Device for enhancing ion membrane-passing mass transfer based on full-channel flow electrode capacitive deionization and seawater desalination system

Abstract

The utility model discloses a device for enhancing ion membrane-passing mass transfer based on full-channel flow electrode capacitive deionization, which comprises solution chambers, a cathode flow electrode chamber and an anode flow electrode chamber, the solution chambers comprise a first solution chamber and a second solution chamber, and an anion exchange membrane is arranged between the solution chambers. The two solution chambers are respectively provided with a guide plate, and each guide plate comprises a high-conductivity saline-water mixed solution channel. And the water flow directions of the two solution chambers are opposite. The first solution chamber and the second solution chamber contain high-conductivity saline mixed liquid which is formed by mixing pretreated seawater and a high-conductivity material. According to the FCDI device and the seawater desalination system, the middle solution chamber is additionally arranged, high-conductivity materials are added into the middle solution chamber, a flow guide channel of the middle solution chamber and mixed solution convection of different solution chambers are designed, and the phenomena of high resistance and membrane-liquid interface concentration polarization of the FCDI device system are solved; the desalting efficiency and the energy consumption performance are enhanced; the operation cost is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of seawater desalination, in particular to a device for enhancing ion transmembrane mass transfer based on full-channel flow electrode capacitive deionization and a seawater desalination system. Background Art

[0002] Due to the uneven spatial and temporal distribution of water resources and the regional concentration of populations, a stable water supply faces severe challenges. Water conservation measures, wastewater reuse, and other "saving" measures have, to a certain extent, alleviated my country's water shortage. On the other hand, utilizing seawater desalination technology to produce more fresh water, as an unconventional water-saving measure, is an effective way to "open up" water resources. Currently, seawater desalination technologies primarily include thermally driven distillation (such as multi-effect distillation and low-temperature flash evaporation), pressure-driven membrane processes (such as nanofiltration and reverse osmosis), and electric field-driven processes (such as electrodialysis and capacitive deionization). Although thermally driven and pressure-driven desalination technologies have been widely adopted, they still suffer from drawbacks such as high energy consumption, expensive membrane costs, the generation of secondary pollutants, and slow desalination rates. Consequently, many scholars and engineers are dedicated to research to address these issues.

[0003] Field-driven flowing electrode capacitive deionization (FCDI) technology, an innovative fusion of membrane capacitive deionization and electrodialysis, demonstrates significant potential for continuous desalination of concentrated brine (including seawater). Leveraging highly conductive flowing electrodes and ion exchange membranes, this technology effectively enhances the efficiency of electrodialysis mass transfer, slows the electrolysis reaction, and suppresses common ion rejection, thereby increasing desalination rates and enabling continuous desalination.

[0004] However, despite its numerous advantages, FCDI technology faces two major technical bottlenecks in its direct application to seawater desalination. First, the mobile electrodes are primarily composed of water (typically exceeding 80wt%), which reduces the overall charge / ion transfer efficiency of the system. This issue weakens the effective electric field strength applied to the device. Second, concentration polarization occurs at the interface between the ion exchange membrane and the solution. This, especially when high voltages are applied, not only fails to accelerate ion migration but can actually induce water electrolysis, further reducing desalination efficiency and increasing energy consumption.

[0005] To address the above difficulties, current solutions mainly focus on introducing ion / electron conductors, such as carbon black, redox couples, carbon cloth, ion exchange resins, titanium mesh, etc., into the flow electrode chamber and / or solution chamber to improve charge transfer and ion migration performance.

[0006] However, these solutions are all accompanied by problems such as high costs, high process energy consumption, and complex device design, which limit their economic and feasibility in large-scale seawater desalination applications. In summary, although the current FCDI technology shows great prospects in the field of seawater desalination, it is limited by the above technical difficulties and high solution costs. The existing FCDI technology cannot achieve an efficient, low-energy, and low-cost mobile electrode capacitive deionization process for seawater desalination. Utility Model Content

[0007] In order to overcome the shortcomings of the above-mentioned existing technologies, the purpose of the present invention is to provide a device for enhancing ion mass transfer through a membrane based on full-channel flow electrode capacitive deionization, which solves the high resistance of the FCDI system and the concentration polarization phenomenon at the membrane-liquid interface, while improving the efficiency of flow electrode capacitive deionization of seawater and reducing process energy consumption and operating costs.

[0008] Another object of the present invention is to provide a seawater desalination system.

[0009] The purpose of this utility model is achieved through the following technical solutions:

[0010] A device for enhancing ion mass transfer across a membrane based on full-channel flow electrode capacitive deionization comprises a solution chamber, a cathode flow electrode chamber, and an anode flow electrode chamber. The solution chamber comprises a first solution chamber and a second solution chamber. The first solution chamber and the second solution chamber contain a highly conductive saltwater mixture, which is a mixture of pretreated seawater and a highly conductive material.

[0011] An anion exchange membrane is provided between the first solution chamber and the second solution chamber; a cation exchange membrane is provided between the first solution chamber and the cathode flow electrode chamber, and a cation exchange membrane is provided between the second solution chamber and the anode flow electrode chamber;

[0012] The first solution chamber and the second solution chamber are respectively provided with guide plates, which are graphite plates containing highly conductive salt water mixed solution channels; the water flow directions of the first solution chamber and the second solution chamber are opposite.

[0013] Preferably, the first solution chamber is a desalination chamber, and the second solution chamber is a concentration chamber.

[0014] Preferably, the concentrating chamber is close to the positive pole of the power supply, and the desalting chamber is close to the negative pole of the power supply.

[0015] Preferably, the anode flow electrode chamber and the cathode flow electrode chamber are further provided with a current collecting plate and a support end plate respectively. The current collecting plate is a graphite plate containing a serpentine flow electrode channel. The current collecting plate is connected to the support end plate through a support gasket.

[0016] Preferably, the current collecting plate further comprises a tab.

[0017] Preferably, the support washer is provided with an inlet and outlet for a highly conductive salt water mixture.

[0018] Preferably, the support end plate is provided with two flow electrode inlet and outlet interfaces and two high-conductivity salt water mixed liquid inlets and outlets at opposite corners.

[0019] Preferably, the anode flow electrode chamber and the cathode flow electrode chamber further contain flow electrodes respectively, and the flow electrodes are formed by mixing Na2SO4 solution and the highly conductive material.

[0020] Preferably, the highly conductive material is a powdered highly conductive material that is easily separable.

[0021] Preferably, the highly conductive material includes activated carbon powder or carbon black.

[0022] Preferably, a guide plate gasket is provided between the guide plate and the adjacent ion exchange membrane.

[0023] Preferably, the guide plate gasket and the support gasket are rubber gaskets.

[0024] Preferably, the guide plate gasket has adhesive backing.

[0025] Preferably, the water flow directions of the first solution chamber and the second solution chamber are opposite, specifically, the highly conductive salt water mixture in the first solution chamber flows in from top to bottom and out from bottom, while the highly conductive salt water mixture in the second solution chamber flows in from bottom to top.

[0026] Preferably, the flow electrodes in the cathode flow electrode chamber adopt a bottom-in-top-out flow mode, and the flow electrodes in the anode flow electrode chamber adopt a top-in-bottom-out flow mode.

[0027] A seawater desalination system comprises the device for enhancing ion mass transfer across a membrane, a mobile electrode storage and regeneration tank, a pumping device and a seawater-conductive material premixing device, wherein the mobile electrode storage and regeneration tank is connected to the anode mobile electrode chamber and the cathode mobile electrode chamber via the pumping device, and the seawater-conductive material premixing device is connected to the first solution chamber and the second solution chamber via the pumping device.

[0028] The present invention has the following advantages and beneficial effects compared to the prior art:

[0029] (1) The present invention solves the problems of high resistance of the FCDI system and concentration polarization at the membrane-liquid interface by adding an additional intermediate solution chamber to the original intermediate solution chamber of FCDI and adding an additional cation exchange membrane. The invention uses a variety of channels such as adding highly conductive materials to the intermediate solution chamber, designing flow channels in the intermediate solution chamber, and convection of mixed solutions in different solution chambers. Compared with the existing technology, the present invention enhances its desalination efficiency and energy consumption performance and reduces operating costs.

[0030] (2) Adding an intermediate solution chamber and a cation exchange membrane makes one intermediate solution chamber a desalination chamber and the other a concentration chamber. The flow electrode chambers at both ends can be repeatedly regenerated through circulating flow, which simplifies the regeneration process of the flow electrodes in the chambers.

[0031] (3) Adding highly conductive materials to the pretreated seawater to form a highly conductive brine premix, making its composition similar to that of the flow electrodes in the two end chambers of the FCDI device, and then pumping it into the FCDI seawater desalination device can effectively reduce the resistance of the intermediate solution chamber, enhance the ion migration efficiency of the intermediate solution chamber, and reduce the concentration polarization degree of the adjacent ion exchange membrane interface, thereby enhancing the mass transfer efficiency of the ion exchange membrane.

[0032] (4) The utility model is designed with a flow channel specifically for the high-conductivity salt water mixture in the intermediate solution chamber to ensure that the flow is stable and does not form clogging, thereby increasing the coverage area of the flow electrode and improving the utilization rate of the high-conductivity material and ion exchange membrane. By designing the pre-mixed seawater flow electrode and the special flow channel of the solution chamber, a full-channel flow electrode capacitive deionization seawater desalination device is formed.

[0033] (5) The flow pattern of the flow electrodes and the high-conductivity brine mixture in the current collecting plate and the guide plate is set so that the mixed solutions in different solution chambers flow relative to each other, thereby effectively reducing the reverse diffusion of ions caused by the concentration difference between the electrolytes in different solution chambers. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a device for enhancing ion mass transfer across membranes based on full-channel flow electrode capacitive deionization.

[0035] Figure 2 An overview of a device for enhanced ion mass transfer across a membrane based on full-channel flow electrode capacitive deionization.

[0036] Figure 3 It is a schematic diagram of the collecting plate.

[0037] Figure 4 Schematic diagram of the guide plate.

[0038] The markings of the components in the accompanying drawings are:

[0039] 1- cathode flow electrode chamber, 2- cation exchange membrane, 3- first solution chamber, 4- anion exchange membrane, 5- second solution chamber, 6- anode flow electrode chamber, 7- support end plate, 8- support gasket, 9- current collecting plate, 91- flow electrode channel, 92- pole ear, 10- guide plate, 101- high conductive brine mixed solution channel, 102- guide plate gasket, 11- flow electrode inlet and outlet, 12- high conductive brine mixed solution inlet and outlet, 13- penetration hole DETAILED DESCRIPTION

[0040] The utility model object of the utility model is further described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the implementation methods of the utility model are not limited to the following embodiments.

[0041] Example 1

[0042] A seawater desalination device based on full-channel flow electrode capacitive deionization comprises a solution chamber, an anode flow electrode chamber 6, a cathode flow electrode chamber 1, two cation exchange membranes 2 and one anion exchange membrane 4;

[0043] The solution chamber includes a first solution chamber 3 and a second solution chamber 5; the first solution chamber 3 is a desalination chamber, and the second solution chamber 5 is a concentration chamber. Figure 1 As shown, from left to right are the cathode flow electrode chamber 1, the cation exchange membrane 2, the first solution chamber 3 (desalination chamber), the anion exchange membrane 4, the second solution chamber 5 (concentration chamber), the cation exchange membrane 2, and the anode flow electrode chamber 6; the desalination chamber and the concentration chamber respectively include a guide plate gasket 102 and a guide plate 10; the cathode and anode flow electrode chambers 6 respectively include a support end plate 7, a support end plate gasket 8 and a current collecting plate 9.

[0044] like Figure 2 As shown, the left end of the anion exchange membrane 4 is connected to the guide plate 10 through the guide plate gasket 102, the left end of the guide plate 10 is connected to the cation exchange membrane 2 through the guide plate gasket 102, the left end of the cation exchange membrane 2 is connected to the collector plate 9, and the left end of the collector plate 9 is connected to the support end plate 7 through the support end plate gasket 8; the two sides of the device are symmetrically arranged about the anion exchange membrane 4, the right end of the anion exchange membrane 4 is connected to the guide plate 10 through the guide plate gasket 102, the right end of the guide plate 10 is connected to the cation exchange membrane 2 through the guide plate gasket 102, the right end of the cation exchange membrane 2 is connected to the collector plate 9, and the right end of the collector plate 9 is connected to the support end plate 7 through the support end plate gasket 8;

[0045] Among them, Figure 3As shown, the current collecting plate 9 is a graphite plate containing a 2 mm deep and 3 mm wide serpentine flow electrode channel 91. The size of the current collecting plate 9 is 60 mm × 63 mm × 8 mm. The electrode channel is located at the center of the outer surface of the current collecting plate 9 away from the support end plate 7. The water inlet is bottom-in and top-out. The current collecting plate 9 is also provided with a pole ear 92 to embed the carbon-based flow electrode into the graphite current collecting plate 9 and circulate the flow, which can effectively promote transmembrane charge / ion permeation. The positive and negative electrodes of the DC power supply are respectively clamped to the pole ears 92 on both sides with metal to apply an electric field; a flow electrode inlet and outlet 11 is provided at the upper right corner and lower left corner of the support end plate 7, the support end plate gasket 8 and the current collecting plate 9, and a high-conductivity brine mixture inlet and outlet 12 is provided at the upper left corner and lower right corner;

[0046] like Figure 4 As shown, the guide plate 10 is connected to its adjacent guide plate gaskets 102 by adhesive bonding. A 2 mm deep and 3 mm wide serpentine channel 101 for the highly conductive saltwater mixture is carved through the center of each of the guide plate gaskets 102 and the guide plate 10. Water enters from the top and exits from the bottom. Inlets and outlets 12 for the highly conductive saltwater mixture are also located at the upper left and lower right corners of the two guide plates. The guide plate 10 measures 60 mm × 63 mm × 2 mm, while the guide plate gasket 102 measures 60 mm × 63 mm × 0.5 mm. The guide plate gasket 102 is made of rubber. Embedding the highly conductive saltwater mixture within the graphite guide plate 10 and allowing it to circulate effectively promotes transmembrane charge / ion permeation.

[0047] The cathode and anode flow electrode chambers contain flow electrodes made of a mixture of Na2SO4 solution and activated carbon. The concentration chamber and desalination chamber contain a high-conductivity brine mixture made of pre-treated seawater and activated carbon.

[0048] The support end plates 7, support end plate washers 8, collecting plates 9 and guide plates 10 at both ends of the device are respectively provided with a circle of through holes 13, totaling 12. Bolts are used to pass through the 12 through holes 13 of the left support end plate 7, extend into the device and connect with the right support end plate 7. Use nuts of corresponding specifications to connect the bolts to fix the above components.

[0049] Example 2

[0050] A seawater desalination system includes the device for enhancing ion mass transfer across a membrane in Example 1, a mobile electrode storage and regeneration tank, a pretreated seawater storage tank, a pumping device, and a seawater-conductive material premixing device. The mobile electrode storage and regeneration tank is connected to the anode mobile electrode chamber 6 and the cathode mobile electrode chamber 1 through the pumping device, and the seawater-conductive material premixing device is connected to the desalination chamber and the concentration chamber.

[0051] Example 3

[0052] The seawater desalination system in Example 2 is used to desalinate seawater, and the specific steps are as follows:

[0053] Before assembling the device, the ion exchange membrane was soaked in 20 g L −1 NaCl solution for at least 24 h. The flow electrode was fed with water in the same manner as above and at a rate of 30 ml min −1 The flow rate circulates in its corresponding flow electrode channel 91 and storage tank.

[0054] The key equipment required for the system operation are as follows: DC power supply, pH / conductivity multi-parameter tabletop meter, four-channel peristaltic pump and magnetic stirrer. -1 Taking NaCl solution as an example to simulate the pretreated seawater, a seawater pumping device was used to pump 200 mL of pretreated seawater into a seawater-conductive material premixing device containing 30 g of analytical grade activated carbon powder to form two parts of highly conductive brine mixture.

[0055] To ensure sufficient sodium ion migration, the flow electrode was composed of 200 mL of 25 g L -1 The Na2SO4 solution was mixed with 30 g of analytical grade activated carbon powder and stored in a mobile electrode storage and regeneration tank.

[0056] The flow electrode and high-conductivity saline mixture were both heated at 30 ml min −1 After the system was allowed to run stably for 10 minutes, a voltage of 1.2 V was applied for 120 minutes.

[0057] The mobile electrode is pumped from the mobile electrode storage and regeneration tank via a pumping system to the mobile electrode inlet / outlet 11 on the support end plate 7 at the left end of the device. It then flows through the mobile electrode channels 91 on the surface of the graphite current collector plate 9 at the left end of the device, and finally exits through the mobile electrode inlet / outlet 11 on the left end of the device and is transported back to the mobile electrode storage and regeneration tank. The mobile electrodes on the support end plate 7 and current collector plate 9 at the right end of the device follow the same path through the device, but in opposite directions. After exiting the device, the mobile electrodes at both ends finally flow into the mobile electrode storage and regeneration tank for electrode regeneration, and the above process is repeated.

[0058] The highly conductive brine mixture is formed by pre-treating seawater and pumping it into the seawater-conductive material premixing device for mixing. It is then pumped from the seawater-conductive material premixing device through the seawater-highly conductive material mixed solution pumping device into the desalination chamber and the concentration chamber respectively. The highly conductive brine mixture in the desalination chamber is transported from the seawater-conductive material premixing device through the pumping device to the high conductive brine mixture inlet and outlet 12 of the support end plate 7 at the left end of the device, flows through the high conductive brine mixture channel 101 in the middle of the left end guide plate 10, flows out through the high conductive brine mixture inlet and outlet 12 of the left end support end plate 7, and finally flows into the high conductive brine mixture solid-liquid separation device, and the above process is repeated subsequently. During the experiment, the device's current response, as well as the pH and conductivity of the highly conductive brine mixture solid-liquid separation device, were recorded at minute intervals using the accompanying software. The NaCl concentration of the highly conductive brine mixture in the desalination chamber of the highly conductive brine mixture solid-liquid separation device was calculated using the conductivity-concentration relationship. While the device was operating, the activated carbon slurry and fresh water were separated. The fresh water could enter post-treatment systems such as disinfection, while the activated carbon slurry was pumped through a pumping device into the seawater-conductive material premixing device for reuse. The highly conductive brine mixture in the concentrating chamber and the support plate on the other side of the device passed through the same path through the device, but in opposite directions. The concentrated chamber and the conductive brine mixture in the concentrating chamber were then transported to the seawater-conductive material premixing device for reuse of the concentrated wastewater and activated carbon slurry.

[0059] Comparative Example

[0060] In this example, an FCDI control group was set up. Except that no activated carbon powder was added to the intermediate solution chamber of the device, all other experimental conditions were the same as above. The results showed that after 120 minutes of desalination experiment, the NaCl concentration of the full-channel flow electrode capacitive deionization decreased by 4.6gL -1 The concentration of the FCDI control group decreased by 3.9 g / L -1 The full-channel flow electrode capacitive deionization has a salt removal concentration that is approximately 17.95% higher, and the average salt removal rate per square meter of effective ion exchange area per second is 2.476 mg m -2 s -1 Adding highly conductive materials to the pretreated seawater can effectively reduce the resistance of the intermediate solution chamber, enhance the ion migration efficiency of the intermediate solution chamber, and reduce the concentration polarization degree of the adjacent ion exchange membrane interface to enhance the mass transfer efficiency of the ion exchange membrane, thereby achieving excellent desalination effect.

[0061] The above specific implementation methods are preferred embodiments of the present invention and cannot limit the present invention. Any other changes or other equivalent replacement methods that do not deviate from the technical solution of the present invention are included in the scope of protection of the present invention.

Claims

1. A device for enhancing ion mass transfer across a membrane based on full-channel flow electrode capacitive deionization, comprising a solution chamber, a cathode flow electrode chamber (1), and an anode flow electrode chamber (6), characterized in that: The solution chamber comprises a first solution chamber (3) and a second solution chamber (5); the first solution chamber (3) and the second solution chamber (5) contain a highly conductive salt water mixture, wherein the highly conductive salt water mixture is a mixture of pretreated seawater and a highly conductive material; An anion exchange membrane (4) is provided between the first solution chamber (3) and the second solution chamber (5); a cation exchange membrane (2) is provided between the first solution chamber (3) and the cathode flow electrode chamber (1); and a cation exchange membrane (2) is provided between the second solution chamber (5) and the anode flow electrode chamber (6); The first solution chamber (3) and the second solution chamber (5) are respectively provided with a guide plate (10), wherein the guide plate (10) is a graphite plate containing a highly conductive salt water mixed solution channel (101); the water flow directions of the first solution chamber (3) and the second solution chamber (5) are opposite.

2. The device for enhancing ion mass transfer across membranes based on full-channel flow electrode capacitive deionization according to claim 1, characterized in that: The first solution chamber (3) is a desalination chamber, and the second solution chamber (5) is a concentration chamber.

3. The device for enhancing ion mass transfer across membranes based on full-channel flow electrode capacitive deionization according to claim 1, characterized in that: The anode flow electrode chamber (6) and the cathode flow electrode chamber (1) are further provided with a current collecting plate (9) and a supporting end plate (7), respectively. The current collecting plate (9) is a graphite plate containing a serpentine flow electrode channel (91). The current collecting plate (9) is connected to the supporting end plate (7) via a supporting gasket (8).

4. The device for enhancing ion mass transfer across membranes based on full-channel flow electrode capacitive deionization according to claim 1, characterized in that: The anode flow electrode chamber (6) and the cathode flow electrode chamber (1) also contain flow electrodes respectively, and the flow electrodes are formed by mixing Na2SO4 solution and the highly conductive material.

5. The device for enhancing ion mass transfer across membranes based on full-channel flow electrode capacitive deionization according to claim 1, characterized in that: The highly conductive material includes activated carbon powder or carbon black.

6. The device for enhancing ion mass transfer across membranes based on full-channel flow electrode capacitive deionization according to claim 1, characterized in that: A guide plate gasket (102) is provided between the guide plate (10) and the adjacent ion exchange membrane.

7. The device for enhancing ion mass transfer across membranes based on full-channel flow electrode capacitive deionization according to claim 1, characterized in that: The water flow directions of the first solution chamber (3) and the second solution chamber (5) are opposite. Specifically, the highly conductive salt water mixture in the first solution chamber (3) flows in an upward direction and out downward direction, while the highly conductive salt water mixture in the second solution chamber (5) flows in an downward direction and out upward direction.

8. The device for enhancing ion mass transfer across membranes based on full-channel flow electrode capacitive deionization according to claim 1, characterized in that: The flow electrode in the cathode flow electrode chamber (1) adopts a bottom-in-top-out flow mode; the flow electrode in the anode flow electrode chamber (6) adopts a top-in-bottom-out flow mode.

9. A seawater desalination system, characterized in that: The invention comprises a device for enhancing ion mass transfer across a membrane as described in any one of claims 1 to 8, a mobile electrode storage and regeneration tank, a pumping device and a seawater-conductive material premixing device, wherein the mobile electrode storage and regeneration tank is connected to the anode mobile electrode chamber (6) and the cathode mobile electrode chamber (1) through the pumping device, and the seawater-conductive material premixing device is connected to the first solution chamber (3) and the second solution chamber (5) through the pumping device.

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