Plasma & Accelerator Environmental Application Lab....

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POSTECHPlasma & Accelerator Environmental Application Lab.

Http://www-ph.postech.ac.kr/~mhcho/pslE-mail: [email protected], 054)279-5862

Study on the Effects of Pellets and Carrier Gas on Characteristics of Silent

Discharge Process

Study on the Effects of Pellets and Carrier Gas on Characteristics of Silent

Discharge Process

Yong-Hwan Lee, Won-Sok Jung, Jae-Woo Chung, Yu-ri Choi, Moo-Hyun Cho, and Won Namkung

School of Environmental Science & Engineering and Pohang Accelerator Laboratory

Pohang University of Science and Technology

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Introduction(I)

Health and EnvironmentalHealth and EnvironmentalImpacts ofImpacts of NOx

Industrial/ Commercial/ Residential 19 %

Utilities 27 %

All Other Sources 5 %

Motor Vehicles 49 %

The Primary Sources ofThe Primary Sources of NOxNOxNOx

Ground level ozone (smog)

Acid rain

Water quality deterioration

Toxic chemicals

Visibility impairment

Global warming

Particles

http://www.epa.gov/oar/oaqps/nox/

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Introduction(II)

Conventional NOx Emissions Control Technologies

NOx Catalysts

Selective Catalytic Reduction

Plasma Technology

Combined Systems (Plasma + Catalyst)

Advanced NOx Emission Control Technologies

Lowering combustion temperatures

Careful air/fuel control during

combustion

Reducing the nitrogen content of

fuels

Injection of water or steam

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Combined Systems for Reducing NOx

N2, O2

Plasma process Catalytic process

NOx

NO → NO2 NO2 →N2, O2

NOx

Glass or alumina bead

Discharge electrode

Pyrex

Copper tape

(N2, O2)

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Principle of Dielectric Barrier Discharge Process

Electron multiplication

Space charge formation

Ionization

Dissociation and excitation

Chemical reactions

Microdischarge formation

Ionic & excited species

25-100 oCGas temperature

1-10 eVElectron energy

1014 – 1015 cm-3Electron density

100-1000 pCTotal charge

100-1000 A/cm2Density

0.1 APeak Current

0.1 mmFilament radius

1-10 nsDuration

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The Experimental Setup for Plasma Catalyst Hybrid System

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Effects of bead type on NO conversion

Effects of bead size on NO conversion

0

20

40

60

80

100

0 20 40 60 80 100 120

Energy density (J/L)

NO

con

vers

ion

rate

(%)

200 ppm-glass 200 ppm-alumina300 ppm-glass 300 ppm-alumina400 ppm-glass 400 ppm-alumina

0

20

40

60

80

0 30 60 90 120 150 180


NO

con

vers

ion

rate

(%)

glass 4mmglass 3mmglass 2mmalumina 2mmalumina 3mm

Diameter of beads: 2 mm

Flow rate: 6.7 LPM

Initial concentration: 300 ppm

Flow rate: 5.4 LPM

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Typical NO and NO2 Conversion Trend in Silent Discharge Process

020406080

100120140160180200220

0 50 100 150 200 250 300 350


Con

cent

ratio

n (p

pm)

NO NO2

Input gas: Air (O2, N2) + NO (200 ~ 400 ppm)

e + O2 e + O(3P) + O(3P, 1D) (1)

e + N2 e + N(4S) + N(4S, 2D) (2)

Dissociation energy: O2 < N2

At a low electron kinetic energy,

O + NO + M NO2 + M (3)

O + O2 + M O3 + M

& O3 + NO NO2 + O2 (4)

At a high electron kinetic energy,

N + O2 NO + O (5)

Low energy density Affected by (3) and (4)

High energy density. Affected by (3), (4), and (5)

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NO Conversion Trend in FPRNO Conversion Trend in SDR

0

10

20

30

40

50

60

70

80

0 30 60 90 120 150


NO

con

vers

ion

rate

(%)

5 LPM10LPM15LPM20LPM30LPM

010

2030

4050

6070

8090

0 20 40 60 80 100Energy density (J/L)

NO

con

vers

ion

rate

(%)

5LPM(1.2sec)8.6LPM(0.7sec)10LPM(0.6sec)12LPM(0.5sec)20LPM(0.3sec)

Diameter of electrode: 35 mm


Beads type: 4 mm Glass

Diameter of electrode: 40 mm


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NO Conversion Trends in the Reactor Filled with and without Beads

0

20

40

60

80

100

0 20 40 60 80 100 120


NO

con

vers

ion

rate

(%)

with beads

without beads

(a)

(b)

(a)

(b)

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Effects of Carrier Gas on NO Conversion

NO Conversion Trend in Plasma Catalyst Hybrid Process

0

50

100

150

200

250

300

0 10 20 30 40 50


Con

cent

ratio

n (p

pm)

Air-NOAir-NO2Ar-NOAr-NO2

0

40

80

120

160

200

0 50 100Energy density (J/L)

Con

cent

ratio

n (p

pm)

Plasma on +cat (NO)

Plasma on +cat (NO2)

Plasma on +cat (NOx)

Plasma off +cat (NO)

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Conclusions

1. There was an optimum bead size for obtaining the maximum NO conversion. 2. Dielectric materials used as a catalyst support affected the conversion

efficiency of NO. The NO conversion rate in the alumina bead filled reactor was lower than that in the glass bead filled reactor.

3. The optimum flow rate existed for the highest NO conversion in the reactor filled with beads. The optimum flow rate was approximately 10 l/min in the reactor filled with 4 mm glass beads in diameter.

4. Flow rate didn’t affect NO conversion in case of using the reactor without beads in our experimental range.

5. With investigating the effect of carrier gas on NO conversion, we have known that oxygen mainly contributes to the conversion of NO to NO2.

6. We investigated the synergetic effect of plasma-assisted catalytic process in reducing NOx.

Plasma & Accelerator Environmental Application Lab....

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