JP2517799B2 - Electrochemical exhaust gas treatment system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention treats harmful gases such as nitrogen oxides (NO _x ) contained in industrial exhaust gas by an electrochemical reaction to render them harmless and electrons generated by an electrochemical redox reaction. according to a preferred electrochemical exhaust gas treatment system to remove efficiently by concentrating the CO ₂ in the combustion exhaust gas and converts into - the electrical energy taken out to an external circuit.

[0002]

2. Description of the Related Art Nitrogen oxides (N
When released into the atmosphere, O _x ) becomes a source of acid rain and photochemical smocks, and its emission regulations are strictly regulated due to pollution problems and global environmental problems. Further, carbon dioxide (CO ₂ ) and the like are attracting attention as substances causing global warming and depleting the ozone layer, and emission control is an urgent issue.

Exhaust gas from a thermal power plant, exhaust gas from a high temperature gas turbine, etc., contains several hundred to several thousand ppm of NO _x ,
On the other hand, CO ₂ is contained in the range of several% to several tens%. The methods conventionally proposed for removing NO _x in exhaust gas are roughly classified into a wet method and a dry method. The wet method is mainly an absorption and adsorption method, and NO is oxidized into NO ₂ and absorbed and dissolved in an alkaline aqueous solution. In this case, the oxidation is O ₃ or Cl in the gas phase.
O ₂ is used, and KMnO ₄ , NaClO ₂ or HNO ₃ is used in the liquid phase. Also, an absorption method using an iron (II) complex solution has been proposed, but all of the absorption methods have problems in the post-treatment method of the absorption solution.

On the other hand, a molten salt absorption method utilizing the reaction between alkali molten salt and NO has been proposed (Pollution prevention equipment and equipment editing committee bias: Pollution prevention equipment and equipment dictionary, P459), but NO is oxidized to NO ₂ . means for requires performs outside the absorption and regeneration of nO in the molten state can not be obtained even there high NOx removal efficiency problem of low oxidation rate, etc. for the low concentration nO _X containing gas, such as flue gas Therefore, it is not effective as a large-volume exhaust gas treatment method.

In the dry method, the catalytic cracking method and the selective reduction method are mainly used.
And the former is Co₃O_Four, YBa ₂Cu₃For Oy catalyst
More NO_xIs a method of directly catalytically decomposing. The latter is V
Selective reduction denitration with ammonia using O-TiO catalyst
Is the law. Also, NO₂To NO by electrochemical reaction
A reduction method is proposed in JP-A-51-86735.
Have been. According to the proposed method, phosphoric acid or sulfuric acid was used
Proton conductive electrolyte fuel cell NO₂NO
NO after returning₂The method of oxidizing and recycling
And NO in combustion exhaust gas_xTo reduce and render harmless
Can not.

By the way, NO _{x in the} exhaust gas of general boilers
NO ₂ is several ppm to several tens of ppm, and NO is several tens of p
The proposed method is not suitable as a method for detoxifying NO _x in the combustion exhaust gas, since it is in the range of pm to several hundreds of ppm and overwhelmingly contains NO. Furthermore, Stanley H. et al. Have attempted to introduce NO _x and SO _x in the exhaust gas of thermal power plants to the cathode side of a proton conductive electrolyte fuel cell using an acid electrolyte (En
vironmental Progress (Vol.5, No.4). In this method, it is necessary to use an expensive precious metal catalyst for the electrode, and it is difficult to carry out a large-volume exhaust gas treatment.

Although various flue gas denitration methods have been proposed as described above, only the selective reduction denitration method using ammonia is currently put into practical use. On the other hand, the CO ₂ treatment method includes an alkali absorption method, an amine absorption method, a calcium oxide adsorption method, a zeolite adsorption method, and the like. Development of concentration technology is desired.

[0008]

NO _x , CO ₂ and SO _x contained in industrial exhaust gas must be removed as much as possible from pollution problems and global environmental problems. An object of the present invention is to electrochemically reduce NO _x contained in exhaust gas and the like using a system similar to a molten carbonate fuel cell to render it harmless, and at the same time, generate electrons along with an electrochemical reaction in an external circuit. It is to take out and generate power, and to efficiently remove CO ₂ from large-capacity exhaust gas and the like by utilizing the CO ₂ concentration effect accompanying the electrochemical reaction.

[0009]

As shown in FIG. 1, the object of the invention is to sandwich the carbonate conductive electrolyte 1 and the anode 2 between them.
And a cathode 3 are arranged, and an anode separator 4 and a cathode separator 5 for supplying a reaction gas to each of the anode 2 and the cathode 3 are provided to form a unit cell, and a cathode side of the cell is formed. NO _x and CO ₂ containing gas 7 is supplied to the anode, and reducing gas 6 such as H ₂ is supplied to the anode, and the following (formula 1) to (formula 3) or (formula 4) is used. This can be achieved by carrying out an electrochemical redox reaction represented by the formula (6).

1) When NO _x is NO Cathode: NO + CO ₂ + 2e-→ CO ₃ ^2- + 1 / 2N ₂ --------- (Chemical formula 1) Anode: H ₂ + CO ₃ ^2- ──── → H ₂ O + CO ₂ ＋ 2e -------- (Chemical formula 2) Overall: NO + H ₂ ───── → H ₂ O + 1 / 2N ₂ --------- -(Chemical formula 3) 2) When NO _x is NO ₂ Cathode: NO ₂ + 2CO ₂ + 4e → 2CO ₃ ^2- + 1 / 2N ₂ ------- (Chemical formula 4) Anode: 2H ₂ + 2CO ₃ ² --> 2H ₂ O + 2CO ₂ + 4e ----- (Chemical formula 5) Overall: NO ₂ + 2H ₂ ---> 2H ₂ O + 1 / 2N ₂ --------- (Chemical formula 6) That is, in the cathode, electrons are obtained from an external circuit and NO _x
Is reduced to N ₂ and CO ₂ is oxidized to CO ₃ ²⁻ ions. CO ₃ ²⁻ ions move to the anode through the electrolyte. At the anode, CO ₃ ^2- ions are converted into CO by H _2.
It is reduced to ₂ and generates electrons. The electrons are taken out to an external circuit and are returned to the cathode. Here, the electron flow taken out to the external circuit is used as electric energy by providing a load on the way.

[0011] cathode - If CO ₂ and NO _x is supplied to the de is mixed with a large amount of N _2, etc., the N ₂ and the like which do not participate in the electrochemical reaction as cathode - flow out of the system than the de outlet, C
Since O ₂ selectively moves to the anode side, a high concentration of CO ₂ is obtained at the anode outlet. Therefore, when this system is applied, CO ₂ can be substantially concentrated and CO ₂ treatment becomes easy.

By the way, this system can be realized by CO ₃ ²⁻ ion conduction from the cathode side to the anode side.
In the present invention, carbonate is used as the ion conductive electrolyte.
As the carbonate, one or a mixture of two or more selected from lithium carbonate, potassium carbonate, sodium carbonate, barium carbonate, strontium carbonate, calcium carbonate and the like is preferable, and a eutectic mixture having a melting point lowering is particularly preferable. .
By using an ion conductive electrolyte fuel cell based on a carbonate as an electrolyte, a base metal can be used for the electrode. Further, since the battery operating temperature is as high as 650 ° C., high temperature combustion exhaust gas can be directly introduced,
This is a desirable form as an effective utilization system of waste heat.

Furthermore, the inventors of the present invention have repeatedly studied the cathode in order to efficiently carry out the electrochemical reduction reaction of NO _{x in} the cathode, and as a result, the porosity is 50 to 80 vo.
It has been found that 1% of a porous electron conducting oxide is effective. When the porosity is 50 vol% or less, the reaction gas is not sufficiently diffused inside the electrode and the performance is deteriorated. Also, 80 vol
%, The electrode strength remarkably decreased, which was not preferable. As the electron conductive oxide, the first component is nickel oxide or cobalt oxide, and the second component is one or two selected from silver, lithium, chromium, copper, iron and aluminum. Composite oxide electrodes formed with more than one metal or oxide showed good performance. The addition amount of the second component is preferably 0.5 to 20 wt% (wt%), and if less than 0.5 wt%, the effect of addition is small.
When it exceeded 20 wt%, an increase in electrical resistance and a decrease in electrode activity were observed for components other than silver. When silver exceeds 20 wt%, a slight decrease in electric resistance is recognized, but there is no particular change in electrode activity.

On the other hand, a porous metal electrode or a porous composite electrode having a porosity of 40 to 75 vol% is effective as an electrode for efficiently carrying out the electrochemical reduction reaction of CO ₃ ²⁻ ions in the anode. there were. Porosity is 40 vol
If it is less than%, the reaction gas is not sufficiently diffused inside the electrode and the performance is deteriorated. On the other hand, if it exceeds 75 vol%, the number of voids in the electrode increases, the amount of the electrode catalyst per unit area decreases, and a sufficient reaction cannot proceed. As the material of the porous metal electrode or the porous composite electrode, the first component is nickel or copper, and the second component is one or more metals selected from aluminum, zirconium, magnesium and yttrium. Alternatively, it is formed by an oxide. Here, the purpose of adding the second component is to stably exhibit the electrode activity for a long period of time, and an alloy or an intermetallic compound composed of the first component and the second component is preferable, but the second component is in the form of an oxide. A composite electrode dispersed in the first component may be used. The addition amount of these second components is 2 to 50 wt%, preferably 2 to 20 wt%. If it is less than 2 wt%, the purpose of addition cannot be achieved. If it exceeds 50 wt%, the electrode activity is lowered, which is not preferable.

By the way, NO is included in general combustion exhaust gas.
O ₂ coexists with ₃ to 10 vol% in addition to _x and CO ₂ . O
The coexistence of ₂ is rather convenient for obtaining high electric energy. When such NO _x , CO ₂ and O ₂ are mixed, it is presumed that the electrochemical redox reaction of the cathode proceeds as shown in the following equation. _{NO + 1 / 2O 2 + 2CO} 2 + 4e─ → 2CO 3 2- + 1 / 2N 2 - oxidation of the (Formula 7) According to the NO _x and O ₂ CO ₂ becomes as follows, formation free energy in the reaction - ( ΔG)
It is as follows when is calculated by adopting the Janaf Thermochemical Tables value.

2NO + 2CO ₂ + 4e ---> 2CO ₃ ^2- + N -------------- (Chem. 8) NO ₂ + 2CO ₂ + 4e ---> 2CO ₃ ^2- + 1 / 2N --- ------ (Chemical formula 9) O ₂ + 2CO ₂ + 4e --- → 2CO ₃ ^2- -------------------- (Chemical formula 10) Free energy generated -((DELTA) G) is (Formula 8) Formula -------------. DELTA.G: 21.6kcal / mol (Formula 9) Formula -------------. DELTA.G: 29.8kcal / mol. (of 10) --------- ΔG: 40.5kcal / mol if presumed easily proceed balanced manner as the value of .DELTA.G is small (.DELTA.G at 650 ° C.), electrochemical for CO ₂ The oxidation reaction is NO> NO ₂ > O ₂
It is expected that the above will be prioritized in this order, and the selective reduction reaction of NO _x proceeds.

Electrochemical Hazardous Gas Treatment System of the Invention
At, in order to extract a large amount of electric energy
Stoichiometry just by introducing combustion exhaust gas directly into the cathode
May be insufficient. In such a case, from the outside
It can be solved by supplementing the lacking gas. Also, the combustion exhaust gas
CO etc.₂CO₃ ^2-Necessary to oxidize to ions
Required NO_xAnd O₂If the two do not coexist, see Figure 2.
As shown in FIG.
It is effective to take the throat and supply it to the cathode. O
₂Supply amount is NO_xCombustion varies slightly depending on the amount of coexisting
CO in exhaust gas ₂1/2 mol equivalent is enough
Is. Also, as shown in FIG.
The purpose can be achieved even if the sodium 8 is added and supplied to the cathode.
You.

By the way, in the anode, a reducing gas such as H ₂ or CO is supplied so that CO ₃ ²⁻ ions are electrochemically converted to CO _{2 2.}
Reduce to. As the anodic gas, H ₂ rich gas obtained by reforming natural gas or naphtha, coal gasification gas containing a large amount of CO, and the like can be applied. As described above, since the anodic exhaust gas contains a high concentration of CO ₂ , it is possible to efficiently collect the CO ₂ in the combustion exhaust gas by installing a CO ₂ device in the anodic gas exhaust line as shown in FIG. It will be possible. It is preferable that the recovered CO ₂ is recycled to the cathode side for effective use in order to improve power generation efficiency.

The method of recovering CO ₂ is not particularly limited, and the conventional alkali absorption method or calcium carbonate adsorption method,
The PSA method or the like can be applied. Generally, C is contained in the combustion exhaust gas.
In addition to O ₂ , O ₂ , NO _x , N _2, etc., SO _x and dust are contained. It is preferable that SO _x and dust that adversely affect the cathode be removed in advance and then supplied to the cathode side.

[0020]

A cell is constructed by arranging an anode and a cathode and an ion conductive electrolyte between them, and a harmful gas containing nitrogen oxides (NO _x ) and CO _2, etc. is supplied to the cathode side. , A reducing gas such as H ₂ is supplied to the anode side to promote an electrochemical redox reaction to reduce NO _{x and the} like to N ₂ and electrons generated by the redox reaction to an external circuit. It is taken out and converted into electric energy.

As another method of using the present invention, by applying an oxidation active catalyst to the cathode, it is possible to electrochemically oxidize NO and absorb it in a molten carbonate to remove NO in exhaust gas. Is.

[0022]

【Example】

[0023]

[Example 1] 10 wt% with an anodized porosity of 70 vol%
% Al-remaining Ni electrode is used, and the cathode has a porosity of 75 vo
A 1% 5 wt% Ag-remaining NiO electrode was used, and a Li ₂ CO ₃ + K ₂ CO ₃ (62:38 molar ratio) mixed carbonate was impregnated into a 1.7 mm thick porous lithium aluminum plate as an electrolyte. Thus, a single cell having an electrode area of 64 cm ² was constructed. After raising the temperature of this cell to 650 ° C., 20 vol.
% NO-20 vol% CO ₂ -remaining N ₂ mixed gas and 50 vol% H ₂ -remaining N ₂ mixed gas were supplied to the anode at 500 ml / min, respectively, and a power generation test was conducted. FIG. 5 shows the result of obtaining the relationship between the load current density and the voltage. A mixed gas of NO and CO ₂ was supplied to the cathode, and an electrochemical reaction proceeded to obtain electric energy.

[0024]

Example 2 cathode during power generation test by the cell used in Example 1 - was a quantitative analysis of the NO _x to de exit of gas using a chemiluminescence analyzer. The analysis results are shown in Table 1, and a high denitration rate was obtained.

[0025]

[Table 1]

[0026]

Example 3 In this example, a cathode electrode was examined. A porous Ni sintered plate was impregnated with silver nitrate, lithium nitrate, chromium nitrate, copper nitrate, iron nitrate, and aluminum nitrate as metal oxides in amounts of 5 wt% each as a second component, dried, and then dried in air at 800 ° C. 2 hours after firing for 1 hour
A component type NiO + α electrode was prepared. These electrodes had a thickness of about 0.7 mm and a porosity of 68 to 71 vol%. These electrodes are used as cathodes, and the anode is 10 wt% Al-having a thickness of 0.65 mm and a porosity of 68 vol%.
The remaining Ni electrode was used and the electrolyte was Li ₂ CO ₃ + K ₂ CO.
₃ (62:38 molar ratio) mixed carbonate was impregnated into a 1.9 mm thick porous lithium aluminum plate to form an electrode area of 64
A single cell of cm ² was constructed. After raising the temperature of this cell to 650 ° C., 20 vol% NO-20 vol% C was added to the cathode.
O ₂ -remaining N ₂ mixed gas, 50 vol% H for anode
_A power generation test was performed by supplying each of the _2- remaining N ₂ mixed gas at 500 ml / min. Table 2 shows the results of analyzing the cell voltage and the NO ₂ concentration at the cathode outlet at a load current density of 90 mA / cm 2.

[0027]

[Table 2]

[0028]

Example 4 In this example, an anode electrode was examined. A porous nickel sintered plate was impregnated with aluminum nitrate, zirconyl nitrate, magnesium nitrate, and yttrium nitrate as the second component in an amount of 8 wt% as a metal oxide and dried, and then 800 ° C. in H ₂ atmosphere at 0.5 ° C. Burned for hours. These electrodes have a thickness of about 0.6 mm and a porosity of 6
It was 5-69 vol%. With these electrodes as anodes, the cathode has a thickness of about 0.7 mm and a porosity of 70 v.
ol% of 5 wt% Ag-remaining NiO is used, and the electrolyte is L
A single cell having an electrode area of 64 cm ² was constructed by impregnating a porous lithium aluminum plate having a thickness of 1.9 mm with a mixed carbonate of i ₂ CO ₃ + K ₂ CO ₃ (62:38 molar ratio). This cell was heated to 650 ° C. in the same manner as in Example 3 and then charged.
20 vol% NO-20 vol% CO ₂ -remaining N ₂ mixed gas was supplied to the anode and 50 vol% H ₂ -remaining N ₂ mixed gas was supplied to the anode at 500 ml / min, respectively, and a power generation test was conducted. Table 3 shows the results of analyzing the cell voltage and the NO _x concentration at the cathode outlet at a load current density of 90 mA / cm.

[0029]

[Table 3]

[0030]

[Embodiment 5] 10 wt% with an anodized porosity of 70 vol%.
% Al-remaining Ni electrode is used, and the cathode has a porosity of 75 vo
A 1% 5 wt% Ag-remaining NiO electrode was used, and as the electrolyte, a mixed carbonate of Li ₂ CO ₃ + K ₂ CO ₃ (62:38 molar ratio) was used to form a porous lithium aluminum alloy having a thickness of 1.7 mm.
A single plate having an electrode area of 100 cm ² was constructed by impregnating the plate.

After raising the temperature of this cell to 650 ° C.
2 vol% NO-14 vol% O-30 vol%
CO ₂ -remaining N ₂ mixed gas at 460 ml / min,
The de 80vol% H ₂ - 164ml remaining N ₂ mixed gas
/ Min supply was performed and the power generation test was conducted. Load current density 15
Cell voltage at 0 mA / cm 2, NO concentration at cathode outlet gas, and CO ₂ concentration at anode outlet gas (dry)
Table 4 shows the measurement results. An electric output of 12 watts, a denitrification rate of 99% and a CO ₂ concentration gas of 62% were obtained.

[0032]

[Table 4]

[0033]

[Embodiment 6] 2% by weight of porosity of 65 vol% in anode
Using MgO-remaining Ni electrode, the cathode has a porosity of 75 vo
1% of 2 wt% Li ₂ O-remaining NiO electrode was used as the electrolyte, and a mixed carbonate of Li ₂ CO ₃ + K ₂ CO ₃ (62:38 molar ratio) was used as a porous lithium aluminum alloy having a thickness of 1.5 mm.
A single plate having an electrode area of 100 cm ₂ was constructed by impregnating the plate.

After raising the temperature of this cell to 650 ° C.
0.012 vol% NO simulating boiler-exhaust gas
-7vol% O₂-12vol% CO₂-Remaining N₂Mixed moth
1150 ml / min, LNG reforming model for anode
70vol% H as pseudo gas ₂-11vol% H₂O-
Remaining N₂Power generation test by supplying 187 ml / min of mixed gas
Did.

Table 5 shows the results of measuring the cell voltage and the NO concentration of the cathode outlet gas at a load current density of 150 mA / cm ² . A cell voltage of 0.75 V and a denitration rate of 99% or more were obtained.

[0036]

[Table 5]

[0037]

[Embodiment 7] FIG. 6 shows an example in which the electrochemical exhaust gas treatment system of the type shown in Embodiments 1 to 6 is used as an electrochemical treatment system for combustion exhaust gas of a thermal power plant. As shown in the figure, this system introduces fuel 14 and air 19 into a boiler 15 and burns them to generate steam to operate a steam turbine 21. The combustion exhaust gas is purified by the dust collector 16 and the desulfurization device 17, and then introduced into the cathode 3 of the cell. On the other hand, the H ₂ rich gas produced by the fuel reformer 18 is introduced into the anode ₂ of the cell to promote an electrochemical redox reaction to take out an electric current. A CO ₂ removal device 11 is provided in the anode discharge line 10 to reduce CO
Collect ₂ . A part of the recovered CO ₂ is returned to the cathode 3 through the CO ₂ gas supply line 13. Also, the air 1
9 is added to the combustion exhaust gas by the air supply line 20.
With this system, nitrogen oxides (NO
_x ) and other harmful gases are treated by an electrochemical reaction to make them harmless, and electrons generated by the electrochemical redox reaction are taken out to an external circuit to be converted into electric energy and CO ₂ in the combustion exhaust gas is concentrated. Can be efficiently removed.

[0038]

Embodiment 8 FIG. 7 similarly shows a system for electrochemically treating the exhaust gas of a high temperature gas turbine. The air 19 is pressurized by the compressor 24 and introduced into the high temperature gas turbine 22 together with the fuel 14 to drive the generator 23, and the combustion exhaust gas is introduced into the cathode 3 of the cell. On the other hand, the fuel reformer 1
The H ₂ rich gas produced in No. 8 is introduced into the anode ₂ of the cell to promote the electrochemical redox reaction to take out an electric current. CO ₂ removal device 11 in the anode discharge line 10
Is provided to collect CO ₂ . Some of the recovered CO ₂ is CO
_{2 The} gas is supplied to the cathode 3 through the gas supply line 13. Further, the air 19 is added to the combustion exhaust gas by the air supply line 20. This system detoxifies harmful gases such as NO _x in high temperature gas turbine exhaust gas with high nitrogen oxide (NO _x ) content by electrochemical reaction and also generates electrons by electrochemical redox reaction in an external circuit. CO in the combustion exhaust gas as well as being converted into electric energy
₂ can be concentrated and removed efficiently.

[0039]

According to the present invention, harmful gases such as nitrogen oxides (NO _x ) contained in industrial exhaust gas are treated by an electrochemical reaction to render them harmless and electrons generated by an electrochemical redox reaction. Is taken out to an external circuit to be converted into electric energy, and CO ₂ in the combustion exhaust gas can be concentrated and removed efficiently.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a unit cell used in an exhaust gas treatment system of the present invention.

FIG. 2 is a schematic sectional view of a unit cell when air is added to combustion exhaust gas.

FIG. 3 is a schematic cross-sectional view of a unit cell when a combustion exhaust gas is added to air.

FIG. 4 is a diagram showing an overall configuration of an exhaust gas treatment system of the present invention.

FIG. 5 is a diagram showing a relationship between load current density and voltage of a test cell.

FIG. 6 is a diagram showing an electrochemical treatment system for combustion exhaust gas from a thermal power plant according to the present invention.

FIG. 7 shows an electrochemical treatment system for high temperature gas turbine exhaust gas according to the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication C25B 5/00 B01D 53/34 135Z H01M 8/06 ZAB 8/14 (72) Inventor Yoshio Iwase Ibaraki 4026 Kujimachi, Hitachi, Ltd., Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor, Kazuo Iwamoto 4026, Kujicho, Hitachi, Hitachi, Ibaraki, Hitachi, Ltd. 4026, Hitachi, Ltd., Hitachi Research Laboratory (72) Inventor, Shigeoki Nishimura, Kujimachi, Hitachi City, Ibaraki Prefecture 4026, Hitachi, Ltd., Hitachi Research Laboratory (56) Reference JP-A-3-106418 (JP, A)

Claims (3)

(57) [Claims] 1. An anode and a cathode and an intervening element therebetween .
That ion conducting electrolyte and the anode - de and cathode - separator for supplying a reactant gas to de - motor constitutes a cell composed installed, the ion-conducting electrolyte is lithium carbonate, Ca
Ium, sodium carbonate, barium carbonate, strontium carbonate
Mixed charcoal of two or more selected from thium and calcium carbonate
The cathode is a porous electrically conductive oxide.
The first component is nickel oxide and the second component is
Select from silver, lithium, chrome, copper, iron, aluminum
Composed of one or more metals or oxides
However, a harmful gas containing nitrogen oxide (NO _x ) and carbon dioxide (CO ₂ ) is supplied to the cathode side, and the anodic side is supplied with the harmful gas.
A reducing gas such as hydrogen (H ₂ ) is supplied to promote an electrochemical redox reaction to reduce NO _x to N ₂ and at the same time, electrons generated by the redox reaction are taken out to an external circuit and converted into electric energy. An electrochemical exhaust gas treatment system characterized by: 2. A porous metal electrode or a porous composite electrode is used as the anode, and the porous metal electrode or the porous composite electrode comprises a first component made of nickel or copper and aluminum, zirconium, magnesium, and The electrochemical exhaust gas treatment system according to claim 1, wherein the electrochemical exhaust gas treatment system is formed by a second component composed of one or more metals or oxides selected from yttrium. 3. A gas containing NO _x , CO ₂ , and O ₂ is supplied to the cathode side, and a gas containing H ₂ and CO is supplied to the anode side in a temperature range of 500 to 800 ° C. Caso
Detoxification treatment of NO _x by advancing an electrochemical reduction reaction of NO _x and an electrochemical oxidation reaction of CO _{2 in} the cathode, and an electrochemical reduction reaction of CO ₃ ²⁻ ion in the anode. The method according to claim 1 or 2, characterized in that
The electrochemical exhaust gas treatment system according to.