Boron-doped diamond electrode electrooxidation system and method for treating fracturing flow-back fluid
By integrating pretreatment and exhaust gas absorption into the system design, the problems of high chloride ions, strong reducing sulfides, and foam in fracturing flowback fluid were solved, achieving efficient and stable fracturing flowback fluid treatment and reducing operating costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-04
- Publication Date
- 2026-04-07
AI Technical Summary
Existing boron-doped diamond electrode electro-oxidation equipment faces problems such as high chloride ion content leading to hypochlorite formation, strong reducing sulfides clogging the electrode, and foam interference when processing fracturing flowback fluid, resulting in low processing efficiency, high cost, and poor system stability.
The system adopts an integrated pretreatment, exhaust gas absorption and circulation design. Sulfides and foam are removed by aeration devices, and hypochlorous acid is recycled using chlorine recovery pipelines. The integrated aeration device and electro-oxidation unit form a closed system and optimize the treatment process.
It effectively removes sulfides and foam, protects electrodes, reduces operating costs, improves oxidation efficiency and system stability, and enables resource recycling.
Smart Images
Figure CN121800370A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of oil and gas fracturing flowback fluid treatment technology, and in particular to a boron-doped diamond electrode electro-oxidation system and method for treating fracturing flowback fluid. Background Technology
[0002] The process of hydraulic fracturing in oil reservoirs involves using a high-pressure, high-volume pump on the surface to inject fracturing fluid (a heterogeneous and unstable chemical system composed of various additives in a specific ratio) with a certain viscosity into the oil reservoir, thereby increasing the pressure inside the wellbore and causing fractures to form in the formation near the bottom of the well. Further injection of proppant-carrying fluid (such as quartz sand and ceramsite) extends the fractures forward and fills them with proppant. After the well is shut in, the fractures close on the proppant, thus forming a sand-filled fracture with a certain geometric size and high conductivity in the formation near the bottom of the well. This improves the flow capacity of formation fluids, thereby enabling the economical and efficient development of oil and gas resources.
[0003] Fracturing flowback fluid is a mixture of fluids that are squeezed back to the surface along with water, salt, metal, oil, organic matter, and soil particles from the formation after hydraulic fracturing operations in oil and gas resources.
[0004] The composition of fracturing flowback fluid is complex and difficult to treat. Using boron-doped diamond (BDD) electrode electro-oxidation equipment to treat raw water presents the following challenges.
[0005] (1) High chloride ion content: The chloride ion concentration in the backflow solution is often as high as 10,000 mg / L or more. When using boron-doped diamond (BDD) electrodes for electrocatalytic oxidation of organic matter, a large amount of hypochlorous acid and its salts (such as NaClO / HClO) will be generated. If these hypochlorous acids and their salts cannot be effectively utilized or removed, it will cause waste of reagents and secondary pollution.
[0006] (2) Interference from strong reducing sulfides: Sulfides (such as H2S, HS) produced by sulfate-reducing bacteria (SRB) in the reflux solution. - Sulfides have strong reducing properties. During electrocatalytic oxidation, sulfides are preferentially oxidized over the target organic matter. The oxidation product of sulfides, elemental sulfur, is a poorly soluble solid that easily adheres to the electrode surface, clogging the electrode pores and severely reducing current efficiency and oxidation capacity. This necessitates increased cleaning frequency and maintenance costs.
[0007] (3) Foam problem: The foaming agent (surfactant) in the backflow liquid is prone to generating a large amount of foam during the circulation process, which affects the normal operation and observation of the equipment.
[0008] Current BDD electro-oxidation equipment typically treats raw water (fracturing flowback fluid) directly, without addressing the aforementioned challenges in a coordinated manner, resulting in low treatment efficiency, high operating costs, and poor system stability. Summary of the Invention
[0009] This application aims to overcome the shortcomings of current boron-doped diamond (BDD) electrode electro-oxidation equipment for directly treating raw water, and to provide a fracturing flowback fluid treatment system and method that integrates pretreatment, efficient oxidation and resource recycling.
[0010] In the first aspect, this application proposes a boron-doped diamond electrode electro-oxidation system for processing fracturing flowback fluid, and adopts the following technical solution.
[0011] A boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid includes a circulation treatment unit, a multifunctional aeration pretreatment unit, and a tail gas absorption and circulation unit. The circulation treatment unit includes a circulation tank, a circulation pump, a filter, and an electrolytic cell. The electrolytic cell uses a boron-doped diamond (BDD) electrode as the positive electrode. The multifunctional aeration pretreatment unit includes an aeration device. The tail gas absorption and circulation unit includes a tail gas absorption device and a chlorine recovery pipeline.
[0012] The pipeline for conveying fracturing flowback fluid is connected to the circulation tank.
[0013] The circulation tank is connected to the electrolytic cell via an inlet pipe. The circulation pump and the filter are installed on the inlet pipe, with the filter positioned closer to the electrolytic cell than the circulation pump. The electrolytic cell is connected to the circulation tank via a return pipe.
[0014] The aeration device is installed inside the circulation tank.
[0015] The circulation tank is connected to the exhaust gas absorption device via an exhaust pipe.
[0016] The two ends of the chlorine recycling pipeline are connected to the circulation tank and the electrolytic cell, respectively.
[0017] By adopting the above technical solution, this application organically integrates three major units—multifunctional aeration pretreatment, tail gas absorption, and circulation—into a closed system. This achieves synergistic and sequential batch treatment of multiple contaminants (sulfides, organic matter, foam, and chloride ions) in fracturing flowback fluid, solving the problems of complex connections, large footprint, and low efficiency in traditional step-by-step treatment processes. This application uses boron-doped diamond electrodes as the positive electrode. Their extremely high oxygen evolution overpotential and strong oxidizing ability can efficiently generate hydroxyl radicals, deeply degrading recalcitrant organic matter. Through a "pretreatment-electrooxidation" process, the system preferentially removes sulfides before oxidation, effectively preventing competitive oxidation, poisoning, and sulfur scale blockage of the BDD electrode by sulfides, significantly extending the service life of the expensive BDD electrode and improving current efficiency. This application integrates the aeration device into the circulation tank, which can generate and enrich foam through aeration during the pretreatment stage, thereby removing foaming agents from the source. This effectively solves the problem of foam overload interfering with equipment operation and observation during fracturing flowback fluid treatment, ensuring continuous and stable system operation. This application designs a chlorine recycling pipeline that regenerates chlorine (a byproduct of electro-oxidation, hypochlorous acid) in a circulating tank through acidification, and then reintroduces it to the front end of the electrolytic cell for reuse. This achieves a closed-loop circulation of the oxidant (active chlorine) within the system, significantly reducing the cost of adding external oxidants and improving overall oxidation capacity, thus realizing waste-to-waste treatment. The entire system uses the circulating tank as the core of the reaction and buffer process. Through the connection of pipes and valves, a clear material circulation path is constructed, allowing processes such as pH adjustment, pollutant removal, and oxidant regeneration to be carried out stepwise and controllably within the same container, resulting in high operational flexibility and system reliability.
[0018] In a preferred embodiment of the boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid, the aeration device is connected to a high-pressure air source.
[0019] By adopting the above technical solution, high-pressure air is introduced into the aeration device from a high-pressure air source, generating a high air flow rate and bubble velocity, which can produce a large gas-liquid contact area and strong turbulence. This greatly accelerates the mass transfer rate of foaming agent bubbling towards the liquid surface, dissolved hydrogen sulfide, and chlorine from the liquid phase to the gas phase, making the removal of foaming agent, sulfides, and chlorine faster and more thorough.
[0020] A preferred embodiment of the boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid is that the tail gas absorption device is loaded with alkaline solution.
[0021] By adopting the above technical solution, the alkaline solution can efficiently and thoroughly absorb acidic hydrogen sulfide and chlorine gas, converting them into harmless or low-harm salts, ensuring that the system's exhaust gas meets environmental protection requirements and basically eliminating the risk of toxic gas leakage.
[0022] In a preferred embodiment of the boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid, valves are installed on both the exhaust pipe and the chlorine recycling pipeline.
[0023] By adopting the above technical solution, the flow direction of exhaust gas / chlorine can be flexibly and reliably switched via valves. During the pretreatment desulfurization stage, the chlorine reuse pipeline is closed and the exhaust pipe is opened to ensure hydrogen sulfide enters the absorption unit; the reverse is true during the chlorine reuse stage. This achieves precise isolation and optimized operation of the system's functions at different treatment stages.
[0024] Secondly, this application also proposes a method for treating fracturing flowback fluid, and adopts the following technical solution.
[0025] A method for treating fracturing flowback fluid, performed using the aforementioned boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid, the method comprising: S1, fracturing flowback fluid containing chloride ions, sulfides, foaming agents and organic matter is fed into the circulation tank.
[0026] S2, shut off the chlorine recycling pipeline, open the exhaust pipe, shut off the circulation pump, turn on the aeration device, adjust the pH of the fracturing flowback fluid in the circulation tank to acidic, so that the sulfides are converted into hydrogen sulfide. The aeration device blows the hydrogen sulfide out of the fracturing flowback fluid and blows foam on the liquid surface at the same time. The hydrogen sulfide is blown into the tail gas absorption device and absorbed, removing the foam enriched with the foaming agent on the liquid surface.
[0027] S3, after removing foam and sulfides, close the exhaust pipe, open the chlorine recycling pipeline, start the circulation pump and the electrolytic cell, and inject the remaining fracturing flowback fluid in the circulation tank into the electrolytic cell. Chloride ions are oxidized to hypochlorous acid, and the boron-doped diamond (BDD) electrode oxidizes and degrades organic matter, while hypochlorous acid also participates in the oxidation of organic matter. The reacted fracturing flowback fluid is returned to the circulation tank through the return water pipe, maintaining the fracturing flowback fluid in the circulation tank in an acidic state. Unreacted hypochlorous acid reacts with chloride ions in the circulation tank to generate chlorine gas. The chlorine gas is blown into the chlorine recycling pipeline under aeration and then into the electrolytic cell to generate hypochlorous acid, which again participates in the oxidation of organic matter. This cycle continues until the organic matter and sulfides in the fracturing flowback fluid are effectively removed.
[0028] S4, close the chlorine recycling pipeline and open the exhaust pipe. Chlorine is blown into the tail gas absorption device and absorbed under the action of aeration.
[0029] By adopting the above technical solution, this method follows the logic of "first desulfurization and defoaming, then electro-oxidation, and simultaneously circulating chlorine." First, under acidic conditions, physical stripping removes most of the sulfides and foaming agents, clearing the way for electro-oxidation. Then, during electro-oxidation, organic matter is degraded and hypochlorous acid is produced. Finally, the hypochlorous acid is acidified, regenerated, and reused in the circulation tank. By operating different pipelines by "closing / opening," the aeration device and circulation tank play different roles at different stages. The recycling of chlorine significantly reduces the energy and chemical consumption required to treat a unit volume of water.
[0030] A preferred embodiment of the method for treating fracturing flowback fluid is as follows: step S2 adjusts the pH of the fracturing flowback fluid in the circulation tank to 3-5, and step S3 maintains the pH of the fracturing flowback fluid in the circulation tank at 3-5.
[0031] By employing the above technical solution, sulfides exist almost entirely in the form of hydrogen sulfide at this pH, resulting in the highest stripping efficiency. At this pH, hypochlorous acid is the dominant form, which is conducive to its reaction with chloride ions to generate chlorine gas.
[0032] A preferred embodiment of the method for treating fracturing flowback fluid is that, after step S4, the batch of fracturing flowback fluid is discharged, and then a new batch of fracturing flowback fluid containing chloride ions, sulfides, foaming agents and organic matter is introduced into the circulation tank.
[0033] By adopting the above technical solution, this method facilitates independent and thorough treatment and quality control of each batch of fracturing flowback fluid, ensuring that the system has sufficient time to circulate and treat until the water quality meets the standards, and avoiding the problem of insufficient treatment that may occur in continuous flow mode.
[0034] A preferred embodiment of the method for treating fracturing flowback fluid is that the tail gas absorption device is filled with a sodium hydroxide solution.
[0035] By adopting the above technical solution, the sodium hydroxide solution has high efficiency and fast reaction rate in absorbing hydrogen sulfide and chlorine.
[0036] In summary, the boron-doped diamond electrode electro-oxidation system and method for treating fracturing flowback fluid of this application have the following beneficial effects: Before the fracturing flowback fluid enters the electro-oxidation unit, sulfides are efficiently removed, eliminating their toxicity to the electrode and competitive oxidation, protecting the BDD electrode, and simultaneously resolving the foaming problem of the flowback fluid, ensuring stable system operation; after the electro-oxidation unit, active chlorine (hypochlorite / chlorine) is effectively removed and recycled, achieving "waste-to-waste treatment," improving oxidation efficiency and reducing reagent dosage. Through the above synergistic design, this application synergistically optimizes the interference and foaming problems caused by high chloride ion content and strong reducing sulfides, comprehensively improving the system's treatment efficiency, economy, and stability. Attached Figure Description
[0037] Figure 1 A schematic diagram of the connection structure of a boron-doped diamond electrode electro-oxidation system for processing fracturing flowback fluid. Detailed Implementation
[0038] The technical solutions in the embodiments are described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the following embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0039] refer to Figure 1 A boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid includes a circulation treatment unit, a multifunctional aeration pretreatment unit, and a tail gas absorption and circulation unit.
[0040] The recycling unit includes a recycling tank, a recycling pump, a filter, and an electrolytic cell. The electrolytic cell uses boron-doped diamond (BDD) electrodes as the positive electrode, and the negative electrode material can be graphite, stainless steel, titanium, or boron-doped diamond (BDD).
[0041] The multi-functional aeration pretreatment unit includes an aeration device.
[0042] The exhaust gas absorption and recirculation unit includes an exhaust gas absorption device and a chlorine recovery pipeline.
[0043] The pipeline transporting the fracturing flowback fluid is connected to a circulation tank. The circulation tank is used to store and regulate the flowback fluid to be processed.
[0044] The circulation tank is connected to the electrolytic cell via an inlet pipe. The circulation pump and filter are installed on the inlet pipe, with the filter positioned closer to the electrolytic cell than the circulation pump. The circulation pump provides the power for liquid circulation. The filter, located after the circulation pump, removes suspended solids and any solid sulfur particles that may be generated in the water, preventing clogging of the BDD electrodes. The electrolytic cell is connected to the circulation tank via a return pipe.
[0045] The aeration device is installed inside the circulation tank and connected to a high-pressure air source. It is used to introduce air into the flowback liquid within the circulation tank. The aeration device plays three key roles at different treatment stages. Role 1 (before electro-oxidation, acidic conditions): Adjusts the pH of the wastewater (fracturing flowback liquid) to acidic conditions, stripping sulfides into hydrogen sulfide gas, which is then removed by the tail gas absorption device. Role 2 (before electro-oxidation): Aeration generates foam, enriching the foaming agent in the wastewater within the foam. After collection and foam breaking, the foam is removed, reducing foam at its source. Role 3 (after electro-oxidation, acidic conditions): After electrolysis produces hypochlorous acid, the pH is adjusted back to acidic, allowing the hypochlorous acid to react with chloride ions to generate chlorine gas, which is then rapidly stripped from the water body through aeration.
[0046] The circulating tank is connected to the exhaust gas absorption device via an exhaust pipe. The exhaust gas absorption device is filled with an alkaline solution, such as sodium hydroxide solution, to absorb hydrogen sulfide (H2S) generated in the pretreatment stage and chlorine gas (Cl2) generated in the posttreatment stage, generating Na2S / NaHS and NaClO respectively, thus achieving the harmless treatment of waste gas.
[0047] The chlorine recovery pipeline connects to a circulation tank and an electrolytic cell at both ends. Valves are installed on both the exhaust pipe and the chlorine recovery pipeline. The chlorine recovery pipeline returns the stripping gas containing chlorine to the electrolytic cell, where it dissolves in water to generate hypochlorous acid, which directly participates in the pre-oxidation of organic matter or residual sulfides in the influent. This design achieves a closed-loop circulation and efficient reuse of "active chlorine" (Cl2 / HClO) within the system, significantly reducing the need for external oxidant addition.
[0048] A method for treating fracturing flowback fluid, performed using the aforementioned boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid, includes the following steps.
[0049] S1, fracturing flowback fluid containing chloride ions, sulfides, foaming agents, and organic matter is fed into the circulation tank. It should be noted that, in this application, "organic matter" refers to organic matter from oil and gas other than foaming agents.
[0050] S2, close the valve on the chlorine reuse pipeline, open the valve on the exhaust pipe, close the circulation pump, and turn on the aeration device. This involves bubbling the circulating fluid into the circulation tank through the aeration device to adjust the pH of the fracturing flowback fluid in the circulation tank to acidic levels, for example, to 3-5. This allows most of the sulfides to be converted into hydrogen sulfide, and the reaction equilibrium is as follows: H2S⇌H + +HS - HS - ⇌H + +S 2- , Under pH conditions of 3-5, the above reaction equilibrium shifts to the left to produce hydrogen sulfide. H2S (dissolved hydrogen sulfide) is volatile and can escape from the water surface into the gas phase, while HS... - (Hydrosulfide ion) and S 2- (Sulfide ions) are non-volatile and cannot be directly blown off.
[0051] The aeration device blows hydrogen sulfide out of the fracturing flowback fluid and simultaneously blows foam onto the liquid surface. The hydrogen sulfide is blown into the tail gas absorption device and absorbed, removing the foam enriched with foaming agent from the liquid surface.
[0052] It should be noted that the step S2, "adjusting the pH of the fracturing flowback fluid in the circulation tank to acidic, for example, adjusting the pH to 3-5", can be performed in step S1, and this application does not impose specific restrictions.
[0053] S3, after removing foam and sulfides, close the valve on the exhaust pipe, open the valve on the chlorine return pipeline, start the circulation pump and electrolytic cell, and inject the remaining fracturing flowback fluid in the circulation tank into the electrolytic cell. Chloride ions are oxidized to hypochlorous acid, and the boron-doped diamond (BDD) electrode oxidizes and degrades organic matter. Simultaneously, hypochlorous acid participates in the oxidation of organic matter. The reacted fracturing flowback fluid is returned to the circulation tank through the return water pipe, maintaining the fracturing flowback fluid in the circulation tank at an acidic level, for example, adjusting the pH to 3-5. Unreacted hypochlorous acid reacts with chloride ions in the circulation tank to generate chlorine gas, as shown in the following reaction formula: HClO + H + +Cl - ⇌Cl2+H2O, Under pH conditions of 3-5, the above reaction equilibrium shifts to the right to produce chlorine gas.
[0054] Chlorine gas, under aeration, is blown into the chlorine recycling pipeline and then into the electrolytic cell to generate hypochlorous acid, which again participates in the oxidation of organic matter. Through circulation, organic matter is continuously fed into the electrolytic cell for degradation. The degradation process of organic matter is as follows: On the one hand, organic matter (R) diffuses to the surface of the BDD electrode (anode), directly loses electrons and is oxidized into a strong oxidizing intermediate R. + The reaction equation is R→R + +e - These highly oxidizing intermediates diffuse in solution and indiscriminately attack organic matter.
[0055] On the other hand, water molecules or hydroxide ions are directly oxidized on the BDD anode surface, generating hydroxyl radicals (·OH) physically adsorbed on the electrode surface. ·OH can attack almost all carbon-hydrogen bonds in organic matter, such as CH, C=C, and benzene rings, ultimately degrading the organic matter into CO2 and water. Other elements (such as N, S, and P) are oxidized into inorganic ions such as nitrate, sulfate, and phosphate. ·OH mainly works near the electrode surface, where active chlorine (HClO / ClO) is present. - It can diffuse into the entire solution phase, forming an oxidation network that combines strong surface oxidation with bulk oxidation.
[0056] The circulation process also precipitates sulfides: on the one hand, a small amount of hydrogen sulfide is not blown off into the tail gas absorption device but enters the electrolytic cell and is oxidized to generate elemental sulfur. Some of these elemental sulfurs are further oxidized to sulfate, while others are recycled back to the circulation tank and intercepted by the filter, which gradually reduces the sulfur content in the liquid entering the electrolytic cell; on the other hand, a small amount of hydrogen sulfide remains in the circulation tank and reacts with the returned hypochlorite to generate elemental sulfur. These elemental sulfurs are intercepted when passing through the filter, thus preventing blockage of the electrode holes.
[0057] The fracturing flowback fluid continues to circulate between the circulation tank and the electrolytic cell until the organic matter and sulfides in the fracturing flowback fluid are effectively removed.
[0058] S4, close the valve on the chlorine reuse pipeline, open the valve on the exhaust pipe, and the chlorine is blown into the tail gas absorption device and absorbed under the action of aeration.
[0059] After step S4, the fracturing flowback fluid of this batch is discharged, and then a new batch of fracturing flowback fluid containing chloride ions, sulfides, foaming agents and organic matter is introduced into the circulation tank, and the circulation of S2~S4 above is restarted.
[0060] It should be noted that during the circulation process, if a large electrolytic cell is used to directly electrolyze the fracturing flowback fluid without the circulation system described in this application, then during the electrolysis process, on the one hand, suspended solids in the water are prone to adhere to the electrodes, reducing the current efficiency; on the other hand, even if pretreatment aeration is used and most of the hydrogen sulfide has been blown out, some hydrogen sulfide remains in the flowback fluid. Direct electrolytic oxidation can easily lead to the continuous generation of elemental sulfur, and the concentration of elemental sulfur in the liquid will become increasingly high, which can easily cover the electrodes and block the electrode pores, reducing the current efficiency.
[0061] The boron-doped diamond electrode electro-oxidation system and method for treating fracturing flowback fluid disclosed in this application have the following advantages: Highly efficient desulfurization and electrode protection: Sulfides are removed physically before electro-oxidation, which completely avoids the problems of competitive oxidation, poisoning and sulfur scale blockage of BDD electrodes by sulfides, and significantly improves current efficiency and service life.
[0062] Defoaming at the source ensures stable operation: By removing foaming agents through aeration and enrichment, the foam interference problem in the backflow liquid treatment process is solved at its source, ensuring continuous and stable operation of the system.
[0063] Resource recycling, cost reduction and efficiency improvement: The unique "chlorine stripping-reuse" mechanism converts the electro-oxidation byproduct hypochlorous acid into chlorine and recycles it, realizing the internal circulation of active chlorine, which greatly reduces operating costs and improves the overall oxidation capacity.
[0064] Synergistic integration, multi-functionality: Through an integrated aeration device and process control, three functions are realized in stages: air stripping desulfurization, air flotation defoaming and chlorine stripping. The system has a high degree of integration, flexible operation and good treatment effect.
[0065] Although this application 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 this application should be included within the protection scope of this application.
Claims
1. A boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid, characterized in that, It includes a circulation treatment unit, a multi-functional aeration pretreatment unit, and a tail gas absorption and circulation unit; the circulation treatment unit includes a circulation tank, a circulation pump, a filter, and an electrolytic cell; the electrolytic cell uses a boron-doped diamond (BDD) electrode as the positive electrode; the multi-functional aeration pretreatment unit includes an aeration device; the tail gas absorption and circulation unit includes a tail gas absorption device and a chlorine recycling pipeline. The pipeline for conveying fracturing flowback fluid is connected to the circulation tank; The circulation tank is connected to the electrolytic cell via an inlet pipe. The circulation pump and the filter are installed on the inlet pipe, with the filter being closer to the electrolytic cell than the circulation pump. The electrolytic cell is connected to the circulation tank via a return pipe. The aeration device is installed in the circulation tank; The circulating tank is connected to the exhaust gas absorption device via an exhaust pipe; The two ends of the chlorine recycling pipeline are connected to the circulation tank and the electrolytic cell, respectively.
2. The boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid according to claim 1, characterized in that, The aeration device is connected to a high-pressure air source.
3. The boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid according to claim 1, characterized in that, The exhaust gas absorption device is filled with alkaline solution.
4. The boron-doped diamond electrode electro-oxidation system for treating fracturing flowback fluid according to claim 1, characterized in that, Valves are installed on both the exhaust pipe and the chlorine recycling pipeline.
5. A method for treating fracturing flowback fluid, characterized in that, The method of treating fracturing flowback fluid is performed using the boron-doped diamond electrode electro-oxidation system according to any one of claims 1-4, wherein the method comprises: S1, fracturing flowback fluid containing chloride ions, sulfides, foaming agents and organic matter is fed into the circulation tank; S2, close the chlorine recycling pipeline, open the exhaust pipe, close the circulation pump, turn on the aeration device, adjust the pH of the fracturing flowback fluid in the circulation tank to acidic, so that the sulfide is converted into hydrogen sulfide. The aeration device blows the hydrogen sulfide out of the fracturing flowback fluid and blows foam on the liquid surface at the same time. The hydrogen sulfide is blown into the tail gas absorption device and absorbed, removing the foam enriched with the foaming agent on the liquid surface. S3, after removing foam and sulfides, close the exhaust pipe, open the chlorine recycling pipeline, start the circulation pump and the electrolytic cell, and inject the remaining fracturing flowback fluid in the circulation tank into the electrolytic cell. Chloride ions are oxidized to hypochlorous acid, and the boron-doped diamond (BDD) electrode oxidizes and degrades organic matter. At the same time, hypochlorous acid participates in the oxidation of organic matter. The reacted fracturing flowback fluid is returned to the circulation tank through the return water pipe, maintaining the fracturing flowback fluid in the circulation tank as acidic. Unreacted hypochlorous acid reacts with chloride ions in the circulation tank to generate chlorine gas. The chlorine gas is blown into the chlorine recycling pipeline under aeration and then into the electrolytic cell to generate hypochlorous acid, which participates in the oxidation of organic matter again. This cycle continues until the organic matter and sulfides in the fracturing flowback fluid are effectively removed. S4, close the chlorine recycling pipeline and open the exhaust pipe. Chlorine is blown into the tail gas absorption device and absorbed under the action of aeration.
6. The method for treating fracturing flowback fluid according to claim 5, characterized in that, Step S2 adjusts the pH of the fracturing flowback fluid in the circulation tank to 3-5, and step S3 maintains the pH of the fracturing flowback fluid in the circulation tank at 3-5.
7. The method for treating fracturing flowback fluid according to claim 5, characterized in that, After step S4, the batch of fracturing flowback fluid is discharged, and then a new batch of fracturing flowback fluid containing chloride ions, sulfides, foaming agents and organic matter is introduced into the circulation tank.
8. The method for treating fracturing flowback fluid according to claim 5, characterized in that, The exhaust gas absorption device is filled with sodium hydroxide solution.