KR100899290B1 - A desalter of sea water - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desalination apparatus for seawater, and more particularly, to desalination by extracting salts by electrical attraction of salts contained in seawater. It is about.

To this end, the present invention, while supplying seawater or deep sea water to the desalting chamber (4) installed inside the salt extraction chamber (3) from the rectifier to the positive electrode (8) and the negative electrode (9) provided outside the desalting chamber (4) from the rectifier When an electric field is formed in the desalination chamber 4 by electrolysis, the cation penetrates through the cation exchange diaphragm 5 on the cathode side by electrophoresis, resulting in a salt. As the anion is moved to the extraction chamber 3, the anion passes through the anion exchange diaphragm 6 toward the anode 8 and moves to the salt extraction chamber 3 while the salt in the desalting chamber 4 is desalted.

The desalination apparatus of the present invention is widely used for the desalination of seawater because the operating cost and facility cost are lower than that of seawater desalination by electrodialysis, reverse osmosis filtration, evaporation / condensation, freezing, solar heat, etc. using the ion exchange membrane of the prior art. It is expected to be.

Seawater, desalination unit, electrodialysis, reverse osmosis filtration, electrophoresis, electric field

Description

A desalter of sea water

The present invention relates to a desalination apparatus of seawater, and more particularly, to desalination of salts contained in seawater, separated into a cation exchange diaphragm and an anion exchange diaphragm in the salt extraction chamber. While supplying seawater to the desalination chamber of the desalination treatment device (hereinafter referred to as "desalination apparatus by electric extraction") provided with the anode and the cathode between the multiple desalination chambers, the direct current is applied from the rectifier to form an electric field in the desalination chamber. The present invention relates to a desalination apparatus of seawater for desalination by extracting salt into a salt extraction chamber by electrophoresis.

In general, desalination of seawater (including deep seawater) includes reverse osmosis, electrodialysis by ion exchange membranes, evaporation by dewatering seawater into steam (multi-stage flash evaporation, multi-evaporation evaporation, steam compression), and others. There is a freezing method and solar heat method, but mainly an evaporation method and a reverse osmosis membrane method are used, and the reverse osmosis membrane method and an electrodialysis method are mainly used for desalination of seawater.

The desalination of seawater by reverse osmosis membrane has to be operated at 2 ~ 3 times the pressure of 25 atm of seawater. Therefore, there is a problem of high power cost and membrane replacement cost, and high energy even in the case of evaporative condensation and freezing. Energy) There is a problem that costs.

When the salinity is removed from the seawater by the electrolysis reaction, the salinity removal rate is excellent, but there are the following problems.

First, when a direct current was applied while the anode chamber and the cathode chamber were separated into anion exchange membrane and cation exchange membrane, Cl ⁻ ions pass through the anion exchange membrane and electrolytic oxidation water such as HClOx and Cl _{2 (g)} In the cathode chamber, Na ⁺ ions may react with water (H ₂ O) while passing through a cation exchange membrane to generate NaOH and hydrogen (H ₂ ).

NaCl contained in seawater was separated into an anion exchange membrane and a cation exchange diaphragm into an anode chamber and a cathode chamber, and a direct current electric current was applied to cause the electrolysis of NaCl to HClOx, HCl, Cl _{2 (g)} and NaOH, H ₂ O. Desalination treatment is carried out.

The current required to remove 1 kg-mole of NaCl in seawater by electrolysis should be applied with a current of 1 Faraday (26.8 mAh / kg-eq), specifically, one kilogram of NaCl ( The theoretically necessary current for desalting 58.5 kg (kg-mole) by electrolysis should be 26,800 amperes, and the applied voltage is 2.2246 Volt of theoretical resolution voltage, positive overvoltage, negative overvoltage, Considering the ohmic resistance of the solution, the ohmic resistance of the conductor, etc., a voltage of 5 Volts or more must be applied.

Second, in order to apply a high current, the facility cost is high because the area of the electrode plate, the area of the ion exchange membrane, the capacity of the rectifier and other devices are increased.

Third, when the applied voltage is increased to improve the desalination efficiency, side reactions may occur in the anode chamber, and gases such as Cl _{2 (g)} and ClO _{2 (g)} may be generated to cause odor.

Desalination by electrolysis is rarely used due to the above-mentioned problems, and in order to compensate for the above problems, a cation exchange diaphragm and an anion exchange diaphragm are alternately provided between the anode and the cathode. Although a method of desalination by an electrodialysis apparatus is used, there are the following problems.

First, in both the anode and cathode chambers, desalination occurs due to electrolysis, and the distance between the anode and the cathode is large. Therefore, a high voltage must be applied. .

Secondly, if the desalination proceeds and the salt concentration drops, the liquid resistance increases, and thus the desalination cannot be performed highly.

Third, the structure of the device is complicated, the price of the device is high.

In order to solve the problems in the conventional seawater desalination treatment method, in the case of the desalination treatment by the electroextraction of Document 1, the positive electrode and the negative electrode are alternately installed between the desalination chambers installed in the salt extraction chamber. There was a problem that the amount of the device is large and the production cost increases due to the large quantity.

[Document 1] Republic of Korea Patent Application No. 10-2006-0053857 2006. 06. 15.

The present invention provides a desalination apparatus with low power consumption of salts contained in seawater by electroextraction in order to solve the problem of desalination of seawater, and desalination of seawater by conventional electrolysis and electrodialysis. It is an object of the invention.

In the present invention, in the desalination of salts contained in seawater, the seawater is supplied to a desalination apparatus by electric extraction, in which a desalination chamber separated by a cation exchange membrane and an anion exchange membrane is installed between the anode and the cathode inside the salt extraction chamber. And a desalination apparatus with low power consumption by applying a direct current electric current from the rectifier to form an electric field in the desalination chamber, extracting salt into the salt extraction chamber by electrophoresis, and desalting treatment. There is a characteristic.

According to the present invention, when the desalination treatment of salts contained in seawater is performed by electroextraction, power consumption is small and operating costs are lower than those of conventional electrodialysis apparatuses and reverse osmosis membranes. It is expected that there will be an effect used.

Sea water in the present invention refers to the surface deep sea water of the ocean, deep seawater deeper than 200m from the sea surface, deep sea fossil seawater taken by excavating seabed rocks ), Which means brine (鹽水) taken by excavating the rock of the island or coast, desalination treatment in the present invention includes all of the above seawater.

In the present invention, in order to solve the problem of high power consumption when desalting seawater with an electrodialysis apparatus or a reverse osmosis filtration apparatus, a cation is formed between the anode 8 and the cathode 9 in the salt extraction chamber 3. The desalination apparatus by electroextraction in which the desalination chamber (4) separated by the exchange diaphragm (5) and the anion exchange diaphragm (6) is installed in multiple stages will be described in detail with reference to the accompanying drawings. .

1 is an explanatory view of a desalination mechanism of seawater by electric extraction, and a cathode 9 is a cation exchange diaphragm 5 between an anode 8 and a cathode 9 installed inside the salt extraction chamber 3. On the anode 8 side, desalination is carried out by desalination of the seawater by the "desalination apparatus by electroextraction" consisting of an anion exchange diaphragm 6 and an isolation desalination chamber 4 having multiple stages. In the case of water purification, the seawater of the seawater storage tank 1 is supplied to the salt extraction chamber 3 and the desalination chamber 4 by the seawater transfer pump 2, and the seawater supplied to the desalination chamber 4 is the seawater storage tank ( While circulating to 1), the air in the atmosphere is blown from the blower 10 through the diffuser 11, and a direct current of 4 to 50 volts is applied from the rectifier to the electric field. ), The cations (Na ⁺ , K ⁺ , Ca ^{2 +} , Mg ^{2 +} , Fe ^{2 +} , Fe ³ ) contained in the seawater of the desalting chamber 4 by electrophoresis. ⁺ , Zn ^{2 +} ..., Etc.) are transferred to the salt extraction chamber 3 through the cation exchange diaphragm 5 on the negative electrode 9 side, and anion (Cl ⁻ , Br ⁻ , NO ₃ ⁻ , SO ₄ ^{2). _{-, HCO 3 -, CO 3}} 2 -, HPO 4 2 -, PO 4 3 - ... and so on) is concentrated as it moves to the positive electrode 8 is extracted by passing through the anion exchange membrane (6) on the side of the salt chamber (3) The concentrated brine is discharged to the salt manufacturing process by operating the solenoid valve (ⓢ: Solenoid valve) when the Baume's specific gravity indicator (BIS) reaches 12-20 ° Be. The desalted water in which the salt is removed from the seawater in the desalination chamber 4 and the electric conductivity of the electric conductivity indicating switch (ECIS) installed in the demineralized water line is in the range of 6-12 mW / cm operates the solenoid valve. It is sent to the low pressure reverse osmosis process to produce fresh water.

The desalination apparatus of seawater actually has a cation exchange diaphragm 5 at the cathode 9 side and a cathode 8 at the inside of the salt extraction chamber 3 as shown in FIG. Anion exchange diaphragm 6 is provided to install the separated desalting chamber 4 between the anode 8 and the cathode 9 in multiple stages, and to the extraction of electricity repeatedly installed alternately depending on the processing capacity. When the seawater of the seawater storage tank 1 is supplied to the seawater transfer pump 2 to the desalination chamber 4 of the desalination system by applying a direct current from the rectifier to form an electric field in the desalination chamber 4, the electrophoresis is performed. The desalination apparatus is applied to desalination by extracting salt into the salt extraction chamber (3) by densification.

In the desalination treatment of the salt contained in the seawater, the seawater of the seawater storage tank 1 is supplied to the salt extraction chamber 3 and the desalination chamber 4 to the desalination apparatus which is desalted by electric extraction to the seawater transfer pump 2. Air is supplied from the blower 10 to the diffuser 11 installed below the salt extraction chamber 3 and aerated while being conveyed to the sea water storage tank 1, and a direct current of 4 to 50 volts is supplied from the rectifier. When an electric field is formed in the desalination chamber 4 by applying it to the anode 8 and the cathode 9, the cations contained in the seawater of the desalination chamber 4 by electrophoresis are negative. (9) is passed through the cation exchange diaphragm (5) side to the salt extraction chamber (3), the anion passes through the anion exchange diaphragm (6) to the anode 8 side to the salt extraction chamber (3) The concentrated brine concentrated in the salt extraction chamber (3) in the range of 12 to 20 ° Be in the BOMEDI specific gravity indicator controller (BIS) Operate the solenoid valve (ⓢ) and discharge it to the salt manufacturing process, and salt is removed from the seawater in the desalination chamber (4) so that the electrical conductivity of the electroconductivity indicator controller (ECIS) of the desalination line is in the range of 6-12㎳ / cm. Demineralized demineralized water is operated by a solenoid valve (ⓢ) and sent to a low pressure reverse osmosis process to produce fresh water.

In the salt extraction chamber 3 of the desalination apparatus of the seawater, a desalination chamber 4 is installed between the anode 8 and the cathode 9 in a group of 2 to 10 in parallel according to the treatment capacity. Multiple stages are installed by a family register.

The electrochemical reaction mechanism in which the salts in the seawater described above are desalted by the "desalting apparatus by electric extraction" is as follows.

NaCl in salts contained in seawater is dissociated into Na ⁺ ions and Cl ^- ions by hydrolysis in seawater as in the following reaction ①.

^{_{NaCl -H 2 O → Na + +}} Cl - ... … … … … … … … … … … … … … … … … … … ①

When a direct current is applied from the rectifier to the anode 8 and the cathode 9 to form an electric field inside the desalination chamber 4, the cations such as Na ⁺ ions contained in the seawater in the desalination chamber 4 by electrophoresis are negative. It passes through the cation exchange diaphragm 5 on the side of (9) and moves to the salt extraction chamber (3). Anions such as Cl ⁻ ions pass through the anion exchange diaphragm (6) on the positive side (8) to the salt extraction chamber. As it moves to (3), salts (NaCl, KCl, CaSO ₄ , CaCO ₃ , MgCl ₂ , MgSO ₄ , MgBr ₂ , SrSO ₄ ...) Are removed from the seawater in the desalination chamber (4), and NaCl In the case of the reaction mechanism is as follows.

Na ⁺ --septum-> Na ⁺ ... … … … … … … … … … … … … … … … … … … ②

Cl ^{- -} Diaphragm ^- → Cl - ... … … … … … … … … … … … … … … … … … … ③

Na ⁺ ions and Cl ⁻ ions transferred to the salt extraction chamber 3 are in situ in the original NaCl state.

Na ⁺ + Cl ⁻ —H ₂ O → NaCl... … … … … … … … … … … … … … … … … … … ④

On the anode 8 and cathode 9 sides, if the following side reactions occur, odor generation and power consumption may increase. Therefore, air from the blower 10 may be diffused into the air. 11) aeration through the following side reactions (副 反 최대한) to the maximum suppressed.

2Cl ⁻ → Cl _{2 ( aq )} + 2e ⁻ . … … … … … … … … … … … … … … … … … … … … ⑤

Cl _{2 ( aq )} → Cl _{2 (g)} ↑. … … … … … … … … … … … … … … … … … … … … … ⑥

Cl _{2 ( aq )} + H ₂ O → HClO _{( aq )} + HCl... … … … … … … … … … … … … … … … … ⑦

^{_{2HClO (aq) + 2H + +}} 2e - → Cl 2 (g) ↑ + 2H 2 O ... … … … … … … … … … … … ⑧

^{_{2H 2 O + 2e - → 2OH}} - + H 2 (g) ↑ ... … … … … … … … … … … … … … … … … … ⑨

At this time, the supply amount of air supplied from the blower 10 through the diffuser 11 is such that the aeration intensity (Intensity of aeration) is 1.2 to 2.0 air (m 3) / tank volume (m 3).

A feature of the present invention is that salts (NaCl, etc.) are not desalted by decomposing reactions at all compared to the desalting method by electrolysis or electrodialysis, and are contained in seawater in the desalting chamber 4. The salt is applied from the rectifier to the positive electrode 8 and the negative electrode 9 to form an electric field. By electrophoresis, cations (Na ⁺ etc.) are transmitted through the cation exchange diaphragm 5 on the negative electrode 9 side. The anion (Cl ^−, etc.) is transferred to the salt extraction chamber 3, and the anion (Cl ^−, etc.) passes through the anion exchange diaphragm 6 on the anode 8 side, and moves to the salt extraction chamber 3 to be in the original salt state. situ) Because the reaction occurs and is extracted and removed, it is characterized by low power consumption because no current is consumed by the decomposition of salt.

The salt extraction chamber (3) and desalination chamber (4) are made of flame resistant stainless steel, titanium, epoxy coated or lining carbon steel, or glass. Lining fiber glass reinforced plastic (FRP).

The material of the negative electrode plate 6 is a steel plate of high hydrogen generation overvoltage, which is made of lined with Raney nickel, or flame-resistant stainless steel or titanium plate. The anode (8) plate is a DSA coated with TiO ₂ -RuO ₂ coated on a titanium plate made of a material having high corrosion resistance and high oxygen and chlorine generation overvoltage. Dimensionally Stable Anode electrode is used.

Seawater is removed by removing all monovalent salts (NaCl, KCl, KBr, etc.) and polyvalent salts (多 價 鹽, MgCl ₂ , MgSO ₄ , CaSO ₄ , FeCl ₂ , FeCl ₃ , SrSO ₄ . In the case of desalination, the cation exchange diaphragm 5 on the cathode 9 side uses a cation exchange diaphragm that transmits all cations, and the anion exchange diaphragm 6 on the anode 8 side transmits all anions. An anion exchange diaphragm is used.

However, even if the desalination efficiency is slightly reduced, the asbestos, nylon, polypropylene, and polyvinylidene fluoride are similarly disposed in the diaphragm on the anode 8 side and the cathode 9 side in consideration of economical efficiency. vinylindene fluoride, polyolefin, polyethylene, polyester, polyester, hexafluoropropylene, polyfluoroolefin, tetrafluoroethylene (TFE: Tetrafluoroethylene), polytetrafluoroethylene (PTFE: Polytetrafluoroethylene), one kind of membrane may be used.

In the case of producing a mineral water containing a large amount of divalent or higher mineral components for use in agricultural water by removing the NaCl component contained in the seawater in excess, it is a polyvalent cation among salts contained in the seawater. When only the monovalent cation is removed without removing the mineral component, a monovalent cation selective exchange diaphragm which selectively permeates only the monovalent cation is used for the cation exchange diaphragm 5 on the negative electrode 9 side.

The one contained in the sea water cations (Na ^+, K ⁺⁾ and sulfate ions (SO ₄ ^{2 -)} to the case of producing the number of minerals removed, an anode (8) an anion exchange membrane (5) of the side is transmitted through all the anions An anion exchange diaphragm is used, and the cation exchange diaphragm 5 on the cathode 9 side uses a diaphragm that selectively exchanges monovalent cations.

The sulfuric acid in the water ions (SO ₄ ^{2 -)} is as to sulfate ions are removed that existed in the low solubility CaSO in water _four calcium ions (Ca ^{2 +)} is a highly soluble salt by following the ⑩ reaction of (CaCl _It exists in the form of ₂ ), the number of minerals with a high calcium content is produced.

CaSO ₄ + MgCl ₂ → CaCl ₂ + MgSO ₄ ... … … … … … … … … … … … … … … ⑩

The monovalent cation selective exchange diaphragm used in the present invention is an exchange membrane that selectively permeates only monovalent cations while suppressing divalent or more multivalent cation permeation and is based on a polystyrene-divinylbenzene system. Side chains and polyethyleneimine or polyvinyl chloride in the load-carrying membranes that hold the negative charge R-SO ₃ ^- in the main chain. Graft polymers such as polyvinylpyridine or graft polymers whose main chains are polystyrene with side chains made of polyethyleneimine or polyvinyl pyridine. Any structure having the same molecular structure as the main chain or the side chain of the cation exchange diaphragm can be used without limitation, and preferably, polyethylene, polypropylene (p) Only monovalent cations permeate into the main or side chains of the polymer molecule structure consisting of a cation exchange diaphragm immobilized with negatively charged R-SO ₃ ^- on olypropylene), polyvinyl chloride, polystyrene, etc. Monovalent cation selective exchange membranes such as polyvinylpyridine, polyvinylamine or polyethyleneimine membranes having a molecular structure of Polystyrene-graft-ethylene imine may be most preferably used.

In contrast to monovalent cation selective exchange diaphragms, monovalent anion selective exchange diaphragms are membranes capable of selectively exchanging monovalent anions only from primary to tertiary amines in the polymer chain of a substrate. The surface of the membrane was modified to selectively permeate monovalent anions to the surface of the positively charged membrane into which amine or ammonium group was fixed to the membrane and aminated to introduce a cation. Anion exchange diaphragm in which the ion exchange group is bridge | crosslinked by aliphatic hydrocarbon, and the membrane surface part has a thin layer of the polymeric material which has a cation exchange group. As a polymer material having a cation exchange group, it is preferable to crosslink with an aliphatic hydrocarbon and to quaternize the monomer introduced into the exchange group. An insoluble polymer having an electrolyte, a linear polymer electrolyte, or a cation exchange group, specifically, a molecular weight of 500 in a sulfonate such as Ligninsulfonate and a phosphate ester salt such as a higher alcohol phosphate ester. Monomer unit having a carboxylic acid group (-COOH) or a sulfonic acid group (-SO ₃ H) such as a polymer electrolyte having a cation exchange group, a methacrylic acid, and styrene sulfonic acid A membrane that selectively exchanges only monovalent anions with a linear polymer electrolyte containing a large number of units, an insoluble polymer having a cation exchange group such as a condensation of phenols and aldehydes including a cation exchange group is used.

The cation exchange diaphragm which permeates all cations is loaded with a negative charge R-SO ₃ ^- in the main chain of the polystyrene-divinylbenzene system. In order to selectively permeate monovalent cations to the surface of the membrane selectively, a cationic polymer electrolyte such as polyethyleneimine is coated or bonded in a thin layer to perform a modification process. Cation exchange membranes are used.

In addition, the anion exchange diaphragm which permeates all anions is a positively charged membrane in which a cation is introduced by amination by amination of primary to tertiary amines or ammonium groups in the polymer chain of the substrate to the membrane. The membrane which does not modify the membrane surface is used so that a monovalent anion may permeate selectively to the surface of a positive electrode.

The diaphragm supporter 7 is flame resistant stainless steel or titanium on the outside of the cation exchange diaphragm 5 and the anion exchange diaphragm 6 on a nonwoven fabric made of synthetic resin such as viscose rayon or nylon having a thickness of 1 to 10 mm. It is supported by a porous plate or grid plate.

Example 1

In the desalting apparatus as shown in FIG. 2, the anode inside the salt extraction chamber having a capacity of 3.6 m 3 (840 mm × 1,200 mm × 4,000 mm) has a DSA electrode which is baked with TiO ₂ -RuO ₂ coated on a 1,000 mm × 1,200 mm titanium plate Two cathodes and two anodes of 1,000 mm × 1,200 mm titanium plate are installed alternately, and the cation exchange diaphragm between each anode and cathode is Aciplex K- of Asahi Kasei Co., Ltd., Japan. 101, and the deionization chamber capacity using Aciplex A-101 of the company is used in the desalination unit by electroextraction, in which 3 sheets of 0.1 m3 (25 mm × 1,000 mm × 4,000 mm) are installed. Deep seawater with a salt concentration of 3.45 wt% in the seawater reservoir is supplied with 0.5 m3 / hr to the salt extraction chamber with a salt extraction chamber and 2 m3 / hr to the desalination chamber, while direct current of 5 to 15 volts from the rectifier. The results of measuring the current and salinity removal rate when electricity is applied to each cathode and anode are different. The contents were as shown in Table 1.

Table 1 Seawater Desalination Test Report

Voltage applied (Volt) 5 10 10 Ampere 33.2 48.62 72.32 Salt concentration in treated seawater (wt%)   0.85  0.32  0.08 Desalination Rate (%) 75.36 90.72 97.68

(Note: The theoretical applied current is 15,347A for desalination by electrolysis up to 0.1wt% of 1Ton / hr of seawater with a salt content of 3.45wt%.)

As shown in Table 1, it can be seen that the desalination of seawater by the "desalination apparatus by electric extraction" of the present invention is less power consumption than the desalination by conventional electrodialysis.

The present invention is expected to have very high availability of seawater in the desalination process in the case of desalination of islands or deep sea waters where freshwater is scarce.

1 is an explanatory diagram of a desalting mechanism of seawater by electric extraction

Figure 2 is a desalination treatment device by electroextraction

<Explanation of symbols for main parts of drawing>

1: Seawater Storage Tank 2: Seawater Transfer Pump

3: salt extraction chamber 4: desalting chamber

5: cation exchange diaphragm 6: anion exchange diaphragm

7: diaphragm supporter 8: anode

9: cathode 10: air blower

11: diffuser ⓢ: Solenoid valve

BIS: Baume's hydrometer indicating switch

ECIS: Electric conductivity indicating switch

Claims (4)

Inside the salt extraction chamber 3, the cathode 9 side is provided with a cation exchange diaphragm 5, and the anode 8 side is equipped with an anion exchange diaphragm 6 to separate the desalting chamber 4 from the anode 8 The seawater of the seawater storage tank (1) is installed in the desalting chamber (4) of the desalting apparatus by the electroextraction, which is provided with multiple stages between the cathodes (9) and alternately repeatedly installed according to the processing capacity. 2) by supplying the salt extraction chamber (3) and the desalination chamber (4) to the seawater storage tank (1) while supplying air from the blower (10) to the diffuser (11) installed under the salt extraction chamber (3) The aeration is carried out, and direct current is applied from the rectifier to the anode 8 and the cathode 9 to form an electric field in the desalination chamber 4, whereby electrophoresis causes desalination chamber 4 Cations in the seawater of the permeate permeate through the cation exchange diaphragm 5 on the negative electrode 9 to the salt extraction chamber 3, and the anion passes through the anion exchange diaphragm 6 on the positive electrode 8 side. To a concentrated brine and concentrated in to be taken to the salt extraction chamber 3 salt extraction chamber 3 is of sea water desalination apparatus that discharges the salt production process, desalting the salt from sea water in the desalting chamber (4). The desalination apparatus of seawater using a monovalent cation selective exchange diaphragm according to claim 1, wherein the cation exchange diaphragm 5 selectively exchanges only monovalent cations. The desalination apparatus of seawater using a monovalent anion selective exchange diaphragm according to claim 1, wherein the anion exchange diaphragm (6) selectively exchanges only monovalent anions. The monovalent cation selective exchange membrane of claim 1, wherein the cation exchange diaphragm 5 selectively exchanges only monovalent cations, and the anion exchange diaphragm 6 selects monovalent anions to selectively exchange monovalent anions. Desalination apparatus of seawater using exchange diaphragm.

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