JPH09267027A - Purifying agent for harmful gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To safely and efficiently purify halogen based gas without causing deterioration of purifying capability even at a dry state by comprising a purifying agent for removing the halogen based gas primarily with manganese dioxide, potassium hydroxide and alkaline earth metal hydroxide. SOLUTION: The halogen based gas such as fluorine, chlorine, tungsten hexafluoride is incorporated in a waste gas discharged from a semiconductor process, etc. Three components of the manganese dioxide, the potassium hydroxide and the alkaline earth metal hydroxide such as magnesium hydroxide are incorporated as a main component in the purifying agent for the halogen based gas. After mixing the three components in a prescribed ratio, the mixture is tableted in the form of spherical, cylindrical, etc., and used by a method, etc., in which the formed body is packed in a purifying cylinder. The purifying agent obtained by this method is excellent in removing performance for the halogen based gas, has no danger such as fire at the time of purifying and removes the gas in high efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a harmful gas purifying agent, and more particularly to a halogen-based gas purifying agent used in semiconductor manufacturing processes such as fluorine, chlorine, tungsten hexafluoride, and chlorine trifluoride. . In recent years, with the development of the semiconductor industry and the oproelectronics industry, the types and the amounts of halogen-based gases such as fluorine, chlorine, tungsten hexafluoride, and chlorine trifluoride used in these industries have increased.

These halogen-based gases are indispensable substances as etching gas, cleaning gas, and film growth gas in the manufacturing process of silicon semiconductors and compound semiconductors. Since these halogen-based gases are used as they are in the semiconductor manufacturing process or after being diluted with helium, argon, nitrogen, etc., they are discharged as they are or in a state further diluted with nitrogen, air, etc. , Its concentration is not constant. Since all of these halogen-based gases are highly toxic and have an adverse effect on the human body and the environment, harmful gases containing these halogen-based gases are used in semiconductor manufacturing processes, etc., and then released into the atmosphere. It needs to be purified.

[0003]

2. Description of the Related Art Conventionally, a scrubber, a spray tower, a rotary fine bubble generator or the like has been used as a means for removing a halogen-based gas contained in a gas, and these gases are contacted with an alkaline aqueous solution such as sodium hydroxide. Method of absorbing and decomposing by adsorption (JP-A-61-240222, JP-A-62-125827 and the like), and an adsorbent such as magnesium, sodium and potassium oxides and carbonates (JP-A-63-232844). Japanese Patent Laid-Open No. 60-6
8051), or an adsorbent containing soda lime as an active ingredient, and more recently, a purifying agent using a composition containing iron trioxide as a main component (JP-A-7-275646) and the like. It has been known.

[0004]

However, the wet method generally has a problem in that post-treatment is difficult, and not only the apparatus is complicated and large, but also the equipment and maintenance are expensive. On the other hand, as a dry method, magnesium,
Adsorbents such as sodium and potassium oxides and carbonates have small removal capacity per unit volume of adsorbent. In addition, a purifier using an adsorbent in which activated carbon is impregnated with a zinc compound and an alkali metal compound does not always have a sufficient removal capacity, and when the concentration of the target gas amount is high or the gas amount is large, Not only is there a problem that it cannot be completely processed, but there is also a risk of fire when processing highly reactive gases such as fluorine.

Further, although soda lime has a processing capacity somewhat higher than that of the above-mentioned cleaning agents, the cleaning agents may be dried,
When the concentration of halogen-based gas is low, there is a problem that the processing capacity is significantly reduced, and soda lime has deliquescent, and the purification tube is clogged due to the amount of water contained in the processing gas. There was an inconvenience such as fear. On the other hand, in the case of a purifying agent containing iron trioxide as the main component,
Although it is an excellent purifying agent that has a large purifying ability at room temperature and can be safely and completely purified, when the purifying agent is dried, the purifying ability deteriorates. Therefore, the harmful gas has a low concentration, and is excellent in removing performance against halogen-based gas discharged from the semiconductor manufacturing process such as a dry state, and there is no risk of fire during purification, and The advent of a cleaning agent that can be removed with high efficiency has been desired.

[0006]

As a result of intensive studies to solve these problems, the present inventors have found that manganese dioxide, potassium hydroxide and alkaline earth metal hydroxide 3
By using a purifying agent whose main component is the removal of halogen-based gas emitted from semiconductor manufacturing processes, etc., the purifying ability does not deteriorate even in a dry state, and there is a risk of causing a fire. The present invention has been completed based on the finding that it can be purified without any risk and with extremely high efficiency. That is, the present invention is a purifying agent for removing a halogen-containing gas from a gas containing a harmful halogen-based gas, such as manganese dioxide, potassium hydroxide,
It is a toxic gas purifier characterized by having three components of alkaline earth metal hydroxide as a main component.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The purifying agent of the present invention is applied to purifying halogen-based gas contained in exhaust gas discharged from a semiconductor process or the like. The harmful gas to be purified includes one or more halogen-containing gases such as fluorine, chlorine, tungsten hexafluoride, chlorine trifluoride contained in nitrogen, argon, helium and air. It is gas. Particularly, the purifying agent of the present invention can purify a large amount of harmful gas rapidly and efficiently at room temperature.

In the present invention, the purifying agent is mainly composed of three components of manganese dioxide, potassium hydroxide and alkaline earth metal hydroxide. Manganese dioxide (MnO
_{As 2} ), powdered products having a purity of 85% or more, or a purity of 91% or more are commercially available, and thus these can be usually used. Potassium hydroxide (KOH) has a purity of 8
Since 5% or more of the products are commercially available, these commercially available products can usually be used.

The hydroxides of alkaline earth metals include magnesium hydroxide (Mg (OH) ₂ ), calcium hydroxide (Ca (OH) ₂ ), strontium hydroxide (Sr).
(OH) ₂ ) and barium hydroxide (Ba (OH) ₂ ). Strontium hydroxide, barium hydroxide octahydrate _{(Sr (OH) 2 · 8H} 2 O, Ba (OH) 2 · 8
H ₂ O) is an ordinary commercial product, so it should be dried in advance.
It is preferably used after being made into an anhydride. These alkaline earth metal hydroxides may be used alone or as a mixture of two or more thereof.

The proportions of manganese dioxide, potassium hydroxide, and hydroxides of alkaline earth metals differ depending on the type of halogen-based gas contained in the harmful gas and cannot be specified unconditionally, but manganese dioxide, potassium hydroxide, alkaline earth metal The molar ratio of the group metal hydroxide (MnO ₂ : KOH: M (hereinafter, the alkaline earth metal hydroxide is abbreviated as M)) is usually 1: 0.2 to 2: 0.1 to 2, preferably. Is 1: 0.25
˜1: 0.3 to 1.5.

Various methods can be used to prepare the purifying agent. For example, a method of uniformly mixing manganese dioxide, potassium hydroxide, and an alkaline earth metal hydroxide at a predetermined ratio and then tableting, or manganese dioxide, potassium hydroxide, and an alkaline earth metal hydroxide at a predetermined ratio. The mixture obtained by adding water to the mixture and stirring the resulting slurry or cake is extruded and molded, and the pellets obtained by cutting into an appropriate length are dried by heating in an inert atmosphere in a dryer for a predetermined period of time, and then a purifying agent. In addition to the above method, a mixed powder of manganese dioxide, potassium hydroxide, and alkaline earth metal hydroxide is granulated using a granulator or the like and heat-dried in an inert atmosphere to obtain a purifying agent. There are ways to do it. In addition to this, manganese dioxide, potassium hydroxide, and alkaline earth metal hydroxides are uniformly mixed at a predetermined ratio,
Any method capable of molding can be applied to the method for preparing the purifying agent of the present invention. Of these, it is generally preferable to extrude into pellets in terms of workability and ease of selection of shape and size.

The size and shape of the molded body are not particularly limited, but typical examples include spherical, cylindrical, cylindrical and granular shapes. If the size is spherical, the diameter is 0.
5 to 10 mm, diameter of 0.5 to 10 mm and height of about 2 to 20 mm for pellets, tablets, etc. It is about 6 mm. The packing density when the molded body is packed in the purification cylinder is usually 0.8 to 2.0 g /
It is about ml.

The purifying agent of the present invention is characterized in that its purifying ability does not decrease even when its water content is low.
The water content in the purifying agent is usually 0 to 1 including crystal water.
About 0 wt% is used. When the water content of the purifying agent is high, drying contraction occurs when the purifying agent comes into contact with dry gas, and a gas drift may occur due to the formation of voids in the purifying cylinder. The content is about 0 to 5 wt%. By adjusting the water content of the purifying agent of the present invention as described above, the purifying ability does not decrease even in the case of dry gas, and the purifying ability can be stably maintained.

When the cleaning agent of the present invention is heated and dried while being kept in contact with air for a long period of time during preparation, the cleaning ability is significantly reduced. Therefore, when heat drying is performed in the preparation of the cleaning agent, it is preferable to perform it under an atmosphere of an inert gas such as nitrogen, argon or helium.

The purifying agent of the present invention can be used not only as a fixed bed but also as a moving bed or a fluidized bed, but it is usually used as a fixed bed. The purifying agent is filled in the purifying cylinder, and the gas containing the halogen-based gas is caused to flow in the purifying cylinder and brought into contact with the purifying agent to remove only the halogen-based gas which is a harmful component. The concentration of the halogen-based gas contained in the harmful gas to which the purifying agent of the present invention is applied is not particularly limited, but generally when purifying exhaust gas during semiconductor manufacturing, from a high concentration of tens of thousands ppm to several ppm Even if the concentration is low, it can be sufficiently purified.

The purifying cylinder is designed according to the halogen-based gas concentration, the amount of harmful gas to be purified, the allowable pressure loss, and the like. 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 and cannot be specified unconditionally, but is usually about 50 to 1500 mm. The inner diameter of the purifying cylinder is designed so that the empty cylinder reference linear velocity (LV) of the gas flowing in the cylinder is about 0.1 to 50 cm / sec. Generally, these are determined by the pressure loss of the packed bed, the gas contact efficiency, the halogen-based gas concentration, and the like.

The temperature at the time of purification is usually 0 to 90 ° C., and when purifying the halogen-based gas contained in the air, the lower temperature is better. It is operated at 40 ° C.) and does not require heating or cooling. After contact, the reaction heat may cause the temperature to rise slightly depending on the type and concentration of halogen-based gas, but there is no danger of ignition because no combustible material such as activated carbon is used. . The pressure at the time of contact is usually atmospheric pressure, but 0.5 to ² kg / cm ² abs
It is also possible to operate under reduced pressure or increased pressure. Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0018]

【Example】

(Preparation of Purifying Agent) Example 1 348 g of manganese dioxide (MnO ₂ ), 225 g of potassium hydroxide (KOH), calcium hydroxide (Ca (OH))
₂ ) 148 g was uniformly mixed, and 30 g of water was added thereto and sufficiently dispersed and mixed (mol ratio, MnO ₂ : KOH:
M = 1: 1: 0.5). The obtained cake was extruded from a 1.6 mmφ nozzle plate by an extrusion molding machine (manufactured by Fuji Paudal Co., Ltd.) to cut a molded product, and a length of 3 to 5 mm.
The resulting pellets were heated and dried in a nitrogen atmosphere at 90 ° C. for 12 hours in a drier to obtain 720 g of a purifying agent A. The packing density of this cleaning agent was 1.31 g / ml. The water content of the purifying agent was measured by a dry-type water content meter (CZA1000 manufactured by Chino Co., Ltd.) and found to be 0.1 wt%.
Met. The results are shown in Table 1.

Example 2 348 g of manganese dioxide, 225 g of potassium hydroxide, 148 g of calcium hydroxide, strontium hydroxide (Sr
61 g of (OH) ₂ and 30 g of water were uniformly mixed (mo
1 ratio, MnO ₂ : KOH: M = 1: 1: 0.625).
The obtained cake was molded in the same manner as in Example 1 and heat-dried at 90 ° C. for 12 hours in a nitrogen atmosphere to obtain 775 g of a purifying agent B. The packing density of this purifying agent is 1.28 g / m
l. The water content of the purifying agent was 0.2 wt%. The results are shown in Table 1.

Example 3 Manganese dioxide 696 g, potassium hydroxide 225 g, calcium hydroxide 148 g, strontium hydroxide 61
g and 60 g of water were uniformly mixed (mol ratio, MnO ₂ :
KOH: M = 1: 0.5: 0.313). The obtained cake was molded in the same manner as in Example 1 and then under a nitrogen atmosphere 9
After heating and drying at 0 ° C for 12 hours, 1125 g of the purifying agent C
I got The packing density of this cleaning agent was 1.31 g / ml. The water content of the purifying agent was 0.1 wt%.
The results are shown in Table 1.

Example 4 Manganese dioxide 348 g, potassium hydroxide 113 g, calcium hydroxide 148 g, strontium hydroxide 61
g and 30 g of water were uniformly mixed (mol ratio, MnO ₂ :
KOH: M = 1: 0.5: 0.625). The obtained cake was molded in the same manner as in Example 1 and then under a nitrogen atmosphere 9
It heat-dried at 0 degreeC for 12 hours, and obtained 665-g purification agent D. The packing density of this cleaning agent was 1.26 g / ml. The water content of the purifying agent was 0.1 wt%. The results are shown in Table 1.

Example 5 Manganese dioxide 348 g, potassium hydroxide 225 g, calcium hydroxide 296 g, strontium hydroxide 61
g and 45 g of water were uniformly mixed (mol ratio, MnO ₂ :
KOH: M = 1: 1: 1.125). The obtained cake was molded in the same manner as in Example 1 and then under a nitrogen atmosphere at 90 ° C.
And dried by heating for 12 hours to obtain 920 g of the purifying agent E. The packing density of this cleaning agent was 1.33 g / ml. The water content of the purifying agent was 0.2 wt%. The results are shown in Table 1.

Example 6 Manganese dioxide 696 g, potassium hydroxide 113 g, calcium hydroxide 148 g, strontium hydroxide 61
g and 60 g of water were uniformly mixed (mol ratio, MnO ₂ :
KOH: M = 1: 0.25: 0.313). The obtained cake was molded in the same manner as in Example 1 and then heat-dried at 90 ° C. for 12 hours in a nitrogen atmosphere to obtain 1006 g of the purifying agent F. The packing density of this cleaning agent was 1.34 g / ml. The water content of the purifying agent was 0.1 wt%.
The results are shown in Table 1.

Example 7 Manganese dioxide (348 g), potassium hydroxide (225 g), calcium hydroxide (148 g), magnesium hydroxide (Mg)
58 g of (OH) ₂ and 30 g of water were uniformly mixed (mo
1 ratio, MnO ₂ : KOH: M = 1: 1: 0.75). The cake thus obtained was molded in the same manner as in Example 1 and then heat-dried at 90 ° C. for 12 hours in a nitrogen atmosphere to obtain 769 g of a purifying agent G. The packing density of this purifying agent is 1.30 g /
ml. The water content of the purifying agent was 0.1 wt%. The results are shown in Table 1.

[0025]

[Table 1] Table 1 Examples mol ratio Packing density Moisture content MnO ₂ : KOH: Ca (OH) ₂ + Sr (OH) ₂ + Mg (OH) ₂ g / ml wt% 1 1 1 0.5 0 1.31 0.1 2 1 1 0.5 0.125 1.28 0.2 3 1 0.5 0.25 0.063 1.31 0.1 4 1 0.5 0.5 0.125 1.26 0.1 5 1 1 1 0.125 1.33 0.2 6 1 0.25 0.25 0.063 1.34 0.1 7 1 1 0.50 0.25 1.30 0.1

Comparative Example 1 348 g of manganese dioxide was uniformly mixed with 15 g of water.
Extrusion machine for the obtained cake (Fuji Paudal Co., Ltd.)
Manufactured by K.K.), a molded product extruded from a 1.6 mmφ nozzle plate is cut into pellets having a length of about 3 to 5 mm, and the pellets are heated and dried at 90 ° C. for 12 hours in a nitrogen atmosphere dryer to obtain 330 g of a cleaning agent. H was obtained. The packing density of this cleaning agent was 1.01 g / ml. The water content of the purifying agent was 0.1 wt%. Table 2 shows the results.

Comparative Example 2 225 g of 5 mmφ granular potassium hydroxide was heated and dried at 90 ° C. for 12 hours in a dryer under a nitrogen atmosphere to obtain 218 g of Purifying Agent I. The water content of this purifying agent was 0.1 wt%. Table 2 shows the results.

Comparative Example 3 148 g of calcium hydroxide was mixed with 15 g of water, molded in the same manner as in Example 1 and dried to obtain 140 g of Purifying Agent J. The packing density of this cleaning agent was 1.12 g / ml. The water content of the purifying agent was 0.1 wt%. Table 2 shows the results.

Comparative Example 4 348 g of manganese dioxide, 225 g of potassium hydroxide and 14 g of water were uniformly mixed, and the obtained cake was molded in the same manner as in Example 1 and then dried by heating at 90 ° C. for 12 hours in a nitrogen atmosphere. Then, 570 g of a purifying agent K was obtained. The packing density of this cleaning agent was 1.12 g / ml. The water content of the purifying agent was 0.1 wt%. Table 2 shows the results.

Comparative Example 5 348 g of manganese dioxide, 148 g of calcium hydroxide,
61 g of dry strontium hydroxide and 15 g of water were uniformly mixed. After molding from the obtained cake in the same manner as in Example 1, heat drying was performed at 90 ° C. for 12 hours in a nitrogen atmosphere,
550 g of purification agent L was obtained. The packing density of this cleaning agent was 1.05 g / ml. The water content of the purifying agent is 0.
It was 2 wt%. Table 2 shows the results.

Comparative Example 6 225 g of potassium hydroxide and 148 of calcium hydroxide
g, 61 g of dry strontium hydroxide and 10 g of water were uniformly mixed. The cake thus obtained was molded in the same manner as in Example 1 and then heat-dried at 90 ° C. for 12 hours in a nitrogen atmosphere to obtain 429 g of a purifying agent M. The packing density of this cleaning agent was 1.18 g / ml. The water content of the purifying agent was 0.2 wt%. Table 2 shows the results.

[0032]

[Table 2] Table 2 Comparative Examples mol ratio Packing density Water content MnO ₂ : KOH: Ca (OH) ₂ + Sr (OH) ₂ + Mg (OH) ₂ g / ml wt% 1 1 1.01 0.1 2 1 0.1 3 1 1.12 0.1 4 1 1 1.12 0.1 5 1 0.5 0.125 1.05 0.2 6 1 0.5 0.125 1.18 0.2

Example 8 After being molded with the same composition as in Example 2, it was subjected to an argon atmosphere at 90
It heat-dried at 12 degreeC for 12 hours, and obtained the purifying agent N of 765g. The packing density of this cleaning agent was 1.30 g / ml. The water content of the purifying agent was 0.1 wt%. The results are shown in Table 3.

Example 9 After molding with the same composition as in Example 2, 90 in a helium atmosphere
It heat-dried at 12 degreeC for 12 hours, and obtained 766g of purifying agent O. The packing density of this cleaning agent was 1.30 g / ml. The water content of the purifying agent was 0.1 wt%. The results are shown in Table 3.

Comparative Example 7 After molding with the same composition as in Example 2, heat drying was performed in air at 90 ° C. for 12 hours to obtain 781 g of the purifying agent P. The packing density of this cleaning agent was 1.25 g / ml. The water content of the purifying agent was 0.1 wt%. The results are shown in Table 4.

[0036]

Table 3 Table 3 Examples mol ratio Dry atmosphere Packing density Moisture content g / ml wt% 8 Same as example 2 Argon 1.30 0.1 9 Same as example 2 Helium 1.30 0.1

[0037]

[Table 4] Table 4 Comparative Examples mol ratio Dry atmosphere Filling density Moisture content g / ml wt% 7 Same as Example 2 Air 1.25 0.1

(Purification Experiment) Examples 1 to 9 and Comparative Examples 1 to 7
With respect to each of the cleaning agents prepared in (1), a cleaning test for harmful gas containing halogen-based gas was conducted. The purification agent is placed in a purification tube made of quartz glass with an inner diameter of 40 mm and a length of 200 mm.
It was filled with 5.6 ml (filling length 100 mm), and nitrogen containing 1000 ppm of various halogen-based gases was filled at 20 ° C. and normal pressure at 2260 ml / min (empty cylinder reference linear velocity LV = 3).
(cm / sec), and the time until breakthrough was measured, and the purification amount (purification ability) of the halogen-based gas per liter of the cleaning agent was obtained from this. To detect the breakthrough of halogen-based gas, a part of the outlet gas of the purification tube is sampled and measured with a detection tube (made by Gastec Co., Ltd.) according to the gas type. did. Table 5 shows the experimental results for each type of purifying agent and gas.

[0039]

[Table 5] Table 5 Experiment number Type of halogen-based gas until breakthrough of halogen-based gas of purifying agent Type Concentration time Purifying ability (Example number) (ppm) (min) (L / L purifying agent) 1 A ( Example 1) Chlorine 1000 2468 45 2 B (Example 2) Chlorine 1000 3134 56 3 B 〃 Fluorine 1000 1589 29 4 B 〃 Hexafluoride tank Sten 1000 883 16 5 B B 〃 Chlorine trifluoride 1000 1199 196 C (Implementation) Example 3) Chlorine 1000 2556 46 7 D (Example 4) Chlorine 1000 2390 43 8 E (Example 5) Chlorine 1000 2223 40 9 F (Example 6) Chlorine 1000 2223 40 10 G (Example 7) Chlorine 1000 2779 50 11 H (Comparative Example 1) Chlorine 1000 15 1> 12 I (Comparative Example 2) Chlorine 100 16 1> 13 J (Comparative example 3) Chlorine 1000 15 15 1> 14 K (Comparative example 4) Chlorine 1000 189 3 15 L (Comparative example 5) Chlorine 1000 16 1 1> 16 M (Comparative example 6) Chlorine 1000 15 1> 17 N (Example 8) Chlorine 1000 3135 56 18 O (Example 9) Chlorine 1000 3096 56 19 P (Comparative Example 7) Chlorine 1000 15 1>

[0040]

EFFECTS OF THE INVENTION The purifying agent of the present invention has a large halogen-based gas purifying ability even in a dry state and can be safely purified. Therefore, it is suitable for purifying gas containing halogen-based gas discharged from a semiconductor manufacturing process or the like. Excellent effect can be obtained.

Claims (4)

[Claims] 1. A purifying agent for removing a halogen-containing gas from a gas containing a harmful halogen-containing gas, which contains three components of manganese dioxide, potassium hydroxide and an alkaline earth metal hydroxide as main components. A toxic gas purifier characterized by: 2. The halogen-based gas is one or two selected from fluorine, chlorine, tungsten hexafluoride and chlorine trifluoride.
The purifying agent according to claim 1, which is more than one kind. 3. The purifying agent according to claim 1, wherein the alkaline earth metal hydroxide is one kind or two or more kinds selected from magnesium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide. 4. The purifying agent according to claim 1, which is prepared without heating and drying in air.