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

Abstract

The invention discloses a device for enhancing ion membrane-passing mass transfer based on all-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 flow guide plate, and the flow guide plate comprises a high-conductivity saline-water mixed solution channel; the water flow directions of the two solution chambers are opposite; the first solution chamber and the second solution chamber contain a high-conductivity saline mixed solution which is formed by mixing pretreated seawater and a high-conductivity material; the invention further discloses a sea water desalination system, the middle solution chamber is additionally arranged, a high-conductivity material is 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 of an FCDI device system and membrane-liquid interface concentration polarization are solved; the desalting efficiency and the energy consumption performance are enhanced; the operation cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of seawater desalination, and 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 distribution of water resources in time and space and the regional concentration of population, the stable supply of water resources faces severe challenges. Water-saving measures, wastewater reuse and other "saving" means have alleviated the water shortage to a certain extent. On the other hand, the use of seawater desalination technology to produce more fresh water, as an unconventional water-saving measure, is one of the effective ways to "open source" water resources. At present, seawater desalination technologies mainly include heat-driven distillation (such as multi-effect distillation, low-temperature flash evaporation), pressure-driven membrane methods (such as nanofiltration, reverse osmosis) and electric field-driven methods (such as electrodialysis and capacitive deionization). Although heat-driven and pressure-driven seawater desalination technologies have been widely used, these technologies still have disadvantages such as high energy consumption, expensive membrane costs, easy generation of secondary pollutants or slow desalination rates. Therefore, many scholars and engineers are still committed to relevant research to address the above problems.

[0003] Electric field driven flowing electrode capacitive deionization (FCDI) technology, as an innovative fusion of membrane capacitive deionization and electrodialysis technology, has shown great potential in the field of continuous concentrated brine (including seawater) desalination. With the assistance of high conductivity flowing electrodes and ion exchange membranes, this technology can effectively improve the mass transfer efficiency of electrodialysis membrane, slow down the electrolysis reaction, and inhibit the phenomenon of common ion rejection, thereby increasing the desalination rate and achieving continuous seawater desalination.

[0004] However, despite the many advantages of FCDI technology, its direct application in seawater desalination still faces two major technical bottlenecks. First, the composition of the mobile electrode is mainly water (generally more than 80wt%), which reduces the overall charge / ion transfer efficiency of the system. This problem weakens the effective electric field strength applied to the device; second, there is concentration polarization at the contact interface between the ion exchange membrane and the solution. Especially when a higher voltage is applied, it not only fails to accelerate ion migration, but may induce water electrolysis reaction, further reducing the desalination effect and increasing energy consumption.

[0005] To address the above challenges, 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 cost, high process energy consumption and complex device design, which limits their economic and feasibility in large-scale seawater desalination applications. In summary, although the current FCDI technology shows broad 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-consumption and low-cost mobile electrode capacitive deionization seawater desalination process. Summary of the invention

[0007] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a device for enhancing ion mass transfer across a membrane based on full-channel flow electrode capacitive deionization, which solves the problems of high system resistance of the FCDI device and concentration polarization 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 the present invention is achieved through the following technical solutions: A device for enhancing ion mass transfer through 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, wherein the solution chamber comprises a first solution chamber and a second solution chamber; the first solution chamber and the second solution chamber contain a high-conductivity salt water mixture, wherein the high-conductivity salt water mixture is a mixture of pretreated seawater and a high-conductivity material; 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; 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.

[0010] Preferably, the first solution chamber is a desalination chamber, and the second solution chamber is a concentration chamber.

[0011] 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.

[0012] Preferably, the anode flow electrode chamber and the cathode flow electrode chamber are further provided with a current collecting plate and a supporting end plate respectively, the current collecting plate is a graphite plate containing a serpentine flow electrode channel, and the current collecting plate is connected to the supporting end plate via a supporting gasket.

[0013] Preferably, the current collecting plate further comprises a pole lug.

[0014] Preferably, the support gasket is provided with an inlet and outlet for a highly conductive salt water mixture.

[0015] Preferably, the support end plate is diagonally provided with two flow electrode inlet and outlet interfaces and two high-conductivity salt water mixed liquid inlets and outlets.

[0016] Preferably, the anode flow electrode chamber and the cathode flow electrode chamber also contain flow electrodes respectively, and the flow electrodes are formed by mixing Na2SO4 solution and the highly conductive material.

[0017] Preferably, the highly conductive material is a powdered highly conductive material that is easily separable.

[0018] Preferably, the highly conductive material includes activated carbon powder or carbon black.

[0019] Preferably, a guide plate gasket is provided between the guide plate and the adjacent ion exchange membrane.

[0020] Preferably, the guide plate gasket and the support gasket are rubber gaskets.

[0021] Preferably, the guide plate gasket has adhesive backing.

[0022] 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 from top to bottom, and the highly conductive salt water mixture in the second solution chamber flows from bottom to top.

[0023] Preferably, the flow electrode in the cathode flow electrode chamber adopts a bottom-in-top-out flow mode, and the flow electrode in the anode flow electrode chamber adopts a top-in-bottom-out flow mode.

[0024] 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 an anode mobile electrode chamber and a cathode mobile electrode chamber via the pumping device, and the seawater-conductive material premixing device is connected to a first solution chamber and a second solution chamber via the pumping device.

[0025] The present invention has the following advantages and beneficial effects compared with the prior art: (1) The present invention solves the problems of high system resistance and membrane-liquid interface concentration polarization of the FCDI device by adding an additional intermediate solution chamber on the basis of the original intermediate solution chamber of FCDI and adding an additional cation exchange membrane, 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 prior art, the present invention enhances its desalination efficiency and energy consumption performance and reduces operating costs.

[0026] (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.

[0027] (3) Adding highly conductive materials to the pretreated seawater to form a highly conductive brine premix, making its composition similar to the composition 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.

[0028] (4) The present invention specifically designs a flow channel for the high-conductivity salt water mixture in the intermediate solution chamber to ensure that its 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 the ion exchange membrane. By designing the pre-mixed seawater flow electrode and the special flow channel of the solution chamber, a seawater desalination device with full-channel flow electrode capacitive deionization is formed.

[0029] (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

[0030] Figure 1 It is a device for enhancing ion mass transfer across membrane based on full-channel flow electrode capacitive deionization.

[0031] Figure 2 An overview of a device for enhanced ion mass transfer across a membrane based on full-channel flow electrode capacitive deionization.

[0032] Figure 3 It is a schematic diagram of the collector plate.

[0033] Figure 4 It is a schematic diagram of the guide plate.

[0034] The markings of the components in the accompanying drawings: 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 salt water mixed solution channel, 102- guide plate gasket, 11- flow electrode inlet and outlet, 12- high conductive salt water mixed solution inlet and outlet, 13- penetration hole DETAILED DESCRIPTION

[0035] The purpose of the present invention is further described in detail below with reference to the accompanying drawings and specific examples. The examples cannot be described one by one here, but the implementation methods of the present invention are not therefore limited to the following examples.

[0036] Embodiment 1 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; 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 supporting end plate 7, a supporting end plate gasket 8 and a current collecting plate 9.

[0037] 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; Among them, Figure 3 As 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 supporting 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 the transmembrane charge / ion penetration. The positive and negative electrodes of the DC power supply are respectively clamped to the pole ears 92 on both sides with metal, thereby applying an electric field; a flow electrode inlet and outlet 11 is respectively provided at the upper right corner and the lower left corner of the supporting end plate 7, the supporting end plate gasket 8 and the current collecting plate 9, and a high-conductivity salt water mixed liquid inlet and outlet 12 is respectively provided at the upper left corner and the lower right corner; like Figure 4As shown, the guide plate 10 and the guide plate gaskets 102 on the adjacent two sides are connected by adhesive bonding; the guide plate gasket 102 and the guide plate 10 center are respectively penetrated by a serpentine high-conductivity salt water mixed liquid channel 101 with a depth of 2 mm and a width of 3 mm, and the water inlet method is up-in and down-out, and the upper left corner and lower right corner of the two are also provided with a high-conductivity salt water mixed liquid inlet and outlet 12. The size of the guide plate 10 is 60 mm × 63 mm × 2 mm, and the size of the guide plate gasket 102 is 60 mm × 63 mm × 0.5 mm; the material of the guide plate gasket 102 is rubber; embedding the high-conductivity salt water mixed liquid into the graphite guide plate 10 and circulating it can effectively promote the cross-membrane charge / ion penetration.

[0038] The anion and cation flow electrode chambers contain flow electrodes made of a mixture of Na2SO4 solution and activated carbon, and the concentration chamber and desalination chamber contain a high-conductivity brine mixture made of pre-treated seawater and activated carbon. 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, 12 in number. 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. Nuts of corresponding specifications are used to connect the bolts to fix the above components.

[0039] Embodiment 2 A seawater desalination system comprises 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, wherein the mobile electrode storage and regeneration tank is connected to an anode mobile electrode chamber 6 and a cathode mobile electrode chamber 1 via the pumping device, and the seawater-conductive material premixing device is connected to a desalination chamber and a concentration chamber.

[0040] Embodiment 3 The seawater desalination system in Example 2 is used to desalinate seawater, and the specific steps are as follows:

[0041] Before the device was assembled, the ion exchange membrane was soaked in 20 g L −1 The flow electrode was placed in a NaCl solution for at least 24 h. The flow electrode was filled with water as described above and the flow rate was 30 ml min −1 The flow rate circulates in its corresponding flow electrode channel 91 and storage tank.

[0042] The key equipment required for the operation of the system are as follows: DC power supply, pH / conductivity multi-parameter tabletop meter, four-channel peristaltic pump and magnetic stirrer. -1Taking 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 portions of highly conductive brine mixtures.

[0043] To ensure sufficient sodium ion migration, the flow electrode was composed of 200 mL of 25 g L -1 The Na2SO4 solution was mixed by adding 30 g of analytical grade activated carbon powder and stored in the mobile electrode storage regeneration tank.

[0044] The flow electrode and high-conductivity saline mixture were heated at 30 ml min −1 The flow rate of the system circulates in its corresponding receiving collector. After the system runs stably for 10 minutes, a voltage of 1.2 V is applied for 120 minutes.

[0045] The mobile electrode is transported from the mobile electrode storage and regeneration tank to the mobile electrode inlet and outlet 11 of the support end plate 7 at the left end of the device through a pumping device, flows through the mobile electrode channel 91 on the surface of the graphite collector plate 9 at the left end of the device, and finally flows out through the mobile electrode inlet and outlet 11 of the support end plate 7 at the left end of the device and is transported back to the mobile electrode storage and regeneration tank. The mobile electrodes of the support end plate 7 and the collector plate 9 at the right end of the device have the same path through the device but in opposite directions. After the mobile electrodes at both ends flow out of the device, they are finally merged into the mobile electrode storage and regeneration tank for electrode regeneration, and the above process is repeated later.

[0046] The highly conductive brine mixture is formed by pre-treating seawater and pumping it into a seawater-conductive material premixing device for mixing, and then being pumped from the seawater-conductive material premixing device into the desalination chamber and the concentration chamber respectively through a seawater-highly conductive material mixed solution pumping device. The highly conductive brine mixture in the desalination chamber is transported from the seawater-conductive material premixing device through a pumping device to the highly conductive brine mixture inlet and outlet 12 of the support end plate 7 at the left end of the device, flows through the highly conductive brine mixture channel 101 in the middle of the left end guide plate 10, flows out through the highly conductive brine mixture inlet and outlet 12 of the support end plate 7 at the left end, and finally flows into the highly conductive brine mixture solid-liquid separation device, and the above process is subsequently repeated. At the same time, during the experiment, the supporting software provided with the corresponding equipment is used to record the current response of the device and the pH and conductivity of the high-conductivity brine mixed liquid solid-liquid separation device at intervals of minutes. The NaCl concentration of the high-conductivity brine mixed liquid in the desalination chamber of the high-conductivity brine mixed liquid solid-liquid separation device is obtained using the conductivity-concentration relationship. The activated carbon slurry and fresh water are separated while the above device is running. The fresh water can enter the post-treatment system such as disinfection, and the activated carbon slurry is pumped into the seawater-conductive material premixing device through the pumping device to achieve the reuse of the activated carbon slurry. The high-conductivity brine mixed liquid on the other side of the support plate and the concentration chamber has the same path through the device but in opposite directions. The conductive brine mixed liquid in the concentration chamber is transported to the seawater-conductive material premixing device after the water is discharged, so as to achieve the reuse of concentrated wastewater and activated carbon slurry.

[0047] Comparative Example In this example, an FCDI control group was set up, that is, except that no activated carbon powder was added to the intermediate solution chamber of the device, other experimental conditions were consistent with the 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 FCDI control group decreased by 3.9 g / L -1 The full-channel flow electrode capacitive deionization has a salt removal concentration that is about 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 having an excellent desalination effect.

[0048] The above specific implementation modes are preferred embodiments of the present invention and cannot be used to 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 protection scope 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 high-conductivity salt water mixture, wherein the high-conductivity salt water mixture is a mixture of pre-treated seawater and a high-conductivity 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 membrane based on full-channel flow electrode capacitive deionization according to claim 1 is 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 membrane 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 membrane 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 membrane 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 membrane 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 membrane 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 mixed solution in the first solution chamber (3) flows in a top-in and bottom-out manner, while the highly conductive salt water mixed solution in the second solution chamber (5) flows in a bottom-in and top-out manner.

8. The device for enhancing ion mass transfer across membrane 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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