation

[0022] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0023] Example 1 A double-helix nested microchannel electrode system was constructed, with the inner helix microchannel 6 having an inner diameter of 2 mm and the outer helix microchannel 7 having an inner diameter of 4 mm, with a helix spacing of 3 mm. The pre-catalytic cathode 2, pre-catalytic anode 3, post-catalytic cathode 7, and post-catalytic anode 8 were all made of stainless steel, with an 8 mm spacing between the pre-catalytic cathode 2 and pre-catalytic anode 3, and between the post-catalytic cathode 7 and post-catalytic anode 8. High-oil-content emulsified wastewater was introduced into the double-helix nested microchannel electrode system at a flow rate of 1 L / min, with the wastewater temperature controlled at 25℃ and the pH value at 7. A composite waveform pulsed electric field was applied with a pulse frequency of 300 Hz, an electric field strength of 1000 V / m, and an action time of 10 min. The treated wastewater was then introduced into an air flotation tank, with an air flow rate of 0.3 m³ / min. 3The flow rate was 0.3 L / min, and the flotation time was 15 min. The flotated wastewater was then introduced into an activated carbon adsorption column loaded with nano-iron. The activated carbon column was 80 cm high and 15 cm in inner diameter. The wastewater flow rate was 0.3 L / min, and the adsorption time was 30 min. After treatment, the oil content in the high-oil emulsified wastewater decreased from the initial 500 mg / L to 20 mg / L, COD decreased from 800 mg / L to 100 mg / L, and suspended solids decreased from 300 mg / L to 30 mg / L.

[0024] Example 2 This embodiment is a variation of Example 1, the difference being that the inner spiral microchannel diameter is 1 mm, the outer spiral microchannel diameter is 3 mm, and the spiral spacing is 2 mm. All other conditions are the same as in Example 1 and will not be repeated. After treatment, the oil content in the high-oil-content emulsified wastewater decreased to 30 mg / L, COD decreased to 120 mg / L, and suspended solids decreased to 40 mg / L.

[0025] Example 3 This embodiment is a variation of Example 1, the difference being that the pulse frequency is 100Hz, the electric field strength is 500V / m, and the treatment time is 15min. All other conditions are the same as in Example 1 and will not be repeated. After treatment, the oil content in the high-oil emulsified wastewater decreased to 40mg / L, COD decreased to 150mg / L, and suspended solids decreased to 50mg / L.

[0026] Example 4 This embodiment is a variation of Example 1, the difference being that the activated carbon column height is 50cm, the inner diameter is 10cm, and the wastewater flow rate is 0.5L / min. All other conditions are the same as in Example 1 and will not be repeated. After treatment, the oil content in the high-oil emulsified wastewater decreased to 50mg / L, COD decreased to 180mg / L, and suspended solids decreased to 60mg / L.

[0027] Example 5 This embodiment is a variation of Embodiment 1, the difference being that the air flow rate introduced into the flotation tank is 0.1 m³ / s. 3 The flotation time was 10 min / h. All other conditions were the same as in Example 1 and will not be repeated. After treatment, the oil content in the high-oil emulsified wastewater decreased to 60 mg / L, COD decreased to 200 mg / L, and suspended solids decreased to 70 mg / L.

[0028] Comparative Example 1 This embodiment is a variation of Embodiment 1, the difference being that the composite waveform pulsed electric field is replaced with a constant voltage electric field with an electric field strength of 1000V / m, while other conditions are completely consistent with Embodiment 1; after treatment, the oil content in the high-oil emulsified wastewater decreased from the initial 500mg / L to 150mg / L, COD decreased from 800mg / L to 600mg / L, and suspended solids content decreased from 300mg / L to 150mg / L; it still cannot meet the national emission standards.

[0029] Comparative Example 2 This embodiment is a variation of Embodiment 1, the difference being that the outer spiral microchannel 5 and the inner spiral microchannel 6 are replaced with straight pipe channels, while other conditions are completely consistent with Embodiment 1; after treatment, the oil content in the high oil emulsified wastewater remains basically unchanged, the COD decreases from 800 mg / L to 750 mg / L, and the suspended solids content remains basically unchanged; it cannot meet the national emission standards.

[0030] The specific embodiments described above are only used to illustrate the spirit of the present invention. The scope of protection of the present invention is not limited thereto. For those skilled in the art, other embodiments can be easily made by means of changes, substitutions or modifications based on the technical content disclosed in this specification. All such other embodiments should be covered within the scope of protection of the present invention.

Claims

1. A method for rapid demulsification and oil removal of highly oily emulsified wastewater based on pulsed electric field and spiral microchannel coupling, characterized in that, Includes the following steps: Step 1: Construct a double-helix nested microchannel electrode system; The double-helix nested microchannel electrode system includes an inlet (1), a pre-electrocatalytic cathode (2), a pre-electrocatalytic anode (3), a pre-connecting terminal (4), an outer spiral microchannel (5), an inner spiral microchannel (6), a post-electrocatalytic cathode (7), a post-electrocatalytic anode (8), a post-connecting terminal (9), an outlet (10), a connecting rod (11), and a base (12). The inlet (1) is embedded in the cavity between the pre-electrocatalytic cathode (2) and the pre-electrocatalytic anode (3). The pre-electrocatalytic cathode (2) and the pre-electrocatalytic anode (3) are separated and connected by a silicone flange gasket, and there is a cavity between them. The cathode wire and anode wire leading out from the front terminal (4) are respectively connected to the front electrocatalytic cathode (2) and the front electrocatalytic anode (3) to provide a composite waveform pulse electric field; One end of the outer spiral microchannel (5) and the inner spiral microchannel (6) are connected to the outlet of the pre-electrocatalytic anode (3). The outer spiral microchannel (5) is wrapped around the inner spiral microchannel (6). The two extend axially in clockwise and counterclockwise directions, respectively. The other end of the outer spiral microchannel (5) and the inner spiral microchannel (6) are connected to the inlet of the post-electrocatalytic cathode (7). The post-electrocatalytic cathode (7) and the post-electrocatalytic anode (8) are separated and connected by a silicone flange gasket. There is a cavity reaction zone between the two. The cathode wire and the anode wire led out through the post-terminal (9) are connected to the post-electrocatalytic cathode (7) and the post-electrocatalytic anode (8), respectively, to provide a composite waveform pulse electric field. The post-electrocatalytic anode (8) is connected to the outlet (10); the pre-electrocatalytic anode (3) and the post-electrocatalytic cathode (7) are fixed by a connecting rod (11) and supported by a base (12); Step 2: Control the temperature to 20~30℃ and the pH value to 6~8. Introduce the high oil content emulsified wastewater into the cavity between the pre-electrocatalytic cathode (2) and the pre-electrocatalytic anode (3) through the inlet (1) at a flow rate of 0.5~2L / min. Apply a composite waveform pulse electric field to perform electrochemical oil separation pretreatment to achieve preliminary oil-water separation. Step 3: The charged, high-oil-content emulsified wastewater that has undergone preliminary oil-water separation penetrates the cavity between the pre-electrocatalytic cathode (2) and the pre-electrocatalytic anode (3) and enters the outer spiral microchannel (5) and the inner spiral microchannel (6) in parallel. Under the throttling effect, it flows in reverse at high speed and further achieves oil-water separation under the action of supergravity. Under the violent impact in the cavity reaction zone between the post-electrocatalytic cathode (7) and the post-electrocatalytic anode (8), a composite waveform pulse electric field is applied again for electrochemical deep treatment. Step 4: Introduce the high-oil-content emulsified wastewater treated in Step 3 into the dissolved air flotation (DAF) tank, and introduce air into the DAF tank at a flow rate of 0.1~0.5 m³ / h. 3 / h, the flotation time is 10~20min, so that the oil droplets float to the water surface; Step 5: Introduce the high oil content emulsified wastewater after air flotation into an activated carbon adsorption column loaded with nano-iron. The height of the activated carbon adsorption column is 50~100cm, the inner diameter is 10~20cm, the flow rate of the high oil content emulsified wastewater is 0.1~0.5L / min, and the adsorption time is 20~40min. Step 6: Conduct water quality testing on the treated high-oil-content emulsified wastewater. The testing items include oil content, chemical oxygen demand, and suspended solids content. If the water quality meets the discharge standards, the wastewater will be discharged or reused. If the water quality does not meet the discharge standards, it will be returned to the inlet (1) and treated again until the water quality meets the discharge standards.

2. The method for rapid demulsification and oil removal of high-oil-content emulsified wastewater based on pulsed electric field and spiral microchannel coupling according to claim 1, characterized in that, In step 1, The inner diameter of the inner spiral microchannel (6) is 1~3mm, the inner diameter of the outer spiral microchannel (7) is 3~5mm, and the spiral spacing is 2~4mm.

3. The method for rapid demulsification and oil removal of high-oil-content emulsified wastewater based on pulsed electric field and spiral microchannel coupling according to claim 1, characterized in that, In step 1, The pre-catalytic cathode (2), pre-catalytic anode (3), post-catalytic cathode (7), and post-catalytic anode (8) are all made of stainless steel. The distance between the pre-catalytic cathode (2) and the pre-catalytic anode (3) and between the post-catalytic cathode (7) and the post-catalytic anode (8) is 5~10mm.

4. The method for rapid demulsification and oil removal of high-oil-content emulsified wastewater based on pulsed electric field and spiral microchannel coupling according to claim 1, characterized in that, In step 2, The composite waveform is composed of square wave, triangular wave and sine wave superimposed, with a duty cycle of 3:2:1, a pulse frequency of 100~500Hz, an electric field strength of 500~1500V / m, and an action time of 5~15min.

5. The method for rapid demulsification and oil removal of high-oil-content emulsified wastewater based on pulsed electric field and spiral microchannel coupling according to claim 1, characterized in that, In step 3, The composite waveform is composed of square wave, triangular wave and sine wave superimposed, with a duty cycle of 5:2:1, a pulse frequency of 100~500Hz, an electric field strength of 500~1500V / m, and an action time of 5~15min.

6. The method for rapid demulsification and oil removal of high-oil-content emulsified wastewater based on pulsed electric field and spiral microchannel coupling according to claim 1, characterized in that, The double-helix nested microchannel electrode system, flotation tank, and activated carbon adsorption column loaded with nano-iron should be cleaned and maintained regularly. The cleaning cycle is 10 to 30 days and the cleaning time is 1 to 3 hours.

7. The method for rapid demulsification and oil removal of high-oil-content emulsified wastewater based on pulsed electric field and spiral microchannel coupling according to claim 1, characterized in that, In step 1, the inner diameter of the inner spiral microchannel (6) is 2 mm, the inner diameter of the outer spiral microchannel (7) is 4 mm, and the spiral spacing is 3 mm.

8. The method for rapid demulsification and oil removal of high-oil-content emulsified wastewater based on pulsed electric field and spiral microchannel coupling according to claim 1, characterized in that, In steps 2 and 3, the pulse frequency of the composite waveform pulsed electric field is 300Hz, the electric field strength is 1000V / m, and the action time is 10min.

9. The method for rapid demulsification and oil removal of high-oil-content emulsified wastewater based on pulsed electric field and spiral microchannel coupling according to claim 1, characterized in that, In step 5, the height of the activated carbon adsorption column loaded with nano-iron is 80cm, the inner diameter is 15cm, and the wastewater flow rate is 0.3L / min.

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