JPH06182150A - Method to make nitrogen oxide containing exhaust gas harmless - Google Patents

Abstract

PURPOSE:To remove NOx from NOx containing exhaust gas highly efficiently with a small electric power by oxiding NOx-containing exhaust gas by plasma and adsorbing and removing the oxidized NOx with an adsorbent. CONSTITUTION:NOx-containing exhaust gas of a combustion furnace 1 is led to a plasma reaction container 5 through a dust removing apparatus 3. When voltage is applied between electrodes 110, 111 from an electric power source 6, plasma of the exhaust gas is generated between the electrodes 110, 111. The plasma excites and dissociates gas molecules of NOx to make them chemically active and thus the following chemical reactions; NO+O3 NO2 +Q2 and 2NO2+O3 N2O5+O2; are caused. The reaction formula shows that NO in the exhaust gas of the combustion furnace 1 which is led to the plasma reaction container 5 is oxidized and the oxidized NO2 and N2O5 are removed in an adsorbing tower 8. In this way, the method wherein NOx is once oxidized and the oxidized NOx is removed with an adsorbing agent can suppress the necessary electric power to about 1/10 as compared with a conventional NOx reducing method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detoxifying exhaust gas containing nitrogen oxides.

[0002]

2. Description of the Related Art A conventional plasma exhaust gas treatment method will be described with reference to FIG. 7, taking a case of treating nitrogen oxides (NOx) in exhaust gas of a diesel engine as an example.

In FIG. 7, a diesel engine 101
Of the exhaust gas is introduced into the plasma reaction container 105 via the cyclone collector 103. Plasma reactor 10
5, for example, as shown in detail in FIG. 2, an internal electrode 110 is inside the cylindrical glass reaction container 109, and an external electrode 1 is outside.
11 is arranged and a power source 106 for applying a voltage to the internal electrode 110 and the external electrode 111 is provided. Electrode 11
By converting the exhaust gas into plasma between 0 and 111,
NOx in exhaust gas is removed by the following principle. That is, when a voltage is applied between the inner electrode 110 and the outer electrode 111 using the power supply 106, the exhaust gas is turned into plasma by the atmospheric pressure glow discharge phenomenon. Then, for example, NOx causes the following chemical reaction by the reduction reaction. 2NOx → 2NO + O ₂ (1) 2NO ₂ + O ₂ → N ₂ + 2O ₂ (2)

Now, when the engine exhaust gas is made into plasma by utilizing the atmospheric pressure glow discharge phenomenon as described above, (N
O + NO ₂ ) concentration of about 50 to 200 ppm and 2
In the range of a flow rate of about 4 m ³ N / h, the plasma generation power, that is, the power supplied from the power supply 106 is several W to several 10
A NOx removal rate of 80 to 90% can be achieved in the range of W. Therefore, it is being used as an exhaust gas pollution control device for various combustion-related devices such as boilers, gas turbines, and diesel engines.

[0005]

In the conventional processing apparatus using plasma, in order to achieve the NOx removal rate of 80 to 90% at the exhaust gas flow rate of about 2 to 4 m ³ N / h, the range of several W to several 10 W is required. Need electricity. This is the number 10,000
When considering a large-capacity exhaust gas treatment device of 0 to several 100,000 m ³ N / h, the required power is several hundred to several 1,000.
It is as large as KW and its industrial value is low.

In view of the above-mentioned state of the art, the present invention is to provide an exhaust gas treatment method capable of reducing the required electric power without reducing the NOx removal rate in the exhaust gas.

[0007]

The present invention is a method for detoxifying a nitrogen oxide-containing exhaust gas, which comprises oxidizing the nitrogen oxide-containing exhaust gas with plasma and adsorbing and removing the oxidized nitrogen oxide with an adsorbent. Is.

[0008]

In the conventional exhaust gas treatment technology using plasma, NOx in the exhaust gas is reduced by plasma, and NOx is directly decomposed into nitrogen and oxygen by electric energy, so that the power consumption rate is extremely high. On the other hand, in the present invention, oxygen contained in the exhaust gas is converted into ozone by plasma, and the ozone is used to oxidize NOx according to the following equations (3) and (4) to convert into NOx which can be easily adsorbed and desorbed by the adsorbent. It is a thing. _{NO + O 3 → NO 2 +} O 2 ··· (3) 2NO 2 + O 3 → N 2 O 5 + O 2 ··· (4)

That is, when a voltage is applied to NO,
As shown in the above formula (3), NO ₂ is oxidized to generate NO ₂ , and when a voltage is further applied, as shown in the above formula (4), it is further oxidized to generate N ₂ O ₅ . A quantitative graph of the relationship between the power consumption and the change in NOx is shown in FIG.

NO ₂ and N ₂ O produced by oxidation of NO
₅ can be removed by an adsorbent.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG.
In FIG. 1, a general-purpose combustion furnace 1 which is an object for taking measures for pollution of exhaust gas is connected to a dust remover (cyclone collector, etc.) 3 by an exhaust pipe 2. The dust remover 3 removes particles contained in the exhaust gas. The exhaust gas from the dust remover 3 is transferred to the plasma reaction container 5 by the exhaust pipe 4. The electrode (not shown) of the plasma reaction vessel 5 is a power source 6
Connected to. The exhaust gas leaving the plasma reaction vessel 5 is introduced into the adsorption tower 8 through the exhaust pipe 7. In the figure, 9 is an exhaust gas outlet pipe.

The plasma reaction vessel 5 has a cylindrical shape as shown in FIG. 2 and contains quartz glass, silica glass,
It has a cylindrical wall 109 made of borosilicate glass, alumina silicate glass, or the like. The inlet of the reaction vessel 5 is connected to the exhaust pipe 4 in FIG. 1, and the outlet is connected to the exhaust pipe 7 in FIG.
Further, the electrode 111 is provided on the outer side of the cylindrical wall 109, and the electrode 110 is provided on the inner side. These electrodes 111,
110 is connected to the power supply 106.

The absorption tower 8 has a cylindrical shape as shown in FIG. 4, and is filled with a zeolite-based adsorbent. Absorption tower 8
The inlet is connected to the exhaust pipe 7 in FIG. 1, and the outlet is connected to the outlet pipe 9 in FIG.

With the above structure, the N of the combustion furnace 1 is
The exhaust gas containing Ox is introduced into the plasma reaction container 5 via the dust remover 3. When a voltage is applied from the power source 6 to the electrodes 110 and 111, plasma of exhaust gas is generated between the electrodes 111 and 110. This plasma excites and dissociates the gas molecules of NOx and brings them into a chemically active state, which causes the chemical reactions of the above formulas (3) and (4).

The above expressions (3) and (4) mean that NO in the exhaust gas of the combustion furnace 1 introduced into the plasma reactor 5 is oxidized, and the oxidized NO ₂ and N ₂ O ₅ Are removed by the adsorption tower 8. As described above, the method of once oxidizing NOx and removing the oxidized NOx with the adsorbent can reduce the required electric power to about 1/10 as compared with the conventional NOx reduction method.

Specific data of the present invention according to this example are shown in Table 1 below in comparison with the data of the conventional reduction method.

[0017]

[Table 1]

A plasma reactor having flat electrodes 110 and 111 as shown in FIG. 3 is used in place of the cylindrical plasma reactor of Example 1, and the tubular adsorption tower of Example 1 is replaced with FIG. A rectangular adsorption tower as shown in was used. As a result, the same results as in Example 1 were obtained.

Further, the adsorption / desorption characteristics of the adsorbent in the composition of NOx are shown in Table 2 below.

[0020]

[Table 2]

As the adsorbent, those of alumina type, zeolite type, silica type, titania type and magnesia type can be used.

[0022]

As described above, according to the present invention, exhaust gas containing NOx can be removed with high efficiency and low power. Further, in the present invention, if a large number of plasma reaction vessels are installed in series or in parallel, or if the size is increased and the adsorption tower is increased in capacity, the amount of exhaust gas treated can be greatly increased. The value above is significantly higher.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an explanatory view of a cylindrical plasma reaction container used in the present invention and a conventional method.

FIG. 3 is an explanatory view of a flat plate type plasma reaction container used in the present invention and the conventional method.

FIG. 4 is an explanatory view of a cylindrical adsorption tower used in the present invention.

FIG. 5 is an explanatory view of a rectangular adsorption tower used in the present invention.

FIG. 6 is power consumption and NOx of the plasma reactor of the present invention.
Quantitative graph showing the relationship between changes in.

FIG. 7 is an explanatory view of an exhaust gas treatment method using a conventional plasma reactor.

Front page continued (72) Inventor Nobuaki Murakami 5-717-1, Fukahori-cho, Nagasaki-shi, Nagasaki Sanhishi Heavy Industries Ltd. Nagasaki Laboratory (72) Inventor Naoyasu Matsuo 5-3, Atsunoura-cho, Nagasaki-shi, Nagasaki Western Japan Hishijukosan Building, 4th floor, within Choryo Design Co., Ltd.

Claims (1)

[Claims] 1. A method for detoxifying a nitrogen oxide-containing exhaust gas, which comprises oxidizing the nitrogen oxide-containing exhaust gas with plasma and adsorbing and removing the oxidized nitrogen oxide with an adsorbent.