KR102258137B1 - Reverse electrodialysis with opentype endplate - Google Patents

Abstract

A reverse electrodialysis salinity difference power generation apparatus including an open end plate without using an electrode spacer is provided. The reverse electrodialysis salt difference power generation device is a cell stack in which a plurality of cells are stacked repeatedly with an anion exchange membrane and a cation exchange membrane, and a spacer for supplying an outermost solution and a shielding membrane are sequentially stacked on both outer sides of the cell stack. A membrane stack, an anode provided at one end of the membrane stack, a first end plate on which the anode is placed and a connector for connection between the anode and an external node is inserted, and is stacked together with the membrane stack to form an anode chamber , A cathode provided at the other end of the membrane stack, a second end plate on which the cathode is placed and a connector for connection between the cathode and an external node is inserted, and is stacked together with the membrane stack to constitute a cathode chamber. And, the first end plate includes an inlet and an outlet for injection and discharge of the electrode solution supplied to the anode chamber, a plurality of pillars to provide a plurality of open spaces are formed on one surface, the pillar The upper surface of is an end plate in direct contact with the anode.

Description

Reverse electrodialysis salinity differential generator with open end plate{REVERSE ELECTRODIALYSIS WITH OPENTYPE ENDPLATE}

The present description relates to a reverse electrodialysis salinity differential power generator (hereinafter, RED) including an end plate, and more particularly, it maintains high power without interference from bubble resistance and suppresses rapid pH change around the shielding membrane. It relates to a RED comprising an open end plate.

REVERSE ELECTRODIALYSIS (RED) is a sustainable energy system that generates electricity from salinity differences without _{thermal pollution or CO 2 emission.} The theoretical energy generated in RED ^{is estimated to be 1.7 MJ when 1 m 3} of seawater is mixed with the same amount of river water. In the RED stack, a spacer that guides the flow of the feed solution is mounted between the cation exchange membrane (CEM) and the anion exchange membrane (AEM), and these cells are repeatedly stacked. As the positive and negative ions diffuse through the ion exchange membrane due to the difference in concentration, the generated membrane voltage is converted into electrical energy through an electrochemical reaction at the electrode. The membrane voltage increases in proportion to the number of cells, so a large RED with hundreds of cells produces a voltage of tens of volts. 1 is a schematic diagram of a RED disclosed in a conventional paper or patent.

Conventional RED is a cell stack 10 in which unit cells composed of a cation exchange membrane (CEM) and an anion exchange membrane (AEM) that are alternately arranged with each other are repeatedly stacked, and the outermost supply solution on both outer sides of the cell stack 10, respectively. A membrane spacer 20, a gasket 22 and a shielding membrane 30 for supplying (OFS, Outermost Feed Solution) are provided to form a membrane stack 40. Each electrode spacer 40 is disposed between the shielding membrane 30 and the mesh-type anode 50 or the mesh-type cathode 60, and a connector for connection between the electrode 50 and an external node (not shown) ( When the 80 is finally sealed by the inserted end plate 70, the anode chamber 55 and the cathode chamber 65 are completed.

In the case of the conventional RED, the supply solution flows through a narrow flow path made of a porous structure of the electrode spacer 40 and the mesh electrode 50 or 60. Since the fluid passes through a narrow flow path, in addition to the reversible redox reaction, when a water redox reaction occurs, a local pH change may be very large.

Specifically, in the anode 50 of the anode chamber 55 of the RED, hydrogen ions, electrons, and oxygen may be generated by an oxidation reaction of water as shown in Formula 1.

[Formula 1]

^{_{H 2 O → 2H + + 2e}} - + 1 / 2O 2 ( anode)

When electrons generated in the anode 50 are supplied to the cathode 60 of the cathode chamber 65 through a load (not shown), hydrogen and hydroxide ions may be generated in the cathode 60 by a reduction reaction of water as shown in Formula 2. have.

[Formula 2]

2H ₂ O + _{2e- → H 2} ↑ + 2OH- (cathode)

Accordingly, in the anode chamber 55, the pH decreases due to hydrogen ions, and in the cathode chamber 65, the pH increases due to hydroxide ions.

The rapid change in pH due to the narrow flow path can be confirmed by a blue reaction of ferricyanide occurring in the anode 60 and the shielding membrane 30 as illustrated in FIG. 2. Ferricyanide/ferrocyanide is a material used as an electrode solution. When the pH decreases, the ferricyanide used as the electrode solution is decomposed and combined with other ferricyanide that has not been decomposed to form a blue precipitate.

As illustrated in FIG. 2, it can be seen that the pH of the anode 60 and the shielding membrane 30 on the anode side have turned blue, and thus the pH is rapidly decreased due to the narrow flow path, and as a result, a blue reaction occurs.

3 shows that the spacer 40 on the anode side is corroded due to a rapid decrease in pH due to the narrow flow path.

Referring back to FIG. 1, in order to generate a high voltage, the number of cells constituting the cell stack is increased to more than a few hundred, and bubbles 2 are formed due to water electrolysis occurring in the RED, and thus generated bubbles ( 2), resulting in bubble resistance. In particular, when the porous electrode spacer 40 is used, bubbles are inserted into the pores of the porous electrode spacer 40 to further increase the problem of increasing resistance. As a result, a phenomenon in which the output of the RED is deteriorated occurs.

On the other hand, when an electrode solution containing ferricyanide/ferrocyanide is used as an electrode solution supplied to the anode chamber 55 and the cathode chamber 65, these redox papers are transferred to the cell stack 10. In order to prevent movement, the RED may be equipped with a cation exchange membrane (CEM) as the shielding membrane 30 as illustrated in FIG. 4. According to this arrangement of the ion exchange membrane, seawater (SEA WATER) is used as the outermost feed solution (OFS) of the portion adjacent to the cathode chamber 65, and the outermost feed solution (OFS) is used as the anode chamber 55. Freshwater (RIVER WATER) can be supplied

However, the seawater supplied to the OFS of RED contains a lot of polyvalent ions (Mg ^{2 +} , Ca ^{2 +,} etc.), so the polyvalent ions move into the cathode chamber 65 through the cation exchange membrane (CEM) and It may produce a precipitate (Mg (OH) ₂ or Ca (OH) ₂₎ by reaction with ^- hydroxyl ion (OH). In addition, when the RED is operated for a long time, such inorganic fouling 80 continuously proceeds to prevent the smooth flow of the electrode solution and to cause a pressure loss, thereby reducing the efficiency of the RED. The generated precipitate is formed on the mesh-type electrode constituting the cathode 60, the porous structure of the electrode spacer, and the surface of the shielding membrane film. 5 shows a photograph of a mesh-type electrode in which a precipitate is sandwiched. As a result, since the electrode solution does not flow smoothly in the cathode chamber 65, the pressure rises, and the surface area of the electrode exhibiting electrochemical activity gradually decreases, resulting in a decrease in output.

^{Meanwhile, as shown in FIG. 6, when an electrode solution containing Fe 2 +/3+} redox couple is used as the electrode solution supplied to the anode chamber 55 and the cathode chamber 65, these In order to prevent the redox species from moving to the cell stack 10, the shielding membrane layer 30 may be formed of an anion exchange membrane (AEM). In such a structure of the membrane stack 40, fresh water is used as the OFS of the cathode chamber 65, and seawater is used as the OFS of the anode chamber 55. Therefore, the polyvalent ion precipitation problem occurring in the cathode chamber 65 side compared to the stack structure disclosed in FIG. 6 may be relatively reduced, but the selectivity of the anion exchange membrane (AEM) is not completely 100%. The polyvalent cation from the OFS seawater passes to the anode chamber 55, and the polyvalent cation moves toward the cathode chamber 65 by the circulation of the electrode solution, so that a precipitate may still be generated. Then, the cathode hydroxide ions produced in the chamber 65, the water reduction reaction (OH ^-) to pass through the shielding membrane film 30 should meet the multivalent ions (Ca ^{2 +,} Mg ^{2 +)} in the OFS form a precipitate. In addition, when the RED is operated for a long time, these deposits become inorganic fouling 80, which lowers the efficiency of the RED.

Prior literature that has been researched and developed until recently is a problem of power reduction due to damage to cathode, anode or shielding membrane due to rapid pH change due to narrow flow path, damage to cathode, anode, or electrode spacer due to polyvalent ion deposits, and bubble resistance. Did not file. Also, it does not present a solution to the problem of generating weapon fouling.

An object of the present disclosure is to provide an end plate for solving a sudden change in pH due to a narrow flow path, and a reverse electrodialysis salinity differential power generator including the same.

The present disclosure is to provide a reverse electrodialysis saline differential power generator for solving bubble resistance.

The present disclosure is to provide a reverse electrodialysis salt differential power generator for solving the problem of precipitation caused by polyvalent ions.

The reverse electrodialysis salinity difference generator according to the embodiments includes an open end plate. In the reverse electrodialysis salinity difference power generation device, a cell stack in which N unit cells consisting of an anion exchange membrane and a cation exchange membrane (N is 100 or more) are stacked, and a spacer for supplying an outermost solution and a shielding membrane are sequentially arranged on both outer sides of the cell stack Membrane stack formed by stacking the same, an anode provided at one end of the membrane stack, the anode is placed, and a connector for connecting the anode to an external node is inserted, and is stacked together with the membrane stack to constitute an anode chamber. A first end plate, a cathode provided at the other end of the membrane stack, the cathode is placed, and a connector for connecting the cathode and an external node is inserted, and a second end plate is stacked together with the membrane stack to constitute a cathode chamber. Includes an end plate, wherein the first end plate includes an inlet and an outlet for injecting and discharging the electrode solution supplied to the anode chamber, and a plurality of pillars is formed on one surface to provide a plurality of open spaces. And, the upper surface of the pillar is an end plate in direct contact with the anode.

Other specifics of aspects of the present invention are included in the detailed description below.

The open end plate of the reverse electrodialysis salinity difference generator according to the embodiments includes a plurality of open spaces without using an electrode spacer to allow free movement of bubbles generated by the water decomposition reaction of the electrode solution and the electrode solution. Since it provides a path, it is possible to easily solve the problem of bubble resistance and rapid pH change due to bubbles.

The reverse electrodialysis salinity differential power generator according to the embodiments includes an optimized stack configuration to effectively solve the precipitation phenomenon caused by polyvalent ions.

1 is a schematic diagram for explaining a problem due to an increase in resistance and a sudden change in pH due to bubbles occurring in a conventional RED.
2 is a photograph showing a cathode and a shielding membrane in which a blue reaction of ferricyanide occurs due to a rapid decrease in pH due to a narrow flow path.
3 is a photograph showing an electrode spacer corroded due to a rapid decrease in pH due to a narrow flow path.
4 is a schematic diagram of a RED for explaining the precipitation phenomenon of polyvalent ions under the condition of using ferricyanide/ferrocyanide redox species as an electrode solution.
5 is a photograph of a mesh-type electrode in which a precipitate of polyvalent ions is sandwiched.
6 is a schematic diagram of RED for explaining the precipitation of polyvalent ions under the condition of using ^{Fe 2 +/3+ redox species as an electrode solution.}
7 is a partial schematic diagram of a RED including an open end plate according to an embodiment.
8 is a plan view of the open end plate used in FIG. 7.
9 is a schematic diagram for explaining that the bubble resistance is removed by the end plate used in FIG. 7.
10 is a photograph showing that a change in pH is suppressed when an open end plate according to an embodiment is used.
11 is a plan view of a rhombic end plate according to another embodiment.
12 is a schematic diagram for explaining a combination of an outermost feed solution (OFS) and a shielding membrane constituting the RED together with an open end plate.
13 is a schematic diagram for explaining another combination of an outermost feed solution (OFS) and a shielding membrane constituting the RED together with an open end plate.
14 is a partial schematic diagram of an open RED according to another embodiment.
15 shows the results of measuring the output for a combination of different outermost solution (OFS) and electrode solution (ES) in the RED according to the comparative example.
16 shows the result of measuring the maximum output after removing the electrode spacer from the RED according to the comparative example.
FIG. 17 shows the results of comparing the maximum output of the case where only one of the cathode is used and the case where the open end plate is used for both the cathode and the anode with the maximum output of the comparative example.
18 is a graph showing the current value at Pmax.
19 is a graph showing a relationship between a flow rate and an output (W) in the RED according to the embodiment and the RED according to the comparative example.
20 is a graph showing a result of measuring resistance generated by BPM when BPM is applied as a shielding membrane for a cathode.
FIG. 21 is a SEM photograph of CEM, AEM, and BPM after applying a shielding membrane for a cathode, respectively, and confirming a precipitation state.
22 and 23 are graphs showing a relationship between an area and an output for determining an appropriate area when the area of the cathode is reduced.

Hereinafter, embodiments will be described in detail so that those of ordinary skill in the art can easily implement them. The embodiments may be implemented in various different forms, and are not limited to the specific embodiments described herein.

7 is a partial schematic diagram of a RED including an open end plate according to an embodiment, FIG. 8 is a plan view of the open end plate used in FIG. 7, and FIG. 9 is a bubble resistance by the end plate used in FIG. 7. It is a schematic diagram for explaining what is removed.

Referring to FIG. 7, an outermost feed solution (OFS) is supplied to the cell stack 110 in which N cells of the anion exchange membrane (AEM) and the cation exchange membrane (CEM) are stacked, and the outermost feed solution (OFS) on both sides of the cell stack 110. A membrane spacer 120, a gasket 122 and a shielding membrane 130 for supplying) are provided to form the membrane stack 140. The shielding membrane 130 and the anode 150 or the cathode 160 are placed in direct contact, and a connector 180 for connection between the anode 150 or cathode 160 and an external node (not shown) is inserted. When the final sealing is achieved by the end plate 170, each of the anode chambers 155 and the cathode chambers 165 are formed, and the RED is completed at the same time.

7 and 8, the end plate 170 according to an embodiment includes an inlet 171 and an outlet of an electrode solution (ES) at both upper and lower ends of the end plate 170. Include (outlet)(172). One surface of the end plate 170 is formed with a plurality of pillars 174 to provide a plurality of open spaces 176 to constitute the open end plate 170. When the RED is assembled under high pressure, the upper surface of the pillar 174 directly contacts the anode 150 or the cathode 160. The pillars 174 in direct contact with the anode 150 or the cathode 160 serve to support high pressure when fastening the membrane stack 140 and the end plate 170.

Since the plurality of open spaces 176 provide an open path through which bubbles generated by the water decomposition reaction of the electrode solution (see 2 in FIG. 1) and the electrode solution can move freely, rapid pH change can be suppressed. And, unlike the prior art, the RED according to an embodiment is an electrode spacer through which an electrode solution can flow between the shielding membrane 130 and the anode 150 or between the shielding membrane 130 and the cathode 160 (see 40 in FIG. 1). Do not use. Since the electrode spacer is not used, the problem of bubble resistance due to bubbles (see 2 in FIG. 1) can be easily solved.

As illustrated in FIG. 9, in the completely open portion 176 without the pillar 174, the fluid moves along the flow path (arrow 4) of the electrode solution. However, in the case of using the end plate 170 according to an embodiment, since the fluid flow is not disturbed, a sudden change in pH can be suppressed. That is, in the conventional RED described with reference to FIGS. 1 to 3, since the flow of the fluid is obstructed by the narrow flow path, the pH of the anode chamber decreases and the pH of the cathode chamber increases as the water redox reaction proceeds. On the other hand, in the case of an embodiment, since the open end plate 170 is used, the flow of the electrode solution is smooth, so even if the electrode reaction continues to occur, a sudden change in pH does not occur.

This can be seen from the photographs of the electrode and the end plate shown in FIG. 10. It can be confirmed through the blue reaction of ferricyanide that abrupt pH change is suppressed. A blue reaction does not occur in a completely open part (arrow display area) in which the pillars 174 are not above and below. On the other hand, in the upper and lower portions of the pillars 174 (circle display areas), the time for the air bubbles to stay below the pillars 174 becomes longer. As such, it can be seen that in the space above and below the pillar 174, the flow of the fluid is slowed and the pH change is relatively large, so that a blue reaction partially occurs.

Referring back to FIG. 7, the RED according to an embodiment is an electrode spacer through which an electrode solution may flow between the shielding membrane 130 and the anode 150 or between the shielding membrane 130 and the cathode 160 (40 in FIG. 1 ). Reference) is not used. In the case of using an electrode spacer (see 40 in FIG. 1) as in the prior art, it is a component inside the anode (see 50 in FIG. 1) or the cathode (see 60 in FIG. 1), so it is involved in the internal resistance of the RED. Therefore, the bubble resistance inserted into the electrode spacer (refer to 40 in FIG. 1) affects the internal resistance and eventually lowers the output of the RED. Accordingly, the RED according to an embodiment does not include an electrode spacer, and the shielding membrane 130 and the anode 150 or the shielding membrane 130 and the cathode 160 directly contact each other. The bubble resistance included in the internal resistance is considered only when it exists between the anode 140 and the cathode 160, and the bubbles flowing through the open end plate 170 exist outside the anode 150 or the cathode 160. Therefore, it does not affect the RED power.

11 is a plan view of a rhombic end plate according to another embodiment. As illustrated in FIG. 11, in order to reduce the retention time of fluid and air bubbles in the bottom portion of the pillar 174, it may be transformed into various shapes such as a rhombus shape. Gases generated by the electrode reaction are freely diffused to be discharged toward the outlet 172 of the electrode solution, and the collected hydrogen gas may be transferred to another platform and used as necessary. Other platforms that require hydrogen gas can be applied to various platforms such as fuel electricity and hydrogen charging stations.

12 is a schematic diagram for explaining a combination of the outermost supply solution (OFS) constituting the RED together with the open end plate 170 and the shielding membrane 130. As in the RED shown in Figs. 4 to 6, fresh water is applied to all the outermost feed solutions (OFS) in order to prevent precipitation of polyvalent ions. As fresh water, river water or tap water may be applied, and tap water having a lower polyvalent ion content may be more preferable. Since fresh water with a small polyvalent ion content is used, the shielding membrane 130 on the cathode chamber 165 side is an anion exchange membrane ( AEM). The shielding membrane 130 on the anode chamber 155 side is formed of a cation exchange membrane (CEM) to prevent the chlorine ions (Cl ^{−) of the OFS on the anode side from passing to the electrode solution.} Accordingly, it is possible to reduce the generation of chlorinated gas, which is a toxic substance, in the anode chamber 155. That is, it can be seen that the configuration of FIG. 6(a) in which the OFS on the cathode side uses fresh water with less polyvalent cations compared to seawater, and the shielding membrane uses AEM, and the OFS also uses fresh water is more suitable.

13 shows a case in which the bipolar membrane (BPM) 130 is applied as the shielding membrane 130 toward the cathode chamber 165. The BPM 130 is arranged so that water splitting can occur. Specifically, the cation exchange membrane 132 faces the anode 150 and the anion exchange membrane 134 faces the cathode 160.

The OH- ions produced in the BPM 130 are directed toward the cathode 160, and the H+ ions are directed toward the anode 150. Therefore, the pH of OFS can be kept low. Multivalent ions contained in OFS are difficult to move toward the electrode solution due to charge neutrality and positive charge of BPM. ^{The OH-} ions produced in the electrode solution are also difficult to move toward OFS due to charge neutrality and negative charge of BPM. As a result, even if the pH of the electrode interface is kept high due to the water reduction reaction of the cathode, the ^{crossover between the OH-} ions of the electrode solution and the polyvalent ions of the OFS ( crossover) can minimize the precipitation of polyions on the electrode surface or the ion exchange membrane surface.

14 is a partial schematic diagram of a RED including an open end plate according to another embodiment.

The outermost feed solution (OFS) is provided on both outer sides of the cell stack 110 and cell stack 110 in which N unit cells consisting of an anion exchange membrane (AEM) and a cation exchange membrane (CEM) are stacked. A membrane spacer 120 for supplying ), a shielding membrane 130A for an anode, and a shielding membrane 130C for a cathode are provided to form the membrane stack 140. The anode 150 is placed in direct contact with the shielding membrane 130A for the anode, and the cathode 160 is placed in direct contact with the shielding membrane 130C for the cathode.

When the connector 180 for connection between the anode 150 and an external node (not shown) is finally sealed by the inserted end plate 170, the anode chamber 155 is formed. In the anode chamber 155, an open end plate 170 as illustrated in FIG. 7 is applied because the main cause is a rapid decrease in pH due to the generation of air bubbles. It includes an inlet 171 and an outlet 172 of an electrode solution (ES) at both upper and lower ends of the open end plate 170. As described in FIG. 7, the open end plate 170 is formed with a plurality of pillars 174 to provide a plurality of open spaces 176 on one side to constitute the open end plate 170. When assembling the RED, the upper surface of the pillar 174 is in direct contact with the anode 150 because it is assembled under high pressure. The pillars 174 in direct contact with the anode 150 serve to support high pressure when fastening the membrane stack 140 and the end plate 170.

Since the plurality of open spaces 176 provide an open path through which bubbles generated by the water decomposition reaction of the electrode solution and the electrode solution can freely move, rapid pH changes can be suppressed. In addition, unlike the prior art, an electrode spacer (see 40 in FIG. 1) through which an electrode solution may flow between the anode shielding membrane 130A and the anode 150 is not used. Since the electrode spacer is not used, the bubble resistance problem caused by bubbles can be easily solved. It is preferable that the shielding membrane 130A for the anode is a cation exchange membrane (CEM).

In the cathode chamber 165, since precipitation of polyvalent ions is more important than the generation of bubbles, the cathode shielding membrane 130C is formed of a BPM including a cation exchange membrane 132 and an anion exchange membrane 134. It goes without saying that the open end plate 170 can be applied to the cathode chamber 165 as well as the anode chamber 155.

The BPM constituting the shielding membrane 130C for the cathode is arranged so that water splitting can occur. Specifically, the cation exchange membrane 132 faces the anode 150 and the anion exchange membrane 134 faces the cathode 160.

When BPM is applied as the cathode shielding membrane 130C, OH- ions produced in the BPM 130C are directed toward the cathode 160 and H+ ions are directed toward the anode 150. Therefore, the pH of OFS can be kept low. Multivalent ions contained in OFS are difficult to move toward the electrode solution due to charge neutrality and positive charge of BPM. OH- ions made in the electrode solution are also difficult to move toward OFS due to charge neutrality and negative charge of BPM. As a result, even if the pH of the electrode interface is kept high due to the water reduction reaction of the cathode, the crossover between the OH- ions of the electrode solution and the polyvalent ions of the OFS is prevented under the condition that water splitting of BPM occurs. By minimizing, the polyion precipitation phenomenon can be minimized.

When the cathode shielding membrane 130C is formed of BPM, since BPM is expensive, it is preferable to use a BPM of as small a size as possible. As the size of the BPM decreases, the area of the cathode in contact with the BPM must also decrease. According to the experimental results described below, when the minimum area of the cathode 160 is 60% of the area of the ion exchange membrane (cation exchange membrane or anion exchange membrane) constituting the membrane stack 140, the RED can be driven with little change in output. have. Accordingly, the size of the cathode 160 can be reduced to at least 60% of the area of the ion exchange membrane (CEM or AEM), and the area of the BPM 130C is also the same as the area of the cathode 160, thereby reducing the size. . That is, the usable area range of the cathode 160 may be 60 to 100% of the area of the ion exchange membrane.

In this case, the OFS supply membrane spacer 120 and the cathode shielding membrane to prevent the risk of leakage of the electrode (cathode) solution through the cathode shielding membrane 130C made of the end plate 170 and BPM. An additional membrane 138 may be further installed between (130C). As the additional membrane 138, a cation exchange membrane may be used. When the cation exchange membrane (CEM) is contacted with an additional membrane 138 immediately next to the cation exchange membrane 132 of the shielding membrane for the cathode (130C), protons formed by water splitting are transferred to the cation exchange membrane 138. It can spread smoothly and move inside the stack. Water separation can also occur effectively when the protons smoothly escape from the cathode shielding membrane 130C made of BPM.

In the case of the additional membrane 138, since the region 190 indicated by x is not directly connected to the cathode chamber 165, it can be free from the problem of precipitation by polyvalent ions, thereby fundamentally reducing the problem of precipitation by polyvalent ions. There is an advantage that can be made.

Hereinafter, preferred experimental examples are presented to aid the understanding of the present invention, but the following experimental examples are only illustrative of the present invention, and the scope of the present invention is not limited to the following examples.

Experimental Example: RED manufacturing including open end plate

The cell stack of the large-capacity RED system with 100 cells consisted of a cation exchange membrane (CEM-Type 1, Fujifilm, Netherlands) and an anion exchange membrane (AEM-Type 1, Fujifilm). Each film was such that the effective area is ^{453.6cm 2 (43.2 x 10.5 cm 2} ). A 0.1mm thick PTFE (Polytetrafluoroethyelene) gasket and a nylon spacer were inserted between the cation exchange membrane and the anion exchange membrane to complete the cell stack.

A spacer, a gasket, a shielding membrane, an electrode, and an open end plate illustrated in FIG. 7 were stacked on both ends of the cell stack, and then sealed by applying pressure to complete the RED.

The open end plate was made of acrylic with a thickness of 5 cm, and the height of the pillar was 5 mm, the width was 12 mm, and the length was 9 mm. As an electrode, a Ti mesh electrode having an effective area of 453.6 cm ² (43.2 x 10.5 cm ^{2) was used.}

Comparative Example: RED Manufacturing Including Closed End Plate

When configuring the RED system including the closed end plate (end plate in Fig. 1), unlike the experimental example, a porous electrode spacer was inserted between the shielding membrane and the electrode to construct the RED, and a platinum (Pt) coated Ti mesh electrode was used. Except that it was used, RED was prepared in the same manner as in the experimental example.

Measure performance

With OFS according to the example, artificial seawater was used by dissolving NaCl salt (Daejeong, Korea) in tap water, and tap water was used as fresh water (river water). The feed solution was fed using two peristaltic pumps at a flow rate of 0.75 cm/s. The performance was measured after power generation was performed using a solution in which 100 mM NaCl was dissolved in tap water as an electrode solution (ES).

The current-power (IP) curve was measured with a scan rate of ^{40 mV s -1} using a Potentiostat (ZIVE SP2, WonaTech, Korea).

15 shows the results of measuring the output for a combination of different outermost solution (OFS) and electrode solution (ES) in the RED according to the comparative example.

When the electrode solution is artificial seawater (conductivity is 50mS/cm), a high output is measured regardless of the conductivity of the outermost solution (OFS). However, when both the outermost solution (OFS) and the electrode solution are tap water, the output decreases significantly, so that the output of OFS(river)/ES(river) is based on OFS(sea)/ES(sea). It decreased by about 16%. As such, it can be predicted that the reason that the result opposite to the assumption for a general electrode system is due to the bubble resistance in the electrode spacer.

16 shows the result of measuring the maximum output after removing the electrode spacer from the RED according to the comparative example.

As a result of removing the electrode spacers, it can be seen that the output is restored to the highest value. It can be seen that the recovered value is the same as the maximum output under the condition of OFS(sea)/ES(sea). From this result, it can be seen that the resistance due to bubbles generated due to the structure of the electrode spacer has a very large influence on the total resistance.

Referring to Table 1 below, when an electrode spacer was used, the internal resistance was calculated as 18 ohm. On the other hand, when the electrode spacers are removed, it can be seen that the internal resistance decreases by about 30% to 12 ohms.

OFS at cathode and anode Electrode solution (ES) Closed
End plate Closed end plate without electrode spacers River River 18ohm 12.05ohm

Fig. 17 shows the results of comparing the maximum output of the case where only one of the cathode is used and the case where the open end plate is used for both the cathode and the anode with the maximum output of the comparative example. P_max increased to 70W when an open end plate without electrode spacers is on the cathode and a sealed end plate with electrode spacers is on the anode. When an open end plate without electrode spacers was present at both the cathode and anode, the P_max reached nearly 80W. From this, it can be seen that when the electrode spacer is removed and the open end plate is applied, a maximum output similar to the output in the case of OFS(sea)/ES(sea) is measured. That is, it can be seen that the bubble resistance can be completely removed by removing the electrode spacer and using the open end plate. In addition, in the case of OFS(sea)/ES(sea) of the same output, a problem due to a polyvalent ion precipitation problem and a pH change due to a narrow flow path is generated, but the embodiment (OFS(river)/ES(river) + open end plate) In this case, there are no polyvalent ion precipitation problems and damage to the RED components due to pH changes. 18 is a graph showing the current value at Pmax. It can be seen that the current value when the open end plate is applied to both the cathode and the anode is 25% higher than when the closed end plate is applied to both the cathode and anode.

Table 2 below shows the results of measuring the internal resistance values in each case.

OFS at cathode and anode Electrode solution (ES) Closed
End plate Open type
End plate River River 18 12.79 River sea water 14.7 12.68

From the results of Table 2, it can be seen that the resistance value decreases when an open end plate that does not use an electrode spacer is used. That is, it can be seen that the bubble resistance can be effectively reduced when an open end plate that does not use an electrode spacer is used.

19 is a graph showing a relationship between a flow rate and an output (W) in the RED according to the embodiment and the RED according to the comparative example. Table 3 shows the net power calculated and described.

Sealed end plate Open end plate Flow rate(cm/S) Net Power (W) Net Power Density(W/m ² ) Flow rate(cm/S) Net Power (W) Net Power Density(W/m ² ) 0.74 35.10 0.387 0.82 50.76 0.559

From the results of Fig. 19 and Table 3, it can be seen that when the open end plate is used, the net power is increased by 44% compared to the closed end plate. 20 is a graph showing a result of measuring resistance generated by BPM when BPM is applied as a shielding membrane for a cathode.

As illustrated in FIG. 14, a current-power curve (ip curve) created after measuring voltage and current while changing resistance for the case of forming a BPM and a case of forming a CEM for the cathode shielding membrane is shown in FIG. 20 Is shown in. Referring to FIG. 20, it can be seen that when BPM is used, the output is reduced by about 7% compared to when AEM is used. Since a minimum voltage of about 600 mV at which water splitting occurs in the BPM is additionally required, the required minimum voltage at which water splitting occurs is subtracted from the membrane voltage produced at 100 cells. As a result, the actual stack voltage across the electrode becomes slightly smaller and the output decreases. In a large RED stack of hundreds of cells, the film voltage is much larger, so the proportion of the voltage required by the BPM can be very small. Therefore, the BPM resistor can be neglected in a large stack. Therefore, it can be confirmed that even if the BPM is applied as a shielding membrane for the cathode to solve the problem of precipitation of polyvalent ions, there is no problem of output degradation due to BPM resistance.

When the cathode shielding membrane is formed of AEM, CEM, and BPM, OFS is applied in seawater (2mS/cm) and the current-power curve (ip curve) is measured 10 times in a row. Afterwards, the precipitation conditions on both sides of each shielding membrane were confirmed and compared through SEM and EDS.

The results are shown in Tables 4 to 6 below.

Element
CEM front (cathode side) CEM back (anode side) Weight% Atomic% Weight% Atomic% C 21.27 29.05 39.32 47.94 N 12.93 13.52 O 54.24 55.60 35.09 32.11 Na 1.69 1.21 2.92 1.86 Mg 15.64 10.55 1.14 0.68 S 6.45 3.30 8.15 3.72 Ca 0.70 0.29 0.46 0.17 TOT 99.99 100 100.01 100

Element
AEM front (cathode side) AEM back (anode side) Weight% Atomic% Weight% Atomic% C 65.99 73.87 N 9.82 9.43 5.56 7.75 O 16.29 13.69 56.51 68.99 Mg 7.87 6.32 Al 1.00 0.72 Si 0.22 0.10 1.41 0.98 Cl 7.68 2.91 27.65 15.23 TOT 100 100 100 99.99

Element
BPM front (cathode side) BPM back (anode side) Weight% Atomic% Weight% Atomic% C 33.99 54.26 84.02 89.45 O 23.13 27.71 10.82 8.64 Na 1.61 1.34 Mg 0.20 0.10 S 4.29 2.56 0.42 0.17 Cl 21.48 11.62 4.54 1.64 Sn 15.51 2.50 TOT 100.01 99.99 100 100

Referring to the results of Tables 4 to 6 and FIG. 21, it can be seen that in the case of CEM, a large amount of precipitate is formed on the front side (front, cathode side) and the back side (back, anode side) in the case of AME. On the other hand, in the case of BPM, it can be seen that a very small amount of sediment is formed on the back side (anode side). Therefore, it can be seen that by applying BPM, precipitation due to polyvalent ions can be greatly reduced.

22 and 23 are graphs showing a relationship between an area and an output for determining an appropriate area when the area of the cathode is reduced.

The membrane stack was composed of an ion exchange membrane having an area of 440.84 cm2, and the areas of the cathode were changed to 257.5 cm2, 250 cm2, 219.6 cm2, and 61 cm2, respectively, and the change in output was confirmed. The results are shown in Figs. 22 and 23.

It can be seen from FIGS. 22 and 23 that the output reduction rate is only 3% when a cathode having an area corresponding to 58% of the area of the ion exchange membrane is used. This is because the contribution of electrode resistance decreases as the number of cells increases, so that the output can be maintained even if the area decreases. In conclusion, it can be seen that when a cathode with an area of at least 60% of the area of the ion exchange membrane is used, there is little reduction in output, and the area of use of BPM can be reduced by that amount, thereby reducing the manufacturing cost of RED.

Although the experimental example has been described above, the scope of the rights is not limited thereto. The implementation form can be implemented in various ways within the scope of the detailed description of the invention and the accompanying drawings, and it is natural that this also belongs to the scope of the rights.

Claims (11)

A cell stack in which N unit cells consisting of an anion exchange membrane and a cation exchange membrane (N is 100 or more) are stacked, and a spacer for supplying an outermost solution and a shielding membrane are sequentially stacked on both outer sides of the cell stack;
An anode provided at one end of the membrane stack;
A first end plate on which the anode is placed, a connector for connection between the anode and an external node is inserted, and is stacked together with the membrane stack to form an anode chamber;
A cathode provided at the other end of the membrane stack; And
And a second end plate on which the cathode is placed and a connector for connection between the cathode and an external node is inserted, and is stacked together with the membrane stack to constitute a cathode chamber,
The first end plate includes an inlet and an outlet for injecting and discharging the electrode solution supplied to the anode chamber, and a plurality of pillars for providing a plurality of open spaces are formed on one surface thereof, and an upper surface of the pillar Is an end plate in direct contact with the anode,
The shielding membrane adjacent to the cathode is an anion exchange membrane,
The shielding membrane adjacent to the anode is a cation exchange membrane. The method of claim 1,
The cathode and the anode, respectively, the reverse electrodialysis salinity difference power generation device in direct contact with the shielding membrane. The method of claim 1,
The second end plate includes an inlet and an outlet for injecting and discharging the electrode solution supplied to the cathode chamber, and a plurality of pillars to provide a plurality of open spaces are formed on one surface thereof, and an upper surface of the pillar Is an end plate in direct contact with the cathode. delete The method of claim 1,
The outermost supply solution is fresh water reverse electric dialysis salinity difference power generation device. A cell stack in which N unit cells consisting of an anion exchange membrane and a cation exchange membrane (N is 100 or more) are stacked, and a spacer for supplying an outermost solution and a shielding membrane are sequentially stacked on both outer sides of the cell stack;
An anode provided at one end of the membrane stack;
A first end plate on which the anode is placed, a connector for connection between the anode and an external node is inserted, and is stacked together with the membrane stack to form an anode chamber;
A cathode provided at the other end of the membrane stack; and
And a second end plate on which the cathode is placed and a connector for connection between the cathode and an external node is inserted, and is stacked together with the membrane stack to constitute a cathode chamber,
The first end plate includes an inlet and an outlet for injecting and discharging the electrode solution supplied to the anode chamber, and a plurality of pillars for providing a plurality of open spaces are formed on one surface thereof, and an upper surface of the pillar Is an end plate in direct contact with the anode,
The shielding membrane adjacent to the cathode is a bipolar membrane,
The cation exchange membrane of the bipolar membrane faces the anode,
The anion exchange membrane of the bipolar membrane is a reverse electrodialysis salinity difference generator facing the cathode. The method of claim 6,
The minimum area of the cathode is 60-100% of the area of the ion exchange membrane constituting the cell stack. The method of claim 7,
The cathode and the bipolar membrane are the same area of the reverse electrodialysis salinity difference power generation device. The method of claim 6,
The shielding membrane adjacent to the anode is a cation exchange membrane. The method of claim 6,
The outermost supply solution is fresh water reverse electric dialysis salinity difference power generation device. The method of claim 6,
The second end plate includes an inlet and an outlet for injecting and discharging the electrode solution supplied to the cathode chamber, and a plurality of pillars to provide a plurality of open spaces are formed on one surface thereof, and an upper surface of the pillar Is an end plate in direct contact with the cathode.

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