JP2006239690A - Nitrogen oxide removing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a removing method for nitrogen oxide and sulfur oxide capable of efficiently removing nitrogen oxide and sulfur oxide in the environment at a low cost while suppressing the occurrence of a by-product, and a purification apparatus of nitrogen oxide and sulfur oxide. <P>SOLUTION: The removing method of nitrogen oxide and sulfur oxide contained in an exhaust gas includes a drying process for forming atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas and a wet process for setting, as a reference value, an application voltage at which the content of NO<SB>2</SB>reaches the maximum value due to oxidation of NO in the gas by formation of low temperature non-equilibrium plasma, to efficiently oxidize NO contained in the gas into NO<SB>2</SB>before reacting the exhaust gas with a reducing agent solution. The nitrogen oxide and sulfur oxide removing apparatus for removing nitrogen oxide and sulfur oxide is also disclosed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an exhaust gas treatment method and a treatment apparatus therefor, including dry treatment using atmospheric low-temperature non-equilibrium plasma (hereinafter referred to as “low-temperature non-equilibrium plasma”) and wet treatment using a reducing agent solution. By controlling the reaction by-products (N ₂ O, HNO ₂ , HNO ₃ , NO ₃ ⁻ , CO) in the exhaust gas by a step process or by a combination of the dry process and the wet process, and The present invention is a method and apparatus for purifying nitrogen oxides that are economically removed.

In general, nitrogen oxides such as nitrogen monoxide (NO) and nitrogen dioxide (NO ₂ ) are discharged as energy is supplied and consumed by power plants and diesel engines. Is done. Nitrogen oxides discharged into the environment cause photochemical smog and the like, and countermeasures are being considered as an important issue for environmental problems in large cities. Further, dinitrogen monoxide (N ₂ O) has attracted attention as a cause of global warming gas, which has been a problem in recent years.

As a method for reducing nitrogen oxides, a combustion method, a catalyst method, a selective catalytic reduction method (SCR), an ammonia injection method, and, in recent years, technologies such as the catalyst method, non-thermal plasma, and electron beam are used. There are known methods for reducing nitrogen oxides by combining them, and other methods for reducing nitrogen oxides by combining the above methods with methods using chemical substances or catalysts such as ammonia, hydrogen peroxide and calcium chloride. It has been.
Japanese Patent Laid-Open No. 6-99030 Japanese Patent Laid-Open No. 48-6974 Japanese Patent Laid-Open No. 51-15158 International Publication No. 99/12638 Pamphlet

  However, the conventional method has a problem that it takes a lot of cost to increase the removal efficiency of nitrogen oxides.

  FIG. 11 shows the cost required for removing 1 ton of nitrogen oxides in the environment having a NOx concentration of about 500 ppm to 1000 ppm with each purification efficiency by the conventional nitrogen oxide purification method.

  As shown in FIG. 11, in order to remove nitrogen oxides in the environment by a technique that has been commercially available, for example, when SCR (shown by a straight line in FIG. 11) is used, 80% to The annual cost to remove 1 ton of nitrogen oxides in the environment with 85% nitrogen oxide purification efficiency is about 1.5 million to 1.6 million yen (about 12,000 dollars), which is expensive. You can see that

  For example, when SCR is used, the nitrogen oxide removal efficiency in the environment is about 80% to 85% even if the high cost is applied.

  In addition, when nitrogen oxides in the environment are removed using low-temperature non-equilibrium plasma or the like, a large amount of electric power of 70 eV to 780 eV is consumed, and there is a problem that high cost is required similarly to the SCR.

In addition, in the conventional method using low-temperature non-equilibrium plasma, in order to decompose and remove nitrogen oxides in the environment, in the reaction process, dinitrogen monoxide (N ₂ O), nitrate ions (NO ₃ ⁻ ), There was a problem that by-products such as nitrous acid (HNO ₂ ) and nitric acid (HNO ₃ ) were produced in large quantities, and these by-products were not removed. In order to purify these by-products by oxidation / reduction, there is a problem that the cost increases further.

  Therefore, the present invention efficiently removes nitrogen oxides in the environment at low cost by using a dry process by generation of low-temperature non-equilibrium plasma and / or a wet process using a strong reducing agent solution, An object of the present invention is to provide a method for purifying nitrogen oxides and sulfur oxides and a purification device for the by-products that can be greatly restricted in the nitrogen oxide removal step.

The invention described in claim 1 of the present application is a nitrogen oxide purification method for removing nitrogen oxides contained in exhaust gas, wherein the purification method generates atmospheric pressure low-temperature non-equilibrium plasma in the exhaust gas to produce nitrogen oxides. An application for generating the atmospheric pressure low temperature non-equilibrium plasma with reference to a value at which NO in the gas is oxidized by the generation of the atmospheric pressure low temperature non-equilibrium plasma and NO ₂ becomes the maximum value. This is a nitrogen oxide purification method for setting the voltage.

When low-temperature non-equilibrium plasma is generated in the exhaust gas, nitrogen N ₂ and oxygen O ₂ in the gas are ionized and excited by discharge of the low-temperature non-equilibrium plasma to become active nitrogen N and active oxygen O. Further, in the presence of moisture, water molecules become OH radicals, and the excitation of these molecules initiates the dissociation of NOx.

That is, of the NOx, a part of nitric oxide NO is reduced to N ₂ by the active nitrogen N without being affected by the temperature. However, this reduction to N ₂ is a small part of NO contained in the exhaust gas, and most of it is oxidized by active oxygen O and oxidized to nitrogen dioxide NO ₂ . These can be expressed by the following equations.

(1) NO + N → N2 + O
(2) NO + O + M → NO ₂ + M
Here, M represents a third body substance, and this third body substance M is a substance that absorbs excess energy obtained by the reaction and effectively promotes the reaction. Shows oxygen.

As shown in the equation (2), almost all of NO contained in the exhaust gas is oxidized to NO ₂ by the generation of the low temperature non-equilibrium plasma. The applied voltage for generating the low temperature non-equilibrium plasma with the maximum amount of NO ₂ is a value significantly lower than the applied voltage used in the conventional plasma method.

When a voltage higher than this is applied, the generated NO ₂ is further reacted under the influence of active nitrogen, and is reduced to N _{2 2 as} represented by the following formula (3). In recent years, N ₂ O has attracted attention as a global warming gas.

(3) NO ₂ + N → N ₂ O + O
Furthermore, in the presence of moisture, a part of NO ₂ is oxidized into nitric acid (HNO ₃ ) as represented by the following formula (4) due to the influence of the third body substance M and the OH radical.

(4) NO ₂ + OH + M → HNO ₃ + M
Further, in the absence of moisture, a part of NO ₂ becomes nitrate ions (NO ₃ ⁻ ) as represented by the following formula (5) by the active oxygen O in the air.

(5) NO ₂ + O + e → NO ₃ ⁻
At the same time, part of NO ₂ is again reduced to NO by active oxygen O in the air, as shown in the following formula (6).

(6) NO ₂ + O → NO + O ₂
Thus, the active oxygen and active nitrogen present in the air, oxidation-reduction cycle of NOx is affected, NO and NO ₂ are oxidation and reduction. Further, the by-products (N ₂ O, HNO ₂ , NO ₃ ^−, etc.) are generated during the oxidation / reduction cycle of the nitrogen oxides. For this reason, it turns out that there is a limit in complete removal of nitrogen oxides. Of the by-products, it is easy to remove HNO ₃ and NO ₃ ⁻ , but it is known that it is difficult to remove N ₂ O gas which has been attracting attention as a global warming gas in recent years.

Due to the generation of low temperature non-equilibrium plasma, NO in the exhaust gas is oxidized to NO ₂ , but when a high voltage is applied and the reaction proceeds further, the NO ₂ is oxidized and reduced to produce the by-product. Is done.

In the present invention, when NO in exhaust gas is oxidized to NO ₂ according to the above equation (2) due to the generation of low-temperature non-equilibrium plasma, the applied voltage at which the amount of NO _{2 is} maximized is used as a reference value. The applied voltage for generating plasma is set, the NO ₂ reaction is suppressed, the generation of by-products due to the promotion of the NO ₂ reaction is reduced, and the NO contained in the nitrogen oxide is changed to NO ₂ in the vicinity of the maximum amount. It becomes possible to oxidize.

Oxidized NO ₂ is relatively easily removed from the exhaust gas using the reducing agent solution. Therefore, the voltage at which the amount of NO ₂ generated from nitrogen oxides in the exhaust gas becomes the maximum value is applied as a reference value. The voltage is set, and NO is oxidized to NO ₂ at a voltage (or significantly lower power) that is significantly lower than the voltage applied by the conventional plasma method, so that energy consumption is reduced and costs are reduced. be able to.

Moreover, since the applied voltage is set with a value at which NO ₂ is maximized as a reference value, it is possible to suppress the amount of by-products generated by the further progress of the NO ₂ reaction, which is difficult to remove. Generation of by-products can be reduced, and an efficient nitrogen oxide purification method can be provided.

In this way, with the voltage at which the amount of NO ₂ is maximized as a reference value, an applied voltage for generating low-temperature non-equilibrium plasma is set, and NO contained in the gas is oxidized to NO ₂ , and then NO is added with a reducing agent. ₂ is processed, it is possible to remove NOx more efficiently than the conventional method such as SCR or the case where only the plasma method is used.

The invention described in claim 2 of the present application is a nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, wherein the purification method generates atmospheric pressure low-temperature non-equilibrium plasma in the exhaust gas to generate nitrogen oxides. NO in the gas is oxidized by the generation of the atmospheric pressure low temperature non-equilibrium plasma to generate NO ₂ , and the NO is not more than a predetermined value, and the NO ₂ generated by oxidation is maximum. A method for purifying nitrogen oxides that sets an applied voltage for generating the atmospheric pressure low temperature non-equilibrium plasma using a value to be a reference value as a set value and an arbitrary value at which a by-product to be generated is a predetermined value or less as a set value It is.

As described above, according to the present invention, NO in the gas becomes a predetermined value or less, NO ₂ generated by oxidation of NO reaches the maximum value, and the reaction of NO ₂ further proceeds, and the amount of by-products generated is increased. The applied voltage is set with reference to a value that becomes a predetermined value or less.

Therefore, according to the method of the present invention, since the reference value is set to a value at which the amount of by-products generated by further progress of the reaction of NO ₂ becomes a predetermined value or less, the generation of by-products is suppressed, the nitrogen oxides in the exhaust gas and easy NO ₂ removal, further, necessary voltage to the NO ₂ generation amount becomes maximum, since the voltage lower than with conventional plasma processes, energy consumption Can be significantly reduced.

The invention described in claim 3 of the present application is the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas. In the purification method, NO in the exhaust gas is oxidized and NO ₂ becomes the maximum value. A step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting an applied voltage using the value as a reference value, and a step of reacting the exhaust gas that has generated the atmospheric pressure low temperature non-equilibrium plasma with a reducing agent solution It is a purification method.

In this way, the applied voltage is set with reference to a value at which NO ₂ generated by oxidation of NO in the exhaust gas becomes the maximum value, and low-temperature non-equilibrium plasma is generated in the exhaust gas, and the reaction of NO ₂ further proceeds. Suppresses generation of by-products.

Further, by the formation of low-temperature nonequilibrium plasma with oxidizes efficiently NO ₂ to NO in the exhaust gas, wet reacting the exhaust gas containing the maximum amount of NO ₂ in a later step and the reducing agent solution process (reduction The nitrogen oxide contained in the exhaust gas is efficiently removed using a chemical process using an agent.

That is, NO ₂ oxidized by generating a low temperature nonequilibrium plasma in the exhaust gas reacts with a reducing agent solution such as sodium sulfite, for example, as shown in the following equation (7), and NO ₂ is N ₂ And Na ₂ SO ₄ .
(7) 2NO ₂ + 4Na ₂ SO ₃ → N ₂ + 4Na ₂ SO ₄
N ₂ is harmless as it is known as a component of air, and Na ₂ SO ₄ is harmless and easily dissolved in water, so that removal is easy.

  Therefore, it is possible to remove the nitrogen oxide in the exhaust gas with high efficiency close to 100% with little influence on the environment and at low cost.

The invention described in claim 4 of the present application is a nitrogen oxide purification method for removing nitrogen oxides contained in exhaust gas, wherein the purification method generates NO in the gas by generating the atmospheric pressure low temperature non-equilibrium plasma. Oxidized to produce NO ₂ , and the NO becomes a predetermined value or less, and the value at which the NO ₂ produced by oxidation is the maximum value is used as a reference value, and the by-product produced is an arbitrary value or less. A step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting an applied voltage with a value as a set value, and a step of causing a reducing agent solution to react with exhaust gas that has generated the atmospheric pressure low temperature non-equilibrium plasma It is a purification method.

As described above, the NO in the exhaust gas is set to a predetermined value or less, the value at which the amount of oxidized NO ₂ is maximized is set as the reference value, and the by-product generated during the reaction is set to a predetermined value or less. Is set to the set value of the applied voltage, the generation of by-products is suppressed to a predetermined value or less, NO contained in the exhaust gas is efficiently oxidized to NO ₂ at a low voltage, and then NO ₂ is maximized. The exhaust gas contained in the limit is reacted with the reducing agent solution, and the action of the reducing agent solution makes it possible to efficiently remove nitrogen oxides contained in the exhaust gas.

The invention described in claim 5 of the present application is a nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, wherein the purification method includes NO in the exhaust gas due to the generation of atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas. A step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting an applied voltage with a value at which NO ₂ is maximized by oxidation of NO ₂ as a reference value, and a reducing agent solution in the exhaust gas that has generated the atmospheric pressure low temperature non-equilibrium plasma Of the nitrogen oxide for removing nitrogen oxides in the exhaust gas by a two-stage process including a dry process for generating the atmospheric pressure low-temperature non-equilibrium plasma and a wet process using the reducing agent solution. It is a purification method.

In this way, the applied voltage is set with the applied voltage at which NO ₂ generated by oxidation of NO in the exhaust gas is maximized as a reference value to generate a low-temperature non-equilibrium plasma, and the reaction of NO ₂ further proceeds. The gas containing the maximum amount of NO ₂ after the step of generating low temperature non-equilibrium plasma while efficiently oxidizing NO in the exhaust gas to NO ₂ while suppressing the production of by-products is reduced to the reducing agent solution. Nitrogen oxides contained in the exhaust gas are efficiently removed by using the two-step process of reacting with the gas.

As in the present invention, since the NO ₂ to set the applied voltage as a reference value a value that is a maximum value, than the conventional plasma method, it is possible to lower the set voltage and energy consumption - by reducing, Cost can be reduced.

  Further, the purification method of the present invention is a two-step process, a dry process for generating a low-temperature non-equilibrium plasma, and a wet process for reacting exhaust gas after generating the low-temperature non-equilibrium plasma with a reducing agent solution. It becomes possible to remove nearly 100% of nitrogen oxides from the exhaust gas, and nitrogen oxides can be removed with higher efficiency than in the conventional method.

The invention described in claim 6 of the present application is a nitrogen oxide purifying method for removing nitrogen oxides contained in exhaust gas, wherein the purifying method generates atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas. NO is oxidized to produce NO _2, and the by-product produced by the NO ₂ reaction is set with reference to a value at which the NO becomes a predetermined value or less and the NO ₂ produced by oxidation is the maximum value. A step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting an applied voltage with an arbitrary value less than or equal to a set value, and a step of reacting the exhaust gas that has generated the atmospheric pressure low temperature non-equilibrium plasma with a reducing agent solution A nitrogen oxide that removes nitrogen oxides in the exhaust gas by a two-stage process including a dry process for generating the atmospheric pressure low temperature non-equilibrium plasma and a wet process using the reducing agent solution. It is a method.

As described above, any value that makes NO in the exhaust gas equal to or less than a predetermined value, sets a value at which the amount of NO ₂ generated by oxidation as a maximum value as a reference value, and sets by-products generated during the reaction to be equal to or less than a predetermined value. By setting the applied voltage to a set value of the applied voltage, the production of by-products is suppressed to a predetermined value or less, and NO contained in the exhaust gas is efficiently oxidized to NO ₂ at a low voltage, and then NO ₂ is maximized. By using a two-stage process in which the exhaust gas contained in the limit reacts with the reducing agent solution, nitrogen oxides contained in the exhaust gas can be efficiently removed by the action of the reducing agent solution.

  Moreover, according to the method of the present invention, it is possible to suppress the generation of by-products that have an influence on the environment and are difficult to remove, and to efficiently remove nitrogen oxides in the exhaust gas at low cost.

The invention described in claim 7 of the present application is a nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, wherein the purification method generates gas by generating atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas. A step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting an applied voltage using a value at which NO in the interior is oxidized and the maximum value of NO ₂ is set as a reference value; A step of reacting a reducing agent solution, wherein the step of generating the atmospheric pressure low temperature non-equilibrium plasma and the step of using the reducing agent solution are combined into a semi-dry one-step process to oxidize nitrogen in exhaust gas. This is a method for purifying nitrogen oxides to remove substances.

  Combining the process of generating low-temperature non-equilibrium plasma with the exhaust gas and the process of reacting with the reducing agent solution makes it a semi-dry type one-step process, which effectively removes nitrogen oxides in the exhaust gas by reducing the number of processes. As a result, significant cost reduction can be achieved.

The invention described in claim 8 of the present application is a nitrogen oxide purification method for removing nitrogen oxides contained in exhaust gas, wherein the purification method generates atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas, NO is oxidized to produce NO _2, and the by-product produced by the NO ₂ reaction with reference to a value at which the NO ₂ is oxidized and the maximum value is obtained. A step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting an applied voltage with an arbitrary value that is less than or equal to a predetermined value as a set value, and reacting the exhaust gas that generated the atmospheric pressure low temperature non-equilibrium plasma with a reducing agent solution A step of generating the atmospheric pressure low-temperature non-equilibrium plasma and removing the nitrogen oxides in the exhaust gas by a semi-dry one-step process in which the process using the reducing agent solution is combined. It is a method for purifying nitrogen oxides.

As described above, when the predetermined voltage is set and the low temperature non-equilibrium plasma is generated, all the nitrogen oxides NO in the exhaust gas are oxidized to NO ₂ . In addition, by-products such as N ₂ O generated by further promoting the reaction of NO ₂ can be suppressed. Then, by reacting the NO ₂ which is oxidized reducing agent solution, it can be easily remove nitrogen oxides contained in the exhaust gas.

  Further, according to the present invention, the voltage to be applied is lower than the voltage used in the conventional plasma method, so that the consumption voltage can be reduced and the cost can be reduced.

  The invention described in claim 9 of the present application is a nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, wherein the purification method is a dry process for generating atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas. And a method of purifying nitrogen oxides comprising a wet process in which the exhaust gas that has generated the atmospheric low-temperature non-equilibrium plasma is reacted with a reducing agent solution.

  In this way, by generating a low-temperature non-equilibrium plasma in the exhaust gas, the nitrogen oxides in the exhaust gas are oxidized, and thereafter, when the reducing agent solution is reacted with the exhaust gas, the nitrogen oxides are easily removed from the exhaust gas. Is possible. In addition, according to the method of the present invention, the applied voltage can be reduced as compared with the conventional method, the energy consumption is reduced, the cost is reduced, and the generation of by-products is suppressed to 100%. Nitrogen oxides can be removed from the exhaust gas with near high efficiency.

  The invention described in claim 10 of the present application is a nitrogen oxide purification method for removing nitrogen oxides contained in exhaust gas, wherein the purification method generates atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas, and A process of reacting a reducing agent solution with exhaust gas that has generated an atmospheric pressure low temperature non-equilibrium plasma, and a two-stage process including a dry process for generating the atmospheric pressure low temperature non-equilibrium plasma and a wet process using the reducing agent solution This process is a method for purifying nitrogen oxides by removing nitrogen oxides in exhaust gas.

  In this way, when nitrogen oxides contained in the exhaust gas are oxidized by the generation of low-temperature non-equilibrium plasma in the exhaust gas, and the exhaust gas and the reducing agent solution are reacted in the subsequent process, the nitrogen oxide is easily removed from the exhaust gas. Can be removed.

  In the method of the present invention, the applied voltage for generating the low-temperature non-equilibrium plasma can be made lower than in the conventional method, the energy consumption can be reduced and the cost can be reduced. Furthermore, by limiting the generation of by-products, it becomes possible to remove nitrogen oxides from exhaust gas with higher efficiency than conventional methods.

  The invention described in claim 11 of the present application is a nitrogen oxide purification method for removing nitrogen oxides contained in exhaust gas, wherein the purification method includes the step of generating atmospheric pressure low-temperature non-equilibrium plasma in the exhaust gas, A step of reacting exhaust gas that has generated atmospheric low-temperature non-equilibrium plasma with a reducing agent solution, and a semi-dry type in which the step of generating atmospheric low-temperature non-equilibrium plasma and the step using the reducing agent solution are combined. This is a method for purifying nitrogen oxides by removing nitrogen oxides in exhaust gas by a step process.

  In this way, when low temperature non-equilibrium plasma is generated in the exhaust gas to oxidize nitrogen oxides contained in the exhaust gas, and then the exhaust gas is reacted with the reducing agent solution, the nitrogen oxides in the exhaust gas can be easily removed from the exhaust gas. It can be removed.

  As described above, when the process of generating low-temperature non-equilibrium plasma and the process of reacting the exhaust gas with the reducing agent solution are combined in a single-stage process, the nitrogen oxide removal process is reduced and the number of treatments is reduced. It becomes possible to simplify the process and reduce the cost.

  According to the twelfth aspect of the present invention, in the step of generating the atmospheric low temperature non-equilibrium plasma, which is the method for purifying nitrogen oxide according to any one of the first to eleventh aspects, a voltage is applied to the atmospheric pressure. As means for generating the low-temperature non-equilibrium plasma, a pulse discharge method, a ferroelectric pellet filling discharge method, a silent discharge (barrier discharge), a creeping discharge, a direct current discharge, or a combination thereof is used.

  As described above, as a means for generating the low temperature non-equilibrium plasma, a pulse discharge method, a ferroelectric pellet filling discharge method, a silent discharge (barrier discharge), a creeping discharge, a direct current discharge, or a combination of these methods may be used. It is possible to generate low-temperature plasma at atmospheric pressure by a relatively simple process without requiring a complicated process such as maintenance of vacuum conditions as in the prior art.

According to the thirteenth aspect of the present invention, the reducing agent used in the method for purifying nitrogen oxides according to any one of the first to twelfth aspects is sodium sulfite (Na ₂ SO ₃ ) and / or sodium sulfide (Na ₂ S). ).

When nitrogen oxides contained in the exhaust gas come into contact with the Na ₂ SO ₃ and / or Na ₂ S solution, NO ₂ reacts as shown in the formula (7).

Further, the sodium sulfite solution reacts with oxygen in the air as shown in the following formula.
(8) 1 / 2O ₂ + Na ₂ SO ₃ → Na ₂ SO _{4 Further} , NO ₂ in the solution also reacts with water, and as shown in the following formula (9), nitrous acid (HNO ₂ ) and nitric acid ( HNO ₃ ) and exist in water as NO ₂ ⁻ ions and NO ₃ ⁻ ions.
(9) 2NO ₂ + H ₂ O → HNO ₂ + HNO ₃ → 2H ⁺ + NO ₂ ⁻ + NO ₃ ⁻
The (9) as shown in the expression, NO ₂ is, NO ₂ in water ^- and NO ₃ ^- is oxidized remaining. The nitric acid and nitrous acid can be easily neutralized with a reducing agent such as sodium hydroxide. However, since a separate reducing agent is required and the cost becomes expensive, Na ₂ SO ₃ is used as the reducing agent. Te as the final product, it is more preferable that the N _2.

  Therefore, it has little impact on the environment as a wet reducing agent and reduces the cost for removing nitrogen oxides using a low-cost reducing agent. Purification of things becomes possible.

The method of the present invention reduces the amount of by-products such as NO ₂ ⁻ ions or NO ₃ ⁻ ions in the reaction solution, reduces NOx in the exhaust gas to N ₂ and removes it from the exhaust gas. Yes. The invention described in claim 14 of the present application is a nitrogen oxide purification method for purifying nitrogen oxides contained in exhaust gas, wherein the purification method comprises a step of reacting exhaust gas with a reducing solution. It is a purification method.

Nitrogen oxides contained in the exhaust gas, for example, NO ₂ react with the reducing agent solution to be harmless N ₂ and harmless and water-soluble Na ₂ SO ₄ as shown in the above formula (7). Nitrogen oxide can be easily removed from the exhaust gas.

The invention described in claim 15 of the present application is the invention of claim 14, wherein the reducing agent uses sodium sulfite (Na ₂ SO ₃ ) and / or sodium sulfide (Na ₂ S).

As described above, when sodium sulfite and / or sodium sulfide is used to remove nitrogen oxides in the exhaust gas, as shown in the above formula (8) or (9), the nitrogen oxide in the exhaust gas is submerged in water. Nitrogen oxides can be removed from the exhaust gas without using NO ₂ ^- or NO ₃ ^- and without using a reducing agent such as sodium hydroxide.

  The invention described in claim 16 of the present application is an exhaust gas purification method for purifying nitrogen oxides and / or sulfur oxides (SOx) contained in exhaust gas, wherein the purification method reacts exhaust gas with a reducing agent solution. A method for purifying nitrogen oxides and / or sulfur oxides comprising a process.

  For example, when sodium hydroxide is used as a strong reducing agent, sulfur oxide (SOx) reacts with this reducing agent solution to produce sodium sulfite.

  Since this sodium sulfite acts as a reducing agent for nitrogen oxides in the exhaust gas, as shown in the formula (7), nitrogen oxides and / or sulfur oxides (SOx) can be removed from the exhaust gas.

  The invention described in claim 17 of the present application is the method for purifying nitrogen oxides and / or sulfur oxides of claim 16, wherein the reducing agent uses sodium hydroxide (NaOH).

As described above, when sodium hydroxide is used as the reducing agent solution, it is assumed that the reaction occurs as in the following formula (10).
(10) SO ₂ + 2NaOH → Na ₂ SO ₃ + H ₂ O
Here, since Na ₂ SO ₃ serves as a reducing agent for nitrogen oxides in the exhaust gas as described above, nitrogen oxides and / or sulfur oxides can be easily removed from the exhaust gas and cleaned. It becomes possible.

The invention described in claim 18 of the present application is the method for purifying nitrogen oxides and / or sulfur oxides of claim 16, wherein the reducing agent is sodium hydroxide (NaOH) and sodium sulfite (Na ₂ SO _3). ) And / or sodium sulfide (Na ₂ S).

When removing nitrogen oxides and / or sulfur oxides in exhaust gas, for example, when sodium hydroxide is used as a reducing agent, sodium hydroxide (NaOH) reacts with sulfur oxides (SO ₂ ), This produces sodium sulfite, which acts as a reducing agent for nitrogen oxides in the exhaust gas.

  When the amount of nitrogen oxides in the exhaust gas is large, or when the amount of nitrogen oxides in the exhaust gas is large compared to the sulfur oxide, the amount of sodium sulfite produced by the reaction between the sulfur oxide and the reducing agent solution decreases. Therefore, a reducing agent sufficient to remove nitrogen oxides in the exhaust gas is not generated.

  For this reason, when sodium sulfite and / or sodium sulfide is added to the sodium hydroxide solution as the reducing agent, a reducing agent sufficient for the reaction of nitrogen oxides and / or sulfur oxides in the exhaust gas is supplied, and the Nitrogen oxides and / or sulfur oxides can be removed.

  The invention described in claim 19 of the present application is a nitrogen oxide purification device for removing nitrogen oxides contained in exhaust gas, the purification device comprising: a reactor for generating atmospheric pressure low temperature non-equilibrium plasma in exhaust gas; The reactor comprises a reactor for reacting exhaust gas with a reducing agent solution, and uses two-stage processing means, a dry process for generating the atmospheric pressure low temperature non-equilibrium plasma, and a wet process using the reducing agent solution. This is a nitrogen oxide purifying device for removing nitrogen oxides therein.

Thus, the nitrogen oxide purification apparatus of the present invention includes a reactor that generates low-temperature non-equilibrium plasma in exhaust gas, and a reactor that reacts exhaust gas and a reducing agent solution, so that low-temperature non-equilibrium plasma is generated inside the first reactor. To oxidize nitrogen oxides in the exhaust gas, and react the oxidized NO ₂ with the reducing agent solution in the second reactor to efficiently remove nitrogen oxides from the exhaust gas.

  When only the conventional plasma method is used, energy consumption such as applied voltage is increased, the cost for removing nitrogen oxides is increased, and nitrogen oxide removal is costly. The use of an apparatus having two-stage means, ie, a dry-type means using a reactor and a wet-type means using a second reactor, reduces the voltage applied to the reactor that generates low-temperature non-equilibrium plasma, thereby reducing the cost. Thus, nitrogen oxides in the exhaust gas can be efficiently removed. In addition, the generation of by-products, which has been a problem in nitrogen oxide removal by the conventional one-stage method, can be limited.

  Moreover, according to the method of the present invention, it is possible to remove nitrogen oxides in exhaust gas with high efficiency close to 100%, which is difficult with only the conventional plasma method.

  The invention described in claim 20 of the present application is a nitrogen oxide purification device for removing nitrogen oxides contained in exhaust gas, the purification device comprising a reactor for generating atmospheric pressure low temperature non-equilibrium plasma in exhaust gas. A means for reacting an exhaust gas that has generated atmospheric low-temperature non-equilibrium plasma with a reducing agent solution inside the reactor, and a process for generating the atmospheric low-temperature non-equilibrium plasma and a process using the reducing agent solution. This is a nitrogen oxide purifying device using a combination of the above.

  As described above, when the reactor is provided with means for bringing the exhaust gas after the generation of the low temperature non-equilibrium plasma into contact with the reducing agent solution, the step of generating the low temperature non-equilibrium plasma on the exhaust gas and the step of reacting the reducing agent solution. Two-stage processing can be performed in one apparatus, and the cost of the apparatus can be reduced and the work space can be reduced.

  The invention described in claim 21 of the present application is a purification device for nitrogen oxides and sulfurized oxides for removing nitrogen oxides and / or sulfur oxides contained in the exhaust gas, wherein the purification device Nitrogen oxide and / or sulfur oxide which has a reactor for reacting with a reducing agent solution and removes nitrogen oxide and / or sulfide oxide in exhaust gas by using a wet processing means using the reducing agent solution It is a purification device.

  As described above, when a reactor for contacting exhaust gas with a reducing agent solution is provided, nitrogen oxide and / or sulfur oxide in the exhaust gas reacts in contact with the reducing agent solution in the reactor, and the (7 ) Or detoxified as shown by formula (10) and removed from the exhaust gas.

  Specific examples of the present invention will be described below with reference to the drawings.

  First, FIG. 1 is a diagram showing a configuration of a plasma reactor according to a specific example of the present invention, which generates atmospheric pressure low-temperature non-equilibrium plasma in exhaust gas. Moreover, FIG. 2 shows the schematic block diagram of the purification apparatus of the exhaust gas which concerns on this example. Based on these drawings, the exhaust gas purifying apparatus will be described.

  As shown in FIG. 1, the plasma reactor 3 of this example is a barrier type packed bed reactor in which a pellet-shaped dielectric material 32 is filled inside a container, and includes a wire-like discharge line at the center. By applying an AC current having a voltage and frequency set to a predetermined value to the discharge line, the apparatus generates low-temperature non-equilibrium plasma in a substance flowing through the plasma reactor 3 under normal temperature and normal pressure.

  As shown in FIG. 1, the plasma reactor 3 includes a reactor body 31 that is a sealed container, in which a predetermined pellet-shaped dielectric material 32 is housed, and a wire-shaped center disposed in the center of the reactor body 31. A plasma electrode composed of an electrode 38 and a mesh screen-like external electrode 39 provided on the outer periphery of the reactor is provided.

  The reactor body 31 is formed in a straight tube shape having a diameter of about 20 mm and a length of about 300 mm using a Pyrex material, and the upper and lower openings are closed by bushes 35 and 36 using a silicon material. Has been.

  Further, the reactor main body 31 is provided with exhaust gas inflow / outflow portions 33 and 34, and the inflow / outflow portions 33 and 34 are respectively connected to connecting members connected to other devices.

  The pellet-shaped dielectric 32 is mounted between the support plates 40 and 41 of the support plates 40 and 41 in the reactor main body 31. The support plates 40 and 41 are formed using a material such as Teflon provided with holes. A dielectric is held in the reactor main body 31 by using the support plates 40 and 41.

  A central electrode 38 disposed in the reactor main body 31 and an external electrode 39 provided on the outer periphery of the reactor main body 31 are electrically connected to the power supply unit 9.

  The central electrode 38 is made of stainless steel wire. The lower side of the central electrode 38 is connected to the center of a support plate 41 provided in the reactor main body 31 and the upper end thereof is connected to the reactor. It passes through the center of the bush 35 that closes the upper opening of the main body 31 and is electrically connected to the power supply unit 9.

  Further, the external electrode 39 is formed in a copper mesh screen shape, is configured to cover the outer periphery of the reactor main body 31, and is electrically connected to the power supply unit 9 similarly to the central electrode 38.

  Therefore, when a current and a voltage are applied from the power supply unit 5 to the central electrode 38 from, for example, a 60 Hz AC power supply (30 kV, 10 mA), a dielectric material having a relatively low dielectric constant located between the central electrode 38 and the external electrode 39. A low-temperature non-equilibrium plasma (ionized gas) can be generated during normal temperature and normal pressure during 32.

  The AC current for applying a voltage to the electrodes 38 and 39 is not limited to 60 Hz described above, and may be set at 1 Hz to 100 MHz depending on conditions.

  For example, by applying a voltage between the central electrode 38 and the external electrode 39, a high electric field is generated in the vicinity of the pellet-shaped dielectric material 32, and active oxygen O is generated from plasma-excited air, resulting in highly reactive radicals. ing.

  In the plasma reactor 3 of this example, exhaust gas (sample gas) is directly circulated between the dielectric materials 32 that are in the high electric field region inside the container, so that the gas molecules and gas molecules of the exhaust gas are energized from the accelerated electrons. Is ionized to form a radical having high reactivity, dissociated and decomposed by radical reaction / ion reaction, and chain-reacted as shown in the above formulas (1) to (6). It is thought that it will progress.

  Next, the exhaust gas purification apparatus 1 provided with the above-described plasma reactor 3 will be described.

  FIG. 2 is a schematic configuration diagram showing the exhaust gas purification device 1.

  As shown in FIG. 2, the exhaust gas purifying apparatus 1 of this example includes a compressor-2, a nitrogen oxide (NO) tank 4 serving as a sample gas, a flow rate adjusting valve 5, and a reducing agent solution inside the plasma reactor 3. The chemical reactor 6 provided with the, and the analyzer 7 are provided. Each device is connected by a connecting member 8 such as a pipe.

  The compressor-2 is connected to an air filter and an air dryer 11, and the air compressed by the compressor-2 is freed of floating particles by the air filter, and moisture is removed by the dryer.

  Moreover, the compressor-2 is equipped with the flow control valve 12, and adjusts the flow volume of the taken-in air. Similarly, the nitrogen oxide tank 4 includes a flow control valve 13.

  After the air taken in from the compressor-2 and the sample gas flowing out of the nitrogen oxide tank 4 are mixed so that the flow rate is controlled by the flow rate control valves 12 and 13 and a predetermined concentration is obtained by the flow rate adjustment valve 5, It flows through the plasma reactor 3 so as to have a predetermined flow rate.

  Further, the plasma reactor 3 is provided with a power source 10 that applies a voltage to the internal electrode 38 and the external electrode 39 described above. Further, in order to measure the voltage applied to the plasma reactor 3 through the electrodes 38 and 39, a high voltage probe (P6015A manufactured by Sony Tektronix) and an oscilloscope (TDS380P manufactured by Sony Tektronix) 9 are provided. Is used to measure the voltage applied to the plasma reactor 3 as a Peak-to-peak voltage (Vp-p).

Further, as the analyzer 7 used for analyzing the sample gas that has passed through the plasma reactor 3, a chemiluminescence type NOx analyzer is used to measure the concentration of NO and NO ₂ in the sample gas, and CO, CO ₂ , N ₂ O , O ₂ gas concentration is measured using an infrared spectrometer (IR: PG-235, VIA-50 manufactured by Horiba, Ltd.). Moreover, the measurement of the ion of NO ₂ ⁻ or NO ₃ ⁻ was performed by an ion chromatograph (Dionex 200i / sp).

  Next, the experimental results performed using the purification device 1 will be described.

  FIG. 3 shows current and voltage characteristics of each dielectric material filled in the reactor 3.

  In this example, two types of plasma reactors were used: a plasma reactor (GPR) filled with glass pellets and a plasma reactor (FPR) filled with pellets made of barium titanate.

GPR is a plasma reactor in which a plasma pellet having a relatively low dielectric constant (ε = 4) is filled in a plasma reactor having a diameter of about 6 mm, and FPR is a dielectric material in which a dielectric pellet is filled in a plasma reactor having a diameter of about 6 mm. It is a plasma reactor filled with pellets made of barium titanate (BaTiO ₃ ) having a relatively high rate (ε> 5,000).

  The barrier type plasma reactor 3 of this example is a plasma reactor using a 60 Hz AC power supply (30 kV, 10 mA), and can generate plasma under normal temperature and normal pressure. As long as low-temperature non-equilibrium plasma can be generated, the type or power supply device need not be limited to the shape of the plasma reactor or the like of this example.

  As shown in FIG. 3, the spark voltage of GPR was 25 kV, and the spark voltage of FPR was 22.5 kV. The power consumption of the plasma reactor 3 was about 27% of the wall plug power.

Next, the results of actual experiments using the experimental apparatus 1 will be described.
<Experiment 1>
First, in order to obtain baseline data, the concentration of nitrogen oxides (NO, NO ₂ ) in dry air was measured.

FIG. 4 shows the measurement of NO concentration and NO ₂ concentration in the dry air after passing through the plasma reactor 3 by changing the flow rate of the dry air using GPR in which the plasma reactor 3 is filled with glass pellets. It is a figure which shows a result.

In this example, the NO concentration and the NO ₂ concentration were measured while changing the dry air flow rate to 2.0 L / min, 4.0 L / min, and 8.0 L / min. The residence time of the dry air at each flow rate is 2.6 seconds when the flow rate is 2.0 L / min, 1.3 seconds when the flow rate is 4.0 L / min, and 0. 0 when the flow rate is 8.0 L / min. 7 seconds. In addition, the said residence time is a numerical value which does not consider the porosity.

As shown in FIG. 4, the NO ₂ concentration in the dry air is such that the residence time in the plasma reactor 3 is long, and the NO applied in the dry air after passing through the plasma reactor 3 increases as the voltage applied to the plasma reactor 3 increases. _{2 It} can be confirmed that the concentration increases.

  On the other hand, the NO concentrations were all 0 ppm after passing through the plasma reactor 3 even when the applied voltage was increased, regardless of the change in residence time.

From this, it can be confirmed that NO is completely oxidized in the plasma reactor 3 at a low voltage, that is, with a small electric power, regardless of the residence time.
<Experiment 2>
Next, as a second experimental example, as the plasma reactor 3, using a FPR filled with barium titanate pellets, a predetermined sample gas is caused to flow inside, and the sample gas in the sample gas after passing through the plasma reactor 3 is used. The results of measuring the NO concentration, the NO ₂ concentration, and the NOx concentration that is the sum of the NO concentration and the NO ₂ concentration are shown. In this experiment, as the sample gas, a nitrogen gas having a concentration of 5% was mixed with dry air to have a predetermined concentration. Further, the sample gas flow rate in this experimental example is adjusted to 2.0 L / min (residence time in plasma reactor 3 is 2.6 seconds).

FIG. 5 is a diagram showing changes in concentrations of NO, NO ₂ and NOx in the sample gas that has passed through the FPR when the applied voltage is changed.

As shown in FIG. 5, when the applied voltage is 0 kV, the initial concentration of NO is 125 ppm, the initial concentration of NO ₂ is 35 ppm, and NOx, which is the sum of the initial NO concentration and the initial NO ₂ concentration, is 160 ppm.

When the applied voltage is increased and the applied voltage is 4.5 kV, the NO concentration decreases from the initial concentration of 125 ppM to about 90 ppm, while the NO ₂ concentration increases from 35 ppm to about 75 ppm. Here, NOx concentration is the sum of the NO concentration and NO ₂ concentration is not changed remain 160 ppm. Accordingly, when a voltage of 4.5 kV is applied to the FPR, NO is not generated by by-products such as N ₂ O and HNO ₃ , and all of the NO is generated by the oxidation reaction represented by the above formula (2). It can be confirmed that it is oxidized to NO ₂ . Therefore, in the reactor, NO in the sample gas is unlikely to undergo a reducing action as in the formula (1), and is all oxidized to NO ₂ by the oxidation reaction represented by the formula (2). I can confirm.

Next, when the voltage applied to the FPR is increased to 6.7 kV, the NO concentration becomes 0 ppm from the initial concentration of 125 ppm. On the other hand, the NO ₂ concentration when the applied voltage is 6.7 kV increases from the initial concentration of 35 ppm to 140 ppm.

Further, the NOx concentration, which is the sum of the NO concentration and the NO ₂ concentration, is changed from an initial concentration of 160 ppm to 140 ppm, and nitrogen dioxide NO ₂ equivalent to 20 ppm compared to the initial concentration is expressed by the above formula (3), (4 ) And the reaction represented by the formula (5), it can be presumed that they are oxidized and reduced to other nitrogen oxides, N ₂ O, and HNO ₃ (or NO ₃ ⁻ ).

Further, when the voltage applied to the FPR is increased to 7.0 kV or more, the NO concentration is maintained at 0 ppm, and the NO ₂ concentration and the NOx concentration are decreased. It can be confirmed that NOx is reduced from the initial concentration of 160 ppm to about 120 ppm.

Here, since the NOx concentration is reduced by about 40 ppm compared with the initial concentration, a part of NO ₂ is reduced to N ₂ O as shown in the above equation (3), and the other NO ₂ is As shown in the above formulas (4) and (5), it can be estimated that they are oxidized to HNO ₃ (or NO ₃ ⁻ ). Further, another part of NO ₂ is reduced to NO as shown in the equation (6), and further, the reduced NO is oxidized again to NO ₂ as shown in the equation (2). It is thought that oxidation / reduction reactions are repeated in a chain.

  Therefore, in order to remove nitrogen oxides in the exhaust gas, it is important to select conditions such that the by-products generated during the reaction are near the minimum value.

Here, in recent years, when low-temperature non-equilibrium plasma is generated in exhaust gas and nitrogen oxides contained in the exhaust gas are reacted, 90% or more of by-products generated by this reaction are HNO ₃ and the remaining small amount. Has been reported to be N ₂ O (Fourth International
Conference on Advanced Oxidation Technologies forWater and Air Remediation
Sept. 1997, p57, and 1997
IEEE-IAS meeting, New Orleans Oct. 5-9, 1997, pp 1937-1941).

Since HNO ₃ produced as a by-product is rich in reactivity, it is easy to process and it is assumed that the purification process is simplified.
<Experiment 3>
Next, as a third experimental example, using a GPR filled with glass pellets as the plasma reactor 3, a predetermined sample gas is caused to flow inside the plasma reactor 3, and the sample gas in the sample gas after passing through the plasma reactor 3 is used. The results of measuring the NO concentration, the NO ₂ concentration, and the NOx concentration that is the sum of the NO concentration and the NO ₂ concentration are shown.

  In this experiment, similar to the second experiment, a sample gas having a predetermined concentration of 5% nitrogen gas mixed with dry air was used. In addition, the sample gas flow rate in this experimental example is adjusted to 4.0 L / min (the residence time in the plasma reactor 3 is 1.3 seconds). FIG. 6 is a diagram showing the results of Experiment 3.

As shown in FIG. 6, the NO initial concentration in the sample gas after passing through the plasma reactor (applied voltage 0 kV) to which no voltage is applied is 70 ppm, the NO ₂ initial concentration is 5 ppm, and the NO initial concentration and initial NOx concentration is the sum of NO ₂ initial concentration is 75 ppm.

  When the sample gas after passing through the plasma reactor 3 to which no voltage is applied passes through the chemical reactor 6 and reacts with the reducing agent solution, the NOx concentration decreases to 68 ppm.

NO does not react at all with the reducing agent solution, in the case of this experiment, with the sodium sulfite solution (Na ₂ SO ₃ solution). On the other hand, NO ₂ in the sample gas reacts with the Na ₂ SO ₃ solution to become nitrogen N ₂ , and nitride is removed from the exhaust gas. Further, the Na ₂ SO ₃ solution, which is a reducing agent solution, is oxidized into a Na ₂ SO ₄ solution. Here, the oxidized Na ₂ SO ₄ dissolves in water and is harmless.

That is, by reacting the sample gas after passing through the plasma reactor 3 with a strong reducing agent solution (Na ₂ SO ₃ solution, Na ₂ S solution, etc.), NO ₂ in the sample gas reacts, and from the sample gas. NO ₂ is removed.

Therefore, as described above, the NOx concentration in the sample gas that has passed through the plasma reactor 3 and the chemical reactor 6 having an applied voltage of 0 kV is decreased because NO is naturally oxidized by air to become NO ₂ . It can be assumed that NO ₂ has been removed by reacting with the solution.

Next, when the applied voltage applied to the plasma reactor 3 is increased to 6.7 kV and the NO concentration is measured, the initial concentration decreases from 70 ppm to 55 ppm, while the NO ₂ concentration increases from the initial concentration of 5 ppm to 20 ppm. The NOx concentration is about 75 ppm. Here, NOx concentration, because it does not change from the initial concentration, NO was reduced compared to the initial concentration can be inferred to have been oxidized in all NO _2.

When the sample gas passes through the chemical reactor 6 after passing through the plasma reactor 3, the NOx concentration, which was 75 ppm after passing through the plasma reactor, decreases to 55 ppm. Therefore, it can be confirmed that the sample gas reacts with the reducing agent solution in the chemical reactor, and about 20 ppm of nitrogen oxides are removed from the exhaust gas by the powerful reducing action of the Na ₂ SO ₃ solution as the reducing agent. .

Next, 13.5 kV which is a half voltage of 25 kV which is the maximum applied voltage of GPR is applied to the plasma reactor 3. At this time, the NO concentration decreases from the initial concentration of 55 ppm to 3 ppm or less. On the other hand, the NO ₂ concentration increases from the initial concentration of 5 ppm to 38 ppm. The NOx concentration is about 38 ppm. Further, when the sample gas is passed through the chemical reactor and brought into contact with the reducing agent solution, the NOx concentration is reduced to 2 ppm. That is, when the sample gas is reacted with the reducing agent solution, nitrogen oxides are removed from the sample gas, Na ₂ SO ₃ is oxidized, and only Na ₂ SO ₄ that is easily dissolved and detoxified is measured. The Rukoto.

In this experiment, NOx decreases from an initial concentration of 75 ppm to a concentration of 38 ppm when a voltage of 13.5 kV is applied, so that about 37 ppm of NO ₂ is oxidized and reduced as a by-product. Moreover, it is surmised that most of this by-product is HNO ₃ which is easy to process from the description of the above-mentioned document.

Therefore, if a voltage is applied to the plasma reactor 3 with the applied voltage at which the amount of NO ₂ generated by the low-temperature non-equilibrium plasma becomes the maximum value as a reference value, the amount of by-products generated is suppressed to the minimum and nitrogen oxides are reduced. It can be assumed that removal is possible.

Further, the applied voltage NO ₂ amount to be generated is the maximum value, rather than the conventional plasma process to reduce the NO ₂ amount by further advancing the reaction, a low voltage, the generated NO ₂ amount is the maximum value By setting the voltage to be applied to the reactor 3 using the applied voltage as a reference value, the energy cost is reduced, and the cost for removing nitrogen oxides can be reduced.
<Experiment 4>
Next, as a fourth experimental example, using a FPR filled with pellets made of barium titanate as the plasma reactor 3, a predetermined sample gas is caused to flow inside the plasma reactor 3, and the sample gas after passing through the plasma reactor 3 is used. The results of measuring the NO concentration, the NO ₂ concentration, and the NOx concentration that is the sum of the NO concentration and the NO ₂ concentration are shown.

  In this experiment, similar to the third experiment, a sample gas having a predetermined concentration of 5% nitrogen gas mixed with dry air was used. In addition, the sample gas flow rate in this experimental example is adjusted to 4.0 L / min (the residence time in the plasma reactor 3 is 1.3 seconds). FIG. 7 is a diagram illustrating the results of Experiment 4. In FIG.

As shown in FIG. 7, the initial concentration of NO in the sample gas after passing through the plasma reactor (applied voltage 0 kV) to which no voltage is applied is 130 ppm, the initial concentration of NO ₂ is 22 ppm, the initial concentration of NOx is the sum of the initial concentration of the initial concentration and NO ₂ of a 152Ppm.

  When the sample gas after passing through the plasma reactor 3 to which no voltage is applied passes through the chemical reactor 6, the sample gas having the above concentration reacts with the reducing agent solution, and the NOx concentration is reduced to about 130 ppm.

  Therefore, about 22 ppm of NO 2 reacts with the reducing agent solution in the chemical reactor 6 and is removed.

Next, when the applied voltage applied to the plasma reactor 3 is increased to 6.7 kV and the concentration of nitrogen oxide is measured, NO decreases from the initial concentration of 130 ppm to 30 ppm, while NO ₂ decreases from the initial concentration of 22 ppm. It has increased to 125 ppm and the NOx concentration has not changed. For this reason, it can be confirmed that NO ₂ is increased by the decrease of NO. When the sample gas that has passed through the FPR to which a voltage of 6.7 kV has been applied reacts with the reducing agent solution in the chemical reactor 6, the NOx concentration shows a value of about 30 ppm that matches the NO concentration. By this reaction, it can be confirmed that almost all of NO ₂ is removed.

Next, when the voltage applied to the plasma reactor 3 is increased to 9.0 kV, the NO concentration becomes 0 ppm and the NO ₂ concentration becomes 130 ppm. Further, NOx concentration, since NO concentration is 0 ppm, the NO ₂ concentration and the same 130 ppm.

Accordingly, when a voltage of 9.0 kV is applied and the sample gas passes through the FPR in which the low-temperature non-equilibrium plasma is generated, NO contained in the sample gas inside the plasma reactor is expressed by the equation (1). Therefore, it can be confirmed that all the reduction action is oxidized to NO ₂ by the oxidation reaction represented by the formula (2).

  Further, when the sample gas after passing through the FPR is caused to pass through the chemical reactor 6 to react with the reducing agent solution and the NOx concentration thereafter is measured, the NOx concentration becomes 0 ppm.

Therefore, it can be confirmed that the NO ₂ in the sample gas is completely removed by the reaction of the sample gas after passing through the FPR with the reducing agent solution.

  Also, comparing the initial concentration of NOx with the NOx concentration after passing through the FPR to which a voltage of 9.0 kV is applied, the NOx concentration is reduced by about 25 ppm, so a by-product of about 25 ppm is generated. Can be confirmed.

From these results, when a low-temperature non-equilibrium plasma is generated in the exhaust gas passing between the FPRs by applying a predetermined voltage, it is included in the exhaust gas due to the influence of active oxygen and active nitrogen generated by the low-temperature non-equilibrium plasma. It can be seen that all NO is oxidized to NO ₂ according to the above equation (2), and when the exhaust gas containing NO ₂ is reacted with the reducing agent solution, all NO _{2 in} the exhaust gas is removed.

Thus, NO contained in the exhaust gas is oxidized to NO ₂ by passing through the inside of the plasma reactor 3 where the low temperature non-equilibrium plasma is generated, and further, the exhaust gas is reacted with the reducing agent solution, It can be confirmed that almost 100% of the oxidized NO ₂ is removed from the exhaust gas.

In addition, since almost 90% of the by-products generated along with the oxidation of NO are oxidized to HNO ₃ that is easy to treat, according to the nitrogen oxide purification method of this experimental example, N ₂ that is difficult to be removed. It can be confirmed that O has a low concentration of about 2.5 ppm.

Therefore, the maximum when a voltage is applied voltage to the plasma reactor 3 as a reference value, the amount of NO ₂ to nitrogen oxides in the exhaust gas is generated by oxidation is the NO of nitrogen oxide is oxidized to maximize NO ₂ On the other hand, it can be seen that the amount of by-products produced by further progress of the NO ₂ reaction is minimized.

Therefore, when the applied voltage is set with a value at which the amount of NO ₂ in the exhaust gas passing through the plasma reactor 3 is the maximum value as a reference value, the by-product is minimized and the subsequent removal reaction is facilitated. The nitrogen oxide in the exhaust gas can be efficiently oxidized to NO ₂ . In addition, when the applied voltage is set with the maximum value of the amount of NO ₂ produced by oxidation as the reference value, the applied voltage is lower than when the nitrogen oxide in the exhaust gas is removed by the conventional plasma method. Therefore, energy cost can be reduced.

  Further, comparing the results of both the third experimental example shown in FIG. 6 and the fourth experimental example shown in FIG. 7, the FPR filled with the barium titanate pellets shown in FIG. It can be confirmed that NOx can be removed at a lower voltage (lower power) than the GPR filled with the glass pellet-shaped dielectric shown in FIG. Furthermore, from the amount of NOx reduction after the reaction, it can be confirmed that the amount of by-products generated in FPR is lower than that in GPR.

Next, another specific example will be described.
<Experiment 5>
Next, in the fifth experimental example, the sample gas flow rate was 2.0 L / min, and the initial concentration of NO was 200 ppm. Further, as a dielectric material filled in the plasma reactor 3, pellets of barium titanate having a diameter of 2 mm were used as described above. In this example, the effective length of the plasma reactor is 180 mm.

  In this experiment, the internal electrodes installed in the plasma reactor were 1.5 mm in diameter and 5 mm in diameter, and the internal electrodes were compared.

  FIG. 8A shows the concentration of each component in the sample gas after applying each voltage using the plasma reactor 3 having an internal electrode having a diameter of 1.5 mm. FIG. 8B shows the concentration of each component in the sample gas, which was similarly tested using a plasma reactor having an internal electrode with a diameter of 5 mm.

As shown in FIG. 8A, when an internal electrode having a diameter of 1.5 mm is used, NO ₂ is about 180 ppm at a low voltage of 16 kV, and the NOx concentration in the entire exhaust gas is similarly 180 ppm. On the other hand, as shown in FIG. 8B, when an internal electrode having a diameter of 5 mm is used, NO ₂ is about 150 ppm and the NOx concentration is also 150 ppm at a low voltage of 16 kV.

  In addition, the NO concentration shows a low value of about 3 ppm in both cases where an internal electrode having a diameter of 1.5 mm or 5 mm is used.

Therefore, from the results shown in FIGS. 8A and 8B, the amount of oxidation from NO to NO ₂ is greater when the thin internal electrode having a diameter of 1.5 mm is used than when the internal electrode having a diameter of 5 mm is used. Since it increases and the amount of NOx does not decrease, it can be confirmed that the generation of N ₂ O and other by-products is suppressed to oxidize from NO to NO ₂ . When oxidized from NO to NO ₂ , after passing through the plasma reactor, NO ₂ reacts with the reducing agent solution in the chemical reactor, and is converted into harmless N ₂ and Na ₂ SO ₄ as shown in the equation (7). As a result, nitrogen oxides are removed from the sample gas.

From the above results, as the diameter of the internal electrode, it can be confirmed that the smaller the internal electrode, the larger the conversion from NO to NO ₂ is suitable.

In recent years, it has been confirmed that when NOx is decomposed using plasma, 90% or more of the reaction product becomes HNO ₃ .

In this experiment, it can be confirmed that about 50 ppm of HNO ₂ and HNO ₃ and about 3 ppm of N ₂ O are generated.

When the ratio of HNO ₂ and HNO _{3 in} the exhaust gas after passing through the purifier is measured by an ion chromatograph, when a voltage of 14 kV is applied to the plasma reactor, NO ₂ ⁻ : NO ₃ ⁻ = 1.77: 1 NO ₂ ⁻ shows a larger value, and when a voltage of 16 kV is applied to the plasma reactor, the numerical value is reversed as NO ₂ ⁻ : NO ₃ ⁻ = 1.77. Therefore, it was confirmed that when the applied voltage was increased, NO ₂ ⁻ was further oxidized to NO ₃ ⁻ .

Such HNO ₂ and HNO ₃ can be easily neutralized with a reducing agent such as sodium hydroxide (NaOH). However, when such a reducing agent is used, the cost of the purification treatment increases, and therefore HNO ₂ It is desirable to reduce generation of HNO ₃ and HNO ₃ as much as possible, and NO ₂ reacted in the plasma reactor in the chemical reactor comes into contact with Na ₂ SO ₃ to remove nitride in the exhaust gas as N ₂ .

Next, an experiment was performed in which the diameter of the dielectric material (BaTiO ₃ ) pellet was changed, and the change in the components in the exhaust gas purified by the change in the pellet diameter was confirmed.
<Experiment 6>
In this experiment, the dielectric material (BaTiO ₃ ) filled in the plasma reactor was in the form of pellets, and the diameter of each pellet was 1 mm, 2 mm, or 3 mm.

  In addition, the plasma reactor used in this experiment was one in which the effective length of the filled pellet was 50 mm and the effective length of the external electrode was 50 mm.

  The flow rate of the sample gas flowing through the plasma reactor was 2.0 L / min, and the initial concentration of NO was 100 ppm.

FIGS. 9A, 9B and 9C show the concentration of each component in the sample gas after passing through the plasma reactor using the pellet-shaped dielectric material of each diameter. FIG. 9 (a) shows the results when pellets with a diameter of 1 mm were used, FIG. 9 (b) shows the results when pellets with a diameter of 2 mm were used, and FIG. 9 (c) shows the results with a diameter of 3 mm. The result at the time of using a pellet is shown. In this example, the concentration of each component in the sample gas was measured after passing through the plasma reactor and before passing through the chemical reactor, that is, in a state in which it did not react with the Na ₂ 2SO ₃ solution.

As shown in FIG. 9C, when a low voltage of 16 kV is applied, when the pellet diameter is 3 mm, the NOx indicating the total amount of nitrogen oxides hardly changes, and the sample It was confirmed that almost all of NO contained in the gas was oxidized to NO _2, and by-products such as HNO ₂ , HNO ₃ , CO and N ₂ O were not generated. Moreover, almost all of the NO is oxidized to NO _2.

On the other hand, as shown in FIGS. 9 (a) and 9 (b), when pellets having a diameter of 1 mm are used, only about half of the initial NO is oxidized to NO ₂ , and the diameter is 2 mm. In this case, only about 3/5 of the initial NO was oxidized to NO ₂ .

Accordingly, when pellets having a diameter of 3 mm or more are used, almost all NO contained in the sample gas can be oxidized to NO ₂ , and this NO ₂ then reacts with Na ₂ SO ₃ in the chemical reactor, 7) Since N ₂ and Na ₂ SO ₄ are obtained as shown in the equation, the nitride can be easily purified from the sample gas.

  Further, in this example, since the applied voltage can be purified at a low value such as 16 kV, the operation condition of the purification device can be operated in a state where the most suitable soft plasma is generated.

  Here, the state in which the soft plasma is generated refers to the operating condition of the purification apparatus that increases the residence time of the purification target gas by lowering the applied voltage.

  Therefore, if the operation can be performed in a state in which soft plasma is generated, the applied voltage is low, so that a significant cost reduction can be achieved.

Further, when the purification apparatus can be operated in a state where soft plasma is most suitable as the operation condition of the purification apparatus, the by-product generated using the value at which NO ₂ is maximum as described above as a reference value. A value that minimizes the thing can be set as the applied voltage, and NOx can be effectively removed from the exhaust gas.

  Next, after passing the sample gas that passed through the plasma reactor through the chemical reactor, each component in the sample gas was measured using the analyzer.

  The results are shown in FIG.

As shown in FIG. 10, the sample gas after passing through the plasma reactor is passed through the chemical reactor, reacts with the reducing agent solution in the chemical reactor as shown in the formula (7) or (10), and is harmless. It becomes N ₂ or water-soluble Na ₂ SO ₄ , and nitrogen oxide is easily removed from the sample gas with high removal efficiency close to 100%.

Further, for example, since the voltage is almost 0 when the voltage is 16 kV, according to the purification apparatus of this example, NO ₂ can be completely removed in the entire voltage region, and N which is a harmful by-product It was confirmed that ₂ O, CO and the like can be almost completely suppressed.

As shown in FIG. 10, even when the low-temperature nonequilibrium plasma is not generated in the sample gas, when the nitrogen oxide contained in the sample gas is (NO ₂ ), the sample gas and the reducing agent are used in the chemical reactor. Nitrogen oxides can be removed by reacting the solution as N ₂ that easily removes NO ₂ in the sample gas.

Furthermore, when harmful sulfur oxides (SOx) are contained in the exhaust gas, if sodium hydroxide (NaOH) is used as a reducing agent, sulfur oxides (eg, SO ₂ ) react with the reducing agent. As shown in the above formula (10), sodium sulfite (Na ₂ SO ₃ ) is produced. As described above, since this sodium sulfite (Na ₂ SO ₃ ) is used as a nitrogen oxide reducing agent as described above, NOx and SOx, which are harmful components in the exhaust gas, are removed.

  Further, from the economical viewpoint, the cost can be effectively reduced by using the purification method or the purification apparatus of this example.

  For example, when the purification apparatus 1 equipped with the barrier type packed bed plasma reactor 3 is operated at 16 kV, the power consumption is 1.44 W, and the flow rate of the sample gas in this case is 2.0 L / min. Therefore, the specific power consumption is 43 J / L, 20 W / cfm, and 58 eV / mol. Therefore, in order to remove 1 ton of NOx, the cost is $ 1,860 (converted to $ 0.05 / kW · hr).

On the other hand, the chemical reactor, to process one ton of NO _2, 440 $ / ton (price _Na 2 SO ₃ is 0.48 US dollars / kg) is required.

  Therefore, the total cost for removing 1 ton of NOx by using a purification apparatus equipped with a plasma reactor and a chemical reactor is $ 2,300.

  As described above, FIG. 11 is a diagram showing the cost of each conventional processing method for removing nitrogen oxides from 1 ton of exhaust gas having a NOx concentration of 500 ppm to 1,000 ppm.

  For example, as shown in FIG. 11, the annual cost for removing nitrogen oxides in the exhaust gas having the above concentration by the conventional SCR method at a removal efficiency of about 80% to 85% is about 12 as described above. Therefore, according to the purification method and / or the purification apparatus of this example, the cost of the conventional method is about 1/10 or less.

  Further, according to the present invention, nitrogen oxides in exhaust gas can be removed with high efficiency up to almost 100%. Furthermore, the ratio of generating by-products can be reduced to a small value of about several ppm.

  In this experimental example, a plasma reactor that generates a low-temperature non-equilibrium plasma in the exhaust gas by applying voltage and a chemical reactor that contacts the exhaust gas and the reducing agent are installed as separate devices. And a two-stage process of a wet process (chemical process) using a reducing agent, but not limited to this experimental example, for example, by providing a means for contacting the reducing agent inside the reactor, Nitrogen oxide removal processing can be performed in one stage of processing section, and it is possible to obtain effects such as efficiency of nitrogen oxide removal, simplification of the system, and reduction of arrangement space. is there.

As described above, the present invention relates to a nitrogen oxide purification method for removing nitrogen oxides contained in exhaust gas, wherein the purification method generates atmospheric pressure low-temperature non-equilibrium plasma in the exhaust gas to remove nitrides. An applied voltage for generating the atmospheric pressure low temperature non-equilibrium plasma is defined with reference to a value at which NO in the gas is oxidized by the generation of the atmospheric pressure low temperature non-equilibrium plasma and NO ₂ becomes a maximum value. This is a nitrogen oxide purification method to be set.

When low-temperature non-equilibrium plasma is generated in the exhaust gas, NOx oxidation and reduction cycles are affected by the active oxygen and active nitrogen present in the air due to the discharge of the low-temperature non-equilibrium plasma, and NO and NO ₂ are oxidized and reduced. Is done.

The present invention, by the generation of low-temperature nonequilibrium plasma, if NO in the exhaust gas is oxidized to NO _2, the reference value applied voltage NO ₂ amount is largest, the applied voltage to generate a low-temperature nonequilibrium plasma Set and oxidize NO in exhaust gas to easily treatable NO ₂ , further suppress the amount of NO ₂ reaction to become a by-product, the maximum amount of NO contained in nitrogen oxides It becomes possible to oxidize to nearby NO ₂ .

Oxidized NO ₂ is relatively easily removed from the exhaust gas using the reducing agent solution. Therefore, the voltage at which the amount of NO ₂ generated from nitrogen oxides in the exhaust gas becomes the maximum value is applied as a reference value. The voltage can be set and NO can be oxidized to NO ₂ at a significantly lower voltage (or significantly lower power) than the voltage applied by the conventional plasma method, thus reducing energy consumption and reducing costs. Can do.

In addition, since the applied voltage is set using the voltage at which NO ₂ is the maximum value as a reference value, the amount of by-products generated can be suppressed, and the generation of by-products that are difficult to remove can be suppressed. Thus, it is possible to provide an efficient nitrogen oxide purification method.

Further, according to the present invention, as a voltage setting for generating the atmospheric pressure low temperature non-equilibrium plasma, NO in the gas is oxidized by the generation of the atmospheric pressure low temperature non-equilibrium plasma to generate NO ₂ , and the NO is below a predetermined value. In addition, the value at which NO ₂ generated by oxidation is the maximum value is set as a reference value, and an arbitrary value at which a by-product generated is a predetermined value or less is set as a set value.

Thus, when the applied voltage is set, the predetermined value voltage is applied to generate a low-temperature non-equilibrium plasma in the exhaust gas, and NO in the exhaust gas is oxidized by active oxygen or the like to generate a low-temperature non-equilibrium plasma. An amount of NO ₂ that can be easily processed in a later step can be generated so as to be in the vicinity of the maximum value.

According to the method of the present invention, since the reference value is set to a value at which the amount of by-products generated by further progress of the reaction of NO ₂ is less than or equal to a predetermined value, NO ₂ can be removed in this step.

In addition, in this method, since the necessary voltage at which the amount of NO ₂ generated becomes the maximum value is applied, the applied voltage is set to a lower value than in the case of using the conventional plasma method, and the energy consumption is greatly reduced. Cost can be reduced.

In addition, the present invention provides a step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting an applied voltage using a value at which NO in exhaust gas is oxidized and NO ₂ becomes a maximum value as a reference value; A step of reacting the exhaust gas that has generated the equilibrium plasma with the reducing agent solution.

In this manner, in the step of setting the predetermined applied voltage and generating the low temperature non-equilibrium plasma, after oxidizing NO contained in the gas to NO ₂ , the exhaust gas containing NO ₂ is reacted with the reducing agent solution. Nitrogen oxides contained in the exhaust gas are efficiently removed using a wet process (chemical process using a reducing agent).

  Therefore, not only a dry process for generating low-temperature non-equilibrium plasma in exhaust gas but also a wet process for reacting exhaust gas after generating low-temperature non-equilibrium plasma with a reducing agent has little impact on the environment, and It is possible to remove nitrogen oxides in the exhaust gas with a high efficiency of nearly 100% at low cost.

  In addition, the present invention provides a semi-dry type one-stage combination of a dry process for setting a predetermined applied voltage for generating atmospheric pressure low-temperature non-equilibrium plasma in exhaust gas and a wet process in which a reducing agent solution is reacted with exhaust gas. This process is a method for purifying nitrogen oxides by removing nitrogen oxides in exhaust gas.

  Combining the process of generating low-temperature non-equilibrium plasma on the exhaust gas and the process of reacting with the reducing agent solution makes it a semi-dry type one-step process, which effectively removes nitrogen oxides in the exhaust gas by reducing the number of processes The cost is greatly reduced.

  In the present invention, means for generating a low pressure non-equilibrium plasma at atmospheric pressure by applying a voltage is a pulse discharge method, a ferroelectric pellet filling discharge method, a silent discharge (barrier discharge), a creeping discharge, a direct current discharge, or A system based on these combinations is used.

  As described above, as a means for generating the low temperature non-equilibrium plasma, a pulse discharge method, a ferroelectric pellet filling discharge method, a silent discharge (barrier discharge), a creeping discharge, a direct current discharge, or a combination of these methods may be used. It is possible to generate low-temperature plasma at atmospheric pressure by a relatively simple process without requiring a complicated process such as maintenance of vacuum conditions as in the prior art.

The reducing agent used in the present invention is sodium sulfite (Na ₂ SO ₃ ) and / or sodium sulfide (Na ₂ S).

  In this way, when sodium sulfite and / or sodium sulfide is used as a reducing agent, nitrogen oxides are removed using a reducing agent that has little environmental impact and does not produce by-products. Therefore, it is possible to purify nitrogen oxides in exhaust gas with high efficiency close to 100%.

  The present invention is also a method for purifying nitrogen oxides and / or sulfur oxides comprising a step of reacting exhaust gas with a reducing agent solution.

  For example, when sodium hydroxide is used as a strong reducing agent, sulfur oxide (SOx) reacts with this reducing agent solution to produce sodium sulfite.

  Since this sodium sulfite works as a reducing agent for nitrogen oxides in the exhaust gas, nitrogen oxides and / or sulfur oxides (SOx) can be removed from the exhaust gas.

  Since the sodium sulfite produced by reacting with the sulfur oxide acts as a nitrogen oxide reducing agent as it is, the cost used in the purification method can be reduced.

  In addition, by adding sodium sulfite and / or sodium sulfide to the sodium hydroxide to obtain a reducing agent, a reducing agent sufficient for the reaction of nitrogen oxides and / or sulfur oxides in the exhaust gas is supplied and efficiently. , Nitrogen oxides and / or sulfur oxides can be removed from the exhaust gas.

  The present invention also includes a reactor for generating atmospheric low-temperature non-equilibrium plasma in exhaust gas, a reactor for reacting the exhaust gas with a reducing agent solution, a dry process for generating the atmospheric low-temperature non-equilibrium plasma, and the reducing agent. This is a nitrogen oxide purifying apparatus that removes nitrogen oxides in exhaust gas using a two-stage processing means of wet processing using a solution.

Thus, the nitrogen oxide purification apparatus of the present invention includes a reactor that generates low-temperature non-equilibrium plasma on exhaust gas, and a reactor that contacts the exhaust gas and the reducing agent solution, so that low-temperature non-equilibrium plasma is generated inside the first reactor. To oxidize nitrogen oxides in the exhaust gas, and react the oxidized NO ₂ with the reducing agent solution in the second reactor to efficiently remove nitrogen oxides from the exhaust gas.

  In addition, the reactor includes means for reacting exhaust gas that has generated atmospheric low-temperature non-equilibrium plasma with a reducing agent solution, and performs processing for generating the atmospheric low-temperature non-equilibrium plasma and processing using the reducing agent solution. The nitrogen oxide purification device using the combined means can perform a two-stage process in one device, a step of generating low-temperature non-equilibrium plasma on the exhaust gas and a step of reacting the reducing agent solution. Cost reduction and work space can be reduced.

  Further, when the purification device includes a reactor for reacting exhaust gas with a reducing agent solution, nitrogen treatment and / or sulfide oxide in the exhaust gas is removed using a wet processing unit using the reducing agent solution. Nitrogen oxide and / or sulfur oxide can be efficiently produced from the exhaust gas by reacting with the reducing agent solution.

  Thus, according to the present invention, nitrogen oxides in the environment can be efficiently removed at a lower voltage than before, and a significant cost reduction corresponding to about 1/10 of the conventional cost can be achieved. In addition, the generation of side reaction products can be suppressed, and nitrogen oxides in the environment can be removed with higher efficiency than before.

It is a longitudinal cross-sectional view explaining the schematic structure of the reactor of the filling barrier discharge type | formula used for this experiment in the specific example of this invention. It is a schematic block diagram which shows the whole structure of the purification apparatus provided with the plasma reactor and chemical reactor shown in FIG. 1 in the specific example of this invention. It is a figure which shows the relationship between the applied voltage and current of a reactor at the time of filling each pellet material into the reactor shown in FIG. 1, and filling each pellet material in the specific example of this invention. In accordance with the first experimental example of the present invention, using a GPR in which a plasma pellet filled with glass pellets having a diameter of 6 mm is used, dry air is passed through the reactor at each flow rate, and voltage change at each flow rate is obtained. NO in the sample gas, it is a graph showing changes in NO ₂ concentration. According to a second experimental example of the present invention, using an FPR in which a plasma reactor is filled with 4 mm diameter barium titanate pellets, a sample gas is passed through the reactor at a flow rate of 4.0 L / min. a voltage applied to the reactor, which is a graph showing changes in the NOx concentration that indicates the sum of the NO concentration in the sample gas after the reactor through flow, NO ₂ concentration and the NO concentration and NO ₂ concentration. According to a third experimental example of the present invention, using a GPR in which a plasma reactor is filled with a glass pellet having a diameter of 6 mm, a sample gas is passed through the reactor at a flow rate of 4.0 L / min. and the voltage applied, NO concentration in the sample gas after the reactor through flow, NO ₂ concentration, and is a graph showing changes in NOx concentration of the applied voltage and the sample gas having passed through the chemical reactor. According to a fourth experimental example of the present invention, using an FPR in which a plasma reactor is filled with pellets made of barium titanate having a diameter of 4 mm, a sample gas is passed through the reactor at a flow rate of 4.0 L / min. a voltage applied to the reactor, NO concentration in the sample gas after the reactor through flow, NO ₂ concentration, and is a graph showing changes in NOx concentration of the applied voltage and the sample gas having passed through the chemical reactor. According to the fifth experimental example of the present invention, (a) shows the result of measuring the concentration of each component in the sample gas after passing through the plasma reactor using the internal electrode having a diameter of 1.5 mm, (b) (A) is a figure which shows the result of having measured the density | concentration of each component in the sample gas after passing the plasma reactor using an internal electrode with a diameter of 5 mm. According to a sixth experimental example of the present invention, (a) is a plasma reactor filled with 1 mm diameter BaTiO ₃ pellets, (b) is a plasma reactor filled with 2 mm diameter BaTiO ₃ pellets, (c) These are figures which show the result of having measured each component in the sample gas after flowing through each plasma reactor at a flow rate of 2.0 L / min using a plasma reactor filled with pellets of BaTiO _{3 with} a diameter of 3 mm. . The figure which shows the result of having measured the density | concentration of each component in the sample gas which flowed through the chemical reactor after flowing sample gas with the flow volume of 2.0 L / min concerning the 6th experiment example of this invention. It is. It is a figure which shows the expense which took in one year in order to remove 1 ton of nitrogen oxides in an environment with respect to each nitrogen oxide removal efficiency in the conventional method and the method of this invention.

Explanation of symbols

1 Purification device 2 Compressor
3 Plasma Reactor 4 Tank 5 Flow Control Valve 6 Chemical Reactor 7 Analyzer 8 Connecting Member 9 Power Supply 10 High Voltage Probe and Oscilloscope 11 Air Dryer 12 Flow Control Valve 13 Flow Control Valve 31 Reactor Body 32 Dielectric Material 33 Inflow Port 34 Outflow portion 35 Bush 36 Bush 37 Disc 38 Central electrode 39 External electrode 40 Support plate 41 Support plate

Claims (21)

In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method generates atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas to remove nitrogen oxide, and the atmospheric pressure Nitrogen oxidation characterized in that an applied voltage for generating the atmospheric pressure low temperature non-equilibrium plasma is set with reference to a value at which NO in the gas is oxidized by the generation of the low temperature non-equilibrium plasma and NO ₂ becomes the maximum value. Purification method. In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method generates atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas to remove nitrogen oxide, and the atmospheric pressure The NO in the gas is oxidized by the generation of the low-temperature non-equilibrium plasma to generate NO ₂ , and the NO is not more than a predetermined value, and the NO ₂ generated by oxidation is the maximum value. A method for purifying nitrogen oxides, wherein an applied voltage for generating the atmospheric pressure low-temperature non-equilibrium plasma is set with an arbitrary value at which a by-product is equal to or less than a predetermined value as a set value. In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method sets an applied voltage with reference to a value at which NO in the exhaust gas is oxidized and NO ₂ becomes the maximum value. And a step of generating atmospheric pressure low temperature non-equilibrium plasma and a step of reacting the exhaust gas that has generated the atmospheric pressure low temperature non-equilibrium plasma with a reducing agent solution. In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method generates NO ₂ by oxidizing NO in the gas by generating the atmospheric pressure low temperature non-equilibrium plasma, together but equal to or less than a predetermined value as a reference value a value that NO ₂ is the maximum values generated oxidized, an arbitrary value by-products is less than or equal to a predetermined value that is generated as a set value, to set the applied voltage And a step of generating a low-pressure non-equilibrium plasma at atmospheric pressure and a step of reacting a reducing agent solution with the exhaust gas that has generated the low-temperature non-equilibrium plasma at atmospheric pressure. In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method is such that NO in the gas is oxidized by the generation of atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas, and NO ₂ becomes the maximum value. A step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting an applied voltage using the value as a reference value, and a step of reacting the exhaust gas that has generated the atmospheric pressure low temperature non-equilibrium plasma with a reducing agent solution, the atmospheric pressure low temperature A method for purifying nitrogen oxides, wherein nitrogen oxides in exhaust gas are removed by a two-step process comprising a dry process for generating non-equilibrium plasma and a wet process using the reducing agent solution. In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method generates NO ₂ by oxidizing NO in the gas by generating atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas, Applying NO as a predetermined value and a value at which NO ₂ generated by oxidation is a maximum value as a reference value, and an arbitrary value as a set value for a by-product generated by NO ₂ reaction as a set value A step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting a voltage; and a step of reacting an exhaust gas that has generated the atmospheric pressure low temperature non-equilibrium plasma with a reducing agent solution to generate the atmospheric pressure low temperature non-equilibrium plasma And nitrogen oxides in the exhaust gas are removed by a two-stage process of the above step and a wet process using the reducing agent solution. In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method is a maximum value in which NO in the gas is oxidized to NO _{2 due} to the generation of atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas. And a step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting an applied voltage with the value of the reference value as a reference value, and a step of reacting exhaust gas that has generated the atmospheric pressure low temperature non-equilibrium plasma with a reducing agent solution, the atmospheric pressure Nitrogen oxide purification characterized by removing nitrogen oxides in exhaust gas by a semi-dry one-step process in which a process of generating low-temperature non-equilibrium plasma and a process using the reducing agent solution are combined. Method. In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method generates NO ₂ by oxidizing NO in the exhaust gas by generating atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas, The value at which NO is reduced to a predetermined value or less, and the value at which NO ₂ generated by oxidation is maximized is set as a reference value, and an arbitrary value at which a by-product generated by NO ₂ reaction is set to a predetermined value or less is set A step of generating an atmospheric pressure low temperature non-equilibrium plasma by setting an applied voltage as a value, and a step of reacting the exhaust gas that has generated the atmospheric pressure low temperature non-equilibrium plasma with a reducing agent solution, the atmospheric pressure low temperature non-equilibrium plasma Of nitrogen oxides in the exhaust gas is removed by a semi-dry one-step process in which a process using a reducing agent solution is combined Method.   In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method includes a dry process for generating atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas, and the atmospheric pressure low temperature non-equilibrium plasma generated. A method for purifying nitrogen oxides, comprising a wet process for reacting exhaust gas with a reducing agent solution.   In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method includes a step of generating an atmospheric low temperature non-equilibrium plasma in the exhaust gas, and an exhaust gas generating the atmospheric low temperature non-equilibrium plasma. A step of reacting a reducing agent solution, and a two-step process of generating a low-pressure non-equilibrium plasma at atmospheric pressure and a wet process using the reducing agent solution, to reduce nitrogen oxides in exhaust gas. A method for purifying nitrogen oxides comprising removing the nitrogen oxides.   In the nitrogen oxide purification method for removing nitrogen oxides contained in the exhaust gas, the purification method includes the step of generating an atmospheric low temperature non-equilibrium plasma in the exhaust gas, and the exhaust gas that has generated the atmospheric low temperature non-equilibrium plasma. A step of reacting with a reducing agent solution, and a step of generating the atmospheric pressure low temperature non-equilibrium plasma and a step of semi-drying in which the step of using the reducing agent solution is combined; A method for purifying nitrogen oxides, characterized by removing water.   In the step of generating the atmospheric pressure low temperature non-equilibrium plasma, as means for generating the atmospheric pressure low temperature non-equilibrium plasma by applying a voltage, pulse discharge method, ferroelectric pellet filling discharge method, silent discharge (barrier discharge), The method for purifying nitrogen oxides according to any one of claims 1 to 11, wherein creeping discharge, direct current discharge, or a combination thereof is used. The method for purifying nitrogen oxides according to any one of claims 1 to 12, wherein sodium sulfite (Na ₂ SO ₃ ) and / or sodium sulfide (Na ₂ S) is used as the reducing agent.   A method for purifying nitrogen oxides for purifying nitrogen oxides contained in exhaust gas, wherein the purification method comprises a step of reacting exhaust gas with a reducing solution. The reducing agent is, purification method of claim 14 nitrogen oxides, wherein the use of sodium sulfite _(Na 2 SO ₃₎ and / or sodium sulfide _(Na 2 S).   In the exhaust gas purification method for purifying nitrogen oxide and / or sulfur oxide (SOx) contained in the exhaust gas, the purification method includes a step of reacting the exhaust gas with a reducing agent solution. For purifying substances and / or sulfur oxides.   17. The nitrogen oxide and / or sulfur oxide purification method according to claim 16, wherein sodium hydroxide (NaOH) is used as the reducing agent. The nitrogen oxide and / or sulfur according to claim 16, wherein the reducing agent is sodium hydroxide (NaOH) and sodium sulfite (Na ₂ SO ₃ ) and / or sodium sulfide (Na ₂ S). Oxide purification method.   A nitrogen oxide purification device for removing nitrogen oxides contained in exhaust gas, the purification device comprising a reactor for generating atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas, and a reactor for reacting the exhaust gas with a reducing agent solution And removing nitrogen oxides in the exhaust gas using a two-stage processing means of a dry process for generating the atmospheric pressure low temperature non-equilibrium plasma and a wet process using the reducing agent solution. Nitrogen oxide purification device.   A nitrogen oxide purification device for removing nitrogen oxides contained in exhaust gas, wherein the purification device has a reactor that generates atmospheric pressure low temperature non-equilibrium plasma in the exhaust gas, Characterized by comprising means for reacting exhaust gas that has generated non-equilibrium plasma with a reducing agent solution, and using means that combines the process for generating the atmospheric pressure low-temperature non-equilibrium plasma and the process using the reducing agent solution. Nitrogen oxide purification device. A nitrogen oxide and sulfur oxide purification device for removing nitrogen oxides and / or sulfur oxides contained in exhaust gas, wherein the purification device comprises a reactor for reacting exhaust gas with a reducing agent solution, and the reduction A nitrogen oxide and / or sulfur oxide purifier for removing nitrogen oxides and / or sulfur oxides in exhaust gas using a wet processing means using an agent solution.

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