JPH06343820A - Treatment of waste gas by steam plasma - Google Patents

Abstract

PURPOSE:To efficiently treat a waste gas without using the electron beam irradiation device by supplying the single substance of steam or the gaseous mixture of the steam and a diluent gas to the plasma generating device as the operating gas of the plasma and oxidizing the harmful component in the waste gas to make harmless. CONSTITUTION:The single substance of steam or the gaseous mixture of the steam and the diluent gas is supplied to the plasma generating device 2 as the operating gas of the plasma, and a generated gaseous steam plasma is supplied into the waste gas, and the harmful component in the waste gas is oxidized by the plasma to make harmless. At that time, ammonia or urea is supplied into the waste gas to solidify the oxidation products of NOx and/or SOx in the waste gas as ammonium salts. In such a way, the active chemical speed such as OH, O, H, HO2 is generated without using the electron beam irradiation device, and waste gas can be treated using the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to NOx, SOx, C contained in combustion exhaust gas from boilers, heating furnaces, incinerators, etc.
The present invention relates to a method for oxidizing and removing toxic organic compounds such as O or dioxin, and more particularly to a method for treating exhaust gas by steam plasma.

[0002]

2. Description of the Related Art A method shown in FIG. 3 has been proposed as a method for simultaneously oxidizing nitrogen oxides (NOx), sulfur oxides (SOx), carbon monoxide (CO), and trace organic compounds in exhaust gas. ing. That is, in this method, in the reaction zone (21) provided in the gas flow path, the electron accelerator (2
The electron beam generated in 2) is applied to the exhaust gas to generate active chemical species, such as OH, O, H, and HO ₂ , in the exhaust gas, and NOx and SO in the exhaust gas are generated by these active chemical species.
After simultaneously oxidizing x, CO, an organic compound, etc., ammonia is added to the exhaust gas, and the oxidation products of NOx and SOx are recovered and rubbed as solid ammonium salts.
In FIG. 3, (23) is a shield wall, (24) is a dust collector, and (25) is a suction blower.

[0003]

In the above-mentioned conventional method, it is necessary to provide an electron beam accelerator, which is an expensive and large-sized device, for irradiating the exhaust gas with the electron beam, and the electron beam is scattered around the electron beam accelerator. Since it is necessary to provide a shielding wall to prevent it, the equipment cost is high, and in addition, there are severe restrictions on the handling of ionizing radiation, and there are difficulties in terms of handling. Therefore, this method has not yet been put to practical use.

The object of the present invention is to efficiently use OH, O, and O without using an electron beam irradiation device in order to overcome the above-mentioned drawbacks.
An object of the present invention is to provide a method for treating exhaust gas by generating active chemical species such as H and HO ₂ and using the chemical species.

[0005]

The exhaust gas treatment method according to the present invention is devised to achieve the above-mentioned object, and plasma generation is performed by using water vapor alone or a mixed gas of water vapor and diluent gas as a working gas of plasma. Supply to the device, supply the generated steam plasma gas into the exhaust gas,
It is characterized by oxidizing harmful components in exhaust gas by plasma to render them harmless.

[0006] In the above method, preferably, ammonia or urea is supplied to the exhaust gas to solidify the oxidation product of NOx and / or SOx in the exhaust gas as an ammonium salt.

As the diluting gas, one or a mixed gas of air, nitrogen, oxygen, carbon dioxide and argon is preferably used.

[0008]

[Operation] Supplying a single water vapor or a mixed gas of water vapor and a diluent gas to the plasma generator,

[Chemical 1] In the reaction described above, active chemical species such as O, OH, H, HO ₂ and O ₃ are generated by converting water vapor and oxygen into plasma.

These active species, O, OH, H, H
O ₂ and O ₃ react with NOx and SO ₂ in the exhaust gas as shown by the following formula to produce the corresponding oxide.

[0010]

[Chemical 2] When supplying ammonia to the exhaust gas, the sulfuric acid and nitric acid generated in the above reaction react with ammonia as shown in the following formula,

[Chemical 3] Solidified as the corresponding ammonium salt. This solid is removed from the exhaust gas in a downstream dust collector.

CO and organic compounds in the exhaust gas react with active chemical species such as O, OH, H and HO ₂ as shown in the following formula,

[Chemical 4] Detoxified.

[0012]

EXAMPLES The exhaust gas treatment method according to the present invention will be specifically described with reference to Examples.

In FIG. 1, a plasma generator (2) is installed above the reaction zone (1) provided in the gas flow path. As shown in FIG. 2, the plasma generator (2) has a positive electrode.
It has a structure in which (3) and a negative electrode (4) are provided, and a high voltage DC power supply (5) is connected to the negative electrode (4).

A simple substance of water vapor or a mixed gas of water vapor and a diluent gas is supplied to the plasma generator (2) as a working gas for plasma. As the diluting gas, one or a mixed gas of air, nitrogen, oxygen, carbon dioxide, and argon is used and is supplied to the plasma generator (2).

The steam plasma gas generated by the above formula [I] or [II] is supplied to the exhaust gas in the reaction zone (1) to oxidize harmful components in the exhaust gas by plasma (the above formulas [III] and [V]). reference).

Further, ammonia gas is injected into the reaction zone (1), and the sulfuric acid and nitric acid generated in the above reaction [III] are solidified as the corresponding ammonium salt by the reaction of the formula [IV]. This solid is removed from the exhaust gas by a dust collector (6) in the downstream.

In FIG. 1, (7) is a suction blower and (8) is a chimney.

[0018]

In the method for treating exhaust gas of the present invention, the water vapor alone or the mixed gas of the water vapor and the diluting gas is made into plasma. Therefore, the active chemical species, O, OH, and It is possible to easily obtain H, HO ₂ , O _{3 and the} like, and it is possible to solve all the problems that are the greatest problems of the electron beam irradiation method, such as the installation of an electron beam accelerator and the restrictions on handling ionizing radiation. Thus, the method of the present invention enables simultaneous multipurpose exhaust gas treatment.

[Brief description of drawings]

FIG. 1 is a flow sheet showing an exhaust gas treatment method according to the present invention.

FIG. 2 is a cross-sectional view showing a plasma generator.

FIG. 3 is a flow sheet showing a conventional method.

[Explanation of symbols]

 1: Reaction zone 2: Plasma generator 3: Positive electrode 4: Negative electrode 5: DC high voltage power supply

Claims (2)

[Claims] 1. A single gas of steam or a mixed gas of steam and a diluent gas is supplied to a plasma generator as a plasma working gas, the generated steam plasma gas is supplied to exhaust gas, and harmful components in the exhaust gas are oxidized by plasma. An exhaust gas treatment method using steam plasma, which is characterized by being rendered harmless. 2. The method according to claim 1, wherein ammonia or urea is supplied to the exhaust gas to solidify an oxidation product of NOx and / or SOx in the exhaust gas as an ammonium salt.