JPH07300302A - Production of chlorine dioxide - Google Patents

Abstract

PURPOSE:To obtain high-purity chlorine dioxide free from chlorine gas produced as a by-product without using any special separating apparatus. CONSTITUTION:Water is previously packed in a reaction tower 1 and a circulation tower 2 and an aqueous solution of a chloric acid salt is introduced from a line 3 and hydrogen chloride gas is introduced from a line 4 into the reaction tower 1 together with air from the line 5. These materials ascend in the reaction tower 1 by air-lift action of air and are led into the circulation tower 2 and the aqueous solution of a chloric acid salt is reacted with hydrogen chloride gas while repeating circulation in the reaction tower 1 to produce chlorine dioxide and chlorine dioxide is taken out together with an aqueous solution containing common salt produced as a by-product from an output port 8 and passed through a transfer line 15 and introduced into an deairing tower 12, where these materials are brought into contact with air introduced from the lower part and chlorine dioxide is recovered together with air from a discharge port 14, while the aqueous solution separated from chlorine dioxide is passed through a return line 16 and returned to the inside of the circulation tower 2, because the aqueous solution contains a small amount of unreacted raw material and the aqueous solution is re-fed for reaction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing chlorine dioxide, and more particularly to a method for producing chlorine dioxide which can be easily produced with high purity using inexpensive and simple equipment.

Since chlorine dioxide has a strong oxidizing power and an excellent sterilizing ability, it bleaches wood pulp for papermaking, disinfects industrial water and drinking water, sewerage, disinfects seafood, vegetables, fruits and the like, and further disinfects livestock houses, Used as an odor control agent.

[0003]

2. Description of the Related Art Conventionally, as a method for producing chlorine dioxide,
For example, in Japanese Unexamined Patent Publication (Kokai) No. 4-342402, an aqueous solution of chlorate and a gas flow of an acid are introduced into a reaction chamber equipped with a Venturi tube to react with each other to generate chlorine dioxide, and a propulsion medium is introduced to introduce chlorine dioxide. A method of mixing with is disclosed.

[0004]

However, in the above method, the reaction conditions such as the flow rate of the raw material and the medium are extremely difficult to adjust and set because the Venturi tube is used for the reaction at the moment, so that the same amount is used. Mixing and reaction is difficult or nearly impossible. As a result, the reaction efficiency becomes poor and unreacted raw materials are mixed in the product, resulting in a decrease in the purity of the product.
Also, since chlorine dioxide is obtained as a mixture with chlorine that is produced at the same time, the purity of chlorine dioxide is low, the excellent oxidizing power and sterilizing ability of chlorine dioxide are reduced, and the use is limited depending on the application. is there. In order to solve this problem, an apparatus for separating chlorine dioxide and chlorine becomes indispensable, and the apparatus cost is increased. The present invention solves the above problems and provides a method capable of easily producing high-purity chlorine dioxide with an inexpensive and simple apparatus.

[0005]

That is, the first aspect of the present invention is to:
A chlorate aqueous solution, an acid gas and an inert gas are introduced from the lower part of the reaction tower, which is connected so that the circulation tower is in communication with the upper part and the lower part, and is circulated in the reaction tower and the circulation tower by an air lift to cause a reaction. The chlorine dioxide production method is characterized in that the produced chlorine dioxide is taken out from the upper part of the reaction tower together with chlorine gas.

In a second aspect of the present invention, the chlorine dioxide produced in the first aspect is taken out together with the aqueous solution, the chlorine dioxide and the aqueous solution are introduced into a degassing tower, and an inert gas is introduced from the bottom of the tower to degas. And recover chlorine dioxide from the top of the tower together with the inert gas and return the aqueous solution to the reaction tower.

A third aspect of the present invention is to introduce an aqueous chlorite solution, chlorine gas and an inert gas from the lower part of the reaction tower, which is connected so that the circulation tower communicates with the upper part and the lower part, and to introduce the chlorite solution into the reaction tower by air lift. A method for producing chlorine dioxide characterized in that the chlorine dioxide produced is taken out from the upper part of the reaction tower by circulating the reaction in the circulation tower and reacting it.

In a fourth aspect of the present invention, the chlorine dioxide produced in the third aspect is taken out together with the aqueous solution, the chlorine dioxide and the aqueous solution are introduced into a degassing tower, and an inert gas is introduced from the bottom of the tower to degas. And recovering chlorine dioxide together with an inert gas from the top of the tower, and returning the aqueous solution to the reaction tower.

An example of an apparatus used in the present invention will be described with reference to the drawings. In FIG. 1, the reactor comprises a reaction tower 1 and a circulation tower 2, and both towers have a structure in which an upper part and a lower part communicate with each other. A first raw material introduction line 3, a second raw material introduction line 4, and an inert gas introduction line 5 are provided in the lower part of the reaction tower 1, and these are connected to an introduction port 6 in the lower part of the reaction tower 1. . 7 is a perforated plate.

An outlet 8 is provided at the top of the reaction tower 1,
Further, a discharge line 9 is provided at the top of the tower. on the other hand,
A heat exchanger 10 is provided in the circulation tower 2.

FIG. 2 shows another apparatus used in the present invention. The apparatus shown in FIG. 1 is further provided with a degassing tower 12. The degassing tower 12 has an inert gas inlet 13 at the bottom.
And an outlet 14 for the inert gas and the product (chlorine dioxide) is provided at the upper part, and the degassing tower 12 is located above the reaction tower 1
Is connected via the transfer line 15 and the circulation tower 2 below via the return line 16.

A method for carrying out the present invention using the above apparatus will be described below. In the following description, water is used as a reaction medium, hydrogen chloride gas is used as an acid gas, and air is used as an inert gas. Water is previously filled in the reaction tower 1 and the circulation tower 2, and an aqueous chlorate solution is supplied from the first raw material introduction line 3, hydrogen chloride gas is supplied from the second raw material introduction line 4, and an inert gas introduction line 5 is supplied. It is introduced into the lower part of the reaction tower 1 through the inlet 6 together with air.

The introduced chlorate aqueous solution, hydrogen chloride gas and air pass through the perforated plate 7, and at this time, the air becomes fine bubbles, and the air lift action causes the air inside the reaction tower 1 together with the chlorate aqueous solution and hydrogen chloride gas. Ascend and circulation tower 2
Be guided inside. Chlorate aqueous solution introduced into the circulation tower 2,
The hydrogen chloride gas and the air are cooled by the heat exchanger 10, have a large specific gravity, descend and descend into the reaction tower 1 and rise again by the air lift action, and the circulation in the reaction tower 1 and the circulation tower 2 is repeated.

By repeating the above circulation, the aqueous chlorate solution and hydrogen chloride gas react with each other to produce chlorine dioxide, which is discharged and recovered as a mixture from the discharge line 9 at the top of the reaction column together with chlorine gas produced as a by-product. On the other hand, the by-produced aqueous solution containing salt overflows from the outlet 8 and is taken out.

Next, the case of using the apparatus shown in FIG. 2 will be described. The introduction of raw materials and air, and the reaction are carried out in the same manner as above. The chlorine gas produced as a by-product is discharged from the discharge line 9 at the top of the reaction tower, and is used for the production of sodium hypochlorite by the alkali treatment. On the other hand, the produced chlorine dioxide is taken out from the outlet 8 together with the aqueous solution containing by-produced salt, introduced into the deaeration tower 12 via the transfer line 15, and the air introduced from the lower inlet 13. Chlorine dioxide is brought into contact and chlorine dioxide is discharged from the upper outlet 1
On the other hand, the aqueous solution which has been recovered together with air from 4, and which has been separated from chlorine dioxide, contains a small amount of unreacted raw material, and therefore is returned to the circulation tower 2 via the return line 16 and is again used for the reaction. As is apparent from the above, when the apparatus of FIG. 2 is used, high-purity chlorine dioxide containing no chlorine gas produced as a by-product can be obtained without using a special separation apparatus.

When an aqueous chlorous acid solution is used as the first raw material and chlorine gas is used as the second raw material, the same operation as described above may be performed, but in this case, chlorine as a by-product is not produced. Therefore, chlorine dioxide can be recovered from the discharge line 9, the saline solution can be overflowed from the outlet 8 and taken out, and high-purity chlorine dioxide can be obtained. The chlorous acid aqueous solution can be used in combination with the chlorate aqueous solution. In this case, in the process of reacting the aqueous chlorate solution with hydrogen chloride to generate chlorine dioxide, the aqueous chlorous acid solution is introduced into the reaction tower through the inlet 11 to generate an aqueous chlorate solution and hydrogen chloride gas. It is possible to generate chlorine dioxide by reacting with chlorine gas which is a by-product of the reaction.

The concentration of the aqueous chlorate solution used in the present invention is preferably 10 to 40% by weight, and the concentration of the aqueous chlorite solution is preferably 5 to 25% by weight. As the acid gas, halogen acid is preferable, and hydrogen chloride gas is particularly preferable. Nitrogen, air and the like are preferable as the inert gas, but air is particularly preferable. Water is preferable as the reaction medium, and the reaction temperature is preferably in the range of 0 to 40 ° C.

[0018]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited thereto.

Example 1 The apparatus (reaction tower volume 23 L) shown in FIG. 1 was used. Water was charged in advance in the reaction tower, a 40 wt% sodium chlorate aqueous solution was 73 g / min, and anhydrous hydrogen chloride gas was 11 L / min.
Air was supplied from the lower part of the reaction tower at a rate of 47 L / min. When the liquid circulation by the air lift was confirmed and the reaction zone temperature was maintained at 25 ° C. and a stable state was reached, sample analysis was performed. 60g of salt solution containing salt as a by-product
Overflow at / min. The target chlorine dioxide was recovered as a mixture of chlorine gas by-produced and air. The recovered chlorine dioxide mixture is treated with ANSI /
When analyzed according to AWWA Standard Method B303-88, the chlorine dioxide production was 14.3 g / min (0.21 mol
/ Min), the amount of chlorine produced is 7.4 g / min (0.10 mol / min)
Minutes). This means that the yield of chlorine dioxide is 78% and the yield of chlorine is 76% with respect to the amount of raw material sodium chlorate supplied. The chlorine dioxide yield was 86% and the chlorine yield was 84% with respect to the amount of anhydrous hydrogen chloride gas supplied.

Example 2 A similar experiment was carried out using the apparatus equipped with the degassing tower shown in FIG. 73 g of 40 wt% sodium chlorate aqueous solution
/ Min, anhydrous hydrogen chloride gas 11 L / min, air 47 L / min
Each was supplied from the lower part of the reaction tower at a rate of minutes. The reaction zone temperature was maintained at 6 ° C and the degassing tower temperature was maintained at 20 ° C. The saline solution containing chlorine dioxide was taken out by overflowing at 1 L / min, introduced into a degassing tower, and introduced at the top of the degassing tower. Air was supplied from the bottom of the tower at a rate of 47 L / min, deaeration was performed to separate chlorine dioxide, and the remaining aqueous solution was again supplied and circulated before the heat exchanger of the circulation tower. The sample analysis was performed while maintaining the liquid circulation by the air lift in a stable state. Chlorine gas produced as a by-product is discharged from the top of the reaction tower and is used for the production of sodium hypozincate, etc. by alkali treatment. The target chlorine dioxide was recovered together with air from the top of the degassing tower. AN as in Example 1
When analyzed in accordance with SI / AWA standard method B303-88, the chlorine dioxide production was 12.5 g / min (0.1
8 mol / min). Mixed by-product chlorine gas is 0.8
It was g / min (0.01 mol / min). The yield of chlorine dioxide was 68% with respect to the supply amount of raw material sodium chlorate, and 76% with respect to the supply amount of anhydrous hydrogen chloride gas.

Example 3 In the same manner as in Example 1, a 25 wt% aqueous sodium chlorite solution was fed from the bottom of the reaction column at a rate of 89 g / min, chlorine gas at 2.7 L / min, and air at a rate of 47 L / min. Supplied. Keeping the reaction zone temperature at 25 ° C and making it stable,
The liquid analysis by the air lift was confirmed, and the sample analysis was performed. The salt solution overflows at 80 g / min,
The desired chlorine dioxide was recovered as a mixture with air. ANSI / AWWA Standard Method B30 as in Example 1
When analyzed in accordance with 3-88, the amount of chlorine dioxide produced was 13.0 g / min (0.19 mol / min). The yield of chlorine dioxide was 78% with respect to the amount of the raw material sodium chlorite supplied.

Example 4 Using the apparatus shown in FIG.
73 g / min of 0 wt% sodium chlorate aqueous solution, 11 L / min of anhydrous hydrogen chloride gas and 47 L / min of air were supplied respectively, and further 25 wt% sodium chlorite aqueous solution was 64 g / min. Feed at rate. The reaction zone temperature was maintained at 25 ° C., a stable state was achieved, liquid circulation by an air lift was confirmed, and sample analysis was performed. The saline portion overflowed at 120 g / min and the desired chlorine dioxide was recovered as a mixture with air. ANSI / AWWA Standard Method B303-8 as in Example 1
When analyzed according to 8, the amount of chlorine dioxide produced is 2
6.1 g / min (0.38 mol / min), chlorine production was 1.
It was 6 g / min (0.02 mol / min). The yield of chlorine dioxide was equivalent to 86% with respect to the total feed amount of the raw material sodium chlorate and sodium chlorite.

[0023]

As described above, according to the present invention, high-purity chlorine dioxide can be easily produced using an inexpensive and simple apparatus.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus used in the present invention.

FIG. 2 is a schematic view showing another example of the apparatus used in the present invention.

[Explanation of symbols]

1 Reaction Tower 2 Circulation Tower 3 First Raw Material Introduction Line 4 Second Raw Material Introduction Line 5 Inert Gas Introduction Line 6 Introduction Port 7 Perforated Plate 8 Outlet 9 Exhaust Line 10 Heat Exchanger 11 Inlet 12 Degassing Tower 13 Inlet 14 discharge port 15 transfer line 16 return line

Claims (8)

[Claims] 1. A chlorate aqueous solution, an acid gas and an inert gas are introduced from the lower part of a reaction tower which is connected so that the upper and lower parts of the circulation tower communicate with each other, and is circulated in the reaction tower and the circulation tower by an air lift. A method for producing chlorine dioxide, characterized in that the chlorine dioxide produced is reacted with the chlorine gas and taken out from the upper part of the reaction tower together with chlorine gas. 2. The chlorine dioxide produced is taken out together with the aqueous solution, the chlorine dioxide and the aqueous solution are introduced into a degassing tower, an inert gas is introduced from the bottom of the tower for degassing, and the chlorine dioxide is inert gas from the top of the tower. The method according to claim 1, wherein the aqueous solution is recovered together with the aqueous solution and returned to the reaction tower. 3. The production method according to claim 1, wherein an aqueous chlorite solution is introduced into the reaction tower. 4. A chlorite aqueous solution, chlorine gas and an inert gas are introduced from the lower part of the reaction tower which is connected so that the upper and lower parts of the circulation tower communicate with each other, and circulated in the reaction tower and the circulation tower by an air lift. A method for producing chlorine dioxide, characterized in that the chlorine dioxide formed is reacted and then taken out from the upper part of the reaction tower. 5. The produced chlorine dioxide is taken out together with the aqueous solution, the chlorine dioxide and the aqueous solution are introduced into a degassing tower, an inert gas is introduced from the bottom of the tower for degassing, and the chlorine dioxide is inert gas from the top of the tower. The method according to claim 4, wherein the aqueous solution is recovered together with the aqueous solution and returned to the reaction tower. 6. The method according to claim 1, wherein the acid gas is a halogen acid gas. 7. The method according to claim 6, wherein the halogen acid gas is hydrogen chloride gas. 8. The method according to claim 1, wherein the reaction temperature is 0 to 40 ° C.