JPH06319938A - Method for cleaning harmful gas - Google Patents

Abstract

PURPOSE:To efficiently remove a basic gas such as ammonia and amine which is used in a semiconductor manufacturing process and others and contained in exhaust gas and air etc., by the leakage etc., of a bomb by contacting a gas containing the basic gas with a cleaning agent in which a copper salt is carried on an inorganic support such as alumina and silica. CONSTITUTION:A basic gas (for example, ammonia) as a harmful component is contacted with a cleaning agent in which a bivalent copper salt is carried on an inorganic support (for example, alumina) to remove the harmful component from the gas. For the bivalent copper salt, one or two kinds of inorganic acids are selected from carbonic acid, silicic acid, nitric acid, sulfuric acid, phosphoric acid, boric acid, chloric acid, perchloric acid, chlorous acid, and hypochlorous acid. As a result, the basic gas such as ammonia and amine can be removed efficiently which is used in a semiconductor manufacturing process and others and contained in exhaust gas and air, etc., by the leakages, etc., of a bomb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing harmful gases, and more particularly to a method for purifying basic harmful gases such as ammonia and amines used in semiconductor manufacturing processes. In recent years, with the development of the semiconductor industry, the optoelectronics industry, and the precision equipment industry, the amount of basic gases such as ammonia and amines used has been increasing. These basic gases are indispensable substances for semiconductor manufacturing processes such as chemical vapor deposition, decorative / protective film manufacturing, and super hard equipment manufacturing, but they are all highly toxic and give off a pungent odor as well as the human body and environment. Adversely affect. The permissible concentrations of these gases are, for example, 25 ppm of ammonia and 10 ppm of trimethylamine, and it is necessary to remove harmful components before using them in the above-mentioned semiconductor manufacturing process and before releasing them into the atmosphere.

These basic gases usually have a volume of 0.1.
It is commercially available by filling a gas cylinder of about 50 L.
In order to prevent the air from directly contaminating the outside air when a gas leaks, the gas cylinder is normally stored in a cylinder container connected to a ventilation duct called a cylinder box, and the gas to the semiconductor process etc. Although it is used by connecting to the supply pipe, there is a risk of sudden leakage such as emptying of the cylinder in a short time of about 5 to 10 minutes due to an unexpected accident, etc. even if it is stored in the cylinder box. There is a strong demand for complete measures that can deal with such accidents.

[0003]

2. Description of the Related Art As a method for removing a basic gas contained in a gas, there is a wet method in which a scrubber is absorbed and decomposed, and an aqueous solution mainly containing an acidic component is used as an absorbing liquid. Further, in the dry method, there is an example in which activated carbon or an inorganic compound-based porous adsorbent is used.

[0004]

However, the wet method has the drawbacks that the size of the apparatus becomes large, the post-treatment is difficult, and the maintenance cost of the apparatus becomes high. further,
Under the present circumstances, the adsorption efficiency is not necessarily high, and in the case of a high concentration of harmful gas, it cannot be completely treated. Further, not only ammonia-based gas but also other harmful gas, for example, silicon compound-based gas represented by silane in the semiconductor industry is used at the same time, which causes a problem that sludge is generated due to generation of oxide powder. . There is a method of adsorption treatment with activated carbon as a dry method, but the detoxifying ability is low,
There is also a risk of fire if a combustible gas such as silane coexists. Therefore, the processing speed and processing capacity of harmful gas are large, and the concentration is relatively low due to abnormalities in the cylinder, etc. There has been a demand for a purification method that has excellent removal performance against harmful gases and the like, has no risk of fire, etc., and that does not cause clogging of the purification column due to products.

[0005]

Means for Solving the Problems As a result of intensive studies to solve these problems, the present inventors have found that the use of a purifying agent in which a copper (II) salt is impregnated on an inorganic carrier causes various problems. The present invention has been completed by finding that harmful gas in a state can be removed extremely efficiently and safely. That is, the present invention is characterized in that a gas containing a basic gas which is a harmful component is brought into contact with a purifying agent in which a copper (II) salt is supported on an inorganic carrier to remove the harmful component from the gas. It is a method of purifying harmful gas. The purification method of the present invention is applied to the purification of basic harmful gas containing ammonia and amines such as dimethylamine, trimethylamine, monomethylamine, hydrazine and dimethylhydrazine in air, nitrogen and hydrogen. In particular, the purification method of the present invention can remove a large amount of harmful gas quickly and at room temperature. For example, when purifying exhaust gas from a semiconductor manufacturing process or when gas leaks rapidly from a cylinder, Excellent effects such as rapid purification of polluted gas (usually air) can be obtained.

In the present invention, copper (II) salt is silica,
A purifying agent carried on an inorganic carrier such as alumina, titania or zirconia is used. As the copper (II) salt,
It is a copper salt of an inorganic acid or an organic acid. Examples of the inorganic acid salts include oxo acid salts and halides. Examples of the oxo acid salts include carbonic acid, silicic acid, nitric acid, sulfuric acid, phosphoric acid, arsenic acid, boric acid, chloric acid, perchloric acid, and chlorous acid. Copper (II) salts such as acids and hypochlorous acid, and examples of halides include copper (II) chloride, copper (II) bromide, and copper (II) iodide. Examples of organic acids include aliphatic monocarboxylic acids such as formic acid, acetic acid, propionic acid, oleic acid and stearic acid, aliphatic dicarboxylic acids such as oxalic acid, adipic acid and sebacic acid, oxy acids such as lactic acid and tartaric acid, and benzoic acid. Acids, aromatics such as toluic acid, and copper (II) salts of various acids such as naphthenic acid. Among these, copper nitrate, copper sulfate, copper chloride, copper bromide, copper acetate and the like are water-soluble and are preferable in terms of easy handling. In addition, copper (I
As the salt I), various hydrates from anhydrate to polyhydrate are known, but they are hydrated because they are easy to handle, have good stability in air, and do not affect purification ability. Are generally preferred.

As the inorganic carrier, silica, alumina,
It can be selected from a wide range such as titania and zirconia, and for example, silica gel, silica alumina, alumina and the like are preferable. Among these, those having a small specific surface area are preferable because they do not adsorb other harmful gases such as silane and therefore do not adversely affect the ability to remove basic gases such as ammonia and amine, and α-alumina is particularly preferable. As α-alumina, a commercially available 0.1
Containing 15% of silica, 1 to 100 m ² / g approximately may be used those having a specific surface area, preferably a specific surface area of 1 m ² / g or less, more preferably 0.001
It is preferably 0.5 m ² / g.

The amount of the copper (II) salt supported on the inorganic carrier is not particularly limited and is selected depending on the kind and concentration of the basic gas. For example, the copper salt is based on 100 parts by weight of α-alumina. As 3 to 100 parts by weight, preferably 10
It is about 80 parts by weight. If the amount of copper salt is less than 3 parts by weight, the purification efficiency is low, while if it exceeds 100 parts by weight, α
-Not well retained on alumina and expensive.
In the present invention, it is desirable to add a certain amount of free water to the purifying agent in addition to the water of crystallization of the copper (II) salt for the purpose of further increasing the efficiency of removing harmful components. The amount of free water retained is usually 1 to 50% by weight, preferably 5 to 30% by weight, based on the total weight of the cleaning agent. The purifying agent can be produced, for example, by dissolving a copper salt in warm water, impregnating it with a carrier such as α-alumina, and then drying it at about 30 to 100 ° C. until a predetermined water content is reached. .

The concentration of harmful gas to which the present invention is applied is usually 1% or less, preferably 1000 ppm or less.
Further, the contact temperature between the purifying agent and the gas is about 0 to 90 ° C., which is usually operated at room temperature (10 to 50 ° C.), and heating or cooling is not particularly required. After the contact is initiated, the reaction heat causes a temperature rise depending on the concentration of the harmful gas. The pressure at the time of contact is usually atmospheric pressure, but reduced pressure to 1 kg / c
It is also possible to operate under pressure such as m ² G. The gas to which the present invention is applied, such as air, nitrogen and hydrogen, may be in a dry state or a wet state as long as it does not cause dew condensation.
It is often used at a relative humidity of 100%, and in such a case, the free water in the purifying agent is preferably about 5 to 30% by weight. Further, it is not adversely affected by carbon dioxide gas in the air.

There is no particular limitation on the concentration and flow rate of the ammonia-based basic gas contained in the gas to be treated in the present invention, but it is generally desirable to decrease the flow rate as the concentration increases. The concentration of removable harmful gas is usually 1%
As described below, when the flow rate is small, it is possible to treat a higher concentration of ammonia-based basic gas. The purifying cylinder is designed according to the harmful gas concentration, the amount of gas to be treated, etc., but at a relatively low concentration of the harmful gas concentration of 0.1% or less, the hollow cylinder linear velocity (LV) is 0.5 to. 50 cm / sec,
When the harmful gas concentration is 0.1 to 1%, the LV is 0.05 to
1 at high concentration such as 20 cm / sec and concentration of 1% or more
It is preferable to design in the range of 0 cm / sec or less.
Therefore, in the case of a high concentration of harmful gas that is constantly discharged from the semiconductor manufacturing process, 10 cm / sec
Below, when harmful gas suddenly leaks from a gas cylinder and is diluted with a large amount of air, the LV is 0.5 to
50 cm / sec is a general standard.

The purifying agent is usually packed in a column for purifying harmful gas and used as a fixed bed, but it can also be used as a moving bed or a fluidized bed. Normally, the purifying agent is filled in the purifying cylinder, and the gas containing the ammonia-based basic gas is caused to flow in the purifying cylinder, and the harmful ammonia-based basic gas is removed by contacting with the purifying agent. . In the present invention, the packing density when the cleaning agent is packed in the cleaning column is about 1.0 to 1.5 g / ml.

The purifying agent is used by being filled in the purifying cylinder 1 as shown in the flow sheets of FIGS. 1 and 2, for example. When purifying the exhaust gas from the semiconductor manufacturing apparatus 2 as shown in FIG. 1, the exhaust gas is connected to the duct 6 led from the manufacturing apparatus 2 and used. In addition, when it is used to treat the leaked gas from the gas cylinder,
As described above, the purification cylinder 1 is used by interposing it between a ventilation box 6 that connects a cylinder box 4 in which a cylinder 3 of harmful gas is stored and a blower 5 for continuously sucking and ventilating air. . The purifying agent generates a large amount of heat when the concentration of the harmful gas exceeds 1%, and thus heat removal means may be required. However, in the equipment as shown in FIG. 2, even if the harmful gas is suddenly leaked, its concentration becomes 1 by mixing with air or a diluting gas such as nitrogen.
A blower of sufficient volume is provided to dilute below 100%. The filling length of the purifying agent in the purifying cylinder varies depending on the flow rate of gas and the concentration of harmful gas, but is usually 5 in practice.
The purification cylinder has an inner diameter of 0.5 to 50 cm / se at an empty cylinder linear velocity (LV) of the gas flowing in the cylinder.
It is designed to be about c and is determined according to the pressure loss of the packed bed, the gas contact efficiency, the concentration of harmful gas, and the like.

[0013]

EXAMPLES Examples 1 to 4 Preparation of Purifying Agent 25 to 250 g of copper sulfate pentahydrate is dissolved in 400 to 800 ml of warm water, and in this vat, α-alumina 86 wt.
%, Silica 12 wt% specific surface area 0.005-0.04
After mixing with 500 g of spherical α-alumina (manufactured by Norton) having a particle density of 0 m ² / g, a packing density of 1.1 g / ml and a diameter of 3/16 inch, the mixture was dried at 100 ° C. to contain copper sulfate and free water. Four types of purifying agents with different amounts were obtained. A purification test for harmful gas was conducted using each of these four types of purifying agents. Purifying agent 85 ml, inner diameter 19 mm, length 50
A 0 mm quartz glass purifying cylinder was filled with dry nitrogen containing 1% of ammonia at 20 ° C. and 170 ml / atmospheric pressure.
It was circulated at a flow rate of min (LV = 1.0 cm / sec). TG-2400B, a gas detector tube (manufactured by Gastec Co., detection lower limit 2 ppm) and a gas detector (manufactured by Bionics Instruments Co., Ltd., TG-2400B) by sampling part of the outlet gas of the purification column
A), ammonia is the upper limit of the permissible concentration (25 pp
The time required to reach m) (effective treatment time) was measured. The results are shown in Table 1.

[0014]

[Table 1] Table 1 Example Copper sulphate Free water Hazardous gas Empty cylinder linear velocity Effective treatment time Content rate Content rate concentration LV (wt%) (wt%) (%) (cm / sec) (min) 1 5 3 1 1.0 4150 2 10 〃 〃 〃 5405 3 20 5 〃 〃 7023 4 50 〃 〃 〃 7865

Examples 5 to 8 Purification tests were conducted in the same manner as in Example 1 except that the same purifying agent as in Example 3 was used and the ammonia concentration and the gas flow rate (LV) were variously changed. The results are shown in Table 2.

[0016]

[Table 2] Table 2 Example Copper sulphate Free water Hazardous gas Empty cylinder linear velocity Effective treatment time Content rate Content rate concentration LV (wt%) (wt%) (%) (cm / sec) (min) 5 205 1.0 10.0 360 6 〃 〃 〃 0.5 14023 7 〃 〃 0.1 10.0 10.0 7150 8 〃 〃 〃 1.0 72010

Examples 9 and 10 Using the same purifying agent as in Example 3, with nitrogen containing 1% of trimethylamine instead of ammonia, the flow rate (L
V) was changed, and a purification test was conducted in the same manner as in Example 1, and the concentration of trimethylamine was the upper limit of allowable concentration (10 ppm).
The time to reach was measured. The results are shown in Table 3.

[0018]

[Table 3] Table 3 Examples Copper sulphate Free water Hazardous gas Empty cylinder linear velocity Effective treatment time Content rate Content concentration LV (wt%) (wt%) (%) (cm / sec) (min) 9 205 1 10.0 350 10 〃 〃 〃 1.0 4503

Examples 11 to 13 In order to see the effect on the purifying ability of basic gas when other gases coexist, the same purifying agent as in Example 3 was used, and the flow rate of nitrogen containing 1% of monosilane was changed. Constant 100
Minutes, 1000 minutes, 5000 minutes, and then, the purifying ability of ammonia was measured for each purifying agent in the same manner as in Example 1. The results are shown in Table 4.

[0020]

Table 4 Table 4 Example Monosilane flow time Effective treatment time of ammonia (min) (min) 11 100 7095 12 1000 7008 13 5000 7000 2525

[0021]

According to the gas purification method of the present invention, ammonia-based basic gases such as ammonia and trimethylamine contained in the gas can be efficiently removed. Efficiently removes harmful gas regardless of high or low concentration
Moreover, it can be removed extremely quickly. In addition, even if other gases such as silane coexist, it does not adversely affect the occurrence of fire and the purification performance, and it can be used in the purification of exhaust gas in semiconductor manufacturing processes and in the event of an emergency such as a sudden leak of harmful gas from a gas cylinder. An excellent effect of detoxification is obtained.

[0022]

[Brief description of drawings]

FIG. 1 is a flow sheet showing an example of a method for purifying harmful gas.

FIG. 2 is a flow sheet showing an example of a purification method of a mode different from that of FIG.

[Explanation of symbols]

 1 Purification Cylinder 2 Semiconductor Manufacturing Equipment 3 Gas Cylinder 4 Cylinder Box 5 Blower 6 Duct

Claims (4)

[Claims] 1. A gas containing a basic gas, which is a harmful component, is brought into contact with a purifying agent comprising a copper (II) salt supported on an inorganic carrier to remove the harmful component from the gas. How to purify harmful gas. 2. The basic gas is ammonia, monomethylamine, dimethylamine, trimethylamine, hydrazine,
The purification method according to claim 1, which is one kind or two or more kinds selected from dimethylhydrazine. 3. A copper (II) salt selected from the group consisting of carbonic acid, silicic acid, nitric acid, sulfuric acid, phosphoric acid, boric acid, chloric acid, perchloric acid, chlorous acid and hypochlorous acid. The purification method according to claim 1, which comprises two or more kinds. 4. The purification method according to claim 1, wherein the inorganic carrier is one or more selected from silica, alumina, titania and zirconia.