JP2000233117A - Method and apparatus for purification of exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve purifying efficiency and simplify after-treatment by a method wherein an exhaust gas containing ammonia is decomposed into nitrogen and hydrogen by bringing it in contact with an ammonia decomposing catalyst, an undecomposed ammonia is separated by adsorption by bringing it in contact with an adsorbent, and thereafter a heating-regenerated exhaust gas of an adsorbent is again brought in contact with the decomposing catalyst. SOLUTION: An exhaust gas is supplied to an ammonia decomposing cylinder 3 from an exhaust gas feed line 1 via a heat exchanger 2. An ammonia decomposing catalyst 4 is filled in the decomposing cylinder 3, heated with a heater 5, and most of the ammonia is decomposed into nitrogen and hydrogen. The gas from the decomposing cylinder 3 is introduced into an ammonia adsorbing cylinder 8 via a pipe arrangement 6, the heat exchanger 2, a cooler 17 and a valve 17. An ammonia adsorbent 9 is filled in the adsorbing cylinder 8, an undecomposed ammonia in the introduced gas is separated by adsorption, and the purified exhaust gas is released to the open air via a valve 11 and an exhaust gas purging line 12. A part of the gas at that time is introduced into an ammonia adsorbing tower 8' in a heated state via a valve 13, and the adsorbent 9' is regenerated by heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for purifying exhaust gas containing ammonia, and more particularly to an exhaust gas containing ammonia discharged from a semiconductor manufacturing process.
Alternatively, the present invention relates to a method and a device for purifying an ammonia-containing exhaust gas discharged from a chemical treatment step or the like.

[0002]

2. Description of the Related Art In recent years, ammonia has been used in each process with the development of semiconductor manufacturing industry, optoelectronics manufacturing industry, precision instrument manufacturing industry, super hard material and decorative article manufacturing industry. Among them, a large amount of ammonia is used in a compound semiconductor nitride film manufacturing process and the like.

[0003] Ammonia is an indispensable substance in the manufacturing process of compound semiconductors, but is highly toxic, and its allowable concentration is 2%.
It is 5 ppm, and when exhaust gas containing ammonia is released into the atmosphere, it has a bad influence on human bodies and the environment. Therefore, it is necessary to purify the exhaust gas containing ammonia discharged after using ammonia in a semiconductor manufacturing process or the like before releasing it to the atmosphere. A large amount of ammonia is also used in the chemical industry. At that time, ammonia-containing gas may be discharged, and it is necessary to purify these exhaust gases when releasing them to the atmosphere.

As a method for purifying exhaust gas containing ammonia, a method of contacting and absorbing an acidic aqueous solution such as sulfuric acid and capturing ammonia as a salt such as ammonium sulfate has been conventionally used. The ammonia is converted into water and nitrogen by introducing it into a combustion furnace. Purification method, method of purification by contact with dry abatement agent, method of contacting ammonia decomposition catalyst with heating to decompose into nitrogen and hydrogen, and further purify by combining ammonia decomposition catalyst with dry abatement agent Methods are known.

[0005]

However, the above method has the following problems. That is, the method of contact absorption with an aqueous solution such as sulfuric acid has a disadvantage that a large amount of ammonium salt is by-produced in the purification treatment. In the method of purifying by introducing into a combustion furnace and burning it, exhaust gas is often not released under steady conditions, so incomplete combustion, abnormal combustion, or explosion due to fluctuations in gas flow rate and flammable component concentration In addition to the inconveniences such as danger, there is a disadvantage that nitrogen oxide which is a harmful substance is by-produced by the combustion treatment. The method of purifying by contacting with a dry abatement agent has a disadvantage that when the amount of ammonia treatment is large, a large amount of the abatement agent is required, the treatment cost is high, and an extremely large treatment apparatus is required.

[0006] In the method of bringing the ammonia decomposition catalyst into contact with the ammonia under heating, the decomposition rate of ammonia is defined by the chemical equilibrium concentration. As a result, tens to hundreds of ppm of ammonia remain in the purified exhaust gas. There is a disadvantage that there is. Furthermore, the method of purifying by combining an ammonia decomposition catalyst and a dry abatement agent has a disadvantage that a large amount of a dry abatement agent is required because the concentration of undecomposed ammonia after ammonia decomposition is tens to hundreds of ppm. there were. From the above, the development of a purifying method and a purifying apparatus which is small in size, has a high purifying ability, is easy to perform post-purification treatment, has a very small flow of ammonia in the purge gas after purification, and can be processed at low cost. Was strongly desired.

[0007]

The present inventors have conducted intensive studies to solve these problems, and as a result, in purifying exhaust gas containing ammonia, the ammonia-containing exhaust gas was brought into contact with an ammonia decomposition catalyst. After being decomposed into nitrogen and hydrogen, the undecomposed ammonia contained in the gas after the ammonia decomposition treatment is brought into contact with the adsorbent to be adsorbed and separated, and then the regenerated exhaust gas of the adsorbent is brought into contact with the decomposition catalyst again. It has been found that ammonia-containing exhaust gas can be almost completely purified. Further, they have found that by bringing the regenerated exhaust gas into contact with an ammonia decomposition catalyst (second ammonia decomposition catalyst) provided separately from the ammonia decomposition catalyst, ammonia can be discharged in a significantly reduced amount, The present invention has been reached.

That is, a first aspect of the present invention is a method for purifying an exhaust gas containing ammonia, wherein the exhaust gas is brought into contact with an ammonia decomposition catalyst under heating to decompose ammonia into hydrogen and nitrogen. In addition to sequentially switching and adsorbing the at least two series of adsorbents provided for adsorbing the decomposed ammonia to purify them, the adsorbents are sequentially switched to regenerate by heating and include ammonia desorbed from the adsorbent at that time A method for purifying exhaust gas, comprising contacting the regenerated exhaust gas with the ammonia decomposition catalyst under heating to purify the exhaust gas.

A second aspect of the present invention is a method for purifying an exhaust gas containing ammonia, wherein the exhaust gas is brought into contact with an ammonia decomposition catalyst under heating to decompose the ammonia into hydrogen and nitrogen. In addition to sequentially switching and adsorbing the at least two series of adsorbents provided for adsorbing the decomposed ammonia to purify them, the adsorbents are sequentially switched to regenerate by heating and include ammonia desorbed from the adsorbent at that time A method for purifying exhaust gas, comprising purifying the regenerated exhaust gas by contacting the regenerated exhaust gas with an ammonia decomposition catalyst provided separately from the ammonia decomposition catalyst under heating.

Further, a third aspect of the present invention is a method for purifying an exhaust gas containing ammonia, wherein the exhaust gas is brought into contact with an ammonia decomposition catalyst under heating to decompose the ammonia into nitrogen and hydrogen. The catalyst is purified by contacting with an adsorbent provided for adsorbing the decomposed ammonia, and then the adsorbent is heated and regenerated, and the regenerated exhaust gas containing ammonia desorbed from the adsorbent at that time is the same as the ammonia decomposition catalyst. Alternatively, there is provided a method for purifying exhaust gas, wherein the purification is carried out by contacting with a separately provided ammonia decomposition catalyst under heating.

A fourth aspect of the present invention is a method of purifying an exhaust gas containing ammonia, the method comprising the step of converting the exhaust gas into at least two systems in parallel so that an ammonia decomposition catalyst and an ammonia adsorption catalyst are provided. The ammonia adsorbent is heated and regenerated by sequentially switching to a series of reagents and contacting them to decompose ammonia into nitrogen and hydrogen, and then adsorbing and separating undecomposed ammonia to purify it. Exhaust gas purifying method by contacting the regenerated exhaust gas with the ammonia decomposition catalyst of the same series as the ammonia adsorbent being regenerated by heating under heating.

A fifth aspect of the present invention is a device for purifying an exhaust gas containing ammonia, wherein the ammonia decomposition catalyst is filled with an ammonia decomposition catalyst and is provided with a heater, and at least two cylinders can be switched in parallel in the subsequent stage. Ammonia adsorption cylinder provided with a heater filled with an ammonia adsorbent provided in a suitable state, and a gas supply means for heating and regenerating the adsorbent, and for supplying regenerated exhaust gas to the ammonia decomposition cylinder An exhaust gas purifying apparatus having equipment.

According to a sixth aspect of the present invention, there is provided an apparatus for purifying an exhaust gas containing ammonia, wherein an ammonia decomposing cylinder filled with an ammonia decomposing catalyst and equipped with a heater, at least two of which can be switched in parallel in a subsequent stage. Ammonia adsorbent column equipped with a heater filled with an adsorbent of ammonia provided in a suitable state, and a gas supply means for heating and regenerating the adsorbent, and the regenerated exhaust gas is provided separately from the ammonia decomposition column. An exhaust gas purifying apparatus, wherein the exhaust gas purifying apparatus is configured to be filled with an ammonia decomposition catalyst and supplied to an ammonia decomposition cylinder provided with a heater.

[0014] A seventh aspect of the present invention is an apparatus for purifying an exhaust gas containing ammonia, which comprises an ammonia decomposing cylinder equipped with an ammonia decomposing catalyst and having a heater, and a heater in which a subsequent stage is filled with an ammonia adsorbent. And a gas supply means for heating and regenerating the adsorbent, wherein the regeneration exhaust gas is supplied to the ammonia decomposition column or a separately provided ammonia decomposition column. It is an exhaust gas purifying device characterized by the following.

In addition, an eighth aspect of the present invention is an apparatus for purifying exhaust gas containing ammonia, the apparatus comprising at least 2 parts.
A series of ammonia decomposition cylinders equipped with heaters and filled with ammonia decomposition catalysts provided in a state that can be switched in parallel, and ammonia adsorption cylinders filled with ammonia adsorbent and equipped with heaters, each series of ammonia adsorption cylinder outlets A portion of the gas can be switched so that it can be supplied as another series of adsorbent regeneration gas, and the regeneration exhaust gas of the other series of adsorbents is further purified by the other series of ammonia decomposition columns. It is an exhaust gas purifying apparatus characterized by being configured as described above.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is applicable to the purification of ammonia-containing exhaust gas discharged from a chemical processing step in addition to the ammonia-containing exhaust gas discharged from a semiconductor manufacturing process. The present invention, after contacting the ammonia-containing exhaust gas with an ammonia decomposition catalyst to decompose nitrogen and hydrogen,
The undecomposed ammonia contained in the gas after the ammonia decomposition treatment is captured by the adsorbent and exhausted, and the regenerated exhaust gas containing ammonia desorbed from the adsorbent when the adsorbent is heated and regenerated is used as the ammonia decomposition catalyst. This is a method of purifying the ammonia-containing exhaust gas by exhausting after re-contacting, or by purifying the regenerated exhaust gas by circulating it through a system in which an ammonia decomposition catalyst and an ammonia adsorbent are combined.

In the present invention, the ammonia decomposition catalyst is not particularly limited as long as it can decompose ammonia into hydrogen and nitrogen in the gas phase, and a known ammonia decomposition catalyst can be used. For example, a catalyst in which a metal or a metal compound such as nickel, iron, palladium, platinum or ruthenium is supported on an inorganic carrier, or containing these metals or a metal compound as an active ingredient, was prepared by tableting or extrusion. There is a catalyst. Further, in addition to a catalyst containing a single component of these metals or metal compounds as an active ingredient, a catalyst containing a plurality of types can also be used. Among these, a ruthenium catalyst is preferable because a high ammonia decomposition activity can be obtained even at a low temperature.

These catalysts are prepared by impregnating or impregnating a carrier such as alumina with a solution of a metal salt, by preparing a powder of a metal compound by tableting with a lubricant or the like, or by including a metal compound. The cake can be prepared by, for example, a method of extruding a cake. However, some of them are commercially available as ammonia decomposition catalysts, so that they can also be used.

The shape of the ammonia decomposition catalyst is not particularly limited, and usually includes a ring shape, a tablet shape, a column shape, a spherical shape and the like. Usually, these catalysts are filled in a metal cylinder (hereinafter referred to as an ammonia decomposition cylinder) and used as a fixed bed. When the ammonia decomposition catalyst is used by filling the ammonia decomposition tube, the filling length is usually 50 to 3000.
Although it is about mm, it is specifically determined by the ammonia concentration in the exhaust gas to be treated, the amount of the treated gas, the reaction temperature, the shape of the catalyst and the like.

The conditions for the decomposition of ammonia in the present invention are not limited to the concentration of ammonia in the exhaust gas, and even if the concentration of ammonia in the exhaust gas reaches 100%, the decomposition of the ammonia in the exhaust gas state may be continued. Can be done. The reaction temperature for ammonia decomposition is usually 450 to 1200 ° C, preferably 600 to 900 ° C.
It is. The pressure is preferably as low as possible, and it can be carried out even at normal pressure or lower.
a, preferably 0.09 to 0.5 MPa.

The cylinder linear velocity (LV) of the exhaust gas in the ammonia decomposition cylinder is determined by the ammonia concentration, the filling length of the decomposition catalyst, the reaction temperature, and the like. It is 200 cm / sec, preferably 1 to 50 cm / sec. By decomposing the ammonia-containing exhaust gas under such conditions, the ammonia concentration in the ammonia decomposing cylinder outlet gas is usually 60 to
It is reduced to about 1000 ppm.

Further, the catalyst filling section of the ammonia decomposition column is maintained at a desired reaction temperature by heating a heater provided in the ammonia decomposition column. Also, when supplying the exhaust gas to be treated to the ammonia decomposition column, the exhaust gas to be treated is heated to a temperature close to the reaction temperature by a preheater, or the exhaust gas to be treated is heated and exchanged with the outlet gas of the ammonia decomposition column, and then supplied to the ammonia decomposition column. You can also.

As the adsorbent for ammonia used in the present invention, adsorbents such as natural zeolite, synthetic zeolite, activated carbon, alumina, silica gel and silica alumina can be used. Among these, synthetic zeolite, activated carbon, and the like are preferable in that a large adsorption capacity can be stably obtained. As the synthetic zeolite, a synthetic zeolite having a pore size of about 4 ° or 5 ° (Molecular sieves 4A, 5A manufactured by Union Showa KK or Linde) is used. These adsorbents are usually used in a state filled in a metal cylinder (hereinafter, referred to as an ammonia adsorption cylinder). After the adsorbent is activated prior to use, it is brought into contact with the ammonia decomposition column outlet gas to adsorb and separate undecomposed ammonia by physical adsorption.

In the present invention, the pressure at which the gas at the outlet of the ammonia decomposition column is brought into contact with the adsorbent is not particularly limited.
The reaction can be performed under normal pressure, reduced pressure or increased pressure. Also,
The linear velocity of the cylinder at the time of bringing the ammonia decomposition cylinder exit gas into contact with the adsorbent is usually about 1 to 30 cm / sec.
Preferably, it is 5 to 15 cm / sec. The temperature at which the outlet gas of the ammonia decomposition tube is brought into contact with the adsorbent is usually 100 ° C. or lower, preferably 70 ° C. or lower, and more preferably a temperature near normal temperature (0 to 50 ° C.).

The adsorbent from which ammonia has been adsorbed and separated is reactivated (hereinafter, referred to as heat regeneration of the adsorbent) by passing dry gas containing no ammonia under heating. The temperature at which the adsorbent is heated and regenerated is set to a temperature higher than the temperature at the time of the adsorption operation. The temperature differs depending on the adsorbent and cannot be specified unconditionally. Heat regeneration of the adsorbent can also be performed by passing a purge exhaust gas (hereinafter, referred to as self-gas) after purifying the ammonia-containing exhaust gas while heating the adsorbent. It can also be performed by ventilating.

Next, the present invention will be described in detail with reference to FIG. FIG. 1 shows an example of the exhaust gas purifying apparatus of the present invention. Exhaust gas containing ammonia is supplied from an exhaust gas supply line 1 to an ammonia decomposition tube 3 via a heat exchanger 2. The ammonia decomposition tube 3 is filled with an ammonia decomposition catalyst 4 and is heated by a heater 5. Ammonia decomposition tube 3
Most of the ammonia is decomposed into nitrogen and hydrogen. The ammonia decomposition tube outlet gas from the decomposition tube 3 is introduced into the ammonia adsorption tube 8 maintained at a temperature near normal temperature via the pipe 6, the heat exchanger 2, the cooler 17, and the valve 7.

The ammonia adsorption column 8 is filled with an activated ammonia adsorbent 9 such as synthetic zeolite. As a result, undecomposed ammonia in the outlet gas of the ammonia decomposition column is adsorbed and separated, and the purified exhaust gas is discharged into the atmosphere via the valve 11 and the exhaust gas purge line 12. At this time, a part of the outlet gas of the ammonia adsorption column 8 is introduced from the valve 13 into the heated ammonia adsorption column 8 ', and the adsorbent 9' adsorbing ammonia is heated and regenerated. At this time, the regenerated exhaust gas containing a large amount of ammonia discharged from the ammonia adsorption tube 8 'is introduced into the ammonia decomposition tube 3 through the cooler 18', the valve 14 ', the blower 15, the pipe 16, and the exhaust gas supply line 1. .

When the regeneration of the ammonia adsorption column 8 'is completed, the heating by the heater 10' is stopped, and the ammonia adsorption column 8 'is cooled to a temperature near normal temperature to prepare for switching to the ammonia adsorption column 8. When the adsorbent in the ammonia adsorption column 8 reaches the saturated adsorption amount and the outflow of ammonia is recognized in the outlet gas, or when the outflow of ammonia is approaching, the gas flow path is changed from the valve 7 to the valve 7 '. , Valve 11
To the valve 11 'to switch the flow path of the ammonia decomposition cylinder outlet gas to the ammonia adsorption cylinder 8' side.

Further, the ammonia adsorption cylinder 8 is heated and regenerated by the same method as the heating and regeneration of the ammonia adsorption cylinder 8 '.
Prepare for switching. Here, the method has been described in which a part of the outlet gas of the ammonia adsorption cylinder 8 (own gas) is supplied as the gas for heating and regeneration of the ammonia adsorption cylinder 8 ′. It can also be performed by supplying a gas.

By doing so, it is possible to completely purify the ammonia contained in the ammonia-containing exhaust gas without releasing it to the atmosphere. The concentration of undecomposed ammonia in the outlet gas of the ammonia decomposition column varies depending on the catalytic cracking conditions, but is usually 60 to 1,000 ppm, and can be very easily adsorbed and separated by the ammonia adsorption column 8 or the ammonia adsorption column 8 '. . According to this method, since the purge gas after purifying the exhaust gas can be released in a state that does not contain any ammonia, it does not require secondary materials to be consumed other than electric power as a heating and power source, and can perform secondary processing. It can be completely purified without producing by-products as required.

In the present invention, as shown in FIG.
At the time of heat regeneration of the adsorbent, the regenerated exhaust gas containing ammonia desorbed from the adsorbent is introduced into an ammonia decomposition column (hereinafter referred to as a second ammonia decomposition column) provided separately from the ammonia decomposition column. Alternatively, ammonia can be decomposed into nitrogen and hydrogen. The second ammonia decomposition column outlet gas also has an undecomposed ammonia concentration of 60 to 1000 ppm.
And the amount is significantly reduced as compared with the first ammonia-containing exhaust gas to be purified, so that it can be directly released into the atmosphere by dilution. In this case, an amount of undecomposed ammonia is necessarily released to the atmosphere based on the decomposition rate in the second ammonia decomposition column.

In the present invention, as shown in FIG.
By combining the ammonia decomposition cylinder and the ammonia adsorption cylinder one by one, it is possible to purify the exhaust gas containing ammonia. In this case, when regenerating the ammonia adsorbent,
A regeneration gas is introduced from an inert gas supply line 24, and a regeneration exhaust gas containing a large amount of ammonia is discharged into an ammonia decomposition column 3.
And the outlet gas of the ammonia decomposition tube at that time is released to the atmosphere as it is. Further, as shown in FIG. 4, the ammonia decomposition column, the ammonia adsorption column, and the second ammonia decomposition column can be combined one by one to purify. However, in any of these cases, during the heating and regeneration of the ammonia adsorption column, the operation of adsorbing the gas at the outlet of the ammonia decomposition column cannot be performed, so that the exhaust gas purification is an intermittent operation.

Further, as shown in FIG. 5, two lines each comprising an ammonia decomposition column and an ammonia adsorption column connected one by one are provided in parallel, and a part of the outlet gas of the ammonia adsorption column of each line is partly adsorbed to another line. The exhaust gas can also be purified by being configured to be supplied as a gas for regenerating the agent, and by alternately switching the gas. Further, even if the ammonia decomposition cylinder and the ammonia adsorption cylinder are arranged and can be switched alternately as in FIG.
The method of supplying an inert gas from the outside as each regeneration gas is included in the combination of the ammonia decomposition column and the ammonia adsorption column of the present invention one by one.

Further, as a post-stage treatment of the second ammonia decomposition column outlet gas, the gas can be purified using a dry ammonia purifying agent. Similarly, purification can be performed by wet absorption using an aqueous acid solution as a post-treatment of the second ammonia decomposition column outlet gas. In addition, the gas may be introduced into the combustion device and purified as a post-process of the second ammonia decomposition tube outlet gas. When these post-processes are combined, auxiliary materials such as a dry purifying agent, an aqueous acid solution, and fuel are required based on the respective processing methods, but since the purge exhaust gas can be released without containing ammonia,
The exhaust gas containing ammonia can be almost completely purified.

Furthermore, as shown in FIGS. 3 and 5, when the regenerated exhaust gas of the adsorbent is introduced into the ammonia decomposition column to be purified and then exhausted as it is, the post-processing of the second ammonia decomposition column outlet gas is performed. The same processing can be performed.

In the present invention, when the adsorbent is heated and regenerated, the regenerated exhaust gas containing desorbed ammonia is supplied to a second ammonia decomposition column and an ammonia adsorption column (hereinafter, referred to as an ammonia adsorption column provided separately from the ammonia adsorption column). (Hereinafter, referred to as a second ammonia adsorption column), and circulation purification may be performed in this system. However, they are basically only modifications of the present invention and are included in the present invention.

The exhaust gas purifying apparatus of the present invention, as shown in FIGS. 1 to 5, has an ammonia decomposing cylinder for decomposing ammonia into nitrogen and hydrogen, and adsorbs and separates undecomposed ammonia contained in the gas after the ammonia decomposition treatment. Exhaust gas purifying apparatus comprising: an ammonia adsorption cylinder for supplying a gas for heating and regeneration of the adsorbent, and a pipe or equipment for supplying a regeneration exhaust gas containing ammonia desorbed from the adsorbent to the ammonia decomposition cylinder It is. As the material of the ammonia decomposition column, it is preferable to use a metal that can withstand the reaction temperature conditions, and a material that is not easily included in hydrogen contained in the exhaust gas and generated by decomposition of ammonia, hydrogen brittleness due to nitrogen, and nitridation. For example, IN
Nickel-chromium alloys of Inc., Incoloy 800, Inconel 600 and the like are used.

A known heating means is used for heating the ammonia decomposition column. For example, a method in which a heater is attached to the outside of the ammonia decomposition tube, a method in which a heater is buried in the ammonia decomposition catalyst filling portion, or an apparatus configuration in which a preheater is provided in front of the ammonia decomposition tube together with these heating means can be adopted. . Further, a configuration may be adopted in which the gas at the inlet of the ammonia decomposition tube is exchanged with the gas at the outlet of the ammonia decomposition tube to improve the thermal efficiency.

The material of the ammonia adsorption cylinder is usually SUS
Corrosion-resistant materials such as 304, SUS316, and SUS316L are used. Further, a method of providing a heater outside the adsorption column or a method of burying the heater inside the adsorption tube is adopted so that the adsorbent can be heated to a temperature required for heat regeneration. In the present invention, it is possible to purify the exhaust gas with only one ammonia adsorption cylinder, but preferably, two or more cylinders are arranged in parallel to alternately perform adsorption of undecomposed ammonia and heat regeneration of the adsorbent. Thereby, the exhaust gas can be continuously purified.

Further, a pipe, a cooler, a valve, and the like for supplying an inert gas or a self-gas for heating and regenerating the adsorbent are provided. As described above, the ammonia adsorption column portion can have the same configuration as a known gas purification device as a device for adsorbing and removing impurities of general-purpose gas such as oxygen and nitrogen. In the present invention, a means for detecting breakthrough can be provided in the latter half of the ammonia adsorption cylinder so that the ammonia adsorption cylinder can be switched to another adsorption cylinder before it breaks through. Further, an ammonia adsorption preparatory cylinder may be provided at a stage subsequent to the ammonia adsorption cylinder, and means for detecting breakthrough may be provided between the two adsorption cylinders. Means for detecting breakthrough include, for example, a sampling pipe for an analysis gas and an ammonia detector.

In the present invention, when the adsorbent is heated and regenerated, a regenerated exhaust gas containing ammonia desorbed from the adsorbent is supplied to the ammonia decomposition column and circulated and purified as a pump, a blower or an inert gas. A gas supply pipe or the like is provided, but the type is not particularly limited. With the exhaust gas purifying apparatus having such a configuration, the ammonia-containing exhaust gas can be continuously and efficiently purified completely.

In the present invention, the regenerated exhaust gas containing ammonia is introduced into a separately provided second ammonia decomposition column, and the ammonia is decomposed into nitrogen and hydrogen. If you do
The structure is such that it can be mixed with a large amount of inert gas or air. When purifying the second ammonia decomposition column outlet gas using a dry purifying agent, an aqueous acid solution, or a combustion furnace, known equipment corresponding to each of the purifying agents can be used. Not something.

In addition, regenerated exhaust gas containing ammonia that is desorbed at the time of heat regeneration of the adsorbent is supplied to a system in which a second ammonia decomposition column and a second ammonia adsorption column are combined, and this system is used for circulating purification. However, these are basically the same as the combination of the ammonia decomposition cylinder and one or more ammonia adsorption cylinders in parallel, and are included in the present invention.

[0044]

EXAMPLES The present invention will be described specifically with reference to Examples.
The present invention is not limited by these.

(Example 1) (Production of an exhaust gas purifying apparatus) As an ammonia decomposition tube, made of Incoloy 800 having an inner diameter of 83 mm and a length of 1000
mm reaction tube was fabricated. The reaction tube was filled with 500 mm of a columnar nickel-based ammonia decomposition catalyst having a diameter of 5 mm and a length of 5 mm supporting 18 parts by weight of nickel with respect to 100 parts by weight of alumina as an ammonia decomposition catalyst. In addition, an electric heater was attached to the reaction tube so that the reaction tube could be heated from the outside, and an ammonia decomposition tube was used.

Next, SUS316 inner diameter 108.3 m
m, two adsorption cylinders having a length of 1350 mm were produced. 1.6 m in diameter as an adsorbent for ammonia
m, 5 mm long cylindrical synthetic zeolite (Molecular Sieves 5A, manufactured by Union Showa Co., Ltd.)
m. In addition, an electric heater was attached to the adsorption cylinder so that heating could be performed from the outside, and an ammonia adsorption cylinder was used. An exhaust gas purifying apparatus as shown in FIG. 1 was manufactured using a heat exchanger, a cooler, and a blower together with the ammonia decomposition column and the ammonia adsorption column.

(Adjustment of Exhaust Gas Purification Apparatus) After replacing the inside of this apparatus with nitrogen, the ammonia decomposition column was heated to 800 ° C. Next, 20 vol% of ammonia, 5 vol of hydrogen
%, Nitrogen 75vol%, normal pressure, 50N
It was supplied at a flow rate of 1 / min from an exhaust gas supply line 1 of the exhaust gas purifying apparatus shown in FIG. The outlet gas of the ammonia decomposition column was discharged from the exhaust gas purge line via the ammonia adsorption column 8. In the meantime, a part of the outlet gas of the ammonia adsorption cylinder 8 (5 Nl / min) is supplied to the ammonia adsorption cylinder 8 ′ heated to 300 ° C. via the valve 13 for 10 hours to regenerate the ammonia adsorption cylinder 8 ′. The operation was performed. Thereafter, the heating of the ammonia adsorption column was stopped, and the ammonia adsorption column was cooled to room temperature to prepare for switching. The regenerated exhaust gas from the ammonia adsorption column 8 'is supplied to the cooler 18' and the valve 1
Exhaust gas supply line 1 via 4 ', blower 15, pipe 16
Was introduced.

After supplying the ammonia decomposition cylinder outlet gas to the ammonia adsorption cylinder 8 for 100 hours, switching to the ammonia adsorption cylinder 8 'side and supplying the ammonia decomposition cylinder outlet gas for 100 hours, during which time the same method as described above is used. , The regeneration operation of the ammonia adsorption column 8 was performed, and the exhaust gas purification device was adjusted. In addition, the adsorption | suction operation | work which came out of the ammonia adsorption cylinder 8 and the ammonia adsorption cylinder 8 'was all performed at 20-40 degreeC.

(Exhaust Gas Purification Experiment) The exhaust gas purification experiment was started by switching the supply of the ammonia decomposition cylinder outlet gas to the ammonia adsorption cylinder 8 maintained at about 30 ° C. At this time, a part of the outlet gas of the ammonia adsorption cylinder 8 (5 Nl
/ Min) was introduced into the ammonia adsorption column 8 'for 10 hours to heat and regenerate the adsorbent. During purification of the ammonia-containing exhaust gas, a part of the outlet gas of the ammonia decomposition tube 3 and a part of the outlet gas of the ammonia adsorption tube 8 were each sampled with time, and the ammonia concentration was measured. As a result, ammonia was not detected in the gas at the outlet of the adsorption column 8 until 198 hours from the start of the flow of the ammonia-containing exhaust gas, and the ammonia concentration at the outlet of the adsorption column 8 exceeded the allowable value at the time when 199 hours had passed. Was. Table 1 shows the results. The ammonia concentration was measured using a gas chromatograph equipped with a heat conduction type detector and a gas detector tube (Gastec Co., Ltd., detection limit: 0.2 ppm).

[0050]

Table 1 Elapsed time of purification experiment and ammonia concentration Elapsed time (h) 550 100 150 199 Decomposition tube outlet concentration (ppm) 620 640 650 630 630 630 Adsorption tube outlet concentration (ppm) nd nd nd nd 30 nd Means not detected.

(Embodiment 2) In an exhaust gas purification experiment using an exhaust gas purifying apparatus and an ammonia-containing exhaust gas of Example 1, while one ammonia adsorption column adsorbs ammonia, the other ammonia adsorption column heats and regenerates the heat. The time (breakthrough time) until the ammonia concentration in the outlet gas of each of the ammonia adsorption column 8 and the ammonia adsorption column 8 'reached the maximum allowable concentration (25 ppm) was measured. The results are shown in Table 2, and it was confirmed that each of the ammonia adsorption column 8 and the ammonia adsorption column 8 'was repeatedly heated and regenerated without decreasing the adsorption capacity.

[0052]

Table 2 Number of repetitions and breakthrough time Ammonia adsorption column 8 Ammonia adsorption column 8 'First 198 202 Second 205 201 Third 196 204 Fourth 208 199 Fifth 197 210

(Example 3) The ammonia-containing exhaust gas in Example 1 was obtained by removing 5 vol% of ammonia and 5 vol of hydrogen.
% And nitrogen at 90 vol%, and the exhaust gas purification experiment was carried out in the same manner as in Example 1 except that the temperature of the ammonia decomposition column was changed to 600 ° C. The change in the ammonia concentration in the outlet gas was measured. The results are shown in Table 3. The ammonia concentration in the outlet gas of the ammonia adsorption column 8 was 168
By the time, it was below the detection limit.
Reached 5 ppm.

[0054]

Table 3 Elapsed time of purification experiment and ammonia concentration Elapsed time (h) 550 100 150 169 Decomposition tube outlet concentration (ppm) 780 760 770 780 780 780 Adsorber tube outlet concentration (ppm) n.dn.d n.dn.d 65

(Embodiment 4) Adsorption tube 2 manufactured in Embodiment 1
150 m from the bottom of the adsorbent filling section for each cylinder
A gas sampling pipe for detecting breakthrough was provided at a position above m. Otherwise, the apparatus configuration was the same as that of the first embodiment. After this, the purification operation of the ammonia-containing exhaust gas and the regeneration of the adsorption column were started under the same conditions as in Example 1.
Then, when the sampling pipe attachment portion of the adsorption cylinder detected breakthrough, the exhaust gas was continuously purified for 1500 hours by switching to another adsorption cylinder. as a result,
At all times during the purification experiment, ammonia was not detected in the purge exhaust gas, and it was confirmed that the purge exhaust gas was completely purified.

Example 5 (Production of an exhaust gas purifying apparatus) The ammonia decomposition column manufactured in Example 1 was used as a first decomposition column. In addition, the two adsorption cylinders manufactured in Example 1 were placed 150 meters from the lower part of the adsorbent filling section.
A sampling pipe for detecting breakthrough was provided at a position of mm. Further, the second ammonia decomposition tube is made of Incoloy 800, having an inner diameter of 83 mm and a length of 600 m.
m was filled with 350 mm of the same catalyst as the ammonia decomposition catalyst in Example 1. By combining these, an exhaust gas purifying apparatus similar to that shown in FIG. 2 was manufactured.

(Exhaust Gas Purification Experiment) The first ammonia decomposition column and the second ammonia decomposition column of this exhaust gas purification device were each maintained at 900 ° C. Further, by a method in which the first adsorption column and the second adsorption column are alternately switched before breakthrough, adsorption is performed at room temperature, and regeneration of the adsorbent is performed at 300 ° C., and ammonia is discharged from the exhaust gas supply line at 20 vol%. ,
Exhaust gas consisting of 5% hydrogen and 75% nitrogen is 50Nl / mi
n flow for 960 hours. During regeneration of the adsorbent during this time, the self gas is passed for 5 hours at a flow rate of 5 Nl / min, the adsorbent regeneration exhaust gas is passed to the second ammonia decomposition column, and the outlet gas of the second ammonia decomposition column is nitrogen gas. And then released into the atmosphere. As a result, no outflow of ammonia was found in the gas at the outlet of the ammonia adsorption column during the experiment. The ammonia concentration in the outlet gas of the second ammonia decomposition column is 520 p at the maximum.
pm.

Example 6 (Production of an exhaust gas purifying apparatus) Two cylinders identical to the ammonia decomposition cylinder in Example 1 were produced. However, the ammonia decomposition catalyst was filled with a catalyst in which 0.3% by weight of metal ruthenium was supported on alumina. In addition, two identical ammonia adsorption cylinders in Example 1 were manufactured. By using these, as shown in FIG. 5, a purifying apparatus having a configuration composed of two systems in which an ammonia decomposition column and an ammonia adsorption column were respectively connected was manufactured.

(Exhaust Gas Purification Experiment) The ammonia decomposing cylinders of both systems of the exhaust gas purifying apparatus were maintained at 600 ° C., respectively. In addition, by alternately switching the adsorption cylinders of both series before the breakthrough, adsorption is performed at room temperature, and regeneration of the adsorbent is performed at three temperatures.
An exhaust gas composed of 20 vol% of ammonia, 5% of hydrogen and 75% of nitrogen was passed through the exhaust gas supply line at a flow rate of 100 Nl / min for 960 hours while performing the method at 00 ° C. During regeneration of the adsorbent during this time, self gas is passed for 5 hours at a flow rate of 5 Nl / min, respectively.
The adsorbent regeneration exhaust gas is passed through each series of ammonia decomposition cylinders, and the outlet gas of the decomposition cylinder is diluted with nitrogen gas.
Released into the atmosphere. As a result, no outflow of ammonia was found in the gas at the outlet of the ammonia adsorption column during the experiment.
The ammonia concentration in the gas after the ammonia decomposition treatment of the adsorbent-regenerated exhaust gas was 860 ppm at the maximum.

(Comparative Example 1) Purification of an ammonia-containing exhaust gas was carried out in the same manner as in Example 1 except that the adsorbent of the ammonia adsorption column 8 and the ammonia adsorption column 8 'in Example 1 was omitted. As a result, 6
It was recognized that ammonia was contained in an amount of 00 ppm or more.

[0061]

According to the purification method and the purification apparatus of the present invention,
Regardless of the ammonia concentration in the exhaust gas, it can be purified very efficiently. In particular, when the recycled exhaust gas from the ammonia adsorption column is introduced into the ammonia decomposition column and the circulation process is performed, the purge gas after the purification process can be discharged without containing ammonia. That is, the ammonia-containing exhaust gas can be continuously and almost completely purified without using an auxiliary material. In addition, when the purified exhaust gas from the ammonia adsorption column is introduced into the second ammonia decomposition column for purification, it can be discharged with a significantly reduced amount of ammonia compared to the first ammonia-containing exhaust gas to be treated. it can. Furthermore, when the purification is performed in combination with any of a dry purifier, an aqueous solution of an acid, or a combustion device as a post-process of the second ammonia decomposition cylinder outlet gas, the purification can be performed almost completely.

[Brief description of the drawings]

FIG. 1 is an example of an exhaust gas purifying apparatus of the present invention (recycled exhaust gas is circulated through an ammonia decomposition column).

FIG. 2 is an example of an exhaust gas purifying apparatus of the present invention (regenerated exhaust gas is directly exhausted after purification in a second ammonia decomposition column).

FIG. 3 is an example of an exhaust gas purifying apparatus of the present invention (a regenerated exhaust gas is directly exhausted after purification in an ammonia decomposition column).

FIG. 4 is an example of an exhaust gas purifying apparatus of the present invention (regenerated exhaust gas is directly exhausted after purification in a second ammonia decomposition column).

FIG. 5 is an example of an exhaust gas purifying apparatus of the present invention (regenerated exhaust gas is exhausted as it is after purification in an ammonia decomposition column).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Exhaust gas supply line 2, 2 'Heat exchanger 3, 3' Ammonia decomposition tube 4, 4 ', 21 Ammonia decomposition catalyst 5, 5', 10, 10 ', 22 Heater 6, 6', 16, 19, 31 Piping 7, 7 ', 11, 11', 13, 14, 14 ', 25,
26, 28, 30, 32, 38, 38 ', 40, 40'
Valve 8, 8 'Ammonia adsorption cylinder 9, 9' Adsorbent for ammonia 12, 23, 29, 34, 41, Exhaust gas purge line 15 Blower 17, 17 ', 18, 18' 27, 33, 39, 39 '
Cooler 20 Second ammonia decomposition cylinder 24 Inert gas supply line

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Otsuka 5181 Tamura, Hiratsuka-shi, Kanagawa Prefecture Inside the Hiratsuka Research Laboratory, Japan (72) Inventor Takashi Shimada 5181 Tamura, Hiratsuka-shi, Kanagawa Prefecture Nihon Pionex Corporation Hiratsuka Plant Inside

Claims (13)

[Claims] 1. A method for purifying exhaust gas containing ammonia, wherein the exhaust gas is brought into contact with an ammonia decomposition catalyst under heating to decompose ammonia into hydrogen and nitrogen, and then provided for adsorbing undecomposed ammonia. The at least two series of adsorbents are sequentially switched to be contacted for purification, and the adsorbents are sequentially switched to regenerate by heating. At that time, the regenerated exhaust gas containing ammonia desorbed from the adsorbent is supplied to the ammonia decomposition catalyst. A method for purifying exhaust gas, comprising purifying by contact under heating. 2. A method for purifying exhaust gas containing ammonia, wherein the exhaust gas is brought into contact with an ammonia decomposition catalyst under heating to decompose ammonia into hydrogen and nitrogen, and then provided for adsorbing undecomposed ammonia. In addition to sequentially switching and contacting the at least two series of adsorbents to purify them, the adsorbents are sequentially switched to heat and regenerate, and at this time, the regenerated exhaust gas containing ammonia desorbed from the adsorbent is treated with the ammonia decomposition catalyst. A method for purifying exhaust gas, which comprises contacting with a separately provided ammonia decomposition catalyst under heating to purify the exhaust gas. 3. A method for purifying exhaust gas containing ammonia, wherein the exhaust gas is brought into contact with an ammonia decomposition catalyst under heating to decompose ammonia into nitrogen and hydrogen, and then provided for adsorbing undecomposed ammonia. The catalyst is purified by contact with the adsorbent, and then the adsorbent is heated and regenerated. At this time, the regenerated exhaust gas containing ammonia desorbed from the adsorbent is supplied to the ammonia decomposition catalyst provided separately from the ammonia decomposition catalyst. A method for purifying exhaust gas, comprising purifying the waste gas by contacting the waste gas with heating. 4. A method for purifying an exhaust gas containing ammonia, wherein the exhaust gas is sequentially switched to a system comprising an ammonia decomposition catalyst and an ammonia adsorbent which are provided in at least two systems which can be switched in parallel. The ammonia is decomposed into nitrogen and hydrogen by contact, then the undecomposed ammonia is adsorbed and separated and purified, and the system is sequentially switched to regenerate the ammonia adsorbent by heating and regenerating the exhaust gas during the heating and regenerating. A method for purifying exhaust gas, comprising contacting an ammonia decomposition catalyst of the same series as the above-mentioned ammonia adsorbent with an ammonia decomposition catalyst under heating to purify the exhaust gas. 5. The exhaust gas according to claim 1, wherein the ammonia decomposition catalyst contains at least one metal selected from nickel, iron, palladium, platinum and ruthenium or a compound thereof as an active ingredient. Purification method. 6. The method for purifying exhaust gas according to claim 1, wherein the temperature at which the exhaust gas is brought into contact with the ammonia decomposition catalyst is 450 to 1200 ° C. 7. The temperature at which the exhaust gas is brought into contact with the adsorbent is 10
The method for purifying exhaust gas according to claim 1, wherein the temperature is 0 ° C. or lower. 8. The method for purifying exhaust gas according to claim 1, wherein the gas used for heat regeneration of the adsorbent is a part of the outlet gas of the ammonia adsorption column or an inert gas. 9. An apparatus for purifying an exhaust gas containing ammonia, comprising: an ammonia decomposition cylinder filled with an ammonia decomposition catalyst and provided with a heater; An ammonia adsorption cylinder filled with an adsorbent and provided with a heater, and a gas supply means for heating and regenerating the adsorbent, and a facility for supplying regenerated exhaust gas to the ammonia decomposition cylinder are provided. Exhaust gas purifier. 10. An apparatus for purifying an exhaust gas containing ammonia, comprising: an ammonia decomposition cylinder filled with an ammonia decomposition catalyst and provided with a heater; An ammonia adsorption cylinder filled with an adsorbent and equipped with a heater, and a gas supply means for heating and regenerating the adsorbent, and a regeneration exhaust gas filled with an ammonia decomposition catalyst provided separately from the ammonia decomposition cylinder An exhaust gas purifying apparatus characterized in that the exhaust gas purifying apparatus is configured to be supplied to an ammonia decomposing cylinder having: 11. An apparatus for purifying an exhaust gas containing ammonia, comprising: an ammonia decomposition cylinder filled with an ammonia decomposition catalyst and provided with a heater; an ammonia adsorption cylinder provided with a heater filled with an ammonia adsorbent at a subsequent stage; and An exhaust gas purifying apparatus comprising a gas supply means for heating and regenerating the adsorbent, and configured to supply regenerated exhaust gas to the ammonia decomposition column or a separately provided ammonia decomposition column. 12. An apparatus for purifying an exhaust gas containing ammonia, comprising: an ammonia decomposition cylinder filled with an ammonia decomposition catalyst provided in at least two systems which can be switched in parallel and provided with a heater; and an ammonia adsorbent. It is composed of an ammonia adsorption cylinder equipped with a filled heater, and a part of the outlet gas of each series of the ammonia adsorption cylinder is switchable so that it can be supplied as another series of adsorbent regeneration gas. An exhaust gas purifying apparatus, characterized in that the adsorbent regeneration exhaust gas is purified by the other series of ammonia decomposition columns. 13. A means for detecting breakthrough of ammonia is provided between the latter half of the ammonia adsorption cylinder or between the ammonia adsorption cylinder and the ammonia pre-adsorption cylinder provided at the subsequent stage. An exhaust gas purifying apparatus according to any one of the above items.