JP3249181B2 - Regeneration method of nitrogen oxide adsorbent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention mainly relates to nitrogen oxides (NOx) such as low-concentration nitric oxide (NO) and nitrogen dioxide (NO ₂ ) contained in ventilation gas from road tunnels and road shelters. The present invention relates to a method for regenerating a NOx adsorbent and enabling the long-term effective use of the NOx adsorbent in a method for adsorbing and removing a NOx adsorbent. The low concentration here is 50
The range is below ppm. In the case of exhaust gas treatment in a normal thermal power plant, the concentration of NOx contained in the exhaust gas is several hundred ppm, and the NOx concentration is reduced by an ammonia catalytic reduction method (SCR (selective catalytic method) using a denitration catalyst.
reduction method) to several tens of ppm. On the other hand, the method of the present invention is intended for the case where the NOx concentration is further reduced from the NOx concentration level contained in the processing gas of the SCR. Applications other than denitrification of ventilation gas from road tunnels include purifying ventilation gas in underground parking lots and multi-story parking lots, or when denitrifying treated gas after treating diesel exhaust gas by the SCR method. Etc. In this case, the high-concentration nitrogen oxides desorbed when the adsorbent once adsorbing the nitrogen oxides is regenerated are returned again before the SCR step.

[0002]

2. Description of the Related Art The main purpose of a ventilation system in a road tunnel is to remove visibility obstacles mainly due to dust, or to maintain the concentration of harmful substances at a level below an allowable concentration, thereby ensuring the safety of tunnel users and reducing discomfort. Is provided. Currently, a ventilation system generally used is a system in which fresh outside air is supplied into a tunnel or contaminated air is ventilated outside the tunnel to dilute the contaminated air. On the other hand, in recent road tunnels, a long tunnel exceeding 10 km may be constructed, and a long tunnel may be planned. In such a long tunnel ventilation equipment, it is necessary to construct a ventilation shaft for exchanging air in the middle part of the tunnel, so that the construction cost related to the ventilation equipment is large and the operation cost is also large. . On the other hand, in the conventional ventilation method, air contaminated at a high concentration in the tunnel is continuously and intensively discharged from a wellhead or a ventilation hole, so that there is a problem of pollution of the surrounding air environment. For this reason, development of a new ventilation system that can save energy and reduce the degree of pollution to the surrounding environment is desired.

As a method of solving these problems, a method of adsorbing and removing nitrogen oxides in air discharged from a tunnel with an adsorbent has been studied. The main adsorbents include activated carbon, zeolite, and alumina-based adsorbents of the present inventors (Japanese Patent Application Nos. 2-368385 and 3-166496). For example, Japanese Unexamined Patent Publication No.
Japanese Patent No. 161582 discloses that a gas containing nitrogen oxide is brought into contact with a substance containing carbon as a main component impregnated with one or more of alkali metal nitrates, nitrites, carbonates and hydroxides. Describes a method for removing nitrogen oxides in a gas. Japanese Patent Application Laid-Open No. 1-155934 describes a method of adsorbing and removing nitrogen oxides by subjecting a moisture in a road tunnel ventilation gas to a moisture absorption treatment with a silica gel-based dehumidifier and then performing a dry treatment with a zeolite-based adsorbent. Have been. Japanese Patent Publication No. Sho 63-22181 discloses that an oxygen-containing gas containing nitrogen oxides is directly contacted with an adsorbent obtained by heating and dehydrating a tuff containing mordenite and / or clinoptilolite without drying. ,
A method for adsorbing and removing nitrogen oxides is described. Furthermore, "Catalyst" Vol. 31No. 8, page 586, α-F
e ₂ O ₃ highly dispersed ACF (activated carbon fiber) is, the nitrogen monoxide (NO) can be adsorbed as a vapor, it is described as.

[0004] The present inventors have also proposed an oxide of at least one element selected from the group consisting of sodium, potassium, magnesium and calcium and at least one oxide selected from the group consisting of iron, copper, cobalt, nickel and manganese. NOx in activated alumina-based adsorbents containing oxides of one element
A method for adsorbing and removing nitrogen oxides by contacting a processing gas containing nitrogen as it is (Japanese Patent Application No. 2-30).
3885, Japanese Patent Application No. 3-166496). In these methods, it is necessary to regenerate the adsorbent after adsorbing nitrogen oxides and use the adsorbent repeatedly, in order to enable long-term effective utilization and long-term stabilization of the adsorbent. Conventionally, as a catalyst regeneration method by heating for the purpose of recovering the activity of a denitration catalyst, heating regeneration with air, heating regeneration with combustion exhaust gas, heating regeneration with steam, and the like are generally known. Furthermore, as shown in Japanese Patent Publication No. 62-11891, the applicant of the present application has a technology for regenerating a denitration catalyst by an ammonia catalytic reduction method using a catalyst, and has a technology for adding and supplying steam to a processing gas.

[0005]

Although the above-mentioned prior art for regeneration is effective in restoring the activity of the denitration catalyst, any of the above-mentioned techniques for the regeneration of low-concentration nitrogen oxides by an adsorbent for tunnel ventilation gas and the like is effective. Adsorption is difficult to regenerate in the denitration process. For example,
In order to regenerate by heating with air, it is necessary to raise the temperature of the adsorption device filled with the adsorbent to a temperature exceeding about 500 ° C., which requires a large amount of energy and a special heat source, and In terms of heat resistance, the structure of the adsorption device,
It is practically difficult, as it requires consideration in selecting the material. The same applies to the case where combustion exhaust gas is used. It is considered that application of steam regeneration is also difficult because the target ammonia reduction denitration catalyst and the adsorbent used in the present invention have different compositions and use conditions (temperature, coexistence of ammonia, etc.). When NOx is adsorbed by the adsorbent in the present invention, ammonia does not coexist.

The present inventors have conducted intensive studies on a method for reducing the regeneration temperature in the regeneration of an adsorbent having adsorbed nitrogen oxides with heated air. As a result, the concentration of water vapor in the heated air was 5 vol% or more, preferably 20 to 20 vol%. It has been found that controlling the volume to 80 vol% has an effect of remarkably promoting the desorption of the adsorbed nitrogen oxides. Also, at this time, by making the hydrocarbon coexist with the heated air together with the steam,
It has been found that there is an effect of further promoting the desorption of the adsorbed nitrogen oxides. That is, when the nitrogen oxide adsorbent continues to adsorb nitrogen oxides, the amount of adsorption increases, gradually approaches the saturated adsorption amount, and the NOx concentration at the outlet of the adsorbent packed layer increases from a certain point. In this case, once the adsorption is stopped, heated air in the range of 450 to 600 ° C., preferably 5
By passing heated air in the range of 00 to 550 ° C. through the adsorbent packed bed and desorbing the adsorbed NOx, the adsorbent can be regenerated,
At this time, the performance can be returned to the initial level. At this time, steam is blown into the circulating heated air used for the regeneration or, on the contrary, partially purged, air outside the system is introduced, and the water concentration is 5 vol% or more, preferably 20 vol. By adjusting the volume to ８０80 vol%, the regeneration is remarkably promoted.
C., preferably 300 to 400 C., and found that the regeneration temperature could be reduced.

At this time, hydrocarbons are introduced into the circulating heated air together with water vapor, and the hydrocarbon concentration is reduced to 20 vol%.
The regeneration is further promoted by adjusting the content to preferably 5 vol% or less, and as a result, the regeneration temperature is set to 100 to 5%.
It has been found that regeneration can be performed at 00 ° C., preferably 150 to 450 ° C., more preferably 250 to 375 ° C., and the regeneration temperature can be reduced. Hydrocarbons used at this time include LPG gas and lower hydrocarbons such as isobutane, butane, and propane, which are components of LPG gas, and lower hydrocarbons having an unsaturated bond such as ethylene, propylene, and butylene;
It has been found that lower hydrocarbons such as alcohols such as methanol, ethanol, propanol and butanol are desirable. The present invention has been made in view of the above points based on the above findings, and has as its object to provide a method for regenerating a nitrogen oxide adsorbent that achieves high regeneration efficiency without making the regeneration temperature relatively high. It is assumed that.

[0008]

In order to achieve the above-mentioned object, a method for regenerating a nitrogen oxide adsorbent according to the first invention of the present application is a method for producing an exhaust gas containing a low concentration of nitrogen oxides of 50 ppm or less. A manganese oxide-activated alumina based adsorbent, or
Manganese oxide-activated alumina
At least one selected from the group consisting of gnesium, iron and copper
After adsorbing and removing nitrogen oxides by contacting with an adsorbent containing an oxide of one kind of element, the adsorption operation is once stopped, and adsorbents adsorbing nitrogen oxides using heated air as a regeneration gas In the method in which the adsorbed nitrogen oxides are desorbed and regenerated by passing through the packed bed, the steam concentration of the regenerating gas is adjusted to 20 to 80 vol %, and at the same time, the temperature of the adsorbent packed layer during regeneration is set to 300 to It is characterized in that reproduction is performed by adjusting the temperature to a range of 400 ° C.

Further, a method for regenerating a nitrogen oxide adsorbent according to the second invention of the present application is as follows: an exhaust gas containing a low concentration of nitrogen oxides of 50 ppm or less is converted into a manganese oxide-activated alumina adsorbent;
Or calcium oxide as a manganese oxide-activated alumina adsorbent
Metal, magnesium, iron and copper
After adsorbing and removing nitrogen oxides by contacting with an adsorbent containing at least one elemental oxide , the adsorption operation is temporarily stopped, and the heated air is used as a regeneration gas to adsorb the nitrogen oxides. In the method for removing adsorbed nitrogen oxides through a packed bed of a regenerating agent and regenerating the same, the steam concentration of the regenerating gas is adjusted to 20 to 80 vol %, and the hydrocarbon is in a range of 10 ppm to 20 vol %. And at the same time, raise the temperature of the adsorbent packed bed at the time of regeneration to 250.
It is characterized in that reproduction is performed by adjusting the temperature in the range of ３375 ° C.

If the moisture concentration in the high-temperature air used for regeneration is too low, the effect of promoting regeneration is reduced, and if the temperature is not higher than 500 ° C., the effect of regeneration is reduced. Therefore, the water concentration is set to 5 vol% or more, preferably 20 to 80 vol%. If the water concentration exceeds 80 vol%, water condensed in the piping becomes conspicuous, and there is a disadvantage that drainage treatment is required. In addition, even when hydrocarbons are not allowed to coexist, the effect of promoting regeneration only with water vapor is sufficient,
It is not necessary that hydrocarbons coexist. Further, when coexisting with carbon and hydrogen, if it is added in an amount exceeding 20 vol%, there is a disadvantage that a fire or an explosion may occur. If the amount of hydrocarbon added is less than 10 ppm, the effect is too small to exert an effect. When the temperature of the high-temperature air used for the regeneration is too low, the regeneration becomes insufficient. When the temperature is too high, it is disadvantageous in terms of economy, and the heat resistance of the material of the device needs to be improved, leading to an increase in cost. For this reason,
The temperature range of the high-temperature air for regeneration is 150 to 500 ° C, preferably 300 to 400 ° C.

FIG. 1 shows an example of an exhaust gas purifying method and apparatus for carrying out the present invention. The method and apparatus shown in FIG. 1 mixes exhaust gas with ozone, oxidizes nitrogen oxides (NOx) to nitrogen dioxide (NO ₂ ) at room temperature in a duct, and then passes the mixture through an adsorption tank filled with an adsorbent. The process of adsorbing and removing nitrogen oxides. By circulating high-temperature air through the adsorbed adsorption tank,
The process of desorbing the adsorbed nitrogen oxides from the adsorbent and regenerating the adsorbent. The desorbed and concentrated nitrogen oxides are removed by the ammonia reduction method (SCR) using a denitration catalyst in a high-temperature air circulation system.
A method and apparatus for purifying exhaust gas, comprising the steps of: reducing to nitrogen (N ₂ ) and water (H ₂ O) to make it harmless; providing a plurality of adsorption tanks and switching with a switching damper, a switching valve, a shutter, and the like. Thus, a method and an apparatus for sequentially reproducing one by one are provided. In the process, if most of the nitrogen oxides in the exhaust gas are nitric oxide, nitrogen dioxide has a higher adsorption speed and adsorption capacity than nitrogen monoxide and is easier to adsorb and remove. This is a process for oxidizing nitrogen to nitrogen dioxide and then dry-treating with an adsorbent to adsorb and remove nitrogen oxides. The device shown in FIG. 1 includes an ozone addition unit 12 connected to an exhaust gas duct 10 and a plurality of units (FIG. 1) connected in parallel to an exhaust gas duct downstream of the ozone addition unit 12 so as to be switchable by an opening / closing unit. In this example, three adsorption tanks 14a, 14b, and 14c are provided, and a circulation blower 16 and a heater 18 connected to each adsorption tank.
And a selective catalytic reduction reactor 22 provided in the high-temperature air circulation system 20.

In FIG. 1, an exhaust gas containing low-concentration NOx (mostly NO and the remaining NO ₂ ) such as exhaust gas from a road tunnel ventilation is introduced into an exhaust gas duct 10, and ozone is added by an ozone adding means 12 such as an ozone generator. Is added, and NO is oxidized to NO ₂ at normal temperature in the exhaust gas duct 10.
This exhaust gas is passed through adsorption tanks 14a and 14c filled with an adsorbent to adsorb and remove NOx. Examples of the adsorbent include manganese oxide-activated alumina-based adsorbent, or manganese oxide-activated alumina-based adsorbent including at least one oxide selected from the group consisting of calcium, magnesium, iron, and copper. Is used. The O ₃ / NOx ratio varies depending on the ratio of NO and NO _{2 in} the exhaust gas. However, in the case of road tunnel ventilation exhaust gas (about ₃ ppm NOx and about 80% humidity), the O ₃ / NOx ratio is 0.8 to 0.5.
9 is obtained. Even if the ozone is supplied in excess, the excess ozone is treated with the above adsorbent,
Ozone does not remain in the treated gas at the outlets of the adsorption tanks 14a and 14c. Two or more adsorption tanks are provided, and adsorption and regeneration are sequentially repeated. Although FIG. 1 shows a case where three adsorption tanks are provided for ease of explanation, a larger number (for example, 16) of adsorption tanks are provided in an actual apparatus.

A high-temperature air circulation system 20 having a circulating blower 16 and a heater 18 is connected to each of the adsorption tanks.
(0 to 500 ° C.), the adsorbed NOx is desorbed, and the adsorbent is regenerated. NOx desorbed from adsorbent
Is decomposed into N ₂ and H ₂ O and made harmless in a selective catalytic reduction reactor 22 provided in a high-temperature air circulation system 20 and filled with a denitration catalyst. Note that a reducing agent such as ammonia or hydrocarbon is added to the upstream side of the reactor 22. Opening and closing means 2 such as a shutter and a damper valve are provided before and after each adsorption tank.
4 and 26 are provided. In FIG. 1, the open / closed means blacked out indicates a closed state, and the open / closed means not filled out indicates an open state.

According to the present invention, in the above-mentioned purification method and apparatus, as shown in FIG. 1, steam or water is added to the high-temperature air circulation system, or when the adsorbent adsorbs nitrogen oxides in exhaust gas. At the same time, the water concentration in the regenerated gas is reduced to 5 vol% by taking advantage of the fact that water in the exhaust gas is adsorbed and released by passing heated air through.
As described above, the control method is preferably controlled to 20 to 80 vol%. At this time, the regeneration can be further promoted by adding a hydrocarbon to the regeneration gas and making it coexist with water or steam. As described above, LPG gas and lower hydrocarbons such as isobutane, butane, and propane, which are components of LPG gas, ethylene, propylene, lower hydrocarbons having an unsaturated bond such as butylene, methanol, ethanol, Propanol,
Lower hydrocarbons such as alcohols such as butanol are used.

If the moisture concentration in the circulating air is too high due to the evaporation of the moisture adsorbed by the adsorbent, as shown in FIG. 2, the air in the system is partially removed by adjusting the pressure in the apparatus. In some cases, the adsorbent is dried at the final stage of the regeneration process by purging or introducing air from outside the system. 1 and 2 show a case in which high-temperature air is circulated to regenerate the adsorbent, but high-temperature air is supplied to the adsorption tank in a one-through manner, and steam or water is added to the high-temperature air to adsorb the adsorbent. It is also possible to play back.

Activated carbon, zeolite and the like can be used as commercially available adsorbents as the adsorbent used in carrying out the present invention. No. 303685, "Nitrogen oxide adsorption remover and method for producing same" and Japanese Patent Application No. Hei 3-1664
The adsorbent described in No. 96 "Method for Removing Nitrogen Oxide", namely, an oxide of at least one element selected from the group consisting of sodium, potassium, magnesium and calcium, and iron, copper, cobalt, nickel and manganese It is particularly desirable to use an adsorbent and removal agent for oxides of at least one element selected from the group consisting of nitrogen and at least one oxide selected from the group consisting of aluminum, silicon, titanium and zirconium. In addition,
As the adsorbent, a honeycomb-shaped adsorbent is used in order to minimize pressure loss in the packed bed of the adsorbent and to prevent clogging due to dust in the processing gas. The shape of the honeycomb is, for example, 40 × 40 with 200 mm square.
A cell with a length of about 1 m is suitable.

[0017]

【Example】

Example 1 Using a low-concentration NOx adsorbent, manganese oxide / calcium oxide-containing active alumina-based adsorbent, 3 ppm of NO ₂
After performing a purification test of air containing water, when regeneration was performed with heated air, moisture was added to the heated air during regeneration, and the effect of moisture coexistence was examined. The test conditions were as follows. Adsorbent composition: manganese oxide 15 wt%, calcium oxide 1
wt% containing activated alumina adsorbent shape: three cells × 3 cell honeycomb molded body processed _{gas: NO 2 3ppm -Air, 15l /} min relative humidity 80% (25 ℃) SV (space velocity): 4,000h ^{- 1} process gas Temperature: 30 ° C. Regeneration gas: Condition 1 Air containing 3 vol% of water Condition 2 Air containing 30 vol% of water The results are shown in FIG. As can be seen from FIG. 3, a remarkable increase in the amount of NOx desorbed was observed at the same time as the water was entrained in the high-temperature air, and a remarkable regeneration effect by the addition of water was confirmed.

Example 2 Using an activated alumina-based adsorbent containing manganese oxide, which is a low-concentration NOx adsorbent, a purification test of air containing 3 ppm of NO ₂ was carried out.
% Of desorbed NOx in regeneration with air containing 0.1% by weight. The test conditions were as follows. Adsorbent composition: manganese oxide 20wt%, calcium oxide 3
wt% containing activated alumina adsorbent shape: three cells × 3 cell honeycomb molded body processed _{gas: NO 2 3ppm -Air, 15l /} min relative humidity 80% (25 ℃) SV (space velocity): 4,000h ^{- 1} process gas Temperature: 30 ° C. Regeneration gas: Condition 1 Air containing 3 vol% of water Condition 2 Air containing 30 vol% of water The results are shown in FIG. 4 (Comparative Example) and FIG. 5 (Example). FIG.
As can be seen from FIG. 5 and FIG. 5, NOx desorption occurs in regeneration with moisture-containing air at a low temperature, and all adsorbed NOx desorbs at 350 ° C. On the other hand, in the case of regeneration with heated air having a low moisture content, 350 ° C.
From the above, it can be seen that there is desorption of adsorbed NOx, and it is necessary to heat to 450 ° C. or more for complete regeneration.
Therefore, the regeneration temperature can be reduced to about 10 by adding moisture.
This has the effect of reducing the temperature by 0 ° C.

Example 3 Using a low-concentration NOx adsorbent, a manganese oxide / calcium oxide-containing active alumina-based adsorbent, a purification test of air containing 3 ppm of NO was carried out, followed by regeneration with heated air. Then, during the regeneration, water and isobutane gas were added to the heated air, and the effect of coexistence of water and hydrocarbons was examined.
The test conditions were as follows. Adsorbent composition: manganese oxide 15 wt%, calcium oxide 1
Activated alumina containing wt% Adsorbent shape: 3 cells x 3 cells Honeycomb molded body Processing gas: NO ₃ ppm-O ₃ 3 ppm-Air, 15 l
/ Min Relative humidity 80% (25 ° C) SV (Space velocity): 4,000h ^-1 Processing gas temperature: 30 ° C Regeneration gas: Condition 1 Air containing 3vol% water Condition 2 Air containing 30vol% water and 500ppm isobutane 6 (Comparative Example) and FIG. 7 (Example). FIG.
As can be seen from FIG. 7 and at the same time that the moisture and the LPG gas were entrained in the high-temperature air, a remarkable increase in the amount of NOx desorbed was observed, and a remarkable regeneration effect by the addition of the moisture and isobutane gas was confirmed.

Example 4 A purification test of diluent gas of diesel engine exhaust gas containing 3 ppm NO by air was performed using an activated alumina-based adsorbent containing manganese oxide / calcium oxide, which is a low-concentration NOx adsorbent, and then heated. During regeneration with air, moisture and LPG gas were added to the heated air during regeneration, and the effect of coexistence of moisture and hydrocarbons was examined. The test conditions were as follows. (LPG gas: propane 35vol
%, Isobutane 22 vol%, butane 43 vol%) Adsorbent composition: manganese oxide 15 wt%, calcium oxide 1
wt% containing activated alumina adsorbent shape: 4 cell × 4 cell honeycomb molded body processed gas: Diesel engine exhaust -O ₃ 3 ppm -
Air, 42 l / min NOx concentration in the processing gas is 3 ppm Relative humidity 80% (25 ° C.) SV (space velocity): 4,000 h ^-1 Processing gas temperature: 30 ° C. Regeneration gas: Condition 1 Air containing 3 vol% of moisture Condition 2 Air containing 30 vol% of moisture and 1000 ppm of LPG gas The results are shown in FIG. 8 (Comparative Example) and FIG. 9 (Example). FIG.
As can be seen from FIG. 9 and at the same time that the moisture and the LPG gas were entrained in the high-temperature air, a remarkable increase in the amount of NOx desorbed was observed, and a remarkable regeneration effect due to the addition of the moisture and the LPG gas was confirmed.

Example 5 A purification test of a diluent gas of a diesel engine exhaust gas containing 5 ppm NO by air was performed using an activated alumina-based adsorbent containing manganese oxide / calcium oxide, which is a low-concentration NOx adsorbent, and then heated. When the air was regenerated, the case where moisture and LPG gas were added to the heated air during the regeneration and the case where only LPG gas was added were compared, and the effect of coexistence of water and hydrocarbons was examined. The test conditions were as follows. (LPG gas: propane 35 vol%, isobutane 22 vol%, butane 43 vol%) Adsorbent composition: manganese oxide 15 wt%, calcium oxide 1
wt% containing activated alumina adsorbent shape: 4 cell × 4 cell honeycomb molded body processed gas: Diesel engine exhaust -O ₃ 5 ppm -
Air, 42 l / min NOx concentration in the processing gas is 5 ppm Relative humidity 80% (25 ° C.) SV (space velocity): 4,000 h ^-1 Processing gas temperature: 30 ° C. Regenerating gas: condition 1 moisture 3 vol%, LPG gas 150
0 ppm containing air Condition 2 Water containing 30 vol%, LPG gas 1500 ppm containing air The results are shown in FIG. 10 (Comparative Example) and FIG. 11 (Example).
As can be seen from FIGS. 10 and 11, a remarkable increase in the amount of NOx desorbed was observed at the same time as the moisture and the LPG gas were entrained in the high-temperature air, and a remarkable regeneration effect by the addition of the moisture and the LPG gas was confirmed.

[0022]

As described above, the present invention has the following effects. (1) Since moisture is contained in the regeneration gas, the speed of desorbing NOx is increased as compared with regeneration by mere heating air, that is, the regeneration efficiency is significantly improved, and as a result, the regeneration temperature can be reduced, thereby saving energy and energy. The cost can be reduced by reducing the heat resistance of the device material. (2) When a hydrocarbon is added together with water to the regeneration gas, regeneration is further promoted in addition to the effect of (1).

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of an apparatus for performing a method for regenerating a nitrogen oxide adsorbent of the present invention.

FIG. 2 is a flow sheet showing another example of an apparatus for performing the method of the present invention.

FIG. 3 shows the results in Example 1, and is a graph showing changes over time in the temperature of the packed bed and the concentration of desorbed NOx in the regeneration gas when steam is mixed.

FIG. 4 is a graph showing the results of Example 2 and showing, as a comparative example, the change over time in the temperature of the packed bed and the concentration of desorbed NOx in the regeneration gas when steam is not mixed.

FIG. 5 is a graph showing the results of Example 2 and showing changes over time in the temperature of the packed bed and the concentration of desorbed NOx in the regeneration gas when steam is mixed.

FIG. 6 is a graph showing the results in Example 3 and showing, as a comparative example, the change over time of the temperature of the packed bed and the concentration of desorbed NOx in the regenerated gas in the case of air containing 3 vol% of water.

FIG. 7 shows the results in Example 3, wherein the water content was 30%.
5 is a graph showing the change over time in the temperature of the packed bed and the concentration of desorbed NOx in the regeneration gas in the case of air containing vol% and isobutane 500 ppm.

FIG. 8 is a graph showing the results of Example 4 and showing, as a comparative example, the change over time in the temperature of the packed bed and the concentration of desorbed NOx in the regenerated gas in the case of air containing 3 vol% of water.

FIG. 9 shows the results in Example 4, where the water content was 30%.
6 is a graph showing the change over time of the temperature of the packed bed and the concentration of desorbed NOx of the regeneration gas in the case of air containing vol% and LPG gas at 1000 ppm.

FIG. 10 shows the results in Example 5, as comparative examples, the temperature of the packed bed and the desorption N in the regeneration gas in the case of air containing 3 vol% of water and 1500 ppm of LPG gas.
It is a graph which shows a change with time of Ox concentration.

FIG. 11 shows the results in Example 5, where water 3
5 is a graph showing the change over time in the temperature of the packed bed and the desorbed NOx concentration of the regeneration gas in the case of air containing 0 vol% and 1500 ppm of LPG gas.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Exhaust gas duct 12 Ozone addition means 14a Adsorption tank 14b Adsorption tank 14c Adsorption tank 16 Circulating blower 18 Heater 20 High temperature air circulation system 22 Selective catalytic reduction reactor 24 Opening / closing means 26 Opening / closing means

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuo Masuyama 3-1-1, Higashikawasaki-cho, Chuo-ku, Kobe-shi, Hyogo Kawasaki Heavy Industries, Ltd. Kobe Plant (72) Inventor Yoshinori Matsuo Higashi-Kawasaki, Chuo-ku, Kobe-shi, Hyogo 3-1-1 Cho-cho Kawasaki Heavy Industries, Ltd. Kobe Factory (56) References JP-A-60-261538 (JP, A) JP-A-50-35067 (JP, A) JP-A-54-2986 (JP, A) A) JP-A-5-154339 (JP, A) JP-A-50-143788 (JP, A) JP-A-55-116443 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) B01D 53/02-53/12 B01D 53/34-53/85 B01J 20/00-20/34

Claims (2)

(57) [Claims] An exhaust gas containing a low concentration of nitrogen oxides of 50 ppm or less is treated with a manganese oxide-activated alumina-based adsorbent,
Is manganese oxide-activated alumina based adsorbent calcium,
Less selected from the group consisting of magnesium, iron and copper
Nitrogen oxides are adsorbed and removed by bringing them into contact with an adsorbent containing an oxide of one element, and then the adsorption operation is temporarily stopped, and adsorbents that have adsorbed nitrogen oxides using heated air as a regeneration gas In the method in which adsorbed nitrogen oxides are desorbed and regenerated by passing through the packed bed, the steam concentration of the regenerating gas is adjusted to 20 to 80 vol %, and at the same time, the temperature of the adsorbent packed layer during regeneration is set to 300 to 80 vol %. A method for regenerating a nitrogen oxide adsorbent, which comprises regenerating at a temperature of 400 ° C. 2. An exhaust gas containing a low concentration of nitrogen oxides of 50 ppm or less is treated with a manganese oxide-activated alumina adsorbent,
Is manganese oxide-activated alumina based adsorbent calcium,
Less selected from the group consisting of magnesium, iron and copper
Nitrogen oxides are adsorbed and removed by bringing them into contact with an adsorbent containing an oxide of one element, and then the adsorption operation is temporarily stopped, and adsorbents that have adsorbed nitrogen oxides using heated air as a regeneration gas In the method of regenerating by removing adsorbed nitrogen oxides through a packed bed, the steam concentration of the regenerating gas is adjusted to 20 to 80 vol %, and the hydrocarbon content is adjusted to 10 ppm or more and 20 vol% or less. A method for regenerating a nitrogen oxide adsorbent, wherein the regenerating is performed while adjusting the temperature of the adsorbent packed layer at the time of regeneration to a range of 250 to 375 ° C. at the same time.