JP2797070B2 - Method and apparatus for producing continuous static chlorine dioxide water - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing chlorine dioxide and chlorine dioxide water which is used in a wide range of applications such as sterilization / disinfection, deodorization, decolorization, insect repellency, and off-flavor improvement. More specifically, the present invention relates to a method and apparatus for producing high-purity chlorine dioxide water statically and continuously at a high conversion rate by using an apparatus having a static mixing effect in a reaction apparatus.

[0002]

2. Description of the Related Art Chlorine dioxide has a melting point of -59.degree.
It is a gaseous substance at normal temperature of ℃, has strong oxidizing power and bactericidal property, and about 3000 ppm with respect to water under normal temperature and normal pressure.
(Mg / l) with a gas concentration of 10 in air.
% Explosive. As a method for producing chlorine dioxide, in a large-scale industrial use such as pulp bleaching, a method of adding a mineral acid alone or a reducing substance such as hydrogen peroxide, sulfur dioxide or methanol to a chlorate is used. For small and medium-sized applications such as sterilization / disinfection of drinking water, improvement of off-flavor taste, deodorization of industrial wastewater, decolorization, insect control in agricultural houses, slime prevention of cooling towers, oil well activation, etc. A known method involves reacting a chlorite aqueous solution with chlorine gas, or a chlorite aqueous solution, hypochlorite and an acid, and absorbing and diluting the generated chlorine dioxide under a back pressure downstream of a water ejector. (Japanese Unexamined Patent Publication No. 3-62641)
No., USP 4,247,531). The method of sucking the supply of these raw chemicals using the reduced pressure created by the water jet ejector has the advantage of being a simple device, but it has the advantage that the chlorine dioxide gas generated under the reduced pressure and the chemical are sucked simultaneously, so the chemical during operation is sucked. The flow rate is unstable, and a small volume of 10 liters per minute or less cannot be manufactured in order to maintain the minimum degree of reduced pressure for sucking the chemical solution.

The method using chlorate and acid or chlorite and acid is economically disadvantageous because the theoretical conversion rate of chlorate or chlorite raw material to chlorine dioxide is 80%. However, in order to actually achieve a conversion of 60%, the acid must be reacted in an excess of 300% of the theoretical amount, and the resulting chlorine dioxide water is strongly acidic and has various disadvantages in use. It is. The method of blowing chlorine gas into chlorite aqueous solution has the advantage that it is easy to control the reaction accurately, the content of chlorine as an impurity can be reduced, and the pH of chlorine dioxide water obtained can be near neutral. ing.
However, there is a drawback that the danger is high because highly toxic chlorine gas is handled. The method of reacting each aqueous solution of chlorite, hypochlorite and acid can reduce the chlorine content as an impurity, and uses hypochlorite as a reducing agent. The amount of acid to be produced is also small, so the pH of chlorine dioxide water obtained is
This method has a great feature of being near neutral, and has a high conversion efficiency of raw materials at normal temperature and normal pressure, and has both economy and safety.

[0004] Since chlorine dioxide in chlorine dioxide water is dissolved as a gas, it is easily volatilized even with extremely weak bubbling or stirring, and the concentration tends to decrease rapidly. In the conventional method for continuously generating chlorine dioxide using the water ejector described above, chlorine dioxide water has a relatively high concentration and is produced by turbulent flow of the water ejector. It was easy to volatilize and the yield was a problem. Also, if the chlorine dioxide water obtained by these methods is used for sterilization or deodorization at a low concentration, the gas will be volatilized even at the time of dilution, which is not only uneconomical but also harmful to the human body. There has been a demand for a simple method for producing chlorine dioxide water having a high concentration.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a chemical reaction rate which is fast at room temperature, has a high conversion efficiency of chlorite to chlorine dioxide, a low content of chlorine as an impurity, It is easy to use, does not use high-pressure gas or harmful compounds as raw materials, and the pH of chlorine dioxide water obtained is weakly acidic.
It is an object of the present invention to provide a method for producing chlorine dioxide water near neutral and an apparatus used for this method.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and have found that aqueous solutions of chlorite, hypochlorite and acid are added while adding water as a diluent. In the method for producing chlorine dioxide water to be reacted, the present inventors have found that the use of a vessel having a static mixing effect as a reaction vessel can achieve the initial purpose, and have completed the present invention. The chlorite used in the present invention,
It is an alkali metal salt of chlorite such as potassium chlorite, sodium chlorite and calcium chlorite, or an alkaline earth metal salt of chlorite. Sodium citrate is preferred. The concentration of these chlorites in the aqueous chlorite solution is 0.1% by weight.
To 25% by weight is preferred. Chlorite concentration of 0.1
If it is less than 10% by weight, the chlorine dioxide generation rate is low, and the yield is low, which is not preferable. Further, an aqueous solution of chlorite in an amount of 25% by weight or more falls under the category 6 oxidizing compound of dangerous substances, and therefore, special consideration is required for storage and handling of raw materials, which is not preferable. The hypochlorite used in the present invention is an alkali metal salt of hypochlorous acid such as potassium hypochlorite, sodium hypochlorite, calcium hypochlorite or an alkaline earth salt of chlorite. Although it is a metal salt, sodium hypochlorite is preferred because it is easily available, has stable quality, and is easy to handle. The concentration of these hypochlorites in the aqueous solution of hypochlorite ranges from 0.1 weight to 12.
5% by weight is preferred. If the concentration of hypochlorite is 12.5% by weight or more, it is not preferable because the concentration decreases quickly. Examples of the aqueous acid solution used in the present invention include aqueous solutions of mineral acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, and aqueous solutions of organic acids such as citric acid and tartaric acid. Hydrochloric acid is preferred from the viewpoints of reactivity and stability of generated chlorine dioxide. The concentration of the acid is preferably from 0.1% by weight to 25% by weight. The above-mentioned chlorite aqueous solution while adding water as a diluent, a reactor having a static mixing effect used as a reactor for reacting the hypochlorite aqueous solution and the acid aqueous solution, a static mixer, Raschig ring, It is a container filled with one kind or a combination of two or more kinds such as a porous body, a granular body, a net-like body, and a fiber filter.

Hereinafter, the present invention will be described with reference to the accompanying drawings. FIG. 1 is a conceptual diagram of a chlorine dioxide water producing apparatus of the present invention. In the figure, 3 is a storage tank, 7, 8 and 9 are chemical tanks, 14 is a reactor, and 15 is a chlorine dioxide water receiver tank. The reactor 14 is intended to statically and homogeneously mix and react the three types of chemicals and water, and includes a static mixer, a Raschig ring, a porous material such as a sintered metal,
It is a cylindrical container filled with a granular material, a mesh such as a stainless steel wire mesh, or a fiber filter. Only one type of the filler may be used, but by using two or more types in combination, the mixing can be made more homogeneous and the reaction efficiency can be improved. For example, at the inlet side, a static mixer for rough mixing is filled in six stages,
An example in which a fine fiber filter is filled (length of the packed layer is 1 to 200 mm) to obtain a homogeneous mixture at the outlet side can be exemplified. The air that has passed through the air filter 1 is blower 2
The pressure is blown into the pressure storage tank 3, and the pressure in the pressure storage tank 3 is adjusted by the pressure control valve 5. Chlorite aqueous solution,
The hypochlorite aqueous solution and the acid aqueous solution are stored in raw material chemical tanks 7, 8, and 9, respectively. The air stored in the pressure storage tank 3 is connected to the raw chemical tanks 7, 8, and 9 by the equalizing pipe 6, and serves to push out the raw chemical. The extruded chemical solution is sent to the reactor 14 through 10 flow control valves, 11 flow meters, and 12 check valves. At this time, the aqueous chlorite solution and the aqueous hypochlorous acid solution merge just before entering the reactor 14. The aqueous acid solution joins downstream of the junction of the two liquids, then joins with the water 13 immediately before the reactor, and is led to the reactor 14. Chlorine dioxide water discharged from the reactor 14 is stored in the receiver tank 14.

[0008] The pressure of the pressure storage tank is required to be equal to or higher than the height of the apparatus in terms of water column pressure, and if the resistance of the liquid in the piping and the reactor is taken into account, the apparatus height plus a few meters (water column) is required. good. The larger the pressure storage tank capacity is, the smaller the pressure fluctuation is preferable. However, in reality, there is no problem if the storage tank capacity is equal to or more than the sum of the three chemical liquid tank capacities. If the blower can obtain an air volume of 100 to 1000 times the reduced amount of the three chemicals, and if a pressure equal to or higher than the pressure of the pressure storage tank can be obtained with the pressure control valve of the pressure storage tank closed, The pressure fluctuation rate of the pressure tank is about 1 to 0.1%, and a sufficiently stable operation can be performed. The inner diameter of the pressure equalizing tube is 1/2 to 2 (inch) because the flow rate of the air passing through the equalizing tube (= the delivery amount of the chemical solution) is small.
It is enough. As the pressure control valve, a ball valve, a probe valve, a gate valve, and the like are preferable. A needle valve that can finely adjust the flow rate of the three chemicals is preferable. Since the flow meter can accurately measure a wide range of flow rate, a rotor meter or a ball type is preferable. (3) A check valve is required in the line of the chemical and the fresh water to prevent the mixture from flowing back. Clear water is required to have a small pressure fluctuation, and pressurized water by pumping or tap water can be used. Since the chlorine dioxide water producing apparatus of the present invention has a structure for supplying a chemical solution at a flow rate corresponding to a desired concentration of chlorine dioxide to be generated in a constant flow of fresh water, when the supply of the fresh water is stopped, it is automatically performed. It is desirable to incorporate a mechanism for stopping the supply of the chemical solution into the apparatus. In addition, it is preferable that the supply of all the liquid chemicals is stopped when any one of the three liquid chemical tanks becomes empty.

The raw chemical liquid tank always sends out the raw chemical liquid at a constant air pressure regardless of the amount of the raw chemical liquid. In the method of the present invention, the low-volume aqueous solution of chlorite, the aqueous solution of hypochlorite, and the aqueous solution of acid are all mixed at a ratio substantially equal to the stoichiometric ratio by a storage tank type raw material chemical supply system. 01 ~
0.5 m / sec. Quantitatively injected into the freshwater stream without pulsation. If the flow rate of the fresh water is less than 0.01 m / sec, the stirring and mixing effect cannot be expected, which is not preferable. or,
If the flow rate of the fresh water exceeds 0.5 m / sec, the reaction solution becomes turbulent, and the chlorine dioxide gas dissolved in the solution becomes bubbles and volatilizes, and the chlorine dioxide concentration is undesirably reduced. The amounts of the three kinds of raw material chemicals to be injected into the fresh water flow depend on the concentration of chlorine dioxide water to be obtained.
0.3 wt% to obtain 000 ppm chlorine dioxide water
Aqueous sodium chlorite solution, 0.2% by weight aqueous sodium hypochlorite solution and 0.2% by weight hydrochloric acid, respectively.
250 ml / min. At a flow rate of Thus, when the flow rate is 0.01 to 0.5 m / sec. The above-mentioned three kinds of raw material solutions in a ratio of the theoretical amount of reaction are sent quantitatively with a small flow rate and no pulsation by the equalizing tank type raw material chemical supply system into the fresh water stream to obtain chlorine dioxide water with a conversion rate of 85% or more. Can be

[0010]

EFFECT OF THE INVENTION Static and continuous, high conversion rate of chlorite to chlorine dioxide, high purity, weakly acidic to neutral pH chlorine dioxide water, economical and safe, simple operation It can be manufactured at In addition, a method can be provided in which chlorine dioxide water having a concentration suitable for the purpose of sterilization and deodorization can be obtained on the spot when needed. The present invention is not only suitable for a low concentration, but also can timely respond to a wide range of concentrations according to various uses.

[0011]

EXAMPLES The present invention will be described more specifically with reference to examples. The chlorine dioxide water concentration was measured by oxidation-reduction titration using sodium thiosulfate standard solution at pH 7, and the chlorine concentration of impurities was measured at two points, pH 7 and pH 2, with sodium thiosulfate standard solution. It was determined by redox titration. Reactor As a chemical tank, three 5-liter glass three-necked flasks were used. Each of these flasks is equipped with a pressure introduction pipe of 0.05 megapascal from the air cylinder, a chemical supply pipe to the reactor, and a cock for releasing pressure. Each of the chemical supply pipes is provided with a needle valve, a flow meter, and a check valve. As a reactor, a static mixer (Noritake Company 1 /
4-N40-112-O type: Inner diameter 8mm, length 100
mm Static mixer with 12 elements). Tap water is supplied to the reactor through a fresh water supply line equipped with a needle valve, a flow meter, and a check valve. Immediately before it is connected to the reactor, the fresh water supply pipe has a confluent pipe of the sodium chlorite aqueous solution and the sodium hypochlorite aqueous solution supply pipe, and the chemical supply pipe of the hydrochloric acid aqueous solution immediately downstream. It is connected.

Examples 1 to 4: Preparation of diluted chlorine dioxide water A sodium chlorite is used as a chlorite, a sodium hypochlorite is used as a hypochlorite, and hydrochloric acid is used as an acid. Prepared. Aqueous sodium chlorite solution 0.75 wt /% Aqueous sodium hypochlorite solution 0.42 wt /% Hydrochloric acid aqueous solution 0.50 wt /% Chlorine dioxide water is produced at the tap water flow rate shown in Table 1 and each chemical solution supply flow rate did. As can be seen from the results in Table 1, dilute chlorine dioxide water which can be used by putting the production water directly into a sterilization tank could be produced with high efficiency, high purity and near neutrality.

[0013]

[Table 1]

Examples 5 to 8: Production Examples of Low Concentration Chlorine Dioxide Water Operations were carried out in the same manner as in Examples 1 to 4, except that the concentration of the starting chemical solution was changed as follows. Sodium chlorite aqueous solution 7.5 wt /% Sodium hypochlorite aqueous solution 4.2 wt /% Hydrochloric acid aqueous solution 5.0 wt /% Table 2 shows chlorine dioxide obtained at each of the tap water flow rate and the three chemical liquid flows. The analysis results of water were shown. 100 to several hundred
This is a production example in a relatively low concentration range of ppm.

[0015]

[Table 2]

Examples 9 to 11: Production Examples of Medium to Highly Concentrated Chlorine Dioxide Water The same operations as in Examples 1 to 4 were carried out except that the concentrations of the raw material chemicals were changed as follows. Sodium chlorite aqueous solution 25.0 wt% Sodium hypochlorite aqueous solution 12.5 wt% Hydrochloric acid aqueous solution 7.5 wt% Medium to high concentration chlorine dioxide water production equipment basically adopts the method shown in FIG. did. (5Nm ³ / mi
n. × 5000 mmAq) turbo blower was used. A 100-liter hard PVC tank was used as the pressure storage tank, and a pressure gauge and a PVC ball valve (40A) pressure control valve were provided. The pressure of the storage tank is 3000mmA
Driven in q. A 20 liter PVC can was used for each chemical tank, and a pressure equalizing tube and a chemical liquid push-up tube were attached to the lid so that the lid could be kept airtight. 20A for equalizing tube
Was used. A needle valve (6A) made of Teflon was used as a flow control valve for the chemical solution, and a rotor meter capable of measuring from 0 to a maximum of 130 milliliters per minute was used as a flow meter. The check valve was made of commercially available plastic (6A), and the supply pipe for the three chemicals was made of hard PVC (6A). Shimizu used tap water and provided a 20A PVC pipe, a globe valve, a rotor meter capable of measuring a maximum of 20 liters per minute, and a check valve. The reactor used was a 60 cm long 50 A PVC tube filled with Raschig rings obtained by cutting a 5 mm outer diameter PVC tube into a 5 mm length. The obtained chlorine dioxide water was analyzed in the same manner as in Examples 1 to 4. Table 3 shows the ratio of the flow rate of tap water to the flow rate of each chemical solution, and the analysis value of chlorine dioxide water obtained under these conditions.
It was shown to. As is clear from the table, a medium to high concentration of chlorine dioxide water could be continuously and easily produced.

[0017]

[Table 3]

[Brief description of the drawings]

FIG. 1 is an example of a chlorine dioxide water generator of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air filter 2 Blower 3 Storage tank 4 Pressure gauge 5 Pressure control valve 6 Equalizing pipe 7 Hypochlorite aqueous solution tank 8 Hypochlorite aqueous solution tank 9 Acid aqueous solution tank 10 Flow control valve 11 Flow meter 12 Check valve 13 Water inlet 14 Reactor 15 Chlorine dioxide water receiver tank

Claims (8)

(57) [Claims] 1. An apparatus for producing chlorine dioxide water, comprising a static mixer (excluding a Venturi tube type mixer) as a reactor. 2. The chlorine dioxide water producing apparatus according to claim 1, wherein said static mixing apparatus does not generate turbulence during mixing. 3. The chlorine dioxide water producing apparatus according to claim 1, further comprising a pressure feeding device for feeding the chemical solution by an air pressure applied to the surface of the chemical solution in the tank, as the chemical solution supply device. 4. A method for producing a chlorine dioxide aqueous solution using a chlorite aqueous solution, a hypochlorite aqueous solution and hydrochloric acid as raw materials, wherein a desired amount of a chlorite aqueous solution, hypochlorous acid is added to a fresh water stream. A method for producing aqueous chlorine dioxide, comprising injecting an aqueous salt solution and hydrochloric acid and reacting them in a static mixer (excluding a Venturi tube type mixer). 5. The method for producing chlorine dioxide water according to claim 4, wherein the static mixing device does not generate turbulent flow during the reaction. 6. A pumping device for feeding a chemical solution from a tank by an air pressure applied to a surface of a chemical solution in a tank with an aqueous solution of chlorite, an aqueous solution of hypochlorite, and hydrochloric acid. The method for producing chlorine dioxide water described in the above. 7. The chlorine dioxide according to claim 4, wherein the aqueous chlorite solution and the aqueous hypochlorite solution are diluted with fresh water before being mixed with hydrochloric acid. Water production method. 8. The flow rate of fresh water supplied to the reactor is 0.01
Meter (m / sec)-0.5 meter (m / sec)
c), and the concentration of chlorine dioxide in the obtained chlorine dioxide water is 0.5 ppm (mg / l) to 3000 ppm (mg / l).
1) characterized in that: 1)
The method for producing chlorine dioxide water according to any one of the first to third aspects.