JPH02211218A - Denitration of nox in waste gas and waste gas treatment apparatus - Google Patents

Abstract

PURPOSE:To perform safe treatment by spraying an aqueous solution having sodium azide dissolved therein from a spray device and charging electric energy in this spray to form plasma. CONSTITUTION:An aqueous azide solution is sent into a spray device 2 by a pump while NOx-containing waste gas is introduced into said spray device for the sake of spray. The flow rate of the aqueous azide solution and that of the NOx-containing waste gas are controlled so as to obtain such a state that the aqueous azide solution is sprayed uniformly and the high frequency power of plasma generating coils 3, 4 is charged to apply electric energy to the wet gas sprayed in a reaction chamber 5 to generate plasma. By this method, a byproduct can be inexpensively removed and the waste gas can be treated efficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a denitrification method and an exhaust gas treatment apparatus for treating NOx in exhaust gas to convert it into a harmless gas.

B0 Summary of the Invention The method of denitrating NOx in exhaust gas of the present invention involves spraying an aqueous solution in which sodium azide is dissolved using NOx-containing exhaust gas as a spraying gas, and injecting electrical energy into the spraying to generate plasma. It generates NOx, activates the substances contained in the spray, and reduces NOx with azide to N!
and H,0 to turn the NOx-containing exhaust gas into a harmless gas.

Further, the exhaust gas treatment apparatus of the present invention includes a plasma reaction tube provided with a plasma generation coil, a spraying device for spraying an azide aqueous solution using NOx-containing gas as a spraying gas, and a spraying device for spraying an azide aqueous solution into the plasma reaction tube using a NOx-containing gas as a spraying gas. It is equipped with a heat exchange device that recovers the heat generated within the tank.

C1 Conventional technology SO in exhaust smoke or exhaust gas generated by combustion of fossil fuels
BACKGROUND ART x, NOx, Go, etc. are harmful substances that promote air pollution, and the ammonia reduction contact method has conventionally been the mainstream method for removing NOx.

Additionally, combined heat and power generation equipment, which is attracting attention as an energy-saving device, is installed in buildings in urban areas and serves as an emergency power source.

D0 Problems to be Solved by the Invention However, the NOx removal equipment using the ammonia reduction contact method is not only large and expensive, but also the ammonia gas used has an illumination limit of 25 ppm and an explosive range of 15.5 to 27.
%, it is a dangerous and highly toxic gas with a strong corrosive and pungent odor, and when used in large quantities, there are many restrictions such as leakage and it is desirable for the operator to have gas handling skills. It is very difficult to install in urban areas or near residential areas.

Additionally, combined heat and power generation equipment generates a considerable amount of NOx;
Since treatment of Ox is difficult as described above, there has been no suitable treatment method for treatment of NOx in combined heat and power generation equipment.

The present invention was made in view of the problems of the prior art, and its purpose is to treat NOx in a safe and clean manner without using dangerous gases such as ammonia. It is an object of the present invention to provide a method for denitrifying NOx in exhaust gas and an exhaust gas treatment device combined with a combined heat and power supply device.

81 Means for Solving the Problems In order to achieve the above object, the method for denitrifying NOx in exhaust gas in the present invention includes spraying an aqueous solution in which sodium azide is dissolved using NOx-containing exhaust gas as a spraying gas from a spraying device, Electrical energy is input into this spray to generate plasma, activate the substances contained in the spray, and N
Ox is reduced by azide and converted into N, H, and 0.

Further, the exhaust gas treatment apparatus of the present invention includes a plasma reaction tube provided with a plasma generation coil, a spraying device for spraying an azide aqueous solution using NOx-containing gas as a spraying gas, and a spraying device for spraying an azide aqueous solution into the plasma reaction tube using a NOx-containing gas as a spraying gas. It is equipped with a heat exchange device that recovers the heat generated inside.

F9 action Plasma is generated when electric energy such as high frequency is input into the atomization process in which an aqueous solution of sodium azide is atomized using NOx-containing exhaust gas as the atomization gas.

The plasma activates the substances contained in the spray.

This allows NOx to be reduced to azide and converted to N, H, and 0.

The exhaust gas treatment device performs the above reaction in a plasma reaction cylinder equipped with a plasma generation coil, and is equipped with a heat exchanger to recover the heat generated by the plasma reaction.

G. Example Example 1 First, the principle of the NOx removal method in exhaust gas will be explained.

This method chemically changes NOx to pJ 1 + Ht 2 O, and uses the following three equations as main reaction equations.

N O+ N O, + Hto→2HNO* ・・
...(1) 6 NaN5+ 6 Hc&-"6 N
sH+ 6 Nac12- (2)2HNO, + 6N
sH→1ONt+4HtO...(3) Normally, it is very inefficient to absorb gas into liquid. The above formula (1) is
This is a reaction in which No and Not are absorbed into water to form HNOt. If this step of the reaction can be carried out efficiently,
The reaction of formula (3) above proceeds smoothly. Above (2)
Perform the reaction in advance.

For the reaction of formula (1) above, especially as a method for efficiently absorbing the gas into a liquid and making it react well, an aqueous solution (formula (2)) in which sodium azide is dissolved in exhaust gas containing NOx is prepared using a two-fluid spray device. Spray to turn it into wet gas.

At the same time, this wet gas is easily discharged from the outside,
In addition, power at a frequency that sustains the discharge is applied to turn the wet gas into plasma, promoting the reactions of equations (1) and (3) above, and plasma-chemically changing NOx into N, H, and 0. This removes NOx.

Examples will be described with reference to the drawings.

In FIG. 1, 1 is a plasma reaction tube, 2 is a spray device for spraying into the plasma reaction tube, 3 and 4 are plasma generation coils wound around the outside of the plasma reaction tube, and 5 is a reaction chamber. An azide aqueous solution prepared in advance based on the above formula (2) is sent to the spraying device 2 using a pump, etc., while N is used for spraying.
Ox-containing exhaust gas is introduced, the flow rates of the azide aqueous solution and NOx-containing exhaust gas are adjusted so that the azide aqueous solution is uniformly sprayed, and high-frequency power is applied to the plasma generation coils 3 and 4, so that the azide aqueous solution is sprayed into the reaction chamber 5. Electrical energy is applied to wet gas to generate plasma. In this case, the frequency of the high frequency power was 13.56 MHz, but since plasma can be generated even with commercial frequency electrical energy, the frequency of the power is not limited to high frequencies.

The plasma generated in the reaction chamber 5 in this manner excites the NOx-containing exhaust gas that has been wetted by spraying, and instantly promotes the reactions of equations (1) and (3) above.

According to the above example, when exhaust gas containing 11,000 pp of NOx was used, NOx could be reduced to 1,100 pp or less.

Example 2 In FIG. 2, 1 is a plasma reactor, 2 is a spray device,
6 is a power supply for plasma generation, 7 is a coil for plasma generation,
8 is an azide solution tank, 9 is an azide solution supply pump, IO is a heat recovery pipe made of a coiled tube, 11 is a human-powered electric wire to the plasma generation power source 6, and 12 is a cooling power source for the plasma generation power source 6. 13 is a NOx-containing gas intake port, and 14 is an outlet for treated exhaust gas.

However, the intake! The exhaust gas from the engine 3 and the azide solution in the tank 8 sent by the pump 9 are sprayed as wet gas into the plasma reaction cylinder by the spraying device 2. Since high-frequency power is supplied to the plasma generation coil 7 from the power supply 6, plasma is generated in the plasma reaction tube 1, and the reactions of equations (1) and (3) above are instantly promoted, resulting in N , Ox is decomposed.

The heat generated in the plasma reaction tube 1 is utilized by extracting the water flowing in the heat recovery piping 10 to the outside as hot water or steam. Moreover, the heat of the plasma generation coil can be taken out by flowing cooling water into the plasma generation coil.

The treated exhaust gas is discharged from the outlet 14 of the plasma reactor l. In the embodiment, the plasma generation coil is wound around the outside of the reaction tube 1, but it may be provided inside.

Embodiment 3 In FIG. 3, the body 15 of the plasma reaction cylinder 1 is constructed in double layers, and a heat exchanger is constructed between which a heat recovery passage 16 is formed, and the other structure is the same as that in FIG. 2. The same parts are given the same reference numerals.

According to this example, the piping of Example 2! The plasma reactor can be configured smaller than that in which the heat exchanger is used as a heat exchanger.

H. Effects of the Invention Since the present invention is configured as described above, it produces the following effects.

■NOx can be treated safely and cleanly without using dangerous gases such as ammonia.

■N, and HtO without producing by-products during processing.
Since it decomposes into , there is no need for a means for removing by-product oxides, and the cost can be reduced.

- All you need is a power source for plasma generation, water, and a small amount of chemicals, and there is no risk of odor or explosion, so it is convenient for installation in urban areas.

■Efficiency is high because the NOx-containing gas wetted with azide aqueous solution is activated by plasma to promote chemical reactions.

■Exhaust gas treatment equipment processes N”Ox from engines, etc.
It can be released into the air as a harmless gas.

■The heat required by the exhaust gas treatment equipment (residual heat) can be recovered through heat exchange, increasing efficiency.

■Since the heat exchanger is integrated with the plasma generator, it does not require a large space for installation.

■The entire device can be made at low cost.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the operation of the method of the present invention, FIG. 2 is a schematic diagram showing an example of the apparatus of the present invention, and FIG. 3 is a schematic diagram showing another example. 1... Plasma reaction tube, 2... Spraying device, 3.4° 7... Plasma generation coil, 5... Reaction chamber, 9...
... Pump, lO... Piping for heat recovery, 16... Passage for heat recovery. Two other people Figure 1 Azide S liquid Figure 3

Claims (2)

[Claims] (1) Spraying an aqueous solution in which sodium azide is dissolved using NOx-containing exhaust gas as a spraying gas from a spraying device, inputting electrical energy into this spraying to generate plasma, and activating substances contained in the spraying, A method for denitrifying NOx in exhaust gas, characterized by reducing NOx with azide and converting it into N_2 and H_2O. (2) A plasma reaction tube equipped with a plasma generation coil, a spraying device that sprays an azide aqueous solution into the plasma reaction tube using NOx-containing gas as the atomizing gas, and recovery of the heat generated in the plasma reaction tube. An exhaust gas treatment device characterized by comprising a heat exchange device.