JP2000325755A - Nitrogen dioxide removing process - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove an NOx of low concentration and improve the regeneration efficiency regardless of the high or low relative humidity by passing gas to be treated through a layer filled with a material having the reducing action from a nitrogen dioxide to a nitrogen monoxide or the like and then passing the gas to be treated through a layer filled with a nitrogen dioxide adsorption and reduction removing agent. SOLUTION: Gas to be treated containing a nitrogen dioxide or a sulfur dioxide is passed through a layer filled with a material having the reducing action from the nitrogen dioxide to the nitrogen monoxide and then passed through a layer filled with a nitrogen dioxide nitrogen adsorption and reduction removing agent composed of a porous carbon material carrying a ruthenium compound. The material to be used is preferably the porous carbon material, and the nitrogen dioxide adsorption and reduction removing agent is preferably an agent carrying an alkali metal compound or an alkali earth metal compound. After removing the nitrogen dioxide, the material and the nitrogen dioxide nitrogen adsorption and reduction agent are heated up to 150-200 deg.C in air to desorb the adsorbed nitrogen dioxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a nitrogen oxide having a relatively low concentration (up to a level of several ppm) near room temperature, which is contained in an atmosphere gas or a ventilation gas of a living space, a road tunnel, an underground parking lot or the like. NO _x: out of nitric oxide (NO) and nitrogen dioxide generic name (NO _2)], a method for the removal of NO ₂ which can be mainly adsorbing and removing NO _2. According to the present invention method, of NO _x, in the short term, direct without substantially removing the low NO harmful, it mainly removing only NO ₂ showing a direct adverse effect on the human body it is possible, compared with the case of removal for the entire NO _x, not only can provide a simple denitration technique to exhibit long NO ₂ removal performance at low cost, if only NO ₂ in the gas to be treated Even if SO ₂ is contained, excellent NO ₂ removal performance can be maintained without being adversely affected by SO ₂ , and an adsorbent whose removal performance has decreased during denitration must be separately supplied to a factory. This is extremely useful from the viewpoint of reducing equipment construction costs and operating costs.

[0002]

2. Description of the Related Art As a technique for removing NO ₂ in low concentrations NO _x contained in road tunnels ventilation gas, etc., for example, the following method has been proposed.

[0003] The gas to be treated containing low concentrations of NO and NO _{2 is} passed through a bed filled with a carbonaceous NO ₂ adsorbent and / or reducing agent to remove NO ₂ , and then the adsorbent is charged with 100%.
A method in which the adsorbent is regenerated by heating to about 200 ° C. (JP-A-8-066612).

[0004] A method of removing NO ₂ in a gas to be treated containing low concentrations of NO and NO ₂ using a NO ₂ adsorbent in which an alkali metal is supported on a Mn-Ti surface-modified titania carrier (Japanese Patent Laid-Open No. Hei 10-212427) ).

[0005] However, according to the results of the study by the present inventors,
It has been found that each of the above methods has the following problems.

First, when the relative humidity of the gas to be treated is low, the carbonaceous adsorbent generally lowers the NO ₂ removing ability, and may not be able to remove NO ₂ sufficiently. Also,
NO ₂ adsorbed on the adsorbent is considered to be fixed as nitrate by reacting with the alkali metal. However, it is presumed that heating to 300 ° C. or more is required to decompose the generated nitrate. Is not preferred.

[0007]

[0008] The present invention has been made in view of the above circumstances, and an object, regardless of the level of relative humidity, NO ₂ contained relatively in low concentrations of the NO _x
It is an object of the present invention to provide a novel NO ₂ removal method which can efficiently remove NO _{2 and which has} high regeneration efficiency.

[0008]

Means for Solving the Problems The removal method of the present invention which can solve the above-mentioned problems is that a gas to be treated which contains nitrogen dioxide and which may further contain sulfur dioxide can be obtained from (1) nitrogen dioxide After passing through a layer filled with a material that has a reducing effect on nitric oxide and may also have an adsorbing effect on sulfur dioxide, (2) nitrogen dioxide in which a ruthenium compound is supported on a porous carbon material It has a gist at a place communicating with a layer filled with the adsorption / reduction removal agent.

Here, the material used in the step (1) is preferably a porous carbon material.
It is preferable that the nitrogen dioxide adsorption / reduction remover used in the step (2) further supports an alkali metal compound and / or an alkaline earth metal compound.

After nitrogen dioxide is removed by the above method, the material and the nitrogen dioxide adsorbing / reducing removing agent are heated to 150 ° C. to 200 ° C. in air or 150 ° C. to 250 ° C. in an inert atmosphere. Therefore, adopting a method of desorbing the adsorbed nitrogen dioxide is extremely useful from the viewpoint of reducing facility construction costs and operation costs.

[0011]

DETAILED DESCRIPTION OF THE INVENTION The present inventors have found that regardless of the level of relative humidity, to provide a NO ₂ removal method the NO ₂ contained relatively in low concentrations of the NO _x can be removed efficiently We have been studying hard. As a result, they found that the intended purpose could be achieved by using a nitrogen dioxide adsorption / reduction / removal agent in which a ruthenium compound was supported on a porous carbon material (hereinafter, sometimes simply referred to as an adsorbent), An application has already been filed (Japanese Patent Application No. 10-014081). This adsorbent is specified by making good use of the fact that the NO ₂ adsorbing ability of a ruthenium compound and the NO ₂ → NO reducing action of a porous carbon material are in conflict with each other in relation to relative humidity.

However, subsequent studies have revealed that the above adsorbent has the following problems to be improved.

As the treatment time becomes longer, the NO ₂ adsorption performance by the ruthenium compound in the adsorbent decreases, and the regeneration cycle becomes shorter, which is not economical. This is not a problem peculiar to the adsorbent and is common to all adsorbents. However, from the viewpoint of minimizing the regeneration frequency, an improved method capable of extending the life of the adsorbent is desired.

It has been found that the NO ₂ adsorption performance by the ruthenium compound may be adversely affected by SO ₂ contained in the gas to be treated. In other words, the gas to be treated often contains a sulfur oxide (SO _x ) such as SO _2, but the ruthenium compound reacts with the SO _x to form a sulfur compound (sulfate, etc.) which accumulates. This is likely to cause deterioration of adsorption performance.

The ruthenium compound constituting the adsorbent is more expensive than a carbon-based material. Therefore, there is a demand for a method capable of reducing the amount of the supported ruthenium compound as much as possible while maintaining excellent NO ₂ removal performance by the ruthenium compound.

Therefore, the present inventors have solved the above-mentioned improvements.
As a result of further study, NO _TwoContaining gas to be treated
Before the treatment with the above adsorbent, beforehand
Representative, NO_Two→ Reducing action to NO
O_TwoFor packed beds containing materials that may have
A wide range of humidity, regardless of the relative humidity,
NO in the gas to be treated even under moderate conditions_TwoAdvanced and long time
Can be removed and the regeneration cycle of the adsorbent can be extended.
SO in natural gas_TwoEven if it contains
Excellent NO by the compound_TwoAdsorption capacity is affected
Advanced NO without_TwoAbility to maintain adsorption capacity,
After the treatment, the above-mentioned material and adsorbent are treated in air at 150 to
Up to 200 ° C or 150-25 in an inert atmosphere
Heated to 0 ° C, NO remaining adsorbed_TwoMost of N
By repeating the regeneration operation for desorption as O,
NO in natural gas_TwoFound that it can be continuously removed,
The present invention has been completed.

Hereinafter, each step including the method of the present invention will be described.

[0018] The removal method of the present invention converts the gas to be treated that contains NO _{2 and} may further contain SO ₂ into (1) a reducing agent from NO ₂ to NO, and further adsorbs SO ₂ After passing through a layer filled with a material having an effect, (2) a NO ₂ adsorption / reduction remover in which a ruthenium compound is supported on a porous carbon material (corresponding to the adsorbent disclosed in the aforementioned Japanese Patent Application No. 10-014081) (Hereinafter referred to as "adsorbent for prior application" or "porous carbon material carrying ruthenium compound").

That is, the method of the present invention comprises the steps of:_TwoContains
NO is also good_TwoImmediately treat the gas to be treated with the adsorbent of the prior application.
Instead of treating the gas to be treated with the packed bed of the above (1),
Pre-processing. Specifically, the gas to be treated is
In advance, "NO_Two→ It has a reducing effect on NO, and
O_TwoA layer filled with a material that may have an adsorption effect on the surface "
To the adsorbent of the earlier application
NO in the gas to be treated _TwoTo reduce adsorbent
This is to reduce the processing load on the system. In addition,
In the description below, for convenience, the packed bed of (1) is referred to as “upstream packed”.
Layer), the layer filled with the adsorbent of the prior application (2)
Layer ".

According to the method of the present invention, the upstream packed bed contains "N
O_Two→ Has a reducing effect on NO, and further has SO2_TwoAdsorption action of
Material that may have
You. That is, the material to be filled in the upstream packed bed is firstly
And NO_Two→ It is required to have a reducing effect on NO
You. If the material has such a reducing action, the downstream packed bed
The load of the prior application adsorbent to be filled in can be reduced,
This is because the regeneration cycle of the adsorbent can be extended. Follow
Therefore, in the method of the present invention, NO_Two→ No reduction action to NO
NO_TwoIt is inappropriate to use a material that has only an adsorption action
It is. If such a material is used, NO_Two
The adsorptive capacity is immediately saturated and the frequency of regeneration increases
This is because the problems described in the present invention cannot be solved. This
In contrast, NO _Two→ Materials that have the effect of reducing NO
If the fluidized bed is filled, NO becomes NO_TwoAccumulation compared to
Is low, so that the reducing action of the material can be maintained.
There are advantages.

From this point of view, it is not preferable that the material to be filled in the upstream packed bed mainly has the NO ₂ adsorbing action like activated alumina, and the reducing action to NO ₂ → NO like porous carbon material. It is preferable to use one having Of course, the porous carbon material is a representative example and is not intended to be limited to this. It goes without saying that any material having a reducing action from NO ₂ → NO can be applied to the method of the present invention.

Second, the material to be filled in the upstream packed bed is required to have an SO ₂ adsorbing action. If a material having such an SO ₂ adsorption action is used, even if the SO ₂ -containing gas to be treated is introduced, S
As a result of the removal of O ₂ by adsorption, the gas to be treated that does not contain SO ₂ is introduced into the downstream packed bed, and the excellent adsorption and removal action of the adsorbent of the prior application can be effectively exhibited. It is.

The material to be filled in the upstream packed bed is
It is necessary to have a reducing action to NO ₂ → NO or to have an SO ₂ adsorbing action. Specifically, if a suitable material is appropriately selected according to the composition of the gas to be treated, etc. good.

For example, when the concentration of SO ₂ in the gas to be treated is not so high, it is preferable to use a material having a function of mainly reducing NO ₂ → NO. Of course, when the above-mentioned material further has an SO ₂ adsorption action, a more excellent effect can be obtained.

On the other hand, when the concentration of SO ₂ in the gas to be treated is high, it is preferable to use a material mainly having an SO ₂ adsorbing action. In this case, a material having an action of adsorbing SO ₂ may be used, or a material having a action of reducing NO ₂ → NO may be used. The most effective material is a material having both these actions. The method to use.

In any case, filling the upstream packed bed with a material having a reducing action from NO ₂ → NO and having an SO ₂ adsorbing action is required in the prior application adsorption packed in the downstream packed bed. This is the most recommended mode in that the load on the agent can be reduced, and the adverse effect of SO ₂ is not adversely affected.
From such a viewpoint, the use of a porous carbon material is recommended.

The required characteristics of the material to be filled in the upstream filling layer are as described above. Such an upstream filling layer may be composed of a single layer or may be composed of a plurality of layers. For example, _two layers having a function of reducing NO ₂ → NO and a layer having a function of adsorbing SO ₂ may be provided, and such an embodiment is also included in the scope of the present invention.

The porous carbon material to be filled in the upstream packed bed is as follows:
The same material as the material to be filled in the downstream packed bed can be used, and specific examples thereof include activated carbon and activated coke. In order to exhibit the desired action effectively, it is preferable that the specific surface area is as large as possible, and it is recommended to use one having a specific surface area of 500 m ² / g or more, more preferably 1000 m ² / g or more.

Next, as the material to be filled in the downstream packed bed, the adsorbent of the prior application can be used as it is. This prior application adsorbent selects a porous carbon material as a carrier, a NO ₂ adsorption-reduction removing agent comprising a structure obtained by supporting a ruthenium compound is a porous material, NO ₂ immobilized ability excellent by ruthenium compound And the excellent action of reducing the NO ₂ → NO by the porous carbon material, which is in opposition to the relative humidity, is successfully used. The configuration is as detailed in the specification of the prior application, but the main components will be repeated.

As the carrier used in the above-mentioned adsorbent, the above-mentioned porous carbon material can be mentioned.

As the ruthenium compound supported on the porous carbon material, those having a strong action of forming a complex with NO ₂ are preferable, for example, ruthenate (sodium ruthenate, potassium ruthenate, etc.), halide (Ruthenium chloride, ruthenium bromide, etc.), ruthenium nitrate and the like. In other forms, for example, ruthenium metal itself or ruthenium oxide, the ability to fix NO ₂ is poor.

The content of the ruthenium compound in the adsorbent is preferably 0.05% by mass or more in terms of ruthenium metal. If it is less than 0.05% by mass, the NO ₂ adsorption action cannot be effectively exhibited. Note that this content is lower than the preferable content (0.05% by mass or more in terms of ruthenium metal) when the above-mentioned adsorbent is used alone. Therefore, when the method of the present invention is employed, there is obtained an advantage that, by using only a small amount of expensive ruthenium, an excellent NO ₂ adsorbing ability equivalent to that of the case of single use can be obtained. It is more preferably at least 0.1% by mass. As the amount of the supported ruthenium compound increases, the NO ₂ adsorbing action improves, but the cost also increases, and even if it is added in excess of 5% by mass, the action is saturated, and is economically useless. The actual amount of ruthenium carried may be appropriately set in a desired range according to the required performance, but generally it is recommended to be 2% by mass or less.

The adsorbent of the prior application basically has the above structure.
But NO by ruthenium compound _TwoFurther absorption
For the purpose of improvement, furthermore, alkali metal compounds and / or
It is recommended to carry a Lucari earth metal compound.
By supporting these compounds, especially low humidity
NO in the area_TwoThe reason why the adsorption capacity is improved is unknown in detail
However, due to the fact that these compounds are hydrophilic,
It is thought that it is.

Specifically, it is preferable to use an alkali metal / alkaline earth metal oxide, hydroxide, nitrate, carbonate, or the like. Potassium or sodium is used as the alkali metal, and potassium or sodium is used as the alkali earth metal. The use of magnesium or calcium is recommended. Such examples include potassium hydroxide, potassium nitrate, potassium carbonate, sodium hydroxide, sodium nitrate, sodium carbonate, magnesium oxide, magnesium hydroxide, magnesium nitrate, magnesium carbonate, calcium oxide, calcium hydroxide, calcium nitrate, and calcium carbonate. And the like. These may be used alone or in combination of two or more.

The content of the alkali metal compound / alkaline earth metal compound in the adsorbent is 10% by mass or less (more preferably 8% by mass or less) in terms of alkali metal / alkaline earth metal. Is preferred. 1
If it exceeds 0% by mass, the ability to remove NO ₂ in a high humidity range is reduced due to the influence of the pore coating of the porous carbon material.

The shape of the adsorbent having such a configuration is not particularly limited, and a shape such as a crushed shape, a columnar shape, a cylindrical shape, and a honeycomb shape can be appropriately selected.

Hereinafter, as one embodiment of the method of the present invention, a method for removing NO ₂ in the gas to be treated when the upstream packed bed is filled with a porous carbon material will be specifically described.

For example, when the relative humidity of the gas to be treated containing NO ₂ is low, first, a part of NO ₂ is reduced to NO by the porous carbon material provided in the upstream packed bed, and is not reduced in the packed bed. Only the remaining NO ₂ is introduced into the downstream packed bed. Part of this NO ₂ is adsorbed by the porous carbon material supporting the ruthenium compound in the downstream packed bed, and the rest is reduced to NO and removed. Here, the NO generated in the upstream packed bed does not have any adverse effect on the ruthenium compound-supporting porous carbon material of the downstream packed bed, and the excellent characteristics of the ruthenium compound and the porous carbon material are effectively maintained. Remains intact. as a result,
The amount of NO ₂ to be adsorbed and accumulated in the ruthenium compound supported porous carbon material of the downstream filling layer is reduced, resulting from the fact that NO ₂ adsorption performance of the ruthenium compound is maintained for a long time, the effect of also extending reproduction period Can be

When the relative humidity of the gas to be treated containing NO ₂ is high, first, most of the NO ₂ is reduced to NO by the porous carbon material provided in the upstream packed bed, and the NO ₂ remains without being reduced. Only the NO ₂ that has been introduced will be introduced into the downstream packed bed. Part of this NO ₂ is adsorbed by the porous carbon material carrying the ruthenium compound in the downstream packed bed, and the rest is reduced to NO and removed. Here, NO generated in the upstream packed bed has no adverse effect on the ruthenium compound-supported porous carbon material of the downstream packed bed, and this is the same as in the case where the relative humidity is low. As a result, the amount of NO ₂ adsorbed and accumulated on the ruthenium compound-supporting porous carbon material is reduced, so that the NO ₂ adsorption performance of the ruthenium compound is maintained for a long time, and the effect of increasing the regeneration cycle is obtained.

The gas to be treated contains not only NO ₂ but also SO ₂
Is included, if the method of the present invention is adopted, S
Since O ₂ is almost completely removed by the porous carbon material filled in the upstream packed bed, a gas substantially free of SO ₂ is introduced into the downstream packed bed. As a result, the porous carbon material supporting the ruthenium-nium compound in the downstream packed bed can exhibit its original excellent performance without any adverse effect due to SO ₂ .

As described above, according to the method of the present invention, the effect of reducing the NO ₂ → NO and the effect of removing SO ₂ by the porous carbon material of the upstream packed layer and the effect of the porous carbon material carrying the ruthenium compound of the downstream packed layer can be obtained. NO ₂ → NO reduction action and N
It can be seen that the synergistic effect of the O ₂ removal action significantly improves the NO ₂ removal performance and greatly improves the regeneration cycle.

In the method of the present invention, the temperature in the gas is set at 50
By setting the temperature to not more than ° C., NO ₂ can be efficiently removed. If the temperature exceeds 50 ° C., the NO ₂ adsorbing ability decreases.

As the material is used, the NO ₂ adsorbing ability of the porous material of the upper packing layer and the porous carbon material carrying the ruthenium compound of the downstream packing layer is reduced, and a part of the NO ₂ adsorbed by these materials remains unchanged. At rest. Therefore, it is effective to recover the adsorption activity by periodically heating these to 150 to 200 ° C. in air or 150 to 250 ° C. in an inert atmosphere. This is because NO ₂ desorbed by heating becomes substantially only NO due to the reducing action of the carbonaceous material as a carrier, and can eliminate the risk of leaking a high concentration of NO ₂ out of the system. In the case of heating in air, the adsorbed NO ₂ cannot be sufficiently desorbed at a temperature lower than 150 ° C. On the other hand, at a temperature higher than 200 ° C., the carbonaceous material may be consumed. Further, when heating in an inert atmosphere, the carbonaceous material is hardly consumed, so that the temperature can be raised to 250 ° C., which is economically extremely useful in extending the life.

The NO ₂ removal performance according to the method of the present invention can be evaluated by the NO ₂ removal rate calculated by the following equation. NO ₂ removal rate (%) = [1- (outlet NO ₂ concentration) / (inlet NO ₂ concentration)] × 100

By adopting the method of the present invention, compared with the case where the ruthenium compound-supported porous carbon material of the prior application was used alone,
The NO ₂ removal rate calculated by the above formula is increased by about 15 to 20%, and excellent removal activity can be maintained for a long time. As a result, it is possible to heat and regenerate at an apparatus site, or take out only the adsorbent and separately It is also possible to regenerate at a factory or the like. The latter case is useful in terms of simplification of the apparatus, because it is not necessary to install a regeneration facility in the removal apparatus according to the method of the present invention.

Hereinafter, the present invention will be described in detail based on examples. However, the following examples do not limit the present invention, and all modifications and implementations without departing from the spirit of the preceding and the following are included in the technical scope of the present invention.

[0047]

EXAMPLE 1 Example 1 (NO ₂ is mainly contained in the gas to be treated)
Case) In this example, the NO ₂ removal rates (relative humidity 30%, 60%) in the gas to be treated were measured when various adsorbents were used for a single-layer or two-layer packed bed. First, the following three types of adsorbents were used in this example.

[No. 1 (porous carbonaceous adsorbent)] Takeda Chemical Industries palm shell porous carbon material (4 to 6 meshes)
, Specific surface area 1350m ^Two/ G) [No. 2 (porous carbonaceous adsorption supported on ruthenium compound
Agent)] potassium ruthenate (K_TwoRuthenium O_Four) 1.
An aqueous solution containing 8 g was prepared. 1 porous charcoal
After impregnating and supporting the raw material, 110 ° C x 2 hours in a dryer
And dried under the following conditions. Rute of the adsorbent obtained in this way
The amount of supported nickel is 0.51% by mass in terms of metal ruthenium.
Met.

[No. 3 (ruthenium compound-supported transition metal oxide)] potassium ruthenate (K ₂ RuO ₄ )
An aqueous solution containing 8 g was prepared and impregnated and supported on a copper-manganese composite oxide (1/8 pellet) manufactured by Nissan Gardler Co., Ltd., and then dried in a dryer at 110 ° C. for 2 hours. The adsorbent thus obtained had a supported amount of ruthenium of 0.51% by mass in terms of metal ruthenium.

Next, the above adsorbent was filled into a stainless steel cylindrical container (cross-sectional area: 4.41 cm ² ) to form a total of six types of packed layers shown in Table 1. In addition, the total of the adsorbent filling height in each packed bed is 10 cm in all cases. In the table, Experimental Examples 2 and 5 are examples of the two-layer packed layer,
The left part of “type of adsorbent” indicates the adsorbent filled in the upstream packed bed, and the filling height ratio thereof is also shown in Table 1.

Next, a gas to be treated [air at a temperature of 35 ° C. and a relative humidity of 30% or 60%;
x: 2 ppm (NO: NO ₂ = 9: 1) / air balance gas] at 29.4 NI / min, and the outlet side NO ₂
The concentration was measured with a chemiluminescent analyzer. The NO ₂ removal rate after 300 hours in each packed bed was calculated by the following equation. NO ₂ removal rate (%) after 300 hours = [1- (exit N after 300 hours)
O ₂ concentration) / (inlet NO ₂ concentration after 300 h) × 100] These results are also shown in Table 1.

[0052]

[Table 1]

Experimental Example 2 employing the two-layer packed layer according to the method of the present invention is similar to Experimental Example 3 (single-layer packed layer containing only the ruthenium compound-supported porous carbonaceous adsorbent of the prior application) not employing the method of the present invention. In comparison, the NO ₂ removal rate could be increased by about 10 to 15% regardless of the relative humidity.

In a single-layer packed bed filled with only a porous carbon material (Experimental Example 1), when the relative humidity is high, NO ₂
The removal rate was about 84%, indicating good removal performance, but decreased to about 50% when the relative humidity became low.

Experimental Example 4 shows that a ruthenium compound was
This is an example of a single-layer packed layer supported on a transition metal oxide instead of a porous carbon material.
The O ₂ removal rate was extremely low at about 30%. Experimental example 5
Is a two-layer packed bed in which a packed bed filled with a porous carbon material is provided on the upstream side of the packed bed of Experimental Example 4, but when the relative humidity is high, the NO ₂ removal rate is as good as about 93%. NO ₂
Demonstrates removal performance, but when relative humidity decreases, 55
%.

Example 2 (NO ₂ and SO _{2 in the} gas to be treated)
In including the case) Example 1, Experiment 2 and Experiment 3 as an adsorbent
And a gas to be treated, air at a temperature of 35 ° C. and a relative humidity of 30% or 60%, NO
x: 2 ppm (NO: NO ₂ = 9: 1) / SO ₂ : 0.1
The NO ₂ removal rate after 300 hours was measured in the same manner as in Example 1 except that a powder having a ppm / air balance was used.

Table 2 shows the obtained results.

[0058]

[Table 2]

As shown in Table 2, Experimental Example 6 employing the method of the present invention.
Is not adversely affected by the SO ₂ in the treated gas, and exhibiting very good NO ₂ removal performance, such excellent removal performance is seen similarly irrespective of the level of relative humidity Was. On the other hand, in Experimental Example 7 in which the method of the present invention was not employed (single-layer packed bed filled only with the ruthenium compound-supported porous carbonaceous adsorbent), the SO _{2 in the} gas to be treated was
The NO ₂ removal rate was as low as about 75% in both cases when the relative humidity was high and when the relative humidity was low.

[0060]

The method of the present invention is constituted as described above.
Since the load on the NO ₂ removal performance of the ruthenium compound-supported porous carbonaceous adsorbent filled in the downstream packed bed can be reduced,
The frequency of regeneration of the adsorbent can be reduced, which is economical. This effect is true regardless of the relative humidity.
Together they found in a wide relative humidity range, even if it contains SO ₂ in the gas to be treated, it is useful in that it is not adversely affected by the SO _2. Furthermore, if the NO ₂ remaining in the adsorbent is desorbed by heating, it can be almost desorbed as NO, so that there is an advantage that leakage of high-concentration NO ₂ can be prevented.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 20/20 B01J 23/89 A 20/34 B01D 53/34 129A 132Z 23/58 53/36 102B 23 / 89 (72) Inventor Satoshi Inoue 1-5-5 Takatsukadai, Nishi-ku, Kobe F-term in Kobe Steel Research Institute Kobe Research Institute (reference) 4D002 AA02 AA12 AC10 BA04 BA06 CA07 DA01 DA04 DA11 DA23 DA24 DA25 DA41 EA08 GA01 GA02 GB01 GB02 GB03 GB08 GB11 GB12 HA03 4D048 AA06 AB02 BA01Y BA02Y BA05X BA14X BA15Y BA32X BA35X BA42X BB01 CA01 CC40 CC50 EA04 4G066 AA04B AA10D AA13B AA15B AA18B AA02BA22A22B AA02A22A BC01B BC03A BC03B BC08A BC31A BC31B BC62A BC62B BC70A BC70B CA03 CA08 CA13 DA06 EA01Y EB18Y EC05Y

Claims (4)

[Claims] 1. A gas to be treated containing nitrogen dioxide, which may further contain sulfur dioxide, has a reducing action from nitrogen dioxide to nitric oxide, and further has an action of adsorbing sulfur dioxide. A method for removing nitrogen dioxide, comprising: passing through a layer filled with a good material, and then passing through a layer filled with a nitrogen dioxide adsorption / reduction remover in which a porous carbon material carries a ruthenium compound. 2. The method according to claim 1, wherein the material is a porous carbon material. 3. The removal method according to claim 1, wherein the nitrogen dioxide adsorption / reduction removal agent further supports an alkali metal compound and / or an alkaline earth metal compound. 4. After removing nitrogen dioxide by the removal method according to any one of claims 1 to 3, the material and the nitrogen dioxide adsorbing / reducing removing agent are removed at 150 ° C. to 200 ° C. in air.
The method according to any one of claims 1 to 3, wherein the adsorbed nitrogen dioxide is desorbed by heating to 150C to 250C in an inert atmosphere.