WO2005065805A1

WO2005065805A1 - Method of treating exhaust gas and apparatus therefor

Info

Publication number: WO2005065805A1
Application number: PCT/JP2004/017049
Authority: WO
Inventors: Masaaki Okubo; Toshiaki Yamamoto; Tomoyuki Kuroki
Original assignee: Osaka Industrial Promotion Organization
Priority date: 2004-01-07
Filing date: 2004-11-17
Publication date: 2005-07-21
Also published as: JPWO2005065805A1; JP4472638B2

Abstract

A method of purifying an exhaust gas containing nitrogen oxides; and an apparatus therefor. The apparatus includes atmospheric pressure low temperature nonequilibrium plasma reactor (1) for converting air to radical gas; line (22) for feeding the radical gas to oxidation reaction zone (10); line (23) for feeding the exhaust gas to the oxidation reaction zone (10) separately from the radical gas formation line; the oxidation reaction zone (10) for oxidizing the nitrogen oxides contained in the exhaust gas with the radical gas into oxidized gas containing NO2; and reduction reaction zone (11) for bringing the oxidized gas into contact with a reducing agent solution so as to effect reduction reaction of NO2 into nitrogen gas (N2), wherein the oxidation reaction zone (10) and the reduction reaction zone (11) are directly connected to each other. Thus, there are provided an exhaust gas treating apparatus and treating method that suppress the occurrence of reaction by-products (for example, N2O, HNO2, HNO3, NO3- and CO) in the exhaust gas, realizing high efficiency.

Description

Specification

Method and apparatus for exhaust gas treatment

Technical field

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for treating exhaust gas, and a reaction by-product in exhaust gas.

(Eg NO, HNO, HNO, NO-, CO) and suppress nitrogen oxides efficiently

2 2 3 3

The present invention relates to a method and apparatus for cleaning.

Background art

Generally, along with the supply of energy represented by power stations and diesel engines and the consumption of such energy, nitrogen acids such as nitrogen monoxide (NO) and nitrogen dioxide (NO 2).

2

Waste is discharged. Nitrogen oxides discharged into the environment are the cause of photochemical smog, etc., and measures are being considered as an important issue of environmental problems in large cities. In addition, one acid, two nitrogen (NO) is also attracting attention as a cause of global warming gas, which has become a problem in recent years.

2

There is.

[0003] As a method of reducing nitrogen oxides, a combustion system, a catalytic system, a selective catalytic reduction system (SCR), an ammonia injection system, and in recent years, the catalytic system, the nonthermal plasma, the electron beam And other techniques to reduce nitrogen oxides, or by combining the above method with a method using chemicals such as ammonia, hydrogen peroxide, calcium chloride and the like, catalysts, and the like. Methods of reducing nitrogen oxides are known.

[0004] Among them, the plasma / chemical hybrid method attracts attention! With respect to the direct non-thermal plasma method based on this principle, the following Patent Documents 1 to 3 have been proposed. Patent Document 1: Japanese Patent Application Laid-Open No. 2000-117049

Patent Document 2: Japanese Patent Application Laid-Open No. 2000-51653

Patent Document 3: Japanese Patent Application Laid-Open No. 2001-300257

However, in the method using a catalyst such as the conventional SCR method, there has been a problem that a large cost is required to increase the nitrogen oxide removal efficiency. In addition, in the conventional method using low temperature non-equilibrium plasma, in order to decompose and remove nitrogen oxides in the environment, dinitrogen monoxide (NO), nitrate ion (NO-), Nitrite (HNO) And by-products such as nitric acid (HNO.sub.2) are produced in large quantities.

3

There was a problem that the removal was done. In order to purify these by-products by oxidation and reduction, there has been a problem that they lead to a further increase in costs. In the method using plasma, the exhaust gas to be treated is flowed directly into the reactor, and the non-thermal plasma is used to acidify NO NO to NO and the two-step method of treating with a chemical scrubber.

2

In other words, the non-thermal direct plasma method has been proposed with relatively low energy efficiency. Since the high temperature gas flows into the plasma reactor, the processing efficiency is reduced. In addition, since the corrosive exhaust gas is allowed to flow into the plasma reactor, there is a problem such as corrosion of electrodes and the like.

[0006] In the method of Patent Document 3, although the exhaust gas is cooled, the harmful gas contained in the exhaust gas is adsorbed on the adsorbent and the plasma decomposition is performed directly, but the corrosive exhaust gas is subjected to a plasma reactor. There is still the problem that corrosion of the electrodes and the like will occur, and removal of byproducts of the gas after plasma decomposition has been carried out.

Disclosure of the invention

In order to solve the above-mentioned conventional problems, the present invention can suppress reaction by-products (eg, NO, HNO, HNO, NO-, CO) in exhaust gas and can process exhaust gas efficiently.

2 2 3 3

An apparatus and method are provided.

The method for treating exhaust gas according to the present invention is a method for purifying an exhaust gas containing nitrogen oxide, wherein air is supplied to an atmospheric pressure low temperature non-equilibrium plasma reactor to generate a radical gas, The nitrogen oxide in the exhaust gas can be supplied by supplying a gas to the acid reaction region and supplying the exhaust gas to a line force separate from the radical gas generation line. Oxidize to NO containing oxidizing gas by radical gas, then

2

NO is reduced to nitrogen gas (N 2) by bringing the acid gas into contact with the reducing agent solution.

twenty two

It is characterized by

The exhaust gas treatment apparatus of the present invention is an apparatus for purifying an exhaust gas containing nitrogen oxide, which comprises an atmospheric pressure low-temperature non-equilibrium plasma reactor for converting air into a radical gas, and the radical gas. A line for supplying an acid reaction region, a line for supplying the exhaust gas to the oxidation reaction region from a line separate from the radical gas generation line, and nitrogen oxides in the exhaust gas are included in the radical To acidify NO-containing oxidizing gas by gas By contacting the oxidation reaction region and the oxidizing gas with a reducing agent solution, NO can be nitrogenated.

A reduction reaction zone for reduction reaction to nitrogen gas (N 2), the oxidation reaction zone and the reduction

2

It is characterized in that the reaction area is directly connected.

Brief description of the drawings

FIG. 1 is a schematic view of an apparatus in which a nonthermal remote plasma method of the present invention and a wet reactor are connected in one embodiment of the present invention.

[Fig. 2] The same, a schematic cross sectional view of a non-thermal plasma reactor.

[Figure 3] The same, schematic cross-sectional view of the chemical scrubber (packing tower).

[FIG. 4] The schematic of the experiment apparatus of the direct plasma method of a comparative example.

[FIG. 5] AB is a graph showing the concentration change in the direct plasma processing method of the comparative example.

FIG. 6A is a graph showing the change in concentration in the comparative example, and FIG. 6B is a graph showing the change in concentration in the treatment method in which the non-thermal remote plasma method and the wet reactor are directly linked in one example of the present invention.

[FIG. 7] AB is a graph which shows the density | concentration change in the direct plasma processing method of a comparative example.

FIG. 8A is a graph showing the change in concentration in the comparative example, and FIG. 8B is a graph showing the change in concentration in the treatment method in which the non-thermal remote plasma method and the wet reactor are directly linked in one example of the present invention.

[Fig. 9] AB is a graph showing the same voltage and current waveforms.

[FIG. 10] A graph showing the plasma consumption energy per unit processing gas volume and the removal efficiency of nitrogen oxides.

FIG. 11 is a schematic view of an apparatus in which boiler exhaust gas in Example 4 of the present invention is treated using the non-thermal remote plasma method of the present invention and a wet reactor.

[Figure 12] Relationship between the NOx removal efficiency and the amount of exhaust gas (Q) Z radical gas (Q) in Example 4

Graph of experimental data for examining G a.

BEST MODE FOR CARRYING OUT THE INVENTION

[0011] The method and apparatus of the present invention comprises: air radicalized with atmospheric pressure low temperature non-equilibrium plasma;

Separately, the exhaust gas is supplied to the oxidation reaction area, the nitrogen oxides in the exhaust gas are oxidized by the radical gas to the oxidation gas containing NO, and then the oxidation gas is brought into contact with the reducing agent solution about

2

Reduces NO to nitrogen gas (N 2). As a result, reaction by-products in the exhaust gas (eg

twenty two

For example, to suppress and efficiently remove NO, HNO, HNO, NO-, CO) it can.

The present invention refers to air as atmospheric pressure low temperature non-equilibrium plasma (hereinafter referred to as “low temperature non-equilibrium plasma”!).

) To generate radical gas, which is supplied to the oxidation reaction zone, reacted with separately supplied exhaust gas, and nitrogen oxides in the exhaust gas contain NO by the radical gas.

2 Acidic acid gas and then contacting the acid gas with a reducing agent solution

2 Reduce to gas (N 2). In the above, the oxidation reaction zone and the reduction reaction zone are one wet process

2

Preferred to be present in the reactor.

The present invention feeds air into a plasma reactor, mixes the radical gas of the air component excited by the low temperature non-equilibrium plasma with the exhaust gas at the bottom of the wet reactor, and oxidizes NO to NO

Then remove by reduction with a chemical scrubber (wet reactor). Hereinafter, the method of the present invention is also referred to as "non-thermal remote plasma-chemical nod method".

The low-temperature non-equilibrium plasma used in the present invention means that the gas temperature is considerably lower than the combustion temperature (about 700-1000 ° C.) of a normal gas, and the plasma in the ionizing state is usually 300 ° C. or less I say plasma. The lower limit temperature may be, for example, 200 ° C. More preferable conditions are temperature: 100 ° C. or less, particularly preferably normal temperature (0-40 ° C.). Other preferable conditions are: pressure: about atmospheric pressure, relative humidity: 60% or less, applied voltage: 10-100 kV, peak current 1 1 100 A, frequency: 250 Hz-1000 Hz.

In the present invention, the oxidation reaction zone and the reduction reaction zone are preferably present in one wet reactor. In particular, it is preferable that the wet reactor be a column or column reactor, the oxidation reaction zone be present at the lower part of the wet reactor, and the reduction reaction zone be present at the upper part of the wet reactor. ,. This will make the device smaller.

[0016] The reducing agent solution is selected from Na 2 SO 4, Na 2 S, NaOH, Na 2 S 2 O, and Ca (OH).

2 3 2 2 2 3 2

It is preferable that it is an aqueous solution containing at least one compound. Aqueous solutions containing these compounds can be recycled with high reducibility.

The exhaust gas that can be treated by the present invention is combustion exhaust gas, and the components to be treated are: soot, soot

Environmental pollution represented by Ν, Ο, Ν O, SO, SO, volatile organic compounds (VOCs) and dioxins

2 2 2 5 2 3

At least one selected from dyestuff, hydrocarbon, CO, CO and steam (H 0) is preferred . For example, nitrogen oxides (NO 2) such as soot, soot, soot, soot, etc. are reduced to nitrogen gas (soot), SO 2, SO 3

Volatilization of sulfur oxides (SO 4) such as 2 2 2 5 x 2 2 3 etc., hydrocarbons, CO, CO, toluene, benzene, xylene, etc.

2

Environmental pollutants such as volatile organic compounds (VOCs), dioxins, halogenated aromatics, and highly condensed aromatic hydrocarbons can be decomposed or converted into harmless substances or substances with low environmental impact.

The advantages of the low temperature non-equilibrium plasma in the present invention are shown below.

(1) Gas force to be plasma-treated Because of the small amount and low temperature compared with the S exhaust gas, the residence time in the reactor is increased, and activated radicals are efficiently formed.

(2) The plasma consumption energy per unit flow rate can be reduced.

(3) Several tens of times of NO can be oxidized by optimization with small flow rate radicals. Therefore, the reactor can be miniaturized.

(4) Adaptable to high temperature exhaust gas. For example, high temperature exhaust gas of 300 ° C. or more can be efficiently oxidized to NO by low temperature remote plasma at room temperature (27 ° C.).

2

One embodiment of the present invention relates to a method and apparatus for treating exhaust gas, which uses a reducing agent solution for radical gas formed by low-temperature non-equilibrium plasma at atmospheric pressure installed separately from the exhaust gas line. Reaction by-products (N 0

2, HNO

3, NO-

3. Provide an apparatus and method capable of suppressing and efficiently treating CO, etc.).

In one embodiment of the present invention, a low temperature non-thermal plasma reactor installed outside the exhaust gas flow path and a wet chemical scrubber (wet reactor) into which activated radicals are injected are directly connected. There is. As a result, since only air is supplied to the low temperature non-thermal plasma reactor, it can be operated at all times. That is, even if the exhaust gas flow rate fluctuates, the operating condition of the low-temperature non-thermal plasma reactor does not have to be fluctuated if the plasma gas generation amount is set to the maximum required amount or more. Moreover, the processing efficiency is high, as it is energy efficient. In addition, since only the air flows in the plasma reactor, the corrosion problems of the electrodes and the like are also improved.

The type of low temperature non-thermal plasma reactor and the type of plasma to be generated are not particularly limited. V can be exemplified as a preferred example of the non-equilibrium plasma reactor described in the following examples. Besides, as a method of applying plasma, a pulse discharge method by alternating current or direct current voltage, no Voice discharge method, corona discharge method, creeping discharge method, barrier discharge method, honeycomb discharge method, pellet packed bed discharge method, arc discharge method, inductively coupled discharge method, capacitively coupled discharge method, microwave excitation discharge method, laser induced A discharge method, an electron beam induced discharge method, a particle beam induced discharge method, or a combination of these can be used. That is, the plasma reactor used in the present invention can adopt various conceivable methods suitable for each method of applying plasma. It is particularly convenient to use the non-equilibrium plasma generated by the non-equilibrium plasma force pulse corona discharge.

The type of wet chemical scrubber is also not particularly limited, and the ability to use various types of scrubbers. A typical chemical scrubber of the Raschig ring filling type described in Example 1 below is a preferred example. Can. Besides, a bubble scrubbing type chemical scrubber in a liquid phase can be mentioned as a suitable example.

Example

(1) Description of Reaction

In this embodiment, the purpose is to remove air pollutants such as nitrogen oxides, NOx and the like emitted from diesel engines and thermal power plants by the hybrid process combining non-equilibrium plasma process and wet chemical reaction process. . The chemical reaction of this process is a combination of the following two reactions.

Plasma process: NO + 0 * (oxygen radical) + M (third body object) → NO + M (1)

2

Wet chemical reaction process: 2NO + 4Na SO → N + 4Na SO (2)

2 2 3 2 2 4

The reaction (1) accounts for the majority of the exhaust gas NO is oxidized to NO at low cost,

2

According to the reaction (2), NO is reduced to harmless and water-soluble Na 2 SO 4 and N. It is different from Na SO

A drug such as Na 2 S 2, 2 3 2 3 3 (eg, Na 2 S, NaOH, Na 2 S 2 O 3, Ca (OH), etc.) may be used.

2 2 2 3 2

In this example, in the non-equilibrium plasma process (in the reaction (1) above, experiments were conducted using the non-thermal remote (indirect) plasma method as compared to the conventional direct plasma method, and the performances of the two were compared) Here, the exhaust gas to be treated flows directly into the reactor to oxidize NO to NO

2

Named as direct plasma method. On the other hand, non-thermal remote method is to flow air or a small amount of additive (hydrocarbon, ammonia, etc.) into the plasma reactor, inject excited radical gas into the exhaust gas flow path, and oxidize NO to NO. Name it (indirect) plasma method. (2) Experimental apparatus of this embodiment

An outline of an experimental apparatus 50 using the non-thermal remote plasma method of the present invention is shown in FIG.

Compressed air is supplied from the compressor 32 to a dryer 33 equipped with an air filter to produce dry air, and this dry air is supplied to the non-thermal plasma reactor 1 at a predetermined flow rate by a mass flow controller 35. The non-thermal plasma reactor 1 is applied with a high-speed rising short width pulse high voltage generated by an IGBT pulse power supply (PPCP Pulsar SMC-30 / 1000, manufactured by Masuda Laboratories) 21. As a result, an active group containing radicals such as 0, 0 *, OH, N, etc.

3

Generated the The applied voltage, current, and power consumption of the non-thermal plasma reactor 1 are measured with an oscilloscope (Yokogawa DL1740) 37, a high voltage probe, and a current probe (SonyTektronix, P6015A and P6021), and the integrated value of instantaneous power I asked for power consumption. The activated gas thus obtained is directly injected into the chemical scrubber 11 of the wet reactor.

On the other hand, NO gas, which is a model gas of exhaust gas, is supplied at a predetermined flow rate from a 2% NO bomb 31 by a mass flow controller 34 and supplied at a predetermined flow rate from an air supply line 51 by a mass flow controller 52. The simulated exhaust gas (air-diluted NOx, concentration 300 ppm) in which NO is adjusted to a predetermined concentration is directly injected into the chemical scrubber 11 by mixing with NO. The reaction (1) takes place in the lower acid reaction zone 10 of the chemical scrubber 11 and the reaction

(2) occurs above the lower part of the chemical scrubber 11. Thus, in the chemical scrubber 11, the reactions (1) and (2) occur continuously. The generated gas was passed through an ozone removal heater 38, and the concentration of NO, NO 2 CO, N 0, CO 2 0 was measured by a gas analyzer (PG-235 and VIA-510 manufactured by Horiba, Ltd.) 39. 40 is a gas outlet, 41 is a Na 2 SO 4 aqueous solution

X, 2 2 2 3 3

(3) Plasma reactor of this embodiment

A schematic cross-sectional view of the nonthermal plasma reactor is shown in FIG. The non-thermal plasma reactor 1 has a cylindrical reaction tube which has a 1.5 mm diameter stainless steel discharge wire electrode 3 passing through an inner space of a Pyrex (registered trademark) glass (quartz glass) cylinder 2 with an inner diameter of 20 mm and an outer diameter of 24 mm. A copper mesh (effective length: 260 mm) was placed on the outer wall of 2 to form a ground electrode 4. A pulsed high voltage power supply 21 was connected between the discharge wire electrode 3 and the ground electrode 4. The lower and upper hollow portions of the cylinder 2 were sealed by silicone rubber stoppers 5 and 6. 7 is a porous plate made of polytetrafluoroethylene, 8 is a gas supply port, 9 Indicates a gas outlet, and a and b indicate gas flows. The reaction (1) is realized by this plasma reactor.

(4) Wet reactor of this example

A schematic cross-sectional view of a chemical scrubber (packed column) 11 which is a wet reactor is shown in FIG. The gas to be treated is made to flow from the lower part to the upper part of the stainless steel tube 12 with an inner diameter of 55.5 mm and an outer diameter of 60.5 mm, and the Na 2 SO 4 aqueous solution 14 is sprayed from the upper part by a spray nozzle 13

twenty three

The wet chemical reaction (2) is carried out. The inside is filled with Raschig ring (made of cylindrical glass, inner diameter 5 mm, outer diameter 7 mm, width 7.2 mm) 15 in order to accelerate the reaction. The reference numeral 15a is an enlarged shape of the lashing. The filling height of the Raschig ring 15 is 160 mm, the height of the liquid spray nozzle 13 is from the gas inlet 16 to 340 mm, and the difference in height from the gas inlet 16 to the Raschig start point is 100 mm. 17 shows a gas outlet, c and d show gas flows. The numeral 18 is a manometer for measuring the height of the liquid, 19 is a valve, 20 is a liquid (drain) outlet, and e is the flow of the discharged liquid.

(5) Experimental apparatus for direct plasma method used in comparative example

An outline of the experimental apparatus 30 of the direct plasma method is shown in FIG. 2% NO gas cylinder 31 Force et al. NO gas is supplied by a mass flow controller 34 at a predetermined flow rate. On the other hand, compressed air is supplied from the compressor 32 to a dryer 33 equipped with an air filter to produce dry air, and this dry air is supplied by a mass flow controller 35 at a predetermined flow rate. Thereafter, the plasma reactor 1 is supplied with a simulated exhaust gas (air diluted NOx, concentration 300 ppm) in which NO is adjusted to a predetermined concentration by mixing with NO. The plasma reactor 1 is applied with a high-speed rising short width pulse high voltage generated by an IGBT pulse power supply (PPCP Pulsar SMC-30 / 1000, manufactured by Masuda Laboratory) 21. This causes the reaction (1) to occur, and then the reduction treatment reaction (2) is performed in the chemical scrubber 11. Next, let it pass through the ozone removal heater 38, gas analyzer (HORIBA's PG-235 and VIA-510) 39 and NO, NO CO, N 0, CO,

X, 2 2

The concentration of O was measured. Applied voltage, current and power consumption of non-thermal plasma reactor 1

2

The power consumption was determined from the integrated value of instantaneous power by measuring with a scope (Yokogawa Electric Corporation DL 1740) 37, a high voltage probe, and a current probe (P6015A and P6021 manufactured by Sony Tektronix). 40 is a gas outlet, 41 is a Na 2 SO 4 aqueous solution tank.

twenty three

(Example Comparative Example 1 1 3) Example 1 uses the apparatus shown in FIG. 1, Comparative Example 1 deals with the direct plasma processing apparatus 30 of FIG. 4 only, and Comparative Example 2 deals with the direct plasma apparatus 30 and wet reactor 11 shown in FIG. In Comparative Example 3, only the non-thermal remote plasma apparatus 50 shown in FIG. 1 was used, and the removal experiment of NO was performed when the flow rate of the simulated gas was 5.0 L / min.

X

The flow rate of the simulated exhaust gas was 5.0 L / min, the flow rate of the radical gas at remote was 0.5 L / min, and the initial concentration of NO was 300 ppm. When the wet reactor 11 is used, the flow rate of the reducing agent aqueous solution to be flowed to the packed column is 0.20 L / min, and the concentration of Na 2 SO 4 is 2.0 g / L. Also, IGBT pulse power

twenty three

The source frequency was set to 420 Hz. The residence time in the plasma reactor at this time was 0.84 s for the direct method and 8.4 s for the remote method.

The above results are shown in FIGS. 5A-B and 6A-B. Fig. 5A shows the direct plasma method only (Comparative Example 1), Fig. 5B shows the process in which the direct plasma method and the wet reactor are directly connected (Comparative Example 2), and Fig. 6A shows the non-thermal remote plasma method only (Comparative Example 3), 6B is data of a process in which a nonthermal remote plasma method and a wet reactor are directly connected (Example 1).

[0030] Comparing FIGS. 5A-B and 6A-B, the non-thermal remote plasma method (FIGS. 6A-B) consumes less reactor power than the direct plasma method (FIGS. 5A-B). It can be seen that the reduction in NOx is also large. In addition, comparing Figs. 6A-B, it can be seen that the reduction amount of NO and NOx in which the power consumption of the reactor is smaller is larger in Fig. 6B. Forces that concern about the generation of N 0 and CO as harmful by-products when the plasma is applied As shown in FIG.

About 22 lO ppm, CO was less than 7 ppm. In addition, the concentration of CO is around 360 ppm, several ppm

2

A decrease was seen.

(Example 2, Comparative Example 4 1 6)

Example 2 uses the apparatus shown in FIG. 1, Comparative Example 4 deals with the direct plasma processing apparatus 30 of FIG. 4 only, and Comparative Example 5 deals with the direct plasma apparatus 30 and wet reactor 11 shown in FIG. In Comparative Example 6, only the non-thermal remote plasma apparatus 50 shown in FIG. 1 was used, and NO removal experiments were conducted when the flow rate of the simulated gas was 7.0 L / min.

X

Next, the flow rate of the simulated exhaust gas was 7.0 L / min, the radical gas at the remote was 0.7 L / min, and the initial concentration of NO was 300 ppm. When the wet reactor 11 is used, the flow rate of the reducing agent aqueous solution to be flowed to the packed column was 0.20 L / min, and the concentration of Na 2 SO was 2.0 g / L. Also, for IGBT pulse power supplies The frequency was set to 420 Hz. The residence time in the plasma reactor at this time was 0.6 s for the direct method and 6.0 s for the remote method.

The results are shown in FIGS. 7A-B and 8A-B. Fig. 7A shows the direct plasma method only (Comparative Example 4), Fig. 7B shows the process in which the direct plasma method and the wet reactor are directly connected (Comparative Example 5), and Fig. 8A shows the non-thermal remote plasma method only These are the data of the processing (Example 2) in which the non-thermal remote plasma method and the wet reactor were connected directly.

[0034] Comparing FIGS. 7A-B and 8A-B, as in the cases of FIGS. 5A-B and 6A-B, the non-thermal remote plasma method (FIGS. 8A-B) consumes less reactor power. In addition, comparing Fig. 8A-B, Fig. 8B also shows that the reduction amount of NO and NOx, where the reactor power consumption is smaller, is larger. In FIG. 8B, which is an example of the present invention, NO was about 10 ppm and CO was 7 ppm or less.

2

The concentration of CO was around 370 ppm, with a few ppm decrease.

2

FIGS. 9A-B show examples of voltage and current waveforms corresponding to FIGS. 8A-B, respectively.

(Example 3, Comparative Example 7)

Unit treatment gas volume for the treatment in which the nonthermal remote plasma method shown in FIG. 1 and the wet reactor are directly connected (Example 3) and the treatment in which the direct plasma method and the wet reactor shown in FIG. We examined the relationship between the per unit plasma consumption energy (SED) and the removal efficiency. That is, the SED (plasma consumption energy per unit processing gas volume) was calculated from the reactor power consumption, and the relationship between SED and NO, NOx removal efficiency was investigated.

The results are shown in FIG. This is the result of simultaneously performing plasma processing and wet processing at a flow rate of 7 L / min. From Fig. 10, when using the non-thermal remote plasma method (remote), about 30% of SED = 35 J / L = 10 Wh / m ³ and about 80% NO when using the direct plasma method (direct). Reduce and remove NOx!

[0038] From the above experiments, the plasma-chemical nanolibritt process using the non-thermal remote plasma method of the present example shows a significant improvement in energy efficiency, and it is approximately compared to the case where the direct plasma method is used. It was confirmed that NOx was reduced and removed with energy per unit flow rate of 30%.

The above experimental powers The advantages of the non-thermal remote plasma method that has been found are shown below.

(a) A plasma rear of the same size because it is small compared to the gaseous exhaust gas to be plasma-treated In the case of using a kuta, the residence time is increased, and miniaturization is possible.

(b) The energy consumption can be further reduced by lowering the plasma consumption energy per unit flow rate.

(c) Several tens of times of NO can be oxidized if optimization is carried out with a small flow rate injection.

Example 4

In Example 4, a pilot test using an actual boiler was conducted to demonstrate the remote non-thermal plasma 'chemical no-e-blit process technology of the present invention.

An experimental device diagram is shown in FIG. The same reference numerals are given to the devices common to FIG. 1 and the description is omitted. As a boiler, a small-sized smoke pipe type small boiler 60 using A fuel oil as fuel was used. The exhaust gas from the boiler 60 was supplied from the exhaust gas supply line 23 to the oxidation reaction zone 10 in the lower part of the chemical scrubber 11. A non-thermal plasma reactor 1 was a pulse discharge reactor. 21 high voltage power supply. The chemical scrubber 11 is filled with a filler as shown in FIG. 3 to promote gas-liquid contact reaction. Also, the Na 2 SO 4 aqueous solution is

The chemical scrubber 11 was supplied from the top of the 2 3 4 tank 41 to the spray 42 to be sprayed, collected at the bottom, and pumped back to the top.

The radical gas generated by the non-thermal plasma reactor 1 by sucking the outside air is carried by the fan 61 rotated by the motor, injected into the exhaust gas flue, and oxidized in the lower part of the chemical scrubber 11. Was supplied. NO in exhaust gas is oxidized to NO by radicals such as ozone, and in the chemical scrubber 11, NO is reduced and removed to Na by Na 2 SO 4,

2 2 2 3 2

The upper force of the chemical scrubber 11 was also exhausted.

Exhaust gas flow from the boiler 60 Q = 450-1170 Nm ³ Zh, radical gas flow Q = 5 gr

Figure 12 shows the relationship between plasma consumption energy per unit process gas volume and NO, NOx removal efficiency when changing to 0-180 Nm ³ Zh. From Fig. 12, it can be confirmed that NO and NOx can be removed efficiently even with high temperature exhaust gas.

[0044] As a result, it was shown that the remote non-thermal plasma 'chemical noble metal process technology of the present invention is also effective for actual boiler exhaust gas.

[0045] (Industrial Applicability)

The exhaust gas treatment method and apparatus of the present invention are a diesel engine, a boiler, a gaster It can be connected to combustion systems such as bottles and incinerators.

Claims

The scope of the claims

[1] A method of purifying exhaust gas containing nitrogen oxide,

Air is supplied to an atmospheric pressure low temperature non-equilibrium plasma reactor to generate a radical gas, and the radical gas is supplied to an oxidation reaction zone,

The nitrogen gas in the exhaust gas is converted into an oxidizing gas containing NO by the radical gas by supplying the exhaust gas to the oxidation reaction region separate from the radical gas generation line. Oxidized

2

Next, NO is converted to nitrogen gas (N 2) by bringing the oxidizing gas into contact with the reducing agent solution.

2. A method of treating exhaust gas characterized by reducing reaction.

[2] The method for treating exhaust gas according to claim 1, wherein the oxidation reaction zone and the reduction reaction zone exist in one wet reactor.

[3] The wet reactor is a column or column reactor, the oxidation reaction zone is present at the lower part of the wet reactor, and the reduction reaction zone is present at the upper part of the wet reactor. A method of treating exhaust gas according to Item 1.

[4] The reducing agent solution may be selected from Na 2 SO 4, Na 2 S, NaOH, Na 2 S 2 O, and Ca (OH).

2 3 2 2 2 3 2

The method for treating exhaust gas according to claim 1, which is also an aqueous solution containing one compound.

[5] The method for treating exhaust gas according to claim 1, wherein the reaction temperature in the low temperature non-equilibrium plasma reactor is 300 ° C. or less.

[6] The method for treating exhaust gas according to claim 5, wherein the reaction temperature in the low temperature non-equilibrium plasma reactor is 100 ° C. or less.

[7] The plasma generating means may be a pulse discharge system by alternating current or DC voltage, silent discharge system, corona discharge system, creeping discharge system, barrier discharge system, honeycomb discharge system, pellet packed bed discharge system, arc discharge system, induction The exhaust gas according to claim 1, which is a coupled discharge system, a capacitively coupled discharge system, a microwave excitation discharge system, a laser induced discharge system, an electron beam induced discharge system, a particle beam induced discharge system, or a combination thereof. Processing method.

[8] The exhaust gas treatment according to claim 1, wherein the non-equilibrium plasma generation conditions in the non-equilibrium plasma reactor which causes air to flow are in the range of applied voltage: 10-100 kV, frequency: 250 Hz-1000 Hz. Method.

[9] The method for treating exhaust gas according to claim 1, wherein the non-equilibrium plasma is a non-equilibrium plasma generated by pulse corona discharge.

[10] A device for purifying exhaust gas containing nitrogen oxides, wherein

An atmospheric pressure low temperature non-equilibrium plasma reactor for converting air into a radical gas; a line for supplying the radical gas to an oxidation reaction zone;

A line for supplying the exhaust gas to the acid reaction region separately from the radical gas generation line;

The nitrogen oxide in the exhaust gas is oxidized by the radical gas to an oxidizing gas containing NO.

2

The oxidation reaction zone for

By contacting the oxidizing gas with a reducing agent solution, NO is reduced to nitrogen gas (N 2).

2 2 including a reduction reaction zone to react

An exhaust gas treatment apparatus characterized in that the oxidation reaction area and the reduction reaction area are directly connected.

[11] The oxidation reaction zone and the reduction reaction zone are present in one wet reactor.

A device for treating exhaust gas according to 0.

[12] The wet reactor is a column type or column type reactor, the supply port for the radical gas and the exhaust gas and the oxidation reaction area exist at the lower part, and the catalytic reaction area with the reducing agent solution exists at the upper part. The exhaust gas treatment system according to claim 10, wherein:

[13] The reducing agent solution may be selected from Na 2 SO 4, Na 2 S, NaOH, Na 2 S 2 O, and Ca (OH).

2 3 2 2 2 3 2

The exhaust gas treatment system according to claim 10, wherein the exhaust gas is an aqueous solution containing one compound.

[14] The apparatus for treating exhaust gas according to claim 10, wherein the reaction temperature in the low temperature non-equilibrium plasma reactor is 300 ° C. or less.

[15] The apparatus for treating exhaust gas according to claim 14, wherein the reaction temperature in the low temperature non-equilibrium plasma reactor is 100 ° C. or less.

[16] The plasma generation means may be a pulse discharge system by alternating current or DC voltage, silent discharge system, corona discharge system, creeping discharge system, barrier discharge system, honeycomb discharge system, pellet packed bed discharge system, arc discharge system, induction Coupled discharge method, Capacitively coupled discharge method, Microwave excited discharge method, Laser induced discharge method, Electron beam induced discharge method, Particle beam induction The exhaust gas treatment system according to claim 10, which is an electromotive discharge system or a combination thereof.

[17] The exhaust gas treatment according to claim 10, wherein the non-equilibrium plasma generation conditions in the non-equilibrium plasma reactor for causing air to flow are in the range of applied voltage: 10-100 kV, frequency: 250 Hz-1000 Hz. apparatus.

[18] The exhaust gas processing device according to claim 10, wherein the non-equilibrium plasma is a non-equilibrium plasma generated by pulsed corona discharge.