JP2001070748A - Method and apparatus for removing nitrogen oxide and sulfur oxide from gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide stable desulfurization efficiency and nitrogen oxide removal efficiency with the lapse of time to a gas containing SOx and NOx, sucb as combustion gases and further convert the nitrogen oxides in harmless substances. SOLUTION: An absorbent containing at least a molten carbonate salt is used while being held in, for example, a porous body 1 and a gas 4 containing SOx and NOx to which an oxygen-containing gas may be added based on necessity, are brought into contact with the absorbent 1 while being used to keep the absorbent 1 in oxidizing ambient environments and on the other hand, the absorbent 1 is brought into contact with reductive ambient environments separately from the contact of the oxidizing ambient environments. If the absorbent 1 is brought into contact simultaneously with the oxidizing ambient environments and the reductive ambient environments, the object gas treatment and the carbonate regeneration can simultaneously be carried out and electric power generation is carried out as well as a fuel cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desulfurization and denitration method for converting sulfur oxides and nitrogen oxides present in an oxidizing atmosphere gas into hydrogen sulfide and nitrogen, and an apparatus used for the method. More specifically, the present invention relates to a denitration and desulfurization method and apparatus which exhibit stable desulfurization or denitration efficiency over time.

[0002]

2. Description of the Related Art Exhaust gas generated from a thermal power plant, a white moving vehicle, etc. includes sulfur oxides (SOx) and nitrogen oxides (NOx).
, Which is one of the causes of air pollution and acid rain. Many proposals have already been made as a method for treating SOx and NOx in exhaust gas.

[0003] As a method for treating NOx, a dry process such as a catalytic cracking method and a catalytic reduction method using a catalyst, an adsorption method using a porous adsorbent, an absorption method using a molten alkali, or an alkaline aqueous solution as a wet process is used. The absorption method used, an oxidation absorption method using sodium chlorite, potassium permanganate, and the like, a complex salt formation absorption method, a reduction method, and the like are known. An absorption method using such methods is known.

[0004] Above all, the absorption method using a molten carbonate can absorb and remove SOx and NOx in a gas at the same time. However, conventionally, the treatment of the molten carbonate after absorbing the SOx and NOx has been conventionally performed. Was not taken into account, and the absorptance declined significantly with time, making practical use difficult. When CO ₂ is contained in the exhaust gas, the denitration efficiency is 15%.
There was a problem that:

[0005]

In the conventional method,
Since the efficiency of desulfurization and denitration decreases with the passage of time, equipment for regenerating molten carbonates, catalysts, and the like is required in addition to the desulfurization and denitration equipment, resulting in a complicated system. Further, waste liquid or waste generated during regeneration of the catalyst becomes a problem. Therefore, there has been a demand for a denitration method for converting nitrogen oxides into harmless substances while maintaining stable desulfurization and denitration efficiencies over time.

Accordingly, it is an object of the present invention to propose a denitration / desulfurization method which has stable desulfurization and denitration efficiency and further converts nitrogen oxides into harmless substances.

[0007]

In order to achieve the above object, a method for removing nitrogen oxides from a gas according to the present invention according to the first aspect of the present invention provides a method for removing oxygen from a gas containing nitrogen oxides as necessary. While adding the containing gas, the gas is brought into contact with the absorbent containing at least the molten carbonate as an oxidizing atmosphere, while the contact with the oxidizing atmosphere is separated to bring the absorbent into contact with a reducing atmosphere comprising a hydrogen-containing gas. I have to.

According to a second aspect of the present invention, there is provided a method for removing a sulfur compound in a gas, wherein an oxygen-containing gas is added as necessary to a gas to be treated containing a sulfur oxide to contain at least a molten carbonate. While the gas is brought into contact with the absorbing agent as an oxidizing atmosphere, the gas is brought into contact with the oxidizing atmosphere, so that the absorbing agent is brought into contact with a reducing atmosphere made of a hydrogen-containing gas.

According to a third aspect of the present invention, there is provided a method for removing nitrogen oxides and sulfur compounds in a gas, wherein an oxygen-containing gas is added to a gas to be treated containing nitrogen oxides and sulfur oxides as necessary. While the gas is brought into contact with the absorbent containing at least the molten carbonate as an oxidizing atmosphere, the gas is brought into contact with the oxidizing atmosphere, and the absorbent is brought into contact with a reducing atmosphere comprising a hydrogen-containing gas. .

[0010] In these cases, NOx in the gas to be treated reacts with the molten carbonate to generate nitrate ions and nitrite ions in the molten carbonate, and SOx reacts with the molten carbonate and reacts with the molten carbonate. To produce sulfate ions and sulfur ions. That is, NOx and SOx are removed from the gas to be treated and purified. And these ions in the molten carbonate are
When contacted with hydrogen in a reducing atmosphere, it reacts with hydrogen to produce nitrogen and hydrogen sulfide to regenerate molten carbonate.

According to a fourth aspect of the present invention, in the method according to any one of the first to third aspects, the contact of the absorbent with the oxidizing atmosphere and the contact of the reducing atmosphere with respect to the contact surface of the absorbent with the respective atmospheres. Are structurally partitioned so that they are performed in parallel in time. In this case, purification of the gas to be treated and regeneration of the molten carbonate proceed simultaneously.

According to a fifth aspect of the present invention, in the method according to any one of the first to third aspects, the contact of the oxidizing atmosphere with the absorbent and the contact of the reducing atmosphere are repeated temporally and alternately. I am trying to be.

According to a sixth aspect of the present invention, in the method according to any one of the first to fifth aspects, carbon dioxide gas is contained in an oxidizing atmosphere, and carbon dioxide gas and water are contained in a reducing atmosphere. So that it can be added. In this case, the carbon dioxide gas prevents decomposition of the carbonate and the water prevents carbon deposition.

According to a seventh aspect of the present invention, in the method according to any one of the first to fourth and sixth aspects, an electrolyte layer is formed by an absorbent containing at least a molten carbonate, and one of the electrolyte layers is formed. The surface is contacted with an oxidizing atmosphere as a positive electrode, and the other surface is brought into contact with a reducing atmosphere as a negative electrode to purify a gas to be treated and simultaneously generate power as a fuel cell.

Further, the invention according to claim 8 is the method according to any one of claims 1 to 7, wherein the gas containing nitrogen oxides and / or sulfur compounds is used as a combustion exhaust gas discharged from a combustion plant. I have. In this case, it is possible to purify the environmental air.

According to a ninth aspect of the present invention, there is provided a gas processing apparatus for use in the method according to any one of the first to third aspects, wherein the absorbent comprises a porous body impregnated with a molten carbonate. Are formed, one surface of which is a contact surface with the oxidizing atmosphere, the other surface is a contact surface with the reducing atmosphere, and the porous body divides a circulating region of the oxidizing atmosphere and a circulating region of the reducing atmosphere. It has a structure.

The invention according to claim 10 is the invention according to claim 9.
In the gas processing apparatus described above, the porous body impregnated with the absorbent has a structure in which both sides of the porous body are sandwiched by another porous body.

Further, the invention described in claim 11 is the first invention.
0, the other porous body sandwiching the porous body impregnated with the absorbent is made of metal or metal oxide, and the combustion exhaust gas discharged from the combustion plant is introduced into the oxidizing atmosphere side and reduced. A reducing gas containing hydrogen is introduced into the atmosphere to purify the gas to be treated and to function as a fuel cell.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail based on an embodiment shown in the drawings.

The present invention is a method for removing nitrogen oxides and / or sulfur oxides from a gas using an absorbent containing at least a molten carbonate, wherein the nitrogen oxides and / or sulfur oxides are removed. Where necessary, an oxygen-containing gas is added to the gas to be treated, and the gas is brought into contact with the absorbent containing at least the molten carbonate as an oxidizing atmosphere while the gas is brought into contact with the oxidizing atmosphere. The contact is made with a reducing atmosphere composed of a hydrogen-containing gas.
The gas to be treated is exemplified by flue gas discharged from a combustion plant. In this case, since oxygen remains in the flue gas, the oxygen is added without any particular addition to the absorbent gas. May be brought into contact with the absorbent, or may be added to the absorbent after adding a shortage of oxygen.

NOx in contact with the molten carbonate-containing absorbent in an oxidizing atmosphere is absorbed into the molten carbonate,
A substitution reaction occurs with carbonate ions to form nitrate ions and nitrite ions. Thus, when the nitrate ion and the nitrite ion present in the molten salt come into contact with the reducing atmosphere, they react with hydrogen (H ₂ ) and are released to the reducing atmosphere side as nitrogen (N ₂ ).

Further, SOx in contact with the absorbent containing a molten carbonate in an oxidizing atmosphere is absorbed in the molten carbonate and causes a substitution reaction with a carbonate ion to form a sulfate ion and a sulfur ion. Thus, when the sulfate ion and the sulfur ion present in the molten salt come into contact with the reducing atmosphere, they react with H ₂ and are released to the reducing atmosphere side as hydrogen sulfide (H ₂ S) nitrogen.

As described above, in the present invention, the molten carbonate functioning as an absorbent for NOx and SOx can release the absorbed nitrogen and sulfur components by coming into contact with the reducing atmosphere. The absorption capacity of the absorbent for NOx and SOx does not decrease.

In the present invention, if both NOx and SOx are present in the gas to be treated, the above-described reactions proceed in parallel, so that denitration and desulfurization can be performed simultaneously.

In the present invention, the contact of the absorbent with the oxidizing atmosphere and the contact of the reducing atmosphere may be performed alternately and repeatedly over time, but preferably, the contact of the oxidizing atmosphere with the absorbent is repeated. The contact with the reducing atmosphere is performed in parallel in time by structurally partitioning the contact surface of the absorbent with each atmosphere. That is, in this embodiment, since the absorbed nitrogen and sulfur components from the absorbent to the reducing atmosphere are released simultaneously with the removal of NOx and / or SOx from the oxidizing atmosphere by the absorbent, the NOx and / or SOx of the absorbent are removed.
Alternatively, the change with time of the SOx absorption capacity is small, and efficient operation can be performed.

In this embodiment, specifically, for example, an absorbent containing at least molten carbonate is held by a plate-like or sheet-like porous body, and one surface thereof is oxidized containing NOx and / or SOx. At the same time as the contact surface with the atmosphere gas and the other surface as the contact surface with the reducing atmosphere,
The porous body (hereinafter referred to as an absorbent holding porous body) separates the oxidizing atmosphere gas flow area and the reducing atmosphere gas flow area, that is, the porous body is an oxidizing atmosphere gas flow area. It can be easily implemented by using an apparatus to be described later having a structure in which one cell and a second cell, which is a flow area of the reducing atmosphere gas, function as a cell separator for hermetic sealing.

In this case, the direction of the flow of the reducing atmosphere gas relative to the flow of the oxidizing atmosphere gas is not particularly limited, and may be any of a parallel flow, a counter flow, and a cross flow.

On the other hand, in the case where the absorbent is alternately brought into contact with the oxidizing atmosphere and the reducing atmosphere in a temporally divided manner, it is not necessary to provide two contact surfaces for the molten carbonate, and only one contact surface may be used. . In this case, at least at the contact portion of the molten carbonate, the oxidizing atmosphere gas and the reducing atmosphere gas flow in the same system. Therefore, when switching the atmosphere, the flow of one atmosphere gas is stopped. After that, it is necessary to completely remove the atmospheric gas from the system once with an inert gas such as nitrogen gas, and then introduce the other atmospheric gas into the system.

In the present invention, NOx as a processing object
Although the gas containing SOx and / or SOx is not particularly limited, for example, a thermal power plant, a boiler,
Examples include flue gas from combustion plants such as industrial heating furnaces, and exhaust gas exhaust equipment for automobiles in tunnels.

In the present invention, an oxygen-containing gas such as pure oxygen or air is added to such a gas to be treated, if necessary, so as to provide an oxidizing atmosphere for the molten carbonate contained in the adsorbent. You. Further in an oxidizing atmosphere, it is desirable in achieving a long life of the suppressing absorber decomposition of carbonate the addition of CO _2, the molar ratio of CO ₂ with respect to O ₂ in the oxidizing atmosphere (O ₂ / Since the denitration and desulfurization efficiency decreases as the CO ₂ ) becomes smaller, it is not desirable to add a large amount of CO ₂ . O ₂ concentration or NOx and / or SOx in oxidizing atmosphere
It also depends on the concentration.

Further, the concentration of NOx and / or SOx in the oxidizing atmosphere brought into contact with the molten carbonate is not particularly limited. However, in an embodiment in which the reaction system is also used to generate power as a fuel cell, NOx and / or SOx must be at or below an allowable concentration, and NOx is about 20 to 50 ppm,
It is desirable that SOx be about 5 ppm.

In an oxidizing atmosphere, N ₂ , Ar, C
Gas components such as O ₂ and O ₂ can be contained, of which N ₂ can be contained up to about 70% by volume of the entire oxygen atmosphere gas.

On the other hand, a reducing atmosphere is composed of of _{H 2} as a main component, for example more than about 10 volume% of the total reducing atmosphere gas. The higher the H ₂ concentration in the reducing atmosphere, the higher the denitration and desulfurization efficiency.

In the reducing atmosphere, preferably, CO 2 is used.
_The addition of ₂ is desirable for suppressing the decomposition of carbonate and prolonging the life of the absorbent in the same manner as described above, and the addition of H ₂ O is desirable for preventing the precipitation of carbon. . For example, CO ₂ is blended as a gas at a rate of about 10% to about 60% by volume of the entire reducing atmosphere gas, and H ₂ O is blended as a gas at a rate of about 20% to about 35% by volume of the entire reducing atmosphere gas.

In the present invention, the carbonate contained in the absorbent is not particularly limited as long as it is stable and does not decompose in the contacting oxidizing atmosphere and reducing atmosphere. For example, various alkalis such as lithium, potassium and sodium are used. Metal carbonates, alkaline earth metal carbonates such as calcium, etc., each alone, or as a mixture of two or more of these compounds in any composition ratio, or as a eutectic salt of two or more components Can be used.

However, in an embodiment in which the reaction system is also used to generate electricity as a fuel cell, the conductivity is large, specifically, for example, 1.0 Ω ⁻¹ · cm ⁻¹ or more and the melting point is relatively low. Specifically, for example, the melting point is 5
Desirably, the temperature is 50 ° C. or lower, for example, a eutectic salt of lithium carbonate and potassium carbonate (melting point: 488 ° C.) in which Li and K are in a ratio of 62:38 (molar ratio), and Li: Na is 53:
It is desirable to use a eutectic salt of lithium carbonate and sodium carbonate at a ratio of 47 (molar ratio) (melting point: 496 ° C.).

The absorbent used in the present invention only needs to contain at least the above-mentioned carbonate, and may be constituted by the carbonate itself. Therefore, as described above, in an embodiment in which the oxidizing atmosphere and the reducing atmosphere are simultaneously brought into contact with the absorbent, in order to stably hold the molten carbonate at a predetermined site, It is desirable to impregnate a stable and large surface area support / porous body, preferably a plate-like or sheet-like porous body, with a carbonate.

The material constituting the porous body for holding the absorbent is not particularly limited. For example, gold, N
metals such as i and Pd, or γ-LiAlO ₂ , α-
It can be made of various materials such as metal oxides such as LiAlO ₂ and ZrO ₂ . However, in a mode in which the reaction system is also used to generate power as a fuel cell, the support or the porous body needs to be insulating, and it is preferable to use γ-LiAlO ₂ , α-LiAlO _2, or the like. . Further, when γ-LiAlO ₂ is used as a porous body, stability of LiAlO ₂ against carbonate (prevention of phase change, prevention of grain growth) is added by adding aluminum oxide, tungsten oxide, magnesium oxide, or the like.
Can be improved.

Further, in the present invention, the efficiency of desulfurization and denitration can be increased by further sandwiching the absorbent holding porous body with another porous body. These porous bodies increase the specific surface area of the reaction in an oxidizing atmosphere and a reducing atmosphere,
Has a catalytic action to promote the reaction. It is necessary to infiltrate the porous body with molten carbonate in an amount corresponding to about 20% to 40% of its own pore volume. Here, another porous body sandwiching the absorbent holding porous body may be the same material as the absorbent holding porous body, or may be a different material. That is, as long as the material is at least stable against molten carbonate (prevent phase change and prevent grain growth), even a material having an insulating property has conductivity such as a metal or a metal oxide. It may be something. When a conductive metal or metal oxide porous body is employed, the reaction system can be made to function as a fuel cell, and the gas to be treated can be purified and used for power generation at the same time. . In this embodiment, the metal or metal oxide (metal oxide is also required to be electrically conductive) porous body that sandwiches the absorbent holding porous body is indispensable in terms of a structure that causes a power generation reaction. Which has the above-mentioned catalytic action and also exhibits a current collecting function. The positive electrode side in contact with the oxidizing atmosphere is, for example, Ni
Various metal oxides having electronic conductivity such as O, CoO, MgO, and Au can be preferably exemplified by a metal porous body such as nickel, Au, and Pd on the negative electrode side in contact with the reducing atmosphere. .

In the present invention, the contact of the absorbent with the oxidizing atmosphere and the reducing atmosphere is performed in a temperature range in which the carbonate contained in the absorbent does not solidify or evaporate. This condition also depends on the type of carbonate used, the concentration of NOx and / or SOx contained in the oxidizing atmosphere, and the like. In addition, as the flow rate of the oxidizing atmosphere and the reducing atmosphere to be brought into contact with the absorbent, if the flow rate increases, the amount of denitration / desulfurization per unit time increases,
Since the removal efficiency decreases, the flow rate should be appropriately selected according to the desired removal rate.

In the present invention, in a mode in which the reaction system is also used to generate power as a fuel cell, the specific operating conditions for generating power as a fuel cell,
For example, it is necessary to satisfy operating temperature, gas temperature, gas composition, pressure difference between reducing atmosphere side and oxidizing atmosphere side, etc., and these operating conditions are based on technical contents known in the field of molten carbonate fuel cells. It can be set appropriately.

As described above, the treatment apparatus which can be suitably used in carrying out the method for removing nitrogen oxides and sulfur compounds according to the present invention comprises, as described above, an absorbent containing at least a molten carbonate. Held by a porous body,
One of the surfaces is a contact surface with an oxidizing atmosphere, the other surface is a contact surface with a reducing atmosphere, and the porous body has a structure in which a flow region of the oxidizing atmosphere and a flow region of the reducing atmosphere are partitioned. It is.

In this processing apparatus, the carbonate used, the porous sheet impregnated with the carbonate and the like are as described above.

Further, since the processing apparatus according to the present invention basically has the structure of a fuel cell, by satisfying the conditions required for a fuel cell, it is possible to simultaneously remove nitrogen oxides and sulfur compounds, and at the same time, as a fuel cell. It is possible to function.

FIG. 1 is a drawing schematically showing the structure of an embodiment of the gas processing apparatus according to the present invention in use. The gas processing apparatus according to this embodiment also has a function as a fuel cell, and includes two cells formed in a housing 10, that is, a processing gas supply pipe 6 and a processed gas exhaust pipe 7. And / or a first gas through which an oxidizing atmosphere gas 4 as a processing target gas containing NOx flows.
A second gas flow path comprising a cell 11, a reducing gas supply pipe 8 and a reducing gas exhaust pipe 9 for flowing a reducing atmosphere gas 8 containing hydrogen;
The cell 12 is airtightly partitioned by a porous body impregnated with molten carbonate, that is, an absorbent holding porous body 1.
Further, a metal porous body on the oxidizing atmosphere side (hereinafter referred to as an oxidizing atmosphere side porous body) is provided on both surfaces of the absorbent holding porous body 1.
3 and a metal porous body on the reducing atmosphere side (hereinafter referred to as a reducing atmosphere side porous body) 2. In the case of this device structure, it is possible to generate power as a fuel cell simultaneously with the removal of nitrogen oxides and sulfur compounds by further satisfying the operating conditions required for the fuel cell.

In this apparatus, the absorbent holding porous material 1
Occurs to the extent that the impregnated carbonate does not solidify or evaporate
Then, the gas 4 containing SOx and NOx is sent from the supply pipe 6.
When the gas reaches the first cell 11 of the apparatus, it is contained in the gas 4.
SOx and NOx are absorbed by the absorbent holding porous body 1.
The SOx is converted into sulfate ions in the porous material 1 holding the absorbent.
NOx and nitrate ions and
Converted to nitrite ions. And SOx and NOx
The removed and purified gas 4 'is discharged from the exhaust pipe 7.
You. On the other hand, on the second cell 12 side, the liquid is supplied from the supply pipe 8.
Contained in the reducing gas 5₂And sulfate ions and sulfuric acid
The yellow ions are reacted with H ions into the second cell 12.₂As S
Release and then H₂The nitrate ion and nitrite ion
And react with N ₂From the exhaust pipe 9₂S,
N₂Is discharged as a gas 5 ′ containing Like this
And always regenerate the carbonate that has absorbed SOx and NOx
Time change in desulfurization and denitration efficiency is small.
It becomes.

At the same time, in this apparatus, one molecule of hydrogen contained in the reducing atmosphere reacts with one carbonate ion of the absorbent holding porous body on the negative electrode side composed of the reducing atmosphere side porous body 2 to form water. And one molecule of carbon dioxide, and two electrons are sent to the electrode. The electrons pass through an external circuit (not shown) and reach the positive electrode composed of the porous body 3 on the opposite side of the oxidizing atmosphere. On the positive electrode side, one molecule of carbon dioxide and 分子 molecule of oxygen contained in the oxidizing atmosphere react with two electrons supplied from the electrode to generate one carbonate ion, and as a whole, one molecule of hydrogen and oxygen 1/2
Electric power is generated by a chemical reaction in which water is generated by molecules.

[0048]

EXAMPLES The present invention will be described below in more detail based on examples.
Will be described. (Example 1) Lithium carbonate and potassium carbonate as absorbents
Using a molten carbonate mixed with a molar ratio of 62:38.
Lithium aluminum as a porous body for holding the absorbent
Neato (0.9mm thickness x 110m length x 110mm width, empty
A porosity of 60% and a center pore diameter of 2 μm) were used. Oxidizing atmosphere
NiO (0.9 mm thick x 110 mm long x 1)
(10mm width, porosity 50%, center pore diameter 6μm)
Ni (0.9 mm thickness x 11)
0 mm length x 110 mm width, porosity 54%, central pore diameter 5
μm) was used. Central empty space for easier retention of absorbent
Minimal pore size, repels molten carbonate more than NiO
Reduction made of Ni with easy (wetting) property
The atmosphere side porous body has the largest pore diameter. still,
The operating temperature is 650 ° C. Also, supply gas for oxidizing atmosphere
Composition (volume ratio, hereinafter the same) is N₂/ CO₂/ O₂= 5
5/60/15, SO₂10 ppm, gas flow rate 1046
ml / min. The feed gas composition in the reducing atmosphere is H
₂/ CO₂/ H₂O = 64/16/20, gas flow rate 32
7 ml / min. The desulfurization efficiency under these conditions is almost
Stable at about 100%. (Example 2) Using the device used in Example 1, the operating temperature was
The temperature was set at 650 ° C. The supply gas composition of the oxidizing atmosphere is N₂
/ CO₂/ O₂= 55/60/15, NOx20pp
m, gas flow rate is 1046 ml / min. Reducing atmosphere
Gas composition at H₂/ CO ₂/ H₂O = 64/16
/ 20 and a gas flow rate of 327 ml / min. This condition
The denitration efficiency in was stable at about 60%. Figure 2
3 shows the time change of the nitrate efficiency.

Further, it has a function as a fuel cell, and generates power at an output density of 1.3 kW / m ² . Example 3 Using the apparatus used in Example 1, the operating temperature was 650 ° C., and the supply gas composition in a reducing atmosphere was H ₂ / CO _2.
/ H ₂ O = 64/16/20, gas flow rate 1046 ml /
min. Further, the feed gas composition of the oxidizing atmosphere _{N 2 / CO 2 / O 2} = 55/60/15, NOx20
The relationship between the denitration efficiency and the gas flow rate is shown in FIG. As the supply gas flow rate on the oxidizing gas atmosphere side increases, the absolute amount of denitration per unit time increases, but the denitration efficiency decreases. (Example 4) Using the apparatus used in Example 1, the gas composition on the oxidizing atmosphere side was changed and the change in the denitration efficiency was measured. The supplied NOx concentration is 50 ppm. FIG. 4 shows the obtained results.
Shown in As shown in FIG. 4, the denitration efficiency increases as the O ₂ / CO ₂ ratio increases.

The change in the denitration efficiency was measured by changing the H ₂ concentration in the reducing atmosphere. The results obtained are shown in FIG.
As shown in FIG. 5, the higher the H ₂ concentration, the higher the denitration efficiency.

[0051]

As described above, the present invention is expected to be a method having stable desulfurization and denitration efficiency, capable of converting nitrogen oxides into harmless substances, and simultaneously desulfurization and denitration. In addition, when the processing device has a specific structure, electricity can be obtained as a fuel cell simultaneously with desulfurization and denitration operations.

[Brief description of the drawings]

FIG. 1 is a drawing schematically showing a structure in a use state of an embodiment of a gas processing apparatus according to the present invention.

FIG. 2 is a graph showing a time change of the denitration efficiency obtained in the example of the present invention.

FIG. 3 is a graph showing a relationship between denitration efficiency and an oxidizing atmosphere gas flow rate obtained in an example of the present invention.

FIG. 4 is a graph showing the relationship between the denitration efficiency and the ratio of O ₂ / CO ₂ in the oxidizing atmosphere gas obtained in the example of the present invention.

FIG. 5 is a graph showing a relationship between denitration efficiency and H ₂ concentration in a reducing atmosphere gas obtained in an example of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 Porous material holding absorbent 2 Porous material on reducing atmosphere 3 Porous material on oxidizing atmosphere 4 Gas to be treated in oxidizing atmosphere containing SOx and NOx 4 'Gas purified by removing SOx and NOx 5 Reducing property containing hydrogen Gas 5′H ₂ S, reducing gas that carries out N ₂ 10 Housing of gas treatment device 11 First cell 12 Second cell

Claims (11)

[Claims] 1. An oxygen-containing gas is added to a gas to be treated containing nitrogen oxides, if necessary, to bring the gas into contact with an absorbent containing at least molten carbonate as an oxidizing atmosphere. Contacting the absorbent with a reducing atmosphere composed of a hydrogen-containing gas to separate nitrogen oxides from the gas. 2. An oxygen-containing gas is added as necessary to a gas to be treated containing a sulfur oxide, and the gas is brought into contact with an absorbent containing at least a molten carbonate as an oxidizing atmosphere. Contacting the absorbent with a reducing atmosphere consisting of a hydrogen-containing gas to remove sulfur compounds from the gas. 3. An oxygen-containing gas is added to a gas to be treated containing nitrogen oxides and sulfur oxides as needed, and the gas is brought into contact with an absorbent containing at least molten carbonate as an oxidizing atmosphere, A method for removing nitrogen oxides and sulfur compounds in a gas, comprising separating the absorbent from a contact with the oxidizing atmosphere and contacting the absorbent with a reducing atmosphere comprising a hydrogen-containing gas. 4. The method according to claim 1, wherein the contact of the oxidizing atmosphere and the contact of the reducing atmosphere with respect to the absorbent are performed in parallel in time by structurally partitioning the contact surface of the absorbent with respect to each atmosphere. The method according to any one of claims 1 to 3, characterized in that: 5. The method according to claim 1, wherein the contact of the oxidizing atmosphere and the contact of the reducing atmosphere with the absorbent are performed repeatedly alternately in a time-separated manner. . 6. The method according to claim 1, wherein carbon dioxide gas is added to the oxidizing atmosphere, and carbon dioxide gas and water are added to the reducing atmosphere. Method. 7. An electrolyte layer is formed with an absorbent containing at least a molten carbonate, one surface of the electrolyte layer is brought into contact with the oxidizing atmosphere as a positive electrode, and the other surface is brought into contact with the reducing atmosphere as a negative electrode. The method according to any one of claims 1 to 4, wherein the gas to be treated is purified and simultaneously generated as a fuel cell. 8. The method according to claim 1, wherein the gas to be treated containing nitrogen oxides and / or sulfur compounds is flue gas discharged from a combustion plant. 9. An apparatus used in the method according to claim 1, wherein the absorbent is formed by a porous body impregnated with a molten carbonate, and one surface of the porous body is formed with an oxidizing atmosphere. Gas treatment characterized by having a structure in which a contact surface and a contact surface with the reducing atmosphere are used as a contact surface with the reducing atmosphere, and a flow region of the oxidizing atmosphere and a flow region of the reducing atmosphere are separated by the porous body. apparatus. 10. The gas processing apparatus according to claim 9, wherein the porous body impregnated with the absorbent has a structure in which both sides of the porous body are sandwiched by another porous body. 11. The another porous body sandwiching the porous body impregnated with the absorbent is made of metal or metal oxide, and the combustion exhaust gas discharged from a combustion plant is introduced into the oxidizing atmosphere while The reducing gas containing hydrogen is introduced into the reducing atmosphere to purify the gas to be treated and to function as a fuel cell.
The gas processing apparatus according to any one of the preceding claims.