Shale gas produced water desalting system regulated and controlled by dynamic electric field

Abstract

The invention discloses a shale gas produced water desalination system regulated and controlled by a dynamic electric field, which comprises an electrochemical hardness removal unit (11), a microfiltration interception unit (13), a reverse osmosis desalination unit (12) and a controller (10), the electrochemical hardness removal unit (11), the microfiltration interception unit (13) and the reverse osmosis desalination unit (12) are sequentially arranged along the inflow direction, the electrochemical hardness removal unit (11) is used for removing hardness components in water through a dynamic electric field, the microfiltration interception unit (13) is used for intercepting precipitates and suspended particles, and the reverse osmosis desalination unit (12) is used for reducing salt; and the controller (10) is respectively connected with the electrochemical hardness removal unit (11) and the reverse osmosis desalination unit (12) and is used for dynamically adjusting the polarity of an electrode so as to relieve membrane pollution in an electric field transformation mode. The invention solves the problems of low efficiency and serious membrane pollution caused by hardness removal and desalination separation in the traditional shale gas produced water treatment process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-salinity wastewater treatment, and particularly relates to a shale gas produced water desalination system with dynamic electric field regulation. BACKGROUND

[0002] Compared with conventional natural gas, shale gas reservoirs have particularity, and a large amount of produced water with complex components and high salt content is generated in the development process thereof. In order to meet the national discharge standard, the produced water needs to be subjected to deep treatment such as desalination. The conventional produced water desalination process first needs to remove the calcium and magnesium ions and other components in the water by a chemical method, and then enters reverse osmosis for desalination. This method can generate a large amount of residual sludge in the hardness removal stage, increase the operation cost, and easily cause membrane pollution in the reverse osmosis stage. The electrochemical method can remove hardness by in-situ generation of hydroxyl ions and electric adsorption effect through electrolysis of wastewater, and can alleviate membrane pollution and degrade pollutants through electrochemical oxidation and electrostatic repulsion. Coupling the electrochemical method with the produced water desalination technology can solve the problems of low efficiency and serious membrane pollution caused by the separation of hardness removal and desalination in the traditional shale gas produced water treatment process, and has important significance for promoting the efficient treatment and green development of shale gas produced water. SUMMARY

[0003] The present application provides a shale gas produced water desalination system with dynamic electric field regulation, so as to solve the problems of low efficiency and serious membrane pollution caused by the separation of hardness removal and desalination in the traditional shale gas produced water treatment process, and is suitable for the resource treatment of high-salinity and refractory wastewater such as shale gas produced water.

[0004] The present application is implemented by using the following technical scheme: a shale gas produced water desalination system with dynamic electric field regulation, comprising an electrochemical hardness removal unit, a microfiltration interception unit, a reverse osmosis desalination unit and a controller, wherein the electrochemical hardness removal unit, the microfiltration interception unit and the reverse osmosis desalination unit are sequentially arranged along the water flow direction, the electrochemical hardness removal unit removes the hardness components in the water through a dynamic electric field, the microfiltration interception unit is used to intercept the precipitated and suspended particles, and the reverse osmosis desalination unit is used to reduce the salt content; the controller is connected with the electrochemical hardness removal unit and the reverse osmosis desalination unit respectively, so as to dynamically adjust the electrode polarity, so as to alleviate the membrane pollution by means of electric field transformation.

[0005] Further, the system further comprises a water inlet pump, which is used to feed water into the system, and the water flow sequentially passes through the electrochemical hardness removal unit, the microfiltration interception unit and the reverse osmosis desalination unit.

[0006] Further, the electrochemical hardness removal unit comprises a first electrode and a second electrode, which are sequentially arranged along the water flow direction, and are used to generate a dynamic electric field through an electrolytic reaction, and promote the removal of Ca 2 + , Mg2+ The ions form metal hydroxide precipitates on and near the surface of the first electrode.

[0007] Further, the microfiltration interception unit comprises a microfiltration membrane arranged downstream of the second electrode, for intercepting the metal hydroxide precipitates and suspended particles.

[0008] Further, the reverse osmosis desalination unit comprises a third electrode arranged downstream of the microfiltration membrane and a reverse osmosis membrane arranged downstream of the third electrode, and a dynamic electric field covers the surface of the reverse osmosis membrane, so as to reduce organic pollution on the reverse osmosis membrane through oxidation.

[0009] Further, the electrode polarity conditions of the third electrode, the second electrode and the first electrode comprise: The third electrode and the second electrode are both anodes, and the first electrode is a cathode at this time. The third electrode and the second electrode are both cathodes, and the first electrode is an anode at this time.

[0010] Further, the power supply is further included, and the controller is connected with the electrochemical hardness removal unit and the reverse osmosis desalination unit respectively through the power supply.

[0011] Further, the detection unit is further included, and the detection unit comprises a pressure detector and a flow meter, the pressure detector and the flow meter are arranged downstream of the reverse osmosis desalination unit and connected with the controller respectively, so as to dynamically trigger electrode polarity reversal based on the real-time membrane flux and the transmembrane pressure difference of the reverse osmosis desalination unit, dissolve the metal hydroxide precipitates adhered to the surface through a local acidic environment, and the frequency of the electrode polarity reversal is once every 0.5 hours to 4 hours, and the duration of each reversal is 1 minute to 10 minutes.

[0012] Further, the condition for the controller to trigger the electrode polarity reversal is that the membrane flux of the reverse osmosis desalination unit decreases to 80% to 90% of the initial value, or the transmembrane pressure difference increases to 1.2 times to 1.5 times of the initial value.

[0013] Further, the controller synchronously injects a low-pressure backwash water flow into the electrochemical hardness removal unit, the microfiltration interception unit and the reverse osmosis desalination unit during the polarity reversal, and the pressure is 0.1 MPa to 0.3 MPa.

[0014] The present application has the following beneficial effects: The present application comprises an electrochemical hardness removal unit, a microfiltration interception unit and a reverse osmosis desalination unit arranged in sequence along the water inlet direction of shale gas produced water, wherein the electrochemical hardness removal unit realizes Ca 2+ , Mg 2+The in-situ precipitation of ions removes the hardness of produced water; the reverse osmosis desalination unit synchronously completes deep desalination under the assistance of an electric field.

[0015] The dynamic electric field generated by the electrolysis process covers the surface of the reverse osmosis membrane and the microfiltration membrane, degrades the organic matter in the produced water and slows down the organic pollution on the membrane surface, the controller dynamically triggers the polarity reversal of the electrode based on the membrane flux and pressure, and the metal hydroxide generated in the original cathode area is dissolved and peeled off in the acidic environment after the reversal, and the negatively charged membrane pollutants attached to the original anode area are detached under the electrostatic action of the reversed electric field, realizing the triple function synergy of electrochemical hardness removal, reverse osmosis desalination and membrane pollution control. BRIEF DESCRIPTION OF DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of the drawings shown.

[0017] Figure 1 The system block diagram of the present application is shown in the figure; In the figure, 1 is a water inlet pump, 2 is a power supply, 3 is a flow meter, 4 is a pressure detector, 5 is a reverse osmosis membrane, 6 is a third electrode, 7 is a microfiltration membrane, 8 is a second electrode, 9 is a third electrode, and 10 is a controller. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical scheme in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0019] It should be noted that: similar numbers and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings.

[0020] The following will combine the drawings to make a detailed description of some embodiments of the present application. In the case of no conflict, the following embodiments and features in the embodiments can be combined with each other.

[0021] Reference Figure 1The application discloses a shale gas produced water desalination system based on dynamic electric field regulation, which comprises an electrochemical water softening unit 11, a microfiltration interception unit 13, a reverse osmosis desalination unit 12 and a controller 10, wherein the electrochemical water softening unit 11, the microfiltration interception unit 13 and the reverse osmosis desalination unit 12 are sequentially arranged along the water inflow direction, the electrochemical water softening unit 11 removes the hardness components such as calcium and magnesium ions in water through electrolysis reaction to generate a dynamic electric field, the microfiltration interception unit 13 is used for intercepting precipitated and suspended particles, and the reverse osmosis desalination unit 12 is used for reducing salt content; the controller 10 is connected with the electrochemical water softening unit 11 and the reverse osmosis desalination unit 12 respectively, and is used for dynamically adjusting the electrode polarity to relieve membrane pollution through electric field transformation; and the system further comprises a water inflow pump 1, which is used for inflowing water into the system, and the water flow sequentially passes through the electrochemical water softening unit 11, the microfiltration interception unit 13 and the reverse osmosis desalination unit 12.

[0022] In the embodiment, the electrochemical water softening unit 11 comprises a first electrode 9 and a second electrode 8, which are sequentially arranged along the water inflow direction, are used for generating a dynamic electric field through electrolysis reaction, and are used for promoting Ca 2+ , Mg 2+ ions in shale gas produced water to form metal hydroxide precipitates on the surface of the first electrode 9 and in the vicinity of the first electrode 9.

[0023] In the embodiment, the microfiltration interception unit 13 comprises a microfiltration membrane 7, which is arranged downstream of the second electrode 8 and is used for intercepting the metal hydroxide precipitates and suspended particles.

[0024] In the embodiment, the reverse osmosis desalination unit 12 comprises a third electrode 6 and a reverse osmosis membrane 5, the third electrode 6 is arranged downstream of the microfiltration membrane 7, the reverse osmosis membrane 5 is arranged downstream of the third electrode 6, a dynamic electric field covers the surface of the reverse osmosis membrane 5, and organic pollution on the reverse osmosis membrane 5 is reduced through oxidation. It should be noted that, in the embodiment, the pore size of the microfiltration membrane 7 is 0.1-1 mu m, and the distance between the third electrode 6 and the second electrode 8 is 1-5 cm, so that the dynamic electric field generated by electrolysis covers the surface of the microfiltration membrane 7.

[0025] In the embodiment, the third electrode 6, the second electrode 8 and the first electrode 9 all adopt titanium-based coating electrodes, the coating material of the first electrode 9 is platinum or ruthenium oxide, and the coating material of the third electrode 6 and the second electrode 8 is ruthenium iridium; in addition, the electrode polarity conditions of the third electrode 6, the second electrode 8 and the first electrode 9 include that the third electrode 6 and the second electrode 8 are both anodes, at this time, the first electrode 9 is a cathode; the third electrode 6 and the second electrode 8 are both cathodes, at this time, the first electrode 9 is an anode.

[0026] In the embodiment, a power supply 2 is further included, and the controller 10 is connected with the electrochemical hardness removal unit 11 and the reverse osmosis desalination unit 12 respectively through the power supply 2. Specifically, at the beginning, the first electrode 9 is a cathode, and the third electrode 6 and the second electrode 8 are both anodes.

[0027] In the embodiment, a detection unit is further included, which comprises a pressure detector 4 and a flow meter 3 arranged downstream of the reverse osmosis desalination unit 12 and used to detect the transmembrane pressure difference and the membrane flux of the reverse osmosis system respectively; the controller 10 is connected with the pressure detector 4 and the flow meter 3 respectively, and is used to dynamically trigger the electrode polarity reversal based on the real-time membrane flux and the transmembrane pressure difference of the reverse osmosis membrane 5, so that the original cathode (the first electrode 9) is converted into an anode after the reversal, and the metal hydroxide precipitate attached to the surface thereof is dissolved through a local acidic environment; the original anode (the third electrode 6 and the second electrode 8) is converted into a cathode after the reversal, and the particles, microorganisms and organic pollutants with negative electricity attached to the surface of the reverse osmosis membrane 5 are desorbed through electrostatic repulsion.

[0028] In the embodiment, the condition for the controller 10 to trigger the electrode polarity reversal is that the membrane flux of the reverse osmosis desalination unit 12 decreases to 80% to 90% of the initial value, or the transmembrane pressure difference increases to 1.2 times to 1.5 times of the initial value, and the frequency of the electrode polarity reversal is once every 0.5 hours to 4 hours, and the duration of each reversal is 1 minute to 10 minutes.

[0029] In the embodiment, the system is suitable for shale gas produced water treatment, the hardness of the raw water is 200 to 2500 mg / L, and the salt content is 10000 to 30000 mg / L; the strength of the dynamic electric field is 50 to 200 V / m, and the current density is 0.5 to 2 mA / cm 2 ; during the polarity reversal, the controller (10) synchronously injects a low-pressure backwash water flow into the electrochemical hardness removal unit 11, the microfiltration interception unit 13 and the reverse osmosis desalination unit 12, and the pressure is 0.1 MPa to 0.3 MPa.

[0030] In summary, the application comprises an electrochemical hardness removal unit, a microfiltration interception unit and a reverse osmosis desalination unit arranged in sequence along the water inlet direction of the shale gas produced water, wherein the electrochemical hardness removal unit realizes the removal of Ca 2+ , Mg 2+The in-situ precipitation of ions reduces the hardness of produced water, and the reverse osmosis desalination unit simultaneously completes deep desalination under the assistance of an electric field. The dynamic electric field generated by the electrolysis process covers the surface of the reverse osmosis membrane and the microfiltration membrane, degrades the organic matter in the produced water, and slows down the organic pollution on the membrane surface. The controller dynamically triggers the polarity reversal of the electrode based on the membrane flux and pressure, so that the metal hydroxide generated in the original cathode area is dissolved and peeled off in the acidic environment after the reversal, and the negatively charged membrane pollutants attached to the original anode area are detached under the electrostatic action of the reversed electric field, thereby realizing the triple functions of synergistic electrochemical water softening, reverse osmosis desalination and membrane pollution control.

[0031] For the foregoing embodiments, for the sake of simple description, they are all expressed as a series of action combinations, but those skilled in the art should know that the present application is not limited by the order of the described actions, because according to the present application, some steps can be performed in other order or simultaneously. Secondly, those skilled in the art should know that the embodiments described in the specification are preferred embodiments, and the actions involved are not necessarily essential to the present application.

[0032] In the above embodiments, the basic principles and main features of the present application and the advantages of the present application are described. Those skilled in the art should understand that the present application is not limited by the above embodiments, and the above embodiments and the description in the specification are only to illustrate the principles of the present application. Any modification and change made by those skilled in the art without departing from the spirit and scope of the present application should be within the protection scope of the claims of the present application.

Claims

1. A dynamic electric field regulated shale gas produced water desalination system, characterized in that, The system comprises an electrochemical hardness removal unit (11), a microfiltration interception unit (13), a reverse osmosis desalination unit (12) and a controller (10), which are sequentially arranged along the water flow direction, wherein the electrochemical hardness removal unit (11) removes the hardness components in water through a dynamic electric field, the microfiltration interception unit (13) is used to intercept the precipitated and suspended particles, and the reverse osmosis desalination unit (12) is used to reduce the salt content; the controller (10) is connected with the electrochemical hardness removal unit (11) and the reverse osmosis desalination unit (12) respectively, and is used to dynamically adjust the electrode polarity to relieve the membrane pollution through the electric field transformation.

2. A dynamic electric field regulated produced water desalination system for shale gas as claimed in claim 1, wherein, The system further comprises a water inlet pump (1) for feeding water into the system, and the water flows through the electrochemical hardness removal unit (11), the microfiltration interception unit (13) and the reverse osmosis desalination unit (12) in sequence.

3. A dynamic electric field regulated produced water desalination system for shale gas as claimed in claim 1, wherein, The electrochemical hardness removal unit (11) comprises a first electrode (9) and a second electrode (8), which are arranged in sequence along the water flow direction, for generating a dynamic electric field through electrolytic reaction and promoting Ca 2+ , Mg 2+ ions in the shale gas produced water to form metal hydroxide precipitates on the surface of the first electrode (9) and in the vicinity thereof.

4. A dynamic electric field regulated produced water desalination system for shale gas as claimed in claim 3, wherein, The microfiltration interception unit (13) comprises a microfiltration membrane (7) arranged downstream of the second electrode (8) and used to intercept the metal hydroxide precipitate and suspended particles.

5. A dynamic electric field regulated produced water desalination system for shale gas as claimed in claim 4, wherein, The reverse osmosis desalination unit (12) comprises a third electrode (6) arranged downstream of the microfiltration membrane (7) and a reverse osmosis membrane (5) arranged downstream of the third electrode (6), and a dynamic electric field covers the surface of the reverse osmosis membrane (5) to reduce the organic pollution on the reverse osmosis membrane (5) through oxidation.

6. A dynamic electric field regulated produced water desalination system for shale gas as claimed in claim 5, wherein, The electrode polarity conditions of the third electrode (6), the second electrode (8) and the first electrode (9) include: The third electrode (6) and the second electrode (8) are both anodes, and the first electrode (9) is a cathode at this time; The third electrode (6) and the second electrode (8) are both cathodes, and the first electrode (9) is an anode at this time.

7. A dynamic electric field regulated produced water desalination system for shale gas as claimed in claim 1, wherein, The system further comprises a power supply (2), and the controller (10) is connected with the electrochemical hardness removal unit (11) and the reverse osmosis desalination unit (12) through the power supply (2).

8. A dynamic electric field regulated produced water desalination system for shale gas as claimed in claim 1, wherein, The system further comprises a detection unit comprising a pressure detector (4) and a flow meter (3), which are arranged downstream of the reverse osmosis desalination unit (12) and connected with the controller (10) respectively, and are used to dynamically trigger the electrode polarity reversal based on the real-time membrane flux and the transmembrane pressure difference of the reverse osmosis desalination unit (12), to dissolve the metal hydroxide precipitate attached to the surface through a local acidic environment, and the frequency of the electrode polarity reversal is once every 0.5 hours to 4 hours, and the duration of each reversal is 1 minute to 10 minutes.

9. A dynamic electric field regulated produced water desalination system for shale gas as claimed in claim 8, wherein, The condition for the controller (10) to trigger the electrode polarity reversal is that the membrane flux of the reverse osmosis desalination unit (12) decreases to 80% to 90% of the initial value, or the transmembrane pressure difference increases to 1.2 times to 1.5 times of the initial value.

10. A dynamic electric field regulated produced water desalination system for shale gas as claimed in claim 9, wherein, The controller (10) synchronously injects a low-pressure backwash water flow into the electrochemical hardness removal unit (11), the microfiltration interception unit (13) and the reverse osmosis desalination unit (12) during the polarity reversal, and the pressure is 0.1 MPa to 0.3 MPa.

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