JP5027328B2 - Salt water purification apparatus and salt water purification method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily reduce bromide ions which are very slightly contained in chlorine-containing salt water such as saline solution, without inclusion of impurities into the salt water when chlorine gas is generated by electrolyzing the salt water. <P>SOLUTION: The salt water is supplied downward into a reaction column from its top, and an oxidizing gas and a desorption gas are circulated upward from the lower side of the reaction column so as to oppose the flow of the salt water. Bromide ions in the salt water are oxidized to bromine gas with chlorine gas, and the bromine gas is then discharged together with the desorption gas and the excess of the oxidizing gas. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a purification apparatus for reducing bromide ions contained in salt water.

  In tap water, chemicals such as chlorine gas, sodium hypochlorite, and salash powder are injected to sterilize pathogenic bacteria. The chemical injection amount is managed so that the effective chlorine concentration at a tap water outlet is a certain value or more. On the other hand, bromine is determined to be 0.01 mg / L or less in the bromic acid concentration in drinking water, and drugs are also regulated.

  The chlorine gas injected into the tap water is manufactured by dissolving a relatively low-purity salt obtained from seawater in water, adjusting the salt solution, and electrolyzing the salt solution. Since seawater salt generally contains about 100 to 150 ppm of bromine, for example, when adjusted to about 26% saline, about 25 to 35 ppm of bromide ions are included. Therefore, if the saline solution is electrolyzed as it is, bromine gas is mixed into the chlorine gas, so it is necessary to remove bromine in the manufacturing process. However, when chemicals or oxidizing agents are used to remove bromine, these chemicals and oxidizing agents are taken up as impurities in the chlorine gas by electrolysis, so treatment with chemicals that are less likely to contain impurities. A method is being considered.

  For example, as described in Patent Document 1, a mixed solution composed of saline and sodium hypochlorite (sodium hypochlorite aqueous solution) as an oxidizing agent is introduced from the top of the radiation tower to oxidize bromide ions. In addition, a method is known in which an inert gas or the like is introduced from the lower side of the radiation tower so as to face the flow of the mixed liquid, and bromine is discharged from the upper part of the radiation tower together with the inert gas as a bromine gas. .

  Since this bromine is in a liquid state at room temperature, the gas and liquid are in an equilibrium state according to the vapor pressure (temperature), and the gaseous bromine gas rises with the inert gas. It will be removed. However, in order to remove it as bromine gas, it is necessary to make the salt solution strongly acidic, and if it is neutral or alkaline, it changes to bromic acid or the like, making it difficult to remove.

  Since the above sodium hypochlorite is in a liquid form, it is easy to handle and can be manufactured using high-purity chlorine gas as a raw material. Since sodium chlorite is a liquid, the liquid volume of the mixed liquid increases, so that there is a demerit that the amount of processing per hour decreases because the saline solution is diluted. In addition, as described below, there is a problem that it is easy to disassemble.

Sodium hypochlorite is an alkaline liquid. When sodium hypochlorite is injected into the saline solution, the salt solution is adjusted to be acidic, so that it changes to hypochlorous acid (HClO) and free chlorine (Cl ₂ ) due to acid dissociation equilibrium. Of these, hypochlorous acid is very easily decomposed and easily decomposes to generate by-products such as chloric acid (HClO ₃ ) and oxygen (O ₂ ). This chloric acid has a very low oxidizing power for bromide ions. In addition to oxygen being a source of impurities, the formation of these by-products results in the expected chlorine acting as an oxidant becoming hydrochloric acid. The oxidative power that was being used can no longer be obtained. Therefore, for example, by reducing the amount of hypochlorous acid, which is a source of chloric acid, by reducing the pH of the mixed liquid to, for example, about 1.0, the generation of by-products is suppressed. In order to adjust the pH of the mixed solution, it is necessary to use, for example, high-purity (low bromine concentration) hydrochloric acid in order to avoid contamination with impurities. However, such hydrochloric acid is expensive, and thus costs increase. However, when hydrochloric acid, which is a liquid, is mixed, the amount of the mixed liquid further increases, so that the processing amount per hour is reduced and the throughput is lowered. Moreover, if the pH of the mixed solution is lowered too much, the solubility of chlorine gas will decrease, and furthermore, when electrolyzing brine from which bromine has been removed, it is necessary to adjust the pH with an alkali. The amount of neutralizing agent also increases, leading to an increase in cost.

By the way, as a gaseous oxidant for oxidizing bromide ions, fluorine gas (F ₂ ), chlorine gas (Cl ₂ ), chlorite gas (ClO ₂ ), ozone gas (O ₃ ), nitrogen dioxide (NO ₂ ). Etc. are known. Among them, chlorine gas is not decomposed by heating at about 70 ° C. to 80 ° C., and it is not necessary to consider the influence of impurities so much, so it is very preferable as a substitute for the above-mentioned sodium hypochlorite. However, an actual apparatus for using chlorine gas as an oxidizing agent has not been studied so far. For example, in a method of bubbling chlorine gas into saline, the reaction efficiency is low, so it is not practical. Absent.

  In addition, when chlorine gas is introduced instead of sodium hypochlorite in the radiation tower of Patent Document 1, the reaction efficiency is slightly improved, but it is not diluted with a liquid such as sodium hypochlorite, Since the almost saturated salt solution flows through the radiation tower, for example, when the moisture of the salt solution evaporates by the inert gas supplied from the lower side of the radiation tower, as shown in the examples described later. For example, salt is deposited at the inlet of the inert gas. Due to the deposition of the salt, the flow path of the inert gas is blocked, and the inert gas may not flow, and there is a possibility that continuous operation cannot be performed. Therefore, in order to remove bromide ions using chlorine gas as an oxidizing agent using the radiation tower of Patent Document 1, it is necessary to dilute the saline with a large amount of water, for example, so that salt does not precipitate. The amount of saline solution per hour is extremely small.

JP 2006-167570 (paragraphs 0008 to 0013, FIG. 1)

  This invention is made | formed under such a situation, and it is providing the apparatus which reduces the density | concentration of the bromide ion contained in salt water.

The salt water purification apparatus of the present invention comprises:
In salt water purification device for removing bromine contained brine in,
A reaction tower for removing bromine salt in water,
A salt water introduction path connected to the upper part of the reaction tower and for introducing a salt solution which is substantially saturated and has a pH of 2.0 or less ;
A salt water discharge port formed at the bottom of the reaction tower for discharging the salt solution descending the reaction tower;
Is connected to the lower part of the reaction tower, the oxidizing gas supply passage for supplying the chlorine gas into the reaction column in order by countercurrent contact in saline to oxidize the bromide ions contained in the brine,
Is connected to the lower part of the reaction tower, and the desorption gas supply path for supplying air to the reaction tower to saline and allowed to flow contact with desorbing bromine gas from brine,
And an exhaust path connected to an upper part of the reaction tower for exhausting the gas in the reaction tower.
The desorption gas supply path and the oxidizing gas supply path are preferably provided with water discharge ports for supplying water and removing precipitates deposited inside .

The salt water purification method of the present invention comprises:
In salt water purification process for removing bromine contained brine in,
A step of introducing a substantially saturated salt solution having a pH of 2.0 or less into the reaction tower from above;
And chlorine gas to oxidize the bromide ions contained in the brine, and the air for desorbing the bromine gas from saline, to counter-current contact with the brine in the reaction column, the reaction column Supplying each from the bottom,
Exhausting the gas in the reaction tower from above;
Discharging the saline solution from which the bromide ions have been released from the lower part of the reaction tower .

  In the present invention, since salt water containing bromide ions is supplied from above the reaction tower and chlorine gas and desorption gas are supplied from the lower side of the reaction tower so as to face the flow of this salt water, A sufficient amount of chlorine gas for oxidizing bromide ions can be passed through the reaction tower, and bromide ions in brine can be rapidly oxidized. In addition, since the water discharge port for supplying water is formed in the oxidizing gas supply path and the desorption gas supply path, even if precipitates are deposited in these supply paths, The precipitates can be removed by passing water through.

It is the schematic which shows an example of the chlorine gas manufacturing apparatus of this invention. It is a longitudinal cross-sectional view which shows an example of the brine purification apparatus of this invention. It is a longitudinal cross-sectional view which shows the enlarged view of the gas supply path for desorption in said brine purification apparatus. It is the schematic which shows the reaction mechanism in said brine purification apparatus. It is a longitudinal cross-sectional view of the salt water refiner | purifier which shows a mode that the bromide ion is reduced in said salt water refiner | purifier. It is a longitudinal cross-sectional view which shows the mode of the removal of the deposit | attachment in said desorption gas supply path. It is a longitudinal cross-sectional view which shows the other structural example of the gas supply path for desorption in the experiment example of this invention.

  An example of the salt water purification apparatus 1 which is embodiment of this invention is demonstrated with reference to FIGS. FIG. 1 shows an outline of a chlorine gas production apparatus 2 to which a salt water purification apparatus 1 is applied. This chlorine gas production apparatus 2 is an apparatus for obtaining high-purity chlorine gas by electrolysis from salt water or the like (hereinafter referred to as “salt water”), which will be described later in order to reduce bromide ions in the salt water. A purification apparatus 1, a pH adjustment bath 3 for adjusting the pH of salt water, and an electrolysis tank 4 for obtaining high purity chlorine gas by electrolysis are provided.

In this salt water, for example, a solute such as salt is dissolved at a high concentration until it is almost saturated, and as an impurity, for example, bromide ions are dissolved only slightly, for example, about 30 ppm. Therefore, the chlorine gas production apparatus 2 is configured to reduce the concentration of bromide ions in the salt water to, for example, about 5 ppm by an oxidation reaction in the salt water purification apparatus 1 before performing electrolysis in the electrolysis tank 4. The bromide ion oxidation reaction is performed by adjusting neutral salt water having a pH of about 9 to an acid having a pH of about 1.5 with an acid such as hydrochloric acid before supplying the salt water to the salt water purification apparatus 1. . When bromide ions are oxidized, bromine (Br ₂ ) and hypobromite (HBrO) are produced, but this hypobromite is unstable and pyrolyzes to bromate (HBrO 3) with extremely low vapor pressure. In this case, this compound cannot be gasified and it becomes difficult to remove bromine, so the pH is made acidic. At this level of pH, even if the above bromic acid is produced, it is rapidly decomposed by hydrochloric acid and heat to become the original bromide ion.
Further, in order to return the salt water to neutral and perform electrolysis thereafter, the pH adjustment bath 3 is configured to neutralize the salt water with a neutralizing agent such as a sodium hydroxide aqueous solution. In FIG. 1, 5, 6, 7, and 10 are a hydrochloric acid source, an oxidizing gas source, a neutralizing agent source, and a salt water source, respectively.

Next, the salt water purification apparatus 1 which is the principal part of this invention is demonstrated. The salt water purification apparatus 1 includes a vertically long reaction tower 11 made of a resin such as FRP, for example, and a nozzle 12 for blowing salt water downward in the reaction tower 11 on the upper side of the reaction tower 11. Is provided. The nozzle 12 is connected to a salt water introduction path 13 having a heat exchanger 13a interposed therebetween. On the upstream side of the salt water introduction path 13, the salt water source 10 is a flow rate adjustment unit including a flow rate control unit and a valve. It is connected via the part 10a. The heat exchanger 13a is for heating salt water with water vapor. In this example, the salt water is heated by the heat exchanger 13a. However, the salt water may be heated by mixing heated water vapor into air that is a desorption gas described later.
In addition, a hydrochloric acid supply path 14 having a flow rate adjusting unit 5a including a flow rate control unit and a valve is connected to the downstream side of the flow rate adjusting unit 10a in the salt water introduction path 13. A hydrochloric acid source 5 is connected to the upstream side.

  In the reaction region, which is a region below the nozzle 12 of the reaction tower 11, the salt water blown into the reaction tower 11 by the nozzle 12 flows down through the inside, thereby causing a contact amount (contact) with chlorine gas or the like to be described later. In order to increase the area), for example, a filler formed of a resin is provided as the filling layer 15. A salt water discharge path 16 is connected to the side surface portion of the reaction tower 11 below the packed bed 15 for taking out the salt water having a reduced bromide ion concentration from the reaction tower 11 through the reaction tower 11. The pH adjusting bath 3 described above is connected to the downstream side of the salt water discharge passage 16.

A desorption gas supply path 17 is connected to the side surface of the reaction tower 11 between the packed bed 15 and the salt water discharge path 16. The desorption gas supply path 17 is connected to the reaction tower 11 so that the salt water accumulates on the floor surface of the reaction tower 11 so as to be above the level of the salt water level. Gas may be blown into the salt water accumulated on the floor of the reaction tower 11. A desorption gas source 18 storing desorption gas, for example, air, is connected to the upstream side of the desorption gas supply path 17 via a flow rate adjustment unit 18a including a flow rate control unit and a valve. The desorption gas may be nitrogen gas or argon gas in addition to air.
In addition, as shown in FIG. 3, an oxidizing gas supply path 19 is connected to the desorption gas supply path 17 on the downstream side of the flow rate adjusting unit 18 a, and the upstream side of the oxidizing gas supply path 19 is connected to the desorption gas supply path 17. A bromide ion oxidizing gas source 6 is connected through a flow rate adjusting unit 6a including a flow rate control unit and a valve.

An ion exchange water discharge port 20 is formed as a water discharge port in the desorption gas supply channel 17 between the oxidizing gas supply channel 19 and the flow rate adjusting unit 18a. An ion exchange water supply path 21 is connected. An ion exchange water source 22 is connected to an upstream side of the ion exchange water supply path 21 via a flow rate adjustment unit 22a including a flow rate control unit and a valve. The ion exchange water stored in the ion exchange water source 22 The water such as pure water is for washing away the deposits 30 such as salt adhering to the inner wall of the desorption gas supply path 17 by precipitation of salt water entering the desorption gas supply path 17. . In this example, the oxidizing gas supply path 19 is connected to the desorption gas supply path 17 to share both gas flow paths, but each may be connected to the reaction tower 11 separately. In that case, an ion exchange water discharge port 20 for supplying ion exchange water to the inner surface may be formed in each of the desorption gas supply path 17 and the oxidizing gas supply path 19.
One end side of an exhaust passage 23 for exhausting the gas flowing through the reaction tower 11 is connected to the side surface of the reaction tower 11 above the packed bed 15 described above, and the other end of the exhaust passage 23 is connected. A detoxification device (not shown) for detoxifying excess oxidizing gas and bromine gas is connected to the side.

Next, the operation of the brine purification apparatus 1 will be described with reference to FIGS. 4 to 7 in the case of using chlorine gas as the oxidizing gas and air as the desorbing gas.
First, air is supplied from the desorption gas supply path 17 into the reaction tower 11 at a predetermined flow rate, and the air is passed through the packed bed 15 from the lower side to the upper side to exhaust the air. Exhaust from the passage 23. Subsequently, salt water heated to a predetermined temperature, for example, 75 ° C. in the heat exchanger 13a is sprayed from the nozzle 12 into the reaction tower 11 at a predetermined pressure and a predetermined flow rate, and oxidized at a predetermined pressure and flow rate from the oxidizing gas source 6. Chlorine gas is supplied into the reaction tower 11 through the gas supply path 19 and the desorption gas supply path 17. The salt water discharged from the nozzle 12 spreads conically in the reaction tower 11 and flows down while being transmitted through the inside of the packed bed 15 (the surface of the packing material). On the other hand, chlorine gas and air rise in the reaction tower 11 from the lower side toward the upper side, come into contact with the salt water in the packed bed 15, and oxidize bromide ions in the salt water to bromine. As described above, since the salt water (in the reaction tower 11) is set to a temperature near the boiling point of bromine, the bromine becomes partially liquid as shown in FIG. A predetermined amount of bromine gas evaporates so as to obtain a vapor pressure corresponding to the gas pressure, resulting in an equilibrium state between the gas and the liquid. When air is allowed to flow through the reaction tower 11 in which bromine is in an equilibrium state, for example, bromine gas that has become extremely small bubbles is attracted to the air bubbles by the surface tension and diffuses into the air bubbles. It becomes a big bubble and rises with air. Further, as shown in FIG. 4B, since bromine which is a gas is removed, the amount of evaporation of liquid bromine increases so that an equilibrium relationship is maintained. Therefore, as bromine gas is removed as it flows downward through the reaction tower 11, the bromide ion concentration in liquid bromine and salt water gradually decreases.

  In addition, when bromine gas rises with air, it may re-condense from the vapor-liquid equilibrium relationship by coming into contact with salt water again. However, bromine (salt water), which is liquid, moves downward in the reaction tower 11. Since the rate of air rise is faster than the rate of flow, and because the salt water temperature is close to the boiling point of bromine and the vapor pressure of bromine is high, it flows relatively upward. Then, it is discharged from the reaction tower 11.

On the other hand, as described above, chlorine gas becomes chloride ions by oxidation of bromide ions, and the concentration decreases. Therefore, the chlorine gas concentration decreases toward the upper side in the reaction column 11, but as described above, a chlorine gas equal to or more than the equivalent of bromide ions is allowed to flow from the lower side into the reaction column 11, and the salt water and Since the contact area with the chlorine gas is increased in the packed bed 15, a sufficient amount of chlorine gas for oxidizing bromide ions is spread in the packed water 15 and dissolved in the salted water. Even if the concentration of bromide ions is very small, the contact probability between bromide ions and chlorine gas is increased, and the reaction time between bromide ions and chlorine gas can be obtained sufficiently. Oxidized and escapes from salt water with air as bromine gas. This bromine gas is exhausted from the exhaust path 23 together with air and surplus chlorine gas, and is separated and purified in a detoxification device (not shown).
Then, the salt water whose bromide ion concentration is reduced to about 5 ppm, for example, flows down from the lower side of the packed bed 15 as shown in FIG. It is discharged from the discharge path 16 to the pH adjustment bath 3.

  At this time, the salt water flowing down from the packed bed 15 is almost saturated with dissolved salt as described above, and a part of the salt water is a desorption gas supply channel. As shown in FIG. 6 (a), moisture is taken away by air and dried, for example, and salt is deposited as the deposit 30 on the inner surface of the desorption gas supply path 17 as shown in FIG. If the deposit 30 is left unattended, the deposit 30 gradually increases and the desorption gas supply path 17 may be blocked. Therefore, for example, ion exchange water at a predetermined flow rate is periodically added every several hours. The discharge pressure is increased from the ion-exchanged water supply path 21 to about 2 kPa, for example, and is discharged vigorously. The deposit 30 adhering to the inner surface of the desorption gas supply path 17 is dissolved in the ion exchange water, and as shown in FIG. 6B, the desorption gas is supplied by the discharge pressure of the ion exchange water. It peels off from the inner surface of the road 17. The deposit 30 is then dissolved in salt water staying below the reaction tower 11 and discharged together with the salt water.

  Thereafter, a neutralizing agent such as an aqueous sodium hydroxide solution is supplied to the salt water with reduced bromide ions in the pH adjusting bath 3 to neutralize the salt water until the pH becomes about 9 or so, and then the salt water. Is electrolyzed in the electrolysis tank 4 to obtain chlorine gas in which bromine is reduced to, for example, about 30 ppm.

  According to the above-mentioned embodiment, since the gaseous chlorine gas is used as an oxidizing agent for oxidizing bromide ions, not a liquid state, the amount of salt water after mixing the oxidizing agent hardly increases. Throughput can be increased without reducing the amount of salt water treated per hour. In addition, while the above-mentioned sodium hypochlorite is easily decomposed under strong acidity, the chlorine gas is difficult to decompose, and bromide is not particularly harmful even under relatively mild pH conditions of about 1.5 pH. Ion oxidation proceeds. In addition, since it is not necessary to replenish the chlorine gas that is deficient due to the generation of chloric acid, for example, the amount of chlorine gas used can be suppressed, and the amount of hydrochloric acid used to make the pH of the salt water acidic is reduced. Further, the amount of the neutralizing agent added to the salt water for neutralization in the pH adjusting bath 3 can also be reduced. Furthermore, as described later, there is an advantage that a counter flow system can be adopted by using gaseous chlorine gas as an oxidizing agent.

  Further, since salt water containing bromide ions is supplied from above the reaction tower 11 and an oxidizing agent is supplied from the lower side of the reaction tower 11 so as to face the flow of this salt water, bromide ions are oxidized. Therefore, a sufficient amount of chlorine gas can be passed through the reaction tower 11, so that bromide ions in the salt water can be rapidly oxidized.

  When the oxidizing gas is supplied in a manner in which the oxidizing gas is mixed with the salt water, the chlorine gas once supplied on the front side of the nozzle 12 is discharged to the reaction tower 11 and then the pressure of the salt water decreases, so that the solubility is reduced. Escapes and is exhausted from the exhaust path 23. Therefore, the chlorine gas flowing into the packed bed 15 is only a small amount remaining undissolved in the salt water, and as described above, the chlorine gas in the salt water is insufficient in the packed bed 15. However, it is not replenished, and as a result, bromide ions cannot be sufficiently oxidized. However, as described above, by introducing chlorine gas into the reaction tower 11 from the lower side, an excess amount of chlorine gas is allowed to flow to the upper part of the reaction tower 11 to compensate for the insufficient chlorine gas in the salt water. Therefore, the bromide ion concentration can be made extremely low.

As in the above example, in the case of using almost saturated salt water, even if a slight amount of water in the salt water evaporates, it becomes supersaturated, and the deposit 30 in the portion where the liquid is difficult to touch, for example, the desorption gas supply path 17. As a result, the chlorine content is left in the reaction tower 11 and the amount of chlorine gas generated in the electrolysis tank 4 is reduced. Further, the desorption gas supply path 17 is blocked by the deposit 30. However, as described above, since the ion exchange water discharge port 20 is formed in the desorption gas supply path 17 to discharge the ion exchange water, the desorption gas supply path is provided. 17, even if the deposit 30 is deposited, the deposit 30 is dissolved by ion-exchanged water, and the deposit 30 is swept away by the discharge pressure of the ion-exchanged water, as shown in the examples below. gas A decrease in production volume and a closing of the desorbed gas supply passage 17 can be prevented.
In the above example, chlorine gas is used as the oxidizing gas. However, fluorine gas, chlorous acid gas, ozone gas, or nitrogen dioxide may be used as the oxidizing gas. Must be taken into account.

Next, the experiment performed in order to confirm the effect of the brine purification apparatus 1 of this invention is demonstrated. The experiment was conducted under the following basic conditions. Moreover, according to the content of each experiment, the bromine concentration and pH in the exit of the reaction tower 11 were measured.
(Basic conditions)
Brine supply amount: 0.8 m3 / h
Salt water concentration: 310 g / L
Hydrochloric acid supply: 3kg / h
Hydrochloric acid concentration: 36% by weight
Ion exchange water supply: 3kg / h
Neutralizing agent: 25% by weight sodium hydroxide Neutralizing agent supply amount: 3.7 kg / h
Air flow rate: 28 Nm3 / h
Air temperature: 10 ° C to 25 ° C (outside temperature)
Example 1
An experiment was conducted to confirm the difference between chlorine gas and sodium hypochlorite as an oxidant for oxidizing bromide ions, and to confirm the difference between the counterflow method and the cocurrent method.
(Experimental example 1)
In the salt water purification apparatus 1 described above, an experiment was performed using chlorine gas as an oxidizing agent and changing the flow rate to 3 l / min and 1 l / min. The chlorine gas was supplied at a pressure of 0.5 MPa using a 50 kg cylinder.
(Comparative Example 1-1)
In the salt water refining device 1 described above, except that the oxidizing gas supply path 19 is connected to the salt water introduction path 13 between the hydrochloric acid supply path 14 and the salt water source 10 so that the introduction method of chlorine gas is a parallel flow system. The experiment was performed under the same conditions as in Experimental Example 1.
(Comparative Example 1-2)
In the above Comparative Example 1-1, sodium hypochlorite was used instead of chlorine gas as the oxidizing agent. The injection amount of sodium hypochlorite was 3 kg / h. The amount of sodium hypochlorite was set so that the amount of sodium hypochlorite was approximately equivalent to the amount of chlorine gas supplied of 3 l / min in terms of effective chlorine.

この結果、併流方式では、酸化剤として塩素ガスを用いた場合でも、次亜塩素酸ソーダを用いた場合でも、対向流方式（向流）と比較して、反応塔１１の出口における臭素濃度が高くなっていた。このことから、対向流方式では、併流方式よりも塩素ガスと臭化物イオンとの反応時間が長くなっており、臭化物イオンを十分酸化できていると考えられる。
また、臭素濃度に対する塩素ガスの流量の影響は確認できなかった。対向流方式では、塩素ガスの流量が１ｌ／ｍｉｎでも反応が十分起こるが、併流方式では、塩素ガスを３ｌ／ｍｉｎまで増やしても、反応が十分に起こっていないと考えられる。 (Experimental result)
The experimental results are shown in Table 1.
(Table 1)

As a result, in the parallel flow system, the bromine concentration at the outlet of the reaction tower 11 is higher than that in the counter flow system (counterflow), regardless of whether chlorine gas is used as the oxidizing agent or sodium hypochlorite. It was high. From this, it is considered that the counter flow system has a longer reaction time between the chlorine gas and bromide ions than the co-flow system, and bromide ions can be sufficiently oxidized.
Moreover, the influence of the flow rate of chlorine gas on the bromine concentration could not be confirmed. In the counter flow system, the reaction sufficiently occurs even when the flow rate of chlorine gas is 1 l / min, but in the cocurrent system, it is considered that the reaction does not occur sufficiently even if the chlorine gas is increased to 3 l / min.

その結果、塩酸の流量を減らすことにより、反応塔１１の出口におけるｐＨが増加していったが、臭素濃度については問題ないレベルであった。このことから、塩酸の流量を従来（ｐＨ＝１．０）の時と比べて、約２／３程度（ｐＨ＝１．５〜２．０）まで減らせることが分かった。また、塩酸の流量を減らせることから、既述のように、電気分解の前において、塩水の中和に必要な水酸化ナトリウム水溶液についても減らせることが分かった。 (Example 2)
In order to confirm how much the pH of the salt water affects the reaction amount when chlorine gas is used as the oxidant, the flow rate of chlorine gas is fixed at 1 l / min as a counter flow method, and the following Table 2 shows As shown, the experiment was carried out by changing the flow rate of hydrochloric acid.
(Table 2)

As a result, the pH at the outlet of the reaction tower 11 was increased by reducing the flow rate of hydrochloric acid, but the bromine concentration was at a level with no problem. From this, it was found that the flow rate of hydrochloric acid can be reduced to about 2/3 (pH = 1.5 to 2.0) compared with the conventional case (pH = 1.0). Further, since the flow rate of hydrochloric acid can be reduced, as described above, it has been found that the aqueous sodium hydroxide solution necessary for neutralization of brine can also be reduced before electrolysis.

塩素ガスの流量を１ｌ／ｍｉｎから０．３ｌ／ｍｉｎまで減らしても、臭素濃度は目標値まで低減されていた。このことから、この塩水を上記の基本条件で処理するために、従来の向流方式において必要であった塩素ガスの流量（３ｌ／ｍｉｎ）を１／１０程度にまで減らすことができることが分かり、また排気ガスの処理の負担についても、大幅に軽減されることが分かった。 (Example 3)
The experiment was conducted by fixing the flow rate of hydrochloric acid at 2 kg / h and changing the flow rate of chlorine gas in the counter flow system. The results are shown in Table 3.
(Table 3)

Even if the flow rate of chlorine gas was reduced from 1 l / min to 0.3 l / min, the bromine concentration was reduced to the target value. From this, it can be seen that the chlorine gas flow rate (3 l / min) required in the conventional countercurrent system can be reduced to about 1/10 in order to treat this salt water under the above basic conditions, It was also found that the burden of exhaust gas treatment was greatly reduced.

空気の流量を変えても、ほとんど臭素濃度に影響がなかったが、塩素ガスの流量を０．３ｌ／ｍｉｎから０．１ｌ／ｍｉｎまで減らすと、臭素濃度が増加していた。この０．１ｌ／ｍｉｎという流量は、塩水中に含まれる臭素濃度とほぼ等ｍｏｌ量であるが、臭化物イオンとほとんど反応していない（初期の臭化物イオン濃度：２７ｐｐｍ）ことから、塩素ガスの流量としては、０．３ｌ／ｍｉｎが下限値だと考えられる。 Example 4
The experiment was conducted by fixing the flow rate of hydrochloric acid at 2 kg / h and changing the flow rate of chlorine gas and the flow rate of air as shown in Table 4 below.
(Table 4)

Even if the air flow rate was changed, the bromine concentration was hardly affected, but the bromine concentration was increased when the chlorine gas flow rate was reduced from 0.3 l / min to 0.1 l / min. The flow rate of 0.1 l / min is approximately equal to the bromine concentration in the salt water, but hardly reacts with bromide ions (initial bromide ion concentration: 27 ppm), so the flow rate of chlorine gas. Is considered to be 0.3 l / min as the lower limit.

この結果、塩水の流量を増やすと、それに伴い、臭化物イオン濃度も増えていることが分かった。このことから、臭化物イオンの除去のためには、反応時間がある程度必要だと考えられる。尚、この実験結果は、ビーカー試験の結果と良好な対応となった。また、塩水精製装置１における反応を安定させるためには、およそ１〜２時間程度必要であることも分かった。 (Example 5)
Next, using the above-mentioned salt water purification apparatus 1, the salt water was continuously treated for 72 hours. At this time, as shown in Table 5 below, the flow rate of the brine was changed every several hours, and the change in bromide ion concentration at the outlet of the reaction tower 11 was confirmed. The flow rate of hydrochloric acid and the flow rate of chlorine gas were adjusted to be proportional to the flow rate of salt water.
(Table 5)

As a result, it was found that when the flow rate of salt water was increased, the bromide ion concentration was increased accordingly. From this, it is considered that a certain reaction time is required for removing bromide ions. This experimental result was in good correspondence with the result of the beaker test. Moreover, in order to stabilize reaction in the salt water refiner | purifier 1, it turned out that about 1-2 hours are required.

(Example 6)
In order to remove the deposit 30 in the desorption gas supply path 17, an experiment was performed by changing the apparatus configuration or the ion exchange water supply method as follows.
(Experimental example 6)
The ion exchange water supply path 21 was connected as shown in FIG. 3 described above, and the same experiment as in Example 5 was performed. At that time, 2 l of ion exchange water was rapidly supplied once every two hours.
(Comparative Example 6-1)
The salt water treatment was performed in the same manner as in Experimental Example 6. At that time, as shown in FIG. 7A, the desorption gas supply path 17 a with the closed end face is connected to the reaction tower 11, and the front end of the desorption gas supply path 17 a is projected into the reaction tower 11. At the same time, the lower side of the protruding portion of the desorption gas supply path 17a is opened, air and chlorine gas are supplied into the reaction tower 11 from the opening, and salt water enters the desorption gas supply path 17a. I tried not to. In addition, it experimented without supplying ion-exchange water at this time.
(Comparative Example 6-2)
The experiment was performed in the same manner as Comparative Example 6-1. Further, as shown in FIG. 7B, an ion exchange water supply passage 21a is provided at the outlet of the desorption gas supply passage 17 (near the connection with the reaction tower 11), and the ion exchange water discharge port 20a is removed. Ion exchange water was continuously supplied at a flow rate of 30 ml / min so as to face into the reaction tower 11 near the center of the opening surface of the separation gas supply path 17.
(Experimental result)
As a result, in Experimental Example 6, no deposit 30 was observed in the desorption gas supply port 17, but in Comparative Example 6-1 and Comparative Example 6-2, the deposit 30 was deposited. . From this, the salt water that has flowed downward through the reaction tower 11 spreads along the wall surface of the reaction tower 11, and the deposit 30 is not easily contacted with salt water such as the desorption gas supply path 17. It was found to precipitate. In order to remove the deposit 30, it is not sufficient to continuously flow ion exchange water in order to dissolve the deposit 30. I found out that it was necessary to rush.

DESCRIPTION OF SYMBOLS 1 Salt water purification apparatus 2 Chlorine gas production apparatus 6 Oxidation gas source 10 Salt water source 11 Reaction tower 17 Desorption gas supply path 19 Oxidation gas supply path 21 Ion exchange water supply path 23 Exhaust path 30

Claims (3)

In salt water purification device for removing bromine contained brine in,
A reaction tower for removing bromine salt in water,
A salt water introduction path connected to the upper part of the reaction tower and for introducing a salt solution which is substantially saturated and has a pH of 2.0 or less ;
A salt water discharge port formed at the bottom of the reaction tower for discharging the salt solution descending the reaction tower;
Is connected to the lower part of the reaction tower, the oxidizing gas supply passage for supplying the chlorine gas into the reaction column in order by countercurrent contact in saline to oxidize the bromide ions contained in the brine,
Is connected to the lower part of the reaction tower, and the desorption gas supply path for supplying air to the reaction tower to saline and allowed to flow contact with desorbing bromine gas from brine,
An apparatus for purifying salt water, comprising: an exhaust passage connected to an upper portion of the reaction tower for exhausting a gas in the reaction tower.   2. The water discharge port is formed in the desorption gas supply path and the oxidant gas supply path to supply water and remove precipitates deposited inside. The brine purification apparatus as described in 2. In salt water purification process for removing bromine contained brine in,
A step of introducing a substantially saturated salt solution having a pH of 2.0 or less into the reaction tower from above;
And chlorine gas to oxidize the bromide ions contained in the brine, and the air for desorbing the bromine gas from saline, to counter-current contact with the brine in the reaction column, the reaction column Supplying each from the bottom,
Exhausting the gas in the reaction tower from above;
Discharging the saline solution from which the bromide ions have been removed from the lower part of the reaction tower.

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