JP6318678B2 - Ion exchange membrane electrolytic cell - Google Patents

Description

The present invention relates to a cathode current collector and an opening in an ion exchange membrane method electrolytic cell comprising a cathode chamber, a cathode current collector, a cathode having an opening, an ion exchange membrane, an anode having an opening, and an anode chamber. parts between a cathode with a metallic coil body packing density is less than 0.14 g / cm ³ or more 0.28 g / cm ^3, or has an elastic cushion mat composed of the metal coil body, The present invention relates to an ion exchange membrane method electrolytic cell that can be used for electrolysis of an aqueous alkali metal chloride solution or the like.

  Among the electrolysis of alkali metal chloride aqueous solutions, the electrolysis industry, represented by salt electrolysis, which has the largest output, is a typical power-intensive industry. In countries with high power costs, such as Japan, the power cost is high. Reduction is an important issue.

  So far, salt electrolysis in Japan has achieved energy cost reduction of about 40% in about 25 years due to the energy saving that is not relaxed by the ion exchange membrane method, but further reduction is required.

  In order to contribute to such a power reduction, in an ion exchange membrane method electrolytic cell used for salt electrolysis, the inter-electrode voltage of the electrolyte solution can be reduced by bringing the anode, the ion exchange membrane and the cathode into close contact or at least as close as possible. Although the electrolysis voltage is reduced by reducing the electrolysis voltage, in a large electrolytic cell with an electrolysis electrode area of several square meters, the anode, ion exchange membrane and cathode are in close contact with each other, and the anode-ion It was extremely difficult to set the distance between the exchange membrane and the cathode to a predetermined value.

  As a means to reduce the distance between the electrodes, the distance between the electrodes or the distance between the electrodes and the electrode current collector, or to maintain a substantially constant value, the anode, the ion exchange membrane and the cathode are uniformly adhered. An electrolytic cell in which an elastic material is interposed between bodies is known.

  Known elastic materials include non-rigid materials such as woven fabrics, non-woven fabrics, and nets of metal thin wires, and rigid materials such as leaf springs.

  Non-rigid material, when it is excessively pressed from the electrode in the opposite direction across the ion exchange membrane after being attached to the electrolytic cell, the electrode will be recessed at that part and the distance between the electrodes will become uneven, or non-rigid There is a disadvantage that the thin wire of the material penetrates between the openings of the cathode or the anode and pierces the ion exchange membrane and breaks the ion exchange membrane. Also, in rigid materials such as leaf springs, the cathode or anode mesh is deformed and pressed strongly against the ion exchange membrane, the ion exchange membrane is damaged, or plastic deformation occurs in the cathode or anode, and the cathode or anode is reused. There was a drawback that it became impossible.

  As described above, the ion exchange membrane method electrolytic cell having a structure in which the anode, the ion exchange membrane, and the cathode are in close contact with each other or at least as close as possible is characterized by the fact that the electrode is uniformly adhered to the ion exchange membrane. In order to avoid damage to the exchange membrane and to keep the distance between the positive and negative electrodes to a minimum, it is a structure in which at least one of the electrodes can move freely in the interelectrode distance direction. The holding pressure can be adjusted.

  Examples of the elastic material include a knitted fabric or woven fabric made of metal wire, or a laminate of these, or a shape that is three-dimensionally knitted or three-dimensionally knitted and then subjected to undulation processing, and metal fibers. There are non-woven fabrics, coil springs (springs), leaf springs, etc., all of which have some spring elasticity.

  On the other hand, in an industrial electrolytic cell such as a salt electrolytic cell, a leaf spring or a metal mesh may be used to smoothly supply power from the electrode current collector to the electrode.

  However, as described above, since the leaf spring and the metal net are rigid bodies, the ion exchange membrane may be damaged, the deformation rate may be small, and sufficient electrical connection may not be obtained.

  In order to eliminate such drawbacks, a metal coil body was mounted between the cathode and the cathode end plate in place of the metal mesh, and the cathode was pressed uniformly in the direction of the diaphragm to bring the electrode and the ion exchange membrane into close contact. An ion exchange membrane method electrolytic cell is disclosed (for example, see Patent Document 1).

  Since this metal coil body has a very small coil wire diameter and a high deformation rate, the electrode and the ion exchange membrane can be sufficiently adhered, and the distance between the electrode and the ion exchange membrane is constant and stable. The electrolytic cell can be operated.

  Further, in an ion exchange membrane method electrolytic cell composed of a cathode chamber, a cathode current collector, a cathode, an ion exchange membrane, an anode, and an anode chamber, an elastic cushion material configured by winding a metal coil body, Disclosed is an ion exchange membrane electrolytic cell characterized in that it is housed between a hydrogen generating cathode and a cathode current collector and / or between an anode and an anode current collector, or between a hydrogen generating cathode and a cathode partition wall and / or between an anode and an anode partition wall. (For example, refer to Patent Document 2).

  In this ion exchange membrane electrolytic cell, an elastic cushion material is provided by winding a metal coil body between an anode or a hydrogen generation cathode and each current collector so that power supply to each electrode occurs reliably. Therefore, more stable electrolyzer operation becomes possible.

Japanese Examined Patent Publication No. 63-53272 Japanese Patent No. 3860132

  On the other hand, in the metal coil bodies disclosed so far, the adhesion is still insufficient, or conversely, the adhesion between the cathode and the metal coil body is high, and uniform power feeding from the cathode current collector to the cathode is possible. Although performed sufficiently, the density of the metal coil body is too high, and the gas generated from the cathode is not smoothly discharged from the opening of the cathode current collector through the metallic coil body to the inside of the cathode chamber. The rising rate of the hydrogen gas flow becomes insufficient, the causticity in the vicinity of the ion exchange membrane is retained, and the concentration locally increases. As a result, the ion exchange membrane may be deteriorated.

  Therefore, the metal coil body is interposed between a cathode and a cathode current collector having an opening, and the cathode is uniformly pressed in the direction of the ion exchange membrane so that the electrode and the ion exchange membrane are in close contact with each other. An object of the present invention is to propose an ion exchange membrane method electrolytic cell in which the above-described ion exchange membrane is unlikely to deteriorate.

As a result of diligent investigations on the above problems, the inventors conducted an ion exchange comprising a cathode chamber, a cathode current collector, a cathode having an opening, an ion exchange membrane, an anode having an opening, and an anode chamber. in the membrane process electrolytic cell between the cathode having a cathode current collector and the opening, the metal coil body packing density is less than 0.14 g / cm ³ or more 0.28 g / cm ^3, or the metal coil When an ion exchange membrane electrolytic cell having an elastic cushion mat composed of a body is used, the filling rate of the metal coil body is optimized so that the rate of gas flow rising to the upper part of the cathode chamber is sufficient. In addition, the inventors have found that the power supply to the cathode is uniformly performed with sufficient adhesion between the electrode and the ion exchange membrane.

  Specifically, since sufficient power is supplied from the cathode current collector to the cathode, the electrolysis voltage is kept low, and the gas generated from the cathode is transferred to the elastic cushion mat (or the elastic cushion mat and the cathode). Is smoothly discharged to the inside of the cathode chamber through the current collector), and a sufficient upward flow to the upper portion of the cathode chamber is secured, so that the caustic concentration in the cathode chamber becomes more uniform. Therefore, the deterioration of the ion exchange membrane is suppressed, and the electrolytic cell can be operated stably for a long time.

  Hereinafter, the present invention will be described in detail.

  The electrolytic reaction carried out in the cathode chamber of the ion exchange membrane method electrolytic cell of the present invention is preferably a production reaction of alkali hydroxide (sodium hydroxide) and hydrogen gas by chloralkali (salt) electrolysis.

  In the following description, an example of salt electrolysis will be described.

In the present invention, a metal coil body packing density is less than 0.14 g / cm ³ or more 0.28 g / cm ³ between the cathode and the cathode current collector of an ion-exchange membrane method electrolyzer, or the metallic An elastic cushion mat constructed by winding a coil body is installed. As a result, sufficient power is supplied from the cathode current collector to the cathode, and hydrogen gas generated from the cathode having an opening is transferred to the elastic cushion mat (or the elastic cushion mat and the cathode current collector). ) Is smoothly discharged to the inside of the cathode chamber, a sufficient upward flow is secured to the upper part of the cathode chamber, the caustic concentration in the cathode chamber becomes uniform, and the caustic concentration in the vicinity of the ion exchange membrane does not increase locally. Therefore, deterioration of the ion exchange membrane is suppressed.

In the case of an elastic cushion mat formed by winding a metal coil body having a packing density of less than 0.10 g / cm ³ , since sufficient adhesion between the cathode and the ion exchange membrane cannot be obtained, an electrolytic voltage is set. It cannot be kept low.

In the case of an elastic cushion mat formed by winding a metal coil body having a packing density of 0.10 g / cm ³ or more and less than 0.14 g / cm ³ , the adhesion between the cathode and the ion exchange membrane is still insufficient. In addition, since a sufficient upward flow of hydrogen gas to the upper part of the cathode chamber is not ensured, it is considered that the caustic concentration in the vicinity of the ion exchange membrane is locally increased and the ion exchange membrane is easily deteriorated.

In the case of a cushion mat formed by winding a metal coil body with a packing density exceeding 0.28 g / cm ³ , sufficient adhesion between the cathode and the ion exchange membrane can be obtained, and the electrolytic voltage can be kept low. However, since the packing density of the metal coil body is too high, it becomes difficult to move the gas generated from the cathode within the metal coil body or the elastic cushion mat, and hydrogen gas is not smoothly discharged into the cathode chamber, and the cathode Since a sufficient upward flow of hydrogen gas is not ensured in the room, the caustic concentration in the vicinity of the ion exchange membrane is locally increased, and the ion exchange membrane is easily deteriorated.

  This metal coil body is made of nickel, nickel alloy, stainless steel, or copper, which has good corrosion resistance against caustic soda and hydrogen gas. It is obtained by processing the manufactured wire into a spiral coil by roll processing. Among these metal coil bodies, nickel or nickel alloy having excellent corrosion resistance against caustic soda and hydrogen gas is preferable. The cross-sectional shape of the wire is preferably a circle, an ellipse, a rectangle with round corners, or the like. In order to prevent damage to the ion exchange membrane, a cross-sectional shape with sharp corners such as a triangle or rectangle is not desirable. For example, when a nickel wire (NW2201) having a diameter of 0.17 mm is rolled, a square wire having a cross-sectional shape of about 0.05 mm × 0.5 mm is formed into a round rectangle, and a coil wire having a winding diameter of about 6 mm is obtained. The coil wire can be preferably used.

  In the present invention, the metal coil body itself is used, or it is used as an elastic cushion mat formed by winding a metal coil body around a corrosion-resistant frame.

  That is, since the metal coil body has a high deformation rate, it is difficult to handle the metal coil itself, and it is often difficult to install it at a predetermined location of the electrolytic cell as intended by the operator. Furthermore, since it is easily deformed (the strength is insufficient), even if it is once installed at a predetermined location of the electrolytic cell, it is displaced by the electrolytic solution or generated gas in the electrolytic cell, and it becomes difficult to uniformly adhere each member. There is.

  For example, an elastic cushion obtained by winding one or a plurality of metal coil bodies so as to obtain a substantially uniform density between two opposing frames of four rectangular rods of a rectangular corrosion resistant frame. The mat can be easily assembled because the assembly work is outside the electrolytic cell, and the obtained elastic cushion material is used to connect the target electrode in the electrolytic cell and the attached current collector when the electrolytic cell is assembled. The elastic cushion mat itself may be mounted so as to be electrically connected, and the elastic cushion mat itself is not deformed so as to hinder the assembly due to the strength of the corrosion-resistant frame, so that it can be easily installed at a predetermined location.

  In this elastic cushion mat, two layers of metal coil bodies are usually laminated on the left and right sides of the corrosion-resistant frame. However, since the metal coil bodies themselves are easily deformed, adjacent coils are meshed with each other in a comb-like shape. The top is a single layer. The elastic cushion mat thus obtained has an appearance like a metal scrub for dishwashing.

  The diameter of the metal coil body (the apparent diameter of the coil) is usually reduced to 10 to 70% by mounting in the electrolytic cell, and elasticity is generated. This elasticity makes the cathode and the cathode current collector elastic. It is easy to connect and feed power to the electrode. If a metal coil body having a small wire diameter is used, the number of contact points between the cathode or the cathode current collector and the elastic cushion mat is inevitably increased, and uniform contact is possible. Since the shape of the elastic cushion mat after being mounted on the electrolytic cell is held by the corrosion-resistant frame, the elastic cushion mat is hardly subjected to plastic deformation and can be reused in most cases even when the electrolytic cell is disassembled and reassembled.

  When assembling the ion exchange membrane electrolytic cell of the present invention, a metal coil body or an elastic cushion mat formed by winding a metal coil body around a corrosion-resistant frame is positioned between the cathode and the cathode current collector. Thereafter, when assembled as usual, an electrolytic cell in which the elastic cushion mat is held at a predetermined position can be obtained.

  In order to perform salt electrolysis using the ion exchange membrane electrolytic cell having the above-described configuration, while supplying an electrolyte solution of a saline solution to the anode chamber and water or a diluted caustic soda solution to the cathode chamber, Energize. In the cathode in which the metal coil body or elastic cushion mat of the present invention is held between the cathode current collector, due to the high strength and toughness of the elastic cushion mat, the adhesion of the cathode-ion exchange membrane is sufficient, Since the close contact state is maintained for a long time, the ion exchange membrane is not mechanically damaged by the cathode, and the cathode is not deformed and power supply is not insufficient, so that the caustic soda can be stably maintained for a long time. Can be manufactured with high efficiency.

  The cathode used in the ion-exchange membrane electrolytic cell of the present invention smoothly discharges the product from the cathode into the cathode chamber through the elastic cushion mat and the cathode current collector having the opening on the back surface. For this purpose, a cathode having an opening in the cathode itself, for example, an opening made of an expanded metal mesh can be used.

  As for the material of the cathode, it is possible to appropriately select and use a cathode of a material used for normal salt electrolysis. For example, platinum of a platinum and a transition metal element on a conductive substrate is used. An electrode for hydrogen generation formed by supporting an alloy (see Japanese Patent Application Laid-Open No. 2005-330575) is less affected by poisoning due to iron ions in the electrolyte, and increases or supports hydrogen overvoltage even during operation, starting and stopping. It is preferable because it is an electrode for hydrogen generation that is excellent in durability and does not drop off.

  The cathode current collector having an opening used in the ion exchange membrane method electrolytic cell of the present invention is not particularly limited. For example, a cathode current collector made of nickel mesh can be used.

  The anode used in the ion exchange membrane electrolytic cell of the present invention smoothly discharges the product from the anode to the inside of the cathode chamber through the elastic cushion mat and the cathode current collector having an opening on the back surface. For this purpose, the anode itself also has an opening. For example, an anode having an opening made of an expanded metal mesh can be used.

  Further, regarding the material of the anode, it is possible to appropriately select and use an anode of a material used in normal salt electrolysis. For example, a platinum group oxide is supported on a conductive substrate. A chlorine generating electrode, usually an anode called DSE, is preferable because it is a chlorine generating electrode that is excellent in durability and does not increase in chlorine overvoltage or drop off during loading, starting and stopping.

  Moreover, about an ion exchange membrane, the normal ion exchange membrane used for salt electrolysis can be used.

  Examples of the elastic cushion material that can be used in the ion exchange membrane electrolytic cell according to the present invention will be described with reference to FIGS. 1 is a plan view of a corrosion-resistant frame, FIG. 2 is a plan view illustrating an elastic cushion mat, and FIG. 3 is a longitudinal sectional view taken along line AA in FIG.

  As shown in FIG. 1, the corrosion-resistant frame 1 is a frame made of a metal round bar or square bar that is resistant to alkali such as nickel.

  The metal coil body 2 shown in FIG. 3 is obtained by rolling a thin metal wire into a coil shape, and is a material that can be freely deformed without rigidity, such as a metal scrubber for cleaning. As shown in FIG. 2, the metal coil body 2 is wound over almost the entire length between a pair of round bars in the longitudinal direction of a nickel corrosion-resistant frame 3 having a diameter of about 2 mm, for example, to form an elastic cushion mat 3. Is manufactured.

  The elastic cushion mat 3 manufactured in this manner is held in the shape of the corrosion-resistant frame because the metal coil body 2 is wound around the corrosion-resistant frame 1, and the metal coil body 2 is detached from the corrosion-resistant frame 1. The metal coil body 2 can be handled as being integrated with the corrosion-resistant frame 1.

  These metal coil bodies and elastic cushion mats are not necessarily fixed to the cathode current collector or the cathode by welding or the like, but may be fixed. Normally, electricity is not fixed but is flowed by contact energization.

  FIG. 4 shows a structure when a metal coil body or an elastic cushion mat is compressed between a cathode current collector and a cathode, and the two coils of the metal coil body shown in FIG. 4 are overlapped to form a metal coil body having the structure shown in FIG. 4, and even in the elastic cushion mat as shown in FIG. 2, the metal coil body constituting the same is a metal coil body having the structure shown in FIG.

  FIG. 5 is a schematic plan view showing an example in which an elastic cushion mat is used for electrical connection between a hydrogen generating cathode and a cathode current collector when a bipolar ion exchange membrane electrolytic cell is used for salt electrolysis.

  The bipolar ion exchange membrane method electrolytic cell in FIG. 5 includes an anode chamber 4, a cathode chamber 5, and an ion exchange membrane 6 that separates them. The anode 7 is disposed on the anode chamber 4 side, and the cathode current collector 9, the elastic cushion mat 3 of the present invention, and the cathode 8 are disposed on the cathode chamber 5 side.

  6 is an enlarged plan view of a portion B in FIG. It is shown that the cathode 8, anode 7 and cathode current collector 9 have openings. The cathode current collector 9 and the elastic cushion mat 3 (or the metal coil body 2) are in electrical contact, and the elastic cushion mat 3 and the cathode 8 are electrically connected. Power is supplied to the cathode 8 through the mat 3.

  Since the metal coil body uses an elastic cushion mat 3 wound around a corrosion-resistant frame, the elastic cushion mat 3 is easy to handle and loses its shape when this bipolar ion exchange membrane electrolytic cell is assembled. There is little to do. Therefore, the hydrogen gas generated from the cathode 8 can pass through the cavity inside the metal coil body 2 in the elastic coil cushion 3 and circulate efficiently in the cathode chamber.

  In this state, when a saline solution is supplied to the anode chamber and a dilute caustic soda solution is supplied to the cathode chamber, and electricity is applied between both electrodes, a concentrated caustic soda solution is obtained in the cathode chamber.

The present invention relates to an ion exchange membrane method electrolytic cell partitioned by an ion exchange membrane into an anode chamber containing an anode having an opening and a cathode chamber containing a cathode having an opening. during the ion exchange membrane and having a resilient cushion mat composed of packing density 0.14 g / cm ³ or more 0.28 g / cm ³ metal coil body is less, or the metallic coil body It is a process electrolytic cell.

  Since the metal coil body can be freely deformed and has sufficient conductivity, the cathode and the cathode current collector can be reliably electrically connected. Using an elastic cushion mat that is formed by winding this metal coil body around a corrosion-resistant frame, the metal coil body is integrated with the corrosion-resistant frame, so that it is easy to handle and the shape is hardly lost. In most cases, it can be reused even when the electrolytic cell is disassembled and reassembled.

It is a top view of the corrosion-resistant frame in an elastic cushion mat. It is a top view which illustrates the elastic cushion mat which can be used by this invention. FIG. 3 is a longitudinal sectional view taken along line AA in FIG. 2. The structure when a metal coil body or an elastic cushion mat is compressed by interposing between a cathode current collector and a cathode is shown. It is a schematic plan view which shows the example which used the elastic cushion mat for the electrical connection of the hydrogen generating cathode and cathode collector of a bipolar salt-electrolyte tank. It is the schematic plan view to which the B section of FIG. 5 was expanded.

  An ion exchange membrane method electrolytic cell using a metal coil body or an elastic cushion mat according to the present invention will be specifically described with reference to the following examples.

Example 1
A unit cell of an ion exchange membrane electrolytic cell was assembled as follows.

  A dimensional stability electrode having an opening made by Permerek Electrode Co., Ltd. was used as the anode, and the cathode was an active cathode of a nickel micromesh substrate. The reaction surface size of the anode and the cathode was 40 mm in width and 75 mm in height, respectively. As the ion exchange membrane, Flemion F-8020 manufactured by Asahi Glass Co., Ltd. was used.

For the metal coil body, a nickel wire (NW2201) having a wire diameter of 0.17 mm and a tensile strength of 620 to 680 N / m ² is formed into a coil wire having a width of about 0.5 mm by roll processing, and the number of turns of the coil is 16 times. A diameter of 6.0 mm was used.

This metal coil body was wound around a nickel round bar frame (corrosion resistant frame) having a diameter of 2 mm to adjust the shape to a rectangular parallelepiped shape, thereby obtaining an elastic cushion mat having an approximate size of 3 mm thick × 40 mm wide × 75 mm long. The coil packing density of this elastic cushion mat was 0.14 g / cm ³ . Nickel expanded metal was used for the cathode current collector.

An elastic cushion mat is inserted between the cathode current collector and the hydrogen generating cathode so as to produce elasticity. The electrolyte solution on the anode chamber side is a 200 g / L NaCl solution, the current density is 4 kA / m ² , and the caustic concentration in the cathode chamber is After electrolysis at 32 wt% for 2 days, the current density was increased to 6.5 kA / m ² and electrolysis was further carried out for 2 days. Subsequently, with the current density kept at 6.5 kA / m ² , the electrolysis voltage and the ion exchange membrane current when electrolysis was carried out for 2 days by increasing the caustic concentration to 36 wt% and further increasing the caustic concentration to 39 wt%. Efficiency was measured.

  Table 1 shows the conditions such as the wire diameter of the metal coil body in Example 1 and the results of electrolysis voltage and current efficiency.

  Thus, a low electrolysis voltage and high current efficiency were maintained even under high caustic concentration conditions of 39 wt%.

Example 2
An elastic cushion mat was prepared in the same manner as in Example 1 except that the number of turns of the coil of the metal coil body was 12 and the winding diameter was 8.5 mm, and the electrolytic evaluation was performed in the same manner.
The results are shown in Table 1.

Examples 3-7
An elastic cushion mat was prepared in the same manner as in Example 1 except that the number of turns of the metal coil body was 20 to 60 and the winding diameter was 5.0 to 7.0 mm.
The results are shown in Table 1.

Comparative Examples 1-4
An elastic cushion mat having a coil filling density outside the range of the present invention was produced in the same manner as in Example 1 by changing the coil diameter, the number of turns of the coil, and the winding diameter of the metal coil body, and the electrolytic evaluation was performed in the same manner.

  The results are summarized in Table 1.

この表１から、コイルの充填密度が本発明範囲（０．１４ｇ／ｃｍ^３〜０．２８ｇ／ｃｍ^３）内の実施例１〜７では、低い電解電圧で高い電流効率となるが、その範囲外の比較例１〜４では電流効率が９０％未満と低いことが明らかである。

From Table 1, in Examples 1 to 7 in which the packing density of the coil is within the range of the present invention (0.14 g / cm ^{3 to} 0.28 g / cm ³ ), the current efficiency becomes high at a low electrolysis voltage. It is clear that in the other Comparative Examples 1 to 4, the current efficiency is as low as less than 90%.

  The ion exchange membrane method electrolytic cell of the present invention is an ion exchange membrane method electrolytic cell in which a metal coil body is interposed between a cathode and a cathode current collector and the cathode is uniformly pressed in the ion exchange membrane direction. This is an ion-exchange membrane electrolytic cell that is unlikely to deteriorate, and can be widely used in the electrolysis industry represented by chloralkali electrolysis such as salt electrolysis. The period can be kept low.

1: Corrosion resistant frame 2: Metal coil body 3: Elastic cushion mat 4: Anode chamber 5: Cathode chamber 6: Ion exchange membrane 7: Anode 8: Cathode 9: Cathode current collector

Claims (3)

Cathode chamber, cathode current collector, cathode having opening, ion exchange membrane, anode having opening, and cathode having cathode current collector and opening in ion exchange membrane method electrolytic cell comprising anode chamber between the metallic coil body packing density is less than 0.14 g / cm ³ or more 0.28 g / cm ^3, or have a resilient cushion mat composed of the metallic coil body, the metallic coil An ion exchange membrane electrolytic cell in which the body material is nickel, a nickel alloy or copper . The ion exchange membrane electrolytic cell according to claim 1, wherein the elastic cushion mat is composed of a plurality of metal coil bodies, and the axial directions of the plurality of metal coil bodies are parallel to each other. An electrolysis method using the ion exchange membrane method electrolytic cell according to claim 1 or 2 , supplying an aqueous alkali metal chloride solution to the anode chamber, and supplying water to the cathode chamber for electrolysis. .

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