JPH10309434A - Method for detoxicating waste gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a facility and save the cost by removing arsine by bringing a waste gas into contact with a solid removing agent which selectively removes arsine and then carrying out combustion detoxification treatment of phosphine by introducing the resultant waste gas to flames of a burner. SOLUTION: A waste gas 4 containing a large amount of phosphine and a small amount of arsine is brought into contact with a combustion of a mixture containing one of manganese oxides such as Mn3 O4 , Mn2 O3 , MnO2 , etc., and one of iron oxides such as FeO, Fe3 O4 , Fe2 O3 , or one selected from one group and a plurality of oxides selected from the other group, or a plurality of oxides selected from each group. In an initial period of the contact detoxification treatment, phosphine and arsine are together adsorbed in the composition and detoxicated. Then, phosphine reaches in adsorption saturated state in an early stage and after the breakthrough, only arsine is selectively adsorbed and removed. Since the gas 5 does not evolves hazardous arsenic even by combustion treatment after the gas is brought into contact with the composition, detoxification treatment of a waste gas 4 containing a large amount of phosphine and a small amount of arsenic is efficiently and safely treated.

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 exhaust gas, and more particularly to a method for removing exhaust gas containing a large amount of phosphine and a small amount of arsine as harmful components.

[0002]

2. Description of the Related Art Phosphorus and arsenic are so-called group V elements, which are constituent elements of group III-V compound semiconductors or doping elements of group IV silicon semiconductors. MOCV
When manufacturing using the D apparatus, phosphine or arsine is supplied into the apparatus as a raw material gas. Therefore, M
Exhaust gas containing unreacted phosphine and arsine is emitted from the OCVD device, but since these are harmful,
Exhaust gas must be removed before it is released to the atmosphere.

[0003] In addition, during the film formation in the MOCVD apparatus, the amount of phosphine supplied is generally larger than that of arsine because phosphorus is less likely to be incorporated into the crystal than arsenic. Therefore, the exhaust gas contains more phosphine than arsine, and the concentration of phosphine in the exhaust gas may be 5 to 10 times the concentration of arsine.

[0004] Conventionally, as a method for removing phosphine and arsine, dry detoxification is carried out by contacting an exhaust gas containing these with a solid abatement agent containing a metal oxide such as copper oxide as a reaction main component. The way has been done. But,
When the concentration of harmful components in the exhaust gas is high and the harm removal load is large, the solid harm removal agent must be replaced frequently, which increases labor and cost. Also, in order to reduce the abatement load, the filling cylinder must be large,
The equipment burden will increase.

On the other hand, as a method for removing a large amount of harmful components having a high concentration of harmful components in the exhaust gas, a method of introducing a flue gas into a burner flame and oxidizing and decomposing the harmful components to make them harmless is combustion detoxification. The method is preferred. But,
In this method, phosphine is decomposed into oxides of phosphorus and water, so there is no problem. However, in the case of arsine, harmful oxides of arsenic, arsenic acid, and arsenous acid are generated by oxidative decomposition. For this reason, when the exhaust gas containing arsine is subjected to the combustion treatment, the exhaust gas containing the harmful arsenic compound is discharged from the combustion abatement apparatus. It was a big deal.

Therefore, conventionally, a large amount of cost has been required for detoxifying an exhaust gas containing a large amount of phosphine and a small amount of arsine discharged from the above-mentioned MOCVD apparatus or the like, and a great deal of cost has been required. I have.

[0007] The inventors of the present invention have conducted intensive studies for the purpose of providing a method capable of efficiently removing a waste gas containing a relatively large amount of phosphine and a small amount of arsine. As a result, it has been found that after exhaust gas containing a relatively large amount of phosphine and a small amount of arsine is brought into contact with a specific removing agent to remove arsine, phosphine may be burned and harmed by a combustion harmless method.

[0008]

That is, the method for removing exhaust gas of the present invention is a method for removing exhaust gas containing a large amount of phosphine and a small amount of arsine as harmful components, wherein the exhaust gas is selected from arsine. After removing arsine by contacting it with a solid remover to be removed, phosphine is introduced into a burner flame to burn and remove phosphine.

Various methods for removing a trace amount of arsine contained in phosphine have been proposed as phosphine purification techniques. For example, a method for removing arsine in crude phosphine with activated carbon (Japanese Patent Publication No. Sho 62-3762, Japanese Patent Application Laid-Open No. Sho 63-17211), or fixing arsine as an arsenic compound in the presence of metal phosphorus or a metal phosphorus compound. A method (Japanese Patent Application Laid-Open No. 60-260412) and the like are known. Although it is possible to selectively remove arsine in the exhaust gas by these methods, however, these methods are effective only when the throughput of arsine is very small, and a treatment agent such as activated carbon. It is not suitable for removing arsine in the exhaust gas because it requires a long contact time with the gas and there is a safety problem. In addition, since the wet type or semi-wet type has difficulty in handling and the like, it is preferable to remove arsine with a solid remover.

[0010] Therefore, in order to selectively remove arsine from an exhaust gas containing a large amount of phosphine and a small amount of arsine, it is necessary to search for a new removing agent. It has been found that a composition comprising a substance and an iron oxide has an ability to separate phosphine and arsine. That is, it has been found that this composition has an ability to adsorb both phosphine and arsine, but the ability to adsorb arsine does not decrease even if the adsorption ability of phosphine becomes saturated. Therefore, if a gas containing phosphine and arsine is brought into contact with the composition in advance after the phosphine is saturated and adsorbed, the phosphine does not react, and only arsine is adsorbed and removed from the gas. Can be separated.

However, when performing the abatement treatment of an exhaust gas containing a large amount of phosphine and a small amount of arsine using the above composition, it is not necessary that the phosphine is saturated and adsorbed in advance. That is, in the initial stage of the abatement treatment, phosphine and arsine are both adsorbed to the composition and are abated, so that the purpose of removing the exhaust gas can be achieved. After a breakthrough in the state, only arsine is selectively adsorbed and removed.

As described above, by using the composition, only arsine can be selectively removed from the gas containing phosphine and arsine. Therefore, the gas after contact with the composition is subjected to combustion treatment. However, no harmful arsenic compound as described above is generated.

The manganese oxides constituting the composition include manganese (III) oxide, manganese (II) (Mn)
₃ O ₄ ), manganese oxide (III) (Mn ₂ O ₃ ), and manganese oxide (IV) (MnO ₂ ) are effective. As iron oxides, iron oxide (II) (FeO), iron oxide ( III) Iron (II) (F
e ₃ O ₄ ) and iron (III) oxide (Fe ₂ O ₃ ) are effective. These manganese oxide and iron oxide are one of the two.
One kind may be mixed, and one kind may be mixed with plural kinds or plural kinds may be mixed. The mixing ratio is arbitrary and can be set appropriately according to the situation. Generally, the ratio of manganese oxide to iron oxide is preferably in the range of 1: 4 to 4: 1. It is.

The present inventors further studied that cerium (IV) oxide (CeO ₂ ) and vanadium (V) oxide
(V ₂ O ₅ ) was found to have the ability to separate phosphine and arsine. CeO ₂ and V ₂ O ₅
Has a function of selectively adsorbing only arsine in phosphine and purifying phosphine without performing any special pretreatment. Therefore, it can be suitably used for removing arsine in exhaust gas in which phosphine and arsine are mixed as described above.

CeO ₂ and V ₂ O ₅ may be used alone or as a mixture of both. Further, it can be used by being supported on a silica, alumina or titania-based carrier.

When the mixture of manganese oxide and iron oxide or CeO ₂ or V ₂ O ₅ is used for separating and removing arsine, these may be used in combination.
Other stabilizers and the like can be mixed. These removing agents may be used in an appropriate shape that does not hinder the flow of gas, for example, formed into pellets, or by supporting these powders on a carrier having an appropriate size.

As described above, when detoxifying an exhaust gas containing a large amount of phosphine and a small amount of arsine discharged from the MOCVD apparatus or the like, the exhaust gas is subjected to a mixed composition of the manganese oxide and the iron oxide. And CeO ₂ , V
By removing arsine by contacting with a solid remover composed of ₂ O ₅ , a large amount of phosphine can be safely burned and removed in a burner flame of a well-known burner.

[0018]

EXAMPLES The following A to G were prepared as solid removers. Commercially available reagents were used for each substance, mixed well and pulverized with a pulverizer, and formed into pellets. Ingredient Composition (weight ratio) pellet size (diameter × length) A dosage _{Mn 3 O 4: Fe 2 O} 3 1: 4 3mm × 3mm B agent _{Mn 2 O 3: Fe 2 O} 3 4: 6 Same as above C agent MnO ₂ : Fe ₂ O ₃ 6: 4 Same as above D agent MnO ₂ : FeO 4: 1 Same as above E agent V ₂ O ₅ −1 mm × 5 mm F agent CeO ₂ − Same as above G agent CeO ₂ / alumina carrier CeO ₂ 30% Same as above (G The agent is an alumina carrier with CeO ₂ supported at a weight ratio of 30%)

Experimental Example 1 300 g of Agent B was packed in a column having an inner diameter of 43 mm and a length of 700 mm (filling height 200 mm). In this column,
Hydrogen containing 1% of phosphine was introduced at a cylinder speed of 1 cm per second (0.87 liters per minute), and the concentration of phosphine in the derived gas was monitored by gas chromatography (the same applies hereinafter). As a result, after about 29 hours, the concentration of phosphine in the derived gas reached the allowable concentration of 0.3 ppm. The processing amount of phosphine so far was 50 liters per kg of the removing agent.

Experimental Example 2 The same operation as in Experimental Example 1 was performed except that hydrogen containing 1% of arsine was introduced into the column, and the concentration of arsine in the derived gas was monitored. As a result, after about 29 hours, the concentration of arsine in the derived gas reached the allowable concentration of 0.05 ppm. The amount of arsine processed so far is 1 kg of remover
50 liters.

Experimental Example 3 Arsine 1 was added to the column in which phosphine broke through in Experimental Example 1.
% Of hydrogen was introduced, and the concentration of arsine in the derived gas was monitored. As a result, after 23 hours, the concentration of arsine in the derived gas reached 0.05 ppm. The treatment amount of arsine so far was 40 liters per kg of the removing agent, and it was found that there was no significant difference in the adsorption behavior of arsine even if the amount of arsenic was exceeded by phosphine.

Experimental Example 4 In the same manner as in Experimental Example 1, hydrogen containing 1% of phosphine and 0.2% of arsine was introduced into a column packed with 300 g of the agent B at a cylinder speed of 1 cm / sec. Was monitored individually. For a while after the start, neither phosphine nor arsine was detected in the derived gas, but after about 24 hours, the concentration of phosphine increased to about 1% in a few minutes, and was maintained thereafter. Further, after 115 hours, the concentration of arsine rose and reached breakthrough. The processing amount of phosphine and arsine at this time is
Approximately 41 liters and approximately 4
It was 8 liters.

Experimental Example 5 The same column as in Experimental Example 1 was filled with 300 g of Agent E (filling height: about 200 mm). This column contains 1% phosphine
And nitrogen containing 0.2% of arsine at a cylinder speed of 1 cm / s
And the concentrations of phosphine and arsine in the derived gas were monitored respectively. Immediately after the introduction of the gas, the concentration of phosphine in the derived gas was not different from the concentration of the introduced gas, and it was found that phosphine did not react with the E agent. On the other hand, arsine was detected only after 143 hours. At this time, the treatment amount of arsine is 50 / kg of the removing agent.
Liters.

EXPERIMENTAL EXAMPLE 6 The same column as in Experimental Example 1 was packed with 300 g of Agent F instead of Agent E, and the same experiment as in Experimental Example 5 was performed. Immediately after gas introduction,
Phosphine in the derived gas is the same as the concentration of the introduced gas,
Arsine was not detected. Arsine was detected after 173 hours, and the throughput of arsine at this time was 1 k of the removing agent.
It became 60 liters per gram.

Example 1 As shown in FIG. 1, a well-known combustion abatement apparatus 2 was arranged downstream of a stainless steel column 1 having an inner diameter of 457 mm. Column 1 is filled with 100 kg of the agent B, and 1 kg of the removing agent
Phosphine equivalent to 60 liters per flow was passed, and the removing agent was previously made to break through the phosphine. Further, LPG and air (air) were supplied to the burner 3 of the combustion abatement apparatus 2 and burned. In addition, burner 3
In the center, there is a flow path for the gas to be harmed in the center, a flow path for the lift gas (using nitrogen (N ₂ )) outside, and a flammability support for burning the combustibles in the gas to be harmed outside. A five-tube structure having a gas (air) flow path, a combustion supporting gas (air) flow path for burning fuel (LPG) outside thereof, and a fuel flow path outside thereof was used.

From the inlet passage 4 of the column 1, hydrogen containing 1% of phosphine and 0.2% of arsine was supplied at a total flow rate of 1 / min.
The gas introduced at a rate of 00 liters (vacuum speed 1 cm per second) was introduced into the burner 3 of the combustion abatement apparatus 2 while the gas introduced into the outlet path 5 of the column 1 was introduced into the exhaust path 6 of the combustion abatement apparatus 2. The concentration of phosphine and arsine in the gas was monitored.

After operating for 8 hours, neither phosphine nor arsine was detected in the gas discharged from the combustion abatement apparatus 2. Further, ICP analysis of the powder generated in the combustion abatement apparatus 2 showed that arsenic was not detected. Similarly, arsenic was not detected in the wastewater discharged from the combustion abatement apparatus 2 to the drain pipe 7.

Examples 2 to 4 In each of the columns 1, 100 kg of Agent A (Example 2), Agent C (Example 3) and Agent D (Example 4) were used instead of Agent B.
The same operation as in Example 1 was carried out as it was, without filling, and without removing the removing agent. As a result, neither phosphine nor arsine was detected in the outgas from the combustion abatement apparatus 2. Further, arsenic was not detected in the powder generated in the combustion abatement apparatus 2.

Example 5 The above column 1 was filled with 50 kg of the agent G and phosphine 1%
The mixture was operated for 8 hours by introducing nitrogen containing 0.2% of arsine and arsine, but neither phosphine nor arsine was detected in the derived gas. Further, arsenic was not detected in the powder generated in the combustion abatement apparatus 2. Similarly, arsenic was not detected in the wastewater discharged from the combustion abatement apparatus 2.

[0030]

As described above, according to the method for removing exhaust gas of the present invention, it is possible to efficiently and safely remove the exhaust gas containing a large amount of phosphine and a small amount of arsine.

[Brief description of the drawings]

FIG. 1 is a system diagram of an abatement apparatus used in an embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Column, 2 ... Combustion abatement apparatus, 3 ... Burner

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akihiko Nitta 1-16-7 Nishi-Shimbashi, Minato-ku, Tokyo Inside Nippon Sanso Corporation (72) Inventor Tadashi Watanabe 1-16-7, Nishi-Shimbashi, Minato-ku, Tokyo Within Nippon Sanso Corporation

Claims (3)

[Claims] 1. A method for abating an exhaust gas containing a large amount of phosphine and a small amount of arsine as a harmful component, wherein the exhaust gas is brought into contact with a solid remover for selectively removing arsine, and then a burner flame. A method for abating exhaust gas, wherein the method is introduced into a plant. 2. The reaction main component of the solid removing agent is Mn ₃
At least one of O ₄ , Mn ₂ O ₃ and MnO ₂ ;
FeO, Fe ₃ O _4, detoxifying method of an exhaust gas according to claim 1, characterized in that a mixture of at least one of Fe ₂ O _3. 3. The reaction main component of the solid remover is CeO.
Detoxifying method of an exhaust gas according to claim 1, wherein a is ₂ and at least one of V ₂ O _5.