ENERGY-SAVING TYPE DIELECTRIC BARRIER DISCHARGE PLASMA NOX REDUCTION DEVICE
Disclosed is a nitrogen oxide reduction device using dielectric barrier discharge plasma. The plasma nitrogen oxide reduction device may limitedly emit nitrogen oxide with a form of NO2 at a final outlet of the plasma nitrogen oxide reduction device by arranging a combustion unit, a wet treatment unit, and a plasma oxidizing unit in a housing. The emitted nitrogen oxide is finally treated in a wet scrubber operated as a reducer at a final exhaust end.
This application claims priority to Korean Patent Application No. 2015-0023940 filed on Feb. 17, 2015 and 2015-0035697 filed on Mar. 16, 2015 in the Korean Intellectual Property Office (KIPO), the entire contents of which are hereby incorporated by reference.
BACKGROUND1. Technical Field
Example embodiments of the present invention relate to a field of waste gas treatment, and more specifically, to an energy saving-type dielectric barrier discharge (DBD) plasma nitrogen oxide reduction device capable of efficiently treating waste gas including nitrogen oxides (NOx) and other pollutants.
2. Related Art
Along with rapid industrialization, energy has served as a fundamental means for industrial activities for satisfactory of human's need. However, as use of the energy is increased, generation of environmental pollution has become inevitable, and also the extent thereof has been getting larger. Since air pollutants are inevitably emitted in a combustion process of fossil fuel, which is the majority of energy source, such as oil, coal, natural gas, and the like, it is necessary for all of mankind to promote a balance between economic growth and environmental preservation to ensure sustainable growth.
Air pollution due to use of energy is classified into local pollution and international pollution according to an effective range and a responsible range. Damage to animals and plants and acid rain due to sulfur oxide, nitrogen oxide, and the like occur relatively locally, on the contrary, green-house gases, such as carbon dioxide, NOx, and the like, have become an international issue in the discussion on global warming.
Due to indiscriminate growth-oriented economic management, air pollution around domestic major cities and industrial complexes has already reached its critical point. Methodology for prevention of domestic air pollution, due to income increase caused by economic growth, and global warming being regulated by being internationally watched with interest and vision of air pollutants according to use of energy have been important issues.
Currently, in a situation in that that use of fluoride compound has been growing day by day as demand related to semiconductor display is increased, a catalytic method is today mainly used as techniques for handling NOx and solving a problem of regulation on total quantity due to large quantity emission of secondary pollutant (NOx) generated after the semiconductor process gas treatment, however, it is required to secure an alternative technique because of excessive use of energy during operation. Therefore, the alternative technique to solve existing problems is needed.
(Patent Document 1) Korean Laid-open Patent Application No. 10-2011-0065985
SUMMARYAccordingly, example embodiments of the present invention are provided to substantially obviate one or more problems due to limitations and disadvantages of the related art.
Example embodiments of the present invention provide a nitrogen oxide reducing-type plasma oxidizing device efficiently treating nitrogen oxides by limitedly emitting nitrogen oxide with a form of NO2 by arranging a combustion unit, a wet processing unit, and a plasma oxidizing unit in a housing of the plasma nitrogen oxide reduction device in order.
In some example embodiments, an energy saving-type DBD plasma nitrogen oxide reduction device configured to treat waste gas includes a combustion unit combusting the waste gas; a wet treatment unit configured to receive the combusted gas from the combustion unit and perform wet treatment on the gas; and a plasma oxidizing unit arranged to insert plasma gas for treating nitrogen oxide included in the gas passing through the wet treatment unit.
The energy saving-type DBD plasma nitrogen oxide reduction device further includes a housing, wherein the combustion unit, the wet treatment unit, and the plasma oxidizing unit are arranged in the housing.
The energy saving-type DBD plasma nitrogen oxide reduction device further includes a main emission tube configured to emit the nitrogen oxide, treated by the plasma gas, to outside of the housing, wherein the plasma oxidizing unit is connected and mounted to a connection path connected to the main emission tube in the housing.
The plasma gas is O3 generated through plasma discharge of the plasma oxidizing unit. The nitrogen oxide is converted into NO2 by oxidizing with O3 generated in the plasma oxidizing unit.
The converted NO2 is treated through a reduction reaction in a wet treatment process which is a post treatment process.
The plasma oxidizing unit includes a rod-shaped internal electrode, a dielectric configured to surround the internal electrode, and an external electrode inserted and mounted into an outer part of the dielectric in a coil form, wherein the internal electrode and the external electrode are applied with alternating current power for generation of plasma.
The external electrode has a surface coated with thermal spraying.
An external surface of dielectric and an external surface of external electrode are formed at the same height.
The plasma oxidizing unit is configured to generate plasma using DBD plasma.
According to the present invention, the plasma nitrogen oxide reduction device may limitedly emit nitrogen oxide with a form of NO2 at a final outlet of the plasma nitrogen oxide reduction device by arranging, in the housing, the plasma oxidizing unit arranged to insert plasma gas for treating the nitrogen oxide included in the gas passing through the combustion unit and the wet treatment unit. Also, the nitrogen oxide is treated by discharging the dielectric barrier discharge plasma of the plasma oxidizing unit made of a coil type electrode without additional equipment, thereby saving energy supplied to equipment.
The plasma oxidizing unit may include an internal electrode, a dielectric configured to surround the internal electrode, and an external electrode inserted and mounted to an outside of the dielectric in a coil form. A surface of the external electrode is coated with thermal spraying, and an external surface of dielectric and an external surface of external electrode are formed at the same height, thereby preventing dusts from adhering between the electrodes, and solving a problem of heat and arc generated between the dielectric and the electrode.
Effects of the present invention are not limited to the above-described effects and other unmentioned effects may be clearly understood by those skilled in the art from the following descriptions.
Example embodiments of the present invention will become more apparent by describing in detail example embodiments of the present invention with reference to the accompanying drawings, in which:
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. In descriptions of the invention, when detailed descriptions of related well-known technology are deemed to unnecessarily obscure the gist of the invention, they will be omitted.
Hereinafter, embodiments will be described in detail by explaining exemplary embodiments of the invention with reference to the attached drawings. In descriptions of the embodiments with reference to the attached drawings, like reference numerals in the drawings denote like elements, and redundant description thereof will be omitted.
Generally, nitrogen oxides are generated by a stationary emission source, such as a thermoelectric power plant, and a mobile emission source, such as a vehicle. Nitrogen oxides generated in a semiconductor process are generated by a reaction between nitrogen and oxygen by a high temperature at the time of combustion in a combustion process in a scrubber through which various harmful gases pass to be safely treated before the gases are emitted into the atmosphere.
NO emitted into the atmosphere is oxidized into NO2, NO3, N2O4, by O3, O2, moisture, and the like in the air. Most of them are NO2, the NO2 is dissolved into the air in an aerosol state to become acid rain or to form photochemical smog by sunlight. With extensive damage, the acid rain and the photochemical smog cause a respiratory disease and sight disability due to eye irritation, corrode metal, and affect growth of plants.
A thermal treatment device is used in a process of treating harmful gases, such as SiH4, NF3, used in a semiconductor process. The thermal treatment device is classified into a fuel-type, an electric heater type, and a plasma type. The thermal treatment devices in these types generate a large amount of nitrogen oxides (NO and NO2) by a reaction between O2, H2O, and the like and N2 during a treatment process. Particularly, the thermal treatment devices in the fuel type and the plasma type has a high operation temperature to generate NO of the nitrogen oxides at a high rate.
As another generation source, NH3 and NF3 of gases used in a semiconductor process generate a large amount of nitrogen oxide (mostly NO) by reacting a nitrogen factor (N+), decomposed from NH3 and NF3 in a decomposing or chemical reaction process, with O2 or H2O in the air.
Referring to
Here, the plasma nitrogen oxide reduction device 300, applied with the plasma oxidizing unit 330 according to the present invention, may be a point of use (POU) scrubber which is a thermal treatment device generally used to treat waste gas. A combustion unit 310 and a wet treatment unit 320 may be included in a conventional POU scrubber. However, in the plasma nitrogen oxide reduction device 300 according to the present invention, the housing 301 may include the plasma oxidizing unit 330 to insert plasma gas for treating nitrogen oxide included in gases passing through the wet treatment unit 320, in addition to the combustion unit 310 and the wet treatment unit 320.
As shown in
The combustion unit 310 uses a method of treating the waste gas by making the waste gas including harmful components pass through flames. To increase fuel efficiency, O2 and CH4 may be injected through a combustion gas injection port 313 provided on an upper part of the combustion unit 301.
However, a large amount of nitrogen oxides (NO and NO2) are generated by a reaction between O2, H2O, and the like and N2 during a treatment process. Particularly, since an operation temperature is high at the time of combustion in the combustion process, the NO of the nitrogen oxides is generated at a high rate.
The waste gas treated in the combustion unit 310 passes through the wet treatment unit 320 to accumulate secondary by-product, dissolve soluble gases, and cool the high temperature combustion gas.
The wet treatment unit 320 may include a first injection nozzle 321, a second injection nozzle 322, a wet water tank 323, a flow rate adjusting device 324, a pump 325, and a water supply tube 326 to receive the gas combusted from the combustion unit 310 and perform wet treatment on the gas.
The wet treatment unit 320 adsorbs and dissolves soluble waste gas and silicon dioxide (SiO2) powders generated in the combustion unit 310 through injection of the injection nozzles 321 and 322, and stores the treated materials, emitted from the combustion unit 310 and the injection nozzles 321 and 322, and emits the treated materials using the wet water tank 323. It is preferable that the first injection nozzle 321 and the second injection nozzle 322 be installed on an upper part of the wet water tank 323.
The first injection nozzle 321 and the second injection nozzle 322 are connected to the water supply tube 326 to receive water from the wet water tank 323, and the pump 325 may be mounted between the wet water tank 323 and the water supply tube 326 to supply, to the injection nozzles 321 and 322 on an upper part the wet water tank 323, the water in the wet water tank 323 mounted at a lower part inside the housing 301. Also, the flow rate adjusting device 324 may be mounted between the wet water tank 323 and the pump 325 to control the amount of water injected by the injection nozzles 321 and 322.
In this way, the wet water tank 323, the flow rate adjusting device 324, the pump 325, and the water supply tube 326 interwork with each other in the wet treatment unit 320 to be functioned as a water circulation means to continuously circulate water at an even temperature water in the wet treatment unit 320.
A main emission tube 327 may be further included at a rear end of the wet treatment unit 320 to emit the treated waste gas to the outside of the housing 301 and then to a device for post-treatment process.
The main emission tube 327 is extended from the inside of the housing 301 to the outside thereof, and the main emission tube 327, formed in the housing 301, of the main emission tube 327 may be connected with the plasma oxidizing unit 330 by a connection path 328 connected to the main emission tube 327.
That is, the plasma oxidizing unit 330 according to the present invention may be arranged along with the combustion unit 310 and the wet treatment unit 320 in the housing 301 of the plasma nitrogen oxide reduction device 300 to be formed as integrated single scrubber equipment.
Also, an alternating current power supply unit 340 may be further included in a lower part of the plasma oxidizing unit 330 to apply alternating current power to the plasma oxidizing unit 330.
In this way, by arranging the plasma oxidizing unit 330 in the main emission tube 327 which is a rearmost end in the plasma nitrogen oxide reduction device 300, the nitrogen oxide (NO) to be finally emitted to the outside of the housing 301 through the main the emission tube 327 may be limitedly emitted as NO2.
That is, O3, generated in the plasma oxidizing unit 330 through plasma discharge, and nitrogen oxide (NO) generated at the time of combustion in a combustion process are converted into NO2 through oxidization, and the converted NO2 is emitted through the main emission tube 327 to the outside of the housing 301. The NO2 emitted to the outside of housing 301 may efficiently treat the nitrogen oxide through a reduction reaction of the wet treatment process which is a post treatment process.
Referring to
The internal electrode 331 has a hollow rod shape and may be formed of a conductive material to apply an electric current. The discharge gas for the plasma discharge is inserted through a reactive gas inlet 336 at a lower part of the internal electrode 331, the plasma gas generated through the plasma discharge may be emitted through a plasma gas outlet 337 at an upper part of the internal electrode 331. Preferably, the discharge gas for the plasma discharge may be O2, and the plasma gas generated through the plasma discharge may be O3.
The dielectric 332 is configured to surround the internal electrode 331 from one end to the other end thereof at a predetermined distance, and has the same rod shape as the internal electrode 331. The dielectric 332 is arranged between the internal electrode 331 and the external electrode 333 to prevent arcing generated between the electrodes by a high voltage applied to the electrodes.
The external electrode 333 may be formed in a coil-type electrode structure having a coil shape, and may be inserted and mounted into an outer surface of the dielectric 332. A coil may be inserted at regular intervals. In a cross-section of the coil, a gap between a groove formed in the dielectric 332 and the coil when the coil is inserted into the dielectric 332 is not allowed. The cross-section of the coil may have a rectangular shape so that the external surface 334 of dielectric and the external surface 335 of external electrode are formed at the same height. However, the shape of the cross-section of the coil may be variously changed depending on users.
Alternating current power is applied to the internal electrode 331 and the external electrode 333 by the alternating current power supply unit 340 mounted to a lower part of the plasma oxidizing unit 330. For example, a voltage is applied to the internal electrode 331, and the external electrode 333 is grounded. Or, polarities of the internal electrode 331 and the external electrode 333 may be changed. High voltages may be applied to both of the two electrodes depending on the alternating current power supply unit 340. That is, a high voltage WI is applied to any one of the internal electrode 331 and the external electrode 333, and the other one is grounded. Or, when a positive electrode is applied to any one of the internal electrode 331 and the external electrode 333, a negative electrode may be applied to the other one.
Also, the internal electrode 331 and the external electrode 333, which are the conductive materials including metal, may be made of any one among aluminum (Al), stainless steel (STS), titanium (Ti), nickel (Ni), chrome (Cr), copper (Cu), tungsten (W), and titanium (Pt) that have strong corrosion resistance, or an alloy thereof. Preferably, hastelloy mainly made of nickel having excellent moldability and corrosion resistance may be applied.
The dielectric 332 may be applied with any one material among MgO, Al2O3, TiO2, and SiO2 that are an oxide ceramic with high dielectric constant.
A surface of the external electrode 333 formed in a coil form may be coated with thermal spraying, and the external electrode 333 may be inserted and mounted to an outer part of the dielectric 332. Also, the external surface 335 of external electrode inserted into the dielectric 332 may be arranged at the same height as the external surface 334 of dielectric.
Like this, the surface of the external electrode 333 is coated with thermal spraying, and the external surface 335 of external electrode is arranged at the same height as that of the external surface 334 of dielectric, thereby preventing dusts from adhering between the electrodes, and solving a problem of heat and arc generated between the dielectric 332 and the electrode.
The plasma oxidizing unit 330 may be implemented in various sizes depending on users. However, in a preferable size of the internal electrode 331 according to the present invention, a height from one end to the other end is set to 1.5 m. In the dielectric 332, a height from one end from the other end is set to 1.2 m. Also, in the external electrode 333 in a coil form, a height from one end from which a coil start to the other end of the coil is set to 0.95 m. Thicknesses of the coil and the dielectric 332 are, as shown in
A dielectric barrier discharge (DBD) plasma device using the coil-type electrode structure is applied with a high frequency and a high voltage to additionally form an induced electric field in an electric field, generated between the two electrodes, by Faraday's Law of Induction, thereby maximizing the strength of electric field. Therefore, consumption of power is remarkably reduced, and plasma with excellent performance may be generated.
As described above, a the plasma oxidizing unit 330 according to the present invention generates plasma using the dielectric barrier discharge plasma, and O2 is converted into O3 by generation of the plasma, and thus the O3 is emitted to the main emission tube 327 through the connection path 328. The O3 emitted to the main emission tube 327 performs oxidation and ionization treatment with pollutant in the main emission tube 327. For example, NO and CO are oxidized into NO2 and CO2, THC is oxidized and ionized, and HF or dust is coarsened.
Therefore, the nitrogen oxide generated during a combustion process in the plasma nitrogen oxide reduction device 300 by the plasma generated in the plasma oxidizing unit 330 according to the present invention is treated by reacting with O3 generated through the plasma discharge, thereby limitedly emitting nitrogen oxide with a form of NO2 at the final outlet of the plasma nitrogen oxide reduction device 300.
A reaction mechanism in which the nitrogen oxide is oxidized by the plasma oxidizing unit 330 is as follows.
NO+O3≧NO2−+O2
The nitrogen oxide oxidized by the plasma oxidizing unit 330 and emitted as NO2 through the main emission tube 327, as shown in
A main reaction mechanism in which the nitrogen oxide is reduced by the wet scrubber 400 is as follows.
NO2+(Na2S+α)=N2+Na2SO4
In this way, the nitrogen oxide generated in the plasma nitrogen oxide reduction device 300 during combustion may be efficiently treated through an oxidation process, caused by the plasma oxidizing unit 330, and a reduction process of the wet scrubber 400.
EXPERIMENTAL EXAMPLE 1To evaluate a process performance of equipment to which the plasma oxidizing unit of the present invention is mounted, a conversion efficiency test in which the nitrogen oxide is converted into NO2 by the plasma discharge of the plasma oxidizing unit is performed.
A table 1 and a table 2 are results of the test of the equipment to which the plasma oxidizing unit of the present invention is mounted.
As conditions according to an experimental example 1, a concentration of plasma O3 of an oxidation stage is set to 40 ppm, and a reference air volume is set to 2 CMM. Under conditions of a superficial velocity of 1 m/s and a residence time of 2 sec., NO2 conversion efficiency of nitrogen oxide at the time of plasma OFF and plasma ON is given in the table 1, and results of an oxidation rate test according to a change in time is given in the table 2.
As shown in the table 1 and the table 2, it is confirmed that the nitrogen oxide may be efficiently converted into NO2 according to whether energy of the plasma is applied.
EXPERIMENTAL EXAMPLE 2In an experimental example 2, to evaluate a process performance of equipment to which the plasma oxidizing unit of the present invention is mounted, a conversion efficiency test in which the nitrogen oxide is converted into NO2 by the plasma discharge of the plasma oxidizing unit after continuous operation for 80 min. is performed.
Tables 3 to 6 are test results of the experimental example 2 for the equipment to which the plasma oxidizing unit of the present invention is mounted.
As conditions of the experimental example 2, a concentration of plasma O3 of an oxidation stage is set to 40 ppm, and a reference air volume is set to 2 CMM, so the conditions are the same as those of the experimental example 1. The test is performed in the same method as that of the experimental example 1 under condition of a superficial velocity of 1 m/s and various residence times.
As the results measured at residence times of 0.5 to 2 sec. in the tables 3 to 6, it is confirmed that every treatment efficiency is 95% or more.
As described above, the plasma nitrogen oxide reduction device 300 may limitedly emit nitrogen oxide with a form of NO2 at the final outlet of the plasma nitrogen oxide reduction device 300 by arranging, in the housing 301, the combustion unit 310 combusting waste gas, the wet treatment unit 320 configured to receive the combusted gas from the combustion unit 310 and perform wet treatment; and the plasma oxidizing unit 330 arranged to insert plasma gas for treating the nitrogen oxide included in the gas passing through the wet treatment unit 320. Also, the nitrogen oxide is treated by emitting the dielectric barrier discharge plasma of the plasma oxidizing unit 330 made of a coil type electrode without additional equipment, thereby saving energy supplied to equipment.
Meanwhile, the embodiments disclosed in this specification and drawings are only examples to help understanding of the invention and the invention is not limited thereto. It is clear to those skilled in the art that various modifications based on the technological scope of the invention in addition to the embodiments disclosed herein can be made.
Claims
1. An energy saving-type DBD plasma nitrogen oxide reduction device configured to treat waste gas, comprising:
- a combustion unit combusting the waste gas;
- a wet treatment unit configured to receive the combusted gas from the combustion unit and perform wet treatment on the gas; and
- a plasma oxidizing unit arranged to insert plasma gas for treating nitrogen oxide included in the gas passing through the wet treatment unit.
2. The device of claim 1, further comprising a housing, wherein the combustion unit, the wet treatment unit, and the plasma oxidizing unit are arranged in the housing.
3. The device of claim 2, further comprising a main emission tube configured to emit the nitrogen oxide, treated by the plasma gas, to outside of the housing, wherein the plasma oxidizing unit is connected and mounted to a connection path connected to the main emission tube in the housing.
4. The device of claim 1, wherein the plasma gas is O3 generated through plasma discharge of the plasma oxidizing unit.
5. The device of claim 4, wherein the nitrogen oxide is converted into NO2 by oxidizing with O3 generated in the plasma oxidizing unit.
6. The device of claim 5, wherein the converted NO2 is treated through a reduction reaction in a wet treatment process which is a post treatment process.
7. The device of claim 1, wherein the plasma oxidizing unit comprises a rod-shaped internal electrode, a dielectric configured to surround the internal electrode, and an external electrode inserted and mounted into an outer part of the dielectric in a coil form, wherein the internal electrode and the external electrode are applied with alternating current power for generation of plasma.
8. The device of claim 7, wherein the external electrode has a surface coated with thermal spraying.
9. The device of claim 7, wherein an external surface of dielectric and an external surface of external electrode are formed at the same height.
10. The device of claim 1, wherein the plasma oxidizing unit is configured to generate plasma using DBD plasma.
Type: Application
Filed: Nov 25, 2015
Publication Date: Aug 18, 2016
Applicant: ECOENERGEN CO., LTD. (Cheonan-Si)
Inventor: Jong Pil Yoon (Cheonan-Si)
Application Number: 14/951,983
