KR101863940B1 - Method and apparatus for denoxing exhaust gas - Google Patents

Abstract

Disclosed are a method and an apparatus for removing nitrogen oxide from exhaust gas. The disclosed method for removing nitrogen oxide from exhaust gas includes a step (S10) of bringing the nitrogen oxide-containing exhaust gas in contact with ozone at room temperature to partially oxidize the nitrogen oxide in the exhaust gas, thereby generating first process gas. The method and apparatus for removing nitrogen oxide from exhaust gas of the present invention can remove nitrogen oxide at room temperature without using a catalyst in high efficiency.

Description

[0001] The present invention relates to a method and apparatus for removing nitrogen oxides from exhaust gases,

A method and apparatus for removing nitrogen oxides from exhaust gases are disclosed. More particularly, a method and apparatus for highly efficiently removing nitrogen oxides from an exhaust gas at ambient temperature in a non-catalytic manner is disclosed.

Nitrogen oxides are collectively referred to as NO, NO ₂ , NO ₃ , N ₂ O and N ₂ O ₅ , but the NO _x concentration as an air quality control item means a sum of NO concentration and NO ₂ concentration.

In the industries such as power generation, incineration and steel, NO _x is mainly generated. Such NO _x is a thermal NO _x generated in a high temperature combustion condition, and most of the NO _x exists in NO form.

1 shows a selective catalytic reduction (SCR) apparatus 10 for removing NO _x from conventional exhaust gases.

Referring to FIG. 1, a conventional selective catalytic reduction apparatus 10 includes a reactor 11, a catalyst 12, and a reducing agent injection nozzle 13.

A selective catalytic reduction device 10 is a universal device which is evaluated as NO _X removal efficiency is very high, exhaust gas (G _in) using a reducing agent (usually NH ₃₎ with the catalyst 12 at a temperature of 200 ~ 400 ℃ (NO) and NO ₂ in the exhaust gas to N ₂ to generate a clean gas (G _out ).

Although the selective catalytic reduction apparatus 10 has an advantage that the NO _x treatment efficiency is stable, it has a problem that the performance and life of the catalyst deteriorate when the catalyst price is high and the particulate matter or poisoning component exists _{in the} exhaust gas .

Further, when the temperature of the exhaust gas (G _in ) is low, it is necessary to use fuel for preheating the exhaust gas (G _in ) _in order to maintain an appropriate catalytic oxidation temperature.

On the other hand, in the case of a selective noncatalytic reduction (SNCR) apparatus (not shown) similar to the selective catalytic reduction apparatus 10 of FIG. 1 but not using a catalyst, High, NO _X The removal rate is as low as about 60%, and if the internal temperature of the reactor exceeds 1,100 ° C, there is a risk of causing NO _x .

2 is a view showing a conventional NO _X removal technology LoTOX ™ device 20 using the ozone oxidation.

Referring to FIG. 2, the LoTOX ™ device 20 includes an ozone generator 21, an oxidation chamber 22, and a wet scrubber 23.

The LoTOX (TM) device 20 is an apparatus invented by the BOC group and currently owned by the Linde group. The LoTOX (TM) device 20 injects the exhaust gas G _in and ozone O ₃ generated in the ozone generator 21 into the oxidation chamber 22 NO _{x in} the exhaust gas (G _in ) is converted to N ₂ O ₅ And this N ₂ O ₅ is injected into the wet scrubber 23 and wet-rinsed with an alkaline cleaning liquid to remove it in the form of nitric acid.

A clean gas (G _out ) containing no NO _X is discharged from the wet scrubber (23).

A similar device to the LoTOX ™ device 20 is the denitration device for exhaust gas disclosed in Korean Patent No. 10-1474979 of Korea Institute of Machinery and Materials.

The above-mentioned conventional NO _x The removal devices are well reacted at very low temperatures, have a high NO _x removal efficiency, and are small in size. Further, the reaction _{(NO + O 3 → NO 2} + O 2) which NO is oxidized to NO ₂ by ozone conversion takes place very well. However, in such devices, in the reaction NO ₂ is oxidized by the ozone that is converted to _{N 2 O 5 (2NO 2 +} O 3 → N 2 O 5 + O 2) to fully remove the NO ₂ at room temperature (about 25 ℃) (O ₃ ) of 3 times or more of the NO ₂ content based on the stoichiometric amount is required, and as a result, the excess ozone component is discharged to the outside of the apparatus, as shown in FIG.

One embodiment of the present invention provides a method for highly efficiently removing nitrogen oxides from an exhaust gas at room temperature in a non-catalytic manner.

Another embodiment of the present invention provides an apparatus for highly efficiently removing nitrogen oxides from an exhaust gas at room temperature in a non-catalytic manner.

According to an aspect of the present invention,

And a step (S10) of contacting the nitrogen oxide-containing exhaust gas with ozone at room temperature to partially oxidize the nitrogen oxide in the exhaust gas to generate a first process gas (S10).

The exhaust gas contains NO and NO ₂ , and the amount of the ozone used in the first process gas generating step (S 10) is adjusted to such an extent that NO and NO ₂ in the exhaust gas are not converted to N ₂ O ₅ by 100% The first process gas may contain NO ₂ and N ₂ O ₅ .

The first process gas production step (S10) may be carried out under the absence of a catalyst.

The nitrogen oxide removal method from the exhaust gas further includes a step (S20) of generating the second process gas by bringing the first process gas into contact with the first process gas containing water after the first process gas generating step (S10) , in the second process gas generating step (S20) the first processing N ₂ O ₅ contained in the gas is converted into HNO _3, wherein the HNO ₃ is separated from the second process gas together with the first washing liquid, and wherein said 2 The process gas may contain NO ₂ .

The first cleaning liquid may be alkaline or neutral.

The nitrogen oxide removal method from the exhaust gas further comprises a step (S30) of generating a clean gas by bringing the second process gas into contact with the second cleaning solution containing a reducing agent after the second process gas generating step (S20) the clean gas generation step (S30) wherein the NO ₂ in the second process gas to NO ₂ ^- Ions. ≪ / RTI >

Wherein the second cleaning liquid is alkaline or neutral and the reducing agent is selected from the group consisting of Na ₂ SO ₃ , Na ₂ S, Na ₂ S ₂ O ₃ , Na ₂ C ₂ O ₄ , FeSO ₄ (NH ₄ ) ₂ SO ₄ , .

According to another aspect of the present invention,

Ozone generator;

An oxidation chamber for partially oxidizing nitrogen oxides in the exhaust gas at room temperature using ozone generated in the ozone generator to generate a first process gas;

A first wet scrubber for cleaning the first process gas discharged from the oxidation chamber with a first cleaning liquid containing water to generate a second process gas; And

And a second wet scrubber for cleaning the second process gas discharged from the first wet scrubber with a second rinse solution containing a reducing agent to generate a clean gas.

The oxidation chamber may convert NO and NO ₂ to NO ₂ and N ₂ O ₅ by partial oxidation with the ozone.

The oxidation chamber may not include a catalyst.

The oxidation chamber may refer to the duct itself, which is a passage through which the exhaust gas flows into the first scrubber.

The first scrubber may convert N ₂ O ₅ to HNO ₃ by reacting with water.

Wherein the second scrubber reacts NO ₂ with the reducing agent to form NO ₂ ^- Ion. ≪ / RTI >

The method and apparatus for removing nitrogen oxides from exhaust gas according to an embodiment of the present invention are characterized in that the fuel is not consumed for raising the reaction temperature due to the reaction at room temperature, No facility is required, NO _x can be treated with high efficiency, no excess ozone is required, and the use amount of the reducing agent can be minimized.

1 is a view showing a selective catalytic reduction apparatus for removing NO _x from a conventional exhaust gas.
2 is a view showing a LoTOX ™ apparatus which is a conventional NO _x removal technique using ozone oxidation.
3 is a view showing an apparatus for removing nitrogen oxide from exhaust gas according to an embodiment of the present invention.

Hereinafter, a method for removing nitrogen oxides from an exhaust gas according to an embodiment of the present invention will be described in detail.

As used herein, the term " exhaust gas " means a waste gas discharged from a power generation, incineration or steel making facility.

As used herein, " nitrogen oxide " means a material commonly referred to as NO _x .

As used herein, " NO _X " means a mixture of NO and NO ₂ .

As used herein, " ambient temperature " means the temperature of the ambient air in the range of 10 to 40 DEG C, for example, in the range of 25 to 30 DEG C.

As used herein, "partial oxidation" refers to a chemical reaction that incompletely oxidizes nitrogen oxides having a low oxygen content ratio to produce nitrogen oxides having a high oxygen content ratio.

As used herein, the term " process gas " means a gas obtained by partially removing nitrogen oxides in an exhaust gas.

In the present specification, "clean gas" means a gas obtained by completely removing nitrogen oxide in the exhaust gas.

A method for removing nitrogen oxide from exhaust gas according to an embodiment of the present invention includes the steps of contacting a nitrogen oxide-containing exhaust gas with ozone (O ₃ ) at room temperature to partially oxidize the nitrogen oxide in the exhaust gas to generate a first process gas (Step S10).

The first process gas production step (S10) is a step of removing all of NO and optionally a part of NO ₂ from the exhaust gas.

The exhaust gas may contain NO and NO _2.

NO is not dissolved in water at all, and NO ₂ is dissolved only in water in a small amount. Thus, NO and NO ₂ are not removed by simple wet scrubbing.

The oxidized NO ₃ than NO ₂ has a high solubility in water, reacts with ozone or oxygen is converted to N ₂ O _5.

The amount of the ozone used in the first process gas generating step (S10) can be adjusted to such a degree that NO and NO ₂ in the exhaust gas are not 100% converted to N ₂ O ₅ . That is, the use amount of the ozone can be adjusted so that the reaction represented by the following reaction formula 1 occurs.

[Reaction Scheme 1]

_{2NO + NO 2 + O 3 →} NO 2 + N 2 O 5

As shown in Scheme 1, residual ozone may not be present after the partial oxidation reaction. Specifically, the step of generating the first processing gas (S10) The NO and NO ₂ are all of N ₂ O, as opposed to using a large excess of ozone to be converted to _5, equivalents required for complete oxidation (i.e., a stoichiometric amount) of NO Only ozone is used. That is, NO is the reactivity with ozone is very high reaction with ozone and preferentially as compared to NO ₂ and, even if the residual ozone is present after the reaction with NO, because such residual ozone is NO ₂ and further reaction, the residual ozone is little or present at all .

As described above, the first part of the process gas generation step (S10) in all of the NO and NO ₂ contained in the exhaust gas is oxidized to NO _2, and may be a N ₂ O ₅ produced.

The first process gas may contain NO ₂ and N ₂ O ₅ .

Also, as described above, the first process gas may contain little or no ozone and NO.

The first process gas production step (S10) may be carried out under the absence of a catalyst.

The nitrogen oxide removal method may further include, after the first process gas production step (S10), the step (S20) of contacting the first process gas with the first process liquid containing water to generate a second process gas.

The second process gas generating step (S20) is a step for removing N ₂ O ₅ from the first process gas.

Specifically, in the second process gas generating step (S20) is the first processing N ₂ O ₅ contained in the gas can be converted to HNO ₃ reacts with water. That is, in the second process gas generating step S20, the reaction represented by the following reaction formula 2 may occur.

[Reaction Scheme 2]

N ₂ O ₅ + H ₂ O → HNO ₃

Referring to Reaction Scheme 2, N ₂ O ₅ produced in the first process gas producing step (S 10) is highly water-soluble and easily converted to HNO ₃ by contact with water.

HNO ₃ thus generated can be separated from the second process gas together with the first rinse solution since it exists in a state dissolved in water.

The first cleaning liquid may be alkaline or neutral. Specifically, the first rinsing liquid may be water or an aqueous solution obtained by dissolving an alkaline agent in water.

The alkaline agent may include calcium hydroxide, ammonia, sodium hydroxide, potassium hydroxide or a combination thereof.

The second process gas may contain NO ₂ .

Further, the second process gas may contain little or no ozone, NO, and N ₂ O ₅ .

The nitrogen oxide removal method may further include a step (S30) of generating a clean gas by contacting the second process gas with a second rinse solution containing a reducing agent after the second process gas generating step (S20).

Clean gas generation step (S30) is a step of removing NO ₂ from the second process gas.

More specifically, in the clean-gas generation step (S30) wherein the NO ₂ in the second process gas NO ₂ ^- Ion (nitrite ion). The NO ₂ ^- Ions can be dissolved and removed in the second cleaning liquid. That is, in the clean gas generating step S30, the reaction represented by the following reaction formula 3 may occur.

[Reaction Scheme 3]

NO ₂ + reducing agent → NO ₂ ^- Ion + by-product

Also, in the clean gas generating step S30, the reducing agent can be removed by converting the excess ozone into oxygen by using the reducing agent even in the presence of excess ozone in the second processing gas.

The second cleaning liquid may be alkaline or neutral. Specifically, the second cleaning liquid may be water or an aqueous solution obtained by dissolving an alkali agent and a reducing agent in water.

The alkaline agent contained in the second cleaning liquid may be the same as the alkaline agent contained in the first cleaning liquid.

The reducing agent may comprise _{Na 2 SO 3, Na 2 S} , Na 2 S 2 O 3, Na 2 C 2 O 4, FeSO 4 (NH 4) 2 SO 4 , or a combination thereof.

When Na ₂ SO ₃ having a relatively low reduction efficiency is used as the reducing agent, the use amount thereof may be increased.

When using the relative Na ₂ S high reduction efficiency as the reducing agent, the amount used can be reduced, but the second do not maintain the pH of the washing liquid increased to more than 10, a hydrogen sulfide (H ₂ S) severe odors May occur. That is, the water is dissociated in Na ₂ S 2 from a cleaning liquid, and Na ⁺ ions present in the state of S ^2- ions (i.e., Na ₂ S → 2Na ⁺ + S ^2-), the S ^2- ion is pH Is less than 10, it can be converted to hydrogen sulfide (H ₂ S) by reacting with water.

Further, the clean gas may contain little or no NO, NO ₂ , N ₂ O _5, and O ₃ .

Hereinafter, an apparatus for removing nitrogen oxides 30 from an exhaust gas according to an embodiment of the present invention will be described in detail with reference to FIG.

The nitrogen oxide removal device 30 from the exhaust gas according to an embodiment of the present invention may include an ozone generator 31, an oxidation chamber 32, a first scrubber 33 and a second scrubber 34 .

The ozone generator 31 is a device for converting oxygen to ozone. For example, the ozone generator 31 is commercially available, and is a device for concentrating oxygen at a high concentration from ambient air and then passing the concentrated oxygen through a voltage-applied electrode (not shown) to generate ozone .

The ozone generator 31 can convert less than 10% (molar basis) of the concentrated oxygen to ozone. Therefore, a mixed gas of oxygen and ozone can be discharged from the ozone generator 31 and supplied to the oxidation chamber 32.

The oxidation chamber 32 is an apparatus for generating a first process gas by partially oxidizing nitrogen oxides (NO, NO _2, etc.) _in the exhaust gas G _in at room temperature by using ozone generated in the ozone generator 31. That is, the oxidation chamber 32 is a device for partially oxidizing NO and NO ₂ to the NO ₂ and N ₂ O ₅ by the ozone.

The oxidation chamber 32 may also convert NO and NO ₂ to NO ₂ and N ₂ O ₅ by partial oxidation of NO and NO ₂ using oxygen introduced from the ozone generator 31 in addition to ozone.

The oxidation chamber 32 may not contain a catalyst.

The oxidation chamber 32 may refer to a duct itself which is a passage through which the exhaust gas flows into the first scrubber 33. However, the present invention is not limited thereto, and the oxidizing chamber 32 may be a separate chamber communicating with the duct.

The nitrogen-containing compound in particular, the exhaust gas (G _in), after it is injected into the oxidation chamber 32, an oxidation chamber (32) containing oxygen and a gas mixture and nitrogen oxides of the ozone discharged from the ozone generator 31, May be partially oxidized by reacting with the ozone and / or oxygen. The amount of ozone supplied from the ozone generator 31 to the oxidation chamber 32 is an amount required for complete oxidation of NO contained in the exhaust gas G _in , It can be limited to an amount such that the process gas does not contain unreacted ozone.

The first wet scrubber 33 is an apparatus for cleaning the first process gas discharged from the oxidation chamber 32 with a first cleaning liquid containing water to generate a second process gas.

Specifically, the first scrubber 33 is a device for converting N ₂ O ₅ into HNO ₃ by reacting with water. The HNO ₃ is separated from the second process gas while being mixed with the first rinse solution.

The second wet scrubber 34 is an apparatus for cleaning the second process gas discharged from the first wet scrubber 33 with a second cleaning liquid containing a reducing agent to generate a clean gas G _out .

Specifically, the second scrubber 34 reacts NO ₂ with the reducing agent to form NO ₂ ^- Ion.

Also, even when excess ozone exists in the second process gas, the second scrubber 34 can be removed by reducing the excess ozone with the reducing agent to convert it to oxygen.

The structure of the first wet scrubber 33 and the second scrubber 34 is not particularly limited and may be any structure as long as nitrogen oxide can be removed from the inflow gas through gas-liquid contact.

For example, the first wet scrubber 33 and / or the second scrubber 34 may comprise a filler or a porous filter, and may not include such a filler and a porous filter.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these embodiments.

Example

Experimental Example  1: Temperature dependent NO _X  Oxidation test

NO _x oxidation test was performed according to the temperature and ozone injection amount in the range of 25 ° C to 200 ° C. As a result of the test, the initial about 200 ppm (by volume) of NO contained in the exhaust gas is oxidized to NO ₂ as the amount of ozone is increased, and the NO ₂ concentration is further oxidized to N ₂ O ₅ by ozone . The conversion of NO to N ₂ O ₅ (ie, the reduction of NO _x ) occurs at lower temperatures and at higher temperatures, it decreases significantly. This is because at higher temperatures, N ₂ O ₅ is decomposed into NO ₂ and NO ₃ This is because the reaction is activated.

Experimental Example  2: Depending on the amount of ozone injected NO _X  Oxidation test

In order to remove more than 90% of NO _x even at 25 ° C, about 600 ppm (by volume) of ozone, ie about three times as much as the initial NO _x (ie NO), is required, . Hundreds of ppm (by volume) of NO _x arising from the etching process in the production process of semiconductors or some of the displays' products is NO: NO ₂ In some cases 3 as the amount of NO ₂ is higher than the content of NO: ratio of 1: 1 to 1. The exhaust gas containing NO _x was sampled at various points in the actual semiconductor field, and the ozone gas generated by the ozone generator was directly contacted with the exhaust gas. The test results are shown in Table 1 below. In the following Table 1, each unit is expressed in ppm (by volume).

No. Content before reaction need
O ₃ content The input O ₃
content Content after reaction Variation NO NO ₂ NO _X NO NO ₂ NO _X O ₃ Exhausted
O ₃ NO _X Oxidation amount One 115 219 334 282 88 38 218 256 2.4 85.6 116 2 55 239 295 202.5 375 0 136 136 170 205 134.5 3 141 0 141 211.5 70.3 56 6 72 0 70.3 119.5 4 13 48 61 43.5 12 0 28 28 0 12 29.5

The ozone oxidation reaction is summarized in the following Schemes 1-1 and 1-2.

[Reaction Scheme 1-1]

NO + O ₃ ? NO ₂ + O ₂

[Reaction Scheme 1-2]

2NO ₂ + O ₃ ? N ₂ O ₅ + O ₂

Assuming that NO is completely converted into NO ₂ in Scheme 1-1, the amount of ozone necessary to completely oxidize the entire NO _x can be calculated by Equation 1 below.

[Equation 1]

Required O ₃ content (ppm) (by volume) = NO + 0.5 (NO + NO ₂ ) = NO + 0.5NO _X

In addition, NO model suggests that the change in the NO _X concentration reaction can be oxidized to NO _2, NO ₂ reaction is oxidized to N ₂ O ₅ is NO _X The amount of NO _x oxidized by the oxidation reaction can be calculated as shown in the following equation (2).

&Quot; (2) "

NO _x oxidation amount =? NO + 0.5 x? NO _x

In Equation 2, ΔNO; means the amount of NO is oxidized to NO _2, and ΔNO _X is the amount that the oxidized NO ₂ to N ₂ O _5.

From the results in Table 2, it can be seen that the exhaust gas collected at the site may be influenced by other components besides NO _x , but the following fact can be confirmed.

First, when a smaller amount of ozone than the necessary amount of ozone is injected, it is understood that the stoichiometric amount of NO _x is oxidized by 30% or more and more than 2 times more than the amount of ozone consumed (Test No. 1 , 3 and 4). Thus, the phenomenon that NO _x is oxidized at a stoichiometric amount more than the amount of ozone consumed can be explained as follows: the gas generated in the ozone generator is composed of 10 mol% ozone and most of the remaining oxygen It is presumed that this oxygen is converted into a state of higher activity than oxygen in general ambient air while passing through the electrode provided in the ozone generator, thereby oxidizing NO much faster than oxygen in ordinary ambient air.

Second, when the power is applied to the ozone in 1.5 times excess ozone content than required, but rather was in a content less than the stoichiometric amount of NO _X exhausted ozone oxidation proceeds, it can also be seen that the excess ozone concentration was high (Sample No. 2).

Experimental Example  3: Depending on the amount of reducing agent injected NO _X  Oxidation test

A wet scrubber for processing a semiconductor exhaust gas containing NO _X: when the operation input to the reducing agent is Na ₂ SO ₃ in the (washing solution pH 7 to more than 10 NaOH aqueous solution in the range), the front end of the wet scrubber and the rear end NO _X The measurement results are shown in Table 2 below. In Table 2, " ORP " means an oxidation-reduction potential.

Operating condition NO ₂ ORP (mV) shear
(ppm) (by volume) Rear end
(ppm) (by volume) Treatment efficiency
(%) 45 65 34.4 47 -112.5 48.8 1.9 96.2 -112.5 42.3 3 92.9 -17.5 58.5 19 67.5

The reducing agent is Na ₂ SO ₃ dissolved in the cleaning liquid Na ⁺ ions and SO ₃ ^2- ions are dissociated, SO ₃ ^2- ions giving electrons to NO ₂ by the radical reaction are NO ₂ NO ₂ in the gas ^phase-ionic form And then dissolved and removed in the cleaning liquid. That is, the reaction shown in the following Reaction Scheme 3-1 occurs.

[Reaction Scheme 3-1]

SO ₃ ^2- + NO ₂ → NO ₂ ^- + SO ₃ ^- (anion radical)

However, since the reducing agent Na ₂ SO ₃ reacts with oxygen in the air or oxygen dissolved in the cleansing water in addition to NO ₂ , the reducing agent is not added in a stoichiometric amount but can be sufficiently retained in the cleansing water , The ORP should be used as a measurement standard.

From the test results in Table 2, it can be seen that when the reducing agent is administered such that the ORP is maintained at -100 mV or lower, the NO ₂ removal rate exceeds 90%. However, the present invention is not limited thereto. The appropriate ORP satisfying the removal rate of NO ₂ may vary depending on the components of the exhaust gas to be treated, the quality of the cleaning liquid, and the like. have.

Referring to Table 1 and Table 2, while keeping the excess ozone, rather than for the complete oxidation of NO ₂ to N ₂ O _5, by introducing only enough ozone to remove the NO using the residual NO _X reducing agent at the trailing wet It was found that cleaning is a method capable of achieving NO _x removal of 90% or more at room temperature conditions.

Unlike exhaust gas generated in power generation, iron manufacturing, and incineration, exhaust gas generated in the etching process at the semiconductor or display production stage is at normal temperature and contains dust particles. Therefore, ozone injection, ozone oxidation, The wet cleaning method is more suitable for these conditions.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, . Accordingly, the scope of protection of the present invention should be determined by the appended claims.

30: nitrogen oxide removal device 31: ozone generator
32: oxidation chamber 33, 34: wet scrubber
G _in : Exhaust gas G _out : Clean gas

Claims (13)

(S10) of contacting the nitrogen oxide-containing exhaust gas with ozone at room temperature to partially oxidize the nitrogen oxide in the exhaust gas to generate a first process gas,
The exhaust gas contains NO and NO ₂ , and the amount of the ozone used in the first process gas generating step (S 10) is adjusted to such an extent that NO and NO ₂ in the exhaust gas are not converted to N ₂ O ₅ by 100% the first process gas is how NOx removal from the exhaust gas containing NO ₂ and N ₂ O _5. delete The method according to claim 1,
The first process gas production step (S10) is performed under the absence of a catalyst. The method according to claim 1,
Further comprising the step (S20) of bringing the first process gas into contact with the first process liquid containing water after the first process gas production step (S10) to generate a second process gas,
In the second process gas generating step (S20) the first processing N ₂ O ₅ contained in the gas it is converted into HNO _3,
The HNO ₃ is separated from the second process gas together with the first rinsing liquid,
The second process gas is how NOx removal from the exhaust gas containing NO _2. 5. The method of claim 4,
Wherein the first cleaning liquid is an alkaline or neutral exhaust gas. 5. The method of claim 4,
Further comprising a step (S30) of generating a clean gas by contacting the second process gas with a second cleaning solution containing a reducing agent after the second process gas generating step (S20)
The clean gas generation step (S30) wherein the NO ₂ in the second process gas to NO ₂ ^- And removing the nitrogen oxide from the exhaust gas. The method according to claim 6,
Wherein the second cleaning liquid is alkaline or neutral and the reducing agent is selected from the group consisting of Na ₂ SO ₃ , Na ₂ S, Na ₂ S ₂ O ₃ , Na ₂ C ₂ O ₄ , FeSO ₄ (NH ₄ ) ₂ SO ₄ , And removing nitrogen oxides from the exhaust gas. Ozone generator;
An oxidation chamber for partially oxidizing nitrogen oxides in the exhaust gas at room temperature using ozone generated in the ozone generator to generate a first process gas;
A first wet scrubber for cleaning the first process gas discharged from the oxidation chamber with a first cleaning liquid containing water to generate a second process gas; And
And a second wet scrubber for cleaning the second process gas discharged from the first wet scrubber with a second cleaning liquid containing a reducing agent to generate a clean gas,
Wherein the oxidation chamber partially oxidizes NO and NO ₂ to the NO ₂ and N ₂ O ₅ by the ozone. delete 9. The method of claim 8,
Wherein the oxidation chamber is a catalyst-free exhaust gas. 9. The method of claim 8,
Wherein the oxidation chamber refers to the duct itself which is the passage through which the exhaust gas enters the first wet scrubber. 9. The method of claim 8,
Wherein the first wet scrubber is configured to react N ₂ O ₅ with water to convert it to HNO ₃ . 9. The method of claim 8,
The second wet scrubber reacts NO ₂ with the reducing agent to form NO ₂ ^- Ion into the exhaust gas.

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