JP5557423B2 - Method for producing aqueous sodium hypochlorite solution and aqueous sodium hypochlorite solution obtained by the production method - Google Patents

Description

The present invention relates to a method for producing a sodium hypochlorite aqueous solution and a sodium hypochlorite aqueous solution obtained by the production method, and more specifically, a novel sodium hypochlorite aqueous solution capable of efficiently reducing the concentration of BrO ₃ ⁻ . The present invention relates to a production method and a sodium hypochlorite aqueous solution obtained by the production method.

Sodium hypochlorite aqueous solution is used as a bleaching agent, disinfectant, disinfecting water, various oxidizing agents, and the like in a wide range of fields such as water purification treatment, wastewater treatment, hospitals, home kitchens and laundry. In water purification plants that supply tap water used for drinking water, etc., problems such as environmental harmony and chemical stability due to toxicity and odor are emphasized with regard to sodium hypochlorite used for disinfection and sterilization. In recent years, sodium hypochlorite aqueous solutions in which BrO ₃ ⁻ is particularly reduced have been desired.

Usually, an aqueous sodium hypochlorite solution is produced by reacting an aqueous sodium hydroxide solution with gaseous chlorine. The gaseous chlorine contains gaseous bromine, which is contained in the aqueous sodium hypochlorite solution. This is the main cause of BrO ₃ ⁻ contained in.

The gaseous chlorine is usually produced by electrolyzing industrial salt. Since industrial salts contain various impurities (for example, bromine-containing inorganic compounds) other than sodium chloride, gaseous chlorine obtained by electrolyzing industrial salts contains various impurities (for example, gaseous bromine). ing. Even if this gaseous chlorine is used for the production of an aqueous sodium hypochlorite solution after being purified by the usual purification method, the physical properties of bromine and chlorine are similar in the usual purification method. It was difficult to remove gaseous bromine from the solution, and the resulting sodium hypochlorite aqueous solution contained BrO ₃ ⁻ .

BrO ₃ contained in an aqueous solution of sodium hypochlorite ^- as a method of reducing the concentration of, liquefied portion of gaseous chlorine used as a raw material, a method of reacting with the remaining gaseous chlorine and an aqueous solution of sodium hydroxide (For example, refer patent documents 1 and 2). The method utilizes the fact that bromine tends to be more liquid when chlorine and bromine are compared.

Although the above method can reduce the concentration of BrO ₃ ^−, the sodium hypochlorite aqueous solution obtained by the method contained a relatively large amount of sodium carbonate (Na ₂ CO ₃ ). If sodium carbonate is contained in the sodium hypochlorite aqueous solution, there arises a problem that sodium carbonate hydrate precipitates in the severe cold season, so there is still room for improvement in the above method.

In addition, since the above method uses gaseous chlorine as a raw material, the quality of the industrial salt that is the raw material of gaseous chlorine, the electrolysis conditions and liquefaction of the industrial salt when producing a sodium hypochlorite aqueous solution continuously for a long period of time. Unless the conditions are kept constant, the content of gaseous bromine contained in the gaseous chlorine of the raw material varies. When the content of gaseous bromine contained in the gaseous chlorine of the material varies, BrO ₃ contained in the sodium hypochlorite solution obtained ^- that the concentration of fluctuates, BrO ₃ ^- high concentration of hypochlorite in There was a problem that a sodium chlorate aqueous solution was obtained. This can be solved by constantly measuring the content of gaseous bromine contained in the gaseous chlorine of the raw material, and changing the production conditions according to the content, but doing this will reduce labor and cost. The problem of rising.

On the other hand, a method for producing a sodium hypochlorite aqueous solution in which gaseous chlorine is liquefied for the purpose of removing dioxin and at least part of it is subsequently vaporized is disclosed (for example, see Patent Document 3). However, dioxin is an organic substance having a melting point of 100 to 300 ° C. or higher and a vapor pressure of 2.5 × 10 ⁻¹⁰ Pa to 1 × 10 ⁻² Pa at room temperature, a melting point of −7.2 ° C. and a boiling point of 58 at normal pressure. Compared with bromine, which is an inorganic substance having a vapor pressure of 3.0 × 10 ⁴ Pa at room temperature of 8 ° C., the physicochemical properties are significantly different. Therefore, the production conditions for removing dioxin and the conditions for removing gaseous bromine Of course it is different. Patent Document 3 neither describes nor suggests removal of bromine in chlorine.
JP-A-2005-314132 JP 2006-131478 A JP 2004-51431 A

The present invention relates to a method for producing an aqueous sodium hypochlorite solution capable of obtaining an aqueous sodium hypochlorite solution having a uniform and low BrO ₃ ⁻ concentration by a simple method, and hypochlorous acid obtained by the production method. An object is to provide an aqueous sodium acid solution.

In order to achieve the above-mentioned problems, the present inventors have made extensive studies and completed the present invention.
That is, in the method for producing a sodium hypochlorite aqueous solution of the present invention, the first step of obtaining gaseous chlorine by evaporating bromine-containing liquid chlorine (A) at an evaporation rate satisfying the following formula (1), and the first step: A second step of separating the obtained gaseous chlorine from the liquid chlorine (B) remaining without evaporation, and reacting the gaseous chlorine separated in the second step with an aqueous sodium hydroxide solution to produce an aqueous sodium hypochlorite solution. And a concentration of BrO ₃ ^{− in} the obtained sodium hypochlorite aqueous solution is less than 20 wppm.

Moreover, the manufacturing method of the sodium hypochlorite aqueous solution of this invention is the 1st process which obtains gaseous chlorine by evaporating the liquid chlorine (A) containing a bromine with the evaporation rate which satisfy | fills following formula (1), and 1st process The second step of separating the gaseous chlorine obtained in step 1 and the liquid chlorine (B) remaining without evaporation, and reacting the gaseous chlorine separated in the second step with the aqueous sodium hydroxide solution, the aqueous sodium hypochlorite solution And the concentration of BrO ₃ ^{− in} the obtained sodium hypochlorite aqueous solution is less than 20 wppm in terms of effective chlorine concentration of 13.0%, Also good.

Formula (1): Y <−0.03970X + 99.95
(In the above formula (1), X is the bromine content (wppm) contained in liquid chlorine (A), and Y is the evaporation rate (%) of liquid chlorine (A).)
The bromine content in the liquid chlorine (A) is preferably 80 to 600 wppm.

In the first step, the liquid chlorine (A) is preferably evaporated under the conditions of a pressure of 100 to 550 kPa (gauge pressure) and a temperature of -15 to 30 ° C.
It is preferable that the content of gaseous bromine in the gaseous chlorine is 90 wppm or less.

The concentration of Na ₂ CO _{3 in} the obtained aqueous sodium hypochlorite solution is preferably less than 0.1% by weight.
The present invention includes an aqueous sodium hypochlorite solution obtained by the method for producing an aqueous sodium hypochlorite solution described above.

According to the method of the present invention, an aqueous sodium hypochlorite solution having a low BrO ₃ ⁻ concentration can be obtained.
In addition, the method of the present invention uses liquid chlorine as a raw material, which is different from the conventional method in which gaseous chlorine obtained by electrolyzing salt water is directly used as a raw material. Since it is not affected, the concentration of BrO ₃ ⁻ can be stably reduced.

Since the sodium hypochlorite aqueous solution obtained by the method of the present invention has a reduced BrO ₃ ⁻ concentration, it can be suitably used in various conventional applications, and is also preferably used in water purification plants supplying drinking water and the like. be able to.

Next, the present invention will be specifically described.
The method for producing a sodium hypochlorite aqueous solution of the present invention is obtained in the first step and the first step of obtaining gaseous chlorine by evaporating bromine-containing liquid chlorine (A) at an evaporation rate satisfying the following formula (1). The second step of separating the gaseous chlorine and the liquid chlorine (B) remaining without evaporating is reacted with the gaseous chlorine separated in the second step and the aqueous sodium hydroxide solution to obtain a sodium hypochlorite aqueous solution. And a concentration of BrO ₃ ^{− in} the obtained sodium hypochlorite aqueous solution is less than 20 wppm.

Moreover, the manufacturing method of the sodium hypochlorite aqueous solution of this invention is the 1st process which obtains gaseous chlorine by evaporating the liquid chlorine (A) containing a bromine with the evaporation rate which satisfy | fills following formula (1), and 1st process The second step of separating the gaseous chlorine obtained in step 1 and the liquid chlorine (B) remaining without evaporation, and reacting the gaseous chlorine separated in the second step with the aqueous sodium hydroxide solution, the aqueous sodium hypochlorite solution And a third step of obtaining a concentration of BrO ₃ ^{− in} the obtained sodium hypochlorite aqueous solution is less than 20 wppm in terms of an effective chlorine concentration of 13.0%.

Formula (1): Y <−0.03970X + 99.95
(In the above formula (1), X is the bromine content (wppm) contained in liquid chlorine (A), and Y is the evaporation rate (%) of liquid chlorine (A).)
In the present invention, the sodium hypochlorite aqueous solution is also referred to as NaClOaq. In the present invention, when a pressure is indicated, unless otherwise specified, the pressure indicates a gauge pressure.

FIG. 1 schematically shows an example of the method for producing an aqueous sodium hypochlorite solution of the present invention.
In the production method of the present invention, liquid chlorine (A) is supplied to the vaporizer 1 and a part of the liquid chlorine (A) is vaporized in the vaporizer 1 to become gaseous chlorine and liquid chlorine (B). (First step). This gaseous chlorine is supplied to the reaction tank 2 through the supply pipe, and the liquid chlorine (B) is stored in the storage tank 3 (second step). A sodium hydroxide aqueous solution is supplied to the reaction tank 2, and gaseous chlorine and sodium hydroxide react in the reaction tank 2 to produce a sodium hypochlorite aqueous solution having a BrO ₃ ⁻ concentration of less than 20 wppm. Yes (third step).

Hereinafter, each process is explained in full detail.
[First step]
The first step according to the present invention is a step of obtaining gaseous chlorine by evaporating liquid chlorine (A) containing bromine at an evaporation rate satisfying the above formula (1).

Liquid chlorine remaining without being vaporized in the first step is referred to as liquid chlorine (B).
The liquid chlorine (A) used in the present invention is a liquid chlorine containing bromine. Even if commercially available liquid chlorine is used, gaseous chlorine obtained by electrolyzing industrial salt (hereinafter also referred to as raw gaseous chlorine). However, a liquefied raw gas chlorine is usually used. As liquid chlorine (A) used in the present invention, raw gas chlorine is liquefied under conditions of a pressure of 0.3 to 0.4 MPa (gauge pressure) and a temperature of 3 to 10 ° C. to produce several days to several weeks. From the viewpoint of industrial mass production, it is preferable to use one stored in a storage tank capable of storing liquid chlorine used in the production. By liquefying and storing raw gaseous chlorine in the storage tank, the sodium hypochlorite aqueous solution can be stored regardless of changes in the content of gaseous bromine in gaseous chlorine due to changes in electrolysis conditions and liquefaction conditions. Can be manufactured.

That is, in the method of using raw gaseous chlorine obtained by conventional electrolysis as it is for the production of an aqueous sodium hypochlorite solution, gaseous bromine in gaseous chlorine is changed depending on the quality of industrial salt, electrolysis conditions and liquefaction conditions. However, the content of bromine in the obtained sodium hypochlorite aqueous solution was not constant. If the content of gaseous bromine in gaseous chlorine is constantly measured and the production conditions are controlled in accordance with the concentration, it is possible to keep the concentration of BrO ₃ ^{− in} the aqueous sodium hypochlorite solution constant. , There was a drawback of increased labor and cost.

On the other hand, if the production method of the present invention is used, liquid chlorine (A) used for production for several days to several weeks is stored in advance in a storage tank, so that the content of bromine in liquid chlorine (A) is almost the same. It becomes constant and the concentration of BrO ₃ ^{− in} the obtained sodium hypochlorite aqueous solution can be made almost constant.

The liquid chlorine (A) used in the present invention usually contains 80 to 600 wppm, preferably 100 to 400 wppm, of bromine. The content of bromine contained in the liquid chlorine (A) used in the present invention is preferably as small as possible to reduce the concentration of BrO ₃ ⁻ in the sodium hypochlorite aqueous solution. However, since liquid gaseous chlorine is usually liquefied and used as liquid chlorine (A), it contains bromine derived from a bromine compound contained in industrial salt and is difficult to reduce by ordinary purification. Therefore, when obtaining liquid chlorine (A) containing bromine at a concentration lower than the above range, another step other than the liquefaction step may be required when obtaining liquid chlorine (A) from raw gaseous chlorine. There is a tendency to be inferior in productivity. On the other hand, if the bromine in the liquid chlorine (A) is within the above range, the concentration of BrO ₃ ^{− in} the obtained sodium hypochlorite aqueous solution can be reduced and the productivity is excellent.

In addition, according to the production method of the present invention, an aqueous sodium hypochlorite solution having a lower Na ₂ CO ₃ concentration can be obtained as compared with the case of producing an aqueous sodium hypochlorite solution without liquefying the gaseous chlorine. . The reason is that the raw gaseous chlorine contains usually CO _2, the raw gaseous chlorine, for example, by liquefying the above conditions, to obtain a CO ₂ concentration (wppm) low liquid chlorine (A) It is because it can do. That is, the raw gaseous chlorine and liquefying the above conditions, since CO ₂ remains substantially gaseous, CO ₂ concentration of the liquid chlorine (A) (wppm) is, CO ₂ concentration in the raw gas in chlorine (wppm) It becomes possible to make low.

The first step in the production method of the present invention is characterized in that gaseous chlorine is obtained by evaporating the above-mentioned liquid chlorine (A) at an evaporation rate that satisfies the above formula (1).
As a result of producing sodium hypochlorite aqueous solutions at various evaporation rates using various liquid chlorines (A) having different bromine contents, the present inventors have found that bromine contained in liquid chlorine (A). Hypochlorous acid by producing a sodium hypochlorite aqueous solution under the condition that the content (wppm) of the liquid and the evaporation rate (%) of the liquid chlorine (A) satisfy the relationship of the above formula (1). It has been found that the concentration of BrO ₃ ^{− in} the aqueous sodium solution is less than 20 wppm.

By producing a sodium hypochlorite aqueous solution at an evaporation rate that satisfies the above formula (1), the concentration of BrO ₃ ^{− in} the sodium hypochlorite aqueous solution obtained by the production method of the present invention can be reduced. . In the production method of the present invention, the greater the bromine content (wppm) contained in the liquid chlorine (A), the more the sodium hypochlorite aqueous solution obtained when evaporated at the same evaporation rate. Although the concentration of contained BrO ₃ ⁻ is increased, an aqueous sodium hypochlorite solution having a low BrO ₃ ⁻ concentration is produced by determining the upper limit of the evaporation rate based on the above formula (1). Can do.

Here, the evaporation rate is represented by (mass of gaseous chlorine / mass of liquid chlorine (A)) × 100 [%].
The evaporation rate is not particularly limited as long as the above formula (1) is satisfied, but the optimum value varies depending on the operational aspect of the production facility and the bromine content in the raw material chlorine, and is usually 50 to 90%, preferably 70. ~ 85%. In the present invention, the higher the evaporation rate, the better the productivity of the aqueous sodium hypochlorite solution, and the lower the evaporation rate, the lower the concentration of BrO ₃ ^{− in} the obtained aqueous sodium hypochlorite solution. When the evaporation rate is within the above range, the balance between the productivity of the obtained sodium hypochlorite aqueous solution and the concentration of BrO ₃ ⁻ contained in the sodium hypochlorite aqueous solution is excellent.

  For example, when the bromine concentration in the liquid chlorine (A) is 80 to 95 wppm, the evaporation rate is 96% or less, preferably 50 to 96%, and the bromine concentration in the liquid chlorine (A) exceeds 95 wppm and is 105 wppm or less. In some cases, the evaporation rate is 95% or less, preferably 50 to 95%. When the bromine concentration in the liquid chlorine (A) is more than 105 wppm and 203 wppm or less, the evaporation rate is 91% or less, preferably 50 to 95%. When the bromine concentration in 91% and liquid chlorine (A) exceeds 203 wppm and is 395 wppm or less, the evaporation rate is 84% or less, preferably 50 to 84%, and the bromine concentration in liquid chlorine (A) is 395 wppm. When it exceeds 600 wppm, the evaporation rate is 76% or less, preferably 50 to 76%.

In the present invention, the bromine content (wppm) in the liquid chlorine (A) is difficult to measure in the liquid state. For example, the bromine is vaporized and absorbed in an aqueous sodium hydroxide solution. It is preferably measured as the concentration of BrO ₃ ^{− in} the aqueous sodium chlorate solution.

In the present invention, the lower limit of the evaporation rate is not particularly limited, and the lower the evaporation rate, the lower the concentration of BrO ₃ ^{− in} the obtained sodium hypochlorite aqueous solution. On the other hand, the lower the evaporation rate, the more liquid chlorine (A) needs to be supplied in order to obtain the same amount of gaseous chlorine. Therefore, the lower limit of the evaporation rate is preferably determined in consideration of appropriate equipment efficiency and the concentration of BrO ₃ ^{− in} the obtained sodium hypochlorite aqueous solution.

  That is, when the supply amount of liquid chlorine is constant, the lower the evaporation rate, the lower the productivity, and in order to avoid the decrease in productivity, it is necessary to increase the supply amount of liquid chlorine and secure the amount of gaseous chlorine to be used for the reaction. . In this case, the production facility for the sodium hypochlorite aqueous solution becomes excessive, and therefore it is preferable to determine the lower limit value of the evaporation rate according to the facility scale.

When the bromine content in the liquid chlorine (A) is in the range of 100 to 600 wppm, the concentration of BrO ₃ ⁻ in the sodium hypochlorite aqueous solution obtained by the formula (1) is less than 20 wppm at an evaporation rate of 75%. When the amount of liquid chlorine supplied is used as a reference, the ratio of the amount of liquid chlorine supplied for the same amount of gaseous chlorine for reaction at the evaporation rate and the amount of liquid chlorine supplied when the evaporation rate is 75% is approximately 20 times or less. In addition, it can be used as an indicator on equipment that it is preferably 15 times or less.

  The conditions for evaporating the liquid chlorine (A) at an evaporation rate satisfying the above formula (1) are usually a pressure of 100 to 550 kPa, a temperature of -15 to 30 ° C., and a refrigerant facility can be provided. If the pressure is 100 to 230 kPa and the temperature is -15 to -2 ° C, the operation is possible.

  In the method for producing an aqueous sodium hypochlorite solution of the present invention, the gaseous chlorine obtained in the first step can reduce the content of high boiling point components (wppm) as compared with liquid chlorine (A).

  That is, in the above evaporation conditions, a part of liquid chlorine is vaporized, but a high boiling point component is not necessarily vaporized. Therefore, a high boiling point component contained in gaseous chlorine is a high boiling point component contained in liquid chlorine (A). Can be reduced. Examples of the high boiling point component include chlorine-containing inorganic compounds and chlorine-containing organic compounds.

  In the first step, gaseous chlorine with a low content of high-boiling components can be obtained, so the amount of high-boiling components contained in the aqueous sodium hypochlorite solution obtained by the production method of the present invention is changed to the conventional production method. It can reduce compared with the sodium hypochlorite aqueous solution obtained by this.

[Second step]
The second step according to the present invention is a step of separating gaseous chlorine obtained in the first step from liquid chlorine (B) remaining without being evaporated.

Separation of gaseous chlorine and liquid chlorine (B) is usually performed by introducing gaseous chlorine into a reaction tank through a pipe and moving liquid chlorine (B) to a liquid chlorine storage tank or the like. Since most of bromine contained in liquid chlorine (A) in the first step remains in liquid chlorine (B), the content of gaseous bromine in gaseous chlorine can be reduced. The content of gaseous bromine in the gaseous chlorine obtained by the first step is usually 90 wppm or less, preferably 50 wppm or less, more preferably 25 wppm or less. In the present invention, the smaller the amount of gaseous bromine contained in gaseous chlorine, the lower the concentration of BrO ₃ ^{− in} the resulting sodium hypochlorite aqueous solution, which is preferable, and as the lower limit of gaseous bromine contained in gaseous chlorine. There is no particular limitation.

  The content of gaseous bromine contained in gaseous chlorine may be measured by sampling gaseous chlorine and measuring the gaseous bromine content, but the sodium hypochlorite aqueous solution produced by the production method of the present invention It can also be determined as a converted value from the content of bromic acid contained therein and the effective chlorine concentration. The converted value can be calculated using the following formula (2).

The molecular weight of Br ₂ was calculated as 159.818, and the molecular weight of BrO ₃ ⁻ was calculated as 127.910.
[Third step]
The third step according to the present invention is a step of obtaining a sodium hypochlorite aqueous solution by reacting the separated gaseous chlorine with a sodium hydroxide aqueous solution.

  As the sodium hydroxide aqueous solution used in the present invention, one having a concentration of 15 to 50% by mass obtained by electrolysis is usually used, and one having a concentration adjusted by appropriately diluting with water can also be used.

In order to react gaseous chlorine with an aqueous sodium hydroxide solution, a method of introducing gaseous chlorine into an aqueous sodium hydroxide solution maintained at a temperature of 25 to 30 ° C. under atmospheric pressure is usually mentioned.
The concentration of BrO ₃ ^{− in} the aqueous sodium hypochlorite solution obtained by the method for producing an aqueous sodium hypochlorite solution of the present invention is less than 20 wppm, preferably 10 wppm or less, particularly preferably 5 wppm or less. There is no particular limitation on the lower limit of the BrO ₃ ⁻ concentration.

In the present invention, the concentration of BrO ₃ ⁻ in the sodium hypochlorite aqueous solution is measured by an ion chromatography analyzer in accordance with Japan Water Works Association Standard JWWA Z 109: 2005. Specifically, a method of preparing a calibration curve by preparing a plurality of potassium bromate aqueous solutions having known concentrations, measuring the BrO ₃ ⁻ content of the aqueous solution with an ion chromatography analyzer, and the like.

In addition, since the detection limit of the BrO ₃ ⁻ concentration analysis in the examples described later performed by the above method is 5 wppm, a lower BrO ₃ ⁻ concentration cannot be measured, but in the examples described later, It has been confirmed that the content of BrO ₃ ⁻ contained in the sodium hypochlorite aqueous solution is less than 5 wppm by adjusting conditions such as bromine content and liquefaction rate in liquid chlorine.

The effective chlorine concentration in the aqueous sodium hypochlorite solution obtained by the method for producing an aqueous sodium hypochlorite solution of the present invention is usually 10 to 14%, and as described above, the BrO _{3 in the} aqueous sodium hypochlorite solution. ^- concentration of less than 20wppm.

However, when a sodium hydroxide aqueous solution having a concentration higher than the above range is used as the above-described sodium hydroxide aqueous solution, a sodium hypochlorite aqueous solution having an effective chlorine concentration exceeding the above range may be obtained. In this case, the concentration of BrO ₃ ^{− in} the aqueous sodium hypochlorite solution may be 20 wppm or more. Even in such a case, the concentration of BrO ₃ ⁻ was reduced if the concentration of BrO ₃ ⁻ when the effective chlorine concentration of the sodium hypochlorite aqueous solution was converted to 13.0% was less than 20 wppm. It can be used as a sodium hypochlorite aqueous solution.

At the time of the effective chlorine concentration of aqueous solution of sodium hypochlorite in terms with 13.0% BrO ₃ ^- concentration, BrO in sodium hypochlorite solution ₃ ^- concentration of the above-mentioned Japanese Water Works Association Standards JWWAZ 109: 2005 After measuring according to the above, it is obtained by calculating according to the following formula (3).

In the present invention, the effective chlorine concentration of the sodium hypochlorite aqueous solution can be measured based on Japan Water Works Association Standard JWWA K 120: 2005.
Further, the concentration of sodium carbonate (Na ₂ CO ₃ ) in the sodium hypochlorite aqueous solution obtained by the production method of the present invention is usually less than 0.1% by weight. When the concentration of Na ₂ CO ₃ exceeds 1% by weight, there arises a problem that sodium carbonate hydrate precipitates in the severe cold season. Therefore, the concentration of Na ₂ CO ₃ is preferably less than 1% by weight. The sodium hypochlorite aqueous solution obtained by the production method of the present invention is preferable because the concentration of Na ₂ CO ₃ is usually less than 0.1% by weight, and there is no fear of precipitation of sodium carbonate hydrate.

In addition, since the amount of sodium hydroxide used as a raw material can be reduced by lowering the concentration of Na ₂ CO ₃ contained in the sodium hypochlorite aqueous solution, Na ₂ CO ₃ The concentration is preferably as low as possible, and particularly preferably less than 0.1% by weight.

The concentration of Na ₂ CO ₃ of hypochlorite in aqueous sodium produced by the process of the present invention, as low why compared to the concentration of Na ₂ CO ₃ in aqueous sodium hypochlorite solution obtained by a conventional manufacturing method This is because liquid chlorine (A) is used as a raw material as described above.

In addition, since the detection limit in the analysis of the concentration of Na ₂ CO ₃ described later is 0.1% by weight, the concentration of Na ₂ CO ₃ lower than that cannot be measured. If it is less than 1 weight%, it can be judged that it is excellent in productivity.

The concentration of Na ₂ CO ₃ is determined by adding hydrogen peroxide to sodium hypochlorite aqueous solution to decompose effective chlorine, and then neutralizing and titrating with hydrochloric acid solution using phenolphthalein solution as an indicator. Can be titrated with hydrochloric acid as an indicator, and a sodium carbonate concentration can be calculated using the amount of hydrochloric acid solution required for titration with a methyl orange solution as an indicator.

Since the sodium hypochlorite aqueous solution obtained by the above production method has a low BrO ₃ ⁻ concentration and a low Na ₂ CO ₃ concentration, it can be used for disinfection and sterilization in water purification plants. It can be used in various fields.

〔Example〕
The following present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

[Analysis method]
(I) Measurement of BrO ₃ ⁻ by ion chromatography analyzer The content of BrO ₃ ⁻ was measured by an ion chromatography analyzer in accordance with Japan Water Works Association Standard JWWA Z 109: 2005.

(II) Measurement of effective chlorine concentration by oxidation-reduction titration The effective chlorine concentration of the sodium hypochlorite aqueous solution was measured based on Japan Water Works Association Standard JWWA K 120: 2005.

  That is, potassium iodide was added to an aqueous sodium hypochlorite solution to release iodine by acetic acid acidity, titrated with sodium thiosulfate solution using starch solution as an indicator, and the amount of sodium thiosulfate solution required for titration was used. The effective chlorine concentration was calculated.

(III) Measurement of sodium carbonate concentration by neutralization titration After adding hydrogen peroxide to sodium hypochlorite aqueous solution and decomposing effective chlorine, the solution was neutralized and titrated with hydrochloric acid solution using phenolphthalein solution as an indicator. The methyl orange solution was titrated with hydrochloric acid as an indicator. The sodium carbonate concentration was calculated using the amount of hydrochloric acid solution required for titration using methyl orange solution as an indicator .

[Reference Example 1]
1000 kg of liquid chlorine containing 105 wppm bromine was vaporized under conditions of a temperature of 25 ° C., a pressure of 400 kPa, and an evaporation rate of 8%, and gaseous chlorine was collected by a pipe branched from a supply pipe at the top of the apparatus.

  Filling the reaction vessel with 1,225 g of 20% aqueous solution of sodium hydroxide and reacting the gaseous chlorine for 35 minutes at a temperature of 24 ° C. and a flow rate of 1.59 L / min while keeping the temperature of the aqueous solution at 27 ° C. It was introduced into a container and reacted with an aqueous sodium hydroxide solution to obtain an aqueous sodium hypochlorite solution.

1,387 g of the obtained sodium hypochlorite aqueous solution has an effective chlorine concentration of 11.7% as analyzed by the oxidation-reduction titration method, and a concentration of BrO ₃ ⁻ of less than 5 wppm (below the detection limit) as determined by the ion chromatography method. The sodium carbonate concentration was less than 0.1% (below the detection limit) by analysis by Japanese titration.

The amount of bromine contained in liquid chlorine (A), the evaporation rate, the concentration of BrO ₃ ⁻ contained in the sodium hypochlorite aqueous solution, the effective chlorine concentration, the BrO ₃ ⁻ in terms of the effective chlorine concentration of 13.0% Table 1 shows the concentration, the amount of gaseous bromine in gaseous chlorine converted from the concentration of BrO ₃ ^−, the concentration of Na ₂ CO ₃ , and the effective chlorine concentration .

[Example 2]
Using the same liquid chlorine in Reference Example 1, was carried out in the same manner as in Reference Example 1 except that the evaporation rate and 51%.
The results are shown in Table 1 .

[Example 3]
A refrigerant facility was provided, and evaporation was performed in the same manner as in Reference Example 1 except that the temperature was −5 ° C., the pressure was 200 kPa, and the evaporation rate was 80%. The results are shown in Table 1 .

[Example 4]
Using the same liquid chlorine in Reference Example 1, the evaporation rate except for using 90% was carried out in the same manner as in Reference Example 1.
The results are shown in Table 1 .

[Example 5]
The same procedure as in Reference Example 1 was performed except that 1000 kg of liquid chlorine containing 83 wppm of bromine was used and the evaporation rate was 96%. The results are shown in Table 1 .

[Example 6]
The same procedure as in Reference Example 1 was performed except that 1000 kg of liquid chlorine containing 203 wppm of bromine was used and the evaporation rate was 85%. The results are shown in Table 1 .

[Example 7]
The same procedure as in Reference Example 1 was conducted except that 1000 kg of liquid chlorine containing 395 wppm bromine was used and the evaporation rate was 75%. The results are shown in Table 1 .

[Reference Example 8]
The same procedure as in Reference Example 1 was conducted except that 1000 kg of liquid chlorine containing 395 wppm bromine was used and the evaporation rate was 85%. The results are shown in Table 1 .

[Example 9]
1000 kg of liquid chlorine containing 590 wppm of bromine was used, a refrigerant facility was provided, and evaporation was performed in the same manner as in Reference Example 1 except that the temperature was −5 ° C., the pressure was 200 kPa, and the evaporation rate was 51%. The results are shown in Table 1 .

[Example 10]
The same procedure as in Reference Example 1 was performed except that 1000 kg of liquid chlorine containing 590 wppm of bromine was used and the evaporation rate was 75%. The results are shown in Table 1 .

[ Reference Example 11]
The same procedure as in Reference Example 1 was performed except that 1000 kg of liquid chlorine containing 83 wppm of bromine was used and the evaporation rate was 3%. The results are shown in Table 1.
[Comparative Example 1]
Using the same liquid chlorine in Reference Example 1, the evaporation rate except for using 96% was carried out in the same manner as in Reference Example 1.

The results are shown in Table 1.
[Comparative Example 2]
The same procedure as in Reference Example 1 was conducted except that 1000 kg of liquid chlorine containing 395 wppm bromine was used and the evaporation rate was 90%. The results are shown in Table 1.

[Comparative Example 3]
The same procedure as in Reference Example 1 was performed except that 1000 kg of liquid chlorine containing 590 wppm of bromine was used and the evaporation rate was 85%. The results are shown in Table 1.
[Comparative Example 4]
Instead of liquid chlorine (A), raw gaseous chlorine containing 83 wppm bromine is used, and the raw gaseous chlorine is continuously liquefied under conditions of a temperature of 3 ° C., a pressure of 300 kPa, and a liquefaction rate of 99.4%. The same procedure as in Reference Example 1 was conducted except that the gaseous chlorine was reacted with an aqueous sodium hydroxide solution. The results are shown in Table 1.
The liquefaction rate of 99.4% means that 99.4% by weight is liquefied and 100% by weight remains as gaseous chlorine per 100% by weight of raw gaseous chlorine.

It is a conceptual diagram which shows the embodiment of the manufacturing method of the sodium hypochlorite aqueous solution of this invention.

1 ... vaporizer 2 ... reaction vessel 3 ... liquid chlorine storage tank (A) Cl ₂ [L] ... Liquid chlorine (A)
Cl ₂ [G] ... gaseous chlorine (B) Cl ₂ [L] ... liquid chlorine (B)
NaOHaq ... Sodium hydroxide aqueous solution NaClOaq ... Sodium hypochlorite aqueous solution

Claims (6)

Bromine content is 80～600Wppm, the liquid chlorine (A) containing bromine, a first step of obtaining a gaseous chlorine is evaporated under Ki蒸 Hatsuritsu,
A second step of separating the gaseous chlorine obtained in the first step and the liquid chlorine (B) remaining without evaporation;
A third step of reacting the gaseous chlorine separated in the second step with a sodium hydroxide aqueous solution to obtain a sodium hypochlorite aqueous solution,
A method for producing an aqueous sodium hypochlorite solution, wherein the concentration of BrO ₃ ^{− in} the obtained aqueous sodium hypochlorite solution is less than 20 wppm.
Evaporation rate (mass of gaseous chlorine / mass of liquid chlorine (A)) × 100 [%]):
When the bromine concentration in the liquid chlorine (A) is 80 to 95 wppm, 50 to 96%,
When the bromine concentration in liquid chlorine (A) is more than 95 wppm and not more than 105 wppm, 50 to 95%
When the bromine concentration in the liquid chlorine (A) exceeds 105 wppm and is 203 wppm or less, 50 to 91%
When the bromine concentration in liquid chlorine (A) is more than 203 wppm and not more than 395 wppm, 50 to 84%
When the bromine concentration in the liquid chlorine (A) is more than 395 wppm and 600 wppm or less, 50 to 76% Bromine content is 80～600Wppm, the liquid chlorine (A) containing bromine, a first step of obtaining a gaseous chlorine is evaporated under Ki蒸 Hatsuritsu,
A second step of separating the gaseous chlorine obtained in the first step and the liquid chlorine (B) remaining without evaporation;
A third step of reacting the gaseous chlorine separated in the second step with a sodium hydroxide aqueous solution to obtain a sodium hypochlorite aqueous solution,
A method for producing an aqueous sodium hypochlorite solution, wherein the concentration of BrO ₃ ^{− in} the obtained aqueous sodium hypochlorite solution is less than 20 wppm in terms of an effective chlorine concentration of 13.0%.
Evaporation rate (mass of gaseous chlorine / mass of liquid chlorine (A)) × 100 [%]):
When the bromine concentration in the liquid chlorine (A) is 80 to 95 wppm, 50 to 96%,
When the bromine concentration in liquid chlorine (A) is more than 95 wppm and not more than 105 wppm, 50 to 95%
When the bromine concentration in the liquid chlorine (A) exceeds 105 wppm and is 203 wppm or less, 50 to 91%
When the bromine concentration in liquid chlorine (A) is more than 203 wppm and not more than 395 wppm, 50 to 84%
When the bromine concentration in the liquid chlorine (A) is more than 395 wppm and 600 wppm or less, 50 to 76% The method for producing an aqueous sodium hypochlorite solution according to claim 1 or 2, wherein the liquid chlorine (A) is a liquefied gaseous chlorine obtained by electrolyzing an industrial salt. Sodium hypochlorite aqueous solution according to any one of claims 1 to 3, the concentration of Na ₂ CO ₃ of the so obtained aqueous sodium hypochlorite solution is equal to or less than 0.1 wt% Manufacturing method. Method for producing sodium hypochlorite aqueous solution according to claim 1 in which the content of gaseous bromine of the gaseous chlorine is equal to or less than 90Wppm. In the first step, liquid chlorine (A) a pressure 100～550KPa (gauge pressure), to any one of claims 1 to 5, the temperature is equal to or evaporating under conditions of -15～30 ° C. The manufacturing method of sodium hypochlorite aqueous solution of description.

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