WO2003066197A1

WO2003066197A1 - Method and apparatus for excluding dioxin and fly ash using high temperature plasma

Info

Publication number: WO2003066197A1
Application number: PCT/KR2002/000923
Authority: WO
Inventors: Sin Do Kim; Jong Ho Kim; Ae Kwon Yoo
Original assignee: Tbi Co., Ltd
Priority date: 2002-02-07
Filing date: 2002-05-17
Publication date: 2003-08-14
Also published as: KR20030067241A; JP2003251146A; AU2002307695A1

Abstract

Disclosed relates to a dioxin removal apparatus, and specifically it relates to a dioxin and particulate removal apparatus and method using a thermal plasma, in which flue gas generated from wastes incineration facilities is completely combusted, and then the flue gas is rapidly cooled by spraying waters to the flue gas to prevent the denovo-synthesis of dioxin r generation of nitrates in the subsequent process and simultaneously various environmental pollutants in the flue gas are washed out. The method of the present invention comprise the steps of a decomposition step of thermo-chemically destroying the flue gas containing dioxin, soot, particulate, and incomplete combustion products, generated from the incineration facility, by using a thermal plasma; a cooling and washing step of rapid cooling the hot flue gas in the decomposition step and simultaneous washing pollutants in the flue gas; a dewatering step of reducing water content in the flue gas cooled in the cooling and washing step; and a wastewater discharging step of discharging cooling water used in the cooling and washing step (200) and in the dewatering step (300).

Description

METHOD AND APPARATUS FOR EXCLUDING DIOXIN AND FLY ASH USING HIGH TEMPERATURE PLASMA

Technical Field

The present invention relates to a dioxin removal apparatus, and more

particularly, to a dioxin and particulate removal apparatus and method using

thermal plasma, in which the flue gas emitted from waste incinerators is

completely combusted, and then the flue gas is rapidly cooled by spraying

cooling and cleaning waters to the flue gas so as to prevent the re-synthesis

(de novo synthesis) of dioxin or generation of nitrogen oxides in the

subsequent process, and simultaneously various environmental pollutants

contained in the flue gas are washed.

Background Art

With a rapid industrialization and urbanization, industrial and municipal

solid wastes are increasing continuously. Therefore, Many technologies are

being developed to treat various wastes more environmental friendlily.

Among them, incineration is recognized to be a favorable wastes treatment

technology that it can greatly reduce the amount of wastes and recover

energy. However, the flue gas generated at the time of the waste incineration includes many kinds of environmental contaminants such as dioxin, nitrogen

oxides, sulfur oxides, particulate, etc. Especially, the generation of dioxin as

a carcinogen and an endocrine disrupter becomes an obstacle to installation

and operation of incinerator.

In general, dioxin refers to organic compound such as polychlorinated

dibenzo-p-dioxins (PGDDs) and polychlorinated dibenxofurans (PCDFs).

The dioxin is not decomposed well in the natural state because its molecular

structure is very stable. Once it is introduced into the human body, it is easily

not excreted but accumulated in the human body, which contributes to the

cause of cancer, the disorder of hormone regulation functions, or the

damage to the reproductive and immune systems. Thus it is a very noxious

substance.

Dioxin is generated through various paths. It is included mainly in

wastes at the facilities for incinerating municipal solid wastes. Also,

chlorinated precursors such as chlorinated phenol, chlorinated benzene,

polyvinyl chloride(PVC), etc., which is generated in an incomplete

combustion process, produce a dioxin through a certain reaction in a

incinerator, or, chlorinates included with organic substances and chlorine

make into a dioxin properly through a substitution reactions. But dioxin is

destroyed in the incinerator when the combustion temperature is above a 900 °C. For example, the amount of dioxin observed at the outlet of the high

temperature incinerator is low relatively.

On the other hand, it is found that hydrocarbons produced by

incomplete combustion in the incinerator react at a temperature of 250 to

350 °C with chlorine donor on the surface of fly ash contained in the

combustion gas. In the process of reaction between hydrocarbon and

chlorine, the amount of dioxin is produced a relatively high concentration. In

other words, it should not be detected at a chimney of incineration facilities

because the dioxin in the incinerator is destroyed in the combustion process.

But it can be seen that dioxin is synthesized in actual after leaving the

incinerator from the fact of a significant amount of dioxin. This has been

already confirmed that an amount of dioxin is generated in combustion gas

emitted through an economizer or electrostatic precipitator at 250 to 350 °C.

As such, the reason why dioxin is generated vigorously at 250 to 350

°C is that chlorine is generated vigorously from chloride by catalysis of

copper, etc., in this temperature range. Therefore, the reduction of dioxin is

accomplished as the followings; firstly, the incinerator should be operated at

the condition of complete combustion to minimize the production of various

precursors by means of maximizing the destruction of organic materials.

Secondly, the temperature range which dioxin can be generated in post- processes should be avoided, or the retention time should be minimized

when the incinerator is operated in the temperature range.

The dioxin removal apparatuses in use in wastes incineration facilities

is largely included a combination of spray dryer absorption (SDA), selective

catalyst reactor (SCR), selective non-catalytic reduction (SNCR), a dust

collector system, and an absorption method using activated carbon.

Especially, a new method added a dust collector system to SDA to remove

acidic gas in flue gas and heavy metals is known to be excellent for removal

of dioxin. It is known that the dust collection system combined with SNCR as

a technology of injecting ammonia into an incinerator for removing NOx in

the incinerator is effective. Such a method is effective in inhibiting the

generation of dioxin. Also, the dust collection system combined with SCR

can achieve above 90% of dioxin removal when the incinerator is operated in

an optimum temperature range. However, the above-mentioned process

requires the additional dust collection system and collected contaminants

should be treated as an industrial wastes. In case of using a catalyst,

catalytic activity can be sharply reduced by heavy metals. Thus the

conventional methods have a problem in that they need a high cost for

installation and operation. For example, a post-treatment facility for removal

of heavy metals and extremely fine dusts needs to be installed. And, a method of absorbing dioxin using a mixture of activated

carbon, coke and limestone are divided into two types. One is a method of

adsorbing dioxin, etc. by allowing flue gas to pass through the fixed-bed

adsorption column. The other is a method of adsorbing dioxin by allowing

flue gas to pass through a bag filter, in which limestone and powered

activated carbon are sprayed into flue gas for the adsorbing dioxin, and

followed by the removal of dioxin in the bag filter. However, the adsorption

methods using activated carbon has many problems as followings; overload

occurring in the dust collection system due to the added activated carbon,

the reduction of life time of the filter bag, difficulty in performance

improvement, and shortage of required space for facility expansion.

Accordingly, there are the needs for developing new technologies

that can solve these problems. In consideration of dioxin formation

mechanisms and practical operation conditions in the incinerator, a presenter

has accomplished the present invention that can completely combust flue

gas emitted from incinerator by using of thermal plasma, and then rapidly

cool and simultaneously wash the flue gas. So that dioxin precursors

contained in the flue gas are prevented from being re-synthesized, and

acidic materials such as nitrate are prevented from being generated. As a

result, various contaminants included in flue gas are removed completely. Disclosure of Invention

Therefore, the present invention has been made in view of the

problems of the prior technologies described above. The main object of the

present invention is to provide a dioxin and particulate removal apparatus

and method which can completely combust dioxin precursors, fly ash, soot,

and other incomplete combustion products contained in flue gas, which is

discharged from various industrial facilities and incinerators using thermal

plasma. And then rapidly cool the flue gas so as to prevent the re-

synthesis(de novo synthesis) of dioxin precursors and the generation of

nitrogen oxides and simultaneously wash the flue gas, thereby removing

various environmental contaminants such as hydrogen chloride, sulfur oxides,

particulate, etc. contained in the flue gas.

To achieve the above mentioned object, according to an aspect of

the present invention, there is provided a dioxin and particulate removal

method using thermal plasma, the method comprising the steps of: a

decomposition step of thermo-chemically destroying dioxin, soot, particulate,

and incomplete combustion products in the flue gas generated from the

incineration facility, by using a thermal plasma; a cooling and washing step

of rapidly cooling the hot flue gas generated in the decomposition step and simultaneously washing pollutants in the flue gas; a dewatering step of

reducing water content in the flue gas cooled in the cooling and washing

step; and a wastewater discharging step of discharging cooling water used

in the cooling and washing step and wastewater condensed in the

dewatering step.

Preferably, the decomposition step keeps the temperature of the flue

gas above 900 °C using thermal plasma, and the flue gas temperature is

lowered by the cooling and washing step rapidly below 200 °C.

According to another aspect of the present invention, there is also

provided a dioxin and particulate removal apparatus using thermal plasma,

comprising: a reaction chamber for introducing flue gas containing dioxin

precursors, soot, fly ash, and incomplete combustion products generated

from incineration facility thereto; thermal plasma torch installed at one side of

the reaction chamber for completely combusting the flue gas introduced into

the reaction chamber using thermal plasma; a cooling and washing chamber

installed adjacent to the reaction chamber and having cooling water spraying

nozzles mounted on the ceiling portion thereof, for rapid cooling the flue gas

discharged from the reaction chamber so as to prevent the denovo-

synthesis of dioxin and the generation of nitrogen oxides and simultaneous

washing hydrogen sulfide, sulfur oxides, particulate, etc., in the flue gas; a demister installed adjacent to the cooling and washing chamber for reducing

water content in the flue gas generated in the cooling and washing chamber;

and a waste water discharging method for discharging wastewater generated

in the cooling and washing chamber and the demister.

Preferably, the thermal plasma torch makes a thermal plasma flame of

above 900 °C by ionizing the nitrogen gas (N2) using direct current arc

electric discharge or high frequency inductive coupling electric discharge.

Preferably, the thermal plasma torch includes a torch body formed of

a cylindrical hollow tube; a cathode rod installed inside of the torch body; a

nitrogen gas inlet installed at one side of the torch body for injecting a

nitrogen gas into the torch body therethrough; cooling water inlet installed at

one side of the torch body for injecting cooling water into the torch body

therethrough so as to circulate the injected cooling water within the hollow

tube of the torch body; and a power supply methods for applying power to

the torch body and the cathode rod.

According to another aspect of the present invention, there is also

provided a dioxin and particulate removal apparatus using thermal plasma,

comprising: a reaction chamber installed on a duct in-line of the wastes

incineration facility for introducing flue gas containing dioxin, dioxin

precursors, soot, fly ash, incomplete combustion products, etc., generated from the incineration facility thereto, the reaction chamber having thermal

plasma torches installed therein for completely combusting the flue gas

introduced thereto; a cooling and washing chamber installed adjacent to the

reaction chamber and having cooling water spraying nozzles mounted on the

ceiling portion thereof, for rapid cooling the flue gas discharged from the

reaction chamber and simultaneous washing pollutants in the flue gas; a

demister adjacent to the cooling and washing chamber for reducing water

content in the flue gas generated in the cooling and washing chamber; and a

wastewater discharging means for discharging wastewater generated in the

cooling and washing chamber and the demister.

Preferably, the temperature of the reaction chamber is maintained

above 900 °C, more preferably, above 1500 °C.

Also preferably, the plasma torches are installed in the reaction

chamber in such a manner as to be arranged in zigzags therein to

homogenize the temperature inside of the reaction chamber or slantingly

arranged to agitate the flue gas injected into the reaction chamber.

Preferably, the reaction chamber is made of a heat resistant material

that can endure high temperature and having a cooling unit installed at the

outside thereof for protecting the inside wall thereof.

Further preferably, the cooling and washing chamber has cooling water spraying nozzles installed on the ceiling portion, reduces the

temperature of the flue gas to below 200 °C rapidly by spraying fine water

droplet.

Brief Description of Drawings

Further objects and advantages of the invention can be more fully

understood from the following detailed description taken in conjunction with

the accompanying drawings in which:

FIG. 1 is a schematic flow diagram showing the dioxin and particulate

removal method using thermal plasma according to the present invention;

FIG. 2 is a cross section showing an example of the thermal plasma

torches according to the present invention;

FIG. 3 is a schematic partial cross sectional view showing the dioxin

and particulate removal apparatus using thermal plasma according to an

preferred embodiment of the present invention;

FIG. 4 is a cross sectional view showing the dioxin and particulate

removal apparatus using thermal plasma according to another preferred

embodiment of the present invention;

FIG. 5 is a cross sectional view showing the dioxin and particulate

removal apparatus using thermal plasma according to still another preferred embodiment of the present invention;

FIG. 6 and FIG. 7 are schematic cross sectional views showing the

dioxin and particulate removal apparatus using thermal plasma according to

further another preferred embodiments of the present invention.

Best Mode for Carrying Out The Invention

FIG. 1 is a schematic diagram showing the dioxin and particulate

removal method using thermal plasma according to the present invention. As

shown in FIG. 1 , the dioxin and particulate removal method of the present

invention includes a decomposition step 100 of destroying thermo-

chemically the flue gas containing dioxin, particulate, and incomplete

combustion products using thermal plasma; a cooling and washing step 200

of rapidly cooling the flue gas of a high temperature generated in the

decomposition step 100 and of simultaneously washing contaminants

contained in the flue gas; a water removal step 300 of removing water

contained in the flue gas cooled in the cooling and washing step 200; and a

cooling wastewater discharge step 400 of discharging cooling water used in

the cooling and washing step 200 and wastewater generated in the water

removal step 300.

The decomposition step 100 according the present invention is performed in an incinerator of wastes incineration facilities. In the

decomposition step, the flue gas containing dioxin, dioxin precursors, fly ash,

incomplete combustion products, etc. is introduced into the reaction

chamber of a proper size, and at the same time, dioxin and dioxin precursors,

fly ash, and incomplete combustion products are completely combusted to

be decomposed, using thermal plasma emitted from one or more thermal

plasma torches installed in the reaction chamber. In other words, dioxin

starts to be decomposed at above 800 °C and is completely decomposed at

1 00 °C. Fly ash is re-combusted at a high temperature. Thus, not only is

dioxin precursors adsorbed in fly ash decomposed, but also its absorption

ability is lost since its structure is destructed. Therefore, the thermal plasma

is maintained preferably above 900 °C, and more preferably above 1500 °C.

As such, the first step of the dioxin and particulate removal method

according to the present invention is a process of making flue gas with non-

toxic materials, by eliminating dioxin and dioxin precursors generated

unavoidably due to incomplete combustion and fly ash involved in dioxin re-

synthesis(de novo synthesis) at post-treatment processes, through re-

combusting flue gas with high temperature.

The flue gas discharged in the decomposition step 100 progresses to

the cooling and washing step 200. That is, the flue gas discharged in the decomposition step 100 is at a high temperature of above 1000 °C, and

when this high temperature state is maintained for more than a certain time,

nitric oxide (NO) reacts with oxygen to produce nitrogen oxides(NOx). Thus

the flue gas should be cooled to below the reaction temperature. Also, when

even dioxin or dioxin precursors decomposed in the decomposition step 100

stay in a proper temperature range of, for example, 250 to 300 °C, for above

a certain time period, they are synthesized again to produce dioxin.

Therefore, it is required to reduce the temperature of the flue gas below 200

°C. Also, when the flue gas is cooled from high temperature to below 200 °C

in the decomposition step 100, it passes through the temperature range

where NOx and dioxin are generated. Hence, it is important to rapidly cool

the flue gas in order to shorten the retention time in the reaction temperature.

As such, the second step of the dioxin and particulate removal

method according to the present invention includes a step of rapidly cooling

flue gas of a high temperature to below 200 °C, more preferably below 70 °C.

The cooling and washing step 200 is a process of cooling the flue gas

through a manifold of cooling water injection nozzles installed in the cooling

and washing chamber(wet scrubbing chamber) of a prescribed size. Thus

the cooling process is rapidly performed by using the latent heat of cooling

water, and also there are an effect of washing particulate and acidic contaminants such as SOx, HCI, etc., contained in the flue gas.

And, cooling water is sprayed directly to the flue gas of a high

temperature to rapidly cool the flue gas in the cooling and washing step 200.

Hence a large amount of water is generated. Therefore, the cooling and

washing step 200 is followed by the wastewater removal step. Cooling

wastewater generated in the cooling and washing step 200 and the water

removal step 300 is drained to the outside through a separate discharge step

400, and preferably is transported to a wastewater treatment unit which in

turn purifies the cooling wastewater for discharge to the water body or reuse

it as cooling water.

As described above, the dioxin and particulate removal processes

using thermal plasma of the present invention are simpler than a

conventional activated carbon adsorption method or a combination of SDA,

or SNCR and a dust collector. In addition, management is easy since a

separate post-treatment except the cooling wastewater treatment is not

required.

Also, since the prior flue gas removal apparatus using low

temperature plasma is big in size and complicated, it requires a separate

post-treatment process necessarily, but the present invention is small in size

and relatively simple in structure. Subsequently, FIG. 2 is a cross sectional view showing an example of

the thermal plasma torches used in the dioxin and particulate removal

apparatus using thermal plasma according to the present invention. These

thermal plasma torches 20 use a direct current arc electric discharge or high

frequency inductive coupling electric discharge to allow a strong electric field

to be generated in inert gases such as Ar and He or used gases such as N2,

H2, air or 02, water vapor, hydrocarbon gas, etc., so as to produce a

thermal plasma by generating electric charges through continuous collisions

of accelerated electrons. The thermal plasma (or heat plasma) is in local

equilibrium, where ionized particles are maintained at the same temperature.

Thus, the plasma is much higher in temperature than low temperature plasma

(or cold plasma) having low heat content, where heavy ions and neutral

particles are in non-equilibrium at a temperature near room temperature.

As shown in FIG. 2, the thermal plasma torch 20 consists of a torch

body 23 formed of cylindrical hollow tubes; a cathode rod 25 installed inside

the torch body 23; and a power supply means for applying a prescribed

voltage between the cathode rod 25 and the torch body 23. Hence, if gases

such as N2, etc. are injected into the torch body installed with the cathode

rod 25, arc electric discharge occurs at an end of the cathode rod 25 to emit

a thermal plasma flame 27. Meanwhile, a cooling water inlet 28 and outlet 29 are installed in a hollow tube of the torch body 23 to allow circulation of

cooling water within the torch body so as to protect the torch body 23 from

high temperature heat.

And, FIG. 3 is a schematic cross sectional view showing the thermal

plasma torch 20 installed at a discharge outlet of an incineration facility. As

shown in FIG. 3, a reaction chamber 24 is formed at the lower portion of the

torch body 23 to re-combust the flue gas generated in the incineration

furnace by the thermal plasma flame 27. Hence, the contaminants contained

in the flue gas introduced into the reaction chamber 24 are decomposed by

thermal plasma to be discharged to the outside through a discharge outlet 37.

Meanwhile, FIG. 4 and FIG. 5 are schematic cross sectional views

showing the dioxin and particulate removal apparatus using thermal plasma

according to a preferred embodiment of the present invention. As shown in

FIG. 4 and FIG. 5, the dioxin and particulate removal apparatus 10 using

thermal plasma according to the present invention includes the thermal

plasma torch 20 for generating the thermal plasma; a cooling and washing

room 30 having cooling water injection nozzles 33 installed therein, for

rapidly cooling flue gas at high temperature discharged after the flue gas is

thermo-chemically decomposed in the reaction chamber 24 installed at the

bottom portion of the thermal plasma torch and simultaneously washing contaminants; a demister 40 for removing water generated in the cooling and

washing room 30; and a storage tank 50 for temporarily storing cooling

wastewater generated in the cooling and washing room 30 and the demister

40.

In other words, as shown in FIG. 4, if a direct current or high

frequency electric power source is connected between the plasma torch

body 23 and the cathode rod 25 and nitrogen is injected into a reaction

chamber through a nitrogen gas inlet (29), then the nitrogen molecules is

decomposed into electrons and positive ions to make a thermal plasma. And,

if the flue gas containing contaminants such as dioxin and dioxin precursors

is injected into the reaction chamber 24 formed at the bottom of the torch

body 23 through flue gas inlet 26, the thermal plasma flame 27, described

above, decomposes organic compounds. The high temperature flue gas

discharged from the reaction chamber 24 is cooled by cooling water sprayed

from a cooling water injection nozzle (33) installed near the plasma torch 20.

Therefore, the flue gas discharged at the plasma torch 20 is rapidly cooled to

below 200 °C, more preferably below 100 °C. Hence, the present invention

prevents the re-synthesis(de novo synthesis) of dioxin and the generation of

nitrogen oxides that may be formed by the retention of flue gas at a

particular high temperature range for more than a certain time period. Meanwhile, FIG. 5 is a cross sectional view showing the dioxin and

particulate removal apparatus using thermal plasma according to the present

invention, in which the reaction chamber 24 for decomposing the flue gas

containing contaminants by plasma gas therein and the cooling and washing

room 30 for cooling the high temperature flue gas with cooling water therein

are divided by a separate partition. That is, the flue gas decomposed

thermo-chemically in the reaction chamber 24 is rapidly introduced into the

cooling and washing room to be cooled with cooling water. Here, since the

flue gas is transferred forcedly by a blower (not shown), the water generated

in the cooling and washing room is not introduced into the reaction chamber.

Subsequently, FIG. 6 and FIG. 7 are cross sectional view showing the

dioxin and particulate removal apparatus using thermal plasma according to

another embodiments of the present invention. As shown in FIG. 6 and FIG.7,

a reaction chamber 60 for decomposing contaminants using thermal plasma

and a cooling and washing room 30 for cooling and washing flue gas using

cooling water are installed on a duct in-line of a wastes incineration facility.

In other words, the reaction chamber 60 is installed for introducing

the flue gas generated from the incineration furnace thereto and has at least

one more thermal plasma torch 20 installed therein. Thus, the reaction

chamber 60 is maintained above at least 900 °C, more preferably above 1500 °C. Especially, since the reaction chamber of the present embodiment is

disposed outside the thermal plasma torch 20, a manifold of plasma torches

20 are properly arranged so that the flue gas passing through the reaction

chamber 60 can contact the thermal plasma flames sufficiently. For example,

in FIG. 6, a manifold of plasma torches 20 are arranged in zigzags to

homogenize the temperature inside the reaction chamber 60, and in FIG. 7, a

manifold of plasma torches 20 are askew arranged to agitate the flue gas to

cause cyclone phenomena, thereby promoting thermal decomposition

reaction.

Meanwhile, the reaction chamber 60 is made of a heat resistant

material that can endure high temperature of above 1500 °C, and a separate

cooling unit 63 is installed outside the reaction chamber 60 for protecting the

inside wall of the reaction chamber 60. And, the size and shape of the

reaction chamber 60 may be properly selected by a engineer skilled in the

field, depending on the discharge amount of flue gas to be discharged from

an incineration facility.

Subsequently, a cooling and washing room 90 is installed adjacent to

the reaction chamber 60 so that the flue gas of a high temperature from the

reaction chamber 60 is rapidly transferred to the cooling and washing room

90 which in turn cools the flue gas. In this case, the flue gas is transferred to the cooling and washing room 90 by a blower and an inlet fan(not shown).

The cooling and washing room (90) is intended for the flue gas of a high

temperature to be cooled by the latent heat absorbed when liquid evaporates

to gas, and has a manifold of cooling water injection nozzles installed on the

ceiling portion of thereof, for spraying cooling water as fine water drops.

Therefore, while the flue gas of a temperature of above 900 °C discharged

from the reaction chamber 60 passes through the cooling and washing room

90, it is rapidly cooled to below 200 °C, more preferably below 100 °C.

Meanwhile, while contaminants such as sulfur oxides, particulate, etc.,

contained in the flue gas, pass through the cooling and washing room 90,

they are cooled by cooling water sprayed from the cooling water injection

nozzles 33. In other words, since inorganic contaminants such as sulfur

oxides are not decomposed in the reaction chamber 60, they are washed in

the cooling and washing room 90 to be removed, thus removing all the

contaminants contained in the flue gas.

And, the flue gas discharged from the cooling and washing room (90)

contains a large amount of water. Thus a demister (40) is installed at the rear

end portion of the cooling and washing room (90), for removing water.

Cooling wastewater generated from the cooling and washing room (90) and

the demister (40) is discharged to the outside through a cooling wastewater collecting part (53) and a discharge tube (55) installed below the cooling and

washing room (90) and the demister (40).

Now, the experimental examples of the dioxin and particulate removal

apparatus using thermal plasma according to the present invention will be

described hereinafter.

Experimental Example 1

The removal apparatus for dioxin and particulate using a thermal

plasma, which was invented here was shown in FIG. 5. Plasma gas produced

while passing through the plasma emission region at a flow rate of 18 L/min

and flue gas containing dioxin were mixed with each other. Nitrogen (N2)

was used [for what?] and water was used for cooling electrodes of the

plasma emission region. The water was sprayed to the hot flue gas passed

through the plasma emission region through cooling water nozzles in order to

prevent nitrogen oxides production or dioxin denovo-synthesis.

Experimental Example 2 Experimental method>

In order to determine the dioxin removal efficiency of the thermal

plasma reactor, flue gas containing dioxin was taken from an incineration

facility at a flow rate of 200 L/min and the flue gas was introduced into the

thermal plasma reaction chamber. The dioxin concentration of flue gas was

measured twice when plasma was on-state and off-state respectively at the

rear end of the reaction chamber. And the dioxin concentration was

determined according to procedure of Article no. 29 of Korean Standard

Method for Air Pollution. When plasma was on, the power consumption was

7.1 kW.

Experimental Example 3

Experimental result>

The measurement results of dioxin concentration were shown in the

following table. The removal efficiency was 97.2%

<Table>

Since the temperature of the high temperature emission region is

higher than 10,000 K and dioxins are decomposed at higher than 900 °C,

can be completely destroyed in this thermal plasma treatment unit. At the

same time, particulate residues which had not been combusted in the flue

gas would be completely combusted at high temperature. Therefore

byproducts generation also is small.

As described above, the dioxin and particulate removal apparatus

using thermal plasma can remove above 92% of dioxin, particulate, and other

various environmental pollutants. Hence, the dioxin and particulate removal

apparatus may be applied to the treatment of flue gas discharged from not

only incineration facilities for domestic solid wastes but also various

industrial facilities such as industrial wastes incineration facilities, thermo-

decomposition facilities for waste plastics, steel factories, oil purification

facilities, etc. Industrial Applicability

As described above, the dioxin and particulate removal method and

apparatus using thermal plasma can completely combusts various pollutants

such as dioxin in flue gas discharged from wastes incinerators using a

thermal plasma, and simultaneously it can rapidly cool and wash the flue gas

so as to prevent denovo-synthesis of dioxin and the generation of nitrogen

oxides. And also it removes various pollutants such as sulfur oxides,

particulate, etc. in the flue gas.

Also, compared to other technologies, in this invention, neither

activated carbon nor lime is used. Also, particulates in the flue gas are

completely combusted using thermal plasma so that little amount of

byproducts are produced in this invention. Therefore, a separate apparatus

for post-treatment processes such as collectors may be omitted. Hence, the

installation cost is reduced and the operation and management is easier.

Claims

1 . A dioxin and particulate removal method using thermal plasma, the

method comprising the steps of:

a decomposition step (100) of thermo-chemically destroying dioxin,

soot, particulate, and incomplete combustion products in the flue gas

generated from the incineration facility, by using a thermal plasma;

a cooling and washing step (200) of rapidly cooling the hot flue gas

generated in the decomposition step (100) and simultaneously washing

pollutants in the flue gas;

a dewatering step (300) of reducing water content in the flue gas

cooled in the cooling and washing step (200); and

a wastewater discharging step (400) of discharging cooling water

used in the cooling and washing step (200) and wastewater condensed in

the dewatering step (300).

2. The dioxin and particulate removal method using thermal plasma

as recited in claim 1 ,

wherein the decomposition step keeps the temperature of the flue gas

above 900 °C using a thermal plasma.

3. The dioxin and particulate removal method using thermal plasma as

recited in claim 1 ,

wherein the cooling and washing step rapidly lowers the flue gas

temperature below 200 °C by spraying cooling water.

4. A dioxin and particulate removal apparatus using thermal plasma,

comprising:

a reaction chamber for introducing flue gas containing dioxin

precursors, soot, fly ash, and incomplete combustion products generated

from incineration facility thereto;

thermal plasma torch installed at one side of the reaction chamber for

completely combusting the flue gas introduced into the reaction chamber

using thermal plasma;

a cooling and washing chamber installed adjacent to the reaction

chamber and having cooling water spraying nozzles mounted on the ceiling

portion thereof, for rapid cooling the flue gas discharged from the reaction

chamber so as to prevent the denovo-synthesis of dioxin and the generation

of nitrogen oxides and simultaneous washing hydrogen sulfide, sulfur oxides,

particulate, etc., in the flue gas;

a demister installed adjacent to the cooling and washing chamber for reducing water content in the flue gas generated in the cooling and washing

chamber; and

a waste water discharging method for discharging wastewater

generated in the cooling and washing chamber and the demister.

5. The dioxin and particulate removal apparatus using thermal plasma

as recited in claim 4,

wherein the thermal plasma torch makes thermal plasma flame of

above 900 °C by ionizing the nitrogen gas (N2) using direct current arc

electric discharge or high frequency inductive coupling electric discharge.

6. The dioxin and particulate removal apparatus using thermal plasma

as recited in claim 4,

wherein the thermal plasma torch includes a torch body formed of a

cylindrical hollow tube; a cathode rod installed inside of the torch body; a

nitrogen gas inlet installed at one side of the torch body for injecting a

nitrogen gas into the torch body therethrough; cooling water inlet installed at

one side of the torch body for injecting cooling water into the torch body

therethrough so as to circulate the injected cooling water within the hollow

tube of the torch body; and a power supply methods for applying power to the torch body and the cathode rod.

7. A dioxin and particulate removal apparatus using thermal plasma,

comprising:

a reaction chamber installed on a duct in-line of the wastes

incineration facility for introducing flue gas containing dioxin, dioxin

precursors, soot, fly ash, incomplete combustion products, etc., generated

from the incineration facility thereto, the reaction chamber having thermal

plasma torches installed therein for completely combusting the flue gas

introduced thereto;

a cooling and washing chamber installed adjacent to the reaction

chamber and having cooling water spraying nozzles mounted on the ceiling

portion thereof, for rapid cooling the flue gas discharged from the reaction

chamber and simultaneous washing pollutants in the flue gas;

a demister adjacent to the cooling and washing chamber for reducing

water content in the flue gas generated in the cooling and washing chamber;

and

a wastewater discharging means for discharging wastewater

generated in the cooling and washing chamber and the demister.

8. The dioxin and particulate removal apparatus using thermal plasma

as recited in claim 7,

wherein the temperature of the reaction chamber is maintained above

900 °C.

9. The dioxin and particulate removal apparatus using thermal plasma

as recited in claim 7,

wherein the plasma torches are installed in the reaction chamber in

such a manner as to be arranged in zigzags therein to homogenize the

temperature inside of the reaction chamber or slantingly arranged to agitate

the flue gas injected into the reaction chamber.

10. The dioxin and particulate removal apparatus using thermal

plasma as recited in claim 7,

wherein the reaction chamber is made of a heat resistant material that

can endure high temperature and having a cooling unit installed at the

outside thereof for protecting the inside wall thereof.

1 1 . The dioxin and particulate removal apparatus using thermal

plasma as recited in claim 7, wherein the cooling and washing chamber has cooling water spraying

nozzles installed on the ceiling portion, reduces the temperature of the flue

gas to below 200 °C rapidly by spraying fine water droplet.