Fracturing flowback fluid discharge treatment process and device

Abstract

The application relates to the technical field of fracturing flowback fluid treatment, and discloses a fracturing flowback fluid discharge treatment process and device, a fracturing flowback fluid discharge treatment process which comprises a pretreatment unit, a membrane concentration and reduction unit and a deep treatment unit, the pretreatment unit comprises an oxidation and gel breaking reaction zone, a gas floatation treatment zone and a magnetic coagulation reaction system, and comprises the following steps: S1, fracturing flowback fluid first enters an adjusting pool and then enters the oxidation and gel breaking reaction zone; S2, the fracturing flowback fluid enters the gas floatation treatment zone; S3, the wastewater first enters the hardening removal reaction tank, enters the coagulation and precipitation zone to carry out reaction and precipitation, and the sludge generated in the process is introduced into the magnetic powder recovery subunit; S4, the water discharged from the pretreatment system enters the membrane concentration and reduction unit; S5, the membrane concentrated liquid enters a BDD electric oxidation system, organic matters in the water are oxidized through a BDD electrode, the water discharged from the BDD electric oxidation system enters an MVR evaporation system to be evaporated, and the mother liquor in the MVR evaporation system enters a mother liquor drying system. The application can improve the treatment efficiency of fracturing flowback fluid as a whole.

Description

Technical Field

[0001] The present application relates to the technical field of fracturing flowback fluid treatment, and in particular to a fracturing flowback fluid discharge treatment process and device. Background Art

[0002] Hydraulic fracturing technology is widely used in the development of unconventional oil and gas resources such as shale gas, tight oil, and coalbed methane. Hydraulic fracturing involves injecting a fracturing fluid containing various chemical additives and proppants (such as quartz sand and ceramsite) into the formation through high-pressure equipment. This creates fractures in the formation, increases the permeability of the oil and gas reservoir, and thus increases oil and gas production. After fracturing, a large amount of fracturing fluid, mixed with formation water, crude oil, and solid particles, is returned to the surface, forming fracturing flowback.

[0003] Fracturing flowback fluid has complex water quality characteristics, fluctuates greatly, and is difficult to treat. On the one hand, it has physical properties such as high salinity (TDS can reach 50,000-200,000 mg / L), high hardness (high Ca²⁺ and Mg²⁺ content), and high suspended solids (including fracturing proppant residue and formation particles). On the other hand, the flowback fluid contains a large amount of organic pollutants, such as guar gum and its derivatives (hydroxypropyl guar gum HPG), cross-linking agents (borates, zirconates), fungicides, surfactants, etc., which makes the flowback fluid have high viscosity and high COD. The COD value is usually as high as 2,000-10,000 mg / L, and some organic matter is biotoxic or difficult to degrade.

[0004] Fracturing flowback fluids contain high levels of organic matter, and advanced oxidation technologies are currently used. However, these technologies are ineffective in oxidizing organic matter in fracturing flowback fluids with high chloride ion content. This is especially true after membrane concentration, where the organic matter content increases significantly. During the evaporation process, these organic matter can lead to poor operational stability of the evaporation system, reduce the settling rate of the crystals, and result in finer crystal size, poor settling properties, and difficulty in separation. These factors can also reduce the whiteness of the crystallized salt, affecting its quality, and increase mother liquor discharge, impacting recovery rates. Summary of the Invention

[0005] In order to further improve the efficiency of fracturing flowback fluid treatment, the present application provides a fracturing flowback fluid discharge treatment process and device.

[0006] In a first aspect, the present application provides a fracturing flowback fluid discharge treatment process, which adopts the following technical solutions:

[0007] A fracturing flowback fluid discharge treatment process includes a pretreatment unit, a membrane concentration and reduction unit, and an advanced treatment unit. The pretreatment unit includes an oxidation and gel breaking reaction zone, an air flotation treatment zone, and a magnetic coagulation reaction system. A regulating tank is provided before the oxidation and gel breaking reaction zone. The process includes the following steps:

[0008] S1. The fracturing flowback fluid first enters the regulating tank and then is transported to the oxidation and gel breaking reaction zone. A gel breaker is added to the oxidation and gel breaking reaction zone to oxidize and break the high molecular weight organic matter and colloid in the fracturing flowback fluid.

[0009] S2, then entering the flotation treatment area, adding coagulant and flocculant reagents into the flotation treatment area respectively, so that the petroleum and suspended matter in the return liquid float to the water surface to form scum, and the scum is scraped off by the scraping mechanism;

[0010] S3, the magnetic coagulation reaction system includes a hardness removal reaction tank, a coagulation sedimentation area and a magnetic powder recovery subunit. The wastewater first enters the hardness removal reaction tank, and sodium carbonate and sodium hydroxide are added and fully mixed. After the water is discharged, it enters the coagulation sedimentation area for reaction and precipitation. The sludge then enters the magnetic powder recovery subunit;

[0011] S4, membrane concentration and reduction unit includes a two-stage DTRO system, and the effluent from the pretreatment system enters the two-stage DTRO system;

[0012] S5, the deep treatment unit includes BDD electro-oxidation system, MVR evaporation system, and mother liquor drying system. The membrane concentrate enters the BDD electro-oxidation system, and the organic matter in the water is oxidized by the BDD electrodes. The BDD effluent enters the MVR evaporation system for evaporation, and the MVR evaporated mother liquor enters the mother liquor drying system for drying.

[0013] By adopting the above technical solution, before coagulation and sedimentation, the viscosity of water is first reduced by adding a gel breaker, so that the residual gel in the water that has not been fully broken is quickly broken, and the wrapping of suspended matter and colloids by sticky substances such as high molecular polymers and guar gum in the water is reduced, thereby improving the effect of subsequent coagulation and sedimentation reactions, ensuring that the concentration of suspended matter in the effluent is significantly reduced, and significantly reducing the clogging of the membrane treatment system by sticky substances; by adding magnetic powder heavy medium to conventional coagulation and sedimentation, the magnetic powder can combine with the flocs, thereby increasing the specific gravity of the flocs, greatly increasing the settling rate of the flocs, and improving the treatment efficiency; the added magnetic powder heavy medium has a large specific surface area, and can increase the coagulation and sedimentation effect through physical-chemical synergy, reduce the amount of coagulants and flocculants, save costs and reduce secondary pollution; the magnetic powder is mainly composed of Fe3O4, which is arranged in a disordered manner. The magnetic powder itself is not magnetic, but it can conduct magnetism and can be recovered by the magnetic powder recovery subunit with a recovery rate greater than 99%. In addition, the other chemical properties of magnetic powder are stable and will not dissolve in water or undergo other reactions. BDD electro-oxidation uses BDD electrodes with high oxidation performance, which has a high removal efficiency for organic wastewater in high-salt wastewater, and is applied to membrane concentrate treatment with high treatment efficiency. The BDD electrocatalytic oxidation system can directly use high chloride ions as electrolytes to generate active chlorine (such as HClO) or strong oxidizing free radicals through electrochemical reactions, achieving "waste treatment with waste" and high efficiency in mineralization of difficult-to-degrade organic matter. During the evaporation process, the reduction of organic matter enables the MVR evaporation system to operate stably, increases the crystallization sedimentation rate, obtains high-quality white crystal salt, and reduces the discharge of mother liquor. Through the process design of "oxidation breaking, flotation slag removal, magnetic coagulation and hardness removal, membrane concentration, and electro-oxidation evaporation", pollutant cascade removal is achieved, and each step has the effect of improving efficiency, thereby greatly improving the overall treatment efficiency of fracturing return fluid and shortening the treatment time.

[0014] Optionally, in S3, the coagulation and sedimentation zone includes a coagulation tank, a magnetic mixing tank, a flocculation tank, and a clarification tank; coagulant PAC is added to the coagulation tank, and after sufficient mixing, it enters the magnetic mixing tank, magnetic powder is added to the magnetic mixing tank for mixing and flocculation, and then enters the flocculation tank, and flocculant PAM is added to the flocculation tank for reaction to generate floc particles, and finally enters the clarification tank for sedimentation.

[0015] By adopting the above technical solution, the step-by-step addition of magnetic powder can achieve controllable growth of flocs and significantly improve the sedimentation efficiency.

[0016] Optionally, in S3, the magnetic powder recovery subunit includes a high shear machine and a magnetic separator. Part of the sludge settled in the clarification tank is returned to the magnetic mixing tank through a magnetic sludge reflux pump to continue to participate in the reaction, and the other part is subjected to magnetic powder sludge stripping by the high shear machine and enters the magnetic separator for magnetic powder recovery. The recovered magnetic powder enters the magnetic mixing tank again to continue to participate in the reaction.

[0017] By adopting the above technical solution, part of the sludge is returned to the magnetic mixing tank (to maintain the magnetic powder concentration of the system), the amount of new magnetic powder added is reduced, costs are saved, the magnetic powder and sludge are stripped (high shear destroys flocs), and the magnetic separator recovers the magnetic powder. The magnetic powder recovery rate is high, and the organic matter content of the sludge is reduced after stripping (which is beneficial for subsequent disposal). The recovered magnetic powder is directly reused to reduce secondary pollution.

[0018] Optionally, in S5, the BDD electro-oxidation system includes an electrocatalytic oxidation device, and the organic matter in the water is oxidized by the electrocatalytic oxidation device.

[0019] By adopting the above technical solution, electrocatalytic oxidation directly acts on the water body to avoid chemical residues; BDD electrooxidation uses BDD electrodes with high oxidation performance, which have a high oxygen evolution potential and have a high removal efficiency for organic wastewater in high-salt wastewater. It has a long service life and is applied to membrane concentrate disposal with high disposal efficiency.

[0020] In a second aspect, the present application provides a fracturing flowback fluid discharge treatment device, which adopts the following technical solution:

[0021] A fracturing flowback fluid discharge treatment device, used in a BDD electro-oxidation system of the above-mentioned fracturing flowback fluid discharge treatment process, comprises:

[0022] a water reservoir for receiving membrane concentrate;

[0023] a cathode plate, installed in the water reservoir and energized;

[0024] Anode plates are installed in the water reservoir and are energized, and the cathode plates and anode plates are arranged alternately;

[0025] A stirring rod is rotatably installed in the water reservoir and close to the anode plate and the cathode plate. A collecting cavity is provided inside the stirring rod, and a collecting groove is provided on the rod wall of the stirring rod.

[0026] A transmission assembly, used for driving the stirring rod to rotate about its own central axis;

[0027] A material collection cylinder is provided, wherein the material collection cylinder is located in the material collection cavity, the rotation centerline of the material collection cylinder coincides with its own central axis, the rotation centerline of the material collection cylinder and the rotation centerline of the stirring rod are perpendicular to each other, the material collection cylinder is provided with a receiving cavity, and the outer peripheral side wall of the material collection cylinder is provided with a connecting groove, when the material collection cylinder is in a material collection state, the connecting groove is connected with the collecting groove, and when the material collection cylinder is in a material discharge state, the material collection cylinder blocks the collecting groove;

[0028] A driving member, used for driving the aggregate drum to rotate;

[0029] A sewage pipe has one end connected to the aggregate cavity and the other end extending out of the water reservoir. When the aggregate cylinder is in a pouring state, the sewage pipe discharges sewage.

[0030] By adopting the above technical solution, the BDD electro-oxidation system is suitable for treating high-chloride ion fracturing return fluid. Stirring rods are installed between the staggered motors, and the sediment in the water is stirred up, reducing the dead zone in the water reservoir, which causes the wastewater to stagnate. During stirring, negative pressure sucks in precipitates on the electrode surface, and the aggregate cylinder is in the aggregate state to adsorb pollutants. When the aggregate cylinder is in the discharge state, the sediment in the water reservoir is collected in the stirring rod and discharged into the sewage pipe, which can achieve a synergistic effect of collection and cleaning. The stirring and aggregation are operated synchronously, which can not only reduce dead zones but also collect sediment in the water.

[0031] Optionally, the transmission assembly includes a driving gear and a driven gear, and a power source for driving the driving gear to rotate, the power source is located outside the water reservoir, the power source is connected to a rotating shaft, the driving gear and the driven gear are located in the stirring rod, the rotating shaft extends into the stirring rod and is fixedly connected to the driving gear, the stirring rod and the rotating shaft are rotatably connected, a ring gear is installed in the stirring rod, the ring gear is engaged with the driven gear, a support column is fixedly installed at the bottom of the water reservoir, the support column passes through the stirring rod and is connected to a support seat, the driving member is installed on the support seat, the driving gear and the driven gear are rotatably installed on the support seat, the stirring rod and the support column are coaxial and rotatably connected.

[0032] By adopting the above technical solution, the stirring rod is driven to rotate through the transmission assembly.

[0033] Optionally, the driving member is a worm gear, and the worm gear and the driven gear are coaxially fixedly connected; the worm gear and the aggregate cylinder are fixedly connected by a connecting rod. When the rotating shaft rotates, the stirring rod and the driving gear rotate synchronously, and the worm gear drives the aggregate cylinder to rotate, so that the stirring rod rotates while the aggregate cylinder is in an aggregate state or a discharge state.

[0034] By adopting the above technical solution, the worm gear converts the stirring power into the rotation of the aggregate drum. The same power source can drive the stirring rod and the aggregate drum, simplifying the structure.

[0035] Optionally, the sewage pipe passes through the support column, one end of the sewage pipe located in the stirring rod extends out of the support column, and the other end of the sewage pipe extends out of the water reservoir.

[0036] By adopting the above technical solution, the sewage pipe is passed through the rotating shaft (space optimization), avoiding external pipelines interfering with the electrode layout.

[0037] Optionally, a water pumping pipe is passed through the support column, one end of the water pumping pipe extends into the stirring rod and is installed with a filter, and the other end of the water pumping pipe extends out of the water reservoir.

[0038] By adopting the above technical solution, the water extraction pipe + filter element directly extracts the clean water in the stirring tube, and the clean water can be poured back into the water reservoir for electrocatalytic oxidation, so that the sewage pipe mainly discharges the precipitated debris in the water.

[0039] Optionally, a stirring paddle is installed on the inner wall of the stirring rod, and the stirring paddle is close to the water suction pipe.

[0040] By adopting the above technical solution, the stirring paddle is used to stir the wastewater in the stirring rod, so that the sediment will not accumulate at the sewage pipe outlet or the water pump pipe outlet.

[0041] In summary, this application has at least one of the following beneficial effects:

[0042] 1. Through the process design of "oxidation breaking, air flotation removal, magnetic coagulation removal, membrane concentration, and electro-oxidation evaporation", the pollutant removal process is achieved in a cascaded manner, with each step improving efficiency. This greatly improves the overall treatment efficiency of fracturing flowback fluid and shortens the treatment time.

[0043] 2. The BDD electrocatalytic oxidation system directly converts chloride ions into oxidants, effectively degrading pollutants. When the electrocatalytic oxidation device treats organic matter, it can achieve a synergistic effect of collection and cleaning. The mixing and aggregation operate synchronously, which can not only reduce dead zones but also collect sediment in the water. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a process flow chart of Example 1 of the present application;

[0045] Figure 2 is a top view of the water reservoir of Example 2 of the present application;

[0046] Figure 3 Schematic diagram of the internal structure of the stirring rod of Example 2 of the present application;

[0047] Figure 4 This is a schematic diagram of Example 2 of the present application showing the aggregate cylinder in the aggregate state;

[0048] Figure 5 This is a schematic structural diagram of the cooperation between the worm gear and the driven gear in Example 2 of the present application;

[0049] Figure 6 This is a schematic diagram of Example 2 of the present application showing the aggregate cylinder in a dumping state;

[0050] Figure 7 yes Figure 4A magnified schematic diagram of .

[0051] Explanation of the accompanying reference numerals: 10, water reservoir; 20, cathode plate; 30, anode plate; 40, stirring rod; 41, stirring paddle; 42, aggregate chamber; 43, collecting tank; 44, ring gear; 50, transmission assembly; 51, driving gear; 52, driven gear; 53, rotating shaft; 60, supporting column; 61, supporting seat; 70, aggregate cylinder; 71, accommodating chamber; 72, connecting tank; 80, driving member; 81, worm gear; 82, worm; 91, drain pipe; 92, suction pipe; 93, filter element. DETAILED DESCRIPTION

[0052] The following is combined with Figure 1 -Attached Figure 7 This application is described in further detail.

[0053] In a first aspect, the embodiments of the present application disclose a fracturing flowback fluid discharge treatment process.

[0054] Reference Figure 1 A fracturing flowback fluid discharge treatment process includes a pretreatment unit, a membrane concentration and reduction unit and a deep treatment unit. The pretreatment unit includes an oxidation and gel breaking reaction zone, an air flotation treatment zone and a magnetic coagulation reaction system. A regulating tank is provided in front of the oxidation and gel breaking reaction zone.

[0055] The fracturing flowback fluid first enters the regulating tank to achieve uniform quality and quantity, and then is lifted by the lifting pump to the oxidation and gel breaking reaction zone. By adding a gel breaker (one of potassium persulfate, sodium persulfate, and sodium hypochlorite), the high molecular organic matter and colloids remaining in the water are quickly oxidized and broken, which reduces the viscosity of the wastewater and ensures the treatment effect of subsequent units.

[0056] The effluent from the oxidation and gel breaking enters the flotation treatment area. Two dosing ports are provided on the flotation treatment area to add coagulant and flocculant respectively. Highly dispersed tiny nanobubbles are used as carriers to adhere to the pollutants, making their buoyancy greater than gravity and floating resistance, so that the petroleum and suspended matter in the return fluid float to the water surface, forming scum. The scum is scraped off by the scraping mechanism to remove the oil and suspended matter.

[0057] The flotation water is lifted by a lift pump to the magnetic coagulation system, which consists of a hardness removal reaction tank, a coagulation and sedimentation zone, and a magnetic powder recovery subunit. The coagulation and sedimentation subunit includes a coagulation tank, a magnetic mixing tank, a flocculation tank, and a clarification tank. Wastewater first enters the hardness removal reaction tank, where sodium carbonate and sodium hydroxide are added for thorough mixing. The effluent then enters the coagulation tank. The coagulant PAC is added to the coagulation tank, where the two are thoroughly mixed. The water then enters the magnetic mixing tank, where it is mixed with magnetic powder recovered from the magnetic powder recovery subunit and returned sludge for flocculation. The magnetic powder binds to the flocs, increasing their specific gravity and significantly speeding up their settling rate, improving treatment efficiency. The wastewater then enters the flocculation tank, where it reacts with the flocculant PAM to form larger floc particles. Finally, the wastewater enters the clarification tank for rapid settling, and the effluent enters the membrane concentration treatment unit.

[0058] The magnetic powder recovery subunit includes a high-shear mill and a magnetic separator. Part of the sludge settled in the clarifier is returned to the magnetic mixing tank via a magnetic sludge return pump to continue the reaction. The remaining part is separated from the magnetic powder sludge by the high-shear mill and then enters the magnetic separator for magnetic powder recovery. The recovered magnetic powder enters the magnetic mixing tank again to continue the reaction, while the remaining sludge enters the subsequent sludge treatment system. The PAC and PAM solutions prepared in the dosing room are transported to the various dosing points by dosing pumps. PAC is added to the coagulation tank, and PAM is added to the flocculation tank.

[0059] The membrane concentration and reduction unit comprises a two-stage DTRO system. The effluent from the high-efficiency pretreatment system enters the two-stage DTRO system, where a high-pressure pump forces the wastewater through the membranes. The produced water enters the clear water tank for discharge or reuse when it meets standards, and the membrane concentrate enters the advanced treatment unit.

[0060] The advanced treatment unit includes a BDD electro-oxidation system, an MVR evaporation system, and a mother liquor drying system. The membrane concentrate enters the BDD electro-oxidation system, which includes an electrocatalytic oxidation device. The BDD electrodes' high-efficiency oxidation properties oxidize organic matter in the water, reducing its impact on evaporation efficiency and crystallized salt quality. The effluent then enters the MVR evaporation system. The primary purpose of BDD electro-oxidation is to reduce the impact of organic matter on subsequent evaporation processes. Traditional methods for removing organic matter include ozone catalytic oxidation, electrocatalytic oxidation, and Fenton oxidation. However, these methods have limitations such as low organic matter removal efficiency in high-salinity wastewater systems, high disposal costs, and short electrode lifespans. Furthermore, the process is applied before membrane concentration, resulting in large water volumes, low electrolysis efficiency, and high costs. BDD electro-oxidation utilizes highly oxidative BDD electrodes with a high oxygen evolution potential. This system has high removal efficiency for organic matter in high-salinity wastewater, a long service life, and high efficiency when applied to membrane concentrate disposal. BDD electro-oxidation is also more suitable for treating high-chloride ion fracturing flowback fluids. It can directly convert chloride ions into oxidants and efficiently degrade pollutants.

[0061] The BDD effluent enters the MVR evaporation system, where mechanical vapor recompression technology efficiently evaporates the membrane concentrate under low-temperature negative pressure. The evaporated salt product is then separated by a centrifuge and dried for industrial use. The evaporated mother liquor is returned to the evaporation system via a circulating pump for further evaporation. When the evaporated mother liquor is concentrated to a certain concentration, it enters the mother liquor drying system. The condensed water enters the clear water tank and is discharged to meet standards or reused.

[0062] The MVR evaporated mother liquor enters the mother liquor drying system, where it is dried under low temperature and negative pressure conditions. The condensed water enters the clear water tank and is discharged or reused when it meets the standards. The salt sludge is outsourced for treatment.

[0063] In a second aspect, an embodiment of the present application discloses a fracturing flowback fluid discharge treatment device.

[0064] A fracturing flowback fluid discharge treatment device is specifically an electrocatalytic oxidation device, which is applied to the BDD electro-oxidation system of the above-mentioned fracturing flowback fluid discharge treatment process. It can directly use high chloride ions as electrolytes to generate active chlorine (such as HClO) or strong oxidizing free radicals through electrochemical reactions, thereby achieving "waste treatment with waste".

[0065] Reference Figure 2 A fracturing flowback fluid discharge treatment device includes a water reservoir 10. The water reservoir 10 is a rectangular parallelepiped structure with a water inlet and a water outlet at both ends of the reservoir body. Multiple groups of cathode plates 20 (titanium-based coating electrodes) and anode plates 30 (BDD electrodes) are arranged in parallel and staggered in the reservoir. One end of the cathode plate 20 and the anode plate 30 are close to the same side wall of the water reservoir 10, and the other end is spaced apart from the other side wall of the water reservoir 10.

[0066] Reference Figure 2 The embodiment of the present application mainly installs a stirring rod 40 in a rotation manner in the water reservoir 10. Part of the stirring rod 40 is located in the gap between the anode plate 30 and the cathode plate 20, and part of the stirring rod 40 is located between the gap left by the plate and the water reservoir 10. When the wastewater in the water reservoir 10 moves under negative pressure, the stirring rod 40 rotates to stir the wastewater, so that the sediment is lifted up and the dead zone is reduced. The main body of the stirring rod 40 is a cylindrical structure, and a stirring paddle 41 is installed on the outer wall of the stirring rod 40. The other structures and principles of the embodiment of the present application remain unchanged. The drawings in the specification of the embodiment of the present application mainly highlight the structure of the stirring rod 40 and the position of the stirring rod 40, and other existing structures are not shown.

[0067] Reference Figure 3 A collecting cavity 42 is provided inside the stirring rod 40 , and a collecting groove 43 is provided on the outer wall of the stirring rod 40 for allowing sediment to enter the collecting cavity 42 .

[0068] Reference Figure 3 and Figure 4, also includes a transmission assembly 50 for driving the stirring rod 40 to rotate, the transmission assembly 50 includes a driving gear 51 and a driven gear 52, and a power source for driving the driving gear 51 to rotate, the power source is located outside the water reservoir 10, the power source is a motor, the power source is connected to a rotating shaft 53, the driving gear 51 and the driven gear 52 are located inside the stirring rod 40. A support column 60 is fixedly connected to the bottom of the water reservoir 10, and the support column 60 passes through the bottom of the stirring rod 40 and is connected to a support base 61, which is used to support the driving gear 51 and the driven gear 52. The driving gear 51 and the driven gear 52 are rotatably mounted on the support base 61, and the support base 61 has a hollow portion so that the collected oxides can fall into the bottom of the stirring rod 40. A gear ring 44 is connected to the inner wall of the stirring rod 40, and the gear ring 44 is meshed with the driven gear 52. When the motor is started, the rotating shaft 53 drives the stirring rod 40 to rotate around its own axis, and the support column 60 remains stationary. When the stirring rod 40 rotates, it rotates relatively around the support column 60, driving the wastewater to flow between the plates.

[0069] Reference Figure 4 and Figure 5 A collection cylinder 70 is provided for rotation inside the stirring rod 40, and a driving member 80 for driving the collection cylinder 70 to rotate is installed on the support seat 61. The collection cylinder 70 is placed horizontally in the collection cavity 42, and the center line of rotation of the collection cylinder 70 is perpendicular to the axis of the stirring rod 40. A accommodating cavity 71 is provided inside the collection cylinder 70, and a connecting groove 72 is provided on the outer periphery of the collection cylinder 70, and the connecting groove 72 occupies one-fifth of the outer periphery of the collection cylinder 70. The driving member 80 is a worm gear 81 and a worm 82. The worm 82 and the driven gear 52 are coaxially fixed and driven by the driving gear 51. The worm gear 81 is fixedly connected to the collection cylinder 70 through a connecting rod.

[0070] Reference Figure 4 When the shaft 53 rotates, the worm gear 81 drives the collecting cylinder 70 to rotate about its own central axis. When the collecting cylinder 70 is in the collecting state, the connecting groove 72 is aligned with the collecting groove 43, and the oxides peeled off from the surface of the electrode plate are sucked into the receiving chamber 71 by the negative pressure.

[0071] Reference Figure 5 When the aggregate cylinder 70 is in the pouring state, the collecting groove 43 is blocked by the outer peripheral side wall of the aggregate cylinder 70, the connecting groove 72 turns to the stirring rod 40, and the accommodating cavity 71 and the aggregate cavity 42 are completely connected.

[0072] Reference Figure 7 The support column 60 is provided with a drainage pipe 91 and a water pumping pipe 92, which are arranged side by side. One end of the drainage pipe 91 extends into the collection chamber 42, and the other end is connected to an external sludge tank. One end of the water pumping pipe 92 extends into the collection chamber 42 and is equipped with a filter element 93, such as a filter screen. The other end of the water pumping pipe 92 is connected to the wastewater recycling pipe. The sludge is discharged through the drainage pipe 91, and the wastewater returns to the water storage tank 10 for further reaction.

[0073] Reference Figure 4 When the water extraction pipe 92 draws clean water from the stirring rod 40, in order to prevent sediment from accumulating at the pipe mouth of the water extraction pipe 92, a stirring paddle 41 is installed on the inner wall of the stirring rod 40. The stirring paddle 41 is close to the end of the water extraction pipe 92. The stirring paddle 41 disturbs the water in the stirring rod 40, reducing the accumulation of oxides around the filter element 93, making it easier for the water extraction pipe 92 to draw.

[0074] It should be noted that the worm wheel 81, worm 82, and gears are made of corrosion-resistant alloys (such as 316L stainless steel) or engineering plastics (such as PEEK). The gears have a wide pitch, so sediment within the stirring rod 40 is unlikely to affect proper gear meshing. Sediment settles to the bottom of the stirring rod 40, and the drain pipe 91 regularly clears the sediment within the stirring rod 40.

[0075] The implementation principle of the fracturing flowback fluid discharge treatment device in the embodiment of the present application is as follows:

[0076] By integrating electrocatalytic oxidation and dynamic self-cleaning functions, the treatment efficiency of high-viscosity membrane concentrate is improved. A rotatable stirring rod 40 is set between the BDD anode plates 30 and cathode plates 20 arranged alternately in the water reservoir 10. The stirring rod 40 is provided with a collection chamber 42 with a collection trough 43 and a rotatable collection cylinder 70. When the transmission assembly 50 drives the stirring rod 40 to rotate, the stirring rod 40 breaks the stagnant zone of the fluid between the electrodes, accelerates the flow of high-viscosity wastewater, and strengthens the contact between organic matter and the electrodes. The gathering cylinder 70 periodically switches its state under the drive of the worm gear 81 and the worm 82. The connecting groove 72 of the gathering cylinder 70 is aligned with the collecting groove 43 of the stirring rod 40, and the oxides and suspended matter peeled off from the surface of the electrode are sucked into the containing chamber 71 by negative pressure; the gathering cylinder 70 rotates to close the collecting groove 43, first opens the pumping pipe 92 to extract some wastewater, and the oxides and suspended matter are left in the containing chamber 71, then closes the pumping pipe 92, and opens the sewage pipe 91, and the oxides and suspended matter are discharged from the stirring rod 40 along with the wastewater. Part of the wastewater that enters the stirring rod 40 is extracted by the pumping pipe 92 and then re-enters the water reservoir 10 for reaction.

[0077] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A fracturing flowback fluid discharge treatment process, characterized in that: The method comprises a pretreatment unit, a membrane concentration and reduction unit and a deep treatment unit. The pretreatment unit comprises an oxidation and gel breaking reaction zone, an air flotation treatment zone and a magnetic coagulation reaction system. A regulating tank is provided before the oxidation and gel breaking reaction zone. The method comprises the following steps: S1. The fracturing flowback fluid first enters the regulating tank and then is transported to the oxidation and gel breaking reaction zone. A gel breaker is added to the oxidation and gel breaking reaction zone to oxidize and break the high molecular weight organic matter and colloid in the fracturing flowback fluid. S2, then entering the flotation treatment area, adding coagulant and flocculant reagents into the flotation treatment area respectively, so that the petroleum and suspended matter in the return liquid float to the water surface to form scum, and the scum is scraped off by the scraping mechanism; S3, the magnetic coagulation reaction system includes a hardness removal reaction tank, a coagulation sedimentation area and a magnetic powder recovery subunit. The wastewater first enters the hardness removal reaction tank, and sodium carbonate and sodium hydroxide are added and fully mixed. After the water is discharged, it enters the coagulation sedimentation area for reaction and precipitation. The sludge then enters the magnetic powder recovery subunit; S4, membrane concentration and reduction unit includes a two-stage DTRO system, and the effluent from the pretreatment system enters the two-stage DTRO system; S5, the deep treatment unit includes BDD electro-oxidation system, MVR evaporation system, and mother liquor drying system. The membrane concentrate enters the BDD electro-oxidation system, and the organic matter in the water is oxidized by the BDD electrodes. The BDD effluent enters the MVR evaporation system for evaporation, and the MVR evaporated mother liquor enters the mother liquor drying system for drying.

2. A fracturing flowback fluid discharge treatment process according to claim 1, characterized in that: In S3, the coagulation and sedimentation area includes a coagulation tank, a magnetic mixing tank, a flocculation tank, and a clarification tank; the coagulant PAC is added to the coagulation tank, and after sufficient mixing, it enters the magnetic mixing tank, magnetic powder is added to the magnetic mixing tank for mixing and flocculation, and then enters the flocculation tank, and the flocculant PAM is added to the flocculation tank for reaction to generate floc particles, and finally enters the clarification tank for sedimentation.

3. A fracturing flowback fluid discharge treatment process according to claim 2, characterized in that: In S3, the magnetic powder recovery subunit includes a high shear machine and a magnetic separator. Part of the sludge settled in the clarification tank is returned to the magnetic mixing tank through a magnetic sludge reflux pump to continue participating in the reaction, while the other part is stripped of magnetic powder sludge by the high shear machine and enters the magnetic separator for magnetic powder recovery. The recovered magnetic powder enters the magnetic mixing tank again to continue participating in the reaction.

4. A fracturing flowback fluid discharge treatment process according to claim 1, characterized in that: In S5 , the BDD electro-oxidation system includes an electro-catalytic oxidation device, and organic matter in water is oxidized by the electro-catalytic oxidation device.

5. A fracturing flowback fluid discharge treatment device, characterized in that: A BDD electro-oxidation system for a fracturing flowback fluid discharge treatment process according to any one of claims 1 to 4, comprising: a water reservoir (10) for receiving membrane concentrate; A cathode plate (20) is installed in the water reservoir (10) and is energized; an anode plate (30) installed in the water reservoir (10) and energized, and the cathode plate (20) and the anode plate (30) are arranged alternately; A stirring rod (40) is rotatably mounted in the water reservoir (10) and is located between the anode plate (30) and the cathode plate (20). A collecting cavity (42) is provided inside the stirring rod (40), and a collecting groove (43) is provided on the rod wall of the stirring rod (40); A transmission assembly (50) is used to drive the stirring rod (40) to rotate with its own central axis as the rotation center; An aggregate cylinder (70), the aggregate cylinder (70) is located in the aggregate cavity (42), the rotation centerline of the aggregate cylinder (70) coincides with its own central axis, the rotation centerline of the aggregate cylinder (70) and the rotation centerline of the stirring rod (40) are perpendicular to each other, the aggregate cylinder (70) is provided with a accommodating cavity (71), and the outer peripheral side wall of the aggregate cylinder (70) is provided with a connecting groove (72), when the aggregate cylinder (70) is in an aggregate state, the connecting groove (72) and the collecting groove (43) are connected, and when the aggregate cylinder (70) is in a dumping state, the aggregate cylinder (70) blocks the collecting groove (43); A driving member (80) for driving the aggregate cylinder (70) to rotate; A sewage pipe (91) has one end connected to the material collecting chamber (42) and the other end extending out of the water reservoir (10). When the material collecting cylinder (70) is in the material discharging state, the sewage pipe (91) discharges sewage.

6. The fracturing flowback fluid discharge treatment device according to claim 5, characterized in that: The transmission assembly (50) includes a driving gear (51) and a driven gear (52), and a power source for driving the driving gear (51) to rotate. The power source is located outside the water reservoir (10). The power source is connected to a rotating shaft (53). The driving gear (51) and the driven gear (52) are located in the stirring rod (40). The rotating shaft (53) extends into the stirring rod (40) and is fixedly connected to the driving gear (51). The stirring rod (40) is rotatably connected to the rotating shaft (53). A gear ring (44) is installed in the stirring rod (40), and the gear ring (44) is meshed with the driven gear (52). A support column (60) is fixedly installed at the bottom of the water reservoir (10), and the support column (60) passes through the stirring rod (40) and is connected to a support base (61). The driving member (80) is installed on the support base (61). The driving gear (51) and the driven gear (52) are rotatably installed on the support base (61). The stirring rod (40) and the support column (60) are coaxial and rotatably connected.

7. The fracturing flowback fluid discharge treatment device according to claim 6, characterized in that: The driving member (80) is a worm wheel (81) and a worm (82), and the worm (82) and the driven gear (52) are coaxially fixedly connected; the worm wheel (81) and the aggregate cylinder (70) are fixedly connected via a connecting rod, and when the rotating shaft (53) rotates, the stirring rod (40) and the driving gear (51) rotate synchronously, and the worm wheel (81) drives the aggregate cylinder (70) to rotate, so that the stirring rod (40) rotates while the aggregate cylinder (70) is in an aggregate state or a discharge state.

8. The fracturing flowback fluid discharge treatment device according to claim 6, characterized in that: The sewage pipe (91) passes through the support column (60), one end of the sewage pipe (91) located inside the stirring rod (40) extends out of the support column (60), and the other end of the sewage pipe (91) extends out of the water reservoir (10).

9. The fracturing flowback fluid discharge treatment device according to claim 8, characterized in that: The support column (60) is provided with a water pumping pipe (92), one end of the water pumping pipe (92) extends into the stirring rod (40) and is installed with a filter element (93), and the other end of the water pumping pipe (92) extends out of the water reservoir (10).

10. The fracturing flowback fluid discharge treatment device according to claim 9, characterized in that: A stirring paddle (41) is installed on the inner wall of the stirring rod (40), and the stirring paddle (41) is close to the water pumping pipe (92).

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