KR101297604B1 - Apparatus and methods for destroying sulfur hexafluoride by using dielectric barrier discharge activated alumina - Google Patents

Abstract

Sulfur hexafluoride is a widely used material for gas insulation and is the most powerful greenhouse gas with a high global warming index of 22,800 times that of carbon dioxide. The present invention relates to an apparatus and method for decomposing sulfur hexafluoride, which is a cause of global warming, and greatly increases the decomposition reaction rate of sulfur hexafluoride by using alumina activated by a dielectric barrier discharge plasma. On the contrary, the present invention provides a device and a method for effectively reacting even at a relatively low temperature. When only the alumina catalyst is used, the decomposition efficiency of sulfur hexafluoride is less than 5% even at a high temperature of 400 ° C. However, when activated by exposing the alumina to the dielectric barrier discharge plasma, the decomposition efficiency rapidly increases at about 400 ° C. This results in the decomposition of most sulfur hexafluorides.

Description

Decomposition Apparatus and Decomposition Method for Sulfur Hexafluoride Using Dielectric Barrier Discharge Activated Alumina {APPARATUS AND METHODS FOR DESTROYING SULFUR HEXAFLUORIDE BY USING DIELECTRIC BARRIER DISCHARGE ACTIVATED ALUMINA}

The present invention relates to an apparatus and a method for decomposing sulfur hexafluoride, which is a global warming cause, and more particularly, to greatly increase the decomposition reaction rate of sulfur hexafluoride, and to effectively react at relatively low temperatures. An apparatus and a method for making the same.

Sulfur hexafluoride (SF ₆ ) is a widely used material for gas insulation and is the most powerful greenhouse gas with a high global warming index of 22,800 times that of carbon dioxide. Conventional techniques that can be used for sulfur hexafluoride decomposition include direct combustion, catalytic decomposition, microwave plasma, inductively coupled plasma, DC arc torch, and the like. . Direct combustion method is a big problem of the large amount of energy required to obtain high temperature and the long time preheating time to reach high temperature. Although the catalytic decomposition method can lower the operating temperature, it still requires a high temperature of 700 ℃ or more and there is a problem that the expensive metal catalyst is easily deactivated and the maintenance cost is increased. Microwave plasmas and inductively coupled plasmas require a high degree of vacuum, and thus high operating costs are a major disadvantage, and direct current arc problems are difficult to solve due to electrode corrosion and excessive power consumption.

The present invention can decompose sulfur hexafluoride faster than the conventional direct combustion method, decomposition using a catalyst, microwave plasma, inductively coupled plasma, or direct current arc torch, and at a relatively low temperature. It provides a device and method that can be disassembled.

According to an exemplary embodiment of the present invention, a sulfur hexafluoride (SF ₆ ) decomposition method includes a dielectric barrier discharge unit including a core electrode and a hollow dielectric tube accommodating a core electrode to which a voltage is applied, and a core electrode and Providing a catalyst agent interposed between the dielectric tubes, supplying a current to the core electrode to induce a dielectric barrier discharge in the dielectric barrier discharge portion, activating the catalyst, and oxygen atoms together with sulfur hexafluoride inside the dielectric tube Supplying a reactive gas comprising, may comprise the step of decomposing sulfur hexafluoride.

At least one of alumina (Al ₂ O ₃ ) or zeolite may be used as a catalyst for decomposing sulfur hexafluoride, and sulfur hexafluoride may induce a reaction between sulfur hexafluoride and a reactive body by an activated catalyst. have.

Dielectric barrier discharges operating at atmospheric pressure can excite, dissociate, and ionize gas molecules. The catalytic adsorption behavior of excited molecules is not only different from the adsorption behavior of the ground state molecules, but the sulfur hexafluoride adsorbed on the catalyst is significantly reduced in binding energy than the gaseous sulfur hexafluoride, which is activated by the dielectric barrier discharge. In catalysts, even at relatively low temperatures, the bonds of sulfur hexafluoride are broken and decomposition occurs. Therefore, sulfur hexafluoride can be effectively decomposed at a relatively low temperature by using a catalyst activated by dielectric barrier discharge.

Reactors containing oxygen atoms, such as oxygen or moisture, can be used to chemically stabilize the degraded sulfur hexafluoride in the form of sulfur dioxide (SO ₂ ).

In addition, the zeolite for decomposition of sulfur hexafluoride remains intact even when high heat is applied, and other fine particles can be adsorbed. This property can be used as an adsorbent. Alumina may be used in the form of ball-shaped alpha (α) -alumina, alumina is a material of high hardness and withstands high voltage and high temperature. The plurality of zeolite or alumina balls may form numerous pores therebetween, so that fluid may enter and exit the hollow dielectric tube.

For reference, a copper foil may be provided on the outer wall of the dielectric tube, and the copper foil may be grounded and used as a ground electrode.

Sulfur hexafluoride may be introduced into the dielectric tube in a gaseous state together with nitrogen, oxygen, and moisture in a gaseous state, and the flow rate of all used gases may be controlled by a mass flow controller. In this case, nitrogen may be supplied in a gaseous state, and when moisture is used as a reactor, nitrogen may be supplied in a saturated state in water.

On the other hand, the decomposition efficiency of sulfur hexafluoride is very sensitive to temperature, the present invention may include a temperature control unit to effectively use this characteristic of sulfur hexafluoride.

The temperature control unit may maximize the decomposition efficiency of sulfur hexafluoride by adjusting the temperature of the dielectric tube through which sulfur hexafluoride passes or the temperature of the catalyst.

Specifically, during decomposition of sulfur hexafluoride, it is desirable to maintain the temperature of the dielectric tube at 400 ° C. or higher. The decomposition efficiency of sulfur hexafluoride gradually increases as the temperature is increased from 135 ° C. to 400 ° C., and then about 400 ° C. This is because the decomposition efficiency increases rapidly. Particularly, when the temperature of the dielectric tube is adjusted to a temperature of 490 ° C. to 500 ° C. by using the temperature controller, the decomposition efficiency of sulfur hexafluoride is also excellent, and energy saving effect can be realized when compared with other conventional decomposition methods. For reference, sulfur hexafluoride can be decomposed at an efficiency of 95% or more at 495 ° C., and thus, it is considered that it is most suitable to adjust the temperature of the dielectric tube to 495 ° C. for effective sulfur hexafluoride decomposition efficiency and energy saving.

In addition, the decomposition efficiency of sulfur hexafluoride is greatly affected by the oxygen concentration. When the oxygen concentration was 5 times the initial concentration of sulfur hexafluoride, that is, 1%, sulfur hexafluoride was decomposed 100% at a temperature of 490 ° C. As it increases, the decomposition efficiency of sulfur hexafluoride tends to decrease. Therefore, in order to decompose more than 90% of sulfur hexafluoride, the oxygen concentration should be within 4%, and the approximate oxygen concentration may be appropriately controlled between 1 and 25 times the initial sulfur fluoride concentration. For example, if the initial concentration of sulfur hexafluoride is 2,000 ppm (0.2%), 4% oxygen is 20 times the initial concentration of sulfur hexafluoride. That is, more than 90% of sulfur hexafluoride may be decomposed when the oxygen concentration is 20 times or less than the initial sulfur hexafluoride concentration.

In addition, sulfur hexafluoride is not converted to sulfur dioxide in the process of decomposition of sulfur hexafluoride into sulfur dioxide (SO ₂ ) by the reaction of sulfur hexafluoride and a reactive gas, and sulfur fluoride (SO ₂ F ₂ ) other than sulfur dioxide and Reaction by-products, including ozone (O ₃ ) may occur. Therefore, the sulfur hexafluoride decomposition method according to the present invention may further include removing a reaction by-product including fluoride sulfide and ozone other than sulfur dioxide.

Specifically, fluorine-containing reaction by-products, such as fluorine sulfide, may be converted to sulfur dioxide using at least one of calcium oxide or calcium hydroxide absorbent and removed, and may be generated when using a reactant such as oxygen. The reaction byproduct ozone can be decomposed by manganese dioxide and converted into oxygen.

According to another exemplary embodiment of the present invention, a sulfur hexafluoride decomposition device is disclosed. The sulfur hexafluoride decomposition device includes a core electrode to which a voltage is applied, and a hollow dielectric tube accommodating the core electrode, and an opening and an opening for supplying a reactor body containing oxygen atoms together with sulfur hexafluoride into the dielectric tube. A dielectric barrier discharge portion including an outlet formed opposite to and interposed between the core electrode and the dielectric tube, the catalyst being activated by the dielectric barrier discharge induced in the dielectric barrier discharge portion, the catalyst being activated by the activated catalyst By inducing the reaction of sulfur hexafluoride and the reactant, sulfur hexafluoride can be decomposed into sulfur dioxide.

In addition, it may include a temperature control unit disposed around the dielectric tube to maximize the decomposition efficiency of sulfur hexafluoride which is very sensitive to temperature.

In addition, a fluoride sulfide reactor including at least one of calcium oxide and calcium hydroxide for converting and removing fluoride sulfide other than sulfur dioxide generated in the process of decomposing sulfur hexafluoride into sulfur dioxide to sulfur dioxide may be provided by connecting to the opening. have.

In addition, an ozone reactor including manganese dioxide for converting and removing ozone other than sulfur dioxide generated in the process of decomposing sulfur hexafluoride into sulfur dioxide may be provided by connecting to the opening. In some cases, the fluorine sulfide reactor and the ozone reactor may be sequentially coupled to the opening.

The sulfur hexafluoride decomposition method and decomposition apparatus of the present invention uses alumina activated by a dielectric barrier discharge plasma to significantly increase the decomposition reaction rate of sulfur hexafluoride with water, and the reaction can effectively occur at atmospheric temperature and low temperature. Therefore, the operation cost can be significantly lowered compared to a method requiring a vacuum, and the power consumption is relatively high when compared to a high temperature plasma (microwave plasma, inductively coupled plasma direct current torch) in which both electrons and gas molecules are heated. small.

The sulfur hexafluoride decomposition method and decomposition apparatus of the present invention can solve the problems of the prior art related to the energy consumption and preheating time problem because the operation temperature of the dielectric barrier discharge is significantly lower than the conventional techniques within 500 ℃.

1 is a schematic diagram of a sulfur hexafluoride decomposition apparatus according to an embodiment of the present invention.
2 is a block diagram of a sulfur hexafluoride decomposition device according to an embodiment of the present invention.
3 is a graph showing the relationship between sulfur hexafluoride decomposition and reaction temperature.
4 is a graph showing the effect of oxygen concentration on sulfur hexafluoride decomposition.
5 is a graph showing the relationship between sulfur hexafluoride decomposition by-products and absorbance according to reaction temperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. For reference, the same numbers in this description refer to substantially the same elements and can be described with reference to the contents described in the other drawings under these rules, and the contents which are judged to be obvious to the person skilled in the art or repeated can be omitted.

1 is a schematic diagram of a sulfur hexafluoride decomposition device according to an embodiment of the present invention, Figure 2 is a block diagram of a sulfur hexafluoride decomposition device according to an embodiment of the present invention.

First, referring to FIG. 1, the sulfur hexafluoride decomposition device 100 includes a dielectric barrier discharge unit 110, an alumina catalyst 120, a fluoride sulfide reactor 130, and an ozone reactor 140.

The dielectric barrier discharge part 110 includes a core electrode 111, a dielectric tube 112, a temperature control part 113, and a discharge part housing 114.

The dielectric barrier discharge unit 110 for inducing the dielectric barrier discharge may excite, dissociate, and ionize gas molecules. The catalytic adsorption behavior of excited molecules is not only different from the adsorption behavior of the ground state molecules, but the sulfur hexafluoride adsorbed on the alumina catalyst 120 is significantly reduced in binding energy than the gaseous sulfur hexafluoride, and thus is activated by dielectric barrier discharge. In the alumina catalyst 120, the bond of sulfur hexafluoride is broken even at a relatively low temperature, so that decomposition may occur.

That is, the sulfur hexafluoride decomposition device 100 according to the present invention can effectively decompose sulfur hexafluoride at a relatively low temperature by using the alumina catalyst 120 activated by the dielectric barrier discharge.

Insulating dielectric tube 112 may be provided as a tube using a ceramic in the present embodiment, it may be provided as a hollow having an outer diameter 28mm, inner diameter 24.5mm.

In addition, the core electrode 111 may use a stainless steel bolt coaxially disposed on the dielectric tube 112, and the stainless steel bolt may have a thickness of 6 mm. Of course, the core electrode 111 may use another metal, for example, tungsten, which has excellent conductivity and also has good heat resistance and strength. As the core electrode 111, an AC high voltage (10-16 kHz) having a frequency of 400 kHz may be supplied from the power supply unit 102.

In addition, the outer wall of the dielectric tube 112 is wrapped with a copper foil 117, the length of the dielectric tube 112 wrapped with the copper foil 117 is 150 mm, the copper foil 117 is grounded to the outside It can be used as a ground electrode.

An alumina catalyst 120 is filled between the inner wall of the dielectric tube 112 and the core electrode 111. In the present embodiment, the alumina catalyst 120 uses alpha (α) -alumina having a diameter of 3 mm, and alpha-alumina is a material of high hardness used for ball milling, and is a material that can withstand high voltage and high temperature well. to be. The filled alumina catalyst 120 has a ball shape having an apparent volume of about 125 cm 3 in the interior of the myriad pores (pore).

The core electrode 111 and the dielectric tube 112 described above may be installed in the discharge unit housing 114 made of stainless steel or other metal material. The discharge part housing 114 has a gas inlet 115 and a gas outlet 116 formed therein, and the gas inlet 115 may introduce sulfur hexafluoride for decomposing, in addition to a reactive body such as oxygen and moisture, And nitrogen may be introduced in a gaseous state. The gas introduced into the gas inlet 115 may be introduced into the dielectric tube 112 through an opening located at an upper side of the dielectric tube 112 in FIG. 1, and the gas outlet 116 may be introduced into the dielectric tube 112. It is in communication with the other side opening of).

In addition, the fluorine sulfide reactor 130 and the ozone reactor 140 are sequentially installed at the end of the gas outlet 116, the volume of the fluorine sulfide reactor 130 and the ozone reactor 140 is 50 cm 3 and 30 cm 3, respectively. Is provided.

Hereinafter, the decomposition of sulfur hexafluoride through the sulfur hexafluoride decomposition device 100 described above, and the sulfur hexafluoride decomposition method according to the present invention through the sulfur hexafluoride decomposition device 100 shown in Figs. It explains in detail.

For reference, the voltage supplied to the core electrode 111 is analyzed using a high voltage probe (model P6015, Tektronix) and a digital oscilloscope (model TDS 3032, Tektronix).

2 is a block diagram of a sulfur hexafluoride decomposition device according to an embodiment of the present invention.

Sulfur hexafluoride decomposition experiment in the sulfur hexafluoride decomposition apparatus 100 of the present invention is performed using a simulation gas consisting of sulfur hexafluoride, nitrogen, and oxygen. The flow rate of the simulated gas supplied to the dielectric barrier discharge part 110 was 60 L / h, and the concentration of sulfur hexafluoride was 2,000 ppm (0.2%). At this time, the concentration of oxygen was adjusted to 1 to 5% range. The flow rates of all the used gases are the mass flow rates provided in the first nitrogen tank 103, the oxygen tank 104, the sulfur hexafluoride tank 105, and the second nitrogen tank 106 connected to the saturator 150, respectively. Controlled by a mass flow controller (MFC). In the experiment using water as an additive, as shown in FIG. 2, it was possible to provide nitrogen in a gaseous state, and in some cases, saturating nitrogen in water using a water saturator 150 to simulate it. It was allowed to mix with gas. The dielectric barrier discharge unit 110 is heated by dielectric heating by the dielectric barrier discharge, and may be heated by the temperature control unit 113 as shown in FIG. 1 to compensate for insufficient temperature. In this embodiment, the temperature control unit 113 may be provided in the form of a heating tape or coil surrounding the dielectric tube 112, the thermal insulator (thermal insulator) outside the temperature control unit 113 so that the provided heat is not easily escaped ( 118 may be further provided.

Mossas discharged after being processed in the dielectric barrier discharge unit 110 flows into the fluoride sulfide reactor 130 installed at the rear stage to remove calcium hydroxide and fluorine-containing inorganic by-products through the reaction. In addition, an ozone reactor 140 is installed at the rear end of the fluorine sulfide reactor 130 to convert ozone, a byproduct, to oxygen. The simulated gas thus treated can be analyzed using a Fourier Transform Infrared Spectrometer (model IFS 66 / S, Bruker).

3 is a graph showing the relationship between sulfur hexafluoride decomposition and reaction temperature. The decomposition efficiency of sulfur hexafluoride is calculated by the following [Formula 1],

Equation 1 removal rate (%) = (SF _{6 , o} -SF _{6 , f} ) / SF _{6 , o} * 100

Here, SF _{6, o} and SF _{6, f} represent the concentrations of the gas inlet 115 and the gas outlet 116, respectively. In this experiment, the concentration of oxygen was 1% and the input power was 100W. As shown in FIG. 3, the decomposition efficiency of sulfur hexafluoride gradually increases as the temperature is increased from 135 ° C. to 400 ° C., and the decomposition efficiency rapidly increases from about 400 ° C. to about 95% or more of sulfur hexafluoride at 495 ° C. Decompose In FIG. 3, the decomposition type of sulfur hexafluoride may be divided into two regions for each temperature based on 400 ° C. FIG. In the region below 400 ° C, the alumina is not activated by dielectric barrier discharge, and the decomposition efficiency increases with temperature increase.In the region above 400 ° C, alumina is activated by the dielectric barrier discharge, so the decomposition efficiency increases rapidly with temperature. Become. Figure 3 also shows the sulfur hexafluoride decomposition efficiency when only alumina is used without dielectric barrier discharge, which does not occur prior to 400 ° C., and exhibits a decomposition efficiency of less than 5% at 400 ° C. and less than 20% at 460 ° C. It was. According to FIG. 3, in order to effectively dissolve sulfur hexafluoride, the operating temperature of the dielectric barrier discharge activated alumina reactor should be increased to 495 ° C. FIG.

4 is a graph showing the effect of the oxygen concentration on the decomposition of sulfur hexafluoride, the experimental results at the input power 100W. As shown in FIG. 4, the effect of oxygen on the decomposition of sulfur hexafluoride is enormous. When oxygen is 1%, sulfur hexafluoride is decomposed 100% at a temperature of 490 ° C., and the decomposition efficiency of sulfur hexafluoride decreases as the oxygen concentration is increased. It shows a tendency to In order to decompose more than 90% of sulfur hexafluoride as shown in Figure 4, the oxygen concentration should be within 4%. Since the initial concentration of sulfur hexafluoride is 2,000 ppm (0.2%), 4% oxygen is 20 times the initial concentration of sulfur hexafluoride. That is, more than 90% decomposition occurs when the oxygen concentration is within 20 times the initial sulfur hexafluoride concentration.

FIG. 5 is a graph showing sulfur hexafluoride by-products, and is an experimental result at an oxygen concentration of 2%, an input power of 100 W, and an initial concentration of sulfur hexafluoride at 2,000 ppm. 5 is the absorbance of the Fourier transform infrared spectrophotometer, which is measured at the rear end of the dielectric barrier discharge unit 110, that is, at the front end of the fluorine sulfide reactor 130. Preferably, sulfur hexafluoride should be converted to sulfur dioxide, but as shown in FIG. 5, some of the sulfur hexafluoride decomposed in the dielectric barrier discharge part 110 is converted into unwanted fluoride sulfide (SO ₂ F ₂ ). The fluoride sulfide reactor 130 is used for the purpose of decomposing and converting the sulfur dioxide into sulfur dioxide. Fluoride sulfide passes through the fluoride sulfide reactor 130 and is converted into sulfur dioxide and absorbed into calcium hydroxide, and calcium hydroxide is converted into fluorite (CaF ₂ ) and calcium sulfite (CaSO ₃ ). When the presence of more than 0.5% of the moisture in the simulated gas was observed a phenomenon that the occurrence of fluoride sulfide, fluorine sulfide reactor 130 is required for the complete removal of fluorine sulfide. Ozone generated when oxygen is used as a reactant is decomposed into oxygen in the ozone reactor 140 at the rear of the fluoride sulfide reactor 130. The resulting gas is a clean gas free of sulfur hexafluoride or harmful by-products.

As described above, although described with reference to the preferred embodiment of the present invention, those skilled in the art various modifications and variations of the present invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

100: sulfur hexafluoride decomposition device 110: dielectric barrier discharge unit
111 core electrode 112 dielectric tube
113: temperature control part 114: discharge part housing
115: gas inlet 116: gas outlet
117: copper foil 120: alumina catalyst
130: fluorine sulfide reactor 140: ozone reactor

Claims (22)

delete delete delete delete delete delete delete delete delete delete delete In sulfur hexafluoride decomposition device,
A core electrode to which a voltage is applied, and a hollow dielectric tube accommodating the core electrode, and an opening for supplying a reactor body containing oxygen and moisture together with the sulfur hexafluoride into the dielectric tube and into the opening. A dielectric barrier discharge portion including an oppositely formed outlet;
A zeolite catalyst interposed between the core electrode and the dielectric tube and provided in the form of a plurality of balls activated by a dielectric barrier discharge induced in the dielectric barrier discharge unit; And
A temperature controller disposed around the dielectric tube to adjust the temperature of the dielectric tube to a temperature of 490 ° C to 500 ° C;
A fluoride sulfide reactor connected to the dielectric barrier discharge part to remove fluoride sulfide generated in the process of decomposing the sulfur hexafluoride, and including at least one of calcium oxide and calcium hydroxide;
An ozone reactor connected to the fluorine sulfide reactor to remove ozone generated in the process of decomposing the sulfur hexafluoride into sulfur dioxide and including manganese dioxide;
A mass flow controller for adjusting the concentration of oxygen supplied into the dielectric tube to 1 to 25 times the concentration of the sulfur hexafluoride initially supplied to the dielectric tube;
And a sulfur hexafluoride decomposing apparatus comprising: decomposing the sulfur hexafluoride using the activated zeolite catalyst. delete delete delete delete delete delete delete delete delete delete

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