JP2008100193A - Method of treating nitrogen oxide-containing gas and apparatus for treating nitrogen oxide-containing gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently remove nitrogen oxide contained in nitrogen oxide-containing gas. <P>SOLUTION: Before a nitrogen oxide-containing gas G<SB>1</SB>is brought into contact with a treatment liquid F, O<SB>2</SB>is mixed with a treatment liquid F. The treatment liquid F and the nitrogen oxide-containing gas G<SB>1</SB>are adjusted not to contain an alkaline agent. Further, the flow rate of O<SB>2</SB>at the time of mixing O<SB>2</SB>with the treatment liquid F is adjusted to be 50% by volume of the flow rate of the treatment liquid after mixing O<SB>2</SB>. O<SB>2</SB>is mixed with the treatment liquid F in form of bubbles. The temperature of the treatment liquid F is adjusted to be about 0°C to 25°C. After the nitrogen oxide-containing gas G<SB>1</SB>is brought into contact with the treatment liquid F, if the waste liquid is recovered and made reusable as the treatment liquid, a concentrated sulfuric acid can be produced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a nitrogen oxide-containing gas processing method and a nitrogen oxide-containing gas processing apparatus.

Nitrogen oxide-containing gas containing nitrogen oxides (NO _X), the exhaust gas of an automobile, dissolution treatment of metals, drainage processing of nitric acid, occurs in various cases. Nitrogen oxides in such gases have a wide range of adverse effects on ecosystems and human bodies. For this reason, attempts have been made to remove nitrogen oxides in the nitrogen oxide-containing gas. For example, a photocatalytic method using a photocatalyst, a soil air purification method that decomposes nitrogen using microorganisms such as denitrifying bacteria in the soil, a nitrogen oxide using water (H ₂ O), ammonia (NH ₃ ), etc. There are treatments (wet cleaning) for cleaning the contained gas (see Patent Documents 1, 2, and 3).

For example, Patent Document 3 proposes wet cleaning using ammonia. That is, in a reaction vessel (first treatment chamber) where oxygen (O ₂ ) is initially present, nitrogen oxide is nitrated by contacting ammonia, which is an alkaline agent, with the nitrogen oxide-containing gas, Ammonium nitrate (NH ₄ NO ₃ ) is produced. Thereafter, the nitrogen oxide-containing gas containing ammonium nitrate is introduced into a gas-liquid contact portion (second treatment chamber) having a packed bed, and water or hydrogen peroxide water (H ₂ O) is introduced in the gas-liquid contact portion. ₂ ) etc., a method of supplying cleaning water (treatment liquid), capturing ammonium nitrate in the cleaning water, and separating and recovering it has been proposed.

JP 2005-118681 A JP 2000-140575 A JP 11-137959 A

By the way, in the conventional wet cleaning method (Patent Document 1), nitric acid (HNO ₃ ) is generated when cleaning water is supplied in the gas-liquid contact portion. That is, the nitrogen remaining in the nitrogen oxide-containing gas can be recovered as nitric acid. However, when nitric acid is generated and oxygen present in the gas-liquid contact portion is consumed, nitric acid is not actively generated. Therefore, in order to promote the production of nitric acid, it is necessary to supply oxygen. For example, before introducing the nitrogen oxide-containing gas into the gas-liquid contact portion, a large amount of nitrogen oxide-containing gas is required. It is conceivable to mix oxygen (O ₂ ). However, in this case, the flow of the nitrogen oxide-containing gas is energized by the mixing of oxygen, and the flow at the gas-liquid contact portion becomes excessively fast. Therefore, there is a concern that the contact efficiency between the nitrogen oxide-containing gas and the cleaning water in the gas-liquid contact portion decreases, and as a result, the nitric acid recovery efficiency decreases. That is, even if oxygen is blown into the nitrogen oxide-containing gas in an attempt to improve the nitrogen oxide removal efficiency, the nitric acid recovery efficiency may be reduced and the nitrogen oxide removal efficiency may be reduced. Thus, in the conventional wet cleaning method, it is difficult to improve the nitrogen oxide removal efficiency.

  This invention is made | formed in view of said point, and provides the nitrogen oxide containing gas processing method which can improve the removal efficiency of nitrogen oxide, and a nitrogen oxide containing gas processing apparatus. With the goal.

In order to solve the above-mentioned problem, according to the present invention, a processing method for removing nitrogen oxide from the nitrogen oxide-containing gas by bringing a treatment liquid into contact with the nitrogen oxide-containing gas, the nitrogen oxide-containing gas A nitrogen oxide-containing gas treatment method is provided, wherein O ₂ is mixed with the treatment liquid before contacting the treatment liquid with gas.

The treatment liquid and the nitrogen oxide-containing gas may not contain an alkali agent. Further, the flow rate of the processing liquid to the O ₂ wherein O ₂ at the time of mixing may be less than or equal to 50 vol% of the flow rate of the treatment liquid after mixing the O _2. The O ₂ may be mixed with the treatment liquid in the form of bubbles. The temperature of the treatment liquid may be 0 ° C to 25 ° C. Further, the concentration of nitrogen oxide in the nitrogen oxide-containing gas may be 10,000 ppm by volume or more.

  When the treatment liquid is brought into contact with the nitrogen oxide-containing gas, the direction in which the nitrogen oxide-containing gas flows and the direction in which the treatment liquid flows may be opposite to each other.

  Further, after the treatment liquid is brought into contact with the nitrogen oxide-containing gas, the waste liquid may be collected and reused as the treatment liquid.

Furthermore, according to the present invention, a processing apparatus that removes nitrogen oxide from the nitrogen oxide-containing gas by bringing a treatment liquid into contact with the nitrogen oxide-containing gas, wherein the processing unit processes the nitrogen oxide-containing gas. When a nitrogen oxide-containing gas introduction path for introducing the nitrogen oxide-containing gas into the processing unit, the processing liquid supply path for supplying the processing solution to the processing unit, and O ₂ supply path for supplying O ₂ wherein the processing liquid supply passage, said O processing liquid in a state in which O ₂ supplied was mixed with ₂ supply path, and supplying to the processing unit, the nitrogen oxide-containing gas treatment apparatus Is provided.

  The processing unit may include a packed bed. The direction in which the nitrogen oxide-containing gas passes through the packed bed and the direction in which the treatment liquid passes through the packed bed may be opposite to each other.

Furthermore, you may provide the cooler which cools the said process liquid. Further, the O ₂ supply path may be connected to the processing liquid supply path.

  You may comprise the circulation line which introduces the waste liquid of the said process part into the said process liquid supply path. For example, a tank for storing the processing liquid may be provided, and the processing liquid supply path and the drainage path of the processing unit may be connected to the tank.

According to the present invention, by mixing O ₂ with the treatment liquid, nitric acid can be efficiently generated when the treatment liquid is brought into contact with the nitrogen oxide-containing gas, thereby removing the nitrogen oxides. it can. O ₂ can be efficiently supplied to improve nitrogen oxide removal efficiency.

  Moreover, the concentration of nitric acid in the treatment liquid (drainage liquid) can be increased by reusing the waste liquid obtained after the removal of nitrogen oxides as the treatment liquid and using it again for the removal treatment of nitrogen oxides. That is, it is possible to generate a highly concentrated nitric acid-containing aqueous solution (concentrated nitric acid) by repeatedly using the treatment liquid for removing nitrogen oxides.

Furthermore, according to the present invention, nitrogen oxides can be removed with a simple configuration without using special agents such as an alkali agent (such as ammonia), a catalyst, and an adsorbent. The nitric acid-containing aqueous solution obtained in such a configuration is mainly composed of water and nitric acid (HNO ₃ ), and does not contain extra substances such as alkali agents. That is, it is possible to produce a nitric acid-containing aqueous solution that can be easily used for other industries.

Hereinafter, an example of an embodiment according to the present invention will be described. FIG. 1 shows a processing apparatus 1 as a nitrogen oxide-containing gas processing apparatus (nitrogen oxide removal processing apparatus and nitric acid-containing aqueous solution generation apparatus) according to this embodiment. This processing apparatus 1 performs wet denitration treatment of a gas to be treated G ₁ as a nitrogen oxide-containing gas by contacting a treatment liquid F (F ₁ ) in which oxygen gas (O ₂ ) is contained in water (H ₂ O). And a treatment liquid F ₂ (exhaust gas) containing a low nitrogen concentration gas G ₂ (exhaust gas) with reduced nitrogen oxide concentration and nitric acid (HNO ₃ ) as a product after treatment. Liquid).

As shown in FIG. 1, the processing apparatus 1 includes a spray tower 2. The internal space of the tower body 2a of the spray tower 2 has a processing unit 3 for denitration process the gas to be treated G ₁ (reaction section). The processing unit 3 is provided with a packed bed 5 in which a denitration reaction is performed by gas-liquid contact between the gas to be processed G ₁ and the processing liquid F ₁ . Also connected to the spray tower 2 are a gas introduction path 11 as a nitrogen oxide-containing gas introduction path for introducing the gas G ₁ to be treated to the processing section 3 and a treatment liquid supply path 12 for supplying the treatment liquid F _1. Has been. Furthermore, an exhaust path 15 from the processing unit 3 to discharge the low nitrogen concentration gas G _2, etc., and, the drainage path 16 for discharging the treatment liquid F _2, etc. from the processing unit 3 is provided. Below the column body 2a, a tank 17 for storing the treatment liquid F ₀ is established.

The processing unit 3 is formed in a vertically long space, for example. The packed bed 5 is configured to allow the gas G ₁ to be processed and the processing liquid F ₁ to pass therethrough. The direction in which the gas to be processed G ₁ passes through the packed bed 5 and the direction in which the processing liquid F ₁ passes through the packed bed 5 are configured to be opposite to each other (counterflow). In the illustrated example, the gas to be treated G ₁ rises, the treatment liquid F ₁ is configured to descend. In addition, as the filling layer 5, for example, a filler that forms the filling layer 5 may be formed of a synthetic resin, ceramic, or the like, or may be formed of, for example, a cylindrical shape or a columnar shape. .

  An outlet end (downstream end) of the gas introduction path 11 is opened at a lower end side wall of the tower body 2 a and is provided below the packed bed 5. The gas introduction path 11 is provided with an on-off valve 11 a that communicates and blocks the gas introduction path 11.

The outlet end (downstream end) of the processing liquid supply path 12 is provided above the packed bed 5. The outlet end of the treatment liquid supply passage 12, the spray nozzle 21 for spraying the treatment liquid F ₁ in the fine particulate is provided. The spray port of the spray nozzle 21 is oriented so as to spray the processing liquid F ₁ downward, that is, to spray on the upper surface of the packed bed 5.

Outside the tower body 2 a, the upstream end of the processing liquid supply path 12 is connected to the tank 17. A pump 22 is interposed in the processing liquid supply path 12. Further, the treatment liquid supply channel 12, _{O 2 O 2} supply path 31 for supplying the gas is connected. In the illustrated example, the O ₂ supply path 31 is connected to the downstream side of the pump 22. O ₂ supply path 31, the flow control valve 31a for performing a flow control of the _{O 2} passing through the _{O 2} in the supply path 31 is provided.

  The inlet end (upstream end) of the exhaust passage 15 is opened at the ceiling of the tower body 2 a and is provided above the packed bed 5 and the spray nozzle 21. On the other hand, the drainage passage 16 is opened at the bottom of the tower main body 2 a and is provided below the exit ends of the packed bed 5 and the gas introduction passage 11.

The tank 17 is provided below the tower main body 2a in the illustrated example. The downstream end of the drainage path 16 is connected to the tank 17. In the illustrated example, the drainage passage 16 is provided so as to extend straight from the bottom of the tower body 2a downward. The downstream end (lower end opening) of the drainage passage 16 is opened near the bottom surface of the tank 17. That is, when the processing liquid F ₀ is stored in the tank 17, so that the treatment liquid F ₀ enters in drains 16. In this way, becomes a state where the lower end of the drain passage 16 is sealed by the treatment liquid F _0, the atmosphere in the processing section 3 can be prevented from leaking to the outside through drains 16, improved safety To do.

For example, a cooler 40 is provided on the side wall of the tank 17. In the present embodiment, the cooler 40 cools the processing liquid F ₀ in the tank 17, thereby cooling the processing liquid F ₁ supplied to the processing unit 3 through the processing liquid supply path 12. Has been.

  Furthermore, a tank water supply path 41 that supplies water (for example, pure water) to the tank 17 is connected to the tank 17. The tank water supply passage 41 is provided with an on-off valve 41 a for connecting and blocking the tank water supply passage 41.

The tank 17 is provided with a tank drain path 42 for discharging the processing liquid F ₀ from the tank 17. The tank drain passage 42 is provided with an open / close valve 42 a that communicates and shuts off the tank drain passage 42. The downstream end of the tank drain path 42 is connected to a recovery unit 43 that stores the processing liquid F ₀ (nitric acid-containing aqueous solution) discharged from the tank 17.

In this embodiment, the processing liquid F (F ₀ , F ₀₎ in the processing apparatus 1 is constituted by the tank 17, the H ₂ O-containing liquid supply path 31, the processing liquid supply path 12, the processing unit 3, and the drainage path 16. ₁ , F ₂ ) is circulated. The circulation line 50 is configured so that the drainage liquid (processing liquid F ₂ ) of the processing unit 3 can be collected and introduced again into the processing liquid supply path 12 and reused as the processing liquid F ₁ .

Next, a nitrogen oxide-containing gas treatment method (a nitrogen oxide removal method and a nitric acid-containing aqueous solution generation method) using the treatment apparatus 1 configured as described above will be described. First, in the processing apparatus 1 before the processing takes place, the water supplied by the tank water supply path 41 (eg pure water), in a state in which the treatment liquid F ₀ stored in the tank 17. In this state, the pump 22 is operated, and the processing liquid F ₀ is sent from the tank 17 to the processing liquid supply path 12. Thus while feeding a treatment liquid _{F 0,} by supplying _{O 2} from _{O 2} supply path 31, in, for example downstream of the pump 22, to merge the _{O 2} from the treatment liquid _{F 0.} Thereby, in the processing liquid supply path 12, a processing liquid F ₁ (mixed fluid of water and O ₂ bubbles) in which O ₂ is mixed is generated.

When the processing liquids F ₀ and O ₂ are mixed in this way, O ₂ may be mixed in a state of being dispersed in, for example, countless fine bubbles with respect to the processing liquid F ₀ , or , it may be dissolved in the processing solution F _O. That way, it is possible to mix a sufficient amount of O ₂ gas to the processing solution F _0. That is, O ₂ consumed by the denitration reaction in the packed bed 5 described later can be sufficiently supplied. Further, in the filling layer 5, it can be uniformly contacted with the treatment liquid F ₀ and O ₂ with respect to the processed gas G _1. In this way, by uniformly and sufficiently bringing the treatment liquids F ₀ and O ₂ into contact with the gas to be treated G ₁ , a denitration reaction in the packed bed 5 described later is efficiently performed, and nitrogen oxides are efficiently produced. Can be removed.

It seems that a larger amount of O ₂ to be mixed with the processing liquid F ₀ is desirable from the viewpoint of promoting the denitration reaction described later. However, if it is too large, the processing liquid F ₀ in the processing liquid supply path 12 is preferred. May lose the pressure of O ₂ blown out from the O ₂ supply path 31, and the processing liquid F ₀ may or may not pass through the processing liquid supply path 12. That is, it is difficult to form a state in which the processing liquid F ₁ and the gas to be processed G ₁ counter flow in the packed bed 5, and there is a concern that the denitration reaction may be suppressed. For this reason, the amount of O ₂ to be mixed with the treatment liquid F ₀ is preferably suppressed to an appropriate amount. That is, the flow rate and the treatment liquid F ₀ of the processing liquid supply path 12, the flow rate of O ₂ in the O ₂ supply path 31, it is preferable that each adjusted to an appropriate amount. For example, _{O 2} supply path flow _{Q O2} of _{O 2} in 31, may be set to be less than about 50 volume percent of the flow rate _{Q F1} of the treatment liquid _{F 1} of the processing liquid supply path 12. More preferably, the flow rate Q _{O2 of} O ₂ is about 10% to 50% by volume (more preferably about 30% to 50% by volume) of the flow rate Q _F1 of the treatment liquid F _1. good.

Further, the processing liquid F ₀ in the tank 17 may be cooled in advance by the cooler 40. That way, the amount of O ₂ that can be mixed in the processing liquid F ₀ is increased. That is, a large amount of O ₂ can be supplied to the packed bed 5 and the denitration reaction can be further promoted. In addition, if the processing liquid F ₀ is cooled, the processing liquid F ₁ after mixing O ₂ also becomes low temperature. In this case, the gas G ₁ to be treated can be cooled by the treatment liquid F ₁ in the packed bed 5 described later. Then, it is possible to condense the moisture contained in the gas to be treated G _1, which makes it possible to further accelerate the denitration reaction. The temperature of the treatment liquid F ₁ may be, for example, about 0 ° C. to 25 ° C., and more preferably about 0 ° C. to 20 ° C. (more preferably, about 0 ° C. to 15 ° C.). .

The treatment liquid F ₁ containing O ₂ generated as described above further passes through the treatment liquid supply path 12 and is introduced into the spray nozzle 21 in the tower body 2a. And it sprays from the spray nozzle 21 and is supplied to the upper surface of the packed bed 5.

In this way, the gas to be treated G ₁ is introduced through the gas introduction path 11 while supplying the treatment liquid F ₁ to the packed bed 5. The concentration of nitrogen oxides in the gas to be treated G ₁ may be relatively high, for example, about 10,000 ppm by volume or more, or about 60,000 volume ppm or more, Furthermore, it may be about 100,000 ppm by volume or more. Even the gas to be treated G ₁ such high concentrations, according to the processing apparatus 1 of the present embodiment, it is possible to sufficiently reduce the nitrogen oxides.

The gas to be treated G ₁ introduced from the gas introduction path 11 is introduced into the packed bed 5 from the lower surface of the packed bed 5 and rises in the packed bed 5. On the other hand, the processing liquid F ₁ is introduced from the upper surface of the packed bed 5 and descends in the packed bed 5. That is, the treatment liquid F ₁ and the processed gas G ₁ flows in opposite directions.

As described above, when the processing gas G ₁ and the processing liquid F ₁ are respectively introduced into the filling layer 5, the processing liquid F ₁ comes into contact with the processing gas G ₁ in the filling layer 5. Thereby, the denitration reaction represented by the following reaction formulas (1) and (2) is performed in the packed bed 5. That is, nitric oxide (NO) and nitrogen dioxide (NO ₂ ), which are nitrogen oxides contained in the gas to be treated G ₁ , react with H ₂ O and O ₂ in the treatment liquid F ₁ , respectively. (HNO ₃ ) is generated.
2NO + O ₂ → 2NO ₂ (1)
4NO ₂ + 2H ₂ O + O ₂ → 4HNO ₃ (2)

Thus, nitrogen oxides (NO, NO ₂ ) are consumed by the denitration reaction in the packed bed 5, so that the nitrogen oxides are decomposed and removed from the gas to be treated G ₁ . That is, the low nitrogen concentration gas G ₂ can be obtained in which the concentration of nitrogen oxides is reduced. On the other hand, the generated HNO ₃ is taken into the processing liquid F ₂ . In addition to the HNO ₃ , the treatment liquid F ₂ contains H ₂ O remaining without being consumed in the reaction.

After the denitration reaction, the low nitrogen concentration gas G ₂ rises in the packed bed 5, is led out from the upper surface of the packed bed 5, and is led out from the processing unit 3 through the exhaust path 15. On the other hand, the processing liquid F ₂ descends in the packed bed 5, falls from the lower surface of the packed bed 5, and is drained from the processing unit 3 through the drain path 16. Thus, the treatment liquid F ₂ and the low nitrogen concentration gas G ₂ are separated from each other.

As described above, the gas to be processed G ₁ and the processing liquid F ₁ are continuously introduced into the packed bed 5 of the processing unit 3 and are sequentially reacted in the packed bed 5. Then, the treatment liquid F ₂ and the low nitrogen concentration gas G ₂ is gradually being continuously discharged from the respective processing unit 3.

By the way, the processing liquid F ₂ is received by the tank 17 after being discharged from the processing unit 3 through the drainage passage 16. Therefore, when the processing liquid F ₂ is mixed with the processing liquid F ₀ in the tank 17, an aqueous solution containing nitric acid (nitric acid-containing aqueous solution) is generated. Then, the aqueous solution is fed by the operation of the pump 22 as the processing liquid F _0. That is, the waste liquid (processing liquid F ₂ ) of the processing unit 3 is collected in the tank 17 and reused as the processing liquid F ₀ .

Similar to the first treatment liquid F ₀ (water), the treatment liquid F ₀ (nitric acid-containing aqueous solution) is mixed with O ₂ gas to become the treatment liquid F ₁ and used for the denitration reaction. As a result, HNO ₃ is newly generated and taken into the processing liquid F ₂ .

As described above, in the processing apparatus 1, the processing liquid F can be repeatedly circulated in the circulation line 50. As the circulation and the denitration reaction are repeated, the amount of H ₂ O in the treatment liquid F (F ₀ , F ₁ , F ₂ ) is consumed for the production of nitric acid and gradually decreases. On the other hand, since the produced nitric acid is taken into the processing liquid F, the amount of nitric acid in the processing liquid F gradually increases. Therefore, the nitric acid concentration of the processing liquid F gradually increases.

Even when the treatment liquid F ₀ becomes a nitric acid-containing aqueous solution, the O ₂ gas is dispersed in the form of countless fine bubbles with respect to the treatment liquid F _{0 in the same} manner as when the treatment liquid F ₁ is water. It is good to mix in the state which made it go. Of O ₂ gas flow rate _{Q O2} is about 50 vol% of the flow rate _{Q F1} of the treatment liquid _{F 1} or less, more preferably about 10 vol% of 50% by volume of the flow rate _{Q F1} (more preferably, about 30 vol% to 50 volume%). The treatment liquid F ₀ in the tank 17 is cooled by the cooler 40, and the temperature of the treatment liquid F ₁ is about 0 ° C. to 25 ° C., more preferably about 0 ° C. to 20 ° C. (more preferably 0 ° C. to 15 ° C. You may adjust so that it may become.

When the concentration of nitric acid in the treatment liquid F ₀ in the tank 17 exceeds a desired value due to the circulation use of the treatment liquid F as described above, the on-off valve 42a is opened and the treatment liquid is passed through the tank drainage passage 42. F ₀ may be sent from the tank 17 to the collection unit 43. Then, new water may be supplied to the tank 17 through the tank water supply path 41. Thus, by adding of H _{2 O} used in the reaction in the packed bed 5, it is possible to continue the denitration reaction.

In this way, the collection unit 43 can collect a high-concentration treatment liquid F ₀ (so-called concentrated nitric acid) in which nitric acid is concentrated to a predetermined value or more. The treatment liquid F _0, such as other industries, can be diverted to various processes.

As described above, according to the processing apparatus 1 according to the present embodiment, the amount of O ₂ necessary for the production of nitric acid can be sufficiently and efficiently supplied by mixing O ₂ with the processing liquid F ₀ . Thereby, the production | generation of nitric acid can be promoted. That is, the removal efficiency of nitrogen oxides can be improved.

Moreover, according to the processing apparatus 1, the processing liquid F ₂ obtained after the removal of nitrogen oxides is reused as the processing liquid F ₀ and used for the generation of new nitric acid, whereby the nitric acid concentration in the processing liquid F is increased. Can be increased. That is, by repeatedly using the treatment liquid F for the production of nitric acid, it is possible to gradually concentrate the nitric acid and produce a highly concentrated nitric acid-containing aqueous solution.

Moreover, according to the processing apparatus 1, nitrogen oxide can be removed with a simple configuration without using a special agent such as an alkali agent (such as ammonia), a catalyst, or an adsorbent. That is, the treatment liquid F, etc. gas to be treated G _1, without the inclusion of an alkaline agent is configured to perform the denitration process. In this case, the treatment liquid F ₀ can be obtained as an aqueous solution mainly composed of water and nitric acid (HNO ₃ ), that is, a solution containing no extra substance such as an alkaline agent. Such a treatment liquid F ₀ is convenient for reuse for other purposes. That is, it is possible to produce a nitric acid-containing aqueous solution that can be easily used for other industries.

  As mentioned above, although preferred embodiment of this invention was described, this invention is not limited to this example. It is obvious for those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea described in the claims. It is understood that it belongs to.

For example, the location where the O ₂ supply path 31 is connected, that is, the position where the O ₂ is blown into the processing liquid F ₀ is not limited to the above embodiment, and as illustrated in FIG. May be. Further, for example, as shown in FIG. 3, the O ₂ supply path 31 may be connected to the tank 17 so that the O ₂ can be mixed with the processing liquid F ₀ in the tank 17. However, from the viewpoint of efficiently mixing O ₂ with the processing liquid F ₀ , it is desirable that the O ₂ supply path 31 is directly connected in the middle of the processing liquid supply path 12. That is, a configuration (FIG. 1 or FIG. 2) in which the O ₂ supply path 31 is connected to, for example, the downstream side or the upstream side of the pump 22 is preferable. That way, blowing O ₂ based on the processing solution F ₀ of the condition being vigorously flows, or to disperse the O ₂ into fine bubbles form, easily or dissolved in the treatment liquid F _0.

(Example 1)
Using what substantially identical processing apparatus 1 and the nitrogen oxide-containing gas treatment method described in the embodiments was performed process for the processing gas G _1. The treated gas G ₁ is a nitrogen oxide-containing gas (specifically generated in the production process of the aqueous solution of the nitrate with the addition of industrial nitric acid in 2.4 L / min, while heating with steam, an aqueous solution of nitrate And gas generated at that time). Nitrogen oxide concentration of the gas to be treated _{G 1} was 950,000 volume ppm. The temperature of the treatment liquid F ₁ was 17 ° C. to 22 ° C., and the flow rate Q _F1 of the treatment liquid F ₁ was 120 L / min. The flow rate Q _{O2 of} O ₂ was 50 L / min. Was subjected to treatment under such conditions, the nitrogen oxides concentration of the low nitrogen concentration gas G ₂ are became 800 volume ppm. Further, the nitric acid concentration of the treatment liquid F ₀ was 21% by mass. That is, the nitrogen oxide concentration in the nitrogen oxide-containing gas can be reduced from 950000 volume ppm to 800 volume ppm by the treatment using the treatment apparatus 1, and is first stored in the tank 17. The aqueous solution with a nitric acid concentration of 21% by mass could be made.

(Example 2)
The gas to be processed G ₁ was processed by setting the temperature of the processing liquid F ₁ to be slightly higher than that in Example 1. That is, the processing apparatus 1 and the gas to be processed G ₁ are the same as those in the first embodiment. The temperature of the treatment liquid F ₁ was 20 ° C. to 23 ° C., and the flow rate Q _F1 of the treatment liquid F ₁ was 120 L / min. The flow rate Q _{O2 of} O ₂ was 50 L / min. When the treatment was performed under such conditions, the nitrogen oxide concentration of the low nitrogen concentration gas G ₂ was 1000 ppm by volume. Further, the nitric acid concentration of the treatment liquid F ₀ was 18% by mass.

(Example 3)
The gas to be processed G ₁ was processed by _reducing the flow rate Q _O2 of the O ₂ gas as compared with Example 1. That is, the processing apparatus 1 and the gas to be processed G ₁ are the same as those in the first embodiment. Temperature of the treatment liquid _{F 1} is set to 18 ° C. through 22 ° C., the flow rate _{Q F1} of the treatment liquid _{F 1} was 120L / min. The flow rate Q _{O2 of} O ₂ was 30 L / min. Was subjected to treatment under such conditions, the nitrogen oxides concentration of the low nitrogen concentration gas G ₂ are became 2000 volume ppm. Further, the nitric acid concentration of the treatment liquid F ₀ was 12% by mass.

(Comparative Example 1)
O ₂ without the supply of _{O 2} gas by supply channel 31 (the flow rate _{Q O2} of _{O 2} and 0L / min), was treated in the subject gas _{G 1.} The processing apparatus 1 and the gas G _{1 to} be processed were the same as those in the first embodiment. The temperature of the treatment liquid F ₁ was 18 ° C. to 32 ° C., and the flow rate Q _F1 of the treatment liquid F ₁ was 120 L / min. When the treatment was performed under such conditions, the nitrogen oxide concentration of the low nitrogen concentration gas G ₂ was reduced only to 5000 ppm by volume. Further, the nitric acid concentration of the treatment liquid F ₀ was 8% by mass.

(Comparative Example 2)
As in Comparative Example 1, the process was performed without supplying O ₂ . The processing apparatus 1 and the gas G _{1 to} be processed were the same as those in the first embodiment. The temperature of the treatment liquid F ₁ was 16 ° C. to 23 ° C., and the flow rate Q _F1 of the treatment liquid F ₁ was 120 L / min. When the treatment was performed under such conditions, the nitrogen oxide concentration of the low nitrogen concentration gas G ₂ was reduced only to 4500 ppm by volume. Further, the nitric acid concentration of the treatment liquid F ₀ was 16% by mass.

(Comparative Example 3)
As in Comparative Example 1, the process was performed without supplying O ₂ . However, the nitrogen oxide concentration of the gas to be treated _{G 1} is low, and the 2200 volume ppm. The processing apparatus 1 was the same as that of the first embodiment. The temperature of the treatment liquid F ₁ was 17 ° C. to 22 ° C., and the flow rate Q _F1 of the treatment liquid F ₁ was 120 L / min. When the treatment was performed under such conditions, the nitrogen oxide concentration of the low nitrogen concentration gas G ₂ was reduced only to 400 ppm by volume. Further, the nitric acid concentration of the treatment liquid F ₀ was 10% by mass.

  The present invention can be applied to a method for treating a nitrogen oxide-containing gas generated in various processes such as a manufacturing process of an aqueous solution of nitrate, and an apparatus for treating the nitrogen oxide-containing gas.

It is a schematic sectional drawing of the processing apparatus concerning this embodiment. It is a schematic sectional drawing of the processing apparatus concerning another embodiment. It is a schematic sectional drawing of the processing apparatus concerning another embodiment.

Explanation of symbols

F (F ₀ , F ₁ , F ₂ ) treatment liquid G ₁ gas to be treated G ₂ low nitrogen concentration gas 1 treatment apparatus 2 spray tower 3 treatment section 5 packed bed 11 gas introduction passage 12 treatment liquid supply passage 15 exhaust passage 16 exhaust Liquid path 17 Tank 22 Pump 31 O ₂ supply path 50 Circulation line

Claims (14)

A treatment method for removing nitrogen oxides from the nitrogen oxide-containing gas by bringing a treatment liquid into contact with the nitrogen oxide-containing gas,
A nitrogen oxide-containing gas treatment method comprising mixing O ₂ with the treatment liquid before bringing the treatment liquid into contact with the nitrogen oxide-containing gas. The method for treating a nitrogen oxide-containing gas according to claim 1, wherein the treatment liquid and the nitrogen oxide-containing gas do not contain an alkali agent. Flow rate of the O ₂ at the time of mixing the O ₂ in the processing solution, characterized by the following 50% by volume of the flow rate of the treatment liquid after mixing the O _2, to claim 1 or 2 The nitrogen oxide containing gas processing method of description. The nitrogen oxide-containing gas treatment method according to claim 1, wherein the O ₂ is mixed in the form of bubbles with respect to the treatment liquid. The nitrogen oxide-containing gas treatment method according to any one of claims 1 to 4, wherein the temperature of the treatment liquid is set to 0 ° C to 25 ° C. The nitrogen oxide-containing gas treatment method according to any one of claims 1 to 5, wherein a concentration of the nitrogen oxide in the nitrogen oxide-containing gas is 10,000 volume ppm or more. When the treatment liquid is brought into contact with the nitrogen oxide-containing gas, a direction in which the nitrogen oxide-containing gas flows and a direction in which the treatment liquid flows are opposite to each other. 6. The nitrogen oxide-containing gas treatment method according to any one of 6 above. The nitrogen oxide-containing gas according to claim 1, wherein after the treatment liquid is brought into contact with the nitrogen oxide-containing gas, the waste liquid is collected and reused as the treatment liquid. Processing method. A treatment apparatus for removing nitrogen oxides from the nitrogen oxide-containing gas by bringing a treatment liquid into contact with the nitrogen oxide-containing gas,
A processing section for processing the nitrogen oxide-containing gas, a nitrogen oxide-containing gas introduction path for introducing the nitrogen oxide-containing gas into the processing section, a processing liquid supply path for supplying a processing liquid to the processing section, and O _An O ₂ supply path for supplying ₂ ;
The treatment liquid supply path, a processing solution in a state in which the O ₂ O ₂ supplied by the supply passage has been mixed, and supplying to the processing unit, the nitrogen oxide-containing gas treatment apparatus. The processing unit includes a packed bed,
The direction in which the nitrogen oxide-containing gas passes through the packed bed and the direction in which the processing liquid passes through the packed bed are configured to be opposite to each other. Item 12. The nitrogen oxide-containing gas treatment device according to Item 9. The nitrogen oxide-containing gas processing apparatus according to claim 9 or 10, further comprising a cooler for cooling the processing liquid. The nitrogen oxide-containing gas processing apparatus according to claim 9, wherein the O ₂ supply path is connected to the processing liquid supply path. The nitrogen oxide-containing gas processing apparatus according to any one of claims 9 to 12, wherein a circulation line for introducing the waste liquid of the processing section into the processing liquid supply path is configured. A tank for storing the treatment liquid;
The nitrogen oxide-containing gas processing apparatus according to any one of claims 9 to 13, wherein the processing liquid supply path and a drainage path of the processing section are connected to the tank.

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