KR20020062865A - Apparatus for volatile organic compounds degradation by non-thermal plasma combined electro-oxidation catalysis. - Google Patents

Abstract

PURPOSE: An apparatus for volatile organic compounds degradation by non-thermal plasma combined electro-oxidation catalysis is provided, which can design energy conservative type by applying decomposing principle of semi-conductor catalyst to production principle of high voltage plasma. The system can treat large volume of harmful gas and high concentration by arranging the treatment equipment in parallel or series, thus curtailing installation area and saving operation cost. CONSTITUTION: The p type semi-conductor catalyst coated composition is formed as follows: (i) first, p type semi-conductor coating composition has the following formula; T-MO, where, T is titanium dioxide, MO is oxidized metal such as oxidized cobalt, the n type semi-conductor composition is prepared by this composition; (ii) second, n type semi-conductor having following composition, T-M, where, T is titanium dioxide, M is silicon, nickel, silver, n type semi-conductor is prepared based on this composition; (iii) third, p type semi-conductor coating composition having following formula, BT-M-MO, where, B is oxidized bismuth, T is titanium dioxide, M is reaction active metal such as platinum, molybdenum, tungsten, silver, cobalt, MD is vanadium pentoxide, oxidized silver, oxidized cobalt, oxidized nickel, zeolite, the p type semi-conductor coating composition is prepared based on this composition; (iv) the electrode is prepared by a sequence of p/n/p type with 30-50 μm/ 10-20 μm/ 30-50 μm; (v) to this electrode AC of 300-400 kHz, 6-10 kV, 0.5-5A and pulse power of +10 to +15 kV, 0.5-2A are applied to remove volatile organic compound and odorizing matter and to decompose dioxin, decomposing matter of ozone layer such as tetrachlorocarbon, freon gas, methyl chloroform and methyl bromide.

Description

Apparatus for volatile organic compounds degradation by non-thermal plasma combined electro-oxidation catalysis.}

In order to remove conventional volatile organic compounds, granular barium titanate (BaTiO ₃ ) having a high dielectric constant is charged between discharge electrodes having a very high power consumption by resistive discharge or by using a K-band high frequency plasma power source. By coating a semiconductor catalyst thin film on the metal electrode that caused the high vacuum plasma discharge, stable capacitive discharge was caused, and the surface current density due to the surface electric field effect was increased to improve the catalyst efficiency on the surface of the semiconductor catalyst coating.

The present invention adds a catalytic action by applying a semiconductor catalyst coating to the electrode to improve this point, by forming a positive pulse electrode to form an electron transfer layer by electron trap between the AC discharge electrode by the electron acceleration principle Its purpose is to efficiently decompose and remove volatile organic compounds, odors, dioxin, carbon tetrachloride, freon gas, halon, methyl chloroform and methyl bromide.

Means to Solve the Problem

The basic structure of the present invention consists of an unheated plasma section, an application of a 6-10 kHz (0.5-5 A) AC power supply having a frequency of 300-400 kHz and a pulse power supply of + 10--15 kHz (FIG. 3). ). Each electrode is coated with a first p type semiconductor coating of 30 to 50 μm, a second n type semiconductor coating of 10 to 20 μm, and a third p type semiconductor catalyst coating of 30 to 50 μm (FIG. 1).

Therefore, when looking at the coating (Fig. 1), first, (surface current density) when a constant voltage is applied to one electrode according to the voltage of the alternating current, when the forward bias is caused by the electrostatic charge, the first type is (+) / p / n / p type. Holes, which are the majority carriers of the first p-type semiconductor coating, pass through the tunnel effect with little coupling with electrons of the second thin-film n-type, and they are combined with the holes, which are the majority carriers of the third p-type semiconductor catalyst coating. Density is amplified (Figure 2). However, when a negative voltage is applied, the coating of negative (-) / p / n type is reverse biased and the flow of current is weak, resulting in the oxidation reaction as the main reaction.

Second, since each semiconductor coating (voltage) consists of a series connection, the series connection capacitance of the entire coating can be expressed by the following equation.

[C _T : total capacitance, C _P1 : first p type capacitance, C _n2 : second n type capacitance, C _P3 : third p type catalyst capacitance]

Therefore, if you calculate the resistance to capacitance in alternating current,

[R: resistance, f: frequency]

Since the resistance value is higher than that of coating the p type semiconductor catalyst once, an effective high voltage is applied to the surface of the final p type semiconductor catalyst by V = IR.

Third, when dielectric films with different dielectric constants (constant and activation energy) are coated, the total dielectric constant corresponds to the sum of the dielectric constants. That is, since ε _T = ε _p1 + ε _n2 + ε _p3 , the dielectric constant of each of the semiconductors coated according to [Example] reaches 50 to 200, and thus exhibits a high dielectric constant of 150 to 600 as a whole. Accordingly, due to the surface field effect, the electric double layer formed by the high current density on the surface of the final p-type semiconductor catalyst activates the diffusion of the volatile organic compound into the electrode surface and at the same time lowers the activation energy barrier required for decomposition.

Fourth, the electric field strength when the (current) thin film is coated Since the thinner the furnace d, the larger the E, according to the [Example], a large amount of current flows to the coating surface in order to neutralize the coated dielectric. I = jS becomes large. (i: current, j: surface field strength, S: area)

Next, look at the electrode arrangement (Fig. 3),

First, (amplification of plasma) the amplification of electrons is caused by the pulse power supply electrode between the two electrodes to which the AC power is applied. This is because the positive (-) / (+) / (+) principle of a three-pole vacuum tube, the negative (-) / (+) / (+) principle of electron acceleration, and the pulse (+) When the electrode is placed, when the pulse voltage Vp is higher than the alternating voltage Va (Vp> Va), an electron transfer layer is formed around the pulse (+) electrode, resulting in a plasma frequency. Shows.

(f _pe : plasma frequency, W _pe : each frequency, n _e : number of electron groups, pc / cm 3)

Second, (displacement current) displacement current between both electrodes by AC power of 300 ~ 400 300 Flows.

(id: displacement current, ε _o : vacuum dielectric constant, A: electrode area, i: conduction current)

That is, the displacement current id is the same current as i flowing in the electrode, and the two electrodes act as one capacitor, but the displacement current is not the current flowing along the resistance but the current flowing along the space between the electrodes. It can be designed to be energy-saving.

Third, when a high-frequency AC power source is used for plasma generation, the number of ions trapped between the electrodes increases as the air gas between the electrodes changes in frequency. In other words It is represented as ( μ _i : ion movement attitude, E: electric field, W: each frequency, ℓ: distance between electrodes)

Fourth, (silent discharge) The application of a high-frequency AC power by applying a semiconductor coating on the surface of the electrode does not cause direct discharge between the electrodes, the silent discharge (Silent discharge) occurs, there is an advantage that can maintain the discharge continuously at low voltage.

Fifth, the dielectric constant of the semiconductor coated on the electrode surface is ε _s , the dielectric constant of the air gas between the electrodes is ε _a , and the electric field of the semiconductor is E _s and the electric field of the air gas is E _a . Since the dielectric constant of the air gas is about 1 and the dielectric constant of the semiconductor is 150 to 600, a strong electric field is applied to the air gas having a weak dielectric strength, so that the breakdown of the air gas occurs easily, and the decomposition of various harmful substances is actively performed.

Next, on the catalyst side

First, (nanoparticles), as in [Example], titanium dioxide, a main catalyst, was prepared in a size of 10-20 nm by a sol-gel method, and platinum, molybdenum, tungsten, silver, Cobalt metal is doped to a size of 1 to 2 nm, which is an atomic absorption unit. And zeolite 13X was used to increase the adsorption amount of gaseous gas.

Second, in order to prepare the (impurity doping) catalyst in p type, n type, impurities were prepared by doping boron in p type and phosphorus in n type, respectively.

Next, in order to increase the residence time in the plasma discharge of the plasma electron population group while forming an (electron effect) efficient electromagnetic field, and to add the Hall effect E _y = Ri _x B _z by the magnetic field, Permanent magnets were installed so that the magnetic field was formed in a direction perpendicular to the direction.

[E _y : intensity of electric field in y direction, R: Hall coefficient, current density in i _x : x direction, magnetic flux density in Bz: z direction (Wbm ^-2 )]

Thus the force of the entire field F = -q [E + B].

(-q is the charge of the electron, : Flow velocity of electrons)

The volatile organic compounds are decomposed and removed as follows by integrating the semiconductor coating side, electrode arrangement and applied power source, catalyst side, and electromagnetic field side.

CxHyOz + high voltage → CxHyOz ^* ------------------------- (Equation 3)

H ₂ O + high voltage → H ₂ O ^* -------------------------------- (Equation 4)

O ₂ + high voltage → O ₂ ^* ---------------------------------- (Equation 5)

High-voltage semiconductor surface + ^{→ e - + h + - -------------------} ( formula 6)

(*: Indicates an electrically excited state)

H ₂ O ^* + h ⁺ + high voltage → H ⁺ + OH ------------------------ (Equation 7)

O ² + h ⁺ + high voltage → (O) + (O) ------------------------ (Equation 8)

Adsorption on catalyst surface and CxHyOz ^* + h ⁺ + OH + (O) + high voltage → CO ₂ + H ₂ O in air gas -------------------- ------------------------ (Equation 9)

Cl, Br + M → MCl, MBr ----------------------- (Equation 10)

(M: trimeric substance)

<< Example >>

<First p type semiconductor electrode fabrication>

Titanium alkoxide is mixed with two solutions with a 5 wt% aqueous sulfuric acid solution / alkoxide molar ratio of 50, followed by stirring for 2-3 hours to cause a hydrolysis reaction. Based on 100 g of ortho titanic acid thus obtained, 200-350 g of boron 0.7-1.5 wt% aqueous solution and 50-75 g of methanol are mixed and stirred for 2 hours under high pressure mercury lamp (1 kPa). Thereafter, 100 to 150 g of copper oxide and 20 to 50 g of cobalt oxide are mixed and finally stirred for 2 to 8 hours.

The dispersion-finished semiconductor composition is coated with a stainless steel mesh, a mat, or a nickel sintered mat at 30 to 50 μm (dry coating film), and then fired at 350 to 500 ° C. for 6 to 12 hours to form a p type semiconductor electrode.

<Second n type semiconductor electrode fabrication>

Titanium alkoxide is mixed with two solutions with a 5 wt% aqueous sulfuric acid solution / alkoxide molar ratio of 50, followed by stirring for 2-3 hours to cause a hydrolysis reaction. Based on 100 g of ortho titanic acid obtained therefrom, 10-30 g of silicon, 200-350 g of phosphorus 0.5-1.0 wt% aqueous solution, and 50-75 g of methanol are stirred for 2 hours under high pressure mercury lamp irradiation. do. Thereafter, 10 to 50 g of nickel and 10 to 50 g of silver are mixed and finally stirred for 2 to 8 hours.

After dispersing, the semiconductor composition is coated on the first p type coated surface with 10 to 20 μm (dry coating), and then fired at 350 to 500 ° C. for 6 to 12 hours to form a p / n type heterojunction.

<The third p type semiconductor catalyst electrode manufacturing>

Titanium alkoxide is mixed with two solutions with a 5 wt% aqueous sulfuric acid solution / alkoxide molar ratio of 50, followed by stirring for 2-3 hours to cause a hydrolysis reaction. Based on 100 g of ortho titanic acid thus obtained, 200-350 g of boron 0.7-1.5 wt% aqueous solution and 50-75 g of methanol are mixed and stirred for 2 hours under high pressure mercury lamp (1 kPa). Then, in order to obtain a reaction active point, 100-200 g of 0.1-1 wt% platinum colloid aqueous solution dispersed in 1-2 nm particle size, 100-200 g of 0.1-1 wt% molybdenum colloid aqueous solution 100-200 g, 0.1-1 wt% tungsten colloid aqueous solution 100- 200 g, 0.1-1 wt% of silver colloid aqueous solution 100-200 g, 0.1-1 wt% Cobalt colloid aqueous solution 50-100 g, and methanol 100-150 g are mixed, and it stirs for 2-3 hours under high pressure mercury lamp irradiation.

Thereafter, 20 to 70 g of bismuth oxide, 2 to 10 g of vanadium pentoxide, 10 to 50 g of silver oxide, 5 to 15 g of cobalt oxide, and 5 to 20 g of nickel oxide are mixed, and 20 to 50 g of zeolite 13X is added, followed by final stirring for 2 to 8 hours. .

The dispersion-finished semiconductor composition is coated on a second p / n type heterojunction on a 30-50 μm (dry coating film) and then fired at 350 to 500 ° C. for 6 to 12 hours to form a final p / n / p type semiconductor catalyst electrode. .

1 is a cross-sectional view of an electrode in which a semiconductor composition is coated with a heterojunction.

2 is an energy band at constant voltage

3 is an electrode arrangement diagram (1 module) of a non-heating plasma system according to the present invention.

4 is an overall configuration diagram of the system (6 modules)

5 is a test result according to the embodiment

<Explanation of symbols for main parts of drawing>

(1) p type semiconductor coating

(2) n type semiconductor coating

(3) p type semiconductor catalyst coating

(4) AC power

(5) pulse power

.

As described above, it is possible to design energy-saving type with low energy consumption by applying decomposition principle of semiconductor catalyst to high voltage plasma generation principle, and process large and high concentration of harmful gas by installing processing devices in parallel and in series. It has the advantage of small installation area and low maintenance cost.

Claims (4)

First: p type semiconductor coating composition having the following formula T-MO Here, T is titanium dioxide, MO is an oxide metal, and corresponds to copper oxide and cobalt oxide, p type semiconductor composition prepared based on this. Second: n type semiconductor coating composition having the following formula T-M Here, T is titanium dioxide, M is a metal, and corresponds to silicon, nickel, silver, n-type semiconductor composition prepared based on this. Third: p type semiconductor catalyst coating composition having the following formula BT-M-MO Here, B is bismuth oxide, T is titanium dioxide, M is a reactive active metal and platinum, molybdenum, tungsten, silver, cobalt, MO is an oxide metal, vanadium pentoxide, silver oxide, cobalt oxide, It corresponds to nickel oxide and zeolite, p-type semiconductor catalyst coating composition prepared based on this. An electrode structure in which each composition of claim 1 is coated at 30 to 50 µm / 10 to 20 µm / 30 to 50 µm in the order of a p / n / p type semiconductor catalyst. The electrode of claim 2 is disposed and applied with alternating current of 300 to 400 kPa, 6 to 10 kPa, 0.5 to 5 A and pulsed power of +10 to +15 kPa, 0.5 to 2 A to remove volatile organic compounds and odors, and to destroy dioxin and ozone layer. A device for decomposing and removing the substances carbon tetrachloride, freon gas, halon, methyl chloroform and methyl bromide. A device structure in which permanent electromagnets are installed in the decomposition device to generate hole electromotive force due to the Hall effect on the semiconductor surface.