JP2002239341A - Method for treating gas containing nh3 and device for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for removing a large amount of NH3 effectively, which suppresses the generation of harmful by-products at a relatively low running cost, and to provide a device for the same. SOLUTION: This method for treating gas containing NH3 is characterized in that the gas containing NH3 is heated at 500 deg.C or higher in an oxygen-free atmosphere to be made to decompose NH3 by heat and that the gas containing undecomposed residual NH3 is adsorbed by an adsorbent at a normal temperature, or is cooled at 200 deg.C or lower and mixed with oxygen to be brought into contact with a NH3 decomposing catalyst heated at 170-200 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a method and apparatus for treating gas containing NH _3, in particular, detoxifies NH ₃ discharged from CVD (chemical vapor deposition) process in the semiconductor industry Method and apparatus.

[0002]

2. Description of the Related Art In the semiconductor industry, various kinds of harmful gases are used in a semiconductor manufacturing process, and there is a concern about environmental pollution. In particular, the exhaust gas from the CVD (Chemical Vapor Deposition) process contains NH ₃ (tolerable concentration: A
CGIH (American Conference of Governmental Industrial)
Hygienists)
LV-TWA (Threshold Limit Value-Time Weighted Average
Concentration (time load average allowable concentration) = 25 ppm), and there is an urgent need to establish a system that removes NH ₃ and makes the exhaust gas harmless.

Conventionally, various methods have been proposed for removing NH ₃ . For example, a wet treatment method using water or an acid solution, a dry treatment method using an adsorbent such as iron sulfate or zeolite, and a thermal decomposition treatment method using a catalyst are generally known.

However, in the wet processing method described above, because it contains NH ₃ in the wastewater generated by the processing, require extensive equipment for decomposing the NH ₃ into N ₂ and H ₂ O Costly. Further, in the above-mentioned dry treatment method, in order to treat a large amount of NH ₃ , a large amount of an adsorbent and an exchanging operation of the adsorbent are required, and there is a problem that a running cost is increased. Furthermore, in the above-mentioned catalyst thermal decomposition treatment method, NH ₃
Flows in at a high concentration, the temperature rises due to the heat of reaction of the catalyst,
Although NH ₃ is decomposed, there is a problem in that a large amount of by-products such as NO _x and N ₂ O are generated, and these are discharged into an environmental atmosphere in excess of an allowable concentration.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention solves the above-mentioned problems of the prior art, suppresses the generation of harmful by-products at a relatively low running cost, and efficiently removes a large amount of NH4. It is an object of the present invention to provide a processing method and a processing apparatus for removing ( ₃₎ .

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies, and as a result, thermally decomposed NH ₃ under an oxygen-free atmosphere, cooled, and then undecomposed NH ₃ . It has been found that a large amount of NH ₃ can be effectively removed at low cost by adsorbing NH ₃ on an adsorbent or contacting the NH ₃ with a NH ₃ decomposition catalyst in the presence of oxygen.

That is, according to the present invention, a gas containing NH ₃ is heated to 500 ° C. or more in an oxygen-free atmosphere to obtain NH _3.
, And then adsorbing the gas containing undecomposed residual NH ₃ onto the adsorbent at room temperature. A method for treating a gas containing NH ₃ is provided.

It is known that NH ₃ starts to decompose at 450 ° C. to 500 ° C. under atmospheric pressure and almost completely decomposes at 500 ° C. to 600 ° C. The decomposition reaction of NH ₃ at this time is represented by the following reaction formula (1)

[0009]

Embedded image

[0010] However, when oxygen is present in the atmosphere during the thermal decomposition of NH ₃ , the following reaction formula (2)

[0011]

Embedded image

Accordingly, NO _x and N ₂ O, which are environmental pollutants,
Are generated in large quantities as by-products. Therefore, the thermal decomposition of NH ₃ , which is the first step of the gas processing method according to the present invention, is preferably performed in an oxygen-free atmosphere. For example, in the case of treating the LP-CVD process exhaust gas by the treatment method of the present invention, this process is performed using NH ₃ and Si.
Since H ₂ Cl ₂ or Si ₂ Cl ₆ gas is used and O ₂ is not used, oxygen is not contained in the exhaust gas.
Therefore, in such a case, it is not necessary to provide a step of removing oxygen from the exhaust gas in order to form an oxygen-free atmosphere during the thermal decomposition of NH ₃ . However, when oxygen is contained in the gas to be treated, it is necessary to remove oxygen from the gas by performing an oxygen removing step such as treating the gas containing NH ₃ with a deoxidizer. is there. Further, the temperature of the NH ₃ thermal decomposition reaction is preferably 500 ° C. or higher. The higher the temperature, the higher the decomposition rate of NH ₃ , but the temperature is lower than the spontaneous ignition temperature of H ₂ generated (571 ° C.). preferable.

In the treatment method of the present invention, in the thermal decomposition step, about 80 to 90% of NH ₃ is thermally decomposed into N ₂ and H ₂ , but about 10 to 20% of NH ₃ is undecomposed. It remains as it is. In the treatment method of the present invention, the gas containing the undecomposed residual NH ₃ is then cooled to room temperature, and the residual NH ₃ is adsorbed and removed by an adsorbent. At this time, if the temperature of the gas containing NH ₃ is high, the desorption of NH ₃ from the adsorbent is promoted and the processing performance is lowered, which is not preferable. NH ₃
Is preferably room temperature, particularly preferably 20 ° C to 30 ° C.

As the adsorbent used in the present treatment method, any adsorbent capable of adsorbing NH ₃ can be used without any particular limitation, and an inorganic particulate solid known as an adsorbent in the art can be used. Specifically, adsorbents selected from the group consisting of synthetic zeolites, iron sulfate, impregnated activated carbon, and combinations thereof, which are commercially available and inexpensively available for industrial use, are particularly preferred. Specific adsorbents that can be used in the present invention for this purpose, Mizusawa Kagaku NH ₃ adsorbing synthetic zeolite, trade name Mizukashibusu 4A-812B, Nissan Zudohemi catalyst made of iron sulfate adsorbent, trade name N- 500, NH manufactured by Takeda ₃
Adsorbed impregnated activated carbon, trade name Granular Shirasagi GTSx, and the like can be given.

Further, undecomposed residual NH ₃ after the thermal decomposition treatment
As a method for treating a gas containing, instead of the method using an adsorbent as described above, it is also possible to adopt a method in which the gas is cooled to 200 ° C. or lower, and oxygen is added thereto, followed by contact with an NH ₃ decomposition catalyst. it can. That is, according to another aspect of the present invention, there is provided a method of treating a gas containing NH _3, in an oxygen-free atmosphere, warmed gas containing NH ₃ over 500 ° C., the NH ₃ thermal Is decomposed, and then the gas containing undecomposed residual NH ₃ is cooled to 200 ° C. or less, and oxygen is added to the gas cooled to 200 ° C. or less, and the gas to which oxygen is added is added.
There is provided a treatment method comprising the steps of contacting with an NH ₃ decomposition catalyst heated to 170 ° C. to 200 ° C.

In the treatment method of this aspect, the undecomposed residual NH obtained by the above-described pyrolysis step
_{After the} gas containing ₃ is cooled to about 200 ° C. or less, oxygen is added. At this time, if the gas temperature is higher than 200 ° C,
The reaction between NH ₃ and O _{2 in} the above formula (2) proceeds to generate a large amount of NO _x and N ₂ O, and harmful nitrogen oxides are generated in the treated gas discharged into the environmental atmosphere. Reference allowable concentration (N
O: 25 ppm, NO ₂ : 3 ppm, N ₂ O: 50 ppm). Further, the amount of oxygen to be added is preferably such that the O ₂ concentration in the gas after adding oxygen becomes about 5% or more, more preferably 6% or more.

Next, the oxygen-added gas is heated to 170 ° C. to 200 ° C.
The catalyst is brought into contact with the NH ₃ decomposition catalyst which has been heated. Where N
If the temperature of the H ₃ decomposition catalyst is over 230 ° C.,
Since the reaction of the above formula (2) proceeds and NO _x and N ₂ O are generated in excess of the above environmental standard allowable concentration, it is not preferable. Further, the gas treated with the NH ₃ decomposition catalyst preferably has a residual NH ₃ concentration of 1% or less. When the residual NH ₃ concentration is over 1%, NH ₃ temperature of the NH ₃ decomposing catalyst by reaction heat during decomposition is increased, NO _x and N ₂ O is produced beyond the environmental standard allowable concentrations of the It is not preferable because it becomes easier.

NH used in the processing method of this embodiment
_{As the 3} cracking catalyst, any granular solid catalyst known in the art as an NH ₃ cracking catalyst can be used. Specifically, one or more catalysts selected from the group consisting of iron oxide, manganese oxide, vanadium oxide, aluminum oxide, chromium oxide, tungsten oxide, copper oxide, and combinations thereof can be preferably used. Specific NH that can be used in the present invention for this purpose
_{3 As the} decomposition catalyst, for example, a treating agent manufactured by Nissan Sudehemie Catalyst (trade name: Imp2-N150; main component Fe ₂ O ₃ : 50 wt.
%, MnO: 25 wt%, V ₂ O ₅ : 5.0 wt%), and an NH ₃ decomposer (trade name: TNH ₃ -2000) manufactured by Toyo CCI.

Further, according to the present invention, there is provided an apparatus for processing a gas containing NH ₃ . The apparatus includes a hollow interior through which the gas can be passed under an oxygen-free atmosphere, a heating means capable of heating the temperature of the hollow interior to 500 ° C. or more, a gas inlet, and a gas outlet for discharging the gas after the treatment. And a cooling pipe arranged in fluid communication with the pyrolysis tank and cooling the gas after pyrolysis; and a cooling pipe arranged in fluid communication with the cooling pipe and cooled. And an adsorbent tank filled with an adsorbent for adsorbing undecomposed NH ₃ in the thermally decomposed gas.

The thermal decomposition tank of the processing apparatus of the present invention is preferably provided with an N ₂ purge line, if necessary, as a means for changing the thermal decomposition atmosphere to an oxygen-free atmosphere.
As the heating means provided in the pyrolysis tank of the present invention,
The temperature of the gas phase formed inside the hollow of the pyrolysis tank is 500 ℃
There is no particular limitation as long as it can be heated as described above, and preferred examples include a ceramic heater such as a ceramic electric tubular furnace, a rod-shaped heater, and the like.

The cooling pipe of the processing apparatus of the present invention is not particularly limited as long as it can cool the gas pyrolyzed in the pyrolysis tank to a predetermined temperature. The cooling medium may be air, water or other known refrigerant. Can be used.

The adsorbent tank of the treatment apparatus of the present invention contains NH ₃
Is filled with the above-mentioned adsorbent. The amount of adsorbent charged varies depending on the amount of NH ₃ to be treated and the dimensions of the adsorbent tank. For example, a gas containing 3.6% NH ₃ is supplied to an adsorbent tank 170 mm in diameter × 750 mm in height at a flow rate of 80 L. In the case where the treatment is carried out by aeration at / min for 30 minutes, the volume can be about 17 L.

According to another aspect of the present invention, there is provided a hollow interior through which the gas can be passed in an oxygen-free atmosphere, heating means capable of heating the temperature of the hollow interior to 500 ° C. or more, a gas inlet, A pyrolysis tank provided with a gas outlet for discharging the gas after the treatment, a cooling pipe arranged in fluid communication with the pyrolysis tank and cooling the pyrolyzed gas, and the cooling pipe and the fluid An oxygen addition unit that is arranged in a communicable state and adds oxygen to the cooled gas after the thermal decomposition, and a catalyst decomposition tank that brings the cooled and oxygen-added gas into contact with the NH ₃ decomposition catalyst is provided. A processing device is provided.

In the processing apparatus of this aspect, the thermal decomposition tank, the heating means, and the cooling pipe may have the same configuration as the thermal decomposition tank, the heating means, and the cooling pipe in the processing apparatus having the above-mentioned adsorbent tank.

In the processing apparatus of this aspect, an oxygen adding means is provided downstream of the cooling pipe or in the catalytic cracking tank in order to add oxygen to the cooled gas. As the oxygen adding means, for example, it may be constituted by an oxygen conduit connected to an appropriate oxygen supply source, and a valve for adjusting the supply of oxygen from the oxygen conduit to a pipe connecting between the cooling pipe and the catalytic cracking tank. it can.

In the processing apparatus of this embodiment, the catalyst decomposition tank is filled with the above-mentioned NH ₃ decomposition catalyst. Further, the catalyst decomposition tank is provided with heating means for heating the catalyst filled therein. As the heating means, the temperature of the catalyst filled in the catalyst decomposition tank is 170 to 200
There is no particular limitation as long as it can be heated to a preferable temperature of ° C, and a ceramic heater such as a ceramic electric tubular furnace and a bar-shaped heater similar to those used in a pyrolysis tank can be preferably mentioned.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings, but the present invention is not limited thereto.

FIG. 1 is a schematic diagram showing a preferred embodiment of a processing apparatus for processing a gas containing NH _{3 according} to the present invention. The processing apparatus 1 includes a hollow interior 10a and a hollow interior 10a that allow a gas containing NH ₃ to pass therethrough under an oxygen-free atmosphere.
A pyrolysis tank 10 provided with a heating means 11 capable of heating the temperature of the pyrolysis tank to 500 ° C. or higher, and a cooling pipe 20 that is disposed in fluid communication with the pyrolysis tank 10 and cools the gas after pyrolysis, An adsorbent tank 30 which is arranged in a fluid communication state with the cooling pipe 20 and is filled with an adsorbent 30a for adsorbing undecomposed NH ₃ in the cooled gas; A first conduit 13 connects the pipes 20 and a second conduit 32 connects the cooling pipe 20 and the adsorbent tank 30 so as to be in fluid communication.

More specifically, in the present embodiment, the thermal decomposition tank 10 is formed of a hollow column made of SUS, and a ceramic heater 11 as a heating means is disposed on the outer periphery of the thermal decomposition tank 10 so that NH ₃ And a thermocouple (not shown) for measuring the temperature of the gas phase formed in the hollow interior 10a. If necessary, in order to make the gas introduced into the pyrolysis tank 10 oxygen-free, the gas inlet conduit 12 or the pyrolysis tank 10
Further, oxygen removing means 14 such as an oxygen scavenger can be further provided.

As the cooling pipe 20, for example, as an air cooling pipe,
A pipe formed by bending a metal pipe to form a curved flow path can be used. The adsorbent tank 30 is formed of a SUS hollow column, and includes an outlet conduit 33 for discharging the gas after the adsorption treatment into an environmental atmosphere or a subsequent processing tank (not shown) as necessary. The above adsorbent is placed inside the adsorbent tank 30.
30a is filled.

When the processing apparatus 1 is used to process a gas containing NH ₃ , for example, exhaust gas containing NH ₃ from a CVD apparatus or the like is removed by an oxygen removing means 14 such as an oxygen scavenger if necessary. After removing oxygen in the gas, the gas is introduced into the pyrolysis tank 10 through the gas inlet conduit 12. The temperature of the gas introduced into the hollow interior 10a of the thermal decomposition tank 10 is heated to 500 ° C. or higher by the ceramic heater 11 to thermally decompose NH ₃ in the gas. This temperature is monitored by a thermocouple (not shown) located in the hollow interior 10a.

Next, the gas after the thermal decomposition treatment is supplied to the thermal decomposition tank 10.
Through the first conduit 13 to the cooling pipe 20, and the gas after the thermal decomposition treatment is air-cooled to room temperature. Thereafter, the cooled gas is introduced from the cooling pipe 20 into the adsorbent tank 30 via the second conduit 32. In the adsorbent tank 30, undecomposed NH ₃ is adsorbed by the adsorbent 30a, and the processing gas is discharged into the environmental atmosphere via the outlet conduit 33 or to a subsequent processing device as required.

FIG. 2 is a schematic diagram showing another embodiment of the gas processing apparatus of the present invention. The processing apparatus 100 has a hollow interior 1 capable of passing a gas containing NH ₃ under an oxygen-free atmosphere.
10a and a pyrolysis tank 110 provided with a heating means 111 capable of heating the temperature of the hollow interior 110a to 500 ° C. or higher, and the pyrolysis tank 11
The cooling pipe 120 is arranged in a fluid communication state with the cooling pipe 120 for cooling the gas after the thermal decomposition, and the cooling pipe 120 is arranged in the fluid communication state with the cooling pipe 120 and is cooled to the gas after the thermal decomposition processing. An oxygen addition means 135 for adding oxygen, and a catalyst decomposition tank 130 for bringing a cooled and oxygen-added gas into contact with the NH ₃ decomposition catalyst are provided. A first conduit 113 is provided between the thermal decomposition tank 110 and the cooling pipe 120. Depending on the cooling pipe 120 and the catalyst decomposition tank 13
Between 0, each is connected by a second conduit 133 in a fluid-communicable state. The configuration of the thermal decomposition tank 110 and the cooling pipe 120 is the same as that of the thermal decomposition tank 10 and the cooling pipe 20 of the processing apparatus 1 shown in FIG.
The configuration is the same as that described above.

In the processing apparatus 100, instead of the adsorbent tank 30, downstream of the cooling pipe, oxygen adding means 135 for adding oxygen to the cooled pyrolyzed gas, and cooled oxygen is added. And a catalyst decomposition tank 130 for bringing the gas into contact with the NH ₃ decomposition catalyst.

Although not shown, the oxygen adding means 135 may be an appropriate adding means having an oxygen gas supply source and a valve for controlling the supply of oxygen gas, and is connected to the second conduit 132. The catalyst decomposition tank 130 is formed of, for example, a hollow column made of SUS, and is an outlet conduit 13 for discharging the gas after the catalyst decomposition processing into an environmental atmosphere or a subsequent processing tank (not shown) as necessary.
3 is provided. Inside the catalyst decomposition tank 130, an NH ₃ decomposition catalyst 130
a is filled, and a thermocouple (not shown) for measuring the internal temperature is arranged. A ceramic heater 131 as a heating means is disposed on the outer periphery of the catalyst decomposition tank 130, and the catalyst 1 filled in the catalyst decomposition tank 130 is disposed.
Heat 30a.

When processing a gas containing NH ₃ using the processing apparatus 110, for example, NH ₃ from a CVD apparatus or the like is used.
After the oxygen in the gas is removed by an oxygen removing means 114 such as an oxygen scavenger, if necessary, the exhaust gas is introduced into the pyrolysis tank 110 through a gas inlet conduit 112 to cause a thermal decomposition reaction. The operation of the pyrolysis tank 110 is the same as that of the pyrolysis tank 10 shown in FIG.
Is similar to that described above. Pyrolysis tank 11
After the thermal decomposition of NH ₃ in the gas at 0, the gas is passed through the cooling pipe 120 through the first conduit 113, and the gas after the thermal decomposition is heated to 200 ° C.
Cool to below.

Thereafter, the cooled gas is passed through the second conduit 132
And is introduced into the catalyst decomposition tank 130. At this time, a required amount of oxygen is introduced into the second conduit 132 via the oxygen adding means 135. Thus, the gas to which the required amount of oxygen has been added is introduced into the catalytic cracking tank 130 via the second conduit 132. In the catalyst decomposition tank 130, the gas is brought into contact with the NH ₃ decomposition catalyst 130a,
Decomposes undecomposed NH ₃ . At this time, ceramic heater 1
The temperature of the catalyst is raised to 170-200 ° C by 31. Thereafter, the processing gas is discharged into the environmental atmosphere via the outlet conduit 133 or to a subsequent processing device as needed.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the processing method and the processing apparatus of the present invention will be described below, but the present invention is not limited to these embodiments.

Example 1 Influence of Gas Phase Temperature on Thermal Decomposition of Gas in Oxygen-Free Atmosphere An experiment was conducted to examine the relationship between the thermal decomposition rate of NH ₃ and the gas phase temperature under an oxygen-free atmosphere. 110m inside diameter as thermal decomposition tank
m, using a SUS hollow column with a length of 400 mm, as a heating means, a ceramic heater attached to the outside of the hollow column, the temperature of the gas phase in the hollow column is measured using a thermocouple arranged in the hollow column did.

As a test gas, NH_ThreeContent of 3.6%
N adjusted to be_TwoUsing gas at a flow rate of 80 L / min
Vent the pyrolysis tank and adjust the temperature of
Heater) to gradually change the outlet gas
The components were analyzed. Analyte is NH_Three, NO, NO_Two,
N_TwoO and NH_ThreeIs the detection tube method (NH _ThreeInspection
Shiretou), NO and NO_TwoIs a chemiluminescence method (manufactured by Shimadzu Corporation)
Chemiluminescence analyzer, model NOA-7000), N_TwoO is gas chromatograph
Graph mass spectrometry (mass chromatography by Anelva
The analysis was performed using an analyzer (model AGS-7000U). Outlet gas
NO in_xAnd N _TwoO is always below the detection limit (1 ppm)
Yes, among the above four types of gases to be analyzed, NH_Threeonly
Was detected.

Table 1 shows the concentration of NH _{3 in} the outlet gas, the decomposition rate of NH ₃ calculated from the concentration value, and the temperature of the gas phase of the pyrolysis tank.

[0042]

[Table 1]

[0043] From these results, the temperature of the gas phase of the thermal decomposition tank by warming to 500 ° C. or higher, it can be seen that the NH ₃ is decomposed more than 70%. Comparative Example 1 An experiment was performed in the same manner as in Example 1 except that oxygen gas was added, and the relationship between the outlet gas composition and the gas phase temperature was examined.

As the test gas, the content of NH ₃ was 3.6%,
N ₂ gas adjusted to have an O ₂ content of 5.5%
Air was passed through the pyrolysis tank at a flow rate of 80 L / min. Table 2 shows the results.

[0045]

[Table 2]

From these results, in the presence of O ₂ , NH ₃
It is desirable gas phase temperature in order to satisfactorily decompose is 380 ° C. or higher, the gas phase temperature exceeds 200 ° C., N ₂
O starts to be generated, and at 300 ° C. or higher, NO and NO ₂ are also generated, and all of NO, NO ₂ and N ₂ O are in the environmentally acceptable concentration (N
O: 25 ppm, NO ₂ : 3 ppm, N ₂ O: 50 ppm).

[0047] Example 2: In order to evaluate the temperature dependency of the performance of decomposing NH ₃ decomposition catalyst of NH ₃ by NH ₃ decomposition catalyst was investigated the relationship between the treatment temperature and the outlet gas components.

As a catalyst decomposition tank, inner diameter 110 mm, height 1600 m
m SUS hollow column, NH _ThreeAs a decomposition catalyst,
Fe_TwoO_Three: 50wt%, MnO: 25wt%, V_TwoO_Five： 5.0wt%
Nissan Sudehemie Catalyst Treatment Agent (Product
Name: Imp2-N150) 15L was charged. Sera as heating means
Using a mic heater, heat from outside the catalytic decomposition tank
Was. The temperature inside the catalytic cracking tank is controlled by a thermocouple placed inside.
The temperature was measured.

As a test gas, the content of NH ₃ was 1.0%,
Using a N ₂ gas whose O ₂ content was adjusted to be 5.8%, the gas was passed through the catalyst decomposition tank at a flow rate of 80 L / min. The components in the outlet gas were analyzed by varying the processing temperature stepwise. Table 3 shows the results.

[0050]

[Table 3]

From the experimental results, it was found that when the processing temperature was lower than 170 ° C., the decomposition treatment of NH ₃ was not good, and when the processing temperature was 230 ° C. or higher, the concentrations of NO ₂ and N ₂ O exceeded the allowable concentrations. From the results of this experiment, it was found that when treated in a temperature range of 170 ° C. to 200 ° C., NH ₃ was well decomposed and NO, NO ₂
And N ₂ O emission concentration is seen that does not exceed the allowable concentration.

Example 3 In order to evaluate the dependency of the treatment performance of the NH ₃ decomposition catalyst on the NH ₃ concentration, the relationship between the NH ₃ inflow concentration and the components in the outlet gas was examined.

Using the same decomposition catalyst tank as in Example 2, the same decomposition gas was used as the test gas except that the NH ₃ concentration was varied to 1.0%, 1.5% and 2.5%. The processing temperature at the start of gas passage in the catalyst tank was set at about 170 ° C., and the components in the outlet gas at the start of gas passage and after 30 minutes of operation were analyzed.
Table 4 shows the results.

[0054]

[Table 4]

From the experimental results, it can be seen that NH ₃ is decomposed satisfactorily regardless of the NH ₃ concentration step, but when the inflowing NH ₃ concentration increases, the temperature of the catalyst rises and the N ₂ O concentration in the outlet gas decreases. It can be seen that the concentration becomes higher, and even if the inflow concentration of NH ₃ is 1.5%, it exceeds the allowable concentration.

Examples 4 and 5: NH ₃ Decomposition Treatment by Combination of Thermal Decomposition and Adsorption under Oxygen-Free Conditions According to the treatment method of the present invention, after a gas containing NH ₃ was thermally decomposed under an oxygen-free atmosphere, it was not decomposed. Was treated by adsorbing NH ₃ on an adsorbent.

As a pyrolysis tank, inner diameter 110 mm, height 1600 mm
Was used, and a ceramic heater was used as a heating means. As the cooling pipe, a pipe made of SUS having a pipe diameter of 25 mmφ and folded into four pieces each having a length of about 730 mm was used, and air was used as a refrigerant. 170mm inside diameter as adsorbent tank,
A 750 mm high SUS hollow column was used, and a synthetic zeolite (synthetic zeolite for NH ₃ manufactured by Mizusawa Chemicals, trade name: Mizuka Sieves 4A-812B) (Example 4) or iron sulfate (iron sulfate adsorbent manufactured by Nissan Sued Hemy Catalyst, A total of 17 L was charged together with N-500 (trade name) (Example 5).

The temperature of the gas phase of the pyrolysis tank was heated to 528 ° C., and the content of NH ₃ as a test gas was adjusted to 3.6 in this gas phase.
% N ₂ gas was passed at a flow rate of 80 L / min. The test gas after pyrolysis was air-cooled to room temperature (about 30 ° C.) via a cooling pipe, and then the cooled test gas was introduced into an adsorbent tank to adsorb NH ₃ on the adsorbent. The NH ₃ concentration in the outlet gas from the adsorbent tank was continuously measured. On the other hand, the same experiment as above was performed except that the gas was passed directly through the adsorbent tank at room temperature without passing through the pyrolysis tank, and the concentration of NH _{3 in} the outlet gas was measured. Table 5 shows the results. Note that NO, NO ₂ and N ₂ O in the outlet gas were all below the detection limit.

[0059]

[Table 5]

From Table 5, it can be seen that according to the treatment method of the present invention in which the thermal decomposition and the adsorption are combined, the N in the outlet gas from the adsorbent tank is compared with the case where only the adsorption is performed without performing the thermal decomposition.
The time required for H ₃ to exceed the allowable concentration was about six times longer. This indicates that the effective operating life of the adsorbent has been greatly increased.

Example 6 According to the treatment method of the present invention, a gas containing NH ₃ was thermally decomposed in an oxygen-free atmosphere, and undecomposed NH ₃ was treated using an NH ₃ decomposition catalyst.

The same pyrolysis tank, heating means, cooling pipe and refrigerant as in Example 4/5 were used. After the cooling pipe, a SUS hollow column having an inner diameter of 110 mm and a height of 1600 mm was used as a decomposition catalyst layer, and 15 L of the same NH ₃ decomposition catalyst as in Example 2 was filled therein.

As a test gas, NH_ThreeContent of 3.6%
N adjusted to be_TwoUsing gas, heat component at flow rate 80L / min
The tank was ventilated. The gas phase temperature of the pyrolysis tank is about 528 ° C
Set to. Next, the pyrolyzed test gas is passed through a cooling pipe.
And air-cool the test gas temperature to about 190 ° C.
O_TwoO so that the concentration is 5.5%_TwoAfter adding
Decomposition catalyst heated so that the internal temperature is about 200 ° C
The tank was aerated. From the decomposition catalyst tank 30 minutes after the start of ventilation
Analysis of the components of the outlet gas of_Three,
NO, NO_TwoAnd N_TwoO is below the detection limit (1ppm)
Yes, NO_xAnd N _TwoWithout releasing O, NH_ThreeIs good
It can be seen that it was decomposed into.

[0064]

According to the processing method and the processing apparatus of the present invention, the problems of increased running costs and generation of by-products such as NO _x and N ₂ O do not occur, and they are effective and effective at low cost. Large amounts of NH ₃ can be removed over time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a preferred embodiment of a processing apparatus of the present invention.

FIG. 2 is a schematic diagram showing another preferred embodiment of the processing apparatus of the present invention.

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Claims (8)

[Claims] 1. A method for treating a gas containing NH ₃ , wherein the gas containing NH ₃ is heated to 500 ° C. or more in an oxygen-free atmosphere to thermally decompose NH ₃ , A process comprising adsorbing a gas containing residual NH ₃ to an adsorbent at room temperature. 2. The method according to claim 1, wherein the adsorbent is an adsorbent selected from the group consisting of synthetic zeolite, iron sulfate, and combinations thereof. _3. A method for treating a gas containing NH ₃ , wherein the gas containing NH ₃ is heated to 500 ° C. or more in an oxygen-free atmosphere to thermally decompose NH ₃ , cooling the residual NH ₃ gas containing up to 200 ° C. or less, in 200 ° C. is cooled below the gas, oxygen is added, the oxygen is added gas, which is heated to 170 ° C. to 200 DEG ° C. N
A treatment method comprising the steps of contacting with an H ₃ decomposition catalyst. 4. The NH ₃ decomposition catalyst includes one or more catalysts selected from the group consisting of iron oxide, manganese oxide, vanadium oxide, aluminum oxide, chromium oxide, tungsten oxide, copper oxide, and combinations thereof. 5. The processing method according to claim 4, wherein: 5. An apparatus for treating a gas containing NH ₃ , comprising: a hollow interior through which the gas can be passed in an oxygen-free atmosphere; and heating means capable of heating the temperature of the hollow interior to 500 ° C. or more. A pyrolysis tank, a cooling pipe arranged in fluid communication with the pyrolysis tank and cooling the gas after pyrolysis, and a cooling pipe arranged in fluid communication with the cooling pipe and cooled. A processing apparatus, comprising: an adsorbent tank filled with an adsorbent for adsorbing undecomposed NH ₃ in decomposed gas. 6. The treatment apparatus according to claim 5, wherein the adsorbent is an adsorbent selected from the group consisting of synthetic zeolite, iron sulfate, and a combination thereof. 7. An apparatus for treating a gas containing NH ₃ , comprising: a hollow interior through which the gas can pass under an oxygen-free atmosphere; and heating means capable of heating the temperature of the hollow interior to 500 ° C. or more. A pyrolysis tank, a cooling pipe arranged in fluid communication with the pyrolysis tank and cooling the gas after pyrolysis, and a cooling pipe arranged in fluid communication with the cooling pipe and cooled. A processing apparatus comprising: oxygen adding means for adding oxygen to a gas after decomposition; and a catalyst decomposition tank for bringing a cooled gas, to which oxygen is added, into contact with an NH ₃ decomposition catalyst. 8. The NH ₃ decomposition catalyst includes one or more catalysts selected from the group consisting of iron oxide, manganese oxide, vanadium oxide, aluminum oxide, chromium oxide, tungsten oxide, copper oxide, and combinations thereof. The processing device according to claim 7, wherein: