JP2003326128A - Treatment method for exhaust gas containing arsenic or arsenic compound and treatment apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inexpensively and certainly removing an exhaust gas containing an arsenic compound (or arsenic), an acidic gas and a fluorine compound such as fluorohydrocarbon, a perfluoro compound or the like. <P>SOLUTION: A method for treating the exhaust gas containing arsenic or the arsenic compound, an acidic gas and/or a fluorine compound includes the first process for passing the exhaust gas through a solid chemical agent bed having an adsorption capacity of arsenic or the arsenic compound and a second process for treating the outflow gas of the first process in a combustion type exhaust gas treatment apparatus and/or a catalytic exhaust gas treatment apparatus and/or a heating oxidation type exhaust gas treatment apparatus. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to AsC in exhaust gas.
The present invention relates to a method for treating arsenic compounds such as l ₃ , AsF ₃ and AsF ₅ .

[0002]

_2. Description of the Related Art In the semiconductor industry, BCl ₃ , Cl ₂ ,
In the exhaust gas discharged from the step of etching the GaAs film of the compound semiconductor with an acidic gas such as SiCl _4, a fluorinated hydrocarbon such as CHF ₃ and a perfluoro compound such as SF ₆ , AsCl ₃ , As
Arsenic compounds such as F ₃ and AsF ₅ are contained. Of these, arsenic compounds are extremely harmful to the human body, and BCl
Acidic gases such as ₃ , Cl ₂ and SiCl ₄ have work management standard values as harmful gases, and fluorocarbons and perfluoro compounds are global warming gases. Has been. Therefore, there is an urgent need to establish a technology for treating such exhaust gas.

However, in the prior art, when an arsenic compound, an acid gas, and a fluorine compound such as a fluorohydrocarbon or a perfluoro compound in exhaust gas are to be treated at the same time, the dry treatment using a solid chemical agent causes the arsenic to be treated. Although compounds and acidic gases can be removed, fluorine compounds such as fluorohydrocarbons and perfluoro compounds cannot be treated. Moreover, if it is attempted to remove the arsenic compound and the acidic gas at the same time only by the dry treatment, the acid gas can be treated in a small amount per unit amount of the drug, so that the acid content is reduced despite the remaining removal capacity for the arsenic compound. Since the gas removing ability is lowered, there is a problem in that the frequency of exchanging the chemicals increases and the running cost increases.

When a combustion type or catalytic type exhaust gas treatment apparatus is used, acidic gases, fluorohydrocarbons and perfluoro compounds can be treated, but arsenic compounds change the form of the compound and Part is discharged as arsenous acid in the waste water and discharged as arsenic oxide into the treated gas. As described above, there is a risk that the arsenic compound changes its form, flows out from the exhaust gas treatment apparatus, diffuses into the drainage system or the exhaust gas duct, and spreads the pollution. In such a case, it is necessary to remove and clean arsenic at the time of repair and maintenance of the facility, and workers need to carry out gas-proof measures, resulting in poor work efficiency and time. There was a problem.

[0005]

As described above, in the prior art, exhaust gas containing an arsenic compound, an acid gas, and a fluorine compound such as a fluorohydrocarbon or a perfluoro compound is treated by a dry method, a combustion method, or a catalytic method. Since any one of the treatment methods has been attempted to cope with this, for example, there is a problem that only a dry treatment removes only a part of these gases, and the replacement frequency of the catalyst is increased. Although all gases can be treated only by the treatment method of the formula, there is a problem that arsenic changes the form of the compound and flows out from the treatment apparatus and diffuses.

Therefore, the present invention provides a method and an apparatus for reliably and inexpensively removing an arsenic compound (or arsenic) and an exhaust gas containing an acidic gas, a fluorine compound such as a fluorohydrocarbon or a perfluoro compound. The purpose is to

[0007]

In order to solve the above-mentioned problems, one embodiment of the present invention is directed to the adsorption of arsenic or an arsenic compound on exhaust gas containing arsenic or an arsenic compound and an acid gas and / or a fluorine compound. A first step of passing through a solid pharmaceutical layer having a function, and an outflow gas of the first step are treated by a combustion type exhaust gas treatment apparatus and / or a catalytic type exhaust gas treatment apparatus and / or a thermal oxidation type exhaust gas treatment apparatus The present invention relates to a method for treating exhaust gas, which comprises two steps.

Another aspect of the present invention is a combustion type exhaust gas treatment apparatus for treating a effluent gas of a first stage section having a solid drug layer having an adsorption ability for arsenic or an arsenic compound and a effluent gas of the first stage section. And / or a second stage section constituted by a catalytic exhaust gas treatment device and / or a thermal oxidation exhaust gas treatment device, and containing arsenic or an arsenic compound and an acidic gas and / or a fluorine compound The present invention relates to a device for treating exhaust gas.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Specific embodiments of the present invention will be described below. The following description shows one specific example of the present invention.
The present invention is not limited by this description.

According to the exhaust gas treatment method of the present invention,
First, as the first step, a solid drug layer having an arsenic or arsenic compound adsorption capacity for an exhaust gas containing arsenic or an arsenic compound and an acidic gas and / or a fluorine compound such as a fluorohydrocarbon or a perfluoro compound. Pass through. Examples of the solid drug that can be used here include zeolite,
Examples include iron-based metal oxides, copper-based compounds, activated carbon, and solid alkaline agents. As zeolite, synthetic zeolite is preferable, for example, Na ₂ O.Al ₂ O ₃
A synthetic zeolite having a chemical formula of 2.5H ₂ O is preferably used, and a zeolite in which sodium oxide is replaced with another alkali metal such as potassium or an alkaline earth metal such as calcium can also be preferably used. As the zeolite, for example, an average pore size of 5 to
Those having a surface area of 10Å and a specific surface area of 400 to 700 m ² / g are preferable. As the iron-based metal oxide, a trivalent oxide (Fe ₂ O ₃ ) as a main component is preferably used, and as the copper-based compound, basic copper carbonate (CuCO ₃ · Cu (O) is used.
Those mainly containing H) ₂ ) are preferably used. As the solid alkaline agent, for example, slaked lime and soda lime can be preferably used.

For example, when synthetic zeolite is used as the solid drug, the acidic gas AlCl ₃ is physically adsorbed in the pores of the synthetic zeolite. Further, arsenic compounds AsF ₃ and AsF ₅ are chemically adsorbed according to the following reaction.

[0012]

[Formula 1]

Arsenic compounds such as AsCl ₃ , AsF ₃ and AsF ₅ are iron oxides (eg Fe ₂ O ₃ ) or copper compounds (eg basic copper carbonate: CuCO ₃ .Cu (O).
H) ₂ ) causes chemisorption according to the reaction of the following equation.

[0014]

[Formula 2]

The shape of the solid drug used in the present invention is not particularly limited, but may be spherical, crushed, or cylindrical as long as it is easy to handle. Further, the particle diameter of the solid medicine is preferably fine in order to make the contact area large within the range where the ventilation resistance at the time of passing gas is not increased, and generally 2 mm to 3 mm is preferable.

In the first step, arsenic or an arsenic compound and the acidic gas are adsorbed, but the adsorption capacity of the acidic gas is saturated in a short time. Therefore, after the acid gas adsorption capacity is saturated, the outflow gas from the first step contains unadsorbed acid gas and fluorine compounds such as fluorohydrocarbons and perfluoro compounds. These are removed in the second step. As the removing means that can be used in the second step, a combustion-type exhaust gas treatment device that decomposes various objects to be processed in the exhaust gas by burning the exhaust gas with a flame in a flame, or decomposes various objects to be processed Any of the catalytic exhaust gas treatment devices by passing a catalyst having the ability to pass through a heated catalyst layer can be used. Examples of the catalyst having the ability to decompose acidic gases and fluorine compounds such as fluorohydrocarbons and perfluoro compounds include, for example, decomposition catalysts in which tungsten oxide is supported on γ-alumina or alumina-zirconium composite oxide. Etc. can be used. It should be noted that these combustion type exhaust gas treatment apparatus and catalytic type exhaust gas treatment apparatus are well known in the art, and those skilled in the art can select an appropriate type of apparatus according to the property of the treated exhaust gas.

Next, an outline of the exhaust gas treating apparatus according to the present invention will be described with reference to the drawings. The following description shows some specific examples of the exhaust gas treating apparatus according to the present invention, and the present invention is not limited by such description.

FIG. 1 is composed of a first-stage section 1 having a solid drug layer capable of adsorbing arsenic or an arsenic compound, and a combustion type exhaust gas treatment apparatus for treating the outflow gas of the first-stage section 1. 1 shows an outline of an exhaust gas treating apparatus according to one embodiment of the present invention, which is composed of a second stage section 2 including the apparatus. Exhaust gas (including arsenic or an arsenic compound, an acid gas, a fluorine compound such as a fluorohydrocarbon or a perfluoro compound) discharged from the reaction furnace 3 is
It is made to flow into the solid medicine packed tower 4 of the stage section 1. As shown in FIG. 1, two solid medicine packing towers 4 are installed in parallel, and when the solid medicine in one of the packed towers is replaced due to its saturated adsorption capacity for arsenic or arsenic compound,
It is preferable that the inflow gas line is switched to another packed column so that the exhaust gas can be continuously treated without stopping the treatment device.

The exhaust gas having passed through the solid medicine packed column 4 and adsorbed and removed arsenic or an arsenic compound then flows into the second stage section 2. In the second-stage section 2, first, the inflowing exhaust gas is introduced into the combustion section 5, and a fuel, for example, propane gas and oxygen as a combustion improver are introduced therein to form a flame, and fluorocarbons in the exhaust gas and Fluorine compounds such as perfluoro compounds are burned and decomposed. After that, the exhaust gas containing the acidic gas is sent to the water scrubber 8 through the primary cooling unit 6 and the secondary cooling unit 7. The water scrubber 8 absorbs and removes acidic gas into water. As shown in FIG. 1, the water used in the water scrubber 8 is temporarily stored in the circulation tank 10, reused by the circulation pump 11 for the water scrubber 8 and the primary cooling device 6 of the combustion unit, and then drained to the outside of the system. The amount of water used can be reduced by discharging as water. The exhaust gas from which the acid gas has been absorbed and removed by the water scrubber 8 is discharged to the outside of the system through the mist separator 9.

As the water scrubber, a structure in which a fan scrubber makes a gas-liquid contact can be used, and as a primary cooling unit, a structure in which a gas stream is sprinkled by a water spray to cool it is used as a secondary cooling unit. As the cooling unit, one having a structure in which heat is exchanged by a chiller unit for cooling while spraying a gas flow with water spray can be used. Further, as the mist separator, one having a structure in which gas is directed upward in a cylindrical container having a structure in which two diversion plates are alternately arranged in the cylinder at equal intervals can be used.

FIG. 2 shows a first-stage section 1 having a solid drug layer capable of adsorbing arsenic or an arsenic compound, a catalytic exhaust gas treatment device for treating effluent gas from the first-stage section 1, and a water scrubber. 2 shows an outline of an exhaust gas treating apparatus according to another aspect of the present invention, which is configured by a second stage section 2 including an apparatus configured by a combination of the above.
The exhaust gas discharged from the reaction furnace 3 is caused to flow into the solid medicine packed tower 4 of the first-stage section 1 having the same configuration as described with reference to FIG. 1, and the arsenic or arsenic compound in the exhaust gas is adsorbed and removed. It

The effluent gas from the first stage section 1 then flows into the second stage section 2. In the second stage section 2, first, the inflowing exhaust gas is the front stage water scrubber 1
2 is introduced and the acidic gas is absorbed and removed in water. Next, the exhaust gas is supplied to the catalytic reactor through the mist separator 13. In the catalytic reactor, the exhaust gas first passes through the heating and oxidizing section 14 heated by the heater 17,
Next, it passes through the catalytic reaction section 15 and is oxidatively decomposed to decompose and remove fluorocarbons and fluorine compounds such as perfluoro compounds. In addition, the acidic gas such as HF generated in the catalytic reactor passes through the cooling unit 16 and passes through the post-stage water scrubber 1
It is absorbed and removed in water at 8. The exhaust gas from which the acid gas has been absorbed and removed by the second-stage water scrubber 18 is discharged to the outside of the system through the mist separator 19. As in the device shown in FIG. 1, the water used in the water scrubbers 12 and 18 and the cooling unit 16 is temporarily stored in the circulation tank 20.
The amount of water used can be reduced by storing the water in the tank, reusing it by the circulation pump 21, and then discharging it to the outside of the system.

In another aspect of the present invention, the second
The stage section 2 can also be configured by a heat oxidation type exhaust gas treatment apparatus in which exhaust gas is subjected to heat oxidative decomposition treatment with a heater.

[0024]

According to the present invention, exhaust gas containing arsenic or an arsenic compound and an acidic gas and / or a fluorine compound such as a fluorohydrocarbon or a perfluoro compound can be treated effectively at low cost. it can. According to the present invention, since arsenic or an arsenic compound does not flow into the exhaust gas treatment device in the latter stage, maintenance of the exhaust gas treatment device in the latter stage or the drainage facility becomes easy. In addition, since the solid medicine packed bed in the former stage can be packed in the packed column, the replacement work is safe and easy.

[0025]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the present invention.

Example 1 An exhaust gas containing an arsenic compound, an acidic gas, a fluorinated hydrocarbon and a perfluoro compound was treated by using the exhaust gas treatment apparatus shown in FIG. As the solid medicine packed column 4 of the first stage section 1, a cylindrical cylindrical container made of stainless steel having an internal volume of 15 L and filled with synthetic zeolite (commercially available from Mizusawa Chemical Co., Ltd., trade name Mizuka Sieves 13X-1420B) was used. In the second-stage section 2, propane gas was supplied at 10 L / min and O ₂ was supplied at 50 L / min to the combustion section of an ordinary combustor to form a flame, and exhaust gas was introduced therein. The city water is supplied to the secondary cooling unit 7 at 7 L / min, and the water from the circulation tank 10 is supplied to the water scrubber 8 and the primary cooling unit 6 at 7 L / min and 6 L / min, respectively.
Supplied at L / min. The structure of the water scrubber 8 is a fan scrubber structure, the structure of the primary cooling unit 6 is a structure for spraying and cooling the gas flow with a water spray, and the structure of the secondary cooling unit 7 is a gas flow. It had a structure in which heat was exchanged by a chiller unit for cooling while spraying water with a water spray.

Filling solid chemicals in such an exhaust gas treatment device
Tower 4, AsCl₃50ppm, Cl ₂To 5000 ppm, C
HF₃700ppm, SF₆To 500ppm
Trimmed N₂Introduce gas at a flow rate of 100 L / min and
The mouth gas is introduced into the combustion unit 5 of the second stage section,
Primary cooling unit 6, secondary cooling unit 7, water scrubber 8, miss
After passing through the separator 9, it was discharged out of the system.

When the outlet gas of the treatment equipment in each step was analyzed 5 hours after the start of the passing of gas, AsCl ₃ was not detected (0.01 mg / m ³ as As or less) in the outlet gas of the solid medicine packed column. Yes, Cl ₂ , CHF ₃ , and SF ₆ leaked at the inflow gas concentration level, but none of the gas components were detected in the exit gas of the mist separator 9 in the second stage section (Cl ₂ = 0.5 ppm Below, CHF ₃ = 1 ppm or less and SF ₆ = 1 ppm or less). For the analysis of each gas component, for AsCl ₃ , an inductively coupled plasma atomic emission spectroscopic analyzer (SPS-7000 manufactured by Seiko Denshi), Cl ₂
Mass spectrometer (Questor-GP manufactured by ABB EXTREL),
For CHF ₃ and SF ₆ , a gas chromatograph equipped with a mass detector (AGS-7000U manufactured by Anerva) was used.

Iron-based oxides (commercially available products of Sudchemy catalyst, trade name N-600) and copper compounds (commercially available products of Mitsui Chemicals, trade name MAC-50) were used as solid medicines in the medicine packing tower 4 respectively.
When the same experiment was performed by filling the same with the above, the same result as when the synthetic zeolite was filled was obtained.

Example 2 An exhaust gas containing an arsenic compound, an acid gas, a fluorinated hydrocarbon and a perfluoro compound was treated using the exhaust gas treatment apparatus shown in FIG. As the solid medicine packed column 4 of the first stage section 1, the same one as in Example 1 was used. The catalytic oxidation device for the second stage section 2 has an internal volume of 21 L,
At the bottom of the SiC ceramic container with a height of 95 cm, gamma-
An alumina catalyst (GB-13 manufactured by Mizusawa Chemical Co., Ltd.) was filled to a height of 35 cm, and the whole container was heated to 750 ° C. with a heater. The cooling unit 16 had a structure of spraying water on a gas stream to cool it. City water is supplied to both the front water scrubber 12 and the rear water scrubber 18 at 1 L / min and 2 L / min, respectively.
The water from the circulation tank was supplied at 7 L / min to the cooling unit 16 of the catalytic reactor.

N containing various gas components having the same composition as in Example 1
₂ gas at a flow rate of 100 L / min was introduced into the solid medicine packed bed 4, and the outlet gas thereof was introduced into the pre-stage water scrubber 12 of the second stage section, then passed through the mist separator 13, and CHF ₃ or Air 20 as an auxiliary gas for decomposition of SF ₆
L / min and 5 mL / min of pure water were further added, introduced into the heating oxidation part 14 of the catalytic exhaust gas treatment apparatus, passed through the catalytic reaction part 15, and then passed through the cooling part 16, the water scrubber 18, and the mist separator 19. , Discharged out of the system.

After 5 hours from the start of passing the gas, the outlet gas of the processing apparatus in each step was analyzed in the same manner as in Example 1. As a result, AsCl ₃ was not detected (0.
01 mg / m ³ as As or less), Cl ₂ , CHF ₃ , SF ₆
Leaked at the inflow gas concentration level, but none of the gas components were detected in the outlet gas of the mist separator 19 in the second stage section (Cl ₂ = 0.5 ppm or less, CHF ₃ = 1 ppm or less, SF ₆ = 1 ppm or less).

Iron-based oxides (commercially available products of Sudchemy catalyst, trade name N-600) and copper compounds (commercially available products of Mitsui Chemicals, trade name MAC-50) were used as solid medicines in the medicine packing tower 4 respectively.
When the same experiment was performed by filling the same with the above, the same result as when the synthetic zeolite was filled was obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an exhaust gas treatment apparatus according to an aspect of the present invention.

FIG. 2 is a conceptual diagram of an exhaust gas treating apparatus according to another aspect of the present invention.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F23G 5/02 B01D 53/34 134E 7/06 53/36 ZABZ 102 (72) Inventor Ichichi Miyazaki Tokyo 11-1 Haneda Asahi-machi, Ota-ku F-term in EBARA CORPORATION (reference) 3K065 AA24 AB01 AC19 BA05 BA10 CA04 3K078 AA05 AA10 BA20 BA21 CA01 DA01 4D002 AA01 AA17 AA18 AA22 AA23 AA31 AB01 AC10 BA02 BA03 BA04 BA01 BA12 BA12 BA01 BA12 BA01 BA12 BA01 CA07 CA13 DA02 DA05 DA11 DA12 DA22 DA23 DA35 DA41 DA45 EA02 EA04 4D048 AA11 AB03 BA03X BA41X CA03 CC52 CD01 CD02

Claims (4)

[Claims] 1. Arsenic or an arsenic compound and an acid gas and / or
Alternatively, a method of treating exhaust gas containing a fluorine compound, wherein the exhaust gas is passed through a first step of passing through a solid drug layer having an adsorption capacity for arsenic or an arsenic compound, and an outflow gas of the first step is burned. Second exhaust gas treatment device and / or catalytic exhaust gas treatment device and / or a second step of treating with a thermal oxidation type exhaust gas treatment device. 2. A solid drug having the ability to adsorb arsenic or an arsenic compound, wherein the solid drug is one or a combination of two or more selected from the group consisting of zeolite, activated carbon, solid alkaline agents, iron-based metal oxides and copper-based compounds. The method of claim 1, wherein 3. Arsenic or an arsenic compound, acid gas and / or
Or a device for treating exhaust gas containing a fluorine compound, the first stage section having a solid drug layer having an adsorption capacity for arsenic or an arsenic compound, and a combustion type exhaust gas for treating the outflow gas of the first stage section A second stage section comprising a treatment device and / or a catalytic exhaust gas treatment device and / or a thermal oxidation type exhaust gas treatment device. 4. The solid drug having the ability to adsorb arsenic or an arsenic compound is one or a combination of two or more selected from the group consisting of zeolite, activated carbon, solid alkaline agents, iron-based metal oxides, and copper-based compounds. The device according to claim 3, wherein