JP2000176243A - Treatment of waste gas containing oxidizing gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of efficiently removing a waste gas containing an oxidizing gas such as high concn. gaseous chlorine without using a compd. containing an alkali metal ion such as sodium ion with a compact device excellent in cost effectiveness. SOLUTION: A waste gas 1 containing an oxidizing gas is subjected to wet treatment in a packed column 5 in which sulfite 50 hardly soluble in water is packed. The oxidizing gas is preferably gaseous chlorine, gaseous bromine, gaseous fluorine or gaseous chlorine trifuloride, and the sulfite is selected from the group consisting of an alkaline earth metal sulfite (e.g. calcium sulfite, magnesium sulfite, barium sulfite, etc.), nickel sulfite and iron sulfite.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for treating an exhaust gas containing an oxidizing gas such as a chlorine gas. In particular, the present invention relates to a method for treating an exhaust gas which can be suitably used for treating an exhaust gas generated in an etching step or the like during semiconductor manufacturing.

[0002]

2. Description of the Related Art Chlorine is a useful substance widely used for etching in the production of semiconductors, but is a substance which is highly toxic and difficult to handle. Exhaust gas generated in the above etching process contains, in addition to chlorine as a raw material gas, hydrogen chloride, hydrogen bromide, fluorine, etc., and when released into the atmosphere as it is, prevents air pollution and occupational safety and health. Is a problem. Therefore, it is necessary to sufficiently remove chlorine and the like before releasing it to the atmosphere.

As a method of treating exhaust gas containing chlorine or the like for etching, there are a dry method in which adsorption treatment is performed on activated carbon or the like and a wet method in which an alkaline solution or the like is used as an absorbing solution. The dry method has a problem in that the operation of replacing the adsorbent is troublesome, and there is a problem in treating the used adsorbent. On the other hand, the wet method generally has poor removal efficiency, and has a problem that the concentration of the alkaline solution must be increased in order to improve the removal efficiency.

As a wet method, Japanese Patent Publication No. 52-195 has been proposed.
No. 56 describes a method of absorbing a chlorine-containing gas with a mixed solution obtained by combining an alkaline drug such as sodium hydroxide and sodium sulfite. However,
Since alkali metal ions such as sodium ions may degrade the product quality of a semiconductor device, there is a problem that the use of a drug containing a high concentration of alkali metal is restricted.

[0005]

Accordingly, the present inventors have increased the absorption efficiency of chlorine gas and the like by using a rotary fine bubble generator in a wet gas processing tank, and at the same time, provided a solid alkali compound which is hardly soluble in water. A method for treating a chlorine-containing gas using a solution containing as an absorbing solution, and a method for treating a chlorine-containing gas, which comprises introducing the treatment gas into a second treatment tank and wet-treating it with a hardly soluble solid alkali compound. However, a more efficient processing method is desired.

[0006] In view of the above situation, the present invention contains a high-concentration oxidizing gas such as chlorine gas by using a compact apparatus which is excellent in economy without using a compound containing an alkali metal ion such as sodium ion. It is an object to provide a method for efficiently removing exhaust gas.

[0007]

Means for Solving the Problems The present inventors focused on reducing sulfites instead of conventional alkaline agents, and filled exhaust gas containing oxidizing gas with water-sulfite which is hardly soluble in water. The present inventors have found that a wet treatment in a packed packed tower can provide a large treatment capacity in spite of an apparatus having a very simple structure, and arrived at the present invention.

That is, the present invention relates to a method for treating an oxidizing gas-containing exhaust gas, which comprises subjecting the exhaust gas containing the oxidizing gas to wet treatment in a packed tower filled with a water-insoluble sulfite.

The wet treatment is realized by, for example, introducing the exhaust gas from the lower part of the packed tower and introducing water in a shower form from the upper part of the packed tower.

In the method of the present invention, an oxidizing gas such as a chlorine gas or a bromine gas reacts with a sulfite which is hardly soluble in water filled in a packed tower, and is converted into a hydrogen halide. The generated hydrogen halide is easily absorbed by water and can be neutralized with alkali.

Examples of the sulfite which is hardly soluble in water used in the present invention include sulfites such as calcium, magnesium, barium, nickel and iron. Among them, sulfites of alkaline earth metals such as calcium sulfite and magnesium sulfite. Is preferably used. Since the sulfite that is hardly soluble in water is used by filling it in a packed tower, the particle size is 1 to 50.
mm, preferably 1 to 10 mm granules are used. The packed tower may be mixed and filled with a porcelain Raschig ring or the like.

The oxidizing gas which can be effectively treated by the method of the present invention includes chlorine gas, bromine gas, fluorine gas and chlorine trifluoride gas. Although the concentration of the oxidizing gas that can be treated in the present invention is not particularly limited, it can be usually treated in the range of 1 ppm to 5% by volume.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for treating an oxidizing gas-containing exhaust gas of the present invention will be described below with reference to the schematic diagram of the treatment apparatus shown in FIG. In this embodiment, a case will be described in which an exhaust gas containing chlorine gas as an oxidizing gas is treated with calcium sulfite as a sparingly soluble sulfite.

Exhaust gas 1 containing chlorine gas is introduced upward from the lower part of the packed tower 5 filled with calcium sulfite 50, and water is introduced as shower water 6 from the upper part of the packed tower 5 by the pump 3. As a result, chlorine in the exhaust gas reacts with calcium sulfite whose surface is wetted and activated by the shower water 6 according to the following formula (1), whereby chlorine is reduced to hydrogen chloride and calcium sulfite is oxidized to calcium sulfate. On the other hand, the exhaust gas from which chlorine has been removed is discharged out of the system as shown by arrow 2.

[0015]

Embedded image The calcium sulfate formed on the surface of calcium sulfite is
It is washed and removed by the continuously supplied shower water 6, and a new wet surface is successively exposed for calcium sulfite. Therefore, by continuously supplying the shower water 6 in the packed tower 5, the chlorine gas can be continuously processed.

The generated hydrogen chloride and calcium sulfate are washed and removed by shower water from below the packed tower 5, and the wastewater 4 containing these products is used to prevent entrainment of the processing gas (exhaust gas). Is discharged through the liquid seal 7. Hydrogen chloride is subsequently neutralized with alkali.

In the above example, the case where chlorine gas as an oxidizing gas is treated has been described. However, bromine gas, fluorine gas or chlorine trifluoride gas as an oxidizing gas is treated with calcium sulfite. The reaction formula in this case is as shown in the following formulas (2) to (4).

[0018]

Embedded image As described above, calcium sulfate and hydrogen halide are generated also in calcium sulfite and other oxidizing gases, and sulfate and hydrogen halide are generated even when the oxidizing gas is treated with another sulfite. . Therefore, oxidizing gases such as bromine gas, fluorine gas or chlorine trifluoride gas can be satisfactorily treated, and oxidizing gases such as chlorine gas can be satisfactorily treated even by using a sulfite other than calcium sulfite. be able to.

Exhaust gas generated in an etching process or the like during semiconductor manufacturing includes harmful gases such as chlorine, boron trichloride, silicon tetrachloride, silicon tetrafluoride, and carbonyl fluoride, as well as aluminum chloride and tungsten chloride. Solids are generally included.

In order to remove these water-soluble gases and solids, a rotary fine bubble generator (rotary atomizer) proposed in Japanese Patent Publication No. 5-80243 and Japanese Patent Application Laid-Open No. 7-213862 as shown in FIG. By performing the pretreatment of the exhaust gas in the gas treatment tank using, the exhaust gas treatment with a wider application range becomes possible.

As shown in FIG. 2, an absorption solution 8 containing an alkali compound which is hardly soluble in water is contained in the gas treatment tank 8 described above.
0 and the rotary fine bubble generator 9
Is provided. This rotary fine bubble generator 9
A cup-shaped rotor 90 rotated by a driving force from a motor M, etc .;
0, and the exhaust gas 1 introduced through the gas introduction pipe 10 is supplied to the rotor 90, and the exhaust gas 1 is dispersed in the absorbing liquid 80 as fine bubbles by the rotation of the rotor 90. It has been made. A plurality of projections (impellers) 91 are attached to the outer surface of the rotor 90, and the agitation state of the absorbing liquid 80 by the rotation of the rotor 90 is uniformized by these projections 91, such as bubbles (exhaust gas) and alkali compounds. Are also uniformed. And
The exhaust gas dispersed in the absorbing solution 80 is pretreated by gas-liquid contact with the absorbing solution 80 and gas-solid contact with the solid alkali compound.

Since the absorbing solution 80 is supplied to the gas treatment tank 8 through the pump 30, the sulfate and hydrogen halide generated by the pretreatment are discharged from the gas treatment tank 8 as wastewater containing these. It is discharged after overflow.
Then, the exhaust gas containing the untreated oxidizing gas is supplied to the above-described packed tower 5 and reduced.

The rotary microbubble generator 9 is not limited to the configuration described with reference to FIG. 2. For example, the rotary microbubble generator 9 may have a number of holes formed in the rotor 90, and the rotor 90 may have a bottomed column. Various structures such as a body can be employed.

[0024]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples.

Example 1 3000 g of granular calcium sulfite having a particle size of 2 to 3 mm was placed in a gas treatment tank having a volume of 5 dm ^3.
(3.6 dm ³ ) to prepare a packed tower. The packed tower is charged with 50 g of nitrogen gas containing 1% by volume of chlorine gas.
at a flow rate of m ³ / min and shower water of 2 dm ³ / min.
min and chlorinated. The processing gas discharged from the gas processing tank was introduced into each of two gas detection tubes (Models “8La” and “14L” manufactured by Gastech Co., Ltd.), and their discoloration was analyzed by an optical method. . By the way, the gas detector tube, in the introduced gas,
The target gas (model "8La" is chlorine gas, model "14
In the case of "L", the presence of hydrogen chloride gas) changes the color of the drug, and the concentration of the target gas can be measured by analyzing the degree of the color change by an optical method or the like. In this embodiment, the chlorine gas concentration was 0.1 ppm or less, and the hydrogen chloride gas concentration was 1 ppm or less.

(Examples 2 to 5) In Example 1, various exhaust gas treatments were performed by changing the composition of the processing gas (oxidizing gas) as shown in Table 1. Other conditions such as the flow rate of nitrogen gas and the amount of shower water were the same as in Example 1. For chlorine trifluoride gas, use a tape type gas detector (manufactured by Riken Keiki Co., Ltd .: trade name "FP-250A").
Other gases are gas detector tubes (Gastec Co., Ltd .:
Type “8La”, “14L”, “15L” and “1”
7 "). The results are shown in Table 1. The tape-type gas detector is a tape coated with a chemical that develops a color when it comes into contact with a target gas (chlorine trifluoride gas). Can be measured.

(Embodiments 6 and 7)
In place of calcium sulfite as a filler, granulated magnesium sulfite (particle size: 1 to 4 mm) or barium sulfite (particle size: 1 to 4 mm) was used. Was processed. The results are shown in Table 2.

Comparative Example 1 The procedure of Example 1 was repeated, except that granular calcium carbonate (particle size: 2 to 3 mm) was used instead of calcium sulfite as a filler.
A gas containing 0% by volume of chlorine was treated. The results are shown in Table 2.

(Comparative Example 2) 0.5% by volume in the same manner as in Example 6 except that granular magnesium carbonate (particle diameter: 2 to 3 mm) was used instead of magnesium sulfite as a filler. Was processed. The results are shown in Table 2.

[0030]

[Table 1]

[0031]

[Table 2]

As is clear from Table 1, when calcium sulfite is used as the filler (sulfite), the processing gas (oxidizing gas) is chlorine gas, bromine gas, chlorine trifluoride gas, or hydrogen chloride. It can be seen that even gas, or a mixed gas of chlorine gas, hydrogen chloride gas, and hydrogen bromide gas, is efficiently treated.

As is clear from Table 2, when a water-sulfite, such as calcium sulfite, magnesium sulfite, or barium sulfite, which is hardly soluble in water, is used as a filler, chlorine gas is satisfactorily treated. On the other hand, it can be seen that when a carbonate which is hardly soluble in water is used, the processing efficiency of chlorine gas is poor.

[0034]

As described above, in the method for treating an oxidizing gas-containing exhaust gas of the present invention, chlorine gas or bromine gas or the like in the exhaust gas is used without using a compound containing an alkali metal ion such as sodium ion. The oxidizing gas can be efficiently removed. Further, since it is not necessary to dissolve the sulfite in a large amount of water or the like, a compact apparatus excellent in economic efficiency can be constructed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an example of an apparatus for realizing an exhaust gas treatment method of the present invention.

FIG. 2 is a schematic view illustrating an example of another use mode of the exhaust gas treatment method of the present invention.

[Explanation of symbols]

 X processing apparatus 1 exhaust gas 5 packed tower 8 processing tank 9 microbubble generator 50 sulfite

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D002 AA17 AA18 AA22 AB01 AC10 BA02 BA03 BA05 BA06 CA01 CA07 CA13 DA04 DA05 DA06 DA13 DA21 DA35 GA02 GB02 GB05 GB12 HA10 4G066 AA14D AA47B BA20 CA31 CA32 DA02 GA11

Claims (5)

[Claims] 1. A method for treating an oxidizing gas-containing exhaust gas, which comprises wet-treating the oxidizing gas-containing exhaust gas in a packed tower filled with a water-insoluble sulfite. 2. The exhaust gas is introduced from a lower part of the packed tower, and water is introduced in a shower form from an upper part of the packed tower.
The method for treating an oxidizing gas-containing exhaust gas according to claim 1. 3. The method according to claim 1, wherein the oxidizing gas is chlorine gas, bromine gas,
3. The method for treating an oxidizing gas-containing exhaust gas according to claim 1, wherein the exhaust gas is a fluorine gas or a chlorine trifluoride gas. 4. The oxidation according to claim 1, wherein the sulfite is at least one selected from the group consisting of a sulfite of an alkaline earth metal, nickel sulfite, and iron sulfite. Of waste gas containing exhaust gas. 5. The method for treating an oxidizing gas-containing exhaust gas according to claim 4, wherein the sulfite of the alkaline earth metal is calcium sulfite, magnesium sulfite, or barium sulfite.