JP2012188327A - Method for making hypochlorite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a constant concentration of metal hydroxide in a reaction solution and a uniform concentration of hypochlorite even when a disturbance such as fluctuation in supply amount of chlorine gas occurs. A production method capable of obtaining an aqueous solution or suspension of hypochlorite is provided.
First, a 25% aqueous sodium hydroxide solution, pure water and chlorine gas are continuously supplied to a first reaction tower 1 to cause a reaction. The reaction liquid derived from the first reaction tower 1 is stored in the storage tank 3. Next, the reaction liquid derived from the storage tank 3 and chlorine gas are continuously supplied to the second reaction tower 2 to be reacted. And the supply amount of the sodium hydroxide aqueous solution to the 1st reaction tower 1 is controlled so that the liquid level height of the reaction liquid stored in the storage tank 3 becomes constant, and the reaction liquid in the 2nd reaction tower 2 is controlled. The supply amount of the reaction liquid led out from the storage tank 3 to the second reaction tower 2 is controlled so that the oxidation-reduction potential becomes constant.
[Selection] Figure 1

Description

  The present invention relates to a method for producing hypochlorite.

  Hypochlorite is produced, for example, by passing chlorine through an aqueous solution or suspension of a metal hydroxide such as an alkali metal hydroxide or an alkaline earth metal hydroxide. In this chlorination reaction, hypochlorite and metal chloride are produced, and the concentration of hypochlorite and metal chloride increases with the progress of chlorination. Therefore, the hypochlorite aqueous solution or suspension contains hypochlorite and metal chloride produced by the chlorination reaction and unreacted metal hydroxide.

  In Patent Document 1, an aqueous solution of sodium hydroxide and chlorine gas as metal hydroxides are continuously supplied to a wet-walled reaction tower to cause a reaction, and a part of the reaction solution is circulated to cause a reaction. A method for producing an aqueous sodium chlorate solution is disclosed.

  In the method for producing a sodium hypochlorite aqueous solution disclosed in Patent Document 1, the sodium hydroxide aqueous solution and the circulating reaction liquid are caused to flow down in the reaction tower at a specific speed or higher, so that the sodium chloride crystals on the tower wall are formed. Since adhesion can be prevented and decomposition of sodium hypochlorite resulting from the heterogeneity of the reaction can be suppressed, a high-concentration sodium hypochlorite aqueous solution can be obtained.

JP 59-102806

  However, in the method for producing an aqueous sodium hypochlorite solution disclosed in Patent Document 1, for example, when the supply amount of chlorine gas supplied to the reaction tower varies, the consumption amount of sodium hydroxide in the chlorination reaction varies. Therefore, the amount of unreacted sodium hydroxide contained in the produced sodium hypochlorite aqueous solution varies, and the concentration of sodium hypochlorite in the sodium hypochlorite aqueous solution becomes uneven.

  Patent Document 1 describes that the supply amount of chlorine gas is controlled so that the oxidation-reduction potential of the reaction solution becomes constant, and the concentration of sodium hydroxide in the reaction solution is made constant. However, when the supply rate of chlorine gas is controlled based on the oxidation-reduction potential of the reaction solution, if a disturbance such as fluctuation of the supply amount of the raw material to the reaction tower occurs if the control response speed is slow, the reaction solution It becomes difficult to make the concentration of sodium hydroxide constant, and the concentration of sodium hypochlorite in the produced sodium hypochlorite aqueous solution becomes uneven.

  Therefore, the object of the present invention is to maintain a constant concentration of the metal hydroxide in the reaction solution even when a disturbance such as fluctuation in the supply amount of chlorine gas occurs, and hypochlorite. It is an object of the present invention to provide a production method capable of obtaining an aqueous solution or suspension of hypochlorite having a uniform concentration.

In the present invention, an aqueous solution or suspension of a metal hydroxide having a predetermined concentration, water, and chlorine gas are continuously supplied to the first reaction tower to react the metal hydroxide and chlorine gas. 1 reaction step,
A storage step of storing the reaction liquid derived from the first reaction tower in a storage tank;
The reaction liquid derived from the storage tank and chlorine gas are continuously supplied to the second reaction tower, and unreacted metal hydroxide and chlorine gas contained in the reaction liquid derived from the storage tank are supplied. A second reaction step for reacting,
In the first reaction step, the supply amount of the metal hydroxide aqueous solution or suspension to the first reaction tower is controlled so that the level of the reaction liquid stored in the storage tank is constant. ,
In the second reaction step, the supply amount of the reaction liquid led out from the storage tank to the second reaction tower is controlled so that the oxidation-reduction potential of the reaction liquid in the second reaction step is constant. A process for producing hypochlorite, characterized in that

  In the hypochlorite production method of the present invention, the time constant of the reaction in the second reaction column is shorter than the time constant of the reaction in the first reaction column.

  In the hypochlorite production method of the present invention, in the first reaction step, sodium hydroxide is used as the metal hydroxide, and sodium hypochlorite is obtained as a hypochlorite. To do.

  According to the present invention, the method for producing hypochlorite includes a first reaction step, a storage step, and a second reaction step. In the first reaction step, an aqueous solution or suspension of metal hydroxide having a predetermined concentration, water, and chlorine gas are continuously supplied to the first reaction tower to react the metal hydroxide and chlorine gas. Let In the storage step, the reaction liquid derived from the first reaction tower is stored in a storage tank. In the second reaction step, the reaction liquid derived from the storage tank and chlorine gas are continuously supplied to the second reaction tower, and unreacted metal hydroxide contained in the reaction liquid derived from the storage tank; React with chlorine gas. In the first reaction step, the supply amount of the metal hydroxide aqueous solution or suspension to the first reaction tower is controlled so that the liquid level of the reaction liquid stored in the storage tank is constant, In the second reaction step, the supply amount of the reaction solution led out from the storage tank to the second reaction tower is controlled so that the oxidation-reduction potential of the reaction solution in the second reaction step is constant.

  As a result, it is possible to control at a high response speed the control for making the liquid level of the reaction liquid stored in the storage tank constant and the control for making the oxidation-reduction potential of the reaction liquid constant in the second reaction step. . Therefore, for example, even when a disturbance such as a change in the supply amount of chlorine gas to the second reaction tower occurs in the second reaction step, the oxidation-reduction potential of the reaction liquid in the second reaction tower is constant. So that the concentration of the metal hydroxide in the reaction solution can be kept constant, and the aqueous solution or suspension of hypochlorite with a uniform concentration of hypochlorite. A liquid can be obtained.

  According to the invention, in the method for producing hypochlorite, the time constant of the reaction in the second reaction tower is shorter than the time constant of the reaction in the first reaction tower. Since the reaction time constant in the second reaction column is short, the redox potential of the reaction solution in the second reaction column can be quickly controlled so as to be constant. Further, since the time constant of the reaction in the first reaction column is relatively long, even when a disturbance such as a change in the amount of chlorine gas supplied to the first reaction column occurs, the disturbance is The propagation speed of the influence exerted on the reaction in the two-reaction tower can be reduced. Therefore, it is possible to secure a time margin until the disturbance affects the reaction in the second reaction column, and to maintain a high accuracy of control for keeping the oxidation-reduction potential of the reaction solution in the second reaction column constant. be able to.

  According to the invention, in the method for producing hypochlorite, sodium hypochlorite is obtained as hypochlorite by using sodium hydroxide as the metal hydroxide in the first reaction step. Can do.

It is a figure for demonstrating the procedure of the manufacturing method of the hypochlorite which concerns on one Embodiment of this invention. It is a figure for demonstrating the procedure of the manufacturing method of the hypochlorite by the 2nd control method in 1st experiment. It is a graph which shows the control result by the 1st control method in the 1st experiment. It is a graph which shows the control result by the 1st control method in the 1st experiment. It is a graph which shows the control result by the 2nd control method in the 1st experiment. It is a graph which shows the control result by the 1st control method in the 2nd experiment. It is a graph which shows the control result by the 1st control method in the 2nd experiment.

  FIG. 1 is a diagram for explaining the procedure of a hypochlorite manufacturing method according to an embodiment of the present invention. The hypochlorite production method of the present embodiment is a method for producing an aqueous solution or suspension of hypochlorite by passing chlorine gas through an aqueous solution or suspension of metal hydroxide. 1 reaction process, a storage process, and a 2nd reaction process are included.

  In the method for producing hypochlorite of the present embodiment, the metal hydroxide used for the chlorination reaction includes alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, water Examples thereof include alkaline earth metal hydroxides such as strontium oxide and barium hydroxide. The form of the metal hydroxide determines the salt form in the hypochlorite produced. For example, when sodium hydroxide is used as the metal hydroxide, an aqueous solution of sodium hypochlorite can be obtained by passing chlorine gas through the aqueous solution of sodium hydroxide. In addition, when lithium hydroxide is used as the metal hydroxide, an aqueous solution of lithium hypochlorite is obtained, and when potassium hydroxide is used, an aqueous solution of potassium hypochlorite is obtained. When strontium was used, a suspension of calcium hypochlorite was obtained. When strontium hydroxide was used, a suspension of strontium hypochlorite was obtained. When barium hydroxide was used, A suspension of barium hypochlorite is obtained.

  Below, the manufacturing method of the hypochlorite of this embodiment is demonstrated using sodium hydroxide as a metal hydroxide, and manufacturing the aqueous solution of sodium hypochlorite as a hypochlorite as an example. .

  The first reaction step is performed in the first reaction tower 1. The first reaction tower 1 includes a metal hydroxide supply means 4 via a first pipe 31, a pure water supply means 5 via a second pipe 32, and a first chlorine gas supply means via a third pipe 33. 6 is connected.

  The metal hydroxide supply means 4 supplies an aqueous solution or suspension of metal hydroxide having a predetermined concentration to the first reaction tower 1. In the present embodiment, the metal hydroxide supply means 4 supplies a sodium hydroxide (NaOH) aqueous solution having a predetermined concentration (25 wt% in this embodiment) to the first reaction tower 1 as an aqueous solution of metal hydroxide. Supply. The amount of sodium hydroxide aqueous solution supplied to the first reaction tower 1 by the metal hydroxide supply means 4 is adjusted by a first on-off valve 21 provided in the first pipe 31. The pure water supply means 5 supplies pure water to the first reaction tower 1. The amount of pure water supplied to the first reaction tower 1 by the pure water supply means 5 is adjusted by a second on-off valve 22 provided in the second pipe 32.

The first chlorine gas supply means 6 supplies chlorine gas (Cl ₂ ) to the first reaction tower 1. The supply amount of chlorine gas to the first reaction tower 1 by the first chlorine gas supply means 6 is adjusted by a third on-off valve 23 provided in the third pipe 33. The chlorine gas supplied by the first chlorine gas supply means 6 can be pure chlorine gas or chlorine gas mixed with air. In the present embodiment, the chlorine gas supplied by the first chlorine gas supply means 6 is a mixture of carbon dioxide gas (CO ₂ ).

  The first reaction column 1 is filled with a packing to increase the gas-liquid contact efficiency and increase the efficiency of the chlorination reaction of the aqueous sodium hydroxide solution. As the filler, for example, known materials such as Raschig rings and pole rings can be used, and examples of the material include fluororesin, vinyl chloride resin, ceramics, and inorganic glass.

A sodium hydroxide aqueous solution is continuously supplied from the metal hydroxide supply means 4, pure water is continuously supplied from the pure water supply means 5, and chlorine gas is continuously supplied from the first chlorine gas supply means 6. In the first reaction tower 1, as shown in the following formula (1), sodium hydroxide (NaOH) and chlorine gas (Cl ₂ ) react to form sodium hypochlorite (NaClO) and sodium chloride (NaCl). And water (H ₂ O) are formed.

In addition, since carbon dioxide gas is mixed in the chlorine gas supplied from the first chlorine gas supply means 6, in the first reaction tower 1, as shown in the following formula (2), sodium hydroxide (NaOH) ) And carbon dioxide gas (CO ₂ ) react to produce sodium carbonate (Na ₂ CO ₃ ) and water (H ₂ O).

  From the bottom of the first reaction column 1 where the reactions represented by the formulas (1) and (2) have occurred, unreacted sodium hydroxide, sodium hypochlorite, sodium chloride, sodium carbonate, and water are included. A reaction solution is derived.

  The reaction liquid led out from the first reaction tower 1 flows through the fourth pipe 34 and is introduced into the storage tank 3. In the storage tank 3, a storage process is executed to store the reaction liquid derived from the first reaction tower 1. The storage tank 3 is connected to a liquid level gauge 12 for measuring the liquid level of the reaction liquid stored inside. An oxidation-reduction potential measuring device (ORP meter) 11 for measuring the oxidation-reduction potential of the reaction solution is connected to the fourth pipe 34 through which the reaction solution derived from the first reaction tower 1 flows. The reaction liquid stored in the storage tank 3 is pumped up by the first pump 8 connected via the fifth pipe 35, flows through the sixth pipe 36, and is returned to the top side of the first reaction tower 1. The reaction is repeated.

  The sixth pipe 36 is provided with a cooler (not shown) that removes heat generated by the reaction in the first reaction tower 1. The reaction liquid flowing through the sixth pipe 36 and returning to the first reaction tower 1 is cooled to 10 ° C. by this cooler. The temperature of the first reaction column 1 depends on the amount of reaction heat generated by the reaction in the first reaction column 1 and the amount of the reaction solution circulating through the sixth pipe 36 and returned to the first reaction column 1. And adjusted as appropriate.

  Further, in the first reaction step by the first reaction tower 1, as will be described in detail later, the liquid level height of the reaction liquid stored in the storage tank 3 measured by the liquid level gauge 12 is constant. The amount of sodium hydroxide aqueous solution supplied to the first reaction tower 1 by the metal hydroxide supply means 4 is adjusted by the first on-off valve 21.

  Further, in the first reaction step by the first reaction tower 1, the adjustment of the supply amount of the sodium hydroxide aqueous solution described above, and the reaction liquid derived from the storage tank 3 in the second reaction step by the second reaction tower 2 described later. According to the adjustment of the supply amount to the second reaction tower 2, the supply of pure water by the pure water supply means 5 with respect to the supply amount of the sodium hydroxide aqueous solution to the first reaction tower 1 by the metal hydroxide supply means 4 The ratio of the amounts is adjusted as appropriate. In the first reaction step, details will be described later, but the ratio of the amount of pure water supplied to the amount of sodium hydroxide aqueous solution supplied to the first reaction column 1 may be controlled to be constant.

  Next, the second reaction step is performed in the second reaction tower 2. The second reaction tower 2 is connected to a seventh pipe 37 branched from a sixth pipe 36 through which the reaction liquid led out from the storage tank 3 flows, and the second chlorine gas supply means 7 is connected via the eighth pipe 38. Is connected. Similar to the first reaction column 1, the second reaction column 2 is filled with a packing material.

  The reaction liquid led out from the storage tank 3 and pumped up by the first pump 8 flows through the sixth pipe 36 and the seventh pipe 37 and is supplied to the second reaction tower 2. The supply amount of the reaction liquid led out from the storage tank 3 to the second reaction tower 2 is adjusted by a fourth on-off valve 24 provided in the seventh pipe 37.

The second chlorine gas supply means 7 supplies chlorine gas (Cl ₂ ) to the second reaction tower 2. The supply amount of chlorine gas to the second reaction tower 2 by the second chlorine gas supply means 7 is adjusted by the fifth on-off valve 25 provided in the eighth pipe 38. The chlorine gas supplied by the second chlorine gas supply means 7 can be pure chlorine gas or chlorine gas mixed with air. In the present embodiment, the chlorine gas supplied by the second chlorine gas supply means 7 is a mixture of carbon dioxide gas (CO ₂ ).

  In the second reaction tower 2 to which the reaction liquid derived from the storage tank 3 is continuously supplied and chlorine gas is continuously supplied from the second chlorine gas supply means 7, as shown by the above formula (1). Then, unreacted sodium hydroxide contained in the reaction liquid derived from the storage tank 3 reacts with chlorine gas to produce sodium hypochlorite, sodium chloride, and water.

  In addition, since carbon dioxide gas is mixed in the chlorine gas supplied from the second chlorine gas supply means 7, in the second reaction tower 2, as shown by the above formula (2), sodium hydroxide and Carbon dioxide gas reacts to produce sodium carbonate and water.

  From the bottom of the second reaction tower 2 where the reactions represented by the formulas (1) and (2) have occurred, unreacted sodium hydroxide, sodium hypochlorite, sodium chloride, sodium carbonate, and water are included. A reaction solution is derived.

  The reaction liquid derived from the second reaction tower 2 flows through the ninth pipe 39, is pumped up by the second pump 9 connected to the ninth pipe 39, and flows through the tenth pipe 40. The sixth on-off valve 26 provided in the pipe 40 is opened and returned to the top side of the second reaction tower 2, and the reaction is repeated. The tenth pipe 40 is provided with a cooler (not shown) that removes heat generated by the reaction in the second reaction tower 2. The reaction liquid flowing through the tenth pipe 40 and returning to the second reaction tower 2 is cooled to 10 ° C. by this cooler. Further, the temperature of the second reaction tower 2 depends on the amount of heat generated by the reaction in the second reaction tower 2 and the amount of the reaction liquid circulating through the tenth pipe 40 and returned to the second reaction tower 2. And adjusted as appropriate. In addition, an eleventh pipe 41 branched from the tenth pipe 40 is connected to the tenth pipe 40. The eleventh pipe 41 is provided with a seventh on-off valve 27, and an end thereof is connected to the product tank 10.

  The second reaction tower 2 is connected with a liquid level gauge 14 for measuring the liquid level of the reaction liquid at the bottom of the tower. An oxidation-reduction potential measuring device (ORP meter) 13 for measuring the oxidation-reduction potential of the reaction solution is connected to the ninth pipe 39 through which the reaction solution derived from the second reaction tower 2 flows. In the present embodiment, when the reaction liquid derived from the second reaction tower 2 reaches the reaction end point when the sodium hydroxide concentration correlated with the oxidation-reduction potential measured by the ORP meter 13 becomes about 1% by weight. To do. When the reaction end point is reached in this way, the reaction liquid derived from the second reaction tower 2, that is, the sodium hypochlorite aqueous solution as a product flows through the tenth pipe 40 and the eleventh pipe 41. The product tank 10 is supplied and stored.

  Further, in the second reaction step by the second reaction tower 2, sodium hypochlorite to the product tank 10 is measured so that the liquid level height of the reaction liquid at the bottom of the tower measured by the liquid level gauge 14 is constant. The supply amount of the aqueous solution is adjusted by the seventh on-off valve 27. Further, in the second reaction step by the second reaction tower 2, the details will be described later, but the reaction solution derived from the storage tank 3 is set so that the oxidation-reduction potential of the reaction solution measured by the ORP meter 13 is constant. The supply amount to the second reaction tower 2 is adjusted by the fourth on-off valve 24.

  Further, in the method for producing hypochlorite of the present embodiment, the time constant of the reaction in the second reaction tower 2 is shorter than the time constant of the reaction in the first reaction tower 1. Here, the time constant is a standard indicating the response time of the reaction process.

  In the method for producing hypochlorite, the reaction between sodium hydroxide and chlorine gas is performed in the first reaction tower 1 and the second reaction tower 2, and the storage tank 3 is led out from the first reaction tower 1. Since it is provided for storing the reaction liquid, the storage step by the storage tank 3 is a part of the first reaction step by the first reaction tower 1. Therefore, the time constant of the reaction in the second reaction tower 2 is shorter than the time constant of the reaction in which the first reaction tower 1 and the storage tank 3 are regarded as one. The time constant is defined by the ratio between the liquid phase volume in the first reaction tower 1 and the storage tank 3 and the liquid phase volume in the second reaction tower 2.

  As described above, the time constant of the reaction in the second reaction column 2 is shorter than the time constant of the reaction in the first reaction column 1 so that the redox potential of the reaction solution in the second reaction column 2 becomes constant. It can be controlled quickly. Even if a disturbance such as a change in the amount of chlorine gas supplied to the first reaction column 1 occurs due to the relatively long time constant of the reaction in the first reaction column 1, the disturbance Can reduce the propagation speed of the influence exerted on the reaction in the second reaction column 2. Therefore, it is possible to secure a time margin until the disturbance affects the reaction in the second reaction column 2, and the control accuracy for making the oxidation-reduction potential of the reaction solution in the second reaction column 2 constant is high. Can be maintained.

  Next, reaction control in the first reaction column 1 and the second reaction column 2 will be described with reference to specific experimental examples.

(First experiment)
Assuming the case where a disturbance in which the supply amount of chlorine gas to the second reaction tower 2 fluctuates occurs, the control responsiveness in the following two control methods was confirmed. The basic initial setting conditions in the first experiment are as follows.

[Internal volume of first reaction tower 1, second reaction tower 2 and storage tank 3]
When the internal volume (m ³ ) of the first reaction column 1 is “1”, the internal volume of the second reaction column 2 is “0.17”, and the internal volume of the storage tank 3 is “0.80”. is there. The ratio of the liquid phase volume in the first reaction tower 1 and the storage tank 3 to the liquid phase volume in the second reaction tower 2 is approximately 5: 1.

[Metal hydroxide supply means 4]
The metal hydroxide supply means 4 supplies a sodium hydroxide aqueous solution having a concentration of 25% by weight.

[First chlorine gas supply means 6]
In the total supply amount of gas supplied by the first chlorine gas supply means 6, chlorine gas is 2.4% by weight, carbon dioxide gas is 0.3% by weight, nitrogen gas is 80.8% by weight, and oxygen gas is 16. 5% by weight.

[Second chlorine gas supply means 7]
In the total supply amount of gas supplied by the second chlorine gas supply means 7, chlorine gas is 56.7% by weight, carbon dioxide gas is 0.3% by weight, and nitrogen gas is 43.0% by weight.

[Raw material supply]
When the initial supply amount (kg / h) of the sodium hydroxide aqueous solution by the metal hydroxide supply means 4 is “1”, the reaction liquid derived from the storage tank 3 (hereinafter referred to as “first reaction liquid”) The initial supply amount (kg / h) to the second reaction column 2 is “1.16”, the initial total gas supply amount (kg / h) by the first chlorine gas supply means 6 is “1.31”, and the second chlorine The initial total gas supply amount (kg / h) by the gas supply means 7 is “0.30”. The supply amount of chlorine gas is greater in the second chlorine gas supply means 7 than in the first chlorine gas supply means 6. Further, the ratio of the initial supply amount of pure water to the initial supply amount of the aqueous sodium hydroxide solution in the first reaction tower 1 was 12.6%.

[Disturbance input conditions]
In the first experiment, a disturbance that increases the supply amount of chlorine gas by 6.3% out of the total supply amount of gas to the second reaction tower 2 by the second chlorine gas supply means 7 was input.

<First control method>
In the first control method, the supply amount of the aqueous sodium hydroxide solution to the first reaction tower 1 by the metal hydroxide supply means 4 so that the level of the reaction liquid stored in the storage tank 3 is constant. Is controlled by the opening / closing operation of the first opening / closing valve 21. In the first control method, the reaction derived from the storage tank 3 so that the oxidation-reduction potential of the reaction liquid in the second reaction tower 2 is constant, that is, the sodium hydroxide concentration of the reaction liquid is constant. The supply amount of the liquid to the second reaction tower 2 is controlled by the opening / closing operation of the fourth opening / closing valve 24. Furthermore, in the first control method, the supply amount of the sodium hydroxide aqueous solution to the first reaction column 1 is controlled, and the supply amount of the reaction liquid derived from the storage tank 3 to the second reaction column 2 is controlled. Accordingly, the ratio of the pure water supply amount by the pure water supply means 5 to the supply amount of the sodium hydroxide aqueous solution to the first reaction tower 1 by the metal hydroxide supply means 4 is controlled to be constant.

<Second control method>
The second control method includes a control for making the liquid surface height of the reaction liquid stored in the storage tank 3 constant and a control for making the oxidation-reduction potential of the reaction liquid in the second reaction tower 2 constant. This is different from the control method. The second control method will be specifically described with reference to FIG. FIG. 2 is a diagram for explaining the procedure of the hypochlorite manufacturing method according to the second control method in the first experiment. In the second control method, the supply amount of the reaction liquid derived from the storage tank 3 to the second reaction tower 2 is adjusted so that the level of the reaction liquid stored in the storage tank 3 is constant. It is controlled by the opening / closing operation of the 4 opening / closing valve 24. Further, in the second control method, the metal hydroxide supply means 4 is used so that the oxidation-reduction potential of the reaction liquid in the second reaction tower 2 is constant, that is, the sodium hydroxide concentration of the reaction liquid is constant. The supply amount of the aqueous sodium hydroxide solution to the first reaction tower 1 is controlled by the opening / closing operation of the first opening / closing valve 21. In the second control method, the ratio of the amount of pure water supplied by the pure water supply means 5 to the amount of sodium hydroxide aqueous solution supplied to the first reaction tower 1 by the metal hydroxide supply means 4 is controlled to be constant. To do.

<Control result>
FIG. 3A and FIG. 3B are graphs showing the control results obtained by the first control method in the first experiment. FIG. 3A (a) is a graph showing controllability for making the oxidation-reduction potential of a reaction liquid (hereinafter referred to as “second reaction liquid”) in the second reaction tower 2 constant, and the horizontal axis represents the second reaction tower. 2 shows the elapsed time (minutes) from the input of a disturbance that increases the supply amount of chlorine gas to 2, and the right vertical axis represents the first reaction liquid derived from the storage tank 3 to the second reaction column 2. The supply amount (relative ratio when the initial supply amount (kg / h) when the elapsed time is 0 minutes is “1”) is shown, and the left vertical axis represents the sodium hydroxide concentration (wt%) of the second reaction solution. ). Moreover, in FIG. 3A (a), line A is a control curve of the supply amount of the first reaction liquid to the second reaction tower 2, and line B is controllability of the sodium hydroxide concentration of the second reaction liquid, That is, it is a curve showing the controllability of the redox potential of the second reaction solution. As is clear from FIG. 3A (a), in the first control method, the line B becomes linear despite the input of a disturbance that increases the amount of chlorine gas supplied to the second reaction tower 2. And controlling the sodium hydroxide concentration of the second reaction liquid in the second reaction column 2 to be constant (constant at about 1.0% by weight), that is, the redox potential of the second reaction liquid to be constant, It can be controlled with a fast response speed.

  FIG. 3A (b) is a graph showing controllability that keeps the liquid level height of the first reaction liquid stored in the storage tank 3, and the horizontal axis indicates the supply of chlorine gas to the second reaction tower 2. The elapsed time (minutes) from the input of the disturbance for increasing the amount is shown, and the right vertical axis represents the supply amount of the aqueous sodium hydroxide solution to the first reaction tower 1 (initial supply amount when the elapsed time is 0 minutes). (Relative ratio when (kg / h) is “1”), and the left vertical axis indicates the liquid level height of the first reaction liquid stored in the storage tank 3 (the liquid level relative to the total height of the storage tank 3). Ratio (%)). In FIG. 3A (b), line C is a control curve of the amount of sodium hydroxide aqueous solution supplied to the first reaction tower 1, and line D is the liquid of the first reaction liquid stored in the storage tank 3. It is a curve which shows the controllability of surface height. As apparent from FIG. 3A (b), in the first control method, the line D becomes linear despite the input of a disturbance that increases the amount of chlorine gas supplied to the second reaction column 2. And controlling the liquid level of the first reaction liquid stored in the storage tank 3 to be constant (the ratio of the liquid level to the total height of the storage tank 3 is constant at about 50%) at a fast response speed. Can be controlled.

  FIG. 3B (c) is a graph showing the fluctuation of the oxidation-reduction potential of the first reaction liquid, that is, the fluctuation of the sodium hydroxide concentration of the first reaction liquid, and the horizontal axis represents the chlorine gas to the second reaction tower 2. The elapsed time (minutes) after inputting the disturbance which increases supply_amount | feed_rate is shown, and a vertical axis | shaft shows the sodium hydroxide concentration (weight%) of a 1st reaction liquid. Further, in FIG. 3B (c), line E is a curve showing the fluctuation of the sodium hydroxide concentration of the first reaction liquid, that is, the fluctuation of the oxidation-reduction potential of the first reaction liquid. In the first control method, the ratio of the amount of pure water supplied to the amount of sodium hydroxide aqueous solution supplied to the first reaction tower 1 is controlled to a constant value of 12.6%. In the first control method, the concentration of sodium hydroxide in the first reaction liquid is determined by the supply amount balance of chlorine gas to each of the first reaction column 1 and the second reaction column 2 and the second reaction in the second reaction column 2. It adjusts suitably according to the sodium hydroxide density | concentration of a liquid. As apparent from FIG. 3B (c), in the first control method, the sodium hydroxide concentration of the first reaction liquid in line E varies within the range of 17.6 to 18.6% by weight.

  FIG. 3B (d) is a graph showing the concentration of sodium hypochlorite in the second reaction liquid, and the horizontal axis represents the input of a disturbance that increases the supply amount of chlorine gas to the second reaction tower 2. The elapsed time (minutes) is shown, and the vertical axis shows the sodium hypochlorite concentration (% by weight) in the second reaction solution. Moreover, in FIG. 3B (d), the line F is a curve which shows the controllability of the sodium hypochlorite density | concentration in a 2nd reaction liquid. As is apparent from FIG. 3B (d), in the first control method, the disturbance of the second reaction liquid in the second reaction liquid is input in spite of the input of a disturbance that increases the supply amount of chlorine gas to the second reaction tower 2. The sodium chlorate concentration can be controlled within the range of 15.7-16.3% by weight.

  As described above, in the first control method, even when a disturbance occurs in which the supply amount of chlorine gas to the second reaction column 2 fluctuates, the hydroxylation of the second reaction solution in the second reaction column 2 occurs. Since the sodium concentration is constant, that is, the redox potential of the second reaction solution can be quickly controlled so as to obtain a sodium hypochlorite aqueous solution having a uniform sodium hypochlorite concentration. Can do.

  FIG. 4 is a graph showing a control result by the second control method in the first experiment. FIG. 4A is a graph showing the controllability that makes the oxidation-reduction potential of the second reaction liquid constant, and the horizontal axis inputs a disturbance that increases the supply amount of chlorine gas to the second reaction tower 2. The right vertical axis represents the supply amount of the aqueous sodium hydroxide solution to the first reaction tower 1 (the initial supply amount (kg / h) when the elapsed time is 0 minutes, “1”. ”, And the left vertical axis represents the sodium hydroxide concentration (% by weight) of the second reaction solution. In FIG. 4A, line G is a control curve for the amount of sodium hydroxide aqueous solution supplied to the first reaction tower 1, and line H is the controllability of the sodium hydroxide concentration of the second reaction liquid. That is, it is a curve showing the controllability of the redox potential of the second reaction solution. As apparent from FIG. 4A, in the second control method, the line H is not linear, and the sodium hydroxide concentration of the second reaction liquid in the second reaction tower 2, that is, the second reaction liquid. The redox potential of cannot be made constant.

  FIG. 4B is a graph showing controllability that makes the liquid level height of the first reaction liquid stored in the storage tank 3 constant, and the horizontal axis indicates supply of chlorine gas to the second reaction tower 2. The elapsed time (minutes) from the input of the disturbance for increasing the amount is shown, and the right vertical axis represents the supply amount of the first reaction liquid to the second reaction tower 2 (initial supply amount when the elapsed time is 0 minutes). (Relative ratio when (kg / h) is “1”), and the left vertical axis indicates the liquid level height of the first reaction liquid stored in the storage tank 3 (the liquid level relative to the total height of the storage tank 3). Ratio (%)). In FIG. 4B, line I is a control curve of the supply amount of the first reaction liquid to the second reaction tower 2, and line J is the liquid of the first reaction liquid stored in the storage tank 3. It is a curve which shows the controllability of surface height. As is clear from FIG. 4B, in the second control method, the line J is not linear, and the liquid level of the first reaction liquid stored in the storage tank 3 can be made constant. Can not.

(Second experiment)
Assuming that a disturbance in which the supply amount of chlorine gas to the first reaction tower 1 fluctuates, the control responsiveness in the third control method shown below was confirmed. The basic initial setting conditions in the second experiment are as follows.

[Internal volume of first reaction tower 1, second reaction tower 2 and storage tank 3]
This is the same as the first experiment described above.

[Metal hydroxide supply means 4]
Similar to the first experiment described above, the metal hydroxide supply means 4 supplies a sodium hydroxide aqueous solution having a concentration of 25% by weight.

[First chlorine gas supply means 6]
In the total amount of gas supplied by the first chlorine gas supply means 6, chlorine gas is 5.2% by weight, carbon dioxide gas is 0.3% by weight, nitrogen gas is 78.5% by weight, and oxygen gas is 16. 0% by weight.

[Second chlorine gas supply means 7]
In the total supply amount of the gas supplied by the second chlorine gas supply means 7, chlorine gas is 41.2% by weight, carbon dioxide gas is 0.5% by weight, and nitrogen gas is 58.3% by weight.

[Raw material supply]
When the initial supply amount (kg / h) of the sodium hydroxide aqueous solution by the metal hydroxide supply means 4 is “1”, the reaction liquid derived from the storage tank 3 (hereinafter referred to as “first reaction liquid”) The initial supply amount (kg / h) to the second reaction column 2 is “1.16”, the initial total gas supply amount (kg / h) by the first chlorine gas supply means 6 is “1.35”, and the second chlorine The initial total gas supply amount (kg / h) by the gas supply means 7 is “0.22”. The supply amount of chlorine gas is greater in the second chlorine gas supply means 7 than in the first chlorine gas supply means 6. Further, the ratio of the initial supply amount of pure water to the initial supply amount of the aqueous sodium hydroxide solution in the first reaction tower 1 was 12.6%.

[Disturbance input conditions]
In the second experiment, a disturbance that reduces the supply amount of chlorine gas by 57% out of the total supply amount of gas to the first reaction tower 1 by the first chlorine gas supply means 6 was input.

<Control method>
As the control method in the second experiment, the first control method in the first experiment described above was applied.

<Control result>
FIG. 5A and FIG. 5B are graphs showing a control result by the first control method in the second experiment. FIG. 5A (a) is a graph showing controllability that makes the oxidation-reduction potential of the second reaction liquid constant, and the horizontal axis inputs a disturbance that reduces the supply amount of chlorine gas to the first reaction column 1. The right vertical axis indicates the supply amount of the first reaction liquid to the second reaction column 2 (the initial supply amount (kg / h) when the elapsed time is 0 minutes, “1”. ”, And the left vertical axis represents the sodium hydroxide concentration (% by weight) of the second reaction solution. In FIG. 5A (a), line K is a control curve of the supply amount of the first reaction liquid to the second reaction column 2, and line L is controllability of the sodium hydroxide concentration of the second reaction liquid, That is, it is a curve showing the controllability of the redox potential of the second reaction solution. As is clear from FIG. 5A (a), in the first control method, the line L is substantially linear even though a disturbance that reduces the supply amount of chlorine gas to the first reaction column 1 is input. The control is performed so that the sodium hydroxide concentration of the second reaction liquid in the second reaction column 2 is constant (constant at about 1.0% by weight), that is, the redox potential of the second reaction liquid is constant. Can be controlled with fast response speed.

  FIG. 5A (b) is a graph showing controllability that makes the liquid level height of the first reaction liquid stored in the storage tank 3 constant, and the horizontal axis indicates supply of chlorine gas to the first reaction tower 1. The elapsed time (minutes) from the input of the disturbance for decreasing the amount is shown, and the right vertical axis represents the supply amount of the aqueous sodium hydroxide solution to the first reaction tower 1 (initial supply amount when the elapsed time is 0 minutes). (Relative ratio when (kg / h) is “1”), and the left vertical axis indicates the liquid level height of the first reaction liquid stored in the storage tank 3 (the liquid level relative to the total height of the storage tank 3). Ratio (%)). 5A (b), the line M is a control curve for the amount of sodium hydroxide aqueous solution supplied to the first reaction tower 1, and the line N is the liquid of the first reaction liquid stored in the storage tank 3. It is a curve which shows the controllability of surface height. As is apparent from FIG. 5A (b), in the first control method, the line N is substantially linear even though a disturbance that reduces the supply amount of chlorine gas to the first reaction column 1 is input. The response level of the first reaction liquid stored in the storage tank 3 is constant (the ratio of the liquid level to the total height of the storage tank 3 is constant at about 50%). Can be controlled.

  FIG. 5B (c) is a graph showing the fluctuation of the oxidation-reduction potential of the first reaction liquid, that is, the fluctuation of the sodium hydroxide concentration of the first reaction liquid, and the horizontal axis represents the chlorine gas to the first reaction tower 1. The elapsed time (minutes) after inputting the disturbance which reduces the supply amount of this is shown, and a vertical axis | shaft shows the sodium hydroxide concentration (weight%) of a 1st reaction liquid. In FIG. 5B (c), the line O is a curve showing the variation of the sodium hydroxide concentration of the first reaction solution, that is, the variation of the oxidation-reduction potential of the first reaction solution. In the first control method, the ratio of the amount of pure water supplied to the amount of sodium hydroxide aqueous solution supplied to the first reaction tower 1 is controlled to a constant value of 12.6%. In the first control method, the concentration of sodium hydroxide in the first reaction liquid is determined by the supply amount balance of chlorine gas to each of the first reaction column 1 and the second reaction column 2 and the second reaction in the second reaction column 2. It adjusts suitably according to the sodium hydroxide density | concentration of a liquid. As is apparent from FIG. 5B (c), in the first control method, the sodium hydroxide concentration of the first reaction liquid on the line O varies within the range of 9.6 to 16.2% by weight.

  FIG. 5B (d) is a graph showing the concentration of sodium hypochlorite in the second reaction liquid, and the horizontal axis represents the input after the disturbance that decreases the supply amount of chlorine gas to the first reaction tower 1 is input. The elapsed time (minutes) is shown, and the vertical axis shows the sodium hypochlorite concentration (% by weight) in the second reaction solution. In FIG. 5B (d), the line P is a curve showing the controllability of the sodium hypochlorite concentration in the second reaction solution. As is clear from FIG. 5B (d), in the first control method, the hypothesis in the second reaction liquid is input despite the input of a disturbance that reduces the supply amount of chlorine gas to the first reaction tower 1. The sodium chlorate concentration can be controlled within the range of 15.1 to 17.7% by weight.

  As described above, in the first control method, the hydroxylation of the second reaction liquid in the second reaction tower 2 is performed even when a disturbance occurs in which the supply amount of chlorine gas to the first reaction tower 1 fluctuates. Since the sodium concentration is constant, that is, the redox potential of the second reaction solution can be quickly controlled so as to obtain a sodium hypochlorite aqueous solution having a uniform sodium hypochlorite concentration. Can do. In the first control method, the ratio of the supply amount of pure water to the supply amount of the sodium hydroxide aqueous solution to the first reaction tower 1 is controlled to be constant. As a result, even when a disturbance occurs in which the supply amount of chlorine gas to the first reaction column 1 fluctuates and the reaction consumption of sodium hydroxide in the first reaction column 1 fluctuates, the first reaction column 1 The amount of pure water supplied to can be adjusted accordingly. Therefore, a sodium hypochlorite aqueous solution having a uniform sodium hypochlorite concentration can be obtained.

DESCRIPTION OF SYMBOLS 1 1st reaction tower 2 2nd reaction tower 3 Storage tank 4 Metal hydroxide supply means 5 Pure water supply means 6 1st chlorine gas supply means 7 2nd chlorine gas supply means 8 1st pump 9 2nd pump 10 Product tank DESCRIPTION OF SYMBOLS 11, 13 ORP meter 12, 14 Liquid level meter 21 1st on-off valve 22 2nd on-off valve 23 3rd on-off valve 24 4th on-off valve 25 5th on-off valve 26 6th on-off valve 27 7th on-off valve 31 1st piping 32 2nd piping 33 3rd piping 34 4th piping 35 5th piping 36 6th piping 37 7th piping 38 8th piping 39 9th piping 40 10th piping 41 11th piping

Claims (3)

A first reaction step of continuously supplying an aqueous solution or suspension of a metal hydroxide having a predetermined concentration, water, and chlorine gas to the first reaction tower to react the metal hydroxide with chlorine gas; ,
A storage step of storing the reaction liquid derived from the first reaction tower in a storage tank;
The reaction liquid derived from the storage tank and chlorine gas are continuously supplied to the second reaction tower, and unreacted metal hydroxide and chlorine gas contained in the reaction liquid derived from the storage tank are supplied. A second reaction step for reacting,
In the first reaction step, the supply amount of the metal hydroxide aqueous solution or suspension to the first reaction tower is controlled so that the level of the reaction liquid stored in the storage tank is constant. ,
In the second reaction step, the supply amount of the reaction liquid led out from the storage tank to the second reaction tower is controlled so that the oxidation-reduction potential of the reaction liquid in the second reaction step is constant. A process for producing hypochlorite, characterized in that   The method for producing hypochlorite according to claim 1, wherein the time constant of the reaction in the second reaction tower is shorter than the time constant of the reaction in the first reaction tower.   3. The hypochlorite according to claim 1, wherein sodium hydroxide is used as the metal hydroxide and sodium hypochlorite is obtained as a hypochlorite in the first reaction step. 4. Manufacturing method.